ABSTRACT
Understanding glacier mass balance (MB) change under global warming is important to assess the impact of glacier change on water resources. This study evaluated the applicability of a modified distributed surface energy balance model (DSEBM) with 3-h temporal and 100-m spatial resolution to the alpine Dongkemadi Glacier (DKMD) in the central Tibetan Plateau region, analyzed the causes of glacier MB variations with respect to energy balance, and evaluated MB changes under various climate scenarios. Results showed that: (i) the modified model can describe surface energy and MB of XDKMD well; (ii) net shortwave and longwave radiation, accounting for more than 80% of total heat flux, dominated the glacier energy balance during both summer and winter months; (iii) summer MB spatial patterns dominated annual MB, consistent with the fact that DKMD is a summer accumulation type glacier; and (iv) effect of increase in air temperature on glacier MB is higher than that of decrease in air temperature. The sensitivity of MB revealed by the modified DSEBM can help to understand MB changes influenced by the climate changes and to regulate water management strategies to adapt to climate changes at the catchment scale.
ABSTRACT
In this study, the spatiotemporal distributions of monthly and annual temperature minima (Tmin) and maxima (Tmax), extreme Tmin and Tmax, the highest (lowest) Tmin (Tmax), frost day (FD), icing day (ID), summer day (SD) and tropical night (TR) at 112 stations and over the ten large river basins on the Tibetan Plateau and its surroundings (TPS) during 1963-2015 are examined. Mann-Kendall test is applied for the trends. The analyses show: the northwest experiences the hottest summer while the central TPS has the coldest winter and most frequent frost and icing days. The northwest (southeast) features the highest (lowest) monthly extreme temperature ranges. The northwest has the most frequent hot summer days, whereas the southeast has the least frequent frost and icing days. The entire TPS displays few tropical nights. Most stations show positive trends for all monthly and annual Tmin and Tmax variables. February displays the most positive trends for both monthly Tmin and Tmax variables while April shows the highest number of stations with decreasing trends in monthly Tmax. The trends of FD and ID are negative, whereas the trends of SU and TR are positive. Over river basins, the trends of monthly Tmin are all positive and statistically significant and the trends of monthly Tmax are all positive except for one negative trend and around 1/3 of the positive trends are statistically significant. Relatively larger increases in monthly Tmin and Tmax are noted for the cold season than the warm. The monthly and annual Tmin variables increase more than Tmax variables.
ABSTRACT
In contrast to the glacier mass losses observed at other locations around the world, some glaciers in the High Mountains of Asia appear to have gained mass in recent decades. However, changes in digital elevation models indicate that glaciers in Karakoram and Pamir have gained mass, while recent laser altimetry data indicate mass gain centred on West Kunlun. Here, we obtain results that are essentially consistent with those from altimetry, but with two-dimensional observations and higher resolution. We produced elevation models using radar interferometry applied to bistatic data gathered between 2011 and 2014 and compared them to a model produced from bistatic data collected in 2000. The glaciers in West Kunlun, Eastern Pamir and the northern part of Karakoram experienced a clear mass gain of 0.043 ± 0.078~0.363 ± 0.065 m w.e. yr-1. The Karakoram showed a near-stable mass balance in its western part (-0.020 ± 0.064 m w.e. yr-1), while the Eastern Karakoram showed mass loss (-0.101 ± 0.058 m w.e. yr-1). Significant positive glacier mass balances are noted along the edge of the Upper Tarim Basin and indicate a decreasing gradient from northeast to southwest.
ABSTRACT
The Tibetan Plateau and the surrounding (TPS) with its vast land mass and high elevation affects regional climate and weather. The TPS is also the headwater of 9 major Asian rivers that provide fresh water for 1.65 billion people and many ecosystems, with wet season (May-September) precipitation being the critical component of the fresh water. Using station observations, ERA-Interim and MERRA2 reanalysis, we find that wet season precipitation displays vertical gradients (i.e., changes with elevation) that vary within the region on the TPS. The decrease of precipitation with elevation occurs in the interior TPS with elevation larger than 4000 m, little or no change over the southeastern TPS, and increase elsewhere. The increase of precipitation with elevation is caused by increasing convective available potential energy (CAPE) and decreasing lifting condensation level (LCL) with elevation overwhelming the effects of decreasing total column water vapor (TCWV) with elevation. The decreasing precipitation with elevation is due to the combined effects of increasing LCL and decreasing TCWV. LCL and CAPE play a more important role than TCWV in determining the spatial patterns. These findings are important for hydrology study in observation scarce mountainous areas, water resources and ecosystem managements in the region.
