OMI UV spectral irradiance: comparison with ground based measurements in an urban environment

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OMI UV spectral irradiance: comparison with ground based measurements in an urban environment. Stelios Kazadzis A. Bais, A. Arola OMI science team meeting Helsinki, June 2008 Finnish Meteorological Institute Laboratory of Atmospheric Physics, Thessaloniki, Greece. Outline. - PowerPoint PPT Presentation

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<ul><li><p>*OMI UV spectral irradiance: comparison with ground based measurements in an urban environmentStelios KazadzisA. Bais, A. Arola</p><p>OMI science team meeting Helsinki, June 2008</p><p>Finnish Meteorological InstituteLaboratory of Atmospheric Physics, Thessaloniki, Greece</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Outline</p><p>OMI ground based UV spectral irradiance comparison statisticsAerosol absorption post correction approachesCampaign: Spacial and temporal UV variability within an OMI grid</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*The problem - absorbing aerosolsCurrent OMI UV algorithm does not account for absorbing aerosols (e.g. organic carbon, smoke, dust ) OMI GB UV comparison statisticsTanskannen et al., JGR 2007Tokyo: +32%</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Thessaloniki Area </p><p>OMI GB UV comparison statisticsHigh aerosol load - Aerosol transport Sahara dust intrusions Biomass burning from NE - Very high PM10 conc.Sahara - Dream modelFire hot spots - summer</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Instrumentation - comparisonOMI GB UV comparison statisticsRooftop of the School of Natural Sciences Brewer instrument (spectral-calibrated, wavelength shift corrected) UV irradiance at 305, 324, 380 nm and CIE Total column ozone spectral AOD at UV wavelengths CIMEL AOD (340nm) , SSA(440nm), .. NILU-UV 305nm, 324nm, 340nm, 380nm Cloud cloudless case separation Pyranometer, observations, sky camera pix Daily OMI overpass time (mean over 15 minutes) Thessaloniki September 2004-December 2007</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Results OMI GB UV comparison statistics 305nm OMI +30% 324nm OMI +17% </p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Results OMI GB UV comparison statistics 380nm OMI +11% CIED OMI +20% </p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Results - statisticsOMI GB UV comparison statistics</p><p>Wavel.(nm)All datacloudlessmR2W10W20mR2W10W203051.300.9443.368.21.270.9564.887.63241.170.8951.373.11.150.9176.992.43801.130.8947.270.71.110.9171.889.7CIED1.200.9351.575.41.190.9575.091.9</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Results - statisticsOMI GB UV comparison statistics</p><p>Wavel.(nm)All datacloudlessmR2W10W20mR2W10W203051.300.9443.368.21.270.9564.887.63241.170.8951.373.11.150.9176.992.43801.130.8947.270.71.110.9171.889.7CIED1.200.9351.575.41.190.9575.091.9</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Post correction methodsPost correction methods - TOMS experienceCloudless cases: Ta() = AOD() * [1 - SSA()]</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*UV attenuation Thessaloniki, cloudless casesPost correction methods</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Post correction : method 1 Ta () = AOD() * [1 - SSA(440nm)] Aerosol absorption CF() = 1.1 + 1.5 * Ta() Post correction methodsno sza dependenceSSA @ UV ?need of GB data </p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Post correction: method 2Tas =Ta / cos(sza) Aerosol absorption CF() = 1.07 + 1.8 * Tas() Post correction methodsSSA @ UV ?need of GB data </p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Post correction: use of RT model Post correction methodsS1: AOD and SSA synchronous measurements S2: AOD and SSA@440 = const S3: AOD= const and SSA@340 = constAbs + scat scat</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Overview of post corrections6th Approach: CF() = 1 + 3 * Ta() Table with all the results of the 6 approaches:Post correction methods</p><p>OMI/Brewer ratio [R]Method305 nm Mean (1)324 nm Mean (1)380 nm Mean (1)ObsOriginalNo correction1.27 (0.15)1.15 (0.10)1.11 (0.12)267S1Apply Ta slope1.17 (0.13)1.07 (0.09)1.05 (0.13)135S2Apply Tas slope1.18 (0.13)1.09 (0.10)1.05 (0.13)135M1Model 1.13 (0.12)1.04 (0.08)1.01 (0.11)135M2Model constant SSA1.14 (0.13)1.03 (0.09)0.99 (0.10)267M3Model const. SSA-AOD1.12 (0.13)1.02 (0.09)0.98 (0.10)267S31 + 3 * Ta ()1.11 (0.13)1.03 (0.10)1.01 (0.11)135</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Overview of post corrections6th Approach: CF = 1 + 3 * Ta() Table with all the results of the 6 approaches:Post correction methods</p><p>OMI/Brewer ratio [R]Method305 nm Mean (1)324 nm Mean (1)380 nm Mean (1)ObsOriginalNo correction1.27 (0.15)1.15 (0.10)1.11 (0.12)267S1Apply Ta slope1.17 (0.13)1.07 (0.09)1.05 (0.13)135S2Apply Tas slope1.18 (0.13)1.09 (0.10)1.05 (0.13)135M1Model 1.13 (0.12)1.04 (0.08)1.01 (0.11)135M2Model constant SSA1.14 (0.13)1.03 (0.09)0.99 (0.10)267M3Model const. SSA-AOD1.12 (0.13)1.02 (0.09)0.98 (0.10)267S31 + 3 * Ta ()1.11 (0.13)1.03 (0.10)1.01 (0.11)135</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Overview of post corrections6th Approach: CF = 1 + 3 * Ta() Table with all the results of the 6 approaches:Post correction methods</p><p>OMI/Brewer ratio [R]Method305 nm Mean (1)324 nm Mean (1)380 nm Mean (1)ObsOriginalNo correction1.27 (0.15)1.15 (0.10)1.11 (0.12)267S1Apply Ta slope1.17 (0.13)1.07 (0.09)1.05 (0.13)135S2Apply Tas slope1.18 (0.13)1.09 (0.10)1.05 (0.13)135M1Model 1.13 (0.12)1.04 (0.08)1.01 (0.11)135M2Model constant SSA1.14 (0.13)1.03 (0.09)0.99 (0.10)267M3Model const. SSA-AOD1.12 (0.13)1.02 (0.09)0.98 (0.10)267S31 + 3 * Ta ()1.11 (0.13)1.03 (0.10)1.01 (0.11)135</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Overview of post corrections6th Approach: CF = 1 + 3 * Ta() Table with all the results of the 6 approaches:Post correction methods</p><p>OMI/Brewer ratio [R]Method305 nm Mean (1)324 nm Mean (1)380 nm Mean (1)ObsOriginalNo correction1.27 (0.15)1.15 (0.10)1.11 (0.12)267S1Apply Ta slope1.17 (0.13)1.07 (0.09)1.05 (0.13)135S2Apply Tas slope1.18 (0.13)1.09 (0.10)1.05 (0.13)135M1Model 1.13 (0.12)1.04 (0.08)1.01 (0.11)135M2Model constant SSA1.14 (0.13)1.03 (0.09)0.99 (0.10)267M3Model const. SSA-AOD1.12 (0.13)1.02 (0.09)0.98 (0.10)267S31 + 3 * Ta ()1.11 (0.13)1.03 (0.10)1.01 (0.11)135</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Correction resultsPost correction methods305nm +11%380nm +0%324nm +2%</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Effects of sza, AOD, SSA, ozone, time on ratiosPost correction methods</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Campaign: 1 to 30 October, 2007Spatial and temporal UV variability within an OMI grid3 sites Each: NILU UV at 305, 324, 380nm CIMEL (AOD, SSA, ..) Pyranometer, sky camera Main site + Brewers Spectral UV, ozone CCD (spectral AOD) 2 Lidars (City Rural) </p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*UV Measurements at the three sitesSpatial and temporal UV variability within an OMI grid</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*AOD variability in an OMI gridSpatial and temporal UV variability within an OMI grid</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*UV differences in an OMI gridSpatial and temporal UV variability within an OMI grid+20%-20%</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Spatial UV variability at 3 stations (2 * sigma / mean)*100Spatial and temporal UV variability within an OMI grid</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Temporal UV variabilitySpatial and temporal UV variability within an OMI grid(2 * sigma / mean)*100</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Conclusions3.5 years of OMI and ground based at Thessaloniki, Greece: measurement comparison showed an OMI overestimation of UV irradiances. Cloudless cases: Main reason is the aerosol absorption. Higher deviations at lower wavelengths</p><p>Possible methods to correct this effect: AOD and SSA measurements or/and an aerosol absorption climatology needed in a global scale</p><p>SSA in the UV: while mean SSA at 440 nm is 0.90 (Thessaloniki) an SSA of 0.82 is needed for eliminating GB and OMI UV differences at 305nm. SSA at UV-B wavelengths needs further investigation. </p><p>Simple public information (e.g. UVINDEX) retrieved from OMI at such populated-urban areas are affected from this bias. +20% on cloudless day. </p><p>Aerosol variation within an OMI satellite pixel can cause UV differences equal to a percentage (~18%) that 90% of cloudless comparison cases lie within. Statistical analysis limitations ?</p><p>Spatial and temporal UV variability has to be taken into account when comparing GB and satellite UV, especially at city areas.</p><p>Comparison under cloudy conditions requires more investigation as absolute differences are large and spatial and temporal UV variability plays a very important role on single station satellite, comparison.</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Thank you</p><p>Campaign acknowledgments:D. Balis, N. Kouremeti, V. Amiridis, M. Zebila,E. Giannakaki, J. Herman, AERONET </p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*OMI GB normalized biases 3 stationsSpatial and temporal UV variability within an OMI grid</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Back up air masses 4 day back traj</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Back up Lidar 2 days </p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Back up TOMS and UVA correction</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Back up Brewer MODIS (2000-2007)</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Back up Brewer AOD (1996-2007)</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Back up SSA Thessaloniki (1998-2005)</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*Back up SSA scout</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p></li><li><p>*Stelios Kazadzis, OMI science team meeting Helsinki, June 2008*</p><p>Spectral measurements of direct and global UV irradiance at the surface were made with two Brewer spectroradiometers. In addition, global (diffuse plus direct) UV irradiance and photosynthetically active radiation (PAR) were measured, on a minute basis, at each of the three sites with three NILU-UV multi-channel radiometers. In-situ measurements of aerosol vertical profiles were derived from two Lidar systems operating at (AUTH) and the site of Epanomi.Total ozone column was derived from the Brewers and cloud observations and sky images at the AUTH site. Cloud observations were performed at all sites at a half hour basis.Sun and sky radiance measurements were conducted with three CIMEL automatic sun tracking photometers, each installed at one of the three sites. These data were used to derive aerosol optical properties such as the aerosol optical depth (AOD), the Angstrom exponent a (AEa) and the single scattering albedo (SSA).</p><p>Spatial and temporal UV variability within an OMI grid</p><p>Stelios Kazadzis, OMI science team meeting Helsinki, June 2008</p><p>*Name, fmi, present resukts*OutlineI will present a comparison of 3.5 years of OMI and GB spectral UV irradiance measurementsReffering to aerosol absorption problem neglected by the OMI UV retrieval algorithm. Introduce some possible post correction proceduresResults of a experimental campaign with UV and aerosol spectrla measurements within an OMI viewing grid*Motivation: current OMI UV algorithm does not account for absorbing aerosolsPrevious work by Tanskannen showed that OMI comparison with pristine sites as Lauder provide good results but Omi overestimates UV irradiance at urban areas.Comparison for the first year of OMI life and for Daily erythemal irradiance*Thessaloniki: Eastern Mediterranean city with 1.2 mil. Highest AOD in European levelBoth local sources and also aerosol transport (saharan dust, aerosol from biomass burning activities from NE) PM10 concentration exceeding daily limit of 50mg/cm3 more than 200 days per year (mean of 70 -80 mg/cm3)</p><p>The site is facing the Aegean Sea to the south and west and is situated along expected pathways through which pollution from central and Eastern Europe influences aerosol loading over the Eastern Mediterranean (Amiridis et al., 2005). Aerosol optical depth (AOD) measurement records (Kazadzis et al., 2007) show that AOD values at Thessaloniki area are among the highest in a European level. </p><p>The color indicates the dominant land cover where the detection occurred. Land cover classes were combined into five final categories which are Forest,.We observe that the main source of smoke from the region of Black Sea is mainly attributed to agricultural burning activities. The type of burning land is critical for the determination of the source emission properties of the smoke.</p><p>*Intercomparison exercise spetember 2004 -december 2007Measurements that were conductedBrewer, cimel, nilu, cloud separationOMI </p><p>*Results Y axsis Br...</p></li></ul>

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