Characteristics of Extratropical Cyclones That Cause Tornadoes in Italy: A Preliminary Study

Atmosphere

卷:12

Hiroshi Niino¹  Roberto Ingrosso²  Leonardo Bagaglini³  MarioMarcello Miglietta⁴  Eigo Tochimoto⁵ 

[1] Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba 277-8564, Japan;

[2] Department of Earth and Atmospheric Sciences, University of Quebec in Montreal, Montreal, QC H3C 3P8, Canada;

[3] National Research Council of Italy—Institute of Atmospheric Sciences and Climate (CNR-ISAC), 00133 Rome, Italy;

[4] National Research Council of Italy—Institute of Atmospheric Sciences and Climate (CNR-ISAC), 35127 Padua, Italy;

[5] National Research Institute for Earth Science and Disaster Resilience, 3-1, Tennodai, Tsukuba, Ibaraki 305-0006, Japan;

关键词: storm-relative helicity;    CAPE;    tornado;    extratropical cyclone;   

DOI  :  10.3390/atmos12020180

来源: DOAJ

【 摘 要 】

Characteristics of extratropical cyclones that cause tornadoes in Italy are investigated. Tornadoes between 2007 and 2016 are analyzed, and statistical analysis of the associated cyclone structures and environments is performed using the JRA-55 reanalysis. Tornadoes are distributed sporadically around the cyclone location within a window of 10° × 10°. The difference in the cyclone tracks partially explains the seasonal variability in the distribution of tornadoes. The highest number of tornadoes occur south of the cyclone centers, mainly in the warm sector, while a few are observed along the cold front. Composite mesoscale parameters are examined to identify the environmental conditions associated with tornadoes in different seasons. Potential instability is favorable to tornado development in autumn. The highest convective available potential energy (CAPE) in this season is associated with relatively high-temperature and humidity at low-levels, mainly due to the strong evaporation over the warm Mediterranean Sea. Upper-level potential vorticity (PV) anomalies and the associated cold air reduce the static stability above the cyclone center, mainly in spring and winter. On average, the values of CAPE are lower than for US tornadoes and comparable with those occurring in Japan, while storm relative helicity (SREH) is comparable with US tornadoes and higher than Japanese tornadoes, indicating that the environmental conditions for Italian tornadoes have peculiar characteristics. Overall, the conditions emerging in this study are close to the high-shear, low-CAPE environments typical of cool-season tornadoes in the Southeastern US.

【 授权许可】

Unknown