Dominant large-scale parameters responsible for diverse extreme rainfall events over vulnerable Odisha state in India

Abstract

The exorable climate changes leads to changes in the frequency and intensity of extreme rainfall events worldwide; however, the amendment in extreme rainfall events is not uniform over space, precisely it is more localized and a great threat to the society. Thus, study of rainfall extremes at a finer spatial scale is essential and identifying the large-scale parameters that are responsible factors is highly needed. Odisha state in India is one of the most vulnerable to weather extremes and considered as a study region. The present study is bi-fold, firstly examining the changes in the extreme rainfall (≥ 204.5 mm/day) over Odisha and exploring the foremost large-scale meteorological parameters responsible for heterogeneous characteristics of extreme rainfall within Odisha during 1980–2017 summer monsoon period. India Meteorological Department gridded high-resolution (0.25° × 0.25°) rainfall analysis and ERA-Interim (0.25° × 0.25°) reanalysis data at daily scale are used for the analysis. The study region has an increasing trend in extreme rainfall events and it is evident that the Indian Ocean is warmer during extreme rainfall events compared to the dry events, particularly near the seashore of Odisha. The stronger (weak) and cyclonic (anti-cyclonic) flows at 850-hPa exhibit during extreme rainfall (dry) events. The moisture flux is convergent during extreme rainfall events, while it is reverse during dry events. The monsoon trough has been shifted to south (north) from its normal position during extreme rainfall (dry) events. A detailed investigation is carried out for extreme rainfall events over five different regions in Odisha. It reveals that the wind at 850 hPa, omega at 500 hPa, and SST play the important role for Region I, while OLR and omega at 500 hPa are dominating for the Region IV in the occurrence of extreme rainfall. Moreover, the role of the dominant climatic parameters for the extreme rainfall occurrence varies for the other three regions. Analysis confirms that the role of main meteorological parameters is statistically significant for the extreme rainfall events over the respective region. Although the Odisha is a small state in India, not only the long-term trend in extreme rainfall varies region-to-region but also responsible factors associated with the climatic conditions differ for the occurrence of the extreme rainfall.