A view on mid- tropospheric CH 4 and CO 2 in the tropics: 6 years from MetOp- A/IASI

Transcription

1 2013 EUMETSAT/AMS Conference Vienna, September 2013 A view on mid- tropospheric CH 4 and CO 2 in the tropics: 6 years from MetOp- A/IASI C. Crevoisier 1, R. Armante 1, N. Meilhac 1, S. Massart 2, C. Cressot 3, L. Crépeau 1, T. Thonat 1,4, N. A. Sco? 1, and A. Chédin 1 1 LMD/CNRS, 2 ECMWF, 3 LSCE, 4 U. of Edinburgh cyril.crevoisier@lmd.polytechnique.fr

2 The IASI onstrument IASI provides IASI (Infrared Atmospheric Sounding Interferometer) is a Fourier Transform Spectrometer that measures infrared radiation emitted from the Earth. It has been developed by CNES, in collaboration with EUMETSAT spectral channels between 645 and 2760 cm 1 ( µm) -with a spectral resolution of 0.5 cm 1 after apodisation ( Level 1c spectra) -the spectral sampling interval is 0.25 cm 1. -nadir FOV: 12 km at nadir. -LT: 9:30 am/pm. CO 2 CH 4

3 Retrieval of GHG from IASI observahons in the thermal IR Retrieval procedure (Crevoisier et al., ACP, 2009ab): - Use of IASI channels around 15 µm for CO 2 and 7.7 µm for CH 4. - Non linear inference scheme based on neural networks (Chédin et al., 2003). - Based on the 4A RT code and the latest edison of the GEISA database. - RadiaSve biases are computed using the ARSA database. - CH 4 and T(p) are insmately correlated in the IR. Use of IR (IASI) and MW (AMSU) observasons to decorrelate T from gas variasons. - The decorrelason between T/gas is easier to do in the tropics. be?er precision in the tropical region. We retrieve a mid/upper- tropospheric content: - clear sky only (no clouds, no aerosols) - by day and night (9:30 am/pm) - over land and over sea Pressure (hpa) WeighSng funcsons CH We have now ~6 years (July 2007 August 2013) of mid- tropospheric CO 2 and CH 4 integrated content from IASI.

4 Mid- tropospheric CO2 and CH4 from IASI CO2 Zonally averaged mid- tropospheric CO2 / CH4 as retrieved from IASI from July 2007 to December 2012 CH4 Crevoisier et al., ACP, 2013 Meilhac, in prep. for AMT

5 Mid- tropospheric CO 2 and CH 4 from IASI CO 2 Zonally averaged mid- tropospheric CO 2 / CH 4 as retrieved from IASI from July 2007 to December 2012 CH 4 Crevoisier et al., ACP, 2013 Meilhac, in prep. for AMT

6 Comparison with aircrav measurements CO 2 IASI CONTRAIL MLO Detrended CO 2 seasonal cycle in northern tropics Decrease in amplitude with altitude Collab. H. Matsueda, T. Machida, T. Schuck IASI: 9-15 km (max at 13 km) JAL/CONTRAIL AIRS: 5-15 km (max at 10 km) MLO: 4 km [GLOBALVIEW-2008] Time lag due to vertical transport: Surf. 1 month mid-tropo 1 month upper tropo aircraft ~10 km [Matsueda et al. 2008; Machida et al. 2008]

7 Comparison with aircrav measurements CH4 IASI CONTRAIL Bias: - 9 ppbv Bias: 3 ppbv Over 13 CARIBIC flights, on a 4 x4 grid: IASI CARIBIC = 7.2 ± 13.1 ppbv NB: IASI CO2/CH4 ~6-16 km aircraf CO2/CH4 ~10 km Collab. H. Matsueda, T. Machida, T. Schuck

8 Growth rate of mid- tropospheric CH 4 and CO 2 from IASI Fit of IASI CH 4 (whole tropical band) CH 4 instantaneous growth rate CH 4 Procedure (following e.g. Dlugokencky et al., 1994): Fit: Polynomial trend + 4 harmonics / filering by low- pass filters. Deseasonalized long- term trend = polynomial trend + filtered residuals. Instantaneous growth rate = derivasve of this funcson. Fit of IASI CO 2 (whole tropical band) CO 2 instantaneous growth rate CO 2 Crevoisier et al., ACD, 2013

9 Growth rate of mid- tropospheric CH 4 from IASI 20N- 15N GR from NOAA surface network EQ- 05S CH 4 instantaneous growth rate CH 4 15N- 10N S- 10S 10N- 05N S- 15S N- EQ S- 20S Very good agreement between IASI and surface tropical growth rate IASI has the potenhal to follow methane trend on the long- term

10 Regional level: the Amazonian case - 30 IASI CH4 annual average (ppbv) Carbon monoxide 30 In 2010: severe drought in Amazonia Decrease in wetland emission Decrease of CH4 of ~10ppbv detected by IASI. TRMM annual precipitason (mm) MulSvariate ENSO index AtlanSc MulSdecadal OscillaSon Maximum water deficit

11 Regional level: the Amazonian case Carbon monoxide 30 IASI CH4 annual average (ppbv) MODIS number of fires In 2010: severe drought in Amazonia Decrease in wetland emission IASI CO diurnal variason IASI CO2 diurnal variason Decrease of CH4 of ~10ppbv detected by IASI. The 2010 very dry condisons also induced an increase in fire achvity well seen on CO and CO2 fields derived from IASI

12 Impact of IASI CH 4 on surface flux eshmahon Carbon monoxide Although IASI is sensisve to mid- troposphere, it does provide informason on surface fluxes. Good stassscal consistency between CH 4 flux essmates from IASI, TANSO- FTS and surface network within a Bayesian inversion system. CH 4 global emissions ( ) and losses ( ) Cressot et al., ACPD, 2013 PRIOR SCIAMACHY SURFACE TANSO-FTS IASI

13 IASI CH 4 for surface flux eshmahon Carbon monoxide IASI CH 4 fields are now assimilated in a delayed- mode within ECMWF IFS system together with TANSO- FTS CH 4 fields in the framework of the MACC- II project. The greatest impact of IASI is in the tropics, above 700 hpa. HIPPO data Analysis - HIPPO TANSO TANSO + IASI Overall, the IASI- TANSO analysis is in be?er agreement with the HIPPO data than the TANSO alone or SCIAMACHY alone analyses, with a global difference of 12.3 ppb. Massart et al., in prep. for AMT

14 Conclusion IASI can provide valuable informason on CO 2 and CH 4 cycles: - Long- term evoluson (IASI- 1, 2, 3 + IASI- NG- 1, 2, 3 ) ESA GHG CCI. - InformaSon on surface emissions (even if CH 4 is retrieved only in the mid- troposphere). Carbon monoxide AssimilaSon within the IFS system. Added value to SWIR observasons: both day and night, both land and sea - Link to climate factors, even at regional scale. The simultaneous retrieval of several gases, day and night, over land and sea is a clear asset to allow monitoring local to global events. PerspecSves: - Processing of IASI onboard MetOp- B and - C. - Higher lastudes: good enough precision to provide informason for CH 4 study? ? +7? IASI-A IASI-B IASI-C Merlin IASI-NG-A Sentinel5/UVNS IASI-NG-B IASI-NG-C