World Climate and World War V. CONRAD Harvard University, Cambridge, Mass.

INTRODUCTION THE CLIMATE OF CENTRAL EUROPE' will not be described. It is much more IT is NOT INTENDED to give climat- moderate than that of New England, ographies either of all war thea- Warm winters and relatively cool ters or of certain ones. Only those summers prevail; precipitation falls climatological peculiarities may be all the year round. Neither cloudi- emphasized which influence warfare in ness nor wind show extreme or sur- an extraordinary way. prising values. I. THE HIGHER LATITUDES OF THE ATLANTIC OCEAN

SYNOPSIS Ice, fog, and wind conditions of the higher latitudes of the North Atlantic Ocean, crossed by the U. S. N. supply route are discussed. The Atlantic air route which rounds Iceland is advantageous, especially in spring, owing to the easterly winds in the surface layers and the westerly winds aloft in the high latitudes. Regarding the AEF in Iceland, some char- acteristic climatic features of this island are described and in an appendix numerical cli- FIG. 1. Average monthly air temperatures at matic tables are given for four places on the Vardo (7y2°N) ( ), and at Archangel (641/2°N ) ( ). north, east, south and west coasts of Iceland. Norway. But also in Russia there is The main supply route from the Alexandrovsk, at the mouth of the United States to U. S. S. R. runs Kola River, which is more advan- across the North Atlantic, passes Ice- tageous than Archangel as far as land, rounds the European North the ice conditions are concerned. Cape, and reaches Archangel on the * • • coast of the White Sea. This course The ice is not only prejudicial for is open only in summer because the reaching the goal of the supply route White Sea is ice-bound from about but also forms a danger for ships November to April, more than half near the American coast in the region of the year (190 days). The Murman of the Newfoundland Banks. The coast and the coast west of it are peril is the greater here as this region much warmer, an effect of the North is also very foggy. The two phe- Atlantic drift. In some years no com- nomena are caused by the oceanic cir- pletely closed ice cover exists there culation and in the last analysis by and only in the coldest years has the the general distribution of pressure. coast been ice-bound for as much as In this part of the sea there are two five months. oceanic currents:—the Labrador Cur- In this connection the average rent from the polar basin and the monthly air temperatures of Vardo Gulf Stream with its tropical warm (70y2°N) and of Archangel (64y2°N) waters. are of interest. (Fig. 1.) Figure 2 shows the stream lines of The average winter temperature of the Labrador Current and the average Vardo is 13 F° higher than that of distribution of the pack-ice of New- Archangel in spite of its location foundland according to the observa- 6° lat. farther north. Vardo is in tions of the International Ice Patrol

Unauthenticated | Downloaded 09/27/21 10:01 AM UTC great and the little Karayak glaciers alone push off 1200, the Jacobshavn glacier 1350 icebergs a year. A num- ber of these icebergs drift by current and wind into the Polar and the Labrador currents and thence to the Newfoundland region.

FIG. 2. Distribution of packice about New- foundland and the streamlines of the cold currents (after Smith). of the United States Coast Guard. FIG. 3. The average annual course of the The boundary lines show the area number of icebergs at Newfoundland, (after covered by ice at the time of the maxi- A. Defant). mum. Here the ice fields and icebergs The diagram, Fig. 3, gives a good place ships in imminent danger. In idea of the average number of ice- time of peace the ice patrol service bergs which arrive there and of the offers an excellent protection against great variation of the monthly num- this peril. In war time such a service bers. The period from the middle of is restricted. The source regions of March through the middle of July is the pack-ice of the Newfoundland the season of icebergs. The number Banks are in the main: Baffin Bay and of icebergs in the individual years is the eastern coast of Labrador. If a subject to great variations. In 1924 thickness of the sea ice of about 5 feet the ice patrol counted only 11 icebergs is assumed, it can be calculated that but in 1929 there were 1300, according the sources mentioned above produce to E. H. Smith. The icebergs, especi- an amount of about 750 cubic miles ally in combination with fogs, are an of ice per year. A good portion of imminent menace to navigation. The these masses is transported southward shipwreck of the steamer "Titanic" of by the Labrador Current and is pre- the White Star Line is still well re- served by the low temperatures of this membered. On the night of April 14 polar current so that parts of these to 15, 1912, the giant new steamer ice fields extend to the south of the sank by collision with an iceberg just Newfoundland Banks where they are at the most southerly point of the finally melted by the more intense Newfoundland Bank. More than 1500 insolation and especially by the warm people were the victims of that catas- waters of the Gulf Stream. trophe and property of immense value Scattered amongst the pack-ice, are was lost. This disaster gave rise to the icebergs also drifting in the Arctic organization with which the U. S. waters of the Labrador Current. They Coast Guard, now of the U. S. Navy, originate in the main from Ellesmere is charged. As long as this service Land and from the glaciers on the warns the ships by radio messages west coast of Greenland. Seven thou- about position and drift of the bigger sand five hundred icebergs are pro- icebergs, and also destroys some of duced there in an average year. The them, navigation in the region men-

Unauthenticated | Downloaded 09/27/21 10:01 AM UTC tioned is well protected. Submarines too are endangered because of the great draught of the icebergs. A rather low iceberg of 100 feet high, has a draught of about 600 to 800 ft. The risk to the allied ships can be diminished by suitable forecasts while the enemy is fully endangered. The entire mass of the icebergs there is negligible in comparison with the huge masses of the pack ice, which offer eventually a sort of protection to the attacking submarines. The mass of the pack ice reaches its maximum south of the Newfoundland Bank in February. The minimum, practically zero, occurs

FIG. 5. The different sorts of water at New- foundland (after Smith). sometimes separated from one an- other only by a narrow strip of mixed water. In Fig. 5 the distance is only 50 miles at the southern point of the tongue of the Arctic water.

FIG. 4. Relative numbers which characterize the mass of packice south of the Newfound- land Bank in the course of the year. from September to December. Fig. 4 gives an approximate representa- tion of these conditions in relative numbers. The difficulties of navigation caused by ice are intensified by fog. Fig. 5 shows the three different sorts of water lying side by side in the Newfoundland region. There is the Arctic water of about 34° F which originates in high latitudes and cov- ers the shelf from Baffin Land to Newfoundland. These Arctic waters drifting southwards represent the core of the Labrador current. Turbu- lence of air and water cause a zone of mixed water of about 45 °F. This oceanic region is bordered by the warm waters of the Gulf Stream of about 61 °F. This and the Arctic water are FIG. 6. Number of hours with fog in the area 40/50°W and 45/50°N for the months.

Unauthenticated | Downloaded 09/27/21 10:01 AM UTC FIG. 7. Frequency (%) of fog on the North Atlantic Ocean (after Schott). Thus great differences of tempera- to take drift measurements on the ture in small distances occur. The sea surface, to sight landmarks and to cold Arctic water gives rise to dense get into and off of airports are diffi- fogs when warm, moist air masses culties not to be minimized. When blow over them, chiefly in summer the fog is near a cyclone the flying and fall (advection fog). Observa- conditions aloft may also be very bad. tions show this summer maximum However, in the Newfoundland region (Fig. 6). the frequency of storms is not too The diagram is related to the area great in winter (22%), and rather of 40-50°W and 45-50°N. This area small in summer (4%). is practically identical with that of the Arctic water east of Newfound- land, and the most fogginess is found there. The two small maps of Fig. 7 show isolines of frequency of fog in the North Atlantic. This representation indicates too the difference between winter and summer and the relatively restricted area with a very great frequency of FIQ. 8. Isolines of the probability of storms fog in summer. Therefore a steam- (% ) on the North Atlantic Ocean in winter (after the "Segelhandbuch fur den Atlanti- ship course somewhat more south schen Ozean", Deutsche Seewarte). avoids the area of greatest frequency The map in Fig. 8 shows the fre- where the probability of meeting a quency distribution of storms over foggy hour exceeds 30% in summer the North Atlantic Ocean in the (only 1 i% in December). Five degrees period December to February. The farther south, the probability in July strip with the high frequency of 30% is reduced to half. lies far south and east of the foggy As far as aviation is concerned the and icy region, where on the average, Newfoundland fogs are not a real a storm occurs only about one out of difficulty because the foggy layer is on every 18 days from June through the average not thicker than 450 feet. August. It is of great importance Extreme thicknesses do not surpass that the perils of ice and fog in the 800 to 1000 feet, according to kite Newfoundland region in summer are ascents from the steamers H. M. S. not intensified by frequent storms. "Scotia" and U. S. S. "Seneca." These Not alone do the supply routes of fogs, so dangerous for navigation on the United States to U. S. S. R. and the sea, usually can be easily flown Scotland create interest in the climate over by aircraft, though the inability of North Atlantic. In the beginning

Unauthenticated | Downloaded 09/27/21 10:01 AM UTC of 1929 W. H. Hobbs O, relying on his experiences in Greenland, sug- gested a new route for transatlantic aviation between the United States and Europe. This route should be in the neighborhood of the great circle of the earth which passes through Chicago and Northern Europe. "After traversing British America to Hudson Strait, this line crosses Baffin Bay and southern Greenland and hits the northern tip of Iceland as it continues to Trondheim, Oslo and Leningrad". This Polar Atlantic Route was used by W. von Gronau for three Atlantic flights from east to west and, later on, by an Italian squadron of 25 airplanes under Balbo. Flights in high latitudes meet a special difficulty because of the fre- quency of undercooled cloud particles. These can easily cause ice accretion on aircraft. The danger of icing is especially great with planes which FIG. 10 and 11. Air pressure and wind at fly over the 10,000 foot ridge of the North Atlantic in February and August Greenland when the route of Hobbs (after Schott). tudes. is fully followed. It was chosen by Figs. 10 and 11 which represent the distribution of pressure and wind above the North Atlantic indicate that in winter and summer, weak easterly winds prevail on the average along the route north of Iceland to Cape Farewell (southern point of Green- land). A. de Quervain O had simultan- FIG. 9. The transatlantic air route via Ice- land. eous pilot balloon ascents made at Gronau only once, and was described Akureyri in north Iceland and on the as being dangerous and risky. west coast of Greenland (Godthavn). Therefore, the route represented in If all easterly and all westerly winds Fig. 9 is reputed to be the most are taken collectively, the following advantageous one in high latitudes. percents result:— Surface 0.5 1.0 2.0 3.0 4.0km Akureyri Easterly winds 65% 50 54 40 28 23 Westerly winds 35% 49 45 61 72 76 Godthavn Easterly winds 84% 85 84 80 68 65 Westerly winds 16% 15 16 20 32 35

O) W. H. Hobbs, An Arctic Airplane Route (*) A. de Quervain, Gleichzeitige Pilotauf- between America and Europe. Arktis, vol. 2, stiege in West Gronland und Island. Beitr. 1929, p. 15. z. Physik d. fr. Atmosphare, vol. V, p. 132.

Unauthenticated | Downloaded 09/27/21 10:01 AM UTC In north Iceland winds with an Polar Circle. Some remarks on the easterly component prevail in the first climate of this island of about 40,000 3000 feet. Above this layer westerly sq. mi., which is located between winds were frequently observed. On Scotland, Norway, and Greenland, the west coast of Greenland the layer seem to be opportune. This geograph- of easterly winds reaches much higher, ical location is of great strategic im- but even here, westerly winds get the portance in this war. upper hand at the height of three or Iceland lies at the northwestern four miles. Undoubtedly these condi- side of the North Atlantic low, one tions are the special result of the of the great "centers of action" of topography of Greenland, and the the atmosphere. Generally the cen- west wind layer comes much lower at ters of the lows pass south of the a distance from the coast. For the island. These pressure conditions air route in question it is important explain the fact that the resultant that there is some probability of a wind directions are from the east as following wind in either direction is shown in Fig. 12 (2). between Cape Farewell and Iceland. The observations of de Quervain are in close harmony with the results of S. P. Fergusson and W. H. Hobbs, obtained on the Greenland expeditions of the University of Michigan (1926- 1929). Also the observations of Alfred Wegener's Greenland Expedition indi- cate easterly winds prevailing on "Eismitte" as well as at the "West Station" which was located at the edge of the inland ice at about 3000 feet. The average wind velocities are FIG. 12. Resultant wind directions at the coasts of Iceland. about 9 mph at the surface and about Single arrows = January. 24 mph at 21 miles height. These Double arrows — July. figures are valid for the months of In conjunction with the great varia- April through June. The steadiness tions of air pressure in this part of of the wind system is surprisingly the Atlantic Ocean (3) storms are great. very frequent. In an average year, In winter the Iceland—Greenland— Papey, on the east coast, has 75 days Labrador route is not so practicable. with storms, Stykkisholm, on the west During the summer frequent fogs coast, has 65. These strong winds, in could cause difficulties. combination with high cloudiness, are In spring, the Iceland route offers very characteristic of the climate of special advantages. "The air pressure Iceland. conditions permit expectation of calm, The north coast of Iceland has a anticyclonic weather more frequently cloudiness 30% greater than Blue Hill than in middle latitudes. Above all, Observatory near Boston. This defi- the wind conditions especially favor ciency of light has a depressive effect flights at this season". (W. Georgii). on many people. On the other hand

An American expeditionary force is (2) The west wind in winter at Berufjordur garrisoned in Iceland in the North may be explained by local factors. (3) The extremes in Reykavik were 1049 and Atlantic between 631 ° N and the 923 millibars within 13 years.

Unauthenticated | Downloaded 09/27/21 10:01 AM UTC Iceland is greatly favored by the the coasts. In unfavorable years such warm Atlantic Current which washes as 1866 the coast was ice bound. As a the south, the west and also the north consequence of these conditions cool coast (Irminger Current) of the summers often follow, because the air island. The water of the east coast is is cooled by the pack-ice and a great even somewhat cooler than that of the portion of the insolation energy is north coast, except in the four months used for the melting process. Then of March to June. The south coast the pastures do not yield the forage is at most favored by a surface tem- necessary for the cattle, so famines perature of 39 °F in January and occur. When the ice blocks the coasts, 50 °F in July. As a result of the great difficulties of supply arise. warm Atlantic current, the win- Because of these possibilities large ter is surprisingly warm. Sum- stocks of food, gasoline, and war ma* mers are indeed very cool. The aver- terial of all sorts should be stored age winter temperature of the island during the next few months while the in 64° N is about 32°F; at Blue Hill coasts will surely be free from ice. Observatory in 42° N, 26° F. The The average low summer tempera- July temperatures in Iceland are 51.5° tures which surpass 50° only in good F, at Blue Hill, 69.5° F. In the course locations, in one or at most two of a long series of years the absolute months, in combination with high minimum of the temperature in Rey- cloudiness and a rocky ground, gener- kavik is - 6.7° F, at Blue Hill, - 21° F. ally prevent the growth of trees. Thus From these examples it is to be seen landscape makes a melancholy im- how mild the winter is in Iceland. pression, especially upon a people However, the great variations of tem- from a country so rich in sunshine perature from year to year should be and forests as it is in a great portion emphasized. March 1856 had an aver- of the United States. age temperature of 40.1° F and that of 1881: 7.5°F. Iceland is situated Nevertheless the climate of Iceland —as we said before—on the western is not at all unhealthy. Only amoebic side of the warm Atlantic current; dysentery and scurvy are endemic but when the distribution of pressure diseases which can easily be prevented is somewhat changed, NW winds be- by present knowledge of hygiene. come the prevailing winds and the Since Iceland does not overlap the inclement weather and climate of East Polar Circle no real polar night exists Greenland is extended to Iceland also. on this island. The "white nights" Seemingly the ice conditions are in summertime are not so exciting as decisive for the great climatic varia- an everlasting polar day, and cause tions on the island. Generally the only good humor—making people margin of the pack-ice does not touch always inclined to be jolly.

APPENDIX For more detailed information about the coastal climate of Iceland a few numerical tables follow. The location of the stations is to be seen from Fig. 12. The data are taken from the "Appendix til det danske meteor- ologiske Instituts Aarbog 1895, II Del.", Copenhagen 1899. Because the source is not generally available the average numbers of hours with fog in the Newfoundland region may be of interest. I have cordially to thank Dr. Charles F. Brooks for having the figures redrawn and for other help. I thank Mr. Ralph Burhoe, acting librarian of the Blue Hill Observatory for all his care to provide me with the necessary literature.

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CLIMATIC TABLES FOR ICELAND Average Extreme mo. mean Absolute extremes of Berufjordur: 64.7°N, 14.3°W, 59 feet, (23 years). temp. temperatures °F temperature °F Cloudiness °F highest lowest Max. Min,( % January 29.0 34 17 51 -10 64 February 29.8 35 22 54 - 3 65 March 28.8 36 15 54 - 7 63 April 34.3 41 26 58 - 1 67 May 38.8 43 35 69 17 69 June 44.6 48 40 78 24 68 July 47.1 50 44 79 33 71 August 46.6 51 43 69 27 69 September 43.7 47 40 69 22 67 October 37.8 42 33 62 13 66 November 33.4 38 28 53 1 65 December 30.0 35 20 53 - 5 64 Year 37.0 40 34 79 -10 67

Precipitation Rel. humidity Number of days with inches % prec. snow fog storm January 4.5 78 17 9 15 1 February 4.2 77 17 8 15 1 March 3.0 76 16 9 15 2 April 3.1 80 14 5 17 1 May 2.6 79 13 4 20 0.5 June 2.8 81 11 1 22 0.1 July 2.4 82 11 0 24 0 August 2.9 81 12 0 21 0.3 September 4.3 81 15 1 19 0.7 October 4.5 79 16 3 16 1 November 4.6 79 17 6 14 1 December 5.0 76 18 8 14 2 Year 43^9 79 177 54 212 10~~

Grimsey (Akureyri); 66°34'N, 18°3'W, 8 feet, (16-22 years). Cloudi- Precipi- tation temp. °F temp. op of temperature °F % inches Highest Lowest Max. Mm. January 28.2 35 8 49 -22 85 1.0 February 26.8 34 13 48 -13 85 1.1 March 24.8 35 2 49 -22 83 1.1 April 29.8 38 19 51 -11 82 0.7 May 34.9 41 31 61 10 80 0.8 June 41.5 47 35 70 20 78 0.9 July 44.4 50 39 67 27 81 1.2 August 44.4 51 36 79 27 78 1.3 September 42.3 47 39 65 23 83 1.7 October 36.9 40 33 53 12 85 2.1 November 32.4 37 25 54 0 88 1.7 December 29.3 36 16 49 - 5 86 1.2 Year 34.7 38 31 79 -22 83 14.8

Unauthenticated | Downloaded 09/27/21 10:01 AM UTC Relative humidity % Number of days with precip. snow fog storm January 83 13 6 1 2 February 82 12 7 1 1 March 82 12 6 2 1 April 82 9 5 4 0.3 May 84 8 4 7 0.2 June 84 9 2 9 0.5 July 86 9 1 13 0.1 August 86 11 1 9 0.3 September 86 13 3 4 1 October 86 16 6 2 2 November 86 16 8 1 2 December 84 15 7 0.4 2 Year 84 143 56 53 12

Stykkisholm: 65.1°N, 22.8°W, 37 feet, (18-23 years). Average Extreme mo. mean Absolute extreme Cloudiness temp. °F temperature °F temperature °F % Highest Lowest Max. Min. January 28.0 34 17 49 -15 71 February 27.5 34 15 48 - 8 71 March 27.9 37 8 49 -13 67 April 33.8 41 25 54 - 6 65 May 39.9 45 36 58 17 61 June 46.6 50 42 68 28 64 July 49.6 54 47 73 33 57 August 48.7 54 44 72 32 59 September 45.1 50 42 61 24 67 October 38.5 44 33 59 17 68 November 33.3 38 28 54 0 71 December 28.8 35 18 49 - 6 70 Year 37.4 39 34 73 -15 66

Precip. Rel. humidity Number of days with inches % prec. snow fog storm January 2.7 88 20 15 0.3 7 February 2.5 88 19 14 0.3 8 March 1.9 87 18 13 0.3 8 April 1.2 87 15 7 0.8 5 May 1.4 83 14 3 1.5 5 June 1.6 82 15 0.4 1.5 3 July 1.3 83 12 0.2 1.6 2 August 1.6 83 13 — 1.0 2 September 3.0 84 17 1 0.7 6 October 2.7 86 17 4 0.3 6 November 2.3 87 18 9 0.3 7 December 2.3 88 19 14 0.4 6 Year 24.5 86 197 81 9.0 65

Unauthenticated | Downloaded 09/27/21 10:01 AM UTC Average Extreme mo. mean Absolute extreme Cloudiness temp. temperatures °F temperature °F % °F highest lowest Max. Min.

January 34.2 38 29 49 7 62 February 34.3 38 28 51 5 65 March 34.2 42 27 51 - 6 61 April 39.7 44 36 54 8 63 May 43.5 48 39 61 15 59 June 48.2 51 45 70 31 63 July 51.3 55 48 66 37 60 August 50.2 54 48 65 31 59 September 46.4 50 43 62 27 66 October 41.2 45 42 55 22 60 November 37.0 40 33 52 3 62 December 33.3 38 26 50 3 60

Year 41.2 43 39 70 - 6 62 Precip. Rel. humidity Number of days with inches % prec. snow fog storm January 4.4 81 22 9 3 4 February 4.4 80 20 9 2 4 March 4.2 79 21 8 2 4 April 3.5 79 18 4 5 2 May 2.4 78 16 2 5 1 June 3.8 82 17 0.3 8 1 July 3.1 82 15 - 7 0.2 August 3.1 82 15 - 6 0.2 September 5.7 83 21 - 6 2 October 5.3 80 19 2 4 2 November 4.8 81 19 4 2 3 December 5.2 81 22 9 2 4

Year 49.9 81 22.5 47 52 27

AVERAGE NUMBERS OF HOURS WITH FOG ON THE NORTH ATLANTIC OCEAN WITHIN 40° TO 60°W AND 35° TO 50°N. (After "Segelhandbuch fur den Atlantischen Ozean," Deutsche Seewarte, 2. Auflage) * £ £ £ * o o o o o © <£> m lO O o © © © © Lat. °N. U5 CO

50°-45° 29 5 201 112 January 45°-40° 43 14 7 July 124 99 21 40°-35° 1 2 2 0 0 2

50°-45° 30 8 August 162 44 February 45°-40° 26 16 7 76 71 12 40°-35° 0 2 3 1 0 1

50°-45° _ 24 20 88 36 March 45°-40° 48 28 10 September 33 45 7 40°-35° 1 1 3 0 0 2

50°-45° 49 20 62 30 April 45°-40° 61 40 8 October 28 38 15 40°-35° 1 2 8 0 0 3

50°-45° 116 35 59 21 May 45°-40° 98 76 14 November 17 29 6 40°-35° 7 6 10 0 0 8

50°-45° 133 66 35 6 June 45°-50° 111 105 33 December 17 11 6 40°-35° 0 2 4 0 2 7

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