Cirrus clouds in the upper troposphere and lower stratosphere (UTLS) can impact the efficiency and effectiveness of
infrared directed energy (laser) applications, including laser communications systems, due to attenuation (absorption
and scattering) of energy. The accurate prediction of cirrus clouds, including subvisual cirrus, is often difficult for
operational numerical weather prediction (NWP) models because the models require high resolution and advanced
cloud microphysics schemes. We solved the fully three-dimensional, moist, compressible, non-hydrostatic Navier-Stokes
equations using a vertically-stretched adaptive grid nested within the Weather Research and Forecasting (WRF) model
over a geographical region of interest. We used an adaptive time-split integration scheme for the temporal
discretization. We used the Thompson cloud microphysical parameterization scheme for the cirrus cloud development.
The initial conditions and boundary conditions for the WRF simulations were extracted from the European Centre for
Medium Range Weather Forecasting (ECMWF) T799L91 global analyses. We ran the simulation for a domain centered
on the coast of Southern California and the results are compared to meteorological satellite and radiosonde
observations for selected locations.
High Resolution WRF (Weather Research and Forecasting)/microscale code simulations are carried to predict
and characterize stratospheric Optical Turbulence (OT) layers induced by jet streams and gravity waves under
various local atmospheric conditions. This information in turn is used to improve prognostic parameterizations
of eddy mixing coefficients and diagnostic parameterizations of optical turbulence for the tropopause and the
lower stratosphere regions. Non-homogeneous, anisotropic, non-Kolmogorov patchy shear-stratified stratospheric
turbulence requires that a fine mesh be used to resolve stiff velocity and temperature gradient profiles. Our
approach is based on vertical nesting and adaptive vertical gridding in nested WRF/microscale codes. We perform
effective ensemble forecasting by using initial and boundary conditions from both GFS and high resolution
T799L91 ECMWF datasets. This methodology is applied to the analysis of field data from the Hawaii 2002
campaign and TREX Campaign (Terrain-induced Rotor Experiment), Owens Valley, CA, 2006. We obtain local
distributions of simulated optical turbulence (C2n
) in the upper troposphere/lower stratosphere using explicit
simulations and parametrization formula that show strongly laminated structures with thin layers of high values
of refractive index. These layers are characterized by steep vertical gradients of potential temperature and are
located at the edges of relatively well mixed regions produced by shear instabilities and wave breaking.
Results from high-resolution, forced, three-dimensional direct numerical simulations on the vertical variability of shear-stratified turbulence and its outer length scales in nonuniformly stratified tropopause jets are presented. Vertical scales 1m-50m are resolved. Turbulent dynamics leads to the formation of an N2-notch which favors gravity wave emission well within the temperature mixing layer. We demonstrate that, in inhomogeneous shear-stratified turbulence, scaling of various turbulent quantities (such as variances, fluxes, mixing efficiency, turbulence outer scales) with respect to a single parameter (such as the gradient Richardson number) typically exhibit multiple branches. Certain qualitative changes in eddy mixing during transitional regimes towards stronger stratification are highlighted. The behaviour of turbulent eddy mixing parameters found in these studies is consistent with some recent observational results in stably stratified atmospheric shear flows. The implication of this study is that such transitions and multiple scalings need to be accounted in the parameterization of microscale atmospheric optical turbulence.
The performance of Airborne Lasers is sensitive to the 3D, nonstationary, intermittent, anisotropic structure of atmospheric turbulence. The upper (stratospheric) layers are dominated by the background stable stratification, as a result of which the turbulence tend to be characterized by thin layers of high refractive index variations known as `pancakes'. In this paper we survey theoretical results and experimental measurements of turbulence spectra and correlations for pancakes in rotating stratified environments. Anisotropic turbulence models developed are benchmarked against both laboratory experimental data bases as well as field data to be gathered in the balloon and the EGRETT campaign of measurements.
Conference Committee Involvement (5)
Atmospheric and Oceanic Propagation of Electromagnetic Waves VI
24 January 2012 | San Francisco, California, United States
Atmospheric and Oceanic Propagation of Electromagnetic Waves V
25 January 2011 | San Francisco, California, United States
Atmospheric and Oceanic Propagation of Electromagnetic Waves IV
25 January 2010 | San Francisco, California, United States
Atmospheric Propagation of Electromagnetic Waves III
26 January 2009 | San Jose, California, United States
Atmospheric Propagation of Electromagnetic Waves II
21 January 2008 | San Jose, California, United States
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