CUMULONIMBUS CLOUDS AND RELATED WEATHER PHENOMENA AT TÂRGU-MUREŞ, ROMANIA
RUSZ OTTILIA
ABSTRACT. Cumulonimbus clouds and related weather phenomena at Târgu Mureş, Romania. Cumulonimbus (Cb) is a vertically developed cloud, associated with some several weather phenomena, such as hail. Yearly (and in some cases monthly) meteorological data from the period 1971-2005 registered at the Târgu-Mureş weather station (lat. 46°32’, lon. 24°32’, elevation 308 m) were studied. However, Altocumulus (relative frequency = 25%) and Stratocumulus (14%) are the most frequently clouds, in summer the presence of Cumulonimbus cloud is remarkable (18%). Mann-Kendall trend analysis and Sen’s slope estimate (Q) show positive and statistically significant trend as regards number of Cumulonimbus clouds (Q=6.458), number of days with rain shower (Q=1.000), number of days with snow shower (Q=0.250) and a decreasing, statistically significant trend in the case of the number of days with hail (Q=-0.043) and number of days with thunderstorm (Q=-0.211). Moreover, monthly number of Cb also indicate an increasing, statistically significant trend in all 12 cases. The Pearson correlation coefficient (r) is statistically significant between the number of Cb and the number of days with rain shower (r=0.827) respectively the number of Cb and the number of days with rain shower (r=0.541). Daily amount of precipitations exceeded 30 mm were registered mainly in summer. They are almost related to Cumulonimbus clouds and rain showers, and they occur most frequently during the presence of TRM (Trough over Central Europe), WZ (Cyclonic Westerly) and BM (Zonal Ridge across Central Europe) synoptic situations (Hess-Brezowsky classification).
Keywords: Cumulonimbus, Târgu-Mureş, showers, hail, thunderstorm