第三章： Iadley环流 WLST 10 AST IND EASTAIND Reference reading EAST WNDS WVEST Vallis Chapter 11.1-11.2;Lindzen 2005,Chapter 7; Held and Hou 1980.JAS 2022.10.13
A brief history of the Hadley circulation A brief history of the Hadley circulation 1. Hadley’s circulation model (1735) Greater solar heating in low latitudes lead to rising motion near the equator and sinking near the poles, with equatorward motion at low levels and poleward motion at low levels and poleward motion aloft completing the circuit. Because of the conservation of absolute velocity, the equatorward motion at low l l t t d h ii t levels turns westward when arriving at high latitudes and forms the trade wind. Hadley did not realize that the conservation involved is absolute ang , ular momentun, rather than velocity. He was also unaware of the effect of the Coriolis force, which would turn the poleward flow westerly. flow westerly. However, there is no simple argument eliminating the possibility of a single direct cell in each hemisphere, with or without the earth’s rotation 7 without the earth s rotation. 第三章： Hadley 环流 2022. 10. 13 Reference reading: Vallis Chapter 11.1-11.2; Lindzen 2005, Chapter 7; Held and Hou 1980, JAS
Zonally averaged meridional circulations Hadley Cell WEST WINDS EAST WINDS MERIDONAL Egustor CRCULAION EAST WINDS H EAST WINDS WEST WINDS 授课教师：张洋3
授课教师：张洋 3 Zonally averaged meridional circulations - Hadley Cell A brief history of the Hadley circulation A brief history of the Hadley circulation 1. Hadley’s circulation model (1735) Greater solar heating in low latitudes lead to rising motion near the equator and sinking near the poles, with equatorward motion at low levels and poleward motion at low levels and poleward motion aloft completing the circuit. Because of the conservation of absolute velocity, the equatorward motion at low l l t t d h ii t levels turns westward when arriving at high latitudes and forms the trade wind. Hadley did not realize that the conservation involved is absolute ang , ular momentun, rather than velocity. He was also unaware of the effect of the Coriolis force, which would turn the poleward flow westerly. flow westerly. However, there is no simple argument eliminating the possibility of a single direct cell in each hemisphere, with or without the earth’s rotation 7 without the earth s rotation
Hadley Cell Observations Meridional wind(y,经向风) From Peixoto and Oort,1992 F可o, 2 .0 ANNUAL -0.5 0.5 -0.2 (m s- 6 .5 0. --0.5 10 -1.0 0.5 二0.25 DJF 8 -0.4 0.25 0.5 -0.25 2.5 0 0 0.5y 10 0.5 1.0 0.5 -0.5 -0.2 0.25 -3.0 0.25 -0.4 2.5 -0.5 10 -0.5 C95 80705 60 50 40302010S 010N 2030 40 50 60 70N80
授课教师：张洋 4 Hadley Cell - Observations http://www.adultpdf.com Created by Image To PDF trial version, to remove this mark, please register this software. n Meridional wind (v, 经向⻛) From Peixoto and Oort, 1992
Hadley Cell Observations Vertical velocity(垂直速度) From Peixoto and Oort,1992 [可o ANNUAL 10-4mbs-1 0 -GLOBE 0.5 NH ---5H 10 DJF 0 0.5 0 8 .0 0 10 A 0 -0.5 -0.8 10 80705 60 50403020105010N203040 50 60 70N -0.5005 5 JX/八丁A/Iμ·J\T
授课教师：张洋 5 Hadley Cell - Observations n Vertical velocity (垂直速度) http://www.adultpdf.com Created by Image To PDF trial version, to remove this mark, please register this software. From Peixoto and Oort, 1992
Hadley Cell Observations Stream function(流函数) 纬向平均的连续方程： [cos [同 =0 R cos oo∂b ∂p 引入流函数： 8ub [可=92πRcosΦ0p ∂妙 [同=-92rR2cosΦ00 授课教师：张洋6
授课教师：张洋 6 Hadley Cell - Observations n Stream function (流函数) @[¯v] cos R cos @ + @[¯!] @p = 0 [¯v] = g @ 2⇡R cos @p [¯!] = g @ 2⇡R2 cos @ 纬向平均的连续⽅程： 引⼊流函数：
Hadley Cell Observations Stream function(流函数) From Peixoto and Oort,1992 0 ANNUAL 2 ID 0 20 2 GLOBE 6 NH 8 10 2 b 0 6 8 7 10 80 70S 6050 4030 2010S0 10N20 30 4050 6070N80-5 5
授课教师：张洋 7 Hadley Cell - Observations n Stream function (流函数) http://www.adultpdf.com Created by Image To PDF trial version, to remove this mark, please register this software. From Peixoto and Oort, 1992
Hadley Cell Observations 585 200 Zonal winds 400 (U,纬向风) 600 800 -2.5 Annual 100 S.P. 60s 40S 20S E.Q. 20N 40N 60N N.P. Subtropical 一0月o 200 400 600 10 800 DJF 100 .P. 60s 40S 20S E.Q. 20N 40N 60N N.P. Subtropical Jet 200 400 600 800 4-2.5 JJA 08 0 60S 40S 20S E.Q. 20N 40N 60N N.P
授课教师：张洋 8 Hadley Cell - Observations n Zonal winds (U, 纬向⻛) S.P. 60S 40S 20S E.Q. 20N 40N 60N N.P. 200 400 600 800 1000 5 5 5 5 5 5 5 10 10 10 10 10 10 15 15 15 15 15 20 20 20 25 25 25 0 0 0 0 0 0 −5 −5 −5 −2.5 −2.5 −2.5 −2.5 Pressure (hpa) S.P. 60S 40S 20S E.Q. 20N 40N 60N N.P. 200 400 600 800 1000 5 5 5 5 5 5 5 10 10 10 10 10 10 15 15 15 15 15 20 20 20 20 20 25 25 30 25 35 40 0 0 0 0 0 0 0 −5 −5 −5 −2.5 −2.5 −2.5 − Pressure (hpa) 2.5 S.P. 60S 40S 20S E.Q. 20N 40N 60N N.P. 200 400 600 800 1000 5 5 5 5 5 5 10 10 10 10 10 15 15 15 20 20 20 25 25 30 30 35 35 40 0 0 0 0 0 0 0 − −10 10 −5 −5 −5 −5 −2.5 −2.5 −2.5 −2.5 Pressure (hpa) Annual DJF JJA Subtropical Jet Subtropical Jet
Hadley Cell Observations RE temperature gradient and observed temperature distribution SW LW solar radiation infrared cooling Qs(x)A(T)- I(T) Atmosphere infrared cooling I=A+BT or Surface 授课教师：张洋9
授课教师：张洋 9 Hadley Cell - Observations n RE temperature gradient and observed temperature distribution Atmosphere Surface SW LW solar radiation = infrared cooling Qs(x)A(T) = I(T) infrared cooling I = A + BT or I = T4 rad
Hadley Cell Observations RE temperature gradient and observed temperature distribution SW solar radiation infrared cooling Qs(x)A(T)= I(T) Atmosphere 300 280 wM) (a) (b) 200 240- 100 200 Incomlng solar Radlative equll.temp. ---Outgoing IR 160 ---Effective emitting temp. 0 30 90 0 30 90 Surface latitude latitude (Vallis,2006) 授课教师：张洋 10
授课教师：张洋 10 Hadley Cell - Observations n RE temperature gradient and observed temperature distribution Atmosphere Surface SW LW solar radiation = infrared cooling Qs(x)A(T) = I(T) I = T4 rad (Vallis, 2006)
Hadley Cell Observations Summary(小结) Temperature field:the equator-pole temperature gradient is much smaller than the RE temperature gradient. Wind fields:meridional winds strongest at tropopause and surface;vertical velocity strongest at mid-level of the troposphere. Jets(zonal winds):strong subtropical jet at upper level with its maximum in the latitudes at the edge or just poleward of the descending branch of the Hadley cell;surface winds-easterlies near the equator and westerlies in the extratropics. Strong seasonal variations:in summer or winter,Hadley cell always appears as a strong single cell across the equator with the ascending branch in the tropics of the summer hemisphere. 授课教师：张洋11
授课教师：张洋 11 Hadley Cell - Observations n Summary （⼩结） n Temperature field: the equator-pole temperature gradient is much smaller than the RE temperature gradient. n Wind fields: meridional winds strongest at tropopause and surface; vertical velocity strongest at mid-level of the troposphere. n Jets (zonal winds): strong subtropical jet at upper level with its maximum in the latitudes at the edge or just poleward of the descending branch of the Hadley cell; surface winds-easterlies near the equator and westerlies in the extratropics. n Strong seasonal variations: in summer or winter, Hadley cell always appears as a strong single cell across the equator with the ascending branch in the tropics of the summer hemisphere
