The responses of the upper ocean to Typhoon Haitang in July 2005 are investigated using Argo float and multiplatform satellite data.The results show decreasing sea surface temperature(SST),a deepening of the mixed layer depth(MLD),and enhanced Chlorophyll-a(Chl-a)concentration.Two extreme cool regions are identified.While the magnitude of SST cooling in the two regions is similar,the biological response(Chla enhancement)differs.To facilitate comparisons,the region to the northeast of Taiwan is defined as region A and the region east of Taiwan as region B.Ekman pumping and the intrusion of the Kuroshio play an important role in the enhancement of Chl-a in region A.Cold eddies provide the material source for the formation of the cold center in region B,where mixing is dominant.Because of the relatively high translation speed(5 m/s)in region B,Ekman pumping has little influence on the cooling and Chl-a enhancement processes.Moreover,the MLD is shallower than the nutricline,which means that mixing does not result in a marked increase in nutrients in the euphotic layer(where the nutrient concentration is uniformly depleted).Sea temperatures,in contrast,gradually decrease with depth below the bottom of the mixed layer.In contrast to region A,region B showed no significant enhancement of Chl-a but strong SST cooling.
Impacts of El Nin o Modoki(ENM), La Nin a Modoki(LNM), canonical El Nin o(CEN) and canonical La Nin a(CLN) on tropical cyclones(TCs) that made landfall over China's Mainland during 1951–2011 are analysed using best-track data from China, the USA and Japan. Relative to cold phase years(LNM and CLN), landfalling TCs in warm years(ENM and CEN) have a farther east genesis location, as well as longer track lengths and durations, both in total and before landfall. ENM demonstrates the highest landfall frequency, most northerly mean landfall position, and shortest after-landfall sustainability(track length and duration), which indicate a more frequent and extensive coverage of China's Mainland by TCs, but with shorter after-landfall influence. CEN has low landfall frequency and the most southerly mean landfall location. LNM has the most westerly genesis location, being significantly farther west than the 1951–2011 average and leading to short mean track lengths and durations both in total or before landfall, all of which are significantly shorter than the 1951–2011 average. Variations in the low-level wind anomaly, vertical wind shear, mid-level relative humidity, steering flow, the monsoon trough and the western Pacific subtropical high(WPSH) can to some extent account for the features of frequency, location, track length and duration of landfalling TCs. Since ENSO Modoki is expected to become more frequent in the near future, the results for ENSO Modoki presented in this paper are of particular significance.
The assertion that the thermohaline circulation(THC)is driven and sustained by mechanical energy has been increasingly accepted.The simplest conceptual model describing the THC is the Stommel two-box model.Given the vertical stratification in the real ocean,layered models were designed and used.In this research,using a two-layer conceptual model based on energy constraint,we studied basic features of thermal-mode and saline-mode circulations.We focused on the effects of freshwater flux and mixing energy on the intensity and multiple equilibrium states of the THC.The results show that more important than affecting the THC intensity,both the decrease of freshwater flux and increase of mixing energy can lead to an"abrupt transition"in the THC from a stable saline to a stable thermal mode,which further develops the THC energy theory.
