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Index functions for CountThresholdedPercentileOccurrences (fixes #197)

Carolina Nilsson requested to merge a002527/climix:Index_Functions_rXpDAYS_rXpSUM_rXpPCT into main

Added one index functions CountThresholdedPercentileOccurrences.

CountThresholdedPercentileOccurrences:

  • Counts the number of wet days (RR >= 1 mm) for a period j, where RR_j for a period j is larger than the 95th percentile of precipitation at wet days in the reference period 1961-1991.
  • Output unit: {1, mm, %} the format of the output is decided from the output unit specified in the index definition.
  • Grid cells with no rain during the reference period is given threshold value 0. However, the input data is still thresholded with RR >= 1 mm.
  • Grid cells with no rain during the period j is given value 0.

Added tests for the Hyndman functions which tests the numerical and the data type output when computing the parameters: j, gamma, k and k_ext, on different inputs.

Regarding the tests against the ngcd dataset for Åland with indices r{PCT}ptot and r{PCT}p, with reference period set to 1971-2019, most of the values are comparable with only a small difference with max difference values from order 10^(-4) to 10^(-5) depending on the percentile value.

However, there can be a few cells where some days that lies on the threshold value are not filtered out in our computation in comparison to the ngcd indices. This probably occurs since our threshold values are not exactly the same as the ngcd threshold values.

Edited by Carolina Nilsson

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