Santiago
Santiago is the demo of a closed basin with a real monitoring network. The Metropolitan Region has winter temperature inversions, a critical-episode regime that is declared every year, and SINCA stations with decades of data — the place where a forecast can be compared with what was measured, not just shown.
| Time zone | America/Santiago |
| Standard evaluated | Chile, MMA (cl-mma) |
| Grid | 109 × 109 cells of 750 m, about 82 × 82 km |
| Output | Every 15 minutes |
| Sources | 22 in 4 groups: 10 stacks, 9 volume sources, 3 area sources |
| Receptors | 12, all SINCA stations |
The stations
Section titled “The stations”Every receptor is a SINCA station, at its official coordinate: Quilicura, Las Condes, Independencia, Cerro Navia, Pudahuel, Parque O’Higgins, Cerrillos and the rest. The reason is simple: a receptor that coincides with a station lets the modelled curve sit beside the measured one, and that comparison is what makes a forecast believable. The coordinates come from the monitoring registry itself, not a hand-written list — nine of them sat 1.5 km north of their station until that source was corrected.
The sources, in four groups
Section titled “The sources, in four groups”The groups are not an administrative classification; each exists so that one difference stays legible in the contribution breakdown.
Renca thermoelectric complex — two adjacent plants on the north bank of the Mapocho: Nueva Renca, a 379 MW combined cycle on natural gas with diesel as backup, and Renca, a diesel backup plant with two 50 MW units. It is the domain’s dominant source of nitrogen oxides and the only one that switches fuel between scenarios. Being dual-fuel is what earns it more than one scenario: sulphur in combustion depends almost entirely on the fuel, so going from gas to diesel multiplies SO₂ by more than two orders of magnitude while NO₂ rises only modestly. The plume changes composition, not just size. Unit 1, disconnected in 2023, is kept at zero rate on purpose: a retired asset is still part of the installation.
Industry of Quilicura, Pudahuel and Cerrillos — eleven sources across the three industrial corridors, the only mix of stacks with volume sources. An industrial park does not emit through an identifiable stack but from a set of buildings; modelled as a volume it stays near the ground and affects the nearby receptors, which is what actually happens.
Santa Marta landfill — in Talagante, far from the thermoelectric group, with three distinct geometries: the working face as an area, the biogas flare as a stack, the leachate plant as a volume. It is the group that separates geometry from magnitude: it emits at ground level and its footprint reads completely differently from a 60 m stack.
Maipo aggregates, fugitive emissions — extraction and crushing on the bank of the Maipo. Particulate matter only, no plume rise, highest near the source and governed by low-level wind. Kept separate, it explains why PM10 behaves differently from SO₂ and NO₂ in the south of the domain.
The scenarios
Section titled “The scenarios”Normal operation on gas is the case the others are read against: Nueva Renca on gas, negligible SO₂, a NOₓ-dominated profile; Renca’s diesel backup is why the base SO₂ is not zero.
Natural gas restriction — Nueva Renca switches to diesel. Not a failure but the plant’s design behaviour: it keeps diesel precisely so it can keep running when gas is short. Worth modelling because the change is not uniform: SO₂ multiplies by more than two hundred, NO₂ rises far less.
Environmental pre-emergency (GEC) — a declared critical-episode day: industry and fugitive sources cut back under the decontamination plan while power generation and the landfill keep operating. It is the scenario that inverts the argument: the others make things worse, this one makes them better, and it answers a question a Chilean regulator or operator genuinely asks — does the restriction help, and at which receptors?
The alerts
Section titled “The alerts”Alerts are evaluated against the Chilean standard (MMA), with the averaging each species requires: hourly for SO₂ and NO₂, 8-hour moving for CO. An alert appears on the map and in the panel when a receptor crosses a level; already-observed past and forecast are told apart by their position relative to the forecast cycle.
A note on the figures
Section titled “A note on the figures”Emission rates are screening values derived from standard emission factors and published plant specifications, calibrated so the model sits below the measurements at the great majority of station/species pairs. They serve to compare scenarios with each other; they are not permit figures nor regulatory declarations.