Climate of the Greenland ice sheet using a high-resolution climate model – Part 1: Evaluation

Abstract

Abstract.A simulation of 51 years has been performed over Greenland using the regional atmospheric climate model (RACMO2/GR) at a horizontal grid spacing of 11 km and forced by ECMWF re-analysis products. To better represent processes affecting ice sheet surface mass balance, such as meltwater refreezing and penetration, an additional snow/ice surface module has been developed and implemented into the surface part of the climate model. The temporal evolution and climatology of the model is evaluated with in situ coastal and ice sheet atmospheric measurements of near-surface variables and surface energy balance components. The bias for the near-surface air temperature (−0.8 • C), specific humidity (0.1 g kg −1 ), wind speed (0.3 m s −1 ) as well as for radiative (2.5 W m −2 for net radiation) and turbulent heat fluxes shows that the model is in good accordance with available observations on and around the ice sheet. The modelled surface energy budget underestimates the downward longwave radiation and overestimates the sensible heat flux. Due to their compensating effect, the averaged 2 m temperature bias is small and the katabatic wind circulation well captured by the model.

Evaluation of the updated regional climate model RACMO2.3: summer snowfall impact on the Greenland Ice Sheet

“…MODIS background ice albedo as prescribed in RACMO2.3, is depicted in green (axis on right). models underestimate summer LW d and overestimate SWd due to an underestimated cloud optical thickness (Ettema et al, 2010;Fettweis et al, 2011). In fact, the inclusion of ice supersaturation in RACMO2.3 might aggravate this problem over the ablation zone, because, for inland-propagating air masses, this process delays cloud condensation to higher ice sheet elevations, as was also seen in simulations of Antarctic climate (Van Wessem et al, 2014).…”

“…The polar version of RACMO2 was developed by the Institute for Marine and Atmospheric Research (IMAU), Utrecht University, to specifically represent the SMB evolution over the ice sheets of Greenland, Antarctica and other glaciated regions. To that end, the atmosphere model has been interactively coupled to a multilayer snow model that simulates meltwater percolation, refreezing and runoff (Ettema et al, 2010). It includes an albedo scheme with prognostic snow grain size (Kuipers Munneke et al, 2011) and a drifting snow routine that simulates interactions between drifting snow, the ice sheet surface and the lower atmosphere .…”

Temperature and Wind Climate of the Antarctic Peninsula as Simulated by a High-Resolution Regional Atmospheric Climate Model

“…RACMO2.3 has been adapted for use over the large ice sheets of Greenland and Antarctica ; it includes a multilayer snow model to calculate melt, percolation, refreezing, and runoff of liquid water (Ettema et al 2010); a prognostic scheme for snow grain size to calculate surface albedo (Kuipers Munneke et al 2011); and a routine that simulates the interaction of drifting snow with the surface and the lower atmosphere (Lenaerts et al 2012a). ERA-Interim data with 6-hourly resolution from January 1979 to December 2013 (Dee et al 2011) are used to force the model at the lateral atmospheric boundaries as well as at the lower ocean boundaries by prescribing sea ice fraction and sea surface temperatures.…”

“…Dynamical downscaling using high-resolution regional atmospheric climate models (RCMs) has proven to be a good method to represent climate at 5-10-km resolution. Moreover, RCMs can be specifically adapted to simulate the climate and surface mass balance of glaciated regions, such as the Antarctic ice sheet (Lenaerts et al 2012c;Van Wessem et al 2014b), but also of smaller partly glaciated regions, such as Greenland (Fettweis 2007;Ettema et al 2010), Patagonia (Lenaerts et al 2014), and Svalbard (Claremar et al 2012;Lang et al 2015).…”

Sensitivity of Greenland Ice Sheet surface mass balance to surface albedo parameterization: a study with a regional climate model

“…For this we use the high resolution climate model RACMO2 (Van Meijgaard et al, 2008;Ettema et al, 2010a), recently extended with a new albedo scheme (Kuipers Munneke et al, 2011). The next section will briefly describe in situ albedo observations, RACMO2 and the albedo scheme and lists the sensitivity tests performed in this study.…”