Dear Saeed,

Thank you for your help.

For my second question,  Uwe Schulzweida from CDO working group provided me with a good method to solve this problem. I need not worry about the additional time slice of the data any longer.

I shifted the hole time axis by a negative increment (e.g. -1 minute) and computed the mean value. This can be done with the operator shifttime:

cdo daymean -shifttime,-1min ifile ofile

Also, the time axis can be shifted back:

cdo shifttime,1min -daymean -shifttime,-1min ifile ofile

However, I’m still confused about my first question, that is, why the RegCM-4.1.1 writes its outputs in two different ways — mean value (e.g. tpr ) and instant value (e.g. tg ).

Regards,

Miao

From: saeed bayat [mailto:saeedbayat7276@gmail.com]
Sent: 2011年10月25日 3:55
To: Miao Yu
Subject: Re: [RegCNET] Help. About time resolution of RegCM-4.1.1 outputs

Dear Miao,
You can edit the timesteps before run the model. For precipitation data, you can sum
tpr variable in CDO by: cdo -r daysum ifile ofile
for last time of your data, you can sum them in GrADS something like this:
open first file
define precip1 = sum(tpr,t=1,t=124)
open second file
define precip2 = tpr
define precip =precip1+precip2

I hope these instructions could help you

Good Luck

Saeed Bayat
M.A Student of Climatology
Department of Geography
Ferdowsi University of Mashhad(FUM) - Iran

On Sat, Oct 22, 2011 at 8:22 PM, Miao Yu <miao.yu@engr.uconn.edu> wrote:

Dear All,

I’m running the RegCM-4.1.1. At first, I set the frequency of ATM and RAD outputs at 6 hours and SRF output at 3 hours. And I use CDO to postprocess the data at daily means. I name the output as o and opost respectively. Then I rerun the model, setting the frequency at 24 hours for all of them. I name its output as odaily.

My questions are as follows.

1. I find that the tpr (total precipitation) written in odaily are daily mean values, while the tg (surface temperature) are instant values. I only compared these two variables, and I don’t know what is about for other variables. Why the model writes them in the two different ways? Besides, if the monthly outputs can be derived straightly from the model?

2. I find that every opost has one additional time slice for all of the variables. It is because that the last time in o is recorded at 0:00 in the next month. When the CDO computes their daily or monthly means, it will not include the last time slice. So the daily or monthly means of opost will ignore the last time of the variables for every month. Although the differences for the last day between the opost and the Fortran processed daily means are small, I think some errors will be caused when using the opost to run another model if I ignore the last time slice of variables. I’m not sure if I’m right.

I hope your help.

Regards,

Miao

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