README for NO2columns and NOcolumns files

These files contain output from the GEOSCCM SAGEIII replay simulation with GMI chemistry (simulation I32_S3_v2). 

Each file includes output every half hour (48 times per file) to represent the monthly averaged diurnal cycle for the given year and month. The output is provided on a global lat/lon grid. In addition to the files for specific years and months (e.g. NO2columns.201805.nc for May 2018), we also provide a monthly climatology created by averaging the values for each month over the years 2017-2020. These files have .clim. in the file name. The clim files can support comparisons to years outside the range for which year-specific output is provided.

The NO2columns and NOcolumns files provide the column sums of NO2 or NO, respectively. The columns are provided as total columns in the tcolNO2 or tcolNO variables and as partial columns that include only the portion of the column above 16km in the scol16NO2 or scol16NO variable. These files are designed to facilitate comparison between simulated and observed NO2 and NO columns and their diurnal variability for different locations. 

The files also include the variable SZA, which represents the solar zenith angle used for the simulation's photolysis. Like the NO and NO2 columns, SZA is provided at each time on a lat/lon grid. Please note that in these files, SZA is unsigned.