1. APOLLO_NG A new cloud retrieval for the CAMS radiation service
Niels Killius1, Lars Klüser1, Shengyin Li1, Marion Schroedter-Homscheidt1 , Philippe Blanc2
1German Aerospace Center (DLR), Wessling, Germany
2MINES Paristech / Armines, Sophia-Antipolis, France

2. Outline
Copernicus atmospheric monitoring service (CAMS) and its radiation service
APOLLO/APOLLO_NG
How can APOLLO_NG improve CAMS radiation service?

3. CAMS and its radiation service
CAMS services: Air quality & composition, climate forcing, eimissions & surface fluxes, …
CAMS radiation service: provides UV information, solar radiation (clear sky + total sky)
Free of charge + well documented / easy to recompute

4. How to compute solar radiation – Heliosat-4 method

5. Heliosat-4 cloud properties
APOLLO (Avhrr Processing scheme Over Land, cLouds and Ocean, Saunders & Kriebel, 1983)  uses AVHRR heritage channels (0.6, 0.8, 1.6/3.9, 10.8, 12µm)
Five different cloud tests (Dynamic visible test, infrared gross temperature test, shortwave reflectance ratio, spatial coherence test, brightness temperature difference)
Cloud mask decision: bit adding scheme of fixed thresholds

6. APOLLO_NG: a probabilistic cloud scheme
Uses the same five cloud tests as APOLLO
Probability instead of binary threshold
Start cloud probability is subsequently updated with cloud test results

7. Which cloud probability threshold fits best to the old world?
Count number of pixels for which APOLLO and APOLLO_NG agree in cloud/no cloud decision
Number of agreeing pixels is highest for an APOLLO_NG cloud probability threshold of 40% in most cases.
Date
Time of observations (UTC)
02:15 – 21:45
02:45 – 21:15
02:15 – 14:00
02:30 – 21:45
02:30 – 21:30

8. Comparison APOLLO_NG vs GFSC cloud product
Three golden days out of Cloud Retrieval Evaluation Workshops (CREW) dataset: 13th June, 22nd June and 3rd July 2008

9. Comparison: cold desert surface
15. January :00 UTC
RGB composite
Cloud mask comparison
pthresh = 40%
Old APOLLO
Cloudfree
Cloudy
APOLLO_NG

10. Comparison with ground measurements
APOLLO_NG vs original APOLLO cloud properties as HS-4 input
Comparison with ground measurements (Plataforma solar de Almería(PSA) & BSRN stations IZA, LIN, PAY, CAM, CAR, SBO, TAM)
Date
Time of observations (UTC)
02:15-21:45
02:15 – 21:45
02:45 – 21:15
02:15 – 14:00
02:30 – 21:45
02:30 – 21:30

11. References
Hoyer-Klick, C., Lefèvre, M., Schroedter-Homscheidt, M., Wald, L., USER’S GUIDE to the MACC-RAD Services on solar energy radiation resources, MACC III project report D57.5, version v4.0, public report accessible via
Klüser, L., Killius, N., & Gesell, G. (2015). APOLLO_NG–a probabilistic interpretation of the APOLLO legacy for AVHRR heritage channels. Atmospheric Measurement Techniques, 8(10),
König-Langlo, G. , Sieger, R. , Schmithüsen, H. , Bücker, A. , Richter, F. and Dutton E.G The Baseline Surface Radiation Network and its World Radiation Monitoring Centre at the Alfred Wegener Institute.
Qu, Z., Oumbe, A., Blanc, P., Espinar, B., Gschwind, G., Lefèvre, M., ... & Klueser, L. (2016). Fast radiative transfer parameterisation for assessing the surface solar irradiance: The Heliosat-4 method. Meteorol. Z.
Roebeling, R., B. Baum, R. Bennartz, U. Hamann, A. Heidinger, A. Thoss, and A. Walther (2012): Evaluating and Improving Cloud Parameter Retrievals. Bulletin of the American Meteorological Society, 94, ES41–ES44,
Saunders, R. W., & Kriebel, K. T. (1988). An improved method for detecting clear sky and cloudy radiances from AVHRR data. International Journal of Remote Sensing, 9(1),

12. Thank you