Advanced Research WRF (ARW) Technical Note - MMM - University ...
Advanced Research WRF (ARW) Technical Note - MMM - University ...
Advanced Research WRF (ARW) Technical Note - MMM - University ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Contents<br />
Acknowledgments ix<br />
1 Introduction 1<br />
1.1 <strong>Advanced</strong> <strong>Research</strong> <strong>WRF</strong> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2<br />
1.2 Major Features of the <strong>ARW</strong> System . . . . . . . . . . . . . . . . . . . . . . . . . 3<br />
2 Governing Equations 5<br />
2.1 Vertical Coordinate and Variables . . . . . . . . . . . . . . . . . . . . . . . . . . 5<br />
2.2 Flux-Form Euler Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6<br />
2.3 Inclusion of Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7<br />
2.4 Map Projections, Coriolis and Curvature Terms . . . . . . . . . . . . . . . . . . 7<br />
2.5 Perturbation Form of the Governing Equations . . . . . . . . . . . . . . . . . . . 9<br />
3 Model Discretization 11<br />
3.1 Temporal Discretization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11<br />
3.1.1 Runge-Kutta Time Integration Scheme . . . . . . . . . . . . . . . . . . . 11<br />
3.1.2 Acoustic Integration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12<br />
3.1.3 Full Time-Split Integration Sequence . . . . . . . . . . . . . . . . . . . . 14<br />
3.1.4 Diabatic Forcing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15<br />
3.1.5 Hydrostatic Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15<br />
3.2 Spatial Discretization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16<br />
3.2.1 Acoustic Step Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . 16<br />
3.2.2 Coriolis and Curvature Terms . . . . . . . . . . . . . . . . . . . . . . . . 18<br />
3.2.3 Advection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18<br />
3.3 Stability Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21<br />
3.3.1 RK3 Time Step Constraint . . . . . . . . . . . . . . . . . . . . . . . . . . 21<br />
3.3.2 Acoustic Time Step Constraint . . . . . . . . . . . . . . . . . . . . . . . 22<br />
4 Turbulent Mixing and Model Filters 23<br />
4.1 Explicit Spatial Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23<br />
4.1.1 Horizontal and Vertical Diffusion on Coordinate Surfaces . . . . . . . . . 23<br />
4.1.2 Horizontal and Vertical Diffusion in Physical Space . . . . . . . . . . . . 24<br />
4.1.3 Computation of the Eddy Viscosities . . . . . . . . . . . . . . . . . . . . 26<br />
4.1.4 TKE equation for the 1.5 Order Turbulence Closure . . . . . . . . . . . . 27<br />
4.2 Filters for the Time-split RK3 scheme . . . . . . . . . . . . . . . . . . . . . . . . 29<br />
4.2.1 Divergence Damping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29<br />
i