Continuous time analogues

 Evaluation of analogues

This figure shows the rms value for the 20 best  analogues, and the corresponding 20 correlation values for the current season. The horizontal bar corresponds to a correlation of 0.65 (the 70th quantile of all correlations).

Return periods

The distribution of analogues allow to compute the probability of observing an SLP pattern (given a history of pattern) and return times of SLP patterns (the time to wait for a pattern to recur).

This figure shows an estimate of the probability of observing a daily SLP pattern from its analogues, from the number of "good analogues", i.e. a spatial correlation larger than 0.65 and an rms lower than the 30th quantile. The lower panel shows the average time between an SLP pattern and its good analogues.

Analogue files

The analogue file contains 61 columns:

• The first column is the analyzed days (from 1st January 1948 to the current day).
• The next 20 columns are the dates of the best analogues, i.e. those that minimize an rms function. The next 20 columns are the values of the rms (actually -rms).
• The last 20 columns are the values of the spatial correlation.

It can be used as input to the Analogue Weather Generator (AnaWEGE) designed by P. Yiou (2014). The software to produce this file (including downloading NCEP reanalysis data) can be obtained from this web site.

We use this file to analyze extreme events. See for example the BAMS report on extremes.

The file is free for academic use (and is provided "as is"). Please contact Pascal Yiou for commercial uses.