Over the past five years, members of the Second Qinghai-Tibet Plateau Scientific Expedition (QTPSE) team have conducted observational research on mountain water vapor transport and heavy precipitation in the vicinity of the Yarlung Zangbo Grand Canyon. They established the Yarlung Zangbo Water Vapor Transport Comprehensive Observation Network (see Figure 1), and through comprehensive analysis of the data collected from this network, they have made a series of significant scientific achievements in the study of water vapor transport, cloud precipitation processes, and mountain-atmosphere interactions. Recently, the prestigious journal Bulletin of the American Meteorological Society (BAMS) published a series of research findings by this expedition team on heavy rainfall processes in the Yarlung Zangbo Grand Canyon.
Dr. Xuelong Chen, a researcher from the Institute of Tibetan Plateau Research, Chinese Academy of Sciences, and the first author of the article, stated that the team successfully applied rain gauges and water vapor change observation networks in the Grand Canyon to study the impact of water vapor transport changes on extreme precipitation (see Figures 2 and 3). The microphysical characteristics of precipitation in southeastern Tibet differ significantly from those in low-altitude areas, confirming the inadequacy of current cloud microphysics parameterization in numerical precipitation models for the Qinghai-Tibet Plateau. The study found dry biases in GPM satellite precipitation data over the Grand Canyon region. Simulating complex mountainous heavy precipitation poses a challenge to precipitation forecasting. The expedition team used WRF and comprehensive observational data to assess the strengths and weaknesses of different cloud precipitation schemes. The results indicate that a high-resolution numerical model using specific cloud precipitation and terrain drag parameterization schemes can accurately predict heavy precipitation in the Grand Canyon region (see Figure 4). These research findings provide important insights for improving the accuracy of complex precipitation forecasts in the Grand Canyon region.
The article systematically elaborates on the scientific objectives, design of observation stations, observed elements, and highlights of the research achievements of the Yarlung Zangbo Grand Canyon water vapor transport observation platform. It was published under the title "Investigation of Precipitation Process in the Water Vapor Channel of the Yarlung Zsangbo Grand Canyon" in BAMS.
Dr. Yaoming Ma and Dr. Xuelong Chen from the Institute of Tibetan Plateau Research, Chinese Academy of Sciences, are co-corresponding authors of the study. This research was jointly funded by the Second Qinghai-Tibet Plateau Comprehensive Scientific Expedition (2019QZKK0105, 2019QZKK0103) and the National Natural Science Foundation of China (41975009).
Public data from the Yarlung Zangbo Water Vapor Transport Comprehensive Observation Network can be downloaded from this link
Figure 1: Deployment Locations of Mountain Precipitation Observation Stations in the Yarlung Tsangpo Grand Canyon (YGC)
The background color represents the terrain (units: meters). Stations marked with black crosses (+) indicate rain gauge installations. Sites marked with red crosses (×) denote locations equipped with GPS water vapor sensors, eddy covariance systems, and rain gauges. Purple asterisks (*) represent stations utilizing automatic weather stations and rain gauges. Blue five-pointed stars indicate sites equipped with GPS water vapor sensors, eddy covariance systems, disdrometers, cloud radars, micro rain radars, microwave radiometers, radio soundings, an all-sky camera, and rain gauges. Blue diamonds denote stations with GPS water vapor sensors, eddy covariance systems, microwave radiometers, radio soundings, an all-sky camera, and rain gauges. Blue hexagons represent sites equipped with GPS water vapor sensors, eddy covariance systems, microwave radiometers, radio soundings, an all-sky camera, micro rain radars, disdrometers, and rain gauges.
Figure 2 shows the total column water vapor (TCWV; in cm) observed at the entrance (a, Motuo) and central (b, Cabu) sites of the Grand Canyon, as well as the variations in daily precipitation observed at different locations within the canyon (c, d, e, and f), during the period from June 24 to July 4, 2021, capturing the most intense rainfall event of the year.
Figure 3 shows the vertical cross-section of humidity (filled colors) and height-zonal wind anomalies (black arrows) preceding extreme precipitation events in Southeastern Tibet (Region 1), spanning one to four days prior to occurrence. The vertical profile extends from 20°N/90°E to 40°N/100°E, with Day 0 representing the day of extreme precipitation.
Figure 4 depicts the water vapor transport flux before and after optimization of the high-resolution WRF model (1 km grid) in panels (a) and (b), respectively, along with the evaluation of precipitation simulation in panel (c). The simulation period covers September 23, 2019, from 11:00 to 17:00. Rainfall observations utilized the average of rainfall gauge data from the Bǎiníng, Mǐrì, Dōngrén, Kǎbù, and 80K stations.
