Predictability of summertime diurnal winds over ungauged mountain glaciers

Abstract

Abstract. Glacier and valley winds are characteristic features of the microclimate of glacierised valleys. The speed of such winds influences the turbulent heat flux, which contributes to ice melt significantly. Sparse in-situ meteorological measurements and the inability of large-scale climate data products to capture such local winds introduce uncertainty into glacier- to global-scale mass-balance calculations. Here, we propose an empirical model having three parameters, namely, the mean wind speed, the sensitivity of the diurnal winds to temperature, and a time-scale parameter, to predict the mean summertime diurnal wind speed on valley glaciers, based only on reanalysis temperature. Utilising data from 28 weather stations on 18 valley glaciers across the globe, we show that the model, driven solely by reanalysis temperature, reproduces the observed mean summertime diurnal wind speed with a mean RMSE of 0.24 m s−1 across stations, which is 8.8 % of the mean observed wind speed. Interestingly, the three model parameters can be estimated even on an ungauged glacier based on the mean temperature and regional slope. A leave-one-out analysis of the stations suggests a root-mean-squared error of 0.85 m s−1 on average, which is a ∼200 % improvement over a standard reanalysis product. The performance of the model is largely independent of the number of stations available for calibration, as long as it is 21 or more. The presented empirical parametrisation can improve wind speed estimates on ungauged glaciers, leading to better glacier mass-balance calculations.