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2 pages, 168 KiB

Open AccessEditorial

Special Issue Atmospheric Composition and Cloud Cover Observations

by Mirela Voiculescu

Atmosphere 2021, 12(1), 56; https://doi.org/10.3390/atmos12010056 - 31 Dec 2020

Viewed by 1437

Abstract

A Special Issue of Atmosphere, “Atmospheric Composition and Cloud Cover Observations”, is focused on presenting some of the latest results of observations of clouds and atmospheric composition, mainly by referring to new equipment or experimental set-ups [...] Full article

(This article belongs to the Special Issue Atmospheric Composition and Cloud Cover Observations)

Research

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14 pages, 4190 KiB

Open AccessArticle

Multi-Sensor Observation of a Saharan Dust Outbreak over Transylvania, Romania in April 2019

by Nicolae Ajtai, Horațiu Ștefănie, Alexandru Mereuță, Andrei Radovici and Camelia Botezan

Atmosphere 2020, 11(4), 364; https://doi.org/10.3390/atmos11040364 - 9 Apr 2020

Cited by 13 | Viewed by 3337

Abstract

Mineral aerosols are considered to be the second largest source of natural aerosol, the Saharan desert being the main source of dust at global scale. Under certain meteorological conditions, Saharan dust can be transported over large parts of Europe, including Romania. The aim [...] Read more.

Mineral aerosols are considered to be the second largest source of natural aerosol, the Saharan desert being the main source of dust at global scale. Under certain meteorological conditions, Saharan dust can be transported over large parts of Europe, including Romania. The aim of this paper is to provide a complex analysis of a Saharan dust outbreak over the Transylvania region of Romania, based on the synergy of multiple ground-based and satellite sensors in order to detect the dust intrusion with a higher degree of certainty. The measurements were performed during the peak of the outbreak on April the 24th 2019, with instruments such as a Cimel sun-photometer and a multi-wavelength Raman depolarization lidar, together with an in-situ particle counter measuring at ground level. Remote sensing data from MODIS sensors on Terra and Aqua were also analyzed. Results show the presence of dust aerosol layers identified by the multi-wavelength Raman and depolarization lidar at altitudes of 2500–4000 m, and 7000 m, respectively. The measured optical and microphysical properties, together with the HYSPLIT back-trajectories, NMMB/BSC dust model, and synoptic analysis, confirm the presence of lofted Saharan dust layers over Cluj-Napoca, Romania. The NMMB/BSC dust model predicted dust load values between 1 and 1.5 g/m² over Cluj-Napoca at 12:00 UTC for April the 24th 2019. Collocated in-situ PM monitoring showed that dry deposition was low, with PM10 and PM2.5 concentrations similar to the seasonal averages for Cluj-Napoca. Full article

(This article belongs to the Special Issue Atmospheric Composition and Cloud Cover Observations)

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17 pages, 47895 KiB

Open AccessEditor’s ChoiceArticle

Cloud Occurrence Frequency at Puy de Dôme (France) Deduced from an Automatic Camera Image Analysis: Method, Validation, and Comparisons with Larger Scale Parameters

by Jean-Luc Baray, Asmaou Bah, Philippe Cacault, Karine Sellegri, Jean-Marc Pichon, Laurent Deguillaume, Nadège Montoux, Vincent Noel, Geneviève Seze, Franck Gabarrot, Guillaume Payen and Valentin Duflot

Atmosphere 2019, 10(12), 808; https://doi.org/10.3390/atmos10120808 - 13 Dec 2019

Cited by 9 | Viewed by 3719

Abstract

We present a simple algorithm that calculates the cloud occurrence frequency at an altitude site using automatic camera image analysis. This algorithm was applied at the puy de Dôme station (PUY, 1465 m. a.s.l., France) over 2013–2018. Cloud detection thresholds were determined by [...] Read more.

We present a simple algorithm that calculates the cloud occurrence frequency at an altitude site using automatic camera image analysis. This algorithm was applied at the puy de Dôme station (PUY, 1465 m. a.s.l., France) over 2013–2018. Cloud detection thresholds were determined by direct comparison with simultaneous in situ cloud probe measurements (particulate volume monitor (PVM) Gerber). The cloud occurrence frequency has a seasonal cycle, with higher values in winter (60%) compared to summer (24%). A cloud diurnal cycle is observed only in summer. Comparisons with the larger scale products from satellites and global model reanalysis are also presented. The NASA cloud-aerosol transport system (CATS) cloud fraction shows the same seasonal and diurnal variations and is, on average, 11% higher. Monthly variations of the ECMWF ERA-5 fraction of cloud cover are also highly correlated with the camera cloud occurrence frequency, but the values are 19% lower and up to 40% for some winter months. The METEOSAT-SEVIRI cloud occurrence frequency also follows the same seasonal cycle but with a much smaller decrease in summer. The all-sky imager cloud fraction (CF) presents larger variability than the camera cloud occurrence but also follows similar seasonal variations (67% in winter and 44% in summer). This automatic low-cost detection of cloud occurrence is of interest in characterizing altitude observation sites, especially those that are not yet equipped with microphysical instruments and can be deployed to other high-altitude sites equipped with cameras. Full article

(This article belongs to the Special Issue Atmospheric Composition and Cloud Cover Observations)

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14 pages, 29312 KiB

Open AccessArticle

An Exceptional Case of Freezing Rain in Bucharest (Romania)

by Simona Andrei, Bogdan Antonescu, Mihai Boldeanu, Luminiţa Mărmureanu, Cristina Antonia Marin, Jeni Vasilescu and Dragoş Ene

Atmosphere 2019, 10(11), 673; https://doi.org/10.3390/atmos10110673 - 1 Nov 2019

Cited by 8 | Viewed by 4648

Abstract

A high-impact freezing rain event affected parts of southeastern Romania on 24–26 January 2019. The freezing rain caused extensive damages in Bucharest, the capital city of Romania. The meteorological analysis highlighted the presence of a particular synoptic pattern involving a high-pressure system advecting [...] Read more.

A high-impact freezing rain event affected parts of southeastern Romania on 24–26 January 2019. The freezing rain caused extensive damages in Bucharest, the capital city of Romania. The meteorological analysis highlighted the presence of a particular synoptic pattern involving a high-pressure system advecting cold air mass at low levels, while at mid-levels a warm and humid intrusion was associated with a low-pressure system of Mediterranean origin. At Bucharest, the vertical profiles from ERA5 and radiosondes emphasized the presence of a thick warm layer between 1000–1400 m above the re-freezing layer close to the surface. A climatology of freezing rain events in Bucharest was built to understand the frequency and intensity of this phenomenon. On average, there were approximately 5 observations of freezing rain in Bucharest per year between 1980–2018. The number of consecutive freezing rain days was used as a proxy for the event severity. Moderate-duration events (2 consecutive days) represented 16 periods of all 59 non-overlapping freezing rain periods in Bucharest and long-duration events (3 consecutive days) represented 3 periods. The monthly distribution showed that freezing rain occurs more frequently between December–February with a maximum in December. The moderate and long-duration freezing rain events were associated with two main sub-synoptic patterns related to the Carpathians lee cyclogenesis. Full article

(This article belongs to the Special Issue Atmospheric Composition and Cloud Cover Observations)

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16 pages, 3241 KiB

Open AccessArticle

Estimation of CO₂ Emissions from Wildfires Using OCO-2 Data

by Meng Guo, Jing Li, Lixiang Wen and Shubo Huang

Atmosphere 2019, 10(10), 581; https://doi.org/10.3390/atmos10100581 - 25 Sep 2019

Cited by 26 | Viewed by 8586

Abstract

The biomass burning model (BBM) has been the most widely used method for estimation of trace gas emissions. Due to the difficulty and variability in obtaining various necessary parameters of BBM, a new method is needed to quickly and accurately calculate the trace [...] Read more.

The biomass burning model (BBM) has been the most widely used method for estimation of trace gas emissions. Due to the difficulty and variability in obtaining various necessary parameters of BBM, a new method is needed to quickly and accurately calculate the trace gas emissions from wildfires. Here, we used satellite data from the Orbiting Carbon Observatory-2 (OCO-2) to calculate CO₂ emissions from wildfires (the OCO-2 model). Four active wildfires in Siberia were selected in which OCO-2 points intersecting with smoke plumes identified by Aqua MODIS (MODerate-resolution Imaging Spectroradiometer) images. MODIS band 8, band 21 and MISR (Multi-angle Imaging SpectroRadiometer) data were used to identify the smoke plume area, burned area and smoke plume height, respectively. By contrast with BBM, which calculates CO₂ emissions based on the bottom–top mode, the OCO-2 model estimates CO₂ emissions based on the top–bottom mode. We used a linear regression model to compute CO₂ concentration (XCO₂) for each smoke plume pixel and then calculated CO₂ emissions for each wildfire point. The CO₂ mass of each smoke plume pixel was added to obtain the CO₂ emissions from wildfires. After verifying our results with the BBM, we found that the biases were between 25.76% and 157.11% for the four active fires. The OCO-2 model displays the advantages of remote-sensing technology and is a useful tool for fire-emission monitoring, although we note some of its disadvantages. This study proposed a new perspective to estimate CO₂ emissions from wildfire and effectively expands the applied range of OCO-2 satellite data. Full article

(This article belongs to the Special Issue Atmospheric Composition and Cloud Cover Observations)

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24 pages, 10386 KiB

Open AccessArticle

Evaluation of Different WRF Parametrizations over the Region of Iași with Remote Sensing Techniques

by Iulian-Alin Roșu, Silvia Ferrarese, Irina Radinschi, Vasilica Ciocan and Marius-Mihai Cazacu

Atmosphere 2019, 10(9), 559; https://doi.org/10.3390/atmos10090559 - 18 Sep 2019

Cited by 9 | Viewed by 3490

Abstract

This article aims to present an evaluation of the Weather Research and Forecasting (WRF) model with multiple instruments when applied to a humid continental region, in this case, the region around the city of Iași, Romania. A series of output parameters are compared [...] Read more.

This article aims to present an evaluation of the Weather Research and Forecasting (WRF) model with multiple instruments when applied to a humid continental region, in this case, the region around the city of Iași, Romania. A series of output parameters are compared with observed data, obtained on-site, with a focus on the Planetary Boundary Layer Height (PBLH) and on PBLH-related parametrizations used by the WRF model. The impact of each different parametrization on physical quantities is highlighted during the two chosen measurement intervals, both of them in the warm season of 2016 and 2017, respectively. The instruments used to obtain real data to compare to the WRF simulations are: a lidar platform, a photometer, and ground-level (GL) meteorological instrumentation for the measurement of temperature, average wind speed, and pressure. Maps of PBLH and 2

m

above ground-level (AGL) atmospheric temperature are also presented, compared to a topological and relief map of the inner nest of the WRF simulation. Finally, a comprehensive simulation performance evaluation of PBLH, temperature, wind speed, and pressure at the surface and total precipitable water vapor is performed. Full article

(This article belongs to the Special Issue Atmospheric Composition and Cloud Cover Observations)

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19 pages, 4384 KiB

Open AccessEditor’s ChoiceArticle

Multiyear Typology of Long-Range Transported Aerosols over Europe

by Victor Nicolae, Camelia Talianu, Simona Andrei, Bogdan Antonescu, Dragoș Ene, Doina Nicolae, Alexandru Dandocsi, Victorin-Emilian Toader, Sabina Ștefan, Tom Savu and Jeni Vasilescu

Atmosphere 2019, 10(9), 482; https://doi.org/10.3390/atmos10090482 - 22 Aug 2019

Cited by 21 | Viewed by 3838

Abstract

In this study, AERONET (Aerosol Robotic Network) and EARLINET (European Aerosol Research Lidar Network) data from 17 collocated lidar and sun photometer stations were used to characterize the optical properties of aerosol and their types for the 2008–2018 period in various regions of [...] Read more.

In this study, AERONET (Aerosol Robotic Network) and EARLINET (European Aerosol Research Lidar Network) data from 17 collocated lidar and sun photometer stations were used to characterize the optical properties of aerosol and their types for the 2008–2018 period in various regions of Europe. The analysis was done on six cluster domains defined using circulation types around each station and their common circulation features. As concluded from the lidar photometer measurements, the typical aerosol particles observed during 2008–2018 over Europe were medium-sized, medium absorbing particles with low spectral dependence. The highest mean values for the lidar ratio at 532 nm were recorded over Northeastern Europe and were associated with Smoke particles, while the lowest mean values for the Angstrom exponent were identified over the Southwest cluster and were associated with Dust and Marine particles. Smoke (37%) and Continental (25%) aerosol types were the predominant aerosol types in Europe, followed by Continental Polluted (17%), Dust (10%), and Marine/Cloud (10%) types. The seasonal variability was insignificant at the continental scale, showing a small increase in the percentage of Smoke during spring and a small increase of Dust during autumn. The aerosol optical depth (AOD) slightly decreased with time, while the Angstrom exponent oscillated between “hot and smoky” years (2011–2015) on the one hand and “dusty” years (2008–2010) and “wet” years (2017–2018) on the other hand. The high variability from year to year showed that aerosol transport in the troposphere became more and more important in the overall balance of the columnar aerosol load. Full article

(This article belongs to the Special Issue Atmospheric Composition and Cloud Cover Observations)

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14 pages, 11247 KiB

Open AccessArticle

Wintertime Variations of Gaseous Atmospheric Constituents in Bucharest Peri-Urban Area

by Cristina Antonia Marin, Luminiţa Mărmureanu, Cristian Radu, Alexandru Dandocsi, Cristina Stan, Flori Ţoancă, Liliana Preda and Bogdan Antonescu

Atmosphere 2019, 10(8), 478; https://doi.org/10.3390/atmos10080478 - 20 Aug 2019

Cited by 9 | Viewed by 4106

Abstract

An intensive winter campaign was organized for measuring the surface air pollutants in southeastern Europe. For a three months period, the gas concentrations of NO

_{x}

, SO

_{2}

, CO, O

_{3}

, and CH

_{4}

as well as meteorological parameters were [...] Read more.

An intensive winter campaign was organized for measuring the surface air pollutants in southeastern Europe. For a three months period, the gas concentrations of NO

_{x}

, SO

_{2}

, CO, O

_{3}

, and CH

_{4}

as well as meteorological parameters were simultaneously sampled to evaluate the variations and characteristic reactions between the gases during winter at the measuring site. The photochemical production of the ozone was observed through the diurnal variation of ozone and the solar radiation, the maximum concentration for ozone being reached one hour after the maximum value for solar radiation. A non-parametric wind regression method was used to highlight the sources of the air pollutants. The long-range transport of SO

_{2}

and two hotspots for CO from traffic and from residential heating emissions were emphasized. The traffic hotspot situated north of the measuring site, close to the city ring road, is also a hotspot for NO

_{x}

. The air quality during the cold season was evaluated by comparing the measured gas concentration with the European limits. During the measuring period, the values for NO

_{2}

, CO, and SO

_{2}

concentration were at least two times lower than the European Union pollution limits. Only twice during the study period was the concentration of O

_{3}

higher than the established limits. Full article

(This article belongs to the Special Issue Atmospheric Composition and Cloud Cover Observations)

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