4 ms·
Radar data is hugely noisy and it can be difficult to suss out what is cloud cover with no precipitation, or what is precipitation, plus filtering out biomass a
by starpilot 7y ago
Radar data is hugely noisy and it can be difficult to suss out what is cloud cover with no precipitation, or what is precipitation, plus filtering out biomass and dust. All of these show up as radar returns. There can be shadowing. Dark Sky does its own pre-processing/denoising of radar and so that can lead to different results from NOAA.
- crazygringo 7y agoAh that's really interesting, thanks for the info. I'm curious then what users see in Seattle when it's raining out the window but the Dark Sky radar maps says it isn't. Are there swiss-cheese holes that are obvious processing artifacts? Is the whole city somehow below some threshold so it doesn't show rain anywhere? Are there patterns of extreme local variation in rain that get mistaken for noise and deleted? The solution is not necessarily simple, but identifying the culprit should be fairly obvious, no?
- starpilot 7y agoReally recommend reading http://jackadam.github.io/2011/how-dark-sky-works/ http://jackadam.github.io/2011/how-dark-sky-works/ and https://en.wikipedia.org/wiki/Weather_radar#How_a_weather_radar_works https://en.wikipedia.org/wiki/Weather_radar#How_a_weather_ra... to get something of a handle on it For one thing, the resolution of radar is finite where one "pixel" (gate) is quite large, and everything under it is assumed to be constant. Precipitation at a spot on the ground is the result of everything happening from sea level up 40,000', and we don't have exact properties (temperature, dew point, humidity) for the atmosphere at all of those locations. We can fill in some gaps with models on supercomputers, but they're just models.