SHADHO: Massively Scalable Hardware-Aware Distributed Hyperparameter Optimization

Computer vision is experiencing an AI renaissance, in which machine learning models are expediting important breakthroughs in academic research and commercial applications. Effectively training these models, however, is not trivial due in part to hyperparameters: user-configured values that control a model's ability to learn from data. Existing hyperparameter optimization methods are highly parallel but make no effort to balance the search across heterogeneous hardware or to prioritize searching high-impact spaces. In this paper, we introduce a framework for massively Scalable Hardware-Aware Distributed Hyperparameter Optimization (SHADHO). Our framework calculates the relative complexity of each search space and monitors performance on the learning task over all trials. These metrics are then used as heuristics to assign hyperparameters to distributed workers based on their hardware. We first demonstrate that our framework achieves double the throughput of a standard distributed hyperparameter optimization framework by optimizing SVM for MNIST using 150 distributed workers. We then conduct model search with SHADHO over the course of one week using 74 GPUs across two compute clusters to optimize U-Net for a cell segmentation task, discovering 515 models that achieve a lower validation loss than standard U-Net.Comment: 10 pages, 6 figure

Impact of supersonic and subsonic aircraft on ozone: Including heterogeneous chemical reaction mechanisms

Preliminary calculations suggest that heterogeneous reactions are important in calculating the impact on ozone from emissions of trace gases from aircraft fleets. In this study, three heterogeneous chemical processes that occur on background sulfuric acid aerosols are included and their effects on O3, NO(x), Cl(x), HCl, N2O5, ClONO2 are calculated

Impact of biogenic very short-lived bromine on the Antarctic ozone hole during the 21st century

Active bromine released from the photochemical decomposition of biogenic very short-lived bromocarbons (VSL_Br ) enhances stratospheric ozone depletion. Based on a dual set of 1960-2100 coupled chemistry-climate simulations (i.e. with and without VSL Br ), we show that the maximum Antarctic ozone hole depletion increases by up to 14% when natural VSLBr are considered, in better agreement with ozone observations. The impact of the additional 5 pptv VSL Br on Antarctic ozone is most evident in the periphery of the ozone hole, producing an expansion of the ozone hole area of ~5 million km 2 , which is equivalent in magnitude to the recently estimated Antarctic ozone healing due to the implementation of the Montreal Protocol. We find that the inclusion of VSL Br in CAM-Chem does not introduce a significant delay of the modelled ozone return date to 1980 October levels, but instead affect the depth and duration of the simulated ozone hole. Our analysis further shows that total bromine-catalysed ozone destruction in the lower stratosphere surpasses that of chlorine by year 2070, and indicates that natural VSL Br chemistry would dominate Antarctic ozone seasonality before the end of the 21 st century. This work suggests a large influence of biogenic bromine on the future Antarctic ozone layer.Fil: Fernandez, Rafael Pedro. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; España. Universidad Tecnologica Nacional. Facultad Regional Mendoza. Secretaría de Ciencia, Tecnología y Postgrado; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Kinnison, Douglas E.. National Center For Atmospheric Research. Amospheric Chemistry División; Estados UnidosFil: Lamarque, Jean Francois. National Center For Atmospheric Research. Amospheric Chemistry División; Estados UnidosFil: Tilmes, Simone. National Center For Atmospheric Research. Amospheric Chemistry División; Estados UnidosFil: Saiz-lopez, Alfonso. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; Españ

A negative feedback between anthropogenic ozone pollution and enhanced ocean emissions of iodine

Naturally emitted from the oceans, iodine compounds efficiently destroy atmospheric ozone and reduce its positive radiative forcing effects in the troposphere. Emissions of inorganic iodine have been experimentally shown to depend on the deposition to the oceans of tropospheric ozone, whose concentrations have significantly increased since 1850 as a result of human activities. A chemistry-climate model is used herein to quantify the current ocean emissions of inorganic iodine and assess the impact that the anthropogenic increase in tropospheric ozone has had on the natural cycle of iodine in the marine environment since pre-industrial times. Our results indicate that the human-driven enhancement of tropospheric ozone has doubled the oceanic inorganic iodine emissions following the reaction of ozone with iodide at the sea surface. The consequent build-up of atmospheric iodine, with maximum enhancements of up to 70% with respect to pre-industrial times in continental pollution outflow regions, has in turn accelerated the ozone chemical loss over the oceans with strong spatial patterns. We suggest that this ocean-atmosphere interaction represents a negative geochemical feedback loop by which current ocean emissions of iodine act as a natural buffer for ozone pollution and its radiative forcing in the global marine environment.Fil: Prados Roman, C.. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Cuevas, Carlos Alberto. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; EspañaFil: Fernandez, Rafael Pedro. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Kinnison, Douglas E.. National Center For Atmospheric Research. Amospheric Chemistry División; Estados UnidosFil: Lamarque, Jean Francoise. National Center For Atmospheric Research. Amospheric Chemistry División; Estados UnidosFil: Saiz-lopez, Alfonso. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; Españ

Longest continous ground-based measurements of mesospheric CO

The longest continuous series of ground-based measurements of mesospheric CO is presented. The continuous data cover the period September 2000 to September 2002. Sporadic measurements from 1988 and 1989 are also reported. The results show a large CO accumulation in the winter mesosphere, which is consistent with generally accepted ideas about the seasonally-varying mean meridional circulation. Comparison of the observations with simulations by the Whole Atmosphere Community Climate Model (WACCM) indicate that the model can reproduce the observed seasonal cycle as well as much of its variability, although calculated columns amounts are smaller than the largest values seen in the data

Bromine partitioning in the tropical tropopause layer: Implications for stratospheric injection

© Author(s) 2014. Very short-lived (VSL) bromocarbons are produced at a prodigious rate by ocean biology and these source compounds (SGVSL), together with their inorganic degradation products (PGVSL), are lofted by vigorous convection to the tropical tropopause layer (TTL). Using a state-of-the-art photochemical mechanism within a global model, we calculate annual average stratospheric injection of total bromine due to VSL sources to be 5 pptv (parts per trillion by volume), with ∼ 3 pptv entering the stratosphere as PGVSL and ∼ 2 pptv as SGVSL. The geographic distribution and partitioning of VSL bromine within the TTL, and its consequent stratospheric injection, is highly dependent on the oceanic flux, the strength of convection and the occurrence of heterogeneous recycling reactions. Our calculations indicate atomic Br should be the dominant inorganic species in large regions of the TTL during daytime, due to the low ozone and cold conditions of this region. We propose the existence of a >tropical ring of atomic bromine> located approximately between 15 and 19 km and between 30°N and 30°S. Daytime Br / BrO ratios of up to ∼ 4 are predicted within this inhomogeneous ring in regions of highly convective transport, such as the tropical Western Pacific. Therefore, we suggest that experimental programs designed to quantify the bromine budget of the TTL and the stratospheric injection of VSL biogenic bromocarbons should include a strategy for the measurement of atomic Br during daytime as well as HOBr and BrCl during nighttime.Peer Reviewe

Historical tropospheric and stratospheric ozone radiative forcing using the CMIP6 database

We calculate ozone radiative forcing (RF) and stratospheric temperature adjustments for the period 1850-2014 using the newly availableCMIP6 ozone dataset. The CMIP6 total ozone RF (1850s-2000s) is 0.28+/-0.17 W m-2 (which is 80% higher than our CMIP5 estimation), and 0.30+/-0.17 W m-2 out to the present day (2014). The total ozone RF grows rapidly until the 1970s, slows towards the 2000s, and shows a renewed growth thereafter. Since the 1990s the shortwave RF exceeds the longwave RF. Global stratospheric ozone RF is positive between 1930 and 1970 and then turns negative, but remains positive in the Northern Hemisphere throughout. Derived stratospheric temperature changes show a localized cooling in the subtropical lower stratosphere due to tropospheric ozone increases, and cooling in the upper stratosphere due to ozone depletion by more than 1K already prior to the satellite era (1980), and by more than 2K out to the present day(2014)

Role of the QBO in modulating the influence of the 11 year solar cycle on the atmosphere using constant forcings

We present a set of six 20 year experiments made with a state-of-the-art chemistry-climate model that incorporates the atmosphere from the surface to the lower thermosphere. The response of the middle atmosphere to the 11 year solar cycle, its impact on the troposphere, and especially the role of an externally prescribed stratospheric quasi-biennial oscillation (QBO) is investigated with NCAR's Whole Atmosphere Community Climate Model (WACCM3). The model experiments use either fixed solar cycle inputs or fixed solar cycle together with prescribed QBO phase. The annual mean solar response in temperature and ozone in the upper stratosphere is in qualitative agreement with other modeling and observational studies and does not depend on the presence of the imposed QBO. However, the solar response in the middle to lower stratosphere differs significantly for the two QBO phases. During solar maxima a weaker Brewer-Dobson circulation with relative downwelling, warming, and enhanced ozone occurs in the tropical lower stratosphere during QBO east conditions, while a stronger circulation, cooling, and decreased ozone exists during QBO west conditions. The net ozone increase during QBO east is the combined result of production and advection, whereas during QBO west the effects cancel each other and result in little net ozone changes. Especially during Southern Hemisphere late winter to early spring, the solar response at polar latitudes switches sign between the two QBO phases and qualitatively confirms observations and other recent model studies. During a poleward downward modulation of the polar night jet and a corresponding modulation of the Brewer-Dobson circulation in time, solar signals are detected all the way down to the extratropical troposphere. Possible limitations of the model experiments with respect to the fixed solar cycle conditions or the prescribed QBO phases, as well as the constant sea surface temperatures, are discussed

Effects of the Mount Pinatubo eruption on the radiative and chemical processes in the troposphere and stratosphere

The Lawrence Livermore National Laboratory two-dimensional zonally-averaged chemical-radiative-transport model of the global atmosphere was used to study the effects of the 15 June 1991 eruption of the Mt. Pinatubo volcano on stratospheric processes. SAGE 2 time-dependent aerosol surface area density and optical extinction data were used as input into the model. By 22 December 1991, a maximum equatorial change of -1.8 percent in column ozone was derived from heterogeneous chemical processes that convert NO(x) into HNO3 on sulfuric acid aerosols. Radiative feedbacks from increased aerosol optical thickness independently changes column ozone by approximately -3.5 percent for the same period. This occurs from increasing the net heating of the lower stratosphere, which indirectly increases chemical reaction rates via their temperature dependence and from changes in actinic fluxes, which directly modify photodissociation rates. Including both heterogeneous and radiative effects changes column ozone by -5.5 percent. The model-derived change overestimates the decrease in column ozone relative to the TOMS instrument on the Nimbus 7 satellite. Maximum local ozone decreases of 12 percent were derived in the equatorial region, at 25 km. Model-derived column NO2 peaked (-14 percent) at 30 deg S in October 1991. The timing of the NO2 peak is consistent with observation, but the model underestimates the magnitude of the decrease. Local concentrations of NO(x) (NO + NO2), ClO(x) (Cl + ClO), and HO(x) (OH + HO2), in the lower stratosphere between 30 deg S and 30 deg N, were calculated to have changed by -40 percent, +100 to +160 percent, and +120 to +140 percent respectively

Ozone Response to Aircraft Emissions: Sensitivity Studies with Two-dimensional Models

Our first intercomparison/assessment of the effects of a proposed high-speed civil transport (HSCT) fleet on the stratosphere is presented. These model calculations should be considered more as sensitivity studies, primarily designed to serve the following purposes: (1) to allow for intercomparison of model predictions; (2) to focus on the range of fleet operations and engine specifications giving minimal environmental impact; and (3) to provide the basis for future assessment studies. The basic scenarios were chosen to be as realistic as possible, using the information available on anticipated developments in technology. They are not to be interpreted as a commitment or goal for environmental acceptability