Cloud and Radiative Properties Derived Over the ARM NSA Domain From AVHRR Data
Heck, P.W., Nguyen, L., Smith, W. L., Jr., Ayers, J.K., Doelling, D.R., and Spangenberg, D.A.,
Analytical Services and Materials, Inc.; Minnis, P., and Young, D.F., National Aeronautics and Space Administration-Langley Research Center
Ninth Atmospheric Radiation Measurement (ARM) Science Team Meeting
The Atmospheric Radiation Measurement (ARM) Program's polar sites on the North Slope of Alaska (NSA) measure time series of various atmospheric, cloud and radiative properties over a few selected areas. Satellite data are needed to provide measurements of similar properties between the sites and to estimate the radiation budget at the top of the atmosphere. Over the other ARM sites in the central United States and the Pacific, geostationary satellite data are used to monitor clouds and radiation on a large scale a with fine time resolution. The geostationary platform facilitates constant monitoring of a given region because the view angles at a given time of day are relatively constant. Thus, the background radiance field is often easily predicted. Over polar regions, sun-synchronous satellites are required for monitoring because the view angle from the geostationary satellite is either extremely large or nonexistent. While a pair of sun-synchronous satellites view a given polar area up to 20 times per day, they observe the region from a different perspective during each overpass. Thus, the angular dependence of the surface must be well characterized for all potential angular conditions. Other factors also exacerbate both the detection of clouds and analysis of their properties. The bright, cold surfaces and inversion-laden atmosphere do not often meet the assumptions of most cloud retrieval algorithms. Furthermore, the cold, highly stratified atmosphere produces cloud structures not often seen in the other ARM regions. This paper begins with the development of a cloud analysis algorithm for the ARM NSA domain using 1-km multispectral Advanced Very High Resolution Radiometer (AVHRR) data taken during the Surface Heat Budget of the Arctic (SHEBA) Field Experiment and the accompanying First ISCCP Regional Experiment (FIRE) Arctic Clouds Experiment (ACE) to determine cloud macrophysical and microphysical properties. Cloud fraction and height, as well as cloud optical depth, phase and effective particle size, are retrieved using selected series of satellite radiances observed at 0.65, 3.75, 10.8, and 12.0 µm. The data were taken from three National Oceanic and Atmospheric Administration (NOAA) satellites during the period encompassing May through July 1998. The results are compared to ARM surface instruments deployed at Point Barrow, Alaska, and on the SHEBA icebreaker. In situ measurements by FIRE ACE aircraft are used to validate the microphysical properties. These analyses represent an important step in the effort to monitor clouds and radiation in the Arctic for ARM.
Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).
