Climate data

Met Station Based Climate Data

Climate data in this form is based on having a single file for each meteorological station available. Each base station is represented by it's own base station file, and separate files for each climate variable as listed in the base station file. At the very least, daily time series of tmin, tmax, and rain are required.

Climate inputs are linked to particular zones by the climate station ID affiliated with that zone. A single climate station (or base station) will typically serve multiple zones within the landscape. Each base station is described by a base station file.

Example Base Station File:

101 base_station_id
100.0 x_coordinate
100.0 y_coordinate
22.9 z_coordinate
2.0 effective_lai
22.9 screen_height
clim\rbw_prime_annual annual_climate_prefix
0 number_non_critical_annual_sequences
clim\rbw_prime_monthly monthly_climate_prefix
0 number_non_critical_monthly_sequences
clim\rbw daily_climate_prefix
2
ndep_NO3
ndep_NH4
0
clim\rbw_prime_hourly hourly_climate_prefix
0 number_non_critical_hourly_sequences

Climate Input Sequence Name / File Extension	Description	Units
rain	precipitation (rain + snow)* required	meters
tmin	minimum daily temperature* required	°C
tmax	maximum daily temperature* required	°C
tavg	average daily temperature	°C
dayl	day length	seconds
daytime_rain_duration	duration of rainfall	hours
LAI_scalar	zone and seasonal scaling of LAI - only applied to stratum of non-zero height	Unitless
Ldown	incoming longwave radiation	KJ / (meters2)/day
Kdown_direct	incoming direct shortwave radiation	KJ / (meters2)/day
Kdown_diffuse	incoming diffuse shortwave radiation	KJ / (meters2)/day
ndep_NO3	nitrogen deposition as NO3	kg / (meters2)/day
ndep_NH4	nitrogen deposition as NH4	kg / (meters2) /day
PAR_direct	incoming direct PAR radiation	KJ / (meters2)/day
PAR_diffuse	incoming diffuse PAR radiation	KJ / (meters2)/day
relative_humidity	Relative Humidity	Range (0-1)
tday	Mean Daytime Temperature	°C
tnightmax	Night time temperature at sundown (used for soil heat flux)	°C
tsoil	Soil temperature	°C
vpd	Vapour pressure deficit	Pa
wind	Wind speed	meters/ sec.
CO2	Carbon Dioxide	parts per million/year
lapse_rate_tmin	minimum daily temperature lapse rate with elevation	°C/m
lapse_rate_tmax	maximum daily temperature lapse rate with elevation	°C/m

All possible base station filenames must be listed in the worldfile header, as described in the discussion of grass2world below.

Format for Time Series Input Files

The first line of each input time series file must give the start date of the time series. The start date of the input must precede the start date listed in the worldfile. Following the start date, time series values are listed sequentially. For example: example_simulation_daily.rain will contain the following

1986 1 1 1
0.0028
0.000
0.0157
0.000
…

Gridded Climate Data

Climate data in gridded form is not tied to any particular met station, but is a grid of climate data over the watershed such as an interpolation between multiple climate stations, or downscaled data from a climate model. While it is possible to fake gridded climate data by representing each grid cell as a unique climate station, using gridded climate files is easier to work with.

Gridded climate data will have only a single base file, and a single file for each climate variable. The base file is identical to that of non-gridded climate data, except that the first line that set the base station id is replaced with a line specifying the total number of grid cells. So if you had a gridded climate dataset identical to the one specified above, but with 4 cells, your climate base file would be:

4 grid_cells
100.0 x_coordinate
100.0 y_coordinate
22.9 z_coordinate
2.0 effective_lai
22.9 screen_height
clim\rbw_prime_annual annual_climate_prefix
0 number_non_critical_annual_sequences
clim\rbw_prime_monthly monthly_climate_prefix
0 number_non_critical_monthly_sequences
clim\rbw daily_climate_prefix
2
ndep_NO3
ndep_NH4
0
clim\rbw_prime_hourly hourly_climate_prefix
0 number_non_critical_hourly_sequences

The climate variable files will look similar to those from the standard met station based climate input with three important differences. (1) The first line specifies the total number of grid cells at the top of the climate file. (2) The third line (after the start date, which is now your second line) specifies the grid cell index for each column of data. These numbers must match up with the values of the GIS map specified as the base_station_ID variable in your template file. (3) The fourth line is the elevation for the grid cell, which will also match the values of your zone elevations within your world file. The following is a climate file with four grid cells with index numbers 1-4, their elevations, and four climate data values specific to their cell:

Grid Cell Index Elevation Climate Data for Grid Cell Index(i) 1 100.1 24 24 21 19 2 200.2 26 25 23 21 3 300.3 27 25 22 19 4 400.4 23 21 22 18

4
1986 1 1 1
1 2 3 4
100.1 200.2 300.3 400.4
24 26 27 23
24 25 25 21
21 23 22 22
19 21 19 18
…

Running RHESSys with Gridded Climate Data

1. Edit your template file to refer to the climate base file.
2. When running RHESSys, use the command line option '-asciigrid' and RHESSs will properly deal with your gridded climate data.
3. There's no step 3.