Upwelling Index Calculator

Both inputs this calculator accepts are restricted to physically upwelling-favorable values -- Wind Stress only accepts positive alongshore stress, and Latitude only accepts 5° to 70° in a convention where the resulting Ekman transport always points offshore. The underlying math for downwelling exists inside the formula, but this calculator's input ranges never reach it, so every combination of allowed inputs produces a positive Upwelling Index and the "Upwelling" label.

Wind Stress, by the widest margin among the three inputs -- across its full 0.001 to 1 Pa range it swings Upwelling Index roughly a thousandfold, more than Latitude's roughly tenfold swing across 5° to 70° and far more than Water Density's sub-2% influence across its realistic seawater range. Stronger alongshore wind is the dominant driver of how much water gets pushed offshore.

The Coriolis Parameter grows with sin(latitude), and Ekman Transport is inversely proportional to it, so the same Wind Stress produces progressively weaker offshore transport at higher latitudes, where Earth's rotation more strongly deflects the flow. This is part of why classic upwelling systems like the California and Peru currents sit in the mid-latitude range this calculator covers, rather than near the poles.

No -- Ekman Layer Depth depends only on Latitude, through the Coriolis Parameter, and a fixed representative eddy viscosity value. Wind Stress and Water Density both move Upwelling Index and Ekman Transport, but they leave Ekman Layer Depth completely unchanged in this calculator's formula.

Strength is a simple magnitude bucket applied to Upwelling Index -- None below 10, Weak from 10 to 50, Moderate from 50 to 100, Strong from 100 to 200, and Very Strong at 200 or above, all in m³/s per 100 m of coastline. These thresholds are a convenience scale built into this calculator rather than a formal oceanographic standard, so use them to compare scenarios relative to each other rather than as an official classification.