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The Relationship between Vertical Airflow Characteristics and Lightning Activity of Thunderstorm

Author: WangChenZuo
Tutor: ZhangYiJun
School: Chinese Academy of Meteorological Sciences
Course: Atmospheric Physics and Atmospheric Environment
Keywords: lightning activity dynamic structure vertical airflow hailstorm
CLC: P446
Type: Master's thesis
Year: 2014
Downloads: 3
Quote: 0
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Abstract


Kinds of observation data, including the cloud-to-ground (CG) lightning data,radar data, sounding data and three-dimensional wind field results, are syntheticallyanalyzed in this dissertation. Based on those data, the spatial and quantitativerelationships between the vertical airflow and CG lightning activity have beendiscussed. The thunderstorm convective cells are identified by a new thunderstormidentification method—Thunderstorm Identification Method Based on Lightning Data(TIMBLD). The characteristics of vertical airflow in the CG lightning start-time andend-time have also been compared, and the dynamic and microphysics mechanismhave been discussed by study a thunderstorm.We found that most CG lightning flashes are located in the weak updraft anddowndraft region, where the vertical speed is from-5m/s to5m/s. The CG lightningflashes in this region accounts for79.1%of total CG lightning flashes. Besides,overall CG lightning flashes tend to occur in the updraft region. In the initial stage,the percentage of CG lightning in the weak updraft region is more than in the maturestage and the dissipating stage. In the dissipating stage, the percentage of CGlightning in the weak downdraft region is more than in the other two stages.The CG lightning rate is closely related to the updraft volume in cell with certainthreshold, and this correlation is evidently different between distinct stages. The mostclose correlation is in the mature stage (r=0.70),and then the dissipating stage(r=0.66),and the initial stage (r=0.60). By considering both the dynamic and radar reflectivityparameter, the multivariate regression correlation is up to0.78. Besides, the lightningactivity is also related to the simulation of the absolute value of the ice particle flux inthe7km level (r=0.71).The dynamic condition in the CG lightning start-time and the end-time aresignificantly different. When the first CG lightning occurs, the updraft inthunderstorm is strong, the region of updraft is wide, and the thunderstorm isdominated by updraft (with the percentage of79%). When the last CG lightning occurs, the updraft in the cell is weak, the region of strong updraft is small, and thethunderstorm is dominated by downdraft (with the percentage of82%).By analyzing a hailstorm which produced large hail and strong wind, we findthat the CG lightning activity and the precipitation structure in the hail-producingstage was different from in the no-hail-producing stage. In the hail-producing stage,the updraft was stronger, while the CG lightning was less than the no-hail-producingstage. We also find that the CG lightning was seldom observed in the main updraftregion and the hail falling region. However, after the hail stage when the main updraftbecame weaker, the CG lightning flashes in those regions increased.Finally, we discussed the possible mechanism of the relationship between CGlightning activity and vertical airflow spatial distribution.

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CLC: > Astronomy,Earth Sciences > Atmospheric science (meteorology ) > Synoptic > Thunderstorm
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