Current Issue

• Relationship between the Snow Cover Day and MonsoonIndex in Tibetan Plateau
• 2010 Vol. 29 (5): 1093-1101. 
• Abstract ( ) PDF (1141KB) ( )
• The basic features and trends of snow cover days over 45 years and the monsoon variations of nearly 60 years, and the further relation between monsoon index and snow cover days in Tibetan Plateau were analyzed using the EOF analysis, the running t\|test and correlation analysis methods, snow cover day data (from 1960 to 2004) obtained from 50 weather stations in Tibetan Plateau region, the monthly NCEP/NCAR reanalysis gridded data 2.5°×2.5° from January 1948 to February 2009, the daily mean 600 hPa height reanalysis gridded data 2.5°×2.5° from January 1, 1979 to December 31, 2009, and the surface heating field intensity data of Tibetan Plateau. The results show that when surface heating field intensity in Tibetan Plateau was strong, the monsoon in midwinter was weak, and the surface heating field intensity was weak in the following spring.The increase (or decrease) of summer monsoon in Tibetan Plateau would result in an increase (or a decrease) of the snow cover days in Tanggula Mountain but a decrease (or an increase) in the Bangoin and north\|eastern Qinghai; the increased (or decreased) winter monsoon in Tibetan Plateau would cause an increase (or decrease) of snowcover days in Himalaya mountains and Tanggula Mountain but a decrease (or increase) in the southern Tibet.

• Preliminary Study on Relationship between Clustering Activity ofTibetan Plateau Vortex and 10～30 day Low\|Frequency Oscillations
• 2010 Vol. 29 (5): 1102-1110. 
• Abstract ( ) PDF (1187KB) ( )
• The temporal\|spatial locations and frequencis of Tibetan Plateau (TP) Vortex occurred from May to September 1998 and 2003 are statistically analyzed, the clustering activity periods of TP Vortex in 1998 and 2003 have been determined, 500 hPa relative vorticity and 10～30 day low\|frequency oscillation (LFO) of OLR are discussed also. The results show that the occurrence of TP Vortex is of clustering activity feature and periodicity. The nine active periods of TP Vortex are closly associated with 10～30 day and 30～60 day LFOs. The most of TP Vortex developed in the positive phase (cyclone) of 10~30 day LFO and negative phase (convection) of convective disturbance. All nine active periods of TP Vortex are corresponding to the cyclonic phase of 10～30 day oscillations. The 10～30 day positive vorticity turbulence provided the cyclonic vortictiy dynamics condition for development and maintenance of TP Vortex to make for the frequently development of TP vortex in positive phase of turbulence. It is found that the 10～30 day oscillations of relative vorticity of atmosphere are of improtant modulation action for clustering activity of TP Vortex. The convective phase of 10～30 day oscillations of convective activity in TP is to take the clustering activity of TP Vortex as main character. TP Vortex repeatedly and continuously develops in convective phase to make for the active development of convective disturbance.

• mKdV Equation for Solitary Rossby Waves with Linear Topography Effect in Barotropic Fluids
• SONG Jian;YANG Lian\|gui
• 2010 Vol. 29 (5): 1137-1141. 
• Abstract ( ) PDF (119KB) ( )
• The modifyKorteweg-de Vries (mKdV) equations, governing the evolution of the amplitude of solitary Rossby waves, are derived from quasi-geostrophic vorticity equation by using the perturbation method. The result manifests that the linear topography effect with the change of latitude can induce solitary Rossby wave.