DOAS-OCM retrieval of Water Vapour from GOME and new CRD Spectroscopy

We report on the application of a single reference spectrum standard DOAS technique as well as a new multiple-spectrum, modified DOAS technique to the retrieval of absolute H2O vertical column densities from GOME data. The modified technique implements a new kind of radiative treatment to correctly sample the net contribution to the total absorption of altitudedependent (ie. temperature- and pressure-dependent) cross-sections for each detector pixel. The standard DOAS technique yields estimates of total water column which correlate remarkably well against ECMWF estimates. Our techniques were also applied to a single radiosonde KNMI rneasurement for cloud coverage smatter than 20%. Unfortunately absolute values produced by standard DOAS are too low. The modified DOAS algorithm reveals better absolute agreement with the data and lends itself easily to level-2 product generation of H2O columns without requiring an independent calculation of airmass factors. We also report on the new measurements of H2O absorption bands between 580 and 605 nm using Cavity Ring Down Spectroscopy (CRDS). These measurements reveal good agreement with existing lines in the HITRAN96 database and add some 800 additional lines.