淮河流域(河南段)连续性暴雨天气分型及环流背景          下载免费PDF全文

梁钰  王君  吴璐 《气象与环境科学》2019,42(2):48-54

利用19812016年68月河南省淮河流域64个国家自动观测站逐日2020时日降水量资料、常规高空探测和地面观测资料等对淮河流域连续性暴雨时间分布特征、影响系统等进行分析和天气分型,结果表明:1)36年淮河流域共发生45次连续性暴雨,2000年的最多,19982008年是高发期,近10年较少,年出现次数无明显减少趋势,存在2~4年和4~6年两个周期;7月连续性暴雨次数最多,6月的最少,旬分布呈正态分布;最长连续时间5天,连续2天的最多。2)影响系统主要有切变线和高低空急流,高空急流在方向转换的过程中,降水有24h左右的减弱期,低空急流有明显的日变化特征,夜间加强,白天减弱。3)连续性暴雨按照500hPa影响系统,分为低槽型、副高边缘型、西北低涡型三类。4)以不同类型的3次典型连续性暴雨为例,从大尺度环流背景、高度距平场、水汽输送、高低空急流等方面探讨了连续性暴雨的维持成因,3次连续性暴雨的发生与异常的500hPa大气环流、高低空急流、切变线和持续偏强的水汽输送等有关。  相似文献   

提高模式分辨率后热带气旋生成迟缓的原因分析          下载免费PDF全文

赵静娴  吴立广  段晶晶 《大气科学学报》2019,42(5):680-694

利用目前国际上最先进的中尺度WRF模式模拟热带气旋生成,网格分辨率从9 km增加到3 km,3 km网格中积云参数化方案不起作用,依靠微物理方案来模拟对流尺度系统特征,模式中热带气旋的生成过程变得迟缓。当低压扰动发展到一定程度后再加入3 km网格,生成过程有加快趋势。本研究针对该现象进行分析。结果表明:只用微物理方案使低层(950～700 hPa)风速的垂直切变减小,不利于对流发展;切变减小主要是由于动量垂直输送项的差异所致。在加入细网格的6 h内,低层对流尺度(减去区域平均)的动量垂直输送量平均增加了一倍,某些时刻达到了5倍以上;动量混合增加是由于微物理方案模拟的垂直速度增加所致。此外,只用微物理方案导致对流有效位能迅速被消耗。低层垂直切变和对流有效位能的减小都不利于对流发展,从而导致热带气旋生成发展过程迟缓。本研究表明,目前WRF中的微物理方案在模拟热带气旋生成过程中的对流发展时仍然存在问题。  相似文献   

基于多普勒天气雷达的低空多普勒速度的切变识别算法研究   总被引：1，自引：0，他引：1  

闫文辉  黄兴友  李盈盈  杨敏  刘燕斐 《热带气象学报》2019,35(2):253-261

低空风切变是影响航空器起飞和着陆安全的重要因素,利用多普勒天气雷达径向速度数据,从风的空间和时间变化上对低空风切变的识别进行了研究,并利用一次飑线过程和一次低空急流过程的资料对识别算法进行了验证。识别算法的核心是分别计算二维合成风切变、垂直风切变和时间风切变。在计算二维合成风切变时,先利用风切变强度因子自适应地选择拟合“窗口”的大小,再利用最小二乘线性拟合方法,得到水平风切变。结果表明:自适应多尺度最小二乘法得到的合成风切变,在低空风切变识别效果、切变连续性和边缘数据处理等方面都优于我国多普勒天气雷达的PUP合成风切变;垂直风切变反映了雷达径向速度的高低空配置情况;时间风切变可提供径向速度随时间的变化情况。算法还可应用于民航机场低空风切变的识别和预警。   相似文献   

台风Chanchu(0601)变性过程中的强度变化及环境场分析     

刘珍圆  王咏青  张秀年  周玉淑 《热带气象学报》2019,35(4):528-538

利用非静力中尺度WRF模式模拟的台风Chanchu(0601)的输出资料,探讨了Chanchu减弱变性过程的强度及结构变化。分析结果表明:在台风Chanchu北移过程中,高层的暖心被破坏,强度快速减弱,眼壁对流发展高度降低,眼壁对流由对称结构演变为非对称,内核对流减弱。此减弱变性过程与惯性稳定度减小、垂直风切变增强、低层锋生等环境要素有关。惯性稳定度与台风强度变化一致,随着惯性稳定度降低,最大切向风减弱并不断外扩,Rossby变形半径增大从而潜热释放不集中难以维持台风强度,台风减弱;同时,内核区的高层暖心更易径向频散,从而高层暖心难以维持;环境的垂直风切变增强使台风的斜压性增强,台风垂直结构的倾斜度增大,对流发展高度降低;低层冷空气侵入台风中心趋于填塞,也利于台风强度减弱;台风登陆以后冷暖空气对比导致的锋生使得不稳定能量释放从而重新加强了Chanchu环流内的中低层对流活动,但较台风最强时刻而言对流强度减弱。总体减少的对流和降低的对流高度,导致潜热能释放减小,其向心输送也减少,不足以维持强暖心结构,最终使得台风减弱并变性。   相似文献   

暴雨过程中逆风区特征及应用判据研究          下载免费PDF全文

赵海军  李柏  潘玲  吴志彦  王庆华 《山东气象》2019,39(2):126-133

为研究暴雨过程中逆风区特征及应用判据,统计分析2010—2017年山东临沂地区暴雨过程中的多普勒雷达观测资料,结果表明：暴雨过程中,风暴内的垂直环流是造成逆风区发生发展的直接原因;逆风区表现为β中尺度和γ中尺度,其形态在不同天气类型下有明显差异;逆风区持续阶段降水强度增大,持续时间与过程累积雨量呈正相关;当雷达最低仰角识别到逆风区,其厚度≥4.0 km、强度≥15 m·s-1、径向速度绝对值最大值≥5 m·s-1且持续30 min以上时,风暴常明显发展,相关特征可用于预报风暴和暴雨的发展。  相似文献   

俯冲带地震诱发机制:研究进展综述   总被引：4，自引：0，他引：4  

邵同宾  嵇少丞 《地质论评》2015,61(2):245-268

俯冲带作为地球循环体系的关键部位,具有构造活跃、地震多发以及地质条件复杂等特征。基于震源位置,俯冲带地震既可划分为板间和板内地震,也可分为浅源、中源和深源地震。俯冲带内的浅源地震包括板间地震和浅源板内地震,而中源和深源地震皆属于板内地震。在地球浅部,温度与压力低,浅源地震是由岩石发生脆性破裂或沿着先存断层发生不稳定摩擦滑移造成的。随着深度增加,温度和压力的增加使得流行于浅部的脆性和摩擦行为在无水条件下被强烈抑制,岩石从而表现为可抑制地震的韧性行为,使得中-深源地震的诱发机制有别于常规的脆性行为。随着研究的逐渐深入,人们了解到中源地震的诱发机制主要是脱水或与流体相关的致脆以及塑性剪切失稳,而深源地震的成因主要是相变致裂。然而,中-深源地震很可能是两种或两种以上机制共同作用的结果。例如,在中源深度既可能是流体相关的致脆导致脱水源区的脆性围岩产生地震,亦可能是脱水的蛇纹岩本身可能在流体孔隙压的作用下作粘滑滑移,而前者比后者更为重要。孕震带宽度大于"反裂隙模型"预测的亚稳态橄榄石冷核宽度的深源地震可能是由第一阶段的相变致裂和第二阶段的塑性剪切失稳诱发,而孕震带的实际宽度与预测宽度相当的深源地震则可能仅由相变致裂引起。只要过渡带内名义无水矿物中的结构水能释放出来,脱水致脆同样可能触发一些深源地震;而塑性剪切失稳不仅能在中-深源地震触发后的扩展阶段起着主导作用,而且还能单独触发一些中-深源地震,因此能够解释大多数反复发生的中-深源地震活动。  相似文献   

New interpretation of the Franciscan mélange at San Simeon coast,California: tectonic intrusion into an accretionary prism     

Yujiro Ogawa  Ryota Mori  Toshiaki Tsunogae  Yildirim Dilek  Ron Harris 《International Geology Review》2015,57(5-8):824-842

Many concepts and interpretations on the formation of the Franciscan mélange have been proposed on the basis of exposures at San Simeon, California. In this paper, we show the distribution of chaotic rocks, their internal structures and textures, and the interrelationship between the chaotic rocks and the surrounding sandstones (turbidites). Mélange components, particularly blueschists, oceanic rocks, including greenstone, pillow lava, bedded chert, limestone, sandstone, and conglomerate, have all been brecciated by retrograde deformation. The Cambria Slab, long interpreted as a trench slope basin, is also strongly deformed by fluidization, brecciation, isoclinal folding, and thrusting, leading us to a new interpretation that turbiditic rocks (including the Cambria Slab) represent trench deposits rather than slope basin sediments. These rocks form an accretionary prism above mélanges that were diapirically emplaced into these rocks first along sinistral-thrust faults, and then along dextral-normal faults. Riedel shear systems are observed in several orders of scale in both stages. Although the exhumation of the blueschist blocks is still controversial, the common extensional fractures and brecciation in most of the blocks in the mélanges and further mixture of various lithologies into one block with mélange muddy matrix indicate that once deeply buried blocks were exhumed from considerable depths to the accretionary prism body, before being diapirically intruded with their host mélange along thrust and normal faults, during which retrograde deformation occurred together with retrograde metamorphism. Recent similar examples of high-pressure rock exhumation have been documented along the Sofugan Tectonic Line in the Izu forearc areas, in the Mineoka belt in the Boso Peninsula, and as part of accretionary prism development in the Nankai and Sagami troughs of Japan. These modern analogues provide actively forming examples of the lithological and deformational features that characterize the Franciscan mélange processes.  相似文献   

大同盆地形成机制的构造研究   总被引：1，自引：0，他引：1  

岑敏  董树文  施炜  周涛发  陈龙  陈兴强 《地质论评》2015,61(6):1235-1247

大同盆地为位于华北地块中部的新生代断陷盆地,自中新世晚期以来经历了持续的强烈伸展作用。基于边界断裂滑动的运动学及动力学分析,结合对本区新生界沉积地层与玄武岩资料的总结归纳以及对区域动力学背景的讨论,本文提出了大同盆地的形成机制:自10~8 Ma以来,鄂尔多斯地块东北缘形成NW向伸展的构造应力场,其中σ1垂直,σ2、σ3水平,σ2的方位角为60°,σ3方位角为150°,此构造应力场控制边界断裂的运动,形成NE向大同断陷盆地。盆地的形成对应岩石圈减薄深部过程,可能受到了印度——欧亚板块碰撞、太平洋——欧亚板块碰撞板缘动力作用的影响。本文将岩石圈浅部构造应力场与深部地幔活动结合起来综合分析大同盆地的形成机制,并提出了一些新的认识:控制大同盆地形成的正断型构造应力场不同于华北区域性走滑型构造应力场;首次测得了与地幔活动相关的大同火山群大峪口玄武岩K-Ar年龄为0.68±0.13Ma;大同盆地具有板内狭窄型裂谷的构造特征。本文为建立鄂尔多斯地块东缘山西地堑系的运动学和动力学模型提供新的依据。  相似文献   

An equilibrium cloud-resolving modeling study of diurnal variation of tropical rainfall     

《Dynamics of Atmospheres and Oceans》2015

The diurnal variation of tropical rainfall is examined through the analysis of an equilibrium cloud-resolving model experiment. Model domain mean rain rate is defined as a product of rain intensity and fractional rainfall coverage. The diurnal variation of the mean rain rate is associated with that of fractional rainfall coverage because the diurnal variation of rain intensity is significantly weakened through the decrease in rainfall in early morning hours. The decrease in rainfall corresponds to the reduction in secondary circulations through the barotropic conversion from the perturbation kinetic energy to the mean kinetic energy under the imposed negative vertical gradient of westerly winds. The fractional rainfall coverage shows the diurnal signal with the maximum in the early morning hours primarily due to nocturnal infrared radiative cooling.  相似文献   

A diagnostic analysis on the effect of the residual layer in convective boundary layer development near Mongolia using 20th century reanalysis data   总被引：1，自引：0，他引：1  

Bo Han  Cailing Zhao  Shihua Lü  Xin Wang 《大气科学进展》2015,32(6):807-820

Although the residual layer has already been noted in the classical diurnal cycle of the atmospheric boundary layer,its effect on the development of the convective boundary layer has not been well studied. In this study, based on 3-hourly20 th century reanalysis data, the residual layer is considered as a common layer capping the convective boundary layer. It is identified daily by investigating the development of the convective boundary layer. The region of interest is bounded by(30°–60° N, 80°–120° E), where a residual layer deeper than 2000 m has been reported using radiosondes. The lapse rate and wind shear within the residual layer are compared with the surface sensible heat flux by investigating their climatological means, interannual variations and daily variations. The lapse rate of the residual layer and the convective boundary layer depth correspond well in their seasonal variations and climatological mean patterns. On the interannual scale, the correlation coefficient between their regional averaged(40°–50°N, 90°–110° E) variations is higher than that between the surface sensible heat flux and convective boundary layer depth. On the daily scale, the correlation between the lapse rate and the convective boundary layer depth in most months is still statistically significant during 1970–2012. Therefore, we suggest that the existence of a deep neutral residual layer is crucial to the formation of a deep convective boundary layer near the Mongolian regions.  相似文献