Climate change impact assessment on maxima daily snowfalls, case study: Tehran

One of the most important impacts of climate change is the change of snowfall regime, especially extreme snowfalls in the future. Extreme snowfalls will be affected by increasing in extreme rainfalls and temperature oppositely in the future climate while the trend of changes is not clear. In this paper, climate change impact on extreme daily rainfalls in the Mehrabad station of Tehran is assessed. Future daily precipitation and temperature projections of the CGCM3 model under B1, A2, and A1B emission scenarios are downscaled using IWG stochastic model. Snowfall is simulated using temperature threshold criteria, and climate change impact is assessed on snowfall in 2036-65 period. Results of the validation tests showed that the IWG model have reproduced a broad range of the temperature and precipitation statistics. Also, snowfall statistics specially the annual maximum daily snowfall distribution are well reproduced. The climate change impact assessment results showed that under various emission scenarios, despite increasing in extreme precipitation in the future in the Tehran Mehrabad station, annual maxima daily snowfalls would greatly decrease. So that, maximum daily snowfall with return period of two years would decrease more than 50% under all considered scenarios.