CDO

Hello,
This is my netcdf header file -

netcdf uwnd_850_2017_2_10_00Z {
dimensions:
time = UNLIMITED ; // (20 currently)
lat = 73 ;
level = 1 ;
lon = 144 ;

time = 1908768, 1908774, 1908780, 1908786, 1908792, 1908798, 1908804, 
    1908810, 1908816, 1908822, 1908828, 1908834, 1908840, 1908846, 1908852, 
    1908858, 1908864, 1908870, 1908876, 1908882 ;

I have data sampled every four hours for five days at a single pressure level. I want the mean value (not average) for this variable i.e. zonal wind at a pressure level. The entire data is present in one file not many files. So there is no need to merge many netCDF files. I just want the statistical mean. Is ensmean the right CDO operator ?

My second question is - I have the data for the period 1981-2010 for a particular variable at a particular pressure level of a particular month and day. I presume there is a way to calculate the climatological mean as well ?

Best regards,
Ashwin.