Meteorology generally follows the MKS system.

• length = meters (m)
• mass = kilograms (kg)
• time = seconds (s)
• temperature = Kelvin (or Celsius)

For these, we can construct other units, such as:

• F, force = mass length / time² = kg m /s² = Newton
• KE, PE, W, energy = mass length² /time ² = kg m² /s² = watt
• p, pressure = mass length /time² / length² = kg /m/s² = pascal ( 1 atm = 101.325 kPa. We will often use millibar, mb, which is 1/1000 of a Bar, or 1 atm)

Winds:

• u = dx/dt westerly (eastward) is positive; easterly (westward) is negative.
• v = dy/dt southerly (northward) is positive; northerly (southward) is negative.
• w = dz/dt upward is positive; downward is negative.
• w = dp/dt w is positive for sinking motion.

Extensive variables are variables whose values change as you partition the volume in which they are contained. Examples: mass, volume, KE and PE

 Intensive variables are independent of the partitioning of the volume in which they are contained. Examples: T, p, r .

 We can turn extensive variables into intensive variables by dividing by mass.

3. Atmospheric structure.

Atmospheric regions are often designated by the temperature vertical profiles, which largely influence the behavior of gases in that region.

 Lapse rate, G = dT/dz. It is positive when T increases with height (positive lapse rate), negative when T decreases with height (negative lapse rate), and neutral when dT/dz = 0.

• 0 – 20 km altitude
• negative lapse rate
• most significant weather

• technically the lowest altitude at which the temperature has changed less than 2 K for 2 km above
• "caps" the troposphere

• 15-50 km altitude
• positive lapse rate
• stable region with only slow vertical motion
• T increases with height because of ozone (O₃) absorption of solar UV light

• level between the stable stratosphere and the mesosphere

• 50 – 90 km altitude
• negative lapse rate
• T decreases with height because of CO₂ cooling to space

• free troposphere. Connections with surface processes are inefficient. Is not influenced on daily time scales by energy deposited at the surface.
• planetary boundary layer. Air is circulated from the ground to the top of the PBL in a matter of about 30 minutes. Typical PBL height is 1-3 km over land and .5 –1 km over the ocean. The nighttime PBL is usually a few hundred meters. Profiles of moisture and T tend to be flat in the PBL.

3. Zonal winds

Why do we feel comfortable taking zonal averages and reporting quantities like the zonal wind?

Examine the wind jets in figure 1.12.