Detection of aerosol pollution sources during sandstorms in Northwestern China using remote sensed and model simulated data

The present paper has used a comprehensive approach to study atmosphere pollution sources including the study of vertical distribution characteristics, the epicenters of occurrence and transport of atmospheric aerosol in North-West China under intensive dust storm registered in all cities of the region in April 2014. To achieve this goal, the remote sensing data using Moderate Resolution Imaging Spectroradiometer satellite (MODIS) as well as model-simulated data, were used, which facilitate tracking the sources, routes, and spatial extent of dust storms. The results of the study have shown strong territory pollution with aerosol during sandstorm. According to ground-based air quality monitoring stations data, concentrations of PM₁₀ and PM_2.5 exceeded 400?μg/m³ and 150?μg/m³, respectively, the ratio PM_2.5/PM₁₀ being within the range of 0.123–0.661. According to MODIS/Terra Collection 6 Level-2 aerosol products data and the Deep Blue algorithm data, the aerosol optical depth (AOD) at 550?nm in the pollution epicenter was within 0.75–1. The vertical distribution of aerosols indicates that the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) 532?nm total attenuates backscatter coefficient ranges from 0.01 to 0.0001?km^?1?×?sr^?1 with the distribution of the main types of aerosols in the troposphere of the region within 0–12.5?km, where the most severe aerosol contamination is observed in the lower troposphere (at 3–6?km). According to satellite sounding and model-simulated data, the sources of pollution are the deserted regions of Northern and Northwestern China.     

Impact of local and global factors and meteorological parameters in temporal variation of atmospheric potential gradient

In this research work, we have performed comparative diurnal variations of atmospheric Potential Gradient (PG) of fair-weather days by using the data of three stations installed in Northern, Pakistan for the year 2018. We investigated the impact of both local and global factors and meteorological parameters in the diurnal variation of atmospheric Potential Gradient on the annual and seasonal time scale. We observed two peaks, primary and secondary. This is because of the land-based measurements of annual and seasonal variations. The annual average curve of Potential Gradient of all three stations: Islamabad (CES), Muzaffarabad (MZF), and Balakot (BKT) demonstrated a notable deviation from the standard oceanic Carnegie curve. The atmospheric Potential Gradient variations are due to numerous meteorological factors e.g., air pollution, humidity, aerosol particles, fog, and temperature. Among three stations, the MZF station is located in highland (mountainous) and it demonstrated a higher atmospheric Potential Gradient. We further differentiate the results of our three stations with global results for authenticity and observed coherence between them. In addition, a positive correlation of fair-weather Potential Gradient is observed with temperature and a notable correlation between relative humidity and atmospheric Potential Gradient for all the three observatories.     

粉末气溶胶抑制热喷流红外辐射特性实验

1引言任何绝对温度高于0K的物体都能产生波长介于可见光和微波之间的0.76~1000μm的红外波。红外波在大气中传播时,会因各种气体分子和悬浮微粒的吸收与散射作用而衰减,理论上称之为消光特性。粉末气溶胶就是由大气与悬浮在其中的固体微粒共同组成的多相体系。当红外线穿过到气     

Detection of volcanic gases and particles by satellite

In this paper the detection of components of volcanic eruption has been carried out investigating, in appropriate bands of the electromagnetic spectrum (6.25, 8.7, 10.8, 12 μm), the values of the brightness temperature. The analysis has been performed in the Thermal Infrared Region (TIR) studying both the absorption–emission and scattering phenomena related to the interactions between electromagnetic radiation and volcanic emissions. The results have been achieved by means of a combined use of numerical simulations, devoted to examining the behaviour of the atmosphere gases and volcanic components, and remotely sensed satellite images. The proposed methodologies allow an estimate of the amount of gaseous and solid components, of the size of the emitted particles, of the height of the volcanic plume and of the distance of the volcanic components from the crater. The processed images come from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) sensor on board the geo-stationary satellite Meteosat Second Generation (MSG) and take into consideration an eruption of the Etna volcano as a study case (1st of April 2012, 04:30 and 05:30 UTC). The procedures are general and may therefore be extended to any other similar case.     

Preliminary results of fair-weather atmospheric electric field in the proximity of Main Boundary Thrust,Northern Pakistan

The atmospheric electric Potential Gradient (PG) variation of fair-weather days at Muzaffarabad (MZF, Northern Pakistan) station is presented for the period of January 2015–October 2017. The present investigations focus on the diurnal variation of atmospheric PG on the seasonal and annual time scale. The fair-weather seasonal and annual average PG variation has revealed two peaks, i.e. a primary maximum peak and a secondary maximum peak. The average maximum PG value found is ～410?Vm^?1. The results are then compared with the well-known standard oceanic Carnegie curve. The diurnal curve of PG is found to deviate from the Carnegie curve. The seasonal PG variation at MZF shows lower values during the summer (monsoon) and autumn (post-monsoon) as compared to the winter and spring (pre-monsoon) which could be due to local aerosol concentration. Global comparison of PG (%) values of the annual mean at different longitude, with MZF observatory, shows local morning and evening peaks depicting local sunrise and sunset effects on the PG. The overall outcomes will certainly contribute to further investigate the Global Electric Circuit (GEC).     

Satellite derived aerosol optical depth climatology over Bangalore,India

Climatological aerosol optical depths (AOD) over Bangalore, India have been examined to bring out the temporal heterogeneity in columnar aerosol characteristics. AOD values at 550 nm derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard NASA’s Terra and Aqua satellites, for the period of 2002–2011 have been analyzed (independently) for the purpose. Frequency distributions of the AOD values are examined to infer the monthly mean values. Monthly and seasonal variations of AOD are investigated in the light of regional synoptic meteorology. Climatological monthly and seasonal mean Terra and Aqua AOD values exhibited similar temporal variation patterns. Monthly mean AOD values increased from January, peaks during May and thereafter (except for a secondary peak during July) fall off to reach a minimum during December. Monsoon season recorded the highest climatological seasonal mean AOD, while winter season recorded the lowest. AOD values show an overall increasing trend on a yearly basis, which was found mainly due to sustained increase in the seasonal averaged AOD during summer. The results obtained in the present study are compared with that of the earlier studies over the same location and also with AOD over various other Indian locations. Finally, the radiative and climatic impacts are discussed.     

Simultaneous determination of aerosol- and surface characteristics from top-of-atmosphere reflectance using MERIS on board of ENVISAT

The determination of aerosol optical thickness (AOT) from nadir scanning multi-spectral radiometers, like SeaWiFS, MERIS or MODIS, requires the separation of spectral atmospheric and surface properties. Since SeaWiFS and MERIS do not provide information at 2.1 μm, like MODIS, the estimation of the surface reflectance cannot be made by the cross correlation approach described by Kaufman et al., 1997. The BAER approach (Bremen AErosol Retrieval), von Hoyningen-Huene et al., 2003, uses a linear mixing model of spectra for ‘green vegetation’ and ‘bare soil’, tuned by the NDVI, determining an apparent surface to enable this separation of aerosol and surface properties from VIS and NIR channels. Thus AOT can be derived over a wide range of land surfaces for wavelengths <0.67 μm. Using MERIS L1 data over Europe, the AOT retrieved is comparable with ground-based observations, provided by AERONET. Regional variation of AOT can be observed, showing the atmospheric variability for clear sky conditions by: large scale variation of aerosol turbidity, regional pollution, urban regions, effects of contrails and cases of aerosol-cloud interaction. Simultaneously with the spectral AOT also spectral surface reflectance is obtained, where all atmospheric influences have been considered (molecules, aerosols and absorbing gases (O₃)) for channels with wavelengths <0.67 μm. The AOT is extrapolated by Angström power law to NIR channels and the atmospheric correction for land surface properties is performed, enabling the further investigation of land use and spectral land properties.     

星载主动遥感气溶胶-云参数技术需求与进展

面对越来越迫切的气象和气候预测及大气环境监测需求，利用主动星载仪器在全球范围内探测云和气溶胶参数成为快速发展的研究领域。相比被动遥感仪器，主动仪器可以获取云和气溶胶参数的垂直分布信息，这将在天气气候模式的改进方面发挥重要作用。通过云和气溶胶遥感需求分析，从雷达数据应用角度，首先介绍了数值模式对云和气溶胶的科学参数需求和定量需求，进一步分析了云和气溶胶联合观测的需求，以及星载微波激光雷达的探测特点；然后对国内外正在规划的星载云和气溶胶微波激光雷达探测任务进行了综述，包括仪器指标和数据产品设计；最后展望这一领域的应用前景。     

A surface reflectance correction model to improve the retrieval of MISR aerosol optical depth supported by MODIS data

Combined use of different satellite sensors are known to improve retrievals of aerosol optical depth (AOD). In this study, we propose a new method for retrieving Multi-angle Imaging SpectroRadiometer (MISR) AOD data supported by Moderate Resolution Imaging Spectroradiometer (MODIS) data in Jiangsu Province, China, over the period of 2016–2018 using MODIS L1B, bidirectional reflectance distribution function (BRDF), MISR 1B2T, and ground-measured AOD data. This method is based on the surface reflectance determined by the MODIS V5.2 algorithm. Through the observation angle and spectral conversion between different sensors, the MISR AOD can be obtained. The correlation coefficient (R) and root-mean-square error (RMSE) between the retrieved MISR and ground-measured AOD data varied between different seasons. The accuracy of the MISR AOD retrieval was notably improved after correcting the MISR surface reflectance. Therefore, the method proposed in this study is feasible for the retrieval of MISR AOD supported by MODIS data, and will be applicable to atmospheric environmental monitoring over large areas in the future.     

Retrieval and validation of aerosol optical depth using GF-1 WFV cameras data

Conventional AOD (Aerosol Optical Depth) retrieval is restricted to the global and regional scale due to the limited spatial resolution of satellites. This does not allow for aerosol monitoring at the city level. The Chinese GF-1 Wide Field of View (WFV) sensors have sufficiently fine resolution as a data source for AOD retrieval with fine spatial resolution and a 4-day revisit time. In this study, principles similar to those in the Deep Blue (DB) and Dark Target (DT) algorithms were used to retrieve AOD at 100 m spatial resolution from GF-1 WFV images supported by Moderate Resolution Imaging Spectraradiometer (MODIS) surface reflectance (SR) products (MOD09A1). The derived GF-1 WFV AOD were compared with a combination of MOD04_3K DT AOD and MOD04_L2 DB AOD (MODIS AOD) to find that they yield reasonable Spearman correlations (R_S > 0.82) over Taiwan and Beijing. The derived GF-1 WFV AOD were also validated against Aerosol Robotic Network (AERONET) AOD; the Spearman correlation values were R_S = 0.911 in Beijing and R_S = 0.858 in Taiwan.