Validation and comparison of cloud layers from radiosonde and WACR-ARSCL VAP data in China

Description

The Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) was deployed in Shouxian, Anhui Province, China, from May 14 to December 28, 2008, but the 95-GHz W-band ARM cloud radar (WACR) was operated only from October to December. By virtue of the radar imagery data and coincident radiosonde launches, cloud vertical distribution was obtained for the longer period of the AMF campaign. If the approach is sound, the method could be applied to generate a cloud climatology over a much longer period and larger spatial domain, pending on the availability of radiosonde data. The recent release of WACR Active Remote Sensing of Clouds (WACR-ARSCL) value-added product (VAP) allows us to evaluate the radiosonde-based detection of cloud layers by comparing the cloud layers obtained from the radiosonde and WACR-ARSCL VAP (WVAP). Overall, the two products agree reasonably well, and each method has its limitations. While the frequency of the radiosonde launches is much less than the frequency of WVAP, cloud layers derived from the radiosonde are similar to the WACR. Many near-surface moist layers are classified as cloud layers by the WVAP but are deemed to be clear by the radiosonde. The former is suspicious because of the low relative humidity (RH). A few cloud layers at high altitudes are detected by the radiosonde but missed by WVAP. Cloud layers that are detected by the radiosonde but missed by WVAP are generally thin and located at high altitudes.