Presented by

Dr. Ángel F. Adames-Corraliza
Assistant Professor
Department of Atmospheric and Oceanic Sciences
University of Wisconsin-Madison

Wednesday, October 21, 2020

To view the recording, please follow this link: 765 Seminar presented by Angel Adames-Corraliza 20201021.mp4


A linear two-layer model is used to elucidate the role of prognostic moisture on quasi-geostrophic (QG) motions in the presence of a mean thermal wind. Solutions to the basic equations reveal two instabilities.  The well-documented baroclinic instability is characterized by growth at the synoptic scale (horizontal scale of∼1000 km) and systems that grow from this instability tilt against the shear.  Moisture-vortex instability— an instability that occurs when moisture and lower-tropospheric vorticity exhibit an in-phase component— exists only when moisture is prognostic.  The instability is also strongest at the synoptic scale, but systems that grow from it exhibit a vertically-stacked structure.  When moisture is prognostic, baroclinic instability exhibits a pronounced weakening when the thermal wind is easterly. On the other hand, moisture-vortex instability is strongest in this mean state. Based on these results, it is hypothesized that moisture-vortex instability is the dominant instability in humid regions of easterly thermal wind such as the South Asian and African monsoons.