PROJECT: Dynamical downscaling capability

[glwagner]

NumericalEarth needs an end-to-end dynamical-downscaling workflow: ingest a global reanalysis dataset, build a NumericalEarth.NestedSimulation that drives a limited-area NumericalEarth.AtmosphereLandModel (Breeze AtmosphereModel + SlabLand + RRTMGP radiation) through open lateral boundary conditions and volumetric Oceananigans.Forcings.Relaxation nudging. This issue tracks the cross-repo work spanning NumericalEarth, Breeze, and Oceananigans.

End-to-end test target: examples/era5_breeze.jl (#233) — SGP-centered ~3 km LAM, HI-SCALE 2016-09-10 case day.

parent: PrescribedAtmosphere(ERA5)
                │
                │  coupling: open lateral BCs + Oceananigans.Forcings.Relaxation
                ▼
NumericalEarth.NestedSimulation
                │
                │  (DFI: balance the interpolated IC)
                ▼
NumericalEarth.AtmosphereLandModel
        ├─ Breeze AtmosphereModel
        │     ├─ acoustic substepping (over terrain)
        │     ├─ open lateral BCs (mass-fluxed)
        │     ├─ WENO advection
        │     ├─ microphysics (1M non-eq / 2M / P3)
        │     └─ boundary-layer turbulence parameterization
        ├─ NumericalEarth SlabLand
        └─ RRTMGP radiation

Status legend: ✅ merged · 🟡 open · ⚪ closed/superseded. "Recent" = closed since 2026-05-01.

---

1. NestedSimulation utility (NumericalEarth)

• 🟡 NestedSimulation abstraction + ERA5 regional hindcast example — NestedSimulation abstraction + ERA5 regional hindcast example #233
• 🟡 Refactor PrescribedAtmosphere: notation, microphysical variables, surface-vs-nesting role — Refactor PrescribedAtmosphere: notation, microphysical variables, surface-vs-nesting role #266

2. Parent data ingest (NumericalEarth)

• 🟡 set! map-projection support for RectilinearGrid (projected-Cartesian LAM variant) — Add map projection support to set! for RectilinearGrid targets #232
• ✅ MetadataSet core + adoption sweep — MetadataSet (#235): core + adoption sweep #259 (closes Introduce MetadataSet (and a generic download) for multi-variable Metadata workflows #235)
• ✅ Per-column z ingest for ERA5 pressure-level data — Per-column z ingest for ERA5 pressure-level data #241 (closes ERA5 pressure-level ingest: per-column geopotential and surface-pressure masking #236)
• ✅ Unify JRA55 onto generic dataset backend; extend region support — (0.4.2) Unify JRA55 onto the generic dataset backend, extend region support across all paths #169
• ✅ Combine all ERA5 examples — Combine all ERA5 examples #209
• ✅ DataWrangling cleanup: standardize download_dataset returns; drop ERA5 dead code — DataWrangling cleanup: standardize download_dataset returns, drop ERA5 dead code #208
• ✅ Add skin temperature to ERA5 single-levels — Add skin temperature to ERA5 single-levels #218
• ✅ Pressure-based formula for surface specific humidity — Pressure-based formula for surface specific humidity #223
• ✅ Add AbstractPrescribedComponent abstract type — Add AbstractPrescribedComponent abstract type #228
• ✅ Reinitialize download progress on new file — Reinitialize download progress when dowloading a new file #243

3. Parent ↔ child coupling

3a. Open lateral boundary conditions

Breeze:

• 🟡 Open lateral boundary conditions for anelastic models — Open lateral boundary conditions for anelastic models Breeze.jl#494
• 🟡 OBC with boundary mass-flux correction — Open boundary conditions with boundary mass flux correction Breeze.jl#129
• ✅ Compressible substepper silently misinterprets nonzero OBC values on momentum as perturbations — Compressible substepper silently misinterprets nonzero OBC values on momentum as perturbations Breeze.jl#716
• ✅ Strip nonzero OBC values from acoustic perturbation halos — Strip nonzero OBC values from acoustic perturbation halos Breeze.jl#724
• ✅ Propagate momentum open boundary conditions to derived velocities — Propagate momentum open boundary conditions to derived velocities Breeze.jl#722 (closes #721)
• ⚪ OpenBoundaryCondition on momentum silently clobbered → NaN — OpenBoundaryCondition on momentum is silently clobbered by impenetrable-default on derived velocities → NaN Breeze.jl#721 (fixed by #722)

3b. Volumetric Relaxation (Oceananigans.Forcings.Relaxation)

Oceananigans:

• 🟡 Simplify Relaxation: drop ContinuousForcing dependency, add transform and Field targets — Simplify Relaxation: drop ContinuousForcing dependency, add transform and Field targets CliMA/Oceananigans.jl#5620
• ✅ Support FieldTimeSeries targets in Relaxation — Support FieldTimeSeries targets in Relaxation CliMA/Oceananigans.jl#5575

Breeze:

• 🟡 Add FieldTimeSeriesRelaxation — Add FieldTimeSeriesRelaxation Breeze.jl#562
• ✅ Streamline forcings by accepting specific-quantity keys — Streamline forcings by accepting specific-quantity keys Breeze.jl#703

3c. Digital filter initialization (DFI)

• 🟡 Digital filter initialization for limited-area cold-start — Digital filter initialization (DFI) for limited-area cold-start Breeze.jl#727

4. Child: Breeze AtmosphereModel

4a. Acoustic substepping

• 🟡 Acoustic substepping on terrain-following coordinates — Acoustic substepping on terrain-following coordinates Breeze.jl#712 (closes #673)
• 🟡 Substepping with terrain-following coordinates: implementation plan — Substepping with terrain-following coordinates: implementation plan Breeze.jl#673
• 🟡 Topology-aware operators for acoustic substepping (+ Distributed optimizations) — Topology-aware operators for acoustic substepping (+ possible Distributed optimizations) Breeze.jl#725
• ✅ Acoustic substepping cleanup — Acoustic substepping cleanup: typed AcousticDampingStrategy + new default + BW example Breeze.jl#622
• ✅ Backward integration in split-explicit substepping — Support backward integration in split-explicit acoustic substepping Breeze.jl#718
• ✅ Allow / use consistent / default FloatType in SplitExplicitTimeDiscretization — Allow passing the float type as argument to SplitExplicitTimeDiscretization Breeze.jl#678, #680 (closes #679), #681
• ⚪ Add / Re-factor AcousticSubstepper — Add / Re-factor AcousticSubstepper Breeze.jl#567

4b. Microphysics

1M non-equilibrium (default for moist downscaling cases):

• 🟡 Use NonEquilibriumCloudFormation in RICO example with 1M precipitation — Use NonEquilibriumCloudFormation in the RICO example with 1M precipitation Breeze.jl#326
• ✅ Fuse multi-output microphysical tendencies for GPU performance — Fuse multi-output microphysical tendencies for GPU performance Breeze.jl#676
• ✅ Complete snow and ice closure for MPNE1M scheme — Complete snow and ice closure for MPNE1M scheme Breeze.jl#587
• ✅ Implement NonEquilibriumCloudFormation (foundation) — Implement NonEquilibriumCloudFormation for 1M microphysics Breeze.jl#284
• ✅ Fix water conservation in 1M / 2M microphysics — Fix water conservation in 1M and 2M microphysics and numerical stability in 2M microphysics Breeze.jl#547

P3 (advanced single-moment, mixed-phase):

• 🟡 Implement PredictedParticlePropertyMicrophysics — Implement PredictedParticlePropertyMicrophysics Breeze.jl#395

5. Child: SlabLand

• 🟡 Add composable SlabLand and atmosphere–land coupling — Add composable SlabLand and atmosphere–land coupling #220
• ✅ Add land as a top-level EarthSystemModel component — (0.3.0) Add land as a top-level EarthSystemModel component #149