Summer Ozone and the Central United States

I was asked to comment on a scientific article and paper pertaining to harmful ozone in the Central United States. The article was published July 4. The hypothesis is that thunderstorms penetrating the tropopause (the atmospheric layer right below the stratosphere) and extending into the stratosphere cause a chemical reaction to occur that can lower concentrations of stratospheric ozone that are good aloft but bad when they reach the ground and then create accordant risks to people.

I admit I have not read the paper. They want (depending on period of time) $10 to $25 for access to the entire paper. I have a philosophical problem paying twice (my tax dollars and the article access fee) for this research. So, I am going to excerpt the article from weathernationtv and comment on each item that I question.

The Paper Begins

A new study out of Harvard University reveals that the protective stratospheric ozone layer above the central United States is vulnerable to erosion during the summer months from ozone-depleting chemical reactions, exposing people, livestock and crops to the harmful effects of UV radiation.

Powerful storm systems common to the Great Plains inject water vapor that, with observed temperature variations, can trigger the same chemical reactions over the central United States that are the cause of ozone loss over the polar regions, according to a new paper published in the Proceedings of the National Academy of Sciences.

If their hypothesis is correct, this could indeed be a problem depending upon the geographic extent and time duration of of the lessened ozone.

The Problem Climate Scientists Sometimes Have With Meteorology
Then they employed recent NEXRAD weather radar observations to demonstrate that on average 4000 storms each summer penetrate into the stratosphere over the central United States, which is far more frequent than was previously thought.

I'm shocked the researchers believed believed "far fewer" than 4,000 storms per year penetrate the tropopause. This is a part of the knowledge loss that occurred when the National Weather Service installed the network of WSR-88D radars from 1991-1996. In that (average) quarter-century since, meteorologists no longer use a display called a Range-Height Indicator (some use an imitation of it that is not as accurate). I used one every day for 21 years.

Range-Height Indicator
University of Oklahoma

Prior to the WSR-88D's National Weather Service radar operators, at least once per hour, were required to switch to the RHI. We saw how frequent it was that storms penetrated into the stratosphere. In fact, since we are talking the entire Central United States, 4,000 seems a little low. The WSR-88D's were a great step forward in many ways, but there were issues with the RHI, timeliness and resolution that are now just being solved.

While this, by itself, is not a major matter it does point out that climate scientists sometimes have issues with understanding weather -- which is the basis of climate. This is hardly the only time meteorology verses climatology knowledge has come up.

The Medical Issue
Stratospheric ozone is one of the most delicate aspects of habitability on the planet. There is only marginally enough ozone in the stratosphere to provide protection from UV radiation for humans, animals and crops. Medical research specific to the United States has determined that a 1 percent decrease in the amount of ozone in the stratosphere corresponds to a 3 percent increase in the incidence of human skin cancer. There are now 3.5 million new cases of skin cancer each year reported in the US alone. Thus, for each 1 percent reduction in ozone, there would be an additional 100,000 new cases of skin cancer annually in the United States.

This is the medical issue proposed by the authors. I am not able to comment on this as it is outside of my area of expertise.

How the Proposed Process Works

“Rather than large continental-scale ozone loss that occurs over the polar regions in winter characterized, for example, by the term Antarctic ozone hole, circumstances over the central US in summer are very different,” said Anderson. “In particular, because of the very frequent storm-induced injection events detailed by studies at Texas A&M and the University of Oklahoma using advanced radar methods, this structure of highly localized but numerous regions of potential ozone loss requires carefully specified observational strategies and systematic surveillance in order to provide the basis for accurate weekly forecasts of ozone loss.”

The researchers are calling for extensive characterization of the stratosphere over the central United States in order to forecast short-term and long-term ozone loss related to increasing frequency and intensity of storm systems, higher levels of atmospheric carbon dioxide and methane, and other factors.

I have some issues with the process as it is described in the illustration above (from the Harvard University Press release). It is difficult for me to understand how, for example, the "North American Monsoon" (a/k/a the Southwest Monsoon that runs from around July 15 to September 15 each year) produces stratospheric moisture as far northeast as Iowa, especially since it occurs only about 1/6th of the year. 

Final Comments

This is an interesting hypothesis. Whether the amount of ozone depletion, if any, is genuinely enough to increase cancer occurrence and other health issues remains to be seen if future work confirms their finding.