nasa-gesdisc/es-publications-researchareas huggingface dataset:
Statistics and Meteorology of Air Pollution Episodes over the South African Highveld Based on SatelliteModel Datasets (2017)

The meteorological conditions associated with air pollution episodes on South Africas Highveld were studied using Ozone Monitoring Instrument (OMI) and Atmospheric Infrared Sounder (AIRS) satellite estimates, MERRA2 reanalysis model products, and in situ weather data. Surface-layer sulfur dioxide (SO
              2
              ) and nitrogen dioxide (NO
              2
              ) display high concentrations during winter (MayJuly) and provide a focus for statistical analysis of monthly and daily time series. Highveld area-averaged monthly model SO
              2
              was temporally correlated with boundary layer height (correlation coefficient of 0.76) and temperature lapse rate (+0.65) for the period of 19802015, but relationships with winds were weak. Daily Highveld area-averaged satellite NO
              2
              was related to dewpoint temperature (0.59) and exhibited pulsing in the range of 724 days for 200515. High concentrations of these short-lived locally generated air pollutants were found over and southeast of Johannesburg as a result of urban and industrial emissions. The spatial regression of daily NO
              2
              onto regional sea level air pressure fields for MayJuly over 200515 revealed the slow eastward movement of an anticyclone. At the climatic time scale, Pacific Ocean La Nina conditions favored an increase of MayJuly SO
              2
              concentrations when sea surface temperatures in the equatorial Atlantic Ocean were warmer than normal. The meteorological pattern underlying the highest-ranked air pollution event of 1825 July 2008 was characterized by sharp anticyclonic curvature of low-level winds that induce subsidence and consequently a stable lapse rate and low dewpoint temperature (5C). The wind vorticity exerted a stronger influence on dispersion than did the surface divergence. This new understanding will underpin better air-quality forecasts over the South African Highveld.

Research areas: Air Quality, Environmental Impacts
Predicting decadal trends in cloud droplet number concentration using reanalysis and satellite data (2018)

Abstract. Cloud droplet number concentration (CDNC) is the key state variable that moderates the relationship between aerosol and the radiative forcing arising from aerosolcloud interactions. Uncertainty related to the effect of anthropogenic aerosol on cloud properties represents the largest uncertainty in total anthropogenic radiative forcing. Here we show that regionally averaged time series of the Moderate-Resolution Imaging Spectroradiometer (MODIS) observed CDNC of low, liquid-topped clouds is well predicted by the MERRA2 reanalysis near-surface sulfate mass concentration over decadal timescales. A multiple linear regression between MERRA2 reanalyses masses of sulfate (SO4), black carbon (BC), organic carbon (OC), sea salt (SS), and dust (DU) shows that CDNC across many different regimes can be reproduced by a simple power-law fit to near-surface SO4, with smaller contributions from BC, OC, SS, and DU. This confirms previous work using a less sophisticated retrieval of CDNC on monthly timescales. The analysis is supported by an examination of remotely sensed sulfur dioxide (SO2) over maritime volcanoes and the east coasts of North America and Asia, revealing that maritime CDNC responds to changes in SO2 as observed by the ozone monitoring instrument (OMI). This investigation of aerosol reanalysis and top-down remote-sensing observations reveals that emission controls in Asia and North America have decreased CDNC in their maritime outflow on a decadal timescale.

Research areas: Validation
Extreme levels of Canadian wildfire smoke in the stratosphere over central Europe on 2122 August 2017 (2018)

Abstract. Light extinction coefficients of 500 Mm1, about 20 times higher than after the Pinatubo volcanic eruptions in 1991, were observed by European Aerosol Research Lidar Network (EARLINET) lidars in the stratosphere over central Europe on 2122 August 2017. Pronounced smoke layers with a 12 km vertical extent were found 25 km above the local tropopause. Optically dense layers of Canadian wildfire smoke reached central Europe 10 days after their injection into the upper troposphere and lower stratosphere which was caused by rather strong pyrocumulonimbus activity over western Canada. The smoke-related aerosol optical thickness (AOT) identified by lidar was close to 1.0 at 532 nm over Leipzig during the noon hours on 22 August 2017. Smoke particles were found throughout the free troposphere (AOT of 0.3) and in the pronounced 2 km thick stratospheric smoke layer at an altitude of 1416 km (AOT of 0.6). The lidar observations indicated peak mass concentrations of 70100 g m3 in the stratosphere. In addition to the lidar profiles, we analyzed Moderate Resolution Imaging Spectroradiometer (MODIS) fire radiative power (FRP) over Canada, and the distribution of MODIS AOT and Ozone Monitoring Instrument (OMI) aerosol index across the North Atlantic. These instruments showed a similar pattern and a clear link between the western Canadian fires and the aerosol load over Europe. In this paper, we also present Aerosol Robotic Network (AERONET) sun photometer observations, compare photometer and lidar-derived AOT, and discuss an obvious bias (the smoke AOT is too low) in the photometer observations. Finally, we compare the strength of this record-breaking smoke event (in terms of the particle extinction coefficient and AOT) with major and moderate volcanic events observed over the northern midlatitudes.

Research areas: Wildfires, Volcanic Eruptions
Elevated black carbon concentrations and atmospheric pollution around Singrauli coal-fired thermal power plants (India) using ground and satellite data (2018)

The tropospheric NO2 concentration from OMI AURA always shows high concentrations of NO2 at a few locations in India, one of the high concentrations of NO2 hotspots is associated with the locations of seven coal-fired Thermal Power plants (TPPs) in Singrauli. Emissions from TPPs are among the major sources of black carbon (BC) soot in the atmosphere. Knowledge of BC emissions from TPPs is important in characterizing regional carbonaceous particulate emissions, understanding the fog/haze/smog formation, evaluating regional climate forcing, modeling aerosol optical parameters and concentrations of black carbon, and evaluating human health. Furthermore, elevated BC concentrations, over the Indo-Gangetic Plain (IGP) and the Himalayan foothills, have emerged as an important subject to estimate the effects of deposition and atmospheric warming of BC on the accelerated melting of snow and glaciers in the Himalaya. For the first time, this study reports BC concentrations and aerosol optical parameters near dense coal-fired power plants and open cast coal mining adjacent to the east IGP. In-situ measurements were carried out in Singrauli (located in south-east IGP) at a fixed site about 10 km from power plants and in transit measurements in close proximity to the plants, for few days in the month of January and March 2013. At the fixed site, BC concentration up to the 95 gm3 is observed with strong diurnal variations. BC concentration shows two maxima peaks during early morning and evening hours. High BC concentrations are observed in close proximity to the coal-fired TPPs (>200 gm3), compared to the outside domain of our study region. Co-located ground-based sunphotometer measurements of aerosol optical depth (AOD) show strong spatial variability at the fixed site, with AOD in the range 0.380.58, and the highest AOD in the range 0.70.95 near the TPPs in transit measurements (similar to the peak of BC concentrations). Additionally, the Angstrom exponent was found to be in the range 0.41.0 (maximum in the morning time) and highest in the proximity of TPPs (~1.0), suggesting abundance of fine particulates, whereas there was low Angstrom exponent over the surrounding coal mining areas. Low Angstrom exponent is characterized by dust from the unpaved roads and nearby coal mining areas. MODIS derived daily AOD shows a good match with the MICROTOPS AOD. The CALIPSO derived subtypes of the aerosol plot shows that the aerosols over Singrauli region are mainly dust, polluted dust, and elevated smoke. The preliminary study for few days provides information about the BC concentrations and aerosol optical properties from Singrauli (one of the NO2 hotspot locations in India). This preliminary study suggests that long-term continuous monitoring of BC is needed to understand the BC concentrations and aerosol optical properties for better quantification and the estimation of the emission to evaluate radiative forcing in the region.

Research areas: Environmental Impacts, Air Quality
Appraisal of Urban Heat Island over Gujranwala and its environmental impact assessment using satellite imagery (1995-2016) (2019)

Rapid urbanization and concretization are the main sources of formation and existence of Urban Heat Island (UHI). Due to high concentration of pollutants in urban environments, the residents are exposed to unexpected health issues. This study aims at delineating the temporal variations in the spatial extent of UHI over Gujranwala using Landsat thermal imagery. It also aims at determining the variations in pollutant concentration in the atmosphere due to vehicles tailpipe emissions and fossil fuel burning by industrial plants. We used various indices e.g., NDVI, NDBI, NDWI and land surface temperature calculations to investigate spatiotemporal variations in urban growth patterns and their impacts on the UHI. The results show that the UHI enlarged in all direction specially in the north west during the study period which is similar to urban growth trends. There also exist positive correlation between industrial and vehicles discharge with pollutants concentration in atmosphere. Remote sensing tools proved elegant in trend mapping and analysis.

Research areas: Heat, Habitat Conversion/Fragmentation, Environmental Impacts
Anomalous lightning behavior during the 26-27 August 2007 Northern Great Plains severe weather event (2018)

Positive polarity lightning strokes can be useful indicators of thunderstorm behavior. A combination of National Lightning Detection Network and Next Generation Radar retrievals is used to analyze the anomalous positive cloud-to-ground (CG) lightning behavior of a rare, late summer severe weather event that occurred on 2627 August 2007 in the Northern Great Plains region of the United States and southern Canada. Seven discrete supercells (SC1SC7) exhibiting frequent and intense lightning were responsible for numerous reports of severe weather (e.g., severe hail and 16 tornadoes) including catastrophic damage to the town of Northwood, North Dakota, caused by SC2. Biomass burning smoke from wildfires in Idaho and Montana was present prior to convective initiation. A positive CG lightning stroke rate of nearly 30 strokes per minute was observed 10 min before the EF4 tornado struck Northwood. SC2 was also responsible for all the reports of tornadoes exceeding an EF2 rating. The strongest peak currents (>200 kA) were observed in SC1SC4 with SC2 having a maximum value of 280 kA. SC2 dominated the statistics of the line of supercells accounting for 27% of all CG lightning strokes. Positive CG lightning accounted for over 40% of all CG lightning strokes in SC4SC7 on average, and the maximum exceeded 90% in SC6 and SC7. Increasing positive CG lightning dominance was correlated with an increasing northward gradient of smoke aerosol loading in addition to severe weather being reported before the maximum in positive CG lighting stroke rate (SC5 and SC6). This suggests that a complex combination of synoptic forcing and aerosol perturbation likely led to the observed anomalous positive CG lightning behavior in the supercells.

Research areas: Severe Storms, Atmospheric/Ocean Indicators, Environmental Impacts
Analysis of local climate variations using correlation between satellite measurements of methane emission and temperature trends within physiographic regions of Ukraine (2019)

Paper aimed to the description of the methods of analysis and measurements of atmospheric greenhouse gases (GHG),
especially, methane concentration using satellite tools for climate change model improvement. The experimental
accuracy estimation of narrow-band spectral indices restoration by the wide-band multispectral image is performed.
Three methods for narrow-band spectral indices restoration are analyzed. The method on the basis of spectra translation
is recommended for practical application.

Research areas: Greenhouse Gases, Atmospheric/Ocean Indicators
Air quality in the Galapagos Islands: a baseline view from remote sensing and in situ measurements (2020)

A characterization of ambient air levels of PM2.5, O3, SO2, NO2 and CO in the Galapagos Islands of Ecuador is presented from in situ and remote sensing observations. PM2.5 was derived from aerosol optical depth (AOD; AERONET) measured at the Universidad San Francisco de Quito, Galapagos Campus (20172019). Boundary layer (BL) ozone was obtained from Southern Hemisphere Additional Ozonesondes (SHADOZ) profiles (19982016). Background SO2 and pollution events during volcanic eruptions (20052018) were estimated from Ozone Monitoring Instrument (OMI) total column measurements through a well-mixed volume approach. Similarly, ambient NO2 was estimated from OMI data (20122019). CO was obtained from Measurement Of Pollution In The Troposphere (MOPITT) observations (20122017). The study was complemented using Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) reanalysis products and backward trajectory model runs. From the results, baseline levels of the analysed species (PM2.5 = 3.8 gm3, O3 = 17 ppbv, SO2 = 3.6 ppbv, CO = 80 ppbv, NO2 in populated islands = 23 pptv as one year averages) are comparable with other pristine regions, but some factors can cause increased concentrations. First, high tourism seasons (FebruaryApril and JulySeptember) raise background PM2.5, NO2 and CO. Furthermore, signals in JulySeptember can be augmented by transport from biomass-burning regions in the Amazon. This latter factor episodically causes ozone to increase up to 4575 ppbv (1 hr mean). Lastly, volcanic eruptions raise SO2 up to almost 700 ppbv (24 hr mean) and increase PM2.5 to 29.5 gm3 (1 hr mean). The present study provides for the first time baseline levels of air contaminants in the Galapagos, and identifies specific sources whose effect in time is necessary to monitor given global conditions of vulnerable environmental quality.

Research areas: Volcanic Eruptions, Air Quality
Estimation of power plant emissions with unscented Kalman Filter (2018)

Emissions from power plants constitute a major part of air pollution and should be adequately estimated. In this paper, we consider the problem of estimating nitrogen dioxide (NOX) emission of power plants by developing an inverse method to integrate satellite observations of atmospheric pollutant column concentrations with species concentrations and direct sensitivities predicted by a regional air quality model, in order to discern biases in the emissions of the pollutant precursors. Using this method, the emission fields are analyzed using a bottom-up approach, with an inversion performed by an unscented Kalman filter (UKF) to improve estimation profiles from emissions inventories data for the Sydney metropolitan area. The idea is to integrate information from the original inventories with tropospheric nitrogen dioxide (NO2) emissions estimated during one month from the air pollution model-chemical transport model, and then, for validation, to compare the resulting model with satellite retrievals from the ozone monitoring instrument (OMI) above the region. The UKF-based estimation of NO2 emissions shows better agreement with OMI observations, implying a significant improvement in accuracy as compared with the original inventories. Therefore, the proposed method is a promising tool for estimation of air emissions in urban areas.

Research areas: Energy Production/Use, Air Quality
Spatial and temporal analysis of precipitation extremities of Eastern Nepal in the last two decades (19972016) (2019)

In recent days there have been discussions regarding the impact of climate change and its vagaries of the weather, particularly concerning extreme events. Nepal, being a mountainous country, is more susceptible to precipitation extreme events and related hazards, which hinder the socioeconomic development of the nation. In this regard, this study aimed to address this phenomenon for one of the most naturally and socioeconomically important regions of Nepal, namely, Eastern Nepal. The data were collected for the period of 1997 to 2016. The interdecadal comparison for two periods (19972006 and 20072016) was maintained for the calculation of extreme precipitation indices as per recommended by Expert Team on Climate Change Detection and Indices. Linear trends were calculated by using Mann-Kendall and Sen's Slope estimator. The average annual precipitation was found to be decreasing at an alarming rate of 20 mm/year in the last two decades' tenure. In case of extreme precipitation events, consecutive dry days, one of the frequency indices, showed a solo increase in its trend (mostly significant). Meanwhile, all the intensity indices of extreme precipitation showed decreasing trends (mostly insignificant). Thus, it can be concluded that Eastern Nepal has witnessed some significant drier days in the last two decades, as the events of heavy, very heavy, extremely heavy precipitation events, and annual wet day precipitation (PRCPTOT) were found to be decreasing. The same phenomena were also seen in the Tropical Rainfall Measuring Mission 3B42 V7 satellite precipitation product for whole Nepal.

Research areas: Atmospheric/Ocean Indicators
Medicanes triggering chlorophyll increase (2019)

Studies have shown that hurricanes and typhoons, apart from being extreme weather phenomena, cause increases in marine chlorophyll-a concentrations and even phytoplankton blooms. Medicanes are the tropical-like Mediterranean cyclones that induce hazardous weather conditions as well. In this study, a couple of medicanes, over the central and eastern parts of the Sea, are examined for the first time in respect to their possible influence on chlorophyll concentrations. The affected area was delineated with the use of numerical model data, while the sea surface temperature and chlorophyll variations were assessed based on satellite-derived data. The results showed that medicanes trigger surface chlorophyll increases; after the cyclones passage, the concentrations were higher compared both with those before and with the climatological monthly values over a large part of the affected area. The mechanisms proposed to explain hurricanes favorable influence on chlorophyll concentration seem to be valid for medicanes as well. Area averaged chlorophyll concentrations presented analogous increases to the ones reported for hurricanes, though on a smaller scale. Despite the much lower intensity of medicanes compared with hurricanes, the observed increase in surface chlorophyll after their passage points to their favorable influence.

Research areas: Severe Storms, Ecosystems
A 10-year record of aerosol optical properties and radiative forcing over three environmentally distinct AERONET sites in Kenya, East Africa (2019)

In the framework of Aerosol Robotic Network (AERONET), the aerosol optical, microphysical, and radiative properties were investigated over three sites (CRPSM_Malindi, Nairobi, and ICIPE_Mbita) in Kenya, East Africa, during 20062015. The annual mean () aerosol optical depth at 440 nm (AOD440) was found high at Mbita (0.27  0.09) followed by Malindi (0.26  0.07), and low at Nairobi (0.19  0.04). Whereas the seasonal mean AOD440 noticed high (low) values during the local dry (wet) seasons. The aerosol optical properties: AOD, single scattering albedo, asymmetry parameter, and complex aerosol refractive index exhibited significant temporal and spectral heterogeneities illustrating the complexity of aerosol types with an abundance of fine-mode aerosols during the local dry (JuneJulyAugust) season. Characterization of major aerosol types revealed the dominance of mixed-type followed by biomass burning aerosols. The aerosol volume size distribution revealed that the coarse- over fine-mode aerosols showed a significant contribution to the total volume particle concentration, especially at high (>0.3) AOD440. Further, the aerosol columnar number size distribution retrieved from the King's inversion of spectral AOD exhibited a power law distribution affirming multiplicity of aerosol sources. The direct aerosol radiative forcing values simulated in the shortwave region using the Santa Barbara DISORT Atmospheric Radiative Transfer model showed good correlation (r = >0.85) with the AERONET-derived ones at the top-of-atmosphere, bottom-of-atmosphere, and within the atmosphere. The annual mean () top-of-atmosphere, bottom-of-atmosphere, and within the atmosphere forcing values were found in the range from 8.10  3.75 to 13.23  4.87, 34.54  4.86 to 46.11  10.27, and 26.63  6.43 to 36.24  7.26 W/m2, respectively, with an atmospheric heating rate of 0.74  0.121.02  0.20 K/day. The Santa Barbara DISORT Atmospheric Radiative Transfer-derived direct aerosol radiative forcing exhibited significant temporal heterogeneity with high (low) during the local dry (wet) seasons. Results derived from the present study forms a basis for regional climate change studies and could increase the accuracy of climate models over this unexplored region of Africa.

Research areas: Atmospheric/Ocean Indicators, Environmental Impacts
Variations of atmospheric aerosol parameters in periods of seismic activity in Tien-Shan (2020)

Combination of numerical modeling (MERRA) and ground-
based (AERONET) monitoring of atmospheric aerosol parameters were
used to discover a possible connection to seismic activities within the
territory of Tien-Shan. The obtained results demonstrated consistent
behavior between increase of aerosol optical thickness (AOT) and powerful
earthquakes, epicenters of which were located within 200 km from the
"Issyk-Kul" station (AERONET). Thereat, the dominant role was played by
fine-dispersed particles, which virtually determined the nature of 
evolution. We also observed well-defined changes of the ratio between mass
fraction PM 1.0 (particles less than 1.0 m aerodynamic diameter) and optical
thickness of aerosol scattering several days before an earthquake of M > 5.0
magnitude.

Research areas: Earthquakes