SBUV/2 Observations of Atmospheric Response to Solar Variations

1
Rotational Timescales
SBUV/2 Observations of Atmospheric Response to
Solar Variations
Impulsive Events

• Solar irradiance shows clear rotational
  modulation for ? lt 265 nm. Amplitude reaches
  6-7 at 205 nm.
• Ozone response depends on chemical time
  constants, peaks at 2 hPa.

• Solar proton events can inject large quantities
  of charged particles into the upper atmosphere.
• Increased ionization leads to rapid ozone loss in
  upper stratosphere (gt 40).
• Short chemical time constants ? typical recovery
  time of 1-2 days.
• Solar cycle 23 shows logarithmic relationship
  between peak proton flux gt10 MeV and maximum
  ozone depletion 0.5 hPa.

Matthew DeLand Science Systems and Applications,
Inc. (SSAI)
Background

• SBUV/2 instruments measure stratospheric profile,
  total column ozone, solar UV irradiance between
  160-400 nm.
• Continuous measurement record available since
  1978. Future data expected through 2015.

DeLand et al. 2004
Chandra and McPeters 1994
Solar Cycle Timescales
Ozone

• Ozone responses to solar cycle variations
  observed in stratospheric layers and integrated
  total column.
• Model predictions of ?O3 response to ?FUV are
  consistent with data for total ozone, disagree on
  altitude dependence.

- Spectral range of solar irradiance observed by
SBUV/2 directly affects stratosphere. Solar
variability increases significantly at shorter
wavelengths.
Hood 1997
McCormack and Hood 1996
McCormack and Hood 1996
Polar Mesospheric Clouds

• Ionization also increases production of odd
  nitrogen (NOx), which has chemical lifetime of
  several months.
• Transport chemistry predicts sustained ozone
  depletion in middle stratosphere. Observations
  support this prediction, but dynamical variations
  complicate interpretation.

• Polar mesospheric clouds (PMCs) are composed of
  water ice, form at 80-85 km in summer polar
  regions.
• SBUV/2 instrument detects PMCs as albedo
  enhancement at short wavelengths.
• Occurrence frequency shows consistent seasonal
  pattern, variations in amplitude.

• Variations in cumulative seasonal frequency are
  anti-correlated with solar Lyman alpha
  variations. This is consistent with
  photochemical model predictions.

DeLand et al. 2003
Conclusions
References
Chandra, S., and R. D. McPeters, The solar cycle
variation of ozone in the stratosphere inferred
from Nimbus 7 and NOAA 11 satellites, J. Geophys.
Res. 99, 20,665-20,671, 1994. DeLand, M. T., E.
P. Shettle, G. E. Thomas, and J. J. Olivero,
Solar backscattered ultraviolet (SBUV)
observations of polar mesospheric clouds (PMCs)
over two solar cycles, J. Geophys. Res. 108(D8),
8445, doi10.1029/2002JD002398, 2003. DeLand, M.
T., R. P. Cebula, and E. Hilsenrath, Observations
of solar spectral irradiance change during cycle
22 from NOAA-9 Solar Backscattered Ultraviolet
Model 2 (SBUV/2), J. Geophys. Res. 109, D06304,
doi10.1029/2003JD004074, 2004. Hood, L. L., The
solar cycle variation of total ozone Dynamical
forcing in the lower stratosphere, J. Geophys.
Res. 102, 1355-1370, 1997. Jackman, C. H., E. L.
Fleming, and F. M. Vitt, Influence of extremely
large solar proton events in a changing
stratosphere, J. Geophys. Res. 105,
11,659-11,670, 2000. McCormack, J. P., and L. L.
Hood, Apparent solar cycle variations of upper
stratospheric ozone and temperature Latitude
and seasonal dependences, J. Geophys. Res. 101,
20,933-20,944, 1996.

• SBUV/2 instruments observe both solar UV forcing
  and atmospheric response.
• Solar UV irradiance data from NOAA-9 and NOAA-11
  SBUV/2 are available on-line. Mg II index data
  are also available.
• Reprocessed Version 8 profile ozone data from all
  instruments (available June 2004) will have
  improved accuracy for trends.
• Continuation of SBUV/2 measurements provides
  invaluable multi-decade data sets for long-term
  studies.

DeLand et al. 2004
Jackman et al. 2000