Identification

Title

The subgrid velocity scale in the bulk aerodynamic relationship for spatially averaged scalar fluxes

Abstract

The exchange coefficients for area-averaged surface fluxes can become anomalously large when the large-scale flow is weak and significant fluxes of heat and moisture are driven by mesoscale motions within the averaging or subgrid area. To prevent this erratic behavior of the exchange coefficient, the "subgrid velocity scale" must be included to account for generation of turbulent fluxes by subgrid mesoscale motions. This velocity scale is obtained by spatially averaging the local time-averaged velocity used in the bulk aerodynamic relationship. The subgrid velocity scale is distinct from the free convection velocity scale included in the bulk aerodynamic relationship to represent transport induced by convectively driven boundary-layer-scale eddies (Godfrey and Beljaars; Beljaars).The formulation of Godfrey and Beljaars is derived by time averaging the velocity scale of the bulk aerodynamic relationship. The behavior of the subgrid velocity scale is explored using data from five different field programs. Ubiquitous "nameless" mesoscale motions of unknown origin are found in all of the datasets. The addition of the subgrid velocity scale reduces the dependence of the exchange coefficients on grid size. Based on the data analysis, the subgrid velocity scale increases with grid size and contains a contribution due to surface heterogeneity.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.org/ark:/85065/d7kk9bkf

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

1995-10-01T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Copyright 1995 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