An observational study on vertical raindrop size distributions during stratiform rain in a semiarid plateau climate zone

Abstract

Vertical raindrop size distributions of two stratiform rain events were measured with a Micro Rain Radar during summer 2009 at a semiarid continental site located in Xilinhot, China (43°38′N, 116°42′E). The sequential intensity filtering technique (SIFT) was used to minimize the effect of the spurious variability on disdrometric data to obtain the reflectivity-rain rate (Z-R) relationship (Z = aR b ). Compared with the least squares regression (LSR) method, SIFT led to a −5% to 4% change in the coefficient (a) and an 8%-15% increase in the exponent (b) of the Z-R relationship at 300 m. Rainfall estimation using the Z-R relationship with SIFT had lower standard deviation than that with LSR. The vertical variability of the mean rain rate, total raindrop numbers, and parameters (a and b) of the Z-R relationship was small below a melting layer, suggesting that using the radar reflectivity of weather radar to estimate stratiform rainfall is relatively accurate, at least in the Xilinhot area. 摘要

Raindrop Size Distribution Characteristics for Tropical Cyclones and Meiyu-Baiu Fronts Impacting Tokyo, Japan

“…The vertical variation in b for both the tropical cyclones and meiyu-baiu front was very similar. The vertical variability in the Z-R relationship has been reported in Australia [40], USA [23], China [20] and Indonesia [41]. For convective rainfall, the value of A decreased with increasing height, and the value of b increased in the studies [23,40], while the value of b decreased from 0.5 to 2.0 km in the study [41].…”

“…Tables 3 and 4 list the comparison of RSD features and Z-R relationships for the tropical cyclone and meiyu-baiu front rainfall measurements in different climate regions and using different equipment. For rainfall from the tropical cyclone, the mean Dm in Tokyo was 1.25 mm (Table 3), which is larger than that in East China (1.13 mm) and lower than that in the Atlantic tropical cyclones (1.67 mm), indicating that The vertical variability in the Z-R relationship has been reported in Australia [40], USA [23], China [20] and Indonesia [41]. For convective rainfall, the value of A decreased with increasing height, and the value of b increased in the studies [23,40], while the value of b decreased from 0.5 to 2.0 km in the study [41].…”

“…For convective rainfall, the value of A decreased with increasing height, and the value of b increased in the studies [23,40], while the value of b decreased from 0.5 to 2.0 km in the study [41]. For stratiform rainfall, the vertical variability in the Z-R relationship was small, including A and b below the bright band [20,40]. Considering the more convective characteristics of the three rain types in this study, our result was similar to the study of Marzuki et al [41], but different from other studies, suggesting that considerable variations in the Z-R relationship exist worldwide.…”

“…The RSD varies not only among climate regions and rainfall types but also with height. Most studies have only observed RSD variability using ground measurements [4,19] or only measured the vertical profile of RSDs using vertically pointing Doppler radar with remote sensing methods [20][21][22]. Much of the RSD equipment assumes that there is zero vertical wind.…”

The Analysis of FSO Link Performance in Ulaanbaatar

“…For the Japanese model, measurements were made at a rain rate of 80-90 mm/h. The researchers noted that using droplet distributions established in other countries could lead to prediction errors when applied to tropical regions [13]. According to the research, it was considered more appropriate to use Marshall Palmer's distribution model in the city of Ulaanbaatar, which has a temperate (arid) region.…”