The Climate System Weather is what happens

The Climate System • Weather is what happens today, tomorrow after tomorrow, next week …… • Climate - average statistic regime of weather (month, years, decades & centuries …… ? ? ? )

Climate System Atmosphere Hydrosphere Lithosphere Cryosphere Biosphere fluctuations in weather over long periods of time (IPCC, 2007)

Earth in Space • The Sun emits energy in all directions • A very small fraction is captured by the Earth. • The Earth emits back the heat to space in the infrared spectral range. • The energy emitted at absolute temperature T, is εσT 4 (Stephan. Boltzmann law): Bs = εσT 4 • Sun is at ~6000 ОK, Earth, in radiative balance would be ~254 ОK, (-19 o. C). • Earth’s surface is warmer than this – natural greenhouse effect.

The Arctic ……why is it cold here?

Poleward heat flow • Due to the difference in net radiation balance between equator and the poles, the Earth’s climate system must redistribute heat poleward. • This is achieved by the atmosphere and the oceans – winds and currents NABOS Summer School 2006 Kapitan Dranitsyn © University of Miami, RSMAS

Heat flow in the ocean surface layers Northward flow of heat in the Gulf Stream and the North Atlantic Current is a wellknown example of poleward heat flow NABOS Summer School 2006 Kapitan Dranitsyn © University of Miami, RSMAS

The Role of Ocean and Atmosphere • The oceans and atmosphere are global features. • The earth is heated by the sun, mostly in the tropics and it is cooled mostly at the poles. • Heat from the sun is absorbed in the tropics, primarily in the oceans, which heat the overlying atmosphere. • The Polar Regions are the heat sink of the planet. • The heat Loss at the poles is by Infrared Radiation. • Clouds and aerosols influence the amount of solar radiation reaching the surface and the regulates the infrared heat loss in Polar Regions.

Vertical structure of the atmosphere NABOS Summer School 2006 Kapitan Dranitsyn © University of Miami, RSMAS

Vertical structure of troposphere • Free atmosphere (up to 10 km) • Atmospheric boundary layer (up to 1. 5 -2 km) • Atmospheric surface layer (up to 100 m)

Global energetic of the atmosphere NABOS Summer School 2006 Kapitan Dranitsyn © University of Miami, RSMAS

What controls surface air temperatures (SAT) in Arctic? I. Direct effects: – Heat transport – Heat storage – Heat of phase changes (water, sea ice, snow, ground) II. Indirect effects: – – – Solar zenith angle (time of day, season and latitude) Surface type (influences heat absorption and storage) Elevation, local topography Continentality Synoptic events (storms) Clouds

I. Direct effects • From above: – Net radiation balance (Long wave and Short wave) – Vertical Turbulent exchanges • From/To below – Heat conduction (through the soil and snow) • Sideways – Advection of heat and moisture in the atmosphere – Advection of heat in the ocean

II. Indirect effects (1) • Solar zenith angle (“illumination” and atmospheric absorption) – Varies with latitude, time of day and season • Surface type: – Bright surfaces reflect more sunlight than dark ones – Dry snow/soil have low thermal capacity – Moist soil have high thermal capacity – Moist surfaces can cool by evaporation

II. Indirect effects (2) • Elevation – Increasing height (above sea level) usually means lower temperatures • Continentality – High thermal capacity of water moderates “smooth” climate in opposite area inside of continent (Siberia ……. Saint-Petersburg)

II. Indirect effects (3) • Clouds and Aerosols – Reduce incoming SW radiation (solar) – Reduce LW radiation losses (greenhouse effect) • Local topography – valleys collect cold air at night (katabatic winds)

See the “Interactive Arctic Climate Map” at www. weather. nps. navy. mil/~psguest/polarmet/climate. Arctic examples + meteorological station, and some modeled points NABOS Summer School 2006 Kapitan Dranitsyn © University of Miami, RSMAS

Compare and contrast…. . NABOS Summer School 2006 Kapitan Dranitsyn © University of Miami, RSMAS

Svalbard (Spitsbergen) +0. 23 o. C/decade

So why is it cold here?

Summary • The Arctic atmosphere is the heat sink of the heat engine that is the coupled ocean-atmosphere system. • The temperature gradients between the tropics and the poles allow “work to be done” and this results in motion in the fluids: air and ocean. • The transfer of heat from the tropics to the poles defines the weather, climate, agriculture, the development of civilization, and our future on this planet. • The Arctic atmosphere should not be considered in isolation from the rest of the globe. It is an integral part of the climate system.

• Thank you for your attention…. . NABOS Summer School 2006 Kapitan Dranitsyn © University of Miami, RSMAS