气候与环境研究
氣候與環境研究
기후여배경연구
CLIMATIC AND ENVIRONMENTAL RESEARCH
2014年
3期
303-310
,共8页
广义Ertel-Rossby不变量%快变流%暴雨%动力结构
廣義Ertel-Rossby不變量%快變流%暴雨%動力結構
엄의Ertel-Rossby불변량%쾌변류%폭우%동력결구
Generalized Ertel-Rossby invariant%Fast-manifold condition%Torrential rain%Dynamical structure
在绝热无摩擦大气中，具有守恒性及可反演性的Ertel位涡（PV）在大尺度天气系统分析中有广泛应用。由于忽略了力管项的作用， PV 用于分析中小尺度天气系统演变时受到局限。从广义速度推导得到的广义Ertel-Rossby 不变量（GERI）除了包含有 PV 的守恒性，还包含了螺旋度效应及力管项的作用，对于分析研究快变流型的中小尺度系统演变有一定优势。用GERI分析2012年7月21日北京地区的特大暴雨过程，表明GERI在暴雨区有明显的异常出现，其异常基本与暴雨出现时间同位相，表明GERI的定义涵盖了螺旋度和PV，也包含了暴雨发生时的旋转斜压大气的力管项效应，确实能体现暴雨过程中的流型快变的特点，可以作为独立的变量来分析和揭示造成暴雨的低涡系统的动力结构，为诊断和预报暴雨落区提供新的动力物理量。
在絕熱無摩抆大氣中，具有守恆性及可反縯性的Ertel位渦（PV）在大呎度天氣繫統分析中有廣汎應用。由于忽略瞭力管項的作用， PV 用于分析中小呎度天氣繫統縯變時受到跼限。從廣義速度推導得到的廣義Ertel-Rossby 不變量（GERI）除瞭包含有 PV 的守恆性，還包含瞭螺鏇度效應及力管項的作用，對于分析研究快變流型的中小呎度繫統縯變有一定優勢。用GERI分析2012年7月21日北京地區的特大暴雨過程，錶明GERI在暴雨區有明顯的異常齣現，其異常基本與暴雨齣現時間同位相，錶明GERI的定義涵蓋瞭螺鏇度和PV，也包含瞭暴雨髮生時的鏇轉斜壓大氣的力管項效應，確實能體現暴雨過程中的流型快變的特點，可以作為獨立的變量來分析和揭示造成暴雨的低渦繫統的動力結構，為診斷和預報暴雨落區提供新的動力物理量。
재절열무마찰대기중，구유수항성급가반연성적Ertel위와（PV）재대척도천기계통분석중유엄범응용。유우홀략료력관항적작용， PV 용우분석중소척도천기계통연변시수도국한。종엄의속도추도득도적엄의Ertel-Rossby 불변량（GERI）제료포함유 PV 적수항성，환포함료라선도효응급력관항적작용，대우분석연구쾌변류형적중소척도계통연변유일정우세。용GERI분석2012년7월21일북경지구적특대폭우과정，표명GERI재폭우구유명현적이상출현，기이상기본여폭우출현시간동위상，표명GERI적정의함개료라선도화PV，야포함료폭우발생시적선전사압대기적력관항효응，학실능체현폭우과정중적류형쾌변적특점，가이작위독립적변량래분석화게시조성폭우적저와계통적동력결구，위진단화예보폭우락구제공신적동력물리량。
For large-scale weather systems, Ertel potential vorticity (PV) is a very useful quantity because of its properties of material conservation and invertibility for an adiabatic frictionless flow. However, for meso-or small-scale systems, applications of PV are limited because the baroclinic solenoid term, which characterizes baroclinicity of the atmosphere, is removed in PV. An alternative invariant is the generalized Ertel-Rossby invariant (GERI), which is derived from generalized velocity. GERI not only keeps the property of conservation but also includes helicity and the baroclinic solenoidal term, making it more suitable for analyzing evolutions of meso-and small-scale weather systems. In this study, the authors apply GERI to analyze an extreme heavy rainfall case that occurred in Beijing on 21 Jul 2012. It is showed that GERI exhibits large anomalies, having nearly the same phase as the appearance of the heavy precipitation region. It is concluded that GERI makes it possible to characterize fast mode properties during heavy rainfall because of the important physical information it contains, i.e., helicity, PV, and the effect of the solenoidal term. Therefore, GERI can be used to analyze and reveal the dynamical structure of the lower vortex that induces heavy rainfall, and provides a new dynamical quantity for diagnosing and forecasting regions of heavy precipitation.
