Rainfall in Guanacaste, Costa Rica, has marked wet/dry phases: the rainy season is punctuated by a short midsummer drought, and the dry season frequently has months of no rain. In this region, spring and summer rainfall peaks are important for local rain-fed agriculture and annual total for groundwater recharge and hydroelectricity production. We propose a novel model of rainfall in this region, the double-Gaussian model, which uses monthly total rainfall data collected from 1980 to 2020 from two meteorological observation stations. Our model provides an intuitive way of describing the seasonality of rainfall, the inter-annual variability of the cycle, and variability due to the monthly Oceanic Niño Index, ONI. We also consider two alternative models, a regression model with ARMA errors and a Tweedie model, as a means of assessing the robustness of our conclusions to violations of the assumptions of the double-Gaussian model. We found that the data provide strong evidence of an increase/decrease in rainfall in both temporal maxima during La Niña/El Niño (negative/positive ONI) conditions but no evidence of a decade-scale trend after accounting for ONI effects. Finally, we investigated the problem of forecasting future rainfall based on our three models. We found that when ONI is incorporated as a predictor variable, our models can produce substantial gains in prediction accuracy of spring, summer, and annual totals over naive methods based on monthly sample means or medians.

The wet‐dry tropics of Central America are characterized by long dry seasons, during which communities often struggle for water. High interannual rainfall variability, driven in parts by the El Niño Southern Oscillation (ENSO), increases these challenges. Further, climate change projections indicate that the region will likely become drier. However, research on impacts on water resources at the watershed scale is limited in the region—yet this information is essential for water managers. Therefore, in this research, we quantified the potential impacts of ENSO and four different climate change scenarios on water resources in two watersheds in the wet‐dry tropics of Guanacaste, Costa Rica, using a hydrological model (Water Evaluation and Planning Tool [WEAP]). Given that the watersheds are human used, we also explored different water demand scenarios. Modeling results indicated that an extreme El Niño can reduce groundwater recharge and streamflow by ∼60% relative to ENSO neutral. For 2075–2100, modeling results indicated that while potential evapotranspiration increases, actual evapotranspiration decreases due to limited water availability. Further, climate change may lead to reductions of mean annual streamflow and groundwater recharge by 40%–45% and 26%–28%, respectively, in comparison to the historical baseline. Importantly, high population growth could further hasten potentially irreversible groundwater storage declines. On the other hand, reduction of per‐capita water demand could slow down, or even reverse, the decline of groundwater storage.

This paper examines the spatiotemporal impact of changing local precursor emissions on a subset of air quality monitors in the coastal Lower Fraser Valley, British Columbia, Canada, over a 25-year period (1990-2014) marked by substantial emissions reductions. The analysis examines summertime (JJA) trends in ambient reactivity of volatile organic compounds (VOCs), , ozone, and odd oxygen (; defined as ) concentrations. To account for the potentially confounding influence of rising background ozone levels on the analysis, summer days are classified by whether appreciable local ozone production is likely or not, with a separate analysis undertaken for each set of conditions. The influence of short- and long-term meteorological variability, hebdomadal (weekly) emissions variability, and within-network spatial variability on long-term trends is accounted for by using Generalized Additive Models (GAM). The analysis suggests that long-term trends in local ambient VOC reactivity and concentrations have not occurred in a uniform fashion nor have they changed in a synchronized way. Declines in VOC reactivity appear to have occurred sooner and at a more uniform rate, but concentrations appear to have remained constant for the first 10 years before rapidly declining. Similarly, we find ozone reductions have not occurred uniformly in time nor has the network response been spatially uniform, with the smallest reductions occurring just downwind of the region's downtown core and the largest reductions about 40 km further downwind. Much of the non-uniformity in response can be attributed to changing odd-oxygen partitioning rather than changing ozone production. During our analysis period, ozone concentrations during days not conducive to ozone photochemistry appear to have increased at a rate consistent with previous background trend analyses over western North America. We use the difference between ozone concentrations on fair-weather summer days and days with little photochemistry to build a response surface for "net-produced" ozone as a function of meteorologically controlled ambient VOC reactivity and concentrations. We find that much of the predicted behaviour in local ambient ozone can be understood in light of VOC-limited conditions and differing rates of local VOC and emissions reductions. It appears that these precursor reductions have largely resulted from evolving light-duty emission control technologies and local fleet turnover.

I review the development of ideas in air pollution modelling by tracing the sequence of ideas presented in the 35 past instances of International Technical Meetings (ITM) on Air Pollution Modelling and its Application. My review reveals a healthy evolution of ideas presented at the ITMs, and confirms my impression that the ITM series is one of, if not the leading air pollution modelling conference series.

In order to assess the potential change in ambient concentrations of ozone and its precursors that may arise from the construction of large industrial facilities in the Terrace-Kitimat valley (TKV), we conducted a study using the WRF, SMOKE and CAMx models for two periods in 2010. We developed and applied control and test cases for each period, the former for model evaluation and the latter to assess pollutant change. Model evaluation showed that CAMx is able to emulate O-3 peaks in an adjacent valley (where monitoring occurred) for both the spring and summer periods. Results for the spring period suggest that the addition of NOX from industrial sources may lead to modest O-3 production outside of the main plume trajectory and on valley walls during afternoon hours as well as overnight O-3 titration along low elevations of the TKV upwards of 80 km downwind of sources. Results from the summer period suggest that the addition of O-3 precursors may at times contribute to a greater than 100 % increase in O-3 production under certain meteorological conditions up to 50 km downwind of sources.

The Lower Fraser Valley (LFV) B.C., a largely deindustrialized region with emissions dominated by the transportation sector, has experienced large reduction in precursor emissions over the last 20 years. While these reductions have resulted in concomitant changes in summertime ambient ozone concentrations, the changes have not been uniform across the region, with trends in long term behavior differing noticeably between the eastern and western portions of the valley. In this work, we draw upon previous modeling, observational and experimental studies to infer how the sensitivity of ground-level ozone to precursor emissions has changed over the last two decades. This work is notable for several reasons. First we establish not only VOC- and NOx-ozone sensitivities during summertime ozone episodes, but across the full range of summertime meteorological conditions. Next, we examine how these sensitivities have changed over the last two decades. We also examine how these sensitivities vary spatially across the LFV and finally we use the above findings to explain observed summertime ozone trends in terms of changing ozone sensitivities and changing emission rates.

Introduction to Atmospheric Modelling explores the power of mathematics to help us understand complex atmospheric phenomena through mathematical modelling. The author has thoughtfully chosen a path into and through the subject that gives the reader a glimpse of the dynamics underlying phenomena ranging from a sea breeze through mid-latitude cyclonic disturbances to Rossby waves, mainly through the lens of scaling analysis. Written for students with backgrounds in mathematics, physics and engineering, this book will be a valuable resource as they begin studying atmospheric science.

With the endorsement and support from the U.S. Environmental Protection Agency, European Commission, and Environment Canada, a project entitled Air Quality Model Evaluation International Initiative (AQMEII) was launched in 2009 by bringing together scientists from Europe and North America (Rao ST, Galmarini S, Puckett K, Bull Am Meteorol Soc 92:23–30, 2011). Several regional-scale numerical photochemical models were applied over the North American and European domains with 2006 emissions inventory. Several papers resulting from this international collaborative effort were accepted for publication in the AQMEII special issue of Atmospheric Environment. Also, a large 4-D database, assembled by EU Joint Research Centre for the AQMEII project, is now available to all scientists interested in developing innovative model evaluation techniques (Galmarini S, Rao ST, Atmos Environ 45(14):2464, 2011). Having successfully completed the first phase of AQMEII, Phase 2 of AQMEII was launched at the 2011 AQMEII workshop in Chapel Hill, NC, USA to focus on the interactions of air quality and climate change. In Phase 2, coupled meteorology-atmospheric chemistry models will be exercised over the two continents with a common emissions database to assess how well the current generation of coupled regional-scale air quality models can simulate the spatio-temporal variability in the optical and radiative characteristics of atmospheric aerosols and associated feedbacks among aerosols, radiations, clouds, and precipitation. The results from AQMEII Phase 2 would be useful to policy makers for developing effective policies to deal with air pollution and climate change.

Air pollution modeling and its application , Air pollution modeling and its application , کتابخانه دیجیتالی دانشگاه علوم پزشکی و خدمات درمانی شهید بهشتی

We propose a statistical air quality model that simultaneously performs two major tasks: (1) provides a computationally inexpensive means of modelling and forecasting complex space-time air pollution processes, (2) enables an informative and statistically defensible approach for evaluation of air quality models. Rather than working with raw data, we analyze the spatio-temporal variability of a pollution process by extracting data features using Empirical Orthogonal Function decomposition. Our modelling approach thus avoids the complications of point-to-point comparison, and the statistical model's flexible structure allows for extensive fine-tuning. We develop and demonstrate our approach on observations and CMAQ model output of ozone episodes in the Lower Fraser Valley (LFV) of British Columbia, Canada. We believe the principle and methodology of our statistical analysis is applicable to a wide range of air pollution problems.

Recirculation of pollutants is often invoked as a cause of degraded air quality episodes. In this modelling study, we investigated recirculation in order to explore its behaviour in the Lower Fraser Valley (LFV), British Columbia. HYSPLIT was used to produce trajectories from WRF output for seven severe episodes, covering the four main circulation regimes conducive to ozone episodes. Both internal and external recirculations within our domain of interest were observable, but they do not have the same frequency for all regimes.

This study investigates the diurnal evolution of sea-breeze (SB) rotation over an island at the middle latitudes. Earlier research on sea breezes in Sardinia shows that the onshore winds around various coasts of the island exhibit both the theoretically predicted clockwise rotation as well as seemingly anomalous anticlockwise rotation. A non-hydrostatic fully compressible numerical model (WRF) is used to simulate wind fields on and around the island on previously studied sea-breeze days, and is shown to capture the circulation on all coasts accurately. Diurnal rotation of wind is examined, and patterns of clockwise and anticlockwise rotation are identified. A dynamical analysis is performed by extracting individual forcing terms from the horizontal momentum equations. Analysis of several regions around the island shows that the direction of rotation is a result of a complex interaction between near-surface and synoptic pressure gradient, Coriolis and advection forcings. An idealized simulation is performed over an artificial island with dramatically simplified topography yet similar dimensions and latitude to Sardinia. Dynamical analysis of the idealized case reveals a rather different pattern of hodograph rotation to the real Sardinia, yet similar underlying dynamics. The research provides new insights into the dynamics underlying sea-breeze hodograph rotation, especially in coastal zones with a complex topography and/or coastline.

Improving resilience to drought in complex social-environmental systems (SES) is extraordinarily important, particularly for rural tropical locations where small changes in climate regimes can have dramatic SES impacts. Efforts to build drought resilience must necessarily be planned and implemented within SES governance systems that involve linkages in water and land use administration from local to national levels. These efforts require knowledge and understanding that links climate and weather forecasts to regional and local hydrology, to social-economic and environmental systems, and to governance processes. In order to provide structure for such complex choices and investments, we argue that a focus on structured decision processes that involve linkages among science, technological perspectives, and public values conducted with agencies and stakeholders will provide a crucial framework for comparing and building insight for pursuing alternative courses of action to build drought resilience. This paper focuses on a regional case study in the seasonally-dry northwest region of Costa Rica, in watersheds rated as most threatened in the country in terms of drought. We present the overall framework guiding the transdisciplinary efforts to link scientific and technical understanding to public values, in order to foster civil society actions that lead to improved drought resilience. Initial efforts to characterize hydrological and climate regimes will be reported along with our approach to linking natural science findings, social inventories in terms of perspectives on SES, and the psychology and patterns of reliance on forecast information that provide the basis for characterizing public understanding. The overall linkage of technical and value information is focused on creating and comparing alternative actions that can potentially build resilience in short and long time frames by building decision making processes involving stakeholders, agencies and interested parties.

A cost-efficient technology for accurate surface ozone monitoring using gas-sensitive semiconducting oxide (GSS) technology, solar power, and automated cell-phone communications was deployed and validated in a 50 sensor test-bed in the Lower Fraser Valley of British Columbia, over 3 months from May-September 2012. Before field deployment, the entire set of instruments was colocated with reference instruments for at least 48 h, comparing hourly averaged data. The standard error of estimate over a typical range 0-50 ppb for the set was 3 ± 2 ppb. Long-term accuracy was assessed over several months by colocation of a subset of ten instruments each at a different reference site. The differences (GSS-reference) of hourly average ozone concentration were normally distributed with mean -1 ppb and standard deviation 6 ppb (6000 measurement pairs). Instrument failures in the field were detected using network correlations and consistency checks on the raw sensor resistance data. Comparisons with modeled spatial O3 fields demonstrate the enhanced monitoring capability of a network that was a hybrid of low-cost and reference instruments, in which GSS sensors are used both to increase station density within a network as well as to extend monitoring into remote areas. This ambitious deployment exposed a number of challenges and lessons, including the logistical effort required to deploy and maintain sites over a summer period, and deficiencies in cell phone communications and battery life. Instrument failures at remote sites suggested that redundancy should be built into the network (especially at critical sites) as well as the possible addition of a "sleep-mode" for GSS monitors. At the network design phase, a more objective approach to optimize interstation distances, and the "information" content of the network is recommended. This study has demonstrated the utility and affordability of the GSS technology for a variety of applications, and the effectiveness of this technology as a means substantially and economically to extend the coverage of an air quality monitoring network. Low-cost, neighborhood-scale networks that produce reliable data can be envisaged.

We conducted a study of ozone formation in the Lower Fraser Valley (LFV), using WRF-SMOKE-CMAQ models, observations and emission inventories in order to understand relationships between the reduction in both amount and location of precursor emissions and spatio-temporal changes in episodic ambient ozone concentrations over the last 20 years. A dynamical model evaluation shows that the modeling framework is able to capture the changes in both magnitude and spatio-temporal structure of ozone concentrations over the 20-year period. We model ozone formation for four episodes, which both capture the observed changes in ozone reduction and the different meteorological regimes that occur during LFV ozone episodes. The SMOKE emission inventories are adjusted to account for temporal changes in amount, and location of emissions, based on population shifts. Model runs allow us to isolate the effects of emission changes from meteorological changes. Results show that the western LFV has been, and remains VOC-sensitive; the central LFV has changed from VOC-limited to NOx-limited; and the eastern LFV has been, and remains NOx-limited. Analysis shows that the ozone production efficiency as a function of NO has increased noticeably in the eastern LFV. This has likely offset some of the benefits resulting from local NOx emission reductions.

As part of efforts to understand the sources of air pollution in Cape Town, this study investigates the local variation of tropospheric ozone (O3) and identifies possible advection paths of O3 pollution from a remote source to Cape Town. Measurements of O3 and wind from three sites in the Cape Town area were analyzed to study the local variations of O3. At each site, the diurnal variation of O3 is found to be mainly driven by photochemical production while the seasonal variation of O3 is mostly driven by wind conditions. The highest concentration of O3 is observed at the remote site (Cape Point) while lowest O3 concentration is observed at the sub-urban site (Goodwood), where there are chemical sinks of O3 such as NOx. Atmospheric pollution over southern Africa was simulated to study the regional transport of O3. The simulations show that extreme O3 levels in Cape Town can be caused by air pollution transported from the industrial Highveld of South Africa, in the lower troposphere. Such extreme O3 pollution events over Cape Town are simulated to occur in January (14%), March (44%), April (28%) and September (14%). Lagrangian trajectories suggest four paths by which air parcels can be transported from the industrial Highveld to Cape Town: a north-easterly path which is the most frequent route, a tropical deviation route, a deviation along the south coastline and an oceanic deviation path which is the less frequent route. The major advection paths associated with poor air quality in Cape Town are the north-easterly route and the path along the south coastline of the country. Hence the study suggests that emissions in the industrial Highveld may contribute to O3 concentration in the Cape Town area.

We present a global dioxin model that simulates one year of atmospheric emissions, transport processes, and depositions to the earth's terrestrial and marine habitats. We map starting emission levels for each land area, and we also map the resulting deposits to terrestrial and marine environments. This model confirms that 'hot spots' of deposition are likely to be in northern Europe, eastern North America, and in parts of Asia with the highest marine dioxin depositions being the northeast and northwest Atlantic, western Pacific, northern Indian Ocean and the Mediterranean. It also reveals that approximately 40% of airborne dioxin emissions are deposited to marine environments and that many countries in Africa receive more dioxin than they produce, which results in these countries being disproportionately impacted. Since human exposure to dioxin is largely through diet, this work highlights food producing areas that receive higher atmospheric deposits of dioxin than others.

A mechanistic exploration of how ozone formation in the Lower Fraser Valley (LFV) has changed over a 20-year (1985-2005) retrospective period was performed using numerical models, observations, and emissions data from four key episodes selected from the 20-year period. The motivation for this study was the observed differences in trends in summertime episodic ozone concentrations recorded at various monitoring stations within the valley; stations in the western part of the valley have generally shown a noticeable reduction in episodic ozone concentrations whereas stations in the eastern part of the valley have shown little or no improvement in their maximum 8-hour averaged ozone concentrations. Concurrent with these air quality changes, there has been a well-documented reduction in ozone precursor emissions along with an observed shift in the population patterns within the valley over the 20-year period. Ozone formation for four episodes, encompassing the different meteorological regimes that occur during LFV ozone events and spanning the retrospective period, were investigated using the Weather Research and Forecasting (WRF)-Sparse Matrix Operator Kernel Emission (SMOKE)-Community Multiscale Air Quality (CMAQ) modelling system. For each episode, two simulations, intended to isolate the effects of emission changes from meteorological changes, were performed: one with emissions set at the 1985 level and the other with emissions set at the 2005 level. Based on analysis of the model output, observational data, and precursor emission inventories, we find that the Port Moody station in the western LFV remains a volatile organic compound (VOC)-sensitive location; the central part of the LFV around the town of Chilliwack has generally changed from being VOC-limited to being NOx-limited; the easternmost part of the valley around the town of Hope has been and remains NOx-limited. Furthermore, based on the observational data and numerical model output, ozone production efficiency as a function of NO has increased noticeably at Chilliwack and likely in the other eastern parts of the valley. This efficiency increase has likely offset some of the benefits resulting from local NOx emission reductions.

5-year 3-hourly wind speed and direction, air temperature over land and sea surface temperature data are analysed in order to characterize sea breezes at Cotonou (Republic of Benin, West Africa). A set of criteria based on the diurnal reversal of wind direction, the thermal gradient and the number of sunshine hours is used to identify sea breeze days. Statistics are presented that describe the occurrence, duration and strength of the sea breezes. It is found that the sea breeze occurs during all seasons in this region.Sea breeze occurrence is found to be strongly influenced by the West African monsoon. The frequency of occurrence shows clearly two regimes characterized by two maxima (December and May). Sea breezes occur about half of the days during non-monsoon season (winter). Land/sea breezes onset and cessation times show a pronounced seasonal variation. Sea breeze strength is greater during the West African monsoon season.A hodograph analysis reveals the existence of both clockwise and anticlockwise rotation. Average hodographs show clearly the onshore-offshore nature of the sea breeze circulation, but have indeterminate rotation. There is a significant seasonal effect of large-scale flows on sea breeze hodograph patterns.