climate and weather protection systems in settlement planning in the arctic regions of northern...
TRANSCRIPT
Energy and Buildings, 11 (1988) 23 - 32 23
Climate and Weather Protection Systems in Settlement Planning in the Arctic Regions of Northern Norway ARNE K. STERTEN*
The Oslo School of Architecture and Department of Geography, University of Trondheim (Norway)
SUMMARY
Planning in the Arctic regions involves a very comprehensive knowledge o f the climatic conditions and regional and seasonal varia- tions. In the climatological analysis it is im- portant to determine which of the climatic factors are causing existing or functional problems and which are the most valuable. In the present case, wind and snowdrifts are defined as the most stressing factors and the duration o f sunshine is the most important factor to consider. On this basis, possibilities for climatic modification, using natural as well as man.made shading components, are discussed. Finally, a practical example of a settlement plan including a complete climatic protection system is described.
1. DESCRIPTION OF LANDSCAPE, WEATHER
AND CLIMATE IN THE HAMMERFEST REGION
OF THE ARCTIC COAST OF NORTHERN NORWAY
As an introduction to this report, the fol- lowing information concerns the geography of the place where the studies were carried out. The city of Hammerfest is located at 70040 , N and 23045 ' E on the northwestern continental border to the Arctic Ocean and the Norwe- gian Sea, 30' south of Nordkapp. The shortest regular flying t ime from Oslo to Hammerfes t is 3 h 15 min.
In a regional survey we can divide the coastal area into 4 climatic zones -- the outer and inner coastal and the outer and inner fiord zones. The outermost coastal zone is dominated by maritime atmospheric processes and has very little landscape influences. The innermost fiord zone has a strong landscape shading effect and a clear dominance of local wind systems. Notice on Fig. 2 the strong distant effect of continental air masses during
*Private address: N-2942 Volbu, Norway.
0378-7788/88/$3.50
CITY OF HAMMERFEST ",~,~,~rii, w ~ 710 N
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Fig. 1. The global position of the research area: (a) within the Arctic region; (b ) the coastal position on the shoreline of northern Norway to the Arctic Ocean.
© Elsevier Sequoia/Printed in The Netherlands
24
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Fig. 2. View of the coastal region of western Finnmazk and the city of Hammerfest. Also indicated are the fre- quencies of wind direction during December, January and February. The wind maps indicate a strong wind, reaching to the outermost coastal line.
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the winter months and the clear climatic dif- ferences in the cros~section from sea to in- land both for wind, precipitation and temper- ature, shown in the Figs. 4, 5 and 6.
The city of Hammerfest {Fig. 3) is located in an outer fiord climatic zone, in a mountain- ous landscape along the shoreline of a bay. Due to the excellent harbour conditions the city has been an important commercial centre over a very long time and received its official
city certification in 1789. The city was totally burned down in November 1944, so the city as you see it today is less than 50 years old. But it has been growing very rapid- ly and the main city has many suburbs in the connecting valleys and at some higher levels above the sea. This expansion is strengthening the impact of weather and climate on build- ings and living conditions and stresses the need for weather protection.
Fig. 3. View of the bay and city of Hammerfest.
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Fig. 6. Coastal cross-section analysis of mean and extreme temperatures. The inner fjord zone (right) has a nearly continental temperature distribution with the six-months mean below 0 °C, and 22 °C difference between the warmest and coldest months. The middle zone (centre) is clearly the warmest with just the four-months mean below 0 °C, and 14 °C difference. The outer coastal zone has respectively five months below 0 °C and 12 °C dif- ference. In the inner fjord zone, the minimum temperature in winter can be up to 15 °C lower than in the coastal zones.
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Fig. 7. A c t u a l sun c o n d i t i o n s at the s i te o f the research project in Hammerfes t . The diagram indicates a loss o f up to 2½ hours o f impor tant morn ing sunshine unti l the middle o f April and after early September , but e x c e l l e n t sun c o n d i t i o n s in the summer.
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2. WEATHER PROTECTION AND SITE PLAN- NING STRATEGY
Our research project was carried out in a small valley 3 - 4 km away from the city centre. This housing project is the fourth in the valley where the airport is located. The valley has a wide open cross-section and a low slope along the valley axis with an outlet to the southwest. The valley sides are not high and the loss of sunshine is not large but it is large enough in late winter and early autumn as it is seen in Fig. 7. The sky is overcast for around 50% of each month with precipitation occurring nearly as of ten except in the months of May, June and July. The amount of precipitation is lowest in early spring with. 36 mm in May and highest in early autumn with 96 mm in October. In connection with building activity, October can be problematic as 68% of the days have precipitation, 22% are snowy and 28% are changeable, either snow or rain, as illustrated in Fig. 8.
The wind conditions indicate some topo- graphical shading effect in the section east to south. Thereby the percentage of dominating inland wind is reduced during the winter months, and is mainly associated with clear and cold weather periods. The strongest wind appears in wintertime and especially in late December and February. This weather type is cyclonic and the wind direction from south to west or from northwest to north, periodically with heavy precipitation. These weather periods are never especially cold, but rela- tively cold in summertime and relatively mild during the winter months.
The monthly mean temperature is lowest in February with - -6 °C and highest in July with 12 °C. These six months have a monthly mean above 0 °C but only June, July and August are total ly free from frost (see Fig. 9).
The climatic conditions are mainly critical during the winter months and the main factor is the wind and the wind effects in relation- ship with the topography. Drifting snow and
M o n t h l y s k y - a n d p r e e i p i t a t i o n e o n d i t i o n M o n t h l y w i n d d i r e c t i o n f r e q u e n c y
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Fig. 8. The sky and precipitation conditions at Hammerfest weather station indicate a climatic character equal to the outer coastal zone, with more days with precipitation than with overcast skies. But the amount of days with clear and partly clear sky is relatively high. The wind diagram (right) indicates wind from many sectors, low influence of inland wind and a high percentage of calm days.
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Fig. 9. The temperature distributions differ much from those associated with the coastal zones, and seem more typical of those for the outer fjord zone. In this case the thermal effect of local topography is a dominating influence.
snow accumulation make problems for all types of roads and especially for the access from roads to houses. We must also realize that all components of the landscape partici- pate in the scenario and support it with their own details--making a real 'pre-eroded winter landscape design'.
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Fig. 10. Natural as well as man-made elements should be combined and used to protect living areas and houses against wind and snowdrift.
We must also realize that trees have a braking effect on winds and snowdrifts and thereby trees can protec t houses and other living areas. And if we do not have any trees, we can establish man-made fences for wind- breaks, both for protect ing houses as well as for growing trees, as shown in Figs. 10 - 13.
Fig. 12. Where the natural protection or shelter is not sufficient, fences of wood and a combination of wood and earthwalls can be used. Areas needed for snow deposit ought to have a depth of up to 10 times the height of the fence, depending on the density of the fence.
Fig. 11. The natural protecting elements have different effects on wind and snowdrift. Ridges elevate the wind- field, causing lee-effects at the ridgefoot and wind erosion on the top. Trees and bushes have a more retarding
effect at the site.
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r
Fig. 13. Earthwalls in combination with trees have an excellent retarding effect on drifting snow, while houses just change the wind flow pattern, causing typical snow deposits on both sides of the houses.
To ensure the functioning of the living en- vironment in a new settlement in an economic way, the most important action is to develop a wind and snowdrift protection system, to use the prevailing winds for main-road snow clearing, and utilize as much as possible of the available solar energy.
This conclusion leads to a goal where the main point in a site plan strategy is to develop a new settlement which has an overall form harmonizing with the surrounding landscape to give protection against the climatic and weather stresses.
3. TRANSFORMING THE SITE-PLANNING STRAT-
EGY TO PRACTICAL USE
To show the practical implications I will use the Hammerfest Project and the way it developed. As a first front against wind and snowdrift, areas were reserved for various
types of shelter-belts as shown in Figs. 14 and 15. These areas are called climatic shelter zones. Within each zone there is firstly a 3-m-high fence of wood with 50% density, then a snow accumulation area of at least 25 m. Then there is a second f e n c e - - a 1.5-m wall of stone and earth with a 1-m wooden fence on the t o p - in total 2.5 m high. At the lee side of this fence, rows of trees are planted. In addition, more protecting lines are provided between the house rows.
Included in the housing strategy was also a simulation of a housing design to obtain houses which functioned well within the outer protecting system and also turned an open facade to the sun.
The building period is still continuing, and more than 50 of nearly 80 houses are built. We are now at a point in the development where we can see more critically what the living conditions will be in our new settle- ment.
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w
Fig. 14. Combinations of shelter-belts serve as a front line against dominating wind and snowdrift.
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-MS
Shetter effect Snow rernovot routes Snow depots Utitity j
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Fig. 15. The site plan area is partly reserved for sheltering purposes and partly for residential use. The west-to- north hilly/rocky terrain has a natural sheltering effect (crosslined). In addition wooden fences are made to strengthen the effectiveness on wind and snowdrift. Also, within the residential area, a system of earth walls and wooden fences is developed.
4. CONCLUSIONS
A critical view of the protect ion system in- dicates that some of the components are working well, but some corrections are neces- sary to give more dense fences in parts of the shelter zone where the wind stress is strongest. And it is clear that more details in the whole system can be developed better. Most interest- ing was the discovery that many of the new house owners wanted to fol low up our inten- tions, especially with planting and sheltering on their o w n lots.
BIBLIOGRAPHY
A. K. Sterten, Local Meteorological Investigation o f the Mountain and Valley Wind Sys tem in Southeastern Norway, K-242, Norwegian Defence Research, 1961.
A. K. Sterten, A Further Investigation o f the Moun- tain and Valley Wind Sys tem in Southeastern Norway, K-254, Norwegian Defence Research, 1963.
A. B. B~brve and A. K. Sterten, Unders@kelser av de naturgitte bygge- og bobetingelser i noen kyst- og fjordomr~der i Finnmark, Arb. Rap. 14, Norwegian Building Research Institute, 1978.
A. B. B~brve and A. K. Sterten, Utvikling av prin-
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(a)
(b)
Fig. 16. View of the Hammerfest research project. ( a ) the north/eastern part in April 86, and (h ) the area in July 86.
A.
sipper for arealbruksplan og reguleringsplan i noen kyst- og tjordomr~der i Finnmark, Arb. Rap. 26, Norwegian Building Research Institute, 1980. K. Sterten, Climatological analysis for LNG- terminal localization, (made for STATOIL
A. 1983 - - restricted). B. B~brve, Settlement and housing design with special regard to local climatic conditions in cold and polar regions. Examples from Northern Nor- way, Energy Build., 11 (1988) 33 - 49.