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The North Atlantic weather war occurred during World War II. The allies (Britain in particular) and Germany vied for access to reliable weather data in the North Atlantic and Arctic Oceans and sought to deny the other weather information. Meteorological data was important as it affected military planning and the routing of ships and convoys. In some circumstances, visibility was necessary (photographic reconnaissance and bombing raids) and in others concealment (keeping ship movements secret or suppressing enemy air activity). D-day planning was greatly affected by weather forecasting; it was delayed by one day in the expectation that a storm would blow out and sea conditions would be acceptable. British sources of data included ships at sea and the weather stations at Valentia Observatory and Blacksod Point, in neutral Ireland. German use of weather ships also exposed their secret Enigma codes. ==Ocean weather vessels== (詳細はUnited States Coast Guard vessels were being used as weather ships to protect transatlantic air commerce.〔 The Atlantic Weather Observation Service was authorized by President Franklin Delano Roosevelt on January 25, 1940. By February 1941, five 327-foot Coast Guard cutters were used in weather patrol, usually deployed for three weeks at a time, then sent back to port for ten days. As World War II continued, cutters were needed for the war effort and by August 1942, six cargo vessels were used. The ships were defenseless during the war, which led to the loss of the USCGC ''Muskeget'' (WAG-48) with 121 aboard on September 9, 1942. In 1943, the United States Weather Bureau recognized their observations as "indispensable" during the war effort.〔 The flying of fighter planes between North America, Greenland, and Iceland led to the deployment of two more weather ships in 1943 and 1944. The United Kingdom established one of their own off their west coast. By May 1945, 16 ships were in use north of the 15th parallel north in the Atlantic, with six more in the tropical Atlantic. A total of 20 United States Navy frigates were used across the Pacific for similar operations. Weather Bureau personnel stationed on weather ships were asked voluntarily to accept the assignment. In addition to surface weather observations, the weather ships would launch radiosondes and pilot balloons, or PIBALs, to determine weather conditions aloft. Due to its value, operations continued after World War II ended, which led to an international agreement in September 1946 that no fewer than 13 ocean weather stations would be maintained by the Coast Guard, with five others maintained by Great Britain and two by Brazil. The Germans began to use weather ships by the summer of 1940. However, three of its four ships were sunk by November 23, which led to the use of fishing vessels for its weather ship fleet. Their weather ships were out to sea for three to five weeks at a time, and would have Enigma codes for several months. Weather observations from the Germans were ciphered using their Enigma machines. Harry Hinsley helped initiate a programme of seizing Enigma machines and keys from the German weather ships, such as the ''Lauenburg'', thereby facilitate Bletchley Park's resumption of breaking of German Naval Enigma, as the inability to decipher German naval codes was seriously affecting the Battle of the Atlantic. The ''Munchen'' and ''Lauenberg'' were boarded by the Royal Navy, who managed to gather valuable information on German codes in each case. The ''Wuppertal'' became trapped in ice and was lost without trace of ship or crew. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「North Atlantic weather war」の詳細全文を読む スポンサード リンク
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