Extinction validation fromUmweltforschungsstation
Schneefernerhaus (UFS) –a proposal for additional
validation measurements• EarthCare validation workshop 16/11/2023

Thomas Popp (DLR), Volker Ziegler (Palas),Peter Marton (UFS), Till Rehm (UFS)Environmental Research Station Schneefernerhaus | Zugspitze
Germany‘s highest research station at 2650 m• High altitude research station
for climate, bio-, hydro- andgeospheric research as well as
for environment and altitude medicine• Observatory
for air pollutants, greenhouse gases,
weather and natural phenomena• Center for communication and meetings
for teaching, education andPhoto: BG UFS GmbHstustainabilitly strategies

www.schneefernerhaus.de2

UFS target area: satellite validation
 Satellite passive observations: large coverage In-situ measurements: tied to SI standards (GAW) Issues to link both

 Ambient air, vertical profiles
 Attempt of routine correction of humidity effects failed (ESA Aerosol_cci) despite ofseveral well equipped stations (ACTRIS Super-Sites / GAW network)

 EarthCare will help close vertical profiles3

 UAV ambient 3D measurements can contribute to close both gaps
 Humidity + meteorology
 Size distribution
 Extinction: Scattering + Absorption
 Low cost PM sensors

International Satellite Aerosol Science network AEROSAT
 International forum for satellite aerosol experts and users Requirement: systematic 3D-in-situ characterisation of aerosol types-> „new OPAC“ needs routine measurement flights over longer period
 To reach statistically significant characterization of air masses
 Optical properties, mass extinction efficiency
 alternative flight concepts
 Medium size aircraft with a set of instruments (Kahn et al.) UAV-swarm flights with selected instruments

4Kahn, R.A., T. Berkoff, C. Brock, G. Chen, R. Ferrare, S. Ghan, T. Hansico, D. Hegg, J.V. Martins, C.S. McNaughton,
D.M. Murphy, J.A. Ogren, J.E. Penner, P. Pilewskie, J. Seinfeld, and D. Worsnop, 2017. SAM-CAAM: A Concept for
Acquiring Systematic Aircraft Measurements to Characterize Aerosol Air Masses. Bull. Am. Meteoro. Soc. 2215-2228,
doi:10.1175/BAMS-D-16-0003.1

UFS feasibility study 2016
 Requirement analysis for passive instruments
Requirement
Spatial resolution: 1km horizontal
Spatial coverage: 10 km including valley areas
Temporal coverage: 1 hour
Vertical resolution: 100m at lower end
Vertical coverage: 0 – 10 km (from valley ground)Temporal matching: ±30 min (10:00 /13:30)
accuracy: < 50% of satellite AOD accuracy
Size distribution 2 – 3 modes
Humidity condition: ambient, no drying
Long-term: humig + dried (to assess humid growth)frequency: 1x per week, all seasons
Duration of regular observations: minimum 1 year
Aggregated (clustered) optical properties statistics: several years
Low / no cloud coverageInternal consistency of all measurements
External consistency with station GAW in-situ measurements
Instrument stability: caution at large temperature / humidity /pressure gradients
Automatization: data analysis
UAV emissions: zero
Data analysis:
Step 1: Integration (x-y / t and z) effective column values
Step 2: Integration to partial AOD values (e.g. fine mode, dust)
Step 3: Tools for external users / on-demand analysis
Synchronisation of separate instruments < 1 sec5

Comment
Single pixel in satellite datasets
Retrieval very difficult in summit areaAerosols can be regarded stable
Individual aerosol layers
Total tropospheric column
AERONET experience
integrated column / pixel values
Switch off above 90% rH (protection)
Reasonable overlap with satellite data
significant statistics
Separate different aerosol types
Contaminate satellite aerosol products
3D integration / optical closure
Optical vs. dynamical methods
at layer boundaries possibly adaptive flight control
Cost reduction/ easy transferability
Avoid miss-interpretation
Comparability of measurement points

UAV flight paths at high altitude mountain stations
 Combined measurements at high + low altitudes
 Can cover significant part of the troposphere Boundary layer
 Long-range transport
 Total column for passive instruments
 Vertical profile for EarthCare Feasibility study

 UAV test flights were made With different types of UAV

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UAV flight paths at high altitude mountain stations

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UFS strategy
 Aim: operate regular UAV flights to measure ambient aerosol in-situ properties Palas wet aerosol spectrometer (adapted)
 Tested at Sonnblick (ACTRIS campaign), Marambio and test mounted on UAV
 Ambient size distribution / aerosol scattering Commercial aethalometer Aerosol absorption

 Procedure for UAV flights beyond the visual line of sight in progress BVLOS Implementation planned from 2024

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Palas aerosol spectrometer as basis
 Adaptation for wet aerosol measurements

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Antarctic campaign (Marambio, 12/2022-3/2023)

BVLOS procedure status• Permission for BVLOS flights has been granted in November 2023 for aseparate project by the German air traffic authority (Luftfahrtbundesamt, LBA)
• The approved airspace is designed for a permafrost monitoring project in theslopes of Mt. Zugspitze (approx. 2 km², height 200m agl)
• BVLOS flights for aerosol measurements / satellite ground truthing will need adifferent air space and thus a separate permission• The current BVLOS project can serve as a blueprint for future applications• The UFS and it‘s partners will have gained considerable experience in theapplication procedures due to the current project10

Applications / relevance Satellite validation:

 Passive radiometers: AOD + aerosol properties
 EarthCare: extinction profiles

 Support to retrieval development Statistics / climatology of optical aerosol properties

11 Users
 Roll-out to GAW stations (mountain locations) Develop analysis and integration tools for users
 Validation of EarthCare products
 Validation + development of Copernicus products
 Algorithm improvement for ESA CCI + Climate-Space / C3S CDRs
 Support to retrieval experts / AEROSAT algorithm development

Summary: EarthCare validation
 Benefits from high altitude starting point
 Will be included within regular flights at UFS
 Will use CAMS forecasts for flight planning Validate extinction profiles in free troposphere EarthCare validation proposal needs to be worked out Funding opportunity from Freistaat Bayern: infrastructure (UAV, instrument)
 Funding for data analysis needs to be raised Extended BVLOS authorization for vertical profiles needs to be obtained

Altitude range limited by authorities

 Using insights of this workshop / requirements12

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Assumed aerosol optical properties for AOD retrieval
Table 1. Parameters describing the microphysical and optical properties of the aerosol
components used in the Aerosol-cci round-robin excersizes.
AerosolReal part
Component Refr Index(550 nm)

Im Part RefrIndex(550 nm)

Reff* Geom. Variance Geom. Comments Aerosol
meanlayer(µm) st dev (ln σi)heightradius(σi)( rgi ,µm)

Dust§

1.56
0.0018
1.94(varies with (varies withwavelength)§ wavelength)§

1.822

0.6

Fixed
0.788 Nonspherical hgt at
2-4km

Sea salt

1.4

01.94

1.822

0.6

0.788 AOD
0-1 kmthresholdconstraint#

Fine modevery weakabs

1.4

0.003

0.142 1.7

0.530.07(ssa at 500 0-2 km
nm: 0.98)

Fine mode
strong-abs

1.50.040

0.142 1.70.530.07(ssa at 500 0-2 km
nm:0.803)§Dubovik et al., 2002

De Leeuw, Holzer-Popp, et al., RSE 2014

Case study in-situ validation of satellite aerosol products• Several well equipped stations (ACTRIS Super-Sites / GAW network)• Attempt of routine correction of humidity effects (ESA Aerosol_cci)

72-hour trajectories; colour: f(85%)

pdfs of (85%) for 5 stations• Conclusion: 40% uncertainty- too large as reference