東北大学 · 環境科学
Pradeep Khatri教授の研究室は、大気中のエアロゾルと雲の相互作用が気候変動に与える影響を、地上観測(SKYNET, AERONET)と人工衛星データ(CloudSat, CALIPSO)を統合して解明しています。特に、エアロゾルの光学特性(単一散乱アルベド、粒子径分布)と雲微物理の関係、ならびに都市・砂漠・工業地域など異なる大気環境下でのエアロゾルの放射冷却効果や気候影響を、長期間にわたる観測データを用いて定量的に分析しています。COVID-19ロックダウン期のエアロゾル減少が気候に与えた影響の評価も重要な研究テーマです。
Figures are computed from collected data and may differ slightly.
Abstract SKYNET and Aerosol Robotic Network (AERONET) retrieved aerosol single scattering albedo (SSA) values of four sites, Chiba (Japan), Pune (India), Valencia (Spain), and Seoul (Korea), were compared to understand the factors behind often noted large SSA differences between them. SKYNET and AERONET algorithms are found to produce nearly same SSAs for similarity in input data, suggesting that SSA differences between them are primarily due to quality of input data due to different calibration
Abstract We analyzed data observed at Fukue‐jima (32.752°N, 128.682°E), the downwind of the East Asian desert and urban areas, during the spring season (March–April) of 2008–2011 aiming to understand the light‐absorption capacity of Asian dust aerosols, which is a topic of controversy. We observed the decreasing tendency of single‐scattering albedo (SSA) with the decrease of Ångström exponent and the increase of the ratio of dust aerosol optical thickness to total aerosol optical thickness, sugg
Abstract Aerosols emitted in densely populated and industrialized Indo‐Gangetic Plain, one of the most polluted regions in the world, modulate regional climate, monsoon, and Himalayan glacier retreat. Thus, this region is important for understanding aerosol perturbations and their resulting impacts on atmospheric changes during COVID‐19 lockdown period, a natural experimental condition created by the pandemic. By analyzing 5 years (2016–2020) data of aerosols and performing a radiative transfer
Abstract Despite the vertically inhomogeneous (VIH) structure of ice clouds, current passive remote sensing methods assume plane‐parallel homogeneous (PPH) layers, which can lead to retrieval errors. An adequate VIH cloud model is required to improve retrieval performance. In this study, CloudSat and CALIPSO satellite measurements in a 1‐year period were analyzed to model cloud vertical inhomogeneity, and its impacts on cloud retrieval were assessed using thermal infrared (TIR) measurements. The
Aerosols play important roles in modulations of cloud properties and hydrological cycle by decreasing the size of cloud droplets with the increase of aerosols under the condition of fixed liquid water path, which is known as the first aerosol indirect effect or Twomey-effect or microphysical effect. Using high-quality aerosol data from surface observations and statistically decoupling the influence of meteorological factors, we show that highly loaded aerosols can counter this microphysical effe
Abstract Aerosol‐cloud interaction remains one of the least understood processes in climate science arena, despite its profound impacts in radiation and water budget perturbations. The aerosol effects on clouds largely depend on aerosol characteristics. Here, we implemented 17‐year (2003–2020) data set of aerosol, cloud, and meteorological factors collected over East Asia—a highly polluted region with recent decreasing trend of air pollution due to control measures—to elucidate atmospheric regim
The present study implements long-term surface observed radiation data (pyranometer observed global flux and sky radiometer observed spectral zenith transmittance data) of multiple SKYNET sites to validate water cloud optical properties (cloud optical depth COD and effective radius Re) observed from space by MODIS onboard TERRA and AQUA satellites and AHI onboard Himawari-8 satellite. Despite some degrees of differences in COD and Re between MODIS and AHI, they both showed common features when v
Abstract The spectral direct and diffuse irradiances observed by a radiometer with a horizontal surface detector have been frequently used to study aerosol optical parameters, such as aerosol optical thickness (τaer) and single scattering albedo (ω). Such radiometers more or less lack an ideal cosine response. Generally, either the cosine error of observed diffuse irradiance was corrected by assuming an isotropic distribution of sky radiance or it was neglected in the past studies. This study pr
The stringent control measures in China to curb the spread of Coronavirus disease (COVID-19) have had profound societal and environmental impacts, including changes in energy consumption practices and thereby in air pollutant emissions. In this study, a suite of satellite and numerically assimilated air pollution and meteorological data combined with information on energy consumption practices and nighttime light (NTL) was used to evaluate the effects of these COVID-19 control measures on air qu
Aerosol effects on deep convective cloud (DCC) have been recognized as one of the complex subjects in climatic studies because of the difficulty in quantifying the sole effect of aerosols on DCC. The complexity further arises if the atmosphere has very strong temporal and spatial variations such as that of Indo-Pacific Warm Pool (IPWP) region. Considering the strong influence of IPWP region on global climate change and water circulation, we investigated aerosol effects on DCC over this region by
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