Identification

Title

Scale dependence of air-sea fluxes over the western equatorial Pacific

Abstract

The goal of this study is to examine the horizontal scale dependence of vertical eddy flux in the tropical marine surface boundary layer and how this scale dependence of flux relates to the bulk aerodynamic relationship and the parameterization of subgrid-scale flux. The fluxes of heat, moisture, and momentum are computed from data collected from 27 NCAR Electra flight legs in TOGA COARE (The Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment) with flight elevations lower than 40 m and flight runs longer than 60 km. The dependence of the fluxes on two length scales are studied: the cutoff length scale, defining the averaging length over which mean components are obtained in order to partition field variables into mean and perturbation components; and the flux averaging length scale, defining the length over which products of perturbations are averaged in order to estimate vertical fluxes. Based on the characteristics of the scale dependence of fluxes, the total flux of each flight leg is partitioned into "turbulent," "large eddy," and "mesoscale" fluxes due to motions smaller than 1 km, between 1 and 5 km, and between 5 km and the flight leg length, respectively. The results show that fluxes are sensitive to the choice of cutoff length scale in the presence of significant mesoscale activity and in the weak wind case where the turbulent fluxes are small. The turbulent momentum flux decreases with increasing flux averaging length scale due to mesoscale modulation of the turbulent stress vector. Mesoscale heat, moisture, and momentum fluxes for individual flight legs can reach 20% of the turbulent fluxes in the presence of well-organized convective cloud systems even at 35 m above the sea surface. The mesoscale flux is less correlated to the wind speed and bulk air-sea difference than turbulent fluxes. The local mesoscale flux can be upward or downward, and therefore, its average value is reduced when averaging over a single flight leg and reduced further when compositing over all of the legs. The mesoscale momentum flux is less systematic than the turbulent stress and is more sensitive to the flux averaging scale than the turbulent stress. Sampling and instrumentation problems are briefly discussed, particularly with respect to mesoscale motions.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.org/ark:/85065/d7b27v4q

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

1996-11-01T00:00:00Z

Frequency of update

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Constraints related to access and use

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Use constraints

Copyright 1996 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statement, requires written permission or a license form the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/AMS) or from the AMS at 617-227-2425 or copyright@ametsoc.org.

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