Distribution of lightning spatial modes and climatic causes in China

本文利用中国气象局国家雷电监测网(CNLDN)的地闪观测数据集,分析了2010-2020年中国陆地区域地闪空间模态分布特征及其可能的气候成因.研究发现,夏季地闪第一模态的方差贡献率为32.86%,其分布从北到南呈现出“-+-”的经向跷跷板模式,当东太平洋和印度洋的海温异常增暖,西北太平洋的海温异常变冷时,在中国黄海,东海及热带西太平洋地区激发出气旋性环流,随着水汽南下至华南地区,与来自孟加拉湾的水汽汇合,上升运动在此加强,从而使得该地区的雷电活动增强.表明厄尔尼诺-南方涛动(ENSO)现象,是发生在中国陆地区域的地闪活动的气候驱动因子。

A Review of Atmospheric Electricity Research in China from 2011 to 2018

Atmospheric electricity research has been conducted actively in China,having profited from the development and application of high temporal and spatial resolution lightning detection and location technologies.This paper reviews the scientific advances made in the field of atmospheric electricity in China from 2011 to 2018,covering the following five aspects:(1)lightning detection and location techniques;(2)discharge processes and parameters associated with rocket-triggered lightning;(3)physical processes in natural lightning and attachment to the ground;(4)lightning activities and charge structure in different thunderstorms;and(5)effects of thunderstorms on the upper atmosphere.In addition,some outstanding questions for future research are outlined.

Simulation of Quasi-Linear Mesoscale Convective Systems in Northern China：Lightning Activities and Storm Structure

Two intense quasi-linear mesoscale convective systems（QLMCSs） in northern China were simulated using the WRF（Weather Research and Forecasting） model and the 3D-Var（three-dimensional variational） analysis system of the ARPS（Advanced Regional Prediction System） model.A new method in which the lightning density is calculated using both the precipitation and non-precipitation ice mass was developed to reveal the relationship between the lightning activities and QLMCS structures.Results indicate that,compared with calculating the results using two previous methods,the lightning density calculated using the new method presented in this study is in better accordance with observations.Based on the calculated lightning densities using the new method,it was found that most lightning activity was initiated on the right side and at the front of the QLMCSs,where the surface wind field converged intensely.The CAPE was much stronger ahead of the southeastward progressing QLMCS than to the back it,and their lightning events mainly occurred in regions with a large gradient of CAPE.Comparisons between lightning and non-lightning regions indicated that lightning regions featured more intense ascending motion than non-lightning regions;the vertical ranges of maximum reflectivity between lightning and non-lightning regions were very different;and the ice mixing ratio featured no significant differences between the lightning and non-lightning regions.

Investigating Lightning Characteristics through a Supercell Storm by Comprehensive Coordinated Observations over North China

Electrical characteristics of an isolated supercell storm observed on 13 June 2014 over Beijing were investigated using lightning data obtained from the Beijing Lightning Network,radar reflectivity,and hydrometeor retrievals during the 6-h lifetime.Positive cloud-to-ground(+CG)lightning took a high percentage of CG lightning.Before and during a hail event,+CG lightning was more frequent than negative cloud-to-ground(-CG)lightning,except that+CG lightning took a high percentage at the beginning and in the dissipating stage.After the hail event ended,-CG lightning dominated and reached its maximum value.An analysis of hydrometeors retrieved by X-band polarimetric radar revealed that the discharge concentrated in the convective region with graupel particles and hailstones,whereas graupel,snow and ice crystals in the stratiform region.Lightning radiation sources were located mainly in the convective region,some of which were distributed along a gradient of radar reflectivity from the convective region to the stratiform region.The indication is that the supercell demonstrated an inverted tripole charge structure before the hail event,which converted to a normal tripole structure after the hail event.

Propagation of positive, negative, and recoil leaders in upward lightning flashes

Leader propagation is a fundamental issue in lightning physics. The propagation characteristics of positive leaders and negative leaders are summarized and compared based on data from high-speed camera and electromagnetic field in rocket-triggered lightning and tower-initiated lightning discharges; available channel base current data recorded in rocket-triggered lightning are also used. The negative leaders propagate in a stepped fashion accompanied by many branches. The stems ahead of the negative leader tip determine the manner and direction of the leader propagation, and even the branching and winding of the lightning channel. The impulsive current, electromagnetic field, and related optical images suggest that the positive leader may develop in a step-like fashion at its initial stage of triggered lightning. However, the stepping processes of the positive leader are obviously different from those of the negative leader. Tower-initiated lightning revealed that the most conspicuous characteristics of the stepwise positive leader involve the intermittent brush-like corona zone in front of the leader tip and the luminosity enhancement of the channel behind the tip. In rockettriggered lightning flashes, the charge transferred during an individual step for the negative leader was nearly an order greater than for the positive counterpart. The successive streamers ahead of the leader tip are essential for both negative and positive leader propagation, and the stems could be formed from one or more streamers in the previous negative streamer zone with the main leader channel dim. High-resolution observation of tower lightning also revealed a new type of bidirectional recoil leader, with polarity contrary to the traditional one, traversing in negative channels associated with tower-initiated and rocket-triggered lightning.

Preface

Laboratory of Middle Atmosphere and Global Environment Observation(LAGEO)was established in 1995and became one of the Key Laboratory of Chinese Academy of Sciences(CAS)in 2008.LAGEO emphasizes both fundamental research and high-tech research and development,and sets the major research directions as middle atmosphere and global environmental observation,which include the following four aspects:1)

Concurrence of high dust aerosol and stratosphere-intruded ozone pollution in super sandstorms

The air quality in China has substantially improved in recent years,as indicated by the declining trends in SO_(2),NO_(2),PM_(2.5)and PM_(10)concentrations.Despite the reduced anthropogenic pollutant emissions;however,sustained increases in surface ozone(O_(3))that may impair the effectiveness of clean air actions have been observed.Moreover,complex heavy pollution episodes can still occur,and some of these episodes are closely linked with weather.For example,two severe sandstorms occurred successively in the early spring of 2021 in North China,despite the sandstorm frequency in China having significantly decreased in recent years[1-3].

Review of Chinese atmospheric science research over the past 70 years: Atmospheric physics and atmospheric environment

Since the founding of the People’s Republic of China 70 years ago,the subject of atmospheric physics and atmospheric environment has developed rapidly in China,providing important support for the development of atmospheric science and guarantee for the development of national economy.In this paper,the general advancement of atmospheric physics and atmospheric environment in last 70 years was described.The main research progress of atmospheric physics and atmospheric environment in the past 40 years of reform and opening-up was reviewed,the outstanding research achievements since the 21 st century were summarized,the major problems and challenges are pointed out,and the key directions and suggestions for future development are put forward.

Increasing trend of lightning activity in the South Asia region

Lightning is an important natural source of wildfires and oxynitride,and hence significantly influences ecological systems and atmospheric chemistry.Here,we choose South Asia,an important region for global water reallocation and global climate changes,to examine lightning variations based on the longest existing lightning dataset from the OTD/LIS observations.We identify a clear increase in lightning density in the research region,increasing at a rate of 0.096 fl km^(-2)a^(-1)over the last two decades.Multiple linear regression analysis is adopted to identify the main influencing factors among ten potential thermodynamic or microphysical factors and the crucial areas contributing to the increases in lightning.The surface latent heat flux along the west coast of the Indian subcontinent is the largest contributor,explaining52%of the lightning variance and contributing to a 0.025 fl km^(-2)a^(-1)increase.The sea surface temperature in the Arabian Sea,the convective available potential energy(CAPE)over the northwestern Indian subcontinent,and the wind shear along the northwestern coast also make important contributions to the lightning increase,indicating that the thermodynamic effects overwhelm the microphysical effects on lightning activity over the South Asia region.

Understanding the dynamical-microphysical-electrical processes associated with severe thunderstorms over the Beijing metropolitan region

The Dynamical-microphysical-electrical Processes in Severe Thunderstorms and Lightning Hazards(STORM973)project conducted coordinated comprehensive field observations of thunderstorms in the Beijing metropolitan region(BMR)during the warm season from 2014 to 2018.The aim of the project was to understand how dynamical,microphysical and electrical processes interact in severe thunderstorms in the BMR,and how to assimilate lightning data in numerical weather prediction models to improve severe thunderstorm forecasts.The platforms used in the field campaign included the Beijing Lightning Network(BLNET,consisting of 16 stations),2 X-band dual linear polarimetric Doppler radars,and 4 laser raindrop spectrometers.The collaboration also made use of the China Meteorological Administration’s mesoscale meteorological observation network in the Beijing-Tianjin-Hebei region.Although diverse thunderstorm types were documented,it was found that squall lines and multicell storms were the two major categories of severe thunderstorms with frequent lightning activity and extreme rainfall or unexpected local short-duration heavy rainfall resulting in inundations in the central urban area,influenced by the terrain and environmental conditions.The flash density maximums were found in eastern Changping District,central and eastern Shunyi District,and the central urban area of Beijing,suggesting that the urban heat island effect has a crucial role in the intensification of thunderstorms over Beijing.In addition,the flash rate associated with super thunderstorms can reach hundreds of flashes per minute in the central city regions.The super(5%of the total),strong(35%),and weak(60%)thunderstorms contributed about 37%,56%,and 7%to the total flashes in the BMR,respectively.Owing to the close connection between lightning activity and the thermodynamic and microphysical characteristics of the thunderstorms,the lightning flash rate can be used as an indicator of severe weather events,such as hail and short-duration heavy rainfall.Lightning data can also be assimilated into numerical weather prediction models to help improve the forecasting of severe convection and precipitation at the cloud-resolved scale,through adjusting or correcting the thermodynamic and microphysical parameters of the model.