Strong Thunderstorms Research Articles

The –WIND RISK project: nowcast and simulation of thunderstorm outflows

–WIND RISK is a research project dealing with measurement and modelling of wind fields within thunderstorm cumulonimbus clouds and outflows at the ground (i.e., downbursts and gust fronts). The general objective of the project is to advance the knowledge about the processes occurring inside thunderstorm clouds responsible for strong outflows, and the identification of the environmental (synoptic and meso-scale) conditions favourable to their development. The area under investigation is Northwestern Italy and the Ligurian Sea, which are among the most exposed regions to strong thunderstorms in Europe. Two measurement campaigns using Doppler weather radars and remote-sensing ground-based anemometry, and ad-hoc simulations using the WRF model are carried out to build a database of thunderstorm wind fields with special focus on downdraft and downburst characterization. All measurements and simulations are shared within the scientific community after the end of the project through datasets published on open access platforms.

A hurricane trigger in desalted ocean water

For forming a hurricane, two things are needed: a strong thunderstorm and warm water of the ocean surface. The first thing accumulates the desalted seawater as a working medium of hurricane, and the second one “feeds” the hurricane engine by this medium. The thin mechanisms of evaporation of the desalted ocean water are considered in this article. It is shown that the local oxidation of seawater under the eye wall can change the power and motion-direction of hurricane.

Lightning characteristics and associated microphysical parameters in a strong thunderstorm with an extreme gale

Lightning characteristics and associated microphysical parameters in a strong thunderstorm with an extreme gale

Analysis of lightning activity characteristics and its relationship with precipitation in a strong convective weather process in Jiangsu Province

Based on multi-source observation data such as lightning locator, atmospheric electric field instrument and hourly precipitation data from automatic stations, the lightning characteristics of the strong convective weather process under the influence of the northeast cold vortex in Nanjing Jiangsu Province on 15 June 2020 was analyzed in depth, and the relationship between the lightning activity and the precipitation was obtained. The results show that this strong convective weather process is formed by the cold air from the back of the northeast cold vortex along the front of the high-pressure ridge and the back of the transverse through southward to the middle and lower reaches of the Yangtze River, which makes the cold and warm air currents converge along the south of the Yangtze River to form the heavy precipitation, and is accompanied by the strong lightning activity in the process of this heavy precipitation. The local thunderstorm electric field in Nanjing is mainly characterized by negative increasing type, positive and negative alternating type, and multi-single thunderstorm electric field, and the thunderstorm activity is mainly dominated by negative ground flashes. During this strong thunderstorm, the stronger precipitation periods corresponded to the stronger lightning frequency periods, and the lightning and precipitation fallout areas showed a consistent spatial distribution. The correlation between the lightning activity and precipitation was analyzed by linear fitting, and the correlation between them is 0.946.

The role of drylines in thunderstorm initiation and record rainfall during an anomalously convective early summer season in South Africa

An average of 12 drylines are associated with thunderstorm development (convective drylines) during December in the western plateau of subtropical southern Africa. During December 2021, 20 convective drylines occurred. This was the highest number since the record began in 2010. December 2021 was also unusually wet over a large part of the summer rainfall region in South Africa. Monthly rainfall records were broken in the Northern Cape, Northwest and Free State provinces. Above-average rainfall had dire consequences for the maize industry over the central interior. The large-scale circulation during December 2021 was very conducive to dryline formation over the western plateau with a deeper than usual surface trough and strong low-level northeasterly moisture flux towards the climatologically dry western plateau region. Above normal wind speeds of mid-tropospheric northwesterlies and large-scale uplift contributed to a favorable environment for strong thunderstorms, as seen during a 6-day convective dryline event. Thunderstorms which were triggered along the dryline travelled east and contributed to the above normal rainfall observed during December 2021. Dryline and rainfall frequencies show large inter-annual variability. However, a positive Pearson correlation (r = 0.45; p < 0.05) between the number of dryline days and rainfall amounts were found between 1979 and 2021. This correlation increased (r = 0.53; p < 0.05) when rainfall amounts immediately east of the western plateau domain were also included, suggesting that dryline-related convection can have a significant influence on rainfall over the western plateau and further downstream.

Using real GNSS data for ionospheric disturbance remote sensing associated with strong thunderstorm over Wuhan city

Using real GNSS data for ionospheric disturbance remote sensing associated with strong thunderstorm over Wuhan city

Determination of the Dynamics of Thunderstorms Through the Dry Adiabatic Lapse Rate and Environmental Lapse Rate

This research aims to determine the types of thunderstorms formed in the thickness of the cloud (determine the Dry adiabatic lapse rate (DALR) and Environmental lapse rate (ELR)) in the case of precipitation during the day. Data were taken by Temperature, Dew point, Atmospheric Pressure, and Height from re-analysis by the (ECMWF) for the heights (0-18000) m, the levels of pressure (1000-100) mbar, low cloud cover data, and the characteristic days ((18, 24, 27) February, 28 April, and 25 November) of the year 2018 for Baghdad station were chosen to obtain the largest possible number of clouds and their diversity to use them in calculating the cloud cover and weather stability in terms of calculating the daily change, temperature, dew point in addition to calculating the low cloud cover with altitude and atmospheric instability. The Sigma Plot program was used in this research to determine the base of clouds and thunderstorms. The change in temperature, Dew point, clouds base, and altitude was determined, then the cloud thickness, types, and classification were calculated. The clouds found are strong thunderstorm clouds characterized by thickness and height, such as the clouds of Nimbostratus (Ns) and Cumulonimbus (Cb).

CHANCES OF WRONG INFORMATION RECEPTION DURING ELECTROMAGNETIC INFLUENCE UPON OPTICAL CABLE

Long-distance communication lines are optical fiber lines in most cases now. This moment PM QPSK system (polarization-division multiplex with quadrature phase shift keying) appear. Polarization-division multiplex uses a fact that the optical signal can propagate as two orthogonal polarized modes that allows to use the modes independently and makes it possible to double carrier capacity (together with already other used multiplex system). Two orthogonal waves using in the same fiber can cause problems during lightning discharges close by cable line. Under influence of external cross electrical field (or longitudinal magnetic) the polarizations plane of lights wave can turns on angle, which depends on field value, light path length upon field action and fiber sensitivity. During the influence of external electromagnetic field issue a part of one polarization signal can pass to other orthogonal plane and it will perceive wrongly. The Wavelength Division Multiplexing (WDM) systems development with increasing number of carriers brought to transmission in the same transparency window some tens or hundreds waves. They are shifted relative to each other for some parts of nanometers during the lightning stroke. Therefore the polarization plane rotation will be different for each wave (other conditions being equal): the short waves rotated greater than the long waves. On input of optical amplifier there will be packet of waves with different polarizations, and it can produce problems to filters, optical insulators and amplifiers, to Raman amplifiers specially, which are sensitive to polarization. It is known that short and long waves are moving with different velocity as refraction index depends upon wave length. Usually the rotation angle quantity is small if resistivity of earth near cable is not heavy and if equipment does not contain sensitive to PMD (Polarization Modes Dispersion). This phenomenon passes usually unnoticed. But sometimes with strong thunderstorm and lightning stroke at a short distance the polarization plane rotation can exceed 45º or even 90º. Hereby, it is possible the complex electrical and magnetic fields influence during thunderstorm on orthogonal polarization using, that can lead to additional component appearance in orthogonal axes and to signal reception error. Error level for year is estimated.

Acceleration of Tropical Cyclone Development by Cloud-Radiative Feedbacks

Abstract A complete understanding of the development of tropical cyclones (TC) remains elusive and forecasting TC intensification remains challenging. This motivates further research into the physical processes that govern TC development. One process that has, until recently, been under-investigated is the role of radiation. Here, the importance of radiative feedbacks in TC development and the mechanisms underlying their influence is investigated in a set of idealized convection-permitting simulations. A TC is allowed to form after initialization from a mesoscale warm, saturated bubble on an f plane, in an otherwise quiescent and moist neutral environment. Tropical storm formation is delayed by a factor of 2 or 3 when radiative feedbacks are removed by prescribing a fixed cooling profile or spatially homogenizing the model-calculated cooling profiles. The TC’s intensification rate is also greater when longwave radiative feedbacks are stronger. Radiative feedbacks in the context of a TC arise from interactions between spatially and temporally varying radiative heating and cooling (driven by the dependence of radiative heating and cooling rate on clouds and water vapor) and the developing TC (the circulation of which shapes the structure of clouds and water vapor). Further analysis and additional mechanism denial experiments pinpoint the longwave radiative feedback contributed by ice clouds as the strongest influence. Improving the representation of cloud-radiative feedbacks in forecast models, therefore, has the potential to yield critical advancements in TC prediction. Significance Statement Our understanding of the development of tropical cyclones, hurricanes, and typhoons is incomplete, and, thus, forecasting tropical cyclone formation and intensification remains challenging. This study investigates the importance of interactions between clouds and solar and infrared radiation for tropical cyclone development. I find that in idealized convection-permitting simulations, tropical cyclone development is accelerated by a factor of 2 or more with the inclusion of these cloud–radiation feedbacks. The interaction of ice clouds associated with strong thunderstorms with infrared radiation has the biggest effect. These results indicate that improving the representation of ice clouds and their radiative feedbacks in forecast models has the potential to yield critical advancements in tropical cyclone prediction.

Traditional rite culture in the context of natural and social cataclysms (on the example of Trans-Kama Udmurts)

This paper, based on published, archival and field ethnographic materials, considers the state of ritual and ceremonial sphere of ethnic culture under the conditions of natural and social cataclysms on the example of the Trans-Kama Udmurts living in the Republic of Bashkortostan and Perm Krai, who didnt undergo baptism and preserved their traditional religious rites. It is shown that the calendar of agrarian ceremonies implied rituals aimed at preventing emergency situations (frost, strong thunderstorms and wind, hail, drought, etc.), preventing crop failure and the onset of famine. There were also special rituals to ward off epizootics and epidemics, which often occurred in the past due to unsanitary conditions and almost complete absence of veterinary and medical care. At the onset of natural calamities, the occasional rituals were actualized to eliminate or minimize their consequences. The harvest and the very life of the members of the rural community depended on their exact and timely execution. In this connection, rites to expel insects, call for rain, etc., were conducted. Epidemics were curbed through propitiatory sacrifices or their expulsion of diseases. Social disasters, such as famine and wars, due to the scarcity of vital resources, led to the minimization of rituals. At the same time various magical practices (fortune-telling) became more active. Extreme situations of the last years (pandemic COVID-19 and drought) have led to the development of new forms of carrying out rites and customs or have revitalized obsolete ones.

Convective‐scale numerical weather prediction and warnings over Lake Victoria: Part II—Can model output support severe weather warning decision‐making?

AbstractThe greater Lake Victoria region was the focus of the ‘HIGHWeather impact lAke sYstem’ project, with the aim of developing an early warning capability for hazardous weather. Strong thunderstorm outflows can cause boats to capsize and lead to drowning. Lightning is also a hazard to fishermen, and over land flash flooding from heavy rainfall is a significant hazard. Between March and October 2019, 16 regional warnings were issued, and 14 days had reported impacts. Only one of the issued warnings aligned with any reported impacts. The issued warnings were verified using three different methodologies and found to have a very low frequency bias, confirming that too few warnings are being issued, especially for precipitation. The skill of the warnings based on the probability of detection and symmetric extremal dependency index was also found to be low. Potential warnings days are derived from individual and multivariate combinations of numerical weather prediction forecasts of mean wind speed, precipitation and a new lightning diagnostic from the 4.4 km Tropical Africa configuration of the Met Office Unified Model. The methodology identified 5–7 times the issued number of warnings, including 50% of days with reported impacts and 25% of days with issued warnings. Overall, 70%–80% of the identified potential warning days appear to be justified, suggesting that for this period not enough warnings were issued. It is shown that a daily aggregate of the lightning diagnostic is a skilful addition to any guidance supporting a decision‐making process.

Effectiveness of array of lightning triggering towers as regional lightning protection for transmission lines in areas with strong lightning activity

The strong and frequent lightning activity in Guangdong, China, severely affects the safe operation of the power grid. In this study, the lightning database of Guangdong Power Grid in Foshan from 2008 to 2020 was used to compare the CG lightning activity intensity parameters in the areas of four high towers before and after the towers began operation. The lightning frequency within a certain distance from the high towers and the lightning current amplitude around the high towers were higher after the construction of the towers . The clustering method was used to count the number of strong thunderstorms and ground–flash activity processes. The temporal and spatial variations in the aforementioned parameters were also obtained. The high towers increased the number of strong cloud-to-ground activity processes in their adjacent areas, increased the proportion of cloud to ground activity trajectories close to the towers, and changed the direction of lightning corridors. Moreover, the lightning current amplitude of the cloud to ground CG lightning activity was decreased away from the tower. What is more, from the statistical results of operation data, it can be seen that the number of lightning tripping of transmission lines in the area of the towers is significantly reduced.

Hydraulic jump dynamics above supercell thunderstorms.

The strongest supercell thunderstorms typically feature an above-anvil cirrus plume (AACP), which is a plume of ice and water vapor in the lower stratosphere that occurs downwind of the ambient stratospheric flow in the lee of overshooting deep convection. AACP-origin hydration of the stratosphere has a poorly constrained role in ozone destruction and surface warming. In this study, we use large eddy simulations corroborated by radar observations to understand the physics of AACP generation. We show that the overshooting top of a simulated supercell can act as a topographic obstacle and drive a hydraulic jump downstream at the tropopause, similar to a windstorm moving down the slope of a mountain but without solid topography. Once the jump is established, water vapor injection deep into the stratosphere may exceed 7 tonnes per second.

Mesoscale convective systems as a source of electromagnetic signals registered by ground-based system and DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite

Abstract. Mesoscale convective systems (MCSs) are especially visible in the summertime when there is an advection of warm maritime air from the west. Advection of air masses is enriched by water vapour, the source of which can be found over the Mediterranean Sea. In propitious atmospheric conditions, and thus significant convection, atmospheric instability or strong vertical thermal gradient leads to the development of strong thunderstorm systems. In this paper, we discuss one case of MCSs, which generated a significant amount of +CG (cloud-to-ground), −CG and intracloud (IC) discharges. We have focused on the ELF (extremely low frequency; &lt; 1 kHz) electromagnetic field measurements, since they allow us to compute the charge moments of atmospheric discharges. Identification of the MCSs is a complex process, due to many variables which have to be taken into account. For our research, we took into consideration a few tools, such as cloud reflectivity, atmospheric soundings and data provided by PERUN (Polish system of the discharge localisation system), which operates in a very high frequency (VHF) range (113.5–114.5 MHz). Combining the above-described measurement systems and tools, we identified a MCS which occurred in Poland on 23 July 2009. Furthermore, it fulfilled our requirements since the thunderstorm crossed the path of the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) overpass.

Detecting Ionospheric TEC Disturbances by Three Methods of Detrending through Dense CORS During A Strong Thunderstorm

Satellite navigation and communications system can substantially be disturbed by ionospheric perturbations. Consequently, monitoring ionospheric anomalous has great significance. In this study, we focus on the short-term irregular disturbances through a strong thunderstorm in Wuhan City, Hubei, China by using ground-based GNSS observations from dense Continuously Operating Reference Stations (CORS) with a sampling rate of 1s. The total electron content (TEC) was used to find possible perturbations after biases have been calibrated for the derived TEC. Additionally, the geomagnetic conditions and the state of solar radiation was checked in the study period to recognize the causes for the ionospheric disturbances. The maxima and minima values of TEC deviations were ~2.5 and 0.5 TECU, respectively. Three methods of Detrended Fluctuations Analysis (DFA) were applied to assess the ionospheric disturbances over GNSS CORS stations; “Multi-step numerical difference”(MSND), “6th order polynomials fitting” (PF), and “one-week average difference”(AD). The analyzed results showed that MSND has the lowest performance. Meanwhile, the fitted TEC data with 6th order polynomials technique presented an improvement and a discrepancy related to MSND. To resolve this discrepancy, we proposed AD technique, it accomplished the best performance related to the TEC disturbances and was compared with the other two techniques. The research findings showed that ionospheric disturbed electrons can be generated with various rates and different velocities through lightning influences.

Storms and the Depletion of Ammonia in Jupiter: II. Explaining the Juno Observations

AbstractObservations of Jupiter's deep atmosphere by the Juno spacecraft have revealed several puzzling facts: The concentration of ammonia is variable down to pressures of tens of bars and is strongly dependent on latitude. While most latitudes exhibit a low abundance, the Equatorial Zone of Jupiter has an abundance of ammonia that is high and nearly uniform with depth. In parallel, the Equatorial Zone is peculiar for its absence of lightning, which is otherwise prevalent most everywhere else on the planet. We show that a model accounting for the presence of small‐scale convection and water storms originating in Jupiter's deep atmosphere accounts for the observations. Where strong thunderstorms are observed on the planet, we estimate that the formation of ammonia‐rich hail (“mushballs”) and subsequent downdrafts can deplete efficiency the upper atmosphere of its ammonia and transport it efficiently to the deeper levels. In the Equatorial Zone, the absence of thunderstorms shows that this process is not occurring, implying that small‐scale convection can maintain a near‐homogeneity of this region. A simple model satisfying mass and energy balance accounts for the main features of Juno's microwave radiometer observations and successfully reproduces the inverse correlation seen between ammonia abundance and the lightning rate as function of latitude. We predict that in regions where ammonia is depleted, water should also be depleted to great depths. The fact that condensates are not well mixed by convection until far deeper than their condensation level has consequences for our understanding of Jupiter's deep interior and of giant‐planet atmospheres in general.

Asia-Pacific Lightning Location Network (APLLN) and Preliminary Performance Assessment

The Asia-Pacific Lightning Location Network (APLLN) is a lightning location system consisting of a series of very low-frequency signal detection sites. Since 2018, 16 detection sites have been deployed with an average baseline longer than 1000 km. The detection site used a trigger sampling method to record the lightning signal with a duration of 2 ms and calculates the lightning arrival time based on digital filtering and the Hilbert envelope method. APLLN used a time difference location algorithm and improved Levenberg–Marquardt non-linear least squares iterative algorithm to calculate and optimize the lightning location results. The analysis results of a strong thunderstorm process show that the average detection efficiency of APLLN was 55.34% for intracloud (IC) strokes, 63.55% for cloud-to-ground (CG) strokes and 61.83% for all strokes (IC + CG). The average location error of APLLN for this thunderstorm is 5–10 km.

Derecho wind storm in Poland on 11–12 August 2017: results of the post-disaster investigation

ABSTRACT Wind storms belong to the most costly natural hazards in Poland. On 11–12 August 2017, a strong thunderstorm happened, which resulted in catastrophic damage in three provinces: Wielkopolskie, Kujawsko-Pomorskie and Pomorskie. This disaster has resulted in the death of six people, injuries to several dozen people and enormous property losses. The objective of this paper is to describe, analyse and learn from such a dangerous extreme weather event. Examples of buildings, with improved stiffness, are presented as the solution for better resistance of wind forces. The final aim is to help humans prepare for and deal with the consequences of severe wind storms in the future.

Variations of cosmic ray muon flux during thunderstorms as a tool for studying electric field distribution and particle production processes in the atmosphere

The recently published result of GRAPES-3 (a strong thunderstorm muon intensity change) and conclusions made on its basis by this collaboration are discussed and compared with the Baksan observations of muon variations during thunderstorms performed much earlier. It is demonstrated that generally both experiments are quite consistent as far as characteristic patterns of events are concerned, as well as conclusions about direct connection between amplitude of muon intensity disturbance and electric field strength in the atmosphere. However, the GRAPES-3 conclusion about gigavolt potentials associated with their event is doubtful and seems to contradict the fundamental limits on electric fields that can exist in the atmosphere.

The unprecedented 2017–2018 stratospheric smoke event: decay phase and aerosol properties observed with the EARLINET

Abstract. Six months of stratospheric aerosol observations with the European Aerosol Research Lidar Network (EARLINET) from August 2017 to January 2018 are presented. The decay phase of an unprecedented, record-breaking stratospheric perturbation caused by wildfire smoke is reported and discussed in terms of geometrical, optical, and microphysical aerosol properties. Enormous amounts of smoke were injected into the upper troposphere and lower stratosphere over fire areas in western Canada on 12 August 2017 during strong thunderstorm–pyrocumulonimbus activity. The stratospheric fire plumes spread over the entire Northern Hemisphere in the following weeks and months. Twenty-eight European lidar stations from northern Norway to southern Portugal and the eastern Mediterranean monitored the strong stratospheric perturbation on a continental scale. The main smoke layer (over central, western, southern, and eastern Europe) was found at heights between 15 and 20 km since September 2017 (about 2 weeks after entering the stratosphere). Thin layers of smoke were detected at heights of up to 22–23 km. The stratospheric aerosol optical thickness at 532 nm decreased from values &gt; 0.25 on 21–23 August 2017 to 0.005–0.03 until 5–10 September and was mainly 0.003–0.004 from October to December 2017 and thus was still significantly above the stratospheric background (0.001–0.002). Stratospheric particle extinction coefficients (532 nm) were as high as 50–200 Mm−1 until the beginning of September and on the order of 1 Mm−1 (0.5–5 Mm−1) from October 2017 until the end of January 2018. The corresponding layer mean particle mass concentration was on the order of 0.05–0.5 µg m−3 over these months. Soot particles (light-absorbing carbonaceous particles) are efficient ice-nucleating particles (INPs) at upper tropospheric (cirrus) temperatures and available to influence cirrus formation when entering the tropopause from above. We estimated INP concentrations of 50–500 L−1 until the first days in September and afterwards 5–50 L−1 until the end of the year 2017 in the lower stratosphere for typical cirrus formation temperatures of −55 ∘C and an ice supersaturation level of 1.15. The measured profiles of the particle linear depolarization ratio indicated a predominance of nonspherical smoke particles. The 532 nm depolarization ratio decreased slowly with time in the main smoke layer from values of 0.15–0.25 (August–September) to values of 0.05–0.10 (October–November) and &lt; 0.05 (December–January). The decrease of the depolarization ratio is consistent with aging of the smoke particles, growing of a coating around the solid black carbon core (aggregates), and thus change of the shape towards a spherical form. We found ascending aerosol layer features over the most southern European stations, especially over the eastern Mediterranean at 32–35∘ N, that ascended from heights of about 18–19 to 22–23 km from the beginning of October to the beginning of December 2017 (about 2 km per month). We discuss several transport and lifting mechanisms that may have had an impact on the found aerosol layering structures.