Chiara Piccolo and Anu Dudhia

1
Precision Validation

• Chiara Piccolo and Anu Dudhia

2
Random error

• mapping of the radiometric noise on the retrieved
  profiles
• proportional to NESR and inverse proportional to
  temperature (it does not directly depend on VMR
  profiles)
• pT error propagation contribution
• does not depend on target species profile
• included in the error budget
• Pressure registration error
• due to lack of knowledge of the pressure at the
  tangent altitude although the pointing is known
• depends on the target species profile
• very small not included in the error budget

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H2O RND time series
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HNO3 RND time series
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RND time series

• Variability of RND with time is evident for both
  species in the polar latitude bands
• peak in polar winter cases
• smaller intensity in Northern Hemisphere
• second peak in Feb04 (Northern polar bands)
• no variation at midequatorial latitudes
• All other species present similar behaviour
• Are these variations due to temperature?
• Does the NESR vary with time?
• Jul-Aug02 and Oct02 missing Antarctic L2 data

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NESR time series
Jul-Aug02 and Oct02 Missing Antarctic L2
profiles Sep03 missing Antarctic NESR data
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Temperature time series
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NESR T time series

• NESR slightly depends on the variation of the
  signal with time through the variation of
  atmospheric temperature
• Temperature variations with time explain quite
  well RND variations in both hemisphere
• the increase of RND error at polar winters
  corresponds to the decrease of temperature
• double peaks in northern polar winters correspond
  to double deeps in temperature
• low (150K) Temperature Oct02 for 20S-EQU?
• September 03 missing Antarctic NESR data?

9
Validation methodology

• Precision dispersion of an ensemble of
  retrievals of the same atmospheric state
• Approximation pairs of measurements located at
  the intersections of MIPAS viewing tracks
• Standard deviation of the ensemble of the profile
  pairs is a combination of the random
  uncertainties and the variability of the
  atmosphere
• Comparison between matching profile pairs and
  predicted random error given by MIPAS Offline L2
  data (but NO2 since large diurnal difference at
  intersections)
• Matching criteria 300km for every 5 days per
  month
• within 6h matches near the poles only
• within 12h matches at three additional latitudes

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Matches locations
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Matches at 80N-90N
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Validation Results

• Time series of the ratio of the statistic of
  observed scatter over the predicted random error
  (with and without pT error contribution included)
  for the four latitude bands (90S-80S, 80S-60S,
  60N-80N, 80N-90N)
• TEM follows seasonal variability
• H2O, O3 and N2O big oscillations that could be
  caused by oscillating matched profiles (time
  series different one day to the next)
• HNO3 and CH4 SD of the matching pairs ensemble
  reasonable explained by predicted random error
  when pT error contribution included

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Only RND error
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RND pT error
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TEM RND time series
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O3 RND time series
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CH4 RND time series
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N2O RND time series