THE CLIMATE OF CYPRUS
Cyprus has an intense Mediterranean climate with the typical seasonal rhythm strongly marked in respect of temperature, rainfall and weather generally. Hot dry summers from mid-May to mid-September and rainy, rather changeable, winters from November to mid-March are separated by short autumn and spring seasons of rapid change in weather conditions.
The central Troodos massif, rising to 1951 metres and, to a less extent, the long narrow Kyrenia mountain range, with peaks of about 1,000 metres, play an important part in the meteorology of Cyprus. The predominantly clear skies and high sunshine amounts give large seasonal and daily differences between temperatures of the sea and the interior of the island which also cause considerable local effects especially near the coasts.
At latitude 350 North, Longitude 330 East, Cyprus has a change in daylength from 9.8 hours in December to 14.5 hours in June.
In summer the island is mainly under the influence of a shallow trough of low pressure extending from the great continental depression centred over southwest Asia. It is a season of high temperatures with almost cloudless skies. Rainfall is almost negligible but isolated thunderstorms sometimes occur which give rainfall amounting to less than 5% of the total in the average year.
In winter Cyprus is near the track of fairly frequent small depressions which cross the Mediterranean Sea from west to east between the continental anticyclone of Eurasia and the generally low pressure belt of North Africa. These depressions give periods of disturbed weather usually lasting from one to three days and produce most of the annual precipitation, the average fall from December to February being about 60% of the annual total.
The average annual total precipitation increases up the southwestern windward slopes from 450 millimetres to nearly 1,100 millimetres at the top of the central massif. On the leeward slopes amounts decrease steadily northwards and eastwards to between 300 and 350 millimetres in the central plain and the flat southeastern parts of the island.
The narrow ridge of the Kyrenia range, stretching 100 miles from west to east along the extreme north of the island, produces a relatively small increase of rainfall to nearly 550 millimetres along its ridge at about 1,000 metres.
Rainfall in the warmer months contributes little or nothing to water resources and agriculture. The small amounts which fall are rapidly absorbed by the very dry soil and soon evaporated in high temperatures and low humidities.
Autumn and winter rainfall, on which agriculture and water supply generally depend, is somewhat variable. The average rainfall for the year as a whole is about 480 millimetres but it was as low as 182 millimetres in 1972/73 and as high as 759 millimetres in 1968/69. (The average rainfall refers to the island as a whole and covers the period 1951-1980). Statistical analysis of rainfall in Cyprus reveals a decreasing trend of rainfall amounts in the last 30 year.
Snow occurs rarely in the lowlands and on the Kyrenia range but falls frequently every winter on ground above 1,000 metres usually occurring by the first week in December and ending by the middlle of April. Altough snow cover is not continuous during the coldest months it may lie to considerable depths for several weeks especially on the northern slopes of high Troodos.
Hail and Thunder
Hail is reported on an average two or three times a year in the lowlands and probably three times as frequently on the mountains, usually, between November and May, in most districts of Cyprus. Months most liable to have hailstorms are December to April but hail occurring rarely in early summer and autumn is more important because of the considerable damage caused locally to fruit crops.
Thunder is rare from June to September but at other seasons is heard on the average on four or five days per month from October to January and two or three days per month from February to May.
Cyprus has a hot summer and mild winter but this generalization must be modified by consideration of altitude, which lowers temperatures by about 5 C per 1,000 metres and of marine influences which give cooler summers and warmer winters near most of the coastline and especially on the west coast.
The seasonal difference between mid-summer and mid-winter temperatures is quite large at 18 C inland and about 14 C on the coasts.
Differences between day maximum and night minimum temperatures are also quite large especially inland in summer. These differences are in winter 8 to 10 C on the lowlands and 5 to 6 C on the mountains increasing in summer to 16 C on the central plain and 9 to 12 C elsewhere.
In July and August the mean daily temperature ranges between 29 C on the central plain and 22 C on the Troodos mountains, while the average maximum temperature for these months ranges between 36 C and 27 C respectively. In January the mean daily temperature is 10 C on the central plain and 3 C on the higher parts of Troodos mountains with an average minimum temperature of 5 C and 0 C respectively.
Frosts are rarely severe but are frequent in winter and spring inland and in some years handicap the economically important production of early vegetable crops and main citrus crops.
In the open sea temperatures rise to 27 C in August and are above
22 C during the six months June to November. During each of the three coolest months, January to March, average sea temperature falls only to 16 or 17 C.
Near all coasts in water three or four metres deep temperatures are very similar to those of the open sea and lie within the range 15 to 17 C in February and 23 to 28 C in August.
There is no significant daily change of sea water temperature except on the coast in the very shallow waters of less than one metre depth.
Seasonal change in mean soil temperatures is from about 10 C in January to 33 C in July at 10 centimetres depth and from 14 C to 28 C at one metre. On the mountains at 1,000 metres above sea level these mean seasonal values are lowered by about 5 C. Even in the highest areas penetration of frost into the ground is insufficient to cause problems.
Absorption of large amounts of solar energy during the day and high radiation losses in clear skies at night cause a wide daily range of soil temperatures in summer. At the soil surface the daily variation on a typical July day in the lowlands is between 15 C near dawn to near 60 C in middle of the afternoon. At only 5 centimetres depth the variation is reduced to between 24 and 42 C and at 50 centimetres depth there is no daily temperature change.
Relative Humidity of the Air
Elevation above mean sea level and distance from the coast also have considerable effects on the relative humidity which to a large extent are a reflection of temperature differences. Humidity may be described as average or slightly low at 65 to 95% during winter days and at night throughout the year. Near midday in summer it is very low with values on the central plain usually a little over 30% and occasionally as low as 15%.
Fog is infrequent and usually confined to the early mornings but there are longer periods on the mountains in winter when cloud often envelops the highest peaks. Visibility is generally very good or excellent but on a few days each spring the atmosphere is very hazy with dust brought from the Arabian and African Deserts.
All parts of Cyprus enjoy a very sunny climate compared with most countries. In the central plain and eastern lowlands the average number of hours of bright sunshine for the whole year is 75% of the time that the sun is above the horizon. Over the whole summer six months there is an average of 11.5 hours of bright sunshine per day whilst in winter this is reduced only to 5.5 hours in the cloudiest months, December and January.
Even on the high mountains the cloudiest winter months have an average of nearly 4 hours bright sunshine per day and in June and July the figure reaches 11 hours.
Over the eastern Mediterranean generally surface winds are mostly westerly or southwesterly in winter and northwesterly or northerly in summer. Usually of light or moderate strength, they rarely reach gale force.
Over the island of Cyprus however winds are quite variable in direction with orography and local heating effects playing a large part in determination of local wind direction and strength. Differences of temperature between sea and land which are built up daily in predominant periods of clear skies in summer cause considerable sea and land breezes. Whilst these are most marked near the coasts they regularly penetrate far inland in summer reaching the capital, Nicosia, and often bringing a welcome reduction of temperature and also an increase in humidity.
Gales are infrequent over Cyprus but may occur especially on exposed coasts with winter depressions. Small whirlwinds are common in summer appearing mostly near midday as "dust devils" on the hot dry central plain. Very rarely vortices, approaching a diameter of 100 metres or so and with the characteristics of water spouts at sea and of small tornadoes on land, occur in a thundery type of weather. Localized damage caused by these has been reported on a few occasions but in general Cyprus suffers relatively little wind damage.
ΤRENDS IN PRECIPITATION AND TEMPERATURE IN CYPRUS
DURING THE 20TH CENTURY AND AT THE BEGINNINGS OF THE 21ST CENTRURY
During the 20th century remarkable variations and trends were observed in the climate of Cyprus, particularly in the two basic climatic parameters, precipitation and temperature. Similar climatic variations and trends were observed in countries of the eastern Mediterranean and the Middle East, which is an evidence of change in the general circulation of the atmosphere in the area.
In Cyprus the precipitation presented a decreasing trend and the temperature presented an increasing trend. The rates of change of precipitation and temperature are greater during the second half of the century compared to those in the first half of the century. In the last decades the number of years of low precipitation and drought is greater than before and the semi – arid conditions both in Cyprus and in the eastern Mediterranean were deteriorated. Also, the most of the warm years in the century were observed in the last 20 years.
The decrease in the amount of precipitation was remarkable. While the average annual precipitation in the first 30-year period of the century was 559 mm, the average precipitation in the last 30-year period was 462 mm, which corresponds to a decrease of 17%.
On the other hand, the average annual temperature in Cyprus, both in urban and in rural areas, presented an increasing trend. The greater increase in temperature in the towns is due to the urbanization effect, however, the fact that an increase is also observed in rural areas, it is indicative of the general increase in temperature in our area as well as globally. In Nicosia the average annual temperature increased from 18.9°C in the first 30-year period of the century to 19.7°C in the last 30-year period, an increase of 0.8°C.
The rate of decrease of the average precipitation in Cyprus during the 20th century and at the beginning of the 21st was one millimeter per year.
The decrease in precipitation occurred mainly in the second half of the century, as a result of the higher frequency of occurrence in the number of years of low precipitation and drought. This is shown in Table 1, where the hydrometeorological years as from 1901-02 are classified according to the normal precipitation of the period 1961-1990.
T A B L E 1
AVERAGE ANNUAL PRECIPITATION IN THE AREA UNDER
CLASSIFICATION OF THE YEARS ACCORDING TO NORMAL (1961-1990)
Similar conclusion in drawn form the examination of the average precipitation in various 30-year periods: 1901-1930: 559 mm, 1931-1960: 524 mm, 1961-1990: 503 mm, 1971-2000: 462 mm. The average precipitation in the last 30-year period is 17% less than in the period 1901-1930.
The average precipitation in the last decade of the century is among the lowest values for the various decades of the century.
T A B L E 2
ANNUAL PRECIPITATION IN THE LAST TWENTY YEARS (1991 - 2011)
(1961 – 1990)
|Average for |
the last twenty years
Temperature in Cyprus during the 20th century followed a reverse trend than the precipitation, with a rate of increase of 0.01°C per year.
In the period 1976-1998 the average rate of increase in temperature was 0.035°C / year in the towns and 0.015°C in the rural areas. The urbanization effect plays an important role in the temperature increase in the towns, however, the increase in the temperature in rural areas is indicative of the climate change in our area in the last decades.
In Cyprus, as well as globally, most of the warm years in the 20th century occurred in the last two decades. The year 1998 was the warmest in Cyprus and globally. In Cyprus during August 1998 we experienced a very severe heat wave. The highest maximum temperatures over Cyprus were recorded at the beginning of August 2010. The highest was recorded at Athalassa on the 1st of August 2010 and the temperature was 45.6 oC.
CLIMATIC- CHANGES - CONDITIONS AFTER 1990
Climatic changes have affected Cyprus. The changes are obvious in Precipitation and Temperature.
The average annual Precipitation in the period 1991/ 92 - 2007/ 08 (17 hydrometeorogical years) is 457 mm or 9% lower than normal (503 mm, period 1961-1990).
The average annual Temperature in the period 1991-2007 is 17,70C or 0,50C higher than normal (17,20C, period 1961-1990).
According to the above rate of changes it is expected that by 2030 Precipitation will decrease by 10 - 15% and Temperature will increase by 1,0 - 1,50C compared to the normal values of the period 1961- 1990.