Observations
CRHM requires as input the climate or meteorological data (which the model refers to as observations) for the watershed being modeled. A program module (e.g. obs) reads the climate or meteorological data from the data file into the model. The model is capable of making use of data from one or more stations. If more than one source of climate or meteorological data is available for an area (watershed) the model is capable of using a specified station set of observations (t, rh, u, p, ppt, Qsi) for each HRU.
The usual modeling time step is a half hour or one hour. Daily data starts at 00:15, 00:30 or 01:00 and finishes at 24:00 or 00:00 of the next day. Gaps in the data must be filled with synthesized data.
Observation data is read from ASCII, space or tab delimited files. An example file is shown in Example 1. Other data formats can be converted by the user using Excel and/or a text editor. Data sets do not have to be merged into one file as the model will access data from multiple observation files. The file extension must be .obs.
Example 1.
Observation data for Bad Lake, Saskatchewan January 01 1973 to December 31 1973
t 1 (°C) 2 meter
rh 1 (%)
u 1 (m/s) 10 meter
SunAct 1 (h) sunshine hours
ppt 1 (mm/d) precipitation mm
form_data 1 ()
Qsi 1 (W/m^2)
Qso 1 (W/m^2)
Qn 1 (W/m^2)
############################################
1973 1 1 0 0 0 -15.10 82.00 5.30 0.00 0.00 0.00 0.00 0.00 -0.11
1973 1 1 1 0 0 -15.50 81.50 3.10 0.00 0.00 0.00 0.00 0.00 -0.09
1973 1 1 2 0 0 -15.60 81.30 1.40 0.00 0.00 0.00 0.00 0.00 -0.09
1973 1 1 3 0 0 -15.50 81.30 3.10 0.00 0.00 0.00 0.00 0.00 -0.08
1973 1 1 4 0 0 -15.30 81.30 1.40 0.00 0.00 0.00 4.50 0.24 0.00 0.00 -0.07
Line 1 is a file description, usually defining where the data is from and any other pertinent information. Starting with line 2, the observations are listed in separate lines. Each entry consists of a variable name, followed by the dimension of the observation. If the observation is an array or profile the number will be greater than one. Next the units of the observation is given enclosed in parentheses, Other information about the observation, such as instrument height, can also be entered as a comment at the end of the line. This comment and will appear in the CRHM observation help box. If the units are not enclosed in parentheses they become part of the comment.
The line containing the string of pound signs #### (minimum of 4 required) defines the end of the header and the beginning of the the data observations. The data is space or tab delimited and starts with year, month, day, hour, minute and then the observations data is listed in the same order as specified in the header. The field delimiter is one or more spaces or a tab.
An alternative to "year, month, day, hour, minute" is decimal time and date used by Microsoft in Excel and other applications. It is much easier to generate observation files using this format. For example, "1998 5 1 10" would be replaced by "35936.875". The two time formats cannot be mixed within an observation file.
It is very important to have no "hanging" tabs at the end of lines or extra record terminators or tabs at the end of observation files.
Notes.
CRHM checks the units of the observation with what is required by the model module and if different reports it to the "log" screen.