In an attempt to better understanding climate and better comprehend the effects of clouds and aerosols on the Earth’s Radiation Budget, NASA has been developing several satellite missions. Among them, the Cloud-Aerosol-Lidar and Infrared Pathfinder Spaceborne Observation (CALIPSO) mission will observe clouds and aerosols with a combination of lidar and passive instruments. CALIPSO will fly in formation with EOS Aqua, EOS Aura, Cloudsat and Parasol. This novel satellite formation will provide a unique comprehensive data set of cloud and aerosol optical and physical properties, and radiative fluxes. In this paper, the characterization of global aerosol properties with sparsely sampled observations is investigated using a dataset of aerosol optical depth (AOD) from the MATCH climate model. MATCH is an offline Chemistry and Transport Model (ChTM) primarily developed by NCAR that includes a number of aerosol sources as well as a variety of transformation and removal mechanisms. The CALIPSO satellite is "flown" through this dataset and the aerosol optical depths at the CALIPSO footprint locations are sampled to produce an AOD subset. Averages computed from the subset are compared with averages from the full model output to investigate the magnitude of uncertainties due to sparse sampling of the aerosol field. Initially, uncertainties in satellite sparsely sampled measurements of global aerosol distribution are quantified in terms of zonal averages. The goal of this effort is to determine the correct satellite average scaling to accurately represent global aerosol coverage. Ultimately, sampling errors will also be assessed at regional scales.
The Lidar In space Technology Experiment (LITE) provided for the first time highly detailed vertical profiles of aerosol and clouds from the Earth’s surface to the middle stratosphere. Validated theoretical results from a Model of Atmospheric Transport and Chemistry (MATCH) can help quantify and qualify the aerosol population as well as identify some consistent patterns of aerosol components for a certain region. The goal of this work is to estimate the degree of confidence on MATCH’s theoretical results, comparing them to the data set retrieved by LITE, in order to improve the lidar aerosol extinction-to-backscatter ratio retrieval algorithm to be applied to the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), NASA’s next mission that will be orbiting a Lidar around the Earth.
Chemistry and transport models for trace species are detailed numerical formulations intended to represent the atmospheric system as a whole, accounting for all the individual processes and phenomena that influence climate changes. The development of computer resources and the retrieval of emission inventories and observational data of the species of interest have enhanced the model evolution towards three-dimensional global models that account for more complicated chemical mechanisms, wet and dry deposition phenomena, and interactions and feedback mechanisms between meteorology and atmospheric chemistry. The purpose of this study is to ascertain the sensitivity of the solar radiative field in the atmosphere to absorption and scattering by aerosols. This effort is preliminary to the study of feedback mechanisms between photolytic processes that create and destroy aerosols and the radiation field itself. In the study a cloud of water-soluble aerosols, randomly distributed in space within hypothetical 1-cm cubes of atmosphere, is generated. A random radius is assigned to each aerosol according to a lognormal size distribution function. The radiative field characterization is analyzed using a Mie scattering code to determine the scattering phase function and the absorption and scattering coefficients of sulfate aerosols, and a Monte Carlo ray- trace code is used to evaluate the radiative exchange. The ultimate goal of the effort is to create a tool to analyze the vertical distribution of absorption by aerosols in order to determine whether or not feedback between photolytic processes and the radiation field needs to be included in a Third Generation Chemistry and Transport model.