Sensitivity of precipitation in the Karakoram to physics parameterization options in WRF

Abstract

Pakistan is one of the most vulnerable countries to climate change due to its large exposure and lack of adaptive capacity. In particular, climate models project an increase in heavy precipitation and flood intensity or frequency in the area. However, some uncertainties remain, which are in part related to its complex orography interacting with local dynamics, mainly in the Karakoram region. As a consequence, convection-permitting high-resolution simulations are needed. These allow for a better representation of steep orography and resolve deep convection, improving the simulation of precipitation. This requires the evaluation of the performance of different physics parameterization options at high-resolution in order to improve these models. This work evaluates the performance of different parameterization schemes in theWeather Research and Forecasting (WRF) model in simulating the extreme precipitation events that occurred in Pakistan in August 2022. This extreme precipitation led to disastrous flooding that resulted in numerous deaths, displaced people and loss of infrastructure and crop production. It was caused by westward propagating cyclones interacting with hot, moist air advected from the Arabian sea, which was promoted by climate change. Results show differences in the spatial distribution and intensity of precipitation, and are most sensitive to the microphysics parametrizations. In particular, the Thompson microphysics scheme produced the best results with respect to observations. However, some biases remain, specially in the representation of the intensity of the troughs and ridges over the high-mountain region, which future research will try to address.