Sensible and latent heat flux in the tropical Pacific from satellite multi-sensor data

Abstract

Satellite multi-sensor data is used to derive sensible heat flux (SHF), Bowen ratio (Bo), and thus latent heat flux (LHF) in the tropical Pacific. The temperature differences at the air–sea interface are determined empirically for regions where strong deep air convection is present due to the buoyancy force. The vertical airflow results in surface wind divergence, which is estimated from scatterometer wind vector fields. The areas of positive temperature differences between sea surface temperature and atmospheric temperature estimated using surface wind divergence and in situ measurements are highly consistent in the tropical Pacific, especially in two convergence zones, i.e., the Intertropical Convergence Zone (ITCZ), and the South Pacific Convergence Zone (SPCZ). The bulk formulated SHF, determined by surface wind divergence (SHF BWD), is compared with a long-term time series (January 1993–December 1999) of the SHF from the National Centers for Environmental Prediction (NCEP) reanalyzed model data (SHF M). In the ITCZ, the correlation coefficients and the Root Mean Square (RMS) differences between SHF BWD and SHF M are over 70% and in the order of less than 4 W/m 2, respectively. Furthermore, the bulk formulated latent heat flux (LHF B) is obtained using the empirical Bowen ratio (Bo E) and SHF BWD. The Bo E for the tropical Pacific was estimated using only sea surface temperature, which is valid when the vapor is saturated near sea surface. The RMS differences between SHF BWD and LHF B are estimated as 3.5 and 39.3 W/m 2, respectively. In addition, the differences of SHF BWD and LHF B during the boreal winters are smaller than that in the boreal summers. Finally, in order to study spatial and temporal variations, we apply Empirical Orthogonal Function (EOF) analysis to SHF BWD and LHF B and compare with EOF analysis of Coupled Ocean and Atmosphere Data Set (COADS)'s SHF and LHF.