Atmospheric Profiling with Microwave Sounders – from Top to Bottom

Hyperspectral infrared sounders, such as AIRS, CrIS and IASI, have become important weather and climate sensors for both operational use and research use, but microwave sounders, in spite of their coarser spatial resolution and poorer sounding accuracy, still play a crucial role in atmospheric research and have the largest forecast impact. That is because they sample certain weather and climate regimes that infrared sounders do not sample well, particularly those associated with full cloud cover, convection and storms. We give an overview of the state of the art in microwave sounding and discuss how such soundings can be obtain from the ground, from aircraft, from low-earth-orbiting (LEO) satellites and even geostationary-earth-orbiting (GEO) satellites. Each vantage point is advantageous for a particular set of observing needs. We show how the JPL High Altitude MMIC Radiometer (HAMSR) can be used to obtain ultra-high resolution of the boundary layer when mounted on the ground and high resolution of hurricanes when mounted on an aircraft. We also review the Advanced Technology Microwave Sounder, a HAMSR analog currently flying on NASA/NOAA LEO satellites that provide global coverage at moderate resolution. Finally, we describe the Geostationary Synthetic Thinned Aperture (GeoSTAR) instrument that has been developed for GEO at JPL and will provide continuous hemispheric measurements. We will also give an overview of retrieval techniques and show illustrative results. We conclude with a brief discussion about applications in weather research and forecasting that benefit the most from these measurements.

Copyright 2019 California Institute of Technology