Global climate models often underestimate aerosol loadings in China, and
these biases can have significant implications for anthropogenic aerosol
radiative forcing and climate effects. The biases may ...be caused by either the
emission inventory or the treatment of aerosol processes in the models, or
both, but so far no consensus has been reached. In this study, a relatively
new emission inventory based on energy statistics and technology,
Multi-resolution Emission Inventory for China (MEIC), is used to drive the
Community Atmosphere Model version 5 (CAM5) to evaluate aerosol distribution
and radiative effects against observations in China. The model results are
compared with the model simulations with the widely used Intergovernmental
Panel on Climate Change Fifth Assessment Report (IPCC AR5) emission
inventory. We find that the new MEIC emission improves the aerosol optical
depth (AOD) simulations in eastern China and explains 22–28 % of the AOD
low bias simulated with the AR5 emission. However, AOD is still biased low in
eastern China. Seasonal variation of the MEIC emission leads to a better
agreement with the observed seasonal variation of primary aerosols than the
AR5 emission, but the concentrations are still underestimated. This implies
that the atmospheric loadings of primary aerosols are closely related to the
emission, which may still be underestimated over eastern China. In contrast,
the seasonal variations of secondary aerosols depend more on aerosol
processes (e.g., gas- and aqueous-phase production from precursor gases) that
are associated with meteorological conditions and to a lesser extent on the
emission. It indicates that the emissions of precursor gases for the
secondary aerosols alone cannot explain the low bias in the model.
Aerosol secondary production processes in CAM5
should also be revisited. The simulation using MEIC estimates the
annual-average aerosol direct radiative effects (ADREs) at the top of the
atmosphere (TOA), at the surface, and in the atmosphere to be −5.02,
−18.47, and 13.45 W m−2, respectively, over eastern China, which are
enhanced by −0.91, −3.48, and 2.57 W m−2 compared with the AR5
emission. The differences of ADREs by using MEIC and AR5 emissions are larger
than the decadal changes of the modeled ADREs, indicating the uncertainty of
the emission inventories. This study highlights the importance of improving
both the emission and aerosol secondary production processes in modeling the
atmospheric aerosols and their radiative effects. Yet, if the estimations of
MEIC emissions in trace gases do not suffer similar biases to those in the
AOD, our findings will help affirm a fundamental error in the conversion from
precursor gases to secondary aerosols as hinted in other recent studies
following different approaches.
Dry deposition is an important process affecting the lifetime and spatial distributions of atmospheric aerosols. Black carbon (BC) plays an important role in the Earth's climate, but is subject to ...large bias in remote regions in model simulations. In this study, to improve the BC simulations, the scheme of Petroff and Zhang () (PZ10) is implemented into the Community Atmospheric Model version 5 (CAM5), and model simulations using PZ10 are compared with the one using the default scheme of Zhang et al. () (Z01) and observations. The PZ10 scheme predicts much lower dry deposition velocity (Vd) than Z01 for fine particles in Aitken, primary carbon, and accumulation modes, resulting in 73.0% lower of global mean BC dry deposition fluxes and 23.2% higher of global mean BC column burdens. CAM5 with PZ10 increases modeled BC concentrations at all altitudes and latitudes compared to Z01, which improves the agreement with observations of BC profiles in the lower troposphere in the Arctic. It also improves the simulation of surface BC concentrations in high‐latitudes remote regions and its seasonality in the Arctic. The global annual mean radiative effects due to aerosol‐radiation interactions (REari) and aerosol‐cloud interactions (REaci) of BC from the CAM5 experiment using Z01 are 0.61 ± 0.007 and −0.11 ± 0.02 W m−2, respectively, compared to slightly larger REari (0.75 ± 0.01 W m−2) and REaci (–0.14 ± 0.02 W m−2) from CAM5 using PZ10. The results suggest that Brownian diffusion efficiency is a key factor for the predictions of Vd, which requires better representation in the global climate models.
Key Points
A newly ‐developed aerosol dry deposition scheme is implemented in CAM5
Lower dry deposition velocities for fine particles results in higher BC concentrations globally
Modeled surface BC concentrations and its seasonality in the Arctic and Antarctic is improved
Ice-nucleating particles (INPs) in the Southern Ocean (SO) atmosphere have significant impacts on cloud radiative and microphysical properties. Yet, INP prediction skill in climate models remains ...poorly understood, in part because of the lack of long-term measurements. Here we show, for the first time, how model-simulated INP concentrations compare with year-round INP measurements during the Macquarie Island Cloud Radiation Experiment (MICRE) campaign from 2017–2018. We simulate immersion-mode INP concentrations using the Energy Exascale Earth System Model version 1 (E3SMv1) by combining simulated aerosols with recently developed deterministic INP parameterizations and the native classical nucleation theory (CNT) for mineral dust in E3SMv1. Because MICRE did not collect aerosol measurements of super-micron particles, which are more effective ice nucleators, we evaluate the model's aerosol fields at other high-latitude sites using long-term in situ observations of dust and sea spray aerosol. We find that the model underestimates dust and overestimates sea spray aerosol concentrations by 1 to 2 orders of magnitude for most of the high-latitude sites in the Southern Hemisphere. We next compare predicted INP concentrations with concentrations of INPs collected on filter samples (typically for 2 or 3 d) and processed offline using the Colorado State University ice spectrometer (IS) in immersion freezing mode. We find that when deterministic parameterizations for both dust and sea spray INPs are used, simulated INPs are within a factor of 10 of observed INPs more than 60 % of the time during summer.
Our results also indicate that the E3SM's current treatment of mineral dust immersion freezing in the SO is impacted by compensating biases – an underprediction of dust amount was compensated by an overprediction of its effectiveness as INPs. We also perform idealized droplet freezing experiments to quantify the implications of the time-dependent behavior assumed by the E3SM's CNT-parameterization and compare with the ice spectrometer observations. We find that the E3SM CNT 10 s diagnostic used in this study is a reasonable approximation of the exact formulation of CNT, when applied to ice spectrometer measurements in low-INP conditions similar to Macquarie Island. However, the linearized 10 s diagnostic underestimates the exact formula by an order of magnitude or more in places with high-INP conditions like the Sahara. Overall, our findings suggest that it is important to correct the biases in E3SM's simulated dust life cycle and update E3SM's INP parameterizations. INP prediction errors of 2 to 3 orders of magnitude can have considerable impacts on the simulated cloud and radiative properties in global climate models. On comparing INP concentrations during MICRE against ship-based campaigns, Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS) and Antarctic Circumnavigation Expedition (ACE), we find that INPs from the latter are significantly higher only in regions closer to Macquarie Island. This alludes to the fact that physical, chemical and biological processes affecting INP concentrations as stimulated by the island could be partly responsible for the high INP concentrations observed at Macquarie Island during the MICRE campaign. Therefore, improvements to both aerosol simulation and INP parameterizations are required to adequately simulate INPs and their cloud impacts in E3SM. It will be helpful to include a parallel measurement of the size-resolved aerosol composition and explore opportunities for long-term measurement platforms in future field campaigns studying INP sources in remote marine regions.
A Lagrangian framework is used to evaluate aerosol-cloud interactions in the U.S. Department of Energy's Energy Exascale Earth System Model (E3SM) version 1 (E3SMv1) for measurements taken at ...Graciosa Island in the Azores where a U.S. Department of Energy Atmosphere Radiation Measurement (ARM) site is located. This framework uses direct measurements of cloud condensation nuclei (CCN) concentration (instead of relying on satellite retrievals of aerosol optical depth) and incorporates a suite of ground-based ARM measurements, satellite retrievals, and meteorological reanalysis products that when applied to over a 1500 trajectories provides key insights into the evolution of low-level clouds and aerosol radiative forcing that is not feasible from a traditional Eulerian analysis framework. Significantly lower concentrations (40 %) of surface CCN concentration are measured when precipitation rates in 48 h back trajectories average above 1.2 mm d.sup.-1 in the Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) product. The depletion of CCN concentration when precipitation rates are elevated is nearly twice as large in the ARM observations compared to E3SMv1 simulations. The model CCN concentration bias remains significant despite modifying the autoconversion and accretion rates in warm clouds.
Nitrate aerosol plays an important role in affecting regional air quality as well as Earth's climate. However, it is not well represented or even neglected in many global climate models. In this ...study, we couple the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) module with the four‐mode version of the Modal Aerosol Module (MAM4) in DOE's Energy Exascale Earth System Model version 2 (E3SMv2) to simulate nitrate aerosol and its radiative effects. We find that nitrate aerosol simulated by E3SMv2‐MAM4‐MOSAIC is sensitive to the treatment of gaseous HNO3 transfer to/from interstitial particles related to accommodation coefficients of HNO3 (αHNO3 ${\alpha }_{{\mathrm{H}\mathrm{N}\mathrm{O}}_{3}}$) on dust and non‐dust particles. We compare three different treatments of HNO3 transfer: (a) a treatment (MTC_SLOW) that uses a low αHNO3 ${\alpha }_{{\mathrm{H}\mathrm{N}\mathrm{O}}_{3}}$ in the mass transfer coefficient (MTC) calculation; (b) a dust‐weighted MTC treatment (MTC_WGT) that uses a high αHNO3 ${\alpha }_{{\mathrm{H}\mathrm{N}\mathrm{O}}_{3}}$ on non‐dust particles; and (c) a dust‐weighted MTC treatment that also splits coarse mode aerosols into the coarse dust and sea salt sub‐modes in MOSAIC (MTC_SPLC). MTC_WGT and MTC_SPLC increase the global annual mean (2005–2014) nitrate burden from 0.096 (MTC_SLOW) to 0.237 and 0.185 Tg N, respectively, mostly in the coarse mode. MTC_WGT and MTC_SPLC also produce stronger nitrate direct radiative forcing (−0.048 and −0.051 W m−2, respectively) and indirect forcing (−0.33 and −0.35 W m−2, respectively) than MTC_SLOW (−0.021 and −0.24 W m−2). MTC_WGT and MTC_SPLC improve nitrate surface concentrations over remote oceans based on limited observations and vertical profiles of nitrate concentrations against aircraft measurements below 400 hPa.
Plain Language Summary
Atmospheric aerosols play an important role in the Earth's climate system through their effects on radiation and clouds, and their representation continues to be a major uncertainty in global climate models (GCMs). Nitrate aerosol accounts for a notable fraction of total aerosol mass, but it is crudely represented or even neglected in many modern GCMs. In this study, we implement a comprehensive but computationally efficient aerosol chemistry module in the U.S. DOE Energy Exascale Earth System Model version 2, a state‐of‐the‐science GCM, to simulate nitrate aerosols and quantify their radiative effects. Modeled nitrate concentrations are in good agreement with aircraft observations but have positive biases relative to ground‐based network measurements. We also find that simulated nitrate lifecycle is sensitive to the treatment of gaseous HNO3 transfer to/from interstitial particles related to a parameter characterizing the sticking probability of a gas molecule at the surface of different aerosols such as dust and sea salt particles.
Key Points
The Model for Simulating Aerosol Interactions and Chemistry module is implemented in Energy Exascale Earth System Model version 2 with Model for Ozone and Related chemical Tracers gas chemistry to simulate nitrate aerosols
Modeled nitrate concentrations are in good agreement with aircraft observations but have positive biases at the surface
Treatments of HNO3 accommodation coefficients and the mixing state of dust and sea salt particles significantly impact nitrate lifecycle
Abstract
Ge‐on‐insulators (GOIs) have been extensively explored as a potential platform for electronic‐photonic integrated circuits (EPICs), enabling various emerging applications. Although an ...efficient electrically‐injected light source is highly desirable, realizing such devices with optimal light emission efficiency remains challenging. Here, the first room‐temperature electrically‐injected Ge waveguide light emitters consisting of a lateral
p–i–n
homojunction on a GOI platform that can be monolithically integrated with EPICs are demonstrated. A high‐quality Ge active layer is transferred onto an insulator layer with the misfit dislocations in the Ge active layer eliminated to suppress unwanted nonradiative recombination. A 0.165% tensile strain is introduced to enhance the directness of the band structure and improve the light emission efficiency. The device comprises a waveguide structure with a significantly improved optical confinement as the optical resonator and a lateral
p–i–n
homojunction structure as the electrical injection structure. Under continuous‐wave electrical current injection at room temperature, enhanced electroluminescence is successfully observed at telecommunications wavelengths covering the C, L, and U bands, with improved efficiency. Theoretical analysis suggests that the quantum efficiency of Ge light emitters is dramatically affected by the defect density. These results pave the way for developing efficient, room‐temperature, electrically‐injected light emitters for next‐generation GOI‐based EPICs.
Poor representations of aerosols, clouds, and aerosol–cloud interactions (ACIs) in Earth system models (ESMs) have long been the largest uncertainties in predicting global climate change. Huge ...efforts have been made to improve the representation of these processes in ESMs, and the key to these efforts is the evaluation of ESM simulations with observations. Most well-established ESM diagnostics packages focus on the climatological features; however, they lack process-level understanding and representations of aerosols, clouds, and ACIs. In this study, we developed the Earth System Model Aerosol–Cloud Diagnostics (ESMAC Diags) package to facilitate the routine evaluation of aerosols, clouds, and ACIs simulated the Energy Exascale Earth System Model (E3SM) from the US Department of Energy (DOE). This paper documents its version 2 functionality (ESMAC Diags v2), which has substantial updates compared with version 1 (Tang et al., 2022a). The simulated aerosol and cloud properties have been extensively compared with in situ and remote-sensing measurements from aircraft, ship, surface, and satellite platforms in ESMAC Diags v2. It currently includes six field campaigns and two permanent sites covering four geographical regions: the eastern North Atlantic, the central US, the northeastern Pacific, and the Southern Ocean. These regions produce frequent liquid- or mixed-phase clouds, with extensive measurements available from the DOE Atmospheric Radiation Measurement user facility and other agencies. ESMAC Diags v2 generates various types of single-variable and multivariable diagnostics, including percentiles, histograms, joint histograms, and heatmaps, to evaluate the model representation of aerosols, clouds, and ACIs. Select examples highlighting the capabilities of ESMAC Diags are shown using E3SM version 2 (E3SMv2). In general, E3SMv2 can reasonably reproduce many observed aerosol and cloud properties, with biases in some variables such as aerosol particle and cloud droplet sizes and number concentrations. The coupling of aerosol and cloud number concentrations may be too strong in E3SMv2, possibly indicating a bias in processes that control aerosol activation. Furthermore, the liquid water path response to a perturbed cloud droplet number concentration behaves differently in E3SMv2 and observations, which warrants further study to improve the cloud microphysics parameterizations in E3SMv2.
Theories of personality have posited an increased arousal response to external stimulation in impulsive individuals. However, there is a dearth of studies addressing the neural basis of this ...association.
We recorded skin conductance in 26 individuals who were assessed with Barratt Impulsivity Scale (BIS-11) and performed a stop signal task during functional magnetic resonance imaging. Imaging data were processed and modeled with Statistical Parametric Mapping. We used linear regressions to examine correlations between impulsivity and skin conductance response (SCR) to salient events, identify the neural substrates of arousal regulation, and examine the relationship between the regulatory mechanism and impulsivity.
Across subjects, higher impulsivity is associated with greater SCR to stop trials. Activity of the ventromedial prefrontal cortex (vmPFC) negatively correlated to and Granger caused skin conductance time course. Furthermore, higher impulsivity is associated with a lesser strength of Granger causality of vmPFC activity on skin conductance, consistent with diminished control of physiological arousal to external stimulation. When men (n = 14) and women (n = 12) were examined separately, however, there was evidence suggesting association between impulsivity and vmPFC regulation of arousal only in women.
Together, these findings confirmed the link between Barratt impulsivity and heightened arousal to salient stimuli in both genders and suggested the neural bases of altered regulation of arousal in impulsive women. More research is needed to explore the neural processes of arousal regulation in impulsive individuals and in clinical conditions that implicate poor impulse control.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Agonists at the N-methyl-D-aspartate (NMDA)-glycine site (D-serine, glycine, D-alanine and D-cycloserine) and glycine transporter-1 (GlyT-1) inhibitor (N-methylglycine, or called sarcosine) both ...improve the symptoms of stable chronic schizophrenia patients receiving concurrent antipsychotics. Previous studies, however, found no advantage of D-serine, glycine, or D-cycloserine added to clozapine. The present study aims to determine the effects of sarcosine adjuvant therapy for schizophrenic patients receiving clozapine treatment.
Twenty schizophrenic inpatients enrolled in a 6-week double-blind, placebo-controlled trial of sarcosine (2 g/day) which was added to their stable doses of clozapine. Measures of clinical efficacy and side-effects were determined every other week.
Sarcosine produced no greater improvement when co-administered with clozapine than placebo plus clozapine at weeks 2, 4, and 6. Sarcosine was well tolerated and no significant side-effect was noted.
Unlike patients treated with other antipsychotics, patients who received clozapine treatment exhibit no improvement by adding sarcosine or agonists at the NMDA-glycine site. Clozapine possesses particular efficacy, possibly related to potentiation of NMDA-mediated neurotransmission. This may contribute to the clozapine’s unique clinical efficacy and refractoriness to the addition of NMDA-enhancing agents.
Due to the delayed and vague symptoms, it is difficult to early diagnose mesenteric ischemia injuries in the dynamics of acute illness, leading to a 60–80 % mortality rate. Here, we found plasma ...fluorescence spectra can rapidly assess the severity of mesenteric ischemia injury in animal models. Ischemia-reperfusion damage of the intestine leads to multiple times increase in NADH, flavins, and porphyrin auto-fluorescence of blood. The fluorescence intensity ratio between blue-fluorophores and flavins can reflect the occurrence of shock. Using liquid chromatography and mass spectroscopy, we confirm that riboflavin is primarily responsible for the increased flavin fluorescence. Since humans absorb riboflavin from the intestine, its increase in plasma may indicate intestinal mucosa injury. Our work suggests a self-calibrated and reagent-free approach to identifying the emergence of fatal mesenteric ischemia in emergency departments or intensive care units.
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