Estimating degree-day factors from MODIS for snowmelt runoff modeling

【摘要】Degree-day factors are widely used to estimate snowmelt runoff in operational hydrological models. Usually, they are calibrated on observed runoff, and sometimes on satellite snow cover data. In this paper, we propose a new method for estimating the snowmelt degree-day factor (DDFS) directly from MODIS snow covered area (SCA) and ground-based snow depth data without calibration. Subcatchment snow volume is estimated by combining SCA and snow depths. Snow density is estimated as the ratio between observed precipitation and changes in the snow volume for days with snow accumulation. Finally, DDFS values are estimated as the ratio between changes in the snow water equivalent and difference between the daily temperature and the melt threshold value for days with snow melt. 继续阅读“Estimating degree-day factors from MODIS for snowmelt runoff modeling”

Diagnostic calibration of a hydrological model in a mountain area by hydrograph partitioning

【摘要】Hydrological modeling can exploit informative signatures extracted from long time sequences of observed streamflow for parameter calibration and model diagnosis. In this study we explore the diagnostic potential of hydrograph partitioning for model calibration in mountain areas, where meltwater from snow and glaciers are important sources for river runoff (in addition to rainwater).  继续阅读“Diagnostic calibration of a hydrological model in a mountain area by hydrograph partitioning”

Correcting the TRMM rainfall product for hydrological modelling in sparsely gauged mountainous basins

【摘要】This study developed a correction approach to improve the rainfall field estimation by TRMM rainfall product in a sparsely gauged mountainous basin. First, Thiessen polygons were generated to define the measurement domain of each raingauge. Second, the rainfall of TRMM pixels in each Thiessen polygon were corrected using a benchmark method based on the difference between the monthly rainfall estimated by raingauge and TRMM pixel that possessed a gauge station (referred to as gauged pixel). Third, the rainfall in the gauged pixels were adjusted to the weighted average value of the gauge rainfall and corrected pixel rainfall. Finally, the rainfall in the non-gauged TRMM pixels were corrected as the sum of two terms.  继续阅读“Correcting the TRMM rainfall product for hydrological modelling in sparsely gauged mountainous basins”

Inter-Comparisons of Rainfall Estimates from TRMM and GPM Multi-Satellite Products over the Upper-Mekong River Basin

【摘要】The aim of this study is to evaluate the accuracy of daily rainfall estimates based on GPM level-3 final product derived from the IMERG algorithm (abbreviated as IMERG) and TRMM 3B42V7 product (abbreviated as 3B42) in the Upper-Mekong River basin, a mountainous region in Southwestern China. High-density rain gauges provide exceptional resources for ground validation of satellite rainfall estimates over this region.  继续阅读“Inter-Comparisons of Rainfall Estimates from TRMM and GPM Multi-Satellite Products over the Upper-Mekong River Basin”

A lake data set for the Tibetan Plateau from the 1960s, 2005, and 2014

【摘要】Long-term datasets of number and size of lakes over the Tibetan Plateau (TP) are among the most critical components for better understanding the interactions among the cryosphere, hydrosphere, and atmosphere at regional and global scales. Due to the harsh environment and the scarcity of data over the TP, data accumulation and sharing become more valuable for scientists worldwide to make new discoveries in this region.  继续阅读“A lake data set for the Tibetan Plateau from the 1960s, 2005, and 2014”

Have GRACE satellites overestimated groundwater depletion in the Northwest India Aquifer?

【摘要】The Northwest India Aquifer (NWIA) has been shown to have the highest groundwater depletion (GWD) rate globally, threatening crop production and sustainability of groundwater resources. Gravity Recovery and Climate Experiment (GRACE) satellites have been emerging as a powerful tool to evaluate GWD with ancillary data. Accurate GWD estimation is, however, challenging because of uncertainties in GRACE data processing. 继续阅读“Have GRACE satellites overestimated groundwater depletion in the Northwest India Aquifer?”

Recent contributions of glaciers and ice caps to sea level rise

【作者】Jacob, Thomas ; Wahr, John; Pfeffer, W. Tad ; Swenson, Sean

Glaciers and ice caps (GICs) are important contributors to present-day global mean sea level rise(1-4). Most previous global mass balance estimates for GICs rely on extrapolation of sparse mass balance measurements(1,2,4) representing only a small fraction of the GIC area, leaving their overall contribution to sea level rise unclear. Here we show that GICs, excluding the Greenland and Antarctic peripheral GICs, lost mass at a rate of 148 +/- 30 Gt yr(-1) from January 2003 to December 2010, contributing 0.41 +/- 0.08 mm yr(-1) to sea level rise. 继续阅读“Recent contributions of glaciers and ice caps to sea level rise”

Asian Water Towers: More on Monsoons Response

【作者】Immerzeel, Walter W.; Bierkens, Marc F. P.

Pithan raises two valid concerns. We agree that future precipitation is highly uncertain and that general circulation models (GCMs) have difficulty in  capturing monsoon precipitation (1,2), and we stress that in our Report. For all five of the river basins we analyzed, the multimodel average (MMA) of future  precipitation shows limited changes both in total quantity and temporal shifts. 继续阅读“Asian Water Towers: More on Monsoons Response”

Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong

【作者】K. O. Winemiller,* P. B. McIntyre, L. Castello, E. Fluet-Chouinard, T. Giarrizzo,S. Nam, I. G. Baird, W. Darwall, N. K. Lujan, I. Harrison, M. L. J. Stiassny. et al.

The world’s most biodiverse river basins—the Amazon, Congo, and Mekong—are experiencing an unprecedented boom in construction of hydropower dams. These projects address important energy needs, but advocates often overestimate economic benefits and underestimate far-reaching effects on biodiversity and critically important fisheries.Powerful new analytical tools and highresolution environmental data can clarify trade-offs between engineering and environmental goals and can enable governments and funding institutions to compare alternative sites for dam building. 继续阅读“Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong”

Impacts of the Three Gorges Dam on microbial structure and potential function

【作者】Qingyun Yan, Yonghong Bi, Ye Deng, Zhili He, Liyou Wu, Joy D. Van Nostrand, Zhou Shi, Jinjin Li, Xi Wang, Zhengyu Hu, Yuhe Yu, Jizhong Zhou

【摘要】The Three Gorges Dam has significantly altered ecological and environmental conditions within the reservoir region, but how these changes affect bacterioplankton structure and function is unknown. Here, three widely accepted metagenomic tools were employed to study the impact of damming on the bacterioplankton community in the Xiangxi River. 继续阅读“Impacts of the Three Gorges Dam on microbial structure and potential function”