| 1. |
- Li, Ying, et al.
(författare)
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Atmospheric Water Transport to the Endorheic Tibetan Plateau and Its Effect on the Hydrological Status in the Region
- 2019
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Ingår i: Journal of Geophysical Research: Atmospheres. - 2169-897X .- 2169-8996. ; 124:23, s. 12864-12881
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Tidskriftsartikel (refereegranskat)abstract
- ©2019. American Geophysical Union. All Rights Reserved. The endorheic Tibetan Plateau (ETP), which consists of all the endorheic basins of the Tibetan Plateau (TP), has exhibited an overall mass gain in recent decades. However, the role played by atmospheric water (AW) transport on the hydrological status over the ETP is poorly understood. In this study, the AW source to the ETP was tracked with the Water Accounting Model-2 layers (WAM-2) and AW transport to the ETP through its boundaries was quantified, with three reanalysis products (ERA-I, MERRA-2, and JRA-55) during 1979/1980–2015. It is found that total AW input to the ETP is about 13–25%, 59–71%, 10–13%, and 3–7% of mean annual totals in spring, summer, autumn, and winter, respectively. At annual scales, the AW source from land (52–54%) dominates the AW contribution to the ETP, while local recycling of AW over the ETP accounts for about 17–22% of the mean annual total AW contribution. Increased precipitation over the ETP during 1979–2015 was mostly attributed to the significantly increased AW contribution from the Indian Ocean, especially from increased AW inputs transported from the western and southern boundaries in summer. Comparisons between the AW budget and terrestrial water storage changes indicate that the AW budget change over the ETP modulated the variations of terrestrial water storage change during 2002–2014 and annual lake mass change during 1989–2015.
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| 2. |
- Sun, He, et al.
(författare)
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Contrasting precipitation gradient characteristics between westerlies and monsoon dominated upstream river basins in the Third Pole
- 2020
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Ingår i: Kexue Tongbao/Chinese Science Bulletin. - 0023-074X .- 2095-9419. ; 65, s. 91-104
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Tidskriftsartikel (refereegranskat)abstract
- © 2020, Science Press. All right reserved. Based on precipitation observations from 256 gauges in the westerly and monsoon dominated upstream river basins of the Third Pole (TP), this study determined the relationships between precipitation and elevation. The basins include the upper basins of the Yangtze, Yellow, Lancang, Nujiang, Yarlung Zangbo, Yarkant, Indus, Amu Darya, and Syr Darya. Using the ERA5 data, this work examined the possible reasons for the difference in the characteristics of precipitation gradient, i.e. analyzing the relationships between the total column water vapor (TCWV), convective available potential energy (CAPE), lifting condensation level (LCL) and elevation, respectively. The feasibility of orographic corrections of precipitation data or observation is validated with the improved VIC land surface hydrological model in two mountain basins in the TP. Mean annual precipitation from gauges generally show decreasing trends (17-128 mm/100 m) with increased elevation (2500-5500 m a.s.l.) in the monsoon dominated basins, i.e. upper Yangtze, Yellow, Lancang, Nujiang, and Yarlung Zangbo, while the orographic enhancements are observed at relatively smaller scales, such as, in the very source regions of the upper Lancang and Nujiang, and Rikaze sub-basin with areas of 11000-67740 km2. On the other hand, in the westerly dominated basins, mean annual precipitation tends to increase with elevation (5-64 mm/100 m) in the upper Yarkant, Indus, Amu Darya, and Syr Darya. The precipitation estimates from ERA5 show a good correspondence with the gauge data (R=0.6-0.9, P<0.05), and exhibit a general consistent precipitation gradient pattern with the gauge observations. The ERA5 variables of TCWV, CAPE, and LCL are useful to understand the factors for the spatial pattern of precipitation vertical gradients in the TP basins with different climate control. The TCWV, CAPE, and LCL represent the vertically integrated moisture, instability and condensation necessary for the generation and development of precipitation. The larger TCWV, higher CAPE and lower LCL enhance precipitation. The decrease of precipitation with elevation in monsoon basins is caused by the decrease of TCWV with elevation, while the increase of precipitation with elevation in westerly dominated basins is a result of increasing CAPE and decreasing LCL with elevation. Hydrological modeling results in the upper Yarkant basin and Rikaze basin indicate that the orographic correction of precipitation data significantly improves the model accuracy, reducing the biases to less than 5% relative to flow observations. This work demonstrates that precipitation correction through vertical gradients is an effective way to derive high mountainous precipitation estimates for hydrological modeling from lowland gauges in the TP, especially in the westerly dominated basins, and in monsoon basins at regional or local scales. Knowledge of the spatial and temporal characters and variations of precipitation over the TP is greatly incomplete, which largely hampers the understanding on climate variability and water availability projections in the TP. This study offers a useful reference to derive reliable mountain precipitation through orographic correction, and also provides a scientific basis to establish precipitation observation network in the Second Tibetan Plateau Scientific Expedition and Research.
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| 3. |
- Sun, He, et al.
(författare)
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Hydrological Evaluation of High-Resolution Precipitation Estimates from the WRF Model in the Third Pole River Basins
- 2021
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Ingår i: Journal of Hydrometeorology. - 1525-755X. ; 22:8, s. 2055-71
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Tidskriftsartikel (refereegranskat)abstract
- In this study, two sets of precipitation estimates that are based on the regional Weather Research and Forecasting (WRF) Model—the high Asia refined analysis (HAR) and outputs with a 9-km resolution from WRF (WRF-9km)—are evaluated at both basin and point scales, and their potential hydrological utilities are investigated by driving the Variable Infiltration Capacity (VIC) large-scale land surface hydrological model in seven Third Pole (TP) basins. The regional climate model (RCM) tends to overestimate the gauge-based estimates by 20%–95% in annual means among the selected basins. Relative to the gauge observations, the RCM precipitation estimates can accurately detect daily precipitation events of varying intensities (with absolute bias < 3 mm). The WRF-9km exhibits a high potential for hydrological application in the monsoon-dominated basins in the southeastern TP (with NSE of 0.7–0.9 and bias from −11% to 3%), whereas the HAR performs well in the upper Indus and upper Brahmaputra basins (with NSE of 0.6 and bias from −15% to −9%). Both of the RCM precipitation estimates can accurately capture the magnitudes of low and moderate daily streamflow but show limited capabilities in flood prediction in most of the TP basins. This study provides a comprehensive evaluation of the strength and limitation of RCMs precipitation in hydrological modeling in the TP with complex terrains and sparse gauge observations.
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