南京大学：《大气环流》课程教学资源（课件讲稿）第二章 大气环流的外部强迫（1/3）

设雾 第二章： 大气环流的外部强迫 Reference reading:PO Chapter 6.3 2022.9.22

第二章： 大气环流的外部强迫 2022.9.22 Reference reading：PO Chapter 6.3

设 大气环流的外部强迫 外部强迫与大气内部变率 选自谢尚平等 《揭开汛期降水变化的奥秘：厄尔尼诺回响曲》 授课教师：张洋 3

⼤⽓环流的外部强迫 授课教师：张洋 3 外部强迫与⼤⽓内部变率 选⾃谢尚平等 《揭开汛期降⽔变化的奥秘：厄尔尼诺回响曲》

设 Outline Global averaged feature 0 TOA(Top of the atmosphere) o Surface Latitudinal distribution(zonal averaged feature) o TOA Surface Zonal distribution o TOA Surface 授课教师：张洋4

Outline ! Global averaged feature " TOA (Top of the atmosphere) " Surface ! Latitudinal distribution (zonal averaged feature) " TOA " Surface ! Zonal distribution " TOA " Surface 授课教师：张洋 4

设雾 From the solar radiation... So--solar constant(1360~1370 W/m2), 太阳辐射通量 S=So Ta2 ≈340Wm-2， 辐射率 Flux 1366 W/m2 Solar Radiation Spectrum 2.5 UV Visible Infrared Sunlight at Top of the Atmosphere .5 5700'C Blackbody Spectrum Effective emission temperature: Radiation at Sea Level H20 74= 1-ap) 0.5 H20 Absorption Bands H20C02 H20 0 250 500 750100012501500175020002250 ,2500 Earth: T。=255K=-18C 实际大气：288K Wavelength(nm) 授课教师：张洋 5

From the solar radiation... 授课教师：张洋 5 So -- solar constant (1360~1370 W/m^2) , 太阳辐射通量 S = So ✓ ⇡a2 4⇡a2 ◆ ⇡ 340 Wm￾2 ，辐射率 Terrestrial Radiation: Effective emission temperature: 4 0 1 4 Earth: 255 18 Observed average surface temperature 288 15 S T a e p T K C e K C  
  
  5700 实际⼤⽓：288K

设 From the solar radiation... shortwave radiation longwave radiation ←TOA 107 Reflected Solar Incoming 235 Outgoing Radiation 342 Solar 3 Longwave 107wm2 (-2 Radiation Radiation 342Wm2 235Wm2 Reflected by Clouds and 77 40 Atmosphere (5 77 Emitted by 165 Atmospheric Atmosphere Window Greenhouse Absorbed by Gases energy 67 Atmosphere (+9) budget (3)24 Latent 78 Heat 5 350 40 324 Reflected by Back Surface Radiation 130 168 -13) 24■ 78 3904 Absorbed by Surtage hermals Evapo- Surface 324(+5) transplration Radlation Absorbed by Surface ←surface sensible heat atent heat 授课教师：张洋6

From the solar radiation... 授课教师：张洋 6 shortwave radiation longwave radiation sensible heat latent heat TOA surface energy budget

设 From the solar radiation... Incident solar radiation 340W/m2 SW~LW Planetary albedo 0.3 ←TOA Absorbed solar radiation 240W/m^2 S(1-a) Outgoing longwave radiation (OLR) 240W/m2 Table:globally and annually averaged TOA radiation budget EARTH'S ENERGY BUDGET Reflected by Reflected Reflected from atm osphere by clouds earth's surface 6% 209% 4% 64% 6% Incoming Radiated to space solar energy from clouds and 1009% atm osphere Absorbed by atmosphere 16% Radiated directly to space from earth Absorbed by clouds 3% Radiation absorbed by Conduction and atmosphere rising air 7% 15% Carried to clouds and atmophere by Absorbed by land latent heat in and oceans 51% water vapor 23%

From the solar radiation... 授课教师：张洋 7 TOA surface energy budget SW ~ LW S(1 ￾ ↵) Incident solar radiation 340 W/m^2 Planetary albedo 0.3 Absorbed solar radiation 240 W/m^2 Outgoing longwave radiation (OLR) 240 W/m^2 Table: globally and annually averaged TOA radiation budget

设雾 From the solar radiation... Planetary albedo(ToA总反射辐射与总入射辐射的比值) penetrate into the atmosphere,absorbed and scattered by: atmospheric gases:H20,03,CO2... aerosols:direct injection,chemical reactions clouds:albedo 30%thin stratus,60-70%thick stratus at the earth's surface --surface albedo,strongly depends on the nature of the surface,vegetation cover, snow cover... Sand Grassland Green crops Forest Dense Forest Fresh snow Old snow Cities 18-28 16-20 15-25 14-20 5-10 75-95 40-60 14-18 授课教师：张洋8

授课教师：张洋 8 From the solar radiation... ! Planetary albedo （TOA总反射辐射与总⼊射辐射的⽐值） ! penetrate into the atmosphere, absorbed and scattered by: ! atmospheric gases: H20, O3, CO2... ! aerosols: direct injection, chemical reactions ! clouds: albedo 30% thin stratus, 60-70% thick stratus ! at the earth’s surface -- surface albedo, strongly depends on the nature of the surface, vegetation cover, snow cover... Sand Grassland Green crops Forest Dense Forest Fresh snow Old snow Cities 18-28 16-20 15-25 14-20 5-10 75-95 40-60 14-18

设 From the solar radiation... SW~LW 107 Reflected Solar Incoming 235 Outgoing 09w Solar 3 a ←TOA S(1-a) od里nd 40 Emitted by 165 Atmospheric Atmosphere Wind ow Absorbed solar(SW) 176Wm-2 Absorbed by Greenhouse Gases 67 Atmosphere (+9) Downward infrared(LW) 312Wm-2 Latent (-3)24 78 Heat Upward infrared(LW1) -385Wm2 350 324 Reflected by Back Radiation Net longwave(LW) -73Wm-2 30 energy 13 390+4 Thermals Evapo- 324+5 Net radiation(SW LW) 103Wm-2 budget Absorbed by Surface transplration Radlation Absorbed by Latent heat(LH) -79Wm2 Sensible heat(SH) -24Wm-2 Table:globally and annually averaged surface energy budget Long term,global average:SW(net)+LW(net)+LH +SH~0 surface 授课教师：张洋 9

From the solar radiation... 授课教师：张洋 9 TOA surface energy budget SW ~ LW S(1 ￾ ↵) Long term, global average: SW(net) + LW(net) + LH +SH ~0 Energy and moisture budgets of the surface and atmosphere The planetary radiation budget has already been briefly discussed. We now consider the energy and moisture budgets of the Earth’s surface and the atmosphere. It is a shocking fact that we do not know enough about the globally averaged surface energy budget to do more than sketch rough annual mean values, as shown in Table 2.2. None of the numbers in the table is known to better than 20% accuracy. Of the 240 W m-2 that is absorbed by the Earth-atmosphere system, 176 W m-2 is absorbed by the Earth’s surface. Thus only about 240 - 176 = 64 W m-2 of solar radiation is absorbed by the atmosphere. That is only about 1/4 of the total solar radiation absorbed by the Earth-atmosphere system. It should be noted, however, that the partitioning of the absorbed solar radiation between the atmosphere and the Earth’s surface is currently a matter of some controversy. The surface receives a total (LW! + SW; see notation defined in Table 2.2) of 488 W m-2, which is given back in the form of LW", LH and SH. By far the largest of these is LW". Keep in mind that the oceans can transport energy from one place to another, so that the energy absorbed by the oceans is not necessarily given back in the same place where it is absorbed. Also, the large heat capacity of the upper ocean allows energy storage on seasonal time scales. In contrast, the continents cannot transport energy internally at a significant rate, and their limited heat capacity forces near energy balance, everywhere, on time scales longer than a few days (at most). Note that the net radiative heating of the surface, which amounts to 103 W m-2, is balanced primarily by evaporative cooling of the surface at the rate of 79 W m-2. As discussed below, moisture is of comparable importance in the energy budget of the atmosphere. The globally averaged energy budget of the atmosphere is shown in Table 2.3. Again, most of the numbers in Table 2.2 and Table 2.3 are only rough estimates. One interpretation of Table 2.3 is that the atmosphere sheds energy through infrared radiation at the rate required to Absorbed solar (SW) Downward infrared (LW!) Upward infrared (LW") Net longwave (LW) Net radiation (SW + LW) Latent heat (LH) Sensible heat (SH) 176 W m-2 312 W m-2 -385 W m-2 -73 W m-2 103 W m-2 -79 W m-2 -24 W m-2 Table 2.2: Components of the globally and annually averaged surface energy budget. A positive sign means that the surface is warmed. Revised Tuesday, February 10, 2009 18 An Introduction to the General Circulation of the Atmosphere Table: globally and annually averaged surface energy budget

设 From the solar radiation... Incident solar radiation 340 W/m^2 SW~LW Planetary albedo 0.3 ←TOA Absorbed solar radiation 240 W/m^2 S(1-a) Outgoing longwave radiation 240Wlm^2 Table:globally and annually averaged TOA radiation budget Absorbed solar radiation(240-176) 64Wm2 Net emitted terrestrial radiation(-240 +73) -167Wm-2 2 州 energy Absorbed solar(SW) 176Wm-2 Net radiative heating -103Wm2 budget Latent heat input 79Wm2 Downward infrared(LW) 312Wm-2 Sensible heat input 24Wm-2 Upward infrared (LW) -385Wm-2 Table:globally and annually averaged Net longwave(LW) -73Wm-2 atmosphere energy budget 为 Net radiation(SW+LW) 103Wm-2 Latent heat(LH) -79Wm-2 Sensible heat(SH) -24Wm-2 SW(net)+LW(net)+LH+SH~0 surface Table:globally and annually averaged surface energy budget 授课教师：张洋10

From the solar radiation... 授课教师：张洋 10 TOA surface energy budget SW ~ LW S(1 ￾ ↵) Long term, global average: SW(net) + LW(net) + LH +SH ~0 Incident solar radiation 340 W/m^2 Planetary albedo 0.3 Absorbed solar radiation 240 W/m^2 Outgoing longwave radiation 240 W/m^2 Table: globally and annually averaged TOA radiation budget Table: globally and annually averaged atmosphere energy budget Energy and moisture budgets of the surface and atmosphere The planetary radiation budget has already been briefly discussed. We now consider the energy and moisture budgets of the Earth’s surface and the atmosphere. It is a shocking fact that we do not know enough about the globally averaged surface energy budget to do more than sketch rough annual mean values, as shown in Table 2.2. None of the numbers in the table is known to better than 20% accuracy. Of the 240 W m-2 that is absorbed by the Earth-atmosphere system, 176 W m-2 is absorbed by the Earth’s surface. Thus only about 240 - 176 = 64 W m-2 of solar radiation is absorbed by the atmosphere. That is only about 1/4 of the total solar radiation absorbed by the Earth-atmosphere system. It should be noted, however, that the partitioning of the absorbed solar radiation between the atmosphere and the Earth’s surface is currently a matter of some controversy. The surface receives a total (LW! + SW; see notation defined in Table 2.2) of 488 W m-2, which is given back in the form of LW", LH and SH. By far the largest of these is LW". Keep in mind that the oceans can transport energy from one place to another, so that the energy absorbed by the oceans is not necessarily given back in the same place where it is absorbed. Also, the large heat capacity of the upper ocean allows energy storage on seasonal time scales. In contrast, the continents cannot transport energy internally at a significant rate, and their limited heat capacity forces near energy balance, everywhere, on time scales longer than a few days (at most). Note that the net radiative heating of the surface, which amounts to 103 W m-2, is balanced primarily by evaporative cooling of the surface at the rate of 79 W m-2. As discussed below, moisture is of comparable importance in the energy budget of the atmosphere. The globally averaged energy budget of the atmosphere is shown in Table 2.3. Again, most of the numbers in Table 2.2 and Table 2.3 are only rough estimates. One interpretation of Table 2.3 is that the atmosphere sheds energy through infrared radiation at the rate required to Absorbed solar (SW) Downward infrared (LW!) Upward infrared (LW") Net longwave (LW) Net radiation (SW + LW) Latent heat (LH) Sensible heat (SH) 176 W m-2 312 W m-2 -385 W m-2 -73 W m-2 103 W m-2 -79 W m-2 -24 W m-2 Table 2.2: Components of the globally and annually averaged surface energy budget. A positive sign means that the surface is warmed. Revised Tuesday, February 10, 2009 18 An Introduction to the General Circulation of the Atmosphere Table: globally and annually averaged surface energy budget