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.

Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Motivation

Results from the: WMO Intercomparison of High Quality Radiosonde Systems Yangjiang, China, 12 July - 3 August 2010 Night Day

J. Nash, T. Oakley, H. Vömel, LI Wei, WMO/TD-No. 1580, 2011

Reinvestigation of Meteolabor radiation correction 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

Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Radiation Measurements through the Atmosphere

SRS-C34 Radiosondes from Meteolabor and CNR 4 Net Radiometer from Kipp and Zonen

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

Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Solar and Thermal Radiation Fluxes

Satellite Radiation Measurements Solar shortwave Radiation Thermal longwave Rad.

LUR LDR SUR 168 SDR LUR Surface Radiation Measurements LDR

Can we measure radiation profiles through the atmosphere ?

Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Longwave Radiation Profiles during the Night

Night flight: 23 Sep 2011, UT21:20

T_n LUR_n LNR_n LDR_n Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Longwave Radiation Profiles during Night and Day

Night flight: 23 Sep 2011, UT21:20 and Day flight: 23 Sep 2011, UT10:13

T_n T_d LUR_n LUR_d LNR_n LNR_d LDR_n LDR_d Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Solar and Thermal Radiation Fluxes

Satellite Radiation Measurements Solar shortwave Radiation Thermal longwave Rad.

SUR SDR LUR LDR SUR 168 SDR LUR Surface Radiation Measurements LDR

Can we measure radiation profiles through the atmosphere ?

Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Shortwave and longwave Radiation Profiles

Night flight: 23 Sep 2011, UT21:20 and Day flight: 23 Sep 2011, UT10:13

LUR SUR LDR SDR SDR =+880 W m -2 DIR DIR = 1344 W m -2

LUR_d LUR_n LDR_d LDR_n SUR SDR DIR

Poster – P3(7) Philipona, Kräuchi, Brocard, GRL, 2012 doi:10.1029/2012GL052087

Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Longwave Radiation Error during the Night

Night flight: 23 Sep 2011, UT21:20

Longwave Net Radiation on Temperature Sensor Cooling e s

T ^4 LDR LUR LDR

e s

T ^4 LNR

e s

T ^4

T

LUR

Heating

LNR

Cooling Glenn E. Daniels, JAM, 1968: • Reduce sensor Size • Reduce sensor Emissivity • Increase sensor Speed Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Longwave Radiation Error during the Night

WMO China, Night results

Cooling

Meteolabor 50

m

T sensor

Heating Cooling smallest Size uncertain Emissivity same Speed Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Longwave Radiation Error during the Night

WMO China, Night results

Heating Cooling Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss All sensors are too warm All sensors are too cold

Solar Radiation Error during the Day

WMO China, Day results

Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Radiation Error during the Day

Day flight: 23 Sep 2011, UT10:13

Total Net Radiation on Temperature Sensor DIR SUR s T ^4 LDR LUR SDR DIR

LDR

e s

T ^4 LNR

e s

T ^4

T

LUR SUR LNR

Longwave Emission Shortwave Absorption e a : (0.05 - 0.3) : (0.01 - 0.2) Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Method to Shade and Unshade -

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

front view SRS C34

T sensor Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

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

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

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

Radiation Error measured in Vacuum Chamber 1 Minute on, 1 Minute off Experiment with one Meteolabor sonde having three thermocouple sensors with wires of 20 m , 50 m and 100 m P = 5 hPa v = 5 m/s

Observatory of Lindenberg

Vacuum Chamber Xenon Arc Lamp, Intensity: ~

1650 Wm -2

P = 10 hPa v = 5 m/s P = 30 hPa v = 5 m/s P = 100 hPa v = 5 m/s P = 300 hPa v = 5 m/s Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Radiation Error: Atmosphere / Laboratory Old correction 100 m Lab New correction 50 m Lab 20 m Lab Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Radiation Error Correction during Day

WMO China, Day results

Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Summary: Radiation Error Night and Day

Night Day

Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss

Summary and Conclusions

WMO China results referenced to new Meteolabor T-correction Night Day

• More night experiments are needed to clarify thermal effects • Future WMO intercomparisons are needed to help improving radiosonde measurements

Thank you for your attention !

Rolf Philipona Federal Office of Meteorology and Climatology MeteoSwiss