Revealing Vertical Distribution of Precipitation in the Glacierized Upper Indus Basin Based on Multiple Datasets

Abstract

The quality and vertical distribution of precipitation are of utmost importance in hydrological modeling studies in glacierized catchments, which have been facing known challenges in the quality, distribution, and magnitude of observed as well as gridded precipitation due to complex topography. The purpose of the study is to reveal the vertical distribution of precipitation based on multiple datasets and evaluate the suitability of these datasets for hydrological applications and in the upper Indus basin (UIB). The performance of five gridded precipitation datasets, that is, APHRODITE, CFSR, Princeton Global Meteorological Forcing Dataset for Land Surface Modeling (PGMFD), TRMM, and High Asia Refined analysis (HAR), was evaluated against the observed precipitation (OBS) during 2001–07. A corrected reference precipitation dataset was constructed based on the water and mass balance using inverse modeling methods. TRMM was identified as the best dataset to represent the spatial and temporal distribution of OBS precipitation. The runoff coefficients for OBS, APHRODITE, TRMM, and PGMFD were greater than 1, indicating that these datasets were underestimated and unable to close the water balance in UIB. The mean annual corrected precipitation was estimated as 593 mm yr−1, while the main water-producing elevation zone was located between 3900 and 6600 m. CFSR had the highest correlation and lowest bias with corrected precipitation along the vertical profile. It is concluded that the OBS and most of the gridded precipitation are insufficient to sustain the water and mass balance in UIB. It is recommended to correct the precipitation based on mass balance at high altitudes (especially along the main water-producing zone) in glacierized catchments before its application in hydrological modeling studies.

Characterization of interannual and seasonal variability of hydro-climatic trends in the Upper Indus Basin

“…3. The mean annual bias corrected CHIRPS precipitation for the study domain was estimated as 536 mm yr -1 which is closer to the results obtained by (Cheema and Bastiaanssen 2012;Reggiani and Rientjes 2015;Rizwan et al 2019;Shafeeque et al 2019) who suggested corrected precipitation 523, 675+100, 550 and 593 mm yr -1 respectively in UIB using various methods. The driest area is located over the South-Western part of the study domain along the Shingo and Zanskar basins followed by the upper part of Hunza, Shigar and the central part of Gilgit, while the highest precipitation values occur over the central part of Indus downstream, Astore, Shingo, and the upper part of Shyok.…”

Observed trends and variability of seasonal and annual precipitation in Pakistan during 1960–2016

“…In Pakistan, topographic diversity and complex land geography have a variable trend of precipitation change and variability. Previous studies have mentioned the elevation‐dependent precipitation variability at the seasonal scale and their respective trend due to global warming (Hanif et al ., 2013; Xu et al ., 2018; Yu et al ., 2018; Shafeeque et al ., 2019). Results of long‐term annual precipitation trends at various elevations classes (<250, 250–500, 500–1,000, 1,000–1,500, 1,500–2,000, >2,000 m) are presented in Figure 9.…”

Author Interactive Response to the Short Comments

“…The correction factors for the adjusted observed precipitation are based on the elevational distribution and hydrological balance of the region (Dahri et al 2018). The effect of elevation on the precipitation has been well demonstrated in previous studies (Immerzeel et al 2015, Shafeeque et al 2019. We will incorporate the important discussions to highlight further the effect of topography on precipitation and its role in classifying the hydrological behavior of the basin.…”