From a hilltop on the Santa Barbara Rincon I look out into fog as impenetrable as that which contributed to the operational difficulties of the conduct of the war in Alaska during the last two years. The sight of this gloomy stuff causes a train of thought to proceed down the cerebral avenues. Our forces in Alaska had two enemies to fight; and as was proved by the laborious eviction of the Nips from Attu and Kiska, not the least of these was weather. Now that the Aleutian campaign is over it might be valuable to discuss in a dispassionate manner some of the aspects of weather in the North Pacific theater and how they bear upon future operations. The strategists point out that one of the four approaches to the heart of the Japanese Empire, and the shortest approach of the four, is through the north. The considerable military establishment already existing, the occupation of the new northern bases and the growing friendly relations with Russia all indicate that Alaska is going to be maintained and quite possibly amplified. It is reasonable to suppose that units now strangers to the region will begin to operate in the north and that regions strange to all our forces, namely, Chishima, Kamchatka, and the Sea of Okhotsk, will yet be visited by them.
The beginning of the war most certainly caught the Army and the Navy flat-footed in Alaska. War materials were being furnished to the Philippine and to the Hawaiian theaters on first priority. Expansion in the north was progressing according to the peace-time development program. Quite naturally the development was accelerated during early 1942. The bases at Kodiak, Sitka, and Dutch Harbor blossomed with war-time construction. The Alaska Defense Command performed the Herculean task of building fields for the Eleventh Air Force as far west as Umnak, in the Aleutians. All this was done between the time of Pearl Harbor and the Battle of Midway. The Nips were frustrated in their northern diversion at Dutch Harbor but settled for the doubtful privilege of occupying the Rat Islands and the Near Islands. The mission of the forces in Alaska became obviously to expel the enemy eventually and to harass him continually. The harassment was done in great measure by air. His bases at Kiska and Attu were visited time and again by the Eleventh Air Force. His activity in the North Pacific was scouted and observed by Fleet Air Wing Four. In the meantime our own bases were developed ever nearer to the objectives in preparation for the final expulsion. In August of 1942 our forces moved to Adak. In early 1943 we had occupied Amchitka, some 60 miles from Kiska. During the whole time our aircraft worked on the Nips from fields far and near. It was not easy flying. Press representatives with the operating forces stressed the feature of weather. Weather was the most outstanding and spectacular subject to be reported in the whole campaign. Weather was strategic. Weather was tactical. Weather was terrible. Weather prevented air support during the initial phases of our invasion of Attu. Weather in the form of all- pervading fog allowed the enemy to evacuate Kiska without detection.
Let us investigate this weather. In the winter it is stormy with the passage of one cyclonic disturbance after another. In the summer it is foggy. For days on end the surface of the sea is covered with the dank pearly blanket of stratus cloud resting at sea level. When is the weather good, if ever? Seldom ever; but the chances are that April and May and October will be better than the other months of the year. Always, however, there are breaks in the weather, winter or summer; and it was during these breaks that the Eleventh Air Force and Fleet Air Wing Four did their glorious work in harassing the enemy. Thousands of hours of tactical flying were done when the weather was not good. Planes were lost. Missions were canceled. The Naval Air Transport Service and the Army Ferry Command hauled tons of freight and hundreds of passengers over this hazardous route on instrument clearances. The air work of our forces did more to discourage the enemy in his abortive attempt to invade North America than any other factor. Fie couldn’t take it. He never succeeded in building serviceable fields. He never operated aircraft aggressively in the northern theater after the bombing of Dutch Harbor. He used only sea planes locally and never in sufficient numbers to be effective. His attempts to bomb Attu from the Paramushiro Jima during our invasion were feeble. Is it possible that our forces are able to surmount the meteorological hazards of the North Pacific while our enemy cannot?
Meteorology and oceanography are kindred sciences. They must both be invoked to understand the physical processes of the weather north of the parallel of forty in the Pacific Ocean. The vast Pacific Basin north of the equator contains a body of water which slowly circulates in a clockwise direction. The western periphery of this circulation is composed of the Kuroshio or Japan Stream which originates in the North Equatorial Current north of the Carolines, passes close to the Philippines, washes the eastern beaches of Taiwan, and then shoots northeastward toward the Aleutians as a well-defined flood of warm tropical water. This current is comparable in many ways to the Gulf Stream in the North Atlantic, but with one exception. This Black Stream of the Pacific does not maintain its identity for long as does the Gulf Stream in the Atlantic. For one reason, there is no wide open gateway for it to pass into the Arctic as exists in the Norwegian Sea. For another, the North Pacific is too vast and unconfining for the Japanese Current to maintain itself against the diffusing forces offered by wind-driven ocean currents set up in the prevailing westerlies north of the fortieth parallel. For another, the Oyashio, a current from out the cold Bering Sea, as well as the great volume of water which the Sea of Okhotsk contributes through the passes of the Kurile Islands, also cold, tends to diffuse the river of tropical water and disintegrate its effect as an entity. It is dispiriting to shatter the old-time illusion of the Japanese Current, that traditional cause of salubrity on the Pacific Slope of our continent, but it must be done. The Kuroshio is a myth after it departs from the shore of Honshu. Its effect upon the North Pacific Ocean is only that of a convenient source of warm water to be diffused into the Kamchatka Current which passes south of the Aleutians to join the eddy of the Alaskan Gulf and into the Northeast Drift Current which is pushed hither and yon by the variable gales and breezes which make up the prevailing westerly winds of the Northern Hemisphere between the latitudes of forty and sixty. The Japanese Current, as such, merely warms up the North Pacific Ocean and establishes the well-marked temperature contrast between Pacific water and Bering Sea water and between Pacific water and Okhotsk water. It furnishes energy to enter the meteorological processes of the atmospheric heat engine of the north. It maintains a heat source in high latitudes. It provides calories or B.T.U.’s, whichever unit you prefer in your thermodynamics, to drive the atmospheric machine which is so active in the northern theater.
Do you remember your physics of heat transfer? Having a column of air, warm at the bottom and cold at the top, is an unstable situation. The air at the bottom expands and decreases in density. This gives rise to the phenomenon known in hydrodynamics as convection. The air at the bottom of the column ascends and is replaced by colder denser air from the top or from the surrounding environment. This colder denser air is in turn heated, if it lies over a warm ocean, by the process of simple conduction, and is itself expanded to continue the phenomenon of convection. If the temperature contrast between the heat source, in this case the Pacific Ocean, and the surmounting atmosphere, in this case the air flowing over that ocean, is great, the convection processes can go on at a great rate and the air will become violently turbulent. If the air stream flowing over the warm ocean is very cold and at the same time is vast in extent, the result will be a widespread area of gusty turbulent air filled with snow squalls, towering masses of cumulus clouds, and the combined undesirable elements which offer hazards to flying such as icing, poor visibility, and roughness.
In contrast to this situation, if the air stream flowing over the warm ocean is warmer than the ocean, the atmospheric column is no longer unstable. The layers of atmosphere superimposed upon the water lose heat by conduction to the sea. These layers become cooler the longer the contact exists. Instead of expanding they will contract and the density of them will increase. This places the colder heavier layers at the bottom of the atmospheric column; a situation not contributory to the phenomenon of convection. Such an air stream will tend to flow over the surface of the sea without turbulence, in answer to any existing barometric gradient. It will tend to hug the surface of the sea and to flow smoothly around terrestrial obstructions, such as islands, rather than burbling bodily over such obstructions. This is stable air. If this air stream has been previously heavily surcharged with water vapor, the cooling which takes place as it loses heat to the colder underlying surface will cause this water vapor to condense out and become low- lying stratus cloud. As the cooling proceeds this stratus will build down and finally rest upon the surface of the sea as fog.
The two general situations of weather in the north are as simple as that. The first is the cold mass situation which occurs from October to April; the second is the warm mass situation which prevails during most of June, all of July and August, and through most of September. During the intervening time, the weather is in a state of transition. It is during this transition time that the really good weather, if any occurs, in any particular year, can be expected. It is also during this transition time that the Pacific Polar Front—the southern boundary to the cold air mass, whose source region is the Arctic Basin, and the continental Land Areas of Arctic America and Arctic Asia—passes first northward of the area under consideration and then southward. Winter weather is produced by the cold air mass from the Arctic Basin. Summer weather is caused by the warm air mass which originates in the low latitudes of the Pacific adjacent to the Equator. The Pacific Ocean north of 40 degrees of latitude and particularly between 40 and 60 degrees—the zone which contains the Aleutians, the Kuriles, and the Sea of Okhotsk, as well as Kamchatka, Sakhalin, and Hokkaido—is a veritable playground of meteorological and oceanographic elements which contribute to changeable and rigorous weather.
In meteorology the air masses are defined as warm or cold masses with respect to the temperature of the underlying surfaces rather than with respect to the actual temperature of the air masses themselves. A warm mass is a homogeneous body of the atmosphere the temperature of which is greater than the temperature of the surface over which it is traveling. Conversely a cold mass is one which is colder than the underlying medium. The masses have been so defined because these definitions indicate immediately what the thermodynamic behavior of the masses will be as they travel over the surface of the globe or as they are projected through the upper levels of the atmosphere in answer to some well-defined circulation established by an existing barometric gradient. To become homogeneous an air mass must be retained for a considerable time in an environment which allows the various meteorological elements, such as temperature, moisture content, and density, to become approximately continuous throughout the length and breadth of the mass. Homogeneity is attained in the great source regions. The source regions are the anticyclones, the semi-permanent areas of high barometric pressure on the surface of the globe. It is characteristic of atmospheric air to flow from regions of high barometric pressure to regions of low barometric pressure along paths which are spirals. The velocity of flow is proportional to the barometric gradient. It can be seen that air masses are continually being supplied by source regions to flow toward centers of low pressure as those centers migrate over the surface of the globe.
There are two source regions for the atmosphere significant to the North Pacific Ocean. One of these is the vast basin of the ocean itself which contains the Pacific Anticyclone. The major axis of this High is roughly along the thirtieth parallel of latitude. The anticyclonic cell may be broken into sub-cells but it usually extends in longitude over about 90 degrees. The southern face of the anticyclone supplies the Trade Winds to the subtropics. The northern face contributes air mass to the prevailing westerlies of the higher latitudes. Since the major part of this cell lies over warm tropical seas, the air mass acquires in this environment the elements of high temperature, high moisture content, and reduced density.
The other source region significant to the North Pacific theater is the Arctic Basin and the Arctic Slopes of Asia and North America. This region contains the Polar Anticyclone. During the summer this anticyclone loses its effectiveness to a great extent and withdraws to the depths of the Polar Regions. In winter it expands under the influence of the boreal darkness and frequently divides into an Asiatic cell and an American cell. This anticyclone contributes the winds known as Polar Easterlies to the high latitudes. Since this source lies almost entirely within the Polar Basin and since its greatest influence is felt during the winter, the meteorological elements contributed to the air mass by such an environment are those of low temperature, low moisture content, and high density.
The zone of discontinuity between the prevailing westerlies from the Pacific source region and the Polar Easterlies from the arctic source region is known in meteorology as the Polar Front. The Polar Front is not continuous around the globe at any one time because it becomes broken at one point or another for various reasons. It is, however, very persistent and continuous in the upper latitudes of the North Pacific Region. It shifts far to the northward in summer, forming a bridge between Asia and North America at about the latitude of Bering Strait. In winter it shifts southward into the Pacific but maintains a mean position at about latitude 50. The section so significant to the weather of Alaska and the Aleutians is known in meteorology as the Pacific Polar Front. It is in this front that the storms of the North Pacific Region are in the habit of forming.
Two such zones of discontinuity exist in the Northern Hemisphere. The other is in the North Atlantic. These zones are attended by semi-permanent low barometric pressure which persists throughout the year. These two areas are known to meteorologists as the Aleutian Low and the Iceland Low. These regions seem to have two functions in the dynamics of the weather of the Northern Hemisphere. First, they are the burial grounds of the storms which form in lower latitudes. Second, they seem to be the birthplaces of new disturbances which move from them eastward into the adjacent land masses. If, for instance, a typhoon shows up in the South China Sea, it is very liable to come roaring up through Balintang Channel on a northeasterly course, pass through the Bonin Islands, and eventually die out in the vicinity of the Andreanof Islands. This typhoon can be a September storm. During the dying-out process the weather in the Aleutians will be attended by gales, low ceiling, and rain. The barometer will take a nose dive to extremely low values. The prevailing summer fog may still persist to such an extent that visibility will remain practically nil in spite of the high wind. On the other hand, on one day, all may be serene at some station in the Aleutians. The sky may be clear, visibility good, and the barometer steady. During the night, the characteristic cloud shield of an approaching disturbance may move in over the station; rain will then begin and the wind will make up, but still the barometer will show little perturbation. A new cyclonic disturbance has been created on the Pacific Polar Front which will move into the continent of North America to be charted on the weather maps from Alberta to Nova Scotia as a well-defined storm.
There are sound dynamical reasons in the science of meteorology for the behavior of the weather in the north. The aerologists in the Navy and the weather officers in the Army have been trained to give adequate and accurate weather advices and forecasts for military purposes. Forecasts can be prepared to cover the periods of tactical missions. Long range forecasts can be prepared, to cover several days, for use in strategical situations. Weather summaries are possible describing the weather and weather trends over extended geographical areas for relatively long periods of time. These summaries can be used in preparing estimates. It must be remembered that the meteorologist cannot influence the weather; he can only tell about it. He can be very useful, nevertheless, in the strategy and tactics of war. Bad weather can be used for evasion and cover; good weather can be used for attack. Our enemy has not failed to use weather to his tactical advantage in his conduct of the war. He must have some very capable meteorologists distributed among the staffs of his task forces. His Midway campaign was launched in phase with an advance southward of the Pacific Polar Front. He hid his carriers under the protective cloud cover of its leading edge. The northern diversion of that campaign at Dutch Harbor was made disconcerting to our own aircraft by the poor flying conditions which ensued even though his own aircraft committed mass hara-kiri in being unable to find their carriers in the same bad weather. The support of his bases at Attu and Kiska was invariably accomplished from his advanced base at Paramushiro under cover of weather through which it was impossible for us to push our patrols.
If we arc going to advance against the Empire along the northern route, the next stop is very obviously Paramushiro Jima. To accomplish this mission without having air bases in Kamchatka is going to be difficult. Weather in the Kuriles is worse than it is in the Aleutians. Siberia becomes the cold pole of the world during winter. The Sea of Okhotsk becomes ice covered. Even the southern limit of drift ice in the Bering is much lower in latitude against the Kamchatka shore than it is in the body of the sea itself. Attu is in a different climatic province than the more eastern islands of the Aleutians and it is reasonable to suppose that this condition is accentuated the nearer one approaches the Asiatic anticyclone during the cold season of the year. At the same time the farther one advances westward and southward the closer one gets to the main stem of warm ocean water, the Kuroshio or Japan Stream. It is easy to visualize what the close proximity of air mass from the Asiatic source region traveling over the warm ocean, south of the Kuriles, will do to the weather. During winter, when that area is north of the Pacific Polar Front, when the prevailing air flow is governed by the semi-permanent High over Siberia, when the winds are strong from the northwest, that area is going to be filled with blinding snow squalls. Aircraft will experience icing, towering cumulus and cumulonimbus clouds, and turbulent air. This will not be favorable for bombing missions from our bases in the Aleutians against enemy bases in the Kuriles. During summer after the Pacific Polar Front has moved northward, the winds will be governed by the Pacific anticyclone, will have a decided southerly component, will be warm and humid, and will contribute warm air mass to the Kuriles even more actively than to the Aleutians. The result will be fog even earlier in season than it occurs in the Aleutians. This again is no help to the operation of combat aircraft.
It is reasonable to suppose that the Sea of Okhotsk under the influence of the winter cold of Siberia transported seaward by prevailing winds of northerly and westerly components becomes ice covered down to the fiftieth parallel. When the spring breakup occurs, this ice must be transported southward and eastward against the Kuriles. It probably packs into and blocks the passes between those islands during some short interval in late April or early May. During the time of the breakup the Sea of Okhotsk undoubtedly offers obstruction to surface navigation. Most of the year, however, that sea must be open to navigation from Cape Lopatka to Karafuto.
In general, winter flying conditions over the Sea of Okhotsk, when it is under the influence of the Asiatic anticyclone, must be similar to those over the Bering between Seward Peninsula and Anadyr. These conditions offer no particular hazards to aircraft when the limitations imposed by sub-zero temperatures are not disregarded. Bases for such operations must be provided with the facilities for cold weather operation. The technique of cold weather operation already has been perfected by the Army Air Force along the staging route through Canada and at the fields in the interior of Alaska. The summer flying conditions over the Sea of Okhotsk in the vicinity of the Kuriles will be bad. That sea will present a cold underlying surface to a warm air mass from the Pacific source region which will be drawn in to Asia under the influence of the monsoon. Okhotsk water will be covered by persistent fog banks from Lopatka to Karafuto; the passes between and the Islands of the Kuriles will be blanked out during the greater part of the summer season. Relief from this condition will come only when the barometric gradient is reversed by the passage northward of a cyclonic depression from the Asiatic coast in lower latitudes. With the reversal of the gradient the monsoon will be reversed temporarily and air mass will be drawn out of Asia, which because of continentality will be dry and relatively dense. This, although still a warm air mass, will tend to lift the fog into a stratus deck with improvement of surface visibility. Along the coast lines of Siberia under the influence of offshore winds the skies will clear. It is therefore possible, even in summer, that the entire island of Sakhalin will experience periods of excellent flying conditions.
The plot therefore unfolds itself. In order to subject industrial Nippon to routine and consistent bombing we must establish bases within range of Honshu, Shikoku, and Kyushu. Until the Soviets present us with some bases in Kamchatka or in the basin of the Amur River, we must look to Karafuto, the southern end of Sakhalin, as our objective. Paramushiro Jima, Matsuwa Jima, and the rest of the Kuriles must be ruled out for air operations because they are too close to the meteorological battle ground between the warm water of the Pacific, the cold water of the Sea of Okhotsk, and the air masses from the Polar and the Pacific source regions. Karafuto is enemy territory which is ours for the taking. It has both winter and summer climates which offer possibilities for consistent flight operations. It is open to attack, after Paramushiro is ours, through the lower reaches of the Sea of Okhotsk, both winter and summer. Our bombers with fighter escort can operate easily from there against the industrial centers of Japan.