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101.
102.
Features of the Extremely Severe Drought in the East of Southwest China and Anomalies of Atmospheric Circulation in Summer 2006 总被引:1,自引:0,他引:1 下载免费PDF全文
The spatial-temporal features of the extremely severe drought and the anomalous atmospheric circulation in summer 2006 are
analyzed based on the NCEP/NCAR reanalysis data, the characteristic circulation indices given by the National Climate Center
of China, and the daily precipitation data of 20 stations in the east of Southwest China (ESC) from 1959 to 2006. The results
show that the rainless period started from early June and ended in early September 2006 with a total of more than 80 days,
and the rainfall was especially scarce from around 25 July to 5 September 2006. Precipitation for each month was less than
normal, and analysis of the precipitation indices shows that the summer precipitation in 2006 was the least since 1959. The
extremely severe drought in the ESC in summer 2006 was closely related to the persistent anomalies of the atmospheric circulation
in the same period, i.e., anomalies of mid-high latitude atmospheric circulation, western Pacific subtropical high (WPSH),
westerlies, South Asian high, lower-level flow, water vapor transport, vertical motion, and so on. Droughts usually occur
when the WPSH lies anomalously northward and westward, or anomalously weak and eastward. The extreme drought in summer 2006
was caused by the former. When the WPSH turned stronger and shifted to the north and west of its normal position, and the
South Asian high was also strong and lay eastward, downdrafts prevailed over the ESC and suppressed the water vapor transfer
toward this area. At the same time, the disposition of the westerlies and the mid-high latitude circulation disfavored the
southward invasion of cold air, which jointly resulted in the extremely severe drought in the ESC in summer 2006. The weak
heating over the Tibetan Plateau and vigorous convective activities over the Philippine area were likely responsible for the
strong WPSH and its northwestward shift in summer 2006. 相似文献
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Light-induced bird strikes are known to occur when vessels navigate during darkness in icy waters using powerful searchlight. In Southwest Greenland, which is important internationally for wintering seabirds, we collected reports of incidents of bird strikes over 2-3 winters (2006-2009) from navy vessels, cargo vessels and trawlers (total n = 19). Forty-one incidents were reported: mainly close to land (<4 km, 78%), but one as far offshore as 205 km. Up to 88 birds were reported killed in a single incident. All occurred between 5 p.m. and 6 a.m. and significantly more birds were involved when visibility was poor (snow) rather than moderate or good. Among five seabird species reported, the common eider (Somateria mollissima) accounted for 95% of the bird casualties. Based on spatial analyses of data on vessel traffic intensity and common eider density we are able to predict areas with high risk of bird strikes in Southwest Greenland. 相似文献
105.
川滇及其邻区中强地震烈度衰减关系适用性研究 总被引:6,自引:0,他引:6
本文选取川滇及邻区作为研究区域,根据地震构造环境和震害分布特点,将该地区分为西南地区和盆地地区,选取该地区6级以上的典型历史震例,将其数字化得到等震线数据,通过对这些数据的统计回归分析,分别建立两个区域的地震烈度沿长轴与短轴的衰减关系、各烈度面积与地震震级的关系、破裂长度与震级的关系.同时,综合利用上述关系建立不同的地... 相似文献
106.
El Ni(n)o or La Ni(n)a manifest in December over the Pacific and will serve as an index for the forecasting of subsequent Indian summer monsoon,which occurs from June to mid-September.In the present article,an attempt is made to study the variation of latent heat flux (LHF) over the north Indian Ocean during strong El Ni(n)o and strong La Ni(n)a and relate it with Indian monsoon rainfall.During strong El Ni(n)o the LHF intensity is higher and associated with higher wind speed and lower cloud amount.During E1 Ni(n)o all India rainfall is having an inverse relation with LHF.Seasonal rainfall is higher in YY+1 (subsequent year) than YY (year of occurrence).However there is a lag in rainfall during El Ni(n)o YY+1 from June to July when compared with the monthly rainfall. 相似文献
107.
本文总结了渐进式扩张洋中脊和渐进式演化海盆的全球空间分布,并将西南次海盆与典型渐进式演化的亚丁湾加以比对,通过对海盆扩张中心的起源、扩张中心分段特征、火山活动、磁异常特征等的比较,为西南次海盆的演化提供新观点,为南海的演化观点寻找新证据.西南次海盆为渐进式扩张的海盆,与东部次海盆属于同一期扩张形成,海盆的渐进式扩张与渐进式扩张的方向很有可能受到地幔热柱(印支地幔柱、南海中部低速柱或海南地幔柱)的控制.南海的扩张演化模式并不是单一的,而是多种模式的综合,在考虑海底演化模式时应该同时考虑地幔柱的影响. 相似文献
108.
Sedimentological analyses of 289 years (AD 1718-2006) of varved sediment from Shadow Bay, southwest Alaska, were used to investigate hydroclimate variability during and prior to the instrumental period. Varve thicknesses relate most strongly to total annual discharge (r2 = 0.75, n = 43, p < 0.0001). Maximum annual grain size depends most strongly on maximum spring daily discharge (r2 = 0.63, n = 43, p < 0.0001) and maximum annual daily discharge (r2 = 0.61, n = 43, p < 0.0001), while varve thickness is poorly correlated with maximum annual grain size (r2 = 0.004, n = 287, p = 0.33). Relations between varve thickness and annual climate variables (temperature, precipitation, North Pacific (NP) and Pacific Decadal Oscillation (PDO) indices) are insignificant. On multidecadal timescales, however, regime shifts in varve thickness and total annual discharge coincide with shifts in NP and PDO indices. Periods with increased varve thickness and total annual discharge were associated with warm PDO phases and a strengthened Aleutian Low. The varve-inferred record of PDO suggests that any periodicity in the PDO varied over time, and that the early 19th century marked a transition to a more frequent or detectable shifts. 相似文献
109.
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Helen C. Bostock Bruce W. HaywardHelen L. Neil Kim I. CurrieGavin B. Dunbar 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(1):72-85
We have compiled carbonate chemistry and sedimentary CaCO3% data for the deep-waters (>1500 m water depth) of the southwest (SW) Pacific region. The complex topography in the SW Pacific influences the deep-water circulation and affects the carbonate ion concentration ([CO32−]), and the associated calcite saturation horizon (CSH, where ??calcite=1). The Tasman Basin and the southeast (SE) New Zealand region have the deepest CSH at ∼3100 m, primarily influenced by middle and lower Circumpolar Deep Waters (m or lCPDW), while to the northeast of New Zealand the CSH is ∼2800 m, due to the corrosive influence of the old North Pacific deep waters (NPDW) on the upper CPDW (uCPDW). The carbonate compensation depth (CCD; defined by a sedimentary CaCO3 content of <20%), also varies between the basins in the SW Pacific. The CCD is ∼4600 m to the SE New Zealand, but only ∼4000 m to the NE New Zealand. The CaCO3 content of the sediment, however, can be influenced by a number of different factors other than dissolution; therefore, we suggest using the water chemistry to estimate the CCD. The depth difference between the CSH and CCD (??ZCSH−CCD), however, varies considerably in this region and globally. The global ??ZCSH−CCD appears to expand with increase in age of the deep-water, resulting from a shoaling of the CSH. In contrast the depth of the chemical lysocline (??calcite=0.8) is less variable globally and is relatively similar, or close, to the CCD determined from the sedimentary CaCO3%. Geochemical definitions of the CCD, however, cannot be used to determine changes in the paleo-CCD. For the given range of factors that influence the sedimentary CaCO3%, an independent dissolution proxy, such as the foraminifera fragmentation % (>40%=foraminiferal lysocline) is required to define a depth where significant CaCO3 dissolution has occurred back through time. The current foraminiferal lysocline for the SW Pacific region ranges from 3100-3500 m, which is predictably just slightly deeper than the CSH. This compilation of sediment and water chemistry data provides a CaCO3 dataset for the present SW Pacific for comparison with glacial/interglacial CaCO3 variations in deep-water sediment cores, and to monitor future changes in [CO32−] and dissolution of sedimentary CaCO3 resulting from increasing anthropogenic CO2. 相似文献