Unveiling precipitation and its concentration over Himachal Pradesh, India

Recently, precipitation concentration studies have gained much attention from geoscientists as they assist them in the recognition of rainfall heterogeneity (irregularity) and extreme events (flood, drought, etc.) over space and time, particularly in mountainous regions. Therefore, this study has attempted to explore the precipitation and its concentration over the north-western Himalayan state of Himachal Pradesh, India, from 1951 to 2020. For this, gridded rainfall data (0.25° × 0.25°) have been obtained from the India Meteorological Department (IMD), Pune, and daily and monthly concentrations have been assessed using concentration index (CI) and precipitation concentration index (PCI), respectively. The results have revealed a noticeable decrease in annual and monsoon precipitation amount, while a significant increase has been recorded in summer. Annually, the daily precipitation (CI) has been found highly concentrated at lower elevations and vice versa. Amongst the seasons, the monsoon season has recorded the lowest daily concentration (CI = 0.55) with a statistically significant increasing trend; however, the highest concentration (CI = 0.76) has been detected during the post-monsoon season but without a trend. Likewise, monthly concentration (PCI) has been found minimum during monsoon season (PCI = 9.7) with a significant positive trend, whereas its maximum value (PCI = 17.1) has been witnessed during summer with a noteworthy declining trend. The trends of CI and PCI indicate towards imminent chances of extreme precipitation events, especially during monsoon season. Finally, the results of this study will help risk reduction managers and policymakers in developing efficient flood and drought mitigation strategies over the Himalayan region.