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Sun L.,Anhui University of Science and Technology | Sun L.,CAS Institute of Atmospheric Physics | Yang Y.-J.,Anhui Institute of Meteorological science | Xian T.,Anhui University of Science and Technology | And 2 more authors.
Marine Ecology Progress Series | Year: 2010

Recent studies demonstrate that chlorophyll a (chl a) concentrations in ocean surface waters can be significantly enhanced due to typhoons. The present study investigated chl a concentrations in the middle of the South China Sea (SCS) from 1997 to 2007. Only the Category 1 (minimal) Typhoon Hagibis (2007) had a notable effect on chl a concentrations. Typhoon Hagibis had a strong upwelling potential due to its location near the equator, and the forcing time of the typhoon (>82 h) was much longer than the geostrophic adjustment time (∼63 h). The higher upwelling velocity and the longer forcing time increased the depth of the mixed-layer, which consequently induced a strong phytoplankton bloom that accounted for about 30% of the total annual chl a concentration in the middle of the SCS. Induction of significant upper ocean responses can be expected if the forcing time of a typhoon is long enough to establish strong upwelling. © Inter-Research 2010.

Yang Y.-J.,Anhui University of Science and Technology | Yang Y.-J.,Anhui Institute of Meteorological science | Sun L.,Anhui University of Science and Technology | Sun L.,State Oceanic Administration | And 3 more authors.
International Journal of Remote Sensing | Year: 2010

The responses of the upper ocean to typhoons were investigated by the observations of sea surface wind (SSW), sea surface temperature (SST), sea surface height anomaly (SSHA), chlorophyll-a (Chl-a) and Argo floats.TyphoonNamtheun had notable impacts on the upper ocean along its track from July to August 2004. The local processes (entrainment and upwelling) dominated the upper ocean responses in the regions of the pre-existing cold eddy and beneath the typhoon track, where the observed locations of upwelling, SSHA changes, SST cooling, and Chl-a enhancement were consistent with each other. Besides, there were cold tongues extending from the cold centres. The trajectories of Argo floats, along with the cold tongues, indicated that the surface advections induced such non-local responses.On the other hand, the following weak typhoon Malou had few impacts on the upper ocean. Finally, the mechanisms of the Chl-a concentration enhancement were sketched as the effects of both the local upwelling and the non-local advection. This study implies that some non-local processes, e.g. horizontal advections,may play a notable role in the upper ocean responses to the typhoons. © 2010 Taylor & Francis.

Sun L.,Anhui University of Science and Technology | Sun L.,State Oceanic Administration | Yang Y.-J.,Anhui University of Science and Technology | Yang Y.-J.,CAS Institute of Atmospheric Physics | And 4 more authors.
Atmosphere - Ocean | Year: 2012

Argo salinity and temperature profiles, along with other sea surface measurements, were used to explore the impacts of Typhoon Namtheun (2004) on the ocean. Namtheun took local enthalpy heat from the sea (0.39-0.7 × 10 8 J m-2), cooled the sea surface water as a result of vertical mixing (maximum 3-4°C) and produced heavy precipitation over the sea (100-180 mm). During this time, the vast latent heat released (2.6-4.4 × 108 J m-2) by the precipitation made a larger contribution to the typhoon's energy budget than the local air-sea enthalpy flux. In the upper ocean, the oceanic responses can be separated into two sub-processes, the fast spin-up accompanied by one-dimensional vertical mixing and the slow spin-down accompanied by the convergence of surface water. From Argo profiles on 28 July, it can be seen that the typhoon-induced surface mixing broke down the seasonal thermocline (approximately 20 db) within one day. In addition, the shallower (<200 db) convergence of the sea surface fresh water as a result of precipitation also made the post-typhoon water fresher (0.04 (practical salinity scale used)). In the deep ocean, the rapid upwelling at the top of the permanent thermocline suggests that the fast spin-up is a barotropic mechanism, probably gravity pressure. During the slow spin-down stage, the upwelling signal propagated downward (approximately 2 m h-1) from the shallow water to the deep ocean for about 10 days; this was a baroclinic process. The baroclinic mechanism was more effective in maintaining a cyclonic eddy than in maintaining an inertial wave, and the low sea surface height anomaly and upwelling lasted much longer than the inertial oscillation (>20 days as opposed to approximately 10 days). This change in vertical structure and long-term upwelling could have impacts on the ocean environment and even on the short-term climate.

Yang J.,Nanjing University of Information Science and Technology | Yang J.,Key Laboratory for Cloud Physics and Weather Modification | Xie Y.-J.,Nanjing University of Information Science and Technology | Shi C.-E.,Anhui Institute of Meteorological science | And 3 more authors.
Pure and Applied Geophysics | Year: 2012

Intensive field experiments focused on fog chemistry were carried out in the northern suburb of Nanjing during the winters of 2006 and 2007. Thirty-seven fog water samples were collected in nine fog events. Based on the chemical analysis results of those samples and the simultaneous measurements of air pollution gases and atmospheric aerosols, the chemical characteristics of fog water and their relations with air pollutants during fog evolution were investigated. The results revealed an average total inorganic ionic concentration TIC = 21.18 meq/L, and the top three ion concentrations were those of SO 4 2-, NH 4 + and Ca 2+ (average concentrations 6.99, 5.95, 3.77 meq/L, respectively). However, the average pH value of fog water was 5.85, which is attributable to neutralization by basic ions (NH 4 + and Ca 2+). The average TIC value of fog water measured in advection-radiation fog was around 2.2 times that in radiation fog, and the most abundant cation was NH 4 + in advection-radiation fog and Ca 2+ in radiation fog. In dense fog episodes, the concentration variations of primary inorganic pollution gases showed a "V"-shaped pattern, while those of volatile organic compounds (VOCs) displayed a "K"-shaped pattern. The dense fog acted as both the source and sink of atmospheric aerosol particles; fog processes enhanced particle formation, leading to the phenomenon that the aerosol concentration after fog dissipation was higher than that before the fog, and at the same time, mass concentration of PM 10 reached the lowest value in the late stage of extremely dense fog episodes because of the progressive accumulated effect of wet deposition of large fog droplets. Both air pollution gases and aerosols loading controlled the ion compositions of fog water. The Ca 2+ in fog water originated from airborne particles, while SO 4 2- and NH 4 + were from both heterogeneous production and soluble particulate species. © 2011 Springer Basel AG.

Bi Y.,Hefei University of Technology | Chen Y.,Hefei University of Technology | Zhou R.,Hefei University of Technology | Yi M.,Hefei University of Technology | Deng S.,Anhui Institute of Meteorological science
Advances in Atmospheric Sciences | Year: 2011

The infrared radiative effect of methane was analyzed using the 2D, interactive chemical dynamical radiative SOCRATES model of the National Center for Atmospheric Research. Then, a sensitivity experiment, with the methane volume mixing ratio increased by 10%, was carried out to study the influence of an increase of methane on air temperature. The results showed that methane has a heating effect through the infrared radiative process in the troposphere and a cooling effect in the stratosphere. However, the cooling effect of the methane is much smaller than that of water vapor in the stratosphere and is negligible in the mesosphere. The simulation results also showed that when methane concentration is increased by 10%, the air temperature lowers in the stratosphere and mesosphere and increases in the troposphere. The cooling can reach 0.2 K at the stratopause and can vary from 0.2-0.4 K in the mesosphere, and the temperature rise varies by around 0.001-0.002 K in the troposphere. The cooling results from the increase of the infrared radiative cooling rate caused by increased water vapor and O3 concentration, which are stimulated by the increase in methane in most of the stratosphere. The infrared radiation cooling of methane itself is minor. The depletion of O3 stimulated by the methane increase results indirectly in a decrease in the rate of solar radiation heating, producing cooling in the stratopause and mesosphere. The tropospheric warming is mainly caused by the increase of methane, which produces infrared radiative heating. The increase in H2O and O3 caused by the methane increase also contributes to a rise in temperature in the troposphere. © 2010 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg.

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