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"Correct reporting of smoke will cause some lifted eyebrows if not more than a little hell raising by those who profess to see no problem in our currently contaminated skies."

On a final approach not too long ago, a stewardess came running into the flight deck of the Boeing Jet with the announcement, "We are on fire! We can smell it!"
Not a hair quivered on my not so bald head. We too had smelled it-- just after entering the smoke envelope for a tight instrument approach. The official weather was listed as follows: clear, three miles and haze, twenty eight point spread, wind West, calm to five. Thus the stewardess was not alone in error. For it was not haze that covered the Eastern United States as a dense and dirty three thousand foot thick blanket that day, it was smoke!
An examination of this discrepancy is in order, for we are involved both as pilots and as reporters.
The Bible of the Weather Bureau is Circular N, titled Manual of Surface Observations. It also serves the U.S. Department of the Air Force, Air Weather Service, and the U.S. Department of the Navy, Naval Weather Service.
Section 3610 defines and describes haze as follows: "Suspended dust or salt particles so small that they cannot be felt, or individually seen by the unaided eye; however, they reduce visibility and lend a characteristic opalescent appearance to the air. Haze resembles a uniform veil over the landscape that subdues its colors. This veil has a bluish tinge when viewed against a dark background, such as a mountain; but it has a dirty yellow or orange tinge against a bright background, such as the sun, clouds at the horizon, or snow-capped mountain peaks. When the sun is well up, its light may have a peculiar silvery tinge owing to haze. These color effects distinguish haze from light fog, whose thickness it may sometimes attain. Note-- Irregular differences in air temperature may cause a shimmering veil over the landscape; this is called 'optical haze.'"
Section 3620 defines and describes smoke like this: "Fine ash particles suspended in the atmosphere. When smoke is present the disk of the sun at sunrise and sunset appears very red and during the daytime has a reddish tinge. Smoke at a distance, such as from forest fires, usually has a light grayish or bluish color and is evenly distributed in the upper air."
What happens in actual practice? If the observer sees the chimney, sees the smoke as a coherent stream, or if he feels it burning his eyes and can smell and taste it, then probably, the report will be smoke. However, if the smoke is from some distance away and is evenly distributed throughout the atmosphere, the observer inclines to lay usage and reports haze. I have quizzed hundreds of aviation industry people, including pilots, tower operators, ground controls, ATC people, dispatchers, and have found only two who were aware that when the Weather Bureau reports haze it is reporting that salt crystals or dust are present in sufficient quantity to reduce the visibility as noted in the mileage figure. Since dust is also a reportable lithometeor by definition salt crystals are the unique feature of haze.
The most casual examination of a weather sequence and the weather map reveals that the Weather Bureau is effectively if unintentionally falsifying the record by reporting smoke as haze.
I have discussed this matter with the Aviation Weather Service and there was agreement that a serious discrepancy existed and that it was of considerable importance. After this discussion, the following was issued:

UNITED STATES DEPARTMENT
OF COMMERCE
WEATHER BUREAU
Washington
"MEMORANDUM
TO:       All Aviation Weather Observing Stations
FROM:     Chief, Observations and Station Facilities Division
SUBJECT:  Reporting of Lithometeors as Obstructions to Vision
REFERENCE: Circular N. Section 3600
Because of increasing interest in air pollution and its effects upon the public, observers should carefully review the definitions of lithometeors given in Section 3600 of Circular N for the purpose of increasing the accuracy with which we distinguish between the several types of phenomena reported. The observer should use past observations, pilots' reports and other knowledge of the community as appropriate, to supplement the definitions in Circular N, in deciding which type of

FEBRUARY, 1964       Page 15