Fall 2009 Climate Center Lecturer

Climate Center Fall 2009 Lecturer

Harry van Loon

September 21 – 25, 2009


|  NorthWest Research Associates |  CoRA (Colorado Research Associates) Division |
| 3380 Mitchell Lane   |  Boulder, CO  80301 |
| (303) 415-9701 ext. 237 | e-mail: vanloon@cora.nwra.com

Short Biography

  • Harry van Loon is originally Danish.
  • He worked as a student in the Danish Meteorological Institute.
  • Studied at Massachusetts Institute of Technology for three years.
  • Worked nine years in the South African Weather.
  • Senior Scientist at the NationalCenter for Atmospheric Research (NCAR).
  • Emeritus at NCAR and Colorado Research Associates/Northwest Research Associates.



Monday, September 21 @ 3 PM in Lamont Hall, LDEO Campus

Wine and Cheese Reception to follow @ 4 PM

The Semi-Annual Oscillation in Middle and High Southern Latitudes

A double wave (second harmonic) dominates the mean annual march of pressure, wind, and temperature gradients in middle and high southern latitudes. Its interannual variability is large, but its phase is stable. It collapsed in 1979-1980, returned quickly in the South Atlantic and most of the South Indian Oceans, but it is still not present in the South Pacific Ocean. Its origin should be sought in the different response to the surface heat budget in the oceanic middle and continental high southern latitudes.



Wednesday, September 23 @ 2 PM in Lamont Hall, LDEO Campus

The Difference in AnnualRange between an Oceanic and a Continental Hemisphere

The annual range of sea-surface temperature and of temperature in the troposphere of the Southern Hemisphere is distributed in concentric zones: low in the tropics, high in the subtropics, low in middle latitudes, and high in the Antarctic. The temperature gradients (thermal winds) between these regions are thus steepest in winter between the tropics and subtropics and between middle and polar latitudes. But they are steepest in summer between the subtropics and middle latitudes, and consequently the wind there is stronger in summer than in winter - in contrast to the Northern Hemisphere. This is due to increasing cloudiness as one goes poleward from lower to higher latitudes and the mixing through the year by winds and currents in middle latitudes.



Tuesday, September 22 or Thursday, September 24 @ 11 AM @ GISS Campus

A Probable Influence by the Sun at its 11-Year peaks on Atmosphere and Ocean in the Pacific Region

An analysis of sea-level pressure and sea-surface temperature suggests that the following happens on average at the peaks of the Decadal Solar Oscillation: The sea-level pressure is above normal below the equator, the SE-trades are thus stronger than average, the upwelling of cooler water is enhanced, and the sea-level pressure becomes above normal in the Gulf of Alaska. The rainfall decreases in the equatorial belt, the Walker Circulation is enhanced and the tropical convergence zones are displaced poleward. The pattern is reminiscent of a cold extreme in the

Southern Oscillation, but its amplitude is smaller. The response in the stratosphere is also widely different from that in a cold extreme. The probable solar effect is an enhancement of the climatological mean. When the solar oscillation is not at its peak, any pattern can occur from cold to warm extremes in the Southern Oscillation.