晴空回波特征与风场信息应用

为研究晴空回波风场信息在对流性降水天气中的预警应用价值,选取山东省临沂雷达站2008—2013年5—9月的观测数据分析降水晴空回波特征。研究发现:临沂地区5—9月约87%的日数会出现晴空回波,且90%以上出现在距离雷达站100km范围之内,反射率因子多在10~25dBz,具有明显日变化;晴空回波的速度产品能提供有效监测对流性降水出现前的大气低层风场信息,能一定程度反映低层湍流的耗散率,对降水过程有一定的指示性,相关研究成果对降低对流天气漏报率和提高预警提前量有重要意义。     

乌鲁木齐市边界层日变化特征

利用乌鲁木齐市晴天CFL-03型风廓线雷达观测资料,分析了边界层日变化特征。得出结论如下:边界层结构季节变化明显。冬、春季300~600m以下风速较小,小于3m/s,且愈近地面风速愈小;以上风速大、风向恒定,基本为东南大风。夏季和秋季风速比冬季和春季小,流场特征较复杂,水平风速和风向变化较活跃,存在明显的风切变。折射率结构常数春、秋和冬季比夏季分别小1个、3个和1~3个量级;夏季最大,集中在10~(-16)~10~(-13) m~(-2/3)之间。春、夏和秋季晴天湍流动能耗散率量级分别在10~(-6)~10~(-2) m~2·s~(-3)、10~(-4)~10~(-3) m~2·s~(-3)、10~(-6)~10~(-3) m~2·s~(-3)之间;白天比夜间约大1个量级。晴天折射率结构常数和湍流动能耗散率日变化特征与风场日变化特征有较好地对应关系,即湍流发展旺盛的区域与风速较大的区域相一致。风廓线雷达资料反演的湍流动能耗散率对春季和夏季边界层结构日变化演变特征的监测较好。夏季夜间稳定边界层约400~500m,残余层可达到约1800m,对流边界层可发展到约2500m,混合层约2200m,夹卷层约300~400m。     

东亚夏季大气环流和气候对冬季海温异常的邻响应和遥响应

本文通过ＩＡＰ－ＧＣＭ的数值模拟,研究了全球大气环流对黑潮海域和赤道东太平洋冬季ＳＳＴ异常的响应,并着重比较东亚大气环流和气候对黑潮区ＳＳＴＡ的响应（邻响应）和对赤道东太平洋ＳＳＴＡ的响应（遥响应）。首先,无论是黑潮区ＳＳＴＡ引起的邻响应还是赤道东太平洋ＳＳＴＡ所引起的遥响应对东亚大气环流和气候变化的影响都是明显而重要的。由于在大气中低频振荡被激发出来,其响应将持续较长时间。进一步分析表明,东亚大气环流对黑潮区或赤道东太平洋冬季正ＳＳＴＡ的响应都将造成华北地区夏季的多雨,其数值模拟结果与观测相一致。另外,赤道西太平洋地区大气的异常（尤其是对流活动）对于东亚地区大气环流和气候变化有重要作用     

Observations of Dynamic Turbulence in the Lower Stratosphere over Inner Mongolia Using a High-resolution Balloon Sensor Constant Temperature Anemometer

We present characterizations of the dynamic turbulence in the lower stratosphere measured by a new balloon-based system designed for detecting finer scale dynamic turbulence. The balloon-based system included a constant temperature anemometer(CTA) operating at a sampling rate of 2 k Hz at an ascent speed of 5 m s^-1(corresponding to a vertical resolution of 2.5 mm), an industrial personal computer, batteries, sensors for ambient temperature and humidity, an A/D converter, and others. The system was successfully launched to 24 km altitude over Bayannur City, Inner Mongolia Province. Results show the spatial intermittence of the turbulence layers, with clear boundaries between turbulent and nonturbulent regions. This is the first time that the dynamic turbulence spectrum down to the viscous sub-range has been obtained throughout the lower stratosphere over China. With that, the energy dissipation rates of dynamic turbulence could be calculated with high precision. The profile of the dissipation rates varied from 7.37 × 10^-7 to 4.23 W kg^-1 and increased with altitude in the stratosphere.     

海雾生成过程中平流、湍流、辐射效应研究

推导出一个相对湿度方程,分析了在海雾生成过程中平流、湍流和辐射的效应.     

关于动力Alfven波的色散与朗道阻尼

根据完全动力论理论,证明了可由简化漂移动力论方程求得动力Ａｌｆｖｅｎ波色散方程,即横向用磁流体力学方程,纵向用Ｖｌａｓｏｖ方程,在初级近似下由此推导出适合于日冕和太阳风的色散关系和Ｌａｎｄａｕ阻尼,得到在性质上与ＭＨＤ　Ａｌｆｖｅｎ波完全不同的动力Ａｌｆｖｅｎ波,太阳风中Ａｌｆｖｅｎ湍流很容易由动力Ａｌｆｖｅｎ波演化而来。提出由动力Ａｌｆｒｅｎ波构筑太阳风高速流模型将更符合观测结果。     

Waveform and packet structure of lion roars

The Equator-S magnetometer is very sensitive and has a sampling rate of normally 128 Hz. The high sampling rate allows for the first time fluxgate magnetometer measurements of ELF waves between the ion cyclotron and the lower hybrid frequencies in the equatorial dayside magnetosheath. The so-called lion roars, typically seen by the Equator-S magnetometer at the bottom of the magnetic troughs of magnetosheath mirror waves, are near-monochromatic packets of electron whistler waves lasting for a few wave cycles only, typically 0.25 s. They are right-hand circularly polarized waves with typical amplitudes of 0.5–1 nT at around one tenth of the electron gyrofrequency. The cone angle between wave vector and ambient field is usually smaller than 1.5°.