Evaluation of near-surface air temperature and specific humidity from hybrid global products and their impact on latent heat flux in the North Indian Ocean

摘要

[1] Daily near-surface air temperature (Ta) and specific humidity (Qa) from three hybrid flux products, namely, Coordinated Ocean-Ice Reference Experiments version II (CORE-II), Objectively Analyzed Air-Sea Fluxes (OAFlux), and Air-Sea Fluxes for the Global Tropical Oceans (TropFlux), are evaluated using in situ data over the North Indian Ocean. The analysis shows that the root-mean-square error (RMSE) value of Ta is ～0.5°C for all products. TropFlux captures the daily variability of Ta very well, but it has a systematic deviation in Ta. The large drop in Ta observed during intense rainfall events is very well captured by TropFlux. All products overestimate Qa by 0.3-1.5 g/kg; OAFlux has the smallest systematic deviation, whereas TropFlux has the highest correlation with buoy data. The overestimation of Qa by the products is mainly caused by high values of Qa, in the range of 18-22 g/kg. The RMSE of Qa ranges from 0.92 to 1.79 g/kg, with OAFlux having the lowest values. Latent heat flux (LHF) computed from a bulk algorithm is underestimated by all products, which can be primarily attributed to the positive bias in Qa. In the southern Bay of Bengal, LHF decreases with increasing Qa during winter and summer monsoons. In this region, a change in 1 g/kg Qa can cause about 11-15 W/m errors in LHF. The air-sea humidity difference is linearly related to sea surface temperature for values greater than 28°C, similar to findings for the western Pacific Ocean.