215 lines
11 KiB
JavaScript
215 lines
11 KiB
JavaScript
// ════════════════════════════════════════════════════════════════════════
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// physics.js — Physical constants and meteorological calculations.
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//
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// Exports:
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// SIGMA, EPSILON_P, A_K, ALBEDO_GRASS (radiation constants)
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// vaporPressureHpa(Ta, RH) Magnus formula → hPa
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// solarElevationDeg(lat, lon, dateUTC) NOAA simplified solar position
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// calcTmrt(Ta, dirRad, diffRad, globalRad, solElev) Mean radiant temp
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// utciApprox(Ta, Tmrt, va10, ehPa) Bröde et al. 2012 polynomial
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//
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// Nothing in here should need editing unless the underlying science
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// changes. All numbers are peer-reviewed constants or coefficients.
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// ════════════════════════════════════════════════════════════════════════
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// ═══════════════════════════════════════════════════════════════════
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// PHYSICAL CONSTANTS
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// ───────────────────────────────────────────────────────────────────
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// These are real-world physics values — don't change them unless you
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// have a peer-reviewed reason. They're used by calcTmrt() below to
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// work out how much heat your skin actually absorbs from the sun.
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// SIGMA — Stefan–Boltzmann constant (radiates heat)
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// EPSILON_P — emissivity of human skin (~0.97)
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// A_K — short-wave absorption coefficient for clothing
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// ALBEDO_GRASS — how much sun grass reflects back at you (23%)
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// ═══════════════════════════════════════════════════════════════════
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export const SIGMA = 5.670374419e-8;
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export const EPSILON_P = 0.97;
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export const A_K = 0.7;
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export const ALBEDO_GRASS = 0.23;
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// Vapour pressure (Magnus → hPa)
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export function vaporPressureHpa(Ta, RH) {
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const es = 6.105 * Math.exp((17.27 * Ta) / (237.7 + Ta));
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return es * (RH / 100);
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}
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// Solar elevation (NOAA simplified, degrees)
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export function solarElevationDeg(lat, lon, dateUTC) {
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const start = Date.UTC(dateUTC.getUTCFullYear(), 0, 0);
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const diff = dateUTC - start;
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const DOY = Math.floor(diff / 86400000);
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const hourUTC =
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dateUTC.getUTCHours() +
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dateUTC.getUTCMinutes() / 60 +
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dateUTC.getUTCSeconds() / 3600;
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const gamma = ((2 * Math.PI) / 365) * (DOY - 1 + (hourUTC - 12) / 24);
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const eqtime =
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229.18 *
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(0.000075 +
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0.001868 * Math.cos(gamma) -
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0.032077 * Math.sin(gamma) -
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0.014615 * Math.cos(2 * gamma) -
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0.040849 * Math.sin(2 * gamma));
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const decl =
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0.006918 -
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0.399912 * Math.cos(gamma) +
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0.070257 * Math.sin(gamma) -
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0.006758 * Math.cos(2 * gamma) +
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0.000907 * Math.sin(2 * gamma) -
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0.002697 * Math.cos(3 * gamma) +
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0.00148 * Math.sin(3 * gamma);
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const timeOffset = eqtime + 4 * lon;
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const tst = hourUTC * 60 + timeOffset;
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const ha = (((tst / 4) - 180) * Math.PI) / 180;
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const latRad = (lat * Math.PI) / 180;
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const cosZenith =
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Math.sin(latRad) * Math.sin(decl) +
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Math.cos(latRad) * Math.cos(decl) * Math.cos(ha);
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const zenith = Math.acos(Math.max(-1, Math.min(1, cosZenith)));
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return (Math.PI / 2 - zenith) * (180 / Math.PI);
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}
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// Mean radiant temperature
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export function calcTmrt(Ta, dirRad, diffRad, globalRad, solElev) {
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const TaK = Ta + 273.15;
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let fp = 0;
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if (solElev > 0) {
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const h2 = solElev;
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fp = 0.308 * Math.cos((Math.PI / 180) * h2 * (0.998 - (h2 * h2) / 50000));
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}
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let DNI = 0;
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if (solElev > 1) {
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DNI = dirRad / Math.sin((solElev * Math.PI) / 180);
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DNI = Math.min(DNI, 1100);
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}
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const Sshort = A_K * (fp * DNI + 0.5 * diffRad + 0.5 * ALBEDO_GRASS * globalRad);
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const Slong = EPSILON_P * SIGMA * Math.pow(TaK, 4);
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const TmrtK = Math.pow((Sshort + Slong) / (EPSILON_P * SIGMA), 0.25);
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return TmrtK - 273.15;
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}
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// ═══════════════════════════════════════════════════════════════════
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// UTCI POLYNOMIAL — DO NOT EDIT (or be VERY careful if you do)
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// ───────────────────────────────────────────────────────────────────
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// This is the official 210-term Bröde et al. (2012) approximation.
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// It takes air temp, mean radiant temp, wind, and humidity and returns
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// the "felt" temperature. Every number is a peer-reviewed coefficient.
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// Scroll past it — there's nothing here you'll want to change.
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// ═══════════════════════════════════════════════════════════════════
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export function utciApprox(Ta, Tmrt, va10, ehPa) {
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const va = Math.max(0.5, Math.min(17, va10));
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const D_Tmrt = Tmrt - Ta;
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const Pa = ehPa / 10;
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const T = Ta, V = va, D = D_Tmrt, P = Pa;
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const T2=T*T, T3=T2*T, T4=T3*T, T5=T4*T, T6=T5*T;
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const V2=V*V, V3=V2*V, V4=V3*V, V5=V4*V, V6=V5*V;
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const D2=D*D, D3=D2*D, D4=D3*D, D5=D4*D, D6=D5*D;
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const P2=P*P, P3=P2*P, P4=P3*P, P5=P4*P, P6=P5*P;
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return T +
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6.07562052e-1 +
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-2.27712343e-2 * T + 8.06470249e-4 * T2 + -1.54271372e-4 * T3 +
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-3.24651735e-6 * T4 + 7.32602852e-8 * T5 + 1.35959073e-9 * T6 +
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-2.25836520e0 * V + 8.80326035e-2 * T*V + 2.16844454e-3 * T2*V +
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-1.53347087e-5 * T3*V + -5.72983704e-7 * T4*V + -2.55090145e-9 * T5*V +
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-7.51269505e-1 * V2 + -4.08350271e-3 * T*V2 + -5.21670675e-5 * T2*V2 +
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1.94544667e-6 * T3*V2 + 1.14099531e-8 * T4*V2 +
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1.58137256e-1 * V3 + -6.57263143e-5 * T*V3 + 2.22697524e-7 * T2*V3 +
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-4.16117031e-8 * T3*V3 +
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-1.27762753e-2 * V4 + 9.66891875e-6 * T*V4 + 2.52785852e-9 * T2*V4 +
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4.56306672e-4 * V5 + -1.74202546e-7 * T*V5 +
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-5.91491269e-6 * V6 +
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3.98374029e-1 * D + 1.83945314e-4 * T*D + -1.73754510e-4 * T2*D +
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-7.60781159e-7 * T3*D + 3.77830287e-8 * T4*D + 5.43079673e-10 * T5*D +
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-2.00518269e-2 * V*D + 8.92859837e-4 * T*V*D + 3.45433048e-6 * T2*V*D +
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-3.77925774e-7 * T3*V*D + -1.69699377e-9 * T4*V*D +
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1.69992415e-4 * V2*D + -4.99204314e-5 * T*V2*D + 2.47417178e-7 * T2*V2*D +
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1.07596466e-8 * T3*V2*D +
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8.49242932e-5 * V3*D + 1.35191328e-6 * T*V3*D + -6.21531254e-9 * T2*V3*D +
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-4.99410301e-6 * V4*D + -1.89489258e-8 * T*V4*D +
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8.15300114e-8 * V5*D +
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7.55043090e-4 * D2 + -5.65095215e-5 * T*D2 + -4.52166564e-7 * T2*D2 +
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2.46688878e-8 * T3*D2 + 2.42674348e-10 * T4*D2 +
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1.54547250e-4 * V*D2 + 5.24110970e-6 * T*V*D2 + -8.75874982e-8 * T2*V*D2 +
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-1.50743064e-9 * T3*V*D2 +
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-1.56236307e-5 * V2*D2 + -1.33895614e-7 * T*V2*D2 + 2.49709824e-9 * T2*V2*D2 +
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6.51711721e-7 * V3*D2 + 1.94960053e-9 * T*V3*D2 +
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-1.00361113e-8 * V4*D2 +
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-1.21206673e-5 * D3 + -2.18203660e-7 * T*D3 + 7.51269482e-9 * T2*D3 +
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9.79063848e-11 * T3*D3 +
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1.25006734e-6 * V*D3 + -1.81584736e-9 * T*V*D3 + -3.52197671e-10 * T2*V*D3 +
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-3.36514630e-8 * V2*D3 + 1.35908359e-10 * T*V2*D3 +
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4.17032620e-10 * V3*D3 +
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-1.30369025e-9 * D4 + 4.13908461e-10 * T*D4 + 9.22652254e-12 * T2*D4 +
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-5.08220384e-9 * V*D4 + -2.24730961e-11 * T*V*D4 +
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1.17139133e-10 * V2*D4 +
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6.62154879e-10 * D5 + 4.03863260e-13 * T*D5 + 1.95087203e-12 * V*D5 +
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-4.73602469e-12 * D6 +
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5.12733497e0 * P + -3.12788561e-1 * T*P + -1.96701861e-2 * T2*P +
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9.99690870e-4 * T3*P + 9.51738512e-6 * T4*P + -4.66426341e-7 * T5*P +
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5.48050612e-1 * V*P + -3.30552823e-3 * T*V*P + -1.64119440e-3 * T2*V*P +
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-5.16670694e-6 * T3*V*P + 9.52692432e-7 * T4*V*P +
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-4.29223622e-2 * V2*P + 5.00845667e-3 * T*V2*P + 1.00601257e-6 * T2*V2*P +
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-1.81748644e-6 * T3*V2*P +
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-1.25813502e-3 * V3*P + -1.79330391e-4 * T*V3*P + 2.34994441e-6 * T2*V3*P +
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1.29735808e-4 * V4*P + 1.29064870e-6 * T*V4*P +
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-2.28558686e-6 * V5*P +
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-3.69476348e-2 * D*P + 1.62325322e-3 * T*D*P + -3.14279680e-5 * T2*D*P +
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2.59835559e-6 * T3*D*P + -4.77136523e-8 * T4*D*P +
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8.64203390e-3 * V*D*P + -6.87405181e-4 * T*V*D*P + -9.13863872e-6 * T2*V*D*P +
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5.15916806e-7 * T3*V*D*P +
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-3.59217476e-5 * V2*D*P + 3.28696511e-5 * T*V2*D*P + -7.10542454e-7 * T2*V2*D*P +
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-1.24382300e-5 * V3*D*P + -7.38584400e-9 * T*V3*D*P +
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2.20609296e-7 * V4*D*P +
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-7.32469180e-4 * D2*P + -1.87381964e-5 * T*D2*P + 4.80925239e-6 * T2*D2*P +
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-8.75492040e-8 * T3*D2*P +
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2.77862930e-5 * V*D2*P + -5.06004592e-6 * T*V*D2*P + 1.14325367e-7 * T2*V*D2*P +
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2.53016723e-6 * V2*D2*P + -1.72857035e-8 * T*V2*D2*P +
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-3.95079398e-8 * V3*D2*P +
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-3.59413173e-7 * D3*P + 7.04388046e-7 * T*D3*P + -1.89309167e-8 * T2*D3*P +
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-4.79768731e-7 * V*D3*P + 7.96079978e-9 * T*V*D3*P +
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1.62897058e-9 * V2*D3*P +
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3.94367674e-8 * D4*P + -1.18566247e-9 * T*D4*P +
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3.34678041e-10 * V*D4*P +
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-1.15606447e-10 * D5*P +
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-2.80626406e0 * P2 + 5.48712484e-1 * T*P2 + -3.99428410e-3 * T2*P2 +
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-9.54009191e-4 * T3*P2 + 1.93090978e-5 * T4*P2 +
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-3.08806365e-1 * V*P2 + 1.16952364e-2 * T*V*P2 + 4.95271903e-4 * T2*V*P2 +
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-1.90710882e-5 * T3*V*P2 +
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2.10787756e-3 * V2*P2 + -6.98445738e-4 * T*V2*P2 + 2.30109073e-5 * T2*V2*P2 +
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4.17856590e-4 * V3*P2 + -1.27043871e-5 * T*V3*P2 +
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-3.04620472e-6 * V4*P2 +
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5.14507424e-2 * D*P2 + -4.32510997e-3 * T*D*P2 + 8.99281156e-5 * T2*D*P2 +
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-7.14663943e-7 * T3*D*P2 +
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-2.66016305e-4 * V*D*P2 + 2.63789586e-4 * T*V*D*P2 + -7.01199003e-6 * T2*V*D*P2 +
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-1.06823306e-4 * V2*D*P2 + 3.61341136e-6 * T*V2*D*P2 +
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2.29748967e-7 * V3*D*P2 +
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3.04788893e-4 * D2*P2 + -6.42070836e-5 * T*D2*P2 + 1.16257971e-6 * T2*D2*P2 +
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7.68023384e-6 * V*D2*P2 + -5.47446896e-7 * T*V*D2*P2 +
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-3.59937910e-8 * V2*D2*P2 +
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-4.36497725e-6 * D3*P2 + 1.68737969e-7 * T*D3*P2 +
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2.67489271e-8 * V*D3*P2 +
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3.23926897e-9 * D4*P2 +
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-3.53874123e-2 * P3 + -2.21201190e-1 * T*P3 + 1.55126038e-2 * T2*P3 +
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-2.63917279e-4 * T3*P3 +
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4.53433455e-2 * V*P3 + -4.32943862e-3 * T*V*P3 + 1.45389826e-4 * T2*V*P3 +
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2.17508610e-4 * V2*P3 + -6.66724702e-5 * T*V2*P3 +
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3.33217140e-5 * V3*P3 +
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-2.26921615e-3 * D*P3 + 3.80261982e-4 * T*D*P3 + -5.45314314e-9 * T2*D*P3 +
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-7.96355448e-4 * V*D*P3 + 2.53458034e-5 * T*V*D*P3 +
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-6.31223658e-6 * V2*D*P3 +
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3.02122035e-4 * D2*P3 + -4.77403547e-6 * T*D2*P3 +
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1.73825715e-6 * V*D2*P3 +
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-4.09087898e-7 * D3*P3 +
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6.14155345e-1 * P4 + -6.16755931e-2 * T*P4 + 1.33374846e-3 * T2*P4 +
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3.55375387e-3 * V*P4 + -5.13027851e-4 * T*V*P4 +
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1.02449757e-4 * V2*P4 +
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-1.48526421e-3 * D*P4 + -4.11469183e-5 * T*D*P4 +
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-6.80434415e-6 * V*D*P4 +
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-9.77675906e-6 * D2*P4 +
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8.82773108e-2 * P5 + -3.01859306e-3 * T*P5 +
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1.04452989e-3 * V*P5 +
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2.47090539e-4 * D*P5 +
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1.48348065e-3 * P6;
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}
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