MEI.v2 is based on EOF analysis of level pressure, sea surface temperature, surface zonal winds, surface meridional winds, and Outgoing Longwave Radiation. The analysis is conducted for 12 partially overlapping 2-month "seasons".
Warm phase is defined as MEI index greater or equal to 0.5. Cold phase is defined as MEI index lesser or equal to -0.5.
Arguments
- use_cache
logical option to save and load from cache. If `TRUE`, results will be cached in memory if `file` is `NULL` or on disk if `file` is not `NULL`.
- file
optional character with the full path of a file to save the data. If `cache` is `FALSE` but `file` is not `NULL`, the results will be downloaded from the internet and saved on disk.
Value
Date: Date object that uses the first of the month as a placeholder. Date formatted as date on the first of the month because R only supports one partial of date time
Month: Bi-moonthly season of record
Year: Year of record
MEI: Multivariate ENSO Index Version 2
Phase: ENSO phase