The responses of Sea Surface Temperature(SST) to greenhouse gas(GHG) and anthropogenic aerosol in the North Pa- cific are compared based on the historical single and all-forcing simulations with Geophysical Fluid Dynamics Laboratory Climate Model version 3(GFDL CM3). During 1860–2005, the effect of GHG forcing on the North Pacific SST is opposite to that of the aerosol forcing. Specifically, the aerosol cooling effect exceeds the GHG warming effect in the Kuroshio Extension(KE) region dur- ing 1950–2004 in the CM3 single forcing. The mid-latitude response of ocean circulation to the GHG(aerosol) forcing is to enhance(weaken) the Subtropical Gyre. Then the SST warming(cooling) lies on the zonal band of 40?N because of the increased(reduced) KE warm advection effect in the GHG(aerosol) forcing simulations, and the cooling effect to SST will surpass the warming effect in the KE region in the historical all-forcing simulations. Besides, the positive feedback between cold SST and cloud can also strengthen the aerosol cooling effect in the KE region during boreal summer, when the mixed layer depth is shallow. In the GHG(aerosol) forcing simulations, corresponding to warming(cooling) SST in the KE region, the weakened(enhanced) Aleutian Low appears in the Northeast Pacific. Consequently, the SST responses to all-forcing in the historical simulations are similar to the re- sponses to aerosol forcing in sign and spatial pattern, hence the aerosol effect is quite important to the SST cooling in the mid-latitude North Pacific during the past 55 years.
Experimental outputs of 11 Atmospheric Model Intercomparison Project(AMIP) models from phase 5 of the Coupled Model Intercomparison Project(CMIP5) are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter. The analysis shows that the main features of the interannual variation of tropical rainfall anomalies, especially over the Central Pacific(CP)(5°S– 5°N, 175°E–135°W) and Indo-western Pacific(IWP)(20°S–20°N, 110°–150°E) are well captured in all the CMIP5/AMIP models. For the IWP and western Indian Ocean(WIO)(10°S–10°N, 45°–75°E), the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation. During El Ni°no/La Ni°na mature phases in boreal winter, consistent with observations, there are geopotential height anomalies known as the Pacific North American(PNA) pattern and Indo-western Pacific and East Asia(IWPEA) pattern in the upper troposphere, and the northwestern Pacific anticyclone(cyclone)(NWPA) in the lower troposphere in the models. Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP, while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO, as the SST anomaly is same in AMIP experiments. It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly.
A sea spray generation function(SSGF)for bubble-derived droplets that takes into account the impact of wave state on whitecap coverage was presented in this study.By combining the new SSGF with a previous wave-state-dependent SSGF for spume droplets,an SSGF applicable to both bubble-derived and spume droplets that includes the impacts of wave state was obtained.The produced SSGF varies with surface wind as well as with wave development.As sea surface wind increases,more sea spray droplets are produced,resulting in larger SSGFs and volume fluxes.Meanwhile,under the same wind conditions,the SSGF is mediated by wave state,with larger SSGFs corresponding to older waves and larger windsea Reynolds numbers.The impact of wave state on sea spray heat flux was then estimated by applying this SSGF while considering the thermodynamic feedback process.Under given atmospheric and oceanic conditions,the estimated sea spray heat flux increases with wind speed,wave age,and windsea Reynolds number.
The self-organizing map method is applied to satellite-derived sea-level anomaly fields of1993-2012 to study variations of the Kuroshio intrusion northeast of Taiwan Island.Four major features are revealed,showing significant seasonal variability of the intrusion.In general,the intrusion increases(decreases) with a high(low) sea-level anomaly at the edge of the East China Sea shelf in winter(summer).Open-ocean mesoscale eddies play an additional role in modulating the seasonal variation of the intrusion.Further analyses are needed to study eddy-Kuroshio interaction dynamics.
The mixed layer is deep in January–April in the Kuroshio Extension region. This paper investigates the response in this region of mixed layer depth(MLD) and the spring bloom initiation to global warming using the output of 15 models from CMIP5. The models indicate that in the late 21 st century the mixed layer will shoal, and the MLD reduction will be most pronounced in spring at about 33?N on the southern edge of the present deep-MLD region. The advection of temperature change in the upper 100 m by the mean eastward flow explains the spatial pattern of MLD shoaling in the models. Associated with the shoaling mixed layer, the onset of spring bloom inception is projected to advance due to the strengthened stratification in the warming climate.
The response of the Pacific Decadal Oscillation(PDO) to global warming according to the Fast Ocean Atmosphere Model(FOAM) and global warming comparison experiments of 11 IPCC AR4 models is investigated. The results show that North Pacific ocean decadal variability, its dominant mode(i.e., PDO), and atmospheric decadal variability, have become weaker under global warming, but with PDO shifting to a higher frequency. The SST decadal variability reduction maximum is shown to be in the subpolar North Pacific Ocean and western North Pacific(PDO center). The atmospheric decadal variability reduction maximum is over the PDO center. It was also found that oceanic baroclinic Rossby waves play a key role in PDO dynamics, especially those in the subpolar ocean. As the frequency of ocean buoyancy increases under a warmer climate, oceanic baroclinic Rossby waves become faster, and the increase in their speed ratio in the high latitudes is much larger than in the low latitudes. The faster baroclinic Rossby waves can cause the PDO to shift to a higher frequency, and North Pacific decadal variability and PDO to become weaker.
