Cloud Properties Derived from Visible and Near-infrared Reflectance in the Presence of Aerosols
| Hofmann, Odele | University of Colorado at Boulder |
| Pilewskie, Peter | University of Colorado |
| Gore, Warren | NASA Ames Research Center |
| Russell, Phil | NASA Ames Research Center |
| Livingston, John | SRI International |
| Redemann, Jens | BAERI/NASA Ames Research Center |
| Bergstrom, Robert | Bay Area Environmental Research Institute |
| Platnick, Steven | NASA-GSFC |
| Daniel, John | NOAA Aeronomy Laboratory |
Category: Cloud Properties
The New England Air Quality Study - Intercontinental Transport and Chemical Transformation (NEAQS-ITCT) experiment conducted in July-August 2004 included objectives on the effects of urban-industrial pollution aerosols on cloud radiative properties, the so-called indirect effect. Measurements of spectral irradiance covering the near-ultraviolet to near-infrared were made from two airborne platforms, the NOAA WP-3D and the Sky Research J-31, using identical Solar Spectral Flux Radiometers (SSFR). The SSFR measured the upwelling and downwelling spectral irradiance between 380-1670 nm from which the spectral albedo (ratio of upwelling to downwelling) and net (difference between downwelling and upwelling) irradiance were derived. Cloud spectral albedo was used to retrieve cloud particle effective radius, optical depth, and liquid water path. The robustness of the optical retrieval method will be examined by comparing the WP-3D SSFR retrievals to in situ measurements made with an FSSP-100 and an OAP 2D-C and to an independent retrieval using Miniaturized Differential Absorption Spectroscopy (MIDAS), also on board the WP-3D. A sunphotometer was also deployed on the J-31, the 14-channel NASA Ames Airborne Tracking Sunphotometer (AATS-14), providing aerosol optical depths at thirteen discrete wavelengths between 354-2138 nm. J-31 flights on 15, 20, and 31 July were of particular interest because AATS-14 data revealed the presence of aerosol layers above clouds. Comparisons between SSFR-derived cloud properties and MODIS cloud retrievals were in close agreement when aerosol optical depth was less than 0.1. Over moderately thick clouds there is evidence that an enhanced aerosol layer, such as that encountered during the 20 July case, may affect the retrieved cloud properties. Such an influence must be distinguished from a true “aerosol indirect effect” in order to accurately quantify the amount by which aerosols modify cloud albedo.
This poster will be displayed at the ARM Science Team Meeting.
