大气环流 1 introduction
# The General Circulation
# 大气环流
Introduction 引言
What makes it go? 生成原因
An overview of the observations. 观测结果
Momentum and Energy 动量、能量
The Mid-latitude Westerlies, Jet Stream and Monsoon. 中纬度西风带、急流、季风
Tropical atmosphere-ocean interations. 热带海气相互作用
Numerical model. 数值模型
# 1. Introduction
# 1. 引言
What‘s the general circulation of the atmosphere?
大气环流是什么？
Horizontal scale : > Thousands of kilometers
水平尺度：大于几千公里
Vertical scale : > 10 km
垂直尺度：大于10公里
Time scale : > 1-2 days
时间尺度：大于1-2天
In general, atmospheric circulation is the large scale movement of air, and the means (together with the ocean circulation) by which heat is distributed on the surface of the
Earth.
总的来说，大气环流就是空气的大尺度运动，是热量在地球表面分布的手段(与海洋环流一起)。
GAC is understood to be a set of different synoptic situations which are constantly (or nearly constantly), such as stream currents, monsoon etc.)
GAC（大气环流）也可以看作急流、季风等连续或近乎连续的一系列不同的天气形势。
The large scale structure of the atmospheric circulation varies from year to year, but the basic structure remains fairly constant. However, individual weather systems mid latitude depressions, or tropical convective cells occur randomly’’.
大气环流的大尺度结构因年而异，但基本结构基本保持不变。然而，个别天气系统中纬度低压或热带对流单体是“随机”发生的。
GAC is also understood to mean the combination of some large scale statistical characteristics of the atmosphere.
GAC也可理解为大气的一些大尺度统计特征的组合。
The circulation is global in extent. The circulation transports dry air, energy, three phases of water, momentum, and too many additional quantities to list here. In the Earth’s atmosphere, the circulations of energy and water are closely linked.
环流在范围上是全球性的。环流输送干空气、能量、水的三相、动量，附加量太多，这里不一一列举。在地球大气中，能量和水的循环是紧密相连的。
The circulation is constantly fighting against friction , but it is sustained by thermal forcing.
环流在受摩擦消耗，但在热力强迫的作用下得以维持。
Fundamental driving force
基本驱动力
The Earth's atmosphere is put into motion because of the differential heating of the Earth surface.
地球表面的热力差异造成了地球大气的运动。
Tropics receive more heat than the poles
热带地区比两极地区接受更多的热量
HADLEY CELL IS A THERMALLY DIRECT CIRCULATION
Hadley环流为热力直接环流
Without surface irregularities or variable heating there would be a mathematically possible steady state zonally symmetric circulation . With the existing irregularities there still exists a circulation with no migratory cyclones or similar disturbances. These circulations are baroclinically unstable, whence the actual circulation contains fully developed large scale migratory eddies.
如果没有地表不规则或变加热，就会有一个数学上可能的稳态纬向对称环流。在已有的不规则性条件下，仍然存在一个没有移动性气旋或类似扰动的环流。这些环流正压不稳定，因为实际的环流中含有充分发展的大尺度迁移涡。
Zonal circulation: 气流沿纬圈方向运动称为纬圈（向）环流
Meriodional circulation: 沿经圈方向移动称为经圈（向）环流
Zonal winds - blow east to west or west to east
纬向风：自东向西或自西向东吹
Meridional winds - blow south to north or north to south
经向风：自南向北或自北向南吹
A brief history of the Hadley circulation
简要介绍哈德来环流的历史
Surface circulation published by Halley(1686 ）.Edmond Halley (November 8 , 1656 January 14 , 1742 ) was an English astronomer , geophysicist , mathematician , meteorologist , and physicist.
哈德来( 1686 ）发表了地表环流。爱德蒙·哈雷( 1656年11月8日-1742年1月14日)是英国天文学家、地球物理学家、数学家、气象学家、物理学家。
He identified solar heating as the cause of atmospheric motions. He also established the relationship between barometric pressure and height above sea level
他将太阳加热确定为大气运动的原因。他还建立了气压与海拔高度之间的关系。
Single cell model
单圈环流
George Hadley(1735)
乔治·哈德利( George Hadley，1735 )
The earth is warmed at the equator.Air expands upward and diverges toward the pole.At the pole air cools and flows back toward the equator.
地球在赤道处被加热。空气向上膨胀并向极点发散。在极点处，空气冷却并向赤道回流。
He related the direction of trade winds to the rotation of the Earth in his famous paper "Concerning the Cause of the General Trade Winds," published in 1735.Because the earth is rotating the wind is shifted to the right (left in SH).Not a very realistic model.
他在1735年发表的著名论文《论一般贸易风的成因》中将贸易风的方向与地球自转联系起来。由于地球是旋转的，风向右偏移(南半球向左 )。不是一个很现实的模型。
The Hadley Cell
哈德来环流
3-cell model
三圈环流
Polar cell 极地环流
Ferrel cell 菲列尔环流
Hadley cell 哈德来环流
Each cell has associated pressure and wind patterns
每个环流都有相关的气压和风的模型
ITCZ = Intertropical convergence zone
Creates the equatorial low, rainiest regions on earth
Little wind (doldrums)
ITCZ =热带辐合带
造成地球上赤道低压、雨量最多的地区
小风(赤道无风带)
A commonly accepted present view of the global meridional circulation
目前普遍接受的全球经圈环流的观点
A complete understanding of the global circulation must answer the following questions:
1.What govern the Hadley circulation?
2.What leads to the thermally indirect Ferrel cell?
3.How do the global circulations redistribute the energy which isoriginally from solar radiation?
4.What about the circulations at upper levels, not just in the troposphere?
5. What about oceanic circulations, and how they interact with atmospheric circulations and how they are involved into the climate system？
对全球环流的完整理解必须回答以下问题：
1 . 哈德来环流是由什么控制的?
2 .是什么导致了非直接热力环流菲列尔环流?
3 .全球环流如何重新分配原本来自太阳辐射的能量?
4 .不仅是对流层的环流，高层的环流又是怎样的?
5 .海洋环流是怎样的，它们是如何与大气环流相互作用的，又是如何参与气候系统的?
主要参考书
延伸阅读
