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Home , Continental climate, Oceanic climate

Cent. Eur. J. Geosci. • 1(2) • 2009 • 176-182 DOI: 10.2478/v10085-009-0013-8

Central European Journal of Geosciences

Continental and oceanic régime in

Research Article

Katerina Mikolaskova∗

Charles University in , Department of Physical Geography and Geoecology, Albertov 6, 128 43, Praha 2,

Received 24 February 2009; accepted 20 April 2009

Abstract: This work considers continentality from the point of view of an annual course of precipitation. It assesses conti- nentality according to percentage of precipitation in and half year, ratio of precipitation in summer to winter half year and the period of half year precipitation in the area of WMO Region VI (Europe). Region VI can be divided into five main regions according to their annual course of precipitation. These regions are: Northwest- ern Europe with precipitation in all , a predominance of winter precipitation and maximum precipitation in December and January; Central Europe with precipitation in all seasons, a predominance of summer precipita- tion and maximum precipitation in July; Eastern Europe with less precipitation over the year than in Northwestern Europe, a predominance of summer precipitation and maximum precipitation in July; the Mediterranean region with a predominance of winter precipitation, a dry in summer and maximum precipitation in November and December; and Western with a variable , a predominance of winter precipitation and maximum precipitation in December and January. Continentality from the point of view of precipitation rises towards the east. In comparison with thermal continentality, according to Gorczynski, it unexpectedly reaches its maximum in the centre of Europe (especially in northeast of the Czech Republic and south of ). Keywords: Climate • continentality • Europe • the • precipitation © Versita

1. Introduction Climate continentality is difficult to quantify because it is governed by a wide range of factors and for this rea- son some simplifications are used. Frequently climate continentality is quantified from two basic viewpoints – Climate continentality is one of the basic characteristics of temperature and precipitation; with temperature the most climate. It represents a degree to which a particular place common. is influenced by land or by ocean. It is a consequence Thermal continentality is characterized by a high annual of the transformation of air mases during their transfer temperature range, which (generally over 15.6°C) [1] in- from the ocean to the mainland or from the mainland to creases eastward and reaches the maximum in the area of the ocean. Climate continentality is characterized by a . In the case of continentality from the precipita- specific course and degree of climate elements such as tion point of view the situation seems to be different. The temperature, precipitation, cloudiness, pressure etc. distribution of temperature over the is dependent on fluxes in radiation, heat and moisture which results ∗E-mail: [email protected] from the distribution of solar radiation with latitude [2].

176 Katerina Mikolaskova

Energy fluxes across the air/land and air/water interfaces are another factor which influences temperature ranges. These fluxes are controlled by the thermal properties of the interface substances and it is suggested that above the land there is a much bigger annual temperature range than above the sea. Thus the increase in the annual range of temperature inland is the most remarkable effect of con- tinental surface. The distribution of temperature does not have as complex pattern as the distribution of precipita- tion, which is more influenced by local factors. In general, coastal areas have maritime , which means cli- mate influenced by the ocean. The air saturates above the ocean and is then transferred to the mainland where the water vapour condenses; as a result there is abun- dant precipitation in coastal areas. Maritime air does not penetrate far inland and the total amount of precipitation decreases the further inland. On the other hand there are significant differences in the amount of precipitation and Figure 1. Major climatic regions in Europe and the position of sta- its distribution among climate zones, as precipitation is tions. generated from different mechanisms. In spite of this it is still possible to classify climate continentality according to annual courses of precipitation in Europe. However, if we measure climate continentality in this way we may get falls, counted in moderate climate from 1st April (in north- different results than if we use temperature. ern hemisphere). As the degree of climate continentality increases the period of half year precipitation gets shorter (prevailing precipitation in summer months), reaching 9 2. Data and methods of analysis months in areas of and 3 months in areas of [6]. The analysis used monthly means of precipitation from Neither of these indicators considers the exact location of the period of 1961 – 1990, which were obtained from 321 the station from the point of view of altitude or orientation stations distributed across Europe and part of western (leeward/windward side) in case of mountain stations. The Asia (WMO Region VI). All records were taken from World aim of this work was to define a divide between oceanic Weather Records 1961 – 1970, 1971 – 1980, 1981 – 1990 and continental climate in Europe, so that inaccuracies (Compiled by WMO). Stations without continuous mea- caused by not including these factors are insignificant. surements for at least 20 years were excluded [3–5]. All map analyses were done in ArcMap 9.1. from ESRI The seasonal distribution of precipitation was the most using Kriging interpolation. important feature of these analyses. The first indicator of analyses is:

summer half year precipitation 3. Distribution of precipitation in R = , winter half year precipitation Europe where the summer half year is defined as a period from 1st April to 30th September and the winter half year as a pe- Europe and can be divided into several major riod from 1st October to 31st March. If R is higher than 1 regions according to the amount of precipitation, their an- it means prevailing precipitation in the summer half year nual course and the factors they are caused by. These ma- (result of convectional rainfalls), and thus a continental jor regions, which were estimated according to the above climate. If R is smaller than 1 it means prevailing precip- features, are: Northwestern Europe, Central Europe, East itation in the winter half year (result of cyclonic rainfalls) Europe, the Mediterranean and Western Asia. The most and thus an oceanic climate. The second indicator – pe- important features are the amount of precipitation and its riod of half year precipitation (H) was arranged by Hru- distribution among summer and winter months. The driest dicka [6]. This indicator expresses the time (counted in and the rainiest months were also considered. The main months) in which half of the total amount of precipitation climatic regions are depicted in Figure 1.

177 Continental and oceanic precipitation régime in Europe

3.1. Northwestern Europe maximum changes from autumn months (September, Octo- ber) in to winter months (December, January) in Precipitation in Northwestern Europe is abundant both and . R decreases southward, with in summer and winter. The total amount of precipitation a value of 0.81 in Norway, 0.72 in Great Britain and 0.66 ranges from 600 to 900 mm per annum. Most of it falls in the north of (Table 1). The driest month is gen- in winter owing to the extension of Icelandic low pressure erally April but February is the second driest in system, to the north-east of the pressure centre in Ice- and Great Britain. Slightly continental climate can be land. This system causes northeasterly winds which are found in French basins (, Garonne) where the mini- very strong and brings heavy rainfalls in winter. In summer mum precipitation occurs in February. The influence of the the Azore anticyclone extends to the north-east of its pres- Atlantic Ocean is blended with influence of the Mediter- sure centre and prevailing winds are westerlies and north- ranean climate in the south of France. The influence of westerlies with less precipitation. The most precipitation the Atlantic Ocean can be observed in the maximum pre- falls in the west of Scandinavian mountains (2061 mm in cipitation in December and January and influence of the ), on islands of Ireland (1430 mm in Valentia) and Mediterranean climate in minimum precipitation in July Great Britain (1529 mm in Eskdalemuir). Moving south and August. the total amount of precipitation decreases and the winter

Table 1. Distribution of precipitation in Northwestern Europe.

Altitude Annual Spring Summer Autumn Winter Summer Winter H R mean half half (months) precipitation year year (m) (mm) (%) (%) (%) (%) (%) (%) BERGEN (NORWAY) 40 2061.4 16 21 38 25 43.83 56.17 7 0.78 VALENTIA (IRELAND) 9 1430.4 21 18 30 31 38.78 61.22 7 0.63 () 35 667.4 21 26 30 23 49.73 50.27 6 0.99 (FRANCE) 6 923.9 24 17 28 31 41.18 58.82 7 0.7

Table 2. Distribution of precipitation in Central Europe.

Altitude Annual Spring Summer Autumn Winter Summer Winter H R mean half half (months) precipitation year year (m) (mm) (%) (%) (%) (%) (%) (%) -TEMPELHOF () 48 597.6 23 33 23 21 58.17 41.83 5 1.39 TRIER-PETRISBERG (GERMANY) 265 784.3 23 27 25 25 50.27 49.73 6 1.01 KLODZKO (POLAND) 316 591.3 23 44 21 12 70.72 29.28 5 2.42 BISTRITA () 366 677.2 25 37 19 19 63.09 36.91 5 1.71 BOURGAS () 28 533.4 25 22 27 26 47.27 52.73 7 0.90 WROCLAW-STRACHOWICE (POLAND) 120 587.2 21 42 22 15 66.61 33.39 5 1.99 DEBRECEN () 111 564.5 24 36 20 20 61.06 38.93 5 1.57

3.2. Central Europe winter. Stable dense air tends to ward off the depressions which give to northwestern Europe and consequently Central Europe doesn’t have as much rainfall in winter. Central Europe is a transition region between the oceanic Pressure is lower in summer, thus it is easier for maritime and continental climate. Most precipitation falls in sum- air to reach Central Europe [7]. The total amount of pre- mer, however, winter precipitation is sufficient to ensure cipitation decreases towards the east and becomes higher that Central Europe doesn’t suffer from droughts in winter. with increasing altitude. The annual precipitation of Cen- High pressure occurs above the cold centre of Europe in

178 Katerina Mikolaskova

The Alps have their own climate which is influenced by al- titude and topography. Anticyclone conditions often dom- inate in both the summer and winter in this region. There is more precipitation in the summer half year than in the winter half year, hence the climate is continental. In the Southern Alps the Mediterranean influence is prominent. As a result autumn precipitation increases and the total amount of annual rainfalls decreases in comparison to the northern part of the mountains.

3.3. East Europe

There is no significant climatic dividing line between Cen- Figure 2. Isolines of ratio of precipitation in summer to winter half tral and Eastern Europe. Neither distribution of precipi- year. tation shows a big difference between these two regions. If there is a difference then the distribution of precipitation between summer and winter half years in East Europe is tral Europe is about 600 mm in lowlands and 700 mm in better balanced than in Central Europe and thus less con- highlands. There is only 550 mm of annual precipitation tinental. The only sign which supports the assumption of a in Danube plains and 300 mm at coast. more continental climate in the east is the total amount of Climate continentality increases from the west to the east precipitation. The total amount of precipitation decreases with the exception of Southern . At the coast of with the increase in climate continentality even though it Kattegat and occasionally in the Gulf of Bothnia oceanic is not as dominant a feature as the annual course of pre- climate can occur. For example, Göteborg is not shadowed cipitation. Total amount of precipitation is lower in the by the Norwegian mainland, and therefore it is more ex- region of East Europe than in Central Europe at the same posed to prevailing westerlies. Although lies more latitude. on the west, it is sheltered in the Oslo Fjord and so has The distribution of precipitation is due to the uniform flat a more continental climate according to the distribution relief of Eastern Europe. That means that there are no sig- of precipitation. In most areas, July is the wettest month nificant changes in the annual course of precipitation or and February the driest. The west of Germany is still the total amount of precipitation towards the east. The to- influenced by the oceanic régime and as a result has a tal amount of precipitation is about 550 mm per year. This secondary maximum in November and minimum in April. amount increases in highlands where it reaches 600 mm The secondary maximum in autumn is lost in the areas and decreases to less than 500 mm at the Black Sea coast. of and Berlin, with spring becoming wetter than Most of the precipitation falls in the summer half year autumn. The amount of precipitation in the summer half when the mainland is well heated. High temperature pro- year is much higher in the east of Germany than in the motes local convection which gives rise to cloud forming western part. processes and as a result precipitation. R ranges from One of the areas with the biggest R values in Europe, 1.1 in the west to 1.3 in the east. Maximum precipitation is south-east Poland, north-east of the Czech Republic, falls in July in both cases. There is more autumn precip- and north-west Romania. About 70% of the total itation than spring precipitation in Eastern Europe. This precipitation falls in the summer half year in these ar- phenomenon differentiates this area from Central Europe. eas, the amount of summer half year precipitation is more The least precipitation falls in February. than twice the amount of precipitation in the winter half The rainiest areas of Eastern Europe are the western parts year; R can reach 2.44 (Zakopane, Poland). The lowest – Lvov, and in Russia. The least precipita- precipitation is in January and February and the highest tion falls in the area of the Caspian Sea where the annual in June. These areas stand out as the most continental average is only 210 mm in . This is one of the areas of Europe from the precipitation’s point of view of most southern and the lowest areas of Eastern Europe. continentality (Figure 2). Although, more precipitation falls in the summer half year Coastal areas of Romania and Bulgaria are influenced by the predominance of summer precipitation is not as strong the Mediterranean climate and accordingly the most pre- as in the neighboring Kuma Manych lowland. Summer cipitation falls in the winter half year. The rainiest months half year precipitation is more than twice the amount of are November and December. the winter half year in this area. It is the second most con-

179 Continental and oceanic precipitation régime in Europe

tinental area in Europe. The highest R is in Pjatigorsk caused by the interpolation method and lack of stations – 2.63; H is 4 months (Table 3). R in the Figure 2 rises in this area. in the eastern part of this region as well but it is mainly

Table 3. Distribution of precipitation in East Europe.

Altitude Annual Spring Summer Autumn Winter Summer Winter H R mean half half (months) precipitation year year (m) (mm) (%) (%) (%) (%) (%) (%) MOSCOW (RUSSIA) 156 672.2 18 36 26 20 58.53 41.48 6 1.41 PJATIGORSK (RUSSIA) 531 585.5 29 40 19 12 72.48 27.52 4 2.63

Table 4. Distribution of precipitation in the Mediterranean.

Altitude Annual Spring Summer Autumn Winter Summer Winter H R mean half half (months) precipitation year year (m) (mm) (%) (%) (%) (%) (%) (%) () 70 1188.9 24 7 26 43 26.29 73.71 9 0.36 MADRID/BARAJAS (SPAIN) 580 411.9 27 11 30 32 37.68 62.32 8 0.60 PESCARA () 9 729.0 22 19 31 28 42.02 57.98 7 0.72 KALAMATA (GRECEE) 5 801.3 17 3 34 46 14.83 85.17 9 0.17 THESSALONIKI/SEDES (GRECEE) 30 445.4 27 19 27 27 41.29 58.71 7 0.70 (BOSNIA-HERZEGOVINA) 630 966.0 23 25 27 25 49.43 50.56 7 0.98 SHKODRA () 437 1632.5 22 9 35 34 32.13 67.87 8 0.47

3.4. The Mediterranean and bring very little precipitation. The driest months are July and August and H is from 8 to 9 months. The Mediterranean lies in the subtropical climate which has a different régime from . The dis- The difference between the west and east coasts is tribution of precipitation differs from place to place in the prominent. Prevailing westerlies mean that west coasts Mediterranean. With the exception of northeast Spain and have much more rainfalls than east coasts. The biggest , winter precipitation dominates the whole difference is Iberia where annual precipitation is over region with the most precipitation falling in the winter 1100 mm on the west coast and about 500 mm on the half year. Continental features can be found in north-east east coast. Moving south the total amount of precipita- Spain. Iberia is large and high pressure occurs there in tion gets smaller and winter precipitation is more dom- winter. Therefore there are out blowing winds towards inant. The further south a particular place lies the less coastal areas and winter precipitation is low. The north summer precipitation occurs there. Mediterranean climate of Italy is influenced by the Alps, with precipitation both occurs only in a narrow costal stripe at Balkan Peninsula in summer and winter. The rainiest months are November and rapidly weakens towards inland. Moving southward and December. There is low pressure above the Mediter- along Dalmatian coast the amount of annual precipita- ranean Sea and high pressure above the Alps in winter. tion almost doubles. The highest annual precipitation is Cold air blows southward and meets warmer air at the in the area of Podgorica and Shkodra; where it reaches coasts, resulting in rainfall. The situation is similar in 1700 mm. At the Dalmatian coast R ranges from 0.58 in summer. High pressure still occurs above the Alps (an the north to 0.49 in the south. Mediterranean climate oc- extension of Azore anticyclone). Low pressure above the curs on the coast of as well. The total amount Mediterranean Sea is lost and new low pressure system is lower than in other parts of the Mediterranean region is developed above Western Asia. Winds are not as strong and decreases towards the south. H ranges from 9 to 10

180 Katerina Mikolaskova

months and R is 0.17 (Table 4) and maximum precipitation moves to December and January. The driest month is July – often without precipitation at all. The Mediterranean climate prevails inland but the total amount of precipita- tion rapidly decreases.

3.5. Western Asia

This is a region with variable climate – Mediterranean in the north and dry or arid in the south, with the excep- tion of the east of Turkey which lies in oceanic climate. The distribution of precipitation differs from place to place but precipitation in the winter half year is predominant in most areas. In eastern Turkey and summer rain- falls are more common. The most rainfalls occur on the north coast of Turkey. With an average of about 700 mm, Figure 3. Degree of continentality for Europe in per cent [8]. but at the base of Rize Mountains it rises to 2164 mm. This is even rainier than Norwegian Bergen. The driest months are July and August, without precipitation in some areas. Winter maximum precipitation differs from place to mer and gives rise to cloud forming processes and in con- place. Continental climate occurs in northeastern Turkey sequence precipitation. Maximum precipitation occurs in (in the area of Erzurum) and extends to Georgia. Moving June and July in the continental régime. Many areas are south to countries of the Near East the total amount of influenced by more factors and so the annual course of precipitation decreases and summer months (July, August) precipitation is more variable in these areas. are without precipitation at all. That is why winter pre- Continentality from the point of view of precipitation in- cipitation increases and exceeds 80% of the total amount creases eastward, from the ocean inland. The increase of precipitation. The rainiest month is January but more in climate continentality is slow from the Atlantic Ocean precipitation occurs until April. There are high mountains towards east. Change in the distribution of precipitation in Syria and Lebanon which influence the total amount of among summer and winter months is much faster in case of rainfalls. the Mediterranean Sea and the Black Sea. This is caused firstly by subtropical climate which has different distribu- tion of precipitation to middle latitudes. Secondly there 4. Conclusion are high mountain ranges at the Mediterranean coast (the Dinar Mountains, the Caucasus) which form a barrier to Distribution of precipitation over Europe is influenced by prevailing westerlies. The total amount of precipitation the air circulation caused by the difference among air decreases rapidly inland and the annual course changes. pressures above the Atlantic Ocean, the Mediterranean The most continental areas are those, which are inland Sea and the mainland. Oceanic régime of precipitation is and sheltered by mountain ranges. The most continental characterized by the predominance of winter half year pre- areas according to the distribution of precipitation are the cipitation. Areas influenced by the Atlantic Ocean have areas of south-east Poland, north-east of the Czech Re- maximum precipitation in December and January. This public, Slovakia and north-west Romania and area south can be connected with the largest extent of Icelandic low of the Caucasus (Figure 2). According to the results of pressure in January. Areas in the Mediterranean have the analysis the area of Russia is less continental than the heaviest rainfalls in autumn and maximum precipita- the centre of Europe and area south of the Caucasus. tion occurs in November and December. Areas where the Distribution of precipitation in Europe doesn’t respond to influence of the mainland is dominant have the most pre- the thermal continentality, at least according to classi- cipitation in summer. This is caused by a high pressure cal continentality indices such as Gorczynski [8] or Chro- system developing above the mainland in winter which mov [9]. Climate continentality (thermal) expressed by prevents maritime air from penetrating inland. There is Gorczynski is represented in Figure 3. According to him low pressure system above in summer, thus oceanic regime penetrates far inland up to Moscow or maritime air can penetrate deeper inland. As a result of Kiev. However, this area according to continentality from well heated mainland, local convection develops in sum- precipitation’s point of view has a considerably continen-

181 Continental and oceanic precipitation régime in Europe

tal regime. Another difference between continentality from školy, nakladatelství Ceskéˇ geografické spoleˇcnosti, the temperature and precipitation viewpoints is in the area Praha, 1999 (in Czech) of the Mediterranean. This area lies in subtropical climate [19] Kartografie Praha, Školní atlas Ceskéˇ republiky, Kar- which is probably the cause of most of the differences be- tografie Praha, 2002 tween the temperature and precipitation patterns there. [20] Kunský, J., Ceskoslovenskoˇ fyzicko zemˇepisné, SPN, Praha, 1974 (in Czech) [21] Mikolášková K., Ombrická kontinentalita v Evropˇea Ceskéˇ republice (bachelor thesis), PˇrF UK, Praha, References 2003 (in Czech) [22] Míková T., Coufal L., Tlak vzduchu na území Ceskéˇ [1] McBoyle G. R., Steiner D., A factor analytic approach republiky v období 1961 – 1990, Národní klimatický to the problem of continentality. Geografiska Annaler program CRˇ – svazek 28, CHMÚ,ˇ 1999 (in Czech) Series A, Phys. Geogr., 1972, 54, 12-27 [23] Okolowitcz W., General Climatology, PWN [2] Driscoll D., M., Yee Fong J. M., Continentality: a Warszawa, 1976 basic climatic parameter re-examined, Int. J. Climatol., [24] Sládek I., Návrh nové míry kontinentality klimatu In: 1992, 12, 185-192 Fyzickogeografický sborník 3, Masarykova Univerzita [3] World Weather Records, Volume 2, 1961 – 1970, De- v Brnˇe, 2005, 144 (in Czech) partment of Commerce, D.C., USA, 1979 [25] Šver C. A., Atmosfernye osadki na territorii SSSR, [4] World Weather Records, Volume 2, 1971 – 1980, De- Gidrometeoizdat, Leningrad, 1976 (in Russian) partment of Commerce, Washington D.C., USA, 1987 [26] Trefná E., Reinhartová J., Struˇcná klimatografie svˇeta [5] World Weather Records, Volume 2, 1981 – 1990, De- pro leteckou a jinou dopravu, Dopravní nakladatelství, partment of Commerce, Washington D.C., USA, 1995 Praha, 1959 (in Czech) [6] Nosek M., Metody v klimatologii, Academia, 1972 (in Czech) [7] Kendrew W.G., The Climates of the Continents, Ox- ford, 1953 [8] Gorczynski L., The calculation of the degree of conti- nentality, Monthly Weather Review, 1922, 50, 370 [9] Chromov S. P.,(): Metorológia a klimatológia, SAV, , 1968 (in Slovak) [10] Brázdil R., Variation of atmospheric precipitation in the CSSR with respect to precipitation changes in European region, Univerzita J.E. Purkynˇe, , 1986 [11] Brázdil R., Koláˇr M., Žaloudík J., Prostorové úhrny srážek na Moravˇe v období 1881 – 1980 In: Meteoro- logické zprávy, CHMU,ˇ 1985, 38, 87(in Czech) [12] Brázdil R., Štekl J., Cirkulaˇcní procesy a atmosférické srážky v CSSR,ˇ Univerzita J.E. Purkynˇe, Brno, 1986 (in Czech) [13] Hanzlík S., Základy meteorologie a klimatologie, Nakladatelství ˇceskoslovenské akademie vˇed, Praha, 1956 (in Czech) [14] Jánský B., Geografie moˇrí a oceánu,˚ Univerzita Karlova, Praha, 1992 (in Czech) [15] Kašparovský K., Zemˇepis II v kostce, Fragment, Havlíˇckuv˚ Brod, 2002 (in Czech) [16] SPN, Pˇrírodní pomˇery Ceskoslovenska,ˇ vybrané kapi- toly z fyzického zemˇepisu, SPN, Praha, 1960 (in Czech) [17] Academia a Ministerstvo životního prostˇredí CR,ˇ Me- teorologický slovník výkladový a terminologický, Min- isterstvo životního prostˇredí CR,ˇ Brno, 1993 (in Czech) [18] CGS,ˇ Ceskᡠrepublika, uˇcebnice zemˇepisu pro stˇrední

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