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721.
In solar cycles 22–23, all solar indices showed maxima near 1990 and 2000 and minima in 1996. The maximum to minimum variation was only 1–2% in the UV range 240–350 nm. Dobson ozone intensities did not show any clear relationship with solar cycle and ozone variations were less than 10%. The UV-B (295–325 nm) observed at ground by Brewer spectrophotometers at some locations had variations of 50–100% for 295–300 nm, and 20–50% for 305–325 nm. The maxima were in different years at different locations (even with separations of only 300 km), did not match with the solar cycle, and were far too large to be explained on the basis of ozone changes (1% decrease of ozone is expected to cause 2% increase of UV-B). Thus, if the data are not bad, the UV-B changes do not match with solar activity or ozone changes and must be mostly due to other local effects (clouds, etc.?). When data are averaged over wide geographical regions, UV-B variation ranges are smaller (10–20%, probably because localised, highly varying cloud effects get filtered out), and are roughly as expected from ozone variations. 相似文献
722.
723.
陈伯舫 《地震地磁观测与研究》2002,23(5):6-8
从太平洋4台的分析显示,APIA,GUAM和PAMATAI台Z分量的太阳黑子周变化与HONOLULU台的相位相反。可是,CANBERRA台的变化又和HONOLULU台同相。这种表现复杂的地方性差异,更反映出太阳黑子周变化源于外场之说的有问题的。 相似文献
724.
地磁长周期变化与日长10年尺度波动的相关分析 总被引:2,自引:1,他引:2
分析1900~2000年期间地磁长期变化和日长变化10年尺度波动的相关性,估算了核幔电磁耦合力矩,并与国外一些研究者的结果进行了对比。结果表明,地磁偶极矩的变化率M&与日长10年尺度波动存在时滞相关,地磁偶极矩变化比日长变化滞后大约10 a;在地幔电导为108~5108 S时,核幔电磁耦合力矩具有与日长10年尺度变化所需力矩的量级。 相似文献
725.
夏季对流和环流10-25天季内变化-5西太平洋暖池热力状况的关系 总被引:4,自引:0,他引:4
主要讨论了西太平洋暖池热力状况年际变化相联系的10-25天季内振荡的特征。在西太平洋暖池处于“暖”夏季和“冷”夏季两种状态时,10-25天季内振荡呈现出明显差异,在所讨论的亚洲-太平洋大部分区域,“暖”夏季时对流活动的10-25天季内变化和“冷”夏季时对流活动的10-25天季内变化表现出显的反相关关系,表明对流活动的年际变化与季内变化的相互作用。当西太平洋暖池上空对流活动的10-25天季内振荡处于最强和最弱阶段时,低层大气表现为Gill型环流响应,即气旋式(反气旋式)环流出现在最强(最弱)对流活动的西北,这种对流和环流关系在西太平洋暖池出于“暖”夏季和“冷”夏季两种状态时均成立。而当西太平洋暖池上空对流活动的10-25天季内振荡处于除此以外其他阶段时,就看不到Gill型环流响应。 相似文献
726.
727.
Temporal changes in meltwater abundance, distribution and characteristics (controlling subglacial processes and ice sheet dynamics) can be inferred from subglacial sediment successions. Field evidence for changes in subglacial meltwater characteristics over time is presented from two sites (Doonan, Drummee) near a former late Weichselian (Devensian) ice centre in the north of Ireland. On a macroscale, both sites investigated show subglacial diamicton overlying glacially planated bedrock platforms. In more detail, primary sedimentary structures and facies variability show a complex relationship between depositional processes and meltwater characteristics at the ice/bed interface (IBI). Sedimentary evidence suggests sediment transport and deposition took place by low-viscosity subglacial slurries (mobile sediment–meltwater admixtures), which are part of a continuum between the processes of subglacial sediment deformation and subglacial meltwater flooding. Subtle changes in meltwater abundance and distribution at the IBI controlled slurry rheology, mechanisms of particle support and detailed sediment depositional processes. 相似文献
728.
Low-Frequency Variations, Chandler and Annual Wobbles of Polar Motion as Observed Over One Century 总被引:1,自引:0,他引:1
Joachim Höpfner 《Surveys in Geophysics》2004,25(1):1-54
Polar motion data are available from the mid-19th century to the present. Basedon time series with a variety of sampling intervals (monthly, 0.05-year, 5-day anddaily), we have separated the low-frequency terms by low-pass filtering and theChandler and annual terms by recursive band-pass filtering of the pole coordinates.Using a simple unweighted least-squares fit to the filtered low-frequency terms, thelinear trends of the rotation pole were estimated. Assessing the estimates based onintercomparisons, the most reliable trend estimate was found. Using a Fast FourierTransform, we have computed the prograde, retrograde and total amplitude spectraof the low-frequency part of polar motion in order to reveal the long-periodic signals.The characteristics and time evolution of the Chandler and annual wobbles aredescribed by changes in their parameters (radii, directions and period lengths) overone century. 相似文献
729.
730.
Interannual and Interdecadal Variations in Atmospheric Circulation Factors and Rainfall in China and Their Relationship 总被引:4,自引:0,他引:4
Wavelet analysis is used to study the interannual and interdecadal variations of rainfall in China and atmospheric circulation factors, including the key atmospheric oscillations, W, C, E patterns and subtropical high. Regression analysis and correlation analysis are both used to study the relationship of atmospheric circulation factors and China rainfall on different time scale and spatial scale. The results are as follows: (1) The variations of atmospheric circulation and rainfall in China are characterized by interannual and interdecadal scales. The variations of atmospheric circulation and rainfall are composed of interannual and interdecadal variations. It is necessary to separate those two time scales when climate changes and forecast are studied. (2) The variations of China rainfall are due to the interaction of multi-factors rather than single factors. The marked factors which influence the interannual and interdecadal variations are various. Subtropical high is one of the marked factors which influence interannual variations of rainfall, while AO, NAO, and NPO are one of the marked factors which influence interdecadal variations of rainfall. (3) The longer the time scale is, and the larger the spatial scale is, and the more remarkable the relationships between atmospheric circulation and rainfall are. 相似文献