Identification

Title

Amplitude modulation of velocity fluctuations in the atmospheric flows over real urban morphology

Abstract

Amplitude modulation (AM) quantifies the top-down interactions between the large-scale motions (LSMs) in the outer layer and the near ground turbulence structures. They are important to the momentum transport and pollutant dispersion in urban atmospheric surface layers (ASLs). The dataset of large-eddy simulation over a densely built region in Kowloon Peninsula, Hong Kong, therefore, is adopted to investigate the AM of small-scale eddies by LSMs in the ASL over real urban morphology. Alike its smooth-wall counterpart, the small-scale eddies are (positively) amplitude modulated by the LSMs in most regions of the roughness sublayer (RSL). However, negative AM is unexpectedly found in the RSL on the building windward side in this study, illustrating the heterogeneity of the urban surface and the flow dynamics being affected aloft. In addition, strong sweep (u ' > 0 and w ' < 0) and ejection (u ' < 0 and w ' > 0) dominate the flows, respectively, in the positive and negative AM zones. In the positive AM zones, the large-scale sweep (u(L)' > 0) leads to the surplus in the small-scale turbulence kinetic energy (TKE), while the large-scale ejection (u(L)' < 0) brings a TKE deficit to the small-scale eddies. By contrast, the large-scale sweeps result in a TKE deficit to the small-scale eddies and the large-scale ejections result in a TKE surplus in the negative AM zones. These findings could help elucidate the AM over different building designs and urban morphology in cities, promoting the momentum transport and pollutant dispersion via proper city planning.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d70k2dg0

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

2023-02-01T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

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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