10A.2 MCS Evolution in Response to Convectively-Generated Low-Frequency Gravity Waves

Wednesday, 6 June 2018: 1:45 PM
Colorado A (Grand Hyatt Denver)
Rebecca Adams-Selin, NOAA; and R. S. Schumacher

Mesoscale Convective Systems (MCSs) frequently generate low-frequency gravity waves that propagate away from the system and modify the surrounding environment. A common wave pattern produced by MCSs consists of a wave or waves associated with subsidence through the depth of the troposphere generated by the first internal mode of heating, or the n=1 wave mode. Lifting over the lower half of the troposphere associated with an n=2 wave mode generated by low-level cooling follows. The n=1 wave(s) decrease the environmental convective instability; the n=2 wave increases the convective instability helping it to “recover”. The strength of the second wave is related to the strength of the low-level microphysical cooling within the MCS. Waves of the n=1 mode also increase surface-level winds toward the MCS, and slightly increase the 0-6 km line-normal shear. These signals are amplified when produced by MCSs in environments with larger initial convective instability or 0-5 km shear. Parcel trajectory analyses will be presented that examine wave impacts on parcels being ingested by the MCS, including environments of varying initial stability or containing a nocturnal stable layer.
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