Operational Dust Prediction - Mineral Dust: A Key Player in the Earth System - page 233

JMA Operational Dust Forecast Model
The Japan Meteorological Agency (JMA) has been providing the “Aeolian Dust
Information” to the general public via its website ( http://www.jma.go.jp/en/kosa/ )
since January 2004. The operational numerical dust forecast in JMA is based on
the Model of Aerosol Species in the Global Atmosphere (MASINGAR) (Tanaka
et al. 2003 ), which is coupled with the MRI/JMA98 AGCM. Dust particles are
logarithmically divided into 10 discrete size bins from 0.1 to 10 minradius.The
operational version of MASINGAR calculates the emission flux of dust as a function
of the third power of 10 m wind velocity, soil moisture, soil type, snow cover and
vegetation cover. Snow cover by JMA surface analysis and monthly mean MODIS-
retrieved leaf area index are used to constrain the erodible surface. JMA is planning
to update the operational dust forecast model to be based on the latest global climate
model MRI-CGCM3 (Yukimoto et al. 2012 ).
Met Office Dust Prediction System
The publicly available dust forecasts from the UK Met Office are produced by the
global NWP configuration of the Met Office Unified Model (MetUM TM ). The dust
scheme is essentially that of Woodward ( 2001 ) with modifications as described in
Woodward ( 2011 ) and Collins et al. ( 2011 ). The dust emission scheme is represents
an initial horizontal/saltation flux in a number of size bins with a subsequent vertical
flux of bare soil particles from the surface into the atmosphere. The global NWP
model uses only two of the original nine size bins. The magnitude of the emission
is a cubic function of the exceedance of the friction velocity over bare soil with
respect to a threshold value, determined from the model wind field and boundary-
layer structure. The horizontal flux is converted to the vertical flux by first limiting
it using the clay fraction in the soil texture data set and then partitioning into the
new bins with a prescribed emitted size distribution. Johnson et al. ( 2011 ) gives an
in-depth description and evaluation of the Met Office dust forecasts in a limited area
model over North Africa.
NASA GEOS-5 Aerosol Forecasting System
The Goddard Earth Observing System (GEOS-5; Rienecker et al. 2008 )isanEarth
system model maintained at the NASA Global Modeling and Assimilation Office
(GMAO) to support NASA missions and climate studies. Aerosols are carried
online and radiatively coupled to the GEOS-5 AGCM using a version of the
Goddard Chemistry Aerosol Radiation and Transport module (GOCART, Chin et al.
2002 ). GOCART treats the sources, sinks, transport and optical properties of dust,
sea salt, black and organic carbon and sulphate. For dust, GOCART employs a