Observación meteorológica de la Agencia Estatal de Meteorología en el Parque Nacional de Ordesa y Monte Perdido

En 2018 y 2019 se ha celebrado el Centenario del Parque Nacional de Ordesa y Monte Perdido, y AEMET no ha sido ajeno a esta fecha tan importante participando en charlas y eventos. Además y como objetivo de este trabajo se ha pretendido rendir un pequeño homenaje a todas las personas, tanto de AEMET como especialmente sobre el terreno, que a lo largo de la historia han ido realizando medidas meteorológicas en esta zona y consolidando una red de observación de gran valor para numerosos ámbitos de la meteorología y climatología. Se pretende mostrar una perspectiva histórica y quizás un tanto romántica de la complejidad asociada a la recogida y supervisión de datos, mostrar mediante valores extremos las características climáticas de la zona y finalmente presentar ciertos resultados científicos, a modo de ejemplo, que muestran la importancia presente y futura de estos datos meteorológicos para el análisis de tendencias climáticas

La red nivometeorológica de AEMET en Aragón y Navarra

Ponencia presentada en: VI Simposio Nacional de Predicción, celebrado en los servicios centrales de AEMET, en Madrid, del 17 al 19 de septiembre de 2018.La disponibilidad de datos de observación sistemáticos manuales con continuidad espacial y temporal a partir de cierta altitud a nivel nacional es escasa. Solamente en el Pirineo aragonés y navarro existe una mínima red de observación en altura que cumpla las premisas anteriores. Esta singularidad de gran valor meteorológico se puede explotar en numerosas aplicaciones como predicción, climatología y zona de ensayo de instrumentos de medida en entornos extremos. Esta red se compone de 20 puntos de observación que de manera continuada los 365 días al año, excepto 4 estaciones de esquí que solo lo hacen en periodo invernal, emiten información de tipo sinóptico además de información nivológica en época invernal. Además, todos los puntos de observación por encima de 2000 m forman parte de la red internacional de Vigilancia de la Criosfera de la Organización Meteorológica Mundial y uno de ellos, Cap de Llauset, es la estación manual a mayor altitud de España (2425 m). Este trabajo presenta la utilidad, las virtudes, las limitaciones y la complejidad asociadas tanto al mantenimiento como a la explotación de sus datos meteorológicos por parte de AEMET

The impact of a windshield in a tipping bucket rain gauge on the reduction of losses in precipitation measurements during snowfall events

Comunicación presentada en: EGU General Assembly 2016 celebrada del 17 al 22 de abril en Viena, Austria

Impact of two different sized Stevenson screens on air temperature measurements

In this study we evaluated the impact of the size of two naturally ventilated wooden Stevenson screens on air temperature measurements in the first‐order meteorological station of Calamocha (northeastern Iberian Peninsula, Spain). The 1‐year field experiment consisted of comparing air temperatures measured at the two most commonly sized Stevenson screens used by the Spanish Meteorological State Agency (AEMET) since last century; the medium‐sized Stevenson screen employed at the second‐order weather stations, versus the large‐sized Stevenson screen mainly used at the first‐order meteorological stations. The main objective was to report the air temperature difference between these two differently sized Stevenson screens, and to study the impact on the observed differences of some weather elements (i.e. relative humidity, wind speed, total cloud cover, atmospheric pressure and global solar radiation). The results show that the medium‐sized Stevenson screen tended to overheat daily maximum air temperatures (0.54 °C on yearly average) and also air temperatures recorded at 1300 UTC. The differences on daily minimum air temperatures were negligible (−0.11 °C on yearly average). This overheating bias (not statistically significant) occurred under anticyclonic situations that lead to clear skies, high solar radiation, weak winds and low relative humidity. The bias appeared throughout the whole year but in particular during the warm season from May through October. Air temperature observations from the nearby station Daroca confirmed an overheating bias introduced by a change from a large‐sized Stevenson screen to a medium‐sized one in Calamocha.This research was supported by (1) the JCI-2011-10263 grant, (2) the projects CGL2011-27574-C02-02 and CGL2011-27536/HID financed by the Spanish Commission of Science and Technology and FEDER and (3) the MEDACC project (LIFE12 ENV/ES/000536)

Impact of wind and temperature on snowfall measurements by Thies LPM and OTT Parsivel2 optical disdrometers compared with DFAR (Double Fence Automated Reference) measurements at WMO.SPICE Formigal-Sarrios site

Póster presentado en: WMO Technical Conference on Meteorological and Environmental Instruments and Methods of Observation celebrada del 8 al 11 de octubre de 2018 en Amsterdam

Wind gusts registered in Zaragoza Airport associated to supercellular convection on 1st July 2018 and its spatial variability

Presentación realizada en la 3rd European Nowcasting Conference, celebrada en la sede central de AEMET en Madrid del 24 al 26 de abril de 2019

Intercomparison of snowfall measurements using disdrometers in two mountainous environments: Weissfluhjoch (Switzerland) and Formigal-Sarrios (Spain)

Comunicación presentada en: TECO-2016 (Technical Conference on Meteorological and Environmental Instruments and Methods of Observation) celebrada en Madrid, del 27 al 30 de septiembre de 2016.One of the objectives of the WMO/CIMO Solid Precipitation Intercomparison Experiment (SPICE) is to assess the performance of emerging technologies such as disdrometers for the measurement of solid precipitation. Numerous studies have assessed the performance of disdrometers for liquid precipitation, but the experience of using such instruments for solid precipitation is still limited. Among others, the Spanish site at Formigal and the Swiss site at Weissfluhjoch were built with very similar design (especially the reference measurement setting in a Double Fence Intercomparison Reference (DFIR)). Moreover, the environment of both sites (siting) is similar. This work evaluates the potential use of disdrometers for solid precipitation measurement in a mountainous environment. At each site two LPM Thies disdrometers, one shielded in a DFIR and the other one outside (with or without a Thies wind shield), are intercompared under different weather conditions (wind speed and direction, temperature and snowfall intensity) against the SPICE reference measurement using a weighing gauge (OTT Pluvio2 in a DFIR). This study will present preliminary results from both sites and will give first conclusion on the impact of various external parameters (such as wind and temperature) on the disdrometer snow accumulation measurement in and outside the DFIR, and with and without a Thies shield. Moreover, new lines of research are recommended in order to better understand the instrument and the raw data output

Impact of weather type variability on winter precipitation, temperature and annual snowpack in the Spanish Pyrenees

The annual frequency of the occurrence of 10 discriminated weather types were summarized using a principal component analysis that revealed 4 different prevailing winter conditions affecting the Spanish Pyrenees. Northeasterly and easterly flows lead to dry and cold winters where snow only accumulates on northern slopes and mainly in the central Pyrenees. North and northwesterly flows favor wet and cold winters and an increase of snow accumulation in the western Pyrenees and on the northern slopes at lower elevations. Cyclonic and westerly flows favor an increase in precipitation and snow accumulation in all the Pyrenees at lower elevations and cold winters. Finally, southerly flows are associated with milder conditions and high precipitation in the central sector of the Pyrenees, where snow only accumulates at high elevations. For most stations, there were no significant trends in precipitation or temperature during the current reference climatic period (1981−2010), which was in agreement with the lack of observed principal component trends during the same period. Focusing on the shorter 1985−2010 period for which snow data were available, snow depth at mid-March demonstrated significant positive trends associated with an increase in westerly, southwesterly and cyclonic weather during this period. The results demonstrate that the changes in precipitation, temperature and snow accumulation are clearly related to changes in circulation patterns, which are the main driver of temporal fluctuations in the considered climatologies.This study was funded by the research project: CGL2014-52599-P "Estudio del manto de nieve en la montaña española, y su respuesta a la variabilidad y cambio climatico" financed by the Spanish Ministry of Economy and Competitiveness

Analysis of the snow water equivalent at the AEMet-Formigal field laboratory (Spanish Pyrenees) during the 2019/2020 winter season using a stepped-frequency continuous wave radar (SFCW)

Snow makes a great contribution to the hydrological cycle in cold regions. The parameter to characterize available the water from the snow cover is the well-known snow water equivalent (SWE). This paper presents a near-surface-based radar for determining the SWE from the measured complex spectral reflectance of the snowpack. The method is based in a stepped-frequency continuous wave radar (SFCW), implemented in a coherent software defined radio (SDR), in the range from 150 MHz to 6 GHz. An electromagnetic model to solve the electromagnetic reflectance of a snowpack, including the frequency and wetness dependence of the complex relative dielectric permittivity of snow layers, is shown. Using the previous model, an approximated method to calculate the SWE is proposed. The results are presented and compared with those provided by a cosmic-ray neutron SWE gauge over the 2019–2020 winter in the experimental AEMet Formigal-Sarrios test site. This experimental field is located in the Spanish Pyrenees at an elevation of 1800 m a.s.l. The results suggest the viability of the approximate method. Finally, the feasibility of an auxiliary snow height measurement sensor based on a 120 GHz frequency modulated continuous wave (FMCW) radar sensor, is shown.This work was supported by DGA-FSE under grant T20_17R to the Photonics Technologies Group of University of Zaragoza

Climatological comparison of 2011-2012 and 2012-2013 snow seasons in Central and Western Spanish Pyrenees and its relationship with the North Atlantic Oscillation (NAO) [Póster]

Póster presentado en: International Snow Science Workshop Grenoble, celebrado en Chamonix Mont-Blanc, del 7 al 11 de octubre de 2013.An analysis of 2011/12 and 2012/13 seasons (NDJFMAM) has been made in the Pyrenees of Navarre and Aragon. The main objective is to highlight the contrast between the two seasons in relation to temperature, precipitation and snowpack behaviour, trying to find a relationship with the NAO