A High-Resolution Modeling Study of the 19 June 2002 Convective Initiation Case during IHOP 2002:Localized Forcing by Horizontal Convective Rolls  

作　　者：Qi-Wei WANG Ming XUE 

机构地区：[1]Key Laboratory of Mesoscale Severe Weather and School of Atmospheric Sciences Nanjing University,Nanjing 210023,China [2]Center for Analysis and Prediction of Storms and School of Meteorology University of Oklahoma,Norman Oklahoma 73072,USA

出　　处：《Advances in Atmospheric Sciences》2018年第10期1243-1253,共11页大气科学进展（英文版）

基　　金：supported by the National Key R&D Program of China (Grant No. 2017YFC1501603);the China National Program on Key Basic Research Project (973 Program) (Grant No. 2013CB430103);the National Natural Science Foundation of China (Grants Nos. 41775054, 41375061 and 40705019)

摘　　要：The initiation processes of one of the initial convective cells near and on the east side of a dryline on 19 June 2002 during the IHOP 2002 field experiment in the central United States is analyzed in detail based on a high-resolution numerical simulation. Prominent horizontal convective rolls and associated near-surface moisture convergence bands [called roll convergence bands(RCBs) here] develop within the convective boundary layer(CBL) due to surface heating, in the hours leading to convective initiation(CI). The RCBs east of the dryline are advected toward the primary dryline convergence boundary(PDCB) by the southerly moist flow as the CBL deepens with time. Backward trajectories of air parcels forming the initial precipitating updraft of the convective cell are found to primarily originate at about 1–1.5 km above ground, within the upper portion of the shallower CBL earlier on. The representative air parcel is found to follow and stay on top of a surface RCB as the RCB moves toward the PDCB, but the RCB forcing alone is not enough to initiate convection. As this RCB gets close to the PDCB, it moves into a zone of mesoscale convergence and a deeper CBL that exhibits an upward moisture bulge associated with the PDCB. The combined upward forcing of the RCB and the mesoscale PDCB convergence quickly lifts the representative air parcel above its level of free convection to initiate convection. A conceptual model summarizing the CI processes is proposed.The initiation processes of one of the initial convective cells near and on the east side of a dryline on 19 June 2002 during the IHOP 2002 field experiment in the central United States is analyzed in detail based on a high-resolution numerical simulation. Prominent horizontal convective rolls and associated near-surface moisture convergence bands [called roll convergence bands(RCBs) here] develop within the convective boundary layer(CBL) due to surface heating, in the hours leading to convective initiation(CI). The RCBs east of the dryline are advected toward the primary dryline convergence boundary(PDCB) by the southerly moist flow as the CBL deepens with time. Backward trajectories of air parcels forming the initial precipitating updraft of the convective cell are found to primarily originate at about 1–1.5 km above ground, within the upper portion of the shallower CBL earlier on. The representative air parcel is found to follow and stay on top of a surface RCB as the RCB moves toward the PDCB, but the RCB forcing alone is not enough to initiate convection. As this RCB gets close to the PDCB, it moves into a zone of mesoscale convergence and a deeper CBL that exhibits an upward moisture bulge associated with the PDCB. The combined upward forcing of the RCB and the mesoscale PDCB convergence quickly lifts the representative air parcel above its level of free convection to initiate convection. A conceptual model summarizing the CI processes is proposed.

关 键 词：CONVECTIVE INITIATION dryline LOCALIZED FORCING HORIZONTAL CONVECTIVE ROLLS 

分 类 号：P4[天文地球—大气科学及气象学]