Results 1 
3 of
3
Analyzing the relationship between terminal velocity of raindrops and VHF backscatter from precipitation
 TAO
"... The exponential relationship between α and β in the expression V PT = α β was first found empirically by Chu et al. (1999), where VT is the mean Doppler velocity of the rain drop with respect to still air, and P is the rangecorrected VHF radar backscatter from precipitation. However, they did not p ..."
Abstract

Cited by 2 (1 self)
 Add to MetaCart
(Show Context)
The exponential relationship between α and β in the expression V PT = α β was first found empirically by Chu et al. (1999), where VT is the mean Doppler velocity of the rain drop with respect to still air, and P is the rangecorrected VHF radar backscatter from precipitation. However, they did not provide a theoretical explanation for this relationship. In this article, we will show theoretically that the mathematical relationship between α and β is indeed in an exponential form, namely, α ξβ = −Aexp ( ) , where A is the coefficient in the relation V ADB = , D is the diameter of the rain drop, and ξ is a factor related to radar parameters and precipitation intensity. An examination of this exponential relationship between α and β shows that the radar experimental result was in excellent agreement with the theoretical prediction. From the observational results made with the ChungLi VHF radar, we find that the value of β varied in the range 0.02 0.14, which is significantly different from the theoretical value of 0.07143. In addition, the β value is found to be positively correlated with the vertical air velocity, which is variable in nature. We, therefore, presume that the vertical air velocity seems to play a crucial factor in governing the change in the β value to explain the large scatter of the observed β values. The application of ξ value to the estimation of the precipitation intensity is also discussed in the text. (Key words: VHF radar, Drop size distribution, Terminal velocity)
Analysis of Terminal Velocity and VHF Backscatter of Precipitation Particles Using ChungLi VHF Radar Combined with GroundBased Disdrometer
, 2006
"... The backscatter from precipitation particles observed by the vertically pointed antenna beam of the ChungLi VHF radar and the drop size distributions measured by a groundbased disdrometer colocated at the radar site are analyzed and studied in this article. We find that the disdrometermeasured ..."
Abstract
 Add to MetaCart
(Show Context)
The backscatter from precipitation particles observed by the vertically pointed antenna beam of the ChungLi VHF radar and the drop size distributions measured by a groundbased disdrometer colocated at the radar site are analyzed and studied in this article. We find that the disdrometermeasured drop size distribution can be well approximated to a Gamma distribution. On the basis of this property and a power law approximation to the fallspeeddiameter relation VD = AD B, we derive the theoretical relation between terminal velocity VD and rangecorrected VHF backscatter P of the precipitation particles. We find that the VD P relation follows a power law in the form of VD = α β P, where α and β are both the functions of the precipitation parameters. Chu et al. (1999) first found that the relation between α and β can be empirically approximated to an exponential
Negative correlation between terminal velocity and VHF radar reflectivity: observation and plausible explanation
"... Abstract. The correlation between precipitation backscatter P (or radar reflectivity Z) and reflectivityweighted terminal velocity Vt has long been thought to be positive. Namely, the larger the magnitude of the terminal velocity is, the stronger the radar reflectivity will be, and vice versa. Howe ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract. The correlation between precipitation backscatter P (or radar reflectivity Z) and reflectivityweighted terminal velocity Vt has long been thought to be positive. Namely, the larger the magnitude of the terminal velocity is, the stronger the radar reflectivity will be, and vice versa. However, we will show in this article the observational evidences of negative Vt–P correlation made with the ChungLi VHF radar. It is found that the negative Vt–P correlation can occur in the regions from close to ground to well above the melting layer. In addition, there is a strong tendency for the negative Vt–P correlation to occur around the bright band region. In light of the fact that the conventional model of single drop size distribution cannot explain this negative correlation, it is proposed that the drop size distribution responsible for the negative Vt–Z correlation is composed of two Gamma drop