CDO

Hi,

Is it possible to calculate "Number of days since a rain day" [1] using CDO?
I would like to create a map that can give information on number of days since a rain day in the last 90 days as of 1 Dec 2015. The date and 90 days is just example. Currently I calculate the number manually using Microsoft Excel.

See the attachment for the illustration.
Before I got the rainfall and raindays number in Excel, I download TRMM data from 2 Sep - 30 Nov 2015, convert it to xyz format and append the data into the worksheet (I will have an Excel file with X, Y, Z1, Z2, .. Zn), X=longitude Y=latitude Z1=rainfall_2Sep and Zn=rainfall_30nov. After that I calculate the raindays using threshold rainfall >=0.5mm. From the raindays, I can calculate the number of consecutive dry days and number of days since a rain day.

Thank you,
Benny

[1] http://drought.unl.edu/MonitoringTools/USRainDaysandDryDays.aspx