Resumo: Considerando a importância da compreensão da dinâmica espaço temporal dos componentes do balanço de energia (BE) em escala regional para o gerenciamento de recursos hídrico e o manejo agrícola, o objetivo principal desta tese foi construir e analisar uma série temporal dos componentes do BE adequada às condições de clima subtropical úmido do Estado do Rio Grande do Sul. Para tanto, inicialmente foi avaliada a adequação de modelos de estimativa de BE para o Estado. Nesta etapa foram utilizados produtos MODIS e dados de referência medidos em uma torre micrometeorológica instalada em Cruz Alta – RS, usando valores instantâneos para um período de estudo de 2009 a 2011. Na sequência foi avaliada a adequação dos modelos em representar a variabilidade espacial dos componentes do BE. Nesta etapa foram usados produtos MODIS, dados de reanálise ERA Interim, dados de referência da torre micrometeorológica e dados de estações meteorológicas do INMET, para o mesmo período de estudo. Na última etapa do trabalho foi construída a série temporal dos componentes do BE usando o modelo METRIC, a qual abrangeu um período de 14 anos, de 2002 a 2016. Os resultados demonstraram que os três modelos analisados apresentam coerência com as medidas de referência, sendo as maiores limitações apresentadas pelo modelo SEBAL, as quais se atribui principalmente às condições ecoclimáticas do Estado e a baixa resolução espacial das imagens. Na análise da variabilidade espacial, o modelo METRIC apresentou maior consistência nos resultados e proporcionou maior número de dias com resultados válidos, sendo assim apontado como o mais apto para realização do restante do estudo. A série temporal construída possibilitou a compreensão dos padrões de distribuição espaço temporal dos componentes do BE no estado do Rio Grande do Sul. Há uma marcada sazonalidade nos componentes do BE, com maiores valores no verão e menores no inverno. G (fluxo de calor no solo) é o componente de menor magnitude e sua distribuição espacial e temporal é determinada pela distribuição de Rn (saldo de radiação). Já os componentes LE (fluxo de calor latente) e H (fluxo de calor sensível), são os que mostram magnitude maior e apresentam padrões de distribuição espacial e temporal coerentes com as condições climáticas e com os tipos de uso e cobertura na área de estudo. Observase um padrão inverso, com um gradiente de LE no sentido noroeste para sudeste e para o componente H, no sentido sudeste para noroeste. Sendo estas informações de grande importância para gerenciamento de recursos hídricos em escala regional, para estudos de zoneamento agrícola. / Abstract: Given the importance of understanding the temporal and spatial dynamics of of the energy balance (EB) components in a regional scale for the management of water resources and agricultural, the main objective of this thesis was to construct and analyze a time series of the components of BE appropriate to the subtropical humid climate conditions of the State of Rio Grande do Sul. In order to reach the objective initially, the adequacy of the models for the humid climate conditions was evaluated, in this step we used MODIS data and reference data measured in a micrometeorological tower installed in Cruz Alta - RS. The analyzes performed with instantaneous values and the study period was from 2009 to 2011. The next step evaluate the spatial variability of the BE components, the data used were the MODIS products, ERA Interim reanalysis data, reference data of the micrometeorological tower and INMET meteorological stations, for the same study period. In the last stage the time series of the BE components was constructed from the METRIC model. The period series was 14 years from 2002 to 2016.The results showed that the three models analyzed were consistent with the reference measurements, with the greatest limitations presented by the SEBAL model, which are mainly attributed to the state's eco-climatic conditions and the low spatial resolution of the images In the analysis of the spatial variability, the METRIC model presented greater consistency in the results and provided greater number of days with valid results, this model thus indicated as the most suitable for the rest of the study. The time series constructed allowed us to understand the temporal distribution patterns of BE components in the state of Rio Grande do Sul. There is a marked seasonality in the BE components, with higher values in summer and lower in winter. G is the smallest magnitude component and its spatial and temporal distribution is determined by the Rn distribution. On the other hand, the LE and H components are those that show higher magnitude and present spatial and temporal distribution patterns consistent with the climatic conditions and the types of use and coverage in the study area. An inverse pattern is observed, with a LE gradient from north-west to south-east and for H-component, from southeast to northwest.

Doctor of Philosophy / Department of Agronomy / Eduardo Alvarez Santos / Measurements of methane (CH₄) emissions from livestock production could provide invaluable data to reduce uncertainties in the global CH₄ budget and to evaluate mitigation strategies to lower greenhouse gas (GHG) emissions. The eddy covariance (EC) technique has recently been applied as an alternative to measure CH₄ emissions from livestock systems, but heterogeneities in the source area and fetch limitations impose challenges to EC measurements. The main objectives of this study were to: 1) assess the performance of a closed-path EC system for measuring CH₄, CO₂, and H₂0 fluxes; 2) investigate the spatial variability of the EC fluxes in a cattle feedlot using flux footprint analysis; 3) estimate CH₄ emission rates per animal (Fanimal) from a beef cattle feedlot using the EC technique combined with two footprint models: an analytical footprint model (KM01) and a parametrization of a Lagrangian dispersion model (FFP); and 4) compare CH₄ emissions obtained using the EC technique and a footprint analysis with CH₄ emission estimates provided by a well-stablished backward-Lagrangian stochastic (bLS) model. A closed-path EC system was used to measure CH₄, CO₂, and H₂0 fluxes. To evaluate the performance of this closed-path system, a well-stablished open-path EC system was also deployed on the flux tower to measure CO₂ and H₂0 exchange. Methane concentration measurements and wind data provided by that system were used to estimate CH₄ emissions using the bLS model. The performance assessment that included comparison of gas cospectra and measured fluxes from the two EC systems showed that the closed-path system was suitable for the EC measurements. Flux values were quite variable during the field experiment. A one-dimensional flux footprint model was useful to interpret some of the flux temporal and spatial dynamics. Then, a more comprehensive data analysis was carried out using two-dimensional footprint models (FFP and KM01) to interpret fluxes and scale fluxes measured at landscape to animal level. The monthly average Fanimal, calculated using the footprint weighed stocking density ranged from 83 to 125 g animal⁻¹ d⁻¹ (KM01) and 75–114 g animal⁻¹ d⁻¹ (FFP). These emission values are consistent with the results from previous studies in feedlots however our results also suggested that in some occasions the movement of animals on the pens could have affected CH₄ emission estimates. The results from the comparisons between EC and bLS CH₄ emission estimates show good agreement (0.84; concordance coefficient) between the two methods. In addition, the precision of the EC as compared to the bLS estimates was improved by using a more rigorous fetch screening criterion. Overall, these results indicate that the eddy covariance technique can be successfully used to accurately measure CH₄ emissions from feedlot cattle. However, further work is still needed to quantify the uncertainties in Fanimal caused by errors in flux footprint model estimates and animal movement.

abstract: The North American Monsoon System (NAMS) contributes ~55% of the annual rainfall in the Chihuahuan Desert during the summer months. Relatively frequent, intense storms during the NAMS increase soil moisture, reduce surface temperature and lead to runoff in ephemeral channels. Quantifying these processes, however, is difficult due to the sparse nature of coordinated observations. In this study, I present results from a field network of rain gauges (n = 5), soil probes (n = 48), channel flumes (n = 4), and meteorological equipment in a small desert shrubland watershed (~0.05 km2) in the Jornada Experimental. Using this high-resolution network, I characterize the temporal and spatial variability of rainfall, soil conditions and channel runoff within the watershed from June 2010 to September 2011, covering two NAMS periods. In addition, CO2, water and energy measurements at an eddy covariance tower quantify seasonal, monthly and event-scale changes in land-atmosphere states and fluxes. Results from this study indicate a strong seasonality in water and energy fluxes, with a reduction in Bowen ratio (B, the ratio of sensible to latent heat fluxes) from winter (B = 14) to summer (B = 3.3). This reduction is tied to shallow soil moisture availability during the summer (s = 0.040 m3/m3) as compared to the winter (s = 0.004 m3/m3). During the NAMS, I analyzed four consecutive rainfall-runoff events to quantify the soil moisture and channel flow responses and how water availability impacted the land-atmosphere fluxes. Spatial hydrologic variations during events occur over distances as short as ~15 m. The field network also allowed comparisons of several approaches to estimate evapotranspiration (ET). I found a more accurate ET estimate (a reduction of mean absolute error by 38%) when using distributed soil moisture data, as compared to a standard water balance approach based on the tower site. In addition, use of spatially-varied soil moisture data yielded a more reasonable relationship between ET and soil moisture, an important parameterization in many hydrologic models. The analyses illustrates the value of high-resolution sampling for quantifying seasonal fluxes in desert shrublands and their improvements in closing the water balance in small watersheds. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2011

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This thesis quantifies the net change of CO2 (NEE) in an irrigated rice crop cultivation in RS (Brazil). The research is part of the project CT-HIDRO, which presents as main purpose the description of surface conditions for different ecosystems in the country. Data were gathered during the cultivation period, from October 2003 to March 2004. During this time, the average air temperature and the incident radiation were suitable for the development of the culture in such an area. The turbulent flows, calculated by the eddy covariance method, overestimated the NEE value, probably due to the low estimate of breathing tax, because, during some night-times, sensor registered little turbulence. Moreover, other factor could have interfered in the result of the flows, for instance, the time in which the flows are calculated. The Webb correction was applied in the curve of NEE, and a value smaller than 1% was found. Such result didn't modify the previous result significantly. The behavior of CO2 flow during the whole analyzed period showed a maximum of -0,47mgCO2 m−2 s −1 in January 2004, what demonstrates the largest absorption of CO2 from the atmosphere by the plant during the day and a smaller liberation at night, due to the development phase in which the plant is. In this case, the Webb correction was also little emphasized, not interfering in the obtained result. The curves that demonstrate the three phases of development of the rice presented a larger absorption of CO 2 during the reproductive phase. The behavior of the flow of CO 2 showed a negative flow during the day, when the plant absorbs CO2 from the atmosphere, and a positive flow during the night, when the inverse process occurs, what was waited for. The latent heat flow presented larger diary average values from January to February, always with positive values, consequence of the rice crop irrigation. Two days with high values of flow of latent heat were obtained, what motivated the analysis of the energy balance. The closing of the energy balance was not reached in both days. A possible reason for that could be the low estimate of flows when the eddy covariance method was applied. / Este trabalho quantifica a troca líquida de CO2 (NEE) em uma área de cultivo de arroz irrigado no RS, como parte do projeto CT-HIDRO, projeto este que tem como finalidade descrever condições de superfície para diferentes ecossistemas do país. Os dados utilizados foram coletados durante o período de cultivo, entre outubro de 2003 e março de 2004. Neste período a temperatura média do ar e a radiação incidente são adequadas para o desenvolvimento da cultura nesta região. Os fluxos turbulentos, calculados pelo método de covariância de vórtices (eddy covariance), superestimaram o valor da NEE, provavelmente devido, a subestimativa da taxa de respiração, pois em alguns períodos noturnos os sensores registraram pouca turbulência. Além disso, outro fator que pode interferir no resultado dos fluxos, como por exemplo, o intervalo em que os fluxos são calculados. Foi aplicada a correção de Webb na curva de NEE e encontrou-se um valor menor que 1%, fato este que não modificou significativamente o resultado encontrado. O comportamento do fluxo de CO 2 durante todo o período analisado, mostrou um pico de -0,47mgCO2 m−2 s −1 , em janeiro de 2004, o que demonstra a maior captura de CO2 da atmosfera pela planta durante o dia e uma menor liberação à noite, devido a fase de desenvolvimento em que a planta se encontra. Neste caso, a correção de Webb também foi pouco acentuada, não interferindo no resultado obtido. As curvas que demonstram as três fases de desenvolvimento do arroz mostraram claramente uma maior absorção de CO 2 durante a fase reprodutiva. O comportamento do fluxo de CO 2 mostra um fluxo negativo durante à dia, quando a planta absorve CO2 da atmosfera e um fluxo positivo durante à noite quando ocorre o processo inverso, o que era esperado. O fluxo de calor latente apresentou maiores valores médios diários entre os meses de janeiro e fevereiro, apresentando sempre valores positivos, conseqüência da irrigação do campo de arroz. Obtivemos dois dias com valores elevados de fluxo de calor latente, o que fez com que analisássemos o balanço de energia. O fechamento do balanço de energia não foi alcançado em ambos os dias. Uma possível razão para isto pode ser o devido à subestimativa dos fluxos quando aplicado o método de covariância de vórtices.

The South Saskatchewan River Basin (SSRB) is amongst the largest watersheds in Canada. It is an ecologically diverse region, containing Montane Cordillera, Boreal Plains and Prairie ecozones. The SSRB is subject to chinooks, which bring strong winds, high temperatures and humidity deficits that alter the storage of water during winter. Approximately 40% of winter days experience chinooks. Ablation during chinooks has not been quantified; it is not known how much water evaporates, infiltrates or runs off. The aim of this thesis is to characterise the spatial variability of surface water fluxes as affected by chinooks over SSRB subbasins and ecozones. The objectives are addressed using detailed field observations and physically based land surface modelling. Eddy covariance was deployed at three prairie sites. During winter chinooks, energy for large evaporative fluxes were provided by downward sensible heat fluxes. There was no evidence of infiltration until March. The Canadian Land Surface Scheme (CLASS) coupled to the Prairie Blowing Snow Model (PBSM) was used as the modelling platform. A multi-physics version of CLASSPBSM was developed, consisting of two parameterisation options each for sixteen processes. Field observations were used to evaluate each of the configurations. Three parameterisations provide both best snow and best soil water simulations: iterative energy balance solution, air temperature and wind speed based fresh snow density and de Vries’ soil thermal conductivity. The model evaluation highlighted difficulties simulating evaporation and uncertainty in simulating infiltration into frozen soils at large scales. A single model configuration is selected for modelling the SSRB. Modelling showed that the SSRB generally experiences no net soil water storage change until March, confirming field observations. Chinooks generally reduce net terrestrial water storage, largely due to snowmelt and subsequent evaporation and runoff. The Prairie ecozone is that which is most strongly affected by chinooks. The Montane Cordillera ecozone is affected differently by chinooks; blowing snow transport increases during winter and runoff increases during spring. The Lower South Saskatchewan is the subbasin most affected by chinooks. The Red Deer is the subbasin least affected by chinooks.

Resumo: Considerando a importância da compreensão da dinâmica espaço temporal dos componentes do balanço de energia (BE) em escala regional para o gerenciamento de recursos hídrico e o manejo agrícola, o objetivo principal desta tese foi construir e analisar uma série temporal dos componentes do BE adequada às condições de clima subtropical úmido do Estado do Rio Grande do Sul. Para tanto, inicialmente foi avaliada a adequação de modelos de estimativa de BE para o Estado. Nesta etapa foram utilizados produtos MODIS e dados de referência medidos em uma torre micrometeorológica instalada em Cruz Alta – RS, usando valores instantâneos para um período de estudo de 2009 a 2011. Na sequência foi avaliada a adequação dos modelos em representar a variabilidade espacial dos componentes do BE. Nesta etapa foram usados produtos MODIS, dados de reanálise ERA Interim, dados de referência da torre micrometeorológica e dados de estações meteorológicas do INMET, para o mesmo período de estudo. Na última etapa do trabalho foi construída a série temporal dos componentes do BE usando o modelo METRIC, a qual abrangeu um período de 14 anos, de 2002 a 2016. Os resultados demonstraram que os três modelos analisados apresentam coerência com as medidas de referência, sendo as maiores limitações apresentadas pelo modelo SEBAL, as quais se atribui principalmente às condições ecoclimáticas do Estado e a baixa resolução espacial das imagens. Na análise da variabilidade espacial, o modelo METRIC apresentou maior consistência nos resultados e proporcionou maior número de dias com resultados válidos, sendo assim apontado como o mais apto para realização do restante do estudo. A série temporal construída possibilitou a compreensão dos padrões de distribuição espaço temporal dos componentes do BE no estado do Rio Grande do Sul. Há uma marcada sazonalidade nos componentes do BE, com maiores valores no verão e menores no inverno. G (fluxo de calor no solo) é o componente de menor magnitude e sua distribuição espacial e temporal é determinada pela distribuição de Rn (saldo de radiação). Já os componentes LE (fluxo de calor latente) e H (fluxo de calor sensível), são os que mostram magnitude maior e apresentam padrões de distribuição espacial e temporal coerentes com as condições climáticas e com os tipos de uso e cobertura na área de estudo. Observase um padrão inverso, com um gradiente de LE no sentido noroeste para sudeste e para o componente H, no sentido sudeste para noroeste. Sendo estas informações de grande importância para gerenciamento de recursos hídricos em escala regional, para estudos de zoneamento agrícola. / Abstract: Given the importance of understanding the temporal and spatial dynamics of of the energy balance (EB) components in a regional scale for the management of water resources and agricultural, the main objective of this thesis was to construct and analyze a time series of the components of BE appropriate to the subtropical humid climate conditions of the State of Rio Grande do Sul. In order to reach the objective initially, the adequacy of the models for the humid climate conditions was evaluated, in this step we used MODIS data and reference data measured in a micrometeorological tower installed in Cruz Alta - RS. The analyzes performed with instantaneous values and the study period was from 2009 to 2011. The next step evaluate the spatial variability of the BE components, the data used were the MODIS products, ERA Interim reanalysis data, reference data of the micrometeorological tower and INMET meteorological stations, for the same study period. In the last stage the time series of the BE components was constructed from the METRIC model. The period series was 14 years from 2002 to 2016.The results showed that the three models analyzed were consistent with the reference measurements, with the greatest limitations presented by the SEBAL model, which are mainly attributed to the state's eco-climatic conditions and the low spatial resolution of the images In the analysis of the spatial variability, the METRIC model presented greater consistency in the results and provided greater number of days with valid results, this model thus indicated as the most suitable for the rest of the study. The time series constructed allowed us to understand the temporal distribution patterns of BE components in the state of Rio Grande do Sul. There is a marked seasonality in the BE components, with higher values in summer and lower in winter. G is the smallest magnitude component and its spatial and temporal distribution is determined by the Rn distribution. On the other hand, the LE and H components are those that show higher magnitude and present spatial and temporal distribution patterns consistent with the climatic conditions and the types of use and coverage in the study area. An inverse pattern is observed, with a LE gradient from north-west to south-east and for H-component, from southeast to northwest.

abstract: Land-atmosphere interactions of semiarid shrublands have garnered significant scientific interest. One of the main tools used for this research is the eddy covariance (EC) method, which measures fluxes of energy, water vapor, and carbon dioxide. EC fluxes can be difficult to interpret due to complexities within the EC footprint (i.e. the surface conditions that contribute to the flux measurements). Most EC studies use a small number of soil probes to estimate the land surface states underlying the measured fluxes, which likely undersamples the footprint-scale conditions, especially in semiarid shrublands which are characterized by high spatial and temporal variability. In this study, I installed a dense network of soil moisture and temperature probe profiles in the footprint region of an EC tower at two semiarid sites: a woody savanna in southern Arizona and a mixed shrubland in southern New Mexico. For data from May to September 2013, I link land surface states to EC fluxes through daily footprints estimated using an analytical model. Novel approaches are utilized to partition evapotranspiration, estimate EC footprint soil states, connect differences in fluxes to footprint composition, and assess key drivers behind soil state variability. I verify the hypothesis that a small number of soil probes poorly estimates the footprint conditions for soil moisture, due to its high spatial variability. Soil temperature, however, behaves more consistently in time and space. As such, distributed surface measurements within the EC footprint allow for stronger ties between evapotranspiration and moisture, but demonstrate no significant improvement in connecting sensible heat flux and temperature. I also find that in these systems vegetation cover appears to have stronger controls on soil moisture and temperature than does soil texture. Further, I explore the influence of footprint vegetation composition on the measured fluxes, which reveals that during the monsoon season evaporative fraction tends to increase with footprint bare soil coverage for the New Mexico site and that the ratio of daily transpiration to evapotranspiration increases with grass coverage at the Arizona site. The thesis results are useful for understanding the land-atmosphere interactions of these ecosystems and for guiding future EC studies in heterogeneous landscapes. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2013

Submitted by Isaac Francisco de Souza Dias (isaac.souzadias@ufpe.br) on 2016-03-30T18:44:44Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Edevaldo_FINAL_TESE_DEFINITIVA.pdf: 15106396 bytes, checksum: 814bee807141ed9abbb1a3325917a0b3 (MD5) / Made available in DSpace on 2016-03-30T18:44:44Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Edevaldo_FINAL_TESE_DEFINITIVA.pdf: 15106396 bytes, checksum: 814bee807141ed9abbb1a3325917a0b3 (MD5) Previous issue date: 2015-01-28 / FACEPE / A atual instabilidade climática verificada através dos estudos dos impactos advindos de eventos extremos como secas e inundações, cujo tempo de recorrência vem sendo cada vez mais reduzido, associado ao aumento da temperatura do planeta, prenuncia um cenário de aumento da temperatura média global. As mudanças climáticas podem provocar uma redução no escoamento superficial e na disponibilidade de recursos hídricos, na qual os processos hidrológicos serão afetados e podem significar diferentes tipos de prejuízos para as comunidades que vivem nas regiões áridas e semiáridas, que são as mais expostas às mudanças climáticas, como por exemplo, o provável aumento da salinização das águas subterrâneas em virtude da elevação da evapotranspiração. No Brasil, a região que é mais exposta aos riscos da variabilidade climática é o nordeste, e os ecossistemas pastagens e caatinga possuem grande importância na regulação das mudanças climáticas globais e no ciclo hidrológico. No entanto, ainda são poucos os estudos medindo os fluxos de água, de energia e de carbono nestes ecossistemas. Desta forma, os objetivos do trabalho foram: (a) Avaliar os fluxos de água no solo, por meio do balanço hídrico, a variação dos fluxos de energia, em áreas de caatinga e de pastagem, (b) Avaliar a variação sazonal e interanual dos fluxos de energia e evapotranspiração, em áreas de caatinga e de pastagem, (c) Comparar os fluxos de CO2 em área de pastagem e de caatinga e (d) Verificar os principais fatores ambientais que controlam os fluxos de energia, evapotranspiração e CO2 em ecossistemas de caatinga e pastagem. Para tal, foram instaladas duas torres experimentais compostas por sensores para mediar a velocidade e direção do vento, umidade relativa e temperatura do ar, radiação solar e saldo de radiação, precipitação pluvial e um sistema de medida da covariância dos vórtices turbulentos (Eddy covariance), que é um método que fornece alta resolução temporal de medições de fluxos de energia, água e CO2 entre a superfície e a atmosfera e nos últimos anos tem sido considerado a ferramenta padrão nesse tipo de estudo. Uma torre foi instalada numa área de pastagem e outra numa área de caatinga, ambas localizadas em São João – PE, na microrregião de Garanhuns. A dinâmica da água no solo também foi analisada, sendo que realizada a caracterização hidrodinâmica dos solos das áreas experimentais, bem como, a determinação das frações granulométricas e dos parâmetros da curva de retenção e de condutividade hidráulica, segundo a metodologia “Beerkan”. As medidas dos fluxos de água no solo e dos fluxos de energia e de CO2 foram realizadas nos anos de 2012, 2013 e 2014. Analisando-se os valores da precipitação pluvial, verificou-se que 2012 foi caracterizado como um ano muito seco, e que, 2013 e 2014 tiveram valores próximos da média histórica da região, sendo o ano de 2012, um dos mais secos dos últimos anos. A evapotranspiração na área da caatinga foi maior que na área de pastagem, com 679,7 mm (2,0 mm d-1) e 645,4 mm (1,9 mm d-1), respectivamente. Em relação ao fluxo de CO2 verificou-se que tanto a pastagem, quanto a caatinga atuaram como sumidouros de CO2. No período chuvoso, a pastagem retirou da atmosfera 4,96 Mg C ha-1, enquanto a caatinga 4,26 Mg C ha-1, já no período seco a pastagem sequestrou 2,97 Mg C ha-1 e a caatinga 0,65 Mg C ha-1. A área de pasto foi melhor que a área de caatinga, no sequestro de CO2 atmosférico, tanto no período seco, quanto no período úmido. A mudança no uso da terra, na área da pastagem, teve efeito direto nos fluxos de água e CO2 e no solo, assim como na evapotranspiração do ecossistema. A retirada da caatinga para plantar pasto no local não aumenta significativamente a taxa de sequestro de CO2, mas aumentará a temperatura atmosférica e as taxas de evapotranspiração. / The current climatic instability verified by studies of impacts from extreme events such as droughts and floods, whose recurrence time is being increasingly reduced, coupled with rising global temperature, portends a scenario of increased global average temperature. Climate change may cause a reduction in runoff and the availability of water resources, in which hydrological processes will be affected and can mean different types of damage to the communities living in arid and semiarid regions, which are the most exposed to climate change such as, for example, the probable increase in the salinity of the groundwater due to the increase in evaporation. In Brazil, the region more exposed to the risks of climate variability is the Northeast, and the grassland caatinga ecosystems and have great importance in the regulation of global climate change and the hydrological cycle. However, there are few studies measuring water flows, energy and carbon in these ecosystems. Thus, the objectives were: (a) assess the water flows into the soil through the water balance, the variation of energy flows in areas of caatinga and grassland, (b) assess the seasonal variation energy and evapotranspiration flows in areas of scrub and pasture, (c) Compare the CO2 streams in pasture and scrub and (d) Check the main environmental factors that control energy flows, evapotranspiration and CO2 caatinga ecosystems and pasture. To this end, were installed two experimental towers composed of sensors to mediate the wind speed and direction, relative humidity and air temperature, solar radiation and net radiation, rainfall and a covariance measurement system of the eddy (Eddy covariance) which is a method that provides high temporal resolution energy flow measurements, water and CO2 between the surface and the atmosphere and in recent years has been considered the standard tool in this type of study. A tower was installed in a pasture area and another in a caatinga area, both located in Saint John - PE, in the micro region of Garanhuns. The dynamics of the water in the soil was also analyzed, and accomplished the hydrodynamic characteristics of the soil of the fields and the determination of granulometric fractions of the parameters and the retention curve and hydraulic conductivity, according to the "Beerkan" methodology. Measurements of water flows in the soil and energy and CO2 fluxes were performed in the years 2012, 2013 and 2014. Analyzing the values of rainfall, it was found that 2012 was characterized as a very dry year, and that 2013 and 2014 had similar values of the historical average for the region, with the year 2012, one of the driest in recent years. Evapotranspiration in the area of the caatinga was higher than in pasture area, with 679,7 mm (2,0 mm d-1) and 645,4 mm (1.9 mm d-1), respectively. Regarding the flow of CO2 was found that both the pasture, as acted as CO2 scrub sinks. During the rainy season, the pasture removed from the atmosphere 4,96 Mg C ha-1, while the caatinga 4,26 Mg C ha-1, as the dry season grazing kidnapped 2,97 Mg C ha-1 and the caatinga 0,65 Mg C ha-1. The pasture area was better than the caatinga area in the sequestration of atmospheric CO2, both in the dry season, as the wet season. The change in land use in the area of pasture, had a direct effect on water flows and CO2 and soil, as well as the ecosystem evapotranspiration. The withdrawal of the caatinga to plant pasture on site does not significantly increase the CO2 sequestration rate but increase the atmospheric temperature and evapotranspiration rates.

In semiarid regions, where water resources are limited and precipitation dynamics are changing, understanding land surface-atmosphere interactions that regulate the coupled soil moisture-precipitation system is key for resource management and planning. We present a modeling approach to study soil moisture and albedo controls on planetary boundary layer height (PBLh). We used Santa Rita Creosote Ameriflux and Tucson Airport atmospheric sounding data to generate empirical relationships between soil moisture, albedo, and PBLh. Empirical relationships showed that similar to 50% of the variation in PBLh can be explained by soil moisture and albedo with additional knowledge gained by dividing the soil profile into two layers. Therefore, we coupled these empirical relationships with soil moisture estimated using a two-layer bucket approach to model PBLh under six precipitation scenarios. Overall we observed that decreases in precipitation tend to limit the recovery of the PBL at the end of the wet season. However, increases in winter precipitation despite decreases in summer precipitation may provide opportunities for positive feedbacks that may further generate more winter precipitation. Our results highlight that the response of soil moisture, albedo, and the PBLh will depend not only on changes in annual precipitation, but also on the frequency and intensity of this change. We argue that because albedo and soil moisture data are readily available at multiple temporal and spatial scales, developing empirical relationships that can be used in land surface-atmosphere applications have great potential for exploring the consequences of climate change.

Since the industrial evolution, the CO2-levels have been increasing in a way that’s never seen in the history of the earth. To mitigate and adapt to the happening climate change it is really important to understand the global carbon cycle and each component that plays a role in it. Some studies suggest that there has been an underestimation on the influence from inland waters in the total carbon budget.To address this issue, there has been Eddy Covariance measurements going on the boreal Indalsälven river in front of the Kattstrupeforsen water dam. In this study continuous data has been collected which includes air-river CO2-flux, pCO2-values in the air and the water and some more meteorological parameters such as the wind speed, relative humidity and the air and water temperature. The aim of this study is to look into the seasonal variation in pCO2-levels and the CO2-fluxes on the Indalsälven river.The data indicates that the CO2-fluxes are mainly positive from January till July (average flux = 0.2 μmol m-2s-1) and mainly negative from September till November (average flux = -0.59 μmol m-2s-1) with an average flux of 0.212 μmol m-2s-1 during 2019. The main range of CO2-fluxes per month lies between -2 and 2 μmol m-2s-1, with the exception of March and December where there is a bigger range of fluxes. The pCO2-levels in the water mainly range between 400 and 1000 ppm. With the exception of 2 periods, one in the end of May where there is a peak to 4000ppm and more which can be explained by the spring flood and in the end of July and beginning of August where there is a peak to 3000 ppm. / <p>2020-06-17</p>