6.4
The use of rotating shadowband radiometers and microwave radiometers to obtain cloud properties in Arctic environments
Jim C. Barnard, PNNL, Richland, WA; and J. C. Liljegren, Q. L. Min, and J. C. Doran
Data from multi-filter rotating shadowband radiometers (MFRSRs) and microwave radiometers (MWRs) have been used to obtain cloud optical depths and liquid water paths, respectively, at the SHEBA Ice Station during the spring and summer of 1998 and at Barrow, Alaska for the summer of 1999. By combining the data from the two instruments it is possible to estimate the effective droplet radii of the clouds as well, but considerable care needs to be taken in processing the data to extract meaningful information from these instruments. The values of cloud optical depths obtained with a MFRSR depend on the albedo of the surface. At SHEBA an area-averaged albedo was measured directly but such information was not available at Barrow. A method for estimating this quantity through the concurrent use of the MFRSR and MWR data time series is described, and the resultant improvement in calculated optical depths at Barrow is shown.
The interpretation of cloud optical depths from a MFRSR can be somewhat problematic under partly cloudy conditions; accordingly, a simple technique for characterizing periods when unambiguous values may be determined is also described. Cloud properties during such periods at the two sites were then evaluated and significant differences in optical depths and effective droplet radii at the two sites are shown. Clouds at the SHEBA Ice Camp tended to be thicker and the effective radii were smaller than the corresponding values at Barrow.
Session 6, Meteorological Measurements in Harsh Environments
Tuesday, 16 January 2001, 4:00 PM-5:14 PM
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