Evaluation of 2-m Air Temperature and Surface Temperature from CMA-RA and ERA5: A Comparison with Buoy Observations in the Arctic during 2001–2024

The Arctic is a critical region for global climate change, where temperature variations profoundly influence sea ice dynamics and atmospheric circulation. Harsh conditions limit in-situ observations in the Arctic, making reanalysis datasets indispensable, while the reliability of these reanalysis products requires systematic validation. This study evaluates the performance of the China Meteorological Administration Global Atmospheric Reanalysis (CMA-RA) and the ECMWF Reanalysis v5 (ERA5) in representing 2-m air temperature (T_a) and surface temperature (T_s) against in-situ observations from a total of 1658 buoys of the International Arctic Buoy Programme (IABP) and Cold Regions Research and Engineering Laboratory of the United States (CRREL) during 2001–2024. The results demonstrate strong consistency between the two reanalysis products and buoy observations, with correlation coefficients (R) of ≥ 0.94 for T_a and ≥ 0.88 for T_s in reproducing seasonal and interannual variations. For T_a, CMA-RA outperforms ERA5 under extreme cold conditions but exhibits a cold bias in long-term simulations (−0.30 ± 1.50°C), whereas ERA5 shows a warm bias (1.13 ± 2.28°C). Both CMA-RA and ERA5 yield high correlations with buoy observations across Arctic subregions. For T_s, both CMA-RA (−4.15 ± 3.55°C) and ERA5 (−2.52 ± 3.21°C) display cold biases, with the largest deviations occurring in winter (< −4°C) and the smallest in summer (> −1.6°C). The relatively higherT_s observed by buoys reveals consistent cold biases in CMA-RA and ERA5, suggesting that model physics, surface parameterizations, and data assimilation strategies jointly contribute to these systematic discrepancies. This study provides a comprehensive spatial evaluation and a relatively long continuous temporal assessment of the performance of CMA-RA and ERA5 over the Arctic to date.