Coriolis Effect: The coriolis effect is influential on most atmospheric circulations on Earth but it was first introduced as the reason why the Hadley doesn't reach from the equator to the pole. Basically north-south motions on the planet are displaced by the coriolis effect to the extent that after traveling about 30 deg in the tropics, the flow is no longer going northward or southward anymore. The coriolis effect can be understood as resulting from the curvature of a body in rotation. On Earth at the equator, an object is moving at a speed of about 1700km/hr. At 60 deg N the speed is half that and at the north pole it is zero (even though the object is still rotation).

The figures I showed in class about how to think about the coriolis effect for north-south and east-west motions are from a web site called "Getting around the Coriolis Effect". I reproduced the one for east-west motions here. The heavy arrow represent displacements for initial eastward (red) or intial westward (green) motions. Note that the displacements are perpendicular to Earth's axis of rotation. The main thing I added in my presentation was about the vertical component (pink arrow pointing perpendicular to the surface) of the heavy red arrow.  I said it can be neglected for most atmospheric motions. The reason is because the effect is swamped by other influences on vertical motion. Thus the coriolis effect is only appreciable in the horizontal plane. Facts about the coriolis effect: Displaces winds to the right in the northern hemisphere and to the left in the southern hemisphere Only acts on something (like the wind) that is in motion on a rotating body (with respect to that body) It is zero at the equator for east-west motions (the case where the displacement arrow in the figure to the right is perpendicular to the surface, which I just noted can be neglected) It is a ficticious force but a useful concept doesn't affect water draining in your sink ... Final thought provoking question: what if the Earth were a cylinder? Where would the coriolis effect act?

I mentioned that the Hadley cell spans the whole tropics but the rising motion is concentrated in intense regional (10s of km) bursts that give rise to bursts of convection. Thus the ITCZ looks like a string of puffy clouds from space, not a continuous line of clouds. The Hadley circulation and ITCZ also migrate seasonally as the most intense rising motion follows the peak in incoming solar radiation. The migration is only to about 8 deg on either side of the equator, but it has a sizeable influence on the seasonal cycle of rainfall (which goes with the convection) and atmospheric heat transport.

I described some of the basic concepts for midlatitude circulations. The concept of a polar front, the jet stream, and geostrophic wind were mentioned and are described well in the text

• wind direction is along contours
• wind speed is highest where contours are closely spaced, this is the location of the jet stream
• winds while meandering, are generally westerly (from west to east)

This figure shows the global warming in  climate model simulations in response to increasing CO2. The CO2 was increased at a rate of 1% per year, which is an idealized guess of future greenhouse gas emissions. The blue wiggly curves prior to year 70  are both responding to the same CO2 rate of increase, but at year 70, the CO2 level is held fixed in one model (the blue line begins to level off) and allowed to continue rising in the other until about year 100 (the blue line that stops at year 100). This is done to illustrate four concepts. "Time of doubling" how long it takes for CO2 to reach twice the starting level (don't need a climate model for this). Its 70 years!

• TCR or "Transient Climate Response" is the warming that has occured at the time of doubling. It is called transient because the climate system has not yet come into equilibrium with the response to the CO2
• If we wait a long long time, the climate will come into equilibrium (see below). When it does the warming that has occured since the start is called the "Climate Sensitivity". 
  
• We use the term "Commitment" to indicate how much warming we have committed to, even though we stop increasing CO2. The blue curve thats carries on out to 500 yrs shows us this commitment for the next few centuries for doubling CO2 over the next 70 years. This is meant to be a lesson in payback time. You can see that this curve doesn't rise as steeply as the one where CO2 is raised even after it has doubled, but it is still rising.