Stratospheric NO y Studies with the SLIMCAT 3D CTM

Stratospheric NOy Studies with the SLIMCAT

3D CTM

Wuhu Feng, Stewart Davies, Jeff Evans and Martyn Chipperfield School of the Environment, University of Leeds, Leeds, UK

AcknowledgmentsBhaswar Sen, Geoff Toon (NASA JPL)and all TOPOZ and VINTERSOL scientists

Studies of NO3 Chemistry

Comparison with balloon and aircraft NOy data

Improved Arctic 2002/03 Winter ozone loss

Coupled microphysical model (DLAPSE/SLIMCAT)

Long-term NO2 trends

SLIMCAT 3D-CTM 3D Off-line Chemical Transport model

Horizontal winds and T from analyses (ECMWF, UKMO)

- vertical coordinate

Tracer Transport

Default advection Scheme: Prather 2nd order moment scheme

Vertical motion: CCM or MIDRAD radiation scheme

Detailed Chemical Scheme:

41 chemical species;

123 gas phase chemical reactions;

32 photolysis reactions

~9 heterogeneous reactions on liquid sulphate aerosols and solid PSCs

http://www.env.leeds.ac.uk/slimcat

Chipperfield M. P., JGR 104, 1781-1805, 1999

NO3 has very simple chemistry in the stratosphere:

NO2 + O3 NO3 + O2 (1)NO3 + h NO2 + ONO3 + 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!)

Stratospheric NO3 Chemistry

1k

3k

SALOMON Balloon observations J.B. Renard et al (CNRS, Orleans)

Nighttime (moonlight) observations of NO3, NO2 and O3.

O3

NO3

21/1/2002

Model underestimates observed NO3, but steady-state a very good approximation 15-40 km.(Not a problem due to O3 which agrees well).

Testing of NO3 Chemistry from Balloon Observations

NO3/O3

k for O3 + NO2

ln(k)

Model underestimates NO3 at high T

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)

Comparison of 6 SALOMON flights with SLIMCAT

• To quantify and understand the degree of chemical ozone loss in

the Arctic stratosphere is an important issue

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.

1) Transport problem (Different Cly and NOy in a given model lead to significant difference in chemical process).

2) Chemistry process

3) Radiative transfer process

4) Microphysics process

5) Complex interaction between theses processes

Polar Ozone loss

Meteorology

Ozone Hole

• SLIMCAT reproduce the O3 column• Also show POAM PSC and MKIV location

MK IV Interferometer Measurements

Trajectory of the MkIV payload from Esrange across Finland and into Russia on December 16, 2002http://mark4sun.jpl.nasa.gov/

• Fourier Transform Infra-Red (FTIR) Spectrometer• By Jet Propulsion Laboratory in 1984• Remote-sensing by solar absorption spectrometry• Provides stratosphere gases including NOy

NOy-N2O Correlation

DenitrificationRenitrification

• Model captures denitrification/renitrification signal well

NOy Partitioning

• Model Captures major features of NOy species distribution• NO2 is poor in the lower stratosphere

ClONO2 and ClO

The model overestimate ClONO2 due to underestimate the chlorine activation!

NOy Ratios

• HNO3 and N2O5, ClONO3 overestimate, NO2 poor below 25Km

M55 Geophysica Aircraft

http://www.knmi.nl/goa/workshopprogr.html

Comparison with Aircraft data (Cold region)

• Different radiation transfer process result in different descent• Good simulation of NOy for the cold region (T< 195K)

Comparison with aircraft data (T>200K)

SLIMCAT model overestimate denitrification due to equilibrium scheme

Comparison with O3 sondes

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.

Ozone loss

Different local ozone loss and polar ozone loss CTM with MIDRAD radiation scheme lead to less O3 loss

1999/2000 Arctic winter

Example 3D results for 19/12/2002 505K

Modelled HNO3 decrease in good agreement with MIPAS

(see EU MAPSCORE Project)

A Lagrangian particle sedimentation model (DLAPSE, Carslaw, Mann et al.) has now been fully integrated with SLIMCAT code.

Fully Coupled Microphysical Model for Denitrification

Two runs:

•1989 – 2003. ECMWF (ERA40/operational) winds. 7.5o x 7.5o x 20 levels (0-60km).

•(1) Time-dependent source gases (CFCs, CH3Br, CH4, N2O etc from WMO [2003])

•(2) As (1) but with fixed N2O after 1990.

Studies of Long-term NO2 trend

Run 311 – with observed surface N2O trend.Run 313 – As 311 but with constant surface N2O after 1990.

3D CTM v Lauder NO2 Observations

am pm am pm am pm

NO28.9 ± 0.4 7.8 ± 0.4 12.3 ± 3.3 9.9 ± 2.6 9.7 ± 3.3 7.5 ± 2.6

NOy-5.0 ± 2.3 -5.2 ± 2.2 -7.5 ± 2.3 -7.6 ± 2.2

N2O 3.5 ± 0.3 3.5 ± 0.3 0.4 ± 0.3 0.4 ± 0.3

Trend model: linear trend, QBO, solar cycle, ENSO, offset annual cycle (K. Kreher, NIWA)

Trend values in %/decade

Obs.Model (with N2O trend)

Model (without N2O trend)

NOy, N2O should not show am/pm difference !

Observed (1/1981- 9/2003) + Modelled (1/1989-6/2003) Lauder Trends

ConclusionsNO3 ChemistryNight-time NO3 is independence on any other NOy species. The assumption of model steady state NO3 is good although model underestimates the observed NO3

Comparison with MK4 Balloon and aircraft data:Model Captures denitrification/renitrification signal and major features of NOy species distribution well, but poor NO2 simulation in the LS;SLIMCAT can simulate the observed low NOy well in the cold region, but overestimate denitrification at high T due to the equilibrium scheme Improved Poalr Ozone lossDifferent radiation scheme result in different transport and ozone loss High resolution simulation gives better NOy partitioning Coupled microphysical model (DLAPSE/SLIMCAT)Successful denitrification compared with MIPAS Long-term NO2 trendModel captures the observed increase NO2 trend,positive N2O give a negative NOy

Future work

Rerun SLIMCAT model using chemical species from Reprobus CTM as initialisation.

Comparison with MIPAS data (NOy..) for 2002/03 winter.

Intercomparison with other CTMs.