Index function for CW, CD, WW, WD
ECA&D defines these two-variable indices as:
| VarName | OUTPUT_long_name |
|---|---|
| CD | Days with TG < 25th percentile of daily mean temperature and RR < 25th percentile of daily precipitation sum ("cold/dry days") |
| CW | Days with TG < 25th percentile of daily mean temperature and RR > 75th percentile of daily precipitation sum ("cold/wet days") |
| WD | Days with TG > 75th percentile of daily mean temperature and RR < 25th percentile of daily precipitation sum ("warm/dry days") |
| WW | Days with TG > 75th percentile of daily mean temperature and RR > 75th percentile of daily precipitation sum ("warm/wet days") |
where TG is "air Temperature near the Ground ", i.e. the usual daily mean temperature tas, and RR is daily total precipitation pr.