Meteorological State Agency of Spain AEMET


Meteorological State Agency of Spain AEMET

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Azorin-Molina C.,Gothenburg University | Menendez M.,University of Cantabria | McVicar T.R.,CSIRO | McVicar T.R.,University of New South Wales | And 5 more authors.
Climate Dynamics | Year: 2017

This study simultaneously examines wind speed trends at the land–ocean interface, and below–above the trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of trade-winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981–2014), including one mountain weather station (Izaña) located above the trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948–2014; and SeaWind II at 15 km for 1989–2014). The results revealed a widespread significant negative trend of trade-winds over ocean for 1948–2014, whereas no significant trends were detected for 1989–2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter–spring–autumn; significant in April and September) of trade-winds. Above the inversion layer at Izaña, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic. © 2017 The Author(s)

Martinez-Ballesteros M.,University of Seville | Salcedo-Sanz S.,University of Alcalá | Riquelme J.C.,University of Seville | Casanova-Mateo C.,University of Valladolid | Camacho J.L.,Meteorological State Agency of Spain AEMET
Chemometrics and Intelligent Laboratory Systems | Year: 2011

In this paper we propose an evolutionary method of association rules discovery (EQAR, Evolutionary Quantitative Association Rules) that extends a recently published algorithm by the authors and we describe its application to a problem of Total Ozone Content (TOC) modeling in the Iberian Peninsula. We use TOC data from the Total Ozone Mapping Spectrometer (TOMS) on board the NASA Nimbus-7 satellite measured at three locations (Lisbon, Madrid and Murcia) of the Iberian Peninsula. As prediction variables for the association rules we consider several meteorological variables, such as Outgoing Long-wave Radiation (OLR), Temperature at 50 hPa level, Tropopause height, and wind vertical velocity component at 200 hPa. We show that the best association rules obtained by EQAR are able to accurate modeling the TOC data in the three locations considered, providing results which agree to previous works in the literature. © 2011 Elsevier B.V.

Dalsoren S.B.,CICERO Center for International Climate and Environmental Research | Myhre C.L.,Norwegian Institute For Air Research | Myhre G.,CICERO Center for International Climate and Environmental Research | Gomez-Pelaez A.J.,Meteorological State Agency of Spain AEMET | And 5 more authors.
Atmospheric Chemistry and Physics | Year: 2016

Observations at surface sites show an increase in global mean surface methane (CH4) of about 180 parts per billion (ppb) (above 10 %) over the period 1984-2012. Over this period there are large fluctuations in the annual growth rate. In this work, we investigate the atmospheric CH4 evolution over the period 1970-2012 with the Oslo CTM3 global chemical transport model (CTM) in a bottom-up approach. We thoroughly assess data from surface measurement sites in international networks and select a subset suited for comparisons with the output from the CTM. We compare model results and observations to understand causes for both long-term trends and short-term variations. Employing Oslo CTM3 we are able to reproduce the seasonal and year-to-year variations and shifts between years with consecutive growth and stagnation, both at global and regional scales. The overall CH4 trend over the period is reproduced, but for some periods the model fails to reproduce the strength of the growth. The model overestimates the observed growth after 2006 in all regions. This seems to be explained by an overly strong increase in anthropogenic emissions in Asia, having global impact. Our findings confirm other studies questioning the timing or strength of the emission changes in Asia in the EDGAR v4.2 emission inventory over recent decades. The evolution of CH4 is not only controlled by changes in sources, but also by changes in the chemical loss in the atmosphere and soil uptake. The atmospheric CH4 lifetime is an indicator of the CH4 loss. In our simulations, the atmospheric CH4 lifetime decreases by more than 8 % from 1970 to 2012, a significant reduction of the residence time of this important greenhouse gas. Changes in CO and NOx emissions, specific humidity, and ozone column drive most of this, and we provide simple prognostic equations for the relations between those and the CH4 lifetime. The reduced lifetime results in substantial growth in the chemical CH4 loss (relative to its burden) and dampens the CH4 growth. © Author(s) 2016.

Levin I.,University of Heidelberg | Naegler T.,University of Heidelberg | Kromer B.,University of Heidelberg | Diehl M.,University of Heidelberg | And 7 more authors.
Tellus, Series B: Chemical and Physical Meteorology | Year: 2010

Global high-precision atmospheric Δ14CO2 records covering the last two decades are presented, and evaluated in terms of changing (radio)carbon sources and sinks, using the coarse-grid carbon cycle model GRACE. Dedicated simulations of global trends and interhemispheric differences with respect to atmospheric CO2 as well as δ13CO2 and Δ14CO2, are shown to be in good agreement with the available observations (1940-2008). While until the 1990s the decreasing trend of Δ14CO2 was governed by equilibration of the atmospheric bomb 14C perturbation with the oceans and terrestrial biosphere, the largest perturbation today are emissions of 14C-free fossil fuel CO2. This source presently depletes global atmospheric Δ14CO2 by 12-14‰ yr-1, which is partially compensated by 14CO2 release from the biosphere, industrial 14C emissions and natural 14C production. Fossil fuel emissions also drive the changing north-south gradient, showing lower Δ14C in the northern hemisphere only since 2002. The fossil fuel-induced north-south (and also troposphere-stratosphere) Δ14CO2 gradient today also drives the tropospheric Δ14CO2 seasonality through variations of air mass exchange between these atmospheric compartments. Neither the observed temporal trend nor the Δ14CO2 north-south gradient may constrain global fossil fuel CO2 emissions to better than 25%, due to large uncertainties in other components of the (radio)carbon cycle. © 2009 The Authors Journal compilation © 2010 Blackwell Munksgaard.

Basart S.,Barcelona Supercomputing Center | PeRez C.,NASA | Nickovic S.,World Meteorological Organization | Cuevas E.,Meteorological State Agency of Spain AEMET | And 2 more authors.
Tellus, Series B: Chemical and Physical Meteorology | Year: 2012

The BSC-DREAM8b model and its predecessor are analysed in terms of aerosol optical depth (AOD) for 2004 over Northern Africa, the Mediterranean and the Middle East. We discuss the model performance and we test and analyse its behaviour with new components. The results are evaluated using hourly data from 44 AERONET stations and seasonally averaged satellite observations. The operational versions strongly underestimate the winter AOD over the Sahel and overestimate the AOD over the Middle East and the Mediterranean achieving a low average annual correlation (~0.35). The use of a more detailed size distribution and a corrected wash-out ratio, together with a new dry deposition scheme, improves the transport over the Mediterranean, although underestimations remain over the Sahel and overestimations over the Middle East. The inclusion of a 'preferential source' mask improves the localisation of the main North African sources and consequently the dust transport towards Europe and the Atlantic. The use of a more physically based dust emission scheme and a new soil texture database leads to significant improvements in the representation of emissions and the transport over the Sahel, achieving an average annual correlation of 0.53. In this case, the use of a preferential source mask does not introduce significant improvements. © 2012 S. Basart et al.

Barreto A.,Meteorological State Agency of Spain AEMET | Cuevas E.,Meteorological State Agency of Spain AEMET | Damiri B.,Cimel Electronique | Guirado C.,Meteorological State Agency of Spain AEMET | And 7 more authors.
Atmospheric Measurement Techniques | Year: 2013

This paper presents the preliminary results of nocturnal Aerosol Optical Depth (τa) and Angström Exponent (α) obtained from a new lunar photometer prototype, trade name Cimel CE-318U. Due to the variation of the moon's illumination inherent to the lunar cycle, the typical Langley-plot Method used in solar photometry to calibrate these instruments cannot be applied. In this paper, we propose three different methods to carry out the lunar-photometer calibration. In order to validate the results, we have selected three events which encompass seven nights and ten days under different atmospheric conditions, including several saharan dust intrusions episodes. Method#1 is introduced in this work as a modification of the usual Langley Method. This technique, called Lunar-Langley Method, requires the extraterrestrial irradiances from a lunar irradiance model, providing similar accuracies on τa to those of AERONET (±0.01-0.02). It makes comparable daytime and nighttime measurements. Method#2 consists of transferring the current calibration from a master used by sunphotometers. Its results are again within the limit of accuracy expected for the instrument. Method#3 uses an integrating sphere and the methodology proposed by Li et al. (2008) to determine sky calibration coefficients (Cj) and the instrument's solid angle field-of-view (Ω), respectively. We observe significant τa differences between Method#1 and #3 (up to 0.07), which might be attributed to the errors propagation in Method#3. The good results obtained from the comparison against a second CE-318U prototype, and against daytime data from a Precision Filter Radiometer (PFR), constitute a valuable assessment of CE-318U performance. Results of α and its spectral variation (δα) show good agreement between daytime and nighttime, being able to identify the aerosol properties associated with each event. © Author(s) 2013.

Gomez-Pelaez A.J.,Meteorological State Agency of Spain AEMET | Ramos R.,Meteorological State Agency of Spain AEMET | Gomez-Trueba V.,Meteorological State Agency of Spain AEMET | Gomez-Trueba V.,Air Liquide | And 2 more authors.
Atmospheric Measurement Techniques | Year: 2013

Atmospheric CO in situ measurements are carried out at the Izaña (Tenerife) global GAW (Global Atmosphere Watch Programme of the World Meteorological Organization - WMO) mountain station using a Reduction Gas Analyser (RGA). In situ measurements at Izaña are representative of the subtropical Northeast Atlantic free troposphere, especially during nighttime. We present the measurement system configuration, the response function, the calibration scheme, the data processing, the Izaña 2008-2011 CO nocturnal time series, and the mean diurnal cycle by months. We have developed a rigorous uncertainty analysis for carbon monoxide measurements carried out at the Izaña station, which could be applied to other GAW stations. We determine the combined standard measurement uncertainty taking into consideration four contributing components: uncertainty of the WMO standard gases interpolated over the range of measurement, the uncertainty that takes into account the agreement between the standard gases and the response function used, the uncertainty due to the repeatability of the injections, and the propagated uncertainty related to the temporal consistency of the response function parameters (which also takes into account the covariance between the parameters). The mean value of the combined standard uncertainty decreased significantly after March 2009, from 2.37 nmol mol-1 to 1.66 nmolmol-1, due to improvements in the measurement system. A fifth type of uncertainty we call representation uncertainty is considered when some of the data necessary to compute the temporal mean are absent. Any computed mean has also a propagated uncertainty arising from the uncertainties of the data used to compute the mean. The law of propagation depends on the type of uncertainty component (random or systematic). In situ hourly means are compared with simultaneous and collocated NOAA flask samples. The uncertainty of the differences is computed and used to determine whether the differences are significant. For 2009-2011, only 24.5% of the differences are significant, and 68% of the differences are between -2.39 and 2.5 nmol mol-1. Total and annual mean differences are computed using conventional expressions but also expressions with weights based on the minimum variance method. The annual mean differences for 2009-2011 are well within the ±2 nmol mol-1 compatibility goal of GAW. © Author(s) 2013.

Prats N.,University of Valladolid | Prats N.,Meteorological State Agency of Spain AEMET | Cachorro V.E.,University of Valladolid | Berjon A.,Meteorological State Agency of Spain AEMET | And 2 more authors.
Atmospheric Chemistry and Physics | Year: 2011

The aim of the present work is to carry out a detailed analysis of columnar microphysical properties obtained from Cimel sun-photometer measurements in the Southwest of Spain within the frame of the Aerosol Robotic Network (AERONET)-Iberian Network for aerosol measurements (RIMA). AERONET level 2 inversion products are analysed, in particular the particle size distribution together with their associated microphysical parameters for both fine and coarse modes: volume concentration, effective radius and the fine mode volume fraction. This work complements previous works based on aerosol optical depth (AOD) and the Ångström exponent (AE) for a global characterization of atmospheric aerosol in this area of southwestern Spain. The analysed dataset spans between February 2000 and October 2008. Time series and statistical analysis has been carried out for these parameters in order to assess their typical values and seasonality together with their relationships with the AOD and AE. Mean values of volume particle concentration are 0.06±0.07 μm 3 μm -2 for total, 0.019±0.015 μm 3 μm -2 for fine and 0.04±0.06 μm 3 μm -2 for coarse mode; mean effective radii are 0.40±0.19 μm for total, 0.14±0.02 μm for fine and 1.96±0.41 μm for coarse mode. The most relevant features are the clear bimodality of the volume particle size distribution, with a slight dominance of the coarse mode in the overall climatology given the prevailing atmospheric conditions at the site (coastal marine). There is a clear prevalence of the coarse mode in summer months plus September and March, in coincidence with the occurrence of desert dust intrusions and highest AOD values. During desert dust outbreaks, the particle size distribution is practically monomodal with strong prevalence of the coarse mode which also shows a shift of the modal radius toward lower values. The size particle predominance defines the characteristic of the site and it has been analysed under two different parameters: the Ångström exponent and the fine mode volume fraction Vf/Vt. We investigated the relationship between them and also their relationship with the effective radius of the size distribution. © 2011 Author(s).

Bennouna Y.S.,University of Valladolid | Cachorro V.E.,University of Valladolid | Torres B.,University of Valladolid | Toledano C.,University of Valladolid | And 3 more authors.
Atmospheric Environment | Year: 2013

The present study focuses on the characterization of aerosol seasonal variability over the northern continental region of the Iberian Peninsula based on remotely sensed aerosol optical properties, and in particular the aerosol optical depth (AOD) and ångström exponent (Alpha) parameters. For this region, a representative annual cycle of these parameters was built based on data from the AERONET-RIMA station of Palencia (Spain, 42N, 4.5W) for the period 2003-2011. The results also examine in details the interannual variability during the whole period. The ability of satellite to reproduce the seasonal patterns and anomalies, is investigated using the MODIS (Moderate Resolution Imaging Radiometer) for the same period. MODIS instantaneous fields are validated against ground-based sunphotometer data, and the differences between monthly values are estimated. The site of Palencia is characterized by a daily AOD (440 nm) of 0.15 ± 0.10 and Alpha (440-870 nm) of 1.29 ± 0.35 on average, thus presenting values typical of a clean continental background. The seasonal pattern corresponds to mid-high turbidity values of the AOD during a period starting in mid-spring to the end of the summer (max 0.19), and a lower AOD during fall and winter months (min 0.09). When using MODIS data, the overall results for Palencia give a higher (by ∼25%) AOD (470 nm) with 0.19 ± 0.15 and a much lower (by ∼50%) Alpha (470-660 nm) of 0.70 ± 0.20. These numbers reflect substantial differences, with overestimations of the monthly means that can be almost double those of AERONET in the summer months. However MODIS satisfactorily reproduces the increase-decrease cycle in the AOD. These large differences tend to be more attributed to the aerosol models used in the MODIS algorithm rather than to the sampling difference between ground and satellite in this season. Despite the poor sampling in winter and the small AOD (<0.1) observed over the area, the best agreement between satellite and ground is found during this period. The seasonal pattern of the ångström exponent derived from MODIS was found to be very different from that of AERONET, the former showing apparently no consistency with the latter. Given the aforementioned values and the fact that the AERONET Alpha value for 470-660 nm is 1.41 ± 0.37 (wavelengths used in the comparison with MODIS), we can conclude that the Alpha derived from MODIS is not representative of the aerosol type characterizing this region of the globe. © 2012 Elsevier Ltd.

Bennouna Y.S.,University of Valladolid | Torres B.,University of Valladolid | Cachorro V.E.,University of Valladolid | Ortiz de Galisteo J.P.,University of Valladolid | And 2 more authors.
Quarterly Journal of the Royal Meteorological Society | Year: 2013

The annual cycle of precipitable water vapour is inferred from the MODIS thermal infrared (IR) and near-infrared (NIR) satellite products under clear-sky conditions for the period 2002-2008 at 18 sites in the Iberian Peninsula, with the aim to evaluate the capabilities of both algorithms. The article presents these results in relation to ground observations using different techniques (GPS, sunphotometer, radiosounding), with a special emphasis on GPS. At all sites the annual cycle presents the typical shape with low values in winter (minimum ∼1 cm) and high values in summer (maximum ∼3 cm), and a smaller cycle amplitude at continental sites than at coastal sites. The satellite results clearly depict the north-south gradient, as well as singular patterns such as the July minimum characterizing the most southern stations. The differences in the monthly means with respect to ground observations are mostly underestimations, ranging between a few percent to 40%, being generally larger in winter than in summer. Overall, NIR performs better than IR, especially in the wintertime. However, NIR presents overestimations in summer that can reach up to 30%. The comparison results of the annual cycle appear much more heterogeneous within coastal than continental areas, in particular for the Mediterranean region. It was found that the performance of IR algorithm is strongly influenced by the seasonal variations, a dependence which is much weaker in NIR retrievals. The time-coincident comparison shows that best MODIS/GPS agreement is found for continental regions (r.m.s.∼0.3) for both methods. The largest regression biases and rms differences are found at the Mediterranean sites. The influence of sampling in the evaluation of the MODIS annual cycle was shown to affect mainly winter values. Errors induced by the retrieval accuracy and those induced by sampling deficiencies sometimes add up or compensate each other partially or totally. © 2013 Royal Meteorological Society.

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