Abstract
Abstract. We evaluate modelled Greenland ice sheet (GrIS) near-surface climate, surface energy balance (SEB) and surface mass balance (SMB) from the updated regional climate model RACMO2 (1958–2016). The new model version, referred to as RACMO2.3p2, incorporates updated glacier outlines, topography and ice albedo fields. Parameters in the cloud scheme governing the conversion of cloud condensate into precipitation have been tuned to correct inland snowfall underestimation: snow properties are modified to reduce drifting snow and melt production in the ice sheet percolation zone. The ice albedo prescribed in the updated model is lower at the ice sheet margins, increasing ice melt locally. RACMO2.3p2 shows good agreement compared to in situ meteorological data and point SEB/SMB measurements, and better resolves the spatial patterns and temporal variability of SMB compared with the previous model version, notably in the north-east, south-east and along the K-transect in south-western Greenland. This new model version provides updated, high-resolution gridded fields of the GrIS present-day climate and SMB, and will be used for projections of the GrIS climate and SMB in response to a future climate scenario in a forthcoming study.
Highlights
Predicting future mass changes of the Greenland ice sheet (GrIS) using regional climate models (RCMs) remains challenging (Rae et al, 2012)
Besides direct RCM simulations, the contemporary surface mass balance (SMB) of the GrIS has been reconstructed using various other methods, e.g. positive degree day (PDD) models forced by statistically downscaled re-analyses (Hanna et al, 2011; Wilton et al, 2016), mass balance models forced by the climatological output of an RCM (HIRHAM4) (Mernild et al, 2010, 2011) and reconstruction of SMB obtained by combining RCM outputs with temperature and ice core accumulation measurements (Box, 2013)
We present a detailed evaluation of the regional climate model RACMO2.3p2 (1958–2016) over the Greenland ice sheet (GrIS)
Summary
Predicting future mass changes of the Greenland ice sheet (GrIS) using regional climate models (RCMs) remains challenging (Rae et al, 2012). At the ice sheet margins, meltwater run-off is underestimated over narrow ablation zones and small outlet glaciers that are not accurately resolved in the model’s ice mask at 11 km This underestimation can exceed several m w.e. yr−1, e.g. at automatic weather station (AWS) QAS_L installed at the southern tip of Greenland (Fausto et al, 2016). This paper is part of a tandem model evaluation over the Greenland (present study) and Antarctic ice sheets (Van Wessem et al, 2017)
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