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The analysis of extreme events is an essential key in the research of the atmospheric ozone due to their importance in biological and radiative effects. Total ozone column (TOC) databases from five ground-based sites equipped with a Brewer spectrometer are used to evaluate extreme ozone events along the Iberian Peninsula for the period 2002–2012. The monthly standard deviation is proved as a reliable metric to identify extreme cases. A total of 465 events (days) are classified as extremes events. For the database used, 2011 presents 32 events with very low TOC values (miniholes), while 2010 is the year with the maximum number (51) of events with very high TOC values (minihighs). The weight of the miniholes (minihighs) over the ozone annual mean can achieve values over the 4% (8%). The relationship between global dynamical features and ozone extreme events is also addressed in this study. Double tropopause events have explained in 2002 and 2004 up to the half of minihole events, while the North Atlantic Oscillation (NAO) negative phase is the condition prevalent in the majority of the minihighs in the entire period. These global characteristics are verified in the analysis of a case study (February–March 2004) exhibiting two periods with double tropopause events and a change in the sign of the NAO index with the consequent change in the tropopause pressure. [ABSTRACT FROM AUTHOR]

Water vapor column (WVC) obtained by GOME-2 instrument (GDP-4.6 version) onboard MetOp-A satellite platform is compared against reference WVC values derived from GPS (Global Positioning System) instruments from 2007 to 2012 at 21 places located at Iberian Peninsula. The accuracy and precision of GOME-2 to estimate the WVC is studied for different Iberian Peninsula zones using the mean (MBE) and the standard deviation (SD) of the GOME-2 and GPS differences. A direct comparison of all available data shows an overestimation of GOME-2 compared to GPS with a MBE of 0.7 mm (10%) and a precision quantified by a SD equals to 4.4 mm (31%). South-Western zone presents the highest overestimation with a MBE of 1.9 mm (17%), while Continental zone shows the lowest SD absolute value (3.3 mm) due mainly to the low WVC values reached at this zone. The influence of solar zenith angle (SZA), cloud fraction (CF), and the type of surface and its albedo on the differences between GOME-2 and GPS is analyzed in detail. MBE and SD increase when SZA increases, but MBE decreases (taking negative values) when CF increases and SD shows no significant dependence on CF. Under cloud-free conditions, the differences between WVC from GOME-2 and GPS are within the WVC error given by GOME-2. The changes of MBE and SD on Surface Albedo are not so evident, but MBE slightly decreases when the Surface Albedo increases. WVC from GOME-2 is, in general, more precise for land than for sea pixels. [ABSTRACT FROM AUTHOR]

As the ozone is one of the most relevant variables in the climate system, to get further in its long-term characterization is a critical issue. In this study, measurements of total ozone column (TOC) from five well-calibrated Brewer spectrophotometers placed in the Iberian Peninsula are analyzed. The temporal trend rate for TOC is +9.3 DU per decade for the period 1993-2012 in Central Iberian Peninsula. However, the low TOC levels during 2011 and 2012 over the study region notably reduce this rate. Empirical linear relationships are established between TOC and pressure, height, and temperature of the tropopause. The linear fits showed seasonal and latitudinal dependence, with stronger relationships during winter and spring. Events with the presence of a double tropopause (DT) are proved to be characteristic of the study region. The decrease in TOC levels when these anomalous events occur is quantified around 10 % in winter and spring with respect to the usual cases with a single tropopause. The total weight of the DT events with respect to the annual values is about 20 %, with a negligible occurrence in summer and autumn and being latitudinal-dependent. The North Atlantic Oscillation (NAO) index explains 30 % of the total ozone variability in winter. The DT events are found to be more frequent during phases with positive NAO. [ABSTRACT FROM AUTHOR]

A better understanding of aerosol radiative properties is a crucial challenge for climate change studies. This study aims at providing a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW) solar spectrum. For this purpose, longterm data sets of aerosol properties from six AERONET stations located in the Iberian Peninsula (southwestern Europe) have been analyzed in terms of climatological characterization and inter-annual changes. Aerosol information was used as input for the libRadtran model in order to determine the aerosol radiative effect (ARE) at the surface in the ultraviolet (AREUV), visible (AREVIS), near-infrared (ARENIR), and the entire SW range (ARESW) under cloudfree conditions. Over the whole Iberian Peninsula, yearly aerosol radiative effects in the different spectral ranges were found to be -1.1 UV <-0.7, -5.7 VIS <-3.5, -2.6 NIR <-1.6, and -8.8 SW <-5.7 (in Wm-2). Monthly means of ARE showed a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE), ARE per unit of aerosol optical depth, has also been evaluated in the four spectral ranges. AFE exhibited a dependence on single scattering albedo as well as a weaker one on the Ångström exponent. AFE is larger (in absolute value) for small and absorbing particles. The contributions of the UV, VIS, and NIR ranges to the SW efficiency varied with the aerosol types. The predominant aerosol size determined the fractions AFEVIS/AFESW and AFENIR/AFESW. The AFEVIS was the dominant contributor for all aerosol types, although non-absorbing large particles caused more even contribution of VIS and NIR intervals. The AFEUV / AFESW ratio showed a higher value in the case of absorbing fine particles. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this work is to analyze the total ozone column (TOC) trends over the Iberian Peninsula during the last 30 years (1979–2008). This study is carried out using TOC data derived from the Multi Sensor Reanalysis (MSR), Total Ozone Mapping Spectrometer (TOMS) and Global Ozone Monitoring Experiment (GOME). The analysis of the long-term ozone trends is focused on two sub-periods (1979–1994 and 1995–2008) in order to detect changes in the ozone trend pattern. The results show that the ozone depletion was statistically significant at the 95% confidence level during the first sub-period (1979–1994) in the entire region of study (except in the Southerner locations), with linear trends from −4.5%/decade to −2.5%/decade. These linear trends present a clear dependence on latitude, being higher for the Northerner locations than for the Southerner. By contrast, the analysis of the second sub-period of study (1995–2008) shows positive ozone trends over the Iberian Peninsula, with the highest values (+2.5%/decade) in the Northeast of this region. This result indicates that the ozone layer may be responding as expected to the controls on ozone-depleting substances imposed by the Montreal Protocol. Additionally, a seasonal trend analysis is performed using the average of the deseasonalized monthly values for each season of the year. The seasonal analysis showed that the negative ozone trends during the first sub-period of study were statistically significant in the spring and winter, while that the seasonal ozone trends obtained during the second sub-period are positive but in general not significant at 95%. [Copyright &y& Elsevier]

Abstract: One of the most important atmospheric composition products derived from the first EUMETSAT Meteorological Operational satellite (MetOp-A) is the total ozone column (TOC). For this purpose, MetOp-A has two instruments on board: the Global Ozone Monitoring Experiment 2 (GOME-2) that retrieves the TOC data from the backscattered solar ultraviolet–visible (UV–Vis) radiance, and the Infrared Atmospheric Sounding Interferometer (IASI) that uses the thermal infrared radiance to derive TOC data. This paper focuses on the simultaneous validation of the TOC data provided by these two MetOp-A instruments using the measurements recorded by five well-calibrated Brewer UV spectrophotometers located at the Iberian Peninsula during the complete 2009. The results show an excellent correlation between the ground-based data and the GOME-2 and IASI satellite observations (R2 higher than 0.91). Differences between the ground-based and satellite TOC data show that the IASI instrument significantly overestimates the Brewer measurements (about 4.4% when all five ground-based stations are jointly used). In contrast, the GOME-2 instrument shows a slight underestimation (~1.6%). In addition, the absolute relative differences between the Brewer and GOME-2 data are quite smaller (about a factor higher than 2) than the Brewer–IASI absolute differences. The satellite viewing geometry (solar zenith angle and the view zenith angle) has no significant influence on the Brewer–satellite relative differences. Moreover, the analysis of these relative differences with respect to the ground-based TOC data indicates that GOME-2 instrument presents a slight underestimation for high TOC values. Finally, the IASI–GOME-2 correlation is high (R2 ~0.92), but with a mean relative difference of about ±6% which could be associated with the bias between UV–Vis and infrared spectroscopy used in the retrieval processes. [Copyright &y& Elsevier]

Abstract: This paper focuses on the spatial–temporal structure of total ozone column (TOC) over Portugal. This relevant region of southwestern Europe has not been evaluated yet in detail due to the lack of continuous and well-covered ground-based TOC measurements. The data used in this study are derived from the NASA''s Total Ozone Mapping Spectrometer (TOMS) for the period 1978–2005. The TOC spatial behavior shows no significant longitudinal variability (smaller than 3%). In contrast, the variation in latitude changes between 3.5% and 6% depending on the calendar month. The TOC in the northern Portugal is, on average, higher than that recorded in the South. The temporal variability was analyzed for three scales: long-term, seasonal and short-term. The long-term TOC changes are analyzed between 1978 and 1999 by means of linear least squares fits. The results show an annual TOC trend of (−2.65±0.70)%/decade which is statistically significant at the 95% confidence level. This TOC decrease is smaller than the trends obtained in other midlatitudes regions which could be partially explained by the compensation due to the observed increase in the tropospheric ozone over the Iberian Peninsula. A trend analysis performed for each individual month shows a statistically significant TOC decline between March and October, with a maximum linear trend value of (−7.30±1.45)%/decade in May. The amplitude of the seasonal TOC cycle over Portugal shows a slight dependence in latitude, varying from 28.6 DU (37.5° N) to 33.6 DU (41.5° N). Finally, the short-term variability showed a notable seasonal behavior, with maximum day-to-day TOC changes in winter (~6%) and minimum in summer (~3%). In addition, the persistence (characterized by the autocorrelation coefficients) strongly decreases after a few days (except in summer months). [Copyright &y& Elsevier]

This paper provides an account of observed variations in Black carbon (BC) aerosol concentrations and their induced radiative forcing for the first time over Granada a measurement site in Southeastern Iberian Peninsula. Column-integrated BC concentrations were retrieved for the period 2005–2012. Monthly averages of BC concentrations (± one standard deviation) ranged from higher values in January and December with 4.0 ± 2.5 and 4 ± 3 mg/m 2 , respectively, to lower values in July and August with 1.6 ± 1.2 and 2.0 ± 0.5 mg/m 2 , respectively. This reduction is not only observed in the average values, but also in the median, third and first quartiles. The average BC concentration in winter (3.8 ± 0.6 mg/m 2 ) was substantially higher than in summer (1.9 ± 0.3 mg/m 2 ), being the eight-year average of 2.9 ± 0.9 mg/m 2 . The reduction in the use of fossil fuels during the economic crisis contributed significantly to reduced atmospheric loadings of BC. According to our analysis this situation persisted until 2010. BC concentration values were analyzed in terms of air mass influence using cluster analysis. BC concentrations for cluster 1 (local and regional areas) showed high correlations with air masses frequency in winter and autumn. In these seasons BC sources were related to the intense road traffic and increased BC emissions from domestic heating. High BC concentrations were found in autumn just when air mass frequencies for cluster 3 (Mediterranean region) were more elevated, suggesting that air masses coming from that area transport biomass burning particles towards Granada. BC aerosol optical properties were retrieved from BC fraction using aerosol AERONET size volume distribution and Mie theory. A radiative transfer model (SBDART) was used to estimate the aerosol radiative forcing separately for composite aerosol (total aerosols) and exclusively for BC aerosols. The mean radiative forcing for composite aerosol was + 23 ± 6 W/m 2 (heating rate of + 0.21 ± 0.06 K/day) and + 15 ± 6 W/m 2 for BC aerosol (heating rate of + 0.15 ± 0.06 K/day). These values of radiative forcing and heating rate for BC aerosol represent about 70% of their values for composite aerosol, which highlights the crucial role that BC aerosols play in modifying the radiation budget and climate. [ABSTRACT FROM AUTHOR]

Sunshine duration (SD) represents a valuable parameter for early years when few or none measurements of surface solar radiation (SSR) are available. In the present work, daily and monthly SD records registered in Lisbon (Portugal) for the period 1890–1940 have been digitized to expand the data series available in electronic format, which starts in 1941. The resulting series for the period 1890–2018 can be considered as the earliest one in Portugal and the second one in the Iberian Peninsula. Cloud cover (CC) data for the same period have also been digitized. The SD series exhibits a weak negative trend (without statistical significance) from the 1890s to the 1910s, which is in line with the early dimming period in SSR reported in some regions. Subsequently, no trends are obtained for the period 1910s–1950s, which indicates that the early brightening is not observed in Lisbon unlike other locations in the Iberian Peninsula. After that, two strong statistically significant trends are found for the periods 1950s–1980s and 1980s–2010s in line with the well-known global dimming and brightening periods in SSR, respectively. On the other hand, the CC series presents an increase from 1890 to the 1980s, followed by a decrease up to 2018 (both being statistically significant), which may partially explain the reported SD trends. An analysis of SD under cloudless conditions proved the utility of this quantity to track long-term changes in atmospheric aerosol load. In addition, this analysis and a seasonal one pointed out that aerosols seem to play a relevant role in SD long-term variability. • Sunshine duration and cloud cover records and trends in Lisbon over 1890–2018. • Cloud cover partially explains sunshine duration variability. • Atmospheric aerosol load seems to play a relevant role in sunshine duration trends. [ABSTRACT FROM AUTHOR]

Abstract: Columnar and ground level aerosol properties as well as mass concentrations of some gaseous pollutants were measured at two urban sites (Granada and Málaga, South Spain) before, during and after an extended stagnation episode from 7 to 13 February 2011. This long lasting event was associated with a very strong and persistent blocking high-pressure system over the Iberian Peninsula, together with very intense and persistent temperature inversions near the ground level. The columnar aerosol load at Granada showed a significant increase during this stagnation episode as indicated by aerosol optical depth at 440 nm, reaching values four times higher (0.6) than before and after the event. A significant increase in aerosol load at night time was also evidenced by star photometer measurements. Similarly, pronounced enhancement in columnar aerosol load was observed at Málaga, indicating the regional extension of this event. Analysis of ground level measurements obtained at Granada showed a significant increase in aerosol scattering coefficients and aerosol number concentrations during the stagnation episode. Furthermore, the analysis of aerosol size distribution measurements has evidenced the large contribution of fine particles at ground level as well as in the atmospheric column during the stagnation period. The fine mode radius measured at Granada showed a large displacement towards larger sizes together with a pronounced increase in the geometric standard deviation of the fine mode during the high pollution event in the morning hours on 9 February. This was attributed to the growth of aerosol particles due to coagulation and condensation processes as a result of the high fine aerosol load next to the surface favoured by the high pressure system and thermal inversion on that day. This increases in the radius and width of the fine mode results in more efficient scattering in the 440–1020 nm spectral range which, in combination with nearly constant and low imaginary refractive index (0.002) leads to high single scattering albedo with neutral spectral dependency. During the persistent temperature inversion episode the daily European PM10 mass concentration limit (50 μg m−3) was exceeded in Granada for most days and in Málaga for three consecutive days. Nevertheless, the mass concentrations of NO2, CO and O3 were below the European thresholds with a noticeable decrease in O3 mass concentration at both sites. [Copyright &y& Elsevier]

Abstract: The southern Iberian Peninsula is an important area for studying the columnar radiative properties of African desert dust air masses reaching Europe. The Aerosol Optical Depth (AOD) and Angström coefficient, α (440–1020nm), have been retrieved during the dust events reached at surface from 2005 to 2010 at Granada (37.18°N, 3.58°W, 680m a.m.s.l), using extinction measurements by means of a CIMEL CE 318-1 sun-photometer. In addition, sky radiance measurements performed in principal plane in conjunction with solar irradiance measurements were used to retrieve columnar aerosol size distributions, single scattering albedo and asymmetry parameter. During these desert dust intrusions, high values of AOD at 440nm (0.27±0.17) and low values of α (0.4±0.2) were found. These values indicate both high aerosol load and predominance of coarse particles during these events. The aerosol volume size distributions were bimodal, with the fine and coarse radius mode centered at 0.20μm and 2.41μm, respectively. The mean coarse to fine volume concentration ratio value was 11±6, showing a predominance of coarse particles in good agreement with α analysis. During these events, columnar aerosol single scattering albedo (ω0) increased with wavelength in accordance with previous works. However, the obtained values of ω0 in all wavelengths were lower than those reported by other authors during desert dust intrusions. The mixing of desert dust with absorbing particles from anthropogenic origin could explain the low ω0 values measured in the study area. [Copyright &y& Elsevier]

Abstract: To study tropospheric ozone variability over the Iberian Peninsula (IP), NASA Langley TOR data have been analyzed for the 1979–2005 period. The maximum tropospheric ozone concentration over the entire IP was found in June (∼41 DU) and a minimum in December (∼29 DU). However the maximum tropospheric ozone concentration was found over West Atlantic Coast (WAC) (∼44 DU), followed by Mediterranean Coast (MC) (∼42 DU), North Atlantic Coast (NAC) (∼41 DU), Central Iberian Peninsula (CIP) (∼40 DU) and Pyrenees Mountain Range (PMR) (∼39 DU) during June-July. The high concentration of tropospheric ozone in July over the Atlantic Ocean near IP is due to the presence of Azores anticyclone and related photochemistry and dynamics, and affects the observed higher tropospheric ozone concentration over WAC zone. Strong seasonal cycle in tropospheric ozone concentration has been observed with large variation over NAC (∼49%), followed by WAC (∼48%) and MC (∼41%) compared to CIP and PMR (∼38%) zones. When the data are compared over the IP for the two periods (1979–1993 and 1997–2005), a systematic increase in the number of months with higher tropospheric ozone concentration has been observed during the second period with respect to the first. These increases are almost 8% to 24% over NAC, 6% to 17% over WAC, 5% to 24% over CIP, 6% to 23% over MC and 13% to 18% over PMR, zones. It has been observed that topography, climatology and population density distribution plays a crucial role in the variability of tropospheric ozone concentration over the IP. [ABSTRACT FROM AUTHOR]

Abstract: In the discussion paper on our article (), de Laat has criticized TOR methodology and TOR data and thus questioned the validity of the findings. He has also pointed out the fact that the authors may have used the OMI/MLS data. In this reply to the discussion, the clarifications and references given herewith endeavour to undoubtedly answer the questions posed by de Laat on TOR methodology and on TOR data and thus proving that the findings of are scientifically justified and therefore entirely valid. Furthermore, reasons were presented to justify the non use of the OMI/MLS data. [Copyright &y& Elsevier]