Jun ZhangNOAA/AOML/HRD
William DrennanUniv. of Miami/ RSMAS
Spectra and Cospectra of Spectra and Cospectra of Turbulence in the Hurricane Turbulence in the Hurricane
Boundary Layer over the OceanBoundary Layer over the Ocean
AMS 89th Annual Meeting, Paper 7A.3Phoenix, 13 January, 2009
Statement of Problem:
Turbulence transport processes are important for the development and maintenance of a storm:
Latent heat or moisture enters a storm through the boundary layer; The boundary layer dynamics and thermodynamics determine the enthalpy and angular momentum flux out of the boundary layer.
However, the hurricane boundary layer has been the least well-observed.
Prior to 2003, there is only one boundary layer in-situ turbulence structure measurement that was conducted by Moss (1978) in the periphery of marginal hurricane Eloise at surface wind speed of about 20 m/s.
Objective
Improve our understanding of the dynamics and structure of the hurricane boundary layer through spectral analysis using data collected during the Coupled Boundary Layer Air-sea Transfer – Hurricane Experiment
The Coupled Boundary Layer Air-sea Transfer (CBLAST) Hurricane Experiment
Six flights in two hurricanes in 2003
3 Hurricane Fabian 3 Hurricane Isabel
N43RF Flux instrumentation - BAT (“Best Aircraft Turbulence”) probe on boom - Rosemount Gust probes in radome and fuselage - Inertial navigation, GPS systems in fuselage
- LICOR LI-7500 hygrometer (modified)
- Rosemount temperature sensors - PRT5 radiometer for sea surface temperature - Stepped Frequency Microwave radiometer (SFMR)
←LICOR head
↓ BAT
Miyake et al. 1970 Kaimal et al. 1972
Suu
Svv
Sww
Mean value of 42 flux runs
Suu
Svv
Sww
Miyake et al. 1970
Kaimal et al. 1972
Sθθ Sqq
SθθSqq
Suw
Svw
Sqw
Miyake et al. 1970
Kaimal et al. 1972
Summary• spectra and cospectra of wind velocity, temperature and humidity
fluctuations from the CBLAST experiment are normalized and compared to other published spectra and cospectra based on Monion-Obukhov similarity theory.
• The CBLAST normalized spectra and cospectra of three components of wind velocity and specific humidity fall into universal shapes.
• However, the potential temperature spectra and cospectra of
potential temperature with vertical velocity cannot be grouped to well-defined universal forms.
• The CBLAST universal spectra curves of wind velocity and humidity shift to the high frequency band compared to standard surface layer universal spectra curves, indicating wavelengths of the dominant turbulent eddies transporting energy in the hurricane boundary layer between the rainbands are relatively smaller than those in a typical boundary layer.
Office of Naval Research (ONR)CBLAST Hurricane Program
NOAA Hurricane Research Division
OAR & USWRP
NOAA/OMAOAircraft Operations Center
Support of National Research Council Fellowship
Acknowledgements:Acknowledgements: