Tropical cyclone （TC） genesis in the South China Sea （SCS） during 1979-2008 underwent a decadal variation around 1993. A total of 55 TCs formed in the SCS from May to September during 1994- 2008, about twice that ...Tropical cyclone （TC） genesis in the South China Sea （SCS） during 1979-2008 underwent a decadal variation around 1993. A total of 55 TCs formed in the SCS from May to September during 1994- 2008, about twice that during 1979-1993 （27）. During the TC peak season （July-September, JAS）, there were 43 TCs fi＇om 1994-2008, but only 17 during 1979-1993. For July in particular, 13 TCs formed from 1994-2008, but there were none during 1979-1993. The change in TC number is associated with changes of key environmental conditions in atmosphere and ocean. Compared to 1979-1993, the subtropical high was significantly weaker and was displaced more eastward during 1994-2008. In the former period, a stronger subtropical high induced downward flow, inhibiting TC formation. In the latter period, vertical wind shear and outgoing longwave radiation all weakened. Mid-level （850-500 hPa） humidity, and relative vorticity were higher. Sea surface temperature and upper layer heat content were also higher in the area. All these factors favor TC genesis during the latter period. The decadal change of TC genesis led to more landfalling TCs in Southern China during the period 1994-2008, which contributed to an abrupt increase in regional rainfall.展开更多
4 Summary and conclusion The JOULE sounding rocket 1 experiment was carried out at Poker Flat Research Range in Alaska around 1200 UT on March 27th,2003 with two instrumented rockets and one chemical tracer rocket.Fro...4 Summary and conclusion The JOULE sounding rocket 1 experiment was carried out at Poker Flat Research Range in Alaska around 1200 UT on March 27th,2003 with two instrumented rockets and one chemical tracer rocket.From the released TMA trails,neutral wind measurements from approximately 85 to 160 km altitude showed a vertically propagating wave and a jet structure around 120 km altitude.Large shears appeared at the bottom side of the jet with Richardson numbers close to or smaller than the critical value of 0.25,which implies the possible existence of Kelvin-Helmholtz instabilities caused by the vertical shear in the fast flows.展开更多
基金Supported by the National Basic Research Program of China (973 Program)(No.2011CB403500)the Knowledge Innovation Program of Chinese Academy of Sciences (Nos. KZCX2-YW-Q11-02, XDA05090404)+1 种基金the National Basic Research Program of China (973 Program) (No. 2010CB950302)the Qianren and Changjiang Scholar Projects, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)and SOEST-8711 & IPRC-901
文摘Tropical cyclone （TC） genesis in the South China Sea （SCS） during 1979-2008 underwent a decadal variation around 1993. A total of 55 TCs formed in the SCS from May to September during 1994- 2008, about twice that during 1979-1993 （27）. During the TC peak season （July-September, JAS）, there were 43 TCs fi＇om 1994-2008, but only 17 during 1979-1993. For July in particular, 13 TCs formed from 1994-2008, but there were none during 1979-1993. The change in TC number is associated with changes of key environmental conditions in atmosphere and ocean. Compared to 1979-1993, the subtropical high was significantly weaker and was displaced more eastward during 1994-2008. In the former period, a stronger subtropical high induced downward flow, inhibiting TC formation. In the latter period, vertical wind shear and outgoing longwave radiation all weakened. Mid-level （850-500 hPa） humidity, and relative vorticity were higher. Sea surface temperature and upper layer heat content were also higher in the area. All these factors favor TC genesis during the latter period. The decadal change of TC genesis led to more landfalling TCs in Southern China during the period 1994-2008, which contributed to an abrupt increase in regional rainfall.
基金supported by the National Science Foundation(NSF)(Grant No.ATM0955629)the National Aeronautics and Space Administration(NASA)(Grant Nos.NNX13AD64G and NNX14AD46G)Air Force Office of Scientific Research(AFOSR)(Grant Nos.FA9550-16-1-0059 and MURI FA9559-16-1-0364)
文摘4 Summary and conclusion The JOULE sounding rocket 1 experiment was carried out at Poker Flat Research Range in Alaska around 1200 UT on March 27th,2003 with two instrumented rockets and one chemical tracer rocket.From the released TMA trails,neutral wind measurements from approximately 85 to 160 km altitude showed a vertically propagating wave and a jet structure around 120 km altitude.Large shears appeared at the bottom side of the jet with Richardson numbers close to or smaller than the critical value of 0.25,which implies the possible existence of Kelvin-Helmholtz instabilities caused by the vertical shear in the fast flows.
