Behavior of predicted convective clouds and precipitation in the high‐resolution Unified Model over the Indian summer monsoon region

Abstract

National Centre for Medium Range Weather Forecasting high-resolution regional convective-scale Unified Model with latest tropical science settings is used to evaluate vertical structure of cloud and precipitation over two prominent monsoon regions: Western Ghats (WG) and Monsoon Core Zone (MCZ). Model radar reflectivity generated using Cloud Feedback Model Intercomparison Project Observation Simulator Package along with CloudSat profiling radar reflectivity is sampled for an active synoptic situation based on a new method using Budyko's index of turbulence (BT). Regime classification based on BT-precipitation relationship is more predominant during the active monsoon period when convective-scale model's resolution increases from 4 km to 1.5 km. Model predicted precipitation and vertical distribution of hydrometeors are found to be generally in agreement with Global Precipitation Measurement products and BT-based CloudSat observation, respectively. Frequency of occurrence of radar reflectivity from model implies that the low-level clouds below freezing level is underestimated compared to the observations over both regions. In addition, high-level clouds in the model predictions are much lesser over WG than MCZ.

Forecasting the monsoon on daily to seasonal time‐scales in support of a field campaign

“…ISRO LuLc gives recent and updated information about the vegetative and nonvegetative model tiles for the India region. Further details of NCMRWF 1.5-km and NCMRWF 4-km configurations, and the benefits they provide for rainfall prediction over India, are given in Jayakumar et al (2017) and Mamgain et al (2018), respectively.…”

Performance of the NCMRWF convection‐permitting model during contrasting monsoon phases of the 2016 INCOMPASS field campaign

“…The high‐resolution NCMRWF version of the regional Unified Model (UM) (hereafter NCUM‐R: Jayakumar et al ., ) was used over a domain covering the eastern portion of the monsoon core zone with a horizontal grid length of 1.5 km over a domain of 1,000 × 1,000 grid boxes; in the vertical there are 80 levels with the model top at 38.5 km and 14 levels below 1 km; the model domain is illustrated by a green box in Figure b,c. The time step for NCUM‐R is 60 s.…”

“…Local to India, Jayakumar et al . () recently used the regional model version of the National Centre for Medium Range Weather Forecasting (NCMRWF) Unified Model (hereafter NCUM‐R) for verifying the occurrence of hydrometeors during active periods of the monsoon using CloudSat satellite data. Verification of the short‐range predictability of hydrometeor amounts and their distribution using CloudSat profiles is limited in accuracy, hence detailed measurement of cloud conditions from flight measurements, as will be used here, is one of the key tools for assessing model fidelity.…”

An operational fog prediction system for Delhi using the 330 m Unified Model

“…A regional model configuration of the Unified Model (NCUM-R, Jayakumar et al, 2017) was used to setup the model over a domain covering the Delhi region at a horizontal grid length of 1.5 km. The initial and lateral boundary conditions are derived from the current operational 17-km grid length NCUM global model (Rakhi, Jayakumar, Sreevathsa, & Rajagopal, 2016).…”

“…Critical relative humidity (RH) for the DM is higher than NCUM-R (Table S1 in Appendix S1, Supporting information) following the approach used in the London Model (Boutle et al, 2016), to simulate less sub-grid cloud cover variability in higher resolution models with respect to the coarse resolution model. The sub-grid turbulence scheme used here is the blended scheme (Boutle, Eyre, & Lock, 2014), which dynamically combines the one-dimensional (1D) boundary-layer scheme of Lock, Brown, Bush, Martin, and Smith (2000) with a 3D Smagorinsky scheme using a mixing factor of 0.5. The model time step of the DM is 12 s, and it uses 80 vertical levels with model top at 38.5 km, and 14 model levels below 1 km.…”