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Air-Sea Interaction: Redistribution of Solar Energy

Explore the crucial role of air-sea interaction in the redistribution of solar energy between the ocean and atmosphere. Understand the processes involved in energy transformation and their impact on the climate system.

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Air-Sea Interaction: Redistribution of Solar Energy

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  1. AIR-SEA INTERACTION Sergey Gulev, gul@sail.msk.ru (+33-6-22.59.72.72) Air-sea interaction is the redistribution of the solar energy through the property exchange between the ocean and the atmosphere and associated processes of the energy transformation in the ocean and in the atmosphere. Critically important for: • Hard core of the ocean-atmosphere coupling • Boundary conditions for ocean and atmospheric GCMs • Global and regional energy budgets of the ocean and • the atmosphere

  2. General assessment of energy sources in the climate system 1024 J/year Incoming solar radiation: Evaporation: 21023 J/year Advection of heat by ocean currents: 51022 J/year Anthropogenic energy production: 51019 J/year

  3. Sea water and atmospheric air

  4. Ocean and atmosphere Sea surface temperature Ocean surface currents Surface air temperature Surface wind

  5. NP Equator SP То, что считается «типичным» механизмом, на самом деле происходит очень редко Ocean’s role in climate – transporting heat from the low latitudes to high latitudes http://www.classzone.com/books/earth_science/ terc/content/visualizations/es2401/es2401page01.cfm?chapter_no=visualization

  6. LW SW Qe Qh Gas fluxes IHa IMa wind α P  Ice thickness Ocean heat and mass balance IMw Ekman currents IHw Surface density flux and water mass transformation wind stress curl Major air-sea interaction processes

  7. Air-sea fluxes: shaping ocean-atmosphere coupling Changing atmospheric state variables and circulation Diabatic sources for the atmosphere Surface fluxes Surface fluxes Changing ocean state and circulation Forcing the ocean

  8. 100 6 20 4 6 38 26 16 15 Wind stress precipitation 3 waves 51 21 7 23 mechanical mixing convective mixing Major sea-air interaction processes

  9. Major sea-air interaction processes Trenberth et al. 2011

  10. Major sea-air interaction processes: our outline Solar radiation (SW): absorption, reflection and scattering Infrared radiation: emission, reflection and absorption Turbulent heat transfer Evaporation Precipitation Buoyancy flux at sea surface Turbulent transfer of kinetic energy by tangential components (stress) Turbulent transfer of kinetic energy by normal components (normal pressure) Ocean surface wave generation and decay Mixing in the atmosphere and generation of atmospheric vorticity in ABL Mixing (mechanical and convective) in the ocean and generation of water masses Gas transfer

  11. Major consequences of sea-air interaction processes: (will not be discussed, but very important) Advection of heat by ocean currents and atmospheric flows 2. Instabilities in the ocean and atmosphere 3. Generation of temperature anomalies in the ocean 4. Generation of circulation anomalies in the atmosphere Annual range of air temperature (Monin 1968)

  12. + - SHORT-WAVE RADIATION AT SEA SURFACE H = SW- LW- Qh- Qe 100658 27 Definition of sign is arbitrary, but important to be set Temperature of the Sun: Tsun 5800K;Esun=Tsun4 99% of energy is within 0.2-3  Solar constant (S0) – the amount of solar energy (W/m²) at normal incidence outside the atmosphere (extraterrestrial) at the annual mean sun-earth distance S0 = 1378 W/m2 (1359 – 1384 W/m2)

  13. Sun brightness How much brighter is the Sun as viewed from Mercury as compared to Earth? How much fainter is it at Jupiter? Inverse square law relates the relative distances of two objects as compared to a third. The amount of the Sun's energy reaching Earth is 1 solar constant. The average distance from the Sun to Earth is 149,597,870.66 kilometers, (1 Astronomical Unit or 1 AU). So Earth is 1 AU from the Sun and receives 1 solar constant. The relationship can be expressed as: 1/d2 where d = distance as compared to Earth's distance from the Sun. At 1 AU, Earth receives 1 unit of sunlight. How much sunlight would a spacecraft receive if it were twice as far from the Sun as Earth? The distance from the Sun to the spacecraft would be 2 AUs so... d = 2. If we plug that into the equation 1/d2 = 1/22 = 1/4 = 25%. The spacecraft is getting only one quarter of the amount of sunlight that would reach it if it were near Earth. This is because the light is being radiated from the Sun in a sphere. As the distance from the Sun increases the surface area of the sphere grows by the square of the distance. That means that there is only 1/d2 energy falling on any similar area on the expanding sphere. Mercury is at 0.387 AUs. 1/d2 = 1/0.3872 = 1/.15 = 666.67%, almost seven times brighter! We can use this method to compare any spot in the Universe if we describe its distance as compared to Earth relative to the Sun. Mars is at a distance of 1.5 AUs from the Sun. 1/d2 = 1/1.52 = 1/2.25 = 44%. Jupiteris at 5.2 AUs so 1/d2 = 1/5.22 = 1/27 = 3.7%

  14. Radiation balance assumption Planet’s average temperature assuming planet is a solid globe with no atmosphere and no albedo Name Temp (K) Albedo T (K) Mercury 438. Venus 322. 228. (75%) Earth 274. 250. (30%) Mars 223. 215. (15%) Jupiter 120. Saturn 89. Uranus 62. Neptune 50. Pluto 44.

  15. Is Solar constant a real constant? Long-term change – amounts to ~1 W/m2

  16. Is Solar constant a real constant? Interannual (e.g. 11-yr) change is ranging by ~3 W/m2 (+/-0.1%)

  17. Seasonal changes in Solar constant (2 factors): • The Earth orbit is elliptic (2) The Earth axis is titled

  18. 152 x 106 km Seasonal changes in Solar constant (2 factors): 147 x 106 km S0=1349 W/m2 S0=1443 W/m2 Solar radiation on the top of the atmosphere:

  19. Solar altitude φis latitude, δ is the Solar inclination angle, h is hourly angle, θ0 is zenith Sun angle.

  20. TOA (top of atmosphere) SW radiation NASA ERBE spacecraft

  21. Exercise: Solar altitude Compute solar altitude for: 07:00 GMT 05.04.2006 35 N, 55 W Derive the dependence of solar altitude on: latitude for 12:00, 04.04.2006 for 45 N Reproduce this picture for S=1368 W/m2 F77: /meolkerg/home/gulev/problems/solar.f to compile: Ifort –o solar solar.f

  22. 413,000 years 100,000 years Milankovitch Cycles Eccentricity - Jupiter’s gravitational force results in Earth’s orbit varying from nearly circular with eccentricity near 0.0 to about 0.06. Current difference in distance to the Sun at perihelion and aphelion is 3-4%. Periods - Dominate period of 413,000 and minor period of 100,000 years Milutin Milanković (1879 –1958) was a Serbian geophysicist "Contribution to the mathematical theory of climate" (1912)

  23. Milankovitch Cycles Obliquity - Change in the tilt of the Earth's axis with a period of 41,000 years. Changes between ~22.1° and ~24.5°

  24. The effect of Milankovitch Cycle on obliquity Change in Ice for past 21,000 years (1/2 period of the tilt cycle) (Matches change in obliquity from 22.1° to 23.5°)

  25. Milankovitch Cycles Precession - Wobble in the tilt of the Earth's axis with a period of 22,000 years. The mechanism – like spinning top due to non-spherical form of the Earth (and the other planets too) Precession of the equinox over the last 750,000 years

  26. Milankovitch Cycles: combined effect

  27. To know how much of solar radiation comes to the surface, you should know what happens with the solar energy in the atmosphere Spectral view: What this range is about?

  28. Surface SW radiation Need to quantify the difference between the TOA and surface radiation

  29. Radiation on the top of the atmosphere Radiation on the Earth’s surface

  30. SW radiation at • sea surface is • determined by: • Solar altitude • Molecular • diffusion • Gas absorption • Water vapor • absorption • Aerosols • diffusion Measurements Modelling Parameterization

  31. Measurements of SW radiation Downwelling shortwave (SW) radiation can be measured with the pyranometer, facing skyward. Modern pyranometers are still based on the Moll-Gorczynski design (Moll 1923) in which radiation falls on a blackened horizontal receiving surface bonded to a thermopile and protected by two concentric precision hemispheric glass domes. • The most important factorsaffecting the accuracy of these instruments: • reliability and stability of calibration, • dome temperature effects, • cosine response, • detector temperature stability. • Another source of error, particular to pyranometers used at sea, is caused by the platform motion. For correct measurement the receiving surface must be horizontal, but both ships and buoys can roll through several degrees. Uncertainty of daily average can be as large as 10-20%. At sea pyranometers must be set in gimbals. Moll-Gorczynski pyranometer Multi-Filter Rotating Shadowband Radiometer (MFRSR)

  32. Measurements of SW radiation in the sea

  33. Important: be sure that you measure at a horizontal surface, otherwise, the correction has to be applied QSW = f Q0sin h,

  34. Where to find/buy/order a perfect package? http://www.arm.gov/instruments/instclass.php?id=radio http://www.kippzonen.com/pages/1250/3/HowcanIkeepb

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