Laserfiche WebLink
<br />and moisture. The mass-weighted average terminal velocities for' raindrops, type A and <br />type B ice are represented by VTR, VTA, and VTS.' During condensation/evaporation <br />of cloud water Cjrlt is calculated making use of the bulk physical assumption where one <br />maintains 100% relative humidity. <br /> <br />. <br /> <br />t ... <br /> <br />J <br />r.", <br /> <br />The model equations are transf'ormed to a nonorthogonal, terrain-following system. of' <br />coordinates (Clark, 1977). The finite-difference formulation of the momentum equations <br />are solved using centered-space and centered time differences according to the second order <br />algorithm of' Arakawa (1966) and Lilly (1965). The second-order-accurate positive-definite <br />advection transport algorithm of Smolarkiewicz (1984) was used for the conservation <br />equations of' heat and moisture, with one corrective iteration. Smolarkiewicz and Clark <br />(1986) found one corrective iteration sufficient for the flow regimes studied by the model. <br /> <br />:.- <br /> <br />r- <br /> <br />I. <br /> <br />I' <br />I <br />! <br /> <br />The present version of the code has interactive grid nesting capabilities allowing an <br />arbitrary number of nested grids (Clark and Farley, 1984 and Clark and Hall, 1991). This <br />allows one to simultaneously capture the larger scale flow patterns and still be able to focus <br />down to the precipitation processes on a cloud scale. Only the boundary conditions for <br />the outer-most domain are speci:6.ed while the boundary conditions for the inner domains <br />are supplied by the outer domain by either a one-way or two-way interactive grid nesting <br />method. <br /> <br />. <br /> <br />The boundary conditions at the outer-most domain include free-slip boundary <br />conditions for the velocity components and zero-flux-type conditions on all thermodynamic <br />I variables at the upper and lower surfaces of the model. To prevent the reflection of' <br />( . <br />vertically propagating gravity waves from the upper boundary, a sponge layer is introduced <br />r '. <br />I in the upper portion of the model domain. This sponge layer employes Rayleigh damping <br />and Newtonian cooling, and grid nesting is not performed in this region. The lateral <br />bounc:1a.rr conditionS in the present simulations are appr~n'lated by an open-boundary <br />extrapolation scheme. <br /> <br /> <br />2.2.2 Ice parameterization <br /> <br />The ice parameterization is based on the K-M work and considers two types of ice <br /> <br />r'.'.' <br />~ . <br />! <br /> <br />. <br /> <br />L...; <br /> <br />31 <br />