Changes between Version 11 and Version 12 of 2019WP/ENHANCE-05_SimonM-Harmonic_Analysis

Timestamp:

2019-08-27T18:50:18+02:00 (5 years ago)

Author:

smueller

Comment:

--

2019WP/ENHANCE-05_SimonM-Harmonic_Analysis

@@ -89 +89 @@
 The development of an external tool for the finalisation of the multiple linear regression analysis using a set of intermediate scalar products as described above is proposed. This new tool would be added at source:/utils/tools/DIAMLR_TOOLS/.
 
+=== Proposed replacement of module `dia25h`
+
+Related to tidal harmonic analysis is the approximative M2-detiding of model output fields provided by module `dia25h` (source:/NEMO/trunk/src/OCE/DIA/dia25h.F90@10641). This functionality roughly approximates the tidal period of the semi-diurnal tidal constituent M2 as 12.5 hours, it provides the detiding of a fixed set of fields, it requires relatively short time steps whose duration in seconds is an integer divisor of 3600 seconds, and its memory footprint is relatively large.
+
+In order to address these issues, the removal of module `dia25h` and its replacement by a XIOS-based alternative mechanism implemented in a new module `diam2detiding` (source:/NEMO/trunk/src/OCE/DIA/diam2detiding.F90) is proposed. While the current implementation in module `dia25h` averages the centred values of 25 1-hour intervals that are centred around the middle of each day (i.e., the values at the top of each hour including midnight at both ends of each 24-hour averaging period), the revised mechanism would identify up to 29 intervals of equal duration that cover 24.842 hours, twice the period of the tidal constituent M2 of 12.421 hours (https://en.wikipedia.org/wiki/Earth_tide#Tidal_constituents), with centre points falling within one complete 24-hour interval centred around midday (it can be shown that 29 is the largest number of periodic samples that achieve this). For each full 24-hour period starting at midnight (not including midnight on one side of this period), a weight would be generated at each time step so that the sum of a model time series multiplied by these weights would compute the average of the centre points of the intervals described above. This time series of weights could be sent to XIOS; with this, XIOS could be configured to provide approximative M2-detiding of any model field that is available for output.
+
 == Tests