Interpret saturation limits without hiding the result

Keep the raw calculation visible

At air temperature 10°C and supplied vapor pressure 20 hPa, saturation pressure over liquid water is about 12.27 hPa. The calculated ratio is therefore approximately 163%. The browser retains that value and marks the proposed state as supersaturated. It does not silently replace the answer with 100%.

Supersaturation means vapor pressure exceeds the selected equilibrium saturation value. It is not a mathematical failure of the positive-pressure ratio. Transient supersaturation can occur in physical systems, but the browser does not model its lifetime or how it relaxes through condensation. The proposal is outside the non-supersaturated equilibrium interpretation used for the basic state comparison.

Diagnose the proposed state step by step

Hold vapor pressure at 20 hPa. Capture temperatures 20, 18, 16 and 10°C. The dew point stays near 17.51°C. The first two temperatures lie above that threshold; the latter two lie below and produce raw RH above 100%.

For every capture, record supplied e, calculated e_s and their ratio. State whether the air-temperature marker is above or below the calculated dew point. These are linked checks of one state relation. Agreement between them is useful for detecting arithmetic errors, but it is not several independent pieces of observational evidence.

If the display were clamped to 100% while the inputs remained unchanged, the equation RH = 100e/e_s would no longer explain the shown number. Clamping would conceal how far the proposal exceeds the threshold. A physically updated equilibrium state would require changing vapor amount or other conditions through a specified process, not merely changing the displayed percentage.

Distinguish a threshold from a condensation amount

The difference e − e_s is a pressure difference. It is not directly a mass of liquid water. Calculating a condensed amount would require a defined parcel or control volume, mass accounting and a process model. Temperature can also change when latent heat is released, and the current browser does not solve that coupled problem.

The controls supply a state, not a cooling experiment. Total pressure is fixed at 1000 hPa, and fixed e implies fixed mixing ratio before the saturation limit is crossed. They do not describe a sealed, fixed-volume vessel whose partial pressures automatically evolve with temperature. The user-selected values remain proposals even when they are incompatible with the simpler equilibrium interpretation.

On paper draw a boundary around a hypothetical parcel and list the additional terms a condensation model would need. Include vapor and liquid masses, heat exchange and the constraints on pressure or volume. Leave the quantities unknown rather than inventing a rainfall result from RH alone.

Ask which observations address the claim

A claim about dew on a surface needs information about that surface and surrounding air. A claim about fog requires more than a bulk RH calculation. A claim about precipitation needs cloud and transport processes absent here. A single saturated state does not determine duration, droplet sizes, rain rate or the location of condensation.

Design an observation ledger for one such question. Separate direct readings, sensor uncertainty, calculated dew point and the process inference. If two sensors disagree, retain both readings and investigate calibration, placement and timing instead of forcing a preferred humidity value.

The numerical relation is an approximation over liquid water. Its phase convention matters: this lesson does not replace it with an ice formula or claim to predict frost. The NWS formula reference supplies the saturation, ratio and inverse relations used here; the browser’s diagnostic interpretation remains explicitly bounded. NWS calculation reference.

Report a useful limitation

A defensible conclusion can say that the supplied values produce a supersaturated proposal and name the missing physics. It should not say that supersaturation is universally impossible, that the calculation measured condensation, or that the number predicts tomorrow’s weather.

Save a non-supersaturated case beside a flagged case and explain which input change crossed the threshold. This comparison preserves both the valid arithmetic and the limits of the physical interpretation.

Transfer: audit a clamped display

A proposed state has e = 15 hPa and e_s = 10 hPa. A dashboard reports 100% RH without changing either pressure. What should its raw ratio be, and what does the correction establish?

Check the saturation-evidence transfer

The raw ratio is 100 × 15/10 = 150%. Reporting it with a supersaturation flag preserves the supplied state relation. This identifies a proposal above liquid-water saturation; it does not calculate how much condenses, how rapidly it occurs or whether precipitation reaches the ground.