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By SAMUEL HAMMER FELIX VOGEL MARKUS KAUL INGEBORG LEVIN 《Tellus. Series B, Chemical and physical meteorology》2009,61(3):547-555
The hydrogen-to-carbon monoxide (H2 /CO) emission ratio of anthropogenic combustion sources was determined from more than two years of quasi-continuous atmospheric observations in Heidelberg (49°24' N, 8°42' E), located in the polluted Rhein-Neckar region. Evaluating concurrent mixing ratio changes of H2 and CO during morning rush hours yielded mean molar H2 /CO ratios of 0.40 ± 0.06, while respective results inferred from synoptic pollution events gave a mean value of 0.31 ± 0.05 mole H2 /mole CO. After correction for the influence of the H2 soil sink on the measured ratios, mean values of 0.46 ± 0.07 resp. 0.48 ± 0.07 mole H2 /mole CO were obtained, which are in excellent agreement with direct source studies of traffic emissions in the Heidelberg/Mannheim region (0.448 ± 0.003 mole H2 /mole CO). Including results from other European studies, our best estimate of the mean H2 /CO emission ratio from anthropogenic combustion sources (mainly traffic) ranges from 0.45 to 0.48 mole H2 /mole CO, which is about 20% smaller than the value of 0.59 mole H2 /mole CO which is frequently used as the basis to calculate global H2 emissions from anthropogenic combustion sources. 相似文献
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Asynchronous data assimilation with the EnKF 总被引：3，自引：0，他引：3
This study revisits the problem of assimilation of asynchronous observations, or four-dimensional data assimilation, with the ensemble Kalman filter (EnKF). We show that for a system with perfect model and linear dynamics the ensemble Kalman smoother (EnKS) provides a simple and efficient solution for the problem: one just needs to use the ensemble observations (that is, the forecast observations for each ensemble member) from the time of observation during the update, for each assimilated observation. This recipe can be used for assimilating both past and future data; in the context of assimilating generic asynchronous observations we refer to it as the asynchronous EnKF. The asynchronous EnKF is essentially equivalent to the four-dimensional variational data assimilation (4D-Var). It requires only one forward integration of the system to obtain and store the data necessary for the analysis, and therefore is feasible for large-scale applications. Unlike 4D-Var, the asynchronous EnKF requires no tangent linear or adjoint model. 相似文献
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By BERNADETT WEINZIERL REAS PETZOLD MICHAEL ESSELBORN MARTIN WIRTH KATHARINA RASP KONRAD KANDLER LOTHAR SCHÜTZ PETER KOEPKE MARKUS FIEBIG 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):96-117
The Saharan Mineral Dust Experiment (SAMUM) was conducted in May/June 2006 in southern Morocco. As part of SAMUM, airborne in situ measurements of the particle size distribution in the diameter range 4 nm < D p < 100 μm were conducted. The aerosol mixing state was determined below D p < 2.5 μm. Furthermore, the vertical structure of the dust layers was investigated with a nadir-looking high spectral resolution lidar (HSRL). The desert dust aerosol exhibited two size regimes of different mixing states: below 0.5 μm, the particles had a non-volatile core and a volatile coating; larger particles above 0.5 μm consisted of non-volatile components and contained light absorbing material. In all cases, particles larger than 10 μm were present, and in 80% of the measurements no particles larger than 40 μm were present. The abundance of large particles showed almost no height dependence. The effective diameter D eff in the dust plumes investigated showed two main ranges: the first range of D eff peaked around 5 μm and the second range of D eff around 8 μm. The two ranges of D eff suggest that it may be inadequate to use one average effective diameter or one parametrization for a typical dust size distribution. 相似文献
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The generation of internal waves from barotropic tides can be quantified in terms of the conversion rates. These have often been obtained by applying the WKB approximation, which yields an expression for the conversion rates which is proportional to the seabed buoyancy frequency N B . For small values of N B or strong variations of the buoyancy profile N ( z ) , this gives unreliable results. Using homogenization theory it is here shown that the conversion rate instead depends on the value of N ( z ) averaged over a vertical region at the bottom of the same magnitude as the vertical length-scale of the internal wave, which for the lowest modes is of the same order as the entire ocean depth. This gives a substantially larger conversion rate. 相似文献
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By ARTEM SARAFANOV HERLÉ MERCIER ANASTASIA FALINA ALEXEY SOKOV PASCALE LHERMINIER 《地球，A辑:动力气象学与海洋学》2010,62(1):80-90
Recent decadal salinity changes in the Greenland-Scotland overflow-derived deep waters are quantified using CTD data from repeated hydrographic sections in the Irminger Sea. The Denmark Strait Overflow Water salinity record shows the absence of any net change over the 1980s–2000s; changes in the Iceland–Scotland Overflow Water (ISOW) and in the deep water column (σ0 > 27.82), enclosing both overflows, show a distinct freshening reversal in the early 2000s. The observed freshening reversal is a lagged consequence of the persistent ISOW salinification that occurred upstream, in the Iceland Basin, after 1996 in response to salinification of the northeast Atlantic waters entrained into the overflow. The entrainment salinity increase is explained by the earlier documented North Atlantic Oscillation (NAO)-induced contraction of the subpolar gyre and corresponding northwestward advance of subtropical waters that followed the NAO decline in the mid-1990s and continued through the mid-2000s. Remarkably, the ISOW freshening reversal is not associated with changes in the overflow water salinity. This suggests that changes in the NAO-dependent relative contributions of subpolar and subtropical waters to the entrainment south of the Iceland–Scotland Ridge may dominate over changes in the Nordic Seas freshwater balance with respect to their effect on the ISOW salinity. 相似文献
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By BIRGIT HEESE DIETRICH ALTHAUSEN TILMAN DINTER MICHAEL ESSELBORN THOMAS MÜLLER MATTHIAS TESCHE MATTHIAS WIEGNER 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):195-205
Vertical profiles of dust key optical properties are presented from measurements during the Saharan Mineral Dust Experiment (SAMUM) by Raman and depolarization lidar at two ground-based sites and by airborne high spectral resolution lidar. One of the sites, Tinfou, is located close to the border of the Sahara in Southern Morocco and was the main in situ site during SAMUM. The other site was Ouarzazate airport, the main lidar site. From the lidar measurements the spatial distribution of the dust between Tinfou and Ouarzazate was derived for 1 d. The retrieved profiles of backscatter and extinction coefficients and particle depolarization ratios show comparable dust optical properties, a similar vertical structure of the dust layer, and a height of about 4 km asl at both sites. The airborne cross-section of the extinction coefficient at the two sites confirms the low variability in dust properties. Although the general picture of the dust layer was similar, the lidar measurements reveal a higher dust load closer to the dust source. Nevertheless, the observed intensive optical properties were the same. These results indicate that the lidar measurements at two sites close to the dust source are both representative for the SAMUM dust conditions. 相似文献
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By KYUNG-SOOK YUN BAOHUA REN KYUNG-JA HA JOHNNY C. L. CHAN JONG-GHAP JHUN 《地球，A辑:动力气象学与海洋学》2009,61(5):565-578
Based on 30–60-day oscillation in the East Asian summer monsoon (EASM), the relationship between its northward propagation and ENSO (El Niño and Southern Oscillation) was investigated. To explicitly describe the 30–60-day monsoonal evolution, an empirical orthogonal function (EOF) analysis was carried out on the temporal-latitude section of the longitudinal average for 115°E–120°E. The principal 30–60-day EASM mode captures a northward propagation of well-organized intraseasonal oscillation (NISO). Using the associated time series of the first mode, we found a significant lagged correlation between interannual variability of the NISO and ENSO. Its lagged correlations with NINO indices have a quasi-biennial (QB) characteristic through the preceding summer and the concurrent summer. Their relationship was found by the regression analysis relating the low-level circulation to the ocean temperature. The western North Pacific anticyclone and the anticyclone-induced easterly vertical wind shear anomalies induce the dynamical linkage between the NISO and QB-type ENSO. It is shown that the NISO is more closely tied with QB-type ENSO in its phase than in its amplitude, and may be connected to the anomalous easterly wind and the eastward evolution of an oceanic Kelvin wave, which is associated with abrupt ENSO transition. The predictability on ENSO and NISO is examined through the canonical correlation analysis. 相似文献
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Fine-grained glaciomarine and glacial deposits on the outer Mid Norwegian continental shelf show complex variations in shear strength and degree of consolidation. At the Smørbukk Sør field (approx. 65°N, 7°E) about 80 m of variably overconsolidated clayey till is found on top of normally- or possibly underconsolidated glaciomarine and marine sediments. A high gas content is found below 60 m, and the porewater in the rather soft sediments in the lower part of the borehole may have been partly trapped by gas hydrates when the overlying hard till was deposited. The variations in geotechnical properties of the 80 m thick till section are suggested to result mainly from compaction below grounded ice during the last glaciation, and we interpret the strength variations in the till to reflect shifts between freeze of sediment porewater onto the base of the ice causing highly overconsolidated intervals, and thermal equilibrium or melting at the ice sole resulting in intervals of softer till.A large ridge northwest of Smørbukk (Skjoldryggen) is probably partly formed by ice push during ice flow oscillations at the same time as the described till at Smørbukk was deposited. This ridge retarded the ice flow and hence the frictional heating at the end of surges, creating pulses of net freezing base ice and consolidation of the substratum. The described process has possibly affected a wide area up-ice of Skjoldryggen, and may be common in areas with a complex glacial history and a fine-grained substratum. 相似文献