1. Development of the NO2 sonde Wesley Sluis Ankie PitersMarc Allaart

2. Requirements Range 1-100 ppb Fast (1 second) Lightweight (100 grams) Little power (1 watt) Cheap (disposable) Not dangerous to finder / environment Works at high altitude

3. Design of the instrument

6. Temperature dependence (1) The housing of the sonde is made of Polystyrene (PS), and is a good insulator. Typical temperature range during a balloon flight (CINDI): 20 – 40 o C. Temperature rising caused by Teflon air pump. What is the influence of the temperature on the emitted light signal?

7. Temperature dependence (2) Set up: - Detector in PS box. - Constant NO 2 concentration introduced to luminol solution. - CO 2 scrubber is used to prevent acidification. -Temperature is monitored. Result: The change in the scaling factor is within 2.0 % per degree Celsius for temperatures starting at 20 o C to 40 o C.

8. pH dependence Acidification caused by CO 2 : CO2 + KOH  KHCO3 KHCO3 + KOH  K2CO3 + H2O It is also possible to estimate the pH as a function of time, and make a parameterization of the signal as a function of pH. This method makes it possible to correct the instrument’s response for any know initial pH.

9. Comparison of the NO2 sonde with an in situ monitor Special thanks to Lou Gast, RIVM

11. Conclusions Temperature is characterized, The change in the scaling factor is within 2.0 % per degree Celsius for temperatures starting at 20 o C to 40 o C. Good comparison with the photolytic analyzer. Measured the same dynamical range of changing NO 2 concentrations. Small variations of 1ppbv NO 2 are well captured by the NO 2 sonde.

12. Outlook Finishing paper about “The development of the nitrogen dioxide sonde”. Complete the calibration of the NO 2 sonde. Focus on launching some sondes this year. Promoting NO 2 sonde, i.e. EGU 2010

13. We: Wesley Sluis Ankie Piters Marc Allaart Thanks: Ruud Hoogeveen (SRON) Jan Venema (RIVM) Yipin.Zhou (EMPA) Enno Peters (University of Bremen) Andre van Londen Richard Rothe Rob Agterberg Ed Worrell Cor van Oort Werkplaats Photos: Piet Stammes Marc Allaart This project is partially financed by NIVR : Sciavisi project