Hazardous Weather Detection and Prediction

1
Hazardous Weather Detection and Prediction

• Kelvin K. Droegemeier
• University of Oklahoma
• Week 1, Lecture 2
• Thursday, 20 January 2005

2
As a Reminder

• Please send an email to kkd_at_ou.edu containing the
  following
• Full name (first, last)
• Social Security or Student ID Number
• Institution
• Major field of study
• Year in school or title if not a student
• Principal email address
• Enrollment status (credit, audit, sitting in)

3
Atmospheric Composition
Lutgens and Tarbuck, The Atmosphere, 8th edition
4
Atmospheric Composition
Seasonal trendrelated to Carbon fixation in
plants via the Calvin Cycle
5
Courtesy NCAR
6
Vertical Structure of the Atmosphere
90 of total mass residesin the lowest 10
km 50 of total mass residesin the lowest 5-6 km
7
Vertical Structure of the Atmosphere

• Key questions
• Why do thunderstorms form in the lower
  parts?
• Do the upper parts have any influence?
• What parts do we need to observe, and
  which variables?

8
The Troposphere

• From the Greek tropein, which means turn or
  change
• Ground-level to 10-12 km
• Where all weather occurs
• Contains 90 of mass and almost all of the H20V
• Average lapse rate (-dT/dz) of 6.5 K km1
• Topped by tropopause (above is isothermal layer)
• Little exchange between troposphere and layers
  above
• Typically find a temperature inversion (temp
  increases with height) in lowest 2 km very
  stable
• Sampled by radiosondes

9
Low-Level Temperature Inversion
Rawinsonde
10
The Stratosphere
The Stratosphere

• 10-50 km in altitude (strato meaning stratified)
• T increases dramatically with height (deep
  inversion) owing to ozone heating
• Max ozone location is optimal region for
  concentration and photochemstry
• T continues to increase above max ozone region
  because of intense molecule excitation at low
  density and high altitude, and because absorbed
  energy at high altitudes does not reach lower
  altitudes
• Thunderstorms sometimes penetrate into
  stratosphere (overshooting top)
• Upper limit is stratopause

11
(No Transcript)
12
The Stratosphere
The Mesosphere

• Meso means middle
• 50-80 km in altitude
• Density is very low and ozone concentrations are
  nil thus air molecules lose more energy than
  they absorb and the atmosphere cools with height
  at a rate of about - 3K km-1
• Coldest temperatures are at the mesopause, the
  top of the mesosphere marking the bottom of
  another inversion

13
The Stratosphere
The Thermosphere

• 80-200 km altitude
• This is an extremely hot layer where molecular
  Oxygen absorbs highly energetic photons
• Mean free path is about 1 km
• Air would not feel warm!
• Temperature is measured indirectly, by orbital
  changes in satellites
• Exospheric temperatures vary significantly in
  time owing to changes in solar activity

14
The Stratosphere
Other Layers
15
Back to Our Questions

• Why do thunderstorms form in the lower
  parts?
• Moisture is present
• Temperature structure
• Do the upper parts have any influence?
• Indirectly (tropopause height, large-scale
  dynamics)
• What parts do we need to observe, and
  which variables?
• Troposphere
• T, P, dens, moisture, soil temp/moisture,
  wind, particulates, precipitation