南海、孟加拉湾不对称环流变化对2009年西南特大秋旱的影响

利用NCEP再分析资料及我国160站降水资料,分析了2009年秋季东亚中、低纬环流特征和水汽输送特征及其对西南干旱的影响。同时讨论了秋季不同ENSO状态下东亚地区水汽输送差异,并与2009年进行比较。结果表明:孟加拉湾(简称孟湾)和南海之间环流形势在2009年秋季发生不对称变化,造成两地上空气压梯度减小,孟湾和南海上空分别出现一个反气旋式和气旋式距平环流中心,我国西南至中南半岛处于两距平环流中心之间偏北距平风控制之下,使得进入我国的西南气流异常减弱。水汽输送随之出现变化,南海南部季风低压水汽环流圈异常偏强,孟湾和南海水汽主体经中南半岛重回南海而未进入我国,最终造成我国西南降水异常偏少,出现干旱。这段时间内,西南地区上空出现异常下沉运动,对流活动受到抑制,加剧了干旱程度。在El Ni o年,我国西南及江南地区秋季水汽通量比La Ni a年明显增大,西北及华北则减少。2009年秋季我国的降水分布及南海一带水汽输送特征与普通El Ni o年特征不符,甚至出现相反状态,经对2009年秋季东亚El Ni o影响特征作简单模拟还原和分析,认为上述差异可能与El Ni o反气旋环流影响位置偏北有关。     

夏季黄河下游地区中尺度对流系统的气候特征分布

利用1996~2008年逐小时卫星资料、NCEP再分析资料及统计方法, 研究了位于黄河下游地区的中尺度对流系统(Mesoscale Convective System, 简称MCS)的气候特征, 其中包括中尺度对流复合体(Mesoscale Convective Complex, 简称MCC)、持续拉长状对流系统(Permanent Elongated Convective System, 简称PECS)、β中尺度对流复合体(Meso-β Scale MCC, 简称MβCCS>)、β中尺度持续拉长状对流系统(Meso-β Scale PECS, 简称MβECS)4类。结果表明:MCC和PECS是黄河下游地区影响夏季降水的主要MCS, 其中7月份MCC最多, 并且MCC的数量明显大于PECS;与发生在美国的MCS比较, 发生在黄河下游地区的MCC和PECS在成熟期的面积和平均偏心率较大、生命史较长, 但MβCCS和MβECS的生命史较短、平均偏心率变化不大;黄河下游地区PECS表现出成熟较快和消亡较慢的特征, 其最低相当[A1] 黑体温度 (BlackBody Temperature, 缩写为TBB) 平均值为-72℃, 比MCC低1℃左右, 生命史比MCC长0.9 h;在MCC的形成、成熟及消亡期, 其日循环特征均表现为明显的双峰特征, 而PECS却呈现出单峰特征;黄河下游地区MCC的发生时间主要集中在2个时段, 一个是在下午形成, 傍晚成熟, 凌晨消亡, 另一个则在后半夜形成, 凌晨成熟, 上午甚至中午才消亡;MCS具有明显的年际变化特点, 在MCS较少的1999年, 500 hPa的副热带高压偏南, 华北地区位势高度较常年明显偏高, 而在MCS较多的2001年, 副高异常偏强, 华北地区位势高度较常年明显偏低, 850 hPa上为一低压槽, 黄河下游地区主要受副高边缘的西南气流影响。     

利用FY-3星载微波资料对热带气旋云系和暖核特征的分析

介绍了中国FY-3系列卫星搭载的微波遥感仪器性能特点,以“1109”超强台风“梅花”为研究个例.通过微波湿度计单通道微波图像和微波成像仪双极化通道散点图,分析了台风云系中云雨粒子对遥感通道辐射的吸收和散射效应,揭示了台风在微波图像上表现形式的内在物理原因.利用微波向量辐射传输模式的模拟表明:微波温度计各氧气吸收通道对热带气旋系统水汽和水凝物含量变化的敏感性不大.因此,可利用权重函数峰值位于对流层中上层的通道3,探测出台风暖核辐射信息.根据两者相匹配的5个较理想时次数据,选取距“梅花”中心400 km范围为研究区域,并提出用于修正扫描点分辨率不均匀所带来取样偏差的方法,分别计算出订正临边效应后的暖核强度,发现它同表征台风强度的中心海平面气压变化趋势相一致.     

浅谈通信基站的防雷措施

通过对雷电对通信基站设备的损害分析,提出通信基站相应的防雷措施。     

Spectral nudging sensitivity experiments in a regional climate model

In this study, the scale selective bias correction (SSBC) method described by Kanamitsu et al. (2010) is further examined by considering the full wind nudging and the vertically weighted damping coefficient. The 2001 June?CJuly?CAugust RSM simulation over a relatively large domain covering much of the Asian continent, the northern part of Australia, and the Indian and western Pacific oceans was the main focus. The full wind nudging shows wind fields closer to the driving global analysis. However, it leads to significantly distorted fields (e.g., temperature and geopotential height) aloft, accompanying excessive precipitation over the western Pacific. The gradual reduction of vorticity nudging from the model top to the ground surface improves rainfall patterns without a discernible distortion of large-scale fields. Further evaluation of a 10-year-summer simulation over East Asia confirmed that this revised SSBC method improves the monsoonal rainfall against the method of Kanamitsu et al. It is therefore concluded that vorticity nudging alleviates largescale errors by maintaining the near geostrophic balance between mass and winds. The reduction of this nudging factor in the lower troposphere allows the ageostrophic component of wind to develop as in nature, which leads to the improvement of precipitation.     

Relationship of the interannual variability of the Indonesian Throughflow with the IOD over the tropical Indian Ocean

Based on the Simple Ocean Data Assimilation (SODA) reanalysis product, the interannual variability of the upper-ocean ITF volume transport from 1958 to 2001 is investigated. The wavelet analysis shows a second prominent interannual oscillation with a period of about 2–4 years. To reveal any relationship between this band-scale oscillation of the upper-ocean ITF and Indian Ocean Dipole (IOD), correlation and wavelet analyses are used. The correlation coefficient between the upper-ocean ITF and IOD reaches –0.35 with the upper-ocean ITF lagging the IOD index by 8 months. The dipole structure of IOD event is reproduced by the correlation with the upper-ocean ITF lagging the SST anomaly over the tropical Indian Ocean by 8 months from 1958 to 2001. The upper-ocean ITF and IOD show high coherency from about 1975 to 2001. The fact that the wavelet power spectrum of the upper-ocean ITF shows similar structure to that of IOD index supports this high coherency. These analyses suggest that the 2–4-year band-scale oscillation of the upper-ocean ITF is uniquely related to IOD over the tropical Indian Ocean.     

Unstable Dynamical Properties of Spiral Cloud Bands in Tropical Cyclones

A nondivergent barotropic model （Model 1） and a barotropic primitive equation vortex model （Model 2） are linearized respectively in this paper. Then their perturbation wave spectrums are computed with a normal mode approach to study the instability problem on an appointed tropical cyclone （TC）-like vortex, thereby, the dynamic instability properties of spiral cloud bands of TCs are discussed. The results show that the unstable mode of both models exhibits a spiral band-like structure that propagates away from the vortex outside the radius of maximum winds. The discrete modal instability of the pure vortex Rossby wave can account for the generation of the eyewall and the inner spiral band. The unstable mode in Model 2 has three parts, i.e., eyewall, inner and outer spiral bands. This mode can be interpreted as a mixed vortex Rossby-inertia gravitational wave. The unbalanced property of the wave outside the stagnation radius of the vortex Rossby wave is one of the important reasons for the formation of the outer spiral band in TCs. Accordingly, the outer spiral band can be identified to possess properties of an inertial-gravitational wave. When the formation of unstable inner and outer spiral bands is studied, a barotropic vortex model shall be used. In this model, the most unstable perturbation bears the attributes of either the vortex Rossby wave or the inertial-gravitational wave, depending on the vortex radius. So such perturbations shall be viewed as an unbalanced and unstable mixed wave of these two kinds of waves.     

070703天长超级单体龙卷的多普勒雷达典型特征

主要使用南京多普勒天气雷达资料,分析了2007年7月3日发生在安徽天长和江苏高邮的龙卷风天气,着重分析了中气旋和龙卷涡旋特征(TVS)等产品的典型特征.龙卷发生在飑线回波带的北端强烈发展的超级风暴单体中,回波带前沿存在强烈的水平风切变,使得回波带上不断有中气旋生成.对产生龙卷的超级风暴单体,龙卷发生30min前,雷达给出了中气旋(M)产品,该中气旋持续了7个体扫的时间(42min),在中气旋出现后第5个体扫,雷达给出龙卷涡旋特征(TVS)产品,龙卷涡旋特征持续了3个体扫,综合切变产品也给出了显著的提醒.实地调查结果,龙卷风和第2个TVS同时发生,龙卷风位置与TVS位置对应,但位于TVS的南侧,位于中气旋最大风速圈的南缘.虽然CINRAD/SA雷达的TVS产品有虚警的情况,但结合反射率因子、平均径向速度、中气旋、综合切变等产品的分析,对于龙卷监测和预警会很有帮助的.     

利用树轮重建小兴安岭五营1796年以来的温度变化

 对黑龙江省小兴安岭五营丰林国家自然保护区建立的红松 (Pinus koraiensis) 树轮宽度年表与五营气象站的气候要素响应分析表明,树轮年表与生长季上一年10月份的平均温度显著相关,由此重建了1796-2004年五营10月份平均温度。此外,4月下旬的温度变化对五营红松树木的径向生长也具有一定的影响。1796-2004年,五营共经历了4个偏冷和4个偏暖期。周期分析表明,重建序列以3.33 a的周期最为显著,对重建序列30 a尺度的突变检验结果表明,1871年和1900年前后,五营地区10月份平均温度出现了显著的均值突变,1851年前后出现了明显的方差突变。