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Inputs and initial conditions
The model initial condition and control information are contained in a file called Init_cons.dat. It looks like a spreadsheet with columns representing different aspects of the initial conditions (time, pressure, latitude, concentrations) and the rows representing different independent simulations of the model.
If the first line of the file contains a *positive integer* this tells the model to run forwards into for that number of seconds. The output of each independent simulation is written to the files Spec_*.dat and Rate_*.,dat where the * represents an integer value representing the simulation number.
If the first line contains -1 the model is run forwards until a
diurnal steady state has been reached with output for the final timestep of all
the independent simulations being output into the files Spec_1.dat and
Spec_2.dat
If the first line contains -2 the model is run forwards until a
diurnal steady state has been reached with output for the final 24 hours for
each independent simulations being written to the files Spec_*.dat and
Rate_*.dat.
The second row in the file should contain the parameters to be input into the model. Each parameter name is 15 characters long, separated by an space (it is read in by the FORTRAN format statement ‘100000(a15,x))’. The following parameters can be set (case sensitive).
| Key | Value |
|---|---|
| PRESS | Pressure hPa |
| H2O | H2O (v/v) |
| LAT | Latitude (decimal degrees) |
| LON | Longitude (decimal degrees) |
| TEMP | Temperature (K) |
| JDAY | Julian day fractional |
| O3COL | Ozone column (Dobsons) |
| ALBEDO | The surface albedo (fraction) |
| SAREA | Surface area of aerosols (m^2/m^3) |
| RP1 | Radius of particles (m) |
| SPECIES NAME | Mixing ratio of species (v/v) |
If a parameter is set which is not in the above list or is a species name as defined by the chemistry of the model the will stop (unless it starts with an X, XOH will not cause the model to crash).
The third line gives information about which values should be constrained and which ones allowed to run freely in the model simulations. Each parameter is 15 characters long, separated by an space (it is read in by the FORTRAN format statement ‘100000(a15,x))’. contain either a "1" or a "0", indicating whether the parameter is to be constrained in the model, with a ‘1’ indicating constraint on the parameter and a ‘0’ indicating no constraint. Subsequent rows contain the input data to the model, with concentrations in mixing ratio.
Where total NOx is to be constrained it is necessary to constrain either NO or NO2, but not both. While the parameter ‘NOx’ must be included in the Init_cons.dat file for total NOx to be constrained, its values in the file can be set to zero.
In order to constrain NOx the model will calculate a number every 24 hours by which the NO (or NO2 if NO2 is constrained in preference to NO) must be multiplied so that its modelled value remains in agreement with its observed value input into the model. All NOx species will subsequently be multiplied by this value, and hence constrained by proxy to NO (or NO2).
If neither J (O(1D)) nor J (NO2) are included in the input file, clear-sky values will be calculated at the altitude in question (determined from the pressure input) using TUV cross-sections at solar zenith angles varying between 0 and 90 degrees in 5 degree steps. The solar zenith angle (SZA) at which the observations were made is then calculated from the observed latitude, longitude and time of day, and a spline fit to the calculated J-values as a function of SZA used to determine the appropriate J-value.
If J (O(1D)) or J (NO2) are present in the input file the model will compare calculated J-values to their observed values and scale all calculated values accordingly.
Unless otherwise stated in the input file the model assigns [CH4] = 1770 ppm, [H2] = 550 ppm, and an ozone column of 260 Dobsons.
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