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khaled_haider

The time step must be an integer divisible into 60

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Hello,

I was trying to run a long-term simulation (for a period of 10 years) in GSSHA. The Precipitation file and the hydrometrological (HMET) file are relatively large. Because I do not want to wait a lot of time and because my meteorological data are hourly, I have chosen the Time step to be 300 seconds. However, the GSSHA Model Checker gave me an Error Message: The time step must be an integer divisible into 60.

According to the GSSHA- User’s Manual (Version 1.43 for WMS 6.1), It is possible to choose Time steps which are multiple of 60 sec.

Here is a Citation from 2.2 Time Steps and Process Updates:

In GSSHA the user specifies the overall model time step, in seconds, that the model uses to loop through he processes, check update times, and update processes. To avoid missing updates of processes, such as rainfall, that may be specified at 1 minute interals, the overall model time step should be integer divisible into 60 seconds or an integer multiple of 60 s (i.e. 5, 10, 15, 20, 30, 60, 120, 180, 300). The model time step also must not be greater than the finest resolution of inputs, such as rainfall (which in my case is hourly). Typical time steps for GSSHA range from 10 to 300 seconds.  Smaller time steps may be required for particularly difficult problems.

 

Thanks.

 

 

 

 

 

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Hi,

Your comment sounds correct.  If you are able to run GSSHA without errors, you can probably ignore the model checker output.

Chris

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Thanks Chris,

I did not notice any significant change in my results when using a Time step = 300 seconds, except for a significant shortcut in the time necessary to complete the simulation. This encouraged me to try even greater values of time steps (for example 600 seconds) to see how this increase can affect the results. Nevertheless, one must be very careful when implementing this increase and must monitor all types of outputs and not focus on a specific output.

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