Evaluation of Black Carbon Estimations in Global Aerosol Models

We evaluate black carbon (BC) model predictions from the AeroCom model intercomparison project by considering the diversity among year 2000 model simulations and comparing model predictions with available measurements. These 5 model-measurement intercomparisons include BC surface and aircraft concentrations, aerosol absorption optical depth (AAOD) from AERONET and Ozone Monitoring Instrument (OMI) retrievals and BC column estimations based on AERONET. In regions other than Asia, most models are biased high compared to surface concentration measurements. However compared with (column) AAOD or BC burden retreivals, the models 10 are generally biased low. The average ratio of model to retrieved AAOD is less than 0.7 in South American and 0.6 in African biomass burning regions; both of these regions lack surface concentration measurements. In Asia the average model to observed ratio is 0.6 for AAOD and 0.5 for BC surface concentrations. Compared with aircraft measurements over the Americas at latitudes between 0 and 50 N, the average model is a 15 factor of 10 larger than observed, and most models exceed the measured BC standard deviation in the mid to upper troposphere. At higher latitudes the average model to aircraft BC is 0.6 and underestimates the observed BC loading in the lower and middle troposphere associated with springtime Arctic haze. Low model bias for AAOD but overestimation of surface and upper atmospheric BC concentrations at lower latitudes 20 suggests that most models are underestimating BC absorption and should improve estimates for refractive index, particle size, and optical effects of BC coating. Retrieval uncertainties and/or differences with model diagnostic treatment may also contribute to the model-measurement disparity. Largest AeroCom model diversity occurred in northern Eurasia and the remote Arctic, regions influenced by anthropogenic sources. 25 Changing emissions, aging, removal, or optical properties within a single model generated a smaller change in model predictions than the range represented by the full set of AeroCom models. Upper tropospheric concentrations of BC mass from the aircraft measurements are suggested to provide a unique new benchmark to test scavenging and vertical dispersion of BC in global models.JRC.H.2-Climate chang

Probabilistic Chemical Abstract Machine and the Expressiveness of Linda Languages

The Chemical Abstract Machine of Berry and Boudol provides a commonly accepted, uniform framework for describing the operational semantics of various process calculi and languages, such as for example CCS, the pi-calculus and coordination languages like Linda. In its original form the CHAM is purely non-deterministic and thus only describes what reactions are `possible' but not how long it will take (in the average) before a certain reaction takes place or its probability. Such quantitative information is however often vital for ``real world'' applications such as systems biology or performance analysis. We propose a probabilistic version of the CHAM. We then define a linear operator semantics for the probabilistic CHAM which exploits a tensor product representation for distributions over possible solutions. Based on this we propose a novel approach towards comparing the expressive power of different calculi via their encoding in the probabilistic CHAM. We illustrate our approach by comparing the expressiveness of various Linda Languages

Metatheories and metaphors of organizational identity: integrating social constructionist, social identity, and social actor perspectives within a social interactionist model

This review examines three dominant metatheories of organizational identity that are grounded in social constructionist, social identity, and social actor theorizing. It focuses on root metaphors of framing, categorization and personification that are associated with each metatheory and outlines differences in their assumptions, key constructs, and forms of analysis. The review shows how the emphasis of each root metaphor serves to direct research along a particular path in ways that often lead to a siloing of research knowledge. However, while laying bare the foundations of each metatheory and discussing the nature of the empirical projects by which they are supported, we also seek to draw them more closely together. In particular, we do this by elaborating an integrative social interactionist model in which organizational identity is understood to be the product of recursive interaction between bottom-up and top-down processes of identity consensualization and contestation