Global mean ocean surface wind anomaly

'''DEFINITION''' The 2019 global ocean surface mean wind anomaly map is obtained from the reprocessed winds of the ASCAT scatterometer on board Metop-A at 25 km resolution (WIND_GLO_WIND_L3_REP_OBSERVATIONS_012_005). The Level 3 scatterometer winds from ascending and descending tracks are combined into monthly averages. These form the basis for the climatology (2007-2014) and annual anomalies. The anomalies are calculated as the difference between annual averages and the climatology (Belmonte Rivas et al., 2019). Grid cells with a limited number of observations (coastal areas) or a large seasonal variability in the number of observations (seasonal sea ice cover) over the climatology period are excluded from the analysis.

'''CONTEXT''' The global ocean mean surface wind plays an essential role in the exchange of heat, gases and momentum at the atmosphere-ocean interface. The large-scale wind field induces the wind-driven ocean circulation, with associated Ekman transport and upwelling. The magnitude of the wind speed is directly related to turbulent heat exchange between the atmosphere and the ocean in the form of latent and sensible heat. Large-scale annual anomalies in the mean surface wind are associated with periodic climate variations like the North Atlantic Oscillation (NAO) and the El Niño-Southern Oscillation (ENSO).

'''CMEMS KEY FINDINGS''' The most prominent feature in the 2019 global mean wind anomaly map is the large easterly anomaly in the Indian Ocean equatorial winds. This anomaly, together with the southeasterly anomaly in the Indian Ocean trade winds and the enhanced westerlies south of Australia, is associated with the strong positive phase of the Indian Ocean Dipole (IOD) in 2019. The strong positive IOD phase was the key driver of major climate anomalies around the Indian Ocean, like severe drought causing extreme bushfires in Australia and flooding and locust outbreaks in eastern Africa. The reduced Pacific Equatorial currents are consistent with the weak El Niño conditions over 2019. Compared to the Indian and Pacific Oceans, anomalies in the Atlantic Ocean are small in 2019.