Characteristics of Extreme Precipitation and Precipitation Estimation under Different Return Periods in the Pamir Plateau

Shujuan Li^1*Jing Chen^2*Hong Huo²Huaming Shang²Xinyu Lu²Tongwen Zhang²JUNQIANG Yao²Weiyi Mao²Mengying Yao²Liyun Ma²Dilinuer Tuoliewubieke²

• ¹Institute of Desert Meteorology,China Meteorological Administration, Urumqi, China
• ²China Meteorological Administration Institute of Desert Meteorology, Urumqi, China

As the "Water Tower of Central Asia", the Pamir Plateau plays a critical role in regional water security. Research on its extreme precipitation is vital for water resource assessment, hydrological modeling, and disaster risk planning. Using daily observations and the Peak Over Threshold method, we constructed extreme precipitation series across the region. Forty-six functions were applied to select the optimal fit for return period extreme precipitation evaluation at each station. We analyzed extreme precipitation characteristics and estimated precipitation amounts across eight return periods. The main findings are as follows: (1) Extreme precipitation in the Pamir Plateau exhibits nonsynchronous variation with annual precipitation. While about two-thirds of stations show increasing daily extremes, 42.9% exhibit opposite trends between the two. Spatially, extremes are lowest in the southwestern plateau and highest in the Fergana Basin—which has the lowest mean annual precipitation.(2) The contribution of extreme precipitation to multiyear totals ranges from 24.0% to 40.0%, peaking at 88.13% in some years, and shows significant negative correlation with annual precipitation. Although precipitation shows weak elevation dependence overall, stations above 3,400 m record higher amounts, suggesting a maximum precipitation belt above the previously recognized 2,000–3,500 m range.(3) Stations with annual precipitation below 150 mm exhibit the strongest extremes, where single precipitation with 50-100 years return periods can approach or exceed half of the local annual precipitation. Combined with persistent drought and fragile ecosystems, this poses high flood risks and ecological vulnerability. (4)As optimal fitting functions for return period precipitation estimation across the Pamir Plateau, the Wakeby and Gen.Pareto distributions show the widest applicability, each fitting for 36% of stations. But no single distribution function can cover all stations. Extreme precipitation increases 2–3 folds as return periods extend from 2 to 100 years, reaching a maximum of 68.1 mm. The southern plateau and the remote mountains of the northwestern Fergana Basin show lower return period precipitation for given return periods.