著者

Liangtao XU Yijun ZHANG Fei WANG Xi CAO

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.97, no.6, pp.1119-1135, 2019 (Released:2019-12-05)

参考文献数

56

被引用文献数

3

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The charge structure evolution of a mesoscale convective system with an anomalous or inverted charge structure, observed in the Severe Thunderstorm Electrification and Precipitation Study, a field project on the Colorado–Kansas border in summer 2000, is simulated using the Weather Research and Forecasting (WRF) model coupled with electrification and discharge processes. Two noninductive electrification schemes are used, based on the liquid water content (LWC) and the graupel rime accretion rate (RAR). The simulation with the LWC-based electrification scheme cannot reproduce the inverted charge structure with a positive charge region sandwiched by two negative charge layers, while the RAR-based electrification scheme produces the evolution process of a normal–inverted–normal charge structure in the convective region, which is consistent with the observations. In the low RAR (< 2 g m−2 s−1) region, graupel is mainly negatively charged when it bounces off ice crystals, while the ice crystals take up positive charge. However, in the zone where the inverted charge structure forms, a strong updraft (> 16 m s−1), high LWC (> 2 g m−3), and high RAR (> 4.5 g m−2 s−1) region appears above the height of the −20°C layer, so that a positive graupel charging region is generated above the −20°C layer of the convective region, resulting in a negative dipole charge structure with negatively charged ice crystals above the positively charged graupel. The negative dipole is superposed on the positive dipole (positive above negative) charge structure at the lower position to form an inverted tripole charge structure.

著者

Xi CAO Renguang WU

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.96, no.4, pp.317-336, 2018 (Released:2018-07-27)

参考文献数

43

被引用文献数

7

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The present study compares contributions of different environmental factors to the tropical cyclone (TC) genesis over the western North Pacific (WNP) during 2015 and 2016. A local instantaneous view of conditions for the TC genesis is adopted in the present study, which is distinct from the previous view of large-scale temporal averaged conditions. The present study also distinguishes the contributions of three time scale variations (synoptic, intraseasonal, and interannual) of a number of factors. Common to 2015 and 2016, the positive contribution of lower-level vorticity and upward motion to the TC genesis is mainly from the intraseasonal and synoptic components; the contribution of the barotropic energy conversion to the development of synoptic disturbances is larger from climatological mean winds and intraseasonal wind variations than from interannual wind variations; all three time scale variations of mid-level specific humidity contribute positively to the TC genesis; the barotropic energy conversion from climatological mean winds is due to the terms in relation to the meridional shear and zonal convergence of zonal wind. In comparison, the positive contribution of lower-level vorticity and mid-level specific humidity is larger in 2015 than in 2016 on all the three time scales; the contribution of the barotropic energy conversion in relation to the meridional shear of interannual variations of zonal wind and the zonal convergence of intraseasonal variations of zonal wind are larger in 2015 than in 2016; the vertical wind shear on all the three time scales and the sea surface temperature on the interannual time scale have a larger positive contribution to the TC genesis in 2016 than in 2015.