Varience correction for autocorrelation

#1
Hi everyone, I need some help in regards to autocorrelation and removing it from my data. I am not good with statistics so I appreciate the help.

I have daily rainfall data for my stations, and I want to carry out trend analysis for some indices like SDII, R10mm, R95p etc. but I need to carry out autocorrelation test first. I did the autocorrlation test for yearly and monthly sums, and found some autocorrelation in my data. I was told I should do variance correction, but I don't know how to do that. Does anyone know how to do variance correction in excel or spss?
 
#3
Oh these variables!

Frankly, I have no idea what this can be. Even if it is commonly used in your area, does not mean that we know what it is.

But maybethis linkcan be of help.
Hi, sorry if I was not clear on the indices earlier. These are rainfall indices, SDII is the Simple Daily Intensity Index, R10mm is the annual count of days when precipitation is greater or equal to 10mm, and R95p is the annual total precipitation that is greater than the 95 percentile.

Thank you for the link.