An ocean general circulation model(OGCM) is used to demonstrate remote efects of tropical cyclone wind(TCW) forcing in the tropical Pacific. The signature of TCW forcing is explicitly extracted using a locally weighted quadratic least-squares regression(called as LOESS) method from six-hour satellite surface wind data; the extracted TCW component can then be additionally taken into account or not in ocean modeling, allowing isolation of its efects on the ocean in a clean and clear way. In this paper, seasonally varying TCW fields in year 2008 are extracted from satellite data which are prescribed as a repeated annual cycle over the western Pacific regions of the equator(poleward of 10 N/S); two long-term OGCM experiments are performed and compared, one with the TCW forcing part included additionally and the other not. Large, persistent thermal perturbations(cooling in the mixed layer(ML) and warming in the thermocline) are induced locally in the western tropical Pacific, which are seen to spread with the mean ocean circulation pathways around the tropical basin. In particular, a remote ocean response emerges in the eastern equatorial Pacific to the prescribed of-equatorial TCW forcing, characterized by a cooling in the mixed layer and a warming in the thermocline. Heat budget analyses indicate that the vertical mixing is a dominant process responsible for the SST cooling in the eastern equatorial Pacific. Further studies are clearly needed to demonstrate the significance of these results in a coupled ocean-atmosphere modeling context.
In view of the limitation and one-sidedness of the traditional cloud tracking algorithm on the satellite image, this paper presents a strong convective cloud automatic tracking algorithm based on image matching and pattern recognition. During the recognition process of the strong convective cloud, we combine with regional smoothing filtering algorithm and dynamic brightness temperature threshold method to eliminate non convective cloud clusters, and then use the cluster method for extraction of the cloud block to complete the identification process. In the tracking process, we use the area matching method and moment invariant matching method to finish the automatic tracking process. Experimental results show that the algorithm can track the complete life history of the strong convective cloud successfully.
Abstract In this paper, it is shown that coherent large-scale low-frequency variabilities in the North Atlantic Ocean—that is, the variations of thermohaline circulation, deep western boundary current, northern recirculation gyre, and Gulf Stream path—are associated with high-latitude oceanic Great Salinity Anomaly events. In particular, a dipolar sea surface temperature anomaly (warming off the U.S. east coast and cooling south of Greenland) can be triggered by the Great Salinity Anomaly events several years in advance, thus providing a degree of long-term predictability to the system. Diagnosed phase relationships among an observed proxy for Great Salinity Anomaly events, the Labrador Sea sea surface temperature anomaly, and the North Atlantic Oscillation are also discussed.
Abstract In this study, a mechanism is demonstrated whereby a large reduction in the Atlantic thermohaline circulation (THC) can induce global-scale changes in the Tropics that are consistent with paleoevidence of the global synchronization of millennial-scale abrupt climate change. Using GFDL’s newly developed global coupled ocean–atmosphere model (CM2.0), the global response to a sustained addition of freshwater to the model’s North Atlantic is simulated. This freshwater forcing substantially weakens the Atlantic THC, resulting in a southward shift of the intertropical convergence zone over the Atlantic and Pacific, an El Niño–like pattern in the southeastern tropical Pacific, and weakened Indian and Asian summer monsoons through air–sea interactions.
Compared with other morphological nanomaterials, nanorods have many unique properties that are closely related to their thermal stability. However, current studies on melting thermodynamic theory of nanorods are still not perfect, and the mechanism and the quantitative regularities of the effect of size of nanorods on melting thermodynamics still remain unclear. Herein, we proposed a melting model of nanorods, derived the thermodynamic relations (free of any adjustable parameters) between the melting temperature, melting enthalpy, and melting entropy, respectively, and the radius of nanorods, and discussed the mechanism of the effect of nanorods and the size dependences of melting thermodynamic properties. Experimentally, taking the melting of Se nanorods as an experimental system, Se nanorods with different diameters were prepared by a Na2SeSO3 disproportionation method, and then the melting temperature and melting thermodynamic properties were determined by differential scanning calorimetry. The effects of the diameter of Se nanorods on the melting temperature and the melting thermodynamic properties were obtained. The experimental results are consistent with the theoretical relations. Both theoretical and experimental results demonstrate that the radius and length of nanorods have significant effects on the melting temperature and the melting thermodynamic properties; for nanorods with a large aspect ratio, the main factors of influence are interfacial tension and radius. Compared with spherical nanoparticles with the same radius, the reduced values of the melting temperature and the thermodynamic properties of nanorods are just half of those corresponding to spherical nanoparticles; the melting temperature, the melting enthalpy, and the melting entropy decrease with the decrease in the radius, and when the radius exceeds 10 nm, these physical quantities are all linearly related to the reciprocal of the radius. The theory can describe the quantitative size-dependent melting thermodynamic properties of nanorods, explain and predict the melting behaviors of nanorods.
We propose a new approach to decompose observed climate variations over the Atlantic Hurricane Basin's main development region (MDR) into components attributable to radiative forcing changes and to internal oceanic variability. Our attribution suggests that the observed multidecadal anomalies of vertical shear (Uz) and a simple index of maximum potential intensity (SIMPI) for tropical cyclones are both dominated by internal variability, consistent with multidecadal variations of Atlantic Hurricane activity; changes in radiative forcing led to increasing Uz and decreasing SIMPI since the late 50's, unfavorable for Atlantic Hurricane activity. Physically, at least for the GFDL model, sea surface temperature (SST) anomalies induced by ocean heat transport variations are more efficient in producing negative Uz anomalies than that induced by altered radiative forcing.
Abstract The ventilation of the central Labrador Sea is important for the uptake of ocean tracers and carbon. Using historical ocean observations, we construct a simple multiple linear regression model that successfully reconstructs the decadal variability of the upper ∼2,000 m of the central Labrador Sea water properties based on observed indices that represent two different open‐ocean ventilation mechanisms. The first mechanism is the modification of deep ocean properties through local decadal variability of the Labrador Sea deep convective mixing. The second, more novel, mechanism is the climatological convective vertical redistribution of upper central Labrador Sea temperature and salinity anomalies associated with the nonlocal large‐scale subpolar Atlantic Multidecadal Variability and the Atlantic Meridional Overturning Circulation. The ventilated decadal central Labrador Sea signal subsequently spreads into the western subpolar North Atlantic. The results have important implications for predicting decadal ventilated signals in the Labrador Sea that are associated with the large‐scale climate variability.
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