Middle-latitude climates - The Global Climate System: Patterns, Processes, and Teleconnections - page 122

Table 4.2 Southern Hemisphere mid-latitude circulation variations, glacial changes on the west coast of
New Zealand, Southern African rainfall, and snow accumulation in Antarctica

Dominant zonal circulation Dominant meridional circulation

Circulation characteristics
Stronger zonal westerlies Weaker zonal westerlies

Weak upper westerly waves (shift west) Stronger upper westerly waves

Westward rotation of wave number 3 by 30-40
degrees

Wave number 3 located more east

Single jet stream Split jet
Below average cyclone activity east of New Zealand Above average cyclone activity east of
New Zealand

Below average cyclone activity, S. Indian Ocean Above average cyclone activity, S. Indian Ocean

Increased anticyclonic activity Decreased anticyclonic activity

Westerlies expand equatorward Westerlies contract poleward

Link to El Ni ˜ o events Link to La Ni ˜ a events

Weaker trade winds Stronger trade winds

Subtropical anticyclone moves equatorward Subtropical anticyclone moves poleward

Weaker poleward transport of heat, moisture,
momentum

Stronger poleward transport of heat, moisture,
momentum

Positive Antarctic Annual Oscillation Negative Antarctic Annual Oscillation

Glacial changes in New Zealand
Glacial advances Glacial retreats

Strongest impact in accumulation season Stronger impact in ablation season

Stronger SW wind anomalies Stronger NE wind anomalies

Increased cloud, lower solar radiation Decreased cloud, increased solar radiation

Increased precipitation, SW coast Decreased precipitation, SW coast

Southern Africa
Drought

Moist

Upper ridge shifts westward Upper ridge shifts eastward

Negative surface pressure anomalies (south of
continent)

Positive surface pressure anomalies

Westerly wind anomalies Easterly wind anomalies

Antarctica
Lower Na þ deposits

Higher Na þ deposits

Lower precipitation Higher precipitation

Contraction of circumpolar trough (CPT) Expansion of circumpolar trough (CPT)

Ridging limited over CPT S of Australia Enhanced ridging over CPT S of Australia

Summarized from Tyson et al.( 1997 ); Goodwin et al.( 2003 ), ( 2004 ).