This is bad...

Have you taken a look outside? You can't see much. This morning we were socked in with dense fog, plus the pollution levels are in the unhealthy range. PM 2.5 concentrations in downtown Salt Lake are over 100 micrograms/m3. That's bad.

Utah county has been quite a bit cleaner than Salt lake County, but I looks like the pollution from Salt Lake is being transported south. Winds are light from the north. This may explain the sudden spike in PM 2.5 concentrations at the Lindon air quality site.

This mornings sounding shows how strong this inversion really is. The ground is cold, below freezing, while the air temperatures in the mountains are above 10 C. Since cold air sinks, all that pollution we emit at the surface stays at the surface. 

Great Salt Lake Summer Ozone Study (draft for grad news)

Clean air is important to our respiratory health. Unfortunately, some areas in Utah often observe unhealthy levels of ozone pollution. While ozone occurs naturally in the upper atmosphere and absorbs harmful ultraviolet radiation, smog-forming ozone created near the surface by other pollutants in the presence of sunlight poses a danger to human’s respiratory health.

This summer a team of atmospheric science students and professors at the University of Utah, Weber State, and Utah State worked together with Utah’s Division of Air Quality to understand how the Great Salt Lake influences ozone concentrations in Northern Utah. The purpose of the Great Salt Lake Summer Ozone Study is to better understand the generation and transport of ozone pollution in northern Utah, particularly areas around the Great Salt Lake.

To accomplish this, graduate and undergraduate students at the University of Utah participated in three intensive observation periods in which ozone levels and weather conditions were measured around the lake. Ozone monitors are installed on a UTA TRAX train, the KSL helicopter, and over twenty-five stationary sites which collected ozone and weather information all summer. Other mobile observations were made from trucks and the University’s “Nerdmobile” while driving routes around the Great Salt Lake. Preliminary analysis of the data collected has already shown interesting trends in ozone concentration around the lake. With this many observations researchers can understand how ozone concentrations change over a day and where the highest levels of ozone occur. This new knowledge will be used to improve air quality forecasts.

More information about the Great Salt Lake Summer Ozone Study can be found on the project’s website at http://meso2.chpc.utah.edu/gslso3s/. Current air quality forecasts issued by the Division of Air Quality can be found at http://air.utah.gov/forecast.php.

Good air quality next few days

Several moist weather disturbances passing through Utah this week will stir the air up enough to keep our ozone pollution at healthy levels this week in most areas. Look at the most current air quality forecasts here: http://air.utah.gov/forecast.php?id=slc

This morning has been rainy with tropical moisture coming up from the south west as remnants of a hurricane move into the states. The HRRR model suggests these widespread showers pass the Wasatch Range by the afternoon. The wet ground will keep our temperatures cooler than usual today with the cloud cover and as more afternoon heating goes to the latent heating by evaporating water rather than heating the air. Below shows the modeled radar reflectivity for 2:00 PM today.

Ozone Chasers

There weren't any storms to chase yesterday. Instead, we chased ozone pollution!

This summer our research group is involved in the Great Salt Lake Summer Ozone Study. The truck is equipped with and ozone monitor and a GPS.

Ozone Monitor

Truck with inlet tube sticking out the window and GPS on top of the truck.

Yesterday we we drove the truck from Ogden to Antelope Island and then to the international airport with an ozone monitor. We never encountered unhealthy levels of ozone, which is good. But ozone pollution in Salt Lake doesn't usually get to unhealthy levels until July because of it's dependence on sunlight. Later this summer we will be taking more observations. Yesterday's ozone chase was to test a route for the University of Utah Nerdmobile.

Of course, I couldn't leave Antelope Island without a bison selfie...

One of the projects I've worked on is providing HRRR sounding plots available for every hour of every day during the summer. I created this page for viewing these plots. These plots are from the HRRR analysis bufr soundings (downloaded from Penn State) and are created with this skew-T python package.

Welcome back to the prolonged inversions and poor air quality

Air quality along the Wasatch Front has been getting worse the last few days. Salt Lake City is the winter home of temperature inversions and bad air. And this is just be beginning of the season. Below are shown measurements of PM 2.5 (Particulate Matter smaller 2.5 micrometers in size).

The air is not super unhealthy yet, but the pollution concentration is increasing. You may have noticed the decreased visibility last time you tried looking at the mountains across the valley. This weekend a storm should blow all this gunk away before it gets much worse, but be prepared for more days like this and try to drive less during these inversion periods if you can.

November 19, 2014 @ 2:50 PM
Photo: kbkb

November 20, 2014 @3:30 PM
Source: WBB webcam

Above is another look at the smog today. The sun is beginning to set. The concentration of the smog actually looks worse due to the fact that we are looking in the direction of the sun. When particles scatter light, they always scatter with constructive interference in the forward direction, toward your eyes if you are looking toward the sun. This optical phenomenon makes the haze look brighter, making it seem there is more stuff in the air. But still, the air is dirty.

source: atmospheric radiation course notes

Los Angeles Air Quality

As part of NASA's Student Airborne Research Program I am looking at meteorological influences on high and low ozone days. I've downloaded data from the EPA's website and put together the following plot using Python. It shows the number of days in each Air Quality Index (AQI) category for the last twenty years.

(c) bkb

The colors represent the number of days LA exceeded the EPA's health standard: 75 ppbv. Over the last twenty years there are fewer days with unhealthy levels. The number of days with 'very unhealthy' air is practically zero.


Here is a plot showing the AQI for each day in 2012:

bkb (c)

Notice that the winter months only have good ozone AQI days. This seasonal trend is noticeable during all years. Ozone forms photochemically in the air when other pollutants react in the presence of sunlight. This explains the low ozone concentrations during the winter months. There is not sufficient energy from the sun to make the ozone form. The daily solar energy is lower during winter months for two reasons. First, days are shorter. And second, the earth's rotation is tilted away form the sun causing sunlight to spread over a larger area.

In comparison here is a plot of ozone AQI values for Salt Lake City in 2012: 

bkb (c)

Again, we see low ozone concentrations in the winter months. (Notice that there is missing data in October and December.) Salt Lake does not have many days that exceed the EPA's National Ambient Air Quality Standard (NAAQS). There are two other factors that can causes the difference in these two cities: emission amounts or type, and weather.

Salt Lake, however, has other pollution problems they deal with. Particulate Matter smaller than 2.5 microns, otherwise known as PM 2.5, is the troublesome pollutant along the Wasatch Front. Unlike ozone, PM 2.5 doesn't seem to follow an annual trend. Not shown in this chart is a long polluted episode throughout January 2013. A strong inversion kept air near the surface. The mountains act as barriers that prevented the pollution to mix away. Meteorology, topography, and emissions play a large role in PM 2.5 concentrations in Northern Utah. The year 2012 was fairly unpolluted, but the beginning of 2013 had several days with very unhealthy air quality. Those episodes occur during periods of strong inversions.

bkb (c)