In order to access SURFRAD irradiance data, I am running the following python command using the pvlib library:
import pvlib
data, meta = pvlib.iotools.read_surfrad(filename, map_variables=True)
I used URL for surfrad solar irradiance data as "https://gml.noaa.gov/aftp/data/radiation/surfrad/Boulder_CO/2020/". However, when applied this to the filename parameter, it doesn't work!