Surface Flux Variability over the North Pacific and North Atlantic Oceans

Abstract

Daily fields obtained from a 17-yr atmospheric GCM simulation are used to study the surface sensible and latent heat flux variability and its relationship to the sea level pressure (SLP) field. The fluxes are analyzed over the North Pacific and Atlantic Oceans during winter. The leading mode of interannual SLP variability consists of a single center associated with the Aleutian low in the Pacific, and a dipole pattern associated with the Icelandic low and Azores high in the Atlantic. The surface flux anomalies are organized by the low-level atmospheric circulation associated with these modes in agreement with previous observational studies. The surface flux variability on all of the timescales examined, including intraseasonal, interannual, 3-10 day, and 10-30 day, is maximized along the north and west edges of both oceans and between Japan and the date line at ϳ35ЊN in the Pacific. The intraseasonal variability is approximately 3-5 times larger than the interannual variability, with more than half of the total surface flux variability occuring on timescales of less than 1 month. Surface flux variability in the 3-10-day band is clearly associated with midlatitude synoptic storms. Composites indicate upward (downward) flux anomalies that exceed |30 W m Ϫ2 | occur to the west (east) of storms, which move eastward across the oceans at 10Њ-15Њ per day. The SLP and surface flux anomalies are also strong and coherent in the 10-30-day band but are located farther north, are broader in scale, and propagate ϳ3-4 times more slowly eastward than the synoptic disturbances. The sensible and latent heat flux are proportional to the wind speed multiplied by the air-sea temperature and humidity difference, respectively. The anomalous wind speed has the greatest influence on surface flux anomalies in the subtropics and western Pacific, while the air temperature and moisture anomalies have the greatest impact in the northeast Pacific and north of 40ЊN in the Atlantic. The covariance between the wind speed and the air temperature or humidity anomalies, while generally small, is nonnegligible on synoptic timescales.

Diurnal precipitation and high cloud frequency variability over the Gulf Stream and over the Kuroshio

“…Synoptic scale disturbances strongly modify air-sea heat fluxes in WBC regions as found in observations (e.g., Alexander and Scott 1997;Zolina and Gulev 2003;Shaman et al 2010;Rudeva and Gulev 2011) and also in modeling studies (e.g., Nonaka et al 2009;Taguchi et al 2009;Brayshaw et al 2011). The sensible and latent heat fluxes are important in maintaining the surface baroclinicity (e.g., Hoskins and Valdes 1990;Nakamura et al 2004Nakamura et al , 2008, which is crucial for developments of extratropical cycles (Hoskins et al 1985) and thus important in determining the nature of the storm tracks (e.g., Inatsu et al 2003;Inatsu and Hoskins 2004;Brayshaw et al 2008Brayshaw et al , 2011Ogawa et al 2012).…”

Atmospheric Response to the Gulf Stream: Seasonal Variations*

“…in the present paper and shorter-term variations including synoptic variability (e.g., Alexander and Scott 1997;Zolina and Gulev 2003;Sampe and Xie 2007;Nakamura et al 2008;Brayshaw et al 2008) should be investigated. Also, since the Gulf Stream is part of the upper limb of the Atlantic meridional overturning circulation, which can give rise to a source of decadal predictability (Keenlyside et al 2008), the shallow and deep heating modes may play some role in shaping predictable patterns of climate over the North Atlantic.…”

Atmospheric Forcing of the Winter Air–Sea Heat Fluxes over the Northern Red Sea

“…On a global scale, air-sea heat exchange is a significant factor influencing the weather and, on longer time scales, the climate regime. On the other hand, atmospheric circulation on various spatial and temporal scales affects the surface energy exchange (Cayan 1992;Alexander and Scott 1997;Bond and Cronin 2008;Shaman et al 2010;Josey et al 2011;Papadopoulos et al 2012a,b,c). From an oceanographic point of view, the air-sea heat exchange regulates the warming/cooling of the sea surface layers, thus fuelling the oceanic thermohaline circulation.…”