Changing tilt does not modify climate

[stella-bourdin]

I am trying to run a 5-year control experiment that is the default PrimitiveWetModel, and two perturbed experiments with axial tilt 0 and 90°.

Here is my code :

# Import SpeedyWeather
using SpeedyWeather
using GeoMakie, CairoMakie

## Control
spectral_grid = SpectralGrid()
# Output
output_writer = NetCDFOutput(spectral_grid, id = "control") # Define writer with experiment name
output_writer.output_dt = Day(1) # Define output frequency
add!(output_writer, SpeedyWeather.TemperatureOutput(), SpeedyWeather.RadiationOutput()...)
delete!(output_writer, :u, :v, :vor)
@show output_writer

model = PrimitiveWetModel(spectral_grid, output = output_writer)
@show simulation = initialize!(model)
run!(simulation, period=Day(365*5+1), output = true) # Set output=true to activate NetCDF output


## tilt 0
tilt = 0
spectral_grid = SpectralGrid()
# Output
output_writer = NetCDFOutput(spectral_grid, id = "tilt_$tilt") # Define writer with experiment name
output_writer.output_dt = Day(1) # Define output frequency
add!(output_writer, SpeedyWeather.TemperatureOutput(), SpeedyWeather.RadiationOutput()...)
delete!(output_writer, :u, :v, :vor)
@show output_writer

model = PrimitiveWetModel(spectral_grid, output = output_writer, planet=Earth(spectral_grid, axial_tilt = tilt))
@show simulation = initialize!(model)
run!(simulation, period=Day(365*5+1), output = true) # Set output=true to activate NetCDF output

## tilt 90
tilt = 90
spectral_grid = SpectralGrid()
# Output
output_writer = NetCDFOutput(spectral_grid, id = "tilt_$tilt") # Define writer with experiment name
output_writer.output_dt = Day(1) # Define output frequency
add!(output_writer, SpeedyWeather.TemperatureOutput(), SpeedyWeather.RadiationOutput()...)
delete!(output_writer, :u, :v, :vor)
@show output_writer

model = PrimitiveWetModel(spectral_grid, output = output_writer, planet=Earth(spectral_grid, axial_tilt = tilt))
@show simulation = initialize!(model)
run!(simulation, period=Day(365*5+1), output = true) # Set output=true to activate NetCDF output

From looking at the simulation.model.planet and simulation.model.solar_zenith, the change in axial tilt is taken into account in both.
The downward surface radiation also looks good:

But the temperature is exactly the same in all experiments: np.abs(control.temp - tilt_0.temp).max() = 0 (whereas np.abs(control.srd - tilt_0.srd).max() = 542.25)

I am confused... Any idea why that is, and how to fix it @milankl ?

[milankl]

Ah sorry by default you are running with a prescribed land and ocean and with a transparent atmosphere. You'll need to use the land and ocean models as Pier Luigi does, see in the coupled notebooks. Otherwise any radiation that hits the surface doesn't do anything as the land/ocean temperatures are not reacting to it but are prescribed instead!

Check

model.land.temperature
model.ocean

both are by default set to SeasonalLandTempereature or SeasonalOceanClimatology meaning they are just reading a climatology from file and interpolating it in time and space.

See here

https://github.com/SpeedyWeather/NCAS_CMSS_2025/blob/main/Introductory_Notebooks/Speedy-Coupling.ipynb