GACP Projects
Airborne Sensors Data Fusion--Aerosol/Cloud Properties
Edward E. Uthe
Abstract: Uncertainties of aerosol/cloud climatologies and optical/radiative properties derived from previous and future satellite sensor observations are needed to assess the value of global and regional climatic change evaluations based on satellite sensor databases. Moreover, accurate aerosol column loadings by particle size, shape, and composition are needed for model evaluations of radiative fluxes. Airborne platforms afford the best means to employ remote and in situ sensor suites to accurately characterize vertical distributions of aerosol/cloud densities, microstructures, and optical/radiative parameters over relatively large regional areas. As expected, airborne atmospheric research campaigns are continually increasing in sensor sophistication for more complete closure of aerosol/cloud property evaluations over extended atmospheric volumes. A recent example is the SUCCESS campaign conducted during April and May 1996 that used three well-instrumented NASA aircraft. SUCCESS afforded the opportunity for deployment and evaluation of several new sensors in addition to commonly used particle, gas, radiation, and meteorological sensors for more complete evaluation of aerosol/cloud properties.
SRI developed and deployed an angular scanning backscatter lidar on the NASA DC-8 research aircraft that could be scanned angularly from vertically upward to forward in direction of aircraft flight to vertically downward or continuously view over vertical, horizontal, or slant paths. The primary objective of the lidar was to help establish aircraft altitudes for achieving best sampling of aerosol and cloud features by other onboard sensors and to help extend the spatial domain of collected sensor databases. The angular scanning lidar provides for atmospheric homogeneous and horizontally homogeneous solutions for aerosol/cloud optical parameters as well as standard solutions based on assumed optical parameter relationships. A current project is directed to fusion of the SUCCESS DC-8 scanning lidar observations with the extensive databases collected by onboard particle, gas concentration, meteorological, and radiometric sensors to characterize aerosol/cloud properties over extended atmospheric volumes. Several results illustrating the value of the airborne scanning lidar approach have been published (GRL, Vol. 25, No. 9, pp. 1339-1342, 1998). More recent data products including movie animations depicting aerosol/cloud properties surrounding the moving aircraft are available at web site http://www.rsed.sri.com/lidar.
Data fusion methods being investigated may provide the best means for characterization of large atmospheric volumes required for effective satellite sensor observation validations and for radiative flux model evaluations. The current study may also identify new airborne sensor suites for convergence to full evaluation of aerosol/cloud properties over regional areas. For example, the NASA airborne sunphotometer provides optical depths needed for solution of extinction profiles from slant-path lidar observations made at near solar viewing angles in support of SAGE-III validations. This study, supported by NASA's Atmospheric Effects of Aviation Program (AEAP) may help define future airborne research campaigns for validation of satellite sensor databases and for measurement of radiative model parameters required for global aerosol forcing investigations. Data products of our study, as they are developed, will be available at the web site given above.
