Satellite Detection of Effects of Absorbing Aerosols on Clouds over Urban Areas

该项目将利用卫星对气溶胶光学厚度与云光学厚度和云部分的反演，以研究是否可以在世界上三个区域检测到“回飞棒”曲线，这三个区域是化石燃料和/或固体生物燃料的大量人为排放源。“回飞棒”指的是随着气溶胶光学厚度的增加，云光学厚度先增加后减少，在巴西观测到了这种现象，在那里生物质燃烧对大气成分产生了主要影响。研究的地区包括中国的一个城市化地区、印度的一个城市化地区和南加州的第三个城市化地区。将对每个区域的五年卫星数据进行分析。污染的城市化地区将成为目标的原因是，COD和AOD的变化应该比非城市化地区更容易检测。不过，选定的区域将足够大，包括农村和城市地区。因此，可以而且也将审查农村和城市地区之间的差异，以确定微物理或辐射效应是否在城市地区比农村地区更占主导地位。将使用当地时间下午1时30分左右Aqua卫星上带有立交桥的中分辨率成像光谱仪（MODIS）仪器的数据。该仪器每天提供几乎覆盖全球的较高空间分辨率（250至500米）数据。将采用MODIS条带2级气溶胶、云、水汽和稳定性产品，结果将为未来的模拟研究提供输入，以减少气溶胶对气候影响的最大不确定性之一，即吸收气溶胶对云量的影响。这将最终促进对吸收气溶胶（特别是炭黑）对气候影响的理解，因为云的吸收效应在迄今为止的所有国际评估中都被忽略了。一名研究生将通过参与该项目接受培训。

This project will use satellite retrievals of aerosol optical depth versus cloud optical depth and cloud fraction to examine whether "boomerang" curves can be detected in three regions of the world that are sources of significant anthropogenic emissions from fossil fuels and/or solid biofuels. "Boomerang" refers to an increase followed by a decrease in cloud optical depth (COD) with increasing aerosol optical depth (AOD), which has been observed over Brazil where biomass burning is a dominant influence on atmospheric composition. The regions to be examined will include one urbanized region in China, one in India, and a third in Southern California. For each region, analyses of five years of satellite data will be carried out. The reason polluted urbanized regions will be targeted is because changes in COD and AOD should be more detectable than in non-urbanized regions. Nevertheless, the regions selected will be large enough to include rural as well as urban areas. As a result, differences between rural and urban areas can and will also be examined to determine whether microphysical or radiative effects dominate more in urban versus rural areas. Data from the Moderate Resolution Imaging Spectrometer (MODIS) instrument onboard the Aqua satellite with overpasses at approximately 1:30 PM local time will be used. This instrument provides relatively high spatial resolution (250 to 500 meters) data with near global coverage on a daily basis. MODIS Swath Level 2 aerosol, cloud, water vapor, and stability products will be employed.The results will provide input for future modeling studies to reduce one of the greatest uncertainties surrounding the effects of aerosols on climate, that of absorbing aerosols on cloudiness. This will ultimately advance understanding of the effects of absorbing aerosol (particularly black carbon) on climate because the cloud absorption effect has been ignored in all international assessments to date. A graduate student will be trained through participation in the project.