P25 Climate sensitivity simulations of monsoon low-pressure systems over India

Sorland, Silje Lund, University of Bergen, Norway, Changhai Liu, Roy Rasmussen, National Center for Atmospheric Research, and Asgeir Sorteberg, University of Bergen, Norway

Monsoon low-pressure systems (LPS) are one of the most rain-bearing synoptic scale systems that develop during the Indian monsoon. This study investigates how sensitive the monsoon LPS is to a changing climate. The Weather Research and Forecasting (WRF) model is used for high-resolution climate sensitivity simulations, and the ERA-Interim reanalysis is used as the initial and boundary conditions. Several cases of monsoon LPS is used for the simulations, and for each case there is one unperturbed run (CTRL), and a perturbed run (PRT). The control run uses ERA-Interim as input without any changes. The method for generating the perturbed run is done in the same way as for the surrogate climate change simulations presented in previous studies. Then the sea surface temperature (SST), atmospheric temperature (on pressure levels) and soil temperature has been increased uniformly with a ΔT. This will lead to a new geopotential height distribution, but to make sure that there is no change in the geopotential gradients at the initial time, the surface pressure has been recalculated. Now the large-scale flow pattern at the boundaries for the CTRL and PRT will be similar, and the difference in the results will be due to the imposed warming.