| 1. |
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| 2. |
- Wendisch, M., et al.
(författare)
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Atmospheric and Surface Processes, and Feedback Mechanisms Determining Arctic Amplification: A Review of First Results and Prospects of the (AC)(3) Project
- 2023
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Ingår i: Bulletin of the American Meteorological Society. - : American Meteorological Society. - 0003-0007 .- 1520-0477. ; 104:1
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Tidskriftsartikel (refereegranskat)abstract
- Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC)(3) project was established in 2016 (www.ac3-tr.de/). It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, shipborne, and satellite data of physical, chemical, and meteorological properties of the Arctic atmosphere, cryosphere, and upper ocean that are available for the Arctic climate research community. Short-term changes and indications of long-term trends in Arctic climate parameters have been detected using existing and new data. For example, a distinct atmospheric moistening, an increase of regional storm activities, an amplified winter warming in the Svalbard and North Pole regions, and a decrease of sea ice thickness in the Fram Strait and of snow depth on sea ice have been identified. A positive trend of tropospheric bromine monoxide (BrO) column densities during polar spring was verified. Local marine/biogenic sources for cloud condensation nuclei and ice nucleating particles were found. Atmospheric-ocean and radiative transfer models were advanced by applying new parameterizations of surface albedo, cloud droplet activation, convective plumes and related processes over leads, and turbulent transfer coefficients for stable surface layers. Four modes of the surface radiative energy budget were explored and reproduced by simulations. To advance the future synthesis of the results, cross-cutting activities are being developed aiming to answer key questions in four focus areas: lapse rate feedback, surface processes, Arctic mixed-phase clouds, and airmass transport and transformation.
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| 3. |
- Kerzenmacher, T., et al.
(författare)
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Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8:19, s. 5801--5841-
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Tidskriftsartikel (refereegranskat)abstract
- Vertical profiles of NO2 and NO have been obtained from solar occultation measurements by the Atmospheric Chemistry Experiment (ACE), using an infrared Fourier Transform Spectrometer (ACE-FTS) and (for NO2) an ultraviolet-visible-near-infrared spectrometer, MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation). In this paper, the quality of the ACE-FTS version 2.2 NO2 and NO and the MAESTRO version 1.2 NO2 data are assessed using other solar occultation measurements (HALOE, SAGE II, SAGE III, POAM III, SCIAMACHY), stellar occultation measurements (GOMOS), limb measurements (MIPAS, OSIRIS), nadir measurements (SCIAMACHY), balloon-borne measurements (SPIRALE, SAOZ) and ground-based measurements (UV-VIS, FTIR). Time differences between the comparison measurements were reduced using either a tight coincidence criterion, or where possible, chemical box models. ACE-FTS NO2 and NO and the MAESTRO NO2 are generally consistent with the correlative data. The ACE-FTS and MAESTRO NO2 volume mixing ratio (VMR) profiles agree with the profiles from other satellite data sets to within about 20% between 25 and 40 km, with the exception of MIPAS ESA (for ACE-FTS) and SAGE II (for ACE-FTS (sunrise) and MAESTRO) and suggest a negative bias between 23 and 40 km of about 10%. MAESTRO reports larger VMR values than the ACE-FTS. In comparisons with HALOE, ACE-FTS NO VMRs typically (on average) agree to ±8% from 22 to 64 km and to +10% from 93 to 105 km, with maxima of 21% and 36%, respectively. Partial column comparisons for NO2 show that there is quite good agreement between the ACE instruments and the FTIRs, with a mean difference of +7.3% for ACE-FTS and +12.8% for MAESTRO.
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| 4. |
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| 5. |
- Strong, K., et al.
(författare)
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Validation of ACE-FTS N2O measurements
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8, s. 4759-4786
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Tidskriftsartikel (refereegranskat)abstract
- The Atmospheric Chemistry Experiment (ACE), also known as SCISAT, was launched on 12 August 2003, carrying two instruments that measure vertical profiles of atmospheric constituents using the solar occultation technique. One of these instruments, the ACE Fourier Transform Spectrometer (ACE-FTS), is measuring volume mixing ratio (VMR) profiles of nitrous oxide (N2O) from the upper troposphere to the lower mesosphere at a vertical resolution of about 3–4 km. In this study, the quality of the ACE-FTS version 2.2 N2O data is assessed through comparisons with coincident measurements made by other satellite, balloon-borne, aircraft, and ground-based instruments. These consist of vertical profile comparisons with the SMR, MLS, and MIPAS satellite instruments, multiple aircraft flights of ASUR, and single balloon flights of SPIRALE and FIRS-2, and partial column comparisons with a network of ground-based Fourier Transform InfraRed spectrometers (FTIRs). Between 6 and 30 km, the mean absolute differences for the satellite comparisons lie between −42 ppbv and +17 ppbv, with most within ±20 ppbv. This corresponds to relative deviations from the mean that are within ±15%, except for comparisons with MIPAS near 30 km, for which they are as large as 22.5%. Between 18 and 30 km, the mean absolute differences for the satellite comparisons are generally within ±10 ppbv. From 30 to 60 km, the mean absolute differences are within ±4 ppbv, and are mostly between −2 and +1 ppbv. Given the small N2O VMR in this region, the relative deviations from the mean are therefore large at these altitudes, with most suggesting a negative bias in the ACE-FTS data between 30 and 50 km. In the comparisons with the FTIRs, the mean relative differences between the ACE-FTS and FTIR partial columns (which cover a mean altitude range of 14 to 27 km) are within ±5.6% for eleven of the twelve contributing stations. This mean relative difference is negative at ten stations, suggesting a small negative bias in the ACE-FTS partial columns over the altitude regions compared. Excellent correlation (R=0.964) is observed between the ACE-FTS and FTIR partial columns, with a slope of 1.01 and an intercept of −0.20 on the line fitted to the data.
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| 6. |
- Kasai, Y., et al.
(författare)
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Validation of stratospheric and mesospheric ozone observed by SMILES from International Space Station
- 2013
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 6:9, s. 2311-2338
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Tidskriftsartikel (refereegranskat)abstract
- We observed ozone (O3) in the vertical region between 250 and 0.0005 hPa (~ 12–96 km) using the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the Japanese Experiment Module (JEM) of the International Space Station (ISS) between 12 October 2009 and 21 April 2010. The new 4 K superconducting heterodyne receiver technology of SMILES allowed us to obtain a one order of magnitude better signal-to-noise ratio for the O3 line observation compared to past spaceborne microwave instruments. The non-sun-synchronous orbit of the ISS allowed us to observe O3 at various local times. We assessed the quality of the vertical profiles of O3 in the 100–0.001 hPa (~ 16–90 km) region for the SMILES NICT Level 2 product version 2.1.5. The evaluation is based on four components: error analysis; internal comparisons of observations targeting three different instrumental setups for the same O3 625.371 GHz transition; internal comparisons of two different retrieval algorithms; and external comparisons for various local times with ozonesonde, satellite and balloon observations (ENVISAT/MIPAS, SCISAT/ACE-FTS, Odin/OSIRIS, Odin/SMR, Aura/MLS, TELIS). SMILES O3 data have an estimated absolute accuracy of better than 0.3 ppmv (3%) with a vertical resolution of 3–4 km over the 60 to 8 hPa range. The random error for a single measurement is better than the estimated systematic error, being less than 1, 2, and 7%, in the 40–1, 80–0.1, and 100–0.004 hPa pressure regions, respectively. SMILES O3 abundance was 10–20% lower than all other satellite measurements at 8–0.1 hPa due to an error arising from uncertainties of the tangent point information and the gain calibration for the intensity of the spectrum. SMILES O3 from observation frequency Band-B had better accuracy than that from Band-A. A two month period is required to accumulate measurements covering 24 h in local time of O3 profile. However such a dataset can also contain variation due to dynamical, seasonal, and latitudinal effects
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| 7. |
- Carleer, M. R., et al.
(författare)
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Validation of water vapour profiles from the Atmospheric Chemistry Experiment (ACE)
- 2008
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Ingår i: Atmospheric Chemistry and Physics Discussion: An Interactive Open Access Journal of the European Geosciences Union. ; 8:2, s. 4499-4559
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Tidskriftsartikel (refereegranskat)abstract
- The Atmospheric Chemistry Experiment (ACE) mission was launched in August 2003 to sound the atmosphere by solar occultation. Water vapour (H2O), one of the most important molecules for climate and atmospheric chemistry, is one of the key species provided by the two principal instruments, the infrared Fourier Transform Spectrometer (ACE-FTS) and the MAESTRO UV-Visible spectrometer (ACE-MAESTRO). The first instrument performs measurements on several lines in the 1362–2137 cm−1 range, from which vertically resolved H2O concentration profiles are retrieved, from 7 to 90 km altitude. ACE-MAESTRO measures profiles using the water absorption band in the near infrared part of the spectrum at 926.0–969.7 nm. This paper presents a comprehensive validation of the ACE-FTS profiles. We have compared the H2O volume mixing ratio profiles with space-borne (SAGE II, HALOE, POAM III, MIPAS, SMR) observations and measurements from balloon-borne frostpoint hygrometers and a ground based lidar. We show that the ACE-FTS measurements provide H2O profiles with small retrieval uncertainties in the stratosphere (better than 5% from 15 to 70 km, gradually increasing above). The situation is unclear in the upper troposphere, due mainly to the high variability of the water vapour volume mixing ratio in this region. A new water vapour data product from the ACE-MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) is also presented and initial comparisons with ACE-FTS are discussed.
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| 8. |
- Clerbaux, C., et al.
(författare)
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CO measurements from the ACE-FTS satellite instrument: data analysis and validation using ground-based, airborne and spaceborne observations
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8, s. 2569-2594
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Tidskriftsartikel (refereegranskat)abstract
- The Atmospheric Chemistry Experiment (ACE) mission was launched in August 2003 to sound the atmosphere by solar occultation. Carbon monoxide (CO), a good tracer of pollution plumes and atmospheric dynamics, is one of the key species provided by the primary instrument, the ACE-Fourier Transform Spectrometer (ACE-FTS). This instrument performs measurements in both the CO 1-0 and 2-0 ro-vibrational bands, from which vertically resolved CO concentration profiles are retrieved, from the mid-troposphere to the thermosphere. This paper presents an updated description of the ACE-FTS version 2.2 CO data product, along with a comprehensive validation of these profiles using available observations (February 2004 to December 2006). We have compared the CO partial columns with ground-based measurements using Fourier transform infrared spectroscopy and millimeter wave radiometry, and the volume mixing ratio profiles with airborne (both high-altitude balloon flight and airplane) observations. CO satellite observations provided by nadir-looking instruments (MOPITT and TES) as well as limb-viewing remote sensors (MIPAS, SMR and MLS) were also compared with the ACE-FTS CO products. We show that the ACE-FTS measurements provide CO profiles with small retrieval errors (better than 5% from the upper troposphere to 40 km, and better than 10% above). These observations agree well with the correlative measurements, considering the rather loose coincidence criteria in some cases. Based on the validation exercise we assess the following uncertainties to the ACE-FTS measurement data: better than 15% in the upper troposphere (8–12 km), than 30% in the lower stratosphere (12–30 km), and than 25% from 30 to 100 km.
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| 9. |
- Reddington, C. L., et al.
(författare)
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Primary versus secondary contributions to particle number concentrations in the European boundary layer
- 2011
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:23, s. 12007-12036
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Tidskriftsartikel (refereegranskat)abstract
- It is important to understand the relative contribution of primary and secondary particles to regional and global aerosol so that models can attribute aerosol radiative forcing to different sources. In large-scale models, there is considerable uncertainty associated with treatments of particle formation (nucleation) in the boundary layer (BL) and in the size distribution of emitted primary particles, leading to uncertainties in predicted cloud condensation nuclei (CCN) concentrations. Here we quantify how primary particle emissions and secondary particle formation influence size-resolved particle number concentrations in the BL using a global aerosol microphysics model and aircraft and ground site observations made during the May 2008 campaign of the European Integrated Project on Aerosol Cloud Climate Air Quality Interactions (EUCAARI). We tested four different parameterisations for BL nucleation and two assumptions for the emission size distribution of anthropogenic and wildfire carbonaceous particles. When we emit carbonaceous particles at small sizes (as recommended by the Aerosol Inter-comparison project, AEROCOM), the spatial distributions of campaign-mean number concentrations of particles with diameter >50 nm (N(50)) and >100 nm (N(100)) were well captured by the model (R(2)>= 0.8) and the normalised mean bias (NMB) was also small (-18% for N(50) and -1% for N(100)). Emission of carbonaceous particles at larger sizes, which we consider to be more realistic for low spatial resolution global models, results in equally good correlation but larger bias (R(2)>= 0.8, NMB = -52% and -29%), which could be partly but not entirely compensated by BL nucleation. Within the uncertainty of the observations and accounting for the uncertainty in the size of emitted primary particles, BL nucleation makes a statistically significant contribution to CCN-sized particles at less than a quarter of the ground sites. Our results show that a major source of uncertainty in CCN-sized particles in polluted European air is the emitted size of primary carbonaceous particles. New information is required not just from direct observations, but also to determine the effective emission size and composition of primary particles appropriate for different resolution models.
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| 10. |
- Wolff, M.A., et al.
(författare)
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Validation of HNO3, ClONO2 and N2O5 from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8:13, s. 3529-3562
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Tidskriftsartikel (refereegranskat)abstract
- The Atmospheric Chemistry Experiment (ACE) satellite was launched on 12 August 2003. Its two instruments measure vertical profiles of over 30 atmospheric trace gases by analyzing solar occultation spectra in the ultraviolet/visible and infrared wavelength regions. The reservoir gases HNO3, ClONO2, and N2O5 are three of the key species provided by the primary instrument, the ACE Fourier Transform Spectrometer (ACE-FTS). This paper describes the ACE-FTS version 2.2 data products, including the N2O5 update, for the three species and presents validation comparisons with available observations. We have compared volume mixing ratio (VMR) profiles of HNO3, ClONO2, and N2O5 with measurements by other satellite instruments (SMR, MLS, MIPAS), aircraft measurements (ASUR), and single balloon-flights (SPIRALE, FIRS-2). Partial columns of HNO3 and ClONO2 were also compared with measurements by ground-based Fourier Transform Infrared (FTIR) spectrometers. Overall the quality of the ACE-FTS v2.2 HNO3 VMR profiles is good from 18 to 35 km. For the statistical satellite comparisons, the mean absolute differences are generally within ±1 ppbv ±20%) from 18 to 35 km. For MIPAS and MLS comparisons only, mean relative differences lie within±10% between 10 and 36 km. ACE-FTS HNO3 partial columns (~15–30 km) show a slight negative bias of −1.3% relative to the ground-based FTIRs at latitudes ranging from 77.8° S–76.5° N. Good agreement between ACE-FTS ClONO2 and MIPAS, using the Institut für Meteorologie und Klimaforschung and Instituto de Astrofísica de Andalucía (IMK-IAA) data processor is seen. Mean absolute differences are typically within ±0.01 ppbv between 16 and 27 km and less than +0.09 ppbv between 27 and 34 km. The ClONO2 partial column comparisons show varying degrees of agreement, depending on the location and the quality of the FTIR measurements. Good agreement was found for the comparisons with the midlatitude Jungfraujoch partial columns for which the mean relative difference is 4.7%. ACE-FTS N2O5 has a low bias relative to MIPAS IMK-IAA, reaching −0.25 ppbv at the altitude of the N2O5 maximum (around 30 km). Mean absolute differences at lower altitudes (16–27 km) are typically −0.05 ppbv for MIPAS nighttime and ±0.02 ppbv for MIPAS daytime measurements.
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| 11. |
- Baron, P., et al.
(författare)
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The level 2 research product algorithms for the superconducting submillimeter-wave limb-emission sounder (SMILES)
- 2011
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Ingår i: Atmospheric Measurement Techniques Discussions. - : Copernicus GmbH. - 1867-8610. ; 4:3, s. 3593-3645
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the algorithms of the level-2 research (L2r) processingchain developed for the Superconducting Submillimeter-Wave Limb-EmissionSounder (SMILES). The chain has been developed in parallel to the operationalchain for conducting researches on calibration and retrieval algorithms. L2rchain products are available to the scientific community. The objective ofversion 2 is the retrieval of the vertical distribution of trace gases in thealtitude range of 18-90 km. An theoretical error analysis is conducted toestimate the retrieval feasibility of key parameters of the processing:line-of-sight elevation tangent altitudes (or angles), temperature and O3 profiles. The line-of-sight tangent altitudes are retrievedbetween 20 and 50 km from the strong ozone (O3) line at 625.371 GHz,with low correlation with the O3 volume-mixing ratio and temperatureretrieved profiles. Neglecting the non-linearity of the radiometric gain inthe calibration procedure is the main systematic error. It is large for theretrieved temperature (between 5-10 K). Therefore, atmospheric pressure cannot be derived from the retrieved temperature, and, then, in the altituderange where the line-of-sight tangent altitudes are retrieved, the retrievedtrace gases profiles are found to be better represented on pressure levelsthan on altitude levels. The error analysis for the retrieved HOCl profiledemonstrates that best results for inverting weak lines can be obtained byusing narrow spectral windows. Future versions of the L2r algorithms willimprove the temperature/pressure retrievals and also provide information inthe upper tropospheric/lower stratospheric region (e.g., water vapor, icecontent, O3) and on stratospheric and mesospheric line-of-sight winds.
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| 12. |
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| 13. |
- Baron, P., et al.
(författare)
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The Level 2 research product algorithms for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)
- 2011
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 4, s. 2105-2124
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the algorithms of the level-2 research (L2r) processing chain developed for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES). The chain has been developed in parallel to the operational chain for conducting researches on calibration and retrieval algorithms. L2r chain products are available to the scientific community. The objective of version 2 is the retrieval of the vertical distribution of trace gases in the altitude range of 18–90 km. A theoretical error analysis is conducted to estimate the retrieval feasibility of key parameters of the processing: line-of-sight elevation tangent altitudes (or angles), temperature and ozone profiles. While pointing information is often retrieved from molecular oxygen lines, there is no oxygen line in the SMILES spectra, so the strong ozone line at 625.371 GHz has been chosen. The pointing parameters and the ozone profiles are retrieved from the line wings which are measured with high signal to noise ratio, whereas the temperature profile is retrieved from the optically thick line center. The main systematic component of the retrieval error was found to be the neglect of the non-linearity of the radiometric gain in the calibration procedure. This causes a temperature retrieval error of 5–10 K. Because of these large temperature errors, it is not possible to construct a reliable hydrostatic pressure profile. However, as a consequence of the retrieval of pointing parameters, pressure induced errors are significantly reduced if the retrieved trace gas profiles are represented on pressure levels instead of geometric altitude levels. Further, various setups of trace gas retrievals have been tested. The error analysis for the retrieved HOCl profile demonstrates that best results for inverting weak lines can be obtained by using narrow spectral windows.
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| 14. |
- Goobar, Ariel, et al.
(författare)
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THE RISE OF SN 2014J IN THE NEARBY GALAXY M82
- 2014
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 784:1
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Tidskriftsartikel (refereegranskat)abstract
- We report on the discovery of SN 2014J in the nearby galaxy M82. Given its proximity, it offers the best opportunity to date to study a thermonuclear supernova (SN) over a wide range of the electromagnetic spectrum. Optical, near-IR, and mid-IR observations on the rising light curve, orchestrated by the intermediate Palomar Transient Factory, show that SN 2014J is a spectroscopically normal Type Ia supernova (SN Ia), albeit exhibiting high-velocity features in its spectrum and heavily reddened by dust in the host galaxy. Our earliest detections start just hours after the fitted time of explosion. We use high-resolution optical spectroscopy to analyze the dense intervening material and do not detect any evolution in the resolved absorption features during the light curve rise. Similar to other highly reddened SNe Ia, a low value of total-to-selective extinction, R-V less than or similar to 2, provides the best match to our observations. We also study pre-explosion optical and near-IR images from Hubble Space Telescope with special emphasis on the sources nearest to the SN location.
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| 15. |
- Poorter, Lourens, et al.
(författare)
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Wet and dry tropical forests show opposite successional pathways in wood density but converge over time
- 2019
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Ingår i: Nature Ecology & Evolution. - : Nature Publishing Group. - 2397-334X. ; 3:6, s. 928-934
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Tidskriftsartikel (refereegranskat)abstract
- Tropical forests are converted at an alarming rate for agricultural use and pastureland, but also regrow naturally through secondary succession. For successful forest restoration, it is essential to understand the mechanisms of secondary succession. These mechanisms may vary across forest types, but analyses across broad spatial scales are lacking. Here, we analyse forest recovery using 1,403 plots that differ in age since agricultural abandonment from 50 sites across the Neotropics. We analyse changes in community composition using species-specific stem wood density (WD), which is a key trait for plant growth, survival and forest carbon storage. In wet forest, succession proceeds from low towards high community WD (acquisitive towards conservative trait values), in line with standard successional theory. However, in dry forest, succession proceeds from high towards low community WD (conservative towards acquisitive trait values), probably because high WD reflects drought tolerance in harsh early successional environments. Dry season intensity drives WD recovery by influencing the start and trajectory of succession, resulting in convergence of the community WD over time as vegetation cover builds up. These ecological insights can be used to improve species selection for reforestation. Reforestation species selected to establish a first protective canopy layer should, among other criteria, ideally have a similar WD to the early successional communities that dominate under the prevailing macroclimatic conditions.
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| 16. |
- Dupuy, T. J., et al.
(författare)
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Multiplicity of cool dwarfs
- 2013
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Ingår i: Astronomical Notes - Astronomische Nachrichten. - : Wiley. - 0004-6337 .- 1521-3994. ; 334:1-2, s. 36-39
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Tidskriftsartikel (refereegranskat)abstract
- Multiple systems have long been used to probe the origin and evolution of stars of all masses. Only in the past 10-15 years have such studies been extended to brown dwarfs and the lowest mass stars through binary surveys of both young star forming regions and the older field population. In addition, a groundswell of interest in M dwarfs in recent years has resulted in large, modern datasets for these most common stars in the Galaxy, thereby enabling renewed perspectives on their multiplicity properties. These latest observational results have in turn fueled the many theories competing to explain the formation of low-mass stars and brown dwarfs. This Cool Stars 17 splinter session examined the current state of this field by reviewing results from the numerous observational techniques - radial velocities, astrometry, direct imaging, and synoptic surveys - that have been used to study multiplicity from the earliest embedded protostars to objects in young star forming regions, old and intermediate-age clusters, as well as the more heterogeneous field population.
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| 17. |
- Gei, Maga, et al.
(författare)
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Legume abundance along successional and rainfall gradients in Neotropical forests
- 2018
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Ingår i: Nature Ecology & Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 2:7
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Tidskriftsartikel (refereegranskat)abstract
- The nutrient demands of regrowing tropical forests are partly satisfied by nitrogen-fixing legume trees, but our understanding of the abundance of those species is biased towards wet tropical regions. Here we show how the abundance of Leguminosae is affected by both recovery from disturbance and large-scale rainfall gradients through a synthesis of forest inventory plots from a network of 42 Neotropical forest chronosequences. During the first three decades of natural forest regeneration, legume basal area is twice as high in dry compared with wet secondary forests. The tremendous ecological success of legumes in recently disturbed, water-limited forests is likely to be related to both their reduced leaflet size and ability to fix N2, which together enhance legume drought tolerance and water-use efficiency. Earth system models should incorporate these large-scale successional and climatic patterns of legume dominance to provide more accurate estimates of the maximum potential for natural nitrogen fixation across tropical forests.
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| 18. |
- Lossow, Stefan, 1977, et al.
(författare)
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Comparison of HDO measurements from Envisat/MIPAS with observations by Odin/SMR and SCISAT/ACE-FTS
- 2011
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 4:9, s. 1855-1874
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of thermal emission in the mid-infrared by Envisat/MIPAS allow the retrieval of HDO information roughly in the altitude range between 10 km and 50 km. From June 2002 to March 2004 MIPAS performed measurements in the full spectral resolution mode. To assess the quality of the HDO data set obtained during that period comparisons with measurements by Odin/SMR and SCISAT/ACE-FTS were performed. Comparisons were made on profile-to-profile basis as well as using seasonal and monthly averages. All in all the comparisons yield favourable results. The largest deviations between MIPAS and ACE-FTS are observed below 15 km, where relative deviations can occasionally exceed 100%. Despite these deviations in the absolute amount of HDO the latitudinal structures observed by both instruments are consistent in this altitude range. Between 15 km and 20 km there is less good agreement, in particular in the Antarctic during winter and spring. Also in the tropics some deviations are found. Above 20 km there is a high consistency in the structures observed by all three instruments. MIPAS and ACE-FTS typically agree within 10%, with MIPAS mostly showing higher abundances than ACE-FTS. Both data sets show considerably more HDO than SMR. This bias can be explained basically by uncertainties in spectroscopic parameters. Above 40 km, where the MIPAS HDO retrieval reaches its limits, still good agreement with the structures observed by SMR is found for most seasons. This puts some confidence in the MIPAS data at these altitudes.
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| 19. |
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| 20. |
- Raskovalova, T, et al.
(författare)
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Diagnostic accuracy of combined cardiac troponin and copeptin assessment for early rule-out of myocardial infarction: : a systematic review and meta-analysis
- 2014
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Ingår i: European Heart Journal. - : Oxford University Press (OUP). - 2048-8726 .- 2048-8734. ; 3:1, s. 18-27
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: This systematic review aimed to investigate the diagnostic accuracy of combined cardiac troponin (cTn) and copeptin assessment in comparison to cTn alone for early rule-out of acute myocardial infarction (AMI).METHODS: Primary studies were eligible if they evaluated diagnostic accuracy for cTn with and without copeptin in patients with symptoms suggestive of AMI. AMI was defined according to the universal definition, using detection of cTn as a marker for myocardial necrosis. Eligible studies were identified by searching electronic databases (Medline, EMBASE, Science Citation Index Expanded, CINAHL, Pascal, and Cochrane) from inception to March 2013, reviewing conference proceedings and contacting field experts and the copeptin manufacturer.RESULTS: In 15 studies totalling 8740 patients (prevalence of AMI 16%), adding copeptin improved the sensitivity of cTn assays (from 0.87 to 0.96, p=0.003) at the expense of lower specificity (from 0.84 to 0.56, p<0.001). In 12 studies providing data for 6988 patients without ST-segment elevation, the summary sensitivity and specificity estimates were 0.95 (95% CI 0.89 to 0.98) and 0.57 (95% CI 0.49 to 0.65) for the combined assessment of cTn and copeptin. When a high-sensitivity cTnT assay was used in combination with copeptin, the summary sensitivity and specificity estimates were 0.98 (95% CI 0.96 to 1.00) and 0.50 (95% CI 0.42 to 0.58).CONCLUSION: Despite substantial between-study heterogeneity, this meta-analysis demonstrates that copeptin significantly improves baseline cTn sensitivity. Management studies are needed to establish the effectiveness and safety of measuring copeptin in combination with high-sensitivity cTnT for early rule-out of AMI without serial testing.
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| 21. |
- Sagawa, H., et al.
(författare)
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Comparison of SMILES ClO profiles with satellite, balloon-borne and ground-based measurements
- 2013
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 6:12, s. 3325-3347
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Tidskriftsartikel (refereegranskat)abstract
- We evaluate the quality of ClO profiles derived from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station (ISS). Version 2.1.5 of the level-2 product generated by the National Institute of Information and Communications Technology (NICT) is the subject of this study. Based on sensitivity studies, the systematic error was estimated as 5–10 pptv at the pressure range of 80–20 hPa, 35 pptv at the ClO peak altitude (~ 4 hPa), and 5–10 pptv at pressures ≤ 0.5 hPa for daytime mid-latitude conditions. For nighttime measurements, a systematic error of 8 pptv was estimated for the ClO peak altitude (~ 2 hPa). The SMILES NICT v2.1.5 ClO profiles agree with those derived from another level-2 processor developed by the Japan Aerospace Exploration Agency (JAXA) within the bias uncertainties, except for the nighttime measurements in the low and middle latitude regions where the SMILES NICT v2.1.5 profiles have a negative bias of ~ 30 pptv in the lower stratosphere. This bias is considered to be due to the use of a limited spectral bandwidth in the retrieval process of SMILES NICT v2.1.5, which makes it difficult to distinguish between the weak ClO signal and wing contributions of spectral features outside the bandwidth. In the middle and upper stratosphere outside the polar regions, no significant systematic bias was found for the SMILES NICT ClO profile with respect to data sets from other instruments such as the Aura Microwave Limb Sounder (MLS), the Odin Sub-Millimetre Radiometer (SMR), the Envisat Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), and the ground-based radiometer at Mauna Kea, which demonstrates the scientific usability of the SMILES ClO data including the diurnal variations. Inside the chlorine-activated polar vortex, the SMILES NICT v2.1.5 ClO profiles show larger volume mixing ratios by 0.4 ppbv (30%) at 50 hPa compared to those of the JAXA processed profiles. This discrepancy is also considered to be an effect of the limited spectral bandwidth in the retrieval processing. We also compared the SMILES NICT ClO profiles of chlorine-activated polar vortex conditions with those measured by the balloon-borne instruments: Terahertz and submillimeter Limb Sounder (TELIS) and the MIPAS-balloon instrument (MIPAS-B). In conclusion, the SMILES NICT v2.1.5 ClO data can be used at pressures ≤ ~30 hPa for scientific analysis.
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| 22. |
- Castellanos-Jankiewicz, A., et al.
(författare)
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Short Article Hypothalamic bile acid-TGR5 signaling protects from obesity
- 2021
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Ingår i: Cell Metabolism. - : Elsevier BV. - 1550-4131. ; 33:7
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Tidskriftsartikel (refereegranskat)abstract
- Bile acids (BAs) improve metabolism and exert anti-obesity effects through the activation of the Takeda G protein-coupled receptor 5 (TGR5) in peripheral tissues. TGR5 is also found in the brain hypothalamus, but whether hypothalamic BA signaling is implicated in body weight control and obesity pathophysiology remains unknown. Here we show that hypothalamic BA content is reduced in diet-induced obese mice. Central administration of BAs or a specific TGR5 agonist in these animals decreases body weight and fat mass by activating the sympathetic nervous system, thereby promoting negative energy balance. Conversely, genetic downregulation of hypothalamic TGR5 expression in the mediobasal hypothalamus favors the development of obesity and worsens established obesity by blunting sympathetic activity. Lastly, hypothalamic TGR5 signaling is required for the anti-obesity action of dietary BA supplementation. Together, these findings identify hypothalamic TGR5 signaling as a key mediator of a top-down neural mechanism that counteracts diet induced obesity.
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| 23. |
- Chazdon, Robin L., et al.
(författare)
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Carbon sequestration potential of second-growth forest regeneration in the Latin American tropics
- 2016
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 2:5
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Tidskriftsartikel (refereegranskat)abstract
- Regrowth of tropical secondary forests following complete or nearly complete removal of forest vegetation actively stores carbon in aboveground biomass, partially counterbalancing carbon emissions from deforestation, forest degradation, burning of fossil fuels, and other anthropogenic sources. We estimate the age and spatial extent of lowland second-growth forests in the Latin American tropics and model their potential aboveground carbon accumulation over four decades. Our model shows that, in 2008, second-growth forests (1 to 60 years old) covered 2.4 million km2 of land (28.1% of the total study area). Over 40 years, these lands can potentially accumulate a total aboveground carbon stock of 8.48 Pg C (petagrams of carbon) in aboveground biomass via low-cost natural regeneration or assisted regeneration, corresponding to a total CO2 sequestration of 31.09 Pg CO2. This total is equivalent to carbon emissions from fossil fuel use and industrial processes in all of Latin America and the Caribbean from 1993 to 2014. Ten countries account for 95% of this carbon storage potential, led by Brazil, Colombia, Mexico, and Venezuela. We model future land-use scenarios to guide national carbon mitigation policies. Permitting natural regeneration on 40% of lowland pastures potentially stores an additional 2.0 Pg C over 40 years. Our study provides information and maps to guide national-level forest-based carbon mitigation plans on the basis of estimated rates of natural regeneration and pasture abandonment. Coupled with avoided deforestation and sustainable forest management, natural regeneration of second-growth forests provides a low-cost mechanism that yields a high carbon sequestration potential with multiple benefits for biodiversity and ecosystem services.
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| 24. |
- Guerin, S, et al.
(författare)
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Radiation dose as a risk factor for malignant melanoma following childhood cancer
- 2003
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Ingår i: European Journal of Cancer. - 1879-0852. ; 39:16, s. 2379-2386
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine therapy-related risk factors for the development of melanoma after childhood cancer. Among 4401 3-year survivors of a childhood cancer in eight French and British centres and 25 120 patients younger than 20 years old at first malignant neoplasm (FMN) extracted from the Nordic Cancer Registries, 16 patients developed a melanoma as a second malignant neoplasm (SMN). A cohort study of the French and British cohorts was performed. In a nested case-control study, the 16 patients who developed a melanoma as a SMN (cases) were matched with 3-5 controls in their respective cohort according to gender, age at the first cancer, the calendar year of occurrence of the first cancer and follow-up. Radiotherapy appeared to increase the risk of melanoma for local doses > 15 Gy, Odds Ratio (OR)= 13 (95% Confidence Interval (CI): 0.94-174). Regarding chemotherapy, we observed an increased OR for both alkylating agents and spindle inhibitors, OR 2.7 (95% CI: 0.5-14). Children treated for a gonadal tumour as a FMN were found to be at a higher risk of melanoma, OR 8.7 (95% CI: 0.9-86). The adjusted OR for the local radiation dose was 1.07 (95% CI: 1.00-1.15). In conclusion, radiotherapy may contribute to an increased risk of melanoma as a SMN, but only at very high doses of low linear energy transfer radiation. Common genetic origins between gonadal tumours and malignant melanomas are likely. (C) 2003 Elsevier Ltd. All rights reserved.
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