Venus Doppler winds at cloud tops observed with ESPaDOnS at CFHT     

Thomas Widemann  Emmanuel Lellouch 《Planetary and Space Science》2008,56(10):1320-1334

We present new wind measurements in Venus’ lower mesosphere from visible spectroscopy during the 2007 worldwide coordinated ground campaign in support of ESA's Venus Express mission. These observations consisted of high-resolution spectra of Fraunhofer lines in the entire visible range (0.37-1.05 μm) to measure the winds near 68 km using the Doppler shift of solar radiation scattered by clouds toward the observer's direction. The observations included various points of the dayside hemisphere at a phase angle of ∼109°. We took advantage of two symmetrical elongations in July and September 2007 at Canada-France-Hawaii's 3.6-m telescope. Kinematical fits to the Doppler winds provide a mean equatorial velocity of (104±10) m s⁻¹ for the zonal retrograde flow. This velocity agrees quite well with the mean value obtained by tracking the UV markings from several spacecraft.  相似文献   

The depth of the convective boundary layer on Mars     

D.P. Hinson  M. Pätzold  B. Häusler 《Icarus》2008,198(1):57-66

We are using observations obtained with Mars Express to explore the structure and dynamics of the martian lower atmosphere. We consider a series of radio occultation experiments conducted in May-August 2004, when the season on Mars was midspring of the northern hemisphere. The measurements are widely distributed in latitude and longitude, but the local time remained within a narrow range, 17.0-17.2 h. Most of the atmospheric profiles retrieved from these data contain a distinct, well-mixed convective boundary layer (CBL). We have accurately determined the depth of the CBL and its spatial variations at fixed local time through analysis of these profiles. The CBL extends to a height of 3-10 km above the surface at the season and locations of these measurements. Its depth at fixed local time is clearly correlated with variations in surface elevation on planetary scales, with a weaker dependence on spatial variations in surface temperature. In general, the CBL is deep (8-10 km) where the surface elevation is high, as in Tharsis Montes and Syrtis Major, and shallow (4-6 km) where the surface elevation is low, as in Amazonis and Utopia. This variability results from the combined effects of conditions near the surface and in the atmosphere above the CBL. Convection arises from solar heating of the ground, and the impact of this heat source on thermal structure is largest where the surface pressure and atmospheric density are smallest, at high surface elevations. The vertical extent of the CBL is in turn constrained by the static stability of the overlying atmosphere. These results greatly reduce the long-standing uncertainty concerning the depth of the CBL.  相似文献   

Have the electric currents produced by plasma and magnetic field gradients been discovered in the solar photosphere?     

S. I. Stepanov 《Astronomy Letters》2008,34(5):337-343

We check whether the currents of inhomogeneities (diffusion, thermodiffusion, and gradient ones) can exist at the photospheric level. For this purpose, the vertical currents are compared with the theoretically estimated currents of inhomogeneities; our comparison shows them to be of the same order of magnitude. Therefore, the currents of inhomogeneities actually exist in the solar photosphere; their exact values are determined by the (electron density, temperature, and magnetic field) gradients, which are not known very well at present. This paper continues the current tendency in describing the atmospheric magnetic field (in particular, its fine structure) that consists in allowing for the Hall, diffusion, and thermodiffusion currents.  相似文献   

MODIS极区遥感应用研究进展   总被引：1，自引：0，他引：1       下载免费PDF全文

鄂栋臣  张辛 《极地研究》2010,22(1):69-78

卫星遥感技术在极地区域的应用日益广泛,中分辨率成像光谱仪(Moderate-resolution Imaging Spectroradiometer,即MODIS)则是遥感领域的重要卫星传感器之一。MODIS传感器,包括它的搭载平台、系统构成、硬件特征、波段范围及一般性应用都在文章中进行了全面性地描述。着重介绍了MODIS在极区遥感应用研究的进展,具体阐述了MODIS在极区地貌、极区大气和极区海洋方面的应用。在每个方面都列举分析了国内外的相关研究实例,充分说明了MODIS在极地区域的广泛应用现状。  相似文献   

商用飞机气象观测温度、风场随机误差分析     

乔晓燕  马舒庆  陶士伟  赵培涛  官福顺 《成都信息工程学院学报》2010,25(2):201-205

随着我国AMDAR资料（商业飞机气象观测）不断增加并已逐步应用于数值天气预报,AMDAR观测资料的质量影响其在天气预报业务中的应用效果。为评估AMDAR数据的质量,利用统计学方法,通过对选定的AMDAR温度及风场观测数据,进行其质量特性量一随机误差均方根的统计分析。分析结果表明：温度的随机误差均方根为0．90℃,风速的观测随机误差均方根为1．24m／s。温度观测随机误差均方根、风速观测误差均方根在边界层较大,边界层以上较小。在300hPa-500hPa气压层达到最小,其温度观测随机误差为0．76℃、风速观测随机误差均方根为1．03m／s。  相似文献   

夜光云内小尺度重力波对冰晶粒径谱的影响规律研究          下载免费PDF全文

卜令兵  张祖熠  郜海阳  霍朝阳  王震  朱红 《地球物理学报》2016,59(2):453-464

本文利用AIM卫星搭载的CIPS云图反照率和冰晶粒径数据,从中提取了2007/08南半球和2008年北半球共6489个小尺度重力波活动(波长5~150km范围)个例,对重力波区域与背景云层冰晶粒径谱进行对比分析,从而研究重力波对冰晶平均半径和谱宽的影响规律.结果表明,北半球重力波区域冰晶的平均半径和谱宽分别比背景云层小2.5nm和6.1nm,南半球则分别减小1.1nm和7.9nm.在随纬度的分布上,小于80°时,南北半球的平均半径扰动值均为负值,绝对值随纬度增大而减小,而大于80°时,负扰动转变为正扰动,且绝对值增加;谱宽扰动的绝对值也随着纬度增加而减小,但均为负值.在季节内随时间的分布上,南北半球重力波对冰晶平均半径和谱宽的扰动在始末阶段以负值为主,且绝对值较大,而在中期阶段正负值相当,且绝对值较小.这一特征与重力波引起冰晶粒径变化的振幅在纬度和时间上的分布趋势一致.重力波的波长均随纬度升高而减小,在季节的始末阶段较大,中期小,且南半球的平均波长和变化幅度都要明显大于北半球的,粒径扰动振幅随波长的变化率为南半球0.207nm·km-1,北半球的0.163nm·km-1.根据分析推断,重力波自身的扰动振幅应与其影响区域内的谱参数相对于背景云层的变化量有直接关系,且振幅越大,平均半径和谱宽的负扰动就越大.  相似文献   

Analysis of observations backing up the existence of VLF and ionospheric TEC anomalies before the Mw6.1 earthquake in Greece,January 26, 2014     

《Physics and Chemistry of the Earth》2015

The present work integrates ground-based ionosphere measurements using very-low-frequency radio transmissions with satellite measurements of the total electron content to draw common conclusions about the possible impact that the Mw6.1 earthquake that took place in Greece on January 26, 2014, had on the ionosphere.Very-low-frequency radio signals reveal the existence of an ∼4-day anomaly in the wavelet spectra of the signals received inside the earthquake preparation zone and a significant increase in the normalized variance of the signals prior to the earthquake (approximately 1 day before).Through total electron content analysis, it was possible to identify a clear anomaly from 15:00 until 20:00 UT on the day before the earthquake that appears again on the day of the earthquake between 07:00 UT and 08:00 UT. The anomalous values reach TEC1Sigma ∼4.36 and 3.11, respectively. Their spatial and temporal distributions give grounds to assume a possible link with the earthquake preparation. The geomagnetic, solar and weather conditions during the considered period are presented and taken into account.This work is an initial and original step towards a multi-parameter approach to the problem of the possible earthquake-related effects on the ionosphere joining observations made from both ground stations and satellites. A well-founded knowledge of these phenomena is clearly necessary before dealing with their application to earthquake prediction purposes.  相似文献   

Analysis software for upper atmospheric data developed by the IUGONET project and its application to polar science     

Yoshimasa Tanaka  Atsuki Shinbori  Tomoaki Hori  Yukinobu Koyama  Shuji Abe  Norio Umemura  Yuka Sato  Manabu Yagi  Satoru UeNo  Akiyo Yatagai  Yasunobu Ogawa  Yoshizumi Miyoshi 《极地研究(英文版)》2013,(4):231-240

To comprehensively understand the Arctic and Antarctic upper atmosphere, it is often crucial to analyze various data that are obtained from many regions. Infrastructure that promotes such interdisciplinary studies on the upper atmosphere has been developed by a Japanese inter-university project called the Inter-university Upper atmosphere Global Observation Network （1UGONET）. The objective of this paper is to describe the infrastructure and tools developed by IUGONET. We focus on the data analysis software. It is written in Interactive Data Language （IDL） and is a plug-in for the THEMIS Data Analysis Software suite （TDAS）, which is a set of IDL libraries used to visualize and analyze satellite- and ground-based data. We present plots of upper atmospheric data provided by IUGONET as examples of applications, and verify the usefulness of the software in the study of polar science. We discuss IUGONET＇s new and unique developments, i.e., an executable file of TDAS that can run on the IDL Virtual Machine, IDL routines to retrieve metadata from the IUGONET database, and an archive of 3-D simulation data that uses the Common Data Format so that it can easily be used with TDAS.  相似文献   

一次典型的区域性降水天气过程分析     

谢东  于莉莉  陈韶华  辛志远  刘亚琴 《内蒙古气象》2011,(5):12-13

高空槽配合低空切变线和地面低压,在渤海水汽通道建立,强烈的辐合上升运动和大气层结不稳定条件下,使锡林郭勒盟南部产生大雨天气。  相似文献   

Water percolation in a thick unsaturated loess layer considering the ground‐atmosphere interaction     

Xiaokun Hou  Tonglu Li  Sai K. Vanapalli  Yu Xi 《水文研究》2019,33(5):794-802

The key objective of this paper is to advance our present understanding of how surface water infiltrates in thick unsaturated loess, which is found in arid and semiarid regions of the world, considering the ground‐atmosphere interaction. In situ data for a period of 1 year in thick loess layer at a site in the Loess Plateau of China that has groundwater table at 97.5 m depth were collected for achieving this objective. Climate factors, mainly rainfall and actual evaporation, were measured. In addition, variations of soil temperature and water content at different depths in the unsaturated zone were also measured. The data were used to interpret the water percolation characteristics by dividing the thick unsaturated zone into three zones; namely, (i) surface zone, which constitutes the top 1.0 m, (ii) unsteady zone, which is from 1.0 to 7.0 m, and (iii) steady zone, which is below 7.0 m. In the surface zone, soil temperature and water content are sensitive to climate factors. There is a variation of water content associated with the cumulative influence of infiltration and evaporation in the precipitation and nonprecipitation periods, respectively. In the unsteady zone, the water content is relatively constant; however, temperature varies in different seasons. Water percolation in this zone is both in liquid and vapour phases. In the steady zone, both soil temperature and water content are constant during the entire investigation period. The percolation velocity in this zone is approximately 1.23 × 10^?8 m/s or 0.39 m/year, which suggests that it will take approximately 230.8 years for surface water to pass through the thick unsaturated zone and recharge the groundwater.  相似文献