Convective updraught evaluation in high-resolution NWP simulations using single-Doppler radar measurements
Convective updraught evaluation in high-resolution NWP simulations using single-Doppler radar measurements
复制标题
使用单多普勒雷达测量进行高分辨率 NWP 模拟中的对流上升气流评估
DOI：
10.1002/qj.2602
复制
发表时间：
2015
影响因子：
8.9
通讯作者：
Nicol J
中科院分区：
文献类型：
--
作者：
Nicol J
本研究在英国气象局统一模式（UM）的高分辨率模拟中对对流上升气流的大小和强度进行了评估。作为对流风暴的动力和微物理演化（DYMECS）项目的一部分，利用Chilbolton先进气象雷达从距离高度指示器（RHI）多普勒速度测量中估计了上升气流速度。基于质量连续性和观测到的径向辐合的垂直积分，由于未检测到交叉辐合，对流云的垂直速度往往被低估。在与雷达观测相对应的分辨率下，UM的速度场被用来对这种估计进行缩放，以减轻固有的偏差。对100多个观测和模拟风暴的分析表明，随着栅格长度的增加，模拟上升气流的水平尺度有减小的趋势；200米的网格长度与观测结果最为吻合。在500米网格长度模拟中，典型的上升气流质量通量比观测到的要大一个数量级，在1.5公里网格长度模拟中则更大。在亚网格湍流方案中，增加混合长度的效果取决于网格长度。在1.5公里模拟中，上升气流减弱，但其水平尺度基本保持不变。在亚公里网格长度上，上升气流逐渐扩大和加剧；水平尺度现在由混合长度而不是网格长度决定。一般来说，模拟的上升气流会随着高度的增加而迅速减弱。这些发现得到了模拟和观测中反射率模式宽度分析的支持。
This study presents an evaluation of the size and strength of convective updraughts in high‐resolution simulations by the UK Met Office Unified Model (UM). Updraught velocities have been estimated from range–height indicator (RHI) Doppler velocity measurements using the Chilbolton advanced meteorological radar, as part of the Dynamical and Microphysical Evolution of Convective Storms (DYMECS) project. Based on mass continuity and the vertical integration of the observed radial convergence, vertical velocities tend to be underestimated for convective clouds due to the undetected cross‐radial convergence. Velocity fields from the UM at a resolution corresponding to the radar observations are used to scale such estimates to mitigate the inherent biases. The analysis of more than 100 observed and simulated storms indicates that the horizontal scale of updraughts in simulations tend to decrease with grid length; the 200 m grid length agreed most closely with the observations. Typical updraught mass fluxes in the 500 m grid length simulations were up to an order of magnitude greater than observed, and greater still in the 1.5 km grid length simulations. The effect of increasing the mixing length in the sub‐grid turbulence scheme depends on the grid length. For the 1.5 km simulations, updraughts were weakened though their horizontal scale remained largely unchanged. Progressively more so for the sub‐kilometre grid lengths, updraughts were broadened and intensified; horizontal scale was now determined by the mixing length rather than the grid length. In general, simulated updraughts were found to weaken too quickly with height. The findings were supported by the analysis of the widths of reflectivity patterns in both the simulations and observations.