The climate input provides the meteorological drivers of a simulation (temperature, precipitation, radiation, humidity, wind and air pressure). Climate data are typically given as daily or sub-daily (e.g., hourly) time series. Items that are not provided are synthesized from the other items and the site attributes given in the attributes section (climate synthesizer, crabmeat).

Attributes

Site attributes are given in the attributes section. Besides the location, they describe the mean climate and are used to synthesize missing items.

Name	Description	Unit	Default
elevation	elevation above sea level	m	100.0
latitude	latitude	degree	45.0
longitude	longitude	degree	10.0
cloudiness	annual mean cloudiness	- (0-1)	0.55
rainfallintensity	rainfall intensity used to distribute precipitation over sub-daily time steps	mm h-1	5.0
windspeed	annual mean wind speed	m s-1	1.5
temperature	annual mean temperature	oC	8.0
temperatureamplitude	annual temperature amplitude	oC	20.0
precipitationsum	annual precipitation sum	mm yr-1	800.0

Time series items and units

Time series items are given as columns in the data section. Column names are case sensitive and must match the names below exactly. Columns with unknown names are ignored silently.

Name	Description	Unit	Aggregation
tavg	mean air temperature	oC	mean
tmax	maximum air temperature	oC	maximum
tmin	minimum air temperature	oC	minimum
prec	precipitation (rain and snow) per record	mm	sum
grad	incoming global (direct and diffuse shortwave) radiation	W m-2	mean of non-zero values
lrad	incoming longwave radiation	W m-2	mean of non-zero values
rh	relative humidity	%	mean
vpd	vapour pressure deficit	kPa	mean
wind	wind speed	m s-1	mean
press	air pressure	mbar	mean

Precipitation is the amount per data record, i.e., mm per day for daily records and mm per hour for hourly records. All other items are mean (or extreme) values of the period covered by a data record.

The units are defined in RECORD_ITEM_UNITS (crabmeat: scientific/climate/climatetypes.cpp).

Data resolution vs. simulation time step

If the data are given at a finer resolution than the simulation time step, records are aggregated using the method given in the column "Aggregation" above.
If the data are given at a coarser resolution than the simulation time step (e.g., daily data and hourly time steps), sub-daily values are synthesized from the daily records (e.g., diurnal courses of temperature and radiation, precipitation distributed with the rainfallintensity).
Missing items are synthesized, e.g., global radiation from extraterrestrial radiation and the daily temperature range, relative humidity from vapour pressure deficit (or assuming saturation at minimum temperature), mean temperature from the annual mean temperature and amplitude.

Time axis

The time stamp of the first record and the record resolution are given by time in the global section, written as YYYY-MM-DD/r with r records per day:

time = "2000-01-01/1" : one record per day (daily data)
time = "2000-01-01/24": 24 records per day (hourly data)

The resolution must be given explicitly. Otherwise, missing parts of time would be taken from the simulation schedule and the records would be misinterpreted (e.g., with schedule "2003-01-01/24", daily records would be read as hourly records). Therefore, the simulation terminates with the error "climate input: time resolution not given" if /r is missing, and with the error "climate input: time not given" if time is missing completely.

A date column (date or datetime) is optional. If given, it is used to check the dates of the records.

If the data end before the end of the simulation, the warning "climate input data ends before end of simulation, values after last data record are synthesized" is logged and missing values are synthesized from the attributes. To repeat the given data instead, set endless in the project file:

<attributes use="0">
    <climate endless="yes" />
</attributes>

Example

Daily climate data:

%global
    time = "2000-01-01/1"
 
%climate
    id = 0
 
%attributes
    elevation = "161.5"
    latitude = "48.9"
    longitude = "1.95"
 
%data
tmax    tmin    tavg    prec    grad    wind
5.81    -0.31   2.75    0.12    19.11   8.21
5.20    0.36    2.78    0.23    32.20   9.79

The following climate attributes can be defined:

air pressure (press) [mbar]
incoming global radiation including direct and diffuse shortwave radiation (grad) [W:m-2]
incoming longwave radiation (lrad) [W:m-2]
precipitation including rain and snow (prec) [mm]
average temperature (tavg) [oC]
maximum temperature (tmax) [oC]
minimum temperature (tmin) [oC]
relative humidity (rh) [%]
vaour pressure deficit (vpd) [kPa]
wind speed (wind) [ms-1]

Climate synthesizer Climate synthesizer