Systematic errors in the WRF model planetary boundary layer schemes for two contrasting monsoon seasons over the state of Odisha and its neighborhood region

Abstract

This study evaluates the characteristics of systematic errors (up to day 4) in the planetary boundary layer (PBL) parameterization schemes over the state of Odisha and its neighboring regions for two contrasting monsoon seasons, i.e., 2013 (normal) and 2014 (deficit), using the Weather Research and Forecasting (WRF) model. A total of 1112 numerical experiments are carried out, each with initial conditions from May 28 to September 29 using four PBL schemes, i.e., Yonsei University (YSU), Mellor-Yamada-Nakanishi-Niino (MYNN), Asymmetric Convective Model version 2 (ACM2), and Medium Range Forecast (MRF) with horizontal resolutions of 27 and 9 km with a lead time up to 96 h. It is found that the PBL parameterizations significantly impact the basic atmospheric variables (i.e., wind, temperature, moisture, and rainfall) and associated convective processes such as moist static energy. The wind and rainfall forecast skill of MRF showed better agreement with European Re-Analysis (ERAI). However, YSU has better skills for 2-m temperature and specific humidity compared to others. All PBL schemes produced a moist bias at the surface except MRF. The principle cause of this moist bias with mid tropospheric warming is attributed to inherent tendency of the model to overestimate moist static energy leading to intense vertical motion and convective instability. The magnitude of errors for wind forecast is higher for the deficit year compared to the normal monsoon year. However, the strength of the cross equatorial flow is found to be weaker in all the experiments for both the seasons. In general, the spread and magnitude of errors are large for 2013 (normal) as compared to 2014 (deficit) year. � 2019, Springer-Verlag GmbH Austria, part of Springer Nature.