Investigation of Liquid Cloud Microphysical Properties of Deep Convective Systems: 2. Parameterization of Raindrop Size Distribution and its Application for Convective Rain Estimation

Abstract

The liquid cloud microphysical properties for stratiform rain (SR) have been investigated in Part 1 of this series. Since convective rain (CR) has characteristics in raindrop size distribution (DSD) and precipitation that are distinct from SR, we investigate the CR properties in this study by using 20 hr of CR samples collected by 17 Automatic Parsivel Units disdrometers during the Midlatitude Continental Convective Clouds Experiment over the Atmospheric Radiation Measurement Southern Great Plains site. A full spectrum of DSD is constructed based on a total of 23 size channels (0.321 to 9.785 mm), and both Gamma and Exponential fitted functions are applied to extract the DSD shape parameters. Compared to SR properties, CR has distinct features including broader size range and narrower exponential slope parameter (λ E ). These results indicate that the assumption of constant exponential intercept parameter (N 0E ) is inappropriate for CR rain rate estimates. Additionally, the subsetting scheme of the CR DSD spectra also has a strong impact on the Gamma/Exponential functions. Therefore, a new CR DSD parameterization scheme is developed by choosing the appropriate spectra subset with the constraint of rain rate and using the constant λ E instead of constant N 0E . With the input of the radar reflectivity at the lowest observed height, the newly calculated CR rain rates match well with the collocated surface rain gauge measurements (127 Mesonet stations and 17 Automatic Parsivel Units), while the rain rates calculated using traditional Z-R relationship are 3-4 times larger, indicating that constant λ E is a better assumption for CR DSD. Figure 7. (a) Comparison of the μ Γ -λ Γ relationships between three different subsets of spectrum from this study and from Cao et al. (2008). (b) Probability distributions of μ Γ from the subsetting scheme of channel 14 and Gaussian.

Using radar observations to evaluate 3-D radar echo structure simulated by the Energy Exascale Earth System Model (E3SM) version 1

“…As shown in previous studies (e.g., Wang et al, 2015Wang et al, , 2016Wang et al, , 2018Feng et al, 2012Feng et al, , 2019, the minimum reflectivity of the 3-D mosaic NEXRAD dataset is 0 dBZ (Fig. 2a).…”

Statistical Characteristics of Raindrop Size Distributions and Parameters in Central China During the Meiyu Seasons

“…The surface DSD measurements could be described by the three‐parameter gamma distribution (Brandes et al, 2004; J. Wang et al, 2015; Kozu & Nakamura, 1991; Smith, 2003; Ulbrich, 1983; J. Wang, Dong, & Xi, 2018; Zhang et al, 2001). The mathematical form of the gamma distribution is as follows: where D (mm) is the volume equivalent diameter of a raindrop and N ( D ) (m −3 mm −1 ) is the number concentration of raindrops at volume equivalent diameter D per unit diameter range.…”

Understanding Ice Cloud‐Precipitation Properties of Three Modes of Mesoscale Convective Systems During PECAN

“…Considering the possible mismatches between the CSA classification and radar‐derived precipitation due to surface wind, the grid boxes that were classified as SR but had PRs greater than 10 mm/hr have been excluded from the analysis for SR. The 10‐mm/hr threshold is often used to discriminate convective precipitation (Han et al, ; Leary & Houze, ; Penide et al, ; Wang et al, ), and previous studies have found that less than 3% of rain rates classified as stratiform are above the 10‐mm/hr threshold (Wang et al, ). The total precipitation amount of pixels having rain rates greater than 10 mm/hr account for less than 8% of the total stratiform precipitation amount in our analysis.…”