Identification

Title

Response of orographic precipitation to subsaturated low-level layers

Abstract

In orographic precipitation events, there are times when subsaturated low-level layers are observed to be below saturated, nearly moist-neutral, upper-level layers. By performing a series of idealized two-dimensional simulations, this study investigates the response of orographic precipitation to subsaturated low-level layers. When the nondimensional parameter N(2)z(t)/U, where N-2 and z(t) are, respectively, the dry Brunt-Vaisala frequency and depth of the subsaturated low-level layer, and U the cross-mountain wind speed, exceeds a critical value, the decelerated region on the upwind side of the mountain moves upwind, resulting in weak surface precipitation near the mountain peak. The critical value determined from the simulations is close to that derived from linear theory. When N(2)z(t)/U is less than the critical value, increasing z(t) has two competing effects: 1) the vapor-transport effect, meaning that increasing z(t) decreases the amount of vapor transported to the mountain, and hence tends to decrease surface precipitation; and 2) the updraft-width effect, meaning that increasing z(t) enhances flow blocking, producing a wider updraft over the upwind slope, and hence tends to increase surface precipitation. When the vapor-transport effect dominates, surface precipitation decreases with z(t). When the updraft-width effect dominates, surface precipitation increases with z(t). Increasing the maximum mountain height h(m) or U generally increases surface precipitation. However, for certain combinations of h(m) and U, the simulations produce lee waves, which substantially reduce surface precipitation. Finally, the response of orographic precipitation in the simulations with both liquid-phase and ice-phase microphysics is similar to that in the simulations with only liquid-phase microphysics.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.org/ark:/85065/d79z9826

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

2019-12-01T00:00:00Z

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

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