ACTRIS TNA Activity Report

Transcription

1 ACTRIS TNA Activity Report Characterization of Aerosol mixtures of Dust And MArine origin by synergy of lidar, sunphotometer and surface/airborne in situ, ADAMA Natalia Kouremeti Introduction and motivation Information about aerosol/cloud characterization is becoming an important topic in the context of current (e.g Flex, CarbonSat) and future Earth Observation optical mission concepts. Related data products are crucial for atmospheric correction or even serve as potential spin off products. Required information about the aerosol and cloud types should be inferred by a common aerosol/cloud classification scheme, applicable to the related missions. Therewith, a clear need to consolidate a harmonized aerosol/cloud database for these purposes exists. The well established European Aerosol Research Lidar Network (EARLINET) offers the unique opportunity to support such an effort. Several EARLINET stations operate multi wavelength Raman lidars, with most of them measuring particle depolarization as well. Network s so called core stations deliver the needed parameter set, so that conversion factors for a variety of aerosol types can be derived experimentally over a comparably long time period. However, EARLINET database suffers from lack of information for specific aerosol types such as marine and mixed dust/marine cases. Unfortunately, these types are not observed in EARLINET s core stations, since the stations are mostly located at continental sites and are influenced by urban pollution. Moreover, the lidar systems near the coastlines suffer from the inability to measure at the first few hundred meters (5 m) due to their technical design, which results in an incomplete laser/telescope overlap region. Thus, no information can be retrieved from the region where we usually find marine particles. The lack of marine characterization from the ground segment is a major problem in space lidar data analysis since the majority of the global retrievals are over oceans. An uncertainty on the spectral conversion factors for marine and marine/mixed aerosol types could directly inherited to any radiative forcing analysis over the globe. For this purpose the ADAMA (Characterization of Aerosol mixtures of Dust And MArine origin by synergy of lidar, sunphotometer and surface/airborne in situ measurements) campaign was organized at Finokalia, Greece during June July 24. Scientific objectives The general objectives of the ADAMA campaign are to derive optical, microphysical and chemical properties of the aerosol marine component and its mixture with dust, employing sophisticated instrumentation installed on Finokalia ACTRIS site. Specifically, aerosol characterization will be established by ground based active/passive remote sensing techniques, surface in situ measurements and airborne UAV observations. The objectives linked to this TNA are to provide high quality aerosol optical depth (AOD) measurements for marine aerosols and the analysis of the radiometric and lidar data to provide microphysical aerosol properties. The PMOD/WRC participated in the campaign providing spectral, high frequency AOD measurements with a new Precision SpectroRadiometer (PSR_3). Reason for choosing station

2 Finokalia station is a remote site unaffected from urban pollution and close to the sea coast; this makes this location ideal for investigating pure marine aerosol cases. The long record of in situ measurements of sophisticated instrumentation for chemical composition analysis as well as the parallel measurements during this experiment would give valuable information. Moreover, the free of obstacles horizon and the moderate elevation of the station, which minimizes sea spray effect on the instrumentation, ensure high quality direct sun and radiance measurements. Method and experimental set up The instrumentation and experimental set up of the ADAMA campaign is described in detail on In this TNA report we are focusing on the aerosol optical depth and irradiance measurements acquired with the Precision SpectroRadiometer (PSR) and the CIMEL (NOA AERONET) sunphotometer as well as the products of GARRLiC inversion algorithm (Generalized Aerosol Retrieval from Radiometer and Lidar Combined data). The PSR provides absolute direct irradiance and aerosol optical depth data in the spectral range 35 2nm with a resolution of.7nm and has been developed by the World Optical Depth Research and Calibration Center (WORCC) of the PMOD/WRC. The measurement frequency of the PSR is less than min, providing high temporal information of the radiation field and the aerosol variability. The PSR was installed at Finokalia station, besides the CIMEL sunphotometer, on 22 June 24 and was operated until the end of the campaign 7 July 24. During this period the instrument performed direct sun measurements from sunrise to sunset, with some interruption due to power failure. Prior to the campaign the PSR was calibrated in Observatory of Izaña, Tenerife, Canary Islands, during the period March June, 24 and compared to the collocated reference CIMEL operated by the federated networks of AERONET, PHOTONS and RIMA. The PSR calibration just before the campaign ensured high quality data. The GARRLiC inversion algorithm (Lopatin et al., 23) is optimized for inversions of combined observations by radiometer and multi wavelength elastic lidar observations. It was further optimized, in the frame of ACTRIS, in order to derive optical, microphysical and chemical properties of the marine component and its mixture with dust. The aim during the campaign was the comparison of the aerosol optical depth and Angstrom exponent between the PSR and CIMEL AERONET (relocated ATHENS NOA) and the investigation of possibly extracting more information of the optical properties of the aerosol types using the whole spectral information. The CIMEL data found in good agreement with the PSR data will be used in the synergetic lidar/sunphotometer GARRLiC algorithm Preliminary results and conclusions The time series of AOD measured during the ADAMA campaign are shown in Figure while in Figure 2 we show an example of the spectral direct irradiance and atmospheric optical depth measured by the PSR on 26 June, 24, which was Saharan dust event. For the comparison of PSR versus CIMEL (Level.5 AERONET) AOD we used the common dataset acquired during the 25days campaign and after excluding instrumental malfunctions we compared in total 7 points (Figure 3 and Table ). For the retrieval of AOD from the PSR we have used dark and stray light corrected spectra and the Izana PSR extraterrestrial spectrum. The ozone optical depth has been accounted for using OMI/Aura Ozone (O3) DOAS Total Column and Bass & Paur cross sections. Finally, the preliminary inversion results, size distribution and single scattering albedo (SSA) from GARRLiC algorithm for 26 Jun 24 are presented in Figure 4. 2

3 .6 CIMEL PSR.5 AOD at 5nm /22 6/29 7/6 7/3 Date & Time(UT) Figure : AOD at 5nm measured during the colocation of PSR and CIMEL at Finokalia ACTRIS site during the ADAMA campaign. PSR_3, Finokalia 26-Jun-24 PSR_3, Finokalia 26-Jun O ptical D epth Direct Irradiance (W.m -2.nm - ) Figure 2 Spectral Direct irradiance (left) and atmospheric optical depth measured by the PSR on 26 June, 24 at Finokalia ACTRIS site Table : Spectral Direct irradiance (left) and atmospheric optical depth measured by the PSR on 26 June, 24 at Finokalia ACTRIS site Wavelength (nm) Intercept Slope Correlation Coefficient

4 .6 34 nm.6 38 nm.6 44 nm nm nm.6 87 nm AOD-PSR nm Jun 23-Jun 24-Jun 25-Jun 26-Jun 28-Jun 29-Jun -Jul 2-Jul Figure 3 : Comparison of aod derived from CIMEL and PSR during period 22 Jun to 7 Jul, 24. In total 7 points were compared.994 SSA.25 volume size distribution SSA fine particles coarse particles total volume concentration (um 3 /um 2 ) fine particles coarse particles total radius (um) Figure 4: Size distribution (left) and SSA of fine (blue), coarse (red) and all (black) particles, on 26 June, 24, at Finokalia, Crete The aerosol optical depth measurements with the CIMEL and PSR revealed a range of aerosol loads at 5nm ranging from.4 to.5 covering the desired aerosol type range marine to marine/mixed. The preliminary results of the comparison between PSR and CIMEL revealed a correlation coefficient better than.99 for all wavelengths and offsets ranging from.5 to.6. Level.5 data will be produced for the PSR accounting for temperature dependencies, wavelength shifts and non linearity, corrections that would affect mostly UV and NIR. A Saharan dust event was 4

5 measured and analyzed using GARRLiC algorithm (26 Jun 24) demonstrating the capabilities of the algorithm. Outcome and future studies A very interesting dataset was acquired during the ADAMA campaign, covering different loads of marine and marine/mixed. The comparison between PSR and CIMEL revealed a correlation coefficient better than.99 for all wavelengths and offsets ranging from.5 to.6. Level.5 data will be produced for the PSR. Following the encouraging results so far, we will continue analyzing more cases from the onemonth campaign in Finokalia, retrieving the optical and microphysical properties of dust particles and their mixture with marine and other particles. References Kazadzis Stelios, Kouremeti Natalia, Giannakaki Elina, Amiridis Vassilis, Mamouri Rodanthi Elissavet, Balis Dimitris, Alexandros Papayannis, The effect of the aerosol vertical distribution on the solar radiation profiles, 26th international laser radar conference at Porto Heli, Greece, 25th 29th june 22 Arola, A., et al. (29), A new approach to correct for absorbing aerosols in OMI UV, Geophysical Research Letters, 36(22). Kazadzis, S., N. Kouremeti, A. Bais, A. Kazantzidis, and C. Meleti (29), Aerosol forcing efficiency in the UVA region from spectral solar irradiance measurements at an urban environment, Annales Geophysicae, 27(6), Kouremeti, N., A. Bais, S. Kazadzis, M. Blumthaler, and R. Schmitt (28), Charge coupled device spectrograph for direct solar irradiance and sky radiance measurements, Applied Optics, 47(), 594. Lopatin, A., O. Dubovik, A. Chaikovsky, Ph Goloub, T. Lapyonok, D. Tanré, and P. Litvinov. Enhancement of Aerosol Characterization Using Synergy of Lidar and Sun Photometer Coincident Observations: The GARRLiC Algorithm. Atmospheric Measurement Techniques Discussions 6 (23):