Role of Net Surface Heat Flux in Seasonal Variations of Sea Surface Temperature in the Tropical Atlantic Ocean

Abstract

The present study used a new net surface heat flux (Q net ) product obtained from the Objective Analyzed Air-Sea Fluxes (OAFlux) project and the International Satellite Cloud Climatology Project (ISCCP) to examine two specific issues-one is to which degree Q net controls seasonal variations of sea surface temperature (SST) in the tropical Atlantic Ocean (20°S-20°N, east of 60°W), and the other is whether the physical relation can serve as a measure to evaluate the physical representation of a heat flux product. To better address the two issues, the study included the analysis of three additional heat flux products: the Southampton Oceanographic Centre (SOC) heat flux analysis based on ship reports, and the model fluxes from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis and the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40). The study also uses the monthly subsurface temperature fields from the World Ocean Atlas to help analyze the seasonal changes of the mixed layer depth (h MLD ).The study showed that the tropical Atlantic sector could be divided into two regimes based on the influence level of Q net . SST variability poleward of 5°S and 10°N is dominated by the annual cycle of Q net . In these regions the warming (cooling) of the sea surface is highly correlated with the increased (decreased) Q net confined in a relatively shallow (deep) h MLD . The seasonal evolution of SST variability is well predicted by simply relating the local Q net with a variable h MLD . On the other hand, the influence of Q net diminishes in the deep Tropics within 5°S and 10°N and ocean dynamic processes play a dominant role. The dynamicsinduced changes in SST are most evident along the two belts, one of which is located on the equator and the other off the equator at about 3°N in the west, which tilts to about 10°N near the northwestern African coast.The study also showed that if the degree of consistency between the correlation relationships of Q net , h MLD , and SST variability serves as a measure of the quality of the Q net product, then the Q net from OAFlux ϩ ISCCP and ERA-40 are most physically representative, followed by SOC. The NCEP-NCAR Q net is least representative. It should be noted that the Q net from OAFlux ϩ ISCCP and ERA-40 have a quite different annual mean pattern. OAFlux ϩ ISCCP agrees with SOC in that the tropical Atlantic sector gains heat from the atmosphere on the annual mean basis, where the ERA-40 and the NCEP-NCAR model reanalyses indicate that positive Q net occurs only in the narrow equatorial band and in the eastern portion of the tropical basin. Nevertheless, seasonal variances of the Q net from OAFlux ϩ ISCCP and ERA-40 are very similar once the respective mean is removed, which explains why the two agree with each other in accounting for the seasonal variability of SST.In summary, the study suggests that an accurate estimation of surface heat flux is crucially important for understandin...

The Nature and Origin of Decadal to Millennial Scale Climate Variability in the Southern Tropics of South America: The Holocene Record of Lago Umayo, Peru

“…Yu et al 2006), a significant portion of which is due to latent heat exchange driven by surface winds (e.g. Carton et al 1996, Chang et al 1997).…”

Surface CO2 parameters and air–sea CO2 flux distribution in the eastern equatorial Atlantic Ocean

“…Des travaux réalisés à partir d'observations (Merle et al, 1980;Foltz et al, 2003) ou de la modélisation (Philander and Pacanowski 1986;Yu et al, 2006;Peter et al, 2006 ;Wade et al, 2010) Il est localisé le long de la frontière nord (~5°N), le long des côtes entre le Cap Palmas (Côte d'Ivoire) et Cotonou (Bénin). Il tend à apparaître dans les concavités des côtes à l'est du Cap Palmas et le Cap des Trois Pointes (Ghana).…”

Study of the equatorial Atlantic Ocean mixing layer using a one-dimensional turbulence model

“…Philander, 1990). Over equatorial regions, the annual variations of the sea surface temperature (SST) are the dominant cycle and depend more on oceanic and air-sea interaction processes than on the annual cycle of the surface heat fluxes (Carton and Zhou, 1996;Yu et al, 2006 for the tropical Atlantic Ocean), prevailing variations of wind-induced vertical mixing, vertical and horizontal advection of heat (Weingartner and Weisberg, 1991a) and wind driven cooling due to evaporation, which is related to ocean-atmosphere feedback processes (e.g. Carton et al, 1996;Chang et al, 2000).…”

“…More recently, Yu et al (2006), using the dataset from OAFlux (Objectively Analyzed Air-Sea Fluxes, Yu et al, 2008), the ISCCP (International Satellite Cloud Climatology Project, Zhang et al, 2004) and the WOA (World Ocean Data, Levitus et al, 1994), estimated the correlation of the local variation of SST and the mixing layer depth (h MLD ) with Q n . They verified at the equator, westward from 20 o W, that the rise in the SST is characterized by the mechanism described by Weingartner and Weisberg (1991a), since a negative correlation between the variation of SST and the h MLD was indentified (the reduction of h MLD being related to an increase in SST, and vice-versa), while eastward of 20 o W, a strong positive correlation appears due to the known upwelling region off the African coast, where the depth of the thermocline responds directly to the strengthening of the easterlies.…”