Atmospheric responses to oceanic eddies in the Kuroshio Extension region

Abstract

We examined atmospheric responses to 35,000+ oceanic eddies in the Kuroshio Extension region during the period of [2006][2007][2008][2009]. Using satellite data, we showed that cold (warm) eddies cause surface winds to decelerate (accelerate) and reduce (increase) latent and sensible heat fluxes, cloud liquid water, water vapor content, and rain rate; all of these changes are quantified. Both the linear correlation between wind divergence and downwind sea surface temperature (SST) gradient and the correspondence between vorticity and crosswind SST gradient support the vertical momentum mixing mechanism, which indicates that SST perturbations modify surface winds by changing the vertical turbulent mixing in the marine atmospheric boundary layer (MABL). High-resolution National Centers for Environmental Prediction Climate Forecast System Reanalysis (CFSR) data can reproduce the atmospheric responses to the oceanic eddies in the MABL albeit with some differences in intensity. In addition, the CFSR data reveal that the atmospheric responses to these oceanic eddies are not confined in the MABL. MABL deepens (shoals) over the warm (cold) eddies; enhanced (reduced) vertical transport of transient zonal momentum occurs over the warm (cold) eddies from the sea surface to about 850 hPa level; vertical velocity anomalies over oceanic eddies penetrate beyond the MABL into free atmosphere; there exists a positive correlated relationship between SST and convective rain rate anomalies, indicative of ocean eddies' impact on the free troposphere. However, the composites of cloud liquid water and rain rate are different from the results based on the satellite data.

Oceanic Eddy Characteristics and Generation Mechanisms in the Kuroshio Extension Region

“…The Kuroshio Extension (KE) region, from Japan eastward to the mid‐Pacific, is one of the two largest eddy kinetic energy (EKE) bands in the northern Pacific Ocean (the other being the subtropical frontal zone; Chow et al, ; Liu et al, ; Qiu & Chen, ; Yang et al, ). Eddy activities in the KE play an important role in the decade variations in the KE system circulation (Qiu & Chen, , ) and air‐sea interaction (Ma et al, ). Ma et al () found that the wind speed is enhanced (weakened) and the precipitation is increased (decreased) with the presence of warm (cold) eddies.…”

“…Eddy activities in the KE play an important role in the decade variations in the KE system circulation (Qiu & Chen, , ) and air‐sea interaction (Ma et al, ). Ma et al () found that the wind speed is enhanced (weakened) and the precipitation is increased (decreased) with the presence of warm (cold) eddies. After the Kuroshio Current leaves the Japanese coast, it enters the open ocean where the constraint of topography is lost.…”

The Benefits of Global High Resolution for Climate Simulation: Process Understanding and the Enabling of Stakeholder Decisions at the Regional Scale

“…The ocean's mesoscale influence on the atmosphere in the extratropics has been known from observational analyses for some time, both near the surface (e.g., Chelton et al 2004;Xie 2004) and in the free troposphere via precipitation, clouds, and upward winds (e.g., Minobe et al 2008Minobe et al , 2010Tokinaga et al 2009;Frenger et al 2013;J. Ma et al 2015;Smirnov et al 2015).…”

“…Ma et al 2015;Smirnov et al 2015). However, it has required deployment of models with sufficient resolution in both the atmosphere and ocean in order to study and understand such interactions at the process level Chelton and Xie 2010;Kwon et al 2010;J. Ma et al 2015;Ma et al 2017).…”

Effects of a Cold Ocean Eddy on Local Atmospheric Boundary Layer Near the Kuroshio Extension: In Situ Observations and Model Experiments

“…The Kuroshio Extension (KE), with steep sea surface temperature (SST) fronts and pinched‐off mesoscale eddies (Yasuda et al, ), induces rich air‐sea interactions through strong surface heat fluxes (Kelly et al, ; Kwon et al, ; Nonaka & Xie, ; Small et al, ). Cold ocean eddies weaken surface wind speed by suppressing turbulent heating (Park et al, ), resulting in surface wind convergences upwind and divergences downwind, and the opposite patterns hold for warm eddies (Frenger et al, ; J. Ma et al, ). Sugimoto et al () used a regional atmospheric model to indicate that oceanic eddies can possibly affect synoptic atmospheric variability.…”