气象科技专业英语 第五课 大气环流知识介绍.pptVIP

P1: ①The general circulation comprises the movements of the atmosphere on a worldwide scale. ②Since it is usually studied by means of data averaged over several days, so that minor, local or day-to-day irregularities are smoothed out, any model of the general circulation must be generalized, and cannot include very many short-lived features of importance for local weather. ③The general circulation is the overall pattern that must obviously affect local weather at sometime or another, directly or indirectly, and is in this sense the greatest single terrestrial cause of climate and weather. P2: ① Technically, the general circulation may be defined as the mean three-dimensional pattern of the meteorological elements, plus the “turbulence”, the oscillation or perturbations of the mean pattern, provided by changing, day-to-day synoptic weather patterns. ②Its basic features may be described in terms of global, seasonal vector mean winds as a function of height, or they may be derived by applying the geostrophic wind relation to means pressure-contour charts. P3: ① The three-dimensional aspects of the general circulation as actually observed must be particularly emphasized. ② For comparative purposes, it is convenient to separate the zonal (east-west) and meridional (north-south) components of the mean motion for the northern hemisphere. ③The mean meridional circulation is about a meter per second in the lower and middle latitudes throughout a substantial depth of the atmosphere: this is a much weaker circulation than the zonal one, but can nevertheless create or destroy momentum at the rate of 10 m per sec. P4: ① The simplest model that incorporates the main features of the observed mean meridional is given in the figures (omitted). ②The three kinds of cells are in the troposphere in each hemisphere: the Hadley cells in the tropics, the Ferrel cells in middle latitudes, and the weak subpolar cells beyond these. ③ Angular momentum is injected into the Ferrel cells as i