Impact of large scale circulation on European summer surface ozone and consequences for modelling forecast

In this study, we investigate the benefit for European ozone simulation of using day-to-day varying chemical boundary conditions produced by a global chemical weather forecast platform instead of climatological monthly means at the frontiers of a regional model. We performed two simulations over Europe using the regional (0.5 × 0.5°) CHIMERE CTM forced by global scale simulations based on the LMDz-INCA CTM. For summer 2005, ozone differences exceeding 20 ppb can be punctually found between these two simulations in the borders of the domain. The mean of the differences ranges between 0 and 3 ppb beyond 15° of the frontiers of the regional model.Correlations with ground-based ozone measurements at more than 400 stations are slightly increased by the use of daily boundary conditions. The simulation of the temporal variability is significantly enhanced in particular for the daily means and daily maxima. As expected, the gain is higher at the borders of the regional domain.The change of percentile distribution shows that the net impact of high temporal resolution boundary conditions is not of major concern for surface ozone peaks which are mainly due to local photochemistry. The use of daily boundary conditions is however necessary to correctly simulate concentrations in the 20–35 ppb range which are of crucial interest for human and vegetation exposure effects.     

Spatiotemporal modelling of ozone distribution in the State of California

This paper is concerned with the spatiotemporal mapping of monthly 8-h average ozone (O₃) concentrations over California during a 15-years period. The basic methodology of our analysis is based on the spatiotemporal random field (S/TRF) theory. We use a S/TRF decomposition model with a dominant seasonal O₃ component that may change significantly from site to site. O₃ seasonal patterns are estimated and separated from stochastic fluctuations. By means of Bayesian Maximum Entropy (BME) analysis, physically meaningful and sufficiently detailed space–time maps of the seasonal O₃ patterns are generated across space and time. During the summer and winter months the seasonal O₃ concentration maps exhibit clear and progressively changing geographical patterns over time, suggesting the existence of relationships in accordance with the typical physiographic and climatologic features of California. BME mapping accuracy can be superior to that of other techniques commonly used by EPA; its framework can rigorously assimilate useful data sources that were previously unaccounted for; the generated maps offer valuable assessments of the spatiotemporal O₃ patterns that can be helpful in the identification of physical mechanisms and their interrelations, the design of human exposure and population health models, and in risk assessment. As they focus on the seasonal patterns, the maps are not contingent on short-time and locally prevalent weather conditions, which are of no interest in a global and non-forecasting framework. Moreover, the maps offer valuable insight about the space–time O₃ concentration patterns and are, thus, helpful for disentangling the influence of explanatory factors or even for identifying some influential ones that could have been otherwise overlooked.     

Analysis of cloud and precipitation chemistry at Whiteface Mountain,NY

Federal and state programs over the past two decades have resulted in the reduction of emissions of precursors of acid rain. Concomitant with these changes, measured concentrations of acidity in precipitation and in watersheds have shown a downward trend or improvement. However, another pathway for these precursors is through cloud and fog events that often tend to occur at high-elevation regions affecting the fauna and flora as well. In this study we report on long-term measurements of cloud water and precipitation chemistry made from 1994 onwards at a high-elevation location, Whiteface Mountain NY, in the northeastern United States. Trends and inter-relationship between the ions were examined along with ambient SO₂ measurements and Adirondack lakes chemistry data.     

Characterization of PM2.5-bound polycyclic aromatic hydrocarbons in Atlanta—Seasonal variations at urban,suburban, and rural ambient air monitoring sites

Twenty-eight polycyclic aromatic hydrocarbons (PAH) and methylated PAHs (Me-PAH) were measured in daily PM_2.5 samples collected at an urban site, a suburban site, and a rural site in and near Atlanta during 2004 (5 samples/month/site). The suburban site, located near a major highway, had higher PM_2.5-bound PAH concentrations than did the urban site, and the rural site had the lowest PAH levels. Monthly variations are described for concentrations of total PAHs (∑PAHs) and individual PAHs. PAH concentrations were much higher in cold months than in warm months, with average monthly ∑PAH concentrations at the urban and suburban-highway monitoring sites ranging from 2.12 to 6.85 ng m^?3 during January–February and November–December 2004, compared to 0.38–0.98 ng m^?3 during May–September 2004. ∑PAH concentrations were found to be well correlated with PM_2.5 and organic carbon (OC) within seasons, and the fractions of PAHs in PM_2.5 and OC were higher in winter than in summer. Methyl phenanthrenes were present at higher levels than their un-substituted homologue (phenanthrene), suggesting a petrogenic (unburned petroleum products) input. Retene, a proposed tracer for biomass burning, peaked in March, the month with the highest acreage and frequency of prescribed burning and unplanned fires, and in December, during the high residential wood-burning season, indicating that retene might be a good marker for burning of all biomass materials. In contrast, potassium peaked only in December, indicating that it might be a more specific tracer for wood-burning.     

Investigations of an intense aerosol loading during 2007 cyclone SIDR – A study using satellite data and ground measurements over Indian region

Tropical cyclones are prominent weather systems characterized by high atmospheric pressure gradients and wind speeds. Intense tropical cyclones occur in India during the pre-monsoon (spring), early monsoon (early summer), or post-monsoon (fall) periods. Originating in both the Bay of Bengal (BoB) and the Arabian Sea (AS), these tropical cyclones often attain velocities of more than 100 km h^?1 and are notorious for causing intense rain and storm surge as they cross the Indian coast. In this study, we examine the changes in the aerosol properties associated with an intense tropical cyclone “SIDR”, that occurred during 11–16 November 2007 over BoB. This cyclone, accompanied with very strong surface winds reaching 223 km h^?1, caused extensive damage over Bangladesh. Ground-based measurements of Aerosol Optical Depth (AOD) in the neighboring urban environment of Hyderabad, India, showed significant variations due to changes in wind velocity and direction associated with the cyclone passage. The Terra-MODIS and AVHRR satellite images showed prevalence of dust particles mixed with emissions from anthropogenic sources and biomass-burning AS, while the aerosol loading over BoB was significantly lower. The positive values of Aerosol index (AI) obtained from the Ozone Monitoring Instrument (OMI) suggested the presence of an elevated aerosol layer over the West coast of India, AS and Thar Desert during and after the cyclone episode. Meteorological parameters from the MM5 mesoscale model were used to study the variations in winds associated with the cyclonic activity. Particulate matter loading over the region during the cyclone period increased by ～45% with an accompanying decrease in columnar aerosol optical depth. The variations in Angstrom parameters suggested coarse-mode particle loading due to dust aerosols as observed in satellite data.     

Heterogeneous uptake of octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) onto mineral dust aerosol under variable RH conditions

We have carried out kinetic studies to characterize the heterogeneous decay of octamethylcyclotetrasiloxane (D₄) and decamethylcyclopentasiloxane (D₅) in the presence of representative mineral dust aerosol in order to obtain a better understanding of the atmospheric fate of these siloxanes. The heterogeneous chemistry of D₄ and D₅ with various mineral dusts was studied in an environmental aerosol reaction chamber using FTIR absorption spectroscopy to monitor the reaction. The apparent heterogeneous uptake coefficient, γ_app, for D₄ and D₅ with various mineral dusts was measured under dry conditions and as a function of relative humidity (RH). In addition, the effect of initial D₄ and D₅ concentration on the rate and yield of the reaction was examined. The uptake coefficient, γ_app, for D₄ and D₅ was similar for the most reactive aerosols tested, with kaolinite ≈hematite > silica. Limited uptake onto carbon black and calcite surfaces was observed for either siloxane. Reaction with hematite and kaolinite resulted in multilayer coverages, suggesting extensive polymerization of D₄ and D₅ on the aerosol surface.     

Population dynamics and the economics of invasive species management: the greenhouse whitefly in California-grown strawberries

In agriculture, relatively few efficacious control measures may be available for an invasive pest. In the case of a new insect pest, insecticide use decisions are affected by regulations associated with its registration, insect population dynamics, and seasonal market price cycles. We assess the costs and benefits of environmental regulations designed to regulate insecticide applications on an invasive species. We construct a bioeconomic model, based on detailed scientific data, of management decisions for a specific invasion: greenhouse whiteflies in California-grown strawberries. The empirical model integrates whitefly population dynamics, the effect of whitefly feeding on strawberry yields, and weekly strawberry price. We use the model to assess the optimality of alternative treatment programs on a simulated greenhouse whitefly population. Our results show that regulations may lead growers to "under-spray" when placed in an economic context, and provide some general lessons about the design of optimal invasive species control policies.     

Effectiveness of a publicly-funded demonstration program to promote management of dryland salinity

Community and catchment-based approaches to salinity management continue to attract interest in Australia. In one such approach, Catchment Demonstration Initiative (CDI) projects were established by the Western Australian (WA) Government in 2000 for targeted investment in large-scale catchment-based demonstrations of integrated salinity management practices. The aim was to promote a process for technically-informed salinity management by landholders. This paper offers an evaluation of the effectiveness of one CDI project in the central wheatbelt of WA, covering issues including: its role in fostering adoption of salinity management options, the role of research and the technical requirements for design and implementation of on-ground works, the role of monitoring and evaluation, the identification and measurement of public and private benefits, comparison and identification of the place and value of plant-based and engineering-based options, reliance on social processes and impacts of constraints on capacity, management of governance and administration requirements and an appreciation of the value of group-based approaches.A number of factors may reduce the effectiveness of CDI-type approaches in facilitating landholder action to address salinity, many of these are socially-based. Such approaches can create considerable demands on landholders, can be expensive (because of the planning and accountability required) on the basis of dollars per hectare impacted, and can be difficult to garner ownership from all involved. An additional problem could be that few community groups would have the capacity to run such programs and disseminate the new knowledge so that the CDI-type projects can impact outside the focus catchment. In common with many publicly-funded approaches to salinity, we found that direct benefits on public assets are smaller than planned and that results from science-based requirements of monitoring and evaluation have long lead times, causing farmers to either wait for the information or act sooner and take risks based on initial results. We also found that often it is a clear outline of the process that is of most importance in decision making as opposed to the actual results. We identified limitations in regulatory processes and the capacity for local government to engage in the CDI.The opportunities that CDI-type approaches provide centre around the value of its group-based approach. We conclude that they can overcome knowledge constraints in managing salinity by fostering group-based learning, offer a structured process of trialling options so that the costs and benefits can be clearly and transparently quantified, and avoid the costly mistakes and “learning failures” of the past.     

Community participatory landscape classification and biodiversity assessment and monitoring of grazing lands in northern Kenya

In this study, we asked the Ariaal herders of northern Kenya to answer "why, what and how" they classified landscape, and assessed and monitored the biodiversity of 10 km(2) of grazing land. To answer the "why question" the herders classified grazing resources into 39 landscape patches grouped into six landscape types and classified soil as 'warm', 'intermediate' or 'cold' for the purpose of land use. For the "what question" the herders used soil conditions and vegetation characteristics to assess biodiversity. Plant species were described as 'increasers', 'decreasers' or 'stable'. The decreaser species were mostly grasses and forbs preferred for cattle and sheep grazing and the increasers were mostly woody species preferred by goats. The herders evaluated biodiversity in terms of key forage species and used absence or presence of the preferred species from individual landscapes for monitoring change in biodiversity. For the "how question" the herders used anthropogenic indicators concerned with livestock management for assessing landscape potential and suitability for grazing. The anthropogenic indicators were related to soils and biodiversity. The herders used plant species grazing preferences to determine the links between livestock production and biodiversity. By addressing these three questions, the study shows the value of incorporating the indigenous knowledge of herders into classification of landscape and assessment and monitoring of biodiversity in the grazing lands. We conclude that herder knowledge of biodiversity is related to the use as opposed to exclusive conservation practices. This type of knowledge is extremely valuable to conservation agencies for establishing a baseline for monitoring changes in biodiversity in the future.     

Virtues of simple hydro-economic optimization: Baja California, Mexico

This paper uses simple hydro-economic optimization to investigate a wide range of regional water system management options for northern Baja California, Mexico. Hydro-economic optimization models, even with parsimonious model formulations, enable investigation of promising water management portfolios for supplying water to agricultural, environmental and urban users. CALVIN, a generalized hydro-economic model, is used in a case study of Baja California. This drought-prone region faces significant challenges to supply water to agriculture and its fast growing border cities. Water management portfolios include water markets, wastewater reuse, seawater desalination and infrastructure expansions. Water markets provide the flexibility to meet future urban demands; however conveyance capacity limits their use. Wastewater reuse and conveyance expansions are economically promising. At current costs desalination is currently uneconomical for Baja California compared to other alternatives. Even simple hydro-economic models suggest ways to increase efficiency of water management in water scarce areas, and provide an economic basis for evaluating long-term water management solutions.