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1.
Medicanes, strong mesoscale cyclones with tropical-like features, develop occasionally over the Mediterranean Sea. Due to the scarcity of observations over sea and the coarse resolution of the long-term reanalysis datasets, it is difficult to study systematically the multidecadal statistics of sub-synoptic medicanes. Our goal is to assess the long-term variability and trends of medicanes, obtaining a long-term climatology through dynamical downscaling of the NCEP/NCAR reanalysis data. In this paper, we examine the robustness of this method and investigate the value added for the study of medicanes. To do so, we performed several climate mode simulations with a high resolution regional atmospheric model (CCLM) for a number of test cases described in the literature. We find that the medicanes are formed in the simulations, with deeper pressures and stronger winds than in the driving global NCEP reanalysis. The tracks are adequately reproduced. We conclude that our methodology is suitable for constructing multi-decadal statistics and scenarios of current and possible future medicane activities. 相似文献
2.
A statistical comparative analysis of tropical cyclone activity over the Arabian Sea and Bay of Bengal (BoB) has been conducted using best-track data and wind radii information from 1977 to 2018 issued by the Joint Typhoon Warning Center. Results have shown that the annual variation in the frequency and duration of tropical cyclones has a significant increasing trend over the Arabian Sea and an insignificant decreasing trend over the BoB. The monthly frequency of tropical cyclones in both the Arabian Sea and the BoB shows a notable bimodal character, with peaks occurring in May and October–November, respectively. The maximum frequency of tropical cyclones occurs in the second peak as a result of the higher moisture content at mid-levels in the autumn. However, the largest proportion of strong cyclones (H1–H5 grades) occurs in the first peak as a result of the higher sea surface temperatures in early summer. Tropical cyclones in the Arabian Sea break out later during the first peak and activity ends earlier during the second peak, in contrast with those in the over BoB. This is related to the onset and drawback times of the southwest monsoon in the two basins. Tropical cyclones in the Arabian Sea are mainly generated in the eastern basin, whereas in the BoB the genesis locations have a meridional (zonal) distribution in May–June (October–November) as a result of the seasonal movement of the low-level positive vorticity belt. The Arabian Sea is dominated by western and northwestern tropical cyclones by that track west and NW, accounting for about 74.6%, whereas the tropical cyclones with a NE track account for only 25.4%. The proportions of the three types of tracks are similar in the BoB, with each accounting for about 33% of the tropical cyclones. The mean intensity and size of tropical cyclones over the Arabian Sea are stronger and larger, respectively, than those over the BoB and the size of tropical cyclones over the North Indian Ocean in early summer is larger than that in autumn. The asymmetrical structure of tropical cyclones over North Indian Ocean is affected by the topography and the longest radius of the 34 kt surface wind often lies in the eastern quadrant of the tropical cyclone circulation in both sea areas. FAN Xiao-ting (樊晓婷), LI Ying (李 英), et al. 相似文献
3.
Regional climate model projections over the Mediterranean region are analysed for the presence of intense, warm-core lows that share some of the characteristics of tropical cyclones. The results indicate that the number of such systems decreases in a warmer world, particularly in winter. Comparison of the simulated numbers to changes in relevant climate diagnostics suggests that numbers decrease due to an increasingly hostile environment for storm formation, combined with a general poleward shift in the incidence of wintertime lows over western Europe. 相似文献
4.
揭示热带气旋在湖南的降水规律可为热带气旋影响湖南的降水预报提供技术支撑。采用近67 a的热带气旋影响资料,通过统计方法,分析了影响湖南降水的热带气旋特点及环流异常特征。结果表明:7—9月是影响的高峰季节,以在广东、福建沿海登陆的热带气旋对湖南影响次数最多、程度最重,浙江、福建沿海登陆的热带气旋在湖南形成的降水范围最大,热带气旋对湖南影响所产生的降水主要集中在湖南省东南部,热带气旋对湖南产生的强降水范围有增大的趋势,降水强度有增强的趋势。福建和广东沿海登陆对湖南影响的热带气旋的环流特征为南亚高压偏强、偏东、偏北,导致西太平洋副热带高压偏强、偏西、偏北,引导副热带高压南侧的东南气流与南海和菲律宾以东洋面的西南风气流汇合,形成季风槽,中国华南和华东沿海为东南气流,有利于热带气旋在该区域登陆影响中国。只是前者表现为南亚高压位置较后者偏北更明显,西太平洋副热带高压更偏北,季风槽更偏东,导致福建登陆对湖南影响的热带气旋在湖南大部为气旋性环流控制,湖南全省降水偏多;而广东登陆对湖南影响的热带气旋在湖南省东南部为气旋性环流控制,该区域降水偏多。 相似文献
5.
登陆热带气旋长久维持与迅速消亡的大尺度环流特征 总被引：61，自引：9，他引：61
采用动态合成分析方法 ,对登陆后长久维持热带气旋 (LTC)和迅速消亡热带气旋 (STC)的大尺度环流特征进行合成分析和动力诊断。研究表明 :(1)LTC登陆后 ,在一个长波槽前有向偏北移动靠近中纬度斜压锋区的趋势 ,而STC登陆后 ,无长波槽靠近 ,并远离中纬度斜压锋区 ;(2 )LTC登陆后 ,仍与一支低空急流水汽输送通道连结 ,而STC登陆后很快与这支水汽通道分离 ;(3)LTC登陆后逐渐变性 ,获取斜压能量 ,其环境风垂直切变增强 ,Δζ2 0 0 -850负值增大 ,而STC登陆后没有这样的特征 ;(4 )LTC登陆后 ,其高层与中纬度急流靠近 ,增强了其向东北方向的高空流出气流 ,而STC不存在这样一支流出气流 ;(5 )LTC登陆后 ,摩擦使其能量耗损 ,但从中高层环境中获得了能量 ,而STC登陆后 ,有同样的能耗却无明显的环境能量补给。因此 ,当一个热带气旋登陆后 ,从其移动趋势、与水汽通道的连结、与斜压锋区的关系和高空流出气流等特征 ,可以初步判断其是长久维持还是迅速衰减。 相似文献
6.
采用恒定的现代外部强迫驱动第一版NUIST地球系统模式,进行了40年全球热带气旋活动模拟,分析了热带气旋活动的气候特征,并与1977—2016年观测资料对比分析。结果表明：该模式能够模拟出与热带气旋类似的结构特征,在热带气旋活动活跃的海区,模拟热带气旋生成的空间分布和影响范围与观测基本一致,但是各个海区热带气旋的生成频数与观测还存在差异。除了北印度洋海区,各个海区热带气旋生成频数的季节变化与观测相似。模式在西北太平洋海区模拟结果最好,能模拟出热带气旋的生成范围和盛行路径;在北印度洋地区模拟结果较差,北印度洋海区的相对涡度模拟与观测存在较大差异,这是模式未能模拟出北印度洋热带气旋双峰特征的主要原因。 相似文献
7.
广东热带气旋降水年代际变化特征的分析 总被引：4，自引：3，他引：1
采用1951—2005年热带气旋和广东省26个测站降水的观测资料,分析了广东热带气旋及其降水的年代际变化特征。结果表明:广东热带气旋降水存在峰值为25年左右的振荡周期,影响广东的热带气旋个数和西北太平洋上热带气旋的形成个数都存在峰值为23年左右的振荡周期;广东热带气旋降水的年代际变化与影响广东的热带气旋个数和西北太平洋上热带气旋的形成个数存在高度正相关;广东热带气旋降水的年代际变化与西太平洋部分区域的年平均SST的年代际变化和北太平洋中高纬部分地区的年平均500 hPa位势高度的年代际变化存在显著的负相关;广东热带气旋降水偏少时期与降水偏多时期相比,一般赤道中、东太平洋的平均SST相对较高,而北太平洋中纬度地区的平均SST相对较低,北太平洋上的东亚大槽相对较强。 相似文献
8.
利用1951—2006年西北太平洋 (含南海) 热带气旋资料, 研究了不同强度热带气旋的气候变化特征。结果表明:超强台风 (近中心最大风速≥58m/s, 简称超强台风Ⅱ) 频数、强度和初、终旋日期的变化特征都不同于其他级别热带气旋; 西北太平洋热带气旋的总频数有长期减少趋势, 主要由热带低压和超强台风Ⅱ的长期减少趋势引起; 随着热带气旋强度增强, 出现月最大频数的月份逐渐推迟; 超强台风月频数最大值发生在秋季; 超强台风Ⅱ频数的年变化与除了超强台风Ⅰ(近中心最大风速为51~58m/s) 外的其他级别热带气旋反相关; 受超强台风Ⅱ减少影响, 热带气旋年平均最大风速有减小的长期趋势; 热带气旋的初、终旋日期没有显著的长期变化趋势, 但超强台风Ⅱ的初旋日期有推迟趋势, 终旋日期有提前趋势, 发生时间缩短。 相似文献
9.
登陆广东热带气旋中尺度降水分布变化特征 总被引：11，自引：1，他引：10
利用每小时地面观测资料和卫星遥感资料 ,以 1 999～ 2 0 0 1年在珠江三角洲地区登陆的热带气旋为研究对象 ,从合成分析和个例分析两方面揭示了登陆广东热带气旋降水的中尺度特征及其分布变化。结果表明 ,热带气旋登陆前后中尺度强降水分布发生明显变化 ,登陆后降水不对称性加大 ;热带气旋登陆后中尺度强降水分布随时间变化 ,登陆后第 1 0个小时之前 ,中尺度强降水基本上分布于热带气旋中心附近 ;而热带气旋登陆第 1 0个小时之后 ,中尺度强降水具有明显的“离心”或“偏心”特征。 相似文献
10.
A. E. Pokhil 《Russian Meteorology and Hydrology》2012,37(5):307-314
Studied is the evolution of the family of tropical cyclones in the Pacific Ocean in 2009. Analyzed is an unusual behavior of real simultaneously existing tropical cyclones (TCs). Investigated is a mechanism of the interaction between a pair of tropical cyclones of various intensities. Considered are the cases of triple interaction between a pair of TCs and the polar front, as well as the transformation and regeneration of TCs due to their entry to the cold front area. The dynamics of groups of real tropical cyclones is compared with the behavior of ideal cyclonic vortices in the experiments with the numerical model. Proposed are the variants of explaining the disappearance and formation of vortices, as well as of loops, zigzags, and sharp turns during their movement. 相似文献
11.
运用美国NOAA-16极轨气象卫星高分辨率的AMSU探测资料和邻近时刻的NCEP数值预报资料，对2002年6月10日至9月10日发生在西北太平洋上的12个热带气旋生命史中的部分时次作了热力结构分析。发现AMSU资料不仅能够敏感地探测到不同强度热带气旋的多种地球物理参数，并且通过对这些参数的进一步处理，能够展示出它们各自重要的热力结构特征；由不同强度热带气旋对流层中上层暖异常区的高度、强度、范围和形状的差异以及其对流层上层温度负距平的高度、大小和分布不同，结合相应的湿度场结构特征，可以探寻其热力结构与气压变化之间的内在联系，通过这种热力结构的变化趋势可以进一步揭示出热带气旋未来的强度变化。 相似文献
12.
Over south-eastern Europe, severe weather events are often associated with Mediterranean cyclones. This paper presents a climatic study of severe storms over Bulgaria produced by synoptic-scale Mediterranean cyclones, which are the main high-impact weather systems for the region during the winter season. The study is based on a synoptically oriented data set that contains systematic information about the pronounced Mediterranean cyclones including their life and trajectories over the Mediterranean area and the severe storms over Bulgaria produced by them. The definition of a severe storm is a storm in which the wind speed and precipitation exceed thresholds of 15 m/s and 30 mm/24 h, respectively. The observed severe storms were split into two groups by the number of districts where they have caused damages. During the last years a trend of decreasing numbers of initiating synoptic-scale Mediterranean cyclones has been observed. However, the number of those producing a high-impact weather phenomenon over Bulgaria has increased. In these high-impact cases, the observed paths of the cyclones are connected to the specific circulation conditions over the region. In the most severe cases, almost 80% of the cyclones move through the southernmost parts of Balkan Peninsula and for a large portion of them, this motion is associated with a blocking regime in the mid-level mass field.The development of such Mediterranean cyclone cases has been studied and results are presented here. The results illustrate the synoptic-scale mechanisms for intensification of a feeding flow of Mediterranean air towards the area affected by extremely severe weather. 相似文献
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14.
利用中国气象局上海台风研究所整编的1949—2019年热带气旋数据,统计分析近71 a影响黑龙江省的热带气旋发生时间、频率、强度、移动路径等特征。结果表明：近71 a影响黑龙江的热带气旋共有77个,平均1.08个·a-1,其中有28 a没有热带气旋影响黑龙江;近10 a是黑龙江受热带气旋影响的活跃期,西北太平洋生成的热带气旋频数与影响黑龙江的频数没有直接相关关系,出现El Ni1o或La Ni1a现象时对影响黑龙江的热带气旋起抑制作用;热带气旋影响黑龙江最早出现在5月,最晚出现在9月,8月出现频率最高,“七下八中下”是每年的活跃阶段;在强度上,影响黑龙江的超强台风居多,但近年趋于减少,更多低级别的热带气旋可维持较长生命史北上产生影响;牡丹江市为黑龙江最易受热带气旋影响的地区;按移动路径可将影响黑龙江的热带气旋分为两类,分别为北上热带气旋和偏东路径热带气旋,其中北上热带气旋又可进一步分为七类,其中经朝鲜半岛东转向出现的频次最多,但对黑龙江影响相对较小;经朝鲜半岛北上和高纬东转向更容易给黑龙江带来严重的风雨影响。 相似文献
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16.
The formation of cyclones over the sea surface is driven by air-sea interaction with feedbacks on wave generation, thermohaline structures, and biochemical properties of upper-ocean layers. In the Mediterranean basin, strong cyclonic systems having tropical-like characteristics are called “medicanes”. The consequences of such events are usually assessed over the land, however, hydrographic effects are particularly difficult to be quantified mostly due to the rarity of oceanographic in-situ monitoring systems. In this study, the hydrographic effects of a high-impact medicane, crossing the central-eastern Mediterranean in late September 2018 are investigated mainly based on Argo float measurements. We traced its hydrographic fingerprint and examined its effects on the upper-layer physical properties by analyzing temperature and salinity profiles from floats that overlapped with its track. Float data is supported by satellite sea surface temperature reanalysis data and meteorological records. The synergistic effects of intense evaporation and vertical mixing mechanisms triggered by the medicane, resulted in abrupt surface cooling, especially in the Ionian and Aegean Seas. A relatively homogenous decrease of temperature in the upper 50-m-depth layer followed, along with the deepening of the mixed-layer depth, corresponding to an estimated per profile average deficit of (-2.72 ± 1.23) x 108 J m−2 in the ocean heat content. Simultaneously, significant upper-layer freshening occurred because of vertical mixing and heavy rainfall. However, a salinity increase in the subsurface waters was observed after the medicane event, which is associated with both horizontal advection and vertical mixing which followed the weakening of the Atlantic Water signal and the dominance of the Levantine Surface Water in this zone. Our findings highlight strong, short-scale hydrographic alterations made available due to the expansion of the marginal seas operational oceanographic network. 相似文献
17.
THE RELATIONSHIP BETWEEN GLOBAL WARMING AND THE VARIATION IN TROPICAL CYCLONE FREQUENCY OVER THE WESTERN NORTH PACIFIC 总被引：3，自引：1，他引：2
The relationship between global warming and the variation in tropical cyclone (TC) genesis
frequency is analyzed using the data of the Tropical Cyclone Year Book by the China Meteorological
Administration and the National Centers for Environmental Prediction (NCEP) reanalysis data from 1949
to 2007. The observational results indicate that the average sea surface temperature (SST) in the
Intertropical Convergence Zone (ITCZ) region (10°N – 20°N, 100°E – 140°E) increases by 0.6°C against
the background of global warming, while the frequency of tropical cyclone geneses in this region decreases
significantly. Generally, the rise of SSTs is favorable for the genesis of tropical cyclones, but it is now
shown to be contrary to the normal effect. Most of the tropical cyclones in the western North Pacific (WNP)
are generated in the ITCZ. This is quite different from the case in the Atlantic basin in which the tropical
cyclones are mostly generated from the easterly wave. Our research results demonstrate that the ITCZ has a
weakening trend in strength, and it has moved much more equatorward in the past 40 years; both are
disadvantageous to the formation of tropical cyclones. Furthermore, our study also found that the ridge of
the subtropical high tends to shift slightly equatorward, which is another adverse mechanism for the
formation of tropical cyclones. 相似文献
18.
对消除了热带气旋环流的500百帕位势高度场在热带气旋活动期间作经验正交函数(EOF)分析,分析表明环境场在很大程度上决定了热带气旋的路径。个例分析表明对热带气旋过程作EOF分析可以把复杂的天气过程深缩为一张过程时间演变图,并能更清楚、更突出过程演变的主要特征。 相似文献
19.
近30年影响我国东南沿海的热带气旋降水强度变化特征分析 总被引：3，自引：0，他引：3
利用中国地面台站逐日降水资料和中国气象局上海台风研究所整编的热带气旋最佳路径资料研究了1978～2007年影响我国热带气旋降水强度的变化及其对我国东南沿海盛夏降水变化的影响.近30年影响我国东南沿海盛夏的热带气旋降水增加是导致我国东南沿海盛夏降水显著增加的主要原因.仅从热带气旋降水来看,东南沿海和内陆(包括江西、湖南东部和湖北南部)热带气旋降水强度显著增加,而影响热带气旋降水频次略有增加.通过对雨量站与引起降水热带气旋的中心距离的变化分析发现:内陆地区影响热带气旋距离显著下降,近距离热带气旋引起降水的增加,是该区域热带气旋降水强度增加的主要来源;而东南沿海地区近距离热带气旋降水增加不明显,热带气旋降水强度的增加主要由于同距离热带气旋降水强度的增加.热带气旋经过频次的空间的变化结果证实,近30年经过中国沿海的TC个数变化不大,仅福建沿海一带略有增加,而内陆地区则增加明显,且经过该区域时热带气旋移动速度变慢,这均与该区域近距离热带气旋降水的增加一致. 相似文献
20.
登陆广东热带气旋特征及其与副热带高压的关系 总被引：4，自引：1，他引：3
2004年登陆广东的热带气旋只有2个,个数明显偏少,粤西无热带气旋登陆;登陆广东的初台偏迟,终台结束早,登陆时间集中于7月;热带气旋移速快,强度弱(为热带风暴),对广东影响利大于弊。对1951~2004年7~9月登陆广东的热带气旋进行统计分析,发现各月登陆广东的热带气旋次数差异较大,最多时一个月有5个,最少时没有。登陆广东的热带气旋个数与西北太平洋副热带高压位置、强度有密切关系,可以将有利于和不利于热带气旋登陆广东的副热带高压各分为3种环流形势。 相似文献