Abstract
A large population relies on water input to the Indus basin, yet basinwide precipitation amounts and trends are not well quantified. Gridded precipitation data sets covering different time periods and based on either station observations, satellite remote sensing, or reanalysis were compared with available station observations and analyzed for basinwide precipitation trends. Compared to observations, some data sets tended to greatly underestimate precipitation, while others overestimate it. Additionally, the discrepancies between data set and station precipitation showed significant time trends in such cases, suggesting that the precipitation trends of those data sets were not consistent with station data. Among the data sets considered, the station-based Global Precipitation Climatology Centre (GPCC) gridded data set showed good agreement with observations in terms of mean amount, trend, and spatial and temporal pattern. GPCC had average precipitation of about 500 mm per year over the basin and an increase in mean precipitation of about 15% between 1891 and 2016. For the more recent past, since 1958 or 1979, no significant precipitation trend was seen. Among the remote sensing based data sets, the Tropical Rainfall Measuring Mission Multi-Satellite Precipitation Analysis (TMPA) compared best to station observations and, though available for a shorter time period than station-based data sets such as GPCC, may be especially valuable for parts of the basin without station data. The reanalyses tended to have substantial biases in precipitation mean amount or trend relative to the station data. This assessment of precipitation data set quality and precipitation trends over the Indus basin may be helpful for water planning and management.
Highlights
The Indus is the westernmost of the major rivers of South Asia
Climate Research Unit (CRU) and Modern-Era Retrospective analysis for Research and Applications (MERRA)-2, despite interpolating or assimilating station precipitation observations, underestimated precipitation amount the most compared to station data, possibly due to too few stations from the Indus basin included in these data sets
JRA-55 precipitation was biased high by 26% and ERA5 precipitation was biased high by 19%
Summary
The Indus is the westernmost of the major rivers of South Asia. The Indus basin’s water resources have been estimated to support 215 million people with an average per capita annual water availability of 1329 m3 [2]. Plateau and drains into the Arabian Sea, and the basin as a whole covers a latitude range of about 24◦. The northern or upper part of the basin includes high mountains of the Himalaya, Karakoram, and Hindu Kush mountain ranges, whereas much of its southern or lower part is flat lowland. Temperatures range from below freezing at high elevations to above 40 ◦ C in spring and summer at low elevations. Located at the margin of the South
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