questions about the detail processes of clmDayTLL and calcDayAnomTLL

From: Xuguang Sun <sunxg007_at_nyahnyahspammersnyahnyah>
Date: Fri Aug 20 2010 - 18:50:24 MDT

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 Fri Aug 20 18:50:31 2010

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