CRONOS Station Ranking Scheme
In the CRONOS inventory, the substitute ranking is designed to provide guidance on which nearby stations would provide the best fit for the station of interest. This would be useful to know, for example, if missing data at a particular station needs to be replaced with that of a nearby station. The ranking is determined using both the correlation and the distance between stations. For the calculation, daily temperature data for each station for 1981-2010 is used. For a given station, the Pearson correlation for the daily maximum temperatures and the daily minimum temperatures is computed between that station and every other station. However, using correlation alone can allow for stations which are a large distance apart to have a high rank. That is, stations that are a large distance apart can have large correlations, but the temperatures at each station may not be representative of the other station. Therefore, the ranking was based on a combination of distance (D, in miles) and the Pearson correlation (ρ) for daily temperatures. The ranking score is calculated as the following:
Where CDR is the correlation to distance ratio. The larger the value of CDR, the closer a nearby station is to a station of interest and the larger the value of the Pearson correlation of the nearby station with the station of interest. Therefore, each nearby station is given a rank based on the value of the CDR. The substitute rank is 1 for the nearby station with the largest value of CDR with the station of interest and is our guidance on which nearby station provides the best fit for missing temperature data for the station of interest. CDR values are calculated separately for daily maximum and minimum temperatures and only data of good quality (checked through the SCO QC procedures) are used in these calculations.