Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) Forum
Re: Near-adiabatic saturated layers
Posted By: John Brown In Response To: Near-adiabatic saturated layers (Scott Dennstaedt)
Date: 11-December-06 2107Z
In Response To: Near-adiabatic saturated layers (Scott Dennstaedt)
Yes, we occasionally see these features [when the lapse rate is absolutely unstable, they are sometimes referred to as MAULs, or Moist Absolutely Unstable Layers, see "Moist Absolute Instability: The Sixth Static Stability State" George H. Bryan and Michael J. Fritsch
As you point out, forecasts can also show these; there is no mechanism in the model to automatically remove them. When these are seen in a forecast it is a sign that vertical motion in the forecast has been strong, and occurring in a convectively unstable environment. The convective parameterization, if activated, will tend to prevent such layers from forming. In a case such as you referenced, explicit grid-scale overturning may have developed on small-scales during the early stages of the forecast. The mixing and precipitation resulting from this would eventually remove the saturation.
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