Simultaneous remote sensing of the optical and microphysical properties of cirrus clouds and tropospheric aerosols using aircraft and satellite data

Tropospheric aerosols and high-level thin cirrus affect the Earth's atmospheric radiation field and vertical heating rate distribution in different manners that are associated with their unique optical properties and altitude. Obtaining microphysical properties of each is essential and to do so on a global scale, satellites must be used. Yet distinguishing between two optically thin media from space is difficult. Presently, retrieval of such information as optical thickness and effective particle size by satellite sensors is made separately. That is, aerosols are only examined in presumed clear sky situations while thin cirrus properties are retrieved while assuming a background aerosol size distribution or obtaining an observed below cloud upwelling radiance. There is evidence that thin/sub-visible cirrus may be substantially more widespread than is currently being detected, especially in the tropics, and is leading to large errors in retrieved aerosol properties.; This dissertation documents the development of a methodology for the remote sensing of both thin cirrus optical depth and mean effective ice crystal size as well as the underlying aerosol optical depth, based on measurements of reflected solar radiation collected by a modern spectroradiometer. The algorithm utilizes lookup tables developed using scattering and radiative transfer methods specifically developed to account for the complex microphysics of cirrus clouds and aerosols. The retrieved results are validated using both in-situ and ground based measurements collected over the Atmospheric Radiation Measurement (ARM) test sites and during field campaigns.; The detection of thin cirrus clouds is a necessary first step of the retrieval process. Use of the 1.38 mum reflection band together with infrared window brightness temperature differences forms a novel approach for identifying these clouds. It is shown that over both land and water surfaces thin cirrus with optical depths as low as 0.02 can be detected over 80% of the time. A secondary algorithm for identifying dust, which can often be interpreted as cirrus, is also presented.; Using a two-step method, aerosol optical depths can first be characterized by the accurate removal of reflectance due to cirrus via an empirical approach. This method is currently limited to non-sun glint, ocean scenes because the surface reflectance is generally well constrained and does not overly dominate the aerosol signal. When opaque clouds are screened out, results well validated by both ground and in-situ measurements. This new method should increase the total area in which aerosol information can be obtained and lower the effect that thin cirrus contamination has upon the aerosol retrieval.