Óliver Meseguer-Ruiz

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.

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.

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.

Sequías en Chile central a partir de diferentes índices en el período 1981-2010

Se analizan las diferentes dimensiones de la sequia meteorologica en Chile central con el proposito de caracterizar su ocurrencia a multiples escalas temporales y encontrar indicios de cambio en su variabilidad y frecuencia. Para ello se ha dispuesto de 27 estaciones meteorologicas a resolucion diaria, las cuales permiten identificar periodos secos bajo el umbral 0,1 mm. Ademas de establecer las rachas de sequias y su persistencia (mediante el indice de Besson), se aplico el indice estandar de precipitacion (SPI) para conocer la varibilidad internanual de la sequia, justamente en una region de clima semiarido y mediterraneo. Los resultados indican mayor persistencia de dias secos en la region de Valparaiso, lo cual es consistente con la longitud de las rachas de sequia, en muchos casos superior a 22 dias al ano. El evento La Nina en el invierno de 1998 provoco la mayor racha de dias secos del trimestre lluvioso (67 dias), sumando en total 86 dias sin lluvia. No obstante, no se ha podido probar cambios en su variabilidad y frecuencia.

Análisis de la fractalidad temporal de la precipitación en Cataluña, España (2010)

Se han contabilizado los intervalos con precipitacion, a resoluciones de 30 minutos hasta 48 horas, de once observatorios de Cataluna durante el ano 2010. Con esto se ha analizado la fractalidad temporal de la precipitacion, que tiene su expresion numerica en el concepto de la dimension fractal (D) y que es representativa de la mayor o menor regularidad temporal de la precipitacion. Asimismo, se han comparado para los mismos once observatorios las dimensiones fractales del semestre calido y del semestre frio, con valores en general mayores en este ultimo. El patron espacial basico anual y del semestre calido de D muestran un aumento de los valores desde el suroeste hacia el nordeste.