Wednesday, 25 January 2012: 8:30 AM
Mechanism Study of Different Precipitation Caused by MCC in China
Room 239 (New Orleans Convention Center )
Using satellite image data, NCEP data and MICAPS data , two rain events caused by MCC at different precipitation-level are compared，respectively in northeast of Sichuan and southwest of Chongqing, China. Results show that heavy rain induced by MCC is more intensive and causes more flooding disaster. Sharp gradient on northern edge of cloud cluster or emergence of cold core with TBB≤-72℃ are considered to be one of characteristics of MCC inducing heavy rain. Otherwise, decrease of area of the cold core with TBB≤-72℃ doesn't denote weakening of rain intensity.On 200 hPa or 150 hPa level, wind shear or small trough appears on upstream of MCC inducing heavy rain, while no apparent low-pressure system on upstream of MCC inducing light rain, which can be regarded as a triggering mechanism of MCC inducing heavy rain. For MCC inducing heavy rain, there is continuous convective instability in previous and cellular stage of MCC development, while only weak convective instability before emergence of MCC inducing light rain. For MCC inducing heavy rain, there is strong divergence above 450 hPa-level, convergence below 450 hPa-level and a strong convergence center less than -10×10-6 between 850～700 hPa level. while strong divergence above 270 hPa level, convergence below 270 hPa, and weak convergence cylinder less than -4×10-6 below 270 hPa for MCC inducing light rain.For MCC inducing heavy rain, ascending motion exits from bottom till the upper layer of troposphere, and forms a less than-3.2×10-3•hPa-1•s-1 center between 600～350 hPa level. For MCC inducing light rain, there is only a less than -2.0×10-3•hPa-1•s-1 ascending center between 400～200 hPa, and descending motion on boundary layer. For MCC inducing heavy rain, there is significant cylinder-featured positive vorticity on below 300 hPa or below 400 hPa level, while insignificant cylinder-featured positive vorticity on below 300 hPa or below 400 hPa level for MCC inducing light rain.For MCC inducing heavy rain, high value area of equivalent potential temperature is coupled with sharp gradient area of water influx on 850 hPa level, while high value area of equivalent potential temperature is coupled with high value area of water influx for MCC inducing light rain.