Re: questions about the detail processes of clmDayTLL and calcDayAnomTLL

Hi, Adam and Dennis,

Thanks a lot for your kind reply.

By your explanation, I think I understand how the two functions works.

But to my opinion, I prefer the arithmetic of calculation of daily climatology by corresponding date (calendar) not the present one in clmDayTLL. What do you think?

Best regards,

Xuguang

--- 10年8月25日，周三, Adam Phillips <asphilli@ucar.edu> 写道：

> 发件人: Adam Phillips <asphilli@ucar.edu>
> 主题: Re: [ncl-talk] questions about the detail processes of clmDayTLL and calcDayAnomTLL
> 收件人: "Dennis Shea" <shea@ucar.edu>
> 抄送: "Xuguang Sun" <sunxg007@yahoo.com.cn>, ncl-talk@ucar.edu
> 日期: 2010年8月25日,周三,下午1:43
> Hi Xuguang,
> It seems that I didn't look at the code of these functions
> close enough. I
> mistook what the function day_of_year does. My apologies.
> Hopefully you
> tested the functions as I suggested. Dennis is correct.
> Here is an example
> of what you may need to do. For example, if you have a 1D
> array of daily
> data named "data", and an array the same size of data named
> "year"
> containing the year:
>
> (This is untested! Please check the end results.)
>
> nyr = 30   ; enter the # of years
> cntr = 0
> climo_366 = new(366,float)
> nyr365 = 0
> nyr366 = 0
> do gg = 0,nyr-1
>    if (isleapyear(year(cntr))) then
>       climo_366 = data(cntr:cntr+365)
>       nyr366 = nyr366+1
>       cntr = cntr+366
>    else
>       climo_366(:58) = data(cntr:cntr+58)
>       climo_366(60:) =
> data(cntr+59:cntr+364)
>       nyr365 = nyr365+1
>       cntr = cntr+365
>    end if
> end do
> climo_366(:58) = (/ climo_366(:58)/(nyr365+nyr366) /)
> climo_366(59)  = (/ climo_366(59)/nyr366 /)
> climo_366(60:) = (/ climo_366(60:)/(nyr365+nyr366) /)
>
> data_anom = data   ; preallocate space for
> new daily anomaly array
> cntr = 0
> do gg = 0,nyr-1
>    if (isleapyear(year(cntr))) then
>       data_anom(cntr:cntr+365) = (/
> data(cntr:cntr+365) - climo_366 /)
>       cntr = cntr+366
>    else
>       data_anom(cntr:cntr+58) = (/
> data(cntr:cntr+58) - climo_366(:58) /)
>   data_anom(cntr+59:cntr+364) = (/
> data(cntr+59:cntr+364)-climo_366(60:)/)
>       cntr = cntr+365
>    end if
> end do
> -------------
> Hope that helps..
> Adam
>
>
>
> > You can see the code used
> > %> less
> $NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl
> > It does not use calendar date. It uses day of year.
> > In a leap year it uses the 1st 365 days *regardless
> of
> > calrndar date*.
> > When all 365-day climatology has been computed the
> 366
> > day is the average of day 1 and day 365.
> > Good luck
> > On 8/20/10 6:50 PM, Xuguang Sun wrote:
> >> Hi, everyone,
> >> I'm now trying to calculate the mean annual cycle
> and anomalies from
> daily data, and it's very good that NCL has such functions,
> like
> clmDayTLL and calcDayAnomTLL, but I'm not very clear about
> their detail
> processes.
> >> I have multi-year daily data with leap and
> non-leap years included,
> that
> >> means there are 365 days in non-leap years and 366
> days in leap years,
> and whether 29Feb is included or not is their only
> difference. If we
> want to calculate climatological daily mean, I think the
> right method
> is
> >> to add the corresponding day of each year (for
> example, 28Feb) together
> and then divide it by the total year number. Especially, as
> for 29Feb,
> because it only exists in leap years, we can simply sum
> them up and
> then
> >> divide it by the leap year number. By the above
> processes I think we
> can
> >> obtain the correct climatological daily mean
> (annual cycle).
> >> Accordingly, we can get the daily anomalies by
> subtracting the
> >> climatological daily mean from the multi-year
> daily data.
> >> I don't know whether clmDayTLL and calcDayAnomTLL
> do the same things
> for
> >> daily climatology and anomaly. Does anyone have
> some ideas?
> >> Thanks.
> >> Best regards,
> >> Xuguang SUN
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Received on Thu Aug 26 03:31:20 2010