Quantifying the influence of vegetation and albedo changes on High Mountain Asia hydrology
Abstract
High Mountain Asia (HMA) snow and glaciers are important sources of freshwater, contributing up to 70% of the annual water supply of over 1.4 billion people in HMA and downstream regions. Several studies have documented a loss of snowpack due to recent warming over this region. These impacts are also reflected in a reduction in surface albedo and in vegetation changes, such as the upslope migration of vegetation. In this study, we evaluate the impact that assimilating remotely sensed Leaf Area Index (LAI) and albedo estimates has on a land surface model's simulation of snowpack and hydrological fluxes and states. LAI and albedo are key parameters controlling interception and absorption of radiation, which in turn impact snowpack evolution. Specifically, we employ the Global Land Surface Satellite (GLASS) LAI and albedo products for assimilation within the Noah-MP land surface model in the NASA Land Information System. The GLASS dataset is generated from MODIS reflectance datasets, which have a temporal resolution of 8 days and a spatial resolution of 1 km. The Ensemble Kalman Filter and Direct Insertion methods are applied for LAI and albedo assimilation, respectively. The model simulation is forced with CHIRPS v2.0 precipitation dataset and other meteorological inputs from ECMWF. The evaluation of snowpack estimates over HMA is a huge challenge due to sparse ground measurements. Thus, model evaluation is performed by directly comparing limited measurements and also using indirect evaluation methods such as extended triple collocation (ETC). ETC allows for the simultaneous estimation of the unknown error standard deviations and correlations of three or more related datasets, without requiring knowledge of a true reference dataset, which is particularly relevant in a data-sparse region such as HMA.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C23C1558Y
- Keywords:
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- 1621 Cryospheric change;
- GLOBAL CHANGE;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 4329 Sustainable development;
- NATURAL HAZARDS;
- 4333 Disaster risk analysis and assessment;
- NATURAL HAZARDS