| 1. |
- Chen, Hans W., et al.
(författare)
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Evaluation of Regional CO2 Mole Fractions in the ECMWF CAMS Real-Time Atmospheric Analysis and NOAA CarbonTracker Near-Real-Time Reanalysis With Airborne Observations From ACT-America Field Campaigns
- 2019
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Ingår i: Journal of Geophysical Research: Atmospheres. - 2169-8996 .- 2169-897X. ; 124:14, s. 8119-8133
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Tidskriftsartikel (refereegranskat)abstract
- This study systematically examines the regional uncertainties and biases in carbon dioxide (CO2) mole fractions from two of the state-of-the-art global CO2 analysis products, namely, the Copernicus Atmosphere Monitoring Service (CAMS) real-time atmospheric analysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the CarbonTracker Near-Real-Time (CT-NRT) reanalysis from the National Oceanic and Atmospheric Administration (NOAA), by evaluation against hundreds of hours of airborne in situ measurements from the summer 2016 and winter 2017 Atmospheric Carbon and Transport (ACT)-America field campaigns. Both the CAMS and CT-NRT analyses agree reasonably well with the independent ACT-America airborne CO2 measurements in the free troposphere, with root-mean-square deviations (RMSDs) between analyses and observations generally between 1 and 2 ppm but show considerably larger uncertainties in the atmospheric boundary layer where the RMSDs exceed 8 ppm in the lowermost 1 km of the troposphere in summer. There are strong variations in accuracy and bias between seasons, and across three different subregions in the United States (Mid-Atlantic, Midwest, and South), with the largest uncertainties in the Mid-Atlantic region in summer. Overall, the RMSDs of the CAMS and CT-NRT analyses against airborne data are comparable to each other and largely consistent with the differences between the two analyses. The current study provides uncertainty estimates for both analysis products over North America and suggests that these two independent estimates can be used to approximate regional CO2 analysis uncertainties. Both statistics are important in future studies in quantifying the uncertainties in regional CO2 mole fraction and flux estimates.
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| 2. |
- Zheng, Fenglian, et al.
(författare)
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Structural and functional hippocampal alterations in Multiple sclerosis and neuromyelitis optica spectrum disorder
- 2022
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Ingår i: Multiple Sclerosis Journal. - : SAGE Publications. - 1352-4585 .- 1477-0970. ; 28:5, s. 707-717
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Tidskriftsartikel (refereegranskat)abstract
- Background: Hippocampal involvement may differ between multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD). Objective: To investigate the morphometric, diffusion and functional alterations in hippocampus in MS and NMOSD and the clinical significance. Methods: A total of 752 participants including 236 MS, 236 NMOSD and 280 healthy controls (HC) were included in this retrospective multi-center study. The hippocampus and subfield volumes, fractional anisotropy (FA) and mean diffusivity (MD), amplitude of low frequency fluctuation (ALFF) and degree centrality (DC) were analyzed, and their associations with clinical variables were investigated. Results: The hippocampus showed significantly lower volume, FA and greater MD in MS compared to NMOSD and HC (p < 0.05), while no abnormal ALFF or DC was identified in any group. Hippocampal subfields were affected in both diseases, though subiculum, presubiculum and fimbria showed significantly lower volume only in MS (p < 0.05). Significant correlations between diffusion alterations, several subfield volumes and clinical variables were observed in both diseases, especially in MS (R = -0.444 to 0.498, p < 0.05). FA and MD showed fair discriminative power between MS and HC, NMOSD and HC (AUC > 0.7). Conclusions: Hippocampal atrophy and diffusion abnormalities were identified in MS and NMOSD, partly explaining how clinical disability and cognitive impairment are differentially affected.
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| 3. |
- Chen, Aifang, 1990, et al.
(författare)
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Rising future tropical cyclone-induced extreme winds in the Mekong River Basin
- 2020
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Ingår i: Science Bulletin. - : Elsevier BV. - 2095-9273 .- 2095-9281. ; 65:5, s. 419-424
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Science China Press The societal impact of extreme winds induced by tropical cyclones (TCs) is a major concern in the Mekong River Basin (MRB). Though no clear trend of landfalling TC intensity along the Vietnam coastline has been observed since the 1970s, climate models project an increasing TC intensity in the 21st century over the Western North Pacific, which is the primary TC source region influencing the MRB. Yet, how future TC activities will affect extreme winds quantitatively in the MRB remains unclear. By employing a novel dynamical downscaling technique using a specialized, coupled ocean-atmospheric model, shorter return periods of maximum wind speed in the MRB for 2081–2100 compared with 1981–2000 are projected based on five global climate models under the RCP8.5 scenario, suggesting increases in the future tropical cyclone intensity. The results point to consistently elevated future TC-related risks that may jeopardize sustainable development, disrupt food supply, and exacerbate conflicts in the region and beyond.
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| 4. |
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| 5. |
- Chen, Hans, 1988, et al.
(författare)
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Regional CO2 inversion through ensemble-based simultaneous state and parameter estimation: TRACE framework and controlled experiments
- 2023
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Ingår i: Journal of Advances in Modeling Earth Systems. - 1942-2466. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric inversions provide estimates of carbon dioxide (CO2) fluxes between the surface and atmosphere based on atmospheric CO2 concentration observations. The number of CO2 observations is projected to increase severalfold in the next decades from expanding in situ networks and next-generation CO2-observing satellites, providing both an opportunity and a challenge for inversions. This study introduces the TRACE Regional Atmosphere-Carbon Ensemble (TRACE) system, which employ an ensemble-based simultaneous state and parameter estimation (ESSPE) approach to enable the assimilation of large volumes of observations for constraining CO2 flux parameters. TRACE uses an online full-physics mesoscale atmospheric model and assimilates observations serially in a coupled atmosphere-carbon ensemble Kalman filter. The data assimilation system was tested in a series of observing system simulation experiments using in situ observations for a regional domain over North America in summer. Under ideal conditions with known prior flux parameter error covariances, TRACE reduced the error in domain-integrated monthly CO2 fluxes by about 97% relative to the prior flux errors. In a more realistic scenario with unknown prior flux error statistics, the corresponding relative error reductions ranged from 80.6% to 88.5% depending on the specification of prior flux parameter error correlations. For regionally integrated fluxes on a spatial scale of 10(6) km(2), the sum of absolute errors was reduced by 34.5%-50.9% relative to the prior flux errors. Moreover, TRACE produced posterior uncertainty estimates that were consistent with the true errors. These initial experiments show that the ESSPE approach in TRACE provides a promising method for advancing CO2 inversion techniques.
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| 6. |
- Chen, Hans W., et al.
(författare)
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Characterization of Regional-Scale CO2 Transport Uncertainties in an Ensemble with Flow-Dependent Transport Errors
- 2019
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 46:7, s. 4049-4058
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Tidskriftsartikel (refereegranskat)abstract
- Inference of CO2 surface fluxes using atmospheric CO2 observations in atmospheric inversions depends critically on accurate representation of atmospheric transport. Here we characterize regional-scale CO2 transport uncertainties due to uncertainties in meteorological fields using a mesoscale atmospheric model and an ensemble of simulations with flow-dependent transport errors. During a 1-month summer period over North America, transport uncertainties yield an ensemble spread in instantaneous CO2 at 100 m above ground level comparable to the CO2 uncertainties resulting from 48% relative uncertainty in 3-hourly natural CO2 fluxes. Temporal averaging reduces transport uncertainties but increases the influence of CO2 uncertainties from the lateral boundaries. The influence of CO2 background uncertainties is especially large for column-averaged CO2. These results suggest that transport errors and CO2 background errors limit regional atmospheric inversions at two distinct timescales and that the error characteristics of transport and background errors should guide the design of regional inversion systems.
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| 7. |
- Lv, J., et al.
(författare)
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Effects of several environmental factors on longevity and health of the human population of Zhongxiang, Hubei, China
- 2011
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Ingår i: Biological Trace Element Research. - : Springer Science and Business Media LLC. - 0163-4984 .- 1559-0720. ; 143:2, s. 702-716
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Tidskriftsartikel (refereegranskat)abstract
- Increasing human health and longevity is of global interest. Environmental, genetic, and stochastic factors all affect longevity. Among these factors, the environment is extremely important. To investigate the relationship between the environment and longevity, we studied the environment in Zhongxiang (China), where the inhabitants commonly have long life spans. Air was analyzed for negative oxygen ions, SO2, and inhalable particles, while drinking water and rice were analyzed for macro- and micro-elements. The air quality in this area was determined to be grade I with high negative oxygen ion content and low SO2 and inhalable particle contents. Apart from Fe, Mn, and F, all tested elements and the pH were within national standards and World Health Organization guidelines. The percentage of long-lived people in the area was closely related to the macro- and micro-element contents of their staple food, rice. The elements in rice could be classified into three categories according to their effect on longevity: Sr, Ca, Al, Mo, and Se, which were positively correlated with longevity; Fe, Mn, Zn, Cr, P, Mg, and K, which had a weak effect on local longevity, and Cu and Ba, which had a negative effect on longevity.
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| 8. |
- Lv, Jinmei, et al.
(författare)
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Identification of human age using trace element concentrations in hair and the support vector machine method
- 2011
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Ingår i: Biological Trace Element Research. - : Springer Science and Business Media LLC. - 0163-4984 .- 1559-0720. ; 143:3, s. 1441-1450
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Tidskriftsartikel (refereegranskat)abstract
- Trace element content in hair is affected by the age of the donor. Hair samples of subjects from four counties in China where people are known to have long lifespan (“longevity counties”) were collected and the trace element content determined. Samples were subdivided into three age groups based on the age of the donors from whom these were taken: children (0–15 years); elderly (80–99 years); and centenarians (≥100 years). We compared the trace element content in hair of different age groups of subjects. Support vector machine classification results showed that a non-linear polynomial kernel function could be used to classify the three age groups of people. Age did not have a significant effect on the content of Ca and Cd in human hair. The content of Li, Mg, Mn, Zn, Cr, Cu, and Ni in human hair changed significantly with age. The magnitude of the age effect on trace element content in hair was in the order Cu > Zn > Ni > Mg > Mn > Cr > Li. Cu content in hair decreased significantly with increasing age. The hair of centenarians had higher levels of Li and Mn, and lower levels of Cr, Cu, and Ni comparing with that of the children and elderly subjects. This could be a beneficial factor of their long lifespan.
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| 9. |
- Ou, Tinghai, et al.
(författare)
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Simulation of summer precipitation diurnal cycles over the Tibetan Plateau at the gray-zone grid spacing for cumulus parameterization
- 2020
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 54, s. 3525-3539
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Tidskriftsartikel (refereegranskat)abstract
- The Tibetan Plateau (TP) is often referred to as the “water tower of Asia” or the “Third Pole”. It remains a challenge for most global and regional models to realistically simulate precipitation, especially its diurnal cycles, over the TP. This study focuses on evaluating the summer (June–August) precipitation diurnal cycles over the TP simulated by the Weather Research and Forecasting (WRF) model. The horizontal resolution used in this study is 9 km, which is within the gray-zone grid spacing that a cumulus parameterization scheme (CU) may or may not be used. We conducted WRF simulations with different cumulus schemes (CU experiments) and a simulation without CU (No_CU experiment). The selected CUs include the Grell-3D Ensemble (Grell), New Simplified Arakawa-Schubert (NSAS), and Multiscale Kain-Fritsch (MSKF). These simulations are compared with both the in-situ observations and satellite products. Results show that the scale-aware MSKF outperforms the other CUs in simulating precipitation in terms of both the mean intensity and diurnal cycles. In addition, the peak time of precipitation intensity is better captured by all the CU experiments than by the No_CU experiment. However, all the CU experiments tend to overestimate the mean precipitation and simulate an earlier peak of precipitation frequency when compared to observations. The frequencies and initiation timings for short-duration (1–3 h) and long-duration (> 6 h) precipitation events are well captured by the No_CU experiment, while these features are poorly reproduced by the CU experiments. The results demonstrate simulation without a CU outperforms those with a CU at the gray-zone spatial resolution in regard to the precipitation diurnal cycles.
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| 10. |
- Wang, Yan, et al.
(författare)
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The Formation of a Dry-Belt in the North Side of Central Himalaya Mountains
- 2019
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 46, s. 2993-3000
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Tidskriftsartikel (refereegranskat)abstract
- ©2019. American Geophysical Union. All Rights Reserved. South Asian monsoon crosses the Himalayan Mountains (HMs) and brings moisture for precipitations in the South Tibetan Plateau. A distinct dry-belt was found in the north of the central HM region, where there are the highest and steepest mountains in the world. Through in situ and remote-sensing observations and convection-permitting numerical experiments, the current study demonstrates that the formation of the dry-belt is mainly due to the depletion of water vapor when the monsoonal flow climbs the steep south slope of the HMs. The foehn phenomenon is notable over the north slope of the HMs, but the hot and dry downslope flow does not significantly reduce the amount of the precipitation; instead, it can delay the peak of the diurnal precipitation in the north side of the HMs.
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