Objectives

A hydrologic cycle in the Himalayas is characterized by high orographic precipitation along the slopes, glaciers, and many headwaters of the major rivers, which provides water resources for millions of people in the major Asian river basins. Precipitation in high-elevation areas (> 3000 m) of the Himalayas plays an essential role in maintaining the high mountain hydrologic cycle. Most of the rain in central and eastern Himalayas fall in summer monsoon season. However, the amount of rain that falls around the glacier area is still not yet well known despite its importance. To better understand precipitation in the high-altitude regions during the summer monsoon season and the mechanisms of its variability, we started an international collaborative research on precipitation in the Himalayas (HiPRECS: Himalaya Precipitation Study) in October 2018. Our research project performs comprehensive research based on in-situ observations including glacier sites, satellite remote sensing (e.g., TRMM, GPM and CloudSat), large-scale and regional-scale data analyses (e.g., ERA5) and numerical simulation by cloud-resolving models (e.g, WRF and CReSS). We focus on the two observation sites around the Rolwaling Valley in eastern Nepal and the Bhimthang Valley in central Nepal where automatic weather stations (AWSs) were installed close to or on the glaciers since 2016. In Phase 1 (2018-2023), we focused on precipitation variability and its driving mechanisms across multiple spatiotemporal scales. In Phase II (2023-2027), we focus on precipitation processes and precipitation systems by using Micro Rain Radar (MRR) and a cloud-resolving model with a horizontal resolution of 200m (JMA-NHM) in addition to data and models employed in Phase I.  In phase II, the rain gauge network will be extended to the adjacent Khumbu Valley with the cooperation of Tribhuvan University.