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Xia C.,Wuhan University | Wang Q.,Wuhan University | Wang Q.,China Earthquake Administration | Yu T.,National Center for Space Weather | And 2 more authors.
Advances in Space Research

We investigate the ionospheric total electron content (TEC) anomalies occurred in the Qinghai-Tibet region before three large earthquakes (M > 7.0). The temporal and spatial TEC variations were used to detect the ionospheric possible precursors of these earthquakes. We identified two TEC enhancements in the afternoon local time 9 days and 2-3 days before each earthquake, between which a TEC decrement occurred 3-6 days before earthquakes. These anomalies happened in the area of about 30° in latitude and the maximum is localized equatorward from the epicenters. These TEC anomalies can be found in all three earthquakes regardless the geomagnetic conditions. The features of these anomalies have something in common and may have differences from those caused by geomagnetic storms. Our results suggest that these ionospheric TEC perturbations may be precursors of the large earthquakes. © 2010 COSPAR. Published by Elsevier Ltd. All rights reserved. Source

Zhou Y.,Nanjing University of Information Science and Technology | Zhou Y.,Institute of Heavy Rain | Niu S.,Nanjing University of Information Science and Technology | Lu J.,Nanjing University of Information Science and Technology
Advances in Atmospheric Sciences

Both direct and indirect effects of freezing drizzle on ice accretion were analyzed for ten freezing drizzle events during a comprehensive ice thickness, fog, and precipitation observation campaign carried out during the winter of 2008 and 2009 at Enshi Radar Station (30°17′N, 109°16′E), Hubei Province, China. The growth rate of ice thickness was 0.85 mm h-1 during the freezing drizzle period, while the rate was only 0.4 mm h-1 without sleet and freezing drizzle. The rain intensity, liquid water content (LWC), and diameter of freezing drizzle stayed at low values. The development of microphysical properties of fog was suppressed in the freezing drizzle period. A threshold diameter (Dc) was proposed to estimate the influence of freezing drizzle on different size ranges of fog droplets. Fog droplets with a diameter less than Dc would be affected slightly by freezing drizzle, while larger fog droplets would be affected significantly. Dc had a correlation with the average rain intensity, with a correlation coefficient of 0.78. The relationships among the microphysical properties of fog droplets were all positive when the effect of freezing drizzle was weak, while they became poor positive correlations, or even negative correlations during freezing drizzle period. The direct contribution of freezing drizzle to ice thickness was about 14.5%. Considering both the direct and indirect effects, we suggest that freezing drizzle could act as a "catalyst" causing serious icing conditions. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg. Source

Numerical simulations with version 3.2 of the Weather Research and Forecasting (WRF) Model are performed to study a localized extremely heavy rainfall event during midsummer in central China. The event occurred in a complex topographical area on 3 July 2008. The extremely heavy rainfall was produced by a quasi-stationary back-building mesoscale convective system (MCS), which was initiated and developed in the exit region of a low-level jet (LLJ). The main mesoscale dynamical process responsible for the MCS formation was the low-level convergence directly generated by the LLJ. The gravity waves excited by the unbalanced dynamics due to the LLJ's abrupt intensification might be another dynamical factor for the MCS initiation. The LLJ was of obvious diurnal variation, which was nearly in an opposite phase with the variations of the planetary boundary layer (PBL) height and of the surface heat and moisture fluxes. The diurnal variation of the LLJ was mainly dominated by the solar-radiation-driven evolution of the PBL height and the surface heat fluxes below the LLJ. The dynamical uplifts forced by the Wufeng mountainous area and the Wushan Mountain were favorable for the formation and development of MCS. The topographic Froude number was less than one at night due to the increase of atmospheric stability in the lower level. The LLJ was blocked mainly by the Dabashan Mountain, and partly by the Wufeng mountainous area and the Wushan Mountain, leading to the MCS in the exit region of the LLJ to remain quasi-stationary and produce the localized extremely heavy rainfall. © 2012 Elsevier B.V. Source

Yang H.,Nanjing University of Information Science and Technology | Yang H.,Institute of Heavy Rain | Jiang Z.,Nanjing University of Information Science and Technology | Li L.,Laboratoire Of Meteorologie Dynamique
Climate Dynamics

A dynamical downscaling is performed to improve the regional climate simulation in China. It consists of using a variable resolution model LMDZ4 nested into three global climate models (GCMs): BCC-csm1-1-m, FGOALS-g2 and IPSL-CM5A-MR, respectively. The regional climate from different simulations is assessed in terms of surface air temperature and rainfalls through a comparison to observations (both station data and gridded data). The comparison includes climatic trends during the last 40 years, statistical distribution of sub-regional climate, and the seasonal cycle. For surface air temperature, a significant part of the improvement provided by LMDZ4 is related to the effect of surface elevation which is more realistic in high-resolution simulations; the rest is related to changes in regional or local atmospheric general circulation. All GCMs and the downscaling model LMDZ4 are, more or less, able to describe the spatial distribution of surface air temperature and precipitation in China. LMDZ4 does show its superiority, compared to GCMs, in depicting a good regional terrain including the Tibetan Plateau, the Sichuan Basin and the Qilian Mountains. © 2016 Springer-Verlag Berlin Heidelberg Source

Zhang R.,Chinese Academy of Meteorological Sciences | Ni Y.,Chinese Academy of Meteorological Sciences | Liu L.,Chinese Academy of Meteorological Sciences | Luo Y.,Chinese Academy of Meteorological Sciences | Wang Y.,Institute of Heavy Rain
Journal of the Meteorological Society of Japan

The South China Heavy Rainfall Experiments (SCHeREX) was staged during 2008 and 2009 in the southern part of China by the Chinese Academy of Meteorological Sciences under the support of the Chinese Ministry of Science and Technology and China Meteorological Administration. SCHeREX aims at obtaining abundant observational datasets at the meso-β scale, better understanding of the structure and evolution of heavy precipitation systems in south China, exploring establishment of an operational platform for heavy rainfall monitoring and prediction, and improving the ability of heavy rainfall monitoring and prediction. Four zones were selected in SCHeREX, namely, the southern China, the middle reaches of the Yangtze River valley, the Huai River valley, and the lower reaches of the Yangtze River valley. The observation phases were May 1-June 10 in the southern China zone and June 10-July 20 in the other three zones. The efforts have led to the establishment of the meso-β scale observing networks with enhanced capacity to observe precipitation systems at the meso- β scale level. The collected data have been utilized in meso-β scale reanalysis not only to reveal the fine structures of the precipitation systems but also to provide better initial conditions for meso-β scale numerical models to make short-term forecasts. Assimilation of the dropsonde data has improved the analysis of the locations and intensities of typhoons Goni and Morakot. With the real-time field data being part of the forecast system, the experiments have allowed more efficient interactions between the observing system and the forecast system and thus improve the performance of meso-β scale heavy rainfall forecasts. © 2011, Meteorological Society of Japan. Source

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