Using a cloud electrification model to study relationships between lightning activity and cloud microphysical structure (original) (raw)
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Quarterly Journal of the Royal Meteorological Society, 1995
In an effort to optimize the value of global-scale measurements obtained with the NASA/MSFC satelliteborne Lightning Imaging System (LIS), a simple computational model of thundercloud electrification has been developed, from which it is possible to derive crude relationships between lightning frequency f (which LIS will measure) and cloud parameters such as radar reflectivity Z, precipitation rate P , updraught speed w , cloud radius R, ice-crystal concentration Ni and graupel-pellet concentration N g . Electric field-growth is assumed to occur via the non-inductive charging mechanism, for both Fletcher and Hallett-Mossop types of glaciation mechanisms. A simple criterion is used to distinguish between cloud-to-ground and intracloud lightning discharges. f is found to be especially sensitive to w in situations where, as updraught speed increases, the temperature at balance level, Tbal, of the upper boundary of the charging zone falls. In these circumstances Ni and the sizes of the ice hydrometeors are significantly increased, with a corresponding enhancement of the effectiveness of charge transfer.
Modelling and observations of thundercloud electrification and lightning
Atmospheric Research, 2001
A two-dimensional lightning frequency model was applied to two case studies of thunderclouds: 9th July 1981, the CCOPE case, and 19th July 1991, the CaPE case. Factors influencing lightning activity were discussed. Although there was a strong link between updraft and lightning frequency, the relationship was not distinct; the initial environmental conditions, the updraft speed and more significantly the graupel number concentration were shown to have a large effect. The model computations suggested the importance of the 2-mm diameter graupel particles. No definite relationship between lightning frequency and cloud ice content could be established in this study. The results demonstrated the limitations of the current charge transfer parameterisation scheme used, with a more detailed structure being required. However, the model was capable of reproducing a realistic cloud structure and lightning activity using a relatively simple dynamical framework. q address: a.gadian@umist.ac.uk A. Gadian . 0169-8095r01r$ -see front matter q 2001 Elsevier Science B.V. All rights reserved.
Cloud-to-ground lightning and Mesoscale Convective Systems
Atmospheric Research, 2011
This work analyzes some of the physical and microphysical properties of Mesoscale Convective Systems (MCS) and cloud-to-ground lightning. Satellite data from the GOES-10 infrared and NOAA-18 and TRMM microwave channels and lightning information from the Brazilian Lightning Detection Network (BrasilDAT) were utilized for the period from 2007 to 2009. Based on an automatic MCS detection method, 720 MCS life cycles were identified during the period and region of study, with a lightning detection efficiency of over 90%. During the diurnal cycle, the electrical activity maximum occurred close to the time of maximum convective cloud fraction and 3 hours after the maximum normalized area expansion rate. The diurnal cycles of both properties are modulated by diurnal heating and thus could be used to monitor the diurnal variability of lightning occurrence. The area growth during the initial phase of the MCS exerted a strong influence on their size-duration, and potential for electrical activity during their life cycle. The average lightning life cycle exhibited a maximum close to MCS maturation, while the maximum of the average lightning density occurred close to the initial MCS life cycle stages. The growth rate of electrical activity during the early stages can indicate the strength of convection and the possible duration of systems with lightning occurrence. The strong condensation processes and mass flux during the growth phase of the systems can provide favorable conditions for cloud electrification and lightning occurrence. A comparison of high microwave frequencies with lightning data showed a strong relationship of the vertically integrated ice content and particle size with lightning occurrence. The polarization difference in the 85 GHZ channel showed that electrical activity increases linearly with polarization reduction, associated with a high value of Pearson's correlation coefficient. This suggests that regions with more intense electrical activity are predominantly located in areas with a high concentration of larger ice particles that are preferentially oriented vertically, due to the existence of intense updrafts and the electric field. These results demonstrate the potential use of thermodynamic, dynamic and microphysical characteristics for analyzing storm severity and as additional information for monitoring of electrical activity over large regions that lack ground-based lightning sensors and for nowcasting.
Quarterly Journal of the Royal Meteorological Society, 2003
This paper presents a study about correlation between cloud-to-ground lightning ash (CG) activity, and the dynamics and microphysics of thunderclouds. Data collected during Intense Observation Period (MAP IOP) 2a of the Mesoscale Alpine Programme Special Observing Period (SOP) over the Lago Maggiore Target Area (LMTA) in northern Italy are used. IOP 2a was the most electrically active period during the SOP, representing 75% of the total CG activity. Thunderclouds were strongly vertically developed (the 30 dBZ echo tops were sometimes higher than 12 km) and produced large amounts of rainfall and some hail. Doppler and polarimetric radar data allow us to retrieve the three-dimensional wind and radar-re ectivity elds from two synchronous Doppler radars, and particle-type elds in the thunderclouds from the S-Pol polarimetric radar. Both polarities of CGs are distinguished. Temporal and spatial relationships from the global activity over the LMTA are rst studied. Then, the temporal correlation between CG rates and dynamics or microphysics for ve individual cells is considered. A very strong correlation is observed between CG and the presence of a mixture of graupel and hail, which strongly supports a non-inductive charging mechanism. CG impacts seem to be located underneath large radar-re ectivity values and around the maximum vertical velocities. Two individual cells are studied in more detail, in order to better understand their different electrical behaviours: the rst produced mainly negative CGs, and the second produced 61% positive CGs in the second phase of its lifetime. The association of positive CGs with severe weather and especially with the presence of hail is observed.
Predicting Cloud-to-Ground and Intracloud Lightning in Weather Forecast Models
Weather and Forecasting, 2012
A new prognostic, spatially and temporally dependent variable is introduced to the Weather Research and Forecasting Model (WRF). This variable is called the potential electrical energy (Ep). It was used to predict the dynamic contribution of the grid-scale-resolved microphysical and vertical velocity fields to the production of cloud-to-ground and intracloud lightning in convection-allowing forecasts. The source of Ep is assumed to be the noninductive charge separation process involving collisions of graupel and ice particles in the presence of supercooled liquid water. The Ep dissipates when it exceeds preassigned threshold values and lightning is generated. An analysis of four case studies is presented and analyzed. On the 4-km simulation grid, a single cloud-to-ground lightning event was forecast with about equal values of probability of detection (POD) and false alarm ratio (FAR). However, when lighting was integrated onto 12-km and then 36-km grid overlays, there was a large im...
Atmospheric Measurement Techniques Discussions, 2016
Cloud electrification and related lightning activity in thunderstorms have their origin in the charge separation and resulting distribution of charged iced particles within the cloud. So far, the ice distribution within convective clouds has been investigated mainly by means of ground based meteorological radars. In this paper we show how the products from Cloud Profiling Radar (CPR) on board CloudSat, a polar satellite of NASA's Earth System Science Pathfinder (ESSP), can be used to obtain information from space on the vertical distribution of ice particles, ice content and relate them to the lightning activity. <br><br> The analysis has been carried out focusing on five convective events occurred over Italy that have crossed by CloudSat overpasses during significant lightning activity. The CPR products considered here are the vertical profiles of cloud Ice Water Content (IWC) and ice particles Effective Radius (ER), to be compared with the number of strokes as meas...
Clouds’ Microphysical Properties and Their Relationship with Lightning Activity in Northeast Brazil
Remote Sensing
The Northeast region of Brazil (NEB) has a high rate of deaths from lightning strikes (18% of the country’s total). The region has states, such as Piauí, with high mortality rates (1.8 deaths per million), much higher than the national rate (0.8) and the NEB rate (0.5). In this sense, the present work analyzes the microphysical characteristics of clouds with and without the occurrence of total lightning. For this purpose, data from the Lightning Imaging Sensor (LIS), TRMM Microwave Imager (TMI) and Precipitation Radar (PR), aboard the Tropical Rainfall Measuring Mission (TRMM) satellite from 1998 to 2013 were used. The TRMM data were analyzed to establish a relationship between the occurrence of lightning and the clouds’ microphysical characteristics, comparing them as a function of lightning occurrence classes, spatial location and atmospheric profiles. A higher lightning occurrence is associated with higher values of ice water path (>38.9 kg m−2), rain water path (>2 kg m−2)...
Atmospheric Research, 1999
0169-8095r99r$ -see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 1 6 9 -8 0 9 5 9 9 0 0 0 0 9 -5 ( ) M. B. Baker et al.r Atmospheric Research 51 1999 221-236 222 anvils: a parameter of climatological importance. The successful launch and continuing satisfacw tory functioning of the OTD Christian, H.Lightning imaging sensor LIS for the earth x observing system. NASA Tech. Memorandum, 4350 make it possible-with a high degree of precision-to measure lightning location, occurrence time and frequency f over extensive areas of the Earth's surface. Measured global distributions of lightning and associated lightning stroke radiance demonstrate that: lightning activity is particularly pronounced over the tropics, much greater over land than over the oceans, and exhibits great seasonal variability; lightning radiance tends to be greater over the oceans, less when lightning activity is high, and greater in the Northern Hemisphere winter than summer. q
Submitted to …, 2008
This work presents a relationship between atmospheric discharges and penetrative convective clouds. It combines Infrared and Water Vapor channels from the GOES-12 geostationary satellite with cloud-ground lightning data from the Brazilian Integrated Lightning Detection Network (RINDAT) during the period from January to February 2005. The difference between water vapor and infrared brightness temperature is a tracer penetrating clouds. Due to the water vapor channel's strong absorption, this difference is positive only during overshooting cases, when convective clouds penetrate the stratosphere. From this difference and the cloud-ground electrical discharge, measured on the ground by RINDAT, it was possible to adjust exponential curves that relate the brightness temperature difference from these two channels to the probability of occurrence of cloud-ground electrical discharges, with a very high coefficient of determination. If WV-IR brightness temperature difference is larger than-15K there is a high potential for cloudground lightning activity. As this difference increases the cloud-ground lightning probably increase, for example: if this difference is equal zero, the probability of having at least one cloud-ground electrical discharge is 10.9 %, 7.0% for two, 4.4% for four, 2.7% for eight and 1.5% for sixteen cloud-ground lightning discharges Through this process, was developed a scheme that estimates the probability of occurrence of cloud-ground lightning over all the continental region of South America.