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1.
T. Neubert M. Rycroft T. Farges E. Blanc O. Chanrion E. Arnone A. Odzimek N. Arnold C.-F. Enell E. Turunen T. Bösinger Á. Mika C. Haldoupis R. J. Steiner O. van der Velde S. Soula P. Berg F. Boberg P. Thejll B. Christiansen M. Ignaccolo M. Füllekrug P. T. Verronen J. Montanya N. Crosby 《Surveys in Geophysics》2008,29(2):71-137
The paper reviews recent advances in studies of electric discharges in the stratosphere and mesosphere above thunderstorms,
and their effects on the atmosphere. The primary focus is on the sprite discharge occurring in the mesosphere, which is the
most commonly observed high altitude discharge by imaging cameras from the ground, but effects on the upper atmosphere by
electromagnetic radiation from lightning are also considered. During the past few years, co-ordinated observations over Southern
Europe have been made of a wide range of parameters related to sprites and their causative thunderstorms. Observations have
been complemented by the modelling of processes ranging from the electric discharge to perturbations of trace gas concentrations
in the upper atmosphere. Observations point to significant energy deposition by sprites in the neutral atmosphere as observed
by infrasound waves detected at up to 1000 km distance, whereas elves and lightning have been shown significantly to affect
ionization and heating of the lower ionosphere/mesosphere. Studies of the thunderstorm systems powering high altitude discharges
show the important role of intracloud (IC) lightning in sprite generation as seen by the first simultaneous observations of
IC activity, sprite activity and broadband, electromagnetic radiation in the VLF range. Simulations of sprite ignition suggest
that, under certain conditions, energetic electrons in the runaway regime are generated in streamer discharges. Such electrons
may be the source of X- and Gamma-rays observed in lightning, thunderstorms and the so-called Terrestrial Gamma-ray Flashes
(TGFs) observed from space over thunderstorm regions. Model estimates of sprite perturbations to the global atmospheric electric
circuit, trace gas concentrations and atmospheric dynamics suggest significant local perturbations, and possibly significant
meso-scale effects, but negligible global effects. 相似文献
2.
利用阿克苏及邻近地区12个气象站1980—2013年雷暴资料,以及同期高空资料,统计了各站年均雷暴日数,对发生区域雷暴天气的环流形势进行分类,归纳出各型的入型指标。通过逐步回归法,建立阿克苏及邻近地区区域雷暴概率回归预报模型,并对2013年进行试预报。结果表明:(1)阿克苏及邻近地区区域雷暴的影响系统主要分为4类:巴湖低槽型、急流型、西北气流型和温度槽型。(2)对2002—2012年5—9月(共1683 d)历史资料进行判别,满足入型条件的样本数为876 d,消空率为48%;对2013年5—9月(共153 d)历史资料进行判别,入型样本数为80 d,消空率为48%。(3)对2002—2012年5—9月所有入型样本进行回代检验,平均准确率为72.0%(平均TS评分为30.1%);对2013年5—9月所有入型样本进行试预报,平均准确率为63.2%(平均TS评分为28.2%)。 相似文献
3.
The thermodynamic structure on top of a numerically simulated severe storm is examined to explain the satellite observed plume formation above thunderstorm anvils. The same mechanism also explains the formation of jumping cirrus observed by Fujita on board of a research aircraft. A three-dimensional, non-hydrostatic cloud model is used to perform numerical simulation of a supercell that occurred in Montana in 1981. Analysis of the model results shows that both the plume and the jumping cirrus phenomena are produced by the high instability and breaking of the gravity waves excited by the strong convection inside the storm. These mechanisms dramatically enhance the turbulent diffusion process and cause some moisture to detach from the storm cloud and jump into the stratosphere. The thermodynamic structure in terms of the potential temperature isotherms above the simulated thunderstorm is examined to reveal the instability and wave breaking structure. The plumes and jumping cirrus phenomena represent an irreversible transport mechanism of materials from the troposphere to the stratosphere that may have global climatic implications. 相似文献
4.
Lightning optical pulse statistics from storm overflights during the Altus Cumulus Electrification Study 总被引：2，自引：0，他引：2
D.M. Mach R.J. Blakeslee J.C. Bailey W.M. Farrell R.A. Goldberg M.D. Desch J.G. Houser 《Atmospheric Research》2005,76(1-4):386
The Altus Cumulus Electrification Study (ACES) was conducted during the month of August 2002 in an area near Key West, Florida. One of the goals of this uninhabited aerial vehicle (UAV) study was to collect time resolved optical pulse data from thunderstorms. During the month long campaign, we acquired 5256 lightning generated optical pulses. Most of these observations were made while quite close to the top of the storms. We divided our data into two amplitude groups based on prior NASA U2 aircraft optical data and the pulse characteristics. The group of strong pulses with radiance greater than 2.1 mW m− 2 sr− 1 had mean and median 10–10% optical pulse widths of 770 and 740 μs, respectively, 50–50% pulse widths of 399 and 355 μs, respectively, and 10–90% risetimes of 292 and 260 μs. These values are very similar to the previous U2 based optical results The other group of pulses consisting of slightly more than a quarter of the total pulses observed had radiances less than the minimum values detected in the U2 study. These weak pulses were narrower than the strong pulses with 50–50% mean and median values of 199 and 160 μs, respectively. Only 12% of the flashes observed contained only weak pulses. The source of these weak pulses is unknown, but we suspect that some are artifacts of the close proximity of the aircraft to cloud top. 相似文献
5.
Earle Williams Bob Boldi Anne Matlin Mark Weber Steve Hodanish Dave Sharp Steve Goodman Ravi Raghavan Dennis Buechler 《Atmospheric Research》1999,51(3-4)
The development of a new observational system called LISDAD (Lightning Imaging Sensor Demonstration and Display) has enabled a study of severe weather in central Florida. The total flash rates for storms verified to be severe are found to exceed 60 fpm, with some values reaching 500 fpm. Similar to earlier results for thunderstorm microbursts, the peak flash rate precedes the severe weather at the ground by 5–20 min. A distinguishing feature of severe storms is the presence of lightning ‘jumps' — abrupt increases in flash rate in advance of the maximum rate for the storm. The systematic total lightning precursor to severe weather of all kinds — wind, hail, tornadoes — is interpreted in terms of the updraft that sows the seeds aloft for severe weather at the surface and simultaneously stimulates the ice microphysics that drives the intracloud lightning activity. 相似文献
6.
The global electrical circuit, which maintains a potential of about 280 kV between the earth and the ionosphere, is thought to be driven mainly by thunderstorms and lightning. However, very few in situ measurements of electrical current above thunderstorms have been successfully obtained. In this paper, we present dc to very low frequency electric fields and atmospheric conductivity measured in the stratosphere (30–35 km altitude) above an active thunderstorm in southeastern Brazil. From these measurements, we estimate the mean quasi-static conduction current during the storm period to be 2.5 ± 1.25 A. Additionally, we examine the transient conduction currents following a large positive cloud-to-ground (+ CG) lightning flash and typical − CG flashes. We find that the majority of the total current is attributed to the quasi-static thundercloud charge, rather than lightning, which supports the classical Wilson model for the global electrical circuit. 相似文献
7.
Cosmic rays and the electric field of thunderclouds: Evidence for acceleration of particles (runaway electrons) 总被引：1，自引：0，他引：1
We present the data on correlations of the intensity of the soft component of cosmic rays with the local electric field of the near-earth atmosphere during thunderstorm periods at the Baksan Valley (North Caucasus, 1700 m a.s.l.). The large-area array for studying the extensive air showers of cosmic rays is used as a particle detector. An electric field meter of the ‘electric mill’ type (rain-protected) is mounted on the roof of the building in the center of this array. The data were obtained in the summer seasons of 2000–2002. We observe strong enhancements of the soft component intensity before some lightning strokes. At the same time, the analysis of the regression curve ‘intensity versus field’ discovers a bump at the field sign that is opposite to the field sign corresponding to acceleration of electrons. It is interpreted as a signature of runaway electrons from the region of the strong field (with opposite sign) overhead. 相似文献
8.
Harold E. Brooks Aaron R. Anderson Kathrin Riemann Irina Ebbers Heather Flachs 《Atmospheric Research》2007,83(2-4):294-305
Annual cycles of convectively important atmospheric parameters have been computed for a variety of from the National Center for Atmospheric Research (NCAR)/National Centers for Environmental Prediction (NCEP) global reanalysis, using 7 years of reanalysis data. Regions in the central United States show stronger seasonality in combinations of thermodynamic parameters than found elsewhere in North America or Europe. As a result, there is a period of time in spring and early summer when climatological mean conditions are supportive of severe thunderstorms.The annual cycles help in understanding the large-scale processes that lead to the combination of atmospheric ingredients necessary for strong convection. This, in turn, lays groundwork for possible changes in distribution of the environments associated with possible global climate change. 相似文献
9.
Spatial patterns in thunderstorm rainfall events and their coupling with watershed hydrological response 总被引：1，自引：0，他引：1
Efrat Morin David C. Goodrich Robert A. Maddox Xiaogang Gao Hoshin V. Gupta Soroosh Sorooshian 《Advances in water resources》2006
Weather radar systems provide detailed information on spatial rainfall patterns known to play a significant role in runoff generation processes. In the current study, we present an innovative approach to exploit spatial rainfall information of air mass thunderstorms and link it with a watershed hydrological model. Observed radar data are decomposed into sets of rain cells conceptualized as circular Gaussian elements and the associated rain cell parameters, namely, location, maximal intensity and decay factor, are input into a hydrological model. Rain cells were retrieved from radar data for several thunderstorms over southern Arizona. Spatial characteristics of the resulting rain fields were evaluated using data from a dense rain gauge network. For an extreme case study in a semi-arid watershed, rain cells were derived and fed as input into a hydrological model to compute runoff response. A major factor in this event was found to be a single intense rain cell (out of the five cells decomposed from the storm). The path of this cell near watershed tributaries and toward the outlet enhanced generation of high flow. Furthermore, sensitivity analysis to cell characteristics indicated that peak discharge could be a factor of two higher if the cell was initiated just a few kilometers aside. 相似文献
10.
The Tornado and Storm Research Organisation (TORRO) was formed in the UK in 1974 in order to determine realistic spatial, temporal and intensity distributions of tornadoes in the UK and, eventually, throughout Europe. Currently, TORRO's databases contain nearly 2000 tornadoes and over 550 waterspouts for the UK alone. In 1972, TORRO's founder, Terence Meaden, devised the Tornado Intensity Scale. This scale enables the wind speeds of tornadoes to be rated on a scale from T0 to T10, or more (since it is an open-ended scale). Using this scale, estimates have been made of the statistical return periods of differing intensities of UK tornadoes. TORRO's research into understanding the conditions of tornado development is ultimately intended to lead to issuing forecasts of tornadoes. In 1991, TORRO issued the first tornado watch in the UK for 12 November and this proved to be accurate—not only did three property-damaging tornadoes strike East Anglia but the forecast maximum intensity of T5 was attained. In 1975, TORRO expanded its activities to include conventional thunderstorm reporting and investigations. In 1982, TORRO incorporated the British and Irish thunderstorm data-collection organisation, the Thunderstorm Census Organisation (TCO), which was established in 1924. By the early 1980s, TORRO's network of voluntary thunderstorm observers, located throughout the UK and Ireland and increasingly in other European countries, numbered around 350 and the network continues to grow. In addition to TORRO's early focus on tornadoes and thunderstorms, its data collection and research has expanded to consider other whirlwinds (such as waterspouts and land devils), hailstorms, lightning (including ball lightning) and blizzards/heavy snowfalls. In 1996, TORRO began providing easy access to its databases (e.g. post-1995 UK and European severe weather events, especially tornadoes and hailstorms) and other information via its internet site at http://www.torro.org.uk/. Building on over 25 years of experience—and of the half a century of the TCO before it—TORRO continues to expand its European role in severe weather data collection and research, helped by the on-going appointment of European representatives and its increasing European membership. 相似文献