THE HYSPLIT4 IER CHEMISTRY MODULE
Last Revised: 29 August 2003


ABSTRACT

	The ozone prediction method,  a semi-empirical approach 
called the Integrated Empirical Rate (IER) model developed by 
Johnson (1984, 1989), is incorporated as the ozone calculation scheme.
The IER model, based on outdoor smog chamber studies for conditions 
typical of Australian cities, is usually applied in conjunction with 
monitoring data, to evaluate the age of photochemical smog and to 
determine whether the air parcel is in the NOx -limited or light-
limited regimes. In the light-limited regime, the smog produced is 
only a function of the accumulated incident light and the hydrocarbon 
concentration. In the NOx-limited regime, the concentration of smog 
produced is assumed to be independent of the amount of incident light
and the smog concentration can only increase by increasing the amount 
of NO available.  An updated version of the IER model by Azzi (1992) 
is used here which includes the loss of NOx to stable nitrate. The
model is based upon the photo-stationary steady-state equation and its 
implementation within Hysplit is uncomplicated because the IER's 
integration of the smog produced is linear and contributions from each
source can be added. More detailed information on the incorporation 
of IER into Hysplit is available elsewhere (Draxler, 2000).

Azzi, M.; Johnson, G.M. Notes on the derivation, The Integrated 
Empirical Rate Model, Version 2.2, 20 March 1992, CSIRO Division 
of Coal and Energy Technology, PO Box 136, North Ryde, NSW 2113, 
Australia.

Draxler, R.R. Meteorological factors of ozone predictability at
Houston, Texas, J. Air & Waste Manage. Assoc. 50:259-271, 2000

Johnson, G.M. A simple model for predicting the ozone concentration
of ambient air, In Proc. 8th Int. Clean Air Conf., 2, 715-731, 
Eds. H.F. Hartmann, J.N. O’Heare, J. Chiodo, and R. Gillis, 
Clean Air Soc. of Australia and New Zealand,  Melbourne, Australia, 
7-11 May 1984.

Johnson, G.M.;  Quigley, S.M.  A universal monitor for photochemical
smog, Proceedings of the 82nd Annual Meeting of the Air and Waste 
Management Assoc., June 25-30, 1989, Anaheim, CA, Paper 89-29.8



PC VERSION

	The model is run by executing the batch file "run_model",
which runs the executable (hysp_ier.exe) in the \Exec directory.
When the simulation completes, the output file "cavrg" will have been
created containing the hourly average concentration fields for all
species.  Executing "run_plot" will create an extract file (xdump)
with just the hourly ozone concentrations and then a Postscript file
"concplot.ps" with maps of hourly concentrations. The output files 
are compatible with all standard Hysplit plotting programs. A Post-
script file viewer or printer is required. The model is pre-configured
to create output for a three-day test period, June 24-27, 2003, over
the Northeast states, using EDAS archive meteorology.  All required 
files are provided in the \Fixed directory. The configuration (CFG) 
and CONTROL files have been pre-set to run this example case. Other 
simulations can be run if the appropriate meteorological data have 
been downloaded and the control and configuration files modified 
accordingly.  A familiarity with the regular PC version of Hysplit is 
strongly suggested prior to trying run this version of the model.  
More detail is provided below about the format of some of the input 
configuration files as well as the emissions inventory.  The use of 
different inventories may require reformatting. 


CONTROL file

	The CONTROL file cannot be edited through the standard HYSPLIT
GUI. Manual editing is required. Point source emissions are not 
supported. A gridded emission inventory is required. The emission 
inputs in the CONTROL file have slightly different meanings when using
a gridded inventory.  The emission duration is the same, but the 
emission rate is a multiplier to the gridded emission value.  Normally
it would be set to 1.0. Gridded emissions can produce many particles 
each time step. To minimize the number of particles, one can set the 
emission duration in the control file to a very small value (0.1 hrs)
and set the emission rate multiplyer in the control to 10, thus the 
total emissions are conserved.

	The top of the snapshot concentration grid should match the top 
of the model domain to avoid the transport of particles that are not 
chemically transformed. All concentration grids should cover the same 
spatial domain. Grid #1 should always be defined as the snapshot grid.
The reactions are determined by the species concentrations on the 
snapshot grid.

	The emission domain is determined by the source lat/lon limits 
set in the CONTROL file.  Note that the source domain must lie entirely
within the meteorological grid limits, otherwise the results may be 
unpredictable. The release height represents the height from the 
ground through which pollutants will be initially distributed. 

Eight species must be defined for IER chemistry.  Only two are defined
in the gridded emissions file.    

8
SP
0.0 
0.0
00 00 00 00 00
NOx
10.0         
0.1 
00 00 00 00 00
VOC
10.0         
0.1   
00 00 00 00 00 
ISOP
10.0         
0.1   
00 00 00 00 00 
NO# 
10.0         
0.1   
00 00 00 00 00 
O3
0.0 
0.0
00 00 00 00 00
NO2
0.0 
0.0
00 00 00 00 00
NO
0.0 
0.0

The model requires a gridded emissions inventory for NMHC 
and NOx, in units of kg/hour.  Model output units will be ppm. 
The following abbreviations are used to identify species:

#  ID	Mol WT	

1: SP	48	- smog produced at time T (Lagrangian integration)
2: NOx	46	- initial NOx (from inventory) 
3: VOC 	13.7	- initial hydrocarbon (from inventory)               
4: ISOP	13.6	- initial isoprene (computed)
5: NO#	30	- initial NO (from inventory [90% of NOx]) 
6: O3	48	- ozone at time T (steady-state solution)
7: NO2	46	- NO2 at time T (steady-state solution)
8: NO	30	- NO at time T (steady-state solution)

Note the negative molecular weight is used in the CONTROL file to flag
a units conversion from mass/volume to volume/volume.


SETUP.CFG NAMELIST FILE

	The standard setup.cfg results in the release of one 
particle at each grid point per time step.  If more particles are
to be released (at substantial computational cost) then the NUMPAR
parameter should to increased to the appropriate multiple of the
initial number of non-zero emission grid points as noted in the 
MESSAGE file. As noted above in the discussion of the control 
file, the model is configured to release all particles in one
time step, each hour (hence qcycle=1.0).  About 350000 particles
will be created over the 3 day test simulation.  Longer duration
simulations will result in particles moving off the domain.

INITD=0 		run in 3D particle mode 
KHMAX=9999 		don't drop any old particles
NUMPAR=500 		one particle per point if < number grid pts
MAXPAR=350000           max number of particles in simulation
MAXDIM=8  		number of species on one particle
QCYCLE=1.0 		new emission cycle each hour
DELT=0.0 		automatic time step computation
ICHEM=4			forces conc grid = meteo grid



EMISSIONS INVENTORY

	The file "emission.txt" contains all the information
that is required to interpred the data in the gridded emission
inventory file. The file's first record contains information 
about the internal grid cell size that is used by the dispersion
model to accumulate the file's emissions. The emission file 
defines the emissions at latititude-longitude points, the values 
at these points are accumulated in an internal grid, the size of 
which is defined on the first record.  This value can be 
arbitrarily changed according to the desired resolution of the 
simulation.  The pollutant puffs are released with an initial 
size comparable to the accumulation cell size.  Because the 
emission file data are remapped to an internal grid, the file 
can consist of emissions data on a regular grid or just a 
collection of individual cells.  The emission rate in the Control
file is used as an additional multiplication factor for the data 
in the emission file.  Also note that previously discussed
particle number restrictions still apply.  The initial number of 
particles are spread out over the duration of the emission and the 
number of grid cells that are defined in the emission domain. 
The format of the emission.txt file is given below:

Record #1
        I4      - Number (n) of pollutant species in file
        I4      - Number of emissions defined for each 24 hour period
        F10.4   - Conversion factor: file units to model units/hour
        2F10.4  - Accumulation cell size (latitude & longitude)

Record #2
        nA4     - Pollutant character identification each pollutant

Record #3
        A       - the /directory/filename of the emission data file


The 1985 NAPAP emissions inventory file was provided by Stu McKeen
(stu@al.noaa.gov) from NOAA's Aeronomy Laboratory. The file 
NOx_VOC_SO2 contains NOx, Volatile Organic Carbon, and SO2 
emissions. The file is an ASCII formatted file od hourly emissions 
for 24472 1/6 deg latitude by 1/4 degree longitude grids between
 24.5 and 59.5 degrees north and 52-135 degrees west longitude.

The records were written with the following FORTRAN write statements:
	
	WRITE(10,'(2I4,2F10.4)')II,JJ,XLON,XLAT
	WRITE(10,'(1P,12E10.3)')(NOX(IH),IH=1,24)
	WRITE(10,'(1P,12E10.3)')(VOC(IH),IH=1,24)
        WRITE(10,'(1P,12E10.3)')(SO2(IH),IH=1,24)

II and JJ are indexes used in the programming. XLON (negative is 
west longitude), and XLAT are the longitude and latitude of the 
south-west corner of each grid square. The emissions in British 
tons per hour per grid cell. The indexing of NOX, VOC, and SO2
are:

	 1 = 0000-0100 (GMT) average
 	 2 = 0100-0200 (GMT) average
	....
	24 = 2300-2400 (GMT) average.

Only grids for which nonzero emissions of either NOX, VOC, or SO2
are within the NAPAP inventory are in the file.  All point, mobile
and nonmobile emissions are included, with no distinction in height 
of emissions from point sources.  The NAPAP85 summertime-weekday 
scenario is used. VOC emissions represent all nonmethane hydrocarbons.
That is, CO and CH4 are not included in the emissions.  VOC emissions
are for 80 degrees F.


IERCHEM.CFG NAMELIST FILE 

	The chemistry routine constants can be controlled from 
by changing parameters in the namelist file IERCHEM.CFG (case 
sensitive).  The default values are summarized below.

Plume background values for O3 (ppm):		BO3=0.000  
Composite ambient background for O3 (ppm):	AO3=0.040
Proportion of SP converted to stable nitrate:	PSTB=0.125
Weighted hydrocarbon reactivity (ppm/ppm-c):	RVOC= 0.0067 
Mixture isoprene reactivity (ppm/ppm-c):	RISO= 0.0117
Smog chamber empirical constant: 		GAMMA= 4.71
Coefficient for NOx limited regime:		BETA= 4.09



COMPILATION (for reference only ... source code not available)

	The Hysplit IER program is a conditional compilation 
variation of the standard model.  The main concentration program, 
source code, hymodelc.F, is compiled with the parameter -DIER to 
create the executable hysp_ier.

The following subroutines are required in addition to the standard
Hysplit library routines:

ierno2.f - returns NO2 photoloysis rate coefficient from the downward
           shortwave flux and solar angle 

iersum.f - integrates light dependent terms for smog produced
           on each particle or puff in the Lagrangian framework 

iercon.f - solves quadratic for NO,O3,NO2 based on integrated smog
           and updates the concentration summation array for the
           dependent species, others are set to zero

iervoc.f - computes the isoprene emissions at each grid point based
	   upon the shortwave flux and temperature

ierset.f - reads the 03chem.cfg namelist file to set chemistry 
	   conversion parameters used in ierno2, iersum, iercon

emsgrd.f - in the standard Hysplit library, uncomment the mass to
           volume conversion for ppm output. Conversion  is initiated
           by the specification of molecular weight in the control 
           file

