Assessment of the Indian summer monsoon in the WRF regional climate model

Abstract

followed by a low-level dry (moist) anomaly. The model is inadequately representing the temporal evolution of vertical moist and thermodynamic processes. The evolution of vertical structures of temperature and WVMR is better simulated in the break phase compared to that of active phase. The evolution of cyclonic vorticity in the model is different from the observations during the convective phase. In short the model has limitations in representing convectively unstable regimes. It is anticipated that these findings will significantly contribute to the regional climate model assessment programs.

Evaluation of the impact of AIRS profiles on prediction of Indian summer monsoon using WRF variational data assimilation system

“…On the other hand, CTRL fails to produce such northward extension. Previous studies have suggested that an easterly vertical wind shear in the zonal mean wind is a critical factor in promoting the northward propagation of intraseasonal oscillations [e.g., Kemball-Cook et al, 2002;Raju et al, 2015a]. This supports the substantial improvement in the large-scale dynamics in ConvAIRS.…”

“…Analysis shows that LLJ in the CTRL is shifted southward in the model (shear is inclined toward south), which is consistent with Raju et al [2015a], concluded inherent problem of improper thermal gradient in the WRF model leading to this type of bias in LLJ. On the other hand, ConvAIRS shows proper location of easterly shear, which indicates the improvement in the meridional temperature gradient leads to improvement in the representation of easterly shear as a consequence of assimilation of AIRS thermodynamic profiles.…”

“…The AIRS satellite data have provided temperature and moisture profile under clear-sky condition at higher resolution. Hence, assimilation of these data has provided improvement in the spatial distribution of temperature Raju et al [2015a] brought out inherent limitations of regional WRF model in simulating ISM such as improper meridional gradient of temperature, leading to circulation bias (low-level jet (LLJ) and tropical easterly jet) and restriction of northward extension of maximum precipitation band. The temporal evolution of soil temperature, soil moisture, tropospheric temperature gradient, and circulation index is carried out (Figure 10) to understand the possible causes and the feedback mechanisms for the improved monsoon character in ConvAIRS.…”

“…The time-split integration uses a third-order Runge-Kutta scheme with smaller time step for acoustic and gravity wave modes. The model setup in this study is similar to earlier studies by Raju et al [2015aRaju et al [ , 2015b. The WRF physics options used in this study consisted of the Purdue Lin [Chen and Sun, 2002] scheme for microphysics, Betts-Miller-Janjic [Janjic, 1994] for convective parameterization, and the Yonsei University planetary boundary layer scheme [Noh et al, 2003].…”

Simulation of the Indian summer monsoon onset-phase rainfall using a regional model

“…Application of RCMs have been proposed for better simulation of the ISM and its seasonal rainfall patterns (Bhaskaran et al, 1996) as they can effectively represent regional orography and sub-grid-scale physical processes. In recent studies, the Advanced Research Weather Research and Forecasting (ARW) regional model has been used to simulate the ISM and its rainfall climatology (Hari Prasad et al, 2011;Mukhopadhyay et al, 2010;Srinivas et al, 2014;Raju et al, 2013Raju et al, , 2014. Srinivas et al (2012) made seasonal-scale simulations of the ISM regional climate with ARW for the decade 2000-2009 and reported that the model reproduces the interannual variations in monsoon characteristics in terms of the pressure, temperature, winds and rainfall associated with ENSO phases and that the simulated monsoon rainfall is sensitive to the convective parameterization.…”