Stratospheric Descent Rates Within the Polar VortexEPA Grant Number: U914953
Title: Stratospheric Descent Rates Within the Polar Vortex
Investigators: Hicke, Jeffrey A.
Institution: University of Colorado at Boulder
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1996 through July 15, 1999
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1996) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Air Quality and Air Toxics , Fellowship - Atmospheric Sciences
The objective of this research project is to calculate stratospheric descent rates at various times and locations in the Southern Hemisphere using several temperature, water vapor, and ozone data sets and a radiative transfer model.
The descent rate within the polar vortex using several radiative transfer models and newly acquired data sets has been investigated. The primary radiative transfer model used is the NCAR CCM2 general circulation model radiation code. A more accurate, but computationally expensive, model called MODTRAN also was used for sensitivity tests and comparisons. Three data sets have been used in the cooling rate calculation. The first data set consists of 1994 temperature retrievals from the airborne (High Resolution Interferometer Sounder) instrument in the antarctic polar vortex. These profiles extend from the surface to the aircraft altitude in the lower stratosphere. They are valuable as an independent comparison with data sets used in previous studies of the descent rate. Data from numerical weather prediction model analyses comprise the second data set. The United Kingdom Meteorological Office (UKMO) analyses are primarily used in this study because of the model’s emphasis on the middle atmosphere. The final data set contains balloon soundings at McMurdo Station, Antarctica. Descent rates have been calculated from these data sets, and comparisons to the UKMO analyses have been made. Results of clear sky calculations, as is typical of previous studies, show lower descent rates.