I want to study trends in rainfall in an annual and seasonal basis. For me the sequence is that:

1) First, i have to homogenize the data (in my case, the data is already homogenized)

2) Analyse the seasonality before study trend . How do I detect seasonality in data (which test can I use - the test ) and what is the best way to remove this effect?

3) Verify the existence of autocorrelated data (independece and randomness) by using Wald-Wolfowitz test.

4) If there are autocorrelated data, there is need to use pre-whitening techniques like trend-free pre whitening adapted to Mann-Kendall trend test

5) If the data are independent and random (non-autocorrelated), I can use the Mann-Kendall test and Sen's slope estimator directly .

Am I right?

What do you think about it?