Gray, L. J.

Kodera, K.

Matthes, Katja

OceanRep

The new SPARC working group on solar variability is an extension of the GRIPS solar inﬂuence intercomparison project (Matthes et al., 2003; Kodera et al., 2003). The objective of this group is “Modelling and understanding the solar inﬂuence on climate through stratospheric chemical and dynamical processes” in collaboration with working group 1 of the SCOSTEP CAWSES (Climate and Weather of the Sun-Earth System) programme.The ﬁrst SOLARIS (SOLAR Inﬂuence for SPARC) workshop was held in October 2006 and hosted by NCARʼs Earth and Sun Systems Laboratory in Boulder, Colorado. This workshop was the latest in a series of meetings, beginning with the December 2004 AGU conference in San Francisco and continuing with the July 2005 IAGA con-ference in Toulouse that provide the middle atmospheric research community with a fo-rum to review the latest results in the ﬁeld of modelling the solar inﬂuence on climate. Approximately 40 participants from Canada, Europe, Japan, Russia and the United States, plus local participants from Boulder (LASP/University of Colorado, NCAR) attended the workshop. The pro-gramme of the workshop and a list of par-ticipants can be found on the SOLARIS website (http://strat-www.met.fu-berlin.de/~matthes/sparc/meetingdetails.html).The ﬁrst day of the meeting included a series of overview talks from invited speakers that were open to the general public. These overviews covered topics ranging from solar variability (T. Woods) to new insights into dynamo theory (M. Dikpati), and observed solar signals in the middle atmosphere and possible trans-fer mechanisms. L. Hood and W. Randel presented the most up to date observa-tional analyses of solar signals in ozone and temperature, which seem to agree bet-ter with each other than previous analyses. K. Kodera described some of the dynami-cal mechanisms through which small direct stratospheric effects can indirectly affect the lower parts of the atmosphere down to the Earthʼs surface. A. Smith talked about aliasing of the solar signal through the QBO and the problem of having data sets that are too short. C. Randall gave an overview about precipitating particles and their effect on stratospheric chemistry and dynamics. In the afternoon each modelling group participating in the SOLARIS project gave a summary of their current activities.The following two days focused on the speciﬁc research activities of each group in order to determine which questions are still open and how they can be stud-ied in more detail through the combined SOLARIS effort. These results were dis-cussed within the context of the ﬁve coor-dinated research themes that comprise the SOLARIS effort (http://strat-www.met.fu-berlin.de/~matthes/sparc/goals.html): I)   Thermospheric and Mesospheric Re- sponse II)    Ozone and Temperature ResponseIII) Dynamical Response Including the Role of the QBOIV)  Stratosphere-Troposphere CouplingV)    Ocean Response and Paleo-ClimateWithin theme I, model studies about Meteor. Soc. 131, 3513-3527.Randel, W.J. et al., 2000: Interannual variability of the tropical tropopause derived from radio-sonde data and NCEP reanalyses. J. Geophys. Res., 105, 15509-15523.Ray, E. A., et al., 1999: Transport into the Northern Hemisphere lowermost stratosphere revealed by in situ tracer measurements, J. Geophys. Res., 104, 26565-26580, doi:10.1029/1999JD900323.Schoeberl M. R., et al., 2003: A compari-son of the lower stratospheric age spectra de-rived from a general circulation model and two data assimilation systems, J. Geophys. Res., 108, 4113, doi: 10.1029/2002JD002652.Report on the ﬁrst SOLARIS workshop4-6 October 2006, Boulder, Colorado, USAK. Matthes, Freie Universität Berlin, Institut für Meteorologie, Berlin, Germany and National Center for Atmospheric Research, Boulder, USA  (kmatthes@ucar.edu)K. Kodera, Nagoya University, Nagoya, Japan (kodera@coe.env.nagoya-u.ac.jp)L. Gray, University of  Reading, Reading, UK (l.j.gray@reading.ac.uk)J. Austin, NOAA Geophysical Fluids dynamical Laboratory, Princeton, NJ, USA (john.austin@noaa.go)A. Kubin, Freie Universität Berlin, Institut für Meteorologie, Berlin, Germany (Anne.Kubin@met.fu-berlin.de)U. Langematz, Freie Universität Berlin, Institut für Meteorologie, Berlin, Germany (ulrike.langematz@met.fu-berlin.de)D. Marsh, National Center for Atmospheric Research, Boulder, USA (marsh@ucar.edu)J. McCormack, Naval Research Laboratory, Washington D.C., USA (mccormack@nrl.navy.mil)K. Shibata, Meteorological Research Institute, Tsukuba, Japan (kshibata@mri-jma.go.jp)D. Shindell, NASA Goddard Institute for Space Studies, New York, USA (dshindell@giss.nasa.gov)1920the inﬂuence of solar proton events on the atmosphere were shown. Figure 1 (colour plate IV) shows one example of an experi-ment with NCARʼs Whole Atmosphere Community Climate Model (WACCM) that incorporated solar protons during the 2003 “Halloween storm.” Increased solar proton ﬂuxes lead to increases in NOy (see Figure 1b, colour plate IV) that are comparable to observations (see Figure 1a, colour plate IV) (presentation by D. Marsh). The ion-ization rates computed from solar ﬂuxes for the period of 1963-2005 used in WACCM were provided by Charles Jackman and are now available on the SOLARIS website. Other studies dealt with solar inﬂuence on tides (presentation by T. Hirooka).A more coherent temperature and ozone response to the 11-year solar cycle from different models came out of the discus-sion from themes II and III. Figure 2 shows examples of the resulting solar sig-nal in ozone from three different coupled chemistry climate models (CCMs) and one 2D chemistry-transport model when the 11-year solar cycle in irradiance was included. In all of the models the solar cy-cle was time-varying, instead of the usual constant solar min/max experiments of the past. The GFDL AMTRAC (Atmospheric Model with TRansport And Chemistry) simulations were run for 135 years (3x45 years) with observed solar cycle, SSTs, GHG, and volcanoes (REF1 simulations of CCMVal) (presentation by J. Austin). Note that AMTRAC does not have an in-ternally generated QBO or a speciﬁed one. The MRI-CCM simulations are similar to the AMTRAC simulations except that the model generates a self-consistent QBO (presentation by K. Shibata). The NRL CHEM2D model was run for 50 years with an interactive parameterization for the QBO (presentation by J. Mc-Cormack). The WACCM simulations had a prescribed QBO (the observed time series were repeated in order to reach 110 years of simulation), ﬁxed SSTs, GHGs and no volcanic aero-sols (presentation by K. Matthes).The discrepancy in the ozone response between observations, and 2D and 3D model simulations carried out in the 1990ʼs seems to be reduced in the latest simulations. More models show the observed vertical structure in the tropical stratosphere, with a maximum in the upper stratosphere, a relative minimum in the middle strato-sphere, and a secondary maximum in the lower stratosphere. Possible factors that may be important in ob-taining the correct vertical structures are a time-dependent solar cycle, a time-varying QBO (either self-con-sistent or synthetic), variable SSTs, and a long enough time series (at least 50 years). Other issues that were dis-cussed and seem to be important for producing a more realistic solar signal include a high-resolution short wave heating scheme as well as a good model climatology (presentation by U. Langematz). Also the question was raised of how high the top of the model has to be to simulate a realistic solar signal in the middle atmosphere. The importance of the background ozone ﬁeld to the resulting tempera-ture response was pointed out as well (pre-sentation by L. Gray).We now have a good set of model experi-ments with different levels of complexity that will be used to understand the relative importance of these factors in producing the solar signal in ozone. As a starting point, J. Austin, E. Rozanov and K. Tourpali have started an intercomparison of the tropi-cal solar signal in ozone by analysing the REF1 simulations of the CCMVal SPARC initiative (Eyring et al., 2006).The SOLARIS model experiments will also be used to investigate the dynamical response of QBO and solar signals. So far the observed modulation of the polar night jet and the Brewer Dobson circu-lation (Kodera and Kuroda, 2002), the modulation of the occurrence of Strato-  a)              b)   c)                d)O3 solar cycle % ∕ 100 unitsO3 % ⁄ 100 units F10.7Pressure (hPa)0.31.03.010.030.0100.0-2 -1 0 1 2 3DJFMAMJJASONCHEM2D O3 SOLAR COEF (%, Max-Min)LatitudeAltitude (km)6050403020-50 0 50O3 (% ∕ F10.7)*1e2  Solar   PRM5_REF1Pressure (hPa)90S 60S 30S EQ 30N 60N 90N0.10.20.5125102050100Latitude0.400.40.81.21.60.80.40.4200.81.2 0.80.82.401.620.41.61.20.80.4000.80.80.4-0.400-0.4 0.4-0.4-0.8-0.400.4-0.4-0.800.4-0.40.80.40.401957-2063 (% per 100 f10.7 units)Pressure (mb)Latitude0.11.010.0100.0-50 0 50Figure 2: a) Simulated seasonal mean ozone solar response in % per 100 units of 10.7 cm ﬂux with the CCMAMTRAC. The results have been averaged over the latitude range 25̊S to 25̊N and over all three ensemble members. The error bars indicate 95% conﬁdence intervals from the linear regression analysis. (From Austin et al., 2006); b) Simulated annual mean ozone solar response in %/max-min from a 50 year simulation of the CHEM2D model. Thick black lines enclose regions where Cs is greater than 2-sigma (From McCormack and Siskind, 2006); c) Simulated annual mean ozone solar response in % per 100 units of 10.7 cm ﬂux from the REF1 simulation of the MRI-CCM (Courtesty of K. Shibata); d) Simulated annual mean ozone solar response in % per 100 units of 10.7 cm ﬂux from 106 years of simulations with the CCM WACCM from 90°S to 90°N and 100 to 0.1 hPa (16 km to 60 km). (Courtesy of K. Matthes.)21T forc-ctrl (K) long term mean 29yr Jan L39Pressure (hPa)Altitude (km)Latitude8070605040302010190S 60S 30S EQ 30N 60N 90N95% 99%3010030085000000 000008642-222-20-6-100spheric Warmings (Labitzke and van Loon, 1988) including the importance of equato-rial winds in the upper stratosphere (Gray et al., 2001a, b; Gray, 2003, Gray et al., 2004) have only been reproduced in a few mod-el simulations (e.g., Matthes et al., 2004, 2006; Palmer and Gray, 2005). Further work is required to investigate the impor-tance of this QBO interaction and whether it impacts the mechanism for transfer of the solar signal to the troposphere.  Within theme IV, different sensitivity studies of strato-sphere-troposphere coupling  were shown.   A perpetual January sensitivity experiment with the ECHAM5-MESSY CCM, in which a momentum forc-ing was introduced in the mid-latitude stratosphere, shows a dynamically in-duced temperature increase in the trop-ical lower strato-sphere (Figure 3) that leads to chang-es in vertical veloc-ity and precipitation in the tropics, and changes in the ex-tratropical regions with an AO-like pattern in the Northern Hemisphere troposphere (presentation by A. Kubin, U. Langematz). This idealised experiment shows that stratospheric changes can have signiﬁcant effects on the tropospheric circulation and conﬁrms earlier ﬁndings of Haigh (1996), Haigh et al. (2005), the presentation by J. Haigh, and Matthes et al. (2004, 2006). Within theme V, the importance of an interactive ocean was discussed. A fully interactive ocean seems to better repre-sent the reconstructed surface tempera-ture signal during the Maunder Minimum (Figure 4, presentation by D. Shindell). J. Meehl showed results from NCARʼs Com-munity Climate System Model (CCSM) in which only total solar irradiance (TSI) changes at the top (~10hPa) were intro-duced, and which does not have a strato-sphere; these results look very similar to the changes that were achieved with a CCM that included spectrally resolved so-lar irradiance changes and a proper strato-sphere (Matthes et al., 2007). The verti-cal structure of the response needs to be investigated further and it needs to be clariﬁed how much of the tropospheric equatorial signal comes from TSI and how much from spectrally resolved UV changes.The short-term (27-day) response of the middle to upper atmosphere was discussed with the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA) (presentation by H. Schmidt), with the GFDL AMTRAC model (presentation by J. Austin) and with the SOCOL model (presentation by E. Rozanov). It was pro-posed to use 27-day cycle simulations to investigate the mechanisms for solar forc-ing in the stratosphere. For a decade or more 27-day processes have been simu-lated reasonably accurately whereas the response to the 11-year solar cycle is only now getting more coherent in the different model simulations. One of the main issues is whether different processes are operat-ing on the 11-year and 27-day timescale. Further progress and updates on our ac-tivities can be found on the SOLARIS website: http://strat-www.met.fu-berlin.de/~matthes/sparc/solaris.html.  AcknowledgmentsWe would like to thank Guy Brasseur, director of NCARʼs Earth and Sun Systems Laboratory, for kindly hosting the work-shop, and Barb Petruzzi for the help with the logistics. The support of SPARC/WCRP enabled a few students to attend. Also, the authors would like to thank R. Garcia for valuable comments on the manuscript.ReferencesAustin, J., et al. (2006), Solar cycle varia-tions of stratospheric ozone and tempera-ture in simulations of a coupled chem-istry-climate model, submitted to ACP.Figure 3: Zonal mean temperature differences in K between the forcing and the control run of the T42L39 perpetual January experiment with the ECHAM5-MESSY CCM. Contour interval is 2 K, light blue (blue) shad-ing denotes statistical signiﬁcance at the 95% (99%) level. (Courtesy of A. Kubin and U. Langematz.)806040200806040200-0.9 -0.7 -0.5 -0.35 -0.2 -0.05 0.05 0.2 0.35 0.5 0.7 0.9Figure 4: Annual average surface temperature change (̊C) due to solar irradiance change of ~1 W/m2 (top of the atmosphere, equivalent to ~0.19 W/m2 at the tropopause) in the GISS ModelE (top) and the regression during the period 1650-1850 between reconstructed solar irradiance (From Lean et al., 1995) and annual average surface temperatures (bottom) (From Mann et al., 1998) ﬁltered to only include contributions from timescales longer than 40 years, with a 20 year lag. The correlation is given in  ̊C per change from roughly the Maunder Minimum to a century later, which is roughly 0.2 W/m2 in recent reconstructions (e.g. Wang et al., 2005). Grey areas indicate no data, while hatched areas indicate statistical signiﬁcance at the 90% level. (Courtesy of D. Shindell.)22Eyring, V., et al., (2006), Assessment of temperatures, trace species, and ozone in chemistry-climate simulations of the re-cent past, J. Geophys. Res., in press. Gray, L.J. (2003), The inﬂuence of the equa-torial upper stratosphere on stratospheric sudden warmings, Geophys. Res. Letts., 30, doi:10.1029/2002GL016430.Gray, L. J., et al., (2001a), Model studies of the interannual variability of the northern hemisphere stratospheric winter circulation: The role of the Quasi-Biennial Oscillation, Q. J. R. Meteorol. Soc., 127, 1413—1432.Gray, L.J., et al.,  (2004), Solar and QBO in-ﬂuences on the timing of stratospheric sud-den Warmings, J. Atmos. Sci., 61, 2777-2796.Gray, L. J., et al., (2001b), A data study of the inﬂuence of the equatorial upper stratosphere on northern hemisphere stratospheric sudden warm-ings, Q. J. R. Meteorol. Soc., 127, 1985--2003.Haigh, J.D. (1996), The impact of solar vari-ability on climate, Science, 272, 981--984.Haigh, J.D.,  et al., (2005), The Response of Tropospheric Circulation to Perturbations in Lower-Stratospheric Temperature, J. Climate, 18, 3672-3685.Kodera, K., and  Y. Kuroda (2002), Dynami-cal response to the solar cycle, J. Geophys. Res., 107, 4749, doi:10.1029/2002JD002224.Kodera, K., et al., (2003), Solar impact on the lower mesospheric subtropical jet in winter: A comparative study with general circulation model simulations, Geophys. Res. Lett., 30 (D6), 1315, doi:10.1029/2002GL016124.Labitzke, K., and H. van Loon (1988), Associa-tions between the 11-year solar cycle, the QBO and the atmosphere, Part I: The troposphere and stratosphere in the northern hemisphere in win-ter, J.  Atmos. Terr. Phys., 50, 197-206.Lean, J., et al., (1995), Reconstruction of solar irradiance since 1610: Implications for climate change, Geophys. Res. Lett., 22, 3195-3198.Lopez-Puertas, et al., (2005), Observation of NOx enhancement and ozone depletion in the Northern and Southern Hemispheres after the October – November 2003 solar proton events, J. Geophys. Res., 110, A09S43, doi:10.1029/2005JA011050.Mann, M. E., et al.,  (1998), Global-scale tem-perature patterns and climate forcing over the past six centuries, Nature, 392, 779-787.Matthes, K., et al.,  (2003), GRIPS solar ex-periments intercomparison projects: Initial results, Pap. Meteorol. Geophys., 54, 71-90.Matthes, K., et al., (2004), Improved 11-Year solar  signal in the FUB-CMAM, J. Geo-phys. Res., 109, doi:10.1029/2003JD004012Matthes, K., et al., (2006), Transfer of the So-lar Signal from the Stratosphere to the Tropo-sphere: Northern Winter, J. Geophys. Res., 111, D06108, doi:10.1029/2005JD006283.Matthes, K., et al., (2007), Modeling the Inﬂu-ence of the 11-Year Solar Cycle and the QBO with the NCAR Whole Atmosphere Community Climate Model, manuscript in preparation.McCormack, J. P., and D. E. Siskind (2006), Simulations of the ozone response to the11-year solar cycle and QBO in a zonally av-eraged photochemical-transport model of themiddle atmosphere, manuscript in preparation.Palmer, M. A. and L. J. Gray (2005), Model-ing the atmospheric response to solar irradiance changes using a GCM with a realistic QBO. Geophys. Res. Lett., 32, L24701, doi:10.1029/2005GL023809.Wang, Y. M., et al., (2005), Modeling the sunʼs magnetic ﬁeld and irradiance since 1713, Astrophysical Journal, 625, 622-538.A note on an AGU spring meeting discussion of the role of atmospheric water vapour in climate and atmospheric composition23-26 May 2006, Baltimore, Maryland, USAN.G. Andronova, University of  Michigan, USA (natand@umich.edu)S. Sherwood, Yale University, USA (Steven.Sherwood@yale.edu)R. Fu, Georgia Institute of  Technology, USA (rong.fu@eas.gatech.edu)I. Folkins, Dalhousie University, Canada (Ian.Folkins@dal.ca)K. Rosenlof, NOAA ESRL Chemical Sciences Division, USA (Karen.H.Rosenlof@noaa.gov)M. Joshi, Hadley Centre, Met Office, United Kingdom (manoj.joshi@metoffice.gov.uk)A. Caboussat, University of  Houston, USA (caboussat@math.uh.edu)A. Stenke, Institut fuer Physik der Atmosphaere, DLR Oberpfaffenhofen, Germany (Andrea.Stenke@dlr.de)IntroductionSince the early 1970s the study of the middle atmosphere has focused on under-standing the variability of its chemical and dynamical states as driven by both natural and anthropogenic processes.  Concurrent with these efforts, studies have been carried out to understand both short- and long-term climatic variations that occur naturally, as well as those due to the emissions and/or alterations of optically active gases and aerosols by humanity.  In these areas of study, stratospheric and tropospheric water vapour (H2O) has been of particular inter-est.  Water vapour is a greenhouse gas and is important for atmospheric chemistry, as it is the source of the hydroxyl radical, OH, which regulates among others the at-mospheric methane lifetime and the pro-duction and destruction of ozone.  Also, water vapour plays an important role in atmospheric heterogeneous chemistry, deﬁning the aerosol effect on climate via formation of the stratospheric clouds.  While some progress has been made in simulat-ing the changing atmosphere, a number of observed phenomena remain unexplained, among them the reasons for the recently 

Report on the first Solar Influence for SPARC (SOLARIS) workshop in Boulder/CO October 3-6 2006

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