Latent and sensible heat fluxes in a very unstable atmospheric surface layer and weak-wind conditions in a tropical coastal ocean

The atmospheric surface layer of the tropical coastal ocean is commonly very unstable and experiences weak-wind conditions. How the latent (LE) and sensible ( H ) heat fluxes behave under such conditions are unclear because of the lack of observation stations in the tropics. Thus, this study aims to analyze LE and H and the microclimate parameters influencing them. The authors deployed an eddy covariance system in a tropical coastal region for seven months. The microclimate parameters investigated were wind speed ( U ), vapor pressure deficit ( Δe ), temperature difference ( ΔT ), wind-vapor pressure deficit ( UΔe ), wind-temperature difference ( UΔT ), and atmospheric stability ( z/L ), where z is height and L is the Monin–Obukhov length. On the daily time scale, the results show that LE was more associated with U than Δe , while H was more related to ΔT than U . Cross-wavelet analysis revealed the strong coherence in the LE– U relationship for periods between one and two days, and for H – ΔT , 0.5 to 1 day. Correlation and regression analyses confirmed the time series analyses results, where strong positive correlation coefficients ( r ) were obtained between LE and U ( r = 0.494) and H and ΔT ( r = 0.365). Compared to other water bodies, the transfer coefficient of moisture ( C E N ) was found to be small (= 0.40 × 10 −3 ) and independent of stability; conversely, the transfer coefficient of heat ( C H N ) was closer to literature values (= 1.00 × 10 −3 ) and a function of stability.