11th Conference on Atmospheric Radiation and the 11th Conference on Cloud Physics

Monday, 3 June 2002: 11:15 AM
Airborne measurements of aerosol optical depth and columnar water vapor in support of the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) experiment, 2001
Jens Redemann, NASA/Ames Research Center, Moffett Field, CA; and B. Schmid, J. M. Livingston, P. B. Russell, J. A. Eilers, P. V. Hobbs, R. Kahn, W. L. Smith Jr., B. N. Holben, C. K. Rutledge, M. C. Pitts, M. I. Mishchenko, B. Cairns, J. V. Martins, and T. P. Charlock
As part of the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) experiment, July 10 - August 2, 2001, the 14-channel NASA Ames Airborne Tracking Sunphotometer (AATS-14) was operated successfully aboard the University of Washington CV-580 during 10 research flights (45.09 flight hours). The CLAMS campaign was a clear sky, shortwave (SW) closure campaign and entailed measurements from the Chesapeake Lighthouse research platform, several land sites, 6 research aircraft and the Terra satellite. CLAMS research goals included validation of satellite-based retrievals of aerosol properties, vertical profiles of radiative fluxes, temperature and water vapor. Suborbital measurements of aerosol optical depth (AOD) and columnar water vapor (CWV) were carried out at several AERONET sites and aboard five of the six airborne platforms using a variety of techniques.

AATS-14 measures the direct solar beam transmission at 14 discrete wavelengths (354-1558 nm), yielding aerosol optical depth spectra and columnar water vapor. Differentiation of AOD (CWV) with respect to altitude in favorable flight patterns allows the derivation of aerosol extinction (water vapor density). During coordinated flights of the UW CV-580, AATS-14 measured full column aerosol optical depth spectra at exact Terra overpass time on at least 7 occasions. For five of these opportunities, AOD at 499nm was at or below 0.1. During Terra overpass time on July 17, 2001, AATS-14 measured the largest AOD encountered during the entire experiment (~0.48 at 499nm), including a horizontal gradient in AOD of more than 0.1 over a distance of ~80 kilometers.

In the first part of this paper, we will present AATS-14 - derived measurements of AOD and CWV, and comparisons to other suborbital measurements obtained using (i) the AERONET sun/sky radiometer at the Chesapeake Lighthouse, (ii) an Oxygen A-Band spectrometer, (iii) a scanning polarimeter, (iv) the MODIS Airborne Simulator (MAS), and (v) AirMISR. Having examined the agreement of the various suborbital AOD measurement techniques we will proceed to show examples of comparisons of suborbital AOD measurements to AOD retrievals using data acquired by MISR, MODIS and CERES aboard the Terra satellite.

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