Assessing Radiative Closure of the EarthCARE ACM-RT product with
Surface Observations
Hartwig Deneke1, Carola Barrientos Velasco1, Rainer Hollmann2, AnjaHünerbein1, Andreas Macke1
Leibniz Institute for Tropospheric Research (TROPOS), Leipzig, Germany
2German Service (DWD), Offenbach, Germany
1

EarthCARE Science and Validation Workshop
Frascati, Italy, 13.-17. Nov. 2023

Motivation

Closure of atmospheric properties and radiative fluxes key scienceobjective of EarthCARE mission
Target accuracy of +/- 10 W/m2 on 100 km2 scale for radiativefluxes at top-of-atmosphere => validation by BBR instrument
However: radiative fluxes at the surface essential forunderstanding energy flows in our climate system
Closure assessment at surface more challenging:– High variability in surface irradiance induced by clouds– Point-like nature of ground-based measurements

EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 2 / 15

EarthCARE Closure ConceptAerosol and cloud retrievals, 3D
scene construction as input for
1D/3D radiative transfer models

Validation with BBR observations

Target accuracy at TOA: 10 W/m2

Figs.: EarthCARE closure concept and scenereconstruction. Source: Illingworth et al., BAMS,
2015, doi:10.1175/BAMS-D-12-00227.1.
EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de| Slide 3 / 15

EarthCARE ACM-RT ProductFigs.: (left) Flowchart of the ACM-RTprocessor. (top) Planned 21 x 5 km2
closure assessment domain. Source: Coleet al., AMT, 2023, doi:10.5194/amt-164271-2023.
EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 4 / 15

Comparison Datasets

EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 5 / 15

Figs.:
Instrumental
networks to be used forplanned
EarthCARE
evaluation
activities.
This includes the global
Baseline
Surface
Radiation
Network(BSRN) and NASA’s
AERONET network, as
well
asregional
networks including theUS SURFRAD networkand the meteorologicalnetwork of DWD.

Past Activities focused on Aerosol

Figs.: Comparison of aerosol radiative effect derived from AERONET
observations and simulated based on the CAMS reanalysis and explicit 1D
radiative transfer (left) at the surface, and (right) at the top-of-atmosphere.
Source: Witthuhn et al., ACP, 2021, doi:10.5194/acp-21-14591-2021.
EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 6 / 15

Past Activities focused on Clouds

Figs.: Comparison of hourly-averaged pyranometer observations and satellite
retrievals in terms of (left) surface solar irradiance and (right) atmospherictransmittance. Source: Deneke et al., RSE, 2008, doi:10.1016/j.rse.2008.03.012.
EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 7 / 15

TROPOS Pyranometer NetworkFigs.: Autonomous pyranometer
network for resolving small-scalevariability in solar irradiance.
Source: Madhavan et al., AMT,
2016, doi:10.5194/amt-9-1153-2016.

EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 8 / 15

Representativity of Single StationsFig.: Expected deviation ofsurface solar irradiance forsingle station and domain
average, for 3 domain sizes,
cloud situations, and different
averaging times. Source:
Madhavan et al., ACP, 2017,
doi:10.5194/acp-17-3317-2017.

EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 9 / 15

Effects of Satellite Resolution
Fig.: Comparison of surface
solar irradiance estimatedfrom METEOSAT SEVIRI atstandard (3x3km2) and HRV(1x1km2)resolution vs.
ground-based pyranometer
network. Source: Deneke etal., AMT, 2021,
doi:10.5194/amt-14-5107-2021.

EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 10 / 15

S2VSR Campaign @ ARM SGP Site
• Small-Scale Variability of Solar
Radiation (S2VSR) Campaign• Centered on ARM SGP CentralFacility, supported by ARM• Aim: resolve variability within 2x2
km2 GOES-ABI (infrared) satellite
pixel, study 3D cloud effects• 12-week period: Jun. - Aug. 2023
• Collaboration with J. Redemann /C.Flynn (both OU)
EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 11 / 15Complementary S2VSR Observations

Fig.: Copernicus Sentinel-2 RGB image acquired on
2023-06-13 at 10m spatial resolution (left). Timematched
COGScloudfield
at 50mres.| deneke@tropos.de(right). | Slide 12 / 15
EarthCARE Sci.
Val. Workshop| Frascati,IT | 13.-17.
Nov. 2023

ACTRIS Radiation Measurements byTROPOS on Cape Verde / Mindelo

Figs.: Radiation station recently established by TROPOS on the roof of the Ocean
Science Centre Mindelo, following BSRN recommendations and including spectral
EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 13 / 15
measurements(0.4.2.5um) (photos by R. Hengst).

Conclusions and Outlook I.
Planned activities shall extend EarthCARE’s closure assessment
to surface radiation based on ACM-RT product
Global and regional operational networks will be used as primarysource of reference data (primarily BSRN&AERONET)
Small-scale variability of clouds limits representativity of single
point-like surface observations
Averaging of multiple stations & overpasses required

Challenge: quantification of (situation-dependent) expected
deviation of single-station obs. and ACM-RT fluxes

EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 14 / 15

Conclusions and Outlook II.


Dedicated field campaign using dense
network of radiation sensors (how many?)
would enable more rigorous closure
assessment for cloudy skies
Complementary cloud observations such asstereo-photogrammetry to assess
EarthCARE scene construction
Recent S2VSR campaign as blueprint?
Feasibility depends on predictability ofEarthCARE ground track!

EarthCARE Sci. Val. Workshop | Frascati, IT | 13.-17. Nov. 2023 | deneke@tropos.de | Slide 15 / 15

Fig.: NOAA mobile
MESONET station.
https://www.nssl.noaa.gov/tools/fofs/