Use Case 5

###Compute departures from a climatological DJF

Use Case: Compute departures from a climatological DJF
Actor: Climate/Data Scientist
Background: Scientist like to focus on seasons (DJF, MAM, JJA, SON), or annual cycle (average of each month). They also like to see which seasons/month/years stand out. They do that by removing the "climatological" season from each individual season
Use Scenario:

1. identify file(s) covering the time period to compute climatology over
2. compute climatological annual cycle over period of reference (climatology is defined usually has a 30 years average) average DJF over the period of reference WARNING DJF is TRICKY for example the first DJF only has 2 months, the last one only has 1 month. Rules need to be put in place to decide how to weight these cases! WARNIG 2: Time bounds MATTER, for dataset expressed in "months since" Jan and February have the same length (1 month), but for dataset expressed in "days since" Jan has a length of 31 whereas Feb has a length of 28 (and even 29 every 4th years) once each DJF has been computed, average them all together, that our climatological DJF
3. identify file(s) covering departures to be computed can be longer than ref period
4. compute seasonal means Repeat the first part of the process for computing the climatology, obtaining the "Seasons"
5. remove climatology from #4
6. dump out result

Difficulties:

• Time bounds matter!
• Missing values!

Alternative Paths: annual cycle instead of DJF
Exceptional Cases:
Frequency: Medium
Criticality: Medium
Risk: Medium