取得一段时间内每个季节的最大降雨量（xarray）

Question

I'm trying to find the maximum rainfall value for each season (DJF, MAM, JJA, SON) over a 10 year period. I am using netcdf data and xarray to try and do this. The data consists of rainfall (recorded every 3 hours), lat, and lon data. Right now I have the following code:

ds.groupby('time.season).max('time')

However, when I do it this way the output has a shape of (4,145,192) indicating that it's taking the maximum value for each season over the entire period. I would like the maximum for each individual season every year. In other words, output should have something with a shape like (40,145,192) (4 values for each year x 10 years)

I've looked into trying to do this with DataSet.resample as well using time=3M as the frequency, but then it doesn't split the months up correctly. If I have to I can alter the dataset, so it starts in the correct place, but I was hoping there would be an easier way considering there's already a function to group it correctly.

Thanks and let me know if you need anymore details!

Answer 1

Resample is going to be the easiest tool for this job. You are close with the time frequency but you probably want to use the quarterly frequency with an offset:

ds.resample(time='QS-Mar').max('time')

These offsets can be further configured as described in the Pandas documentation: http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases