In recent decades, average rainfall in arid-semi-arid zones has been reduced to normal values or lowers than these, in a return to drier climatic conditions. Inter-decadal averages of precipitation are falling relative to the previous long rainy period of 1950-2000. Severe impacts can be seen in agricultural ecosystems, water behaviour of surface and underground basins, agricultural productions and others not evaluated to date, where the anthropic transformations carried out are complemented by changes in the climate. An attempt is made in this work to show some physical and statistics aspects of the change in this extensive arid - semiarid region and its possible permanence in time.

The study of the spatial and temporal variability of the precipitation concentration is necessary, due to its high environmental and socioeconomic impact. For this reason, this study aims to contribute to the knowledge of daily rainfall in southeastern South America. Daily records of precipitation for 48 stations are used (period 1979–2018) to calculate the concentration index (CI). High CI is linked to rapid physical processes such as convection, and low CI can be interpreted as a consequence of regular patterns such as the continuous passage of fronts. The spatial and temporal distribution of CI brings information about frequency and changes in heavy rainfall days. The spatial distribution of the CI at an annual level has a range of variation between 0.54 and 0.68. The CI temporal variation shows different regional behaviour. In Brazil, there is an increase in the CI, while in Uruguay and the north‐central part of Argentina negative trends are present in the four seasons.

Most hydrocarbons have a group of molecules known as biomarkers capable of remaining stable during the aggressive conditions under which they formed. The objective of this paper is analyze key biomarkers of the four samples of crude oil extracted from the Del Mosquito reservoir in the Austral Basin in Southern Argentina, which allows the characterization of their precursor organic matter, the lithology and depositional environment of source rock and the thermal evolution. Biomarker profiles were analyzed by GC / MS from aliphatic and aromatic fractions after separation by column chromatography. Specific parameters such as Pr/Ph,Pr/n-C-17,Fi/n-C-18,T-24/T-23,T-26/T-25 and H-29/H-30 indicate that the crude oil from the Del Mosquito seems to have been generated from type II-III organic matter (mixed), associated with a siliclastic source rock in marine sedimentation environment with moderate oxygen concentration, and in the oil generation window. The results show correlation with the Springhill geological formation, defined for the Austral Basin.

The Tropical-Subtropical region of the Earth is home to the main watersheds, sources of water and food on the planet. It dominates Hadley's global convective circulation affected by major changes in its vertical movements of the air, resulting in the generation of cloudiness, precipitation and drought. In the last decades, persistent droughts have been observed in the subtropical zone of the planet, particularly in Chile Central, South of Africa and Mediterranean Zone called Type K. Also in the instrumental period it was possible to observe two atmospheric warming processes with positive trends, which were later correlated to regional drought annual indices. This study shows the relationship between Global Warming and the drought indexes standing out: I) positive or increasing trends of drought indices in the Subtropics, and II) decreasing negative trends in Ecuador and monsoonal zone. Also, in parts of the Subtropics there are two distinct periods, one with frequent droughts in the first half of the last century, and a second with excessive rainfall in the second half of the 20th century. In the last ten years there have also been long drought processes that would be contributing to changes in the general trends. From the study it is concluded that the Global Warming would be contributing to the drying process in the subtropical regions with 25% of the regions analyzed, while 58% of the regions show a Type F oscillation that extends throughout the past century XX, end of the XIX century and beginning of the XXI.

During the last 20 years, Argentina experienced several extreme and widespread droughts in many different regions, including the core cropland areas. The most devastating recent events were recorded in the years 2006, 2009 and 2011. Reported impacts of the main events induced losses of more than 4 billion U.S. dollars and more than 1 million persons were reported to be directly or indirectly affected. In this paper, we analyse the drought risk in Argentina, taking into account recent information on drought hazard, exposure and vulnerability. Accordingly, we identified the most severe droughts in Argentina during the 2000–2015 period using a combination of drought hazard indicators and exposure layers. Three main events were identified: (1) during spring 2006 droughts peaked in the northeast of Argentina, (2) in 2009 precipitation deficits indicated a drought epicenter in the central Argentinian plains, and (3) in 2011 the northern Patagonia region experienced a combination of natural disasters due to severe drought conditions and a devastating volcanic eruption. Furthermore, we analysed the dynamics of drought exposure for the population and the main economic sectors affected by municipality, i.e., agriculture and livestock production. Assets exposed to droughts have been identified with several records of drought impacts and declarations of farming emergencies. We show that by combining exposure and vulnerability with drought intensity it is feasible to detect the likelihood of regional impacts in different sectors.

Fil: Llano, Maria Paula. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmosfera y los Oceanos; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Resumen Se analizan las estructuras de las autocovarianzas y autocorrelaciones de las temperaturas máximas y mínimas en estaciones de referencia en el sudeste de Sudamérica. A través de estas propiedades se observa que existen oscilaciones de períodos entre 18 y 25 años en las series bajo estudio, aunque estas periodicidades presentan cambios con el tiempo, especialmente entre los años 1950-1970. La excepción es Río Gallegos donde la periodicidad de 18 años se observa durante todo el registro. La persistencia definida mediante el primer coeficiente de autocorrelación es función de la cantidad de términos de autocovarianza negativas. No obstante, durante algunos años es dependiente de la magnitud de los términos positivos dados por las irrupciones cálidas o frías intensas. Entre los años 1950 y 1970 se ha observado un aumento de la variabilidad con una alta alternancia entre períodos de mayor y menor persistencia. Estos cambios analizados en la persistencia sugieren una variación en la frecuencia de distintos tipos de circulación que tienen un impacto directo en la estructura térmica regional. Así mismo, variaciones de este tipo pueden tener serios impactos socio-económicos ya que estos afectarían directamente la frecuencia y duración de los eventos extremos. Esto tiene importancia también en el diseño de métodos de control y consistencia ya que en ellos es posible considerar como outlier o información errónea los cambios producidos por las irrupciones de escala sinóptica mencionadas anteriormente.

ABSTRACTThe impact of climate variability on exportable surpluses of maize and soya beans in producing/exporting countries is well known. This situation necessitates the study of climate variability and yields in some of the major producer countries (Argentina, Brazil and the United States). This study aims to characterize the climate regimes of each region, seeking the highest degree of regional homogeneity and representativeness of yields and climate variables. The series variability is analysed according to various effects (different stages of crop development and conditioning of yield). The temperatures and rainfall occurring during the flowering stage exert greater conditioning on yield at the end of the crop cycle. Different theoretical fit models of yield are obtained for both crops with climate information from their core areas of high production.

Se describen algunas variables vinculadas al sistema Cuasi Monzonico Sudamericano (CMS) para identificar a las de mayor peso en el analisis temporal y evaluar a los saltos climaticos (SC). Los SC son cambios bruscos en el clima de una region lo suficientemente importantes como para afectar los niveles de productividad agricola y otras actividades humanas. Por el poco conocimiento que se tiene sobre la generacion de los mismos, hacen que estos sean al presente imposible de ser pronosticados con modelos, pero si se los puede identificar en el momento que estan ocurriendo para poder alertar a las sociedades afectadas. El CMS tiene su epicentro de impacto en las lluvias estivales del corazon del continente, y en el pasado se han detectado por lo menos dos eventos en el periodo 1884-2011, pasando de un periodo fresco-humedo-lluvioso a otro calidoseco en la decada de 1910 y posteriormente a otro fresco-humedo-lluvioso en la decada de 1950. Estos dos ultimos han ocasionado cambios muy contrastantes del clima con sus impactos, y existen evidencias recientes de que pudiera estar ocurriendo otro salto sobre comienzos de esta decada del 2010 hacia condiciones mas secas-calurosas.

This paper studies the climatic conditions of warm and cold dry months in the humid and semi-humid Argentine region and some aspects of the regional circulation related to these cases. The climatic analysis of warm (temperatures above percentile 80) and cold (temperatures below percentile 20) dry months is based on precipitation and temperature data registered at reference stations over a period of at least 70 years, while the associated circulation is derived from daily data of geopotential height at 500 hPa from NCEP-DOE Reanalysis 2 database. The reference station for the center of the country registered a greater number of warm dry months during both the warm season (October–March) and the cold season (April–September), whereas the reference stations in the north-east and center-east showed differences depending on the time of the year, with more cold dry months during the April–September season and more warm dry months in the October–March season. A classification of daily fields of geopotential height anomalies at 500 hPa was used to analyze the atmospheric circulation related to warm and cold dry months. The circulation patterns were obtained by applying principal component analysis and cluster analysis. Findings show that some mid-level circulation patterns occur with a significant different frequency during the warm dry months or the cold dry months studied. Finally, cases of spatially extended precipitation-deficit conditions (hereinafter generalized droughts) were studied, noting dominant patterns that are coherent with the previous results.

The main goal of this work was to conduct an intraseasonal climate variability analysis using wavelet and principal component analysis over a southeastern South American daily maximum and minimum temperature series from the end of the nineteenth until the beginning of the twenty-first century. The analysis showed that there is a definite and coherent signal in the intraseasonal maximum and minimum temperatures. The most noticeable signal was observed during the winter months. The frequency of the intraseasonal signal was more complex for the maximum temperature, and in some stations, it displayed a bimodal distribution. A defined pattern that described a coherent variability between 30 and 60 days throughout the entire region was observed. This pattern potentially allows classification of the regional variability and adjustments to the temperature forecasting models on a daily basis.

A climatology of various properties of precipitation in intervals of three days is developed. This climatology has a particular importance for the extended forecast of precipitation. Therefore the main objective of this climatology is the development and the initiation of extended forecasts of 6 to 10 days in terms of probabilities divided into categories. For this, the frequencies of days with precipitation in three days windows are analyzed. Each frequency of zero days of precipitation for day i is the result of a lack of rainfall in three days moving windows centered on i, in the same way the frequencies are obtained up to three days with precipitation, respectively. We used data from 94 stations in a common period (1959-1998) in the study area. Annual waves of the properties obtained for precipitation and their synthesis are studied through harmonic decomposition. A vector representation of the defining properties of harmonic analysis is propose, such as date of occurrence of the maximum (phase) and amplitude. Finally, special emphasis is placed on the study of extreme precipitation events, such as the annual march of the maximum represented by the 90th percentile of daily precipitation.

Una climatología de distintas propiedades de la precipitación en intervalos de tres días es desarrollada en el presente trabajo, la cual es de especial importancia para el pronóstico extendido de precipitación. Por lo tanto el objetivo fundamental de esta climatología es el desarrollo y el inicio de pronósticos extendidos de 6 a 10 días en términos de probabilidades divididas en categorías. Para esto, se analizan las frecuencias de días con precipitación en ventanas de 3 días. Cada frecuencia de cero días de precipitación para el día i es el resultado de la ausencia de precipitación en ventanas móviles de tres días centradas en el día i, de la misma forma se obtienen las frecuencias hasta tres días con precipitación respectivamente. Se emplean los datos de 94 estaciones en un período común (1959-1998) en el área de estudio. Se estudian las ondas anuales de las propiedades obtenidas para las precipitaciones y su síntesis a través de la descomposición en armónicos. Se propone una representación vectorial de las propiedades que definen el análisis armónico, tales como la fecha de ocurrencia del máximo (su fase) y su amplitud. Finalmente, se pone especial énfasis en el estudio de las condiciones extremas de eventos de precipitación, como por ejemplo, la marcha anual de los máximos representados por el percentil 90 de precipitación diaria.A climatology of various properties of precipitation in intervals of three days is developed. This climatology has a particular importance for the extended forecast of precipitation. Therefore the main objective of this climatology is the development and the initiation of extended forecasts of 6 to 10 days in terms of probabilities divided into categories. For this, the frequencies of days with precipitation in three days windows are analyzed. Each frequency of zero days of precipitation for day i is the result of a lack of rainfall in three days moving windows centered on i, in the same way the frequencies are obtained up to three days with precipitation, respectively. We used data from 94 stations in a common period (1959-1998) in the study area. Annual waves of the properties obtained for precipitation and their synthesis are studied through harmonic decomposition. A vector representation of the defining properties of harmonic analysis is propose, such as date of occurrence of the maximum (phase) and amplitude. Finally, special emphasis is placed on the study of extreme precipitation events, such as the annual march of the maximum represented by the 90th percentile of daily precipitation.

espanolEs conocido el impacto que tiene la variabilidad del clima sobre los saldos exportables de maiz y soja en los paises productores y exportadores. Esta situacion obliga a estudiar la variabilidad climatica y de los rendimientos en algunos de los principales paises productores y exportadores (Argentina, Brasil, Estados Unidos y China). En el presente estudio se pretende tipificar los regimenes climaticos de cada region, buscando el mayor grado de homogeneidad y representatividad regional de los rendimientos y de las variables climaticas. Se analiza la variabilidad de las series en funcion de varios efectos (diferentes estaciones, diferentes etapas de desarrollo, condicionamiento del rendimiento). Visto que el mayor grado de impacto sobre los rendimientos de los cultivos esta dado por los extremos en las variables climaticas se sintetiza la circulacion asociada a los eventos secos y humedos por regiones como un aporte al estudio de la climatologia sinoptica y con el objetivo de desarrollar un diagnostico de las condiciones climaticas en estos paises productores y analizar las relaciones con los rendimientos. EnglishIt is known the impact on the exportable balance of corn and soybean due to the climate variability. This compels to study the climate variability and the yields in the main producing and exporting countries (Argentina, Brazil, the United States of America and China). This study is intended to typify the climate regimes of each producing zone of the four countries trying to achieve the biggest level of homogeneity and regional representation of the climate variables measured by stations. The analysis of the variability of the series related to several effects (different stations, stages, and yield conditioning). Considering that the biggest impact on the cultivation yields in the above mentioned countries occurs because of the extremes in the climatic variables, and as a contribution to the synoptic climatology work, here it is studied by regions the circulation associated to the dry and wet events. This explains what is the grade of coherence between the climatic extremes and the different yields among countries.

La eleccion en el metodo de estimacion de efectos deterministicos dentro de series climaticas es el punto de partida de la mayoria de estudios sobre variabilidad climatica. Este analisis es mas sensible cuando se desea explorar sobre la presencia de fenomenos no lineales. Por esto, en este trabajo se analiza la robustez y estabilidad de diferentes metodos para estimar la onda anual en series de temperatura y precipitacion diaria. Se comparan distintos estimadores robustos y se muestra que el calculo de la onda anual a partir de la mediana produce una estimacion mas robusta para periodos de informacion menores a 50 anos. Sin embargo, para periodos mayores de informacion no se observan diferencias entre los distintos estimadores. Para la precipitacion se evidencia que la longitud de registros analizados (100 anos de informacion diaria) es insuficiente para obtener una estimacion estable. Respecto a la persistencia de las series de temperatura se muestra que existe una dependencia entre el tiempo de independencia (To) y el periodo analizado (hay una variacion interanual de To que puede variar entre 3 y 7 dias). Ademas se observa un mayor To si se considera el termino no lineal de las anomalias, es decir el analisis de esta componente conduce a estimar efectos mas persistentes que se ven afectados por la pendiente de la onda anual. Aqui se muestra la presencia de asimetrias en la onda anual de temperatura que en algunos casos son producto de interacciones no lineales entre la onda anual y las perturbaciones. Por ultimo, los procesos que muestran una mayor dependencia con la onda anual evidencian una mayor persistencia de las anomalias calidas. Esto esta asociado a procesos advectivos lentos donde las masas de aire calido permanecen durante varios dias, efecto que se evidencia mejor sobre la temperatura minima. Por esto se propone que en general, la estimacion o diseno de las anomalias respecto de la onda anual debe ser considerada como un desarrollo que considere a los efectos independientes (lineales) y dependientes (no lineales) de la onda anual.

An important goal of this work is to study the variability of corn and soya bean crop yields in four countries with large production and substantial commercial trade in these commodities. This problem can be investigated in terms of the role that these two crops play in food programmes and in terms of the use of both crops for energy production. Four countries were chosen and divided into six production areas. A climatic summary was made of the annual cycles of extreme temperatures and precipitation. Their assessment in agriculture programmes was likewise summarized. It is seen that the variability range of the temperatures and precipitation are broad and different for each region. This finding indicates the high adaptability of these crops. This concept of adaptability is used to compare the coefficients for precipitation and crop yield. Results of the study show that corn crops show less year-to-year variability than do soya bean crops. The United States and the northern part of China are the regions that best use the rain supply with respect to crop yield. Soya bean crops show a greater year-to-year variability in the ratio of precipitation to crop yields. Argentina, the United States and northern China are the areas that best use the rain supply. To compare crop yields with climatic variables in the different regions, three types of regression model were used. The best fit is obtained by using the maximum temperatures and accumulated precipitation for each growth stage over the growing season. Copyright (C) 2011 Royal Meteorological Society