Quantitative analysis of meso- β -scale convective cells and anvil clouds over North China

This paper proposes several quantitative characteristics to study convective systems using observations from Doppler weather radars and geostationary satellites. Specifically, in order to measure the convective intensity of each system, a new index, named the “Convective Intensity Ratio” (CIR), is defined as the ratio between the area of strong radar echoes at the upper level and the size of the convective cell itself. Based on these quantitative characteristics, the evolution of convective cells, surface rainfall intensity, rainfall area and convectively generated anvil clouds can be studied, and the relationships between them can also be analyzed. After testing nine meso- β -scale convective systems over North China during 2006–2007, the results were as follows: (1) the CIR was highly correlated with surface rainfall intensity, and the correlation reached a maximum when the CIR led rainfall intensity by 6–30 mins. The maximum CIR could be at most ∼30 mins before the maximum rainfall intensity. (2) Convective systems with larger maximum CIRs usually had colder cloud-tops. (3) The maximum area of anvil cloud appeared 0.5–1.5 h after rainfall intensity began to weaken. The maximum area of anvil cloud and the time lag between maximum rainfall intensity and the maximum area of anvil cloud both increased with the CIR.