Abstract

This paper will discuss the science measurements and systems design of imagers and sounders including the Atmospheric Infrared Sounder (AIRS) and the Moderate Resolution Imaging Spectroradiometer (MODIS). Each provides its own level of imaging and sounding with the AIRS providing the high spectral/low spatial resolution sounding (high vertical/low horizontal resolution) and MODIS, with its infrared channels, provides low spectral/high spatial resolution imaging (low vertical/high horizontal resolution). Key variables measured by both include temperature, water vapor, cloud properties and surface properties. AIRS and MODIS individually provide approximately 5-6 hours improvement on the 5 day forecast and are used operationally. Scientists in recent years have demonstrated the value of using these instruments together to improve understanding of earth system processes and improve measurement accuracy, particularly in the presence of clouds. Engineering tradeoffs and technology development have shown imaging sounders are now possible with AIRS spectral resolution and MODIS spatial resolution. Limitations in spatial resolution of the sounders is shown to lead to sampling errors, and higher uncertainty in the measured products. Conversely, the imagers have shown limitations in product vertical resolution and accuracy due to reduced spectral resolution and knowledge of the spectral response functions. Improved surface temperature and emissivity over land and ocean are expected with hyperspectral imagers. Trends in global and regional model horizontal resolution show a need for higher spatial resolution temperature and water vapor products, on the order of 1-2 km, in the next decade. Higher spatial resolution imaging sounders will improve regional forecast, initiate and validate the next generation of climate models, and aid in identifying sources and transport f greenhouse gases.

© 2011 Optical Society of America