Aerosol-Induced Changes of Convective Cloud Anvils Produce Strong Climate Warming

The effect of aerosol on clouds poses one of the largest uncertainties in estimating the anthropogenic contribution to climate change. Small human-induced perturbations to cloud characteristics via aerosol pathways can create a change in the top-of-atmosphere radiative forcing of hundreds of Wm(exp-2) . Here we focus on links between aerosol and deep convective clouds of the Atlantic and Pacific Intertropical Convergence Zones, noting that the aerosol environment in each region is entirely different. The tops of these vertically developed clouds consisting of mostly ice can reach high levels of the atmosphere, overshooting the lower stratosphere and reaching altitudes greater than 16 km. We show a link between aerosol, clouds and the free atmosphere wind profile that can change the magnitude and sign of the overall climate radiative forcing. We find that increased aerosol loading is associated with taller cloud towers and anvils. The taller clouds reach levels of enhanced wind speeds that act to spread and thin the anvi1 clouds, increasing areal coverage and decreasing cloud optical depth. The radiative effect of this transition is to create a positive radiative forcing (warming) at top-of-atmosphere. Furthermore we introduce the cloud optical depth (r), cloud height (Z) forcing space and show that underestimation of radiative forcing is likely to occur in cases of non homogenous clouds. Specifically, the mean radiative forcing of towers and anvils in the same scene can be several times greater than simply calculating the forcing from the mean cloud optical depth in the scene. Limitations of the method are discussed, alternative sources of aerosol loading are tested and meteorological variance is restricted, but the trend of taller clouds; increased and thinner anvils associated with increased aerosol loading remains robust through all the different tests and perturbations

Discernible rhythm in the spatio/temporal distributions of transatlantic dust

The differences in North African dust emission regions and transport routes, between the boreal winter and summer, are thoroughly documented. Here we re-examine the spatial and temporal characteristics of dust transport over the tropical and subtropical North Atlantic Ocean, using 10 yr of satellite data, in order to better characterize the different dust transport periods. We see a robust annual triplet: a discernible rhythm of transatlantic dust weather . The proposed annual partition is composed of two heavy loading periods, associated here with a northern-route period and southern-route period, and one light-loading period, accompanied by unusually low average optical depth of dust. The two dusty periods are quite different in character: their duration, transport routes, characteristic aerosol loading and frequency of pronounced dust episodes. The southern-route period lasts ~4 months. It is characterized by a relatively steady southern positioning, low frequency of dust events, low background values and high variance in dust loading. The northern-route period lasts ~6.5 months and is associated with a steady drift northward of ~0.1 latitude day−1, reaching ~1500 km north of the southern-route. The northern period is characterized by higher frequency of dust events, higher (and variable) background and smaller variance in dust loading. It is less episodic than the southern period. Transitions between the periods are brief. Separation between the southern and northern periods is marked by northward latitudinal shift in dust transport and by moderate reduction in the overall dust loading. The second transition, between the northern and southern periods, commences with an abrupt reduction in dust loading and rapid shift southward of ~0.2 latitude day−1, and ~1300 km in total. Based on cross-correlation analyses, we attribute the observed rhythm to the contrast between the northwestern and southern Saharan dust source spatial distributions. Despite the vast difference in areas, the Bodélé Depression, located in Chad, appears to modulate transatlantic dust patterns about half the time

Correlation of tunneling spectra with surface nano-morphology and doping in thin YBa2Cu3O7-delta films

Tunneling spectra measured on thin epitaxial YBa2Cu3O7-delta films are found to exhibit strong spatial variations, showing U and V-shaped gaps as well as zero bias conductance peaks typical of a d-wave superconductor. A full correspondence is found between the tunneling spectra and the surface morphology down to a level of a unit-cell step. Splitting of the zero bias conductance peak is seen in optimally-doped and overdoped films, but not in the underdoped ones, suggesting that there is no transition to a state of broken time reversal symmetry in the underdoped regimeComment: accepted to ep

Aerosols' influence on the interplay between condensation, evaporation and rain in warm cumulus cloud

International audienceA numerical cloud model is used to study the influence of aerosol on the microphysics and dynamics of moderate-sized, coastal, convective clouds that develop under the same meteorological conditions. The results show that polluted convective clouds start their precipitation later and precipitate less than clean clouds but produce larger rain drops. The evaporation process is more significant at the margins of the polluted clouds (compared to the clean cloud) due to a higher drop surface area to volume ratio and it is mostly from small drops. It was found that the formation of larger raindrops in the polluted cloud is due to a more efficient collection process

Scanning tunneling spectroscopy of a-axis YBa_2Cu_3O_7-\delta films:k-selectivity and the shape of the superconductor

Tunneling spectroscopy of epitaxial (100) oriented \chem{YBa_2Cu_3O_{7-\delta}} films was performed using an STM at 4.2 K. On atomically smooth areas, tunneling spectra revealing clear U-shaped gaps with relatively low zero bias conductance were measured. These spectra can be well fitted to the tunneling theory into a d-wave superconductor only when introducing a strong dependence of the tunneling probability on the wave-vector \emph{\textbf{k}}. Possible origins for this \emph{\textbf{k}}-selectivity in STM measurements will be discussed. On other areas, V-shaped gaps as well as zero bias conductance peaks are observed, indicating relaxation of \emph{\textbf{k}}-selectivity and the effect of nanofaceting, respectively.Comment: 7 epl pages, 4 embeded figure

Aerosols\u27 influence on the interplay between condensation, evaporation and rain in warm cumulus cloud

A numerical cloud model is used to study the influence of aerosol on the microphysics and dynamics of moderate-sized, coastal, convective clouds that develop under the same meteorological conditions. The results show that polluted convective clouds start their precipitation later and precipitate less than clean clouds but produce larger rain drops. The evaporation process is more significant at the margins of the polluted clouds (compared to the clean cloud) due to a higher drop surface area to volume ratio and it is mostly from small drops. It was found that the formation of larger raindrops in the polluted cloud is due to a more efficient collection process

Role of Interfaces in the Proximity Effect in Anisotropic Superconductors

We report measurements of the critical temperature of YBCO-Co doped YBCO Superconductor-Normal bilayer films. Depending on the morphology of the S-N interface, the coupling between S and N layers can be turned on to depress the critical temperature of S by tens of degrees, or turned down so the layers appear almost totally decoupled. This novel effect can be explained by the mechanism of quasiparticle transmission into an anisotropic superconductor.Comment: 13 pages, 3 figure

Просторово-часовий розподіл пожеж у природних ландшафтах Рівненської області

Integrated fire management during the epoch of climate and land use change need to be organized on landscape level on the basis of strong vertical and horizontal co-operation between forestry and emergency agencies and local communities and requires clear understanding of fire regime and factors that it determined both in temporal and spatial aspects. For this purpose, fire regimes of natural and cultural landscapes of Rivne Oblast, Ukraine, for the period of 2001–2018 were studied based on remote sensing data. For getting better understanding of long-term pathways of wildfire regimes of natural landscapes of Rivne Oblast of Ukraine, we used data about hotspots from MOD14/MYD14 for number of fires, data about contours and areas of fires from MCD64A1and Landsat 8 OLI with classification of all fires on different levels of intensity and landcover type and data from three local meteorological stations on the fire weather danger level. The study showed that in Rivne Oblast for the period 7 fire maximums occurred, in particularly in 2002, 2009, 2012, 2015 and 2018. Official statistical data presents essentially underestimated area of fires: 257 ha in 2002 (while this study shows 750 ha based on RS data or 143 ha in 2015 (563 ha based on RS data). On average during the period, 190 wildfires with a total area of 12.6 thousand hectares occurred annually in landscapes of Rivne Oblast. The highest amount of fires occurred in the north part of the region – Rokytnivskii (62 000 ha burned), Dubrovitskii (26 000 ha), Kostopilskii (19 400 ha), Zarichnenskii (14 900 ha), Volodymyretskii (10 300 ha) districts. The main driver of fires is drought periods: 54.3 % of days in fire season determined as highest emergency level fire weather class – V, 15.3 % days – IV class, 18.5 % – III class. High level of fire weather danger in the region and permanent presence of ignition sources of human origin determine seasonal patterns of burning. Seasonal fire peaks occur in March (80 000 ha burned)-April (87 300 ha burned or 29.6 % of the average number of wildfires), August (32.2 %) and September (19.9 %) – totally 127 000 ha burned, when the maximum level of preparedness of fire-fighting brigades should be provided. Long-term dynamic showed increase of the average annual fire area for the period from 7.4 to 17.8 thousand hectares. The increase of annual amount of days with high and emergency fire whether levels from 24 to 62 during last 13 years is detected. Shortcomings of the existing system of statistical data collection on wildfires as an important component of fire management are discussed.Аналіз історичної динаміки пожеж та встановлення їх просторово-часових особливостей є основою для розроблення плану управління пожежами та стратегічного розміщення протипожежних сил і засобів на місцевості, а також здійснення попереджувальних заходів. Використовуючи дані дистанційного зондування Землі, отримано основні показники горючості природних територій Рівненської області за період з 2001 по 2018 рр. та виконано їх аналіз. Щорічно на території області відбувається в середньому 190 випадків пожеж на загальній площі 12,6 тис. га. Усереднені дані свідчать про тенденцію до зростання показників горючості території, зокрема середньорічна площа пожеж за період з 2001 по 2018 рр. зросла від 7,4 до 17,8 тис. га. За результатами дослідження встановлено, що найбільше пожеж стається у березні-квітні (29,6 %), серпні (32,2 %) та вересні (19,9 %), що повинно бути основою для максимальної готовності протипожежних служб у ці періоди. Виконано аналіз погодно-кліматичних показників за багаторічний період та досліджено їх зв'язок з основними показникам горючості. Зроблено висновки щодо проблеми пожеж у природних ландшафтах Рівненської області. Наведено недоліки наявної системи моніторингу пожеж як важливої складової системи охорони природних територій від пожеж

Magnetic field dependence of the proximity-induced triplet superconductivity at ferromagnet/superconductor interfaces

Long-ranged superconductor proximity effects recently found in superconductor-ferromagnetic (S-F) systems are generally attributed to the formation of triplet-pairing correlations due to various forms of magnetic inhomogeneities at the S-F interface. In order to investigate this conjecture within a single F layer coupled to a superconductor, we performed scanning tunneling spectroscopy on bilayers of La2/3Ca1/3MnO3 (LCMO) ferromagnetic thin-films grown on high temperature superconducting films of YBa2Cu3O7- (YBCO) or Pr1.85Ca0.15CuO4 (PCCO) under various magnetic fields. We find a strong correlation between the magnitude of superconductor-related spectral features measured on the LCMO layer and the degree of magnetic inhomogeneity controlled by the external magnetic field. This corroborates theoretical predictions regarding the role played by magnetic inhomogeneities in inducing triplet-pairing at S-F interfaces.This research was supported in parts by the joint German-Israeli DIP Project (G.K. and O.M.), the United States-Israel Binational Science Foundation (O.M.), the Harry de Jur Chair in Applied Science (O.M.), the Karl Stoll Chair in advanced materials at the Technion (G.K.), the Leverhulme Trust through an International Network Grant (J.W.A.R., M.G.B. and O.M.) and the Royal Society (J.W.A.R.).This is the accepted manuscript version. The final published version is available from the publishers at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.180506. © 2014 AP