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ClIMa: Evaluation of ground-based lidar methodologies for continuous profiling of Cloud condensation and Ice nuclei concentrations in the Mediterranean

Start date: 01-04-2017 - End date: 30-04-2017

Status: Confirmed

Open to sharing: Yes

Confidential: No

Transnational Access: Yes

Open to training: No

Grounded / Maintenance: No


Aircraft name: FA20 - DLR

Airport: Finokalia is a core station of the ACTRIS RI located on the north coast of Crete, Greece (35.338°N, 25.670°E). The station is located at the top of a hilly elevation (150m above sea level), facing the sea within a sector of 270° to 90°. No touristic or other human activities can be found at a distance shorter than 20 km within the aforementioned sector. In-situ measurements are performed in Finokalia continuously for the last 20 years. The station has been equipped recently with a sophisticated EARLINET lidar system (PollyXT), which is ideal for CCN and IN profiling from natural aerosols, mainly of dust and marine origin which are present 95% of the time on the site.

Project description

Project theme: TA-021. Applications of atmospheric in-situ measurement

Project abstract: Large uncertainties in weather and future-climate predictions arise from the inability to comprehensively account for the interactions of aerosol with liquid-water, mixed-phase and cirrus clouds (Seinfeld et al., 2016). Aerosols directly modulate clouds by serving either as the cloud condensation nuclei (CCN) to form liquid droplets or as heterogeneous ice-nucleating particles (INP) via numerous ice nucleating pathways (e.g., deposition, immersion, contact freezing; e.g., Hoose and Mohler, 2012). Progress in aerosol-cloud interaction research requires global datasets of CCN and INP concentration which may be addressed with the unparalleled sampling of atmospheric volumes by remote sensing. The ill-posed nature of aerosol retrievals remains a limitation, which is gradually yielding to algorithmic developments. Extensive evaluation of retrievals against in-situ measurements is required before they can become operational. CLIMA aims to evaluate the suitability of lidar-derived aerosol number and surface area distribution for determining the concentrations of CCN and IN. Exploratory studies to date (Mamouri and Ansmann, 2016; Argyrouli et al., in review) have demonstrated the feasibility of retrievals with tolerable uncertainty. CLIMA will extensively evaluate the methodologies presented in these studies, comparing the lidar-derived CCN and particle size distribution profiles with airborne in-situ measurements. We propose to perform continuous ground-based lidar measurements in the ACTRIS core stations of Finokalia in Crete and Limassol in Cyprus, accompanied by sunphotometric and surface in-situ measurements. We request EUFAR TA to airborne in-situ profiling of CCN number concentration and particle size distributions and advanced microphysics which can be provided by the DLR Falcon-20 or the BAe146 FAAM aircraft.

Measurements to be made by aircraft: Trustworthy predictions of the overall indirect aerosol effect on climate are impossible without accurate estimations of CCN and IN concentrations. The study of Mamouri and Ansmann (2016) showed the potential of polarization lidar to provide vertical profiles of CCN and IN number concentrations. By means of the polarization lidar technique, the desert dust aerosol component can be easily separated from other continental aerosol components as well as from marine aerosol. After the separation of the basic aerosol types, the particle number and surface area concentrations are determined from the lidar-derived particle extinction coefficients, and are used as input in the CCN and IN parameterization schemes. There is room for validation and improvements of the method and this is what we plan to address during CLIMA campaign: we will provide extended comparisons of the lidar-derived CCN profiles with respective airborne in situ observations, as well as comparisons of the aerosol concentration derived with lidar and measured from airborne in-situ instruments, to assess the IN lidar retrievals. Moreover, we will tackle the open question how to handle the water-uptake effect by the particles in the retrieval of the required dry-particle microphysical properties. The selected site for the field experiment is the Finokalia atmospheric observatory, a core station of the “Aerosols, Clouds, and Trace gases Research Infrastructure- ACTRIS” European Research Infrastructure, located in the island of Crete in Greece. Being away from direct urban influence, the station is not affected by anthropogenic activities, especially during the dry season (from April to October) when intense Saharan dust events are frequently recorded (see The station is equipped with ground-based remote sensing instruments (i.e., the PollyXT-NOA multi-wavelength polarization lidar, the CIMEL sunphotometer) and surface in-situ instruments, providing ozone measurements, various aerosol particle parameters (PM10 mass, mass and number size distributions, scattering and absorption coefficients) and meteorological parameters (temperature, relative humidity, wind speed and direction). The CCN and IN profiles produced from the PollyXT-NOA lidar measurements in Finokalia will be validated against CCN and particle concentration measured with the in-situ instrumentation onboard the Falcon research aircraft during the ClIMA campaign. The PollyXT-NOA lidar water vapor channel and airborne in-situ RH measurements will be used to estimate the effect of humidity on the calculated CCN and IN profiles. A parallel experiment will be employed in Cyprus ACTRIS station, utilizing the LACROS facility of TROPOS. The CLIMA validation study will add to the efforts taken for the development of new products from remote sensing in the framework of the ACTRIS. The results will also be valuable for the simulation studies currently performed at ESA in anticipation of future lidar satellite missions (e.g. ADM-AEOLUS, EarthCARE, Sentinels). The results from the proposed experiment will be published in high-impact journals (e.g. Atmospheric Chemistry and Physics, Atmospheric Measurements and Techniques). Reference: Mamouri, R.-E. and Ansmann, A.: Potential of polarization lidar to provide profiles of CCN- and INP-relevant aerosol parameters, Atmos. Chem. Phys., 16, 5905-5931, doi:10.5194/acp-16-5905-2016, 2016.

Season: April – May 2017

Weather constraints: Cloud-free conditions are required for aerosol remote sensing retrievals. Measurements during dust advection from Sahara Desert are of added value for the experiment, in order to test and validate dust discrimination methodologies.

Time constraints: Periods of Saharan dust advection over Crete are targeted. April is the month of highest frequency for Saharan dust episodes in Eastern Mediterranean (e.g. Marinou et al., 2016), thus, the preferred time window of the campaign is 01/04/2016 – 30/04/2016. The proposed project is clustered with the DoGMA and SEAMAN EUFAR projects, which have been scheduled for the same time period. Additional synergies are created by clustering the proposed project with the ERC Starting Grant Project A-LIFE (Absorbing aerosol layers in a changing climate: aging, lifetime and dynamics) during which an airborne field experiment with the DLR research aircraft Falcon will be conducted in the Eastern Mediterranean. For A-LIFE, the DLR research aircraft Falcon will be based in Paphos/Cyprus. CLIMA is an aerosol campaign focused on CCN and IN retrievals utilizing lidars, thus having completely different objectives from DoGMA and SEAMAN which are concentrated on dust model validation and new particle formation respectively. Due to the episodic nature of dust advection the flights will be scheduled according to dust forecasts. The dataset that will be collected by the cluster of the campaigns over Crete will be used for cal/val activities as well. At NOA we target ESA missions like Sentinel 3, thus, overpass time constrains may have to be considered. ESA has expressed interest on participating on this cluster of campaigns.

Flights (number and patterns): In total, three flights are requested that correspond to 3 aircraft missions. The duration of each flight is approximately 04:00 hr. The flights pattern is illustrated in Figure 2. After take-off in Paphos, the Falcon aircraft will climb to 12 km altitude and fly westwards towards Crete thereby characterizing the dust layer with the airborne lidar instrument. Over Finokalia, the Falcon will descend with a stepped profile containing 4 steps at different altitudes between 0.3 km and the dust layer top, each of 7 minutes duration. Before landing at Paphos, a vertical profile with 4 steps at different altitudes in the dust layer will be flown over the ground-based lidar at Limassol, Cyprus.

Instruments: None

Other constraints: None

Project website:

Scientific contact

Name: AMIRIDIS Vassilis

PI email: