(after Stephens et al. 2012)

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1 Energy Balance

2 Incoming solar radiation 34 Reflected solar radiation Outgoing longwave radiation 1 24 TOA 75 Atmospheric absorption Atmospheric reflection 77 Atmospheric window Clear Sky Cloud effect Absorbed SW Reflected SW SH LH LW up LW down (after Stephens et al. 212)

3 At the surface SW Radiation LW Radiation c s S # L " F L F S div F O Latent Heat (LH) Flux Sensible Heat (SH) Flux

4 Bulk Aeordynamic Formulae SH = Ωc p C D,T kv s k(t s T (z a )) LH = ΩLC D,q kv s k q s q(z a), = k k where T a := T (z a ), q a := q(z a ) ([q] =kg/kg) denote the respective fields at a reference height z a, typically 2 1m above the surface. The latent heat expression can be simplified by expanding the saturation water vapour q

5 SH Flux 45 N ANN 45 N -5 Latitude Latitude 9 N 25 ANN E W JJA N 45 N N 9 N E 12 W 1-25 JJA S 45 S S S E N 1 DJF 2 Wm Latitude W 9 N S 12 E S Latitude Latitude 12 W DJF 45 N Latitude N 9 S S 45 S 9 S S 9 S 12 E 12 W Longitude 12 E 12 W Longitude 1 W m 2 W m 2 9 N LH Flux

6 Angular Momentum and Surface Winds

7 Earth s surface winds 3 N 3 S Speed: m/s (Source: NCEP/NCAR reanalysis)

8 Earth s surface winds 3 N equatorward & westward NE Trades 3 S SE Trades Speed: m/s (Source: NCEP/NCAR reanalysis)

9 Earth s surface winds 3 N 3 S Speed: m/s (Source: NCEP/NCAR reanalysis)

10 Earth s surface winds 3 N Westerlies poleward (!) & eastward 3 S Speed: m/s (Source: NCEP/NCAR reanalysis)

11 Earth s surface winds Westerlies 3 N NE Trades SE Trades 3 S Westerlies Speed: m/s (Source: NCEP/NCAR reanalysis)

12 Earth s surface winds Note: very turbulent winds, esp. above continents 3 N sailors on oceans only in time mean clear evidence of pattern 3 S Speed: direction of the wind m/s (Source: NCEP/NCAR reanalysis)

13 Mariners used the prevailing winds... Columbus First Voyage (1492) 3 N Westerlies NE Trades (Source: science remained in the Dark Ages.

14 What is wind? It is absurd to suppose that the air which surrounds us becomes wind simply by being in motion. [...] Winds are formed by the gradual collection of small quantities of [dry and moist] exhalation, in the same way that rivers form when the earth is wet. [...] We have thus given an account of the nature and origin of the wind. Aristotle, Meteorologica, 2, iv (c. 34 BC)

15 Finally the Royal Society takes on the subject... Among the known Sea Plants, the Sargosse, is not to be forgot. [...] From the daily and constant breath of that Plant, the Trade or Tropick Winds do in great part arise: because the matter of that wind coming (as we suppose) from the breath of only one Plant, it must make it constant and uniform. (Image: Martin Lister, Phil. Trans., 15 (1684)

16 Finally the Royal Society takes on the subject... Among the known Sea Plants, the Sargosse, is not to be forgot. [...] From the daily and constant breath of that Plant, the Trade or Tropick Winds do in great part arise: because the matter of that wind coming (as we suppose) from the breath of only one Plant, it must make it constant and uniform. d e v i l n o t w e N c aa 6 s I 2 : 7 e Not 6 1 (Image: Martin Lister, Phil. Trans., 15 (1684)

17 Help is on the way... Wind is most properly defined to be the Stream or Current of the air. [...] It remains to [find] a cause agreeable to the known properties of Air and Water, and the laws of the Motion of fluid Bodies. Such a [cause] is, I conceive, the Action of the Sun Beams upon the Air and Water, as he passes every day over the Oceans. Edmond Halley, Phil. Trans., 16 (1686)

18 Halley s view of the trade winds West East

19 Halley s view of the trade winds West East

20 Halley s view of the trade winds West East

21 Earth s rotation matters The causes of the General Winds have not been fully explained by any of those who have written on that Subject, for want of more particularly and distinctly considering the Share the diurnal Motion of Earth has in the Production of them. George Hadley, Phil. Trans., 39 (1735)

22 Hadley s view of winds and the general circulation 3 N Equator 3 S

23 Hadley s view of winds and the general circulation (Source: 3 N Equator 3 S

24 Hadley s view of winds and the general circulation 3 N Equator 3 S

25 Hadley s view of winds and the general circulation 3 N Equator 3 S

26 Hadley s view of winds and the general circulation The NE and SE Winds within the Tropics must be compensated by as much NW and SW [Winds] in other Parts; otherwise some Change must be produced in the Motion of the Earth round its Axis. 3 N Equator 3 S Concerning the Cause of the General Trade-Winds. G. Hadles (1735)

27 Theories about the general circulation How to explain the poleward motion of the mid-latitude westerlies???

?? poleward directed westerlies calm regions three cells only

28 Theories about the general circulation How to explain the poleward motion of the mid-latitude westerlies??? poleward directed westerlies calm regions three cells only zonally symmetric circulation cyclones and storms were studied but no interaction

29 What do we know today?

30 Eastward wind (January) Pressure (mbar) 2 8 a km/h 8 Easterlies Westerlies Westerlies Latitude 5 (Schneider, Ann. Rev. Earth Planet. Sci., 26)

31 4 Eastward wind (January) Pressure (mbar) 2 8 Ferrel cells Hadley cells 8 Easterlies Westerlies Westerlies Latitude 5 (Schneider, Ann. Rev. Earth Planet. Sci., 26)

33 Jupiter from Cassini (Cassini Imaging Team 2)

34 Hadley circulation confined to tropics 3 N Equator 3 S Extratropical macroturbulence transports angular momentum into regions of wave generation

35 (1) Solar heating: driving force for air circulation (Halley, 17) differential heating: poleward flow no east-west component (2) AM conservation (equiv. to Coriolis force): east-west component (Hadley, 1735) problems: mid-latitude westerlies (3) Multi-cellular structured circulation (Ferrell, Thomson, 18-19) (4) Storms and Macroturbulence (19) observations: upper-level mean meridional circulation not sufficient for poleward energy transport finite extent of Hadley cell, not up to poles observations WWII: no upper level winds from tropics to higher latitudes importance of zonal deviations (eddies) turbulence theory for heat transport where do asymmetries come from? (baroclinic) instabilities (Rossby, 194; Eady, Charney, 195)

36 f Mean Flows and Eddies Time mean ( ) 1 T Z T ( ) dt Transient eddy ( ) ( ) ( ) Zonal mean [ ] 1 2 Z 2 ( ) d Stationary eddy ( ) ( ) f ( ) g Reynolds properties

37 Eddy angular momentum transport (ERA-4 Atlas,

38 Macroturbulence in control Any theory of atmospheric circulations and of climate must be based on a theory of atmospheric macroturbulence. Because we have no complete theory of macroturbulence, the causes of the General Winds still have not been fully explained by any of those who have written on that Subject (Hadley).

39 Energy Balance & Transport

40 f Mean Flows and Eddies Time mean ( ) 1 T Z T ( ) dt Transient eddy ( ) ( ) ( ) Zonal mean [ ] 1 2 Z 2 ( ) d Stationary eddy ( ) ( ) f ( ) g Reynolds properties

41 Z Flux Decomposition f g Decomposing fluxes, e.g., meridional energy flux ve, with v v + v [v][e] + v E. So and zonal- and temporal-mean flux ve vē + v E (7.17) [ve] [v][e] + [v E ] (7.18) f ve g f vē g + f v E g (7.19) [ v] f Ē g + f v Ē g + f v E g (7.2) This is a decomposition into mean circulations, stationary eddies, and transient eddies.

42 MSE Transport Transient eddies (KJ m kg 1 s 1 ) Pressure (hpa) S 45 S 45 N 9 N Altitude (km) Stationary eddies (KJ m kg 1 s 1 ) Pressure (hpa) S 45 S 45 N 9 N Altitude (km) Mean meridional circulation (KJ m kg 1 s 1 ) Pressure (hpa) S 45 S 45 N 9 N Latitude Altitude (km)

43 Vertically Integrated MSE Transport 9 ANN DJF Transient eddies Mean meridional circulations 45 S 45 N Stationary eddies Total MSE flux (PW) JJA 45 S 45 N S 45 N Latitude

Introduction to Atmospheric Circulation

Introduction to Atmospheric Circulation Start rotating table Cloud Fraction Dice Results from http://eos.atmos.washington.edu/erbe/ from http://eos.atmos.washington.edu/erbe/ from http://eos.atmos.washington.edu/erbe/