Assessment of Atmospheric Reanalysis Data Based on Buoy Observations over the Tropical Western Indian Ocean in 2019

Atmospheric reanalysis data are an important data source for studying weather and climate systems. The sea surface wind and sea level pressure observations measured from a real-time buoy system deployed in Kenya’s offshore area in 2019 conducted jointly by Chinese and Kenyan scientists were used to evaluate the performance of the major high-frequency atmospheric reanalysis products in the western Indian Ocean region. Compared with observations, the sea level pressure field could be accurately simulated using the atmospheric reanalysis data. However, significant discrepancies existed between the surface wind reanalysis data, especially between meridional wind and the observational data. Most of the data provide a complete understanding of sea level pressure, except for the Japanese 55-year Reanalysis data, which hold a significant system bias. The Modern-Era Reanalysis for Research and Applications, Version-2, provides an improved description of all datasets. All the reanalysis datasets for zonal wind underestimate the strength during the study period. Among reanalysis data, NCEP-DOE Atmospheric Model Intercomparison Project reanalysis data presents an inaccurate description due to the worst correlation with the observations. For meridional wind, most reanalysis datasets underestimate the variance, while the European Centre for Medium-Range Weather Forecasts Atmospheric Composition Reanalysis 4 has a larger variance than the observations. In addition to the original data comparison, the diurnal variability of sea level pressure and surface wind are also assessed, and the result indicates that the diurnal variations have a significant gap between observation and reanalysis data. This study indicates that the current high-frequency reanalysis data still have disadvantages when describing the atmospheric parameters in the Western Indian Ocean region.