Temperature and Precipitation Trends in Belgrade and Indicators of Changing Extremes for Serbia

GEOGRAPHICA PANNONICA Volume 12, Issue 2, 62-68 (2008) ISSN 1820-7138 (online) Temperature and Precipitation Trends in Belgrade and Indicators of Changing Extremes for Serbia Smilja V. Đorđević1 Received: June 2008 | Revised: August 2008 | Accepted: August 2008 Abstract Deviations and trends are analysed of seasonal and annual mean and extreme air temperatures, precipitation sums and the number of days with precipitation in Belgrade for the longer period of 1888-2006 for the purpose of recording climate changes. On the territory of Serbia, climate changes were monitored by the calculation of the indicators of changing extremes for temperature on 15 stations in the shorter period of 1957-2006 and for precipitation on 19 stations for the period 1961-2006. These climate extreme indices include the extremely hot days, cold days, warm nights, cold nights, the heat wave duration end the annual fraction due to extreme precipitation events. Key words: extreme climate indices; heat wave; extreme precipitation events; tendency analysis; climate change detection. Introduction Critical values of temperature and precipitation in percen- Climate changes due to global warming are unmistakable. tiles are shown in Table 1. Homogeneity has not been done. This can be seen in the rise of global mean air and ocean Available data have been used in such form for all climate temperatures, increasing intensity of permafrost melting as analyses so far. well as in the increase in mean sea level (Climate Change, Table 1 Critical values of temperature and precipitation in 2007). percentiles In this paper indicators of climate changes were obtained using two methods. The first method was used to analyse Percentiles Air temperature Precipitation deviations, 5-year moving means and trends of seasonal 1 extremely cold extremely dry and annual mean, minimum and maximum air tempera- 2 – 9 very cold very dry tures, precipitation sums and number of days with precip- 10 – 24 cold dry itation for Belgrade in the period 1888-2006, (WMO, 1983). 25 – 75 normal normal The other method meant the observation of climate changes in Serbia by calculating the indicators of changing ex- 76 – 90 hot humid tremes (Djordjevic, 2002; Djordjevic and Jovanovic, 2006; 91 – 98 very hot very humid Jovanovic and Djordjevic, 2006) defined by the World Me- 98 extremely hot extremely humid teorological Organization (Peterson, et al., 2001). This method was applied on 15 main stations for the tempera- On 15 stations in Serbia for the period 1957-2006, the fol- ture in the period 1957-2006 and on 19 main stations for the lowing indicators of changing extremes for temperature precipitation in the period 1961-2006. were calculated (Peterson, et al., 2001), as listed with their shortened names: Methodology and data 1. Tn90, that represents minimum temperature above the Daily climatological data on air temperature and precipita- 90th percentile with the meaning of very high values of tion quantity were used. All the anomalies were calculated minimum temperature, for each year in relation to the basic period 1961-1990 and 2. Tn10, that represents minimum temperature below the then trend lines were assessed by the least square method. 10th percentile with the meaning of very low values of Percentiles were used for obtaining the range of normal and minimum temperature, extreme temperature and precipitation values (WMO, 1983). 1 Republic Hydrometeorological Service of Serbia, Kneza Višeslava 66, Belgrade, Serbia, e-mail: [email protected] 62 Smilja V. Djordjević 3. Tx90, that represents maximum temperature above the Table 2 Deviation trend cоеfficients as per seasons of mean, 90th percentile with the meaning of very high value of maximum and minimum temperatures in Belgrade in the period of 1888-2006 maximum temperature, 4. Tx10, that represents maximum temperature above the Seasons Tmean Тmax Тmin 10th percentile with the meaning of very low value of (°C/100 years) (°C/100 years) (°C/100 years) maximum temperature, Spring +1.32 +0.54 +1.92 5. HWDI, that represents maximum number of consecu- Summer +1.04 -0.02 +1.95 tive days during the year with the maximum tempera- Autumn +0.74 +0.31 +1.69 ture 5°C above the 1961-90 daily normal or so-called heat waves, Winter +1.95 +1.68 +2.97 6. TxGE30, that represents days when maximum temperature is ≥ 30°C. of straight line is called temperature trend coefficient and serves as the assessment of temperature change tendency. For 19 stations in Serbia precipitation indicator was cal- Significant positive temperature trend coefficients are culated for the period 1961-2006, observed in all three cases. Thus, in observed period, the 7. R95T, that represents the fraction of annual total precipi- rise of mean, maximum and minimum annual air tem- tation due to events exceeding the 95th percentile. perature was prominent. Among all the cases, trend coefficient has the highest value for minimum temperature in Besides mentioned indicators, average values were also the amount of +2.10°C/100 years. This shows that the rise of calculated of the indicators of changing extremes from (1) minimum temperature was the greatest. to (7) for the basic period 1961-1990, deviations from aver- Coefficient of trends as per seasons (first column) of age values for each individual year and trend of these de- mean (second column), maximum (third column) and min- viations. imum (fourth column) temperatures are shown in this order in Table 2. It is evident that in all cases trend coefficients Results are positive, except in summer season with maximum tem- Belgrade - Temperature perature when the trend value is slightly below zero. Thus Deviation of mean annual, maximum and minimum mostly mean, maximum and minimum seasonal air tem- temperatures from the basic period 1961-1990 are shown peratures have risen, except in summer when maximum in three panels of Figure 1 going downwards. Also, black temperature showed the tendency of slight decrease. Out curves show 5-year moving means, and straight lines are of all seasons, winter has the highest value of trend coeffi- temperature trends. Besides the mentioned, trend equations cient for minimum temperatures when the highest value of are given where Tmean, Тmax and Тmin are mean, maximum +2.97°C/100 years was obtained. This shows that the rise of and minimum temperature and t is a year. Slope coefficient minimum temperature is the highest during winter. 2.5 Belgrade - Serbia 2.0 1.5 1.0 0.5 0.0 -0.5 Temperature anomalies in °C Temperature -1.0 -1.5 -2.0 Tmean = -0.89 + 0.0122 (t-1988) -2.5 1888 1890 1892 1894 1896 1898 1900 1902 1904 1906 1908 1910 1912 1914 1916 1918 1920 1922 1924 1926 1928 1930 1932 1934 1936 1938 1940 1942 1944 1946 1948 1950 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 t (years) Figure 1a Deviation, 5-year moving means and deviation trends of annual mean temperature for Belgrade for the period 1888-2006 Geographica Pannonica • Volume 12, Issue 2, 62-68 (2008) 12, Issue Volume • Pannonica Geographica 63 64 Geographica Pannonica • Volume 12, Issue 2, 62-68 (2008) Deviation of annual precipitation quantities and the Figure 1c Figure 1b number daysof with mm ≥ precipitation 0.1 from the basic precipitation precipitation trends. Also, trend equations are given where periodare 1961-1990 presented on two panels using pillars Belgrade –Precipitation curves show 5-year moving means, and straight lines are on Figure 2 going downwards in order. As in Figure 1, blackinFigure As 1, downwardsgoinginorder. Figure 2 on and Indicatorsof Extremes Changing for Serbia Belgrade in and Precipitation Trends Temperature Temperature anomalies in °C Temperature anomalies in °C -4.0 -3.0 -2.0 -1.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 0.0 1.0 2.0 3.0 Deviation, moving 5-year means and deviation trends of annual minimum temperature for Belgrade for the period 1888-2006 Deviation, moving 5-year means and deviation trends of annual maximum temperature for Belgrade for the period 1888-2006 1888 1888 1890 -SerbiaBelgrade 1890 -SerbiaBelgrade 1892 1892 1894 1894 1896 1896 1898 1898 1900 1900 1902 1902 1904 1904 1906 1906 1908 1908 1910 1910 1912 1912 1914 1914 1916 1916 1918 1918 1920 1920 1922 1922 1924 1924 1926 1926 1928 1928 1930 1930 1932 1932 1934 1934 1936 1936 1938 1938 1940 1940 1942 1942 1944 1944 t (years) t (years) R and NBR for annual precipitation quantity and number tation quantity in the amount of +8.9 mm/100 years and trend coefficient serves asthe assessment ofprecipitation negative for the number of days with precipitation in the change tendency. of of days with precipitation ≥ 0.1 mm. Again, precipitation 1946 1946 Positive Positive coefficienttrend is evidentfor annualprecipi 1948 1948 1950 1950 1952 1952 1954 1954 1956 1956 1958 1958 1960 1960 1962 1962 1964 1964 1966 1966 1968 1968 1970 1970 T 1972 T 1972 max min 1974 1974 =-1.75+0.0213(t-1888) 1976 1976 =-0.34+0.0062(t-1888) 1978 1978 1980 1980 1982 1982 1984 1984 1984 1984 1986 1986 1988 1988 1990 1990 1992 1992 1994 1994 1996 1996 1998 1998 2000 2000 2002 2002 2004 2004 2006 2006 - for Belgrade for the period 1888-2006 Figure 2b for Belgrade for the period 1888-2006 Figure 2a Deviations (days) Departures in % of normal -40.0 -30.0 -20.0 -10.0 -60.0 -40.0 -20.0 10.0 20.0 30.0 40.0 50.0 20.0 40.0 60.0 0.0 0.0 Deviation, moving 5-year means and deviation trends of annual precipitation quantity Deviation, moving 5-year means and deviation trends of number mm ofwith days precipitation ≥0.1 1925 1888 Belgrade -SerbiaBelgrade 1890 -SerbiaBelgrade 1928 1892 1894 1896 1931 1898 1900 1934 1902 1904 1937 1906 1908 1940 1910 1912 1943 1914 1916 1918 1946 1920 1922 1949 1924 1926 1952 1928 1930 1955 1932 1934 1936 1958 1938 1940 1961 1942 1944 t (years) t (years) 1964 1946 1948 1967 1950 1952 1970 1954 1956 1958 1973 1960 1962 1976 1964 1966 1979 1968 1970 NBR =4.46-0.0596(t-1888) 1982 1972 1974 R =-7.22+0.089(t-1888) 1976 1985 1978 1980 1988 1982 1984 1991 1984 1986 1994 1988 Djordjević V.

Load more