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首页> 外文期刊>Journal of Physical Oceanography >Potential Enthalpy: A Conservative Oceanic Variable for Evaluating Heat Content and Heat Fluxes
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Potential Enthalpy: A Conservative Oceanic Variable for Evaluating Heat Content and Heat Fluxes

机译：潜在焓：用于评估热量和热通量的保守海洋变量

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Potential temperature is used in oceanography as though it is a conservative variable like salinity; however, turbulent mixing processes conserve enthalpy and usually destroy potential temperature. This negative production of potential temperature is similar in magnitude to the well-known production of entropy that always occurs during mixing processes. Here it is shown that potential enthalpy―the enthalpy that a water parcel would have if raised adiabatically and without exchange of salt to the sea surface―is more conservative than potential temperature by two orders of magnitude. Furthermore, it is shown that a flux of potential enthalpy can be called "the heat flux" even though potential enthalpy is undefined up to a linear function of salinity. The exchange of heat across the sea surface is identically the flux of potential enthalpy. This same flux is not proportional to the flux of potential temperature because of variations in heat capacity of up to 5%. The geothermal heat flux across the ocean floor is also approximately the flux of potential enthalpy with an error of no more that 0.15%. These results prove that potential enthalpy is the quantity whose advection and diffusion is equivalent to advection and diffusion of "heat" in the ocean. That is, it is proven that to very high accuracy, the first law of thermodynamics in the ocean is the conservation equation of potential enthalpy. It is shown that potential enthalpy is to be preferred over the Bernoulli function. A new temperature variable called "conservative temperature" is advanced that is simply proportional to potential enthalpy. It is shown that present ocean models contain typical errors of 0. 1℃ and maximum errors of 1.4℃ in their temperature because of the neglect of the nonconservative production of potential temperature. The meridional flux of heat through oceanic sections found using this conservative approach is different by up to 0.4% from that calculated by the approach used in present ocean models in which the nonconservative nature of potential temperature is ignored and the specific heat at the sea surface is assumed to be constant. An alternative approach that has been recommended and is often used with observed section data, namely, calculating the meridional heat flux using the specific heat (at zero pressure) and potential temperature, rests on an incorrect theoretical foundation, and this estimate of heat flux is actually less accurate than simply using the flux of potential temperature with a constant heat capacity.
机译：潜在温度在海洋学中被使用，就好像它是盐度之类的保守变量一样。但是，湍流混合过程会保留焓并通常会破坏潜在的温度。这种潜在的负温度产生在数量上类似于在混合过程中总是发生的众所周知的熵产生。此处显示了潜在的焓（如果在不加盐的情况下绝热地上升到海面，水包裹将产生的焓）比潜在的温度保守两个数量级。此外，显示出即使焓焓直到盐度的线性函数都未定义，势焓的通量也可以称为“热通量”。整个海面的热交换是潜在焓的通量。由于高达5％的热容变化，因此相同的通量与潜在温度的通量不成比例。穿过海床的地热通量也大约是潜在焓的通量，误差不超过0.15％。这些结果证明，潜在的焓是其对流和扩散等于海洋中“热”对流和扩散的量。即，已经证明，以非常高的精度，海洋中热力学的第一定律是潜在焓的守恒方程。结果表明，与伯努利函数相比，潜在的焓更可取。提出了一个新的温度变量，称为“保守温度”，它与潜在的焓成正比。结果表明，由于忽略了潜在温度的非保守性产生，目前的海洋模型在温度上的典型误差为0. 1℃，最大误差为1.4℃。通过这种保守方法发现的通过海洋部分的子午热通量与当前海洋模型所使用的计算方法相差高达0.4％，在当前海洋模型中，忽略了潜在温度的非保守性质，而海面的比热为假定为常数。已推荐并经常与观测剖面数据一起使用的另一种方法，即使用特定热量（在零压力下）和势能温度计算子午热通量，是建立在不正确的理论基础上的，并且这种热通量估算为实际上不如简单地使用具有恒定热容量的潜在温度通量来精确。

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