89 



Mr. Synar. Let's conclude at that point and we will get into some 

 more things in the questions. 

 Professor Michaels. 



STATEMENT OF PATRICK J. MICHAELS, ASSOCIATE PROFES- 

 SOR, STATE CLIMATOLOGIST, UNTVERSITY OF VIRGINIA, 

 CHARLOTTESVILLE, VA, ACCOMPANIED BY GREGORY CLAY- 

 TON, DIRECTOR, FREDERICKSBURG ALR OFFICE, VIRGINIA 

 DEPARTMENT OF ENVIRONMENTAL QUALITY 



Mr. Michaels. Good morning. My name is Patrick Michaels. I 

 am associate professor at the University of Virginia and State Cli- 

 matologist for Virginia. I would like to thank you for soliciting my 

 testimony on the topic of air visibility. 



It is the perception of declining visibility, as shown by the earlier 

 witnesses, that is one of the most potent forces empowering this 

 issue. It is particularly true here and particularly important in the 

 Shenandoah National Park. 



I am also a resident of the Shenandoah Valley and I share your 

 concern for the park. As a scientist I have an academic interest in 

 large-scale environmental issues. 



The question I would like to address for a few moments has to 

 do with the visibility of the park. The Federal Aviation Administra- 

 tion and its forerunners in the National Weather Service have em- 

 ployed approximately 100 specially trained observers for visibility 

 that resides at airports; in this case, the four airports that sur- 

 round the park. 



Airport data is very tricky to deal with. Air visibility can differ 

 from airport to airport because there are different horizon markers. 

 Some airports have mountains that observers can see and others 

 do not. 



What is important is that the data is recognized as valid when 

 it changes uniformly across a region like this. When it is a hazy 

 day at Dulles, it is a hazy day for Lynchburg, and the same for 

 Richmond. 



These data are highly correlated with each other and they sur- 

 round the park; therefore, they are representative of the park. We 

 analyze hourly observations of these data on CD-ROM from the 

 U.S. Department of Commerce. I would like to show you results of 

 mean monthly visibility analyses at noontime. 



This is winter. This is January mean visibility. This is 1960; this 

 is 1990. What you see is no trend in the airport visibility data. 

 When we go to the spring data, you see the same thing. There is 

 no trend whatsoever. 



I will skip over to the fall for a second, ignoring summer. Again, 

 no trend in the four airports that surround the park. It is in the 

 summer and, in fact, in 2 months in the summer we do see some 

 trends in visibility. And I think these are worth looking at. 



What there is is a trend for statistically significant decline in vis- 

 ibility that occurred in the 1960's in this record. It ends in 1970 

 in July, in 1973 in August. 



Since then, since 1969, there are no statistically significant de- 

 clines in visibility for any month at any airport. Five of the airport- 

 month combinations, in fact, show significant increases in visibility. 



