## How to set the river_time

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liangliang
Posts: 61
Joined: Mon Jul 20, 2009 2:41 pm
Location: Port And Costal Engineering Laboratory

### How to set the river_time

Hello:
everyone!
I am a newer to roms.I want to simulata an estuary,so i need to create a forcing file of river.There is a variable of river_time.In the case of latte_C,i found that the river_time is from -370 to 260.I want to know how to set the river_time.Why can the river_time be negative? And what is the relation between Dstart(in the ocean.in) and river_time?
Thanks!

kate
Posts: 3804
Joined: Wed Jul 02, 2003 5:29 pm
Location: CFOS/UAF, USA

### Re: How to set the river_time

Pick a time origin and be consistent. I'm in a group which discussed this no end, but we finally decided on a time origin of January 1, 1900, before any of our runs begin. This is what goes in TIME_REF. Then DSTART is in days, relative to the TIME_REF. I currently have DSTART=25202, early in 1969. If I were to start a run before 1900, then I could have negative times. As for river_time, make sure your earliest time is before or the same as DSTART and your latest time is equal to or after the end of the run.

liangliang
Posts: 61
Joined: Mon Jul 20, 2009 2:41 pm
Location: Port And Costal Engineering Laboratory

### Re: How to set the river_time

kate wrote:Pick a time origin and be consistent. I'm in a group which discussed this no end, but we finally decided on a time origin of January 1, 1900, before any of our runs begin. This is what goes in TIME_REF. Then DSTART is in days, relative to the TIME_REF. I currently have DSTART=25202, early in 1969. If I were to start a run before 1900, then I could have negative times. As for river_time, make sure your earliest time is before or the same as DSTART and your latest time is equal to or after the end of the run.
kate:
I think i have understanded your meaning.But I have another question . For example ,i pick a time origin of January 1,2006 as my TIME_REF,and my DSTART is 94 (April 5,2006), if the earliest time of river is same as the TIME_REF (January 1,2006),then the first value of river_time is 0,or -94?
In other words,TIME_REF and DSTART,which is the reference time of river_time ?
Thanks!

kate
Posts: 3804
Joined: Wed Jul 02, 2003 5:29 pm
Location: CFOS/UAF, USA

### Re: How to set the river_time

TIME_REF is the time origin for the river_time. DSTART is (I think) only used to compute how many timesteps to take from the current initial time. ROMS will attempt to run until DSTART+DT*NTIMES.

rduran
Posts: 139
Joined: Fri Jan 08, 2010 7:22 pm
Location: Theiss Research

### Re: How to set the river_time

Does this mean that my forcing netcdf files need to be modified if I want to start running my model latter in the year?

In other words:

I have been running a model starting Jan 1st 2005, now I want it to start Apr 1st 2005, does setting DSTART = 90 (instead of 0), without changing the forcing file do the trick?

Rodrigo.

kate
Posts: 3804
Joined: Wed Jul 02, 2003 5:29 pm
Location: CFOS/UAF, USA

### Re: How to set the river_time

rduran wrote:I have been running a model starting Jan 1st 2005, now I want it to start Apr 1st 2005, does setting DSTART = 90 (instead of 0), without changing the forcing file do the trick?
Yes