Scavenging

Treatment of large scale scavenging in LMDZ.

Various schemes may be used depending on the value of the flag iflag_lscav:

  iflag_lscav=0 ==> no large scale scavenging
  iflag_lscav=1 ==> Genthon (1992) scheme
  iflag_lscav=2 ==> Genthon (1992) scheme modified by Ph. Heinrich
  iflag_lscav=3 ==> Reddy-Boucher (2004) scheme
  iflag_lscav=4 ==> Reddy-Boucher (2004) scheme modified by R. Pilon

The basic equations of the last scheme are in the appendix of: Pilon et al (2014) Representation of transport and scavenging of trace particles in the Emanuel moist convection scheme. Q. J. Roy. Meteorol. Soc., 141, 1244-1258.

In the last two schemes, aerosols are scavenged in-cloud by condensation, scavenged below-cloud by impaction, transported by precipitation, and released by evaporation. The flux of aerosols at the surface due to large scale precipitation (the wet deposition rate due to LS precipitation) is presently calculated as the integral of the tendency of aerosol concentration due to LS condensation processes. Of course this procedure ensures that there is conservation of aerosols in the large scale condensation scheme. However, the concentration of aerosols in the precipitation is actually computed (variable qPrls in phytrac) and could also be used to compute the large scale wet deposit. This is not what is done in the present version of LMDZ.