Nonlinear Atmospheric Adjustment

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The Principal Investigator will investigate nonlinear atmospheric adjustment to generalized atmospheric forcing. Atmospheric adjustment is defined as the response of a moist, compressible atmosphere to a prescribed forcing. Immediately after an instantaneous forcing of arbitrary shape, the atmosphere will, in general, be in a state of geostrophic and hydrostatic imbalance. The study of atmospheric adjustment describes the subsequent tendency of the air to achieve a state of geostrophic and hydrostatic balance. It is an extension of the classic problem of geostrophic adjustment to include the effects of compressibility and to allow for nonhydrostatic and moist processes. The forcings studied will be completely general and include momentum, mass, thermal, and moisture forcings. Thus, the research will provide insight into the fundamental workings of the atmosphere as well as into the specific dynamics of clouds, mesoscale convective systems, and other nonhydrostatic circulations driven by moist convection. Although both heating and moistening correspond to an addition of buoyancy to the air mass, there is a fundamental difference. An addition of heat can be transformed to other forms of energy that can be propagated away; an addition of water must be conserved and cannot be transformed (in the absence of phase changes) and propagated out of the system. The response to injections of vertical momentum will gain insight into the initialization of updrafts in numerical weather prediction models. A suite of nonlinear numerical problems will be used to examine the full effects of compressibility in the adjustment to generalized forcings. The numerical models will be benchmarked against analytic solutions to the linear adjustment problem. The broader impacts include the training of graduate students in the running and testing of numerical models and in the writing and communicating of scientific research at professional meetings and in journal articles. It also includes the knowledge gained that can be disseminated to the undergraduate and graduate students in the classroom and the societal benefit through a better understanding of atmospheric adjustment and its implications to numerical weather prediction and moist convection.