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Volume 10
Issue 3
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Atmosphere, Volume 10, Issue 3 (March 2019) – 59 articles

Cover Story (view full-size image): In this study, a coupling of the Conformal Cubic Atmospheric Model and the Chemical Transport Model (CCAM-CTM) was undertaken, with 11 emission scenarios segregated from the 2008 New South Wales Greater Metropolitan Region (NSW GMR) Air Emission Inventory, to investigate major source contributions to ambient PM2.5 and exposure. The natural and human-made sources were found to contribute 60% (3.55 µg/m3) and 40% (2.41 µg/m3) to the population-weighted annual average PM2.5 (5.96 µg/m3), respectively. The major source groups “wood heaters”, “industry”, “on-road motor vehicles”, “power stations”, and “non-road diesel and marine” account for 31%, 26%, 19%, 17%, and 6% of the total human-made sources contribution, respectively. These quantitative results can be the basis for air quality management interventions that aim to deliver improved public health outcomes. View this paper.
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18 pages, 6483 KiB  
Article
Impact of Different Types of ENSO Years on Intensity Changes of Landfalling Tropical Cyclones over China
by Lu Liu
Atmosphere 2019, 10(3), 161; https://doi.org/10.3390/atmos10030161 - 26 Mar 2019
Cited by 7 | Viewed by 3566
Abstract
This study examines whether there are significant differences in intensity and destructiveness of landfalling tropical cyclones (TCs) over China in central Pacific warm (CPW), eastern Pacific warm (EPW) and La Niña (LA) years. By analyzing different seasons and locations of TCs making landfall [...] Read more.
This study examines whether there are significant differences in intensity and destructiveness of landfalling tropical cyclones (TCs) over China in central Pacific warm (CPW), eastern Pacific warm (EPW) and La Niña (LA) years. By analyzing different seasons and locations of TCs making landfall over China, it was found that TCs in LA years generally had a larger power dissipation index (PDI) and may cause more disasters in China, while TCs in EPW years had a larger PDI over South China in autumn. A larger PDI of TCSC (landing location in Southern China) usually occurred in EPW years and a larger PDI of TCEC (landing location in Eastern China) occurred in LA years, compared with CPW years. The TCs in LA years were generally stronger, more frequent, and of longer duration over China, because of the positive relative humidity (RH) anomalies, the significant anomalous cyclone that occupied the South China Sea (SCS), and the easterly wind anomalies providing a beneficial steering flow for TCs making landfall. In EPW years, although TCs were less frequent, they had stronger intensity when making landfall and a longer lifetime over land which was mainly caused by a broad band of anomalous westerlies over the SCS giving rise to a belt of positive relative vorticity anomalies, as well as the slow translation speed of TCs before landfall supplying more energy for TCs to survive over land. Overall, we conclude that greater caution is warranted when TCs occur in LA and EPW years, as they may result in more serious disasters in China. Full article
(This article belongs to the Section Meteorology)
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19 pages, 32570 KiB  
Article
The Moisture Sources and Transport Processes for a Sudden Rainstorm Associated with Double Low-Level Jets in the Northeast Sichuan Basin of China
by Fangli Zhang, Guoping Li and Jun Yue
Atmosphere 2019, 10(3), 160; https://doi.org/10.3390/atmos10030160 - 25 Mar 2019
Cited by 16 | Viewed by 4373
Abstract
A sudden rainstorm that occurred in the northeast Sichuan Basin of China in early May 2017 was associated with a southwest low-level jet (SWLJ) and a mountainous low-level jet (MLLJ). This study investigates the impact of the double low-level jets (LLJs) on rainfall [...] Read more.
A sudden rainstorm that occurred in the northeast Sichuan Basin of China in early May 2017 was associated with a southwest low-level jet (SWLJ) and a mountainous low-level jet (MLLJ). This study investigates the impact of the double low-level jets (LLJs) on rainfall diurnal variation by using the data from ERA5 reanalysis, and explores the characteristics of water vapor transport, including the main paths and sources of moisture, by using the HYSPLIT-driven data of the ERA—interim, GDAS (Global Data Assimilation System), and NCEP/NCAR reanalysis data. The analysis shows that the sudden rainstorm in the mountain terrain was located at the left side of the large-scale SWLJ at 700 hPa, and at the exit region of the meso-scale MLLJ at 850 hPa. The double LLJs provide favorable moisture conditions, and the enhancement (weakening) of the LLJs is ahead of the start (end) of the rainstorm. The capacity of the LLJ at 850 hPa with respect to moisture convergence is superior to that at 700 hPa, especially when the MLLJ and the southerly LLJ at 850 hPa appear at the same time. The HYSPLIT backward trajectory model based on Lagrangian methods has favorable applicability in the event of sudden rainstorms in mountainous terrain, and there is no special path of moisture transport in this precipitation event. The main moisture sources of this process are the East China Sea–South China Sea, the Arabian Sea–Indian Peninsula, the Bay of Bengal, and the Middle East, accounting for 38%, 34%, 17% and 11% of the total moisture transport, respectively. Among them, the moisture transport in the Bay of Bengal and the South China Sea–East China Sea is mainly located in the lower troposphere, which is below 900 hPa, while the moisture transport in the Arabian Sea–Indian Peninsula and the Middle East is mainly in the middle and upper layers of the troposphere. The moisture changes of the transport trajectories are affected by the topography, especially the high mountains around the Sichuan Basin. Full article
(This article belongs to the Special Issue Analysis of Oceanic and Terrestrial Atmospheric Moisture Sources)
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17 pages, 5696 KiB  
Article
Analysis of Severe Droughts in Taiwan and its Related Atmospheric and Oceanic Environments
by Chih-wen Hung and Ming-Fu Shih
Atmosphere 2019, 10(3), 159; https://doi.org/10.3390/atmos10030159 - 25 Mar 2019
Cited by 8 | Viewed by 4058
Abstract
Drought is one of the important issues in climate studies. A drought index, Taiwan Meteorological Drought index (TMD index), was previously proposed and is applied here to identify historical severe droughts in Taiwan in order to clarify the corresponding large-scale backgrounds as a [...] Read more.
Drought is one of the important issues in climate studies. A drought index, Taiwan Meteorological Drought index (TMD index), was previously proposed and is applied here to identify historical severe droughts in Taiwan in order to clarify the corresponding large-scale backgrounds as a potential alert to the society in future. Through the TMD index, several historical severe drought cases in Taiwan are detected and characterized by significant seasonal variability in the annual cycle. Composites for large-scale atmospheric and oceanic environments over different periods within the dry season are conducted. From October to December, the colder sea surface temperature (SST) pattern of Pacific Meridional Mode (PMM) and the PMM-induced local anomalous anticyclones over the South China Sea are both in charge of the extremely dry conditions in Taiwan. From January to February, cold SST in the South China Sea and its adjacent oceans dominates local atmospheric conditions above these regions and creates an unfavorable environment for convection systems. From March to May, a massive anomalous anticyclonic circulation centering beside Alaska and extending its properties to East Asia and Taiwan generates a descending environment and in turn suppresses convection systems to develop. Therefore, the extremely dry conditions under this system are expected. Full article
(This article belongs to the Section Meteorology)
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17 pages, 2928 KiB  
Article
Inferring Fine-Mode and Coarse-Mode Aerosol Complex Refractive Indices from AERONET Inversion Products over China
by Qi-Xiang Chen, Wen-Xiang Shen, Yuan Yuan, Ming Xie and He-Ping Tan
Atmosphere 2019, 10(3), 158; https://doi.org/10.3390/atmos10030158 - 25 Mar 2019
Cited by 10 | Viewed by 3979
Abstract
Detailed knowledge of the complex refractive indices (m) of fine- and coarse-mode aerosols is important for enhancing understanding of the effect of atmospheric aerosol on climate. However, studies on obtaining aerosol modal m values are particularly scarce. This study proposes a [...] Read more.
Detailed knowledge of the complex refractive indices (m) of fine- and coarse-mode aerosols is important for enhancing understanding of the effect of atmospheric aerosol on climate. However, studies on obtaining aerosol modal m values are particularly scarce. This study proposes a method for inferring m values of fine- and coarse-mode aerosol using the inversion products from the AERONET ground-based aerosol robotic network. By identifying the aerosol type, modal m values are constrained and then inferred based on a maximum likelihood method. Numerical tests showed that compared with the reference values, our method slightly overestimates the real parts of the refractive indices (n), but underestimates the imaginary parts (k) by 2.11% ± 11.59% and 8.4% ± 26.42% for fine and coarse modes, respectively. We applied this method to 21 AERONET sites around China, which yielded annual mean m values of (1.45 ± 0.04) + (0.0109 ± 0.0046)i and (1.53 ± 0.01) + (0.0039 ± 0.0011)i for fine- and coarse-mode aerosols, respectively. It is observed that the fine mode n decreased from 1.53 to 1.39 with increasing latitude, while fine mode k values were generally larger than 0.008 over most of China. The coarse-mode n and k ranged from 1.52 to 1.56 and from 0.002 to 0.006, respectively. Full article
(This article belongs to the Special Issue Atmospheric Aerosol Regional Monitoring)
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14 pages, 2642 KiB  
Article
Size-Segregated Characteristics of Carbonaceous Aerosols during the Monsoon and Non-Monsoon Seasons in Lhasa in the Tibetan Plateau
by Nannan Wei, Chulei Ma, Junwen Liu, Guanghua Wang, Wei Liu, Deqing Zhuoga, Detao Xiao and Jian Yao
Atmosphere 2019, 10(3), 157; https://doi.org/10.3390/atmos10030157 - 24 Mar 2019
Cited by 11 | Viewed by 3507
Abstract
In this paper, we intensively collected atmospheric particulate matter (PM) with different diameters (size ranges: <0.49, 0.49–0.95, 0.95–1.5, 1.5–3.0, 3.0–7.2, and >7.2 μm) in Lhasa during the monsoon and non-monsoon seasons. The results clearly showed that the concentrations of PM, organic carbon (OC), [...] Read more.
In this paper, we intensively collected atmospheric particulate matter (PM) with different diameters (size ranges: <0.49, 0.49–0.95, 0.95–1.5, 1.5–3.0, 3.0–7.2, and >7.2 μm) in Lhasa during the monsoon and non-monsoon seasons. The results clearly showed that the concentrations of PM, organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) during the non-monsoon season were much higher than the concentrations during the monsoon season. During the monsoon season, a bimodal size distribution of the OC and WSOC, which were at <0.49 μm and >7.2 μm, respectively, and a unimodal size distribution at <0.49 μm for the EC were observed. However, during the non-monsoon season, there was a trimodal size distribution of the OC and WSOC (<0.49 μm, 1.5–3.0 μm, and >7.2 μm), and a unimodal size distribution of the EC (<0.49 μm). Possible sources of the carbonaceous components were revealed by combining the particle size distribution and the correlation analysis. OC, EC, and WSOC were likely from the photochemical transformation of biogenic and anthropogenic VOC, and the incomplete combustion of biomass burning and fossil fuels at <0.49 μm, whilst they were also likely to be from various types of dust and biogenic aerosols at >7.2 μm. OC and WSOC at 1.5–3.0 μm were likely to have been from the burning of yak dung and photochemical formation. The above results may draw attention in the public and scientific communities to the issues of air quality in the Tibetan Plateau. Full article
(This article belongs to the Special Issue Carbonaceous Aerosols: Sources, Physical and Chemical Characterization, and Toxicity)
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21 pages, 8071 KiB  
Article
Analysis of a Severe Pollution Episode in December 2017 in Sichuan Province
by Shenglan Zeng and Yiyu Zheng
Atmosphere 2019, 10(3), 156; https://doi.org/10.3390/atmos10030156 - 23 Mar 2019
Cited by 13 | Viewed by 3486
Abstract
To analyze a pollution process in Sichuan from 12 December 2017 to 2 January 2018, hourly pollutant data from 90 environmental monitors with surface data and sounding data from 21 meteorological stations were used to determine the sources of pollutants and the correlation [...] Read more.
To analyze a pollution process in Sichuan from 12 December 2017 to 2 January 2018, hourly pollutant data from 90 environmental monitors with surface data and sounding data from 21 meteorological stations were used to determine the sources of pollutants and the correlation between pollution levels and meteorological conditions. The results show that the whole process could be divided into two parts: (1) from 20 December 2017 to 30 December 2017, when, driven by a static stable atmosphere, the Sichuan basin experienced a long-lasting haze episode with an air quality index (AQI) that exceeded 150; and (2) after 30 December 2017, when a Mongolian cyclone developed and brought a large amount of cold air to Sichuan that improved the horizontal and vertical turbulence exchange and removed most of the pollutants. However, the northern part of Sichuan, affected by the cold air that carried dust from Shanxi and Qinghai, suffered an abrupt change in the extent of PM10 that led to an aggravation of this pollution process. Full article
(This article belongs to the Section Air Quality)
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21 pages, 3034 KiB  
Article
Simulating Sundowner Winds in Coastal Santa Barbara: Model Validation and Sensitivity
by Gert-Jan Duine, Charles Jones, Leila M.V. Carvalho and Robert G. Fovell
Atmosphere 2019, 10(3), 155; https://doi.org/10.3390/atmos10030155 - 22 Mar 2019
Cited by 16 | Viewed by 4891
Abstract
This study investigates the influence of planetary boundary layer (PBL) schemes and land surface models (LSMs) on the performance of the Weather Research & Forecasting model in simulating the development of downslope windstorms in the lee of the Santa Ynez Mountains in Santa [...] Read more.
This study investigates the influence of planetary boundary layer (PBL) schemes and land surface models (LSMs) on the performance of the Weather Research & Forecasting model in simulating the development of downslope windstorms in the lee of the Santa Ynez Mountains in Santa Barbara, California (known as Sundowner winds). Using surface stations, a vertical wind profiler, and a multi-physics ensemble approach, we found that most of the wind speed biases are controlled by the roughness length z 0 , and so by the choice of LSM. While timing characteristics of Sundowners are insensitive to both LSM and PBL schemes, a clear sensitivity in the horizontal extent of strong surface winds is found for both PBL parameterization and z 0 , which are related to patterns of self-induced wave-breaking near the mountaintop, and the erosion of the marine layer. These results suggest that LSMs with relatively high values of z 0 , and TKE-based or hybrid PBL schemes adequately simulate downslope windstorms in the lee of mountain ranges, specifically in areas where downslope windstorms interact with the marine boundary layer with stably stratified characteristics. Full article
(This article belongs to the Special Issue Weather Research and Forecasting (WRF) Model)
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24 pages, 5722 KiB  
Article
Urban Trees and Their Impact on Local Ozone Concentration—A Microclimate Modeling Study
by Helge Simon, Joachim Fallmann, Tim Kropp, Holger Tost and Michael Bruse
Atmosphere 2019, 10(3), 154; https://doi.org/10.3390/atmos10030154 - 22 Mar 2019
Cited by 27 | Viewed by 6936
Abstract
Climate sensitive urban planning involves the implementation of green infrastructure as one measure to mitigate excessive heat in urban areas. Depending on thermal conditions, certain trees tend to emit more biogenic volatile organic compounds, which act as precursors for ozone formation, thus hampering [...] Read more.
Climate sensitive urban planning involves the implementation of green infrastructure as one measure to mitigate excessive heat in urban areas. Depending on thermal conditions, certain trees tend to emit more biogenic volatile organic compounds, which act as precursors for ozone formation, thus hampering air quality. Combining a theoretical approach from a box model analysis and microscale modeling from the microclimate model ENVI-met, we analyze this relationship for a selected region in Germany and provide the link to air quality prediction and climate sensitive urban planning. A box model study was conducted, indicating higher ozone levels with higher isoprene concentration, especially in NO-saturated atmospheres. ENVI-met sensitivity studies showed that different urban layouts strongly determine local isoprene emissions of vegetation, with leaf temperature, rather than photosynthetic active radiation, being the dominant factor. The impact of isoprene emission on the ozone in complex urban environments was simulated for an urban area for a hot summer day with and without isoprene. A large isoprene-induced relative ozone increase was found over the whole model area. On selected hot spots we find a clear relationship between urban layout, proximity to NOx emitters, tree-species-dependent isoprene emission capacity, and increases in ozone concentration, rising up to 500% locally. Full article
(This article belongs to the Special Issue Air Quality Prediction)
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13 pages, 4855 KiB  
Article
The Internal Multidecadal Variability of SST in the Pacific and Its Impact on Air Temperature and Rainfall over Land in the Northern Hemisphere
by Hua Chen, Donglin He and Zhiwei Zhu
Atmosphere 2019, 10(3), 153; https://doi.org/10.3390/atmos10030153 - 21 Mar 2019
Cited by 5 | Viewed by 2884
Abstract
Based on the centennial-scale observations and re-analyses, this paper employs the ensemble empirical mode decomposition to separate the internal multidecadal variability (IMV) from the externally-forced variability of sea surface temperature (SST), and then defines new indices that represent the IMV of SST in [...] Read more.
Based on the centennial-scale observations and re-analyses, this paper employs the ensemble empirical mode decomposition to separate the internal multidecadal variability (IMV) from the externally-forced variability of sea surface temperature (SST), and then defines new indices that represent the IMV of SST in the North Pacific (NPIMV) and South Pacific (SPIMV), respectively. The spatial structure of NPIMV/SPIMV shows remarkably positive SST anomaly only in the index-defined region; meanwhile, the temporal evolutions of NPIMV and SPIMV are uncorrelated, indicating their independence of each other. Both NPIMV and SPIMV play a critical role in the near-surface air temperature and rainfall over land in the Northern hemisphere, especially in the season when their intensity is the strongest. It is through teleconnection wave trains that NPIMV and SPIMV exert influences on remote regions. Results from another two rainfall datasets are found to be consistent in the majority of the Northern hemisphere in response to NPIMV/SPIMV, yet disagreement exists in certain regions due to large uncertainties of rainfall datasets. Full article
(This article belongs to the Section Meteorology)
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26 pages, 20905 KiB  
Article
Isoprene, Methyl Vinyl Ketone and Methacrolein from TROICA-12 Measurements and WRF-CHEM and GEOS-CHEM Simulations in the Far East Region
by Alexander N. Safronov, Yury A. Shtabkin, Elena V. Berezina, Andrey I. Skorokhod, Vadim S. Rakitin, Igor B. Belikov and Nikolai F. Elansky
Atmosphere 2019, 10(3), 152; https://doi.org/10.3390/atmos10030152 - 21 Mar 2019
Cited by 6 | Viewed by 4738
Abstract
Spatial and temporal distributions of isoprene and its oxidation products, methyl vinyl ketone and methacrolein in the Far East region of Russia were investigated. The measurement data were obtained from a mobile laboratory, which moved along the Trans-Siberian railway and from WRF-CHEM (Weather [...] Read more.
Spatial and temporal distributions of isoprene and its oxidation products, methyl vinyl ketone and methacrolein in the Far East region of Russia were investigated. The measurement data were obtained from a mobile laboratory, which moved along the Trans-Siberian railway and from WRF-CHEM (Weather Research and Forecasting Chemical Model) and GEOS-CHEM (Goddard Earth Observing System Chemical Model) simulations. During the simulations, the RACM-MIM and MOZART mechanisms, included in the mesoscale WRF-CHEM model, as well as the Caltech Isoprene Scheme (CIS), built in the global GEOS-CHEM model, have been used. We found that the temporal distribution of the measured isoprene is in good agreement with the simulations. The measured isoprene, methyl vinyl ketone (MVK) and methacrolein (MACR) concentrations demonstrate pronounced diurnal variations. The correlation between the measured isoprene and MVK + MACR was good (R ~ 0.60–0.86). However, the simulated correlation between MVK + MACR and isoprene is very low, with the data for the night-time and daytime values varying. The simulated MVK + MACR to isoprene ratio, in comparison with the experimental result, has pronounced diurnal variations. During twilight and the night-time, the simulated MVK + MACR to isoprene ratio is more than 10. We propose that, due to the validity of the kinetic equations only in the homogeneous system, all chemical and transport (CTM) models, based on these kinetic equations, are not able to show an adequate simulation at night in the weak mixing atmosphere, when the atmospheric structure becomes heterogeneous. At moderate latitudes, we recommend the use of the turbulent Damköhler number and the Kolmogorov Damköhler numbers, which characterize the limits of CTM applicability, as the quality flags at the air quality forecast simulations. Full article
(This article belongs to the Section Air Quality)
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17 pages, 5188 KiB  
Article
The Sensitivity of Urban Heat Island to Urban Green Space—A Model-Based Study of City of Colombo, Sri Lanka
by Dikman Maheng, Ishara Ducton, Dirk Lauwaet, Chris Zevenbergen and Assela Pathirana
Atmosphere 2019, 10(3), 151; https://doi.org/10.3390/atmos10030151 - 21 Mar 2019
Cited by 33 | Viewed by 7612
Abstract
Urbanization continues to trigger massive land-use land-cover change that transforms natural green environments to impermeable paved surfaces. Fast-growing cities in Asia experience increased urban temperature indicating the development of urban heat islands (UHIs) because of decreased urban green space, particularly in recent decades. [...] Read more.
Urbanization continues to trigger massive land-use land-cover change that transforms natural green environments to impermeable paved surfaces. Fast-growing cities in Asia experience increased urban temperature indicating the development of urban heat islands (UHIs) because of decreased urban green space, particularly in recent decades. This paper investigates the existence of UHIs and the impact of green areas to mitigate the impacts of UHIs in Colombo, Sri Lanka, using UrbClim, a boundary climate model that runs two classes of simulations, namely urbanization impact simulations, and greening simulations. The urbanization impact simulation results show that UHIs spread spatially with the reduction of vegetation cover, and increases the average UHI intensity. The greening simulations show that increasing green space up to 30% in urban areas can decrease the average air temperature by 0.1 °C. On the other hand, converting entire green areas into urban areas in suburban areas increases the average temperature from 27.75 °C to 27.78 °C in Colombo. This demonstrates the sensitivity of UHI to vegetation cover in both urban and suburban areas. These seemingly small changes are average grid values and may indicate much higher impacts at sub-grid levels. Full article
(This article belongs to the Special Issue Urban Climate)
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14 pages, 6900 KiB  
Article
Physics Parameterization Selection in RCM and ESM Simulations Revisited: New Supporting Approach Based on Empirical Copulas
by Patrick Laux, Noah Kerandi and Harald Kunstmann
Atmosphere 2019, 10(3), 150; https://doi.org/10.3390/atmos10030150 - 19 Mar 2019
Cited by 5 | Viewed by 4118
Abstract
This study aims at a new supplementary approach to identify optimal configurations of physics parameterizations in regional climate models (RCMs) and earth system models (ESMs). Traditional approaches separately evaluate variable performance, which may lead to an inappropriate selection of physics parameterization combinations. Besides [...] Read more.
This study aims at a new supplementary approach to identify optimal configurations of physics parameterizations in regional climate models (RCMs) and earth system models (ESMs). Traditional approaches separately evaluate variable performance, which may lead to an inappropriate selection of physics parameterization combinations. Besides traditional approaches, we suggest an additional selection approach by considering the joint dependence structure (covariance structure) between key meteorological variables, i.e., precipitation P and temperature T. This is accomplished by empirical P and T copula functions and the χ 2 -test, and is demonstrated in two locations in Kenya with different major precipitation processes. It is shown that the selection based on traditional approaches alone may lead to nonoptimal decisions in terms of joint dependence structure between P and T. It was found that the copula-based approach may reduce the need for complex multivariate bias correction, as demonstrated using local intensity scaling for P and linear scaling for T. The new approach may contribute to improving RCM and ESM simulations and climate-impact studies worldwide. Full article
(This article belongs to the Section Meteorology)
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15 pages, 6735 KiB  
Article
The Foshan Total Lightning Location System in China and Its Initial Operation Results
by Li Cai, Xin Zou, Jianguo Wang, Quanxin Li, Mi Zhou and Yadong Fan
Atmosphere 2019, 10(3), 149; https://doi.org/10.3390/atmos10030149 - 19 Mar 2019
Cited by 23 | Viewed by 3898
Abstract
In the summer of 2013, a three-dimensional (3D)-based Foshan Total Lightning Location System (FTLLS), embedded with differential time of arrival (DTOA) techniques, was installed and started its operation in Foshan, Guangdong Province, China. In this paper, the geographical distribution and set-up information of [...] Read more.
In the summer of 2013, a three-dimensional (3D)-based Foshan Total Lightning Location System (FTLLS), embedded with differential time of arrival (DTOA) techniques, was installed and started its operation in Foshan, Guangdong Province, China. In this paper, the geographical distribution and set-up information of FTLLS, the estimated locating errors and locating results, as well as its initial operation results are presented. FTLLS consists of nine sub-stations that receive electromagnetic waves associated with lightning discharges and locates VLF/LF (200 Hz–500 kHz) radiation sources in 3D. The remote sub-stations acquired triggered waveforms with a duration of 0.5 ms, a resolution of 12-bits, and a GPS-based sferic time tags of 24 h per day. Cloud-to-ground (CG) lightning events, intra-cloud (IC) lightning events and narrow bipolar events (NBEs) were located by FTLLS. Based on the Monte Carlo simulation, the two-dimensional horizontal location error is basically less than 100 m, and the vertical error (altitude) is less than 200 m when the lightning event occurs within the network. On the other hand, over 14 million lightning strikes were recorded successfully by FTLLS during the period of May to October in 2014, among which IC events, CG events and NBEs accounted for 65%, 34% and 1%, respectively. It is shown that FTLLS is capable of a fine three-dimensional (3D) location, in which the altitude parameters obtained are reasonable and well consistent with observed data in the previous studies. The location results of thunderstorms were additionally verified through simultaneously-observed radar data. Full article
(This article belongs to the Section Meteorology)
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11 pages, 705 KiB  
Communication
Towards Hyper-Dimensional Variography Using the Product-Sum Covariance Model
by Jovan M. Tadić, Ian N. Williams, Vojin M. Tadić and Sébastien C. Biraud
Atmosphere 2019, 10(3), 148; https://doi.org/10.3390/atmos10030148 - 18 Mar 2019
Cited by 4 | Viewed by 3000
Abstract
Modeling hyper-dimensional spatial variability is a complex task from both practical and theoretical standpoints. In this paper we develop a method for modeling hyper-dimensional covariance (variogram) structures using the product-sum covariance model initially developed to model spatio-temporal variability. We show that the product-sum [...] Read more.
Modeling hyper-dimensional spatial variability is a complex task from both practical and theoretical standpoints. In this paper we develop a method for modeling hyper-dimensional covariance (variogram) structures using the product-sum covariance model initially developed to model spatio-temporal variability. We show that the product-sum model can be used recursively up to an arbitrarily large number of dimensions while preserving relative modeling simplicity and yielding valid covariance models. The method can be used to model variability in anisotropic conditions with multiple axes of anisotropy or when temporal evolution is involved, and thus is applicable to “full anisotropic 3D+time” situations often encountered in environmental sciences. It requires fewer assumptions than the traditional product-sum modeling approach. The new method also presents an alternative to classical approaches to modeling zonal anisotropy and requires fewer parameters to be estimated from data. We present an example by applying the method in conjunction with ordinary kriging to map photosynthetically-active radiation (PAR) for 2006, in Oklahoma, CA, USA and to explore effects of spatio-temporal variability in PAR on gross primary productivity (GPP). Full article
(This article belongs to the Special Issue Leaf to Ecosystem: The Latest in Measuring Bio-Atmospheric Integrations at Multiple Scales)
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2 pages, 136 KiB  
Editorial
Monsoons
by Kyung-Ja Ha
Atmosphere 2019, 10(3), 147; https://doi.org/10.3390/atmos10030147 - 18 Mar 2019
Viewed by 3313
Abstract
Monsoon climates affect the daily lives of two-thirds of the world population [...] Full article
(This article belongs to the Special Issue Monsoons)
15 pages, 2204 KiB  
Article
Modeling Dust Direct Radiative Feedbacks in East Asia During the Last Glacial Maximum
by Xugeng Cheng, Xiaoning Xie, Zhengguo Shi, Xinzhou Li, Tianliang Zhao and Xiaodong Liu
Atmosphere 2019, 10(3), 146; https://doi.org/10.3390/atmos10030146 - 18 Mar 2019
Cited by 5 | Viewed by 3165
Abstract
In this study, using the fourth version of the Community Atmosphere Model (CAM4) with a bulk aerosol model parameterization (BAM) for dust size distribution (CAM4-BAM), East Asian dust and its direct radiative feedbacks (DRF) during the Last Glacial Maximum are analyzed by intercomparing [...] Read more.
In this study, using the fourth version of the Community Atmosphere Model (CAM4) with a bulk aerosol model parameterization (BAM) for dust size distribution (CAM4-BAM), East Asian dust and its direct radiative feedbacks (DRF) during the Last Glacial Maximum are analyzed by intercomparing results between the experiments with (Active) and without (Passive) the DRF. This CAM4-BAM captures the expected characteristics that the dust aerosol optical depth and loading over East Asia during the Last Glacial Maximum (LGM) were significantly greater compared to the current climate. A comparative analysis of the Active and Passive experiments reveals that consideration of the dust–radiation interaction can significantly reduce dust emissions and then weaken the whole dust cycle, including loading, transport, and dry and wet depositions over East Asia. Further analysis of the dust–radiation feedback shows that the DRF decreases surface sensible heat, mainly owing to the negative surface forcing induced by dust with a value of −11.8 W m−2. The decreased surface sensible heat weakens the turbulent energy within the planetary boundary layer and the surface wind speed, and then reduces the regional dust emissions. This process creates a negative DRF–emission feedback loop to affect the dust cycle during the LGM. Further analysis reveals that the dust emissions in the LGM over East Asia were more reduced, with amounts of −77.2 Tg season−1 by the negative DRF–emission feedback, compared to the current climate with −6.8 Tg season−1. The two ratios of this reduction to their emissions are close to −10.7% for the LGM and −7.5% for the current climate. Full article
(This article belongs to the Special Issue Mineral Dust: Sources, Atmospheric Processing and Impacts)
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16 pages, 3117 KiB  
Article
Present and Future Climate—Tourism Conditions in Milos Island, Greece
by Panagiotis T. Nastos and Andreas Matzarakis
Atmosphere 2019, 10(3), 145; https://doi.org/10.3390/atmos10030145 - 18 Mar 2019
Cited by 27 | Viewed by 5812
Abstract
The objective of this study is to analyze the present and future climate-tourism conditions in Milos Island, Cyclades, Greece, by means of the assessment of the three climate components (physical, thermal, and aesthetic), which interprets the so-called climatic tourism potential. Milos Island is [...] Read more.
The objective of this study is to analyze the present and future climate-tourism conditions in Milos Island, Cyclades, Greece, by means of the assessment of the three climate components (physical, thermal, and aesthetic), which interprets the so-called climatic tourism potential. Milos Island is chosen as a representative island of the Cyclades complex in the Aegean Sea. Future climate change conditions are analyzed using the high-resolution simulations (grid size 0.11° × 0.11°) of the Regional Climate Model ALADIN 5.2 from Centre National de Recherche Meteorologiques, Meteo France (CNRM). The climate simulations concern the future periods 2021–2050 and 2071–2100 against the reference period 1961–1990, under two Representative Concentration Pathways, RCP4.5 and RCP8.5. Based on regional climate simulations, the tourism potential can be described in a meaningful and simple way by applying the Climate-Tourism-Information-Scheme (CTIS), which depicts detailed climate information that could be used by tourists to foresee the thermal comfort, aesthetic, and physical conditions for planning their vacations. More specifically, the thermal climate component is interpreted by the Physiologically Equivalent Temperature (PET), which is one of the most popular physiological thermal indices based on the human energy balance. The findings of the analysis could be used by stakeholders and the tourism industry in decision-making regarding the destination of Milos for tourism planning and touristic infrastructure development. Full article
(This article belongs to the Special Issue Tourism Climatology: Past, Present and Future)
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7 pages, 208 KiB  
Editorial
Recent Advances in Urban Ventilation Assessment and Flow Modelling
by Riccardo Buccolieri and Jian Hang
Atmosphere 2019, 10(3), 144; https://doi.org/10.3390/atmos10030144 - 16 Mar 2019
Cited by 24 | Viewed by 4259
Abstract
The Atmosphere Special Issue “Recent Advances in Urban Ventilation Assessment and Flow Modelling” collects twenty-one original papers and one review paper published in 2017, 2018 and 2019 dealing with several aspects of ventilation in urban areas (https://www [...] Full article
(This article belongs to the Special Issue Recent Advances in Urban Ventilation Assessment and Flow Modelling)
16 pages, 2032 KiB  
Article
A Short Note on the Potential of Utilization of Spectral AERONET-Derived Depolarization Ratios for Aerosol Classification
by Il-Sung Zo and Sung-Kyun Shin
Atmosphere 2019, 10(3), 143; https://doi.org/10.3390/atmos10030143 - 16 Mar 2019
Cited by 6 | Viewed by 4424
Abstract
We herein present the spectral linear particle depolarization ratios (δp) from an Aerosol Robotics NETwork (AERONET) sun/sky radiometer with respect to the aerosol type. AERONET observation sites, which are representative of each aerosol type, were selected for our study. The observation [...] Read more.
We herein present the spectral linear particle depolarization ratios (δp) from an Aerosol Robotics NETwork (AERONET) sun/sky radiometer with respect to the aerosol type. AERONET observation sites, which are representative of each aerosol type, were selected for our study. The observation data were filtered using the Ångström exponent (Å), fine-mode fraction (FMF) and single scattering albedo (ω) to ensure that the obtained values of δp were representative of each aerosol condition. We report the spectral δp values provided in the recently released AERONET version 3 inversion product for observation of the following aerosol types: dust, polluted dust, smoke, non-absorbing, moderately-absorbing and high-absorbing pollution. The AERONET-derived δp values were generally within the range of the δp values measured from lidar observations for each aerosol type. In addition, it was found that the spectral variation of δp differed according to the aerosol type. From the obtained results, we concluded that our findings provide potential insight into the identification and classification of aerosol types using remote sensing techniques. Full article
(This article belongs to the Special Issue Remote Sensing of Aerosols)
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15 pages, 620 KiB  
Article
Analysis of Two Dimensionality Reduction Techniques for Fast Simulation of the Spectral Radiances in the Hartley-Huggins Band
by Ana del Águila, Dmitry S. Efremenko, Víctor Molina García and Jian Xu
Atmosphere 2019, 10(3), 142; https://doi.org/10.3390/atmos10030142 - 16 Mar 2019
Cited by 14 | Viewed by 3789
Abstract
The new generation of atmospheric composition sensors such as TROPOMI is capable of providing spectra of high spatial and spectral resolution. To process this vast amount of spectral information, fast radiative transfer models (RTMs) are required. In this regard, we analyzed the efficiency [...] Read more.
The new generation of atmospheric composition sensors such as TROPOMI is capable of providing spectra of high spatial and spectral resolution. To process this vast amount of spectral information, fast radiative transfer models (RTMs) are required. In this regard, we analyzed the efficiency of two acceleration techniques based on the principal component analysis (PCA) for simulating the Hartley-Huggins band spectra. In the first one, the PCA is used to map the data set of optical properties of the atmosphere to a lower-dimensional subspace, in which the correction function for an approximate but fast RTM is derived. The second technique is based on the dimensionality reduction of the data set of spectral radiances. Once the empirical orthogonal functions are found, the whole spectrum can be reconstructed by performing radiative transfer computations only for a specific subset of spectral points. We considered a clear-sky atmosphere where the optical properties are defined by Rayleigh scattering and trace gas absorption. Clouds can be integrated into the model as Lambertian reflectors. High computational performance is achieved by combining both techniques without losing accuracy. We found that for the Hartley-Huggins band, the combined use of these techniques yields an accuracy better than 0.05% while the speedup factor is about 20. This innovative combination of both PCA-based techniques can be applied in future works as an efficient approach for simulating the spectral radiances in other spectral regions. Full article
(This article belongs to the Special Issue Radiative Transfer Models of Atmospheric and Cloud Properties)
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14 pages, 1848 KiB  
Article
Features of K-Changes Observed in Sri Lanka in the Tropics
by Sankha Nanayakkara, Mahendra Fernando and Vernon Cooray
Atmosphere 2019, 10(3), 141; https://doi.org/10.3390/atmos10030141 - 14 Mar 2019
Cited by 1 | Viewed by 3161
Abstract
General characteristics of K-changes, including their duration and probability of occurrence associated with ground flashes in Sri Lanka in the tropics, together with their fine structure, are presented. In 98 ground flashes where the small step changes associated with K-changes are clearly visible, [...] Read more.
General characteristics of K-changes, including their duration and probability of occurrence associated with ground flashes in Sri Lanka in the tropics, together with their fine structure, are presented. In 98 ground flashes where the small step changes associated with K-changes are clearly visible, there were about two K-changes per flash on average. The mean K-change time duration observed in this study is 0.38 ms. In 53 of the ground flashes, there were 120 consecutive K-changes. In these cases, the geometric mean of the time interval between K-changes was 12 ms. Analysis of the fine structure of the K-changes reveals the K-changes are always associated with either a chaotic pulse train or a combination of chaotic and regular pulse trains. The results suggest that the small step-like static electric fields identified in the literature as K-changes are the step-like static fields associated with the processes that generate chaotic or a combination of chaotic and regular pulse trains. Thus, at larger distances where the static fields are negligible, K-changes may appear as a chaotic pulse train or a combination of chaotic and regular pulse trains. Full article
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11 pages, 2168 KiB  
Article
Changes in Means and Extreme Events of Sea Surface Temperature in the East China Seas Based on Satellite Data from 1982 to 2017
by Qingyuan Wang, Yan Li, Qingquan Li, Yiwei Liu and Ya-nan Wang
Atmosphere 2019, 10(3), 140; https://doi.org/10.3390/atmos10030140 - 14 Mar 2019
Cited by 14 | Viewed by 3749
Abstract
Marginal seas are fundamental to humans for their importance in mariculture resources and commerce. Based on the NOAA 0.25 degree daily Optimum Interpolation (OI) sea surface temperature (SST) data set, spatiotemporal changes in mean and extreme SST in the East China Seas (ECSs) [...] Read more.
Marginal seas are fundamental to humans for their importance in mariculture resources and commerce. Based on the NOAA 0.25 degree daily Optimum Interpolation (OI) sea surface temperature (SST) data set, spatiotemporal changes in mean and extreme SST in the East China Seas (ECSs) were examined for from 1982 to 2017. As a regional average, the annual mean SST has notably increased at a rate of 0.21 ± 0.08 °C per decade. The warming SST during 1982–2017 is probably related to the influence from a recent strengthening and westward extension of the WPSH. There are also notable warming trends in annual minimum and maximum SST. Spatially, the rapid warming of annual mean SSTs are located in the vicinity of the Yangtze Estuary, exceeding 0.2 °C per decade and part of the ECS-Kuroshio. This pattern may be largely affected by the spatial changes of minimum SST. Rapid warming of maximum SST can be found across the region, from the northern East China Sea (ECS) to the Bohai Sea. Since 1982, extreme hot days (EHDs) have undergone an obvious increasing trend, at a rate of 15.2 days per decade. Conversely, extreme cold days (ECDs) have been decreasing. Notably, the largest increase of EHDs appears in the western ECS and the Bohai Sea, which both have rich marine ecosystems. The trend of EHDs has a significant relationship to mean SST, suggesting that there will be a further increase in EHDs under continued warming in the ECSs. These findings emphasize the importance and urgency of strategies which should be planned for the adaptation and mitigation of specific types of extreme hot events in this region. Full article
(This article belongs to the Special Issue Climate Change Impacts on Coastal Areas)
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13 pages, 4384 KiB  
Article
Impacts of Onset Time of El Niño Events on Summer Rainfall over Southeastern Australia during 1980–2017
by Lingli Fan, Jianjun Xu and Liguo Han
Atmosphere 2019, 10(3), 139; https://doi.org/10.3390/atmos10030139 - 14 Mar 2019
Cited by 3 | Viewed by 4058
Abstract
El Niño–Southern Oscillation (ENSO) has large impacts on Australia’s rainfall. A composite analysis technique was utilized to distinguish the impact of onset time of El Niño on summer rainfall over southeastern Australia. Summer rainfall tended to be lower than normal in austral autumn [...] Read more.
El Niño–Southern Oscillation (ENSO) has large impacts on Australia’s rainfall. A composite analysis technique was utilized to distinguish the impact of onset time of El Niño on summer rainfall over southeastern Australia. Summer rainfall tended to be lower than normal in austral autumn El Niño events during December–January–February (DJF) and higher than normal in austral winter El Niño events, in 1980–2017. During autumn El Niño events, the Walker circulation and meridional cells served as a bridge, linking the warmer sea surface temperature (SST) in the eastern equatorial Pacific (EEP) and lower summer rainfall over southeastern Australia. This physical process can be described as follows: During DJF, a positive SST anomaly in the EEP was concurrent with anomalous downdraft over southeastern Australia via zonal anomalous Walker circulation, meridional anomalous cells along 170° E–170° W, and a Pacific South American (PSA) teleconnection wave train at 500 hPa. In addition, an anomalous convergence at 200 hPa depressed the convection. Meanwhile, an 850 hPa abnormal westerly was not conducive to transport marine water vapor into this area. These factors resulted in below-normal rainfall. During winter El Niño events, a positive SST anomaly in the central equatorial Pacific (CEP) and the changes in Walker circulation and meridional cells were weaker. The PSA teleconnection wave train shifted westward and northward, and there was a low-level anomalous ascent over southeastern Australia. At the western flank of the anomalous anticyclone, northerly transported water vapor from the ocean to southeastern Australia resulted in a sink of water vapor over this area. The development of low-level convective activity and the plentiful water vapor supply favored more rainfall over southeastern Australia. Onset time of El Niño may be a useful metric for improving the low predictive skill of southeastern Australian summer rainfall. Full article
(This article belongs to the Special Issue Large-Scale Atmospheric Circulation Variability and Its Climate Impacts)
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24 pages, 5211 KiB  
Article
Major Source Contributions to Ambient PM2.5 and Exposures within the New South Wales Greater Metropolitan Region
by Lisa T.-C. Chang, Yvonne Scorgie, Hiep Nguyen Duc, Khalia Monk, David Fuchs and Toan Trieu
Atmosphere 2019, 10(3), 138; https://doi.org/10.3390/atmos10030138 - 13 Mar 2019
Cited by 27 | Viewed by 6589
Abstract
The coupled Conformal Cubic Atmospheric Model (CCAM) and Chemical Transport Model (CTM) (CCAM-CTM) was undertaken with eleven emission scenarios segregated from the 2008 New South Wales Greater Metropolitan Region (NSW GMR) Air Emission Inventory to predict major source contributions to ambient PM2.5 [...] Read more.
The coupled Conformal Cubic Atmospheric Model (CCAM) and Chemical Transport Model (CTM) (CCAM-CTM) was undertaken with eleven emission scenarios segregated from the 2008 New South Wales Greater Metropolitan Region (NSW GMR) Air Emission Inventory to predict major source contributions to ambient PM2.5 and exposure in the NSW GMR. Model results illustrate that populated areas in the NSW GMR are characterised with annual average PM2.5 of 6–7 µg/m3, while natural sources including biogenic emissions, sea salt and wind-blown dust contribute 2–4 µg/m3 to it. Summer and winter regional average PM2.5 ranges from 5.2–6.1 µg/m3 and 3.7–7.7 µg/m3 across Sydney East, Sydney Northwest, Sydney Southwest, Illawarra and Newcastle regions. Secondary inorganic aerosols (particulate nitrate, sulphate and ammonium) and sodium account for up to 23% and 18% of total PM2.5 mass in both summer and winter. The increase in elemental carbon (EC) mass from summer to winter is found across all regions but particularly remarkable in the Sydney East region. Among human-made sources, “wood heaters” is the first or second major source contributing to total PM2.5 and EC mass across Sydney in winter. “On-road mobile vehicles” is the top contributor to EC mass across regions, and it also has significant contributions to total PM2.5 mass, particulate nitrate and sulphate mass in the Sydney East region. “Power stations” is identified to be the third major contributor to the summer total PM2.5 mass across regions, and the first or second contributor to sulphate and ammonium mass in both summer and winter. “Non-road diesel and marine” plays a relatively important role in EC mass across regions except Illawarra. “Industry” is identified to be the first or second major contributor to sulphate and ammonium mass, and the second or third major contributor to total PM2.5 mass across regions. By multiplying modelled predictions with Australian Bureau of Statistics 1-km resolution gridded population data, the natural and human-made sources are found to contribute 60% (3.55 µg/m3) and 40% (2.41 µg/m3) to the population-weighted annual average PM2.5 (5.96 µg/m3). Major source groups “wood heaters”, “industry”, “on-road motor vehicles”, “power stations” and “non-road diesel and marine” accounts for 31%, 26%, 19%, 17% and 6% of the total human-made sources contribution, respectively. The results in this study enhance the quantitative understanding of major source contributions to ambient PM2.5 and its major chemical components. A greater understanding of the contribution of the major sources to PM2.5 exposures is the basis for air quality management interventions aiming to deliver improved public health outcomes. Full article
(This article belongs to the Special Issue Air Quality in New South Wales, Australia)
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20 pages, 3666 KiB  
Article
Temporal Changes in Air Quality during a Festival Season in Kannur, India
by Resmi CT, Nishanth T, Satheesh Kumar MK, Balachandramohan M and Valsaraj KT
Atmosphere 2019, 10(3), 137; https://doi.org/10.3390/atmos10030137 - 13 Mar 2019
Cited by 11 | Viewed by 5982
Abstract
This study looked at the variation in air quality during the periods of fireworks as assessed from the change in ambient concentrations of air pollutants like particulate matter (PM10), O3, and NO2 for pre-, post-, and Vishu days [...] Read more.
This study looked at the variation in air quality during the periods of fireworks as assessed from the change in ambient concentrations of air pollutants like particulate matter (PM10), O3, and NO2 for pre-, post-, and Vishu days for four consecutive years in 2015, 2016, 2017, and 2018 in Kannur, India. Enhanced levels of O3, NO2, NO, and PM10 were observed during the intense usage of fireworks. The concentration of metals in PM10 increased and the percent increase was found to be different for metal traces. A pronounced increase in the aerosol optical depth (AOD) in the lower wavelength region of solar radiation reveals the abundance of fine mode particles. The concentrations of O3 and NO2 were observed to increase by more than 100% on Vishu day than the control days for the observational period. Simulation using the National Center for Atmospheric Research (NCAR) Master Mechanism photochemical box model indicates a more than 100% enhancement in NO2 photolysis rates during the fireworks episode, which leads to a 100% increase in the surface ozone production. Observations as well as model simulations indicate that the enhanced photochemical ozone production from NO2 photolysis is possibly the main driver of ozone production during the Vishu at this site. The air quality index (AQI) revealed the deterioration of air quality at the observational site during the period of Vishu. Full article
(This article belongs to the Section Air Quality)
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19 pages, 2956 KiB  
Article
New Interpretative Scales for Lichen Bioaccumulation Data: The Italian Proposal
by Elva Cecconi, Lorenzo Fortuna, Renato Benesperi, Elisabetta Bianchi, Giorgio Brunialti, Tania Contardo, Luca Di Nuzzo, Luisa Frati, Fabrizio Monaci, Silvana Munzi, Juri Nascimbene, Luca Paoli, Sonia Ravera, Andrea Vannini, Paolo Giordani, Stefano Loppi and Mauro Tretiach
Atmosphere 2019, 10(3), 136; https://doi.org/10.3390/atmos10030136 - 13 Mar 2019
Cited by 39 | Viewed by 5909
Abstract
The interpretation of lichen bioaccumulation data is of paramount importance in environmental forensics and decision-making processes. By implementing basic ideas underlying previous interpretative scales, new dimensionless, species-independent “bioaccumulation scales” for native and transplanted lichens are proposed. Methodologically consistent element concentration datasets were populated [...] Read more.
The interpretation of lichen bioaccumulation data is of paramount importance in environmental forensics and decision-making processes. By implementing basic ideas underlying previous interpretative scales, new dimensionless, species-independent “bioaccumulation scales” for native and transplanted lichens are proposed. Methodologically consistent element concentration datasets were populated with data from biomonitoring studies relying on native and transplanted lichens. The scale for native lichens was built up by analyzing the distribution of ratios between element concentration data and species-specific background concentration references (B ratios), herein provided for Flavoparmelia caperata and Xanthoria parietina (foliose lichens). The scale for transplants was built up by analyzing the distribution of ratios between element concentration in exposed and unexposed samples (EU ratio) of Evernia prunastri and Pseudevernia furfuracea (fruticose lichens). Both scales consist of five percentile-based classes; namely, “Absence of”, “Low”, “Moderate”, “High”, and “Severe” bioaccumulation. A comparative analysis of extant interpretative tools showed that previous ones for native lichens suffered from the obsolescence of source data, whereas the previous expert-assessed scale for transplants failed in describing noticeable element concentration variations. The new scales, based on the concept that pollution can be quantified by dimensionless ratios between experimental and benchmark values, overcome most critical points affecting the previous scales. Full article
(This article belongs to the Special Issue Biomonitoring of Atmospheric Pollution)
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12 pages, 4207 KiB  
Article
Simulation of an Asian Dust Storm Event in May 2017
by Ping Song, Jianfang Fei, Changshun Li and Xiaogang Huang
Atmosphere 2019, 10(3), 135; https://doi.org/10.3390/atmos10030135 - 13 Mar 2019
Cited by 13 | Viewed by 3798
Abstract
Dust particles in the atmosphere play an important role in air pollution, climate change, and biogeochemical cycles. Some of the dominant sources of dust in mid-latitude regions are in Asia. An intense dust storm engulfed Northern China at the beginning of May 2017, [...] Read more.
Dust particles in the atmosphere play an important role in air pollution, climate change, and biogeochemical cycles. Some of the dominant sources of dust in mid-latitude regions are in Asia. An intense dust storm engulfed Northern China at the beginning of May 2017, and PM10 mass concentrations of 1500–2000 μg m−3 were measured near the dust source region. We combined numerical simulations, air quality monitoring data, and satellite retrievals to investigate dust emission and transport during this event. We found that the event was closely related to cold front activity, characterized by increased wind speed, which increased dust emission. We improved the dust scheme using a local dust size distribution to better simulate the dust emission flux. We found that accurate parametrization of the dust size distribution was important to effectively simulate both dust emission and ambient particle concentration. We showed that using a local dust size distribution substantially improved the accuracy of the simulation, allowing both the spatial distribution of pollution caused by the dust storm and temporal variability in the pollution to be captured. Full article
(This article belongs to the Special Issue Urban Particulate Matters: Composition, Sources, and Exposure)
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15 pages, 12337 KiB  
Article
Autumn Cold Surge Paths over North China and the Associated Atmospheric Circulation
by Bo Cai, Gang Zeng, Guwei Zhang and Zhongxian Li
Atmosphere 2019, 10(3), 134; https://doi.org/10.3390/atmos10030134 - 12 Mar 2019
Cited by 17 | Viewed by 3930
Abstract
Using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, we tracked the paths of 46 autumn cold surges affecting North China from 1961 to 2014, and classified them by clustering analysis, thereby investigating their changes and associated atmospheric circulation evolution. Our results indicate [...] Read more.
Using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, we tracked the paths of 46 autumn cold surges affecting North China from 1961 to 2014, and classified them by clustering analysis, thereby investigating their changes and associated atmospheric circulation evolution. Our results indicate that autumn cold surges affecting North China can be classified into three types according to their paths: the north type, west type, and northwest type, with occurrences of 12, 16, and 18 respectively. Different types of cold surges have different atmospheric circulation characteristics. The north type is associated with a blocking type of atmospheric circulation pattern, with an enhanced stretching northeast ridge over the Ural Mountains and a transverse trough over Lake Baikal. However, the northwest type is characterized by a ridge–trough–ridge wave-train pattern that is located over the Barents Sea, West Siberian Plain, and Sakhalin Island, respectively. The west-type cold surge is related to a conversion type: a blocking system over the Ural Mountains forms four days before the cold surge occurrence, after which it becomes a wave-train type. The atmospheric signals detected prior to the occurrences of the three types of cold surges are also explored. The main signal of the north-path cold surges is that the energy propagates eastward from the Azores Islands to the Ural Mountains, and then forms a blocking high over the Urals. However, for the northwest-path cold surges, there is a weak trough over the Ural Mountains that gradually strengthens because the blocking high collapses over the Norwegian Sea. The key signal of the formation of the west-path cold surges is a blocking high over the Norwegian Sea’s continuous enhancement and extension to Novaya Zemlya, which results in a transmission of energy to the Ural Mountains and leads to the formation of a blocking system over here. When the above-mentioned different types of atmospheric circulation characteristics appear, the type of cold surge path and its impact area can be potentially forecasted in advance, which may reduce the losses that result from cold surges. Full article
(This article belongs to the Special Issue Weather and Climate Extremes: Current Developments)
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16 pages, 5443 KiB  
Article
Extreme Weather Impacts on Inland Waterways Transport of Yangtze River
by Lijun Liu, Yuanqiao Wen, Youjia Liang, Fan Zhang and Tiantian Yang
Atmosphere 2019, 10(3), 133; https://doi.org/10.3390/atmos10030133 - 12 Mar 2019
Cited by 15 | Viewed by 4448
Abstract
The impact of extreme weather events on the navigation environment in the inland waterways of the Yangtze River is an interdisciplinary hotspot in subjects of maritime traffic safety and maritime meteorology, and it is also a difficult point for the implementation of decision-making [...] Read more.
The impact of extreme weather events on the navigation environment in the inland waterways of the Yangtze River is an interdisciplinary hotspot in subjects of maritime traffic safety and maritime meteorology, and it is also a difficult point for the implementation of decision-making and management by maritime and meteorological departments in China. The objective of this study is to review the variation trends and distribution patterns in the periods of adverse and extreme weather events that are expected to impact on inland waterways transport (IWT) on the Yangtze River. The frequency of severe weather events, together with the changes in their spatial extension and intensity, is analyzed based on the ERA-Interim datasets (1979–2017) and the GHCNDEX dataset (1979–2017), as well as the research progresses and important events (2004–2016) affecting the navigation environment. The impacts of extreme weather events on IWT accidents and phenomena of extreme weather (e.g., thunderstorms, lightning, hail, and tornadoes) that affect the navigation environment are also analyzed and discussed. The results show that: (1) the sections located in the plain climate zone is affected by extreme weather in every season, especially strong winds and heat waves; (2) the sections located in the hilly mountain climate zone is affected particularly by spring extreme phenomena, especially heat waves; (3) the sections located in the Sichuan Basin climate zone is dominated by the extreme weather phenomena in autumn, except cold waves; (4) the occurrence frequency of potential flood risk events is relatively high under rainstorm conditions and wind gusts almost affect the navigation environment of the Jiangsu and Shanghai sections in every year; (5) the heat wave indices (TXx, TR, and WSDI) tend to increase and the temperature of the coldest day of the year gradually increases; (6) the high occurrences of IWT accidents need to be emphasized by relevant departments, caused by extreme weather during the dry season; and (7) the trends and the degree of attention of extreme weather events affecting IWT are ranked as: heat wave > heavy rainfall > wind gust > cold spell > storm. Understanding the seasonal and annual frequency of occurrence of extreme weather events has reference significance for regional management of the Yangtze River. Full article
(This article belongs to the Special Issue Weather and Climate Extremes: Current Developments)
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16 pages, 9994 KiB  
Article
Influence of the Heights of Low-Level Jets on Power and Aerodynamic Loads of a Horizontal Axis Wind Turbine Rotor
by Xuyao Zhang, Congxin Yang and Shoutu Li
Atmosphere 2019, 10(3), 132; https://doi.org/10.3390/atmos10030132 - 11 Mar 2019
Cited by 9 | Viewed by 3735
Abstract
The influence of the heights of low-level jets (LLJs) on the rotor power and aerodynamic loads of a horizontal axis wind turbine were investigated using the fatigue, aerodynamics, structures, and turbulence code. The LLJ and shear inflow wind fields were generated using an [...] Read more.
The influence of the heights of low-level jets (LLJs) on the rotor power and aerodynamic loads of a horizontal axis wind turbine were investigated using the fatigue, aerodynamics, structures, and turbulence code. The LLJ and shear inflow wind fields were generated using an existing wind speed spectral model. We found that the rotor power predicted by the average wind speed of the hub height is higher than the actual power in relatively weak and shallow LLJ inflow conditions, especially when the LLJ height is located inside the rotor-swept area. In terms of aerodynamic loads, when the LLJ height is located inside the rotor-swept area, the root mean square (RMS) rotor thrust coefficient and torque coefficient increase, while the RMS rotor unbalanced aerodynamic load coefficients, including lateral force, longitudinal force, tilt moment, and yaw moment, decreased. This means that the presence of both positive and negative wind shear in the rotor-swept area not only increases the rotor power but also reduces the unbalanced aerodynamic loads, which is beneficial to the operation of wind turbine. Power spectrum analysis shows no obvious difference in the power spectrum characteristics of the rotor torque and thrust in LLJ inflow conditions with different heights. Full article
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