Fewer clouds in the Mediterranean: consistency of observations and climate simulations

Sánchez-Lorenzo, Arturo; Enriquez-Alonso, Aarón; Calbó, Josep; González, Josep‐Abel; Wild, Martin; Folini, Doris; Norris, Joel R.; Vicente‐Serrano, Sergio M.

doi:10.1038/srep41475

Cited by 56 publications

(44 citation statements)

References 61 publications

(77 reference statements)

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“…Also, in some previous studies the dimming period observed between the 1950s and 1980s was mainly attributed to cloud changes instead of direct aerosol effects (Liepert, ). Stjern et al () and Parding et al () also found that changes in clouds are the main reason for trends in SSR in northern Europe, and in the Mediterranean observations indicate fewer clouds for the period 1971 to 2005 (Sanchez‐Lorenzo et al, ). In the United States, observed positive trends in SSR since the 1990s are also mainly attributed to changes in cloud cover (Augustine & Dutton, ).…”

Section: Discussionmentioning

confidence: 94%

Trends and Variability of Surface Solar Radiation in Europe Based On Surface‐ and Satellite‐Based Data Records

et al. 2018

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The incoming solar radiation is the essential climate variable that determines the Earth's energy cycle and climate. As long‐term high‐quality surface measurements of solar radiation are rare, satellite data are used to derive more information on its spatial pattern and its temporal variability. Recently, the EUMETSAT Satellite Application on Climate Monitoring (CM SAF) has published two satellite‐based climate data records: Surface Solar Radiation Data Set‐Heliosat, Edition 2 (SARAH‐2), and Clouds and Radiation Data Set based on AVHRR (advanced very high resolution radiometer) Satellite Measurements, Edition 2 (CLARA‐A2). Both data records provide estimates of surface solar radiation. In this study, these new climate data records are compared to surface measurements in Europe during the period 1983–2015. SARAH‐2 and CLARA‐A2 show a high accuracy compared to ground‐based observations (mean absolute deviations of 6.9 and 7.3 W/m2, respectively) highlighting a good agreement considering the temporal behavior and the spatial distribution. The results show an overall brightening period since the 1980s onward (comprised between 1.9 and 2.4 W/m2/decade), with substantial decadal and spatial variability. The strongest brightening is found in eastern Europe in spring. An exception is found for northern and southern Europe, where the trends shown by the station data are not completely reproduced by satellite data, especially in summer in southern Europe. We conclude that the major part of the observed trends in surface solar radiation in Europe is caused by changes in clouds and that remaining differences between the satellite‐ and the station‐based data might be connected to changes in the direct aerosol effect and in snow cover.

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Section: Discussionmentioning

confidence: 94%

Trends and Variability of Surface Solar Radiation in Europe Based On Surface‐ and Satellite‐Based Data Records

et al. 2018

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“…New dynamic thresholds for infrared-brightness temperature-difference features have been introduced, in particular for the differences relative to the 3.7 micron channel over arid and semi-arid regions. For CLARA-A1 some static thresholds were used previously which led to occasional false cloudiness and unrealistic cloud distributions and trends over semi-arid regions, as reported by Sun et al (2015) and Sanchez-Lorenzo et al (2017). The new thresholds are functions of surface emissivity (from MODIS climatologies) and viewing angles.…”

Section: Cloud Productsmentioning

confidence: 99%

CLARA-A2: the second edition of the CM SAF cloud and radiation data record from 34 years of global AVHRR data

et al. 2017

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Abstract. The second edition of the satellite-derived climate data record CLARA ("The CM SAF Cloud, Albedo And Surface Radiation dataset from AVHRR data" -second edition denoted as CLARA-A2) is described. The data record covers the 34-year period from 1982 until 2015 and consists of cloud, surface albedo and surface radiation budget products derived from the AVHRR (Advanced Very High Resolution Radiometer) sensor carried by polar-orbiting, operational meteorological satellites. The data record is produced by the EUMETSAT Climate Monitoring Satellite Application Facility (CM SAF) project as part of the operational ground segment. Its upgraded content and methodology improvements since edition 1 are described in detail, as are some major validation results. Some of the main improvements to the data record come from a major effort in cleaning and homogenizing the basic AVHRR level-1 radiance record and a systematic use of CALIPSO-CALIOP cloud information for development and validation purposes. Examples of applications studying decadal changes in Arctic summer surface albedo and cloud conditions are provided.

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“…On the other hand, 10 there are studies arguing that these changes in SSR, especially in pristine or remote areas, were mainly driven by natural changes in cloud cover and/or cloud properties (Dutton et al, 2006;Long et al, 2009;Augustine and Dutton, 2013;Stanhill et al, 2014). However for Europe, several studies have reported either no statistically significant trends in cloud cover since 1990 or no strong evidence that changes in cloud cover were mainly responsible for the observed SSR trends (Norris and Wild, 2007;Sanchez-Lorenzo et al, 2009, 2012, 2017aVetter and Wechsung, 2015). Furthermore, other studies that 15 focused on Europe pointed to aerosols, and especially the direct effect, as the main driver for the brightening since the mid1980s (Ruckstuhl et al, 2008(Ruckstuhl et al, , 2010Ruckstuhl and Norris, 2009;Folini and Wild, 2011;Wang et al, 2012b;Cherian et al, 2014;Nabat et al, 2014;Turnock et al, 2015;Manara et al, 2016).…”

Section: Introductionmentioning

confidence: 94%

Modeling the impact of solar brightening on summer surface ozone over Europe between 1990 and 2010

Oikonomakis

Aksoyoğlu

Wild

et al. 2018

Preprint

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10Surface solar radiation (SSR) observations have indicated an increasing trend in Europe since the mid-1980s, referred to as solar "brightening". In this study, we used the regional air quality model, CAMx (Comprehensive Air Quality Model with extensions) to simulate and quantify, with various sensitivity runs (where the year 2010 served as the base case), the effects of increased radiation on photolysis rates (PHOT1, PHOT2 and PHOT3 scenarios) and biogenic volatile organic compounds (BVOCs) emissions (BIO scenario), and their consequent impacts on summer surface ozone concentrations over Europe 15 between 1990 and 2010. The PHOT1 and PHOT2 scenarios examined the effect of doubling and tripling the anthropogenic PM 2.5 concentrations, respectively, while the PHOT3 investigated the impact of an increase in just the sulfate concentrations by a factor of 3.4 (as in 1990), applied only to the calculation of photolysis rates. In the BIO scenario, we reduced the 2010 SSR by 3% (keeping plant cover and temperature the same), re-calculated the biogenic emissions and repeated the base case simulations with the new biogenic emissions. The impact on photolysis rates for all three scenarios was an increase (in 2010 20 compared to 1990) of 3-6% which resulted in daytime (10:00-18:00 Local Mean Time (LMT)) mean surface ozone differences of 0.2-0.7 ppb (0.5-1.5%), with the largest hourly difference rising as high as 4-8 ppb (10-16%). The effect of changes in BVOCs emissions on daytime mean surface ozone was much smaller (up to 0.08 ppb, ~ 0.2%), as isoprene and terpene (monoterpene and sesquiterpene) emissions increased only by 2.5-3% and 0.7%, respectively. Overall, the impact of the SSR changes on surface ozone was greater via the effects on photolysis rates compared to the effects on BVOCs 25 emissions, and the sensitivity test of their combined impact (PHOT3+BIO = COMBO scenario) showed nearly additive effects. In addition, all the sensitivity runs were repeated on a second base case with increased NO x emissions to account for any potential underestimation of modeled ozone production; the results did not change significantly in magnitude, but the spatial coverage of the effects was profoundly extended. Finally, the role of the solar "brightening" in the European summer surface ozone trends was suggested to be more important when comparing to the order of magnitude of the ozone trends 30Atmos. Chem. Phys. Discuss., https://doi

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Fewer clouds in the Mediterranean: consistency of observations and climate simulations

Cited by 56 publications

References 61 publications

Trends and Variability of Surface Solar Radiation in Europe Based On Surface‐ and Satellite‐Based Data Records

Trends and Variability of Surface Solar Radiation in Europe Based On Surface‐ and Satellite‐Based Data Records

CLARA-A2: the second edition of the CM SAF cloud and radiation data record from 34 years of global AVHRR data

Modeling the impact of solar brightening on summer surface ozone over Europe between 1990 and 2010

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