Changes between Version 26 and Version 27 of Branches/Driver_Improvements

Timestamp:

2016-05-27T17:37:41+02:00 (8 years ago)

Author:

aducharne

Comment:

--

Branches/Driver_Improvements

@@ -65 +65 @@
 '''AD(27/05/2016): I disagree with the above statement that motivates the development of a new interpolation method''' : "The time-stepping is done independently from the physical time. [...] The issue becomes more complicated when we consider fluxes which are averaged over an interval. The only valid assumption is that the dates corresponding to index itau_n is within the time interval over which the average was performed. In readim2.f90 there is no information if the date of n is at the start, end or anywhere else within the averaging period." 
 
-First, the time is defined without ambiguity from the initial time and the nb of records that were read.  Second, when we read a flux at the record itau_nm1, we perfectly know to which interval it corresponds. For WFDEI for instance, we know from http://www.eu-watch.org/gfx_content/documents/README-WFDEI%20(v2016).pdf that the record at itau_n holds the average flux over the 3-hourly period that precedes the "time stamp" of itau_n (t0+dt according to the above notations). This is perfectly clear, and perfectly coherent with the first panel of the above graphics, thus with dim2driver.
+First, the time is defined without ambiguity from the initial time and the nb of records that were read.  Second, when we read a flux at the record itau_n, we perfectly know to which interval it corresponds. For WFDEI for instance, we know from http://www.eu-watch.org/gfx_content/documents/README-WFDEI%20(v2016).pdf that the record at itau_n holds the average flux over the 3-hourly period that precedes the "time stamp" of itau_n (t0+dt according to the above notations). This is perfectly clear, and perfectly coherent with the first panel of the above graphics, thus with dim2driver.
+
+It further means that, whichever the interpolation we perform, for WFDEI case, the average of the interpolated flux over the 3h that precede t0+dt must equal the value read in record itau_n. It thus implies that any interpolation that does not preserve the mean over [t0,t0+dt] is inappropriate for such a flux. 
+
+Looking at LWdown at the bottom of  the 2nd panel above, the mean between [itau_nm1,itau_n]=[t0,t0+dt] is not equal to the value read at itau_n in any of these two cases: (a) uniform values over the green and brown intervals, (b) linear interpolation betwen the centre of the green and the centre of the brown intervals. Maybe another solution is coded, but then, it would be nice to explain it.