Microwave Soundings in the Planetary Boundary Layer

The recent NASA Earth Science Decadal Survey recommended developing observing systems for probing the planetary boundary layer (PBL), i.e. the lowest 1-2 km of the atmosphere. The panel viewed existing observing systems inadequate and proposed an Incubator activity to explore and develop new technologies and measurement techniques. In this presentation we discuss two of the driving challenges in observing the PBL: the difficulty of achieving high vertical resolution near the surface from space, and the problem caused by pervasive low PBL clouds. Microwave spectroradiometric sounding provides a ready solution for penetrating clouds, but existing microwave sounders typical have 2-3 km vertical resolution, inadequate to meet PBL measurement objectives. Hyperspectral sounding techniques, using hundreds of narrow spectral channels has the potential to improve vertical resolution, especially over ocean where there is a large radiometric contrast between the atmosphere and the surface. We will discuss measurement objectives, new instrument technologies, and observation system sensitivity experiments to predict performance and compare with science measurement objectives.