Leipziger Staubtag, 6th March 2014

Martina Klose*, Yaping Shao, Xiaolan Li, Hongsheng Zhang, Masahide Ishizuka, Masao Mikami, John Leys

*mklose@uni-koeln.de

Convective Turbulent Dust Emission

University

of Cologne

Institute for Geophysics and Meteorology

Martina Klose - mklose@uni-koeln.de

Concept of Turbulent Dust Emission

a) Saltation induced by mean wind momentum

b) Aerodynamic entrainment induced by intermittent large-eddy

momentum; saltation does not need to be involved.

Motivation

from Klose and Shao (2013)

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Martina Klose - mklose@uni-koeln.de

Objectives

• Convective turbulent dust emission (CTDE)

dust model and numerical experiments (LES)

• CTDE case studies

calibration and validation

• Long-term regional application

budget estimation

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Martina Klose - mklose@uni-koeln.de

f …. lifting force determined by instantaneous momentum flux;

resolved in LES

p(f) in regional models

Ideal conditions

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fi ....cohesive force follows log-normal distribution (Zimon, 1982)

CTDE parameterization

Convective turbulent dust emission (CTDE)

Martina Klose - mklose@uni-koeln.de

Numerical experiments

WRF V3.2 Large-Eddy model coupled with dust mobilization scheme

Land-surface: homogeneous (loam soil)

constant surface heat flux

p(d) and p(fi) pre-specified

Atmospheric initialization:

Various atmospheric stability and background-wind conditions determined by

a) surface heat flux H (H = -50, 0, 200, 400, and 600 W m-2) and

b) initialization with logarithmic wind profile based on friction velocity u

* (u

* = 0.15, 0.3, and 0.5 m s-1)

15 different stability and background wind constraints

WRF-LES/D

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Martina Klose - mklose@uni-koeln.de

Turbulent dust emission LES experimental results

from Klose and Shao (2013)

• large eddies can produce

significant dust emission

• strongest emissions at

A updraft convergence lines

B downdraft centers

C vortices

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Martina Klose - mklose@uni-koeln.de

Turbulent dust emission LES experimental results

Dust concentration modeled with WRF/LES_D

Visualization in cooperation with the Regional Computing Centre, University of Cologne

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http://www.geomet.uni-koeln.de/allgemein/das-institut/ag-shao/galerie/

Martina Klose - mklose@uni-koeln.de

CTDE parameterization

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Lifting force (ideal conditions)

• new similarity approach for instantaneous momentum flux (f)

• approximated as Weibull distribution

• shape parameter α dependent on stability (z/L)

• scale parameter β constant (scaling with u* and w*)

(a) p(f) from LES experiments (b) Weibull approximation of p(f)

from Klose et al. (2014)

Martina Klose - mklose@uni-koeln.de

Field data from • Horqin sand-storm monitoring station (Li et al., 2014)

• Japan-Australia Dust Experiment (Ishizuka et al., 2008)

CTDE modeling

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Case studies

CTDE criteria:

F > 0

w* > 0

u* < u*t

modified from Klose et al. (2014)

• 18 CTDE cases

• αN ≈ 6*105 m-2

• rsd ≈ 49%

Martina Klose - mklose@uni-koeln.de

CTDE Modeling

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Long-term regional simulation

• WRF/Chem V3.51 with dust

• dx = dy = 20 km, 1 month simulation time (January 2001)

• necessary condition is u* < u*t

Martina Klose - mklose@uni-koeln.de

Concluding remarks

• Dust cycle can be modeled with WRF/LES_D

• CTDE is a stochastic variable

• CTDE and instantaneous momentum flux are controlled by few atmospheric parameters, e.g. u*, w*

• Order of magnitude of CTDE is ~ 1-100 µg m-2 s-1

• Process of CTDE seems to be captured by parameterization

• Calculation of turbulent dust emission in regional model WRF/Chem_dust offers possibility of long-term quantitative estimates

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Thank You!

References:

Klose, M. and Y. Shao, 2012: Stochastic parameterization of dust emission and application to convective atmospheric conditions, Atmos. Chem. Phys., 12, 7309-7320.

Klose, M. and Y. Shao, 2013: Large-Eddy Simulation of Turbulent Dust Emission, Aeolian Research 8, 49-58.

Klose, M., Y. Shao, X. L. Li, H. S. Zhang, M. Ishizuka, M. Mikami, and J. F. Leys, 2014: Further development of a parameterization for convective turbulent dust emission and validation with field observations, J. Geophys. Res., submitted.

Li, X. L., M. Klose, Y. Shao, and H. S. Zhang, 2014: Convective turbulent dust emission (CTDE) observed over Horqin Sandy Land area and validation of a CTDE scheme, J. Geophys. Res., submitted.

Ishizuka, M., M. Mikami, J. F. Leys, Y. Yamada, S. Heidenreich, Y. Shao, and G. H. McTainsh, 2008: Effects of raindroplet crust on saltation and dust emission, J. Geophys. Res., 113, D24212.

Zimon, A. D., 1982: Adhesion of dust and powder, Consultants Bureau, New York, USA.