USA winter
weather of 1939/40 as a consequence of the war in Europe? (2_32)

Extract from: “Climate Change & Naval War," pp.117-122; USA winter weather 1939/40 caused by war (2_32) United States pushed into the cold    USA deprived of rain    Natural variation?    Summery    LITERATURE

The United States pushed into the cold.

First signs of a ‘real’ winter emerged at Christmas time 1939, when except for the Deep South and California, the United States had snow and extreme cold (NYT, 26 Dec.39). Winter came earnestly in early January 1940, with a frigid wave that gripped most of the United States (NYT, 06 Jan.40). Icy north-westerly winds swept over New York with force, on January 06, causing temperatures to drop to an average of 10 degrees (F) below normal (NYT, 07Jan.40). From the Continental Divide to the Atlantic Coast there were strange occurrences as compared with normal weather conditions. Frigid waves even touched the northern parts of Florida (ditto). Was this due to the unusually dry air in November 1939, as noted by Dr. James Kimball in ‘The New York Times’ on January 7^th  (NYT, ditto), which actually continued well into December 1939 (see below)? That December had not been as dry as November in statistical terms, may be due to snow that fell with the Christmas cold, e.g. between St. Louis and Louisville the snow generally was 6 inches deep (Lit.: Brooks, Winter 39/40)[1].

The less humid the atmospheric air is, the more easily it can be replaced by colder air. If the amount of water in the atmosphere is less than average, the ‘vacuum’ thus created, is filled by colder air. If the atmosphere is ‘water free’ as on the moon, the temperature range there is about 300°, it is somewhat plus 150° or higher when the sun shines, without the sun shining, temperature on the moon is in the range of minus 150° or lower. On the earth the water in the air makes the difference in global air temperature. About the equivalent of three-metre deep water layer of the ocean surface is usually in the atmosphere. If a portion of this water ‘has been taken out of the air’ for a brief period of time during sun-less winter months, arctic air sweeping in from the North Pole region may cause a frigid blast causing surprising cold winter conditions.

This paper will show that, the United States had an extremely dry weather from October to December 1939, presumably caused by the war in Europe. 

USA deprived of rain

Since the initial days of September 1939 a several hundred kilometres long battle line stretched through Central Europe from Straits of Dover and Helgoland Bight to Switzerland with attacks of various intensity; missions and encounters taking place every day. As has been explained elsewhere, (Rain-Making 1939, 2_31), it rained excessively in Central Europe, presumably due to military activities over land and at sea. In early September the Russian and Japanese Armies met in a severe encounter in the Outer Mongolia (2_33), whereby California experienced an eight days heat wave since about the September 16^th followed by a severe tropical storm (NYT, 25 September) and record rain (see below). 

Accepting the status-quo as it is, it might be interesting to see whether it is possible to identify a reflex action in the air that reached North America from the French-German front in Europe, either from the fires burning in Warsaw during the second half of September, or from the fighting in China?. Actually, with regard to contemporary climatic conditions in the United States, it is a fact that the weather changed suddenly from too wet to too dry between summer 1939 and winter 1939/40.

Winter of 1938/39 in the United States was abnormally wet particularly in the eastern United States and in the Southwest, with larger part of the country having above–normal condition . Spring of 1939 was exceptionally dry with only a few States from the Mississippi Valley eastward having somewhat more than normal rainfall. From the Great Plains westward, all States experienced deficient rainfall. The summer was relatively wet eastward of the Great Plains, except in the Northeast, where rainfall was deficient in almost all sections. The fall season was extremely dry over large areas, although amounts of precipitation were a little bit  above normal in Utah, Colorado and Arizona. For whole of the areas eastward of the Rocky Mountains it was the driest fall on record. (Lit.: Martin, The Weather)[2].

With regard to anthropogenic rain making due to military activities in Europe and Asia, and due to the fact that, ‘aerosols’ from battle fields, for example in Poland during September 1939, could easily make their way to the USA, it should at least be mentioned here that in California precipitation in September 1939 was 370 % above normal (Alabama, 119%; Arizona, 335%; Nevada 327%; Utah 261%. Without drawing any conclusions from this fact. however, in most other States, September 1939 was exceptionally dry.

A closer look at a  few areas which received  above normal rain in fall of 1939 reveals that it was the result of high precipitation levels in September. Figures given below show the percentage of normal precipitation. It may be noted that the States named by Martin above (Lit.M Martin)[3] are normally very dry during the months October –December. 

Source: (Lit.: Martin, The Weather)[4].

During this period of time California recorded the highest percentage of 370 above average rain in September 1939.   South Dakota and Wyoming recorded a mere 1 percent and North Dakota and Nebraska recorded just 5 percent. Only Arizona exceeded the ‘average mark’ by 136 percent. November 1939 was the driest month in the history of whole USA.  For the whole of the USA, the November 1939 rain average was about 30 percent lower than the ‘ dry spring average’, with the driest months May (72 percent) and April (94 percent).

Total precipitation in the 42 States of USA during the closing months of the year 1939 as listed by the Monthly Weather Review (Lit.: Martin)[5] was as follows:

The ‘unusual dry air’ during November 1939 was quickly noticed (NYT, 07 Jan.40). The recorded dry months of October to December 1939 coincides perfectly with the excessive rain in central Europe where the battles were being waged.

Natural variation?

The ‘timing’ between excessive rain in Europe and the dry months in the United States is a perfect indication of the relationship between both the events. Any ‘interchange’ between dry and wet air takes  time.  A dry or humid air body can exist up to several days or a few weeks. An ‘air body’ needs a couple of weeks to circle the Northern Hemisphere. Interaction of air between the hemispheres may take  several months, as  based on observations made on movement of air in the wake of the outbreak of the volcano Krakatoa in 1883 (Lit.: Furneaux)[6] and (Lit.: Wexler, Spread)[7]

Scherhag, who analysed  disruption in  circulation of air  in the  winter of 1940, states with regard to air movements that there must have been a subsequent air-body-transfer (Massentransport) from the Southern Hemisphere towards the Arctic  (Lit.: Scherhag, Zirkulationsstoerung)[8]. This remark makes it clear, that ‘dry air’ from Europe could have circled the globe for some time before a ‘humidity gap’ could be refilled. It also confirms that there was a ‘humidity gap’ in the first place. If this dry-air-gap was not caused by military activities, what else caused it?

The Regions Covered: January 1940 was cold in all Northern Hemisphere regions, viz. North America, Northern Europe and Northern Asia, (The war in China, 2_33). This is a strong indication that there was too little humidity in the air (as proved in the case of the USA - above), giving arctic air a free path to penetrate deep into southern regions. At least the first cold wave in the second half of December of 1939 can be clearly related to the prevalent ‘dry air’ condition. Additional causes (e.g. snow cover) may have contributed to subsequent weather events. Nevertheless, presumably the ‘dry air’ in late 1939 did not move away quickly, due to scant sunshine available during the winter season in the northern hemisphere.

Difference between the winters in USA and Europe: A further piece of evidence is the fact that severity of the winter in the United States was over by the end of January 1940 (Lit.: Martin)[9], whereas extreme winter conditions prevailing in Northern Europe even during February 1940 show that a number of countries e.g. Holland, Northern Germany and Southern Scandinavia, experienced their coldest winter for more than 100 years,.

Lower air circulation: Only few years after WWII, Richard Scherhag, came to the conclusion that winter of 1939/40 was the result of a comprehensive general disruption in the atmospheric circulation, which could be regarded as a ‘prototype’ for a weakened circulation (Lit.: Scherhag, Zirkulationsstoerung)[10].

Summary

This paper provides a number of indications to show that the war in Europe may have significantly influenced winter weather conditions over large distances. In this case, North America had a severe cold January in 1940. However, this was presumably initiated by lack of usual rain in the United States during the months of October to December 1939 in the first place. This could have been caused by excessive ‘rain making’ on account of military activities along the Western Front in Europe. The evidently low humidity in the atmosphere in late 1939, made it easy for arctic air to travel forcefully over the northern parts of the continents in the Northern Hemisphere at low temperatures.  The timing of ‘dry air’ and the invasion of polar air into all continents in the Northern Hemisphere with severe impacts also in USA and China seem to suggest that this was not a mere natural variation.

Although the ‘dry-USA’ aspect together with are highly interesting contributory events, neither is however, the principal cause of the severe war winters of 1939-42 in Europe, (e.g. Winter 1939-40 2_11), and the subsequent global cooling from 1939 until the 1970s, (Sea system effected, 4_12). But these aspects should be regarded as a collection of ideas for further investigations and study.

That something strange had been going on with the weather many thousand kilometres away from the war in Europe, is briefly indicated by an excerpt from Brook’s paper (Lit.: Brook, p. 160)[11]: “Paradoxically, most of eastern Canada north of latitude 48° was above normal, with temperatures running up to more than 25° above normal north of latitude 58° and 18° above normal in the interior of Alaska. Missouri was actually as cold as the Hudson Bay region for the month”. The key for this erratic behaviour was the war in Europe.

LITERATURE:

Brooks, Charles F.; ‘Some Remarkable Features of the past winter’, in.: Bulletin American Meteorological Soc. , Vol. 21, 1940, pp. 157-162.

Furneaux, Rupert; ‘Krakatoa’; Englewood Cliffs, N.J. 1964; p. 158.

Martin, R.J.; ‘The Weather of 1939 in the United States’, in: The Monthly Weather Review, Vol.67, 1939, pp. 444 - 445.

Scherhag, Richard, (Zirkulationsstoerungen);  ‘Die grosse Zirkulationsstoerung im Jahr 1940’, in: Annalen der Meteorologie, 4. Jahrgang, Heft 7-9, 1951, p.321-329.

NYT; The New York Times.

Wexler, H. (Spread); ‘Spread of the Krakatoa Volcanic Dust Cloud as related to high-level circulation’, in: Bulletin American Meteorological Soc., Vol. 32, No.2, February 1951, pp. 48-52.

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