Evaluating the Variability of Simulated Raindrop Size Distributions in the “21·7” Henan Extremely Heavy Rainfall Event

Abstract

Significant variability of raindrop size distributions (DSDs) has been observed in the “21·7” Henan extremely heavy rainfall event (the “21·7” Henan EHR event), while the capability of model to reproduce such complicated heavy rainfall DSDs is yet unclear. This study primarily evaluates the simulated DSDs of multiple microphysics schemes by comparing with the observations from a network of 50 disdrometers. Constrained DSD variability is identified in most schemes that the simulated raindrop mean sizes are gradually restricted around specific values as the growth of heavy rainfall intensity. The schemes are also incapable of reproducing the different raindrop mean sizes from deep convection and shallow convection. Moreover, simulations show unrealistic evolutions of raindrop mean size standard deviations as height declines. By investigating the empirical formula and performing sensitivity experiment, the constrained DSD variability in heavy rainfall is largely blamed on the insufficient parameterizations of the self‐collection (breakup) processes.

Raindrop Size Distributions Simulated Using a Bin Microphysics Scheme: Different Biases in Stratiform and Convective Rain From an Extratropical Cyclone

“…An interesting result is that in P2 when convective rain is largely involved, the standard deviations of D m and log 10 N w in the simulation are rather smaller than those in the observation, as opposed to P1. This result agrees with that of Chen et al (2023), who simulated a convective rainfall event and saw a lack of RSD variability in the simulation using a bin microphysics scheme compared to the observation.…”

“…Contrary to the simulated snow particle size distributions that showed some discrepancy with the aircraft observations, the simulated RSDs at the surface showed good agreement with the disdrometer observations. Chen et al (2023) evaluated the performances of different cloud microphysics schemes (five bulk microphysics schemes and one bin microphysics scheme) in reproducing the observed RSD variability in an extreme rainfall event that occurred in Henan Province, China. In their results, the simulation with the bin microphysics scheme best reproduced the observed RSD variability although the simulated RSD variability was still not large enough.…”

“…The evaluation of RSDs simulated using bin microphysics schemes has been mostly based on a few RSD parameters that are thought to successfully represent the whole RSD characteristics (e.g., Chen et al, 2023;Iguchi, Matsui, et al, 2012). This approach is not different from what has been used to evaluate the RSDs simulated using bulk microphysics schemes (e.g., Jin & Baik, 2023;Lin et al, 2022;Wang et al, 2020).…”

“…There have been some studies that evaluated the hydrometeor size distributions simulated using bin microphysics schemes (Chen et al, 2023;Fridlind et al, 2017;Hernández Pardo et al, 2021;Iguchi, Matsui, et al, 2012;Khairoutdinov & Kogan, 1999;Morrison et al, 2022;Shpund et al, 2019;Witte et al, 2019). Khairoutdinov and Kogan (1999) and Witte et al (2019) evaluated the simulated cloud drop size distributions in marine stratocumulus in comparison with aircraft observations and both found prominent discrepancies at the cloud boundaries.…”

“…The evaluation of raindrop size distribution (RSD) has been performed using ground-based disdrometers (Chen et al, 2023;Iguchi, Matsui, et al, 2012;Shpund et al, 2019). Iguchi, Matsui, et al (2012) evaluated the simulated RSDs in a rainfall event during MC3E.…”