Outline Review Global averaged feature 0 TOA(Top of the atmosphere) Surface Latitudinal distribution(zonal averaged feature) o TOA Surface Zonal distribution TOA Surface 授课教师：张洋3
Outline n Global averaged feature ¡ TOA (Top of the atmosphere) ¡ Surface n Latitudinal distribution (zonal averaged feature) ¡ TOA ¡ Surface n Zonal distribution ¡ TOA ¡ Surface 授课教师：张洋 3 Review
From the solar radiation... Review shortwave radiation longwave radiation ←TOA Re'lected Solar Incom ng 235 Outgoing Radiation Solar Lorgwave 107wm2 Radiation 342wm2 239Wm? Reflected by Clouds anc 40 Atmosphere 77 Emitted by 165/ 30 Atmospherc Atmosphere Window Greenhouse Absorbed by Gasos energy 67 Atmosphere (+9 budget Latent (324 78 Heat 5 350 324 Reflected by Back Surface Radiation 13 16g 590刚 hermals Evapo- Surface 324(+5 Absorbed by Surtae transpiration Radlatlon Absorbed by Surtace ←surface sensible heat latent heat 授课教师：张洋4
From the solar radiation... 授课教师：张洋 4 shortwave radiation longwave radiation sensible heat latent heat TOA surface energy budget Review
From the solar radiation... Review Incident solar radiation 340WWm^2 SW~LW Planetary albedo 0.3 ←TOA Absorbed solar radiation 240 W/m^2 S(1-a) Outgoing longwave radiation 240 W/m^2 Table:globally and annually averaged TOA radiation budget Absorbed HolHr IadiHl (240 -176) 84 m> Nel erlled lutestral tadialon (-2410+/3) -16/w1r2 energy 176Wm-2 Net raciative heating -103wm2 Absorbed solar(SW) budget I Hlenl hesl inpul 79 W mr2 Downward infrared(LW) 312Wm-2 Senil:l heal inpul 24 W mr2 Upward infrared (LW) -385Wm-2 Table:globally and annually averaged Net longwave(LW) -73Wm-2 为调 atmosphere energy budget 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 5
From the solar radiation... 授课教师：张洋 5 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 Review
及愈 Outline Global averaged feature o TOA (Top of the atmosphere) Surface Latitudinal distribution (zonal averaged feature) o TOA Surface Zonal distribution o TOA o Surface 授课教师：张洋6
Outline n Global averaged feature ¡ TOA (Top of the atmosphere) ¡ Surface n Latitudinal distribution (zonal averaged feature) ¡ TOA ¡ Surface n Zonal distribution ¡ TOA ¡ Surface 授课教师：张洋 6
From the solar radiation... At TOA Earth zenith Sun Kpic ol Cancer 5R10r 作r21 Z ropic of Capricorm c0t.21 Tropic of Cancer Equtor SW=S(dm/d)2 cosZ 少 d--earth-sun distance T环R[are June 27 dm--mean earth-sun distance Z--zenith angle Solar radiation varies with latitude and season 授课教师：张洋7
n At TOA 授课教师：张洋 7 From the solar radiation... Solar radiation varies with latitude and season SW = S (dm/d) 2 cosZ d -- earth-sun distance dm -- mean earth-sun distance Z -- zenith angle zenith Z
From the solar radiation... Earth Sun SW=S(dm/d)2cosz kepic ol Cancar 服0 作r d--earth-sun distance Tropic of Cap-icerm c0t.21 dm--mean earth-sun distance Z--zenith angle Tropic of ancer time of sunset Tropic of Capricorn Q=S (dm/d)2 50w10r】 cos Z dt time of sunrise Equiatnr solar radiation depends on: ropk clCaker June 2 元：da酸rIa earth-sun distance length of the day zenith 授课教师：张洋8
Q = S (dm/d) 2 Z time of sunset time of sunrise cosZ dt 授课教师：张洋 8 From the solar radiation... SW = S (dm/d) 2 cosZ d -- earth-sun distance dm -- mean earth-sun distance Z -- zenith angle n solar radiation depends on: n earth-sun distance n length of the day n zenith
From the solar radiation... At TOA ERBE Top-of-Atmosphere 3WINC 00 MnM Mean 152 80N 标卡卡持特 July 1286 500 500- 60 100 100 400- 200 200 40 300 300 20 400 SQLAR 200 DECLNATION 400 0 400 1D0- &x 20 300 0 00 30 5 -30 (0 -90 lattade 500 200 500 40 Figures:the zonally averaged incident solar 100 radiation,observed in the Earth Radiation Budget Experiment(ERBE).(from Randall 2009) 60 80S J FM A M JJ A S From Peixoto and Oort.1992 授课教师：张洋 9
授课教师：张洋 9 From the solar radiation... to the astronomical theory of the ice ages, extensive glaciation is favored when the minimum insolation occurs during the Northern Hemisphere winter, because the Northern Hemisphere contains about twice as much land as the Southern Hemisphere (e.g., Crowley and North, 1991). As you probably already know, the infrared radiation emitted by the Earth is very nearly equal to the solar radiation absorbed by the Earth, i.e., it is about 240 W m-2. This near balance between absorbed solar radiation and emitted terrestrial radiation has been directly confirmed by analysis of satellite data. The balance is observed to hold within a few Watts per square meter, which is the within the uncertainty of the measurements. Fig. 2.3 shows aspects of the Earth's radiation budget as observed in the Earth Radiation Budget Experiment (ERBE; Barkstrom et al., 1989). The zonally averaged incident (i.e. incoming) solar radiation at the top of the atmosphere varies seasonally in response to the Earth's motion around the sun. The zonally averaged albedo, which is the fraction of the zonally averaged incident radiation that is reflected back to space, is highest near the poles, due to snow and ice as well as cloudiness, but it tends to have a weak secondary maximum in the tropics, again associated with high cloudiness there. The zonally averaged terrestrial radiation at the top Figure 2.2: The seasonal variation of the zonally (or diurnally) averaged insolation at the top of the atmosphere. The units are W m-2. 200 300 400 500 500 500 200 200 300 300 400 400 100 100 100 SOLAR DECLINA TION J F M A M J J A S O N D 0 80N 80S 60 40 20 20 40 60 Revised Tuesday, February 10, 2009 3 An Introduction to the General Circulation of the Atmosphere n At TOA Figures: the zonally averaged incident solar radiation, observed in the Earth Radiation Budget Experiment (ERBE). (from Randall 2009) From Peixoto and Oort, 1992
Radiation budget at TOA ERBE To-of-Atmosphere 3WINC IHHI Irg-ot-Atmo*phere Alsedo DB Mean t 4 ””” 500 0后 400 05 300- 04 na 200 02 1D0 Planetary albedo 30 0 s我de bEu.v From Randall,2009 授课教师：张洋10
授课教师：张洋 10 Radiation budget at TOA Planetary albedo From Randall, 2009
Radiation budget at TOA ERBE To-of-Atmosphere 3WINC IHHI Irg-ot-Atmo*phere Alsedo 0 084 Mean t蛋 Jaruery 1986 / #t+培+JUy86 UR ime A 50 44 0后 400 05 300 04 na 200 02 10 Planetary albedo -30 -90 s我du bEu.v EHHE lop-c1-Atmo:phcrc U.H EREE Tp-o-Awee人dRai I20 a 220 40 2C0 1亿0 1c0 -a物a130 10 AmulD-N84-87 20 44.0F获7 一++…+80 OLR Net Rad: 0 90 -29 0 0 30 a:tuce From Randall,2009 授课教师：张洋11
授课教师：张洋 11 Radiation budget at TOA Planetary albedo OLR Net Rad. From Randall, 2009
Radiation budget at TOA ERBE Top-of-Atmosphere Net Radiation 120 80- M 40 ”4…4… warming 0 cooling -40 cooling、 -80 -120 Annual D-N 86-87 DJF86-87 EI8NENI8I8 JJA 87 -160 90 60 30 0 -30 -60 -90 latitude From Randall,2009 授课教师：张洋12
授课教师：张洋 12 Radiation budget at TOA warming cooling cooling From Randall, 2009