Investigating the relationship between climate Teleconnection Indices and Autumnal Rainfall in Iran Watersheds

Seasonal and annual precipitation variations are subject to numerous natural and climatic factors such as climate teleconnection indices (CTIs). The purpose of this study is to investigate the correlation between CTIs and autumnal precipitation in 30 catchments of Iran. For this purpose, autumnal precipitation data were selected from 717 synoptic, climatological and rain gauge stations over a 28-year (1988–2015) climate period, and their correlation with eight CTIs including SOI, MEI, NAO, AO, NCP, C-SST, M-SST, and P-SST were obtained in eight-time lags. Finally, their correlation significance were investigated and analyzed. The results showed a significant positive correlation between the MEI (29.1% to 43.3% of the western, southern, eastern and northeast watershed stations) and the NAO (29.4% of the northwest basin stations), While the SOI (23.3-53.7 stations of the western, southern, eastern and northeast watersheds) and C-SST (23.3 of the southeast watershed stations) had significant negative correlation. In terms of the time step, it was found that the Oct-MEI (43.3% of the stations had a positive correlation) and Aug-SOI (53.7% of the stations had a negative correlation) had a significant correlation with most of the studied stations. From the watershed point of view, it was found that the frequency of significant correlations in different catchments varied between 10.9 and 36%. The results of this study show that about 10 watersheds have a significant correlation with more than 30% of CTIs which changes in each watershed. Consequently, the CTIs with different time steps can be used as predictor variables for autumn precipitation in Iran watersheds.