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Analysis of Thunderstorms Using Atmospheric Instability Indices in Kermanshah
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Taghi Tavousi *   1, Shima Rostami Jalilian2 |
1- University of Sistan and Baluchestan
2- Tehran University |
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Abstract: (5170 Views) |
Introduction: The climatology of Thunderstorms is an important component in research for severe weather. Thunderstorms are among the first meteorological phenomena, which have attracted human attention (Khorshiddoust et al, 2017). Thunderstorms are dangerous and one of the most important, abundant and severe atmospheric hazards. Thunderstorms can be associated with a number of hazards. This phenomenon is associated with severe storms, showery precipitation, hail, and thunder and lightning. Heavy rains can lead to flash flooding events. High winds generated by thunderstorm can cause damage to homes, overturn vehicles, uproot or damage trees, causing wide spread power outages. Generally, researchers consider the intense weather instability as a result of convection in lower levels of the atmosphere with high levels enough of humidity. Usually statistic instability, the humidity of lower levels of the atmosphere and lifting mechanisms near the ground are the main factors leading to convection. Moreover, the combination of three factors, instability, humidity and convergence in lower levels of the atmosphere plays an important role in increasing the possibility of thunderstorms (Masoompour Samakosh et al, 2016). In connection with thunderstorms extensive research work has been carried out in Iran and the world in including: Chignon et al. (2001), Manzato, (2003), Doswell et al. (2005), Henderson (2006), Sadeghi et al. (2006), Romero et al. (2007), Schmeits et al. (2008), Siedlecki (2009), Sanaeinejad et al. (2010), Tajbakhsh et al. (2010), Ghavidel Rahimi (2011), Masoompour Samakosh et al. (2014) Masoompour Samakosh et al. (2016), Tavousi (2016), Dehani (2017), Khorshiddoust et al. (2017), Tavousi et al. (2016).The city of Kermanshah is the capital of the Kermanshah province and is located in the west of Iran. The latitude of the Kermanshah meteorological station is 34: 21 N and the longitude is 47: 9 E and altitude 1318.6 meters. Kermanshahchr('39')s climate is classified as warm and temperate. The winters are rainier than the summers in Kermanshah. The climate here is classified as Csa by the Köppen-Geiger system. The average annual temperature is 13.3 °C in Kermanshah. The average annual rainfall is 437 mm (Climate data for cities worldwide, 1982-2012). Kermanshah has annually been witnessing a variety of thunderstorms systems and associated precipitation. This city has suffered lots of damage resulted from the phenomena caused by thunderstorms.
Matherials & Methods: In this research, instability conditions of heavy precipitation in Kermanshah are investigated. For this purpose, high atmospheric instability indices such as lifted index, showalter index, K index, convective available potential energy (CAPE) index, precipitable water capacity (PWC) and thermodynamic diagram Skew-T Atmospheric is studied using the radiosound data. The data of upper atmosphere (radio-sound data), available in the website of Wayoming University, were applied to investigate the thermodynamic features of the occurred thunderstorms. The thermodynamic features include KI, SI, TT, LI, CAPE indices and skew- T chart in RAOB software.
Discussion of Results & Conclusions: The results showed that the valuses of K index in days with heavy precipitation were 20.7-34.8 and in a day before 20.9 - 37.7. The lowest values recorded in January, February and March, and the peaked were in November, April and May. This suggests heavy precipitation in winter with less instability and is accompanied by more instability in the fall and spring. The lifted index in 1997 and 2002 in days has heavy precipitation were 0 to -2.2, which represents the probability of storms with rain and snow showers. The value of the lifted index in a day before precipitation on November 1, 1993 was zero to -2 and on May 12, 1993, November 21, 1994, and April 18, 2002 from -2 to - 5, which represents the probability of thunderstorm occurring. Study of precipitable water capacity (PWC) in the peak days of precipitation and one day before is showed that is most matches with the days that air convection has been intense. On peak precipitation days, the PWC was between a minimum of 35/7 on16 January 1997 and a maximum of 19.92 on 2 November 1993. The wind speed has been between 40-50 knots in all days, except on March 11, 2005, the wind had a speed of about 80 knot. The Prevailing winds are southwest which shows the direction of the Westerly winds system to this area. Investigation of thermodynamic charts showed that rapid convective ascent of available potential energy depending on the weather in the region has been so high and caused the weather to approach three days in advance to the upper layers of the atmosphere and atmospheric turbulence was created for the region. |
Article number: 4 |
| Keywords: Heavy Precipitation, Thermodynamic, Skew-T, Vertical Profiles |
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Full-Text [PDF 2638 kb]
(267 Downloads)
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Type of Study: Research |
Subject:
Special
Received: 2020/10/6 | Accepted: 2021/06/16 | Published: 2023/10/2
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