Read the new Book Publication - 2012
Book details:
Author Dr. Arnd Bernaerts;
Manufactured and published by: Books on Demand GmbH, Norderstedt ; ISBN 978-3-8448-1284-8,
232 pages, about 200 figures (if maufactured in the USA the 14 color pages are only in b/w).
at: www.seaclimate.com

C6 Jet stream blocked by bombs and mines?
Rev:09May

 C61 Air flow blocking – Understood? – An introduction

Fig.1(not enlargable)

The most forceful meteorological blocking of the 20^th Century, if not during the last 150 years or longer, established at the onset of the Second World War in autumn 1939. The matter was never scientifically recognised. On the other hand recent atmospheric blocking events received high attention. Why was the winter 2009/2010  unexpectedly the coldest winter for 30 years? Why was Russia caught in a heat wave in summer 2010? And why had the global mean temperature for December 2010 actually been below the previous 30-year mean?  Europe, North America, and Australia saw much below average December temperatures, while the Arctic saw much above average temperatures. Many question, for which more convincing  answers would be available, if science had been more attentive about what had happened at the onset of WWII, namely, what has caused the blocking of usual weather pattern in autumn 1939, and whether that had had anything to do with naval war activities in the seas off European coast lines. 

In the recent debate many question are raised and discussed. The issue is about an anticyclone block or disruption of the more normal westerly flow that prevent depressions from following their usual routes. A often heard assumption correlates  the event with the El Niño  phenomenon. This shall have a global knock-on effect causing a change to the path of the jet stream, and thereby affecting the North Atlantic oscillation in a way that it is reducing the warm air flow into Europe. Others have found that there is a correlation between warming in the stratosphere and cold or warm winter periods[1], based on a thesis by  R. Scherhag back in 1952, who argued that the first war winter had been the result of a great interruption in the circulation (see e.g. A25). Another explanation refer to the so called negative Arctic Oscillation, explained as the relationship between high pressure in the mid-latitudes and low pressure over the Arctic. When the pressure systems are weak, the difference between them is small, and air from the Arctic flows south, while warmer air seeps north that influences winter weather in the northern hemisphere. 

Not one of the current explanation attempts should be regarded as irrelevant, but recognised that they are very superficial with regard to reasonable answers on the reason behind. What is the physical source of the deviation. That is not served by a claim, for example, about a circulation disruption, or warming in the stratosphere, but requires the naming of the physical source. Was it a sun spot? Was it a volcanic interruption? Was it the sea? A thorough analysis of the largest scale experiment with climate mankind ever undertook during the first few months of WWII, as explained in a previous section, would have answered many question since long. The focus here is on showing an evident link between war activities and the change in the marine and aerial pattern that contributed to extreme winter condition. 

Fig.2 (not enlargable)

C62 The first days and the cyclone in the German Bight 

 The weather was fine when the German Luftwaffe and Heer (Air force and Army) had begun the invasion of Poland at its western boarders at 04:48 local time on September 1^st, 1939, while the first Naval gunfire of World War II came from the old German battleship “Schleswig Holstein”  which bombarded a Polish garrison off Gdansk, what was then Danzig, a Free City in the east of the Baltic Sea. 

Nothing exceptional was expected from anyone at the weather forecast front. The weather during the first few war days indicated a tendency to continental conditions, known as Indian Summer. The daily weather analysis of the SEEWARTE, mentioned for example this: 

• 01 September 1939: Over Central Europe (CE) the air pressure increases.

• 02 September 1939: Modest pressure changes in CE . The general weather situation is determined by a extensive Low over the North Atlantic and a High over Northern Scandinavia. 
• 03 September 1939: In the east of the Scandinavian High polar cold air is pushed toward Germany.
• 04 September 1939: the cold air thrust (03/Sept) has reached the Black Sea and Caspian Sea. 
• 05 September 1939: The centre of the European Highs has moved further to south-eastwards.

The usual flow of circulation may have been effected by numerous war activities. I want to bring only one example, which links the naval activities, with the move of a cyclone, which is one of the piece that eventually contributed to the atmospheric blocking of the jet stream over Europe. 

The story lasted from 10^th to 13^th September, and could be titled: Cyclone attracted by naval warfare activities in the Helgoland Bight (German Bight). 

Naval Activities: A huge number of the Kriegsmarine vessels was in the North Sea from day zero, and was highly active. The Royal Navy and Air forces showed up around the island of Helgoland and the German coast several times with submarine, bomber and sea mine laying mission. German Navy was particularly engaged in planting contact mines from Holland’s coastal waters (off Terschelling) northwards across the German Bight up to the entrance of the Skagerrak, at a distance between 50 and 100 km off the coast of Schleswig-Holstein and Denmark, called the “Westwall”. The most north-westerly point announced by the Germans as ‘Dangerous zone’ was the position: 56° 30’ North and 4° 25’ East. That was about half the distance between Skagerrak and Scotland. The first minefield locations were off Terschelling, Esbjerg, near Helgoland and two places off Jutland. (NYT, 5 September 1939). As many as 300 mines an hour could be laid by one minelayer. (NYT, 18 February 1940), and the German Navy had presumably several dozen in service to plaster the North Sea off the German coast with ten-thousand of sea mines.

Figure 3: The move of a Cyclone according naval activities?

Cyclone attracted: In the north of Scotland arrived on the 10^th September a low, presumably bound to travel via Skagerrak eastwards to the Baltic Sea and beyond. It did almost, but before entering the Skagerrak it swung southwards and went straight to the center of naval activities,  and further along Holland to the Belgium coast on 13^th September, as shown in Figure 3. And again just two days later on 15th, at 8 a.m., there was a small low-pressure centre (1,005 mb) north of Helgoland close to meanwhile already large sea mines fields (not shown). 

 The evident correlation:  During September the sea water temperature decrease at the station of Helgoland is so unusual that one has to take notice. First there is a jump up of one degree, to fall by three degree against average in September. A high figure for a corresponding period as in September 1939 had been recorded only once before, i.e. in September 1875. The steep rise and drop in September 1939 has something to do with the high naval ship movements and military activities that took place, ‘shovelling’ lower and warmer water up to the surface. Once warmer water reached the surface, evaporation increased and subsequently seawater cooled more quickly. It is as simple as that, and in this case it can be evidently demonstrated. 

It is also the explanation why the cyclone movement from the 10^th to 13^th September took the way via the German Bight, which actually contributed to a more continentality of Europe. Many thousand more events over the next months established the blocking finally. 

 Fig. 4: The deviation of SST at Helgoland in autumn 1939 demonstrate the impact of naval activities.

 C63  Blocking observed but not understood. 

 It took from here, mid September, until the first week of December, that the atmospheric blocking established in full, when server cold flooded the whole of Europe (NZZ[2], 14 January 1940), and not loosen the tight grip over the entire winter season. The Seewarte, the military weather service, recognised early that something strange was going on, but had no idea what are the consequences, and that it all had something to do with the naval activities in the North and Baltic Sea. Here are a few excerpts from the daily analysis: 

• 19 September 1939; Cyclonic activities over the Polar Sea area are intensive. The west-drift in the North will consequently move more and more to the South.
• 23 September 1939; With the advance of Atlantic air into Middle Europe a more forceful cyclone can develop along this channel which could extend its influence in the Middle Europe later. 
• 29 September 1939; General weather situation towards the end of the month clearly reveals changes indicating the end of the Indian summer spell which leads to a time of increased cyclone frequency in Europe. In the weather chart this is indicated by a decline in the Northwest-European high–pressure area (anticyclone), which dominated the general weather for a long time. This high, that usually is located far to the East (cf. the weather situation a year earlier) is responsible for the well-known late summer period of fine weather, now pushed so far to the West that Germany lay at its Eastern rim and thus got into the cold Northern stream which was interspersed with disturbances.  

Fig. 5 & 6, Weather map 31 October 1939 

• 13 October 1939; Along with a peripheral low, the first effective gust of maritime air has reached Northern Germany. A continuous WWD, however, cannot be expected yet.
• 19 October 1939; A broad high-pressure bridge has formed between the Atlantic and Scandinavia high.
• 23 October 1939; Usual weather is changing now and the high pressure bridge which links the Azores high with the West Russian high is broken up. A transition to a west wind situation is on the verge of the German seas.
• 28 October 1939; Since a high pressure bridge from Middle Scandinavia to Scotland remains, a further stream of cold air from the Nordic Sea area is cut off. 
• 5 November 1939: It appears that now – like in many earlier years – a WWD with lively cyclone activities will begin to move over Europe at about the middle of the month.
• 14 November 1939; It seems that a mainly sectional circulation is going to take over in the general weather situation: its pressure field will be characterized by a long high pressure zone – Azores –Southern Germany –Southern Russia – and WWD-like turbulence activity in the North of these regions. 
• 29 November 1939; West Siberian high is slowly retreating towards the East thereby allowing the disturbance coming from the West to penetrate still deeper into the regions of European Russia.  
• 30 November 1939; A very distinct west wind weather situation rules over North and Middle Europe.

In summary the expectations of the weather analyst for ‘lively cyclone activities’ did not materialize. Seawater temperature changes by a devastating war machinery was not imaginable to weathermen then.

 C64   Not competent to read the wind?

At the end of October 1939 the Seewarte analysts had realised that the wind pattern over Northern Europe had changed completely (Fig.6) , but lacked the competence to read the sign. According their own observation:

• Hamburg reported winds from the North-Eastern quadrant on almost two thirds of the dates observed (33% easterly winds out of 65%) while North-Eastern winds accounted only for a quarter (26%) of several previous years’ averages. Otherwise most frequent direction of the wind – South-West (24%) – accounted for 9% of all cases. Thus the observations at this station alone show what the weather charts of an extensive area will obviously indicate as well. (Seewarte, 02 Nov.1939) 

Fig. 7: Change of wind direction in autumn 1939

This is a very strong and clear indication that huge air masses moved towards the North Sea, due to unusual high evaporation in all sea area affected by naval war. While the water of the seas was ‘stirred and turned’ the ‘steam’ rose upwards into the sky, causing air to flow in from easterly direction, which subsequently prevented low-pressure systems to travel along the west-wind-drift channel via the North Sea and Central Europe into the eastern hemisphere. 

C65  The whole winter season affected.

Figure 8.  

 The foregoing investigation stressed the significance of the observed change of wind direction in Hamburg during October 1939. Wind direction had dramatically changed from prevailing SW winds to dominating NE winds. 

 Even more significant is the already mentioned research by A.J. Drummond (1943) (above A21)   that of the prevailing wind directions in South-West England (Kew Observatory near London) had changed dramatically. During 155 winter from 1788 to 1942 only 21 had easterly resultants whereby the few winters 1814, 1841, and 1940 had resultants from NE to ENE, meaning northerly than East. Another small number of winters since 1841 (1845,1870,1879, 1891, 1895, 1904, 1929) had prevailing SSE to ESE. Fig.7. With the exception of the winters 1801 and 1804 all of these 21 winters with predominant easterly winds had a temperature below average (40,1°F; 4,5°C). While eleven of the above winters had means between 34°F and 36°F, only few westerly resultants had means lower than 37°F (2,8°C), these being 1820,1830,1847,1855 and 1886. That was blocking pure, but there is no signs that science has paid any attention to this important observation. 

 C66 Due for an extreme winter. 

Figure 9 & 10 , Weather map 12 December 1939

The development of severe weather conditions during the first war winter of 1939/40 was not an erratic incident by nature. This could be well illustrated by various comments on the missing “west-wind-drift” by meteorologists at the ‘Seewarte’ that had been responsible for the preparation of daily weather charts. In the absence of usual weather behaviour, their task of making reliable weather forecasts was complicated. Direction and intensity of maritime air from the North Atlantic are particularly relevant in this matter. But since mid December Europe was solidly under the control of a high pressure bringing in air from Greenland or Russia’s North. But meanwhile there have been seven decades time to explain in detail why the weather happened in late 1939 as it did. But climatology does not show any interest. Do they really think the autumn-winter blocking came from nowhere?   Do they fear an admission that they understand too little about their subject of research?

 In summary it can be established, that winter 1940 clearly played in the league of the Little Ice Age. Rhe west wind drift was suddenly blocked. It was the only winter with wind from the NE quadrant since the end of the Cold Medieval Age Period, which brought General Frost right in the Center of Europe. Naval warfare did change conditions in the marine environment. By early December 1939 the North and Baltic Sea had lost too much of their heat capability to steer Northern Europe through a moderate winter. The coldest winter since the early 19th Century was due.