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Institution

University of Bremen

EducationBremen, Germany
About: University of Bremen is a education organization based out in Bremen, Germany. It is known for research contribution in the topics: Population & Glacial period. The organization has 14563 authors who have published 37279 publications receiving 970381 citations. The organization is also known as: Universität Bremen.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the absorption cross-sections of NO2 at atmospheric temperatures (223-293 K) and pressures (100 and 1000 mbar) were measured in the 250-800 nm (12500-40000 cm −1 ) region using Fourier-transform spectroscopy, at spectral resolutions of 0.5 cm − 1 above 435 nm and 1.0 cm−1 below 435 nm (corresponding to about 8 and 16 pm at this wavelength).
Abstract: The absorption cross-sections of NO2 at atmospheric temperatures (223–293 K) and pressures (100 and 1000 mbar) were measured in the 250–800 nm (12500–40000 cm −1 ) region using Fourier-transform spectroscopy, at spectral resolutions of 0.5 cm −1 above 435 nm and 1.0 cm −1 below 435 nm (corresponding to about 8 and 16 pm at this wavelength). The wavenumber accuracy of the new cross-sections is better than 0.1 cm −1 (about 0.5 pm at 250 nm and about 6.4 pm at 800 nm), validated by recording of I2 absorption spectra in the visible using the same experimental set-up (light source, beam splitter, interferometer optics). The NO 2 absorption spectra were recorded at five different sample temperatures between 223 and 293 K, and at each temperature at two total pressures (100 and 1000 mbar) using pure N2 as buffer gas. Despite the weakness of this effect compared to the density of the NO2 absorption structures, pressure-broadening was clearly observed at all temperatures. The pressure-broadening was partially modeled using a convolution of the low-pressure NO2 absorption spectra with a Lorentzian lineshape. The pressure-broadening coefficient increases significantly with decreasing temperature, as already observed in the mid- and near-infrared vibration–rotation spectra of NO2. This effect is of importance for high-resolution spectroscopy of the earth’s atmosphere in the UV–visible region. © 2002 Elsevier Science B.V. All rights reserved.

184 citations

Journal ArticleDOI
TL;DR: In this article, a retrieval error related to inaccuracies in water vapor spectroscopic parameters was identified, causing a substantial overestimation of methane correlated with high water vapor abundances.
Abstract: Methane retrievals from near-infrared spectra recorded by the SCIAMACHY instrument onboard ENVISAT hitherto suggested unexpectedly large tropical emissions Even though recent studies confirm substantial tropical emissions, there were indications for an unresolved error in the satellite retrievals Here we identify a retrieval error related to inaccuracies in water vapor spectroscopic parameters, causing a substantial overestimation of methane correlated with high water vapor abundances We report on the overall implications of an update in water spectroscopy on methane retrievals with special focus on the tropics where the impact is largest The new retrievals are applied in a four-dimensional variational (4D-VAR) data assimilation system to derive a first estimate of the impact on tropical CH_4 sources Compared to inversions based on previous SCIAMACHY retrievals, annual tropical emission estimates are reduced from 260 to about 201 Tg CH_4 but still remain higher than previously anticipated

184 citations

Posted Content
TL;DR: This work presents a principled solution to the problem of manifold encapsulation where the structure of the manifold S is encapsulated by two operators, state displacement and its inverse :SxS->R^n, and exploits the idea of encapsulation from a software engineering perspective in the Manifold Toolkit.
Abstract: Common estimation algorithms, such as least squares estimation or the Kalman filter, operate on a state in a state space S that is represented as a real-valued vector. However, for many quantities, most notably orientations in 3D, S is not a vector space, but a so-called manifold, i.e. it behaves like a vector space locally but has a more complex global topological structure. For integrating these quantities, several ad-hoc approaches have been proposed. Here, we present a principled solution to this problem where the structure of the manifold S is encapsulated by two operators, state displacement [+]:S x R^n --> S and its inverse [-]: S x S --> R^n. These operators provide a local vector-space view \delta; --> x [+] \delta; around a given state x. Generic estimation algorithms can then work on the manifold S mainly by replacing +/- with [+]/[-] where appropriate. We analyze these operators axiomatically, and demonstrate their use in least-squares estimation and the Unscented Kalman Filter. Moreover, we exploit the idea of encapsulation from a software engineering perspective in the Manifold Toolkit, where the [+]/[-] operators mediate between a "flat-vector" view for the generic algorithm and a "named-members" view for the problem specific functions.

184 citations

Journal ArticleDOI
TL;DR: In this article, the authors used time-series traps to measure the flux of organic carbon, biogenic silica and carbonate in the Southern Ocean and estimated the annual primary production for the entire Southern Ocean (south of 50°S), using various subsystems with characteristic carbon fluxes, is in the order of 1 × 109tons year−1; the organic carbon flux out of the photic layer is 0.17 × 109tonn year− 1.

184 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of plant genotype, soil type and nutrient use efficiency on the composition of different bacterial communities associated with rice roots were investigated using PCR, followed by denaturing gradient gel electrophoresis (PCR-DGGE).

184 citations


Authors

Showing all 14961 results

NameH-indexPapersCitations
Roger Y. Tsien163441138267
Klaus-Robert Müller12976479391
Ron Kikinis12668463398
Ulrich S. Schubert122222985604
Andreas Richter11076948262
Michael Böhm10875566103
Juan Bisquert10745046267
John P. Sumpter10126646184
Jos Lelieveld10057037657
Michael Schulz10075950719
Peter Singer9470237128
Charles R. Tyler9232531724
John P. Burrows9081536169
Hans-Peter Kriegel8944473932
Harald Haas8575034927
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
2023343
2022709
20212,106
20202,309
20192,191
20181,965