1. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Thermal and solar radiation errors on air temperature measured with upper-air radiosondes R. Philipona 1, A. Kräuchi 2, G. Romanens 1, G. Levrat 1, P. Ruppert 3, E. Brocard 1, P. Jeannet 1, D. Ruffieux 1, B. Calpini 1 1 Federal Office of Meteorology and Climatology MeteoSwiss, CH-1530 Payerne, Switzerland. 2 Institute for Atmospheric and Climate Science, ETH Zurich, CH-8057-Zurich, Switzerland. 3 Meteolabor AG, CH-8620 Wetzikon, Switzerland.

2. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Motivation WMO Intercomparison of High Quality Radiosonde Systems Yangjiang, China, 12 July - 3 August 2010 NightDay J. Nash, T. Oakley, H. Vömel, LI Wei, WMO/TD-No. 1580, 2011 Reinvestigation of Meteolabor radiation correction Results from the:

3. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Experiments: Atmosphere / Laboratory 1 Measurements of solar and thermal radiation flux profiles through the atmosphere 2 Measurements of the radiation error on unshaded and shaded temperature sensors in flight 3 Measurements of the radiation error on temperature sensors of different diameters in a vacuum chamber

4. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss SRS-C34 Radiosondes from Meteolabor and CNR 4 Net Radiometer from Kipp and Zonen Radiation Measurements through the Atmosphere

5. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Radiation Measurements on Radiosondes Pyranometer and Pyrgeometer measuring downward fluxes Pyranometer and Pyrgeometer measuring upward fluxes

6. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Solar shortwave Radiation Kiehl and Trenberth SUR Thermal longwave Rad. Kiehl and Trenberth 168 Solar and Thermal Radiation Fluxes LDR LUR SDR Can we measure radiation profiles through the atmosphere ? Surface Radiation Measurements Satellite Radiation Measurements LDR LUR

7. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss LDR_nLNR_nLUR_nT_n Night flight: 23 Sep 2011, UT21:20 Longwave Radiation Profiles during the Night

8. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Night flight: 23 Sep 2011, UT21:20Day flight: 23 Sep 2011, UT10:13 and LDR_dLNR_dLUR_dT_d LDR_nLNR_nLUR_nT_n Longwave Radiation Profiles during Night and Day

9. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Solar shortwave Radiation Kiehl and Trenberth SUR Thermal longwave Rad. Kiehl and Trenberth 168 Solar and Thermal Radiation Fluxes LDR LUR SDR Can we measure radiation profiles through the atmosphere ? Surface Radiation Measurements Satellite Radiation Measurements LDR LUR SURSDR

10. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss LDRLURSURDIRSDR Shortwave and longwave Radiation Profiles LUR_d SUR LUR_n DIR SDR LDR_d LDR_n Night flight: 23 Sep 2011, UT21:20Day flight: 23 Sep 2011, UT10:13 and SDR =+880 W m -2 DIR = 1344 W m -2 Poster – P3(7) Philipona, Kräuchi, Brocard, GRL, 2012 doi:10.1029/2012GL052087

11. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Longwave Radiation Error during the Night Longwave Net Radiation on Temperature Sensor Night flight: 23 Sep 2011, UT21:20 T LNR LUR LDR  T ^4 LDR LUR Cooling Heating  T ^4 LNR Glenn E. Daniels, JAM, 1968: Reduce sensor Size Reduce sensor Emissivity Increase sensor Speed Cooling

12. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Longwave Radiation Error during the Night Cooling Heating WMO China, Night results Meteolabor 50  T sensor smallest Size uncertain Emissivity same Speed Cooling

13. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Longwave Radiation Error during the Night Cooling Heating All sensors are too cold All sensors are too warm WMO China, Night results

14. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Solar Radiation Error during the Day WMO China, Day results

15. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Radiation Error during the Day Day flight: 23 Sep 2011, UT10:13 DIR SUR T LDR LUR  T ^4 LNR LDRLUR  T ^4 SUR DIRSDR LNR Longwave Emission   : (0.05 - 0.3) Shortwave Absorption   : (0.01 - 0.2) Total Net Radiation on Temperature Sensor

16. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss - Aluminium plate (brilliant / black) attached to Meteolabor sonde - Temperature sensors on both sides (5cm distance) - Alternately one sensor is exposed to the sun Reference sensor Method to Shade and Unshade SRS C34 SRS C34 front view T sensor

17. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Radiation Error on Meteolabor temperature sensor 50 micron thermocouple temperature sensors unshaded and shaded

18. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Radiation Error on Temperature

19. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Radiation Error on Temperature

20. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss P = 5 hPa v = 5 m/s P = 10 hPa v = 5 m/s P = 300 hPa v = 5 m/s P = 100 hPa v = 5 m/s P = 30 hPa v = 5 m/s Radiation Error measured in Vacuum Chamber Observatory of Lindenberg Vacuum Chamber Xenon Arc Lamp, Intensity: ~ 1650 Wm -2 Experiment with one Meteolabor sonde having three thermocouple sensors with wires of 20 , 50  and 100  1 Minute on, 1 Minute off

21. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Radiation Error: Atmosphere / Laboratory Old correctionNew correction 20  Lab 50  Lab 100  Lab

22. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Radiation Error Correction during Day WMO China, Day results

23. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss Summary: Radiation Error Night and Day NightDay

24. MeteoSwiss Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss NightDay Summary and Conclusions Thank you for your attention ! Future WMO intercomparisons are needed to help improving radiosonde measurements WMO China results referenced to new Meteolabor T-correction More night experiments are needed to clarify thermal effects