Shortwave Absorption Bug Fix & Stability Investigation (#978)

* Fix order of operations in one-band shortwave radiative transfer calculation

* update changelog

---------

Co-authored-by: Milan Kloewer <milankloewer@gmx.de>

Author: nviebig

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Changelog
 
 ## Unreleased
+
+- Bug fix: Cloud reflectivity on half level above not below [#978](https://github.dev/SpeedyWeather/SpeedyWeather.jl/pull/978)
 - Fix absorptivity_water_vapor and absorptivity_cloud_base default values [#974](https://github.com/SpeedyWeather/SpeedyWeather.jl/pull/974)
 - Particle advection GPU ready [#897](https://github.com/SpeedyWeather/SpeedyWeather.jl/pull/897)
 - Enzyme compat relaxed as Enzyme bug was fixed and uv_from_vordiv! kernel version used on CPU as well [#971](https://github.com/SpeedyWeather/SpeedyWeather.jl/pull/971)

SpeedyWeather/src/physics/radiation/shortwave_radiation.jl

@@ -225,8 +225,8 @@ One-band shortwave radiative transfer with cloud reflection and ozone absorption
     U = U_surface_albedo + U_stratocumulus
     for k in nlayers:-1:1
         U_out = U * t[ij, k]
-        U_out += k == cloud_top ? U_reflected : zero(U)
         dTdt[ij, k] += flux_to_tendency((U - U_out) / cₚ, pₛ, k, model)
+        U_out += k == cloud_top ? U_reflected : zero(U)
         U = U_out
     end