SCIAMACHY solar irradiances during solar cycle 23 and beyond Mark Weber, Joseph Pagaran, Stefan Nol, Klaus Bramstedt, and John P. Burrows [email protected] TOSCA Workshop, Berlin, 14-16 April 2012 Motivation 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: x
Grey et al., 2010 continuous SCIA spectral range above 300 nm solar cycle variability is below 1% Optical degradation affects longterm stability of UV SSI Atmospheric and climate impact requires knowlege of spectral solar variability (particularly in theUV) Topics
ENVISAT/SCIAMACHY mission Solar irradiance observations Comparisons with other SSI data SCIA proxy model Degradation correction SCIAMACHY SCIAMACHY = SCanning Imaging Absorption spectroMeter for Atmospheric CHartograpY Features: UV/Vis/NIR grating spectrometers: 220 - 2380 nm Moderate spectral resolution: 0.2 1.5 nm Measurement Geometries:
Launch date: February 28, 2002 Polar, sun-synchronous orbit Descending node: 10:00 LST Altitude: 800 (783) km 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) Photo from PLEIADES (April 15, 2012) TIRA radar image of ENVISAT
(image courtesy Spiegel Online News, April 14, 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: 2301700 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 H2O 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 SCIAMACHY irradiance comparisons: VIS/NIR 0.2%
March 2004 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 SCIAMACHY SSI comparisons: UV Comparison of satellite data to Hall-Anderson spectra in the UV w. WLS SCIA data: low SNR below 240 nm
optical degradation in the UV: ~-15% Correction possible by using w/o WLS internal white lamp sources (WLS) Agreement within 3% However: data is over corrected since WLS also degrades with time March 2004 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
Scaling parameters derived from several solar rotations PSI index piecewise polynomials (degradation, anomaly corrections) Mg II index Pagaran et al., 2009 PSI index 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 ~ -0.4% Pagaran et al., 2009 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) SCIA proxy in solar cycle 23 Irradiance change
during solar cycle 23 (1996 to 2002) Below 400 nm faculae brightening dominating, with nonneglible contribution from sunspot blocking in the near UV (>300 nm) dark faculae near 14001600 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 Pagaran et al., 2011b 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.) 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, Oberlnder 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) Outlook 300-400 nm 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 Oberlnder, 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. Lbken, to be published by Springer, Dordrecht, The Netherlands, 2012. additional slides solar- earth atmosphere coupling solar irradiance charged particles (e,p)
NH SH 49 km Rohen et al. 2005 Solar influence on atmosphere via radiation & charged particles Impacts chemistry and dynamics (transport/circulation) courtesy Langematz Long-term trends in stratospheric O3 x Adapted 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.  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 3month 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) Dikty et al. 2010b
blue: ozone black: Mg II index NH polar chemical ozone loss and QBO W Arctic ozone hole 2010/11 SCIAMACHY observation during descending phase of SC23 (mostly close to solar min conditions) Sonkaew et al., 2011 n Feb-Mar warm
warm cold warm Arctic winters with high PSC rates and high ozone loss during QBO west phase (in most cases) Camp & Tung, 2007
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