Pablo Sarricolea

Climatic regionalisation of continental Chile

ABSTRACT The updated Köppen–Geiger climate classification for continental Chile is a cartographic product of great interest for climate research in the South American context. This study included 200 weather stations and climate surfaces at a scale of 1:1,500,000. The results indicate that the climates of continental Chile are essentially arid (B), temperate (C) and polar (E), the latter due to the elevation of the Andes. The predominant climates are high tundra (ET) and mediterranean (Cs). We have concluded that the use of climate surfaces enables the development of new classifications and indices as a function of scale. With respect to latitude, the climates of northern Chile are arid due to the Atacama Desert, and those of southern Chile are temperate, ranging from mediterranean to marine west coast.

On the definition of urban heat island intensity: the “rural” reference

One of the fundamental objectives of many studies on urban heat islands (UHI) involves establishing their intensity on determined nights or, if there is a sufficiently high number of observations, their maximum intensity and average intensity can also be ascertained. Regardless of the methodology employed, whether it refers to (1) differences between two fixed observatories, one urban and another peripheral or non-urban, (2) mobile urban transects or (3) remote sensing, in the end it is a question of providing a value of thermal differences between contrasted points or sectors, one urban and another that could be termed non-urban. Thus, the intensity of the UHI is seen in the temperature difference expressed at a given time between the hottest sector of the city and the non-urban space surrounding this. The intensity of the heat island is the simplest and most quantitative indicator of the thermal modification imposed by the city upon the territory in which it is situated and of its relative warming in relation to the surrounding rural environment at night time (Kim and Baik, 2002; Memon et al., 2009).

Análisis de la concentración diaria de las precipitaciones en Chile central y su relación con la componente zonal (subtropicalidad) y meridiana (orográfica)

This paper analyzes the spatial and temporal distribution of irregularity of daily rainfall in central Chile (32° 50’S - 34°12 ‘S), using the concentration index (CI). The concentration index was calculated for a total of 16 meteorological stations, and for the period 1965 to 2010. The purpose was to generate a climate regionalization based on a daily rate which measures the erratic rainfall. Theoretically two hypotheses were tested: the first proposes that CI decreases from north to south associated with the subtropical component, the second hypothesis is that the effect of topography on CI, causing a reduction in the rate from the intermediate depression to the Andes and a west-east decreasing gradient. The results obtained do not account for a reduction to the south as expected, but they confirmed a significant CI decreased to the coastal range and the Andes.

Trends in the frequency of synoptic types in central-southern Chile in the period 1961–2012 using the Jenkinson and Collison synoptic classification

Atmospheric circulation patterns in southern Chile (42° 30′ S) were studied in order to determine and analyse the most characteristic synoptic types and their recent trends, as well as to gain an understanding of how they are associated with low-frequency variability patterns. According to the Jenkinson and Collison (J&C) classification method, a 16-point grid of sea-level pressure data was employed. The findings reveal that some synoptic types show statistically significant trends with a 95% confidence level, positively for anticyclonic westerly hybrids (AW) and advective types for third and fourth quadrant wind flows (W, NW, and N) and negatively for SW and cyclonic hybrids (CS and CSW). A model has been constructed of the linear regression of some weather types with teleconnections that most affect Chile: the undetermined types (U), AW were associated with El Niño or the warm phase of the Pacific Decadal Oscillation (PDO), whereas the cyclonic northerly and cyclonic northeasterly types (CN and CNE) were associated with La Niña or cool phase of the PDO. The weather types associated with Antarctic Oscillation (AAO) in its positive phase are anticyclonic northerly and northeasterly and northerly advection types, while in its negative phase are cyclonic southwesterly and advection types.

La isla de calor urbana del área metropolitana de Santiago (AMS) de Chile a partir de diferencias térmicas de los observatorios de Talagante y Cerrillos

Este articulo presenta el analisis de la intensidad de la isla de calor urbana (ICU) de Santiago para el ano 2010. El objetivo es conocer la hora en que la ICU se manifiesta con mayor intensidad, y con ello, se modela mediante un conjunto de parametros meteorologicos. Los resultados indican que la ICU en promedio es mas intensa en verano y primavera. El maximo desarrollo de la ICU se consigue a medianoche, con diferencias medias entre 2,8 oC y 4,8 oC. La maxima anomalia termica en el orden estacional se alzo por encima de los 9 oC, tanto en verano como en primavera. Las variables explicativas de la ICU fueron la nubosidad, la humedad relativa y la presion atmosferica. Como conclusion, se puede senalar que es posible generar un sistema de pronostico de la ICU mediante la obtencion de los valores de humedad relativa, la presion atmosferica y la nubosidad, desde las predicciones sinopticas y mesoescalares.

Spatial behaviour of daily observed extreme temperatures in Northern Chile (1966–2015): data quality, warming trends, and its orographic and latitudinal effects

According to the intergovernmental panel on climate change, Northern Chile will be one of the most affected territories by changes in the atmospheric dynamics in next years. These climate change effects will be noticed in several ways, and temperatures will be one of the most sensitive variables to these changes, and with high importance because of their relationship with the hydrological cycle in one of the most arid regions in the world. Extreme temperatures of 77 observatories have been analysed by the calculation of 14 indices and their temporal trends. Also, the relationship of these indices between them, between observatories, with elevation and latitude has been taken into consideration, while they imply significant differences of the behaviour of the analysed indices. The results showed general warming trends but with particular differences depending on the behaviour of minimum temperatures. Examining the relationship between the indices and elevation, it appears that this variable has more implications in minimum temperatures. The analysis showed significant correlations also between the indices and latitude, agreeing with not evident general warming trends in the intertropical area of Northern Chile. Considering the different behaviours of the trends and their relationships with latitude and elevations, it has to be analysed in the future the possible existing relations with the spatial and temporal changes in the hydrological cycle such as precipitations.

ANÁLISIS DE LAS TEMPERATURAS MEDIAS Y SUS EXTREMOS A PARTIR DE DIFERENTES ÍNDICES DURANTE EL PERÍODO 1966-2015 EN EL NORTE GRANDE CHILENO

espanolSegun el V informe del Intergovernmental Panel on Climate Change, el norte de Chile es uno de los territorios que mas se veran afectados por los cambios en las dinamicas atmosfericas en los proximos anos. Dentro de este contexto general, un pilar capital lo constituyen las temperaturas y las modificaciones que en ella se han venido registrando. Se ha estudiado el comportamiento de las temperaturas de 4 observatorios del norte de Chile. Para detectar posibles tendencias en las series, se ha aplicado el test no parametrico de Mann-Kendall, en primer lugar, a las temperaturas medias mensuales, y, posteriormente, a 12 indices diferentes calculados a partir de los extremos diarios de temperaturas desde 1966 hasta 2015. Si bien las medias mensuales no muestran unas tendencias claras significativas en el periodo estudiado, coincidiendo con los estudios que senalan la observacion del Global Warming Hiatus, los otros indices de los extremos muestran tendencias significativas (90%), que indican, principalmente, un claro aumento de las temperaturas minimas, asi como una disminucion evidente del numero de dias anuales en los que se registran temperaturas del percentil inferior. EnglishAccording to the AR5 from the Intergovernmental Panel on Climate Change, northern Chile is one of the most affected region by the next years-changes in the atmospheric dynamics. Within this general context, the temperature and its modifications constitute a capital pillar. The behavior of the temperatures from 4 observatories in northern Chile have been studied. To detect possible trends in the time series, the non-parametrical Mann-Kendall test has been applied to the monthly mean temperatures in a first place, and, after that, to twelve different indices calculated according to the daily extreme temperature from 1966 to 2015. While monthly means do not show a significant trend in the studied period, coinciding with studies indicating the observation of the Global Warming Hiatus, the other extremes indices show significant (90%) trends, indicating a clear increase in minimum temperatures and a clear decrease in the number of annual days with minimum temperatures in the lower percentile.

TENDENCIAS DE LA PRECIPITACIÓN EN EL NORTE GRANDE DE CHILE Y SU RELACIÓN CON LAS PROYECCIONES DE CAMBIO CLIMÁTICO

Se analizan las tendencias de la precipitacion en el Norte Grande de Chile mediante el test no parametrico de Mann-Kendall y el test de Sen, lo que permite detectar, para las sesenta estaciones meteorologicas disponibles, la posibilidad de cambios decadales de la precipitacion con significancia estadistica (p<0,1). Los resultados muestran que es el Altiplano la region donde se aprecia una reduccion significativa de la precipitacion anual entre 1972 y 2013. La zona de precordillera posee tendencias de incremento para Poroma y San Pedro de Atacama. El desierto costero no muestra tendencias significativas, lo que implica la mantencion de las condiciones hiperaridas. Estos resultados son comparables con las proyecciones de cambio climatico a fines del siglo XXI. Se concluye la importancia de seguir monitoreando las tendencias, aumentar la densidad de estaciones a la vez que se mantienen las ya existentes.