$Header$ -*-text-*-

The Aerosol Model DEAD---Dust Entrainment And Deposition

DEAD is an aerosol model suitable for running in standalone
mode and for embedding in large scale atmospheric models. 
Currently DEAD only simulates dust, but its framework is more general
and eventually other aerosols will be added. 
This code sometimes refers to itself as "the aerosol model".
This directory contains Fortran routines to simulate aerosol
physics and chemistry offline and in GCM and CTM models.  

The "box model" (BXM) refers to the stand-alone version of the aerosol 
model. This box model is driven from the top level routine dead.F90,
which supplies all the information normally supplied by the host
GCM or CTM. The box model may be run for arbitrary numbers of 
timesteps and environmental conditions.

The same code is used in large scale atmospheric host models as in the
box model, only the entry points are different. The box model
is a standalone program with entry point dead.F90, the embedded model
has multiple hooks which must be called by the global model.
Currently there are about 10 hooks. These are used to initialize
external datasets (dsttibds.F90, dsttvbds.F90), control budget
diagnostics (dstbdg.F90), initialize lower level modules
(dstcmnini.F90). The physics entry points control source processes
(dstmbl.F90), sink processes (dstdpsdry.F90, dstdpswet.F90), chemistry
(dstchm.F90), optical depth (dstodx.F90), particle size distributions
(dstpsd.F90), and radiative forcing (dstrad.F90).

The best way to understand the model physics is to read the main
physics loop (phyzlic.F90) which calls most of the physics entry
points directly. To embed DEAD in another host model, simply call
the same entry points in roughly the order (but make sure to
do the required initializations performed in dead.F90 first too!).
For example, to embed DEAD in the NCAR MATCH model, modify the files 
src/main.F and src/physlic.F to contain the same initializations
and physics hooks as dead.F90 and phyzlic.F90 in DEAD.
Of course to run DEAD in a global model, you must also have the source
code for that global model. DEAD has been successfully embedded in
(at least) NCAR CAM and MATCH, UCI CTM, and U. Oslo global models. 

Running the Box Model version of DEAD:

As explained in the dead.F90 file, environmental conditions in the box
model may be set from the command line. Most of the flags are
identical to my "mie" program used for microphysics development
(that some of you may also have). Although the box model supplies
useful defaults, it is instructive to run sensitivity studies, to,
e.g., midlayer windspeed. Such a study might be performed by calling
the box model as follows, and varying the final parameter:

dead --dbg=5 --time_nbr=1 \
--prs_mdp=1000.0e+02 \
--prs_ntf=1013.15e+02 \
--q_H2O_vpr=0.001894183 \
--tpt_gnd=267.0 \
--tpt_mdp=264.0 \
--oro=1.0 --sfc_typ=2 \
--wnd_mrd_mdp=1.0 --wnd_znl_mdp=10.0

ncks -C -H -F -u -v prs_mdp,tpt_mdp,wnd_frc_dps,q_H2O_vpr,mno_lng_dps,\
tpt_gnd,wnd_mdp,oro,sfc_typ dead.nc 

When the model is run, it will produce two output files, dead.nc and
dst_mss_bdg.nc. dead.nc records the time-varying state of the box model
in great detail (currently over 150 variables are automatically
recorded). dst_mss_bdg.nc records the time-varying mass budget of the
box model and is mainly intended for diagnosing the mass budget of
aerosols in host global models. Each timestep the global mean mass
budget is computed and recorded as a scalar. In addition, some
diagnostics such as the change in mass due to specific processes are
also recorded. Both of these files, dead.nc and dst_mss_bdg.nc, are
purely diagnostic.