convective turbulent dust emission - tropos...martina klose - [email protected] objectives •...
TRANSCRIPT
Leipziger Staubtag, 6th March 2014
Martina Klose*, Yaping Shao, Xiaolan Li, Hongsheng Zhang, Masahide Ishizuka, Masao Mikami, John Leys
Convective Turbulent Dust Emission
University
of Cologne
Institute for Geophysics and Meteorology
Martina Klose - [email protected]
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 - [email protected]
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 - [email protected]
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 - [email protected]
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 - [email protected]
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 - [email protected]
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 - [email protected]
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 - [email protected]
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 - [email protected]
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 - [email protected]
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.