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The nature of windstorms and wind-induced damage
Published in John D. Holmes, Seifu A. Bekele, Wind Loading of Structures, 2020
John D. Holmes, Seifu A. Bekele
The effects of global warming on severe winds from smaller storms, such as tornadoes (Section 1.3.4) and thunderstorm downbursts (Section 1.3.5) are difficult to determine as their scales are too small to resolve with current computational climate models. However, since these events are driven by strong convection of moisture-laden air, followed by latent heat release, it would be expected that warming would enhance these processes, and hence generate stronger storms. For example, Allen and Karoly (2014) have identified possible increasing trends in numbers of severe thunderstorms in Eastern Australia, by studying changes in convective available potential energy (CAPE).
The phenomenon of thunderstorm asthma in Bavaria, Southern Germany: a statistical approach
Published in International Journal of Environmental Health Research, 2022
Annette Straub, Verena Fricke, Patrick Olschewski, Stefanie Seubert, Christoph Beck, Daniela Bayr, Franziska Kolek, Maria P. Plaza, Vivien Leier-Wirtz, Sigrid Kaschuba, Claudia Traidl-Hoffmann, Wolfgang Buermann, Michael Gerstlauer, Athanasios Damialis, Andreas Philipp
Various large-scale gridded variables from the Global Forecast System Analyses (GFSA) from the National Oceanic and Atmospheric Administration (NOAA) were utilised in three-hourly temporal resolution in order to characterise the atmospheric circulation (geopotential height ‘HGT’, air temperature ‘TMP’, relative humidity ‘RH’, wind speed ‘WSPD’, each at the 1000 hPa-, 500 hPa- and 200 hPa geopotential height level) as well as the atmospheric stability (planetary boundary layer height ‘HPBL’, convective available potential energy ‘CAPE’, four-layer lifted index ‘4LFTX’, convective inhibition ‘CIN’). The CAPE index is a measure of the energy available in the atmosphere for convection. High values of this index imply that intense convective movements and, therefore, severe thunderstorms are possible (Riemann-Campe et al. 2009). The lifted index is calculated as the difference of an air parcel’s temperature lifted adiabatically from ground level to the 500 hPa level and the surrounding temperature at the 500 hPa level (Galway 1956). Thus, positive values indicate a stable atmospheric layering, and negative values indicate unstable conditions. In this study, a variant based on four vertical levels is used. The convective inhibition describes the energy an air parcel has to overcome in order to reach the level of free convection in the atmosphere, i.e. it is a limiting factor for convection. Low values of the convective inhibition are beneficial for the development of thunderstorms (Riemann-Campe et al. 2009). A domain covering Europe and the North Atlantic (−30–40°E, 30–70°N) with 0.5°x0.5° spatial resolution was taken into account.
New Insights into the Convective System Characteristics Over the Indian Summer Monsoon Region Using Space-Based Passive and Active Remote Sensing Techniques†
Published in IETE Technical Review, 2020
Kandula V. Subrahmanyam, Karanam Kishore Kumar, Nelli Narendra Reddy
The CAPE (Convective Available Potential Energy) is a measure convective instability and is directly related to the maximum potential vertical speed within an updraft and thus the higher CAPE values indicate the greater possibility for the occurrence of severe convective systems. It should be remembered that not always large CAPE values result in the formation of deep convective systems. The CAPE is estimated using temperature and humidity measurements from the COSMIC satellite for six continuous years (2006–2011) over ISM region. Though radiosonde observations were available at few stations, these are limited to two timings i.e. at 00 and 12 UT, which are not sufficient for obtaining the seasonal mean as they will be biased towards these two local times. It is also known that CAPE has pronounced diurnal variability [23]. On the other hand, COSMIC provides CAPE observations at different local times and thus can be used for representing the seasonal mean. In the present study, we have used the wet profiles of COSMIC which are derived from the refractivity profiles. The temperature profiles derived from GPS-RO technique have an accuracy better than 0.5 K ([24]) and the specific humidity biases are around 0.1 g/kg [25]. CAPE can be estimated by vertically integrating the parcel buoyancy between the level of free convection (LFC) and level of neutral buoyancy (LNB) and it can be expressed mathematically by the following equation [26], where, Tp designates the temperature of the parcel, Te is the temperature of the environment, and g is the acceleration due to gravity. By using the above equation, we computed CAPE over the study region. Thus using a combination of four satellites, the stability of the atmosphere in terms of CAPE, the frequency of occurrence of types of convective clouds and their vertical structure and associated rainfall are investigated.
Evaluating the impact of topography on the initiation of Nor’westers over eastern India
Published in Geomatics, Natural Hazards and Risk, 2023
Rajesh Kumar Sahu, Sridhara Nayak, Kuvar Satya Singh, Hara Prasad Nayak, Bhishma Tyagi
The model simulation has been run to examine how thermodynamic indices alter when the elevation of topography of CNP is modified (increased/decreased) versus when it is left intact and how the change affects thunderstorm initiation and propagation. The thermodynamic indices Convective Available Potential Energy (CAPE), Convective INhibition (CIN), Cross Total Index (CTI), Vertical Total Index (VTI), Totals Total Index (TTI), Humidity Index (HI), K-Index (KI), and Severe Weather Threat Index (SWEAT) were incorporated in this study to compare the topographical changes over CNP and the associated eastern India region. CAPE is the vertically integrated, positive buoyancy force of an adiabatically rising air parcel (Moncrieff and Miller 1976). Higher CAPE values often indicate stronger convection, and they are used to examine the conditional instability of the atmosphere (Williams and Renno 1993). Especially in the eastern Indian region, operational forecasting can certainly benefit from the use of CAPE, which serves as a reliable warning of the onset of convection (Roy Bhowmik et al. 2008). To what extent buoyant energy and moist instability are present in the atmosphere is shown by CAPE (Neelin 1997). Higher CAPE values represent higher convective activities over any region. The CIN index is helpful because it measures the amount of negative buoyant energy applied to an air parcel, which slows down rising air and reduces the likelihood of convection (Colby 1984). In general, the likelihood of convective activity decreases (increases) as CIN values increases (decreases), which is proportional to the magnitude of the change. The K Index (KI) is another helpful predictor of convective commencement (George 1960). By combining the difference in temperature between 850 and 500 hPa with the dew point or moisture between 850 and 700 hPa, this is a metric used to identify the air mass that is producing thunderstorms (George 1960). By measuring the KI, one can infer about the amount of moisture present in the lower atmosphere and the height to which it extends. Total Totals Index (TTI) is an important empirical index for predicting thunderstorms and other convective occurrences. It can withstand a variety of storm intensities. Nonetheless, it did not necessitate latent instability at pressures below 850 hPa (Miller 1967). It incorporates both CTI and VTI. This index considers the lapse rate and the moisture level in the lower atmosphere to determine the parameters for static stability. TTI values ranging ≥55 results in strong thunderstorm, it is also used for forecasting severe local thunderstorms (Reap and Foster 1979).