Difference between revisions of "Parcel method"

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<div class="definition"><div class="short_definition">(<br/>''Also called'' path method.) A method of testing for [[instability]] in which a displacement  is made from a [[steady state]] under the assumption that only the [[parcel]] or parcels displaced  are affected, the [[environment]] remaining unchanged.</div><br/> <div class="paragraph">Although this method has been applied to various problems (e.g., [[inertial instability]]), its most  familiar context is with vertical displacements from [[hydrostatic equilibrium]], in which the parcel  displaced is assumed to undergo [[adiabatic temperature changes]], and the [[buoyant force]] resulting  from its contrast with the unchanged environment leads to the criterion for [[stability]], &#x003b3; &lt; &#x00393;, where  &#x003b3; is the [[lapse rate]] of [[virtual temperature]] with height and &#x00393; is the [[dry-]] or [[saturation-adiabatic  lapse rate]], according to the condition of the parcel. <br/>''Compare'' [[slice method]].</div><br/> </div>
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<div class="definition"><div class="short_definition">(''Also called'' path method.) A method of testing for [[instability]] in which a displacement  is made from a [[steady state]] under the assumption that only the [[parcel]] or parcels displaced  are affected, the [[environment]] remaining unchanged.</div><br/> <div class="paragraph">Although this method has been applied to various problems (e.g., [[inertial instability]]), its most  familiar context is with vertical displacements from [[hydrostatic equilibrium]], in which the parcel  displaced is assumed to undergo [[adiabatic temperature changes]], and the [[buoyant force]] resulting  from its contrast with the unchanged environment leads to the criterion for [[stability]], &#x003b3; &lt; &#x00393;, where  &#x003b3; is the [[lapse rate]] of [[virtual temperature]] with height and &#x00393; is the [[dry-]] or [[saturation-adiabatic  lapse rate]], according to the condition of the parcel. <br/>''Compare'' [[slice method]].</div><br/> </div>
 
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Revision as of 15:48, 20 February 2012



parcel method

(Also called path method.) A method of testing for instability in which a displacement is made from a steady state under the assumption that only the parcel or parcels displaced are affected, the environment remaining unchanged.

Although this method has been applied to various problems (e.g., inertial instability), its most familiar context is with vertical displacements from hydrostatic equilibrium, in which the parcel displaced is assumed to undergo adiabatic temperature changes, and the buoyant force resulting from its contrast with the unchanged environment leads to the criterion for stability, γ < Γ, where γ is the lapse rate of virtual temperature with height and Γ is the dry- or saturation-adiabatic lapse rate, according to the condition of the parcel.
Compare slice method.