Application of a Degree-Day Model for Determination of Mass Balance of Urumqi Glacier No. 1, Eastern Tianshan, China

In order to verify the feasibility and stability of a degree-day model on simulating the long time series of glacier mass balance, we apply a degree-day model to simulate the mass balance of Urumqi Glacier No. 1 for the period 1987/1988-2007/2008 based on temperature and precipitation data from a nearby climate station. The model is calibrated by simulating point measurements of mass bal-ance, mass balance profiles, and mean specific mass balance during 1987/1988-1996/1997. The opti-mized parameters are obtained by using a least square method to make the model fit the measured mass balance through the model calibration. The model validation (1997/1998-2007/2008) indicates that the modeled results are in good agreement with the observations. The static mass balance sensitiv-ity of Urumqi Glacier No. 1 is analyzed by computing the mass balance of the glacier for a temperature increase of 1 ℃, with and without a 5% precipitation increase, and the values for the east branch are -0.80 and -0.87 m w.e. a-1·℃-1, respectively, and for the west branch, the values are -0.68 and -0.74 m w.e. a-1·℃-1, respectively. Moreover, the analysis of the parameter stability indicates that the parame-ters in the model determined from the current climate condition can be applied in the prediction of the future mass balance changes for the glacier and provide a reference for extending the model to other small glaciers in western China.