Identification

Title

Effects of local‐scale orography and urban heat island on the initiation of a record‐breaking rainfall event

Abstract

A record-breaking rainfall event was initiated between the urban heat island (UHI) and a small trumpet-shaped mountain (Huadu Mountain) to its north in Guangzhou City at midnight of May 6, 2017. Numerically simulating the convection initiation (CI) was challenging due to insufficient model resolution and inaccurate boundary layer parameterization, this study therefore examined the pre-convective mesoscale processes based on their four-dimensional analyses obtained through data assimilation of radar and surface observations using the four-dimensional Variational Doppler Radar Analysis System (VDRAS). Results suggested that the Huadu Mountain to the north of Guangzhou City played a crucial role in the CI through orographic blocking and nighttime cooling. Dynamically, the mountain blocked the upstream airflow causing an accumulation of water vapor in boundary layers; thermally, the large near-surface temperature gradients between the mountain and its southern foot area induced northerly downslope winds and low-level convergences and updrafts. The downslope winds enhanced the accumulation of boundary-layer water vapor, which was then transported to higher altitudes over the CI region by the updrafts, thus resulting in the formation and growth of cloud water above the altitude of 1 km. In addition to the mountain, the UHI also played an important role by increasing the magnitude of the low-level convergence and influencing its horizontal distribution. These findings urge attentions to the critical roles of small-scale orography and its interaction with urban underlying surface in initiating local rainstorm events.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7154mhv

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

2021-08-27T00:00:00Z

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

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