Differences in deep convective transport characteristics between quasi-isolated strong convection andmesoscale convective systems using seasonal WRF simulations

摘要

We utilize the Weather Research and Forecasting (WRF) model with chemistry to simulate mass transport during the 2007 convective season in the U.S. Southern Great Plains at convection-allowing scale. Resolved storms are classified using an object-based classification scheme. This scheme uses model-derived radar reflectivity to classify storm type as quasi-isolated strong convection (QISC) or mesoscale convective system (MCS). Differences between QISCs and MCSs are investigated by analysis of two transport parameters for each convective object: the level of maximum detrainment (LMD) and the detrainment mass flux. Analysis of the mean LMD showed differences between the two regimes is statistically significantly different in May, as the mean QISC LMD is 440 m higher than the mean MCS LMD in May, and statistically insignificant in July where the mean QISC LMD is only 350 m higher. The detrainment flux per deeply convective object showed statistically significant differences between the two regimes in both May (MCS 4.8 times greater than QISC) and July (MCS 6.8 times greater than QISC). Over the entire study period, MCS storms accounted for 72% of the total mass detrainment, even though QISCs were twice as common as MCSs. However, differences in the detrainment flux per unit area of deep convection showed that QISCs exhibited stronger flux (1.1 times greater) than MCSs in both months. Analysis of tropopause-relative LMDs showed that QISCs detrained the maximum amount of mass closer to the tropopause altitude than MCSs for both months. However, only in May is the difference statistically significant (430 m closer).