a test over the Pacific stay in the stratosphere?

why is there a maximum

of fallout at the earth's surface during the spring season?

why does the maximum fallout occur at middle latitudes while most of the large tests

its momentum, energy and mass budgets? This more fundamental understanding can then be applied to other problems as well as the questions originally posed and it is obviously pertinent to the global pollution problem under discussion today. I wish to apply the results of these studies to two particular aspects of SST operations: the introduction of water vapor and

the introduction of particulate matter (or gases from which particulates may form) into the stratosphere. I will close with some general remarks concerning global atmospheric contamination and the steps I consider desirable to reduce this contamination. I should emphasize that all the items represent my views as an individual scientist rather than the views of my institution, or sponsoring agency. For those interested in the details three of my published papers dealing with water vapor, volcanic dust and the global pollution problem are attached.

2. WATER VAPOR

The lowest 12-16 km of the atmosphere in which temperature decreases with height is called the troposphere, a word really meaning "well stirred". From 16 to 50 km the region is called the stratosphere and in this region the vertical motions are much smaller relative to the horizontal motions, than is the case in the troposphere. Temperature is either constant with altitude or increases with altitude in the stratosphere. The boundary between the regions is known as the tropopause and can easily be recognized from a graph of temperature versus height. It is thought that most of the air in the stratosphere enters through the tropical tropopause; because this region is very cold moisture freezes out of the air there until the moisture content corresponds to at most the saturated vapor concentration at that temperature ( -80°C) which is close to 2 microgram of water vapor

per gram of air. Most of the moisture measurements made between the tropopause and 30 km the limit of balloon sounding are in the range 1-4 micrograms per gram (1). The stratosphere is kept dry by this natural freeze-out mechanism and the total moisture content above 16 km is about 1015 grams.

The flux of moisture into the stratosphere based upon current estimates of the mean vertical velocity at the tropopause (2, 3) is between 7 and 10 million grams per second. It is possible that some water is formed in the stratosphere from methane and hydrogen passing up from the troposphere and oxygen already in the stratosphere (4). This possibility contributes to the uncertainty in the flux figure. For flux values of 7 and 10 million grams per second the mean residence times (content derived by flux) are 4.5 and 3.2 years respectively. Recent estimates of the mean residence times of carbon 14 and tritium are 3.3 years and 3.5 years respectively (5, 6). These residence times for gases are of course longer than those for particles which are usually taken to be about 1 1/2 to 2 years in the region below 25 km.

The water vapor observations fit together well, with perhaps the main uncertainty being the methane contribution, and the natural flux is bracketed in the range 7-10 million grams per second.

500 planes will contribute about 2 million grams per second the main difference being that this water vapor is added above the cold trap. In the long run then the stratospheric water vapor content will go up by 2030%. (Content = mean flux times residence time). Locally in regions of high travel density there will of course be regions of much higher concentration. Patches of air with radioactivity concentrations well above the global mean persist for many months after nuclear tests and radioactive tungsten from the 1958 Pacific shots was seen to have higher concentrations in the tropical stratosphere than in the high latitude stratosphere for more than two years.

Water vapor enters the stratosphere at low latitudes in the rising motion region of the Hadley cell circulation (see figures in my Scientific American article attached). There are no major middle latitude sources;

if there were there would be a much higher mean concentration observed in the stratosphere for the temperatures are much higher at middle latitudes. Much has been said in the press concerning thunderstorms ás a source of stratospheric water vapor. Thunderstorms are certainly an integral part

of the mean Hadley cell circulation at low latitudes but they cannot introduce more than the number quoted above of 7-10 million grams per second. If they did the stratosphere would very soon show evidence of increasing water vapor concentrations. The hypothesis in these letters to the press that one thunderstorm introduces as much as 2 million grams per second and that thousands are penetrating to 70000ft. at any one time implies rapid flooding of the stratosphere. It is clearly an incorrect hypothesis and it is significant to me that it has not been offered seriously in the scientific literature; I cannot even trace its originator!

There are three consequences of this additional water vapor: it will change the radiative cooling in the stratosphere; it will interact with ozone to reduce the ozone concentration; and it may give rise to additional clouds.

The change in radiative cooling due to the presence of the vapor alone is expected to be small (7). Basically this is because water vapor plays a subsidiary role to ozone and carbon dioxide in the stratosphere. The problems of computing the ozone concentration in an atmosphere containing water vapor have been studied by a number of people in the past few years (8-13). Ozone (03) is formed when atomic oxygen (0) originating from molecular oxygen (02) by the absorption of short wavelength radiation, combines with molecular oxygen (02). The studies show an expected decrease of ozone; for example Harrison of the Boeing Company predicts a decrease in ozone of about 4% from the additional SST water vapor. Basically the decrease occurs because the hydrogen from the water vapor acts as a catalyst to change ozone back to molecular oxygen. The reactions that take place at these high altitudes are not known with certainty

it is quite possible that hydrogen introduced from the fuel in forms other than water vapor would act in the same way to further

deplete the ozone.

Professor MacDonald has raised the possibility that

the decrease in ozone will permit more ultraviolet to reach the surface and that this in turn will increase the incidence of skin cancer. It is straightforward to estimate the magnitudes involved in the first part of his hypothesis. For example at the latitude of Miami in summer ultraviolet at 3000 wavelength would increase by 11% if ozone decreased by 4%, assuming all other factors remain constant. Much has been written on the topic of the biological effects of ultraviolet light (e.g. 14, 15) and it is not appropriate for me to discuss this topic here.

I discussed the possibility of cloud formation one year ago and there have been no scientific rebuttals in the literature since. It is also discussed in the M.I.T. Study of Critical Environmental Problems (16).

Clouds form in air which is saturated with water vapor; the air can hold less water vapor at low temperatures and in the stratosphere rising motion and adiabatic expansion coupled with radiative processes produce Clouds occur naturally in the 22-27 km height range

the low temperatures.

at high latitudes in winter.

These mother-of-pearl clouds are often

reported as patches over Norway but as continuous sheets over the Antarctic where temperatures are lower. The region of cloud formation would be expected to grow in extent as the water vapor concentration increases. The feedback of the clouds on the temperature distribution cannot properly be assessed without a comprehensive dynamical model and this is not yet available. The region of increased cloudiness will correspond fairly closely with the region of lowest temperatures at 25 km. In January this region is over Norway, Greenland and Iceland and sometimes moves over Alaska. (see two examples in Figure 1). Temperatures are normally too high for additional clouds to form in the summer season near 25 km.

Clouds form near 80 km in summer at high latitudes; again they occur in regions of low temperatures and rising motions. These noctilucent clouds are often obsrved over Norway and Sweden. Again increased water vapor would be expected to result in increased clouds.

I note here that changes in other gaseous constituents such as the oxides of nitrogen and hydrogen as mentioned earlier, can alter ozone amounts. Few computations have been performed (11).

All the estimates of the influence on the real atmosphere require a full dynamical model simulation before they can be properly assessed; this applies to the photochemical computations which need to have the effects of atmospheric motions included (after all they are dominant in the lower stratosphere) as well as the discussion of clouds. In addition a careful study of all other possible reactions is needed. Measurements are required of all the gaseous and particulate components of the stratosphere and for a full understanding these should be on a global basis.

The SST fleet will introduce small particles directly into the stratosphere and as there are no processes acting to wash them out their residence time is long, typically 2 years. This hold-up of particulate debris was quite evident in the nuclear test observations and contrasts sharply to the case of the troposphere where most of the nuclear debris was removed within 30 days (much by rainfall). The amounts of aerosols that might be involved are discussed in the M.I.T. Summer-Study book (16) and I will not repeat the discussion here. Not discussed at length there is the possibility of smog formation from the gases introduced by the SST. Large quantities of oxides of nitrogen are expected, together with traces of hydrocarbons and these seem to be the necessary ingredients of smog. The short-wave flux favorable to smog formation is stronger in the stratosphere than at the surface and there is of course ozone in abundance. topic of particle formation in the stratosphere is at a very rudimentary stage and needs much more work. In fact the joint interaction between ozone, water vapor and oxides of nitrogen is another area where much remains to be done.

The whole

Parenthetically suppose that you had been told in 1920 that the emissions from autos in California would build up to the point where in 50 years

time school-children would be kept indoors and told not to excercise

what