ALBERT

Description: The organization of convection is ubiquitous, but its physical understanding remains limited. One particular type of organization is the spatial self-aggregation of convection, taking the form of cloud clusters, or tropical cyclones in the presence of rotation. We show that several physical processes can give rise to self-aggregation, and highlight the key features responsible for it using idealized simulations. Longwave radiative feedbacks yield a “radiative aggregation" . In that case, sufficient spatial variability of radiative cooling rates yields a low-level circulation, which induces the up-gradient energy transport and radiative-convective instability. Not only do vertically-integrated radiative budgets matter, but the vertical profile of cooling is also crucial. Convective aggregation is facilitated when downdrafts below clouds are weak (“moisture-memory aggregation" ), and this is sufficient to trigger aggregation in the absence of longwave radiative feedbacks. These results shed some light on the sensitivity of self-aggregation to various parameters, including resolution or domain size.

Description: With 69% of the world's population predicted to live in cities by 2050, modification to local climates, in particular Urban Heat Islands, have become a well studied phenomenon. However few studies have considered how horizontal winds modify the spatial pattern in a process named Urban Heat Advection (UHA) and this is most likely due to a lack of highly spatially resolved observational data. For the first time, this study separates the two-dimensional advection-induced UHI component, including its pattern and magnitude, from the locally-heated UHI component using a unique dataset of urban canopy temperatures from 29 weather stations (3 km resolution) recorded over 20 months in Birmingham, UK. The results show that the mean contribution of UHA to the warming of areas downwind of the city can be up to 1.2 °C. Using the inverse Normalized Difference Vegetation Index as a proxy for urban fraction, an upwind distance at which the urban fraction has the strongest correlation with UHA was demonstrated to be between 4–12 km. Overall, these findings suggest that urban planning and risk management needs to additionally consider UHA. However, more fundamentally, it highlights the importance of careful interpretation of long term meteorological records taken near cities when they are used to assess global warming.

Description: Diabetes mellitus is a metabolic disorder characterized by hyperglycemia. We investigated the effect of a prior thirty days voluntary exercise protocol on STZ-diabetic CF1 mice. Glycemia, and the liver and skeletal muscle glycogen, mitochondrial function and redox status were analyzed up to five days after STZ injection. Animals were engaged in the following groups: Sedentary vehicle (Sed Veh), Sedentary STZ (Sed STZ), Exercise Vehicle (Ex Veh) and Exercise STZ (Ex STZ). Exercise prevented fasting hyperglycemia in the Ex STZ group. In the liver: There was decreased on glycogen level in Sed STZ group but not in EX STZ group. STZ groups showed decreased mitochondrial oxygen consumption compared to vehicle groups, whereas mitochondrial H2O2 production was not different between groups. Addition of ADP to the medium did not decrease H2O2 production in Sed STZ mice. Exercise increased GSH level. Sed STZ group increased nitrite levels compared to other groups. In quadriceps muscle: glycogen level was similar between groups. The Sed STZ group displayed decreased O2 consumption, and exercise prevented this reduction. The H2O2 production was higher in Ex STZ when compared to other groups. Also, GSH level decreased whereas nitrite levels increased in the Sed STZ compared to other groups. The PGC1 α levels increased in Sed STZ, Ex Veh and Ex STZ groups. In summary, prior exercise training prevents hyperglycemia in STZ-induced diabetes associated with increased liver glycogen storage, and oxygen consumption by the mitochondria of skeletal muscle implying in increased oxidative/biogenesis capacity, and improved redox status of both tissues. This article is protected by copyright. All rights reserved

Description: Non-compensated dilated cardiomyopathy (DCM) leading to death from heart failure is rising rapidly in developed countries due to aging demographics, and there is a need for informative preclinical models to guide the development of effective therapeutic strategies to prevent or delay disease onset. In this study, we describe a novel model of heart failure based on cardiac-specific deletion of the prototypical mammalian BAR adapter-encoding gene Bin1, a modifier of age-associated disease. Bin1 deletion during embryonic development causes hypertrophic cardiomyopathy and neonatal lethality, but there is little information on how Bin1 affects cardiac function in adult animals. Here we report that cardiomyocyte-specific loss of Bin1 causes age-associated dilated cardiomyopathy (DCM) beginning by 8-10 months of age. Echocardiographic analysis showed that Bin1 loss caused a 45% reduction in ejection fraction during aging. Younger animals rapidly developed DCM if cardiac pressure overload was created by transverse aortic constriction. Heterozygotes exhibited an intermediate phenotype indicating Bin1 is haplo-insufficient to sustain normal heart function. Bin1 loss increased left ventricle (LV) volume and diameter during aging, but it did not alter LV volume or diameter in hearts from heterozygous mice nor did it affect LV mass. Bin1 loss increased interstitial fibrosis and mislocalization of the voltage-dependent calcium channel Ca v 1.2, and the lipid raft scaffold protein caveolin-3, which normally complexes with Bin1 and Ca v 1.2 in cardiomyocyte membranes. Our findings show how cardiac deficiency in Bin1 function causes age- and stress-associated heart failure, and they establish a new preclinical model of this terminal cardiac disease. This article is protected by copyright. All rights reserved

Description: Eruptive activity at Turrialba volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here, we use high frequency gas monitoring to track the behavior of the volcano between 2014 and 2015, and to decipher magmatic vs. hydrothermal contributions to the eruptions. Pulses of deeply-derived CO 2 -rich gas (CO 2 /S total  〉 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to two weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8-10 km deep, whereas the shallow magmatic gas source is at ~3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H 2 S/SO 2 varies over two orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases whereas the second did not. Massive degassing ( 〉3000 T/day SO 2 and H 2 S/SO 2  〉 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H 2 S/SO 2  〈 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.

Description: The first Nitryl Chloride (ClNO 2 ) measurements in the United Kingdom were made during the summer 2012 ClearfLo campaign with a chemical ionisation mass spectrometer, utilising an I − ionisation scheme. Concentrations of ClNO 2 exceeded detectable limits (11 ppt) every night with a maximum concentration of 724 ppt. A diurnal profile of ClNO 2 peaking between 4 and 5 am, decreasing directly after sunrise was observed. Concentrations of ClNO 2 above the detection limit are generally observed between 8 pm and 11 am. Different ratios of the production of ClNO 2 : N 2 O 5 were observed throughout with both positive and negative correlations between the two species being reported. The photolysis of ClNO 2 and a box model utilising the Master Chemical Mechanism modified to include chlorine chemistry was used to calculate Cl atom concentrations. Simultaneous measurements of hydroxyl radicals (OH) using low pressure laser-induced fluorescence and ozone enabled the relative importance of the oxidation of three groups of measured VOCs (alkanes, alkenes and alkynes) by OH radicals, Cl atoms and O 3 to be compared. For the day with the maximum calculated Cl atom concentration, Cl atoms in the early morning were the dominant oxidant for alkanes, and over the entire day contributed 15%, 3% and 26% towards the oxidation of alkanes, alkenes and alkynes, respectively.

Description: Analytical modeling of heat transport was used to address effects of uncertainty in thermal conductivity on groundwater-surface water exchange. In-situ thermal conductivities and temperature profiles were measured in a coastal lagoon bed where groundwater is known to discharge. The field site could be divided into three sediment zones where significant spatial changes in thermal conductivity on meter to cm scale show that spatial variability connected to the sediment properties must be considered. The application of a literature-based bulk thermal conductivity of 1.84 Wm -1 °C -1 , instead of field data that ranged from 0.62 to 2.19 Wm -1 °C -1 , produced a mean overestimation of 2.33 cm d -1 that, considering the low fluxes of the study area, represents an 89 % increase and up to a factor of 3 in the most extreme cases. Incorporating the uncertainty due to sediment heterogeneities leads to an irregular trend of the flux distribution from the shore towards the lagoon. The natural variability of the thermal conductivity associated with changes in the sediment composition resulted in a mean variation of + 0.66 cm d -1 in fluxes corresponding to a change of + 25.4 %. The presence of organic matter in the sediments, a common situation in the near-shore areas of surface water bodies, is responsible for the decrease of thermal conductivity. The results show that the natural variability of sediment thermal conductivity is a parameter to be considered for low flux environments and it contributes to a better understanding of groundwater-surface interactions in natural environments. This article is protected by copyright. All rights reserved.

Description: The breaking of internal tides is believed to provide a large part of the power needed to mix the abyssal ocean and sustain the meridional overturning circulation. Both the fraction of internal tide energy that is dissipated locally and the resulting vertical mixing distribution are crucial for the ocean state, but remain poorly quantified. Here we present a first worldwide estimate of mixing due to internal tides generated at small-scale abyssal hills. Our estimate is based on linear wave theory, a non-linear parameterization for wave breaking and uses quasi-global small-scale abyssal hill bathymetry, stratification and tidal data. We show that a large fraction of abyssal-hill generated internal tide energy is locally dissipated over midocean ridges in the Southern Hemisphere. Significant dissipation occurs above ridge crests, and, upon rescaling by the local stratification, follows a monotonic exponential decay with height off the bottom, with a non-uniform decay scale. We however show that a substantial part of the dissipation occurs over the smoother flanks of mid-ocean ridges, and exhibits a mid-depth maximum due to the interplay of wave amplitude with stratification. We link the three-dimensional map of dissipation to abyssal hills characteristics, ocean stratification and tidal forcing, and discuss its potential implementation in time-evolving parameterizations for global climate models. Current tidal parameterizations only account for waves generated at large-scale satellite-resolved bathymetry. Our results suggest that the presence of small-scale, mostly unresolved abyssal hills could significantly enhance the spatial inhomogeneity of tidal mixing, particularly above mid-ocean ridges in the Southern Hemisphere. This article is protected by copyright. All rights reserved.

Description: Leaf area index and leaf area density profiles are key variables for upscaling from leaves to ecosystems, yet are difficult to measure well in dense and tall forest canopies. We present a new model to estimate leaf area density (LAD) profiles from discrete multi-return data derived by airborne waveform light detection and ranging (LiDAR), a model based on stochastic radiative transfer theory. We tested the method on simulated ray tracing data for highly clumped forest canopies, both vertically homogenous and vertically inhomogeneous. Our method was able to reproduce simulated vertical foliage profiles with small errors and predictable biases in dense canopies (leaf area index = six) including layers below densely foliated upper canopies. As a case study, we then applied the method to real multi-return airborne LiDAR data for a 50 ha plot of moist tropical forest on Barro Colorado Island, Panama. The method is suitable for estimating foliage profiles in a complex tropical forest, which opens new avenues for analyses of spatial and temporal variation in foliage distributions.