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Sergey Gulev, gul@sail.msk.ru , sgulev@ifm-geomar.de

AIR-SEA INTERACTION. Sergey Gulev, gul@sail.msk.ru , sgulev@ifm-geomar.de.

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Sergey Gulev, gul@sail.msk.ru , sgulev@ifm-geomar.de

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  1. AIR-SEA INTERACTION Sergey Gulev, gul@sail.msk.ru, sgulev@ifm-geomar.de Air-sea interaction is the redistribution of the solar energy through the exchange of properties between the ocean and the atmosphere and associated processes of the energy transformation in the ocean and the atmosphere. • Hard core of the ocean-atmosphere coupling • Boundary conditions for ocean and atmospheric GCMs • Global and regional energy budgets of the ocean and • 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. 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

  5. Major sea-air interaction processes: our outline Solar radiation (SW): absorption, reflection and scattering Infrared radiation: emission, reflection and absorbtion 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

  6. 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 tempe-rature (Monin 1968)

  7. + - 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) – annual mean amount of solar radiation at the top of the atmosphere S0 = 1378 W/m2 (1359 – 1384 W/m2)

  8. The Earth’s orbit is not a perfect circumference, but an ellipse Solar constant may vary while the Earth is rotating Solar radiation on the top of the atmosphere:

  9. Sun brigthness How much brighter is the Sun as viewed from the planet Mercury as compared to Earth? How much fainter is it at Jupiter? These questions can be answered through the inverse square law. The equation relates the relative distances of two objects as compared to a third. Typically one of the objects is Earth, the second is a space craft and the third is the Sun. There is a certain amount of sunlight reaching Earth at any given moment. This is not an absolute quantity because Earth is closer to the Sun at some times of the year verses others and the number of sunspots effects the Sun's energy output. Overall, however, the Sun is remarkably constant in its behavior. 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 most simply as: 1/d2 where d = distance as compared to Earth's distance from the Sun. At 1 AU, Earth receives 1 unit of sunlight; what we generally might associate with a bright sunny day at noon. 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%

  10. 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?

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

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

  13. 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)

  14. 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

  15. 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 hour for 45 N /home/gulev/problems/solar.f

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