On the Impact of Anthropogenic Heat Fluxes on the Urban Boundary Layer: A Two-Dimensional Numerical Study

The heat generated in buildings and the manner in which this heat is exchanged with the ambient environment can play an important role in urban climate. Recent studies have shown that anthropogenic heat from air-conditioning facilities can increase the exterior ambient temperature and should be taken into account for a more complete urban heat island (UHI) mitigation study. For this purpose, the first part of the present work is focused on the coupling of a new building energy model (BEM) and an urban canopy parameterisation (UCP). The new scheme is implemented in a finite volume mesoscale model (MM) and tested in a two-dimensional (2D) configuration of a city over flat terrain. A sensitivity study is performed with respect to different parameters in order to test the simulation system and enhance the understanding of the possible impacts of the BEM on the exterior microclimate.     

Towards a spatial data infrastructure for technological disasters: an approach for the road transportation of hazardous materials

Spatial data have been used for the environmental monitoring of the consequences of accidents that involve the transportation of hazardous chemical products. This spatial data infrastructure (SDI), which was created for the sharing and use of spatial data, is limited by the absence of policies to support its establishment. The main objective of this study was to explore the use of social network analysis (SNA) as a tool to identify spatial data sharing between organizations involved in the management of accidents related to road transport of hazardous materials (RTHM). In addition, to discuss the existing policies and institutional agreements, and to initiate a conceptual SDI framework for RTHM sector. In this context, the institutions that are involved with RTHM were identified and information concerning their interest in the use and sharing of spatial data via a SDI was collected through interviews and consolidated. The interviews were at 39 institutions with representative employees. The interview data were tabulated and entered into the UCINET software (2000 version) to calculate metrics of centrality. From the SNA, the flow of data among the participating institutions was identified through the visual representation of the spatial data sharing and use networks. Subsequently, the existing institutional agreements for spatial data sharing were analyzed and discussed. The compiled results enabled the proposal of a conceptual SDI framework to support the management of disasters involving RTHM, based on the application of SNA theory, and the development of a methodology that supports the analysis of interactions among the various actors of an SDI. The purpose is to facilitate the formulation of policies for the sharing of spatial data for decision-making and preventive disaster management. The results indicate that the 39 institutions share spatial data, but this sharing is not always predetermined by formal agreements. Furthermore, there is a strong demand, by the institutions involved in the management of RTHM accidents, regarding legal mechanisms governing the sharing of data for the purpose of producing maps that help to describe actions of preparedness, prevention, management and immediate relief involving RTHM incidents. Finally, it was possible to propose a conceptual framework with data that is considered essential for creating an SDI for RTHM.     

Negligent killing of scientific concepts: the stationarity case

Abstract

In scientific vocabulary, the term “process” is used to denote change in time. Even a stationary process describes a system changing in time, rather than a static one that keeps a constant state all the time. However, this is often missed, which has led to misuse of the term “nonstationarity” as a synonym of “change”. A simple rule to avoid such misuse is to answer the question: can the change be predicted in deterministic terms? Only if the answer is positive is it legitimate to invoke nonstationarity. In addition, we should have in mind that models are made to simulate the future rather than to describe the past; the past is characterized by observations (data). Usually future changes are not deterministically predictable and thus the models should, on the one hand, be stationary and, on the other hand, describe in stochastic terms the full variability, originating from all agents of change. Even if the past evolution of the process of interest contains changes explainable in deterministic terms (e.g. urbanization), it is better to describe the future conditions in stationary terms, after “stationarizing” the past observations, i.e. adapting them to represent the future conditions.     

Mechanistic and Kinetic Study of the Gas-Phase Reaction of Atomic Chlorine with Cyclohexanone using an Absolute and a Relative Technique; Influence of Temperature

The reaction of Cl with cyclohexanone (1) was investigated, for the first time, as a function of temperature (273–333 K) and at a low total pressure (1 Torr) with helium as a carrier gas using a discharge flow-mass spectrometry technique (DF-MS). The resulting Arrhenius expression is proposed, k ₁= (7.7 ± 4.1) × 10^–10 exp[–(540 ± 169)/T]. We also report a mechanistic study with the quantitative determination of the products of the reaction of Cl with cyclohexanone. The absolute rate constant derived from this study at 1 Torr of total pressure and room temperature is (1.3 ± 0.2) × 10^–10 cm³ molecule^–1 s^–1. A yield of 0.94 ± 0.10 was found for the H-abstraction channel giving HCl. In relative studies, using a newly constructed relative rate system, the decay of cyclohexanone was followed by gas chromatography coupled with flame-ionisation detection. These relative measurements were performed at atmospheric pressure with synthetic air and room temperature. Rate constant measured using the relative method for reaction (1) is: (1.7 ± 0.3) × 10^–10 cm³ molecule^–1 s^–1. Finally, results and atmospheric implications are discussed and compared with the reactivity with OH radicals.     

Do we have enough pieces of the jigsaw to integrate CO2 fluxes in the coastal ocean?

Annually integrated air-water CO₂ flux data in 44 coastal environments were compiled from literature. Data were gathered in 8 major ecosystems (inner estuaries, outer estuaries, whole estuarine systems, mangroves, salt marshes, coral reefs, upwelling systems, and open continental shelves), and up-scaled in the first attempt to integrate air-water CO₂ fluxes over the coastal ocean (26×10⁶ km²), taking into account its geographical and ecological diversity. Air-water CO₂ fluxes were then up-scaled in global ocean (362×10⁶ km²) using the present estimates for the coastal ocean and those from Takahashi et al. (2002) for the open ocean (336×10⁶ km²). If estuaries and salt marshes are not taken into consideration in the up-scaling, the coastal ocean behaves as a sink for atmospheric CO₂(−1.17 mol C m⁻² yr⁻¹) and the uptake of atmospheric CO₂ by the global ocean increases by 24% (−1.93 versus −1.56 Pg C yr⁻¹). The inclusion of the coastal ocean increases the estimates of CO₂ uptake by the global ocean by 57% for high latitude areas (−0.44 versus −0.28 Pg C yr⁻¹) and by 15% for temperate latitude areas (−2.36 versus −2.06 Pg C yr⁻¹) At subtropical and tropical latitudes, the contribution from the coastal ocean increases the CO₂ emission to the atmosphere from the global oceam by 13% (0.87 versus 0.77 Pg C yr⁻¹). If estuaries and salt marshes are taken into consideration in the upscaling, the coastal ocean behaves as a source for atmospheric CO₂ (0.38 mol C m⁻² yr⁻¹) and the uptake of atmospheric CO₂ from the global ocean decreases by 12% (−1.44 versus −1.56 Pg C yr⁻¹) At high and subtropical and tropical latitudes, the coastal ocean behaves as a source for atmospheric CO₂ but at temperate latitudes, it still behaves as a moderate CO₂ sink. A rigorous up-scaling of air-water CO₂ fluxes in the coastal ocean is hampered by the poorly constrained estimate of the surface area of inner estuaries. The present estimates clearly indicate the significance of this biogeochemically, highly active region of the biosphere in the global CO₂ cycle.