Dear Users,
I try to count anomaly from daily climatology through multiple years.
It is a 30-year data set with a normal Gregorian calendar axis:
yes? sh axis treal
name axis # pts start end
TREAL TIME 10957 r 01-JAN-1961 12:00 31-DEC-1990 12:00
T0 = 01-JAN-1961 00:00:00
I define the modulo time axis, then I count daily climatology, finally I extract it from my time series:
def axis/t=0:365.2425/edges/npoints=365/t0=1-JAN-0001/units=days/modulo daily1
let t2m_clim=t2m[gt=daily1@mod]
let t2m_anom=t2m-t2m_clim
The problem is that it does not take into account February 29s, and thus it gives an error:
**ERROR: inconsistent sizes of data regions: T axis
T2M61A has 10950 points (L=00001:10950)
_expression_ has 10957 points (L=00001:10957)
If I reduce my t2m to 10950 days (in order to simulate "skipping" february 29s), It does the extraction, though, some tiny bias might occur as a consequent of this.
It raises some further questions:
Why do not the following two take feb 29s into account? The daily2 is almost the same as daily1. Furthermore, the daily3 axis is giving a totally different result.
def axis/t=0:365.2425/edges/npoints=366/t0=1-JAN-0001/units=days/modulo daily2
def axis/t=0:365.2425:1/edges/t0=1-JAN-0001/units=days/modulo daily3
If I define my modulo axis to skip feb 29, it gives obviously bad results.
def axis/t=0:365/edges/npoints=365/t0=1-JAN-0001/units=days/modulo daily4
I enclose a plot with the 4 daily climatological axes.
Which one is correct? Why is there huge difference between the axes? How can I make a daily climatology which takes into account February 29?
Thanks in advance,
Peter Szabo