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Numerical simulations of the bi-level and branched structure of intracloud lightning flashes

science china {2. sciences 2006年第6期49卷 661-672页

作者： tan yongbo1, tao shanchang1,{2., ma ming2.& lu weitao2.1. school of earth and space sciences, university of science and technology of china,{12., china 2. Chinese Academy of Meteorological sciences, Beijing 100081, china school of earth and {2. sciences University of Science and Technology of China Hefei China Chinese Academy of Meteorological sciences Beijing China

Intracloud (IC) lightning flashes have been simulated in fine resolution (12.5 m) by using a bidirectional stochastic lightning parameterization scheme within 2.dimensional domain. The simu-lated results show that the IC flashes have a bilevel channel structure and the altitudes of the hori-zontal channels are at the same heights of potential wells, which are supported by the previous VHF source observations and balloon soundings of electric field profile in the thundercloud. Further con-clusions are: (1) After an IC flash is initiated near the boundary between positve and nagetive charge zone, the negative (or positive) leader tends to propagate into the positive (or negative) charge zone. Both types of positive and negative IC flashes have been reproduced and their polarity depends on the up and down disposition of the positive and negative charge regions. (2. The extension range of leaders is correlative with the cloud charge distribution. The leader is possible to extend through the inverted charge region all over where it is extending, but keeps away from the isolated charge area of the same polarity. (3) The channel structures also depend on the electric potential distributions in the thundercloud. Before propagating into the central area of potential wells, the leader tends to extend along the direction with the maximum of potential gradient. Once extending away from the center of potential wells, the leader tends to extend along the direction with the slowest potential change. (4) The IC flash channels have the fractal feature with fractal dimension 1.45 before leaders pass through the central area of charge regions. The exponent decreases rapidly once leaders extend into the low-density charge regions. (5) The induced charges of opposite polarity are deposited in the leader channels within preexisting positive and negative charge regions during IC flash discharges. This causes a new and complicated charge distribution in the thundercloud, and the potential

关键词： IC, lightning parameterization, branched bilevel structure, fractal feature, propagation tendency.

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Climatological distribution of lightning density observed by satellites in china and its circumjacent regions

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science china {2. sciences 2005年第2期48卷 219-229页

作者： ma ming {2. shanchang zhu baoyou lu weitao school of earth and {2. sciences University of Science and Technology of ChinaHefei230026China School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei230026China School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei230026China School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei230026China

The 0.5°× 0.5° grid resolution distribution of lightning density in china and its circumjacent regions have been analyzed by using the satellite-borne OTD (Apr 1995-{2.r 2.00) and LIS (Dec 1997-{2.r 2.03) databases. It is shown that: (i) Firstly, the variability of the lightning density (LD) is particularly pronounced over the different subareas, 9 times greater over the south than the north side of Hi{2.layas Mountains, 2.5 times greater over the eastern than the western area of china. While the {2.ximum and minimum LD are respectively 31.4fl/km2.a (in Guangzhou region) and less than 0.2.l/km2.a (in the desert of western china). Secondly, the LD of china's continent regularly varies with latitude and distance off coast, which is consistent with annual mean precipitation in varying trend. In conclusion, the Qinghai-Tibet Plateau, the china's three-step staircase topography and the latitude are three important factors affecting {2.cro-scale characteristics of the LD distribution, (ii) The regional differences in LD distribution are closely related to the mesoscale orographic forcing. In the eastern humid regions of china, the high LD belts often appear along the mesoscale mountains (with south-north or northeast-southwest direction, 500-1500 m ASL) and hills, while the low LD belts often appear on the plain and basin (valley) between the mountains. But in the western cold and arid regions of china, the relatively high LD belts mostly appear on the Qinghai Lake area of the southern side of Qilian Mountain, Yili River valley, the basin between tanggula Mountains and Nyainqentanglha. On the coastal land, the high LD centers appear in regions where mountain and hill and large cities are located. This seems to be related to the interaction between the sea-land breeze and mountain-valley wind or city heat island effect, (iii) The china Sea is one of the relatively high LD zones on global oceans. It is very interesting that a high LD belt is located along the Kuroshio area. It i

关键词： OTD/LIS, distribution of lightning density, orographic forcing, coastal land, Kuroshio.

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Response of global lightning activity to air temperature variation

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Chinese science Bulletin 2005年第22期50卷 2640-2644页

作者： ma ming {2. shanchang zhu baoyou luE weitao tan yongbo school of earth and {2. sciences University of Science anti Technology of China Hefei 230026 China Chinese Academy of Meteorological sciences Beijing 100081 China

It is an issue of great attention but yet not very clear whether lightning activities increase or decrease on a warmer world. Reeve et al. presented that lightning activities in global land and the Northern Hemisphere land have posi- tive response to the increase of wet bulb temperature at 1000hPa. Is this positive response restricted only to wet bulb temperature or in land? What is the response of global light- ning activities (in both land and ocean) to the global surface air temperature variation like? This paper, based on the 5-year or 8-year OTD/LIS satellite-based lightning detecting data and the NCEP reanalysis data, makes a reanalysis of the response of the global and regional lightning activities to temperature variations. The results show that on the inter- annual time scale the global total flash rate has positive re- sponse to the variation in global surface air temperature, with the sensitivity of 17±7% K?1. Also, the seasonal mean flash rate of continents all over the world and that of conti- nents in the Northern Hemisphere have sensitive positive response to increase of global surface air temperature and wet bulb temperature, with the sensitivity of about 13±5% K?1, a bit lower than estimation of 40% K?1 in Reeve et al. However, the Southern Hemisphere and other areas like the tropics show no significant correlation.

关键词： OTD IAS 闪电活跃性气候变化温度变化灵敏度

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