Changes in aerosols cause a change in net top-of-the-atmosphere
(ToA) short-wave and long-wave radiative fluxes; rapid adjustments in clouds,
water vapour and temperature; and an effective radiative ...forcing (ERF)
of the planetary energy budget. The diverse sources of model uncertainty and
the computational cost of running climate models make it difficult to isolate
the main causes of aerosol ERF uncertainty and to understand how observations
can be used to constrain it. We explore the aerosol ERF uncertainty by using
fast model emulators to generate a very large set of aerosol–climate model
variants that span the model uncertainty due to 27 parameters
related to atmospheric and aerosol processes. Sensitivity analyses shows that
the uncertainty in the ToA flux is dominated (around 80 %) by uncertainties
in the physical atmosphere model, particularly parameters that affect cloud
reflectivity. However, uncertainty in the change in ToA flux caused by
aerosol emissions over the industrial period (the aerosol ERF) is controlled
by a combination of uncertainties in aerosol (around 60 %) and physical
atmosphere (around 40 %) parameters. Four atmospheric and aerosol parameters
account for around 80 % of the uncertainty in short-wave ToA flux (mostly
parameters that directly scale cloud reflectivity, cloud water content or
cloud droplet concentrations), and these parameters also account for around
60 % of the aerosol ERF uncertainty. The common causes of uncertainty mean
that constraining the modelled planetary brightness to tightly match
satellite observations changes the lower 95 % credible aerosol ERF value from
−2.65 to −2.37 W m−2. This
suggests the strongest forcings (below around −2.4 W m−2)
are inconsistent with observations. These results show that, regardless of
the fact that the ToA flux is 2 orders of magnitude larger than the aerosol
ERF, the observed flux can constrain the uncertainty in ERF because their
values are connected by constrainable process parameters. The key to reducing
the aerosol ERF uncertainty further will be to identify observations that can
additionally constrain individual parameter ranges and/or combined parameter
effects, which can be achieved through sensitivity analysis of perturbed
parameter ensembles.
A 1200×1200 km2 area of the tropical South Atlantic Ocean near Ascension Island is studied with the HadGEM climate model at convection-permitting and global resolutions for a 10-day case study period ...in August 2016. During the simulation period, a plume of biomass burning smoke from Africa moves into the area and mixes into the clouds. At Ascension Island, this smoke episode was the strongest of the 2016 fire season.The region of interest is simulated at 4 km resolution, with no parameterised convection scheme. The simulations are driven by, and compared to, the global model. For the first time, the UK Chemistry and Aerosol model (UKCA) is included in a regional model with prognostic aerosol number concentrations advecting in from the global model at the boundaries of the region.Fire emissions increase the total aerosol burden by a factor of 3.7 and cloud droplet number concentrations by a factor of 3, which is consistent with MODIS observations. In the regional model, the inversion height is reduced by up to 200 m when smoke is included. The smoke also affects precipitation, to an extent which depends on the model microphysics. The microphysical and dynamical changes lead to an increase in liquid water path of 60 g m−2 relative to a simulation without smoke aerosol, when averaged over the polluted period. This increase is uncertain, and smaller in the global model. It is mostly due to radiatively driven dynamical changes rather than precipitation suppression by aerosol.Over the 5-day polluted period, the smoke has substantial direct radiative effects of +11.4 W m−2 in the regional model, a semi-direct effect of −30.5 W m−2 and an indirect effect of −10.1 W m−2. Our results show that the radiative effects are sensitive to the structure of the model (global versus regional) and the parameterization of rain autoconversion. Furthermore, we simulate a liquid water path that is biased high compared to satellite observations by 22 % on average, and this leads to high estimates of the domain-averaged aerosol direct effect and the effect of the aerosol on cloud albedo. With these caveats, we simulate a large net cooling across the region, of −27.6 W m−2.
Aerosol measurements over the Southern Ocean are used to constrain
aerosol–cloud interaction radiative forcing (RFaci) uncertainty in a global climate model. Forcing uncertainty is quantified using 1 ...million climate model variants that sample the uncertainty in nearly 30 model parameters. Measurements of cloud condensation nuclei and other aerosol properties from an Antarctic circumnavigation expedition strongly constrain natural aerosol emissions: default sea spray emissions need to be increased by around a factor of 3 to be consistent with measurements. Forcing uncertainty is reduced by around 7 % using this set of several hundred measurements, which is comparable to the 8 % reduction achieved using a diverse and extensive set of over 9000 predominantly Northern Hemisphere measurements. When Southern Ocean and Northern Hemisphere measurements are combined, uncertainty in RFaci is reduced by 21 %, and the strongest 20 % of forcing values are ruled out as implausible. In this combined constraint, observationally plausible RFaci is around 0.17 W m−2 weaker (less negative) with 95 % credible values ranging from −2.51 to
−1.17 W m−2 (standard deviation of −2.18 to −1.46 W m−2). The Southern Ocean and Northern Hemisphere measurement datasets are complementary because they constrain different processes. These results
highlight the value of remote marine aerosol measurements.
Desert dust simulations generated by the National Center for Atmospheric Research's Community Climate System Model for the current climate are shown to be consistent with present day satellite and ...deposition data. The response of the dust cycle to last glacial maximum, preindustrial, modern, and doubled‐carbon dioxide climates is analyzed. Only natural (non‐land use related) dust sources are included in this simulation. Similar to some previous studies, dust production mainly responds to changes in the source areas from vegetation changes, not from winds or soil moisture changes alone. This model simulates a +92%, +33%, and −60% change in dust loading for the last glacial maximum, preindustrial, and doubled‐carbon dioxide climate, respectively, when impacts of carbon dioxide fertilization on vegetation are included in the model. Terrestrial sediment records from the last glacial maximum compiled here indicate a large underestimate of deposition in continental regions, probably due to the lack of simulation of glaciogenic dust sources. In order to include the glaciogenic dust sources as a first approximation, we designate the location of these sources, and infer the size of the sources using an inversion method that best matches the available data. The inclusion of these inferred glaciogenic dust sources increases our dust flux in the last glacial maximum from 2.1 to 3.3 times current deposition.
The role of direct radiative forcing of desert dust aerosol in the change from wet to dry climate observed in the African Sahel region in the last half of the twentieth century is investigated using ...simulations with an atmospheric general circulation model. The model simulations are conducted either forced by the observed sea surface temperature (SST) or coupled with the interactive SST using the Slab Ocean Model (SOM). The simulation model uses dust that is less absorbing in the solar wavelengths and has larger particle sizes than other simulation studies. As a result, simulations show less shortwave absorption within the atmosphere and larger longwave radiative forcing by dust. Simulations using SOM show reduced precipitation over the intertropical convergence zone (ITCZ) including the Sahel region and increased precipitation south of the ITCZ when dust radiative forcing is included. In SST-forced simulations, on the other hand, significant precipitation changes are restricted to over North Africa. These changes are considered to be due to the cooling of global tropical oceans as well as the cooling of the troposphere over North Africa in response to dust radiative forcing. The model simulation of dust cannot capture the magnitude of the observed increase of desert dust when allowing dust to respond to changes in simulated climate, even including changes in vegetation, similar to previous studies. If the model is forced to capture observed changes in desert dust, the direct radiative forcing by the increase of North African dust can explain up to 30% of the observed precipitation reduction in the Sahel between wet and dry periods. A large part of this effect comes through atmospheric forcing of dust, and dust forcing on the Atlantic Ocean SST appears to have a smaller impact. The changes in the North and South Atlantic SSTs may account for up to 50% of the Sahel precipitation reduction. Vegetation loss in the Sahel region may explain about 10% of the observed drying, but this effect is statistically insignificant because of the small number of years in the simulation. Greenhouse gas warming seems to have an impact to increase Sahel precipitation that is opposite to the observed change. Although the estimated values of impacts are likely to be model dependent, analyses suggest the importance of direct radiative forcing of dust and feedbacks in modulating Sahel precipitation.
Observational constraint of simulated aerosol and cloud
properties is an essential part of building trustworthy climate models for
calculating aerosol radiative forcing. Models are usually tuned to ...achieve
good agreement with observations, but tuning produces just one of many
potential variants of a model, so the model uncertainty cannot be determined.
Here we estimate the uncertainty in aerosol effective radiative forcing (ERF)
in a tuned climate model by constraining 4 million variants of the
HadGEM3-UKCA aerosol–climate model to match nine common observations
(top-of-atmosphere shortwave flux, aerosol optical depth, PM2.5, cloud
condensation nuclei at 0.2 % supersaturation (CCN0.2), and
concentrations of sulfate, black carbon and organic carbon, as well as
decadal trends in aerosol optical depth and surface shortwave radiation.) The
model uncertainty is calculated by using a perturbed parameter ensemble that
samples 27 uncertainties in both the aerosol model and the physical climate
model, and we use synthetic observations generated from the model itself to
determine the potential of each observational type to constrain this
uncertainty. Focusing over Europe in July,
we show that the aerosol ERF uncertainty can be reduced by about 30 % by
constraining it to the nine observations, demonstrating that producing
climate models with an observationally plausible “base state” can
contribute to narrowing the uncertainty in aerosol ERF. However, the
uncertainty in the aerosol ERF after observational constraint is large
compared to the typical spread of a multi-model ensemble. Our results
therefore raise questions about whether the underlying multi-model
uncertainty would be larger if similar approaches as adopted here were
applied more widely. The approach presented in this study could be used to
identify the most effective observations for model constraint. It is hoped
that aerosol ERF uncertainty can be further reduced by introducing
process-related constraints; however, any such results will be robust only if
the enormous number of potential model variants is explored.
The radiative forcing caused by a volcanic eruption is dependent on several eruption source parameters such as the mass of sulfur dioxide (SO2) emitted, the eruption column height, and the eruption ...latitude. General circulation models with prognostic aerosol and chemistry schemes can be used to investigate how each parameter influences the volcanic forcing. However, the range of multidimensional parameter space that can be explored is restricted because such simulations are computationally expensive. Here we use statistical emulation to explore the radiative impact of eruptions over a wide covarying range of SO2 emission magnitudes, injection heights, and eruption latitudes based on only 30 simulations. We use the emulators to build response surfaces to visualize and predict the sulfate aerosol e‐folding decay time, the stratospheric aerosol optical depth, and net radiative forcing of thousands of different eruptions. We find that the volcanic stratospheric aerosol optical depth and net radiative forcing are primarily determined by the mass of SO2 emitted, but eruption latitude is the most important parameter in determining the sulfate aerosol e‐folding decay time. The response surfaces reveal joint effects of the eruption source parameters in influencing the net radiative forcing, such as a stronger influence of injection height for tropical eruptions than high‐latitude eruptions. We also demonstrate how the emulated response surfaces can be used to find all combinations of eruption source parameters that produce a particular volcanic response, often revealing multiple solutions.
Key Points
We demonstrate the feasibility and value of using statistical emulation to quantify the radiative impact of volcanic eruptions
Emulated response surfaces illustrate the dependencies of model output such as net radiative forcing on eruption source parameters
Emulated response surfaces can also be used to constrain the eruption source parameters for a particular volcanic response
The objectives of the study were to clarify the characteristics of dysphagia and the incidence of pneumonia in Myotonic dystrophy type 1 (DM1) patients, and to investigate the relationship between ...the development of pneumonia and the DM1 patient's background, especially concerning swallowing function evaluated by endoscopy.
The subjects were 88 DM1 patients who underwent swallowing function evaluation. The severity of disease in DM1patients was assessed based on the muscular impairment rating scale (MIRS), and the number of CTG repeats. Patients were divided into two groups; those who developed aspiration pneumonia within two years after swallowing assessment and those who did not develop aspiration pneumonia. Swallowing function was assessed using the food intake level scale (FILS), repetitive saliva swallowing test (RSST), the modified water swallowing test (MWST), and the Hyodo score.
Onset of pneumonia within two years of assessment was observed in 22 cases (25%). Age, FILS, and Hyodo score were significantly different between pneumonia and non-pneumonia groups. There was a significant difference in swallowing function tests such as FILS, RSST, and Hyodo score between males and females. The Hyodo score cutoff value for predicting pneumonia within two years was determined by ROC analysis. A cutoff value of 6 was found to have a sensitivity of 0.545 and a specificity of 0.833 (area under the curve=0.722).
It is important to evaluate the swallowing function of DM1 patients by endoscopy to prevent aspiration pneumonia. In addition, male patients are more likely to deteriorate in swallowing function and should be carefully monitored.
The Japanese Surveillance Committee conducted a second nationwide surveillance of antimicrobial susceptibility patterns of uropathogens responsible for acute uncomplicated cystitis (AUC) in ...premenopausal patients aged 16–40 years old at 31 hospitals throughout Japan from March 2015 to February 2016. In this study, the susceptibility of causative bacteria (Escherichia coli, Klebsiella pneumoniae, Staphylococcus saprophyticus) for various antimicrobial agents was investigated by isolation and culturing of organisms obtained from urine samples. In total, 324 strains were isolated from 361 patients, including E. coli (n = 220, 67.9%), S. saprophyticus (n = 36, 11.1%), and K. pneumoniae (n = 7, 2.2%). The minimum inhibitory concentrations (MICs) of 20 antibacterial agents for these strains were determined according to the Clinical and Laboratory Standards Institute (CLSI) manual. At least 93% of the E. coli isolates showed susceptibility to fluoroquinolones and cephalosporins, whereas 100% of the S. saprophyticus isolates showed susceptibility to fluoroquinolones and aminoglycosides. The proportions of fluoroquinolone-resistant and extended-spectrum β-lactamase (ESBL)-producing E. coli strains were 6.4% (13/220) and 4.1% (9/220), respectively. The antimicrobial susceptibility of K. pneumoniae was retained during the surveillance period, while no multidrug-resistant strains were identified.
In summary, antimicrobial susceptibility results of our second nationwide surveillance did not differ significantly from those of the first surveillance. Especially the numbers of fluoroquinolone-resistant and ESBL-producing E. coli strains were not increased in premenopausal patients with AUC in Japan.
•This is a report on muscle MRI findings in childhood-onset caveolinopathies.•Skeletal muscle MRI images showed peripheral involvement of the rectus femoris.•Secondary CAV3 deficiency due to PTRF ...mutations showed same patterns of involvement.
Caveolinopathies, caused by CAV3 mutations, can include several phenotypes such as rippling muscle disease, limb-girdle muscular dystrophy type 1C, distal myopathy, familial hypertrophic cardiomyopathy, and idiopathic hyperCKemia. Here we present characteristic skeletal muscle imaging findings in four patients with genetically defined childhood-onset RMD caused by CAV3 mutations and in one patient with congenital generalized lipodystrophy type 4 with muscular dystrophy due to polymerase I and transcript release factor (PTRF) mutations, which may have caused secondary deficiency of caveolin-3. Muscle MRI revealed that the rectus femoris and semitendinosus muscles were most commonly affected in the rippling muscle disease patients. Peripheral changes in the rectus femoris were specific and observed even in one of the younger patients in this study. Furthermore, muscle involvement extended to the semitendinosus muscles, biceps femoris, and gracilis with disease progression or increase in its severity. Similar patterns of involvement were observed on reviewing skeletal muscle images of various previously reported phenotypes of caveolinopathy; interestingly, patients with secondary deficiency of caveolin due to PTRF mutations revealed the same pattern. Thus, primary caveolinopathies and secondary deficiency of caveolin demonstrated specific findings on skeletal muscle imaging, regardless of the broad phenotypic spectrum of these two conditions.
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