Predictability of mean summertime diurnal winds over ungauged mountain glaciers

Abstract. Glacier and valley winds are typical characteristics of the microclimate of glacierised valleys. The speed of such winds determines the turbulent heat flux, which contributes to ice melt. 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 response time, 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 reproduces the observed mean summertime diurnal wind speed reasonably well. Furthermore, we show that the three model parameters can be estimated at any glacier using a few topographic variables, allowing prediction of wind speed on ungauged glaciers. A leave-one-out analysis of the stations suggests a root-mean-squared error of 0.76 ms^-1 on average, which is a ∼300 % 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 20 or more. More work is needed to explain the physical mechanisms underlying the predictability of the mean diurnal wind speed on ungauged glaciers based solely on reanalysis temperature and a few topographic variables. The presented model can improve wind speed estimates on ungauged glaciers, leading to better glacier mass-balance calculations at various spatial scales.