Simulations of an observed elevated mesoscale convective system over southern England during CSIP IOP 3
Simulations of an observed elevated mesoscale convective system over southern England during CSIP IOP 3
复制标题
DOI：
10.1002/qj.2787
复制
发表时间：
2016-07
影响因子：
8.9
通讯作者：
B. White;A. Blyth;J. H. Marsham
中科院分区：
文献类型：
--
作者：
B. White;A. Blyth;J. H. Marsham
在对流风暴启动项目（CSIP）期间，对英格兰南部观测到的一个中尺度对流系统（MCS）的模拟提供了对英国发生的对流升高情况的第一个详细的模拟研究。研究表明，从大尺度气流到地表加热过程和对流系统内的非绝热冷却，许多因素都可以影响高深对流的维持。研究还表明，稳定层与风暴之间的相互作用和反馈机制可以维持深层对流。模拟成功地再现了低水平稳定潜流之上的高MCS，潜流中的波与后流入射流（RIJ）相连。对流来自高空（840 hPa）源层，CAPE约为350 J kg−1。模拟中的暗流深度约为1公里，约为观测值的一半。与观测到的MCS不同，由于预先存在的大尺度θe梯度、平流和地面加热的综合作用，模拟中发生了从高空到地面对流的转变，导致系统遇到越来越不稳定的低层空气和更容易被下沉气流穿透的较浅稳定层。向地表对流的转变伴随着冷池外流的发展和系统速度从大约6到10 m s−1的增加。模拟中微物理过程的非绝热冷却增强了暗流，增强了RIJ。这加强了暗流中的波浪，导致了更广泛的对流。讨论了对流、RIJ和稳定层之间正反馈过程的存在性。天气尺度的不确定性在潜流中产生误差是对流尺度预报误差的主要来源。
Simulations of an elevated mesoscale convective system (MCS) observed over southern England during the Convective Storm Initiation Project (CSIP) provide the first detailed modelling study of a case of elevated convection occurring in the UK. The study shows that many factors can influence the maintenance of elevated deep convection, from large‐scale flow through to surface heating processes and diabatic cooling within the convective system. It is also shown that interactions and feedback mechanisms between a stable layer and the storm can act to maintain deep convection. The simulation successfully reproduced an elevated MCS above a low‐level stable undercurrent, with a wave in the undercurrent linked to a rear‐inflow jet (RIJ). Convection was fed from an elevated (840 hPa) source layer with CAPE of about 350 J kg−1. The undercurrent in the simulation was approximately 1 km deep, about half that observed. Unlike the observed MCS, a transition from elevated to surface‐based convection occurred in the simulation due to the combined effects of a pre‐existing large‐scale θe gradient, advection and surface heating causing the system to encounter increasingly unstable low‐level air and a shallower stable layer that was more susceptible to penetration by downdraughts. The transition to surface‐based convection was accompanied by the development of cold‐pool outflow and an increase in system velocity from about 6 to 10 m s−1. Diabatic cooling from microphysical processes in the simulation enhanced the undercurrent and strengthened the RIJ. This strengthened the wave in the undercurrent and led to more extensive convection. The existence of a positive feedback process between the convection, RIJ and stable layer is discussed. Uncertainty in the synoptic scale generating errors in the undercurrent is shown to be a major source of error for convective‐scale forecasts.