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19 pages, 9095 KiB

Open AccessArticle

Analysis of Temperature Semi-Annual Oscillations (SAO) in the Middle Atmosphere

by Ming Shangguan and Wuke Wang

Remote Sens. 2023, 15(3), 857; https://doi.org/10.3390/rs15030857 - 3 Feb 2023

Cited by 1 | Viewed by 1944

Abstract

The middle atmosphere plays an important role in the research of various dynamical and energy processes. Microwave Limb Sounder (MLS), reanalyses and model simulations with NCAR’s Whole Atmosphere Community Climate Model (WACCM) data in the range between 100 and 0.1 hPa from 2005 [...] Read more.

The middle atmosphere plays an important role in the research of various dynamical and energy processes. Microwave Limb Sounder (MLS), reanalyses and model simulations with NCAR’s Whole Atmosphere Community Climate Model (WACCM) data in the range between 100 and 0.1 hPa from 2005 to 2020 have been analyzed with a focus on the temperature semi-annual oscillations (SAO). Significant SAO of temperature is prominent in the tropical region (20

^{°}

S–20

^{°}

N) around 1–3 hPa, which is consistent with previous studies. We also found significant SAO in the northern hemisphere (NH) high latitudes between 8 and 0.3 hPa and southern hemisphere (SH) high latitudes between 0.5 and 0.1 hPa, which has been of less concern in previous studies. The thermal budget based on MERRA2 and simulations is used to explain the mechanism of SAO in the middle atmosphere. In the tropics, the two temperature peaks are mainly determined by radiative processes. In the NH high latitudes of the stratosphere, the temperature peak in January is mainly related to dynamical processes, while the temperature peak in July is determined by a combination of dynamical and radiative processes. In the NH high latitudes of the lower mesosphere, the first peak in June is primarily associated with dynamical and radiative processes, while the second peak in December is primarily associated with the dynamical processes. In the SH high latitudes of the lower mesosphere, the first temperature peak in July is mainly due to dynamical processes while the second temperature peak in December is mainly due to radiative processes. Various features are present in the SH and NH high latitude SAO in the lower mesosphere. Furthermore, we performed model simulations with and without SAO in sea surface temperatures (SST-SAO) to study the connection between SST and temperature SAO. WACCM6 results indicate that the SAO in the middle atmosphere is partially affected by the existence of an SST-SAO. By removing SAO in SST, the PSD magnitude of the SAO decreases in the tropical region and increases in the polar region. The amplitudes of total heating rates are also modified. The WACCM experiment confirms the relationship between SST-SAO and temperature SAO in the middle atmosphere. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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10 pages, 3022 KiB

Open AccessCommunication

Different Influences on “Wave Turbopause” Exerted by 6.5 DWs and Gravity Waves

by Wei Ge, Zheng Sheng, Yingying Huang, Yang He, Qixiang Liao and Shujie Chang

Remote Sens. 2023, 15(3), 800; https://doi.org/10.3390/rs15030800 - 31 Jan 2023

Cited by 2 | Viewed by 1294

Abstract

“Wave turbopause” is defined as the mesospheric altitude level where the temperature fluctuation field indicates a substantial increase in wave amplitude in the vertical direction. It is similar to turbopause in seasonal and latitudinal variations, providing an almost global analysis of turbopause on [...] Read more.

“Wave turbopause” is defined as the mesospheric altitude level where the temperature fluctuation field indicates a substantial increase in wave amplitude in the vertical direction. It is similar to turbopause in seasonal and latitudinal variations, providing an almost global analysis of turbopause on the basis of satellite measurements rather than localized detection. Previous studies of “wave turbopause” were based on standard deviation of temperature, which is an integrated measure of wave activity. In this study, we distinguish different atmospheric waves and investigate their influences on “wave turbopause”. By comparing the altitude of “wave turbopause” with peak height of amplitude (PHA) for gravity waves and 6.5 days waves (6.5 DWs), whose period is approximately 6.5 days in the mesosphere and lower thermosphere, we find that the seasonal variation in altitude of “wave turbopause” is higher at the winter pole and lower at the summer pole, correlated with PHA for 6.5 DWs but anti-correlated with PHA for gravity waves. We infer that gravity waves reach saturation and break at lower altitudes in the winter when Brunt–Vaisala frequency is also lower between 80 and 100 km altitudes. Finally, the results may imply that seasonal variations of the “wave turbopause” are driven mainly by 6.5 DWs. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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18 pages, 4525 KiB

Open AccessArticle

Estimation of Moist Atmospheric Profiles from Refraction and Attenuation Measurements by Using Centimeter and Millimeter Wave Links between LEO Satellites

by Zhihua Zhang, Xin Wang and Daren Lyu

Remote Sens. 2023, 15(2), 391; https://doi.org/10.3390/rs15020391 - 8 Jan 2023

Viewed by 1658

Abstract

Microwave occultation using centimeter and millimeter wave links between low Earth orbit (LEO) satellites provide a potential way to estimate the moist atmospheric profiles based on refraction and attenuation measurements, which is called the LEO-LEO microwave occultation (LMO) technique. It has not yet [...] Read more.

Microwave occultation using centimeter and millimeter wave links between low Earth orbit (LEO) satellites provide a potential way to estimate the moist atmospheric profiles based on refraction and attenuation measurements, which is called the LEO-LEO microwave occultation (LMO) technique. It has not yet been implemented in orbit. In this paper, we analyzed the attenuation properties at different heights of centimeter and millimeter waves based on simulations. The observing capabilities with different frequency combinations at the X, K, and M bands were analyzed. The results show that LMO may improve the retrieval accuracy of bending angles above 35 km. By using several appropriate frequencies at the X+K+M band, water vapor profiles from the near-surface to the lower stratosphere (~24 km) can be obtained. When the M-band frequencies were added, the temperature retrieval accuracy does not change obviously, but the accuracy of water vapor retrieval can significantly improve above 15 km, especially at about 17–24 km, and the RMS errors decrease from over 20% to less 10%. For promoting the LMO mission in the real world, a frequency combination at the X+K band is proposed, which can provide the potential to observe the temperature profiles at about 2.5–50 km and water vapor profiles at about 2.5–15 km accurately under clear and cloudy conditions. This study demonstrates that LMO can greatly extend the capabilities of the radio occultation technique and improve our ability to measure the moist atmospheric profiles globally. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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11 pages, 5674 KiB

Open AccessCommunication

The Troposphere-to-Stratosphere Transport Caused by a Rossby Wave Breaking Event over the Tibetan Plateau in Mid-March 2006

by Jinyao Zhu, Xin Jin, Chunhua Shi and Dan Chen

Remote Sens. 2023, 15(1), 155; https://doi.org/10.3390/rs15010155 - 27 Dec 2022

Cited by 4 | Viewed by 1758

Abstract

Based on reanalysis data, satellite ozone concentration observations, and a Lagrangian trajectory simulation, a Rossby wave breaking (RWB) event and its effect on stratosphere–troposphere exchange (STE) over the Tibetan Plateau in mid-March 2006 were investigated. Results showed that the increased eddy heat flux [...] Read more.

Based on reanalysis data, satellite ozone concentration observations, and a Lagrangian trajectory simulation, a Rossby wave breaking (RWB) event and its effect on stratosphere–troposphere exchange (STE) over the Tibetan Plateau in mid-March 2006 were investigated. Results showed that the increased eddy heat flux from the subtropical westerly jet magnified the amplitude of the Rossby wave, which contributed to the occurrence of the cyclonic RWB event. The quasi-horizontal cyclonic motion of the isentropic potential vorticity in the RWB cut the tropical tropospheric air mass into the extratropical stratosphere, completing the stratosphere–troposphere mass exchange. Meanwhile, the tropopause folding zone extended polewards by 10° of latitude and the tropospheric air mass escaped from the tropical tropopause layer into the extratropical stratosphere through the tropopause folding zone. The particles in the troposphere-to-stratosphere transport (TST) pathway migrated both eastwards and polewards in the horizontal direction, and shifted upwards in the vertical direction. Eventually, the mass of the TST particles reached about 3.8 × 10¹⁴ kg, accounting for 42.2% of the particles near the tropopause in the RWB event. The rest of the particles remained in the troposphere, where they moved eastwards rapidly along the westerly jet and slid down in the downstream upper frontal zone. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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16 pages, 7038 KiB

Open AccessArticle

Extreme Change Events of Stratospheric HCl and N₂O in the Mid-Latitude Region of the Northern Hemisphere

by Yuanyuan Han, Fei Xie, Fei Cui, Feiyang Wang, Xin Li and Wuhu Feng

Remote Sens. 2022, 14(23), 6114; https://doi.org/10.3390/rs14236114 - 2 Dec 2022

Cited by 1 | Viewed by 1657

Abstract

Hydrogen chloride (HCl) is the main reservoir species of chlorine and chemical decomposition of nitrous oxide (N₂O) is the primary source of NO_x (=NO + NO₂) in the stratosphere. Changes in stratospheric HCl and N₂O play [...] Read more.

Hydrogen chloride (HCl) is the main reservoir species of chlorine and chemical decomposition of nitrous oxide (N₂O) is the primary source of NO_x (=NO + NO₂) in the stratosphere. Changes in stratospheric HCl and N₂O play a critical role in modulating variations in stratospheric ozone. Thus, long-term trends in stratospheric HCl and N₂O have been investigated in many studies, whereas short-term changes have not received enough attention. Here, using satellite observations and a chemical transport model, we found that two extreme change events for HCl and N₂O in the Northern Hemisphere mid-latitude middle and lower stratosphere have occurred over past decades, which are characterized by a sharp increase in HCl and a decrease in N₂O over several months; for example, HCl increased (and N₂O decreased) by 0.135 ppbv (−33.352 ppbv) in 1987/1988 and by 0.196 ppbv (−28.553 ppbv) in 2010/2011. Further analysis shows that the extreme change events of stratospheric HCl and N₂O in these two periods are closely related to anomalous residual circulation caused by the joint effects of the strong easterly phase of the semi-annual oscillation and the strong polar vortex. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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17 pages, 4503 KiB

Open AccessArticle

The Long-Term Trends and Interannual Variability in Surface Ozone Levels in Beijing from 1995 to 2020

by Jin Hong, Wuke Wang, Zhixuan Bai, Jianchun Bian, Mengchu Tao, Paul Konopka, Felix Ploeger, Rolf Müller, Hongyue Wang, Jinqiang Zhang, Shuyun Zhao and Jintao Zhu

Remote Sens. 2022, 14(22), 5726; https://doi.org/10.3390/rs14225726 - 12 Nov 2022

Cited by 6 | Viewed by 2288

Abstract

Tropospheric ozone is an important atmospheric pollutant as well as an efficient greenhouse gas. Beijing is one of the cities with the most serious ozone pollution. However, long-term date of observed ozone in Beijing are limited. In this paper, we combine the measurements [...] Read more.

Tropospheric ozone is an important atmospheric pollutant as well as an efficient greenhouse gas. Beijing is one of the cities with the most serious ozone pollution. However, long-term date of observed ozone in Beijing are limited. In this paper, we combine the measurements of the In-service Aircraft for a Global Observing System (IAGOS), ozonesonde observations as well as the recently available ozone monitoring network observations to produce a unique data record of surface ozone (at 14:00 Beijing time) in Beijing from 1995 to 2020. Using this merged dataset, we investigate the variability in surface ozone in Beijing on multiple timescales. The long-term change is primarily characterized by a sudden drop in 2011–2012 with an insignificant linear trend during the full period. Based on CAM-chem model simulations, meteorological factors played important roles in the 2011–2012 ozone drop. Before and after this sudden drop, ozone levels in Beijing increased significantly by 0.42 ± 0.27 ppbv year⁻¹ before 2011 and 0.43 ± 0.41 ppbv year⁻¹ after 2013. We also found a substantial increase in the amplitude of the ozone annual cycle in Beijing, which has not been documented in previous studies. This is consistent with ozone increases in summer and ozone decreases in winter. In addition, the results by the Ensemble Empirical Mode Decomposition (EEMD) analysis indicate significant interannual variations in ozone levels in Beijing with different time oscillation periods, which may be associated with natural variabilities and subsequent changes in meteorological conditions. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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14 pages, 19198 KiB

Open AccessCommunication

Influence of Stratospheric Ozone Changes on Stratospheric Temperature Trends in Recent Decades

by Lingyu Zhou, Yan Xia and Chuanfeng Zhao

Remote Sens. 2022, 14(21), 5364; https://doi.org/10.3390/rs14215364 - 26 Oct 2022

Cited by 5 | Viewed by 1971

Abstract

Associated with the recovery of stratospheric ozone, stratospheric cooling has decelerated since the late 1990s. This study investigates the contribution of ozone changes to the long-term stratospheric temperature trends in recent decades using satellite observations and model simulations. Observational analysis shows that total [...] Read more.

Associated with the recovery of stratospheric ozone, stratospheric cooling has decelerated since the late 1990s. This study investigates the contribution of ozone changes to the long-term stratospheric temperature trends in recent decades using satellite observations and model simulations. Observational analysis shows that total column ozone experienced little depletion in the Northern Hemisphere (NH) and weak recovery in the Southern Hemisphere (SH) in the period 1998–2020. It is found that the cease of stratospheric ozone depletion has reduced the stratospheric cooling from 1998 onwards, especially in the summer hemisphere. The correlation analysis indicates that the lower-stratospheric temperature is primarily regulated by ozone changes. The ozone recovery in the SH is associated with the weak warming in the lower stratosphere in the period 1998–2020 in summer. The impact of ozone changes is further isolated in the ozone-only experiments from CMIP6. We find that ozone depletion results in significant cooling in the summer hemisphere in the period 1979–1997, especially in the upper and lower stratosphere, while ozone recovery leads to significant warming in the summer hemisphere in the period 1998–2020 in the upper stratosphere. Our results also suggest that the wave-mean flow interactions associated with stratospheric ozone variations may play an important role in regulating the strength of polar vortex in winter. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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16 pages, 4651 KiB

Open AccessArticle

Identifying a Leading Predictor of Arctic Stratospheric Ozone for April Precipitation in Eastern North America

by Xuan Ma, Fei Xie, Xiaosong Chen, Lei Wang and Guanyu Yang

Remote Sens. 2022, 14(19), 5040; https://doi.org/10.3390/rs14195040 - 9 Oct 2022

Cited by 1 | Viewed by 1710

Abstract

An analysis of the relationship between changes in Arctic stratospheric ozone (ASO) and precipitation in eastern North America (38°–54°N, 65°–87°W; PENA) was performed using observational and reanalysis data coupled with the Whole Atmosphere Community Climate Model version 4 (WACCM4). We found that March [...] Read more.

An analysis of the relationship between changes in Arctic stratospheric ozone (ASO) and precipitation in eastern North America (38°–54°N, 65°–87°W; PENA) was performed using observational and reanalysis data coupled with the Whole Atmosphere Community Climate Model version 4 (WACCM4). We found that March ASO exhibits a strong correlation with PENA in April, indicating that the one-month leading ASO exerts a potentially strong impact on April PENA. Changes in tropospheric circulation over the North Pacific and North America can be influenced by ASO anomalies via stratosphere–troposphere interactions. Increased ASO typically results in the transport of drier, colder air from northwest to eastern North America and suppresses local convective activity by enhancing regional downwelling. These conditions lead to a decrease in regional atmospheric water vapor content (1000–600 hPa). Abnormally high ASO may therefore suppress precipitation, whereas abnormally low ASO serves to enhance precipitation, and the finding is supported by WACCM4 simulations incorporating these ASO anomaly signals. We also present an ASO-based statistical linear model for predicting April PENA. Results confirm that the linear model reproduces April PENA for both training and testing periods, based on March ASO, demonstrating the reliability and stability of this linear model. This study verifies that ASO is a viable predictor for projecting April PENA and thus improving forecasts of regional seasonal precipitation. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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19 pages, 13412 KiB

Open AccessArticle

Combined Effects of the ENSO and the QBO on the Ozone Valley over the Tibetan Plateau

by Shujie Chang, Yongchi Li, Chunhua Shi and Dong Guo

Remote Sens. 2022, 14(19), 4935; https://doi.org/10.3390/rs14194935 - 2 Oct 2022

Cited by 10 | Viewed by 2125

Abstract

The El Niño–Southern Oscillation (ENSO) and the quasi-biennial oscillation (QBO) are two major interannual variations observed in the tropics, yet the joint modulation of the ENSO and QBO on the ozone valley over the Tibetan Plateau (TP) in summer has not been performed. [...] Read more.

The El Niño–Southern Oscillation (ENSO) and the quasi-biennial oscillation (QBO) are two major interannual variations observed in the tropics, yet the joint modulation of the ENSO and QBO on the ozone valley over the Tibetan Plateau (TP) in summer has not been performed. This study investigates the combined effects of the ENSO and the QBO on the interannual variations of the ozone valley over the TP using the ERA5 reanalysis data from 1979 to 2021. The results show that the ENSO leads the zonal deviation of the total column ozone (TCO*) over the TP by about 6 months. This means the TCO* in the summer of the following year is affected by the ENSO in the current year. This is consistent with the theory of recharge oscillation. In terms of dynamic conditions, the anomalous circulation resulting from the combined effect of El Niño and the easterly phase of the QBO (EQBO) lead to strengthened and upward anomalies of the South Asian high (SAH) over the TP, followed by reduced ozone valley with more negative anomalies over the TP in summer. As to thermodynamic conditions, affected by both El Niño and the EQBO, the atmospheric stability shows positive anomalies from the lower troposphere to the upper troposphere, and the positive anomaly areas are larger than those in other conditions. These findings indicate an unstable atmosphere, where convection is more likely to cause ozone exchange. The turbulent mixing of ozone at low levels and high levels leads to the ozone valley over the TP, with more negative anomalies in the upper troposphere and lower stratosphere (UTLS). Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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21 pages, 7802 KiB

Open AccessArticle

Evaluating Long-Term Variability of the Arctic Stratospheric Polar Vortex Simulated by CMIP6 Models

by Siyi Zhao, Jiankai Zhang, Chongyang Zhang, Mian Xu, James Keeble, Zhe Wang and Xufan Xia

Remote Sens. 2022, 14(19), 4701; https://doi.org/10.3390/rs14194701 - 21 Sep 2022

Cited by 3 | Viewed by 2432

Abstract

The Arctic stratospheric polar vortex is a key component of the climate system, which has significant impacts on surface temperatures in the mid-latitudes and polar regions. Therefore, understanding polar vortex variability is helpful for extended-range weather forecasting. The present study evaluates long-term changes [...] Read more.

The Arctic stratospheric polar vortex is a key component of the climate system, which has significant impacts on surface temperatures in the mid-latitudes and polar regions. Therefore, understanding polar vortex variability is helpful for extended-range weather forecasting. The present study evaluates long-term changes in the position and strength of the polar vortex in the Arctic lower stratosphere during the winters from 1980/81 to 2013/14. Simulations of the Coupled Model Intercomparison Project Phase 6 (CMIP6) models are compared with Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA2) reanalysis dataset. Overall, the CMIP6 models well capture the spatial characteristics of the polar vortex with spatial correlation coefficients between the potential vorticity (PV) in the lower stratosphere from simulations and MERRA2 products generally greater than 0.85 for all CMIP6 models during winter. There is a good agreement in the position and shape of the polar vortex between the CMIP6 multi-model mean and MERRA2, although there exist differences between simulations of individual CMIP6 models. However, most CMIP6 models underestimate the strength of polar vortex in the lower stratosphere, with the largest negative bias up to about −20%. The present study further reveals that there is an anticorrelation between the polar vortex strength bias and area bias simulated by CMIP6 models. In addition, there is a positive correlation between the trend of EP-flux divergence for wavenumber one accumulated in early winter and the trend in zonal mean zonal wind averaged in late winter. As for the long-term change in polar vortex position, CanESM5, IPSL-CM5A2-INCA, UKESM1-0-LL, and IPSL-CM6A-LR well capture the persistent shift of polar vortex towards the Eurasian continent and away from North America in February, which has been reported in observations. These models reproduce the positive trend of wavenumber-1 planetary waves since the 1980s seen in the MERRA2 dataset. This suggests that realistic wave activity processes in CMIP6 models play a key role not only in the simulation of the strength of the stratospheric polar vortex but also in the simulation of the polar vortex position shift. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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19 pages, 10982 KiB

Open AccessArticle

Relationship between the Intraseasonal Oscillation over Mid-High-Latitude Eurasia and the Stratospheric Sudden Warming Event in February 2018

by Linjie Fan, Shuangyan Yang, Jinggao Hu and Tim Li

Remote Sens. 2022, 14(8), 1873; https://doi.org/10.3390/rs14081873 - 13 Apr 2022

Cited by 5 | Viewed by 3355

Abstract

Taking the stratospheric sudden warming (SSW) event in February 2018 as an example, the relationship between the SSW event and the intraseasonal oscillation (ISO) mode over mid-high-latitude Eurasia is investigated by daily reanalysis data. First, the 2018 SSW event and mid-high-latitude ISO are [...] Read more.

Taking the stratospheric sudden warming (SSW) event in February 2018 as an example, the relationship between the SSW event and the intraseasonal oscillation (ISO) mode over mid-high-latitude Eurasia is investigated by daily reanalysis data. First, the 2018 SSW event and mid-high-latitude ISO are reviewed. The 2018 SSW event is a typical vortex-split event defined by the NCEP-DOE dataset, and the ISO mode features a southeastward propagation. Along with the ISO propagation, temperature anomalies developed from troposphere to stratosphere in the 2018 wintertime. It is also found that a strong ISO event occurred before the onset of SSW in this wintertime. Our analysis reveals that the correlation is significant when mid-high-latitude ISO leads the 2018 SSW event by 9–13 days. Occurrence of strong ISO 9–13 days before the SSW event is found to be conducive to its onset. The diagnosis of planetary wave activity indicates that stronger ISO leads to strengthened wavenumber-2 geopotential height anomalies; then, its in-phase superposition of climatological geopotential height makes up for the upward-propagating tropospheric planetary waves, which is in favor of the onset of the 2018 SSW event. The outcome of energy conversion equations also reveals that ISO perturbation contributes to the onset of SSW. Lastly, the contribution of the vertical component of Plumb wave activity flux propagated upward from the region of mid-high-latitude ISO is estimated at approximately 69%. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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Other

Jump to: Research

13 pages, 15827 KiB

Open AccessTechnical Note

Spatiotemporal Distribution of CO in the UTLS Region in the Asian Summer Monsoon Season: Analysis of MLS Observations and CMIP6 Simulations

by Ziling Liang, Fangrui Zhu, Tian Liang, Fuhai Luo and Jiali Luo

Remote Sens. 2023, 15(2), 367; https://doi.org/10.3390/rs15020367 - 7 Jan 2023

Cited by 3 | Viewed by 1502

Abstract

In this study, CO is used as a tracer to evaluate the chemical field related to the Asian summer monsoon anticyclone (ASMA) in the upper troposphere and lower stratosphere (UTLS) region simulated by Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models from [...] Read more.

In this study, CO is used as a tracer to evaluate the chemical field related to the Asian summer monsoon anticyclone (ASMA) in the upper troposphere and lower stratosphere (UTLS) region simulated by Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models from a multi-spatiotemporal perspective. The results show that the simulations of the six selected CMIP6 global climate models are well correlated with the MLS observations, while each model has its own advantages and disadvantages in the simulation of the ASMA and related chemical and geopotential height fields. Compared with MLS data, all six CMIP6 models can reasonably simulate the high CO values and the corresponding anticyclone, although certain biases exist in the simulations. Each model output has certain degrees of deviation in the simulation of the ASMA center position. In terms of time series, the six CMIP6 global models all exhibit an interannual variation CO mixing ratio over the ASM region while the interannual variation features are different from that in MLS. In general, it is impossible to identify a single determined model that can well reproduce the observations. In future work to assess the development trend and location of the ASMA, simulations of CESM2-WACCM and GFDL-ESM4 might be used due to their better performance than other models. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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11 pages, 6387 KiB

Open AccessTechnical Note

A New Exospheric Temperature Model Based on CHAMP and GRACE Measurements

by Xu Yang, Xiaoqian Zhu, Libin Weng and Shenggao Yang

Remote Sens. 2022, 14(20), 5198; https://doi.org/10.3390/rs14205198 - 17 Oct 2022

Cited by 1 | Viewed by 1571

Abstract

In this study, the effective exospheric temperature, derived from CHAMP and GRACE density measurements during 2002–2010, was utilized to develop a new exospheric temperature model (ETM) with the aid of the NRLMSIS 2.0 empirical model. We characterized the dominant modes of global exospheric [...] Read more.

In this study, the effective exospheric temperature, derived from CHAMP and GRACE density measurements during 2002–2010, was utilized to develop a new exospheric temperature model (ETM) with the aid of the NRLMSIS 2.0 empirical model. We characterized the dominant modes of global exospheric temperature using the principal component analysis (PCA) method, and the first five derived empirical orthogonal functions (EOFs) captured 98.2% of the total variability. The obtained mean field, first five EOFs and the corresponding amplitudes were applied to build ETM using the polynomial method. The ETM and NRLMSIS 2.0 models were independently validated by the SWARM-C and GRACE Follow-On (GRACE-FO) density measurements. ETM can reproduce thermospheric density much better than the NRLMSIS 2.0 model, and the Root Mean Square Errors (RMSE) of ETM predictions were approximately 26.45% and 26.17% for the SWARM-C and GRACE-FO tests, respectively, while they were 39.52% and 44.41% for the NRLMSIS 2.0 model. In addition, ETM can accurately capture the equatorial thermospheric anomaly feature, seasonal variation and hemispheric asymmetry in the thermosphere. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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16 pages, 4851 KiB

Open AccessTechnical Note

Analysis of the Atmospheric Duct Existence Factors in Tropical Cyclones Based on the SHAP Interpretation of Extreme Gradient Boosting Predictions

by Lang Huang, Xiaofeng Zhao, Yudi Liu and Pinglv Yang

Remote Sens. 2022, 14(16), 3952; https://doi.org/10.3390/rs14163952 - 14 Aug 2022

Cited by 1 | Viewed by 1904

Abstract

The atmospheric duct (AD) is an anomalous structure in which electromagnetic waves can make transhorizon propagation. ADs often occur in the formation, development and disappearance of tropical cyclones (TCs). In this work, the eXtreme Gradient Boosting (XGBoost) model is used to predict TC [...] Read more.

The atmospheric duct (AD) is an anomalous structure in which electromagnetic waves can make transhorizon propagation. ADs often occur in the formation, development and disappearance of tropical cyclones (TCs). In this work, the eXtreme Gradient Boosting (XGBoost) model is used to predict TC ducts and a relatively high accuracy of 81.3% is obtained. Shapely additional explanations (SHAP) values of the features including TC parameters and local meteorological parameters are employed to interpret XGBoost model predictions of the TC ducts existence. Furthermore, the importance ranking of the features is revealed, among which the distance between dropsondes and TC eyes is the most important. In addition, the detailed relationships between the AD existence and the features are presented. Hence, this work can not only improve the knowledge of the relationship between TC ducts and the features, but also be of great value to the ducts prediction. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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14 pages, 3894 KiB

Open AccessTechnical Note

Contributions of Various Sources to the Higher-Concentration Center of CO within the ASM Anticyclone Based on GEOS-Chem Simulations

by Yuepeng Yang, Qian Li, Haoyue Wang, Zhixuan Bai, Dan Li, Weiguo Wang and Jianchun Bian

Remote Sens. 2022, 14(14), 3322; https://doi.org/10.3390/rs14143322 - 10 Jul 2022

Cited by 3 | Viewed by 1728

Abstract

Satellite observations show that carbon monoxide (CO) concentration centers exist in the tropopause region of the Tibetan Plateau, while their sources and formation mechanism still remain uncertain. In this paper, the 3-D chemical transport model GEOS-Chem is used to conduct sensitivity analysis in [...] Read more.

Satellite observations show that carbon monoxide (CO) concentration centers exist in the tropopause region of the Tibetan Plateau, while their sources and formation mechanism still remain uncertain. In this paper, the 3-D chemical transport model GEOS-Chem is used to conduct sensitivity analysis in 2016. Combined with the analysis data and satellite data, the contribution of three important emission sources (South Asia, East Asia and Southeast Asia) and two important chemical reaction species (CH₄ and nonmethane volatile organic compounds (NMVOCs)) to CO in the upper troposphere and lower stratosphere (UTLS) are studied. The results show that in the Asian monsoon region CO emissions originating from the surface are transported to the upper troposphere via a deep convection process and then enter the Asian Summer Monsoon (ASM) anticyclone. The strong ASM anticyclone isolates the mixing process of air inside and outside the anticyclone, upon entry of carbon monoxide-rich air. In the lower stratosphere, the intensity of the ASM anticyclone declines and the air within the anticyclone flows southwestward with monsoon circulation. We found that in the summer Asian monsoon region, South Asia exhibited the highest carbon monoxide concentration transported to the UTLS. CH₄ imposed the greatest influence on the CO concentration in the UTLS region. According to the model simulation results, the CO concentrations in the Asian monsoon region at 100 hPa altitudes were higher than those in other regions at the same latitudes. Regarding effects, 43.18% originated from CH₄ chemical reactions, 20.81% originated from NMVOC chemical reactions, and 63.33% originated from surface CO emissions, while sinks yielded a negative contribution of −27.32%. Regarding surface CO emissions, East Asia contributed 13.56%, South Asia contributed 39.27%, and Southeast Asia contributed 7.15%. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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14 pages, 4076 KiB

Open AccessTechnical Note

Data-Driven Artificial Intelligence Model of Meteorological Elements Influence on Vegetation Coverage in North China

by Huimin Bai, Zhiqiang Gong, Guiquan Sun and Li Li

Remote Sens. 2022, 14(6), 1307; https://doi.org/10.3390/rs14061307 - 8 Mar 2022

Cited by 7 | Viewed by 2321

Abstract

Based on remote sensing data of vegetation coverage, observation data of basic meteorological elements, and support vector machine (SVM) method, this study develops an analysis model of meteorological elements influence on vegetation coverage (MEVC). The variations for the vegetation coverage changes are identified [...] Read more.

Based on remote sensing data of vegetation coverage, observation data of basic meteorological elements, and support vector machine (SVM) method, this study develops an analysis model of meteorological elements influence on vegetation coverage (MEVC). The variations for the vegetation coverage changes are identified utilizing five meteorological elements (temperature, precipitation, relative humidity, sunshine hour, and ground temperature) in the SVM model. The performance of the SVM model is also evaluated on simulating vegetation coverage anomaly change by comparing with statistical model multiple linear regression (MLR) and partial least squares (PLS)-based models. The symbol agreement rates (SAR) of simulations produced by MLR, PLS, and SVM models are 55%, 57%, and 66%, respectively. The SVM model shows obviously better performance than PLS and MLR models in simulating meteorological elements-related interannual variation of vegetation coverage in North China. Therefore, the introduction of the intelligent analysis method in term of SVM in model development has certain advantages in studying the internal impact of meteorological elements on regional vegetation coverage. It can also be further applied to predict the future vegetation anomaly change. Full article

(This article belongs to the Special Issue Effects of Stratosphere-Troposphere-Land-Ocean Interaction on the Atmospheric Environment and Ecosystem)

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