Influence of cloud microphysical parameterization on the characteristics of monsoon depressions over the Indian region

Abstract

Indian summer monsoon (ISM) low‐pressure systems are considered as the lifeline for seasonal monsoon rainfall over the Indian region. However, the current models have limitations in predicting their characteristics and rainfall. This study assesses the influence of five cloud microphysical parameterization Schemes (MP) on simulations of 14 monsoon deep depressions (DD) using the weather research and forecasting (WRF) model. The simulations are carried out with a lead time up to 96 hr in a nested domain resolution of 27, 9, and 3 km. The five cloud microphysical parameterizations, that is, WRF Double moment (WDM6), WRF single moment (WSM6), Milbrandt (MIL), Thompson (THOM), and Aerosol Aware Thompson (AAT), are considered in this study, leading to a total of 70 simulations. The results are validated through composite analysis at a radial distance of 300 km from the respective storm centres. The choice of MP significantly impacts the key characteristics of the monsoon DDs such as rainfall, wind, temperature, moisture, humidity, hydrometeors, and associated convective processes. In terms of rainfall, it is found that WDM6 (AAT) has the best (worst) performance with a lead time up to day‐4. Besides, WDM6 has simulated the best result in terms of temperature and specific humidity. Examining the hydrometeors distribution around the storm intense convective region (i.e., 300 km), it is noted that frozen hydrometeors (i.e., ice, snow, and graupel) are mainly modulating the rainfall. There is a general tendency to overestimate snow and graupel among MP except WDM6. Further, ice hydrometeors are well represented in WDM6 compared with others leading to better rainfall forecast. The moisture flux convergence and absolute vorticity are two major mechanisms determining the convection within the storm's core zone, and WDM6 stands out the best among these schemes. The findings of this study are relevant and have direct consequences to the operational applications.

Simulating Moisture Transport Over the Tibetan Plateau in Summer of 2015 Across Scales With a Global Variable‐Resolution Model (MPAS‐A)

“…It usually has a warm core overlying the low-level cold core surrounded by strong wind aloft due to the strong latent heating in the troposphere from convective precipitation. Most of previous studies focused on the track and structure of the monsoon depression and its influence on the precipitation of South Asia (Baisya et al, 2017;Hazra & Pattnaik, 2021;Hunt & Fletcher, 2019;Hunt & Turner, 2017;Hunt et al, 2016;Johnson et al, 2016;Pattanaik et al, 2011;Potty et al, 2000), wherein the monsoon depression has been proved to be sensitive to model horizontal resolution, microphysical scheme, and convective parameterization etc. For example, Johnson et al (2016) investigated the simulated South Asian Monsoon at resolutions from 1.9°to 0.35°(approximately 200-40 km) and found that monsoon depressions strengthened precipitation over the northeastern India with increased resolution.…”

Simulating moisture transport over the Tibetan Plateau in Summer across hydrostatic to non-hydrostatic scales with a global variable-resolution model

“…It usually has a warm core overlying the low-level cold core surrounded by strong wind aloft due to the strong latent heating in the troposphere from convective precipitation. Most of previous studies focuses on the track and structure of the monsoon depression and its influence on the precipitation of South Asia (Baisya et al, 2017;Hazra & Pattnaik, 2021;Hunt et al, 2016;Hunt & Fletcher, 2019;Hunt & Turner, 2017;Pattanaik et al, 2011;Potty et al, 2000), wherein the monsoon depression has been proved to be sensitive to model horizontal resolution, microphysical scheme, and convective parameterization etc. So far, only minimal studies investigated the impacts of resolution across hydrostatic to non-hydrostatic scales on regional-scale systems, such as the monsoon depression system, and then on the moisture transport over the TP.…”

Role of cloud microphysics and energetics in regulating different phases of the monsoon low‐pressure systems over the Indian region

“…Using satellite data (tropical rainfall measuring mission [TRMM] precipitation radar), Stano et al (2002) performed a composite study and showed that stratiform rain was found to be aroused where the melting layers were located near 5 km from the surface; they were able to capture some more features of MD, for example, melting layer, melting layer, and so forth. Hazra and Pattnaik (2021) conducted a composite study using 14 deep depressions over the eastern India region. They found that the WRF double-moment scheme has a more significant edge in predicting the rainfall (compared with TRMM data) over other MP schemes.…”