“ Humanity a Poor Weather Thermometer ”

Lake County Mail, Issue 9, 23 July 1947, Page 1

“ Humanity a Poor Weather Thermometer ”

Says Mr H. D. Walker

Bodily reactions to the weather being what they are people who, awaking gratefully, inhale the comfortable air of a mild winter morning, find it difficult to believe that there may have been a 14-degree frost overnight, and vice versa. But weather-recording instruments, like the camera, cannot lie, and humanity is a poor thermometer, according to Mr H. D. Walker; Queenstown weather recorder, who writes:

“So much controversy has taken place lately regarding frost in Queenstown that the following explanation may not he out of place. Some people appear to he confusing night ground-frost with morning air temperature,” said Mr Walker. “It is also erroneous to confuse freezing point of water with frost point because injury to the tissue ®f growing' plants is not caused until the temperature has .fallen appreciably below the freezing point of water .(32 degrees F.). A ground frost is regarded as having occurred when the thermometer on the grass has fallen to 30.4 degrees F. so that the air temperature reading is always below the frost read-

mg. «The minimum grass thermometer i* equipped with a needle which drops back with each succeeding cold air w-aye and if the temperature rises the Hcedlc stays at the lowest recording. The greatest degree of frost might occur at any time between sunset and sunrise. If the lowest reading of grass temperature, say 14 degrees of frost occurred at 5 a.m., and mild conditions prevailed after this it would naturally confuse people to arise on a relatively mild morning and be told that there had been 14 degrees. A person who rises from bed at 7.30 a.m. will experience milder conditions on a morning when the air temperature stands at 10 degress below freezing point and there have been 14 degrees of night frost than on a morning with 11 degrees below freezing point (air temperature) and only 11 degrees night frost. “ We are inclined to think that the greater frost occurs when we get out o? bed. “Minimum air temperature readings during the first week in July have been exceeded, so early in the season, on two occasions only during the past 10 12 years. The greatest frosts occur ( July 15 and August 15, and then only after the first heavy fall of snow. So there is plenty of time left i» which to break a recoi'd. “The gorge wind which moved with exceptional vigour and at 16 degrees holow freezing point during the first weak in July was sufficient to put as much strain on taps and water pipes sm many more degrees of frost on a cajm night. The penetrating qualities of this wind arc sufficient to invade the most sheltered places. I am not prepared to argue regarding degrees of fropt outside the observatory, in this part of the town or that, because i(- is ajy duty to take observations at the weather station only. “Nevertheless the grass thermometer, which is checked for accuracy at 6.30 p.n. daily, is in the same position as it h&e been for years and did not register aay phenomenal frost, . although admittedly the severe frost was earlier usual and the gorge wind whieh normally moves at rate two actually mered into the town several degrees taster. ■* “ My main reason. for writing this

article is to point out the fact that the air temperature when people are going to work at 0 a.m. can he so far removed from the night ground temperature as to make the frost readings appear ridiculous, “In other words it is impossible for any person wrapped up fgst asleep in bed to arise in the morning and estimate the night frost. The fact that the effect of evaporation of moisture cm the skin will cause people to experience colder conditions whilst the air temperatiue is actually rising is sufficient to prove that humanity is a poor thermometer.