Identification

Title

Observed and simulated variability of droplet spectral dispersion in convective clouds over the Amazon

Abstract

In this study, the variability of the spectral dispersion of droplet size distributions (DSDs) in convective clouds is investigated. Analyses are based on aircraft measurements of growing cumuli near the Amazon basin, and on numerical simulations of an idealized ice-free cumulus. In cleaner clouds, the relative dispersion epsilon, defined as the ratio of the standard deviation to the mean value of the droplet diameter, is negatively correlated with the ratio of the cloud water content (q(c)) to the adiabatic liquid water content (q(a)), while no strong correlation between epsilon and q(c)/q(a) is seen in polluted clouds. Bin microphysics numerical simulations suggest that these contrasting behaviors are associated with the effect of collision-coalescence in cleaner clouds, and secondary droplet activation in polluted clouds, in addition to the turbulent mixing of parcels that experienced different paths within the cloud. Collision-coalescence simultaneously broadens the DSDs and decreases q(c), explaining the inverse relationship between epsilon and q(c)/q(a) in cleaner clouds. Secondary droplet activation broadens the DSDs but has little direct impact on q(c). The combination of a rather modest DSD broadening due to weak collision-coalescence with enhanced droplet activation in both diluted and highly undiluted cloud regions may contribute to maintain a relatively uniform epsilon within polluted clouds. These findings can be useful for parameterizing the shape parameter (mu) of gamma DSDs in bulk microphysics cloud-resolving models. It is shown that emulating the observed mu-q(c)/q(a) relationship improves the estimation of the collision-coalescence rate in bulk microphysics simulations compared to the bin simulations.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d77h1p1k

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

2021-10-27T00:00:00Z

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