Daily Precipitation Extremes in Iran: Decadal Anomalies and Possible Drivers

Abstract

This study focuses on the empirical statistical analysis of the anomalies in daily precipitation extremes by applying the quantile perturbation method (QPM) to data from 31 Iranian weather stations during the period between 1961 and 2005. The possible causes behind the anomalies in precipitation extremes are identified by analyzing their relationship with the anomalies in eight atmospheric indices (i.e., NAO, SOI, PDO, AMO, NCP, DMI, WeMO, SSN). In terms of decadal oscillations, the country was generally wet in the 1960s and 1970s with most stations exhibiting periods of higher quantile perturbations, whereas lower quantile perturbations were dominant in the 1980s and 1990s. The highest perturbation in extreme precipitation quantiles prevails in Central Iran during the early 1980s, in which the quantiles are about 50% higher than the ones based on the full time series. The frequency of significant precipitation anomalies for winter season was greater than that for spring and autumn seasons. For the summer season, the humid region in North Iran demonstrates strong positive anomalies. The results highlight the noticeable role of large‐scale climatic factors in the anomalous behavior of precipitation extremes in Iran. The atmospheric drivers of the quantile anomalies in extreme precipitation were found to differ from one season to another.

Temporal and spatial variability of extreme river flow quantiles in the Upper Vistula River basin, Poland

“…Similarity with results of Tabari and Willems () for anomalies of daily precipitation extremes in Iran is also visible in periods of positive anomalies in the 1970s. Dissimilarity is apparent in the negative anomalies that are observed in the 1990s–2000s in Tabari and Willems () and only in the 1990s for most catchments in the UVB.…”

“…Nyeko-Ogiramoi, Willems, and Ngirane-Katashaya (2013) studied extreme anomalies in rainfall, temperature, and streamflows for selected stations in the Lake Victoria basin. Onyutha and Willems (2015) detected spatial and temporal variability of seasonal and annual rainfall totals in the Nile Basin, and Tabari and Willems (2016) identified periods of high and low perturbations of precipitation extremes for various seasons in Iran. The QPM is similar to the frequency-perturbation approach applied in climate change scenarios.…”

Local impact analysis of climate change on precipitation extremes: are high-resolution climate models needed for realistic simulations?

“…For the future climate analysis, the climate change signals are obtained as relative changes in precipitation intensities calculated as the ratios of precipitation quantiles derived from each climate model scenario simulation over those from the corresponding climate model control simulation with the same nonexceedance probability or return period. This methodology has been applied in several recent climate change studies, e.g., on the basis of statistical downscaling applying quantile mapping or quantile perturbations (Willems and Vrac, 2011;Gudmundsson et al, 2012;Maraun, 2013;Ntegeka et al, 2014;Rana et al, 2014;Sunyer et al, 2015) and also a similar procedure for analyzing the decadal precipitation anomaly (Tabari et al, 2014;Tabari and Willems, 2016). For sub-daily precipitation, independent extremes are selected using a peak over threshold (POT) method.…”

Decadal variability analysis of extreme precipitation in Turkey and its relationship with teleconnection patterns

“…These confidence intervals are computed on the basis of the parametric bootstrapping method. See Ntegeka and Willems (2008), Willems (2013), and Tabari and Willems (2016) for details about the QPM.…”