Fog stability index calculator

Input contract, response shape, and error behaviour

Example: eight degrees at the surface, a dew point of seven, and ten degrees at eight hundred fifty hectopascals yields a moisture term of two, a stability term of negative four, and an index of negative two, which is high risk under a surface inversion. POST a JSON object with three required finite numbers, all in degrees Celsius. surface_temperature is the screen-level dry-bulb air temperature T; aliases t_surface, ts, t_sfc, temperature, temp_surface, and surface_temp are accepted. dew_point is the surface dew-point temperature Td; aliases td, dewpoint, surface_dew_point, dew_point_temperature, and t_dew are accepted. temperature_850 is the air temperature at the eight-hundred-fifty hectopascal pressure level, the required sounding-level input; aliases t_850, t850, temp_850, temperature_850_hpa, t_850_hpa, and level_temperature_850 are accepted. Each field may arrive as a JSON number or as a numeric string; missing, blank, or non-finite values fail with invalid_input naming the field. If temperature_850 is omitted the message states that the eight-hundred-fifty hectopascal level temperature is missing, because inventing T850 would fabricate the stability term. If dew_point exceeds surface_temperature the request is rejected as unphysical: relative humidity would then exceed one hundred percent. On success the body echoes the rounded surface_temperature, dew_point, and temperature_850, returns dew_point_depression as T minus Td and temperature_difference_850 as T minus T850, reports moisture_term and stability_term as the doubled contributions, and publishes fog_stability_index as their sum. category is high, moderate, or low; category_label restates the radiation-fog band in words; high_threshold is thirty-one and moderate_threshold is fifty-five; unit is celsius. formula and equation reprint FSI equals two times (T minus Td) plus two times (T minus T850) with the substituted numbers, method is fog_stability_index_temperature, and steps walks through both differences, both doubled terms, the sum, and the briefing band for teaching UIs. Failed validation is not billed; successful analytic calls use the published $0.002 base price with no model tokens and no outbound network.

Where a fog stability index calculator earns its keep

Aviation weather offices and flight-school labs need a deterministic oracle that reproduces the temperature-only fog stability index exactly so a briefing slide, a student worksheet, and an automation script never disagree on rounding or on the thirty-one and fifty-five bands. Agricultural frost-and-fog planners use the same two-term score overnight when a nearby sounding already reports screen temperature, dew point, and the eight-hundred-fifty hectopascal temperature, and they want a fail-closed check rather than a guessed upper-air value. Research and grading pipelines that batch thousands of (T, Td, T850) triples need fixed twelve-decimal rounding and a hard missing-level error they can assert in tests. Content sites that rank for fog stability index calculator benefit from a live tool whose free browser path matches the prepaid automation path on the same pure module, without competing for generic dew-point or heat-index queries that other landings already serve. Keep all three temperatures in Celsius, never omit the eight-hundred-fifty hectopascal level, pin fog_stability_index and category in tests, and you get a reproducible radiation-fog score for courses, docs, and edge workers without standing up a sounding library of your own.