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Report on the 34th COSPAR Scientific Assembly
Houston, TX, USA, October 10-19, 2002

COSPAR A.1.1/C.2.7 Event: Climate change processes in the stratosphere and at the tropopause

Main Scientific Organizer: J. Gille (gille@ucar.edu), Sponsor: SPARC

To highlight the connection between space-based data and SPARC, J. Gille and J. Remedios organised this 1.1/2-day session aimed to discuss numerous new measurements now becoming available and analysis methods, models showing the roles of stratospheric process in climate change, and studies of transports across the tropopause and other atmospheric barriers.

Twenty-three oral papers and six posters were presented. The attendance was very good. Tentative plans are to have another such session at the next COSPAR Assembly.

V. Ramaswamy described the evidence for the downward trend in stratospheric temperatures. He put as the next challenge the full documentation and understanding of the inter-annual variations on continental to global spatial scales observed in the last three decades.

Some talks presented early results from Envisat. H. Fischer introduced the MIPAS FTIR spectrometer, preliminary profiles and cross-sections of temperature, O3, H2O, and 12 other gases. The operational analysis of MIPAS spectra, using microwindows, was outlined by B. Carli, with examples of the ozone hole and tight N2 O/CH4 correlations. J. Burrows followed with NO2, and O3 results, and spectral fitting in the CH4 band from SCIAMACHY. A new kind of data was retrievals of O3 and NO2 from limb scattering. The GOMOS stellar occultation experiment was introduced by E. Kyrola. It is designed to measure O3, NO2, NO3, O2, H2 O, and possible BrO and OClO, although these have not yet been seen. J.L. Bertaux described first results of the 27000 occultations showing good agreement with climatological values at low latitudes. A. Hauchecorne discussed the validation of GOMOS ozone profiles through direct comparison with NDSC lidars, and through the use of data assimilation to allow comparisons at exact “coincidences”. Comparisons with lidar, HALOE and POAM looked promising.

M. Schoeberl described NASA’s plans for the “A-Train”, a series of satellites following each other in orbit. The EOS Aqua satellite (launched May of 2002) carrying temperature and H2O sounders, and providing IR properties of clouds lead the series. CALIPSO, Cloudsat, and Parasol, all of which will obtain detailed information on clouds and aerosols techniques will follow it. The EOS Aura spacecraft follows these, but is only about 8 minutes behind Aqua. These combinations will be very synergistic. Aura, scheduled for launch in early 2004, is designed to answer the following 3 questions: Is Earth’s ozone layer recovering? Is air quality getting worse? Is Earth’s climate changing?

Beginning a series of talks on the Aura instruments, J. Gille described HIRDLS, able to determine temperature, O3, H2O, 8 other species and aerosols with high vertical and horizontal resolution, and to probe the tropopause region. J.H. Jiang presented the MLS, which will greatly improve on the UARS measurements of upper troposphere humidity and add cloud ice determinations. It also will study the causes of stratospheric aridity . G. Osterman then went over TES, a nadir-viewing IR spectrometer, which will measure tropospheric temperature, O3, CH4 and CO. In the limb HNO3, NO and NO2 will be added. It will also measure some isotopic species, starting with HDO. The OMI experiment from the Netherlands was described by J. Verfkind. Building on the GOME experience, it will have a pixel size of only 13 by 24 km. It expects to retrieve ozone profiles in the troposphere and stratosphere, as well as measuring NO2 and other species.

M.P. McCormick presented results on SAGE III (launched December 2001) vertical profiles of ozone, aerosols, and other trace gases. A. Thompson presented data on the variability of ozone in the tropical UT/LS from sondes, noting again the wave one pattern in tropical total ozone, and the effects of sub-tropical STE. B. Schaeler outlined results of a study of trace gas transports at the tropopause using CRISTA data and data assimilation; these showed filaments of H2O penetrating the tropical barrier, as well as providing information on effective diffusivities. A complementary paper by V. Grewe used a model to track the transport and chemisty of NOx from the tropical UT to the lowermost stratosphere. He found that tropical lightning had the potential to increase mid-latitude 03.

COSPAR C2.3 Event: Long-term trends in the thermosphere-mesosphere-stratosphere coupling

Main Scientific Organizer: D.K. Chakrabarty ( dkchakra@icenet.net)

The concentrations of several minor gases in the atmosphere are dependent on the transport/coupling processes. The aim of this meeting was to examine if long-term changes in these processes occurred during the past century. The 23 papers presented dealt with neutral species, temperature, tropopause characteristics, dynamics, layers, ions and NLC.

Increases in the concentrations of CFCs, CO2, CH4, N2O and hydrocarbons have been reviewed by P. Fabian. Anthropogenic Cl in the stratosphere has reached its peak but that of Br is still rising (to peak in ~2005). Recovery will start from 2005 in the SH and 2010 in NH.

J. Olivero reports that water vapour responds to forcing and coupling throughout the atmosphere from tropopause to lower thermosphere. The increases in stratospheric water vapour are much too large to be explained by the existing forcing processes. A secondary source of H2O is needed.

D.E. Siskind shows the HALOE data evidence of signatures of descent of mesospheric air into the polar stratosphere in winter. In most years mesospheric NO is evident only in the SH springtime polar stratosphere. However, in 1999, NOx of mesospheric origin was also observed in the late winter NH stratosphere. This is due to long-term changes in the transport field.

Ozone sonde measurements display narrow layers of increased or decreased ozone concentrations, the so-called positive and negative laminae. J. Lastovicka reports a strong negative trend in the total ozone content in laminae per profile from early 1970 to early 1990s for Europe, Canada and Japan. In Europe and Japan they change to positive trend in the mid-1990s, due to changes in dynamics.

From the orbital decay data of five Earth satellites with perigee altitudes near 375 km, a decline in atmospheric density at this altitude from 1976 to 1996 averaging 10 ±1% has been found by G.M. Keating. It should be the integrated effect of the changes in the troposphere, stratosphere, mesosphere and thermosphere.

D.K. Chakrabarty has analysed the rocket electron density data of Thumba. At 80 km, it is approximately proportional to [NO]. Using this theory he finds a decreasing trend of NO with time. Umkehr increasing O3 data at Kodaikanal (near Thumba) in the upper stratosphere also imply a decreasing trend of NO. A decreasing trend in NO in the lower thermosphere has already been reported. That means there has been a decreasing trend in the production rate of NO in the lower thermosphere and this is due to a decrease in N2 density as reported by G.M. Keating.

M.-L. Chanin presented results from the reanalysis of the rocketsonde temperature data from US and Japan sites since the 1960’s. She also commented on the results from the SPARC, Stratospheric Temperature Trend Assessment Group showing evidence of a cooling at essentially all latitudes.

From balloon data at a British Antarctic station, H.K. Roscoe showed that winter temperatures at 100 hPa decreased by ~1.6 K from 1980 to 2000. The source of H2O at 100 hPa in Antarctic winter is H2O at mid-latitudes in the upper stratosphere. The negative trend in temperature at 100 hPa has been reproduced theoretically using the observed trends in mid-latitude H2O.

Rocket data of Volgograd were analysed by A. Krivolutsky. A negative trend is seen in temperature and pressure in the stratosphere from 1970 to 1990. These data have been used in a 1-D photochemical model. The results show a negative trend in ozone below 90km.

From balloon data at Vostok and Amundsen-Scott in the past 40 years, L.N. Makarova showed that stratospheric temperature had good correlation with solar wind dynamic pressure. The data of the two stations showed good correlation only in summer. When Amundsen-Scott (and North Pole) show warming in the stratosphere, Vostok data show cooling during that period.

The radiosonde tropopause records of several stations from tropical Pacific region over the past four decades show (G.C. Reid) an increase in tropopause height. Temperature decrease at tropopause level has not been observed at all the stations. An increase in tropopause height has also been observed as the latitude increases from 0 to 25°N. Tropics appear to be expanding.

Results of several 2-D model studies have been presented.

The WACCM programme was used by a NCAR group in which CO2, CH4, N2O and CFCs were increased in accordance with observations. D.R. Marsh reported that trends in water vapour, temperature and ozone in the stratosphere and mesosphere agree fairly well with UARS data.

A fully interactive NCAR 2-D chemical-dynamical-radiative model study was made by H. Lee and A.K. Smith. It is shown that when the effects of both QBO and volcanic eruptions on the 11 year solar cycle are considered, the resulting ozone solar signal has a dipole pattern similar to that observed.

An interactive 2-D model SOCRATES was used to study the sensitivity of the MLT region to changes in CO2, CH4 , H2O in the stratosphere and solar activity level. A 100 years simulation results were presented by S. Chabrillat.

C.H. Jacobi found that if CO2 is increased and O3 is decreased by 1 %, due to a reduction of gravity wave filtering through stratospheric/mesospheric easterly jet, the mesopause region meridional wind at northern mid-latitudes in summer decreases by 25 %, i.e. up to 2m/s. These results agree with the radar wind measurements.

With the Spectral MLT Model, R.A. Akmaev finds that the CO2 increase in the atmosphere leads to an overall cooling in the mesosphere/thermosphere. This cooling results in hydrostatic contraction of the atmosphere and mass density reduction in the thermosphere.

Mean annual trend in the upper mesosphere is a difficult trend parameter as it is derived from a signal with very large fluctuations. D. Offermann proposed two new parameters: (1) The temperature standard deviation, which could indicate changes in the atmospheric transport, (2) The Equivalent Summer Duration (ESD), a parameter defined in analogy to the duration of the vegetation period on the ground. ESD shows a long-term increase at the mesopause level over Wuppertal.

The nighttime ionospheric reflection height of LF radio waves was measured at Collm since 1983 (C.H. Jacobi). A decrease ~90m/yr has been derived. J Bremer finds that the mean reflection height is ~82 km and shows solar cycle and QBO dependence. The temperature trend in the stratosphere and mesosphere has been derived from GCM COMMA-IAP which supports the measured trends of ionospheric absorption in the LF range.

According to G.E. Thomas, water vapour variation is responsible for the doubling of the NLC sightings since the mid-1960s. The long-term cloud forcing is predominantly due to methane build up, and to increases in the injection of water vapour through the tropical tropopause. There is need of a secondary source of water vapour as well. NLC occurrence is found to be maximum at LSA and minimum at HSA.

B.R. Clemesha presented the lidar data of INPE (Brazil) since 1972. The centroid height of the atmospheric sodium layer decreases linearly by ~740 m from 1972 to 1994, after which there is a fast rise. The long-term variation is best described by a 22-year oscillation.

Stratospheric electrical conductivity measurements were made from high altitude balloons for more than 30 years. E.A. Bering showed that short term variations owing to Forbush decreases, geomagnetic storms, aerosol injections by volcanoes and forest fires, etc. completely obscure any long term trend.

COSPAR C2.5 Event: Cosmic Forcing on Atmospheric Chemistry and Dynamics

Main Scientific Organizer: A. Krivolutsky ( alkriv@netclub.ru), Deputy Organizer: L. Hood, Editor: J. Lastovicka. Sponsors: IUGG/IAGA, SCOSTEP

During the 1-day session, 21 papers have been presented. The main topics were:

Several reports were devoted to the unique UARS mission. C. Jackman gave an overview of the UARS observations in 1991-2002 with information about availability of the data base for scientific community. 11-year measurements of solar UV irradiance by SUSIM were analysed by L. Floyd et al., and by SOLTICE by G. Rottman and T. Woods. The mesosphere-lower thermosphere wind field (1991 to 2001) was presented by W. Skinner.

First results from GOMOS on-board ENVISAT were presented by A. Hauchecorne . A. Krivolutsky presented an overview of cosmic ray influence on the ozone layer. A solar signal in the stratospheric and mesospheric temperature was found by A. Hauchecorne et al. from lidar observations in France. Differences between simulations and observations of the tidal component in mesospheric ozone were discussed (A. Smith and D. Marsh). Solar modulation of transport processes in the winter middle atmosphere was discussed by N. Arnold and T. Robinson. J. Lastovicka and P. Krizan found a cosmic ray signal in total ozone at northern mid-latitudes.

Several reports (A. Krivolutsky et al., D. Rusch et al., A. Shirochkov et al., Kh. Fadel et al., and C. Jackman et al.) were devoted to calculated and observed response of the ozonosphere to solar proton events. Good agreement was found between photochemical simulations of ozone response and observations from UARS. At the same time observed NOX production by SPE in July 2000 was weaker than in model runs (C. Jackman ). A. Ondraskova et al. calculated the response of electron density and some ions in the D-region after strong SPE using 1-D models for neutral and ionized chemical compounds. Special focus was made to understand the response of the D-region in night conditions. The stratospheric aerosols data sets from 1953 were analysed jointly with galactic cosmic ray (GCR) data (F. Vanhellemont et al.). The analysis partly supported the idea that the link between GCRs and stratospheric aerosols exists, but it needs special effort to understand a physical mechanism.

So, the present growth of satellite data archive (UARS, first of all) supported by computations provide the opportunity to look at the atmosphere being influenced by cosmic factors (like strong SPE) as at a great Natural Laboratory. At the same time new questions and problems arise.

The proceedings of the Session C2.5 will be published in Advances in Space Research.

COSPAR D2.3/E3.3 Event: Solar Variability and Climate Change

Main Scientific Organizer: J. Pap ( papj@marta.gsfc.nasa.gov), Co-Chairs: Labitzke, J. Kuhn, Scientific Organizing Committee: J. Beer, B. Fleck, P. Fox, E. Friis-Christensen, C. Frohlich, J. Haigh, L. Hood, K. D. Shindell, S. Solanki, W. Sprigg, W. Wagner, and S.T. Wu.

This COSPAR event, sponsored by commissions D2.3/E3.3, was also sponsored by SCOSTEP, IAMAS, NASA, NSF, and ESA.

The 2.5-day meeting was divided into three major parts: (1) solicited talks, (2) contributed talks, and (3) contributed poster papers. The meeting consisted of 5 major sessions:

Nineteen review papers summarised recent knowledge on solar irradiance and particle variations (both measurements and theory) and their effect on the Earth's atmosphere and climate system. In addition to these reviews, 17 contributed talks were presented and 50 poster papers were displayed. Two evening sessions were devoted to discussing the results presented in the posters, and P. Fox and P. Brekke gave a summary of posters. The papers will be published in the Advances of Space Research to be edited by K. Labitzke, J. Kuhn and J. Pap.

The presentations and discussions have clearly demonstrated that the Earth's climate, radiative environment and atmospheric chemistry are influenced by the varying solar energy flux. One of the most over-arching questions today is whether the Earth's atmospheric and climate system changes in a way that we can understand and predict. The important question: what is the degree to which various causal agents -both natural variability and man-made- may affect climate was widely discussed. It was pointed out by several papers that although the Sun supplies most of the energy for the Earth's atmospheric and climate system, the measured level of solar irradiance variations is generally considered to be too small to cause changes in climate above its intrinsic noise. In contrast, the correlation between observed historical solar changes and that of climate implies that there is a solar forcing which is unaccounted for, as highlighted by J. Beer, P. Damon, C. Keller, and G. North. Papers by J. Haigh, M. Salby, M. Schlesinger and U. Langematz discussed possible mechanisms for the effect of solar changes on the atmosphere and climate. Measurements of the solar energy flux, both electromagnetic and particles, were summarised by G. Rottman and D. Reames, while modelling and theoretical results were presented by P. Fox and J. Kuhn. D. Gray summarised recent results on solar-stellar connections. The role of cosmic rays in climate change was debated by E. Friis-Christensen and J. Kristiansson.

Twenty-seven of the poster papers described the effect of solar variability on the Earth's atmosphere and climate. They fall into four major categories: (1) description of long-term climate changes and solar variability, (2) connection between solar variability and regional climate changes, (3) the response of ozone and other stratospheric constituents to solar variations, and (4) the effect of solar particle and cosmic ray variations on atmospheric constituents and climate.

Additional 22 poster papers were presented on solar variations and described various irradiance monitoring experiments, compared and some combined time series of various EUV, UV and total irradiance measurements, and ground-based observational programs some extending over several solar cycles and one calling into question the possibility of a missed sunspot cycle. Several papers were presented on various image processing techniques developed for proxy irradiance modelling describing also derived parameters for the area and contrast of sunspots, faculae and the network. Possible long-term trends in solar irradiance variations were addressed and debated as well.

Programmatic summaries on international research activities were presented by B. Schmieder (CAWSES, sponsored by SCOSTEP), J. Pap (ISCS Working Group 1 Activities), E. Friis-Christensen (S-RAMP/Climate Activities), and K. Kodera (GRIPS Solar Experiments Intercomparison Project).

The meeting was closed by T. Bogdan (NSF), pointing out the achievements on solar-terrestrial physics since the end of the 1800’s and emphasising the need of coordinated research activities to better understand solar variability, its effect on Earth and its climate.

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