The water dimer millimeter-wave spectrum at ambient conditions: A simple model for practical applications

•A simple model for quantitative analysis of warm water dimer spectra has been developed.•The model correlates well with the experimental observations.•A possibility of direct detection of the water dimer in the atmosphere is shown.

A simple model of the water dimer millimeter-wave spectrum at pressures and temperatures typical of Earth׳s atmosphere is proposed. The model is based on high accuracy ab initio calculations and is supported by experimental observations of the dimer spectrum in cold molecular beams. It is demonstrated that the model corresponds to the spectra calculated ab initio and recorded at room temperature. The model is used for assessing atmospheric brightness temperature variations caused by the water dimer absorption. A possibility of direct radiometric observation of the dimer in the Earth׳s atmosphere is shown.