Abstract
Precipitation is a central quantity of hydrometeorological research and applications. Especially in complex terrain, such as in High Mountain Asia (HMA), surface precipitation observations are scarce. Gridded precipitation products are one way to overcome the limitations of ground truth observations. They can provide datasets continuous in both space and time. However, there are many products available, which use various methods for data generation and lead to different precipitation values. In our study we compare nine different gridded precipitation products from different origins (ERA5, ERA5-Land, ERA-interim, HAR v2 10 km, HAR v2 2 km, JRA-55, MERRA-2, GPCC and PRETIP) over a subregion of the Central Himalaya and the Southwest Tibetan Plateau, from May to September 2017. Total spatially averaged precipitation over the study period ranged from 411 mm (GPCC) to 781 mm (ERA-Interim) with a mean value of 623 mm and a standard deviation of 132 mm. We found that the gridded products and the few observations, with few exceptions, are consistent among each other regarding precipitation variability and rough amount within the study area. It became obvious that higher grid resolution can resolve extreme precipitation much better, leading to overall lower mean precipitation spatially, but higher extreme precipitation events. We also found that generally high terrain complexity leads to larger differences in the amount of precipitation between products. Due to the considerable differences between products in space and time, we suggest carefully selecting the product used as input for any research application based on the type of application and specific research question. While coarse products such as ERA-Interim or ERA5 that cover long periods but have coarse grid resolution have previously shown to be able to capture long-term trends and help with identifying climate change features, this study suggests that more regional applications, such as glacier mass-balance modeling, require higher spatial resolution, as is reproduced, for example, in HAR v2 10 km.
Highlights
High Mountain Asia (HMA) is the major water source of large river systems, especially of the Yangtze, the Yellow, the Brahamputra, the Ganges and the Indus river
To illustrate how the different precipitation products compare within the study region and period, we provide the cumulative sum of precipitation from May to September 2017 (Figure 3), the sum of precipitation for each month within the study period (Figure 4), and a spatial plot with per-pixel sums over the study period (Figure 5)
Despite the missing lower-lying areas (
Summary
High Mountain Asia (HMA) is the major water source of large river systems, especially of the Yangtze, the Yellow, the Brahamputra, the Ganges and the Indus river. It forms the freshwater supply for billions of people in Asia who depend on it as a drinking and agriculture water supply or source for hydropower electricity, and it is among the most vulnerable water towers globally [1,2]. It is becoming increasingly important to monitor and model water availability as the climate is changing. Precipitation measured with rain-gauge stations can provide information about spatial and temporal patterns, and they are essential for monitoring and modeling. Direct observations at rain-gauge stations are (i) only available as point measurements;
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