How It's Built — Andrew Tandy

Sky

Sun

The sun's altitude, computed exactly for this location rather than fetched, sets the base palette from night indigo through twilight to pale day. Turn it off and there is no light source at all, so the canvas goes black and every other layer can be seen clearly on its own.

Moon

The moon's position and phase are also computed, not fetched. When it is above the horizon it appears as a soft disc, brighter near full and dimmer near new, placed in its true compass direction.

Air

Wind field

Wind speed and direction across a grid of twenty-four points from the coast to the mountains steer hundreds of small particles into the flow that makes up most of the piece. Turned off, the particles do not stop, they wander on their own instead of following the real wind.

Gusts

When the wind at a point is gusting, occasional bright flickers appear at the tips of the moving lines. This only shows anything if wind field is also on, since a gust is a kick off the real streamline, not its own motion.

Air temperature

The current air temperature colors the wind field white through blue when it is cold, yellow through orange to red when it is hot, judged against how warm it normally runs at this time of year rather than a fixed scale. With this off, the wind draws in a neutral tone so its shape can be seen without the color.

Humidity

Relative humidity is scattered across the canvas as a fine, barely visible grain once it climbs above about 30 percent.

Pressure

A falling barometric trend over the last six hours thickens the flow field's lines and brightens them slightly, a small visual tension. Steady or rising pressure leaves the lines at their calm, thin default.

Air quality

When the air quality index climbs above 50, the whole palette, sky and lines alike, is pulled toward a dusty tan. Good air leaves the palette untouched.

Water

Tide

The current tide height, read from NOAA's Scripps Pier station, sets how high the horizon band sits, and its rate of change gently bends the flow of nearby particles as they pass it. That second effect goes a little beyond the tide's usual job of just setting the horizon's height, worth knowing if this layer is split apart later.

Swell

Wave height, period and direction from the Open-Meteo marine model, read just offshore of Pacific Beach. The horizon breathes at the swell's period, so a long groundswell from a distant storm makes the piece move slowly and deeply, while short wind chop makes it quick and shallow.

Sea temperature

Sea surface temperature, also from the marine model, colors the horizon band with the same white through blue, cold, to yellow, orange, red, warm gradient the wind uses. Unlike air, this one runs against San Diego's fixed real annual range (roughly 59 to 70 degrees) rather than a seasonal baseline, since the ocean barely swings beyond its own normal range across the year.

Ground

Sediment

Thirty days of past daily weather settle into thin horizontal bands at the bottom of the canvas, oldest at the very bottom, each one colored by that day's warmth and rainfall.

Seismic ripples

Ambient ground vibration from a nearby seismic station, when that feed exists and is recent, sends out faint rings whose pace quickens as the ground gets busier than its usual seven day baseline. A real, nearby earthquake rings once, clearly larger and brighter than the ambient rhythm.