共查询到20条相似文献，搜索用时 31 毫秒
1.
《Journal of Atmospheric and Solar》2000,62(13):1177-1187
Continuous MF radar measurements of mesospheric mean winds are in progress at the observatories in Yamagawa (31.2°N, 130.6°E) and Wakkanai (45.4°N, 141.7°E). The observations at Yamagawa and Wakkanai were started in August 1994 and September 1996, respectively. The real-time wind data are used for the study of major large scale dynamic features of the middle atmosphere such as mean winds, tides, planetary waves, and gravity waves, etc. In the present study of mean winds, we have utilized the data collected until June 1999, which include the simultaneous observation period of little more than two and a half years, for the two sites. The database permits us to draw conclusions on the characteristics of mean winds and to compare the mean wind structure over these sites. The mean prevailing zonal winds at both sites are dominated by westward/eastward motions in summer/winter seasons below 90 km. Meridional circulation at meteor heights is generally southward during most times of the year and it extends to lower mesospheric heights during summer also. The summer westward jet at Wakkanai is consistently stronger than those at Yamagawa. However, the winter eastward winds have identical strength at both locations. Meridional winds also show larger values at Wakkanai. The mean wind climatology has been examined and compared with the MU radar observations over Shigaraki (34.9°N, 136.1°E). The paper also presents the results of the comparison between the MF radar winds and the latest empirical model values (HWM93 model) proposed by Hedin et al. (1996. Journal of Atmospheric and Terrestrial Physics 58, 1421–1447). Hodograph analyses of mean winds conducted for the summer and winter seasons show interesting similarities and discrepancies. 相似文献
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Ali Osman Öncel Ian Main Ömer Alptekin Patience Cowie 《Pure and Applied Geophysics》1996,147(1):147-159
We investigate the nature of temporal variations in the statistical properties of seismicity associated with the North Anatolian Fault Zone between longitudes 31°–41°E during the instrumental period 1900–1992. Temporal variations in the seismicb value and the fractal (correlation) dimensionD
c
of earthquake epicenters are examined for earthquakes of magnitudeM
S
4.5, using sliding windows of 100 consecutive events.b varies temporally between 0.6 and 1.0, andD
c
between 0.6 and 1.4, both representing significant fluctuations above the errors in measurement technique. A strong negative correlation (r=–0.85) is observed betweenb andD
c
, consistent with previous observation of seismicity in Japan and southern California. Major events early in this century (M
S
7) are associated with lowb and highD
c
, respectively consistent with greater stress intensity and greater spatial clustering of epicenters—both implying a greater degree of stress concentration at this time. 相似文献
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Irina V. Medvedeva Anatoly I. Semenov Vladimir I. Perminov Alexander B. Beletsky Andrey V. Tatarnikov 《Acta Geophysica》2014,62(2):340-349
Data about the variations of mesopause temperature (～87 km) obtained from ground-based spectrographic measurements of the OH emission (834.0 nm, band (6-2)) at Irkutsk and Zvenigorod observatories were compared with satellite data on vertical temperature distribution in the atmosphere from Aura MLS v3.3. We analyzed MLS data for two geopotential height levels: 0.005 hPa (～84 km) and 0.002 hPa (～88 km) as the closest to OH height (～87 km). We revealed that Aura MLS temperature data have lower values than ground-based (cold bias). In summer periods, that difference increases. Aura cold biases compared with OH(6-2) at Irkutsk and Zvenigorod were calculated. For the 0.002 hPa height level, the biases are 10.1 and 9.4 K, and for 0.005 hPa they are 10.5 and 10.2 K at Irkutsk and Zvenigorod, respectively. When the bias is accounted for, an agreement between Aura MLS and OH(6-2) data obtained at both Irkutsk and Zvenigorod is remarkable. 相似文献
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利用气象、电离层和气候卫.星联合观测系统COSMIC掩星2007-2013年探测资料,分析了120°E经线附近电离层E层区域(70~140km)闪烁指数的季节、地方时和空间变化.结果表明强电离层闪烁主要集中在磁纬度±30°内,夏季达到最大,冬季其次,春季最小.闪烁峰值大小与太阳辐射有关,但北半球夏冬季闪烁峰值大于南半球观测结果,秋半球闪烁峰值大于春半球观测结果.地磁高纬地区较强闪烁现象出现在地方时傍晚之后,午夜前后达到最大值.地磁中纬和低纬区域日出后即出现较为明显的闪烁现象,一直持续至夜间甚至凌晨,分别约在中午和傍晚前达到最大值.磁赤道区闪烁现象通常始于地方时日出后,最大值发生在傍晚1800LT左右.电离层E区的闪烁峰值大都集中110km高度,但高纬地区的峰值高度略有降低.此外,太阳和地磁活动的增强一定程度上会抑制E层闪烁现象.相关研究结果有利于分析E层不规则结构及物理形成机制,同时为电离层区域闪烁模型的建立提供有用的信息. 相似文献
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《地球物理学进展》2017,(4)
本文利用中国廊坊站(39.4°N,116.7°E)流星雷达在2012年4月1日至2013年3月31日期间的水平风场观测数据,分析了廊坊上空中间层和低热层(MLT,80~100 km)大气纬向风、经向风潮汐的季节变化特征.研究表明:廊坊MLT区域周日潮汐和半日潮汐波动比较显著,有明显的季节变化特征.周日潮汐振幅在88 km以下为半年变化,极大值位于2-3月和10月,极小值位于冬、夏季;在88 km以上为周年变化,振幅冬末春初最强,夏季最弱.周日潮汐相位在秋、冬季比春、夏季提前.半日潮汐主要呈现半年变化,在5月和9月最强,冬、夏季最弱.半日潮汐相位在春、夏季比秋、冬季提前.此外,廊坊风场潮汐的观测结果与WACCM4模式模拟结果进行比较,结果表明两者的主要特征相似,在细节上有显著区别.与40°N附近其他站点风场潮汐观测结果的比较结果表明中纬度MLT风场潮汐有显著的随经度变化特性. 相似文献
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鄂尔多斯地块紧邻青藏高原东北缘,位于华北克拉通的西部,在我国中生代、新生代以来东部地区的构造活动中起到了重要作用.对鄂尔多斯及其周缘地区的研究可以提供有关华北克拉通的形成、演化和破坏过程的重要信息.本文选取了纵贯鄂尔多斯的107.6°E附近南北剖面上的44个流动地震台站进行分析,采用接收函数方法,进行Kirchhoff偏移成像,并且结合在该区域内前人的地震面波频散进行联合反演,获得剖面下方的地壳内部精细结构.研究结果显示:(1)莫霍面在鄂尔多斯北部较平缓,约45km深;在鄂尔多斯南部有所加深,达到50km;其北边的河套盆地的地壳厚度约为50km;南边的渭河盆地到秦岭地区及四川盆地的地壳厚度从约为40km增厚到47～50km.(2)河套盆地下方存在大规模的低速异常,最深可达25km,反映了其显著的拉张构造和沉积历史.(3)秦岭造山带下方的低速异常对应于其主要为长英质的地壳组分,可能是由于中生代的拆沉作用导致的地壳下部基性岩石层的缺失.(4)以38°N为界的鄂尔多斯地块,南北部地壳速度结构存在差异,可能表明了这两部分经历的构造历史不同. 相似文献
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Wind and temperature profiles measured routinely by rockets at Ryori (Japan) since 1970 are analysed to quantify interannual changes that occur in the upper stratosphere. The analysis involved using a least square fitting of the data with a multiparametric adaptative model composed of a linear combination of some functions that represent the main expected climate forcing responses of the stratosphere. These functions are seasonal cycles, solar activity changes, stratospheric optical depth induced by volcanic aerosols, equatorial wind oscillations and a possible linear trend. Step functions are also included in the analyses to take into account instrumental changes. Results reveal a small change for wind data series above 45 km when new corrections were introduced to take into account instrumental changes. However, no significant change of the mean is noted for temperature even after sondes were improved. While wind series reveal no significant trends, a significant cooling of 2.0 to 2.5 K/decade is observed in the mid upper stratosphere using this analysis method. This cooling is more than double the cooling predicted by models by a factor of more than two. In winter, it may be noted that the amplitude of the atmospheric response is enhanced. This is probably caused by the larger ozone depletion and/or by some dynamical feedback effects. In winter, cooling tends to be smaller around 40–45 km (in fact a warming trend is observed in December) as already observed in other data sets and simulated by models. Although the winter response to volcanic aerosols is in good agreement with numerical simulations, the solar signature is of the opposite sign to that expected. This is not understood, but it has already been observed with other data sets. 相似文献
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《Journal of Atmospheric and Solar》1999,61(5):377-384
A method of computing the vertical flux of zonal momentum (associated with equatorial waves) from the zonal and vertical components of the winds measured by the Indian MST radar at Gadanki (13.5°N, 79.2°E) is presented. The application of the method to the radar data gives flux values of 16×10−3, 8.0×10−3 and 5.5×10−3 m2 s−2 for slow Kelvin (12-day period), fast Kelvin (5.33-day period) and Rossby-gravity (RG) (3.43-day period) waves, respectively, in the upper troposphere. These flux values compare quite well with the values 4×10−3 m2 s−2 and 1×10−3 m2 s−2 obtained from radiosonde zonal wind and temperature data by Wallace and Kousky, 1968for slow Kelvin and RG waves, respectively. An estimate of the error in the fluxes gives a value of ∼ 1.2×10−3 m2 s−2. 相似文献
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《Journal of Atmospheric and Solar》2002,64(3):367-376
Observations of winds in mesospheric airglow layers have been made at Mt. John (44°S,170°E), New Zealand for some years. We present a modelling study of airglow emissions which shows that the properties of wind detection based on airglow emission means that high-frequency gravity waves are effectively filtered from the wind spectrum observed. This filtering means that any waves with periods of the order of hours should be detectable in the record (as they will not be hidden in the noise of the higher-frequency waves ubiquitous at these heights). One example of such a wave is shown. As part of the analysis, we show that because the airglow layers differ in width, some waves might be observed in only one airglow layer, even when present in both. 相似文献
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Prabha R. Nair K. Susan George K. Parameswaran Marina Aloysius Denny P. Alappattu Mannil Mohan P.K. Kunhikrishnan 《Journal of Atmospheric and Solar》2009,71(17-18):1771-1783
In-situ measurements of number density, size distribution, and mass loading of near-surface aerosols were carried out at Kharagpur, a site on the eastern part of Indo-Gangetic Plains during the winter month of December 2004. The data have been used to investigate wintertime characteristics of aerosols and their effects on the occurrence of haze. The aerosol number density is found to be of the order of 109 m?3 and mass loading is ~265±70 μg m?3 (5–8 times that reported from south Indian sites). The diurnal patterns and day-to-day variations in aerosol number density and mass loading are closely associated with atmospheric boundary layer height. During haze events, the number density of submicron particles is found to be 2–5 times higher than that during non-hazy period. This could be attributed to the enhanced concentration of anthropogenic aerosols, low atmospheric boundary layer height/ventilation coefficient and airflow convergence. 相似文献
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利用为期一年的卫星遥感温度（SABER/TIMED）资料重建了120°E子午圈内中间层和低热层大气潮汐各主要频率分量（周日、半日和8小时潮汐）.这些主要频率分量随高度振幅增大，在97 km高度达到显著的振幅；其中迁移性周日潮汐在97 km高度出现极大振幅，然后随高度衰减.本文从考察迁移性成分和非迁移性成分各自在总潮汐中贡献角度出发，着重讨论了那些对形成该子午圈中97 km高度上整体潮汐扰动起控制作用的潮汐成分.结果显示，对周日和半日频率这两种潮汐而言，迁移性成分控制了它们的总体时空分布.在春分季节，迁移性周日潮的控制作用最显著，决定了赤道和两半球热带的活动中心；其中北半球副热带地区的季节变化形势与以往利用武汉（30°N，114°E）流星雷达风测量资料开展分析得到的结果是一致的；其他季节受非迁移性成分明显影响，例如，在本文关注的2005年中，夏至季节受（1，0）模、（1，-3）模和（1，-2）模的共同影响形成了从赤道向南延伸的活动中心，极值中心位于赤道附近，振幅达到了20 K以上，是全年的最大值.受迁移性成分控制，半日潮活动主要出现在两半球热带地区，北半球活动中心位于秋分季节（振幅达到13 K），南半球活动中心位于春分和夏至之间.其他季节受非迁移成分的影响，形成若干分布在两半球的活动中心.在本文关注的40°S～40°N范围内，与周日潮和半日潮相比，8小时潮汐具有显著较低的振幅；另外，虽然迁移性成分在一年中的大部分时间系统地分布在两半球热带地区，但是非迁移成分具有与迁移性成分相当或更大的振幅，在整体上控制了这种潮汐的时空分布. 相似文献
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The interannual variations in salt flux on the 80°E section in the equatorial Indian Ocean were explored based on the ORAS5 data, which was quite consistent with the observational data among the four available reanalysis datasets. The results indicated that the area with significant interannual variations in salt flux coincided with that of significant climatological mean salt flux in general and was mainly located in the upper 150 m layer. Specifically, three important areas were identified in ... 相似文献
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利用为期一年的卫星遥感温度(SABER/TIMED)资料重建了120°E子午圈内中间层和低热层大气潮汐各主要频率分量(周日、半日和8小时潮汐).这些主要频率分量随高度振幅增大,在97km高度达到显著的振幅;其中迁移性周日潮汐在97km高度出现极大振幅,然后随高度衰减.本文从考察迁移性成分和非迁移性成分各自在总潮汐中贡献角度出发,着重讨论了那些对形成该子午圈中97km高度上整体潮汐扰动起控制作用的潮汐成分.结果显示,对周日和半日频率这两种潮汐而言,迁移性成分控制了它们的总体时空分布.在春分季节,迁移性周日潮的控制作用最显著,决定了赤道和两半球热带的活动中心;其中北半球副热带地区的季节变化形势与以往利用武汉(30°N,114°E)流星雷达风测量资料开展分析得到的结果是一致的;其他季节受非迁移性成分明显影响,例如,在本文关注的2005年中,夏至季节受(1,0)模、(1,-3)模和(1,-2)模的共同影响形成了从赤道向南延伸的活动中心,极值中心位于赤道附近,振幅达到了20K以上,是全年的最大值.受迁移性成分控制,半日潮活动主要出现在两半球热带地区,北半球活动中心位于秋分季节(振幅达到13K),南半球活动中心位于春分和夏至之间.其他季节受非迁移成分的影响,形成若干分布在两半球的活动中心.在本文关注的40°S~40°N范围内,与周日潮和半日潮相比,8小时潮汐具有显著较低的振幅;另外,虽然迁移性成分在一年中的大部分时间系统地分布在两半球热带地区,但是非迁移成分具有与迁移性成分相当或更大的振幅,在整体上控制了这种潮汐的时空分布. 相似文献
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S. Sridharan K. Raghunath S. Sathishkumar D. Nath 《Journal of Atmospheric and Solar》2010,72(14-15):1139-1146
Rayleigh lidar observations at Gadanki (13.5°N, 79.2°E) show an enhancement of the nightly mean temperature by 10–15 K at altitudes 70–80 km and of gravity wave potential energy at 60–70 km during the 2009 major stratospheric warming event. An enhanced quasi-16-day wave activity is observed at 50–70 km in the wavelet spectrum of TIMED–SABER temperatures, possibly due to the absence of a critical level in the low-latitude stratosphere because of less westward winds caused by this warming event. The observed low-latitude mesospheric warming could be due to wave breaking, as waves are damped at 80 km. 相似文献
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Averaged seasonal variations of wind perturbation intensities and vertical flux of horizontal momentum produced by internal gravity waves (IGWs) with periods 0.2/1 h and 1/6 h are studied at the altitudes 65/80 km using the MU radar measurement data from the middle and upper atmosphere during 1986/1997 at Shigaraki, Japan (35°N, 136°E). IGW intensity has maxima in winter and summer, winter values having substantial interannual variations. Mean wave momentum flux is directed to the west in winter and to the east in summer, opposite to the mean wind in the middle atmosphere. Major IGW momentum fluxes come to the mesosphere over Shigaraki from the Pacific direction in winter and continental Asia in summer. 相似文献