Dutch Atmospheric Large-Eddy Simulation Model (DALES v3.2) CGILS-S11 results Stephan de Roode Delft University of Technology (TUD), Delft, Netherlands Mixed-layer model analysis: Melchior van Wessem (student, TUD) DALES development: Thijs Heus (MPI-Hamburg, Germany) Chiel van Heerwaarden (Un. Wageningen, Netherlands) Steef Boing (Delft University of Technology) McICA code: Robert Pincus (NOAA) Bjorn Stevens (MPI-Hamburg) Many thanks to the CGILS-LES group for helpful suggestions!
Dutch Atmospheric Large-Eddy Simulation Model (DALES v3.2) Open source code (GIT) KNMI, University of Wageningen, Delft Technical University of Technology (Thijs Heus: MPI-Hamburg) Benefits to users: Additions of new physics routines McICA Radiation: Pincus and Stevens 29, implemented by Thijs Heus CGILS-radiation scheme close to be fully operational in DALES v3.2 Coupled Surface Energy Balance model: van Heerwaarden, Wageningen University However, it requires a lot of dedication to keep up with the modifications increase in the number of switches
CGILS Simulation details Simulation time 1 days adaptive time step, dtmax = 1 secs radiation time step = 6 secs Domain size 4.8 x 4.8 x 4 km 3, 96 x 96 x 128 grid points (Δz = 25 m in lower part) Total CPU hours on 32 processors 27 hours
CGILS Inversion height z inv t = w e + w subs ( z = z inv )
CGILS Cloud liquid water path (LWP)
CGILS Cloud cover
more evaporation Turbulent Surface Fluxes
Top Of Atmosphere Net Radiative Fluxes
CGILS Hourly-averaged vertical mean profiles during the last 5 hours
CGILS Hourly-averaged turbulent fluxes during the last 5 hours
Steady state solutions Example: longwave radiative cooling at cloud top 1.2 1.8 w e Δθ L ΔF /( ρc p ) Steady state θ L t = z/z i.6.4.2 Requires constant flux wθ L z = -.8 -.6 -.4 -.2.2 <wθ l > (mk/s)
Steady state solutions Example: no precipitation 1.2 1.8 w e Δq T Steady state q T t = z/z i.6.4.2-1 1-5 1 1-5 2 1-5 3 1-5 Requires constant flux wq T z = <wq t > (m/s)
z/z i 1.2 1.8.6 w e Δθ L ΔF /( ρc p ) Steady state solutions: <w θ v >.4.2 -.8 -.6 -.4 -.2.2 <wθ > (mk/s) l 1.2 z/z i 1.2 1.8.6.5 wθ L +11 wq T 1.8 w e Δq T.4.2 wθ L +18 wq T z/z i.6.4.2-1 1-5 1 1-5 2 1-5 3 1-5 <wq > (m/s) t -.1.1.2.3 <wθ v > (mk/s) no decoupling
Steady state solutions Example: longwave radiative cooling large-scale horizontal advection 1.2 w e Δθ L 1 z/z i.8.6.4.2 ΔF /( ρc p ) turbulent flux divergence balances advective cooling wθ L z = U θ L z large scale -.8 -.6 -.4 -.2.2 <wθ l > (mk/s)
1.2 1.8 w e Δθ L ΔF /( ρc p ) Steady state solutions: <w θ v > z/z i.6 z/z i.4.2 -.8 -.6 -.4 -.2.2 <wθ > (mk/s) l 1.2 1.8.6.4 w e Δq T z/z i 1.2 1.8.6.4.2 -.2 -.1.1.2.3 <wθ v > (mk/s).5 wθ L +11 wq T wθ L +18 wq T.2-1 1-5 1 1-5 2 1-5 3 1-5 <wq t > (m/s)
Steady state solutions & decoupling No decoupling (#) if wθ V > at cloud base height z base So wθ L z base > B d A d wq T zbase Flux divergence: wθ L z = wθ L wθ z L base < z base B d A d wq T z base + wθ L z base (#) This is a weak criterion. In fact, the flux can be slightly negative without the BL getting decoupled
Steady state solutions & decoupling Steady state if wθ L z = B d A d wq T z base + wθ L z base = U θ L x large scale
Steady state solutions & decoupling Steady state if wθ L z = B d A d wq T z base + wθ L z base = U θ L x large scale 15 height where <wθ v >= 1 5 CGILS -.3 -.2 -.1 Large-scale advection (K/h)
Steady state solutions & decoupling Decoupling due to large-scale advection alone not very likely However, two other processes cause steeper <w θ v > gradients In the subcloud layer: evaporation of drizzle longwave radiative cooling
CGILS: Inversion jumps (after 1 days) 2 ASTEX -2 Δq t [g/kg] -4-6 buoyancy reversal criterion ** S11 CTL P2K EUROCS -8 DYCOMS II -1 5 1 15 2 Δ θ l [K]
Mixed-layer model BL mean ψ ML t entrainment flux ( ) = w e ψ FA ψ ML surface flux c D U ML ψ ψ ML + ΔS ψ z i ( ) source/sink 1.2 1.2 θ L,FA q T,FA 1 1.8.8 z/z inv.6 z/z inv.6 q T,ML.4 θ L,ML.4.2.2 q T, θ L, 29 292 294 296 298 3 32 liq. wat. pot. temp. θ L (K) 2 4 6 8 1 12 total water content q T (g/kg)
Mixed-layer model BL mean ψ ML t entrainment flux ( ) = w e ψ FA ψ ML surface flux c D U ML ψ ψ ML + ΔS ψ z i ( ) source/sink z inv t = w e + w subs = w e Dz i
Mixed-layer model BL mean ψ ML t entrainment flux ( ) = w e ψ FA ψ ML surface flux c D U ML ψ ψ ML + ΔS ψ z i ( ) source/sink z inv t = w e + w subs = w e Dz i Closure (#) : w e = A ΔF rad θ L,FA θ L,ML (#) This closure is inspired by Moeng (2). Other closures need humidity jumps, cloud base height etc.
Mixed-layer model BL mean ψ ML t entrainment flux ( ) = w e ψ FA ψ ML surface flux c D U ML ψ ψ ML + ΔS ψ z i ( ) source/sink z inv t = w e + w subs = w e Dz i Closure: w e = A ΔF rad θ L,FA θ L,ML Upper BC: θ L,FA ( z) = θ L, + Γ θ z q T,FA = q T, + Δq T
Mixed-layer model solutions z inv t = w e + w subs = w e Dz i Closure: w e = A ΔF rad θ L,FA θ L,ML Approximation: (surface jump much smaller than inversion jump) θ L, θ L,ML << Γ θ z i Equilibrium height for the boundary layer z i = AΔF rad DΓ θ
CGILS Conclusions S11 goes to an equilibrium state Longwave radiative cooling, entrainment warming and large-scale advection Evaporation, entrainment drying, and large-scale advection Radiation in a future climate Hardly any change in radiation at top of the atmosphere if SST + 2K Outlook Do shallow cumulus and stratus runs Check influence advection scheme