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Comparing aerosol extinctions measured

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Comparing aerosol extinctions measured by Stratospheric Aerosol andGas Experiment (SAGE) II and III satellite experiments in 2002 and2003Glenn K. YueNASA Langley Research Center, Hampton, Virginia, USACheng-Hsuan LuRS Information Systems, McLean, Virginia, USAPi-Huan WangScience and Technology Corporation, Hampton, Virginia, USAReceived 3 September 2004; revised 10 December 2004; accepted 15 March 2005; published 1 June 2005.[1] SAGE II and SAGE III are two satellite experiments designed to measure aerosolextinctions and concentrations of trace gases in the atmosphere by using the techniques ofsolar and/or lunar occultation. SAGE II was launched in October 1984, while SAGE IIIwas launched in December 2001. Four of the nine aerosol channels used by SAGE IIIare centered at wavelengths very close to that of the four SAGE II aerosol channels. Since27 February 2002, the first day of SAG E III data set, there are occasions when SAGE IIand III measurement locations on the same day are nearly coincident, thereby providingopportunities for a unique measurement comparison. In this paper, the comparison ofaerosol extinctions and optical depths at four wavelengths measured by SAGE II andSAGE III in 2002 and 2003 is reported. It was found that in the main aerosol layer,between about 18 to 26 km, differences are less than about 30%. Larger differences areshown at altitudes near the tropopause and around 30 km. In general, SAGE IIIextinctions at 385 nm are higher than that measured by SAGE II, but the opposite is truefor 1020 nm. At 452 nm, SAGE II and SAGE III extinctions are in good agreement andthe differences are about 10 to 15%.Citation: Yue, G. K., C.-H. Lu, and P.-H. Wang (2005), Comparing aerosol extinctions measured by Stratospheric Aerosol and GasExperiment (SAGE) II and III satellite experiments in 2002 and 2003, J. Geophys. Res., 110, D11202, doi:10.1029/2004JD005421.1. Introduction[2] Aerosol exti nctions are major products of severalsolar occultation experiments i ncluding NASA’s Strato-spheric Aerosol Measurement (SAM) II, StratosphericAerosol and Gas Experiment (SAGE) I, SAGE II, andSAGE III. Other satellite experiments, such as Polar Ozoneand Aerosol Measurement (POAM) II and III [Lucke et al.,1999], Halogen Occultation Experiment (HALOE) [Russellet al., 1993], and Improved Limb Atmospheric Spectrom-eter (ILAS) [Sasano et al., 1995], also measure aerosolextinctions in the atmosphere. SAM II was launched on24 October 1978 aboard the NIMBUS 7 satellite. SAGE Iwas launched on 18 February 1979 aboard the ApplicationExplorer Mission-B satellite [McCormick et al., 1979].SAM II and SAGE I already ceased collecting data manyyears ago.[3] SAGE II and SAGE III are still operational. SAGE IIwas launched on 5 October 1984 aboard the Earth RadiationBudget Satellite. The sensors in SAGE II measure aerosolextinctions at 385, 452, 525, and 1020 nm [ Mauldin et al.,1985; McCormick, 1987; Yue, 1999]. The SAGE III missionis a joint partnership between NASA and the RussianFederal Space Agency (FSA). The primary scientific objec-tive of SAGE III is to obtain high quality, global measure-ments of key components of atmospheric compositionincluding aerosols, clouds, trace gases, temperature, andtheir long-term variability [Chu et al., 2002]. The SAGE IIIinstruments were launched aboard a Meteor-3M spacecrafton 10 December 2001 and started routinely collecting datasince 27 February 2002. The nine aerosol channels inSAGE III are centered at 385, 449, 521, 602, 676, 756,869, 1020, and 1550 nm. Two of the nine aerosol wave-lengths match identically to two SAGE II aerosol wave-lengths (e.g., 385 and 1020 nm); two others match veryclosely to two other SAGE II aerosol wavelengths (e.g., 449and 521 nm). SAGE II conducts solar occultation measure-ments only, but SAGE III conducts both solar and lunaroccultation measurements. Solar occultation measurementsare designed to measure the intensity of solar radiationtraversing the Earth’s limb, during each sunrise and sunsetevent encountered by the spacecraft as it orbits the Earth.Lunar occultation measurements are designed to measureJOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D11202, doi:10.1029/2004JD005421, 2005Copyright 2005 by the American Geophysical Union.0148-0227/05/2004JD005421$09.00D11202 1of11the intensity of radiation reflected by the moon, and areused for monitoring trace gases only. Both SAGE II andSAGE III aerosol measurements have a vertical resolutionof 0.5 km.[4] When instruments in two satellites are meas uringaerosol extinctions on the same day, their measurementlocations may be very close to each other, and hence theyprovide opportunities for comparative study. Comparingmeasurements by different sensors can provide a criticalassessment of the end-to-end performance of the measure-ment systems and can validate the consistency of theinferred aerosol vertical extinction profiles at differentwavelengths. Most importantly, comparative studies allowus to assess the feasibility of linking different data recordsfor long-term trend investigation.[5 ] A comparison of SAM II and SAGE I aerosolextinction was reported by Yue et al. [1984]. A similarstudy of SAM II and SAGE II was reported by Yue et al.[1989]. The extinctions of main aerosol layers measured bydifferent satellite experiments are in reasonably good agree-ment. Comparisons of aerosol properties after the eruptionof Pinatubo observed by SAGE II and lidar measurementswere reported by Yue et al. [1995a]. Comparisons of aerosolsurface area densities deduced by SAGE II extinctions andmeasured by Stratospheric Photochemistry, Aerosols andDynamics Expedition (SPADE) experiments were reportedFigure 1. SAGE II and SAGE III latitudinal coverage from 2002 to 2003.Table 1. Dates and Latitude Ranges for Different Coincidence GroupsCoincidenceGroup DateLatitude RangeNumber of MeasurementsSage II SAGE IIIA 8 –9 May 2002 52.6°N –55.1°N 53.0°N –53.4°N6B 8 June 2002 44.9°N –46.2°N 46.5°N –47.0°N6C 25 –27 April 2003 58.9°N –62.7°N 60.6°N –61.4°N13D 6 –8 Sept. 2003 69.4°N –71.2°N 70.0°N –70.7°N13E 4 –5 April 2002 46.4°S –49.9°S 47.8°S – 48.7°S9F 22 –24 Aug. 2002 51.3°S –53.6°S 52.2°S – 54.0°S13G 6 –7 Nov. 2002 43.7°S –46.7°S 44.3°S – 46.0°S9H 17 –18 Jan. 2003 34.1°S –36.9°S 34.8°S – 36.4°S4I 25 –26 March 2003 48.5°S –50.6°S 48.9°S – 50.8°S8J 24 –25 Oct. 2003 48.1°S –50.8°S 48.8°S – 50.4°S8D11202 YUE ET AL.:


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