Earth Observation for Water Cycle Science 2015, 20th -23rd October, ESA-ESRIN
Two Decades of Water Vapour Total Column from ATSRs using the Advanced Infra-Red Water
Vapour Estimator (AIRWAVE) tool
S. Casadio1,3, A. Burini2,3, B.R. Bojkov3, E. Castelli4, B.M. Dinelli4, E. Papandrea4
1
SERCO s.p.a.; 2 RHEA Group S.a.; 3 ESA/ESRIN; 4 ISAC-CNR Bologna
Figure 1: TCWV field (10 km grid, 1991-2012 average)
AIRWAVE is a new algorithm for the retrieval of the atmospheric water vapour total
column (TCWV) using the Thermal InfraRed (TIR) measurements from the two TIR
channels of the Along Track Scanning Radiometer (ATSR) instrument series, on board the
European Space Agency’s ERS-1, ERS-2 and ENVISAT satellites spanning 1991 to 2012.
The use of the dual view capability of the ATSR-type instruments allows for the accurate
and precise, day-time and night-time retrievals of cloud free TCWV over oceans. The
retrieval scheme uses the instrument physical characteristics, in combination with
advanced radiative transfer models and a sea surface spectral emissivity database. The
retrievals therefore do not require algorithm tuning or adjustments to independent water
vapour datasets (Casadio et al., 2015).
1
α=
λ1
∆σ FWD
 J1 
1−
ln λ2  − Ε − χ − ∆σ CO 2 ⋅ ρCO 2
δ
⋅
∆
σ
NAD
J
Φ=

2

∆σ H 2O
TCWV = α ⋅ Φ NAD + β ⋅ Φ FWD
1
β=
δ ⋅ ∆σ NAD
1−
∆σ FWD
Figure 2: Left panel: AIRWAVE (ATSR-2) TCWV at 1x1 km2 resolution (10am local time); centre
panel: AIRWAVE TCWV aggregated at SSM/I spatial resolution (0.25°x0.25°); right panel:
collocated SSM/I TCWV (1pm local time)
Figure 3: Left panel: TCWV from Weather Research and Forecasting Model (WRF, WRF: http://www.wrfmodel.org/index.php); right panel: AIRWAVE (AATSR) TCWV. Lee waves, generated by Mistral wind
(NW),after the passage of a cold front, are clearly visible downwind Corse and Sardinia in both datasets
Figure 5: AIRWAVE TCWV zonal average anomalies (reference: 1999-2002). The following El Niño events are clearly
detectable: 1991-1992 (moderate), 1997-1998 (very strong); 2003 (moderate); 2009-2010 (moderate)
Figure 4: Upper plot: percentage of cloud-free ATSR pixels (ocean, monthly mean). Centre plot: blue =
ERA_I – ERA-I(cloud free), green = ERA-I – AIRWAVE; brown = ERA-I(cloud-free) – AIRWAVE; red =
ERA-I – AIRWAVE (collocated). Lower plot: same as centre plot but for RMSE (standard deviation).
Vertical lines indicate the different ATSR operation periods.
Figure 7: AIRWAVE vs. Analyzed RadioSoundings Archive (ARSA) TCWV (1991-2012). Left panel: AIRWAVE
vs. ARSA scatterplot; right panel: location of ARSA stations used for validation. Colours indicate the number of
collocations (red=high, blue=low)
References
Casadio et al. (2015), Total Column Water Vapour from Along Track Scanning Radiometer Series
Using Thermal Infrared Dual View Ocean Cloud Free Measurements: the Advanced Infra-Red
WAter Vapour Estimator (AIRWAVE) algorithm, Remote Sensing of Environment (accepted)
Figure 6: Upper panel: TCWV zonal averages for 2-5 December 1995. ATSR-1 (red),
ERA-Interim (black, left plot), SSM/I (black, right plot); lower panel: same as upper
panel but for ATSR-2
ARSA: http://ara.abct.lmd.polytechnique.fr/index.php?page=arsa
Contact:
[email protected] ([email protected])