Geo 105, Role of atmosphere >> blanket & circulation ,,, continued

Atmosphere & Ocean

Recall that:
• we expect to see: hot air from equator moving toward poles at top of troposphere, cold air from poles moving along surface toward equator.
• Instead, we observe surface winds that blow east-to-west in an equatorial band, then switch to blow west-to-east at higher latititudes. why?
• the Coriolis effect.
  we measure winf direction with respect to the rotating earth, so even if the air moves from the equator to the pole in a striaght line, we will see it following a spiral path because we rotate around several times before the air can travel from equator to pole.
• Alos, instead of one big convection cell that stretches from pole to equator, it breaks up into two or three separate cells, and the direction of air motion switches back-and-forth between each cell, as depidted by the atmospheric circulation figure in your book.
• The prevaling winds drive the surface ocean currents, and they help to transport heat from the equator toward the poles (e.g. the Gulf Stream current in the Atlantic Ocean).
• However, these surface currents cannot transport "enough" heat, and the thermal energy builds up and can cause transient events called tropical cyclones or hurricanes.
• Hurricane winds flow around the pressure center due to Coriolis effect
• Hurricanes cause terrible damage & destruction
• Hurricanes do help transport heat from equator to pole, in both hemipsheres
• All of this atmosphere & ocean action serves to transport significant thermal energy toward the poles
• ...back to the thermal blanket:
• "Cartoon" version of Greenhouse effect:
  • intro
  • ...next...
  • ...finally
• a quantitative look at "transparency" of atmosphere to incoming wavelengths (1 to 0.1 microns) shows that significant energy at the shorter wavelengths is absorbed by the atmosphere, ozone is important here.
• a quantitative look at "opaqueness" of atmosphere to outgoing wavelengths (5 to 50 microns) shows that some energy at the longer wavelengths does go through the atmosphere. For those wavelengths that are absorbed, water and carbon dioxide are probalby the two most important components that absorb the outgoing energy.

carbon dioxide

• First, estimates of CO2 in atmosphere over geologic show that it was at much higher levels back in the Cretaceous, when we also think that the Earth was warmer, (and sea level was higher). Your book discusses this history
• what controls CO2 in atmosphere?
  the carbon cycle on Earth is quite complicated, the tiny amount of CO2 in the atmosphere is the result of interactions between air, ocean, & land reservoirs, with most of the carbon inventory residing in rocks.