Sensitivity study on the role of Western Ghats in simulating the Asian summer monsoon characteristics
- 340 Downloads
The Advanced Research Weather Research and Forecasting (AR-WRF) model is used to study the influence of Western Ghats situated along the west cost of peninsular India in the mean characteristics of the Asian summer monsoon (ASM) through numerical simulations. A control simulation (CTRL) is carried out using 11-year (2000–2010) mean initial and lateral boundary conditions from the ERA-Interim reanalysis to simulate the mean atmospheric features of the ASM. The Modern-Era retrospective analysis for research and applications (MERRA) data along with the Tropical Rainfall Measuring Mission (TRMM, 3B42 daily rainfall) data are used to validate the CTRL simulation. The simulated dynamical features and precipitation characteristics during the ASM period agree well with the MERRA reanalysis and TRMM observations. In order to examine the role of Western Ghats on the mean characteristics of the ASM, a sensitivity simulation (NoWG) is carried out with orography reduced to surface over a domain bound between 5°–28°N and 72°–90°E, keeping all other conditions unchanged. This sensitivity analysis showed an enhancement in the low level monsoon flow over the Indian Ocean and peninsular India in the absence of Western Ghats. The prominent up-draft over the west coast of peninsular India observed in the CTRL simulation also decrease in the absence of Western Ghats. The simulated rainfall show a considerable decrease over the west coast and an enhancement over the east coast of peninsular India in the absence of Western Ghats. These simulations clearly depict the importance of Western Ghats in the circulation dynamics and rainfall features during the ASM period.
KeywordsAsian summer monsoon Orography Regional climate model
Global Modeling and Assimilation Office (GMAO) and the GES DISC for the dissemination of MERRA data. The ECMWF data portal for obtaining ERA-Interim data. The authors are thankful to the Editor and anonymous reviewers for their constructive comments.
- Chakraborty A, Nanjundiah RS, Srinivasan J (2002) Role of Asian and African orography in Indian summer monsoon. Geophys Res Lett 29(20). doi: 10.1029/2002GL015522
- Chakraborty A, Nanjundiah RS, Srinivasan J (2008) Impact of African orography and the Indian summer monsoon on the low-level Somali jet. Int J Climatol. doi: 10.1002/joc.1720
- Dee DP et al. (2011) The era-interim reanalysis: configuration and performance of the data assimilation system. Q J R Meteorol Soc 137(656):553–597Google Scholar
- Flohn H (1964) Investigations on the tropical easterly jet. Bonn Meteor Abh 4:1–83Google Scholar
- Mukhopadhyay P, Taraphdar S, Goswami BN, Kumar KK (2010) Indian summer monsoon precipitation climatology in a high resolution regional climate model: impact of convective parameterization on systematic biases. Weather Forecast 25:369–387Google Scholar
- NCL-Software (2012) The NCAR Command Language (Version 6.0.0) [Software] Boulder, Colorado, UCAR/NCAR/CISL/VETS, http://dx.doi.org/10.5065/D6WD3XH5
- Rienecker MM, Coauthors (2011) MERRA: NASA’s Modern-Era retrospective analysis for research and applications. J Clim 24:3624–3648Google Scholar
- Skamarock WC, Klemp JB, Dudhia J, Gill DO, Barker DM, Wang W, Powers JG (2005) A description of the Advanced Research WRF version 2. In: Technical report, National Centre for Atmospheric Research, Boulder, COGoogle Scholar
- Webster PJ, Magana VO, Palmer TN, Shukla J, Tomas RA, Yania M, Yasunari T (1998) Monsoons: processes, predictability, and the prospects for prediction. J Geophys Res 103 (no C7):14,451–14,510Google Scholar
- Yanai M, Li CF, Song ZS (1992) Seasonal heating of the Tibetan Plateau and its effects on the evolution of the Asian summer monsoon. J Meteorol Soc Jpn 70:319–351Google Scholar