# Configuration File - Basic Settings

## What is in the file?

Every .CF file begins with a fixed structure, which is essential for EACH simulation: This is how the first part might look like (the line numbers are for this documentation only!):

00: %---------------------------------------------ENVI-met Configuration File V3.1
00: %-----------------------------------------------------------------------------
00: %MAIN-DATA
01: Name for Simulation (Text):                  =Simple Example
02: Input file Model Area                        =C:\mysim\input\street.in
03: Filebase name for Output (Text):             =StreetA
04: Output Directory:                            =C:mysim\results\StreetA
05: Start Simulation at Day (DD.MM.YYYY):        =23.16.1998
06: Start Simulation at Time (HH:MM:SS):         =06:00:00
07: Total Simulation Time in Hours:              =24.00
08: Save Model State each ? min                  =60
09: Wind Speed in 10 m ab. Ground [m/s]          =3
10: Roughness Length z0 for Reference Point      =0.1
11: Wind Direction (0:N..90:E..180:S..270:W..)   =225
12: Initial Temperature Atmosphere [K]           =293
13: Specific Humidity in 2500 m [g Water/kg air] =7
14: Relative Humidity in 2m [%]                  =50
15: Database Plants                              =Plants.dat

Basically, this is all you need to define your own simulation task.

### Some important things to look after when working with this file

• Do not change the sequence of the entries inside a section. ENVI-met does not check what stands in front of the line. It always needs, for example, the output directory to stand in line 04. (See next point)
• You can place remark lines anywhere you need them. Lines beginning with „%“ are ignored and ENVI-met continues reading the next line. So, if we refer to line 04, this is meant without counting additional remark lines.
• The values/ information in each line begin with “=”.Text can be quoted, but this not necessary. Don't use ”=“ inside the explanation text!

## What do the lines mean?

#### 00: Remark lines

Because of the „%” at the beginning. Can be deleted.

#### 01: Name of Simulation

Give your simulation task a name. This name is stored in the data files and shown while running the model.

#### 02: Input File Model Area

Select the name of the file and define your Input Area. Full file names must be given here!
If you want to exchange data with other users or want to keep the directory structure flexible, we recommend to use an alias instead of absolute filenames (see XXXXX).

ENVI-met provides the following system aliases:

"[HOME]"   = the folder where the program is installed.
"[INPUT]"  = [HOME]\INPUT
"[OUTPUT]" = [HOME]\OUTPUT

All other aliases must be defined in MYALIAS.DAT

For example, if ENVI-met is installed to “C:\envimet” the filename “[INPUT]\myfiles\test.in” will be translated to “C:\envimet\input\myfiles\test.in”.
ENVI-met 3.1 supports long filenames and spaces in filenames.

#### 03: Filename Base for Output

This name will be used to construct the name of the output files.
Restrictions: Only use valid file names for your operation system!

For WINDOWS for example „Trees+Houses“ is NOT a valid name. ENVI-met tries to build output files containing „..Trees+Houses..” which will be refused by the operation system because of the “+” !
Also do not use anything that could be interpreted as directory information („:,\”…)

#### 04: Output Directory

Location to where ENVI-met writes the output data.
A row of sub folders will be created, to give the data a better structure (See Output Folders).
You can use absolute file names as well as alias-filenames.

#### 05,06: Start Simulation at Date/Time

This is at what (model-)time the calculation starts. Use the format DD.MM.YYYY, HH:MM:SS!

Remember: A numerical model needs initialisation time! Do not try to start your simulation at high noon, the model will not be able to „guess” the right start conditions. Best time to start is in the night or at sunrise, so that the calculation can follow the atmospheric processes.

#### 07: Total simulation time in hours

Time to calculate. Should be at least 6 hours, depending on your problem, probably more. If you use less calculation time, you will get data still influenced by the initialisation !

#### 08: Save Model State each ? Min

Time interval to write the model state to disk. In addition, a final set of data is written after the simulation has finished. This refers to the Main Data Files. For RECEPTORS, a different output interval can be chosen.

#### 09: Wind Speed in 10m above Ground

This is the first of a number of meteorological input data for your simulation task. This defines the wind speed in 10m above ground. Not further used after initialisation.

#### 10: Roughness Length z0 at Reference Point

Complementary to the Wind Speed. Defines the surface roughness at the location, where the wind speed in 10m (08) was measured. Both values are used to calculate the geostrophic wind. Not further used after initialisation.

#### 11: Wind Direction

Given in degrees where 0 is North (or from the upper side in the bird-view of the area), 90 is East (or left) and so on.

Remember: If you have a rotated domain, the inflow of the wind will change as the degrees refer to the earths co-ordinate system.

#### 12: Initial Temperature Atmosphere

Sets the start value for all layers in the atmosphere and the constant reference temperature in 2500 m height.
Temperature values are always given in potential temperature!
ENVI-met starts with a zero-gradient and lets the thermal stratification develop during the initialisation based on the initial surface temperature.

#### 13: Specific Humidity in 2500m

Value for the top of the model. Basically defined by the advected mesoscale air mass and (like the temperature and the geostrophic wind) kept constant during the simulation.

#### 14: Relative Humidity in 2m

Value given in %. Used together with the spec. Humidity in 2500m to calculate the vertical humidity gradient. Not further used after initialisation.

#### 15: Database Plants

This line is no longer interpreted, bust must be kept. The global plants.dat file MUST be in \sys.basedata!

With these information, it is possible to run a simulation task, but still a lot of options are unused. These are presented in the following sections: