Change of the climatic characteristics of the Belgrade region and its influences on the both grass water shortage and excess water

Abstract

In order to determine the influence of changes of the climatic characteristics of the Belgrade region on crop water shortage or crop excess water, measured data of air temperature and precipitation in the period of 1888 - 2000 has been used from the meteorological station Belgrade. Calculation of grass water shortage and excess water was based on difference between precipitation and grass water requirement that achieve full production. Grass water requirement can be equalized with reference evapotranspiration (ETo). The reference evapotranspiration was calculated by Penman-Monteith method. For the period 1888 - 1975, ETo was calculated with simplified Penman-Monteith method, where minimum and maximum air temperature were needed only. For the period of observation 1975 - 2000, ETo was calculated by both Penman-Monteith method using all measured data such as minimum and maximum air temperature, minimum and maximum air humidity, wind velocity and insolation and by simplified one, in order to compared these data. Very high correlation between those data were obtained (r*=0.957). Therefore, the simplified method were used for further analysis. The trend of grass water shortage and excess water is extremely variable. In order to damp out the random variation of the variable a 5 year moving mean was used. Excess water was appearing every year during the cold period (November February) with increasing trend. Grass water shortage was observed during the warm period, but with decreasing trend. Although, drought period is enhanced in July and August in Belgrade region, even that, long term of water shortage demonstrated decreasing trend. The tendency of mean annual air temperature increment of 1.2 °C for 113 years of observation was evident in one side, and increment of precipitation of 57 mm was observed as well. A decrease of water shortage in warm period can be explained by the fact that air temperature increment is emphasized the mostly during the winter. The analysis of mean annual and seasonal air temperature and precipitation show the climatic changes of Belgrade region. The changes has a certain impact on grass water shortage and excess water. These impact don't provoke only negative consequence on the crop growth, but positive, too.

Da bi se odredile promene karakteristika područja Beograda i njihov uticaj na deficit i suficit vode travnatog pokrivača, uzeti su podaci o temperaturi vazduha, relativnoj vlažnosti vazduha, insolaciji, brzini vetra i padavinama sa meteorološke stanice Beograd, za period osmatranja 1888 - 2000. godine. Deficit i suficit vode travnatog pokrivača određen je na osnovu razlike padavina i potrebne količine vode travnatom pokrivaču da ostvari maksimalni prinos. Potrebna količina vode travnatog pokrivača se može izjednačiti sa referentnom evapotranspiracijom (ETo), i te vrednosti su izračunate metodom Penman-Monteith-a. Za period kada je merena samo temperature vazduha rcferentna evapotranspiracija je izračunata uprošćenom metodom Penman-Monteith-a. Preciznost uprošćene metode utvrđena je izuzetno visokim koeficijentom determinacije (r2 = 0,957) podataka ETo pomenutim metodama za period 1975-2000. Trend.suficita i deficita vode je veoma promenljiv. Da bi se smanjile ekstremne vrednosti promenljive korišćena je metoda pokretnih sredina za period od 5 godina. Analizom suficita vode utvrđena je njegova stalna pojava, sa tendencijom stalnog porasta. Utvrđen je i stalan nedostatak vode, ali sa trendom opadanja. Analiza deficita vode u najsušnijem delu godine (juli i avgust), takođe pokazuje trend opadanja deficita vode. Iako je uočen trend povećanja temperature vazduha za 1,3 °C za 113 godina, s druge strane se javlja trend povećanja padavina za 57 mm. Da deficit vode ima trend opadanja, idu u prilog podaci da se porast temperature vise ispoljava u zimskim mesecima nego u letnjim. Na osnovu dobijenih rezultata može se zaključiti da dolazi do globalnih klimatskih promena na području Beograda ali da one ne moraju imati samo negativan uticaj na rast biljaka, već i pozitivan, a čak se mogu postići bolji agronomski i ekonomski efekti.