Long-Term Precipitation Variability in Macedonia

1. Long-term Variability of Precipitation in Republic of MacedoniaNIKOLA SLAVOV, TANIA MARINOVA, PECE RISTEVSKI* BULGARIAN ACADEMY OF SCIENCES National Institute of Meteorology and Hydrology 1. Introduction2. Material and investigation methods3. Analysis of the results4. Conclusions *Hydrometeorological Service – Skopje, FY Republic of Macedonia

2. Materialand investigation methods The rainfall regime in Republic of Macedonia is investigated on the basis of monthly sums of precipitation in 5 meteorological stations with the longest period of observations during the last century: Skopje (1925 – 2000), Bitola (1925–2000), Prilep (1924–2000),Stip (1926–2000), Demir Kapija (1933–2000). • Mean monthly precipitation sumsare used to evaluate the anomalies of rainfall conditions during the different parts of the year as follows: • Mean seasonal precipitation Winter XII, I, II • Spring III, IV, V • Summer VI, VII, VIII • Autumn IX, X, XI • Mean half-year precipitation • Cold half-year Х, ХІ, ХІІ, І, ІІ, ІІІ • Warm half-year ІV, V, VІ,VІІ, VІІІ,ІХ • Mean annual precipitation I – XII Fig.1. Locations of the meteorological stationswithin the limits of agricultural production

3. In order to assess the tendencies of change in annual precipitation and in precipitation during the different parts of the year for the last century, the corresponding linear trends are obtained. • The analysis of periodicities and their duration is completed on the basis of 5-years running average. • Variability of rainfall regime in the last century is evaluated by means of the deviations from the mean long-term precipitation amounts during the different periods of the century.

4. Fig.2. Mean annual precipitation variations in Macedonia The mean long-term annual precipitation sum is 539.5 mm The maximum negative deviation from the mean long-term annual precipitation sum is –214.9 mm in the year 2000s during the driest period at the end of the last century. Rainfall periodsMaximum annual R 1933–19421937 (787.4 mm) 1954–19641962 (721.8 mm) 1972–19831981(725.5 mm) Dry periodsMinimum annual R 1924 – 1932 1932 (358.1 mm) 1943–19531953(409.2 mm) 1965–19711965 (414.2 mm) 1984–20002000 (324.6 mm)

5. Fig.4. Mean precipitation variations in winter in Macedonia The mean long-term precipitation in winter is 138.1 mm. The maximum negative deviation of winter precipitation amounts is 103.2 mm in 1948s. The winter period of 1934s is characterized with the highest precipitation amount of 317.9 mm. The driest winter period is in 1948swith 34.9 mm.

6. Fig.6. Mean precipitation variations in spring in Macedonia The mean long-term precipitation in spring is 142.2 mm. The maximum positive deviation of spring precipitation amount is 95.3 mm (1958) and the maximum negative deviation is –98.7mm (1945) The wettest spring is in 1958s (237.5 mm) and the driest one – in 1945s (43.5 mm).

7. Fig.8. Mean precipitation variations in summer in Macedonia The mean long-term precipitation in summer is 106.8 mm. The maximum positive deviation of summer precipitation is 146.8 mm (1983) and the maximum negative one is –79.1 mm (1978). The wettest summer is in 1983s (254.5 mm);the driest summer – in1978s (27.7 mm).

8. Fig.10. Mean precipitation variations in autumn in Macedonia The mean long-term precipitation in autumn is 152.4 mm. The maximum positive deviation of autumn precipitation is 121.7 mm (1962) and the maximum negative one is –130.3 mm(1969) The wettest autumn is in 1962s (274.1 mm)and the driest one – in 1969s (22.1 mm).

9. Fig.12. Mean precipitation variations in the cold half-year in Macedonia The mean long-term precipitation in the cold half-year is 295.9 mm The maximum positive deviation of cold half-year precipitation is 259.5 mm (1961) and the maximum negative one is –150.5 mm (1976). The wettest cold half-year is in 1961swith555.4 mm and the driest one – in 1976s with145.4 mm.

10. Fig.14. Mean precipitation variations in the warm half-year in Macedonia The mean long-term precipitation in the warm half-year is 243.7 mm. The maximum positive deviation is 170.0 mm (1983) and the maximum negative one is –134.7 mm (1993). The wettest warm half-year is in 1983s (413.7 mm) and the driest one – in1993s (109.0 mm).

11. Conclusions The results obtained in the present study on the long-term variations in precipitation during the period 1924–2000 in Republic of Macedonia can be summarized as follows: 1. It is found out that the trend in annual precipitation variations is towards drought. 2. Similar tendency is peculiar to both cold and warm half-year precipitation amounts especially after the year 1983s of the last century. 3. The regions where the annual precipitation decreases more and more often below 300 mm are most vulnerable as degradation processes of plant ecosystems begin.