let me elaborate my query. The link you forwarded was impressive but I am still doubtful about my problem.I have 10 years JJAS daily data i.e 10 x 122 =1220 time steps.Now I need to calculate the variance for each year over a certain [lat x lon box].So I expect that output will be of 10 timesteps.But through the method given in the link, I am getting the output of 1220 timesteps.