这是一个好问题,答案是,空气动力阻力* *不是* *定义反向。而是,定义在一个上下文通常是误解。在你的问题,你说空气动力阻力基本上是多少的粗糙度表面空气流动放缓下来。这种说法是不正确的,它似乎源于上下文的误解。由De Groot专著(1963)还表明,分子转移过程所表现出的一般形式类似于电路@Deditos '答:$ $通量= \ dfrac{力}{阻力}$ $这也是对海气界面和其他通用油接口。通量是一个量的转移(动量,焓、质量等)通过接口和相关的边界层(说,空气、水、树冠、土壤,等等)。电路类比,迫使电位梯度的特点,耐逆的导电性。重要的一点,就是抵抗* *不是* *接口到空气动力流阻力——我们直观地想象摩擦或压力。事实上,* *强迫* *的接口。的势头,这意味着同等的迫使,高电阻收益率低通量。 Thus, lower resistance translates to rougher surface. This is why forest has lower resistance values than grass or open ocean. *Example: Given equal forcing, rougher surface results in higher stress compared to smoother surface. It can be said that the rougher surface is "more permitting", or "less resistant" of momentum flux.* In the electric circuit analogy, *Flux*, *Force* and *Resistance* are symbolic, conceptual entities. Force is not necessarily in $N$, and may be a temperature or humidity gradient like it is given on slide 16 in the presentation you linked. Resistance may thus take different formulations. Note that nowadays, in both modeling and theory, we often use exchange coefficients to characterize momentum ($C_{D}$) and enthalpy ($C_H$, $C_E$) fluxes through the interface, which act as conductivity and not resistance. For example, in case of momentum: $$ \boldsymbol{\tau} = \rho C_{D}|\mathbf{U}|\mathbf{U} $$ where $\boldsymbol{\tau}$ ($N/m^{2}$) is vertical flux of horizontal momentum (wind stress), $\rho$ ($kg/m^{3}$) is air density and $\mathbf{U}$ ($m/s$) is wind vector at some reference height above the surface. $C_{D}$ (non-dimensional) has different values depending on the surface properties. In that particular presentation that you linked in your question, it is not clear to me why resistance $r_a$ has units of $s\ m^{-1}$. For sensible and latent heat flux ($W/m^{2}$) formulations on slide 16, the units don't quite work out, but it is possible that the equations shown were more illustrative than exact. Because bulk flux formulae are most often based on theoretical, empirical and dimensional grounds, $r_{a}$ can be defined in various dimensions (units) depending on the bulk flux formulation. Reference: De Groot, S. R. Thermodynamics of Irreversible Processes. North Holland Publishing Co., 1963.