Generalized Lapse Rate Formulas for Use in Entraining CAPE Calculations
Generalized Lapse Rate Formulas for Use in Entraining CAPE Calculations
复制标题
用于进行 CAPE 计算的广义失效率公式
DOI：
10.1175/jas-d-21-0118.1
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发表时间：
2022
影响因子：
3.1
通讯作者：
Chavas, Daniel R.
中科院分区：
文献类型：
--
作者：
Peters, John M.;Mulholland, Jake P.;Chavas, Daniel R.
抬升气团温度直减率公式中的常见假设包括忽略混合、流体静力平衡、一旦形成就移除所有冷凝物（伪绝热）和/或保留所有冷凝物在气团内（绝热）。这些公式通常是从熵守恒出发推导的，当存在非平衡混合相冷凝物时，这会导致误差。为了评估这些假设，一个新的一般直减率公式来自能量守恒的表达式，而不是熵守恒。这个新的公式包括混合的包裹与周围环境，放松流体静力学假设，允许非平衡混合相冷凝，并可以制定为伪绝热或绝热上升。新公式证明了可逆上升的熵守恒。新公式的预测相比，旧的和不太一般的公式。以往公式中的误差来自于流体静力平衡的假设，由于忽略了浮力的能量汇，导致了相当大的暖偏差。预测的上升与夹带使用新的公式，然后比较包裹属性沿着轨迹在大涡模拟。模拟的包裹属性更好地预测公式使用稀释的模拟绝热上升，其中冷凝物被稀释在相同的速率作为其他包裹属性，比稀释的模拟伪绝热上升，其中所有的冷凝物被删除。这些结果表明，CAPE应计算绝热，而不是伪绝热，包裹上升。
Common assumptions in temperature lapse rate formulas for lifted air parcels include neglecting mixing, hydrostatic balance, the removal of all condensate once it forms (pseudoadiabatic), and/or the retention of all condensate within the parcel (adiabatic). These formulas are commonly derived from the conservation of entropy, which leads to errors when nonequilibrium mixed-phase condensate is present. To evaluate these assumptions, a new general lapse rate formula is derived from an expression for energy conservation, rather than entropy conservation. This new formula incorporates mixing of the parcel with its surroundings, relaxes the hydrostatic assumption, allows for nonequilibrium mixed-phase condensate, and can be formulated for pseudoadiabatic or adiabatic ascent. The new formula is shown to exactly conserve entropy for reversible ascent. Predictions by the new formula are compared to that of older and less general formulas. The errors in previous formulas arise from the assumption of hydrostatic balance, which results in considerable warm biases due to the neglect of the energy sink from buoyancy. Predictions of ascent with entrainment using the new formula are then compared to parcel properties along trajectories in large eddy simulations. Simulated parcel properties are better predicted by the formula using a diluted analogy to adiabatic ascent, wherein condensate is diluted at the same rate as other parcel properties, than by the diluted analogy to pseudoadiabatic ascent, wherein all condensate is removed. These results suggest that CAPE should be computed with adiabatic, rather than pseudoadiabatic, parcel ascent.