Brief communication: Evaluation of the near-surface climate in ERA5 over the Greenland Ice Sheet

Abstract

Abstract. The ERA5 reanalysis, recently made available by the European Centre for Medium-Range Weather Forecasts (ECMWF), is a new reanalysis product at a high resolution replacing ERA-Interim and is considered to provide the best climate reanalysis over Greenland to date. However, so far little is known about the performance of ERA5 over the Greenland Ice Sheet (GrIS). In this study, we compare the near-surface climate from the new ERA5 reanalysis to ERA-Interim, the Arctic System Reanalysis (ASR) as well as to a state-of-the-art polar regional climate model (MAR). The results show (1) that ERA5 does not outperform ERA-Interim significantly when compared with near-surface climate observations over GrIS, but ASR better models the near-surface temperature than both ERA reanalyses. (2) Polar regional climate models (e.g., MAR) are still a useful tool to downscale the GrIS climate compared to ERA5, as in particular the near-surface temperature in summer has a key role for representing snow and ice processes such as the surface melt. However, assimilating satellite data and using a more recent radiative scheme enable both ERA and ASR reanalyses to represent more satisfactorily than MAR the downward solar and infrared fluxes. (3) MAR near-surface climate is not affected when forced at its lateral boundaries by either ERA5 or ERA-Interim. Therefore, forcing polar regional climate models with ERA5 starting from 1950 will enable long and homogeneous surface mass balance reconstructions.

Greenland surface air temperature changes from 1981 to 2019 and implications for ice‐sheet melt and mass‐balance change

“…Version 3.9 of MAR is used here at a resolution of 15 km, and was forced at 6-hour timesteps by five Earth System Models (CESM2, CNRM-CM6-1, CNRM-ESM2-1, MRI-ESM2-0 and UKESM1-0-LL) from the CMIP6 database. We refer to Fettweis et al (2017) for a more detailed description of MAR, and to Delhasse et al (2020) for the validation of MARv3.9. The MAR model, forced by NCEP-NCARv1 (1950-2019 and ECMWF ERA-40 (1958ERA-40 ( -1978 and ERA-5 (1979ERA-5 ( -2019 reanalysis data using the set-ups of Fettweis et al (2017) and Fettweis et al (2020) (respective grid resolutions of 20 km and 15 km), is also used to map the recent observed warming over the GrIS.…”

Unprecedented atmospheric conditions (1948–2019) drive the 2019 exceptional melting season over the Greenland ice sheet

“…The MAR regional climate model The regional climate model MAR combines atmospheric modeling (Gallée and Schayes, 1994) with the Soil Ice Snow Vegetation Atmosphere Transfer Scheme (De Ridder and Gallée, 1998) and has been extensively evaluated and used to simulate surface energy balance and mass balance processes over GrIS (e.g., Fettweis, 2007;Fettweis et al, 2011). In this study, we use version 3.10 of MAR, at a horizontal spatial resolution of 20 km as in Fettweis et al (2017) and 6 h temporal resolution forced with the NCEP/NCARv1 reanalysis (Kalnay et al, 1996).…”

Surface melting over the Greenland ice sheet from enhanced resolution passive microwave brightness temperatures (1979–2019)

“…In this study, we use the output from MAR version v3.11.2 characterized by an enhanced computational efficiency and improved snow model parameters (Fettweis et al, 2017;Delhasse et al, 2020). The model is forced at the boundaries using ERA5 reanalysis (Hersbach et al, 2020), the newest generation of global atmospheric reanalysis data that superseded ERA-Interim (Dee et al, 2011), and output is produced at a horizontal spatial resolution of 6 km.…”