Analysis of waterspout environmental conditions and of parent‐storm behaviour based on satellite data over the southern Aegean Sea of Greece

Abstract

ABSTRACT:A frequent area of waterspout formation is identified over the southern Aegean Sea. The objectives of this study are threefold: (1) to investigate the temporal evolution of Cloud Top Temperature (CTT) of cloud lines (waterspouts' parent clouds) that triggered the formation of single or multiple waterspout events, by using Meteorological Satellite Second Generation infrared satellite data, cloud base height data and weather observations from the closest Hellenic National Meteorological Service meteorological station; (2) to synthesize a detailed climatology of the thermodynamic environment during waterspout activity and (3) to explore the sea-surface temperature (SST) seasonal distribution and its possible relationships with the temperature of the middle and lower troposphere during waterspout days over the southern Aegean Sea.It was found that the CTT of waterspout parent clouds decreases close to waterspout formation time, which is consistent with growing clouds. The Severe Weather Threat Index (SWEAT), the Bulk Richardson Number (BRN) and the Convective Potential Available Energy during the autumn season were consistent with a shallow-convection environment. The instability parameter ΔT 1000 (difference in the air temperature between 1000 hPa and that at other pressure levels) exhibited a symmetric distribution about the median during both seasons and at all levels. More than 75% of autumn waterspout activity over the southern Aegean Sea developed with SST values varying from 22 to 24.5 ∘ C, while the instability parameter ΔT SST (the temperature difference between the SST and the temperature at various pressure levels) exhibited a symmetrical distribution about the median for both seasons and for all pressure levels, consistent with the ΔT 1000 seasonal distribution. A statistical analysis showed that the means of SWEAT, BRN, convective inhibition, SST, ΔT SST and ΔT 1000 from air temperature at 700 hPa differ statistically significant (p < 0.001) between waterspout and non-waterspout days in autumn, over the southern Aegean Sea, during 2005-2012.

An updated “climatology” of tornadoes and waterspouts in Italy

“…As anticipated above, the WS that reach the shore are considered also in the category of TR, although their intensity may be very weak. Following Matsangouras et al (2017), the occurrence of several WS in a limited region and in a limited period of time (i.e., a few hours) is counted as one event. In contrast, the few cases where inland TR occur in time and space proximity are considered separately, in order to record the different areas affected with damage.…”

Sounding‐derived parameters associated with tornadic storms in Catalonia

“…Most studied parameters do not present differences between WAT and NTT soundings; this is a similar result to those of Matsangouras et al . () and Renko et al . (): Only VGP 04 presents values which are significantly different. Waterspouts that hit land (54% of EF0 tornado cases) present substantially different mid‐level WS values and UTI values from EF0 tornadoes formed inland.…”

“…That is why all of them limit the distance and the elapsed time between the sounding and the event (Monteverdi et al, ; Taszarek and Kolendowicz, ). Some of them are much more restrictive with the distance between the sounding station and the event (Groenemeijer and van Delden, ) than others (Matsangouras et al, ).…”

“…The main differences in their findings, with respect to those of the United States, are that SBCAPE and also composite parameter values are not as high. Moreover, there are studies of environmental conditions that specifically favour waterspouts (Sioutas and Keul, ; Renko et al, ; Matsangouras et al, ), which are usually related with shallow convection.…”

Impact of SST diurnal cycle on ENSO asymmetry

“…To assess the diurnal cycle of instability of the moist air in HCi and DCi, we use the K-index developed by George (2014). K-index is widely used to asses the instability of moist air (Serbis et al 2013;Matsangouras et al 2016;Tian and Fan 2013), and is defined as:…”