Clamp in ZonalWind to [0, 1] for sqrt (#649)

* clamp in ZonalWind to [0, 1] for sqrt

* update changelog

* Test initialize + time step for uncommon resolutions

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Bug: ZonalWind had sqrt of negative for uncommon resolutions [#649](https://github.com/SpeedyWeather/SpeedyWeather.jl/pull/649)
 - Spectral Gradients are now differentiable, with correctness check in extended CI [#638](https://github.com/SpeedyWeather/SpeedyWeather.jl/pull/638)
 - Tracer advection [#579](https://github.com/SpeedyWeather/SpeedyWeather.jl/pull/579)
 - Buildkite CI with dummy pipeline [#646](https://github.com/SpeedyWeather/SpeedyWeather.jl/pull/646)

src/dynamics/initial_conditions.jl

@@ -289,7 +289,7 @@ function initialize!(   progn::PrognosticVariables{NF},
             R = radius*perturb_radius # spatial extent of perturbation
 
             # great circle distance to perturbation
-            X = sinφc*sinφ + cosφc*cosφ*cosd(λij-λc)
+            X = clamp(sinφc*sinφ + cosφc*cosφ*cosd(λij-λc), 0, 1)
             X_norm = 1/sqrt(1-X^2)
             r = radius*acos(X)
             exp_decay = exp(-(r/R)^2)

test/resolutions.jl

@@ -0,0 +1,9 @@
+@testset "Single time step at uncommon resolutions" begin
+    @testset for trunc in rand(15:200, 10)
+        spectral_grid = SpectralGrid(; trunc, Grid=FullClenshawGrid)
+        model = PrimitiveWetModel(spectral_grid)
+        simulation = initialize!(model)
+        run!(simulation, period=Day(0))
+        @test simulation.model.feedback.nars_detected == false
+    end
+end

test/runtests.jl

@@ -52,6 +52,7 @@ include("random_process.jl")
 include("stochastic_physics.jl")
 
 # INITIALIZATION AND INTEGRATION
+include("resolutions.jl")
 include("run_speedy.jl")
 
 # EXTENSION