Setting up: the three stages, and moving between them
Choosing what to open
One model is included, QG Cyclones. The Launcher opens directly on its Model Launch card, without a model picker, and the panel offers the sections that model declares.
The Launcher
The first stage asks where the design comes from.
| Preset | A design included with the app, chosen from the Select preset list. Its file is fetched on choice. A tickbox appears beneath the list for each optional block the chosen entry carries, ticked. Include land takes the painted terrain, and unticked opens the design over open ocean. Start from snapshot launches from the stored state and bypasses the Builder’s design steps; unticked, the design goes through the Builder and starts from a fresh seed. The land box is held ticked while the snapshot is, since the stored fields were integrated over that mask. Stored view settings apply to the preview and the run either way. Presets require an HTTP server (see the quick start). When the page is opened as a local file, the list is empty and Import still works. |
| Import | A saved design pasted as JSON. Each valid parse updates the preview, and the line beneath states what the file carries. An invalid paste reports the error and blanks the stage. A tickbox appears for each optional block the file carries, ticked by default. Import land takes the painted terrain, and unticked opens the design over open ocean. Import snapshot launches from the saved state and bypasses the Builder’s design steps. Import view settings applies the saved map settings to the preview and the run. It is offered only with a snapshot, and is disabled while the snapshot box is off. |
| Blank | A minimal two-layer design, to be shaped in the Builder. |
Leaving Preset clears its selection, while a paste is retained and re-parsed on return to Import. Until a source defines a design, the green button beneath the card stays hidden. The button then appears, reading Next, or Initialize when a flat design launches from a stored snapshot. A hemispheric design with a stored snapshot stops first at the Compute card.
The Compute card
The Builder’s third step, offered for a hemispheric domain only, since only the hemispheric kernel runs threaded. It sets how the kernel executes on the present machine and is stored in no design and no snapshot. A stored hemispheric snapshot, whose design steps are sealed, therefore stops here between the Launcher and the run, with the corner Setup control as its only retreat.
| Kernel execution | Single-core runs the serial kernel.
Multi-core shards each step across CPU cores and requires a cross-origin-isolated
page, which the local server and the deployed site provide and a file:// open
does not. Where unavailable, the Multi-core button is disabled and a note beneath states the reason.
It is the default where available on a machine of at least four cores. |
| CPU cores | From 2 to the smaller of the machine’s count and 8. The default leaves two cores free for the interface and the browser. Disabled under Single-core. |
Each launch starts the engine as the card states, and the running panel’s read-only Compute tab reports what engaged.
The Builder
Next moves the design here, and the stage label reads BUILDER. Every structural setting is edited in this stage, and under a run these definitions are read-only. The Builder has two steps, three for a hemispheric design. Step one, Domain, sets the geometry, the Coriolis treatment, the domain’s size and position, the deformation radius, the resolution and the initial jet. Step two, Vertical Column, shapes the layers. A hemispheric design adds the Compute card as step three. The green button reads Next until the final step, where it reads Initialize. A full-width Back button beneath it returns one step, and the corner Setup control returns to the Launcher from any step. The built-in forcings are runtime controls on the running panel’s Forcing tab.
The domain’s shape
Periodic wraps in both directions and is square. Channel adds free-slip walls across the flow and, on an f- or β-plane, is twice as wide as tall. Hemisphere is a pole-to-equator polar cap on the sphere, drawn as a disc with the pole at the centre and the equator at the rim. A channel opens the Coriolis selector. f-plane holds the Coriolis parameter uniform and needs no latitude. β-plane varies it linearly at the gradient of the Central latitude (5–80° N), with β quoted beneath. Earth-like takes the real variation over a latitude band and needs walls, so leaving a channel returns such a design to the β-plane. A periodic domain hides the selector and keeps the f- or β-plane treatment last chosen.
| Domain size | 500–20,000 km. The side of a periodic domain, or the width of an f- or β-plane channel, half as tall. |
| Lower latitude, Upper latitude | Earth-like only. The band’s edges, 0–85° N. Their separation is the domain’s height, at 111 km per degree. |
| Domain width | Earth-like only. A power-of-two multiple of the band’s height, ×1 to ×16. The line beneath states the fraction of the latitude circle covered at the band’s mid-latitude, in amber above 100 percent, where the domain overlaps itself. |
| Resolution | Cells per deformation radius, stepping through the row counts the kernel can reach for the domain’s shape. The line beneath states the grid and the cell size. Fewer than 2 suppresses the eddies, and 4–8 resolves them. |
| Initial mean zonal jet | 0–80 m/s. The peak speed of the sech² jet from which the run starts. The uppermost tropospheric layer and any stratospheric layer carry the full speed, the surface layer a fixed fraction of it and the layers between a linear share. |
| Regenerate initial state | Re-seeds the initial condition, moving the precursor from which the first storm grows. |
The hemisphere removes most of these controls, since the cap’s size, latitudes and Coriolis treatment are the planet’s. What remains is the resolution, counted in rings with the ring spacing Δs beneath, the deformation radius card, the jet, which on the cap seeds an annular westerly centred at 45° N, and the Regenerate button. The equator is a wall. The dynamics are quasi-geostrophic, so the flow near the equatorial rim is a boundary condition rather than a prediction.
The deformation radius
Ld sets the size of eddies. The Deformation Radius card carries its slider, 100–5,000 km, and on an Earth-like channel or the hemisphere, the two designs with latitude structure, a Treatment selector. Constant applies one value across the domain. Latitude-dependent takes Ld = c/f with f = 2Ω sin φ, so the radius falls toward the pole. The slider then states Ld at the band’s midpoint, 45° N on the hemisphere, and a sketch beneath draws Ld across the band with a dot at the midpoint and the value at each end. Saturate toward the equatorial radius, ticked by default, stops c/f diverging where f approaches zero, the governing scale becoming √(c/β). The tropical end of the sketch flattens. Unticked, the raw c/f rises to the top of the frame, and beyond it where the band reaches low latitudes or on the hemisphere. The Resolution readout then states cells per Ld at the largest and the smallest radius over the band, and the small-radius end is the one the grid must resolve.
The radius and the resolution hold for the whole run. Changing either requires Back to Builder, which discards the run, and a new Initialize. For an Earth-like or hemispheric design, the running panel’s System card reports the radius read-only.
The vertical column (step two)
The troposphere always spans 10 km and a stratosphere is added above it, so the tropopause stays at 10 km. The kernel carries at most eight layers.
| Troposphere layers | 2 to 8, less the stratosphere’s count. |
| Surface grading | ×1 to ×6. At ×1 the layers are equal. Above it the surface slab is thinned to 1/g of an interior slab’s share, the thinning decaying with a one-layer e-folding. |
| Density | Uniform holds the density constant with height. Earth-like lets it fall as exp(−z/H) and opens Density scale height, H = 4–16 km. |
| Stratosphere layers | None, 2 or 3 slabs above the troposphere. The total is capped at eight, so a stratosphere on a tall troposphere reduces the troposphere’s count. |
| Stratosphere depth | 5–10 km, divided equally among the stratospheric slabs, so the column stands 15–20 km. Shown with a stratosphere only. |
| Stratosphere stiffness | ×1 to ×8. How much more strongly the air above the tropopause resists vertical motion. Shown with a stratosphere only. |
A live cartoon beneath draws the slabs at their true thicknesses, each slab of sufficient height labelled with its index, its thickness Δ and its density relative to the surface value ρ0. The axis marks the boundaries’ heights and the standard atmosphere’s pressure there, an interior tick yielding where a thin slab would crowd it. Stratospheric slabs are tinted more strongly as the stiffness rises, and the tropopause is the amber dashed line. A design launched from a stored snapshot never stops here, since the file carries its column with its state.
Leaving the Builder
| Setup (top left of the stage) | Returns to the Launcher from any Builder step. The launcher controls keep their values. A Preset or Import design is re-derived from its source at once, so Builder edits do not carry over, while a Blank design keeps its edits. The view mode, the pointer tool and every display setting return to their defaults, or to the source’s look where a Preset stores view settings or an Import’s view box is ticked. |
| Back to Builder (from a run) | Discards the run and returns to the Builder with a fresh preview of the design. Display settings are kept and the floating windows close. Initialize starts a new run. A run launched from a stored snapshot did not pass through the Builder, so its button reads Back to Launcher and returns there, with the look reset as Setup resets it, to the defaults or to the source’s look where a Preset stores view settings or an Import’s view box is ticked. |