Water vapour column abundance retrieval using multispectral radiometer measurements in Sydney, Australia

Water vapour column abundances in Sydney were derived from Multifilter Rotating Shadowband Radiometer (MFRSR) solar transmittance measurements in the 0.934 µm band using the modified Langley technique. The atmospheric models LOWTRAN 7 and MODTRAN 3 were used to calculate the water vapour transmittance in the region centred at 0.934 µm, in order to determine the instrument coefficients required for water vapour retrieval. We also propose the use of eigenvalue analysis to predict aerosol optical thickness at the water vapour channel, in comparison to the quadratic form relationship. Long-term measurements were used to study the diurnal and temporal variability of water vapour column abundances. An apparent seasonal pattern of maximum water vapour column values during the summer season and minimum values during the winter season was observed during a whole year of measurements.