Global measurements of isoprene from CrIS
Kelley Wells, Dylan Millet, Dejian Fu, Vivienne Payne With thanks to: Julian Deventer, Kevin Bowman, Timothy Crawford, Brian Drouin, Annemarie Eldering, Evan Manning, Ruth Monarrez, Keeyoon Sung, Shanshan Yu, Chris Barnet, SENEX/SEAC4RS teams
IGC9, 6 May 2019
VOCs
O3, CO, formaldehyde (HCHO)
Secondary Organic Aerosols (SOA)
OH, hν Isoprene impacts
O3 and SOA, N-cycle,
other oxidants
Bottom-up emission estimates span a wide range, space-based constraints using HCHO present challenges
535 570
150
Isoprene Methane Anth VOCs
Global Annual Emissions (Tg/yr)
235 Tg/y
• Emission uncertainties due to meteorology, land cover, canopy parameterization, etc.
• Top-down constraints based on HCHO hindered by non-linear relationship across NOx regimes, other HCHO sources
Wolfe et al., 2016
MEGANv2.1 in GEOS-Chem
Measurements of TIR absorption cross section of isoprene enable direct retrievals from CrIS
Cross-track Infrared Sounder (CrIS): • Launched 10/2011 (Suomi-NPP),
11/2017 (NOAA-20), expected 2022 • Near global coverage twice daily • Equator overpass ~1:30 LT • Low noise
Brauer et al., 2014
893.125, 893.75 “peak”
894.375, 895 “rhs”
Global distribution via Tb difference:
ΔTb = Tb,rhs – Tb,peak
From single-footprint cloud-screened Level 1B data
Isoprene H2O HNO3
Wavenumber (cm-1)
ν28 ν27
• Training set = one year RT simulation over land (~165,000 spectra) • GEOS-Chem isoprene w/ noisy scaling • 10 random extractions
• Forward prediction: MERRA-2 T and H2O, CLIMCAPS CrIS HNO3
HNO3 column Isoprene column
We employ an artificial neural network to derive global isoprene from CrIS Tb difference
ΔTb
Satellite view angle
Thermal contrast
H2O vapor column
Surface pressure
Input layer Hidden layers Output layer
e.g., IASI NH3, methanol, formic acid, PAN, acetone
(Whitburn et al., 2016, Franco et al., 2018; 2019)
CrIS isoprene consist with aircraft measurements over US Southeast
June-July 2013
Aug-Sept 2013
July 2013
[molec/cm2]
[molec/cm3]
[molec/cm3]
CrIS isoprene column GEOS-Chem isoprene column
July 2013
First global space-based isoprene distribution
April 2013
Seasonality of CrIS isoprene consistent with in situ measurements in Amazon basin, seasonal shift in phenology
Jan Apr
Jul Oct
Low LAI corresponds to dominance of young leaves
between wet and dry seasons = low isoprene emissions
Wei et al., 2018
Wet season Dry season
Extra slides
ANN performs well against full synthetic data set, uncertainties higher for low isoprene amounts and low thermal contrast
“True” isop (molec/cm2)
Pred
icte
d iso
p (m
olec
/cm
2 )
Ther
mal
con
tras
t (K)
“True” isop (molec/cm2)
Seasonality of CrIS measurements consistent with in situ measurements in SE Australia
Jan Apr
Jul Oct
CrIS isoprene consistent with detailed bottom-up inventory for Southern Africa
Jan Apr
Jul Oct
Jan Jul
Otter et al., 2003
