WHAT WILL BE CHANGED IN THE CONVECTION PACKAGE ON 28 MAR 2000?
In the Eta-10, we modified all the DSP’s based on the surface pressure, which made it easier (too easy) to get convective precip at all high-terrain points. We also changed the shallow/deep switch to 2000m (? from 290mb). In what we are implementing, we only change the DSP’s for points where the cloud base is above a layer that is 150 mb below the freezing level. The DSP’s used to be a constant (-30mb) value, which was too moist and made it very difficult to produce precip. Now they are similar to DSP’s for clouds that have bases well below the freezing level, the DSP’s at and below the freezing level are set to DSP0 (~ -70 mb depending on cloud efficiency), and are linearly interpolated from freezing level to cloud top, just like in the “normal” clouds. Plus we set the deep/shallow switch to 200mb*(psfc/1000). That’s probably too much detail. Basically, the difference is that in the Eta-10, we changed ALL the DSP’s, and went too far (too dry, too easy to get precip) at higher terrain.
