Cross Equatorial Systems
 Northern and Southern Hemisphere Intrusions
Mike Davison
HPC International Desks

Slide 2

Characteristics of Northern Hemisphere Ridges and Troughs
Ridge
Warm Core
Anticyclonic (negative/clockwise) relative vorticity increases with height
High tropopause heights
Trough
Cold Core
Cyclonic (Positive/
    counterclockwise) relative vorticity increases with height
Low tropopause heights

Northern Hemisphere
Upper Ridge/Trough Pattern

Northern Hemisphere Ridge
Winds and Temperature

Northern Hemisphere Ridge
Winds and Potential Temperature

Northern Hemisphere Ridge
Winds and Relative Vorticity

Northern Hemisphere Trough
Winds and Temperature

Northern Hemisphere Trough
Winds and Potential Temperature

Northern Hemisphere Trough
Winds and Relative Vorticity

Characteristics of Southern Hemisphere Ridges and Troughs
Ridge
Warm Core
Anticyclonic (Positive/
    counterclockwise) relative vorticity increases with height
High tropopause heights
Trough
Cold Core
Cyclonic (negative/clockwise) relative vorticity increases with height
Low tropopause heights

Southern Hemisphere
Upper Trough/Ridge Pattern

Southern Hemisphere Ridge
Winds and Temperature

Southern Hemisphere Ridge
Winds and Potential Temperature

Southern Hemisphere Ridge
Winds and Relative Vorticity

Southern Hemisphere Trough
Winds and Temperature

Southern Hemisphere Trough
Winds and Potential Temperature

Southern Hemisphere Trough
Winds and Relative Vorticity

What Happens When a Southern Hemisphere System Crosses the Equator?
Northern Hemisphere
Southern Hemisphere

Does it behaves like a Nrn Hemisphere Ridge or a Srn Hemisphere Trough?

Case Study
31 Oct 2001

Evaluation of Upper Circulation over the Tropical Atlantic

Vertical Cross Section of Temperature (C) and Winds

Vertical Cross Section of Relative Vorticity and Winds

Vertical Cross Section of Potential Temperature (K), Winds, and Relative Vorticity

Vertical Cross Section of  Potential Temperature (K) and Winds

250 hPa Winds and Divergence
Objective Analysis

250 hPa Winds

250 hPa Winds and Divergence
Objective Analysis

Verification

IR Loop

WV Loop