Nobody likes breathing dirty air, but further contributing to the January gloom in the lowlands along the Wasatch Front is the lack of sunshine.
Over the past five days, our observing site across the street from Alta Ski Area measured a maximum in incoming solar radiation of almost 650 Watts per square meter (yellow line below). The only day that was lower was yesterday when there were high clouds around.
In contrast, at our observing site at the University of Utah, we've only reached a maximum of about 475 Watts per square meter (yellow line below), a reduction of about 25%.
The reduction is due all the haze and smog in the valley, which reflects some of the incoming sunlight back to space before it reaches the ground. This is an extreme local example of what is known as global dimming, which is a slight reduction in the average incoming solar radiation at the Earth's surface due to the presence of smog and haze from the burning of fossil fuels, forests, etc. This global dimming has a slight cooling effect and helps to offset a portion of the warming due to the increase in greenhouse gasses in the atmosphere. However, we're getting a huge dose of it, adding to our misery by reducing sunlight and keeping afternoon temperatures down.