什么是 Dynamic method？

The dynamic method computes the geostrophic current between two hydrographic stations from the density measured at both, relative to a reference pressure level where the current is taken to be zero or known. The geopotential distance between two pressure surfaces, $\int\alpha\,\mathrm dp$ with $\alpha = 1/\rho$ the specific volume, is split into a standard part, the same at both stations, and the geopotential anomaly $\Delta\Phi$; the current at the upper surface, at right angles to the line between stations $A$ and $B$, a distance $L$ apart, is