355 FROST AND THAW – RISK CLIMATIC PHENOMENA IN DOBROGEA M. LUNGU 1 , LILIANA PANAITESCU 1 , G. CRACU 1 , SIMONA NI 2 , MIHAELA ELENA ONEL 1 ABSTRACT. – In meteorology it is considered that frost days are those days when the minimum temperature is below or equal to 0 C. Thaw is characterized by warm weather during the cold period of the year, when air temperature rises to 0 C or exceeds this value. If the frost interval is accepted as existing from the first to the last day with minimum temperature below 0 C, in what regards the thaw period, there is no unanimous opinion. In this paper, the thaw interval was considered according to the researches, which accept that a new beginning for thaw can be considered after the frost has stabilized, that is, after the maximum temperature < 0°C is registered consecutively for a particular number of days. The end of thaw is considered the time when the daily average temperature is permanently over 0°C. Frost and thaw are part of the phenomena whose action influences negatively different economical activities. These phenomena have very harmful effects in agriculture. Thus, late spring frost interrupts the vegetation period of plants, while early autumn frost leads to the loss of the crop. Thaw in turn, accompanied by the sudden melting of the snow layer, endangers the autumn cultivation or contributes to soil erosion. The constructors pay special attention to the alternation of frost and thaw as they affect the resistance of materials. Negative effects of these phenomena are also encountered in industry, transport etc. Keywords: Dobrogea, frost, thaw, risk 1. INTRODUCTION The risk factors and climatology aspects in Dobrogea (including frost and thaw), have been researched on papers written by D. â tea etc. (1967), I.F. Mih ilescu (1986, 1999, 2001), Bogdan Octavia (1978, 1996, 1999), S. Chiulache and Nicoleta Ionac (1995), Cr. P ltineanu etc. (2000), M. Lungu (2009). Frost and thaw are part of the phenomena whose action influences negatively different economical activities. These phenomena have very harmful effects in agriculture. Thus, late spring frost interrupts the vegetation period of plants, while early autumn frost leads to the loss of the crop. Thaw in turn, 1 Ovidius University of Constan a, Faculty of Nature Science and Agriculture Science, Bd. Mamaia 124, RO-900527 Constan a, Romania 2 University of Agricultural Sciences and Veterinary Medicine of the Banat Timi oara, Faculty of Agriculture, Calea Aradului 119, 300654, Timi oara, Romania