First, we collected hourly data from ECONET stations in North Carolina. Overall, there are currently 37 ECONET stations across the state; however 15 of the stations either didn't have enough data, or had too many bogus observations. We ultimately kept the stations that had at least 7 years of data, as that would give us enough observations to obtain more accurate statistics. The data period that we chose was from 2003 to 2009.
We retrieved the data from the State Climate Office's CRONOS Database and saved each file in Excel format. For each station, we created scatter plots of solar radiation versus air temperature, soil temperature, and relative humidity. We then calculated the correlation between solar radiation and the other 3 parameters using Excel's correlation function. We copied all of the correlation values into a single Excel spreadsheet, and then converted the spreadsheet to a shapefile using ArcCatalog. ArcCatalog is a program within ArcGIS that allows you to organize spatial data. We then used ArcMap to display our correlations.