Livingston, J.M., Redemann, J., Schmid, B., Russell, P.B., Eilers, J.A., Pilewskie, P., Pommier, J., Browell, E.V., Hair, J.W., Chu, D.A., Kahn, R., Wendisch, M., Hardesty, M., and Senff, C., (2004). Airborne Sunphotometer and Related Measurements Acquired Over the Gulf of Maine during INTEX-ITCT 2004. Eos Trans. AGU, 85(47), Fall Meet. Suppl. 2004, Abstract # A33D-0110
The NASA Ames 14-channel Airborne Tracking Sunphotometer (AATS-14) took measurements from aboard a Jetstream 31 (J31) twin turboprop aircraft during 19 science flights (~53 flight hours) over the Gulf of Maine during 12 July - 8 August 2004. The flights were conducted in support of the INTEX-NA (INtercontinental chemical Transport EXperiment-North America) and ITCT (Intercontinental Transport and Chemical Transformation of anthropogenic pollution) field studies. AATS-14 measures the solar direct-beam transmission at 14 discrete wavelengths (354-2138 nm), and provides instantaneous measurements of aerosol optical depth (AOD) spectra and water vapor column content, in addition to vertical profiles of aerosol extinction and water vapor density during aircraft ascent and descent. Also on board the J31 during the mission was the NASA Ames Solar Spectral Flux Radiometer (SSFR). SSFR consists of separate nadir and zenith viewing hemispheric FOV sensors that yield measurements of downwelling, upwelling, and net solar irradiance at a spectral resolution of ~8-12 nm over the wavelength range 300-1700 nm. The objectives of the J31-based measurements were to validate MODIS (MODerate-resolution Imaging Spectroradiometer) and MISR (Multi-angle Imaging Spectro-Radiometer) aerosol retrievals, quantify sea surface spectral albedo (which can contribute the largest uncertainty to MISR aerosol retrievals for low aerosol loading), test closure (consistency) among suborbital results, test chemical-transport models using AOD profiles, and assess regional radiative forcing by combining satellite and suborbital results. Combination of coincident AATS-14 and SSFR measurements allows derivation of aerosol radiative forcing from simultaneously measured radiative flux and AOD gradients, and the derivation of spectra of aerosol absorbing fraction from spectra of radiative flux and AOD. Specific J31 flight patterns were designed to address the science goals, and these patterns included a mixture of vertical profiles (spiral and ramped ascents and descents) and constant altitude horizontal transects at a variety of altitudes. Flight plans often included profiles above NOAA Ship Ronald H. Brown and, in a few cases, coordination with other mission aircraft - namely, the NOAA DC-3 and the NASA DC-8. In general, flight plans were designed to include a near sea surface horizontal transect in a region of minimal cloud cover during or near the time of an AQUA (MODIS) and/or TERRA (MODIS and MISR) satellite overpass. Twelve J31 flights included segments that were temporally and/or spatially near-coincident to the satellite overpasses. These included four MISR local mode events, of which one involved a successful J31 and DC-8 flight coordination. In this paper, we focus on satellite validation measurements obtained with AATS-14.
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