Observed trends in frost and hours of cold in Majorca

The observed trends in some cold indices in the island of Majorca are analysed using the available series of the daily minimum temperatures of the Majorca Airport (1972–2008), supplemented with the inspection of eight more climatological stations of the island covering at least 30 simultaneous years. The analysis yields a statistically significant trend to a rise of about 0.6 °C per decade for the ensemble of the stations. There is also a clear shortening of the season with days with T below 0 °C or 7°C, but the yearly minima or the dates of the first and last occurrence of these values do not show so well-defined tendencies. A rise in night-time cloud cover could be related to such behaviour

Parametrización de la turbulencia en modelos meteorológicos

Ponencia presentada en: IV Simposio Nacional de Predicción del Instituto Nacional de Meteorología, celebrado en 1999 en MadridLos modelos numéricos necesitan una parametrización de los movimientos sub-rejilla, puesto que éstos influyen en las escalas resueltas por el modelo por interacciones no lineales. Se presentará un esquema de turbulencia para modelos de circulación general y de mesoescala, junto con sus validaciones a muy alta resolución con un modelo no hidrostático. Se trata de un esquema de orden 1,5, con la energía cinética turbulenta como variable fundamental. Se mostrarán resultados del esquema aplicado a situaciones de capa límite convectiva, capa límite con cizalladura de viento y un caso de Stratocumulus

Surface-Energy-Balance Closure over Land: A Review

Quantitative knowledge of the surface energy balance is essential for the prediction of weather and climate. However, a multitude of studies from around the world indicate that the turbulent heat fluxes are generally underestimated using eddy-covariance measurements, and hence, the energy balance is not closed. This energy-balance-closure problem, which has been heavily covered in the literature for more than 25 years, is the topic of the present review, in which we provide an overview of the potential reason for the lack of closure. We demonstrate the effects of the diurnal cycle on the energy balance closure, and address questions with regard to the partitioning of the energy balance residual between the sensible and the latent fluxes, and whether the magnitude of the flux underestimation can be predicted based on other variables typically measured at micrometeorological stations. Remaining open questions are discussed and potential avenues for future research on this topic are laid out. Integrated studies, combining multi-tower experiments and scale-crossing, spatially-resolving lidar and airborne measurements with high-resolution large-eddy simulations, are considered to be of critical importance for enhancing our understanding of the underlying transport processes in the atmospheric boundary layer

OBSERVATIONS AND SIMULATIONS OF KATABATIC FLOWS DURING A HEATWAVE IN ICELAND

Katabatic flows during the night of 11–12 August 2004 in Iceland are studied using observations and a numerical weather prediction model. During this period, there was a heatwave in Iceland. In relation with the very high daytime temperatures, weak synoptic winds and clear skies, a radiative surface cooling in excess of 10–15◦C was observed during the night at many locations throughout Iceland. The situation has been simulated with the Meso-NH model. The results indicate that katabatic winds develop in the stable nocturnal boundary layer when the cold and heavy air descends from the highlands and mountains down to lower lying areas. The simulations are made at a high horizontal and vertical resolution, forced with boundaries and initial conditions from the ECMWF. The simulations and initial conditions are compared to available ground based observations and satellite images showing the surface radiative temperature. The simulations seem to reproduce well most of the observed winds, including patterns where weak synoptic winds or katabatic flow interact with orography. The simulations also give valuable indications of locations of relatively strong katabatic winds, where no observations are currently available. A similar simulation has been performed with the MM5 atmospheric model and an intercomparison is under way

Aplicación de un modelo unidimensional para predicciones en el Aeropuerto de Madrid-Barajas

Ponencia presentada en: V Simposio Nacional de Predicción, celebrado en 2001 en Madrid.Actualmente está en desarrollo la aplicación de un modelo de predicción unidimensional (1D) para pronósticos locales. El modelo se basa en el esquema de turbulencia que se encuentra operativo en HIRLAM (CBR). Un modelo 1D presenta la ventaja de permitir trabajar con resoluciones verticales y temporales mucho mejores que las de los modelos convencionales 3D. Con ello se pretende conseguir una mejora en las predicciones a corto plazo para lugares y fenómenos meteorológicos que requieran una especial precisión. Se analizan los distintos métodos utilizados en el modelo para obtener información de los intercambios tierra atmósfera (momento, calor y humedad) y del estado tridimensional de la atmósfera (gradiente horizontal de presión, divergencia horizontal de masa, advecciones horizontales de temperatura, humedad y viento) y se analizan sus ventajas e inconvenientes

Consideraciones sobre el uso climatológico de parámetros de capa límite atmosférica y estado del suelo: modelos y métodos de teledetección

Ponencia presentada en: II Congreso de la Asociación Española de Climatología “El tiempo del clima”, celebrado en Valencia del 7 al 9 de junio de 2001[ES]Tradicionalmente, los estudios climatológicos se han realizado mediante el análisis de series temporales de las variables atmosféricas básicas, tales como la precipitación, la temperatura, la humedad y la velocidad y la dirección del viento. En la actualidad, nuevas metodologías de trabajo, por ejemplo el uso de modelos numéricos de predicción del tiempo o del clima y la utilización de datos de teledetección, exigen series largas de otros parámetros, tales como el contenido de humedad del suelo, la temperatura superficial o los flujos de intercambio entre la superficie terrestre y la atmósfera. En este texto se presentan los requerimientos de series largas de parámetros no contemplados en la climatología tradicional, para satisfacer las necesidades de validación en tiempo pasado y tener un buen conocimiento en un área geográfica determinada del comportamiento del suelo y la capa límite atmosférica. Se introduce la necesidad de disponer de localizaciones de medida de referencia para dichos parámetros. En la segunda parte se insiste en la conveniencia de tener en cuenta la fenomenología de la Capa Límite Atmosférica y se sugiere el uso de simulaciones mesoscalares a nivel de cuenca hidrográfica como nuevas fuentes de información en el análisis de series temporales, especialmente en los métodos de homogeneización de series y estudios de clima regional.[EN]Traditionally, the climatological studies have been performed through the analysis of time series of the basic atmospheric variables, say the precipitation, the temperature, the humidity and the wind speed and direction. Nowadays, new methodologies such as numerical models for weather forecast or climate scenarios and the use of remate sensing data, requiere long series of other parameters, say soil moisture content, surface temperature or exchange fluxes between the earth surface and the atmosphere. In this paper the requirements of long series of parameters not considered in the traditional climatology are discussed, to fullfill the needs of validation in past time and to improve the knowledge in a certain geographical area of the behaviour of the soil and the Planetary Boundary Layer. The necessity of reference measuring sites of these parameters is introduced. In the second part of the paper, the convenience of taking into account the phenomenology of the Planetary Boundary Layer is emphasized and the use of mesoscale simulations at the level of hydrographic bassin is introduced, as a new source of information in the analyses of temporal series, especially in the methods of series homogeneization and regional clima studies

Investigación en atmósfera y clima en España

Número monográfico dedicado a la meteorología.En este artículo, se pretende describir la actividad investigadora en España en los últimos años en temas de Atmósfera y Clima, tomando como información de partida los proyectos financiados por el Plan Nacional de I+D+I (PNIDI) desde 1995. Se señalan primero las entidades financiadoras de I+D a nivel general, particularizando seguidamente las diferentes líneas definidas en el subprograma de Atmósfera y Clima

Representación en modelos de tiempo y clima de las nubes de capa límite

Ponencia presentada en: V Simposio Nacional de Predicción, celebrado en 2001 en Madrid.Las nubes son uno de los fenómenos meteorológicos de más difícil representación en los modelos numéricos de la atmósfera. Su gran importancia en los balances de energía y materia las convierten en factores clave para una integración realista de dichos modelos. En el marco del proyecto europeo EUROCS1 se procede al estudio de varios regímenes nubosos de capa límite: ciclo diurno de estratocúmulos sobre océanos, ciclo diurno de cúmulos de buen tiempo y ciclo diurno de convección profunda sobre tierra. A través de la simulación explícita de estos regímenes con modelos no hidrostáticos de muy alta resolución, se evalúan las parametrizaciones frente a las observaciones. Mediante este procedimiento, se identifican y evalúan las carencias de las diferentes parametrizaciones, para su posterior mejora en las implementaciones de los modelos operativos. En esta presentación se mostrarán los trabajos realizados en el INM con los modelos MESO-NH y HIRLAM-1D

OBSERVATIONS AND SIMULATIONS OF KATABATIC FLOWS DURING A HEATWAVE IN ICELAND

Katabatic flows during the night of 11–12 August 2004 in Iceland are studied using observations and a numerical weather prediction model. During this period, there was a heatwave in Iceland. In relation with the very high daytime temperatures, weak synoptic winds and clear skies, a radiative surface cooling in excess of 10–15◦C was observed during the night at many locations throughout Iceland. The situation has been simulated with the Meso-NH model. The results indicate that katabatic winds develop in the stable nocturnal boundary layer when the cold and heavy air descends from the highlands and mountains down to lower lying areas. The simulations are made at a high horizontal and vertical resolution, forced with boundaries and initial conditions from the ECMWF. The simulations and initial conditions are compared to available ground based observations and satellite images showing the surface radiative temperature. The simulations seem to reproduce well most of the observed winds, including patterns where weak synoptic winds or katabatic flow interact with orography. The simulations also give valuable indications of locations of relatively strong katabatic winds, where no observations are currently available. A similar simulation has been performed with the MM5 atmospheric model and an intercomparison is under way

Verification of a clear-sky mesoscale simulation using satellite-derived surface temperatures

A mesoscale simulation for Majorca Island is made using the Méso-NH model for a spring night, under a slack synoptic pressure gradient with weak general winds and clear skies. The circulations over and around the island are driven mostly by the locally generated flows, due to the topography and the land–sea thermal contrast. The verification of mesoscale simulations in clear-sky conditions is difficult, especially if the network of stations is not very dense. The main objective of this work is to try to verify the mesoscale simulation using measurements from automatic weather stations and satellite measurements. The model outputs are compared with the available instrumental data and the representativeness of the stations is discussed. Furthermore, complete two-dimensional comparisons are made between the radiative surface temperatures produced by the model and those processed from the National Oceanic and Atmospheric Administration and Meteosat Second Generation (MSG) satellite sensors. The high temporal resolution of the MSG images also allows comparison of the temporal evolutions of the surface temperature between satellite pixels and model grid cells. The procedure permits assessment of the closeness of the simulation to in situ and remote sensing observations. The results of the comparison show that the model is able to reproduce most of the observed patterns, such as intense local cooling or persistent outflows at the largest basins.Funding was provided by the Spanish Government (Research Projects REN2003-09435, CGL2005-07105, and CGL2006-12474)