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

AIR-SEA INTERACTION

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

General assessment of energy sources in the climate system

Advection of heat by ocean currents:

1024 J/year

21023 J/year

Incoming solar radiation:

Evaporation:

51019 J/year

51022 J/year

Anthropogenic energy production:

Sea water and atmospheric air

parameter Sea water Air

Density 1025 kg/m3 1.2 kg/m3

Specific heat capacity (p=const)

4.2103 J/(kg K) 1103 J/(kg K)

Kinematic viscosity 0.8-1.810-6 m2s-1 12-1510-6 m2s-1

Laminar sublayer thickness /U

10-5 m 10-6 m

Dynamic viscosity 110-3 Nsm-2 1103 Nsm-2

Major sea-air interaction processes

100 6 20 4 6 38 26

16

15

3

51 21 7 23

precipitationWind stress

mechanicalmixing

waves

convectivemixing

Major sea-air interaction processes: our outline

1. Solar radiation (SW): absorption, reflection and scattering

2. Infrared radiation: emission, reflection and absorbtion3. Turbulent heat transfer4. Evaporation5. Precipitation6. Buoyancy flux at sea surface7. Turbulent transfer of kinetic energy by tangential

components (stress)8. Turbulent transfer of kinetic energy by normal

components (normal pressure)9. Ocean surface wave generation and decay10.Mixing in the atmosphere and generation of

atmospheric vorticity in ABL11.Mixing (mechanical and convective) in the ocean and 12.generation of water masses13.Gas transfer

Major consequences of sea-air interaction processes:(will not be discussed, but very important)

1. Advection of heat by ocean currents and atmospheric flows

2. Instabilities in the ocean and atmosphere3. Generation of temperature anomalies in the ocean4. Generation of circulation anomalies in the atmosphere

Annual range of air tempe-rature(Monin 1968)

SHORT-WAVE RADIATION AT SEA SURFACE

H = SW - LW - Qh - Qe 100 65 8 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)

Sun

Earth

Earth

So = 1349 W /m*m

So = 1443 W /m*m

The Earth’s orbit is not a perfect circumference, but an ellipse

Solar constant mayvary while the Earthis rotating

Solar radiation on the top of the atmosphere: )(

sin)( 0

0 t

hShQ

Sun brigthnessHow 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%. Jupiter is at 5.2 AUs so 1/d2 = 1/5.22 = 1/27 = 3.7%

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?

Radiation on thetop of theatmosphere

Radiation on the Earth’ssurface

SW radiation at sea surface is determined by:

Solar altitude Molecular diffusion Gas absorption Water vapor absorption Aerosols diffusion

ozon ozon

water vapor water vapor

clouds

top of the atmosphere

ocean surface

clear sky cloud sky

diffusion in space (7%)

ozon absorption (3%)

100%

water vapor absorption (10%)

reflection byclouds (45%)

cloud absorption (10%)

8 0 % 2 5 %

Measurements Modelling Parameterization

Measurements of SW radiation

Moll-Gorczynski pyranometer

Multi-Filter Rotating Shadowband Radiometer (MFRSR)

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 factors affecting 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.

http://www.arm.gov/instruments/instclass.php?id=radio

Where to find/buy/order a perfect package?

http://www.kippzonen.com/pages/1250/3/HowcanIkeepb

Solar altitude

coscoscos

sinsinsin h

Compute solar altitude for: 07:00 GMT 05.04.2006 35 N, 55 W

Derive the dependence ofsolar altitude on: latitude for 12:00, 04.04.2006 hour for 45 N

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