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STATEMENT OF PROF. ELMAR R. REITER, DEPARTMENT OF ATMOS

PHERIC SCIENCE, COLORADO STATE UNIVERSITY

Mr. REITER. I have a statement here which is mainly concerned with the meteorological peculiarities of the Denver area as they may tend to aggravate or to magnify the air pollution problems specifically for this region here. The statement is broken down into two chapters. One is the meteorology of the Denver area and the second one is the meteorological research needs as related to air pollution.

First, the meteorology of the Denver area.

The meteorology and climatology of the Denver area is characterized by:

(1) Its location in the center of a large continent.
(2) Its proximity to a high mountain range.

(3) Its relatively great elevation above mean sea level. Since most of the moisture in the lower atmosphere is deposited on the western slopes of the Rocky Mountains, the air to the lee of the mountains over the South Platte Valley is dry. This constitutes a rather significant difference from the air pollution problems of some of the eastern cities. In dry air the diurnal temperature variation tends to be large. During the evening hours a temperature inversion will form near the ground. It will intensify during the night and trap all pollutants within a shallow layer close to the ground. Such inversions are particularly long lived in the Denver area during the winter season in the wake of outbreaks of cold arctic air sweeping southward over the plains east of the Rockies. Anticyclonic weather conditions, which normally follow such cold outbreaks, are characterized by weak winds and poor ventilation. Pollution then may be trapped for days over the metropolitan area with increasing concentration; the only import of unpolluted air in such weather situations comes from local drainage winds. Now, this may

be seen in more detail in this report which also has been passed out. There are several case studies contained which shows the drift of polluted air over the city of Denver.

Exceptionally good ventilation of the metropolitan area occurs during strong chinook or foehn winds which descend in strong gusts from the mountains and rapidly remove the pollution east ward. Unfortunately, not all chinook situations are strong enough to penetrate with their gusty winds to the ground. A pool of cold and stagnant polluted air sometimes remains over the South Platte Valley.

Air samples taken below strong inversions may easily approach values ascribed to Los Angeles pollution : Dr. James Lodge (National Center of Atomspheric Research, Boulder) reports readings in Denver on January 9, 1964, 9 a.m. of one-half part per million of olefin concentration, and three-tenths part per million of nitrogen oxides, which may be taken as an index of total pollution. Such values would indicate serious pollution hazards at warm summer temperatures. At that time of year the inversion normally is destroyed in midmorning by the strong incoming radiation from the sun.

The second part relates to meteorological research needs as related to air pollution.

Under a research contract with the U.S. Department of Health, Education, and Welfare, Public Health Service, 17 stations with wind and temperature measuring equipment will be set up in the Denver metropolitan area. In addition, stations maintained by the Weather Bureau and other sources will furnish wind and temperature information. The location of the stations can be obtained from the chart which has been included here. (See chart on opposite page.)

With this network of measurement sites the microclimate and especially the local wind systems of Denver, will be studied mainly in the 1964-65 winter. The study will be augmented by air sampling measurements conducted by the Colorado Public Health Service, the city of Denver and other collaborators.

It is hoped that this combined research effort will help to answer the following questions:

1. How does the heavy pollution accumulate? 2. Which weather situations aggravate the pollution problem?

The results of this study should allow legislative authorities to evaluate possible steps for alleviating the Denver aid pollution problem.

Senator MUSKIE. Professor Reiter, without objection, "A Study of Denver Air Pollution, that is contained in this very useful pamphlet, will be included as an exhibit and appropriately marked, and the chart will be made an exhibit. As a matter of fact, on that report which I just referred to, if the text isn't too long it might be just as well to put that in the record.

Meteorological conditions, as I understand it, Mr. Reiter, are one of the principal causes for concern here in the Denver area.

Mr. REITER. That is correct.

Senator Muskie. It isn't so much that the current air pollution problem is critical in the sense that it is in the Los Angeles area,

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for example, but in your meteorological conditions you can see the potential danger here as the sources for air pollution multiply and increase; am I correct?

Mr. REITER. That is very correct, sir.

Senator MUSKIE. Now, with respect to meteorological conditions, you described very well in your statement but I would like to pinpoint, if I may, some of the factors for emphasis. What is the nature of the inversion problem here, how low to the ground does it get?

Mr. REITER. Well, on cold nights or after cold nights, and a very typical example of this is today's weather situations or last night's weather situations, the inversion is very low. As a matter of fact, we have photographs of situations like this where some of the downtown tall buildings are sticking out on top of the inversion. You may see them from a distance if you go south of Denver on these hills and take photographs from there. There are a few tall buildings in the downtown region that stick up above the inversion. So in their case the inversion would be of an order of about 300 feet of thinly polluted air on top and heavily polluted air underneath.

The reason for that is, you have a very stable stratification of very warm air on top of the cold air so the cold air cannot mix up into the warm air and all the pollution which is contained in the cold air below the inversion just stays there.

Senator MUSKIE. For the record and for the public, who are here in some numbers, what happens is that air pollution is the consequence of everything that we burn?

Mr. REITER. That is right.

Senator MUSKIE. And so it is a consequence of our standard of living, of our civilization? Mr. REITER. Right.

Senator MUSKIE. It is very difficult to deal with it after the pollutants have been emitted into the air?

Mr. REITER. That is correct.

Senator MUSKIE. And the only means for dealing with it after it is emitted into the air is nature itself?

Mr. REITER. That is correct.
Senator MUSKIE. Winds, rainfall, and so on?
Mr. REITER. Yes.

Senator MUSKIE. But the inversion is nature's way of blocking nature's cleanup program, is that not right?

Mr. REITER. That is very correct.

Senator MUSKIE. Now, a 300-foot inversion in the Los Angeles area could produce fatal conditions, could it not?

Mr. REITER. That is correct.

Senator MUSKIE. So that if you permit the air pollution problem in Denver to progress to the point that it has in Los Angeles, with your inversion situation here, you could produce conditions that would be fatal to human life itself?

Mr. REITER. That is very correct, Senator.

Senator Muskie. Now, in the meantime, are you in a position to comment at all upon the effects of your current air pollution problem on health and upon property?

Mr. REITER. No, sir; I am not in a position to testify on health hazards. This would have to be done by a medical doctor, I suppose.

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