Jun Zhang NOAA/AOML/HRD William Drennan Univ. of Miami/ RSMAS Spectra and Cospectra of Turbulence in the Hurricane Boundary Layer over the Ocean AMS 89 th Annual Meeting, Paper 7A.3 Phoenix, 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 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. 1970Kaimal et al S uu S vv S ww Mean value of 42 flux runs S uu S vv S ww

Miyake et al Kaimal et al S θθ S qq S θθ S qq

S uw S vw S qw Miyake et al 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/OMAO Aircraft Operations Center Support of National Research Council Fellowship Acknowledgements: