The horizontal pressure gradient force, Coriolis force, flux divergence of momentum (the friction term), velocity tendency, and advection are all dominant forcing terms in the horizontal momentum equation important to a dynamical description of the Great Plains Low Level Jet (LLJ). Efforts under previous grants with the PI have enabled an accurate estimate of all forcing terms associated with the LLJ, including friction. The scientific objective of this research is to employ a fully-instrumented research aircraft as an observational platform to measure the forcing terms in the horizontal momentum equation responsible for the diurnal behavior of the LLJ. The PI will emphasize the evaluation of the friction term during the period of decoupling attending the cessation of turbulent mixing around sunset, and the subsequent adjustment of the horizontal windfield.
