I am using monthly data. How do I create data representing annual totals?

Let's start with the NOAA/NCDC/GHCN/v2beta dataset for New York City.

Open the example data.

1. Click on "Expert Mode" in the table at the top of the page. Check Step
2. Below the text that is already in the text box enter the following lines:

   T 12 splitstreamgrid
   [T] sum
   

   and then click "OK". Check Step

   You have just calculated annual precipitation totals for the entire time series for New York City.

3. If you had wanted to limit the data to specific years (e.g. 1980-1989), then you would have wanted to either use the Data Selection option first (as described in another Q&A and in the Data Library Tutorial) or put the following line above those in Step 2:

   T (Jan 1980) (Dec 1989) RANGE
   

   CAUTION: If there are any missing values, then your annual totals will be artificially low.