Vertical Structure of Cloud Occurrence in Korean Peninsula for Ground-Based Millimeter Wavelength Radar Observations

The cloud observations from ground-based millimeter wavelength radar provide vertical distribution of cloud layers with good accuracy and high vertical resolution and can be utilized to produce cloud type climatologies. We examine statistical cloud properties according to the cloud types using Ka-band cloud radar (KCR) that are operated by National Institute of Meteorological Research (NIMR) of Korea Meteorological Administration (KMA) since 2013.

For stable and accurate statics of cloud information, system biases in measurements from KCR were calibrated. The calibration of system biases in reflectivity from KCR was conducted by using observations from collocated external instrument. The system biases in KCR reflectivity were corrected by direct comparison with reflectivity from vertically pointing X-band radar (VertiX) and Micro Rain Radar (MRR) that are pre-calibrated by using drop size distributions from two-dimensional video disdrometer (2DVD) and PARticle SIze VELocity (PARSIVEL) for rain events. Furthermore, strong echoes from insects in the boundary layers were then removed using linear depolarization ratio (LDR) and reflectivity thresholds.

For the analysis of cloud properties (i.e., cloud occurrence, top and base heights of the cloud, and cloud thickness) were examined according to the cloud types that were objectively classified with their altitude, presence of precipitation, and vertical extents in vertical profiles of reflectivity. First, clouds were categorized into high, middle and low clouds based on height of cloud base. The low clouds were then divided into “rain” and “non-rain” based on presence of precipitation. The “rain” clouds were classified into deep and shallow clouds by their vertical extents. Preliminary analysis shows that the cloud occurrences of high and deep rain clouds are dominant in comparison with other cloud types during summer season (JJA). On the other hand, the occurrence of middle and low rain clouds are dominant during winter season (DJF).