Improvement in forecast skill from 1981-2003for ECMWF 5-km hemispheric flow pattern

Highlights of the past recent decades

Increased evidence of human impact:Antarctic ozone hole

TOMS (Total OzoneMapping Spectrometer) satellite

CCL4 mixing ratio declining, also that of other ozone-depletors

Increased evidence of human impact: Greenhouse Warming

Monthly-mean C02 concentrations, 1958-2002

Carbon Dioxide

Increased evidence of human impact: Aerosols

Fig. xx, left panel: Sea ice concentrationAnomalies for September 2002, 2003, and 2004, along with the 1979-2000 median September ice edge (pink line), derived from passive microwave satellite imagery. These reveal that sea ice extent reached a record minimum in Sept. 2002, followed by two more low-ice years. While sea ice declinecan result from natural variability associatedwith the dynamical Arctic Oscillation (AO),greenhouse warming also favors the AO phase most conducive to warming.Image courtesy of NSIDC, Boulder, CO(http://nsidc.org/)Arctic surface air temperatures haveobserved to increase in the past 50 yearsin Alaska and Siberia, with a cooling inSouthern Greenland.

Additional declines of roughly10-50% in annual average sea-iceextent are projected by 2100 inmodel simulations. Loss of seaice is projected to be greater duringsummer than in the annual average.Top and left Figures provided byThe Arctic Climate Impact Assessment(http://www.acia.uaf.edu).

Links to Climate Dynamics: The Arctic

Overview of the atmosphere: Coordinate System Convention

dx = r dcos

dy = r d

at greenwich

is longitude, is latitude

x positive east, y positive north

1 degree latitude = 111 km

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

Atmosphere very thin: 99.9% of airMass in a layer < 1% of Earth’s radius

r approximated as the Earth’s radius ~ 6.37 * 106 m

Velocity