1. ATM OCN 100 - Summer 2002 LECTURE 31
MID-LATITUDE WEATHER SYSTEMS: PART IV: SURFACE-UPPER AIR LINKAGE
A. INTRODUCTION
How do surface weather features develop and move?
How do surface & upper air weather features relate?

2. B. UPPER AIR WEATHER CONDITIONS
Jet Stream Structure
Types of Major Jet Streams
Polar Jet
Subtropical Jet
Seasonal Variations in Jet Streams
Reasons for Jet Streams
The Thermal Wind Relationship

3. Formation of a Jet Stream

4. Reasons for Jet Stream The “Thermal Wind” Relationship
Wind speed increases with height in region of strong horizontal temperature contrast;
Wind direction turns with height to parallel lower-level isotherms, with... Colder air to left in Northern Hemisphere.

5. Waves in the Jet -- A ridge - An intrusion of warm air

6. Waves in the Jet -- A trough - An intrusion of cold air

7. An upper air chart example

8. The Surface Low & the Jet

9. C. RELATING SURFACE & UPPER AIR CIRCULATION SYSTEMS
Weather Regimes
Types of Flow Patterns Aloft
Zonal Flow
Meridional Flow
Cutoff Lows
Blocking Patterns

10. Zonal Circulation Regime Figure 10.10 Moran & Morgan (1997)

11. Meridional Circulation Regime Figure 10.10 Moran & Morgan (1997)

12. Stagnant Circulation Regime with Cut-off Lows & Blocking Highs Figure 10.13 Moran & Morgan (1997)