Identification

Title

Influence of convective adjustment time scale on the tropical transient activity

Abstract

The influence of convective adjustment time scale (τ) in simulating the tropical transient activity is examined using the NCAR-Community Atmosphere Model (CAM). In the default configuration of the model, the prescribed value of τ, a characteristic time scale with which convective available potential energy (CAPE) is removed at an exponential rate by convection, is assumed to be 1 h. However, some recent observational findings suggest that it is larger by around one order of magnitude, and subsequent modeling studies showed its impact on mean climate and suggest a value of 8 h. To see if alteration of this time scale could affect the transient features of climate, numerical experiments are conducted in aquaplanet and real-planet frameworks. The analysis includes the tropical intraseasonal variability (ISV), convectively coupled equatorial waves (CCEW), diurnal and sub-diurnal variability of precipitation, and intensity and frequency of rainfall. Two sets of simulations are conducted: one with a time scale of 1 h (CTRL) and another with 8 h (EXPT). EXPT produces more reasonable ISV, with prominent, coherent, and organized eastward propagation. The active phases of the ISV constitute hierarchical substructures embedded within them, which are absent in CTRL. The Kelvin waves become slow, Madden-Julian oscillation (MJO) become energetic, n = 1 equatorial Rossby (ER) and n = 0 eastward inertio-gravity (EIG) waves become prominent, with the increase of τ. On the contrary, the mixed Rossby-gravity (MRG) waves at higher wavenumber regimes become weak. The amplitude of diurnal variability decreases, but the phase remains largely unchanged. At sub-diurnal scales, the variability of precipitation increases. In CTRL, precipitation always occurs in the tropics with light or moderate intensity, which becomes intermittent when s is increased to 8 h.

Resource type

document

Resource locator

Unique resource identifier

code

https://n2t.org/ark:/85065/d7mk6dmw

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

2011-10-01T00:00:00Z

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

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