1. TECO-2010, Helsinki | 30 August 2010 Laboratory and Field Evaluation of the NubiScope Wiel Wauben * Fred Bosveld Henk Klein Baltink KNMI * R&D Information and Observation Technology Regional Climate Department

2. TECO-2010, Helsinki | 30 August 2010 Contents Introduction NubiScope Laboratory tests contamination Field evaluation cloudiness Conclusions and outlook

3. TECO-2010, Helsinki | 30 August 2010 3 Automated cloud observations SYNOP cloud observations fully automated since 2003 Hourly manual SYNOP versus LD40 with cloud algorithm 6 stations with 3 years overlap data Introduction

4. TECO-2010, Helsinki | 30 August 2010 4 Experiences AUTO versus Observer Missing high clouds / sensitivity Moist layer reported as cloud / threshold “Gaps” in cloud deck during precipitation Missing information during shallow fog Faulty isolated hits / instrumental noise, precipitation, aircraft,... Fewer cases with 1 and 7 okta compared to observer Missing spatial representativeness  scanning Introduction

5. TECO-2010, Helsinki | 30 August 2010 5 NubiScope scanning pyrometer (passive day & night) 8-14m thermal IR (contribution of moisture) FOV=3° (mixed scenes) scan every 10 minutes step azimuth 10° step zenith 3° 1080 sky temperatures 2 surface temperatures T range -70+50°C Total cloud cover >20° low, middle, high cloud cloud mask FD12P De Bilt Test Overview

6. TECO-2010, Helsinki | 30 August 2010 6 Sun Polynomial fit to clear sky Eliminates moisture/contamination Deviations indicate clouds Horizon gives T ambient, start of standard T profile Boundary cloud processing < 70° SZA Sky temperatures NubiScope

7. TECO-2010, Helsinki | 30 August 2010 7 Discontinuity near NorthDerived cloud mask Cloud mask NubiScope

8. TECO-2010, Helsinki | 30 August 2010 8 Laboratory tests Setup

9. TECO-2010, Helsinki | 30 August 2010 9 Laboratory tests Effect contamination pyrometer lens

10. TECO-2010, Helsinki | 30 August 2010 10 Laboratory tests Stability pyrometer (clean lens) ε Galai = 97.3 % 2 years

11. TECO-2010, Helsinki | 30 August 2010 11 Manual evaluation total cloudiness NubiScope versus LD40 (10-minute window used in METAR) Using Total Sky Imager (TSI) images at start/end of scan Evaluation by observers Rotterdam airport (25 km from Cabauw) Data and evaluation via Web tool. Field evaluationWeather Dpt.

12. TECO-2010, Helsinki | 30 August 2010 12 Overview manual evaluations Period 1 June to 16 August 2009 243 evaluations (10’ or longer periods) Scores assigned to NubiScope and LD40 +1 (good) of -1 (false) “Scores” of NubiScope much better than LD40 Discrepancies of LD40 mainly due to lack of spatial representativeness NubiScope generally better than LD40 at detection of middle and high clouds... but sometimes not NubiScopeLD40 # +1717 # -128184 Field evaluationWeather Dpt.

13. TECO-2010, Helsinki | 30 August 2010 13 Evaluation total cloud cover Evaluation fractional cloudiness LD40, NubiScope, LIDAR, cloud radar, long wave IR radiation Goal: optimal cloud product for Cabauw  presentation 2(4) Example: Total cloud cover NubiScope versus LD40 for period 14 May 2008 - 30 September 2009 Field evaluationClimate Dpt.

14. TECO-2010, Helsinki | 30 August 2010 14 Evaluation total cloud cover contingency matrix Scores LD40 versus NubiScope in agreement with LD40 versus OBS and better 0-1 en 7-8 okta behaviour Field evaluationClimate Dpt.

15. TECO-2010, Helsinki | 30 August 2010 15 Effect of scanning Field evaluationClimate Dpt. n = 0 and 8 ▼ n = 1 and 7 ▲ n = 2 to 6 ▲

16. TECO-2010, Helsinki | 30 August 2010 16 Conclusions NubiScope has added value for total cloudiness compared to LD40 mainly due to scanning / better spatial representativeness Effect of contamination is “small” and can be monitored. Climate Dept. decided to keep the NubiScope as part of the Cabauw/CESAR infrastructure Weather Dept. noted added value of NubiScope but accurate height information is essential / required Make NubiScope operational (maintenance,...) Improve timeliness by scanning continuously with “running” updates Investigate / improve NubiScope cloud base height (coincidences with LD40, T-profile, moisture correction,...) Conclusions & Outlook Outlook

17. TECO-2010, Helsinki | 30 August 2010 17 Thank you for your attention! Lookup conference paper for more information See paper 2(4) for more details on evaluation of cloudiness Acknowledgements Rob van Krimpen, Cor van Oort, Mark Savenije, Siebren de Haan, and observers at Rotterdam Airport (all KNMI) Hans Möller (IMK) and Theo Sattler (Sattler-SES)