Langley plots are plots of the ln(V0
) vs. air mass m used to calibrate sun radiometers, mainly, to determine the aerosol component of the atmosphere assuming attenuation follows V
). This is simple if the atmosphere is stable since the intercept of this plot is ln(V0
), which can then be used to solve for tau for any measured V
. The atmosphere is not stable; therefore, 11 methods to measure V0
s and determine robust estimates of V0
s for interesting field sites are discussed.