Niu Ruoyun, Zhang Zhigang, Jin Ronghua. The atmospheric circulation features of two persistent heavy rainfalls over Southern China in the summer of 2010. J Appl Meteor Sci, 2012, 23(4): 385-394.
Citation:
Niu Ruoyun, Zhang Zhigang, Jin Ronghua. The atmospheric circulation features of two persistent heavy rainfalls over Southern China in the summer of 2010. J Appl Meteor Sci, 2012, 23(4): 385-394.
Niu Ruoyun, Zhang Zhigang, Jin Ronghua. The atmospheric circulation features of two persistent heavy rainfalls over Southern China in the summer of 2010. J Appl Meteor Sci, 2012, 23(4): 385-394.
Citation:
Niu Ruoyun, Zhang Zhigang, Jin Ronghua. The atmospheric circulation features of two persistent heavy rainfalls over Southern China in the summer of 2010. J Appl Meteor Sci, 2012, 23(4): 385-394.
The large scale rainstorm flooding induced by the persistent heavy rainfall in summer is the main meteorological disaster in China. Still more efforts are needed to improve the quantitative and refined forecast ability on the characteristic quantity of the persistent heavy rainfall, such as starting and ending time, drop location and the intensity of precipitation. By using daily intensive observed precipitation data and NCEP/NCAR reanalysis data, two persistent heavy rainfalls in Southern China is analyzed and compared to investigate the spatial-temporal evolutioning features and the influencing mechanism of the large scale key influence systems, and atmospheric circulation features of the two processes are summarized as below.During the periods of persistent heavy rainfalls over Southern China in the summer of 2010, the westerly trough over coastland reformed and strengthened frequently and the mid-latitude frontal zone maintained steadily, the low level southwest jet strengthened repeatedly and the strong gradient belt of meridional wind on the left side of the low level southwest jet axis are relatively stable. Meanwhile the latitude location of the subtropical westerly jet, the ridge of South Asia high and the west Pacific subtropical high are also relatively stable in East Asia. Under the joint influences of the large scale key influence systems mentioned above, vapor convergence in the low layer and divergence in the upper layer occurs repeatedly, and the vertical ascending motion strengthens over the heavy rainfall belt, which leads to the formation of the persistent heavy rainfall over Southern China.Before the persistent heavy rainfall in Southern China, the trough in western Siberian keeps reforming and strengthening, shifting to east of Mascarene high and its western high. The subtropical upper westerly jet is also established and maintains in East Asian.The heavy rainfall belt of the persistent heavy rainfall lies in these areas: The strong gradient convergence belt of meridional wind on the left side of the low level southwest jet axis, the strong divergence zone between the south boundary of subtropical upper westerly jet and the ridge axis of South Asia high, the belt of high updraft vertical velocity in the middle layer in East Asian, the south margin of the middle-latitude frontal zone in the middle-upper troposphere, and the north boundary of the west Pacific subtropical high.
Fig.
1
Spatial and temporal distribution of the persistent heavy rainfalls over Southern China in the summer of 2010 (a) altitude-time cross section of daily precipitation averaged over 110°—122.5°E from June to July, (b) accumulated precipitation from 13 June to 28 June, (c) accumulated precipitation from 3 July to 16 July
Fig.
2
Altitude-time cross sections of geopotential heights at 200 hPa from June to July in 2010 averaged over 70°—80°E (a) and 120°E (b)(dashed lines show the trough lines; two rectangles: 25.3°—28.7°N shows the heavy rainfall belt of the persistent heavy rainfall over the south Yangtze valley in June, 29°—32°N shows the heavy rainfall belt of the persistent heavy rainfall over the middle and lower reaches of the Yangtze)
Fig.
4
Daily variations of southwest jet area index over Southern China and the maximum of southwest wind at 850 hPa (a), time-altitude cross section of southwest wind vector above 4 m·s-1with meridional wind above 1 m·s-1 (b) and vertically integrated water vapor transport flux from surface to 700 hPa (vectors and contours, unit: kg·m-1·s-1) averaged over 110°—122.5°E and its divergence (shaded) from June to July in 2010(c)(rectangle is same as in Fig. 2)
Fig.
5
Longitude-time cross section of the maximum of geopotential heights (shaded) between 10°—50°S and the maximum of southwest wind (contours, unit: m·s-1) between 20°—32.5°N in 100°—122.5°E, and the lag correlation coefficient of southwest jet area index over Southern China against the maximum of geopotential heights between 10°—50°S at 850 hPa from June to July in 2010
(light and deep shaded areas show passing the test of 0.10 and 0.05 levels, respectively)
Fig.
6
Altitude-time cross section of zonal wind (thin solid line, unit: m·s-1), geopotential heights (dotted lines, unit: dagpm) and horizontal divergence (shaded, unit: 10-6s-1) averaged over 110°—122.5°E at 200 hPa from June to July in 2010
(thick solid line is the South Asia high ridge; rectangle is same as in Fig. 2)
Fig.
7
Altitude-time cross section of geopotential heights (solid line, unit: dagpm) and vertical speed (shaded) averaged over 110°—122.5°E at 500 hPa from June to July in 2010(rectangle is same as in Fig. 2)
Fig.
8
Latitude-altitude cross sections of vertical speed(unit: 10-2Pa·s-1),water vapor transport flux(unit: g·m-1·s-1·Pa-1) and specific humidity(shaded) and θse(unit: K) averaged over 110°—122.5°E in the persistent heavy rainfalls over Southern China in 2010
(dashed lines show the area of the heavy rainfall belt)
Figure 1. Spatial and temporal distribution of the persistent heavy rainfalls over Southern China in the summer of 2010 (a) altitude-time cross section of daily precipitation averaged over 110°—122.5°E from June to July, (b) accumulated precipitation from 13 June to 28 June, (c) accumulated precipitation from 3 July to 16 July
Figure 2. Altitude-time cross sections of geopotential heights at 200 hPa from June to July in 2010 averaged over 70°—80°E (a) and 120°E (b)(dashed lines show the trough lines; two rectangles: 25.3°—28.7°N shows the heavy rainfall belt of the persistent heavy rainfall over the south Yangtze valley in June, 29°—32°N shows the heavy rainfall belt of the persistent heavy rainfall over the middle and lower reaches of the Yangtze)
Figure 3. Averaged geopotential heights at 200 hPa and 500 hPa during the persistent heavy rainfalls over Southern China in the summer of 2010
Figure 4. Daily variations of southwest jet area index over Southern China and the maximum of southwest wind at 850 hPa (a), time-altitude cross section of southwest wind vector above 4 m·s-1with meridional wind above 1 m·s-1 (b) and vertically integrated water vapor transport flux from surface to 700 hPa (vectors and contours, unit: kg·m-1·s-1) averaged over 110°—122.5°E and its divergence (shaded) from June to July in 2010(c)(rectangle is same as in Fig. 2)
Figure 5. Longitude-time cross section of the maximum of geopotential heights (shaded) between 10°—50°S and the maximum of southwest wind (contours, unit: m·s-1) between 20°—32.5°N in 100°—122.5°E, and the lag correlation coefficient of southwest jet area index over Southern China against the maximum of geopotential heights between 10°—50°S at 850 hPa from June to July in 2010
Figure 6. Altitude-time cross section of zonal wind (thin solid line, unit: m·s-1), geopotential heights (dotted lines, unit: dagpm) and horizontal divergence (shaded, unit: 10-6s-1) averaged over 110°—122.5°E at 200 hPa from June to July in 2010
Figure 7. Altitude-time cross section of geopotential heights (solid line, unit: dagpm) and vertical speed (shaded) averaged over 110°—122.5°E at 500 hPa from June to July in 2010(rectangle is same as in Fig. 2)
Figure 8. Latitude-altitude cross sections of vertical speed(unit: 10-2Pa·s-1),water vapor transport flux(unit: g·m-1·s-1·Pa-1) and specific humidity(shaded) and θse(unit: K) averaged over 110°—122.5°E in the persistent heavy rainfalls over Southern China in 2010