10-20 d和30-60 d低频振荡对华南前汛期持续性暴雨的影响差异及机制研究
The impacts of 10-20 d vs. 30-60 d low-frequency oscillations on South China pre-flood season persistent heavy rainfall:Comparison and associated mechanisms
臧钰歆 1徐邦琪 1高迎侠2
作者信息
- 1. 南京信息工程大学气象灾害教育部重点实验室/气象灾害预报预警与评估协同创新中心,南京,210044
- 2. 内蒙古大学生态与环境学院,呼和浩特,010021
- 折叠
摘要
利用中国气象局发布的《区域性重要过程检测和评价业务规定》中对省级区域性暴雨过程的统计数据,NOAA气候预测中心降水、向外长波辐射(OLR)资料以及ERA-Interim再分析资料,探讨了 10-20 d和 30-60 d两类低频振荡对华南前汛期持续性暴雨的相对重要性,并基于尺度分离的水汽方程和垂直速度方程诊断了相关物理机制.结果表明,10-20 d准双周振荡对暴雨强度的影响较为显著,而 30-60 d季节内振荡与暴雨持续时间相关较高,表明持续性暴雨事件与低频降水的发生和演变关系密切.通过对低频降水的热力和动力过程诊断,发现 10-20 d低频降水的水汽来源主要为水汽平流过程,而导致水汽平流正距平的主要原因是 10-20 d风场和背景水汽场的相互作用;而对于 30-60 d低频降水而言,水汽平流和水汽辐合均为扰动水汽的累积做正贡献,但其中水汽平流更加重要,其主要来源于平均风场和 30-60 d水汽场的相互作用.有利于两类低频降水发生的动力条件,即垂直上升运动,其主要源于平均风场和扰动涡度场相互作用引发的垂直涡度平流梯度.以上结果显示,提高模式中低频振荡与季节平均状态尺度相互作用的刻画能力,是改进预报持续性暴雨的关键.
Abstract
Based on the persistent heavy rainfall dataset produced by China Meteorological Administration(CMA),the National Oceanic and Atmospheric Administration(NOAA)Climate Prediction Center daily precipitation and Outgoing Longwave Radiation(OLR)dataset,and the ERA-Interim reanalysis product,this study analyzes relative importance of two types of low-frequency oscillations,i.e.,10-20 d and 30-60 d oscillations,for persistent heavy rainfall events during the pre-flood period over southern China.The associated mechanisms are diagnosed using the scale decomposed moisture equation and vertical velocity equation.The results reveal that the 10-20 d quasi-biweekly oscillation has a more significant impact on the intensity of persistent heavy rainfall events,while the 30-60 d intra-seasonal oscillation shows a higher correlation with the duration of heavy rainfall events.This result suggests that persistent heavy rainfall events are closely related to the occurrence and evolution of low-frequency precipitation anomalies.Based on the moisture budget diagnosis,it is found that the 10-20 d precipitation anomaly mainly comes from horizontal moisture advection induced by the interaction between wind perturbation and background moisture.For the 30-60 d precipitation anomaly,both the moisture advection and convergence processes make positive contributions to the accumulation of moisture anomalies,although advection process related to the interaction between background wind fields and 30-60 d moisture perturbation is the primary contributor.The upward motion anomaly,which results from vertical gradient of vorticity advection by the background wind-vorticity perturbation interaction,provides a favorable dynamic condition for the occurrences of both 10-20 d and 30-60 d precipitation anomalies.The above results suggest that better understanding of the scale interaction processes between low-frequency oscillations and background mean state in numerical models is the basis for accurate forecast of persistent heavy rainfall.
关键词
华南前汛期/低频振荡/尺度相互作用/持续性暴雨Key words
Pre-flood period/Low-frequency oscillation/Scale interaction/Persistent heavy precipitation引用本文复制引用
基金项目
国家自然科学基金(42225502)
国家自然科学基金(42005021)
内蒙古大学高层次人才科研启动基金(10000-21311201/071)
出版年
2024
国家科技期刊平台
NSTL
万方数据