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41.
QING SEN LI ) YU MEI JIN ) ZHI CHENG MIAO ) WEN ZHONG JIA ) GUI CAI JIANG ) ) Zhangjiakou Meteorological Observatory of Hebei Province Zhangjiakou China ) Forth Middle School of Zhangjiakou 《地震学报(英文版)》1998,(6)
IntroductionAteighttotwelveo′clockonJanuary10,1998,thereoccuredastrongearthquakeofMS=6.2atZhangbeiCountyinthenorthwesternpar... 相似文献
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对咸阳机场的两次能见度突然转差的天气进行分析比较,探讨该类形势下大雾的成因及周边地理环境对成雾的影响,并对此类天气的预报思路提出几点建议。 相似文献
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2009年石家庄暴雪过程降雪雷达估测 总被引:1,自引:1,他引:0
介绍了天气形势和采用多普勒雷达资料进行降雪估测的原理,利用雷达与降雪加密观测资料,对2009年11月10—12日石家庄地区暴雪过程采用卡尔曼滤波法进行降雪估测。研究表明:①卡尔曼滤波降雪估测法对石家庄地区的降雪估测效果较好,尤其是对较强降雪(大于等于2 mm/h)的估测。②采用卡尔曼滤波估测法对石家庄地区进行降雪估测,要根据不同的地理特征和雷达反射率因子、回波顶高等特征采用不同的仰角进行降雪估测,与雷达降水估测的仰角选取有一定的差别。因此,充分利用雷达产品与降雪加密观测资料能够估测降雪分布,可以为决策服务提供一定的科学依据。 相似文献
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Data from in situ probes and a vertically-pointing mm-wave Doppler radar aboard a research aircraft are used to study the cloud microphysical effect of glaciogenic seeding of cold-season orographic clouds. A previous study (Geerts et al., 2010) has shown that radar reflectivity tends to be higher during seeding periods in a shallow layer above the ground downwind of ground-based silver iodide (AgI) nuclei generators. This finding is based on seven flights, conducted over a mountain in Wyoming (the Unites States), each with a no-seeding period followed by a seeding period. In order to assess this impact, geographically fixed flight tracks were flown over a target mountain, both upwind and downwind of the AgI generators. This paper examines data from the same flights for further evidence of the cloud seeding impact. Composite radar data show that the low-level reflectivity increase is best defined upwind of the mountain crest and downwind of the point where the cloud base intersects the terrain. The main argument that this increase can be attributed to AgI seeding is that it is confined to a shallow layer near the ground where the flow is turbulent. Yet during two flights when clouds were cumuliform and coherent updrafts to flight level were recorded by the radar, the seeding impact was evident in the flight-level updrafts (about 610 m above the mountain peak) as a significant increase in the ice crystal concentration in all size bins. The seeding effect appears short-lived as it is not apparent just downwind of the crest. 相似文献
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张恒德 《沙漠与绿洲气象(新疆气象)》2013,7(1):1-8
本文主要对2010年3月14日华北强降雪进行了模拟、诊断和特征分析。此次华北降雪在中、低层主要受西风槽、低涡及切变线影响,蒙古气旋东移加强、地面倒槽发展及东风廽流建立构成了有利地面天气形势,西北涡、强势的西南暖湿气流及稳定的环渤海高压对此次强降雪至关重要。垂直速度、散度、涡度、螺旋度的分布和演变反映出在此次降雪过程中,强降雪区出现了很强的辐合上升运动,降雪区上空螺旋度呈“下负上正”的垂直结构,螺旋度大值区对应强降雪中心;而锋生条件为降雪的形成和维持提供了一定的能量;相对湿度和水汽通量散度的分布说明强降雪区整层湿度较大,且水汽供应充足。 相似文献
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Snowfall and the subsequent evolution of the snowpack have a large effect on the surface energy balance and water cycle of the Tibetan Plateau (TP). The effects of snow cover can be represented by the WRF coupled with a land surface scheme. The widely used Noah scheme is computationally efficient, but its poor representation of albedo needs considerable improvement. In this study, an improved albedo scheme is developed using a satellite-retrieved albedo that takes snow depth and age into account. Numerical experiments were then conducted to simulate a severe snow event in March 2017. The performance of the coupled WRF/Noah model, which implemented the improved albedo scheme, is compared against the model’s performance using the default Noah albedo scheme and against the coupled WRF/CLM that applied CLM albedo scheme. When the improved albedo scheme is implemented, the albedo overestimation in the southeastern TP is reduced, reducing the RMSE of the air temperature by 0.7°C. The improved albedo scheme also attains the highest correlation between the satellite-derived and the model-estimated albedo, which provides for a realistic representation of both the snow water equivalent (SWE) spatial distribution in the heavy snowbelt (SWE > 6 mm) and the maximum SWE in the eastern TP. The underestimated albedo in the coupled WRF/CLM leads to underestimating the regional maximum SWE and a consequent failure to estimate SWE in the heavy snowbelt accurately. Our study demonstrates the feasibility of improving the Noah albedo scheme and provides a theoretical reference for researchers aiming to improve albedo schemes further. 相似文献
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本文利用1960~2020年共61年遵义市12个国家站点的地面观测日资料和一般统计学方法对遵义市降雪时空分布特征做出分析,并利用NCEP(美国国家环境预报中心)再分析资料分析了遵义市3次暴雪个例的环流特征。结果表明:遵义市1960~2020年降雪年变化呈波动变化特征,整体呈下降趋势。月平均降雪日数呈现单峰特征,1月份达到峰值。各站点月降雪日数1月和2月明显多于其他月份。空间上,西北方向的习水到东部的凤冈一线降雪日数较多,大部分站点降雪日数分布与站点海拔正相关。另外,遵义市2000年以来的暴雪个例都是暖湿气流在冷垫上爬升,造成暴雪天气。 相似文献