Les précipitations solides jouent un rôle crucial dans le système climatique terrestre, ainsi que dans le maintien des écosystèmes et le développement des activités humaines. Les incertitudes associées aux estimations quantitatives des précipitations ainsi que celles concernant les projections des modèles climatiques font de cette composante du cycle hydrologique un sujet de recherche important. La télédétection permet de suivre les précipitations et les nuages dans des régions où les observations in situ sont rares et dispersées, mais avec une résolution temporelle limitée ainsi qu’une zone aveugle près du sol pour les capteurs spatiaux, et une visibilité limitée dans la basse atmosphère en terrain complexe pour les radars au sol. Les objectifs de cette thèse sont les suivants : 1) caractériser les nuages et les précipitations en Antarctique, en détectant la présence d’eau liquide surfondue et de particules de glace près du sol à l'aide d'un lidar 532-nm, polarisé, au sol ; 2) caractériser la structure verticale des précipitations dans deux régions contrastées mais importantes de la cryosphère, l’Antarctique et les Alpes, dans la basse troposphère, en utilisant des radars au sol.Dans cette étude, une méthode de détection des hydrométéores dans les nuages et les précipitations est proposée à l'aide de données lidar complétées par celles d’un <<micro rain radar>> (MRR) en bande K pour améliorer la détection des précipitations, ces deux instruments étant déployés à la station Dumont d'Urville (DDU) en Antarctique de l’Est. Une méthode fondée sur le facteur de dépolarisation lidar, le coefficient de rétrodiffusion atténué et l'utilisation d’un partitionnement en k-moyennes est développée. La classification des particules des nuages et des précipitations permet de documenter la distribution verticale de l'eau liquide surfondue, ainsi que des particules de glace sous différentes formes. La comparaison entre les classifications obtenues depuis le sol et celles obtenues à partir des données satellitaires montre des formes similaires pour la distribution verticale de l'eau liquide surfondue dans les nuages.La structure verticale des précipitations près de la surface est analysée à l'aide des moments Doppler obtenus à partir de trois MRRs situés à DDU, à la station Princess Elisabeth (PE) à l'intérieur de l'Antarctique de l’Est, et à la station du Col de Porte (CDP) dans les Alpes françaises. Ces analyses montrent que le climat local joue un rôle important dans la structure verticale des précipitations. En Antarctique, les forts vents catabatiques soufflant du haut plateau jusqu'à la côte diminuent le facteur de réflectivité radar près de la surface en raison de la sublimation des flocons de neige. Les moments Doppler fournissent aussi de riches informations pour comprendre les processus liés aux précipitations, tels que l'agrégation et le givrage, observés notamment à DDU et au Col de Porte.Les résultats montrent également qu'à l'intérieur du continent Antarctique, une partie significative (47%) des profils de précipitations présentent une sublimation complète avant la surface en raison des conditions atmosphériques sèches, alors que sur la côte de l'Antarctique, cela ne concerne qu’environ un tiers des profils (36%). Dans les Alpes, ce pourcentage est réduit à 15%. La majeure partie de la sublimation est observée en dessous de l'altitude où les profils de CloudSat sont contaminés par la proximité du sol. Par conséquent, ce phénomène ne peut pas être entièrement décelé depuis l'espace avec les capteurs actuels.Cette thèse contribue à l'étude de la structure verticale des précipitations neigeuses dans la basse troposphère ; elle est utile pour l'évaluation des produits de télédétection concernant les précipitations qui peuvent présenter de fortes limitations à la proximité de la surface. / Solid precipitation plays an important role in the Earth's climate system, as well as for the maintenance of ecosystems and the development of human society. The large uncertainty in precipitation estimates and the discrepancies within climate model projections make this component of the hydrological cycle important as a research topic. Remote sensing allows to monitor precipitation and clouds in regions where in-situ observations are scarce and scattered, but with limited temporal resolution and a blind zone close to the ground level for spaceborne sensors, and limited visibility in the lower atmosphere in complex terrain for ground-based radars. The objectives of this dissertation are the following: 1) to characterize cloud and precipitation in Antarctica, detecting the presence of supercooled liquid and ice particles near the ground level using a ground-based 532-nm depolarization lidar; 2) to characterize the vertical structure of the precipitation in two contrasted but important regions of the cryosphere, Antarctica and the Alps, in the low troposphere using ground-based radars.In this study, a cloud and precipitation hydrometeor detection method is proposed using lidar data, complemented with a K-band micro rain radar (MRR) to improve the detection of precipitation, both instruments deployed at the Dumont d'Urville (DDU) station in East Antarctica. A method based on lidar depolarization and attenuated backscattering coefficient and the use of k-means clustering is developed for the particle classification. The classification of cloud and precipitation particles provides the vertical distribution of supercooled liquid water, as well as planar oriented ice and randomly oriented ice particles. The comparison between ground-based and satellite-derived classifications shows consistent patterns for the vertical distribution of supercooled liquid water in clouds.The vertical structure of precipitation near the surface is analyzed using the Doppler moments derived from three MRR profiles at DDU, the Princess Elisabeth (PE) station, at the interior of East Antarctica, and at the Col de Porte (CDP) station, in the French Alps. These analyses demonstrate that local climate plays an important role in the vertical structure of the precipitation. In Antarctica, the strong katabatic winds blowing from the high plateau down to the coast decrease the radar reflectivity factor near the surface due to the sublimation of the snowfall particles. Doppler moments also provide rich information to understand precipitation processes, such as aggregation and riming, as observed at DDU and CDP.The results also show that in the interior of the Antarctic continent a significant part (47%) of the precipitation profiles completely sublimate before reaching the surface, due to the dry atmospheric conditions, while in the coast of Antarctica it corresponds to about the third part (36%). In the Alps, this percentage is reduced to 15%. The major occurrence of particle sublimation is observed below the altitude where CloudSat profiles are contaminated by ground clutter. Therefore, this phenomenon cannot be fully captured from space with the current generation of sensors.This dissertation contributes to the study of the vertical structure of snowfall in the low troposphere, useful for the evaluation of precipitation remote sensing products, which may have severe limitations in the vicinity of the surface.

No description available.

[ES] El vapor de agua es la llave del ciclo hidrológico, del balance energético atmosférico y el principal gas natural de efecto invernadero. Su estudio, es, por tanto, esencial para entender la dinámica climática y para la previsión de fenómenos meteorológicos. El uso de las observaciones GNSS para obtenerlo, contribuye de forma notable a su estudio, dada su alta resolución espacial y temporal. Para que se pueda obtener el vapor de agua a partir de observaciones GNSS, estas deben procesarse de un modo que asegure una alta precisión en la obtención de la componente troposférica. En esta tesis, se muestra una estrategia de cálculo con el programa científico Bernese 5.2, basado en Dobles Diferencias de fase, y detallada con sus diferentes opciones. Esa estrategia se aplicó sobre un conjunto de estaciones GNSS situadas desde la ciudad de Vigo, hasta la ciudad francesa de Brest con un total de nueve estaciones principales, a las que se sumaron otras 8 para el diseño de la red de procesamiento. La estrategia fue validada con los productos oficiales de referencia, EPN REPRO2, con las 13 estaciones comunes entre la red de procesamiento y la red EUREF, obteniendo un valor de error medio cuadrático de aproximadamente 3 milímetros. Después se procedió al cálculo del vapor de agua precipitable, con el uso del modelo GPT3 completando cuatro años de datos. Para la validación de estas series de vapor de agua se usaron observaciones de radiosonda, de dos estaciones, situadas cerca de la estación de GNSS de A Coruña y de Santander. La comparación del vapor de agua, arrojó valores máximos de error medio cuadrático de 3 milímetros. Con las series de vapor de agua, se procedió al estudio de su caracterización espacial y temporal. Se constató la disminución del vapor de agua al ascender en la latitud. Así mismo, se observó en la variación temporal una componente anual mucho más significativa que la semianual, así como una distribución claramente estacional del vapor de agua, con valores en la estación de verano muy superiores a la estación de invierno. Las anomalías diarias mostraron ciertas similitudes, con un valor mínimo en la noche, ascendiendo hacia un pico o valor máximo, generalmente en la tarde. Su comportamiento también se mostró claramente estacional, con una variación mucho más significativa y de mayor amplitud en el verano que en el invierno. La serie de vapor de agua de la ciudad de A Coruña, junto con los datos de una estación meteorológica, se aplicaron al estudio de su relación con otras variables atmosféricas. En el caso de la temperatura y el vapor de agua, el estudio mostró una fuerte correlación. Sin embargo, el estudio de la relación entre el vapor de agua y precipitación no mostró ninguna relación entre ambas. Además, la serie de vapor de agua permitió estudiar el índice de Eficiencia de Precipitación, encontrándose una baja efectividad de los mecanismos que producen la precipitación más acusada en verano que en invierno, a pesar del nivel alto de vapor de agua en la estación estival. Además, se estudiaron nueve episodios de lluvia de diferentes estaciones climáticas, estudiando la evolución temporal del vapor de agua antes, durante y después del fenómeno. Esto permitió observar un patrón de comportamiento similar con un claro aumento del vapor de agua antes del comienzo de la lluvia y un fuerte descenso posterior, que fue parametrizado en forma de diferentes indicadores, en los que, de nuevo, se constató una fuerte componente estacional. Además, se pudo observar un comportamiento más significativo en la ventana de 12 horas previas a los episodios de lluvia. / [CA] El vapor d'aigua és la clau del cicle hidrològic, del balanç energètic atmosfèric i el principal gas natural d'efecte d'hivernacle. El seu estudi, és, per tant, essencial per a entendre la dinàmica climàtica i per a la previsió de fenòmens meteorològics. L'ús de les observacions GNSS per a obtindre'l, contribuïx de manera notable al seu estudi, donada la seua alta resolució espacial i temporal. Perquè es puga obtindre el vapor d'aigua a partir d'observacions GNSS, estes han de processar-se d'un mode que assegure una alta precisió en l'obtenció de la component troposfèrica. En esta tesi, es mostra una estratègia de càlcul amb el programa científic Bernese 5.2, basat en Dobles Diferències de fase, i detallada amb les seues diferents opcions. Eixa estratègia es va aplicar sobre un conjunt d'estacions GNSS situades des de la ciutat de Vigo, fins a la ciutat francesa de Brest amb un total de nou estacions principals, a les quals es van sumar altres 8 per al disseny de la xarxa de processament. L'estratègia va ser validada amb els productes oficials de referència, EPN REPRO2, amb les 13 estacions comunes entre la xarxa de processament i la xarxa EUREF, obtenint un valor d'error mig quadràtic d'aproximadament 3 mil·límetres. Després es va procedir al càlcul del vapor d'aigua precipitable, amb l'ús del model GPT3 completant quatre anys de dades. Per a la validació d'estes sèries de vapor d'aigua es van usar observacions de radiosonda, de dos estacions, situades prop de l'estació de GNSS de la Corunya i de Santander. La comparació del vapor d'aigua, va llançar valors màxims d'error mig quadràtic de 3 mil·límetres. Amb les sèries de vapor d'aigua, es va procedir a l'estudi de la seua caracterització espacial i temporal. Es va constatar la disminució del vapor d'aigua en ascendir en la latitud. Així mateix, es va observar en la variació temporal una component anual molt més significativa que la semianual, així com una distribució clarament estacional del vapor d'aigua, amb valors en l'estació d'estiu molt superiors a l'estació d'hivern. Les anomalies diàries van mostrar unes certes similituds, amb un valor mínim en la nit, ascendint cap a un pic o valor màxim, generalment en la vesprada. El seu comportament també es va mostrar clarament estacional, amb una variació molt més significativa i de major amplitud en l'estiu que en l'hivern. La sèrie de vapor d'aigua de la ciutat de la Corunya, juntament amb les dades d'una estació meteorològica, es van aplicar a l'estudi de la seua relació amb altres variables atmosfèriques. En el cas de la temperatura i el vapor d'aigua, l'estudi va mostrar una forta correlació. No obstant això , l'estudi de la relació entre el vapor d'aigua i precipitació no va mostrar cap relació entre ambdues. A més, la sèrie de vapor d'aigua va permetre estudiar l'índex d'Eficiència de Precipitació, trobant-se una baixa efectivitat dels mecanismes que produïxen la precipitació més acusada a l'estiu que a l'hivern, malgrat el nivell alt de vapor d'aigua en l'estació estival. A més, es van estudiar nou episodis de pluja de diferents estacions climàtiques, estudiant l'evolució temporal del vapor d'aigua abans, durant i després del fenomen. Això va permetre observar un patró de comportament similar amb un clar augment del vapor d'aigua abans del començament de la pluja i un fort descens posterior, que va ser parametritzat en forma de diferents indicadors, en els quals, de nou, es va constatar una forta component estacional. A més, es va poder observar un comportament més significatiu en la finestra de 12 hores prèvies als episodis de pluja. / [EN] Water vapour is the key of the hydrological cycle and the atmospheric energy balance and the most important natural greenhouse gas. Its study is therefore essential for understanding climate dynamics and for forecasting meteorological phenomena. The use of GNSS observations to obtain it contributes significantly to its study, given its high spatial and temporal resolution. In order to obtain water vapour from GNSS observations, these must be processed in a way that ensures high accuracy in obtaining the tropospheric component. In this thesis, a calculation strategy with the scientific programme Bernese 5.2, based on Double Phase Differences, is shown, and detailed with its different options. This strategy was applied on a set of GNSS stations located from the Spanish city of Vigo to the French city of Brest with a total of nine main stations, to which another 8 were added for the design of the Double Difference processing network. The strategy was validated with the official reference products, EPN REPRO2, with the 13 common stations between the processing network and the EUREF network, obtaining a mean square error value of approximately 3 millimetres. Then, four years series of precipitable water vapour was calculated, using the GPT3 model. For the validation of these water vapour series, radiosonde observations from two stations, located near the GNSS station of A Coruña and Santander were used. The comparison between both sets of water vapour information was performed yielding maximum values of mean square error of 3 millimetres. Using the water vapour series, the spatial and temporal characterisation of water vapour in the working area was studied. It was then possible to observe the decrease in water vapour with increasing latitude. Likewise, a much more significant annual component than the semi-annual one was observed in the temporal variation, as well as a clearly seasonal distribution of water vapour in the whole working area, with values in the summer season much higher than in the winter season. The daily anomalies showed some similarities, showing in general a minimum value at night, rising towards a peak or maximum value in the afternoon. Their behaviour was also clearly seasonal, with a much more significant variation and greater amplitude in the summer than in the winter. The water vapour series of the city of A Coruña, together with data from a meteorological station, were applied to the study of their relationship with other atmospheric variables. In the case of temperature and water vapour, the study showed a strong correlation. However, the study of the relationship between water vapour and precipitation showed no relationship between the two. In addition, the water vapour series allowed the study of the Precipitation Efficiency index, finding a low effectiveness of the mechanisms that produce precipitation more pronounced in summer than in winter, despite the high level of water vapour in the summer season. Finally, nine rainfall events were studied in different climatic seasons, studying the temporal evolution of water vapour before, during and after the event. This allowed a similar pattern of behaviour to be observed, with a clear increase in water vapour before the onset of the rain and a sharp decrease afterwards, which was parameterised in the form of different indicators, in which, once again, a strong seasonal component was observed. In addition, a more significant behaviour was observed in the 12-hour window prior to rainfall events. / Perdiguer López, R. (2024). Estrategia de cálculo del vapor de agua a partir de las observaciones GNSS para su caracterización y aplicación climática [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/205795

Este trabalho teve como objetivo analisar as condições meteorológicas favoráveis e desfavoráveis à dispersão de poluentes, com ênfase no ozônio, nas áreas urbanas associadas à Região Metropolitana de São Paulo (RMSP) e a Grande Santiago (GS). Medidas de concentração de estações localizadas em ambas as áreas de estudo foram utilizadas para determinar o comportamento médio, o número de ocorrências de ultrapassagens de padrão de qualidade do ar e o aumento noturno das concentrações de ozônio num período de dez anos. Foi encontrado que o máximo horário acontece próximo das 14 horas (horário local) nas duas regiões, e que existe uma tendência à diminuição no número de ultrapassagens do padrão de qualidade do ar associado a este poluente. Na RMSP é possível observar um máximo secundário durante a madrugada, enquanto que este fenômeno não é claramente observado nos valores médios de concentração na GS. Com dados da Reanálise do NCEP/NCAR foi visto que a ocorrência deste fenômeno está associada a configurações sinóticas específicas na GS, enquanto que na RMSP não existe padrão sinótico específico que diferencie casos com e sem aumento de ozônio noturno. Um novo módulo fotoquímico (NPM), contendo 95 reações foi inserido no modelo BRAMS na tentativa de melhorar o prognóstico das concentrações de poluentes, principalmente em relação ao ozônio. O NPM mostrou melhor desempenho que o módulo fotoquímico original do modelo (SPM; Simple Photochemical Module) para todos os poluentes considerados, salvo o ozônio, para o qual o SPM apresentou melhores índices estatísticos em 5 das 7 estações avaliadas. As características locais associadas à ocorrência simultânea ou não de aumento na concentração de ozônio foram estudadas utilizando o modelo BRAMS com o módulo SPM ativado, sendo verificado que o aumento de ozônio na RMSP está associado, principalmente, ao transporte vertical deste poluente a partir de níveis mais elevados da atmosfera, enquanto que o transporte horizontal é a maior contribuição para o aumento das concentrações de ozônio durante o período noturno na GS. / This work aimed to analyze the favorable and unfavorable meteorological conditions for pollutant dispersion, especially ozone, at the Metropolitan Area of São Paulo (MASP) and the Greater Santiago (GS). Ozone concentration measurements from stations located in both urban areas were used to determinate the mean behavior, the number of standard air quality exceedances and the increase on nocturnal ozone concentration over a 10 years period. It was found that the diurnal maximum occurs around 14 local time in both urban areas, and that there is a diminishment tendency of the total cases of standard air quality exceedances during all period. A secondary maximum of ozone concentration was observed in MASP at night, which was not clearly seen on mean values over GS. By using the NCEP/NCAR Reanalysis data it was seen that the occurrence of this phenomenon is associated to specific synoptic patterns for GS, while there is no specific synoptic pattern for the MASP cases, with or without nocturnal increase in ozone concentrations. A New Photochemical Module (NPM), containing 95 reactions was coupled to BRAMS model in an attempt to improve the prediction of air pollutants, especially ozone. The NPM showed a better performance than the original module, the SPM (Simple Photochemical Module), for all considered pollutants but ozone. For this pollutant, the SPM presents better statistical indexes for 5 of the 7 stations analyzed. The local characteristics related to simultaneous occurrence of nocturnal ozone increase was studied using the SPM-BRAMS model, which showed that the secondary nocturnal maximum of ozone concentrations in MASP are related to vertical transport of this pollutant from higher levels of the atmosphere to the surface, while the horizontal transport is a major contributor to the increase of ozone concentrations in the GS during the night.

Made available in DSpace on 2014-06-11T19:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-12-07Bitstream added on 2014-06-13T20:01:31Z : No. of bitstreams: 1 sapucci_lf_dr_prud.pdf: 3782471 bytes, checksum: af4cccfc2f5cb3b6dd4ba86dfb21c180 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A quantificação do vapor d'água integrado na atmosfera (IWV - Integrated Water Vapor), ao contrário de outras variáveis meteorológicas, é algo que ainda se apresenta como um grande desafio para as Ciências Atmosféricas. Diversos mecanismos, envolvendo diferentes técnicas, têm sido empregados e testados para esse fim em diferentes regiões do globo por pesquisa dores das mais variadas áreas da ciência. Essa tese apresenta uma contribuição a esse tema ao empregar receptores GPS (Global Positioning System) em bases terrestres, localizados no Brasil, envolvendo instituições de pesquisa na área de Geodésia e de Meteorologia. Os objetivos principais desse trabalho são validar os valores do IWV obtidos a partir das observações GPS e contribuir com a viabilização da utilização de redes ativas de receptores GPS, existentes atualmente e futuras, no monitoramento do IWV como suporte às atividades da Meteorologia e Climatologia no Brasil. Os resultados obtidos mostram que, com a efetivação desse processo, poderá ser obtida uma fonte adicional de informações da umidade para Previsão Numérica de Tempo (PNT). Além disso, é mostrado também que a alta resolução temporal dos valores do IWV obtidos a partir das observações GPS pode contribuir para a melhoria dos resultados gerados por outras técnicas empregadas na mesma tarefa. Em contrapartida, um modelo de PNT é utilizado para gerar previsões da influência da troposfera nos sinais GPS, visando beneficiar aplicações GPS em tempo real. Os resultados gerados nesse trabalho são frutos da sinergia entre as duas áreas envolvidas e mostram que, atualmente, há boas perspectivas para essa parceria no Brasil. / Quantification of Integrated Water Vapor (IWV), unlike other meteorological variables, still represents a significant challenge to the Atmospheric Sciences. In this task several techniques using different mechanisms have been employed and tested in different regions of the planet. Many researchers from several areas of science have been involved in this process. This thesis presents a contribution to this theme, employing ground-based GPS receivers installed on Brazilian territory, involving Geodesy and Meteorology research institutes. The main aim of this work is to contribute in order to make enable the use of the existing networks of continuously operating GPS receivers, and those that will be installed in the future, in IWV monitoring to support meteorological and climatological activities in Brazil. The results generated show that in this process it is possible to obtain an additional source of humidity information for Numerical Weather Prediction (NWP). Furthermore, the prospect of using the ground-based GPS receivers to monitor atmospheric water vapor is promising because thehigh temporal resolution of IWV values from GPS observations can improve the results generated from other techniques employed in the same task. At the same time, a NWP model is applied to generate predictions of the atmosphere's influence over radiofrequency signals, to improve real time GPS applications. The results of this work stem from the synergy between the two areas of science involved. They show that the current outlook for this partnership in Brazil is good, and that both Meteorology and Geodesy will benefit.

A base case modelling investigation was conducted to explore the chemical and physical behaviour of ground-level ozone (O3) and its precursor nitrogen dioxide (NO2) in Ontario using the U.S. Environmental Protection Agency (EPA) Community Multiscale Air Quality (CMAQ) model. Two related studies were completed to evaluate the performance of CMAQ in reproducing the behaviour of these species in both rural and urban environments by comparing to surface measurements collected by the Ontario Ministry of the Environment (MOE) network of air quality stations. The first study was a winter examination and the second study was conducted for a period during the summer of the same year. The municipality of North Bay was used to represent a rural setting given its smaller population relative to the city of Ottawa which was the base of the urban site. Statistical and graphical analyses were used to validate the model output. CMAQ was found to replicate the spatial variation of O3 and NO2 over the domain in both the winter and summer, but showed some difficulty in simulating the temporal allocation of the species. Validation statistics for North Bay and Ottawa showed overall O3 mean biases (MB) of 3.35 ppb and 2.25 ppb, respectively, and overall NO2 MB of -8.75 ppb and -4.37 ppb, respectively for the winter. Summer statistics generated O3 MB of 4.66 ppb (North Bay) and 10.05 ppb (Ottawa) while both MB for NO2 were between -2.20 ppb to -2.55 ppb. Graphical analysis showed that the model was not able to reproduce the lower levels of O3, especially at night, or the higher levels of NO2 during the day at the North Bay site for either season. This was expected since the comparisons were made between point measurements and 36 km grid-averaged model results. The presence of high amounts of NO2 emissions local to the monitoring sites compared to the levels represented in the emissions inventory may also be a contributing factor. The simulations for Ottawa demonstrated better agreement between model results and measurements as CMAQ provided a more accurate reproduction of both the higher and lower mixing ratios of O3 and NO2 during the winter and summer seasons. Results indicate that CMAQ is able to simulate urban environments better than rural ones.

Halogen-driven ozone and nonmethane hydrocarbon losses in springtime Arctic boundary layer are investigated using a regional chemical transport model (CTM). Surface observation of O3 at Alert and Barrow and aircraft observations of O3 and hydrocarbons during the TOPSE experiment from February to May in 2000 are analyzed. We prescribe halogen radical distributions based on GOME BrO observations and calculated or observed other halogen radical to BrO ratios. GOME BrO shows an apparent anti-correlation with surface temperature over high BrO regions. At its peak, area of simulated near-surface O3 depletions (O3 LT 20ppbv) covers GT 50% of the north high latitudes. Model simulated O3 losses are in agreement with surface and aircraft O3 observations. Simulation of halogen distributions are constrained using aircraft hydrocarbon measurements. We find the currently chemical mechanism overestimate the Cl/BrO ratios. The model can reproduce the observed halogen loss of NMHCs using the empirical Cl/BrO ratios. We find that the hydrocarbon loss is not as sensitive to the prescribed boundary layer height of halogen as that of O3, therefore producing a more robust measure for evaluating satellite column measurement. Tropospheric tracer transport and chemical oxidation processes are examined on the basis of the observations at northern mid-high latitudes and over the tropical Pacific and the corresponding global 3D CTM (GEOS-CHEM) simulations. The correlation between propane and ethane/propane ratio is employed using a finite mixing model to examine the mixing in addition to the OH oxidations. At northern mid-high latitudes the model agrees with the observations before March. The model appears to overestimate the transport from lower to middle latitudes and the horizontal transport and mixing at high latitudes in May. Over the tropical Pacific the model reproduces the observed two-branch slope values reflecting an underestimate of continental convective transport at northern mid-latitudes and an overestimate of latitudinal transport into the tropics. Inverse modeling using the subsets of observed and simulated data is more reliable by reducing (systematic) biases introduced by systematic model transport model transport errors. On the basis of this subset we find the model underestimates the emissions of ethane and propane by 14 5%.

Biogenic isoprene plays an important role in tropospheric chemistry. We use HCHO column measurements by the Global Ozone Monitoring Experiment (GOME) to constrain isoprene emissions. Using the global Goddrad Earth Observing SystemChemistry (GEOS-Chem) as the forward model, a Bayesian inversion of GOME HCHO observations from September 1996 to August 1997 is conducted. Column contributions to HCHO from 12 sources including 10 terrestrial ecosystem groups, biomass burning, and industry are considered and inverted for 8 geographical regions globally. The a posteriori solution reduces the model biases for all regions, and estimates the annual global isoprene emissions of 566 Tg C yr-1, ~50% larger than the a priori estimate. Compared to the Global Emissions Inventory Activity (GEIA) inventory (~500 Tg C yr-1), the a posteriori isoprene emissions are generally higher at mid latitudes and lower in the tropics. This increase of global isoprene emissions significantly affects tropospheric chemistry, decreasing the global mean OH concentration by 10.8% to 0.95106 molecules/cm3. The atmospheric lifetime of CH3CCl3 increases from 5.2 to 5.7 years. Positive matrix factorization (PMF), an advanced method for source apportionment, is applied to TRAnsport of Chemical Evolution over the Pacific (TRACE-P) measurements and it is found that cyanogenesis in plants over Asia is likely an important emission process for CH3COCH3 and HCN. This approach also is applied to estimate source contributions to the tropospheric ozone (O3) with Tropospheric Ozone Production about the Spring Equinox (TOPSE) and TRACE-P measurements. The corresponding GEOS-Chem simulations are applied to the same factor-projected space in order to evaluate the model simulations. Intercontinental transport of pollutants is most responsible for increasing trend of springtime O3, while stratospheric influence is the largest contributions to troposperic O3 variability at northern middle and high latitudes. On the other hand, the overall tropospheric contributions to O3 variability are more important at northern low latitudes by long-range transport, biomass burning, and industry/urban emissions. In general, the simulated O3 variabilities are comparable with those of observations. However, the model underestimates the trends of and the contributions to O3 variability by long-range transport of O3 and its precursors at northern middle and high latitudes.

Two long-standing air quality challenges in the United States are the control of tropospheric ozone and particulate matter, both of which are responsible for widespread damage to human health and the environment. This thesis presents three modeling applications in support of policy development and regulatory actions for control of these pollutants in the eastern United States, taking advantage of recent advancements in sensitivity techniques in a regional Eulerian photochemical air quality model. A broad evaluation of regional atmospheric pollution and transboundary air quality management, including the international scale, and an analysis of successful transboundary management efforts are also presented. The first modeling application is an evaluation of local and interstate impacts on ozone and fine particulate matter (PM2.5) from ground-level and elevated nitrogen oxide plus nitrogen dioxide and from sulfur dioxide emissions from individual states. This analysis identifies states responsible for a significant amount of regional secondary pollution, and states which do not have independent control over much of their pollution concentrations. An average of approximately 77% of each state s ozone and PM2.5 concentrations that are sensitive to the emissions evaluated are found to be formed from emissions from other states. The second application is an assessment of impacts from emissions from a single power-plant on resulting regional ozone concentrations. Three sensitivity techniques and two 3D photochemical models are applied. Ozone increases greater than 0.5 ppbv are found over eight states downwind from the power-plant. The third application supports the extension of a body of research aimed at advancing understanding of the ozone formation potential, or reactivity , of VOCs for use in regional-scale, rather than urban-scale, regulations. Air quality impacts of VOCs emissions from solvent use and manufacture are presented, scientific barriers to accounting for reactivity in regulations are discussed, current and upcoming regulatory applications are described, and results from a regional scale evaluation of reactivity quantification are presented.

Tropical and extratropical Pacific decadal climate variability substantially impact physical and biological systems in the Pacific Ocean and strongly influence global climate through teleconnection patterns. Current understanding of Pacific decadal climate variability centers around the El Niño-Southern Oscillation (ENSO), the Aleutian Low (AL), and the Pacific Decadal Oscillation (PDO). However, recent literature has highlighted the emerging roles of secondary modes of variability of the tropical and extratropical Pacific atmosphere and ocean in global climate change: the Central Pacific Warming (CPW) phenomenon, the North Pacific Oscillation (NPO), and the North Pacific Gyre Oscillation (NPGO). This work analyzes the statistics and uncertainties behind Pacific interannual and decadal-scale climate variability, and focuses on better understanding the roles of the CPW, NPO, and NPGO in the climate system. The study begins by examining the dynamics of the NPO and its role in Pacific interannual and decadal climate variability. Results illustrate that the individual poles of the NPO have relations at high frequencies, but only the southern node contains a deterministic low-frequency component, which is forced by tropical Pacific sea surface temperature (SST) variability, as shown with a modeling experiment. The NPO-induced variability by the tropical Pacific SST is then integrated by the underlying ocean surface to form the decadal-scale NPGO signal. Thus, a new link between the CPW, the NPO, and the NPGO is formed, expanding the current framework of Pacific decadal variability and its implications for weather and climate. The new framework of North Pacific decadal variability (NPDV) is then evaluated in 24 state-of-the-art coupled climate models. Results indicate that the models in general have difficulty reproducing the leading modes of NPDV in space and time, particularly the NPGO mode and its connection to the NPO. Furthermore, most models lack the proper connections between extratropical and tropical Pacific, for both the ENSO/AL/PDO and CPW/NPO/NPGO connections. Improvements in these teleconnections are thus needed to increase confidence in future climate projections. The last part of the dissertation explores further the importance of the CPW mode by comparing and contrasting two popular paleoclimate SST anomaly reconstruction methods used for tropical Indo-Pacific SSTs. The first method exploits the high correlation between the canonical ENSO mode and tropical precipitation; the second method uses a multi-regression model that exploits the multiple modes of covariability between tropical precipitation and SSTs, including the CPW mode. The multi-regression approach demonstrates higher skill throughout the tropical Indo-Pacific than the first approach, illustrating the importance of including the CPW phenomenon in understanding past climates.