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
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
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
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.
IGARSS- Vancouver – July 24-29 2011The DOMEX Campaign TOWER VIEW Air temperature Mean: - 53 degs Max: - 23 degs Min: - 78 degs Concordia base
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
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 !!!
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
IGARSS- Vancouver – July 24-29 2011Domex-2 : 2010 campaign Power Failure Problem PC crash April 10 Solved –July 2010 11 months data
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?
IGARSS- Vancouver – July 24-29 2011Possible Explaination: wind effect Lines= High Wind Speed (> 7 m/s)
IGARSS- Vancouver – July 24-29 2011DOMEX- Angular Trend
IGARSS- Vancouver – July 24-29 2011SMOS – comparison: Angular Trend dots – SMOS lines - DOMEX SMOS data provided by CESBIO
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!
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
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).
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).
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
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
RADOMEX looking in the Antarctic night IGARSS- Vancouver – July 24-29 2011 Thanks for the attention!