An assessment of observed and simulated temperature variability in Sierra de Guadarrama

This work provides a first assessment of temperature variability at interannual and decadal timescales in Sierra de Guadarrama, a high mountain protected area of the Central System in the Iberian Peninsula. Observational data from stations located in the area and simulated data from a high-resolution simulation (1 km) with the Weather Research and Forecasting (WRF) model, fed from ERA Interim reanalysis, are used in order to analyse the temperatura variability in the period 2000–2018. Comparison among all datasets allows evaluation of the realism of the model simulations. The results show that the model tends to underestimate the observational mean temperatures and anomalies at high-altitude stations. A linear mean temperature vertical gradient of −5.81 ◦C/km is observed, but it is overestimated by the model (−6.56 ◦C/km). The variability of the daily temperature anomalies for both observations and, to a lesser extent, simulations increases with height. The added value that the WRF offers against the use of the ERA Interim is evaluated. The results show that the WRF provides a better performance than the reanalysis, as it shows smaller biases with respect to observational temperature anomalies. Finally, the study of temperature trends over the Sierra de Guadarrama and its surroundings for the period 2000–2018 shows a warming in the area, significantly pronounced in autumn. When extended to the last decades, observations show that this warming has been happening since the first half of the 20th century, especially during the period 1970–2018, but not as much as during 2000–2018.This research was funded by CEI Moncloa UPM-UCM-Ciemat Cooperation Agreement: GuMNet (Guadarrama Monitoring Network) Initiative, Ministerio de Ciencia e Innovación: GreatModelS (RTI2018-102305-B-C21d), Ministerio de Ciencia e Innovación: GreatModelS (RTI2018-102305-B-C21d), Ministerio de Ciencia e Innovación: ILModels (CGL2014-59644-R/CLI)

An assessment of long term temperature variability in the Sierra de Guadarrama

Ponencia presentada en: XI Congreso de la Asociación Española de Climatología celebrado en Cartagena entre el 17 y el 19 de octubre de 2018.[ES]Este trabajo proporciona un primer análisis de la variabilidad de la temperatura a escalas interanuales y decadales en la Sierra de Guadarrama (SG), un área protegida de alta montaña del Sistema Central en la Península Ibérica. Se utilizan datos observacionales de estaciones situadas en la zona y una simulación regional de alta resolución (1km) del modelo Weather Research and Forecasting (WRF) para analizar la variabilidad de la temperatura durante el periodo 2000-2015. La comparación entre ambos conjuntos de datos permite evaluar el grado de realismo con el que las simulaciones representan la variabilidad observada. Los resultados muestran que el modelo tiene tendencia a infraestimar los valores medios y las anomalías de las temperaturas observacionales en las estaciones de mayor altitud. Se observa un gradiente vertical de temperatura media de -3.95ºC/km, que es sobreestimado por el modelo (-6.52ºC/km).La variabilidad de las anomalías térmicas aumenta con la altitud para las observaciones y, en menor medida, para las simulaciones. Se evalúa el valor añadido que ofrece WRF frente al uso del reanálisis ERA Interim, que proporciona las condiciones iniciales y de contorno a la simulación regional. Se observa un menor sesgo de las temperaturas que proporciona el modelo regional en comparación con el reanálisis. Se lleva a cabo un Análisis de Componentes Principales (PCA) sobre el campo de anomalías de temperatura de WRF para la evaluación de su variabilidad. Este análisis proporciona un primer modo muy dominante que explica el 94% de la varianza total y cuya componente principal muestra una gran correlación con las anomalías observacionales. La variabilidad de la temperatura en la SG muestra una gran relación con la temperatura en el interior de la Península Ibérica y con una gran parte del suroeste de Europa. El patrón de regresión entre la temperatura proporcionada por la simulación y la que procede del reanálisis permite obtener una estimación de la variabilidad de la temperatura en la SG en los últimos 40 años.[EN]This work provides a first assessment of temperature variability at interannual and decadal timescales in the Sierra de Guadarrama (SG), a high mountain protected area of the Central System in the Iberian Peninsula. Observational data from stations located in the area and simulated data from a high-resolution configuration (1 km) of the Weather Research and Forecasting (WRF) model, fed from ERA Interim inputs, are used in order to analyse the temperature variability in the period 2000-2015. The comparison between both datasets allows for the evaluation of the realism of the model simulations. Results show that the model tends to underestimate observational mean temperatures and anomalies at high altitude stations. A linear mean temperature vertical gradient of -3.95ºC/km is observed and overestimated by the model (-6.52ºC/km).The variability of temperature anomalies for both the observations and, to a lesser extent, the simulations increases with height. The added value that WRF offers against the use of ERA Interim is evaluated. Results show that WRF provides a better performance than the reanalysis, as it shows smaller biases with the observational temperature anomalies. A Principal Component Analysis (PCA) is performed over the temperature anomalies field of WRF for the assessment of its variability. This analysis provides a very dominant first mode that explains the 94% of the total variance and whose PC shows a large correlation with the observational anomalies. Temperature variability in the SG shows a large relationship with temperature in the midland Iberian Peninsula and broadly over south-western Europe. The regression patterns between WRF and the reanalysis are calculated in order to obtain an estimate of the temperature variability over the SG during the last 40 years