Toward Understanding the Properties of High Ice Clouds at the Naqu Site on the Tibetan Plateau Using Ground-Based Active Remote Sensing Measurements Obtained during a Short Period in July 2014

Abstract

his study describes the microphysical properties of high ice clouds (with bases above 5 km) using ground-based millimeter cloud radar cirrus-mode observations over the Naqu site of the Tibetan Plateau (TP) during a short period from 6 to 31 July 2014. Empirical regression equations are applied for the cloud retrievals in which the parameters are given on the basis of a review of existing literature. The results show a unimodal distribution for the cloud ice effective radius re and ice water content with maximum frequencies around 36 ?m and 0.001 g m?3, respectively. Analysis shows that clouds with high ice re are more likely to occur at times from late afternoon until nighttime. The clouds with large (small) re mainly occur at low (high) heights and are likely orographic cumulus or stratocumulus (thin cirrus). Further analysis indicates that ice re decreases with increasing height and shows strong positive relationships between ice re (?m) and depth h (m), with a regression equation of re = 35.45 + 0.0023h + (1.7 ? 10?7)h2. A good relationship between ice re and temperature T (°C) is found, re = 44.65 + 0.1438T, which could serve as a baseline for retrieval of characteristic ice re properties over the TP.