Planetary-Scale Mountain Waves

• Planetary-scale waves are observed that remain fixed with respect to the earth’s surface:

• Possible causes are geographic distribution of:– Mountains (Charney and Eliassen 1949)

– Land/sea differences and inequitable distribution of sensible and latent heating (Smagorinsky 1953)

• After 30 years of debate, answer settled that both are important, but mountains perhaps a little more so

500 mb Height

Sea Level Pressure

Gross-simplification of planetary-scale stationary waves

Himalayas/Tibetan Plateau

Rockies

Upper-tropospheric flow

Kur

oshi

o

Gul

f S

trea

m

Ertel’s Potential Vorticity

• P = ( + f ) / p

• Potential vorticity conserved for adiabatic, large-scale motion

Mountain

p p

E

Conservation of Potential Vorticity

Mou

ntai

n

•P = ( + f ) / p

anticyclonic; clockwise

cyclonic; counterclockwise

700 mb Height (Stone 2001)

700 mb Vorticity (Stone 2001)

Held

Held

Manabe and Terpstra (1974)Observed

Manabe and Terpstra (1974)With Mountains

Observed

Manabe and Terpstra (1974)Without Mountains

Observed

200 mb Height (Stone 2001)