On the relationship between stable isotopes and major impurity species as inferred from a two-dimensional firn sampling approach at EDML, East Antarctica

<p>Ice cores constitute a major palaeoclimate archive by recording, among many others, the atmospheric variations of stable oxygen and hydrogen isotopic composition of water and of soluble ionic impurities. While impurities are used as proxies for, e.g., variations in sea ice, marine biological activity and volcanism, stable isotope records are the main source of information for the reconstruction of polar temperature changes.</p><p>However, such reconstruction efforts are complicated by the fact that temperature is by far not the only driver of isotopic composition changes. A single isotopic ice-core record will comprise variations caused by a multitude of processes, from variable atmospheric circulation and moisture pathways to the intermittency of precipitation and finally to the mixing and re-location of surface snow by wind drift (stratigraphic noise). Under the assumption that specific trace components are originally deposited with the precipitated snow and its isotopic composition, the retrieved impurity records should display a similar spatial and seasonal to interannual variability as the isotope records, caused by local stratigraphic noise as well as the time-variable and intermittent precipitation patterns, respectively.</p><p>In this contribution, we investigate the possible relationship between isotope and impurity data at the East Antarctic low-accumulation site EDML. We sampled and analysed isotopic composition and major impurity species on a four metre deep and 50 metre long trench. This enables us (1) to study the spatial (horizontal times vertical) relationship in the data, and (2) to analyse and compare the seasonal and interannual variability after removing the strong contribution of local stratigraphic noise. By this, the study improves our understanding of the depositional mechanisms that play an important role for the formation of ice-core records, and it offers to investigate the potential of using impurities to correct isotopic variability in order to improve temperature reconstructions.</p>

O uso de dados de temperatura e precipitação de MERRA2 para compreender a dinâmica ecológica do A. aegypti no município de Chapecó/SC - 2007 a 2017 (The use of MERRA2 temperature and precipitation data to understand the ecological dynamics of A. aegypti in the municipality of Chapecó / SC - 2007 to 2017)

O mosquito Aedes aegypti transmite dengue, febre do zika vírus, febre chikungunya e febre amarela. Em Santa Catarina, ocorrências dessas doenças foram registradas nos últimos anos, assim como o aumento dos focos de A. aegypti, principalmente num padrão específico de sazonalidade. Estudos que busquem identificar a ecologia do mosquito em função da diversidade climática no Brasil são fundamentais para melhoria de políticas públicas e para o controle de focos nos municípios. Conduziu-se este trabalho, com o objetivo de avaliar a relação existente entre ocorrência de focos de A. aegypti e variabilidade dos elementos climáticos temperatura e precipitação, no município de Chapecó, durante os anos de 2007 a 2017. Os dados climatológicos foram obtidos pela reanálise MERRA2 (Modern-Era Retrospective analysis for Research and Applications) da NASA (National Aeronautics and Space Administration). Os dados dos focos do mosquito foram obtidos da Divisão de Vigilância Epidemiológica de Santa Catarina (DIVE). Os resultados obtidos mostram, para o município de Chapecó, uma relação direta entre a elevação (redução) da temperatura e o aumento (diminuição) dos focos registrados. Também foi identificada uma influência da elevação da temperatura na ocorrência e registro dessa espécie, ao longo dos anos. Com relação à distribuição da precipitação, sugere-se que a chuva bem distribuída no mês que antecede o registro do foco, influencia no desenvolvimento do vetor. Entende-se que as variações climáticas contribuem para o aumento de focos, todavia, as condições socioeconômicas da população e a ação antrópica devem ser contempladas na investigação das influências na proliferação do vetor. A B S T R A C TThe mosquito Aedes aegypti is the transmitting agent of dengue fever, zika virus and chikungunya fever. In Santa Catarina, occurrences of these diseases have been recorded in recent years, as well as the increase of A. aegypti outbreaks, mainly in a specific pattern of seasonality. Studies that seek to identify mosquito ecology as a function of climatic diversity in Brazil are fundamental for the improvement of public policies and for control of outbreaks in municipalities. The objective of this study was to evaluate the relationship between occurrence of A. aegypti outbreaks and variability of temperature and precipitation elements in Chapecó between 2007 to 2017. The climatological data were obtained by MERRA2 from NASA. Outbreaks data were obtained from the Epidemiological Surveillance Director. The results show, for Chapecó, a direct relation between flotation of the foci with a cycle marked by the high temperatures and the intermittent precipitation. The favorable temperature range for vector development is between minimum average temperature of 14.8 °C to 19.2 °C and maximum average temperature of 25.5 °C at 29.1 °C. An influence of temperature elevation on the occurrence and record of this species was also identified over the years. Regarding the distribution of precipitation, it is suggested that the precipitation up to 5 mm in the month preceding the focus record influences the development of the vector. Climatic variations contribute to the increase of outbreaks, however, the socioeconomic conditions of the population and anthropic action should be considered.Keywords: Mosquito, climate, reanalysis data.

Evaluación del escurrimiento superficial de los modelos de Curva Numérica y Green-Ampt en la cuenca río Chapingo, México.

Hydrological models are a fast and low-cost option to estimate surface runoff in a rainfall event in ungauged basins. Prior to their use, the models must be evaluated; their results, if reliable, are useful in def ining sound policies for rational management of the water resource. The purpose of this research was to evaluate the degree of f it of the numerical curve runoff Model of the extinct U.S. Soil Conservation Service (SCS-CN) and the Green-Ampt (GA) inf iltration model to reproduce direct runoff hydrograms in ungauged basins. These models were integrated into a hydrological model structured in HEC-HMS software. Seven well-def ined rainfall events and one prolonged event with intermittent precipitation occurring in the Chapingo River Basin, Mexico, were chosen. In the analysis of the set of eight events, the SCS-CN model estimated the total runoff volume better (RMSE of 5430 m3), while the GA model estimated the peak flow better (RMSE of 0.72 m3 s-1). The GA model best estimated the hydrograms of three well-def ined rainfall events whose runoff volumes were greater than 8.31 × 103 m3 and Qp ≥ 1.93 m3 s-1 with RMSE of 0.14 to 0.43 m3 s‑1, MRE of 0.20 to 0.28 and Nash-Sutcliffe eff iciency of 0.92 to 0.95. For the other four well-def ined events with runoff volumes lower than 6.35 × 103 m3 and Qp ≤ 1.44 m3 s-1, both models estimated the hydrograms identically and without effectiveness with a Nash-Sutcliffe index of -1.38 to -7.34. Estimation of the hydrogram of the prolonged event was identical in both models with an RMSE of 0.07 m3 s-1, an MRE of 0.35 and a Nash-Sutcliffe eff iciency of 0.71. The hydrogram of the prolonged event was identical in both models, with an RMSE of 0.07 m3 s-1, an MRE of 0.35 and a Nash-Sutcliffe eff iciency of 0.71.

Response of Water Vapor and CO2 Fluxes in Semiarid Lands to Seasonal and Intermittent Precipitation Pulses

Precipitation pulses are important in controlling ecological processes in semiarid ecosystems. The effects of seasonal and intermittent precipitation events on net water vapor and CO2 fluxes were determined for crested wheatgrass (Agropyron desertorum), juniper (Juniperus osteosperma), and sagebrush (Artemisia tridentata) ecosystems using eddy covariance measurements. The measurements were made at Rush Valley, Utah, in the northern Great Basin of the United States. Data were evaluated during the growing seasons of 2002 and 2003. Each of these communities responds to precipitation pulses in all seasons, but these responses vary among season and ecosystem, and differ for water vapor and CO2. The degree and direction of response (i.e., net uptake or efflux) depended upon the timing and amount of precipitation. In early spring, both evapotranspiration (ET) and CO2 fluxes responded only slightly to precipitation pulses because soils were already moist from snowmelt and spring rains. As soils dried later in the spring, ET response to rainfall increased. The summer season was very warm and dry in both years, and both water and CO2 fluxes were generally reduced as compared to fluxes in the spring. Water vapor fluxes increased during and immediately after periodic summer rain events at all sites, especially at juniper, followed by the sagebrush and crested wheatgrass sites. Net CO2 exchange changed significantly at the juniper and sagebrush sites but changed very little at the crested wheatgrass site due to senescence of this grass. However, in the wetter summer of 2003, the grass species maintained physiological activity and responded to rain events. In the fall of both years, responses of ET and CO2 fluxes to precipitation were very similar for all three communities, with only small changes, presumably due to significantly lower temperatures in the fall. This research documents the importance of the temporal distribution of rainfall on patterns of ET and CO2 fluxes and suggests that soil moisture and stand-level leaf area index (LAI) are critical factors governing ET and CO2 responses to precipitation in these communities.