The Annals of Valahia University of Târgovişte, Geographical Series, Tome 4-5,

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1 THE PLUVIOMETRIC CHARACTERISATION, ACCORDING TO THE STANDARDIZED ANOMALY OF PRECIPITATION DURING THE LAST 25 YEARS OF THE TH CENTURY IN THE NORTHERN PART OF OLTENIA Iulica Văduva * Key words: quantities in excess, scanty quantities, Oltenia. Rezumat: În lucrarea de faţă au fost calculate cantităţile excedentare şi deficitare de precipitaţii din perioada 1976-, la patru staţii meteorologice (Râmnicu Vâlcea, Polovragi, Tg. Jiu şi Apa Neagră) din nordul Olteniei, prin intermediul anomaliei standardizate de precipitaţii (ASP). The quantities of precipitations in excess and the scanty ones during the period, at four meteorological stations (Ramnicu-Valcea, Polovragi, Targu-Jiu and Apa Neagra) in the northern part of Oltenia were determined, using the standardized anomaly of precipitations (RSA). The RSA calculus on values thresholds was used to determine the frequency of the excess and scanty pluviometric periods (Table 1). For the excess and scanty pluviometric precipitations the years were separated by the differences mentioned in the above-mentioned table. For a correct hierarchy, we considered it was necessary to highlight the framing differences, according to RSA, such as droughty, normal and rainy (Vasenciuc, 2). Table 1 Pluviometric ratings depending on the value of the standardized anomaly of precipitations RSA value Class Symbol Pluviometric class/of intensity (rating) >3. P5 Extremely rainy. Imminent floods P4 Excessively rainy. Danger of floods in summer and winter in case of liquid rainfall P3 Extremely rainy P2 Very rainy P1 Moderately rainy N Almost normal. There are no deficit or surplus periods. In summer, it is possible to appear dry periods S1 Moderately dry S2 Very dry S3 Extremely dry S4 Excessively dry <3. S5 When there are registered excessive deficits for months desertification. Source: Barbu, Popa, 3 Excess quantities of precipitations The pluviometric analysis of the last 25 years of the th century highlights the existence of three or four consecutive years with humidity excess at the meteorological stations in the northern part of Oltenia. During the interval, excessive quantities of precipitations were registered at the meteorological stations, as follows: * Spiru Haret University of Bucharest 123

2 - three consecutive years at Apa Neagra; - four consecutive years at Ramnicu-Valcea and at Polovragi and Targu-Jiu. During the interval, excessive quantities were registered at the meteorological stations at Polovragi and Ramnicu-Valcea (Fig. 1) Fig. 1 The variation of annual quantities of precipitations as compared to the multi-annual mean (1976-) The calculus according to RSA allowed the classification of the analyzed years, as follows (Table 2): 124

3 Table 2 The hierarchy of years during the period in the northern part of Oltenia according to RSA stations Polovragi Tg. Jiu Apa Neagră Râmnicu Vâlcea year/rsa 1976 P5 P5 P5 P N N S5 S N S5 N P P5 P5 P5 P5 19 P5 P5 P5 P P5 P5 P5 P P2 P5 S5 S S5 S5 S5 S P5 P5 P5 P S5 S5 S5 S S5 S5 S5 S S4 S5 P3 P S5 S5 S5 P S5 S5 S5 S5 199 S5 S5 P5 S P5 P5 P5 P S5 S5 S5 S S5 S5 S5 S S5 N S5 S P5 P5 P5 P S4 P3 P1 S P3 S5 S5 P P5 P5 P5 P P5 P5 P5 P5 S5 S5 S5 S5 According to RSA, the exceedingly rainy characteristic is allotted for the years: 1979 at Polovragi, Tg.-Jiu, Rm.-Valcea and 1999 at Apa Neagra. For the last decade of the th century, 1999 was the exceedingly rainy year for all the analysed stations. The extremely rainy characteristic is allotted for 1987 at Apa Neagra; 1996 at Tg.- jiu and 1997 at Polovragi. The very rainy characteristic regards only the meteorological station at Polovragi in 1982, and the restrained rainy category characterizes only that at Apa Neagra in Scanty quantities of precipitations The lack of precipitations during a period of time that is long enough causes negative effects on the flora, soil and hydrography. From a pluviometric point of view, years with deficit are considered those during which the quantities are per cent lesser than the multi-annual means (Vasenciuc, 2). The drought period stretches for at least 14 consecutive days during the cold interval (October-March) and at least 1 consecutive days during the warm interval of the year (April-September), if the quantity of fallen precipitations did not exceed.1 mm (according to Hellmann, cited by Donciu, 1928). The analysis of the period highlights the particular situation of the year, when the mean average quantities were much smaller than the multi-annual means (percentage) at all the stations within the northern part of Oltenia. 125

4 Scanty quantities of precipitations were also registered in other years (Table 2), but their duration and intensity was much lesser. Just as the quantities of precipitations in excess, the scanty ones were also registered during three up to six consecutive years (6 years: at Polovragi and Tg.-Jiu; 3 years: at Polovragi, Apa Neagra and Ramnicu-Valcea). According to RSA, and the scanty pluviometric characteristic, there were established five classes: S1 Reduced droughty; S2 Very droughty; S3 Extremely droughty; S4 Excessively droughty and S5 when months on end excessive deficits are registered. The S5 class is present at all analyzed stations. The S4 class is present only at Polovragi in 1987 and 1996, and S3 class at Ramnicu-Valcea in The S1 and S2 classes are not present at any station (Table 2). The analysis of droughty and rainy situations highlights the predominance of the first classes at Targu-Jiu, Polovragi and Apa Neagra, except for Ramnicu-Valcea station where the rainy situations are more frequent than the droughty ones (Văduva, 3a). The pluviometric characterization of the year The year, considered by some researchers as one of the droughtiest years of the th century, was characterized by scanty quantities of precipitations in most part of the Romanian territory and, consequently, in the northern part of Oltenia. Table 3 The means of October at the meteorological stations stations Polovragi Tg. Jiu Apa Neagră Râmnicu Vâlcea year/rsa The pluviometric analysis of the year emphasizes scanty quantities of precipitations from January until August and then from October until September, when the quantities of precipitations exceeded by 4 up to 42 per cent the multi-annual mean (4 per 126

5 cent at Polovragi, 22 per cent at Tg.-Jiu, and 42 per cent at Ramnicu-Valcea. October is the month with the smallest quantities of precipitations, being considered as the droughtiest October month from the northern part of Oltenia in the last 25 years (Table 3). 1 Polovragi Tg. Jiu 1 Apa Neagra Râmnicu Vâlcea Fig. 2 The multi-annual mean of precipitations compared to the mean of the year The most recent drought phenomenon registered in the northern part of Oltenia during August and October is explained by the frequency of the days without precipitations, as follows: 1.Targu-Jiu registered in: - August 12 days without precipitations; - October 31 days without precipitations. 2.Apa Neagra registered in : 127

6 - October 31 days without precipitations. Taking into consideration the annual quantities of precipitations that fell in the northern part of Oltenia in, there is a very important hydric deficit compared to the multi annual means. The lowest annual quantities of precipitations were registered at Tg.- Jiu (333.4 mm), then at Apa Neagra (338.1 mm), Polovragi (395.1 mm) and Ramnicu- Valcea (63.2 mm) (Fig. 2). This resulted in a serie sof deficits and lacks in providing the population with agro-alimentary products, being constrained to import (Văduva, 3 b). Using the mass-media means, it was said that this drought had greater consequences than that of 1946, but it was an exaggeration. In 1946, the consequences were very severe, due to the total lack of the vegetal production and the maximum diminution of the animal production, by the draining of rivers and springs, by the dry up of grasslands etc (Ionescu-Sisesti, 1946, Văduva, 4). In conclusion, we may say that in the northern part of Oltenia, the droughty situations are more frequent than the rainy ones, except for Ramnicu-Valcea (where the situation is reversed) due to the specific climatic influences and those with a local character. Bibliography Barbu, I., Popa, I. (3), Monitoringul secetei în pădurile din România, Ed. Tehnică silvică, 128p. Ionescu-Siseşti, G.(1946), Seceta anului 1946, Buletinul Facultatii Agronomice Bucureşti, an II, 3-4 Vasenciuc, Felicia (2), Caracterizarea pluviometrică, conform anomaliei standardizate de precipitaţii, în contextual ultimului deceniu al secolului XX, în Dobrogea, Analele Univ. Ovidius -Seria Ştiinţele Naturii, Constanţa Văduva, Iulica (3 a), Low and high rainfall quantities within the County of Buzău, Analele Univ. Ovidius -Seria Ştiinţele Naturii, Constanţa Văduva, Iulica (3 b), Aspecte ale fenomenelor de uscăciune şi secetă, evidenţiate cu ajutorul anomaliei standardizate de precipitaţii, în Podişul Dobrogei de Sud, Comunicări de Geografie, VI Văduva, Iulica (4), Clima Podişului Dobrogei de Sud cu privire specială asupra fenomenelor de uscăciune şi secetă, Edit.Universitară, Teza de doctorat, 35p. 128