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结合数值试验结果对台风Megi(2010)不同半径内的位涡倾向(potential vorticity tendency,PVT)质心位置变化与台风移动的关系进行了探讨,并对PVT方程中不同因子影响PVT质心位置的作用范围进行了研究。结果表明,较小台风半径内的正PVT质心位置变化与台风移动具有较好对应关系,可指示"Megi"转向,较大台风半径内的PVT分布变化虽不直接指示"Megi"转向,但可反映对应区域内大气动力、热力状况发生了有利于"Megi"转向的调整。PVT质心移动受位涡水平平流项的影响较大,受垂直平流项和非绝热加热项的影响相对较小,PVT方程中与台风内部对流活动有关的垂直平流项和非绝热加热项可对"Megi"中心附近PVT分布产生影响,而与台风水平环流有关的水平平流项除可对较小台风半径内PVT分布造成影响外,还可将台风位涡向外输送,是导致不同半径内PVT质心位置差异的主要原因。 相似文献
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Based on the annual frequency data of tropical cyclones from 1960 to 2005 and by the polynomial fit and statistical analysis, this work has discovered that TC activity in the 46a exhibits significant decadal- scale variability. It has two high frequency periods (HFP) and two low frequency periods (LFP). Significant differences in the number of TCs between HFP and LFP are found in active TC seasons from July to October. Differences of large-scale circulation during HFP and LFP have been investigated with NCEP/NOAA data for the season. In HFP, the condition includes not only higher sea surface temperature,lower sea level pressure, larger divergence of upper air, larger relative vorticity at low levels and smaller vertical shear, but also 500-hPa wind vector being more available for TC activity and moving to western North Pacific, the position of the subtropical anticyclone over the western Pacific shifting more northward,and South Asian Anticyclone at 100-hPa being much smaller than that in LFP. The precipitation of western North Pacific has no clear influence on TC activity. 相似文献
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本文利用WRF模式,通过开展敏感性试验讨论了单个热带气旋（Tropical Cyclone, TC）——“鲇鱼（Megi）”影响下不同等压面上西太平洋副热带高压脊线的移动特征,并分析了Megi活动影响副高脊线垂直分布的可能机理。结果表明,Megi活动期间,副高脊线在TC的影响下总体发生了向南移动,且TC活动所导致的脊线南移在高层相对较大,而在低层相对较小。TC影响副高脊线垂直分布的可能机理为,副高脊线的经向运动受其附近纬向风异常的直接影响,而Megi活动所导致的脊线附近纬向风异常与温度异常总体满足热成风关系,当Megi活动造成副高脊线附近出现温度经向梯度异常时,纬向风异常会随高度增加而发生切变,因此会导致副高脊线的垂直分布状况发生改变。另外,利用温度倾向方程的诊断分析结果表明,TC活动所激发的脊线附近不同物理过程项的异常在时空剖面上有很大区别,其中温度水平平流异常和非绝热加热异常的作用主要可使大气温度异常升高,而温度的垂直输送异常则可使温度降低。总之,TC的热力效应对西太平洋副热带高压脊线垂直分布的影响十分显著。 相似文献
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利用2006—2013年南京站、安庆站和杭州站探空资料,讨论华东地区探空气球的漂移特征。设计不考虑气球漂移、考虑全部气球漂移和考虑部分气球漂移3个试验,比较3种情况下三角形法计算的散度差异。结果表明:气球漂移主要受大气环流及其变化影响,纬向上7月和8月气球随高度增加,先向东漂移、后向西漂移,其他月份以向东漂移为主,冬季漂移距离大;经向上受季风影响明显。考虑全部和部分气球漂移与不考虑气球漂移的散度对比表明,平均绝对偏差各月在对流层顶附近均有极大值;相对偏差季节分布明显,前者在6—9月较大,极大值略大于7%,后者冬季大,1月在200 hPa达到25%,在50 hPa超过50%。因此,利用三角形法计算散度所在层次较高或所使用资料中传统探空和特种探空并存时,均需考虑气球漂移影响。 相似文献
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In order to achieve the best predictive effect of the Partial Least Squares (PLS) regression model, Particle Swarm Optimization (PSO) algorithm is applied to automatically filter the optimal subset of a set of candidate factors of PLS regression model in this study. An improved version of the Particle Swarm Optimization-Partial Least Squares (PSO-PLS) regression model is applied to the station data of precipitation in Southwest China during flood season. Using the PSO-PLS regression method, the prediction of flood season precipitation in Southwest China has been studied. By introducing the precipitation period series of the mean generating function (MGF) extension as an alternative factor, the MGF improved PSO-PLS regression model was also build up to improve the prediction results. Randomly selected 10%, 20%, 30% of the modeling samples were used as a test trial; random cross validation was conducted on the MGF improved PSO-PLS regression model. The results show that the accuracy of PSO-PLS regression model and the MGF improved PSO-PLS regression model are better than that of the traditional PLS regression model. The training results of the three prediction models with regard to the regional and single station precipitation are considerable, whereas the forecast results indicate that the PSO-PLS regression method and the MGF improved PSO-PLS regression method are much better than the traditional PLS regression method. The MGF improved PSO-PLS regression model has the best forecast performance on precipitation anomaly during the flood season in the southwest of China among three models. The average precipitation (PS score) of 36 stations is 74.7. With the increase of the number of modeling samples, the PS score remained stable. This shows that the PSO algorithm is objective and stable. The MGF improved PSO-PLS regression prediction model is also showed to have good prediction stability and ability. 相似文献
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珲春煤田下含煤段沉积与聚煤特征 总被引：2，自引：0，他引：2
从收集整理以往资料入手，阐述了煤层分布特征，分析珲春煤田下含煤段的沉积与聚煤特征，即下含煤段第一阶段沉积特征以冲积扇、河流、小型湖泊沉积为主，形成的煤层结构复杂、稳定性差；第二阶段沉积特征以三角洲平原沉积为主，形成的煤层分布面积较大、结构较简单、稳定性较好。聚煤特征为富煤带位于盆地的中西部，富煤中心位于向斜(凹陷)核部。得出同沉积构造控制盆地的沉积环境，沉积环境直接控制聚煤作用的结论。今后的找煤工作应依据聚煤规律，采用物探和钻探相结合的方法较为适宜。 相似文献
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青藏高原东西部积雪效应的模拟对比分析 总被引：7，自引：1，他引：6
采用引入次网格尺度地形重力波拖曳的NCAR区域气候模式(RegCM2),以SMMR微波逐候积雪深度观测值为依据,加入较合理的积雪强迫,通过数值模拟,研究了青藏高原(下称高原)东、西部积雪异常对后期区域环流的不同影响。模拟结果的对比分析表明,高原西部多雪对高原东部积雪存在正的反馈作用,有利于高原东部积雪的增加,而高原东部多雪对高原西部积雪的影响很小。高原西部积雪偏多和高原东部积雪偏多对后期大气温度场和高度场的影响具有基本相同的分布形态,只是影响强度有所不同。高原西部积雪的融化要迟于高原东部积雪,高原西部积雪效应的持续性较强。另外,高原西部多雪对高原东部积雪存在正的反馈作用,高原东部积雪的增加进一步加大了整个高原积雪的异常,因此,高原西部积雪偏多对后期环流的综合影响明显大于高原东部积雪偏多的影响。 相似文献