Introducing VESPA-22: a ground- based microwave spectrometer for measuring middle atmospheric water vapour at polar latitudes 27 April 2012 EGU General Assembly April 2012 EGU General Assembly 2012 Pietro Paolo Bertagnolio, Giovanni Muscari, Irene Fiorucci and Massimo Mari Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy Department of Earth Sciences, University of Siena Distributed under Creative Commons Attribution 3.0 Creative Commons Attribution 3.0Creative Commons Attribution 3.0 Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy Department of Earth Sciences, University of Siena Distributed under Creative Commons Attribution 3.0 Creative Commons Attribution 3.0Creative Commons Attribution 3.0

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 1/14 Our goal To observe changes in the water vapour concentration profile in the stratosphere and mesosphere in the polar regions Long-term (decadal trends) Short-term (diurnal cycle) With a new ground-based microwave spectrometer to measure the GHz transition of water vapour as part of the NDACC network

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 2/14 Outline Stratospheric H2O and its impact on PSCs The observational challenges of the 22-GHz H2O line How does the technique work? Our instrumental setup First measured and calibrated spectra Conclusions and future work

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 3/14 Decadal change in stratospheric H2O as yet not well understood Steady rise since % decrease in 2000 Influence on surface warming 30% of GHG from “Contributions of stratospheric water vapor to decadal changes in the rate of global warming.” S. Solomon et al. – Science

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 4/14 Impact of H2O increase on Arctic PSC formation from “Quantifying Denitrification and Its Effect on Ozone Recovery”, Tabazadeh at al. – Science ppmv H2O

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 5/14 The observational challenge tropo strato meso thermo

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 6/14 Balanced Beam-Switching Measurement Technique Troposphere Compensating Sheet Stratosphere Signal beam Reference beam

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 7/14 VESPA-22 (water Vapor Emission Spectrometer for Polar Atmospheres at 22 GHz)

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 8/14 Parabolic antenna Half-Power Beam Width (HPBW) = 3.5° Sidelobes < -40 dB below main lobe Cross-polarization < -24 dB below main polarization

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 9/14 Noise diode calibration Cold body (LN2)Calibration sources Hot body

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 10/14 Noise diode calibration Trec = 312 K

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 11/14

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 12/14

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 13/14 Future work (now the fun starts…) Improve baseline flatness: –λ/4 wobbler instead of fixed shift –Delrin compensating sheet –Front-end optimization Improve sensitivity and Trec –Test single-sideband mixer Test with longer integration times from an high-altitude observatory (Gran Sasso) Set up inversion algorithm Conclusions Long-term monitoring of polar stratospheric water vapour is needed We designed and built a new 22-GHz spectrometer for polar observations We measured the first atmospheric spectra (“first light”) Long-term monitoring of polar stratospheric water vapour is needed We designed and built a new 22-GHz spectrometer for polar observations We measured the first atmospheric spectra (“first light”)

EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – EGU G ENERAL A SSEMBLY 2012 – 27/04/2012 P IETRO P AOLO B ERTAGNOLIO – 14/14 References Bertagnolio, P. P., Muscari, G., & Baskaradas, J. (2012). Development of a 22 GHz ground-based spectrometer for middle atmospheric water vapour monitoring. European Journal of Remote Sensing, doi: /EuJRS Solomon, S., Rosenlof, K. H., Portmann, R. W., Daniel, J. S., Davis, S. M., Sanford, T. J., & Plattner, G.-K. (2010). Contributions of stratospheric water vapor to decadal changes in the rate of global warming. Science (New York, N.Y.), 327(5970), doi: /science Tabazadeh, A., Santee, M. L., Danilin, M. Y., Pumphrey, H. C., Newman, P. A., Hamill, P. J., & Mergenthaler, J. L. (2000). Quantifying Denitrification and Its Effect on Ozone Recovery. Science, 288(5470), doi: /science Thank you for your attention!