Turbulence in the Upper Levels of Tropical Cyclones
Abstract
Turbulence in the cirrus canopy of tropical cyclones (TCs) can give an indication about the physical processes that occur in this expansive cloud deck. The low stability and/or large shear that likely coincides with turbulent layers can be produced by radiative forcing, convective forcing, and sublimation of frozen precipitation from the cirrus canopy. As a result, turbulence in the cirrus canopy can give an indication about the impact of various physical processes in tropical cyclones. A direct measure of turbulence is available from the flight-level vertical aircraft acceleration data from the NOAA G-IV aircraft. This 1 Hz data on about a 250 m scale has been collected for years but to our knowledge has not been examined in any detail. Turbulence distributions with respect to radius, storm intensity, height, and time of day were examined. The highest turbulence was located between the 0-200 km radii and 14.2-14.6 km heights. Major TCs exhibited larger turbulence than minor TCs. Turbulence during the nighttime exceeded that from during the day. The turbulence distributions were then broken up further into cirrus canopy categories. These groupings were defined with broad IR brightness temperature ranges from the GOES satellite. The nighttime average within the cirrus canopy was 28% larger than the daytime outside the cirrus canopy. Overall, it appears that convective intensity and vertical gradients of radiative heating play a significant role in the turbulence distribution. Lastly, the distribution of extreme turbulence (99.9 percentile) was examined for five selected storms.
- Publication:
-
Masters Thesis
- Pub Date:
- 2017
- Bibcode:
- 2017MsT.........26R
- Keywords:
-
- Atmospheric sciences;Meteorology