“diamond dust”: a very thin ice-cloud in the near-surface ...€¦ · “diamond dust”: a...

“Diamond dust”:

A very thin ice-cloud

in the near-surface

inversion layer.

“Diamond dust”:

A very thin ice-cloud

in the near-surface

inversion layer.

It’s a mixing-cloud.

(Saturation vapor

pressure as a function

of temperature is

concave-upward.)

Snow crystals falling in winter at South Pole (temperature –60 C).

Small grid is 50 microns. Photo by Steve Warren.

Shimizu crystals (~ 10 µm × 1 mm)

Nacreous clouds (Polar Stratospheric Clouds, PSC)

above McMurdo Station (78°S), September 2009

Snow accumulation

(centimeters liquid equivalent

per year):

East Antarctic Ridge 2-3

Peninsula >40

Average for Antarctica ~17

Global average 100 cm

(40 inches)

Snow accumulation

(centimeters liquid equivalent

per year):

East Antarctic Ridge 2-3

Peninsula >40

Average for Antarctica ~17

Global average 100 cm

(40 inches)

At South Pole (7 cm/yr), a

large fraction of the snowfall

comes from a few warm

storms.

On the East Antarctic Ridge

(2 cm/yr), most may come

from diamond-dust.

Snow accumulation

(centimeters liquid equivalent

per year):

East Antarctic Ridge 2-3

Peninsula >40

Average for Antarctica ~17

Global average 100 cm

(40 inches)

At South Pole (7 cm/yr), a

large fraction of the snowfall

comes from a few warm

storms.

On the East Antarctic Ridge

(2 cm/yr), most may come

from diamond-dust.

During the last ice age: Lower

temperature, less snowfall.

With future global warming:

Probably more snowfall.

Wind direction at the surface

Wind

Wind direction at the surface

Average wind speed

South Pole

summer 8 knots

winter 13 knots

Cape Denison

annual 40 knots

Threshold for drifting snow

~ 14 knots

Blowing snow (as well as a few falling-snow crystals)

Climate changes

(1) Mean annual temperature

South Pole Antarctic Peninsula (west side)

Turner 2004

Climate changes

(2) Wind speed

Late winter (July-Sept)

South Pole

Annual

Lazzara et al. 2012

Climate changes

(3) Snow accumulation

South Pole

Antarctica

Depth of ice: average 2.2 km, maximum 4.8 km

About 86% of the ice is in East Antarctica

Mean annual temperature

from -60°C on East Antarctic Plateau

(Vostok, Dome C, Plateau Station)

to -3°C on Antarctic Peninsula

Temperature extremes at surface

World record low temperature: -89°C (at Vostok)

Record high temperature at South Pole: -12°C

Snow accumulation

average 14-19 g cm-2 yr-1

on Plateau 5 g cm-2 yr-1