Cloud Optical Properties from the Multi-Filter Shadowband Radiometer (MFRSRCLDOD): An ARM Value-Added Product

Turner, DD ; Lo, C ; Min, Q

Pacific Northwest National Laboratory (U.S.)

关键词: Optical Properties;    Spectrometers;    Clouds;    Wavelengths;    Radiometers;   

DOI  :  10.2172/1020280
RP-ID  :  DOE/SC-ARM/TR-047
RP-ID  :  DE-AC05-7601830
RP-ID  :  1020280

美国|英语

来源: UNT Digital Library

【 摘 要 】

The Min and Harrison algorithm has been incorporated into an ARM Value-Added Product (VAP) called MFRSR CLDOD. This version of the VAP (1Min) uses the diffuse transmission at 415 nm from the MFRSR. Therefore, the results are only valid for “horizontally homogeneous” stratiform clouds with optical depths larger than approximately 7. The retrieval assumes a single cloud layer consisting solely of liquid water drops. As specified by Min and Harrison (1996), the wavelength at 415 nm was chosen due to the lack of gaseous absorption and the relatively constant surface albedo (in the absence of snow) at this wavelength. The MFRSR CLDOD VAP (henceforth referred to as “the VAP”) retrieves cloud optical depth (τ) from the MFRSR measurements. If the LWP is available from a coincident MWR observation, then the droplet effective radius (re) can be determined. Knowledge of the estimated re can be used to improve the estimate of τ because there is a slight dependence on the extinction coefficient, single scattering albedo, and asymmetry parameter on effective radius at this wavelength. However, if the MWR’s LWP is not available, then the VAP assumes that re = 8.0 μm. The primary output from the VAP is τ and re.