Uncertainty Analysis of IDF Curves Simulation under Climate Change Scenarios Using a Weather Generator Model (Case Study: Tehran)

The main objective of this research is evaluating IDF curves variation in the future using the observed rainfall and the forecasted one by PRECIS, while focused on yielding the uncertainties of the forecast via employing the K-NN WG model under two historical and wet scenarios. The historical climate change scenario and the B2 emission scenario were used to generate the lower and upper-reliability bounds of the forecast, respectively. By applying the shuffling and perturbation mechanisms, those random data, which are not recorded in the observing period but will be probably happened in the future, were generated and the results were employed for developing the IDF curves of 2, 5, 10, 20, 50, and 100-year return periods. Comparing the two climate change scenarios and the base period IDFs reveal the increase in the intensity of the extreme short-duration rainfalls. Moreover, it was found that the maximum amount of rainfall for the duration of 10 minutes to 3 hours on average would have a difference of 26 to 31 percent under the historical and wet scenarios concerning the base period, respectively. This difference between the historical and wet scenario is limited to 4.8%. The small difference between the historical scenario, as the lower bound, and the wet one, as the upper bound of the probable storms in the future, firstly shows the accuracy of PRECIS in simulating rainfall in the study region; secondly, it shows the certain increase in the intensity of the design storms which matter in urban flood management.