Identification

Title

Potential low bias in high-wind drag coefficient inferred from dropsonde data in hurricanes

Abstract

Understanding momentum exchange at the air-sea interface is important for accurate hurricane predictions and understanding fundamental storm dynamics. One method for estimating air-sea momentum transfer in high winds is the flux-profile method, which infers surface momentum fluxes and the corresponding drag coefficient from mean velocity profiles obtained from either dropsondes or meteorological towers, under the assumption that the boundary layer wind profile at low altitudes exhibits a logarithmic profile with height. In this study, we use dropsonde data from reconnaissance aircraft, as well as "virtual sondes" from a turbulence-resolving simulation of an intense tropical cyclone, to critically analyze the diagnosis of drag coefficient C-D at hurricane-force wind speeds. In particular, the "rolloff" of the drag coefficient, where C-D decreases at 10-m wind speeds > 35 m s(-1), is called into question based on uncertainty due to relatively low sample size and a lack of robustness of the flux-profile method at high winds. In addition, multiple factors appear to favor an underestimate of C-D at hurricane-force winds relative to their true values, including uncertainty in the height of recorded dropsonde data, in violation of Monin-Obukhov similarity theory near the eyewall, and the short vertical extent of the logarithmic layer. Due to these and other related sources of uncertainty, it is likely that a quantitative limit has been reached in inferring the specific values of u(*) and C-D using the flux-profile method, while at the same time the potential for underestimation may cast doubt on the C-D-U-10 relationship inferred from this method at high winds.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.org/ark:/85065/d7dz0crx

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2021-07-01T00:00:00Z

Frequency of update

Quality and validity

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Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact