From 6734422673b832e2ca4d52afae77c5f4283d6e42 Mon Sep 17 00:00:00 2001
From: fraxle <fraxle@yahoo.co.uk>
Date: Mon, 1 Jun 2026 14:47:17 +0100
Subject: [PATCH] 2.1.1

Physics update
---
 assets/js/physics.js | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/assets/js/physics.js b/assets/js/physics.js
index 8a01f69..363efc6 100644
--- a/assets/js/physics.js
+++ b/assets/js/physics.js
@@ -630,7 +630,12 @@ export function calcTmrt(Ta, dirRad, diffRad, globalRad, solElev) {
 // -------------------------------------------------------------------
 export function utciApprox(Ta, Tmrt, va10, ehPa) {
   const va = Math.max(0.5, Math.min(17, va10));
-  const D_Tmrt = Tmrt - Ta;
+  // Clamp Tmrt-Ta to the polynomial's validated domain. The UTCI fit is only
+  // valid for a mean-radiant offset of -30..+70 -C; on hot urban/concrete
+  // profiles the modelled Tmrt can exceed Ta by more than +70-, where the
+  // polynomial extrapolates and loses accuracy. Clamping keeps the felt
+  // temperature inside the range the coefficients were derived for.
+  const D_Tmrt = Math.max(-30, Math.min(70, Tmrt - Ta));
   const Pa = ehPa / 10;
   const T = Ta, V = va, D = D_Tmrt, P = Pa;
   const T2=T*T, T3=T2*T, T4=T3*T, T5=T4*T, T6=T5*T;