The MODIS sensors on the Terra and Aqua satellites have observed global distributions of aerosols and have provided information regarding aerosol amount (e.g. aerosol optical thickness), and size (e.g., fine vs. coarse). MISR on Terra provides similar information as well as estimates of the fraction of nonspherical aerosols and, in some cases, plume heights. Unfortunately, the vertically-resolved information provided by the MODIS/MISR aerosol retrievals is generally quite limited. This is a limitation since vertically-resolved information on aerosol optical and microphysical parameters are required for determining the direct radiative forcing of absorbing aerosols, assessing aerosol/cloud indirect radiative forcing, and evaluating aerosol model parameterizations of aerosol transport and removal processes.
We have developed and implemented retrievals that combine airborne lidar and MODIS measurements to derive extinction profiles for both the fine and coarse mode aerosols. Multiwavelength lidar profiles of aerosol backscattering at 300, 588, and 1064 nm and depolarization at 588 nm acquired by the NASA Langley airborne DIAL system during recent field experiments conducted over the Pacific (TRACE-P, 2001) and eastern U.S. coastal region (INTEX-NA, 2004) have been combined with MODIS spectral radiance measurements in recently developed algorithms to retrieve profiles of aerosol extinction for both fine and coarse particle modes, and particle effective radius. Attempts to evaluate/validate these algorithms have been limited due to the paucity of coincident and collocated airborne remote sensing and in situ data.
We propose to use a combination of existing and future field campaign and satellite data to evaluate, validate, and extend these algorithms. In addition to performing these retrievals using data from the airborne DIAL system, we shall also use the airborne data acquired by the new Langley High Spectral Resolution Lidar (HSRL). In addition to measuring aerosol backscatter and depolarization at 532 and 1064 nm, this lidar system is unique in that it directly measures aerosol extinction at 532 nm without additional information or assumptions about aerosol properties. These measurements will be used in two ways: 1) to directly validate the aerosol extinction profiles derived using the existing algorithms that use aerosol backscattering profiles and MODIS retrievals, and 2) to develop new algorithms that directly use the additional information provided by the HSRL aerosol extinction profile.
We propose to use HSRL and airborne DIAL data acquired during the INTEX-B/MILAGRO field campaign for these investigations. This campaign provided measurements of additional aerosol types that were not observed during the TRACE-P and INTEX-NA campaigns. INTEX-B/MILAGRO employed extensive ground-based and airborne in situ and remote sensing measurements to help evaluate these retrievals. We shall also use HSRL and MODIS/MISR data to be acquired during two additional missions; the TexAQS/GoMACCS field campaign to occur over and around Houston during August-September 2006, and the CHAPS field campaign to occur over Oklahoma during the summer 2007. In both cases, additional airborne in situ and remote sensing measurements will be used to further evaluate/validate these retrievals. The lidar measurements will be also be used to assess MISR retrievals of nonspherical aerosol amounts and plume heights.
We shall also use the combined lidar and MODIS/MISR results to evaluate the corresponding simulations from the GOCART global aerosol transport model. These results will be used to evaluate the ability of this model to simulate the vertical distribution of aerosol extinction and aerosol types.
