1. GROUND-BASED SAOZ–UV-VIS NDACC
ORIGIN OF SATELLITES AND SAOZ/NDACC TOTAL OZONE DIFFERENCES IN THE TROPICS AT BAURU IN BRAZIL AND REUNION ISLAND
J.-P. Pommereau(1), A. Frihi(1), F. Goutail(1), S. Bekki(1), A. Pazmino(1), C. Clerbaux(2), J. Hadji-Lazaro(2), A. Boynard(2), C. Lerot(3), M. Van Rozendael(3), T. Dackaert(3), P.F. Coheur(4), T. Portafaix(5)
(1) LATMOS, CNRS, UVSQ, St Quentin, France (2) LATMOS, CNRS, UPMC, Paris, France, (3) BIRA-IASB, Brussels, Belgium, (4) ULB, Brussels, Belgium,(5) LACY, Univ. La Réunion, France
TOTAL OZONE MEASUREMENTS
SATELLITES overpasses above SAOZ stations
GOME CCI ( ), GOME2 CCI ( ), SCIAMACHY ( ), TOMS ( ), NPP ( ), SBUV ( ), OMI-TOMS ( ), OMI-DOAS ( ), IASI ( )
GROUND-BASED SAOZ–UV-VIS NDACC
REUNION Island (21°S, 55°E) and BAURU Brazil (22°S, 49W)
Zenith sky at twilight 86-91° SZA, Visible Chappuis bands
Version 2 retrieval following NDACC WG recom
Daily Air Mass Factors from TOMS V8 ozone profiles climatology
Data cleaned for thick clouds and rainfall from SAOZ O4 and H2O
INTERANNUAL VARIABILITY
13 MONTHS RUNNING MEAN
SBUV
SAOZ
Very similar variations in the two independent measurements
Difference of opposite sign (SBUV TOC larger in Reunion, the opposite on SAOZ TOC)
Increasing difference between Bauru and Reunion on SAOZ but absent on SBUV
TROPOSPHERIC OZONE IN BAURU and REUNION
from RS, SHADOZ, MOZAIC and Lidar in REUNION and BAURU
OZONE PROFILES MOL/CM3
INTEGRATED PROFILES (DU)
REUNION
BAURU
REUNION: biomass burning export from Austral Africa
Max O3 between 3-8 KM in Sep-Nov
BAURU: Local O3 biomass burning production below 3 km in Aug-Nov
OZONE-Pause Tropopause at 16 km in Bauru and 13 km in Reunion
30% (15 DU) smaller Tropospheric column in BAURU
Excellent agreement between OMI MLS and integrated profiles
TOC % DIFFERENCE BETWEEN BAURU AND REUNION
SEEN BY SBUV AND SAOZ
Similarity of high frequency SAOZ and Satellites TOC measurements
REAL TOC VARIATIONS, HIGH PRECISION
Mean SAOZ 1%TOC increase between not seen by SBUV and other SAT
CONSEQUENCES ON SATELLITES AND SAOZ TOC
Satellites TOC larger in Reunion
SAOZ TOC Stratosphere only, no difference between Bauru and Reunion
Both near InterTropical Convergence Zone (ITCZ) in summer
But BAURU continental and REUNION oceanic
SAOZ TOTAL OZONE
BAURU REUNION
Satellite and SAOZ Avg Kernels
SAOZ not sensitive to tropospheric ozone
SUMMARY OF FINDINGS
Large agreement between Satellites Bauru and Reunion TOC in (although some small satellite dependent biases in Reunion)
Excellent correlation between high frequency Satellites and SAOZ TOC variations
REUNION SBUV TOC 10DU larger than BAURU TOC. The opposite on SAOZ
III. IMPACT OF OZONE PROFILE CHANGES
Ozone profiles TOMSV8 climatology at 15° and 25°S
used in SAOZ Air Mass Factor calculation
Hendrick et al. 2011
Seasonality DU, Oct max, QBO
SAOZ TOC little larger in BAURU
Increasing difference after 2004
DISCUSSION
ORIGIN OF DIFFERENCES BETWEEN AND SATELLITES AND BETWEEN BAURU AND REUNION
SATELLITE-SAOZ MONTHLY MEAN % DIFFERENCE
Limited biases <1% between most satellites, except IASI 3, OMID -2%
Sharp negative peaks in summer (larger on SBUV and OMIT)
2% mean seasonnality, smaller on IASI 3%, OMID -2%
Bias and Seasonality reduction after 2012
REUNION
BAURU
Similar biases between all satellites and SAOZ (IASI and NPP +1%)
2-3% Seasonality
Biases reduction after 2004, even larger after 2014
Latitude and total ozone dependences
I. CLOUD IMPACT ON SATELLITES OBSERVATIONS
TOC varying between 240 and 280 DU in Bauru and 245 and 290 DU in Reunion
Geographic latitude almost identical (21°S in Reunion, 22°S in Bauru)
Northward shift of Bauru Equivalent Latitude (EqL)
Bansi
11 Jan
Dumile
3 Jan
Bejisa
Haliba
9 Mar
Gelane
22 Feb
Fanele
21 Jan
Diwa
5 Mar
Ernest
22 Mar
Gaël
1 Fev
Giovanna
13 Feb
Hondo
28 Feb
Sat-SAOZ before cloud top cleansing,
Bias corrected
Gamede
25 Feb
Hurricanes in REUNION
1-2 episodes per year in Dec-Mar. Several hundred km diameter anvil at 16-18km for 3-5 day
SAOZ data cleansed for high O4 and H2O
Satellites: removal from cloud top or indices when available
Tropospheric ozone replaced by zonal climatology
Equivalent latitude (EqL) evolution since 1992 at 475K level (22 km) in Bauru and Reunion
Bauru mean EqL of 15-17°S in winter and 25°S in summer
Bauru EqL shift northward at an average rate of 1° per year
Reunion EqL at 22°S in winter and 27-28°S in summer
Reunion EqL shift southward at a rate of 0.5°/ year
Development of deep convective clouds in the afternoon frequently overhooting up to km
CONSEQUENCES ON SAOZ AMF AND TOC
SAOZ Air Mass Factors
CONSEQUENCES
Underestimation of ozone TOC in summer
Generation of apparent SAT-SAOZ seasonnality
SATELLITES AND SAOZ
TOTAL OZONE
SEASONALITY AND BIAS
REUNION
BAURU
Seasonality 35 DU
Smaller on IASI and NPP
Seasonality 25 DU
Smaller on IASI
larger on SAOZ
2% mean amplitude
Austral summer minimum
OMID not significant
GOME anomaly
Lesser amplitude
Summer min shifted to Oct-Nov
II. TROPOSPHERIC OZONE
OZONE PRODUCTION BY BIOMASS BURNING DURING THE DRY SEASON
IN THE SOUTHERN TROPICS IN AUG-NOV
MODIS Fires Counts Climatology
Yamasoe et al., Tellus B 2015
OMI MLS Tropospheric Ozone
Ziemke et al. ACP, 2011
AMF increase by 1.6% on average at all seasons since 2004 in Bauru
Apparent 4 DU TOC increase consistent with Satellite SAOZ difference
CONCLUSIONS
Difference between Satellites and SAOZ of similar shape with all satellites but of variable amplitude
Seasonality could be coming from ignorance of seasonal change of equivalent latitude in AMF calculations
Perturbations of satellite measurements by hurricanes high clouds not properly identified in IASI, OMI-T, OMI-CCI, NPP, SCIA, GOME2
Slow increase of Reunion Island Equivalent Latitude
PERSPECTIVE
Improved detection and correction of very high clouds in satellite data
Improved Air Mass Factor calculations
The authors thank the SAOZ stations operators. The SAOZ network is part of NDACC (Network for detection of Atmospheric Compostion Change).
The authors thank gratefully Cathy Boone at French « ESPRI Data Center » (former ETHER) for providing ECMWF operational and re-analysis data (ERA-Interim)
Satellites data sets are found on : for OMI-T and for OMI-D; ftp://toms.gsfc.nasa.gov/pub/sbuv/MERGED/ for SBUV r5.v8 ftp://toms.gsfc.nasa.gov/pub/omps_tc/overpass/ for NPP.
MOZAIC Ozone tropospheric profiles are on