Simulating performance of CHIMERE on a late autumnal dust storm over Northern China Supplementary Materials

1 Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China; masiqi15@mails.ucas.ac.cn (S.M.); gaochao@iga.ac.cn (C.G.); xiuaijun@neigae.ac.cn (A.X.); zhaohongmei@neigae.ac.cn (H.Z.); zhangshichun@neigae.ac.cn (S.Z.) 2 University of Chinese Academy of Sciences, Beijing 100049, China * Correspondence: zhangxuelei@neigae.ac.cn (X.Z.); tongquansong@neigae.ac.cn (Q.T.)

1 Dust emission equation in CHIMERE 1.1 The [Marticorena and Bergametti, 1995] (MB) scheme In this dust scheme, the vertically integrated saltation flux is estimated by using the equation from White [1]: where K is a constant which equals 1 and the air density (  ) is considered as 1.227 kg m -3 following the parameterizations of Marticorena and Bergametti [2]. * is friction velocity calculated using the roughness length, z0, and  *  is threshold friction velocity, depending on the soil particle diameter size Dp and z0.The flux is calculated only if  * >  *  .Then the corresponding vertical dust flux is estimated by using vertical-tohorizontal dust flux ratio (α) with a constant value of 2×10 -6 and is then projected into three modes (fine, coarse and big modes) using constant percentages (0.2, 0.6 and 0.2).

The [Alfaro and Gomes, 2001] (AG) scheme
The equation of horizontal dust flux in this AG scheme is the same with MB scheme.While α is computed based on the partitioning of the kinetic energy of individual saltating aggregates and the cohesion energy of the populations of dust particles.This algorithm assumes that dust emitted by sandblasting is characterized by three modes whose proportion depends on the wind friction velocity.Three dust modes, which are considered as independent of the soil types, described the three modes using log-normal distributions with diameters d1=1.5 μm, d2=6.7 μm and d3=14.2μm, and their associated standard deviation, respectively σ1=1.7, σ3=1.6 and σ3=1.5.In order to apportion the available kinetic energy between the three modes, a constant cohesion energy ei is associated to each mode values.The numerical values of ei were determined by adjusting the predicted aerosols size distribution to those measured in wind tunnel under different wind conditions, using an iterative least square routine.The recommended values are used: e1 =3.61, e2 =3.52 and e3 =3.46 g cm 2 s -2 .The kinetic energy is expressed as a function of the soil particle diameter after Alfaro et al. [3] and Shao and Lu [4]: It is compared to the cohesion energy of the three aerosol modes in order to compute the proportion pi(Dp) of these three modes to the total dust size distribution (Table S1).In addition, according to the description of Alfaro et al. [3], Equation S2 is only used when u*<0.27 m s -1 , the equation for 0.27 m s -1 < u*<0.55 m s -1 is showed as where Uh,t=0.54m s -1 .TableS1 Fraction (pi) of the kinetic energy (ec) of individual saltating aggregates used to release particles from each of the three possible aerosol modes of binding energies ei Vertical-to-horizontal dust flux ratio (α) in this scheme can be written as: ), (S7) with the constant dimensionless coefficients Ce=2.0 and Cd0=4.4×10 - .
1.4 friction velocity u* and threshold friction velocity u*t The friction velocity, u*, is estimated under neutral conditions, as follows: with U the 10 m mean wind speed, k=0.41, the Karman constant, z the height above ground level where the wind speed is estimated by the meteorological model, in CHIMERE, z=10 m, and z0 is the roughness length.
The threshold friction velocity, u*t, in CHIMERE can be calculated using the two schemes: [Iversen and White, 1982 where the constant parameters an=0.0123 and γ= 300 kg m -2 .The particle density ρp=2.65×10 3 kg m -3 is chosen to be representative of quartz grain clay minerals.
2 Vertical distribution of KOK scheme 3 Vertical-to-horizontal dust flux ratio (α) [Kok 2014] (KOK) scheme The vertical dust flux in KOK was acquired directly without converting from horizontal flux to vertical flux [5]   =         ( * 2 fbare is the fraction of the surface that consists of bare soil, fclay is the soil clay fraction and ρa is air density.u*st is this friction velocity but for a standard atmospheric densityρa0=1.225kg m -3 : represents u*st for an optimally erodible soil and was chosen as u*st0=0.16m s -1 .The dimensionless coefficient Cαis chosen as 2.7.The dust emission coefficient Cd represents the soil erodibility as:   =  0 × exp (−   *  − * 0  * 0

Figure S1 .
Figure S1.Vertical distributions of aerosol extinction coefficient from the CALIPSO and CHIMERE simulated PM10 concentrations at 18:00 UTC on Nov. 25 (left panel) and at 5:00 UTC on Nov. 26 (right panel).
used in the second time step whereas the latter is used at the start of the calculation.ust is the threshold friction velocity over smooth surfaces, Dp is the diameter of the soil particle,  is the kinematic viscosity of air, ρp is the particle density, ρair is the air density and g is the gravitational acceleration.[Shao and Lu, 2000] (SL) scheme. *  (  ) = √  (