Increasing heavy rainfall events in south India due to changing land use and land cover
Through an analysis of land use and land cover (LULC) data for the years 2005 and 2017 from the Advanced Wide Field Sensor onboard the Indian Remote Sensing satellite, we find considerable changes in the LULC in three major states of south India, namely, Tamil Nadu, Telangana and Kerala. This change...
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Veröffentlicht in: | Quarterly journal of the Royal Meteorological Society 2020-10, Vol.146 (732), p.3064-3085 |
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Zusammenfassung: | Through an analysis of land use and land cover (LULC) data for the years 2005 and 2017 from the Advanced Wide Field Sensor onboard the Indian Remote Sensing satellite, we find considerable changes in the LULC in three major states of south India, namely, Tamil Nadu, Telangana and Kerala. This change is mainly due to increasing urbanization, in addition to the change of prevalent mixed forest into deciduous needle/leaf forest in Kerala. Motivated by this finding, we study the impact of these LULC changes over a decade on the extremes of twelve heavy rainfall events in these states through several sensitivity experiments with a convection‐permitting Weather Research and Forecasting model, by changing the LULC boundary conditions. We particularly focus on three representative heavy rainfall events, specifically, over (a) Chennai (1 December 2015), (b) Telangana (24 September 2016), and (c) Kerala (15 August 2018). The simulated rainfall patterns of the three heavy rainfall events are found to be relatively better with the use of the 2017 LULC boundary conditions. The improvement is statistically significant in the case of the Chennai and Kerala events. On analysis of these simulations, and output from additional simulations we have conducted for nine other heavy rainfall events, we suggest that the recent LULC changes result in higher surface temperatures and sensible heat fluxes, and a deeper and moist boundary layer. This causes a relatively higher convective available potential energy and, consequently, heavier rainfall. We find the LULC changes in the three states, mainly dominated by the increasing urbanization in Telangana and Tamil Nadu, enhance the rainfall during the heavy rainfall events by 20–25%. This is the first extensive investigation of multiple and multi‐regional cases over the Indian region.
We find that heavy rainfall events are increasing in three major south Indian states: Telangana, Tamil Nadu and Kerala. Increasing urbanization is contributing by 20–25% to extremes of rainfall events during the monsoon, as demonstrated through our simulation and Land Use Land Cover change sensitivity experiments for twelve events with a convection‐resolving high‐resolution regional weather model. The following figure shows, as an example, the Chennai event from three observations (top panel), and the simulations with different LULCs. |
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ISSN: | 0035-9009 1477-870X |
DOI: | 10.1002/qj.3826 |