Stuttgart in germany is a city within a deeper valley, so many times there is no wind trough that. Primary problem is the sum of particles flying in the air, because the European Union has set 50 micrograms as upper limit. So there is dust alert called out on many days and now the city government want to place bans on car traffic and home fireplaces.
Nearby all cities have a measurement system with stations placed everywhere to get informations.
But Stuttgart have, like all regions lacking wind another huge problem, that cause a lot of nano dust and disables raining.
Strategic Aerosol Geoengineering blows several tons of dust into the skies every day and night. This results to pretty effects like visible light fingers from the sun and widespread red sundowns, but is the same as at light shows in your cinema, where the laser becomes visible as beam through airborne particles.
Dear people in Stuttgart, enjoy your foot walk to your job when driving is forbidden and have an open eye to the skies, where tanker planes place the particles, your car is blamed for.