Stratospheric NO y Studies with the SLIMCAT 3D CTM. Wuhu Feng , Stewart Davies, Jeff Evans and Martyn Chipperfield School of the Environment, University of Leeds, Leeds, UK. Studies of NO 3 Chemistry Comparison with balloon and aircraft NOy data
Wuhu Feng, Stewart Davies, Jeff Evans and Martyn Chipperfield
School of the Environment, University of Leeds, Leeds, UK
Bhaswar Sen, Geoff Toon (NASA JPL)
and all TOPOZ and VINTERSOL scientists
3D Off-line Chemical Transport model
Default advection Scheme: Prather 2nd order moment scheme
Vertical motion: CCM or MIDRAD radiation scheme
41 chemical species;
123 gas phase chemical reactions;
32 photolysis reactions
~9 heterogeneous reactions on liquid sulphate aerosols and solid PSCs
Chipperfield M. P., JGR 104, 1781-1805, 1999
NO3 has very simple chemistry in the stratosphere:
NO2 + O3NO3 + O2 (1)
NO3 + h NO2 + O
NO3 + h NO + O2
NO3 + NO2 + M N2O5 + O2 (2)
At night in the low-mid stratosphere NO3 can still be in steady state:
[NO3] = k1[NO2][O3]/(k3[NO2][M]) = k1[O3]/(k3[M])
Nighttime [NO3] determined solely by O3 and T (no dependence on NOy!)
SALOMON Balloon observations
J.B. Renard et al (CNRS, Orleans)
Nighttime (moonlight) observations of NO3, NO2 and O3.
Model underestimates observed NO3, but steady-state a very good approximation 15-40 km.
(Not a problem due to O3 which agrees well).
Model underestimates NO3 at high T
O3 + NO2
Can derive best fit for k1:
k1 = 6 x 10-13 exp(-2740/T)
compared to JPL:
k1 = 1.2 x 10-13 exp(-2450/T)
Renard et al., J. Atmos Chem (submitted)
But current models can’t give a satisfactory of the observed ozone loss based on the fact that models can not reproduce the observed ozone.
Trajectory of the MkIV payload from Esrange across Finland and into Russia on December 16, 2002
The model overestimate ClONO2 due to underestimate the chlorine activation!
SLIMCAT model overestimate denitrification due to equilibrium scheme
SLIMCAT model (2.8 x 2.8) with CCM radiation scheme can successfully reproduce observed O3 in the polar region and midlatitude.
Large O3 depletion occurred by the end of March.
A Lagrangian particle sedimentation model (DLAPSE, Carslaw, Mann et al.) has now been fully integrated with SLIMCAT code.
Example 3D results for 19/12/2002 505K
Modelled HNO3 decrease in good agreement with MIPAS
(see EU MAPSCORE Project)
Run 311 – with observed surface N2O trend.
Run 313 – As 311 but with constant surface N2O after 1990.
Trend model: linear trend, QBO, solar cycle, ENSO, offset annual cycle (K. Kreher, NIWA)
Trend values in %/decade
Model (with N2O trend)
Model (without N2O trend)
NOy, N2O should not show am/pm difference !
SLIMCAT can simulate the observed low NOy well in the cold region, but overestimate denitrification at high T due to the equilibrium scheme
Different radiation scheme result in different transport and ozone loss
Successful denitrification compared with MIPAS
Model captures the observed increase NO2 trend,positive N2O give a negative NOy