Evaluation of the ERA5 Sea Surface Temperature Around the Pacific and the Atlantic

Ling Yao,Jiaying Lu,Yangxiaoyue Liu,Xiaolin Xia,Wenlong Jing

doi:10.1109/access.2021.3051642

Abstract

Sea surface temperature (SST) is a key factor for both climate and weather. Most studies focus on evaluation of satellite SSTs in different oceanic regions, but the performance of ERA5 reanalysis SST datasets (ERA5 SSTs) has not been systematically evaluated. In this article, buoy measurements from 46 National Data Buoy Center (NDBC) sites around the Pacific and the Atlantic are used to make an analysis of the deviations of the ERA5 SSTs on an hourly basis and its variations on a daily basis. Overall, ERA5 SSTs have a global coverage with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 0.04\,\,^{\circ }\text{C}$ </tex-math></inline-formula> bias and 4.60 °C standard deviation in the study area. It is worthwhile to notice that ERA5 SSTs exhibit significant differences in the amplitude and the phasing of their spatial patterns. The products are found to meet the accuracy criterion, except in near coastal areas, which may result from the near-coastal mixture effect and the warm SST. The results reveal that ERA5 SSTs completely capture the diurnal variability of SST under all wind speed conditions, especially in the situation when wind speed is above 6 m/s. There is a slight cold bias when wind speed is below 6m/s, indicating that ERA5 SSTs are not affected by solar radiation heating. These findings contribute to the sensible use of ERA5 SSTs around the Pacific and the Atlantic.

Highlights

Sea surface temperature (SST) is a key climate and weather factor which is important for the exchange of energy, momentum and moisture between the ocean and the atmosphere [1]
Since ERA-interim does not provide hourly SST, the evaluation is performed on a daily scale, using daily National Data Buoy Center (NDBC) buoy measurements as ground truth data
The ERA5 SSTs correlated with ground truth data better than ERA-interim, with smaller mean absolute error (MAE) (0.44 versus 1.34), smaller root mean squared error (RMSE) (0.66 versus 1.90) and higher correlation (0.86 versus 0.80)

Summary

INTRODUCTION

Sea surface temperature (SST) is a key climate and weather factor which is important for the exchange of energy, momentum and moisture between the ocean and the atmosphere [1]. Most studies focus on evaluation of satellite-based SST products in different regions [19]–[21], while paying little attention to reanalysis data of SST. Most existing studies on these datasets [23], [24] lack the evaluation of the SST data, and a quantitative evaluation of the ERA5 SSTs at site scale has not been carried out yet. The spatiotemporal uncertainties in hourly ERA5 SSTs around the Pacific and the Arctic are evaluated based on buoy retrievals from the National Data Buoy Center (NDBC). The deviations at different time scales and locations are quantitatively displayed Such analyses and comparisons are relevant for understanding the causes of the errors, rational applications of the reanalysis products, and potential improvements of next-generation products

DATA AND METHODS

TAYLOR DIAGRAMS

RESULTS AND DISCUSSION

CONCLUSION