1.6.0
Fix and enhance the concrete calculation Minify the about.css file
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fraxle
+181
-16
@@ -6,7 +6,9 @@
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//
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// Exports (in order of appearance):
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// SIGMA, EPSILON_P, A_K, ALBEDO_GRASS, ALBEDO_CONCRETE (radiation constants)
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// calcConcreteTemp(Ta, globalRad, windSpeed) urban surface temp
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// LAG_HOURS_CONCRETE slab thermal time constant
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// calcConcreteTemp(Ta, globalRad, windSpeed, ...) urban surface temp (instantaneous target)
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// calcConcreteTempPass(arrays...) thermal-lag pass over full hourly arrays
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// calcIndoorTempPass(TaArr, globArr, elevArr, buildingType) passive indoor temp
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// calcManagedIndoorTempPass(TaArr, globArr, elevArr, buildingType) managed indoor temp
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// calcVehicleInteriorTemp(Ta, globalRad, solElev, vehicleType, ventilated)
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@@ -42,26 +44,189 @@ export const ALBEDO_CONCRETE = 0.30;
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// CONCRETE SURFACE TEMPERATURE (Urban profile)
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// -------------------------------------------------------------------
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// Estimates the surface temperature of exposed concrete using a
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// simplified energy-balance approach:
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// - Absorbed solar = globalRad - (1 - albedo)
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// - No latent heat (no evaporation - concrete is dry)
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// - Convective loss to air proportional to wind speed
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// - Result is clamped to a physically plausible range
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// multi-factor energy-balance approach. Six physical effects are
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// modelled beyond the basic solar-gain / convective-loss pair:
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//
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// This is what matters for contact heat stress in cities - the UTCI
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// standard uses grass, which runs ~5-15 -C cooler than urban concrete
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// on a sunny day because grass sweats (transpires).
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// 1. SUN ANGLE CORRECTION
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// At low solar elevation the sun hits the surface obliquely,
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// spreading energy over a larger area. A sin(elev) factor
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// reduces absorbed solar proportionally. Clamped at a 5-deg
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// minimum so the result stays finite near the horizon.
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//
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// 2. CLOUD TYPE TRANSMITTANCE
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// Cloud cover category drives a transmittance multiplier.
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// Low cloud (stratus) is far more opaque than high cirrus:
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// clear 1.00 - full beam reaches the surface
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// wispy 0.92 - cirrus barely attenuates
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// scattered 0.72 - broken cumulus, significant blocking
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// overcast 0.28 - thick stratus, mostly diffuse remains
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// The raw effectiveRad already dims with cloud cover from the
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// API, but this adds the qualitative distinction between cloud
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// types that the single radiation number does not capture.
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//
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// 3. UV CLARITY FACTOR
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// UV index is a proxy for atmospheric clarity beyond cloud cover -
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// aerosols, haze, and humidity all reduce it. A UV of 8+ indicates
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// a very clean, dry atmosphere with maximum direct-beam intensity.
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// Normalised to a 0.85-1.00 range so it modulates rather than
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// dominates. No UV data defaults to neutral (1.0).
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//
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// 4. EVAPORATIVE COOLING FROM SOIL MOISTURE
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// Wet concrete loses heat via evaporation. Soil moisture at 0-1cm
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// is used as a proxy for surface wetness (0 = bone dry, 1 = fully
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// saturated). A saturated surface loses up to ~8-C relative to
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// the dry case - consistent with published wet-pavement studies.
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//
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// 5. RAIN-WET SURFACE
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// Active precipitation forces surface wetness regardless of soil
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// moisture data. Above 0.5 mm/h the surface is considered fully
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// wet and the maximum evaporative penalty applies.
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//
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// 6. SNOW COVER
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// Snow on concrete insulates the slab from solar gain AND strongly
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// reflects incoming radiation (albedo ~0.80 for fresh snow vs 0.30
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// for bare concrete). When snowfall is active or lying snow is
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// implied (snow > 0), absorbed radiation is cut by 85% and a small
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// insulating offset is applied instead.
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//
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// Colour thresholds (same as before - surface contact risk):
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// < Ta - should not occur (clamped)
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// Ta - 45 -C - warm but bearable contact
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// 45 - 60 -C - pain threshold for bare skin contact
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// > 60 -C - burns on contact (relevant for paws / bare feet)
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// -------------------------------------------------------------------
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export function calcConcreteTemp(Ta, globalRad, windSpeed) {
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export function calcConcreteTemp(Ta, globalRad, windSpeed, solElev, uv, cloudCat, soilM, precip, snow) {
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if (globalRad == null || Ta == null) return null;
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const absorbed = globalRad * (1 - ALBEDO_CONCRETE); // W/m-
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// Convective heat transfer coefficient: ~10 W/m-K still air, rises with wind
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// (10 reflects realistic natural convection; 5 was too low and ran too hot)
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// -- 6. Snow short-circuit --------------------------------------------
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// Snow-covered concrete behaves like a white reflective insulator.
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// Absorbed solar collapses; slab temp stays close to air temp.
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if (snow != null && snow > 0) {
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const snowAbsorbed = globalRad * (1 - 0.80); // fresh snow albedo ~0.80
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const hcSnow = 10 + 4.5 * Math.sqrt(Math.max(windSpeed || 0, 0));
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const Ts = Ta + snowAbsorbed / hcSnow;
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return Math.max(Ta - 1, Math.min(Ts, 40)); // snow-covered slab rarely exceeds 40-C
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}
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// -- 1. Sun angle correction ------------------------------------------
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// Low-angle sun spreads energy across a larger surface area.
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// sin(elev) = 1.0 at 90-deg (overhead), ~0.17 at 10-deg (grazing).
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// Default to sin(45-deg) ~0.71 when elevation is unknown.
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const elevDeg = (solElev != null) ? Math.max(5, solElev) : 45;
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const angleCorrection = Math.sin(elevDeg * Math.PI / 180);
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// -- 2. Cloud type transmittance --------------------------------------
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// Modulates beam quality beyond what raw radiation already captures.
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const cloudTransmit = cloudCat === 'clear' ? 1.00
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: cloudCat === 'wispy' ? 0.92
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: cloudCat === 'scattered' ? 0.72
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: /* overcast */ 0.28;
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// -- 3. UV clarity factor --------------------------------------------
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// UV index as atmospheric-clarity proxy. Scaled to 0.85-1.00 range.
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// uv=0 (night or heavy cloud) - neutral 1.0 (no adjustment needed,
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// radiation already near-zero). uv=8+ - max clarity bonus of 1.0.
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const uvClarity = (uv && uv > 0)
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? 0.85 + 0.15 * Math.min(1, uv / 8)
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: 1.0;
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// -- Absorbed solar with all modifiers --------------------------------
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const absorbed = globalRad * (1 - ALBEDO_CONCRETE)
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* angleCorrection
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* cloudTransmit
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* uvClarity;
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// -- Convective loss --------------------------------------------------
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const hc = 10 + 4.5 * Math.sqrt(Math.max(windSpeed || 0, 0));
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// Surface temp: Ta + solar gain / convective loss
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// -- Dry surface temperature ------------------------------------------
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const Ts = Ta + absorbed / hc;
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// Clamp: can't be cooler than air, cap at 85 -C (melting asphalt territory)
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return Math.max(Ta, Math.min(Ts, 85));
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// -- 4 + 5. Evaporative cooling ---------------------------------------
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// Rain-wet surface overrides soil moisture - surface is fully saturated.
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const surfaceWet = (precip != null && precip >= 0.5)
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? 1.0
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: Math.max(0, Math.min(1, soilM ?? 0));
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// Max evaporative delta ~8-C at full saturation (published wet-pavement data).
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const evapCooling = surfaceWet * 8;
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const TsCooled = Ts - evapCooling;
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// -- Final clamp: no cooler than air, no hotter than 85-C -------------
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return Math.max(Ta, Math.min(TsCooled, 85));
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}
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// -------------------------------------------------------------------
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// CONCRETE THERMAL LAG TIME CONSTANT
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// -------------------------------------------------------------------
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// A standard urban pavement slab (~100 mm thick, exposed top surface,
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// air below via sub-base) has moderate thermal mass. Real-world
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// measurement studies put the e-folding time constant at 1.5-2 h for
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// this geometry - we use 1.5 h as representative of the thin end of
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// typical footway construction (block paving, tarmac-over-hardcore).
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//
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// If this ever needs to vary by surface type, pull it into a
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// SURFACE_TYPES preset object mirroring BUILDING_TYPES in utils.js.
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// For now a single named constant keeps the intent obvious.
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// -------------------------------------------------------------------
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export const LAG_HOURS_CONCRETE = 1.5;
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// -------------------------------------------------------------------
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// CONCRETE SURFACE TEMPERATURE - THERMAL LAG PASS
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// -------------------------------------------------------------------
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// Wraps calcConcreteTemp in the same exponential-blending pattern used
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// by calcIndoorTempPass. Instead of snapping to the instantaneous
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// target each hour, the slab temperature blends toward it at a rate
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// controlled by LAG_HOURS_CONCRETE.
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//
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// Effect in practice:
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// - A slab baking at 55-C when cloud rolls in will still read ~48-C
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// an hour later and ~44-C two hours later - not instantly 22-C.
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// - A cold slab at dawn takes 2-3 hours of strong sun to fully heat.
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// - Post-rain cool-down persists into the next hour even if it stops.
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//
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// Call AFTER building hourlyRows (same pattern as calcIndoorTempPass).
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// Returns a Float64-like plain Array of concrete temps, one per hour.
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//
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// Arguments are parallel arrays (one value per forecast hour):
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// TaArr - air temperature (-C)
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// radArr - effectiveRad (dir + dif*0.2) (W/m-)
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// vaArr - wind speed (m/s)
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// elevArr - solar elevation (degrees)
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// uvArr - UV index
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// cloudCatArr - cloud category string
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// soilMArr - soil moisture 0-1cm (0-1 fraction)
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// precipArr - precipitation (mm/h)
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// snowArr - snowfall (cm/h)
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// -------------------------------------------------------------------
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export function calcConcreteTempPass(TaArr, radArr, vaArr, elevArr, uvArr, cloudCatArr, soilMArr, precipArr, snowArr) {
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const n = TaArr.length;
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const result = new Array(n);
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const alpha = 1 - Math.exp(-1 / LAG_HOURS_CONCRETE);
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// Seed from the first hours instantaneous value so we start somewhere
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// physically reasonable rather than zero.
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let Tc = calcConcreteTemp(
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TaArr[0], radArr[0], vaArr[0],
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elevArr[0], uvArr[0], cloudCatArr[0],
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soilMArr[0], precipArr[0], snowArr[0]
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) ?? TaArr[0];
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for (let i = 0; i < n; i++) {
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const target = calcConcreteTemp(
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TaArr[i], radArr[i], vaArr[i],
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elevArr[i], uvArr[i], cloudCatArr[i],
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soilMArr[i], precipArr[i], snowArr[i]
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) ?? TaArr[i];
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// Blend slab temp toward this hours target.
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Tc = Tc + alpha * (target - Tc);
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// Slab cannot be cooler than air (no active cooling mechanism).
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result[i] = Math.max(TaArr[i], Tc);
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}
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return result;
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}
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// -------------------------------------------------------------------
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