SCIAMACHY solar irradiances during solar cycle 23 and beyond

Mark Weber, Joseph Pagaran, Stefan Noël, Klaus Bramstedt, and John P. Burrows

weber@uni-bremen.de

TOSCA Workshop, Berlin, 14-16 April 2012

Motivation

• x

• SCIAMACHY observes SSI in UV/vis/near-IR

• solar irradiance changes in the optical range and (near) UV

– relevant for TSI composition (near UV and vis)

– atmospheric heating rates (uv)

• Challenges:

– above 300 nm solar cycle variability is below 1%

– Optical degradation affects long-term stability of UV SSI

• Atmospheric and climate impact requires knowlege of spectral solar variability (particularly in theUV)

Grey et al., 2010

continuous SCIA spectral range

Topics

• ENVISAT/SCIAMACHY mission • Solar irradiance observations• Comparisons with other SSI data• SCIA proxy model• Degradation correction

SCIAMACHY

• Launch date: February 28, 2002• Polar, sun-synchronous orbit • Descending node: 10:00 LST• Altitude: 800 (783) km

Features:• UV/Vis/NIR grating spectrometers:

220 - 2380 nm• Moderate spectral resolution:

0.2 – 1.5 nm• Measurement Geometries:

SCIAMACHY = SCanning Imaging Absorption spectroMeter for Atmospheric CHartograpY

ENVISAT mission status

• SCIAMACHY instrument: was healthy, no large data gaps (2002-2012)

• lost complete communication with ENVISAT on Easter Sunday (April 8th)

• ESA declared mission end (May 10th)– attempts to re-establish contact will

continue until end of June /chances are slim

• Causes of failure:– loss of the power regulator blocking

irreversibly telemetry and telecommand– short circuit, triggering a 'safe mode' (kind

of shutdown) with subsequent platform anomaly (orientation change)

TIRA radar image of ENVISAT (image courtesy Spiegel Online News, April 14, 2012)

Photo from PLEIADES (April 15, 2012)

SCIAMACHY data products

– ozone chemistry (nadir/limb/occult)• NO2, O3, OClO, BrO, H2O, aerosol

– greenhouse gases (nadir)• CH4, CO, CO2

– air pollution/biogenic (nadir)• NO2, O3, BrO, IO, H2CO, glyoxal, SO2,

H2O

– Other:• Limb: PSC, NLC/PMC, OH* /mesopause T,

mesospheric metals • Nadir: pytoplanctons/ocean colour,

clouds, surface reflectance, mesospheric metals, thermospheric NO

• spectral solar irradiance (SSI)

Solar irradiance measurements by SCIAMACHY

• Continuous coverage: 230-1700 nm

• Spectral resolution: < 1.5 nm

• Spectrometer design: double monochromator (predisperser prism and gratings in each channel)

• Reticon linear diode array detector

Pagaran et al., 2011a

Solar irradiance measurements by SCIAMACHY

• Daily full solar disc measurements using diffuser

• Radiometrically calibrated before launch

• Degradation correction using several optical paths (combination of mirrors and/or diffuser, lamp sources)

– So far assumes constant irradiance

– only suitable for atmospheric applications

– new degradation corrections are in preparation (see later)

• Challenges: instrument and ENVISAT platform anomalies maintenances

Pagaran et al., 2011a

H2O

SCIAMACHY irradiance comparisons: VIS/NIR

– Direct comparisons to SOLSPEC/ATLAS3:

• SCIA agreement to within 3% in the visible and 5% in near IR wrt to other data

– over several solar rotations• relative accuracy ~0.1%!

Pagaran et al., 2011a

0.2% March 2004

SCIAMACHY SSI comparisons: UV

Comparison of satellite data to Hall-Anderson spectra in the UV • SCIA data:

– low SNR below 240 nm– optical degradation in the UV:

~-15%– Correction possible by using

internal white lamp sources (WLS)• Agreement within 3%• However: data is over

corrected since WLS also degrades with time

March 2004

w. WLS

w/o WLS

Solar proxies from SCIAMACHY: Mg II index

• Mg II core-to-wing ratio near 280 nm

– Correlates well with UV and EUV SSI changes (Deland and Cebula 1993, Viereck et al., 2001)

– insensitive to instrumental degradation (to first order) (Heath & Schlesinger 1986)

– composites available from multiple sensors

– used for UV SSI reconstruction and calibration corrections

• Is the solar cycle 24 minimum (~2009) lower than prior minima?

– thermospheric contraction (unusually low neutral density) due to below normal solar activity? (Emmert et al. 2010, 2011, Solomon et al. 2011)

SCIAMACHY solar proxy model

SCIAMACHY proxy model

– Parameterization of SCIAMACHY SSI changes in terms of scaled solar proxies, here Mg II index (faculae brightening) and photometric sunspot index PSI (sunspot darlening, Balmceda et al. 2009)

– allows reconstruction of solar cycle change in SSI

– assumes that magnetic surface activity are responsible for irradiance variations (Fligge et al., 2000)

– assumes that solar rotation changes scale up to solar cycle like the proxies

– similar approach: Lean et al., 1997, 2000

SCIAMACHY SSI at a reference date

Mg II index PSI index

piecewise polynomials (degradation, anomaly corrections)Scaling parameters derived

from several solar rotations

Mg II index

PSI index

Pagaran et al., 2009

Halloween 2003 solar storm

– Irradiance change during Halloween 2003 solar storm

– Lowest PSI value since thirty years

– SCIA proxy model separates faculae and sunspot contributions

– TSI reduction (-0.4%) about four time higher magnitude than change during solar cycle (~0.1%)

– dark facula near 1500 nm detected by SCIAMACHY, but is underestimated (see also Unruh et al. 2008)

TSI ~ -0.4%

Pagaran et al., 2009

SCIA proxy in solar cycle 23

• Irradiance change during solar cycle 23 (1996 to 2002)

• Below 400 nm faculae brightening dominating, with non-neglible contribution from sunspot blocking in the near UV (>300 nm)

• dark faculae near 1400-1600 nm

Pagaran et al., 2011b

Error estimates for SCIA proxy• Error estimate from the proxy fit to

observations• Other systematic errors difficult to

assess and are unknown• Solar cycle changes in the visible/NIR

are statistically insignificant except for 1400-1600 nm (dark faculae)

Pagaran et al., 2011b

Comparisons over several solar cycles

Observations:• Some issues in the late 1980 with the de Land

UV composite (related to N9/N11 SBUV2 data) in the late 1980s (see also Lockwood et al., 2011)

• Larger SIM trend in the UV in SC 23

Models• SATIRE SC variations are bit larger than NRLSSI

& SCIA proxy• Lower variability in SIP/Solar2000 (Tobiska et

al.)

Pagaran et al., 2011b

Comparisons: SSI solar cycle changes

– Comparisons of SSI changes during part of descending phases of SC 21-23• SCIA proxy model (Pagaran et al., 2009,

2011b)• NRLSSI model (Lean 2000)• SATIRE model (Krivova et al. 2009)• Deland & Cebula (2008) UV composite• SIM/SORCE and SUSIM observations

– SIM changes during SC 23 four times larger than the models and doubled the changes of SUSIM and UV composite during SC 22• challenges the validity of models

assuming solar surface magnetic activity as a primary source of SSI changes

• large impact on atmospheric heating rates (Cahalan et al. 2010, Haigh et al. 2010, Oberländer et al., 2012) and mesospheric ozone (Merkel et al., 2011)

Pagaran et al., 2011b

Summary & conclusions

– Spectral solar irradiance from SCIAMACHY:

• Daily irradiance and Mg II measurements since 2002-2012

• SCIA proxy model for extrapolating SSI from solar rotations to solar cycle (SC)

– Not reproducing SC changes seen with SIM

– challenges the validity of proxy based and empirical models assuming magnetic surface activity as primary source of SSI variations

• Clear need for continued spectral solar measurements

– Issues: long-term stability

– SC changes above 300 nm are well below 1%!

– Other solar related SCIA studies:

• 27-day solar signature in stratospheric ozone (Dikty et al., 2010) and polar mesospheric clouds/NLCs (Robert et al., 2009)

• NH polar ozone losses in connection with QBO and solar activity (Sonkaew et al., 2011)

• Solar proton related mesopsheric ozone loss (Rohen et al., 2005)

300-400 nm

Outlook

Goal: • derivation of SC 23 (24) trends directly from SCIA SSI (w/o proxies)• test if SSI UV changes scale from rotational to SC time scale in a different way

than the Mg II index (and SCIA proxy)This requires the application of suitable degradation corrections to SCIA SSI:• Exploit the different rate of optical degradation in the different optical paths • Main cause of degradation: contaminants on mirror & diffuser surfaces

(azimuth and elevation scanner)

Degradation correction: contamination model

A optical degradation model has been developed that fits contamination thicknesses as a function of time to the various optical surfaces

• Promising results• But: this model assumes no natural

variability of SSI

Need to improve upon separation of instrumental and natural effects on SSI changes in the contamination model Detector heat up

(ice removal on NIR detectors)

Further work

• Improving optical degradation model for SCIAMACHY – derive SSI trends independent of proxies

• Combine GOME1 (1995-2011) and GOME-2 (2007-present) SSI data to extend the SCIAMACHY SSI record– Channel 1-4 of the GOMEs (240-800 nm) similar to

SCIAMACHY in terms of spectral resolution

Publications

• Oberländer, S., U. Langematz, K. Matthes, M. Kunze, A. Kubin, J. Harder, N. A. Krivova, S. K. Solanki, J. Pagaran, and M. Weber, The Influence of spectral solar irradiance data on stratospheric heating rates during the 11 year solar cycle, Geophys. Res. Lett., 39, L01801, doi:10.1029/2011GL049539, 2012.

• Pagaran, J., M. Weber, J. P. Burrows, Solar variability from 240 to 1750 nm in terms of faculae brightening and sunspot darkening from SCIAMACHY, Astrophys. J., 700, 1884-1895 , 2009.

• Pagaran, J., J. Harder, M. Weber, L. Floyd, and J. P. Burrows, Intercomparison of SCIAMACHY and SIM vis-IR irradiance over several solar rotational timescales, Astron. Astrophys., 528, A67, doi:10.1051/0004-6361/201015632, 2011.

• Pagaran, J., M. Weber, M. DeLand, L. Floyd, J. P. Burrows,Solar spectral irradiance variations in 240-1600 nm during the recent solar cycles 21-23, Sol. Phys., 272, 159-188, doi:10.1007/s11207-011-9808-4, 2011.

• Pagaran, J. A., Solar spectral irradiance variability from SCIAMACHY on daily to several decades timescales, Ph.D. thesis, University of Bremen, 2012.

• Weber, M., J. Pagaran, S. Dikty, C. von Savigny, J. P. Burrows, M. DeLand, L. E. Floyd, J. W. Harder, M. G. Mlynczak, H. Schmidt, Investigation of solar irradiance variations and their impact on middle atmospheric ozone, Chapter 3, in: Climate And Weather of the Sun-Earth System (CAWSES): Highlights from a priority program, ed. F.-J. Lübken, to be published by Springer, Dordrecht, The Netherlands, 2012.

additional slides

solar- earth atmosphere coupling

– Solar influence on atmosphere via radiation & charged particles

– Impacts chemistry and dynamics (transport/circulation)

courtesy Langematz

solar irradiance charged particles (e,p)NH SH

49 km

Rohen et al. 2005

Long-term trends in stratospheric O3

• xAdapted from Steinbrecht et al., Ozone and temperature trends in the upper stratosphere at five stations of the Network for the Detection of Atmospheric Composition Change, Int. J. Rem. Sens. [2009]

27 day signature in SCIAMACHY stratospheric ozone

– Different frequency analyses of ozone

• CWT, FFT, cross-correlation

– max. cross-correlation during SC is 0.38, weaker than in prior solar cycles (see also Fioletov, 2009)

– 27d signal is varying and vanishes for selected 3-month periods (max correlation r=0.7)

– About a factor 2 smaller than observed in other studies and earlier solar cycles (e.g. Gruzdev et al., 2009)

blue: ozoneblack: Mg II indexDikty et al. 2010b

NH polar chemical ozone loss and QBO

– SCIAMACHY observation during descending phase of SC23 (mostly close to solar min conditions)

– Arctic winters with high PSC rates and high ozone loss during QBO west phase (in most cases)

Camp & Tung, 2007

Sonkaew et al., 2011

10-50 hPa polar temperature change in Feb-Mar

warm

cold

warm

warm

W Arctic ozone hole 2010/11