Change timestep to 40min at T31 (#623)

* change timestep to 40min at T31 * update changelog * schedule tests updated * Rossby-Haurwitz docs with shorter dt * reduce stochastic stirrin strength
SpeedyWeather · Dec 9, 2024 · 4f07e4d · 4f07e4d
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Change default timestep to 40min at T31 [#623](https://github.com/SpeedyWeather/SpeedyWeather.jl/pull/623)
+
 ## v0.13
 
 - AbstractSurfacePerturbation introduced [#631](https://github.com/SpeedyWeather/SpeedyWeather.jl/pull/631)

diff --git a/docs/src/forcing_drag.md b/docs/src/forcing_drag.md
@@ -42,7 +42,7 @@ using SpeedyWeather
     decorrelation_time::Second = Day(2)
 
     "Stirring strength A [1/s²]"
-    strength::NF = 5e-11
+    strength::NF = 2e-11
 
     "Stirring latitude [˚N]"
     latitude::NF = 45

diff --git a/docs/src/initial_conditions.md b/docs/src/initial_conditions.md
@@ -202,7 +202,9 @@ initial_conditions = InitialConditions(
                         pres=PressureOnOrography())
 
 orography = NoOrography(spectral_grid)
-model = PrimitiveDryModel(spectral_grid; initial_conditions, orography, physics=false)
+time_stepping = Leapfrog(spectral_grid, Δt_at_T31=Minute(30))   # 30min timestep scaled linearly
+
+model = PrimitiveDryModel(spectral_grid; time_stepping, initial_conditions, orography, physics=false)
 simulation = initialize!(model)
 run!(simulation, period=Day(5))
 nothing # hide

diff --git a/src/dynamics/time_integration.jl b/src/dynamics/time_integration.jl
@@ -16,7 +16,7 @@ $(TYPEDFIELDS)
 
     # OPTIONS
     "Time step in minutes for T31, scale linearly to `trunc`"
-    Δt_at_T31::Second = Minute(30)
+    Δt_at_T31::Second = Minute(40)
 
     "Radius of sphere [m], used for scaling"
     radius::NF = DEFAULT_RADIUS

diff --git a/test/schedule.jl b/test/schedule.jl
@@ -1,7 +1,7 @@
 @testset "Periodic schedule" begin
     # especially T170 uses 337500 milliseconds time steps
     # not representable as seconds
-    for trunc in (31,42,63,85,127,170,255,341)
+    for trunc in (31, 42, 63, 85, 127, 170, 255, 341)
         spectral_grid = SpectralGrid(trunc=trunc, nlayers=1)
         time_stepping = Leapfrog(spectral_grid)
 
@@ -10,7 +10,7 @@
         SpeedyWeather.set_period!(clock, period)
         initialize!(clock, time_stepping)
 
-        hour = Hour(1)
+        hour = Hour(2)
         schedule = Schedule(every=hour)
         initialize!(schedule, clock)