Construction of rainfall change scenarios over the Chilka Lagoon in India

- Rainfall change scenarios over Chilka Lagoon of India using multiple observational data and CMIP5 GCMs during 1901-2004
- 17-40% enhanced rainfall in the monsoon while 30-42% of deficit in the pre-monsoon over Chilka at the end of 21st century
- Downscaled rainfall indicates a wide range of future scenarios (111.3 to 373.4 mm/95 year) compared to without downscaling.

The present study attempted to quantify long-term seasonal and annual rainfall change for the period 1901-2004 over the Chilka Lagoon in India, the second largest lagoon in the world using multiple gridded data sources. The future rainfall projection is also constructed using the four Representative Concentration Pathways (RCPs) of the Global Circulation Models (GCMs) of the Coupled Model Intercomparison Project phase 5 (CMIP5). Skill of GCMs to simulate the observed rainfall over the lagoon was investigated through estimation of long-term trends and comparison of mean seasonal cycles using Taylor diagram. Finally based on the combined results obtained through trend analysis as well as seasonal cycles, 12 better performing GCMs were selected. Ensemble mean of better performing GCMs reveal that the rainfall in annual, monsoon and winter seasons have increased in the last century similar to three observational gridded data sources. The projected seasonal cycle of rainfall from different RCPs shows a dipole like characteristics where the drier (winter) and moist (monsoon) seasons show a surplus of rainfall (11-25%) while the premonsoon and the postmonsoon seasons show a deficient rainfall (3-52%) at the end of 21st century. It is interesting to note that the Chilka Lake will expected to receive an increasing amount of annual rainfall by 3-7% in 2020s, 7-11% in 2050s and 10-21% in 2080s. Ensemble mean of future downscaled scenarios revealed that the annual rainfall will increase slightly higher rate as compared to without downscaling indicating high uncertainty in future projection.