Preliminary characterization of columnar aerosol properties (AOD-AE) at the saharan tamanrasset (Algeria) station

Postprint (published version

Caracterización preliminar de las propiedades del aerosol en columna (EOA-EA) en la estación sahariana de Tamanrasset (Argelia)

A Cimel sun photometer has been in operation at Tamanrasset station since late 2006. In this study, more than two years of aerosol measurements have been analyzed from October 2006 to January 2009. Two parameters, aerosol optical depth (AOD) and Ångström exponent (AE), have been used for this preliminar characterization. At this station, the mean AOD is 0.25±0.15 and the mean AE is 0.48±0.23. Both time series data show a clear seasonal cycle. A dry-cool season (fall and winter time), characterized by low AOD and high AE values, and a wet-hot season (in spring-summer), with strong and frequent mineral dust storms, giving high AOD and low AE values, are observed at Tamanrasset. Both, AOD and AE values show the behaviour of a station where desert mineral dust is the prevailing aerosol defining the characteristic of the site. However a significant number of episodes with AE values around 1 together with AOD greater than 0.2 have been found, what suggests the presence of pollution derived aerosols.Financial supports from the Spanish MICIIN (ref. CGL2008-05939-CO3-00/CLI and CGL 2009-09740) and from the GR-220 Project of the Junta de Castilla y León are gratefully acknowledged

PHOTONS/AERONET sunphotometer network overview. Description – Activities - Results

Fourteenth International Symposium on Atmospheric and Ocean Optics/Atmospheric Physics celebrado del 24 al 30 de junio de 2007 en Buryatia, Russia

The AERONET-Europe calibration facility: access within the ACTRIS project

Comunicación presentada en: 2012 European Aerosol Conference (EAC-2012), B-WG01S2P30, celebrada del 2 al 7 de septiembre de 2012 en Granada.This work has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement N. 262254. Financial support from the Spanish Ministry of Science (MICINN) under projects with ref. CGL2009-09740, CGL2011-23413, CGL2010-09480-E and CGL2011-13085-E as well as from Junta de Castilla y León are gratefully acknowledged

Pointing error and field of view of AERONET CIMEL-318 sun photometers

Resumen de la comunicación oral presentada en: 1st Iberian Meeting on Aerosol Science and Technology – RICTA 2013, celebrado del 1 al 3 de julio de 2013 en Évora, Portugal

Assessment of nocturnal aerosol optical depth from lunar photometry at the Izaña high mountain observatory

This work involves a first analysis of the systematic errors observed in the AOD retrieved at nighttime using the Sun–sky–lunar CE318-T photometer. In this respect, this paper is a first attempt to correct the AOD uncertainties that currently affect the lunar photometry by means of an empirical regression model. We have detected and corrected an important bias correlated to the Moon's phase and zenith angles, especially at longer wavelength channels.AERONET Sun photometers at Izaña have been calibrated within the AERONET Europe TNA, supported by the European Union’s Horizon 2020 research and innovation program under grant agreement no. 654109 (ACTRIS-2)

Quantification of surface water volume changes in the Mackenzie Delta using satellite multi-mission data

Quantification of surface water storage in extensive floodplains and their dynamics are crucial for a better understanding of global hydrological and biogeochemical cycles. In this study, we present estimates of both surface water extent and storage combining multi-mission remotely sensed observations and their temporal evolution over more than 15 years in the Mackenzie Delta. The Mackenzie Delta is located in the northwest of Canada and is the second largest delta in the Arctic Ocean. The delta is frozen from October to May and the recurrent ice break-up provokes an increase in the river's flows. Thus, this phenomenon causes intensive floods along the delta every year, with dramatic environmental impacts. In this study, the dynamics of surface water extent and volume are analysed from 2000 to 2015 by combining multi-satellite information from MODIS multispectral images at 500 m spatial resolution and river stages derived from ERS-2 (1995–2003), ENVISAT (2002–2010) and SARAL (since 2013) altimetry data. The surface water extent (permanent water and flooded area) peaked in June with an area of 9600 km2 (±200 km2) on average, representing approximately 70 % of the delta's total surface.\ud Altimetry-based water levels exhibit annual amplitudes ranging from 4 m in the downstream part to more than 10 m in the upstream part of the Mackenzie Delta. A high overall correlation between the satellite-derived and in situ water heights (R > 0.84) is found for the three altimetry missions. Finally, using altimetry-based water levels and MODIS-derived surface water extents, maps of interpolated water heights over the surface water extents are produced. Results indicate a high variability of the water height magnitude that can reach 10 m compared to the lowest water height in the upstream part of the delta during the flood peak in June. Furthermore, the total surface water volume is estimated and shows an annual variation of approximately 8.5 km3 during the whole study period, with a maximum of 14.4 km3 observed in 2006. The good agreement between the total surface water volume retrievals and in situ river discharges (R =  0.66) allows for validation of this innovative multi-mission approach and highlights the high potential to study the surface water extent dynamics

Column aerosol optical properties and aerosol radiative forcing during a serious haze-fog month over North China Plain in 2013 based on ground-based sunphotometer measurements

In January 2013, North China Plain experienced several serious haze events. Cimel sunphotometer measurements at seven sites over rural, suburban and urban regions of North China Plain from 1 to 30 January 2013 were used to further our understanding of spatial-temporal variation of aerosol optical parameters and aerosol radiative forcing (ARF). It was found that Aerosol Optical Depth at 500 nm (AOD500 nm) during non-pollution periods at all stations was lower than 0.30 and increased significantly to greater than 1.00 as pollution events developed. The Angstrom exponent (Alpha) was larger than 0.80 for all stations most of the time. AOD500 nm averages increased from north to south during both polluted and non-polluted periods on the three urban sites in Beijing. The fine mode AOD during pollution periods is about a factor of 2.5 times larger than that during the non-pollution period at urban sites but a factor of 5.0 at suburban and rural sites. The fine mode fraction of AOD675 nm was higher than 80% for all sites during January 2013. The absorption AOD675 nm at rural sites was only about 0.01 during pollution periods, while ~0.03–0.07 and 0.01–0.03 during pollution and non-pollution periods at other sites, respectively.This work is financially supported by grants from the National Key Project of Basic Research (2011CB403401 and 2014CB441201), the Project (41005086, 41275167 and 41130104) supported by NSFC, the Strategic Priority Research Programme of the Chinese Academy of Sciences (Grant no. XDA05100301), CAMS Basis Research Project (2012Y02 and 2013Z007). Cimel master calibration of CARSNET was performed at the AERONET-EUROPE calibration center (LOA and AEMET-Tenerife), supported by ACTRIS (European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 262254

Evaluation of night-time aerosols measurements and lunar irradiance models in the frame of the first multi-instrument nocturnal intercomparison campaign

The first multi-instrument nocturnal aerosol optical depth (AOD) intercom-parison campaign was held at the high-mountain Iza ̃na Observatory (Tener-ife, Spain) in June 2017, involving 2-minutes synchronous measurements fromtwo different types of lunar photometers (Cimel CE318-T and Moon Preci-sion Filter Radiometer, LunarPFR) and one stellar photometer. The Robotic Lunar Observatory (ROLO) model developed by the U.S. Geological Survey(USGS) was compared with the open-access ROLO Implementation for Moonphotometry Observation (RIMO) model. Results showed rather small differ-ences at Iza ̃na over a 2-month time period covering June and July, 2017(±0.01 in terms of AOD calculated by means of a day/night/day coherencetest analysis and±2 % in terms of lunar irradiance). The RIMO model hasbeen used in this field campaign to retrieve AOD from lunar photometricmeasurements. No evidence of significant differences with the Moon’s phase angle wasfound when comparing raw signals of the six Cimel photometers involved inthis field campaign.The raw signal comparison of the participating lunar photometers (Cimeland LunarPFR) performed at coincident wavelengths showed consistent mea-surements and AOD differences within their combined uncertainties at 870 nmand 675 nm. Slightly larger AOD deviations were observed at 500 nm, point-ing to some unexpected instrumental variations during the measurement pe-riod.Lunar irradiances retrieved using RIMO for phase angles varying between0◦and 75◦(full Moon to near quarter Moon) were compared to the irradi-ance variations retrieved by Cimel and LunarPFR photometers. Our resultsshowed a relative agreement within±3.5 % between the RIMO model andthe photometer-based lunar irradiances.The AOD retrieved by performing a Langley-plot calibration each nightshowed a remarkable agreement (better than 0.01) between the lunar pho-tometers. However, when applying the Lunar-Langley calibration using RIMO,AOD differences of up to 0.015 (0.040 for 500 nm) were found, with differ-ences increasing with the Moon’s phase angle. These differences are thoughtto be partly due to the uncertainties in the irradiance models, as well asinstrumental deficiencies yet to be fully understood.High AOD variability in stellar measurements was detected during thecampaign. Nevertheless, the observed AOD differences in the Cimel/stellarcomparison were within the expected combined uncertainties of these twophotometric techniques. Our results indicate that lunar photometry is amore reliable technique, especially for low aerosol loading conditions.The uncertainty analysis performed in this paper shows that the com-bined standard AOD uncertainty in lunar photometry is dependent on thecalibration technique (up to 0.014 for Langley-plot with illumination-basedcorrection, 0.012-0.022 for Lunar-Langley calibration, and up to 0.1 for the 2 Sun-Moon Gain Factor method). This analysis also corroborates that theuncertainty of the lunar irradiance model used for AOD calculation is withinthe 5-10 % expected range.This campaign has allowed us to quantify the important technical diffi-culties that still exist when routinely monitoring aerosol optical propertiesat night-time. The small AOD differences observed between the three typesof photometers involved in the campaign are only detectable under pristinesky conditions such as those found in this field campaign. Longer campaignsare necessary to understand the observed discrepancies between instrumentsas well as to provide more conclusive results about the uncertainty involvedin the lunar irradiance model