ACVE-2 template

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Validation of MIPAS-ENVISAT Ozone Data
U. Cortesi, IFAC-CNR with contributions of the
ENVISAT Atmospheric Chemistry Validation Team
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OUTLINE

MIPAS operation and products

Overview of MIPAS O3 validation activities within
the ENVISAT Atmospheric Chemistry Validation
Programme - Ground-based measurements -
Aircraft/balloon measurements -
Satellite-satellite intercomparisons

Work in progress - Merging of the information
from individual MIPAS O3 validation
datasets - Validation approach and first
results - Future activity and plans for
publication of final results
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MIPAS operation and products
MIPAS is a Fourier transform spectrometer that
was launched on the ENVISAT satellite on 1st of
March 2002 Limb measurements of the atmospheric
emission spectrum spectral range 685
2410 cm-1 (l 14.6 4.15 mm) spectral
resolution 0.025 cm-1 Target species
Temperature, O3, HNO3, H2O, CH4, N2O and
NO2 MIPAS operated until the 26th March 2004
providing NRT and OL products for all the target
species. The instrument was stopped on 26th March
2004 for too frequent anomalies in the
interferometric mirrors drive. Operation at
reduced spectral resolution (0.0625 cm-1) and
with a new measurement scenario resumed in
January 2005 (the quality of Level-2 operational
products is only marginally reduced).
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Ground-based correlative measurements
O3 data from different stations and independent
techniques operated within the Network for
Detection of Stratospheric Changes.
Station Latitude Measurement techniques Kiruna
68N FTIR Uccle 51N O3
sondes Hohen-peissenberg 48N Lidar Payerne
46N O3 sondes, MWR Mauna Loa 20N O3
sondes, Lidar, MWR Lauder 45S O3 sondes,
Lidar, MWR, FTIR Arrival Heights 78S FTIR
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Relative differences between MIPAS O3 profiles
and ground-based correlative measurements
Altitude range km O3 sondes Lidar MWR FTIR
lt 20 gt 20 gt 20 15
20 30 10 10 5 12
30 40 10 10
40 -50 gt 20 10-20
A good agreement is obtained in the 2040 km
range, with differences within the combined error
bars
Larger discrepancies below 20 km and above 40 km,
where MIPAS O3 VMR values tend to exceed those
measured by lidars and MWR
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Intercomparison with satellite measurements
Systematic comparisons of O3 data retrieved by
MIPAS and co-located satellite measurements for
the period July December 2002 - HALOE,
SAGE-II, POAM-III (Solar occultation sensors) -
GOME, TOMS (Nadir sounders) - Odin
SMR (Limb sounder) Generally good agreement at
pressures lt 50 hPa, with MIPAS bias respect to
other sensors 5-10 in the range 50 0.5 hPa
(except PSCs) Larger deviations for pressure gt
50 hPa, below a thresold altitude that decreases
with increasing latitude in the autumn hemisphere
(consistently in comparisons with solar
occultation and nadir sounders). Differences are
particularly pronounced in the tropics, due
to (1) the combined effect of O3 steep vertical
gradients and different sampling/ vertical
resolution of MIPAS and other satellite
instruments (2) Cirrus contamination
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Aircraft and balloon-borne correlative
measurements
MIPAS O3 validation included intercomparisons
with snapshot measurements acquired in the frame
of the ESABC activity - Balloon-borne FTIR
(FIRS-2, IBEX, MIPAS-B, LPMA, MANTRA-SPS),
SAOZ, TDL (SPIRALE) and UV-Vis (SALOMON)
spectrometers, - In-situ and remote-sensing
payloads aboard the FALCON and the M-55
Geophysica aircraft platforms in general, good
agreement is found between 20 and 40 km
Significant differences are observed, in
several cases, at lower altitudes (i.e. below 20
km)
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Validation of MIPAS O3 Operational Products WORK
IN PROGRESS
Objective to exploit the information from the
available datasets of correlative measurements
for an overall assessment of MIPAS O3 data
quality during the instrument full resolution
mission (06.07.2002 26.03.2004)
Validation approach MIPAS data versions adopted
for the validation task IPF v4.61 or
v4.62 Stringent criteria for space-time
coincidence. Baseline 300 km, 3 h Additional
criterion based on PV differences to be taken
into account for intercomparison of polar winter
measurements Use of trajectory calculations to
enhance the number of useful coincidendes
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Pseudo-global comparison with NDSC/GAW ground-base
d network data (Lambert et al., BIRA-IASB,
Belgium)
Analysis of time series of the differences
between MIPAS and ground-based O3 partial column
data (39 O3s, 8 lidars, 7 MWR) collected from
NDSC, SHADOZ, ENVISAT Cal/Val and WOUDC
archives. Data analysis and interpretation based
on assimilated ozone fields by the BASCOE data
assimilation system Error budget estimate of
individual contributions from differences in
vertical and horizontal smoothing and from
spatial mismatch Co-location 500 km, 12 h
(O3s and lidars), 15 min to 2 h (MWR) Partial
columns defined on 5 layers, ranging from 75 to
0.8 hPa (approximately 18 50 km)
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Time series of the percentage relative difference
in O3 partial columns between MIPAS and O3
sondes/lidar data from Western and Central Europe
stations
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Intercomparison of time series of O3 partial
column data conclusions

• Observed differences
• Lower stratosphere gt ? synoptic
  behaviour (dynamics)
• Higher stratosphere gt ? zonal
  behaviour (photochemistry)
• Total error budget
• Errors due to MIPAS gt uncertainty associated
  to gt errors due to vertical
• horizontal smoothing geolocation
  differences smoothing differences
• The different error components generally account
  for the observed
• differences in O3 partial columns, with the
  following exceptions
• In the 75-35 hPa layer at mid-latitudes, equator
  and tropics
• In the 35-15 hPa layer at equator,tropics and
  Antarctica during O3 hole
• In the 3-0.8 hPa layer at European stations

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Comparison of MIPAS v4.61/4.62 O3 profiles with
SAGE II v6.2 (A. Bracher and M. Weber, Univ.
Bremen, Germany)
Latitude Mean Relative Deviation RMS Month/Year N
60S 90S 2 - 8 _at_701.8 hPa 4 10 Dec02, Feb04 69
28S 60S -4 - 8 _at_600.5 hPa 5 10 Jan03/04, Apr-May03, Jul03 64
30N 60N -5 - 4 _at_ 70-0.6 hPa 4 10 JanMar03, Apr03, Jul02/03 29
60N 90N -5 - 4 _at_ 70-0.6 hPa 4 10 AprJun03, Jul02/03, Sep03 155
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Northern Hemisphere
Southern Hemisphere
Mid latitudes
High latitudes
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Coordinated activity for MIPAS O3 validation will
be completed by the end of 2005.

Final results will be collected in a paper, that
is presently in preparation for a MIPAS special
issue to be submitted to Atmospheric Chemistry
and Physics in the first months of 2006.