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 data essential, though their accuracy requires validation. This study evaluates the performance of CMA-RA and ERA5 reanalysis data in representing 2-m air temperature (Ta) and surface temperature (Ts) against in-situ observations from 1,658 IABP and CRREL buoys spanning 2001-2024. The results demonstrate strong consistency between both reanalysis products and buoy observations in capturing seasonal and interannual variations (Ta: R ≥ 0.94; Ts: R ≥ 0.88). For Ta, CMA-RA outperforms ERA5 under extreme cold Ta conditions but exhibits a cold bias in long-term Ta (-0.30 ± 1.50℃), whereas ERA5 shows a warm bias (1.13 ± 2.28℃). Both CMA-RA and ERA5 exhibit a high correlation with buoy observations in Arctic subregions. For Ts, both CMA-RA (-4.15 ± 3.55℃) and ERA5 (-2.52 ± 3.21℃) display significant cold biases, with the largest deviations in winter (< -4 ℃ ) and the smallest in summer (> -1.6 ℃ ). The relatively higher Ts observed by buoys reveals a consistent cold bias in CMA-RA and ERA5, suggesting that model physics, surface parameterizations, and data assimilation strategies jointly contribute to these systematic discrepancies. This study offers a broad spatial coverage and a relatively long continuous temporal assessment of CMA-RA and ERA5 reanalysis data over the Arctic Ocean to date.