Band-pass filter weights

From: SB Ratna <satyaban_2001_at_nyahnyahspammersnyahnyah>
Date: Mon Aug 06 2012 - 00:39:57 MDT

Dear User,I have daily OLR data for the period of 30 years. I would like to use Band-pass filter on various time scale using&nbsp;the function "band_pass_latlon_time".&nbsp;However, I am bit confuse to use the filter wights in this function,&nbsp;bpf = (/20,100,201/), which is the filter on the scale 20-100 days and 201 is&nbsp; filter weights.Could you please suggest me what weights should be used for the filtering the daily data on (i) 2-6 days (ii) 10-90 days (iii) 1-3 years.I got confusion due to the below description provided in the NCL site.The description for the function&nbsp;"band_pass_latlon_time" is mentioned as below (http://www.ncl.ucar.edu/Document/Functions/Diagnostics/band_pass_latlon_time.shtml)."The user must be aware that the appropriate number of filter weights is a direct function of the band pass period. The shorter the period, the more weights that will be required to sufficiently resolve the desired period."However, the description of "filwgts
 _lanczos"&nbsp;is mentioned as below (http://www.ncl.ucar.edu/Document/Functions/Built-in/filwgts_lanczos.shtml).
"A scalar indicating the total number of weights (must be an odd number;&nbsp;nwt&nbsp;&gt;= 3). The more weights, the better the filter, but there is a greater loss of data"
Thanks.
RegardsSB ratna

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Received on Mon Aug 6 00:40:21 2012

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