TH1.T04.2_MULTI-FREQUENCY MICROWAVE EMISSION OF THE EAST ANTARCTIC PLATEAU_IGARSS_2011_DOMEX_presentation.pdf

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  • 1. IGARSS- Vancouver – July 24-29 2011 MULTI-FREQUENCY MICROWAVE EMISSION OF THE EAST ANTARCTIC PLATEAUMarco Brogioni G.Macelloni, S. Pettinato CNR-IFACR. Zasso, A. Crepaz CVA-ARPAVB. Padovan, J. Zaccaria PNRAM. Drinkwater ESA-ESTEC
  • 2. IGARSS- Vancouver – July 24-29 2011Outline Objectives and background The Domex experiment Satellite (SMOS- AMSR-E) and ground data The e.m. model Model comparison Conclusions and Perspectives
  • 3. IGARSS- Vancouver – July 24-29 2011Objectives Verify the applicability of the East Antarctic plateau as an extended target for calibrating and monitoring low frequency microwave radiometers using ground based (the Domex-2 experiment) and satellite data (SMOS) Understanding the multi-frequency microwave emission of the Antarctic plateau by using satellite and ground data in combination to e.m. model
  • 4. IGARSS- Vancouver – July 24-29 2011 Dome C and the Antarctic Plateau © CSA • The site is view on a sub-daily frequency by polar-orbiting satellites, at a variety of incidence and azimuth angles. • Homogeneity of snow surface at the 100 km scale. Dome C • Small surface roughness relative to other ice sheets. • Low snow accumulation rate (around 3.7cm/yr). • Clear sky, and extremely dry and stable atmosphere. • Well known topography and environmental conditionConcordia Station (Dome C): 75.125 S, 123.25 E 3270 a.s.l
  • 5. IGARSS- Vancouver – July 24-29 2011The Domex-2 experiment With a view to the launching of the ESA’s SMOS satellite, an experimental activity called DOMEX, supported by ESA and PNRA, was started at Dome-C, Antarctica in 2005 with a first pilot project (Domex-I, duration one month) and continue with Domex-2. The main scientific objective is to demonstrate the stability of the site in order to provide L-band microwave data for SMOS calibration. DOMEX-2 experiment consisted in an L-band and an infrared (8-14 µm) radiometers (RADOMEX) installed at Concordia base on an observation tower at a height of 15 m respect to the ice sheet. Data were collected continuously (24/24 h) over two entire Austral annual cycle, starting from December 2008. Snow measurements (including snow stratigraphy, density, grains size and shape, temperature) and meteorological data, were also collected during the experiment.
  • 6. IGARSS- Vancouver – July 24-29 2011The DOMEX Campaign TOWER VIEW Air temperature Mean: - 53 degs Max: - 23 degs Min: - 78 degs Concordia base
  • 7. IGARSS- Vancouver – July 24-29 2011Complementary Snow measurements Summer Snow deposition: Grains shape and Size Classification(precipitati on, hoar,wind, etc.) Winter Snow layers: Temperature Hardness Density Grains shape and Size Dielectric Constant
  • 8. IGARSS- Vancouver – July 24-29 2011Domex -2 – 2009 campaign 250 No temperature control  240 Low temperature /High fluctuation 230 Theta = 42° SMOS angle Brightness Temperature [K] 220 210 Tv Th 200 190 180 170 Power Failure > 10 days 01/12/08 01/01/09 01/02/09 04/03/09 04/04/09 05/05/09 05/06/09 06/07/09 06/08/09 06/09/09 07/10/09 Time Radomex Temperature < -60°C !!!
  • 9. IGARSS- Vancouver – July 24-29 2011Temporal Stability – corrected values 220 20 215 18 Tbv = 209 K - Dev.st = 0.3 K Sky Brightness Temperature [K] 210 16 Snow Brightness Temperature [K] 205 14 200 12 195 10 Tv 190 8 Th Tbv = 186.3 K - Dev.st = 0.6 K Tv 185 6 180 4 175 2 170 0 01/12/08 01/01/09 01/02/09 04/03/09 04/04/09 05/05/09 Time 6 Months Scale = December 2008 – May 2009
  • 10. IGARSS- Vancouver – July 24-29 2011Domex-2 : 2010 campaign Power Failure Problem PC crash April 10 Solved –July 2010 11 months data
  • 11. IGARSS- Vancouver – July 24-29 2011SMOS comparison - Temporal Trends The target response is very stable. Fluctuation are typical of the SMOS data. Domex Tb could be used as a benchmark for improve SMOS some jumps: surface effect (?) data?
  • 12. IGARSS- Vancouver – July 24-29 2011Possible Explaination: wind effect Lines= High Wind Speed (> 7 m/s)
  • 13. IGARSS- Vancouver – July 24-29 2011DOMEX- Angular Trend
  • 14. IGARSS- Vancouver – July 24-29 2011SMOS – comparison: Angular Trend dots – SMOS lines - DOMEX SMOS data provided by CESBIO
  • 15. IGARSS- Vancouver – July 24-29 2011 Multi-frequency Tb data: temporal trends almost a Black Body Obs. angle 55 deg V pol H pol L C X Ku Ka L C X Ku KaMean 218 200.23 194.93 184.83 169.88 175 153.16 152.84 154.70 150.36Std Dev - 0.50 0.57 0.81 1.80 - 1.15 1.29 1.65 2.12 V pol fluctuates less because of the Brewster angle!
  • 16. IGARSS- Vancouver – July 24-29 2011Tb – StdDev vs Frequency (AMSR-E & DOMEX) . 2.5 2.0 Ka Tbh 1.5 TB Sdev [K] Ku 1.0 X C L 0.5 Tbv 0.0 1 10 100 Frequency [GHz] Tb sdev decreases when frequency decreases The site is stable at L band
  • 17. IGARSS- Vancouver – July 24-29 2011The electromagnetic modelThe snowpack is modeled as a stack of n layers with planar boundaries overa half-space medium. zEach layer is characterize by: qi temperature Tl, d0 grain radius rl, d1 d2 depth dl, d3 . density rl, n layers . . dn-1 fractional volume fl, dn permittivity eeff l. Half-spaceAll the parameters used in the model are derived from Dome C snowpackmeasurements (EPICA, Drinkwater et al.,2003).
  • 18. IGARSS- Vancouver – July 24-29 2011The electromagnetic model The permittivity of the layers is modeled by using the SFT. The model is based on the wave approach which accounted for the reflection and transmission between the layers by means of the propagating matrix (Kong,1990). The vertical and horizontal brightness temperatures are expressed by adding the contributions of the snow layers by means of the fluctuation dissipation theorem (Jin,1984).
  • 19. IGARSS- Vancouver – July 24-29 2011Model Results Comparison of temporal trends 1.4 GHz The model is able to estimate the 6.8 GHz e.m. data with 10 GHz a good accuracy 19 GHz Some discrepancy are present 37 GHz at Ku- and Ka-band
  • 20. IGARSS- Vancouver – July 24-29 2011Model Results Penetration depthsFrequency Penetration (GHz) depth (m) 1.4 165 6.8 22 10 12 19 3.5 37 1.5 Penetration Depth
  • 21. IGARSS- Vancouver – July 24-29 2011Conclusions The DOMEX-2 experiment started in November 2008 and ended in December 2010. The high temporal stability of Tb at V polarization is confirmed in both 2009 and 2010. Tb at H polarization exhibits a high fluctuation due to the surface and sub-surface effect (as expected). The angular and temporal trends exhibit a very good agreement with SMOS data Multi-frequency data emphasize the mechanisms that dominate the emission of the ice sheet A e.m. was developed and validated using satellite and ground data The e.m. is able to explain the jumps observed in H pol. data
  • 22. RADOMEX looking in the Antarctic night IGARSS- Vancouver – July 24-29 2011 Thanks for the attention!