From 20dffac141f868aa7a57481c92900b59043d0752 Mon Sep 17 00:00:00 2001
From: Zhaoyi Shen <11598433+szy21@users.noreply.github.com>
Date: Sun, 16 Jun 2024 16:08:49 -0700
Subject: [PATCH] limit cos of zenith angle between -1 and 1 in 
 ZenithAngleCalc.jl

---
 Project.toml           | 2 +-
 src/ZenithAngleCalc.jl | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/Project.toml b/Project.toml
index 6b34534..e900cac 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "Insolation"
 uuid = "e98cc03f-d57e-4e3c-b70c-8d51efe9e0d8"
 authors = ["Climate Modeling Alliance"]
-version = "0.9.2"
+version = "0.9.3"
 
 [deps]
 Artifacts = "56f22d72-fd6d-98f1-02f0-08ddc0907c33"
diff --git a/src/ZenithAngleCalc.jl b/src/ZenithAngleCalc.jl
index 850a604..cd82adf 100644
--- a/src/ZenithAngleCalc.jl
+++ b/src/ZenithAngleCalc.jl
@@ -122,7 +122,10 @@ function instantaneous_zenith_angle(
     η = mod(η_UTC + λ, FT(2π))
 
     # zenith angle, radians
-    θ = mod(acos(cos(ϕ) * cos(δ) * cos(η) + sin(ϕ) * sin(δ)), FT(2π))
+    θ = mod(
+        acos(max(FT(-1), min(FT(1), cos(ϕ) * cos(δ) * cos(η) + sin(ϕ) * sin(δ)))), 
+        FT(2π),
+    )
 
     # solar azimuth angle, ζ = 0 when due E and increasing CCW
     # ζ = 3π/2 (due S) when η=0 at local solar noon