Modeling Satellite Correlations of Aerosol Optical Depth Versus Cloud Optical Depth Over Megacities

该项目旨在更好地了解气溶胶/云的相互作用及其对全球温度的影响。这项研究是基于对几个全球特大城市上空大气中气溶胶(小颗粒)和云的厚度的卫星测量进行的调查。先前一项超过2个大城市的研究数据表明，随着大气中气溶胶厚度的增加，云的密度也趋于增加到某一点，但随后开始下降。由于卫星数据可以显示相关性，但不能显示因果关系，而模型可以显示因果关系，因此该项目将使用计算机模型来模拟三个特大城市的云和气溶胶之间的关系。这些结果将有助于提高计算机模式预测全球气候变化的能力。本研究的重点是调查几个大城市的气溶胶光学厚度(AOD)和云光学厚度(COD)的卫星测量，以评估不同类型的气溶胶反馈对云的相对重要性。以前发现了一条回旋镖曲线(COD随AOD的增加先增加后减少)，其中在低AOD时COD的增加被认为是由于微物理(间接)效应，而在高AOD时COD的减少被认为是由于辐射效应(云吸收效应和半直接效应)。该项目由三项任务组成：1)完成对印度新德里一个大城市区域的项目第一部分进行的卫星反演工作；2)使用嵌套的全球直达局部3-D模式(GATOR-GCMOM)来确定卫星数据中发现的回旋镖曲线是否可归因于吸收气溶胶；3)运行一项为期24年的全球基线模拟和敏感性模拟，考察化石燃料烟尘、固体生物燃料烟尘和气体、生物质燃烧烟尘和气体、甲烷和所有人为成分对全球气候的单独影响，包括间接影响、半直接影响和云吸收效应。为了评估模型结果的重要性，将使用对不等方差的不等样本大小的双边t检验来确定计算机模拟的基线模拟和敏感性模拟之间的给定参数的差异是否相对于气候模式中的混沌变化具有统计学意义。

This project seeks to gain a better understanding of aerosol/cloud interactions and the effects of these on global temperatures. The research is based on investigating satellite measurements of the thickness of aerosols (small particles) and clouds in the atmosphere over several global megacities. Data from a prior study over 2 megacities suggest that as the thickness of aerosols increases in the atmosphere, the density of clouds tends also to increase to a point, but then begins to decrease. Since satellite data can show correlations but not cause and effect, and models can show cause/effect, a computer model will be used in this project to simulate the relationship between clouds and aerosols over three megacities. The results will help to improve the ability of computer models to predict global climate change.This research focuses on the investigating satellite measurements of aerosol optical depth (AOD) and cloud optical depth (COD) over several megacities to assess the relative importance of different types of aerosol feedbacks on clouds. Previously a boomerang curve was identified (an increase then a decrease of COD with increasing AOD) where the increase in COD at low AOD is believed to be due to microphysical (indirect) effects and a decrease in COD at high AOD is thought to be due to radiative effects (cloud absorption effects and the semidirect effect).The project consists of three tasks: 1) complete the satellite retrieval worked performed for the first part of the project over one more megacity region, New Delhi India; 2) use a nested global-through-local 3-D model (GATOR-GCMOM) to determine whether the boomerang curves found in the satellite data can be attributed to absorbing aerosols; and 3) run a 24-year global baseline simulation and sensitivity simulations examining the separate effects of fossil-fuel soot, solid biofuel soot and gases, biomass burning soot and gases, methane, and all anthropogenic components on global climate, accounting for indirect effects, semi-direct effect, and the cloud absorption effect. To evaluate the significance of the model results, a two-sided t-test for unequal sample sizes of unequal variance will be used to determine whether the computer modeled difference in a given parameter between a baseline simulation and a sensitivity simulation is statistically significant relative to chaotic variation in a climate model.