Sounding the lower atmosphere using a ground-based hyperspectral infrared sounder - the Bureau of Meteorology AERI

The use in Australia of a ground-based hyperspectral infrared (IR) sounder to continuously profile the atmospheric boundary layer (1-3 km) is described. The automated system developed for this purpose represents an important new capability providing significant information for the verification and improvement of numerical weather prediction (NWP) and climate models in the boundary layer and also a potential new capability for making significant contributions to operational weather forecasting and to applications such as fog prediction. The system described here comprises a Fourier Transform Spectrometer covering the spectral range 3 to 18 mu m with a spectral resolution of better than 1 cm(-1). The interferometer is housed in a weatherproof enclosure and is controlled from and provides information to the Bureau of Meteorology Head Office in Melbourne. The method used to retrieve temperature and moisture profiles in the planetary boundary layer from downwelling spectral radiance observations is described. The system provides high temporal resolution soundings (approximately every seven minutes) of temperature and water vapour concentration and for the first time provides high temporal resolution depiction of important mesoscale features in the planetary boundary layer. The paper describes examples of the utility of the system and shows where hyperspectral observations may provide useful information for assessing and improving the planetary boundary layer in numerical weather prediction models.