First Results from the Solar Mesosphere Explorer

N_A_ru_RE_v_o_L_JOS_I _SEPTE__ MB_E_R_I_98_3 ------NEWSANDVIEWS------15

and changes in environmental variables demonstrating the complementarity of the getic particles - caused by a solar proton (such as food density) are well known. two approaches. 0 event4, for example. The largest event in Previously, comparative studies and op the current solar cycle occurred on 13 July timality theory have addressed rather dif 1982, and the notable decrease of ozone ferent kinds of ethological issue. The ap Paul H. Harvey is a lecturer in the School of concentration it caused was measured by plication of optimal foraging models to Biological Sciences, University of Sussex, SME. Proton events of this kind inject large data on interspecies differences in territory BrightonBN19RH, andGeorginaM. Mace is a research associate at London Zoo and at the numbers of high-energy protons into the size may throw light on the precise form of Department of Anthropology, University Col middle atmosphere, changing the concen cross-species relationships, as well as lege ofLondon, London WCIE 6BT. trations of ionized hydrogen, nitrogen and oxygen, and thus the ozone destruction rate and density. SME's near-infrared Atmospheric chemistry spectrometer observed ozone depletion reaching 70 per cent at 65° latitude, 78 km altitude, on the morning side and 10-20 per First results from the cent on the afternoon side. All the observations, including those of Solar Mesosphere Explorer the proton event, have been satisfactorily from Guy Brasseur compared with a particularly elaborate two-dimensional model which takes into THE first results from the Solar Meso foreseen by the Chapman theory in 1930, account most chemical reactions related to sphere Explorer (SME), a satellite designed and show that atmospheric temperature is the mesosphere and the fundamental specially to study atmospheric ozone, are the principal cause of changes in ozone dynamical mechanisms5•6 • now becoming available (Geophys. Res. density in the lower mesosphere. As the The enormous advance the SME satellite Lett. 10, 237; 1983). The results are of temperature decreases, the ozone density has made is to present an impressive series particular importance given the recent increases, and vice versa. In the vicinity of of data at different latitudes and for dif worries that chemical species produced by the stratopause (50 km), ozone is mainly ferent seasons. Rapid processing of the industrial and agricultural activity might lost through its recombination with atomic primary data is enabling it to be effectively affect atmospheric ozone concentrations. oxygen: 0 + 0 3 -->202, a reaction which has exploited. Measurements that are applied Ozone is present in the atmosphere only at a direct temperature dependence and to the mesosphere will, however, have to be a low concentration but plays a vital part in which therefore introduces an inverse supplemented by programmes that study protecting the biosphere from the Sun's dependence between ozone density and the stratosphere, where ozone chemistry is ultraviolet radiation. temperature. far more complicated. Stratospheric Above an altitude of about 15 km, ozone Observations made by the SME limb balloon measurement experiments and, in is produced from the photodissociation of scanning ultraviolet spectrometer between particular, the Balloon Intercomparison molecular oxygen. In the stratosphere, its 48 and 66 km altitude1 and by the limb Campaign (BIC) sponsored by NASA, the destruction is facilitated by nitrogen oxide scanning infrared spectrometer between 50 Chemical Manufacturers Association and and, to a lesser extent, by chlorine oxide, and 90 km (ref. 2) show that the ozone con the Commission of the European whose origin is partly anthropogenic. The centration varies greatly in time and space Communities, are not limited to ozone study of stratospheric ozone is complicated and that its behaviour is closely related to data, but are also devoted to molecules

because of atmospheric dynamics (general atmospheric dynamics. Below 60 km, a such as HCl, HF, HN03 , NO and N02 or circulation, planetary waves and so on), seasonal variation appears in the mixing radicals of the OH and ClO type. They which introduce a great variability in the ratio, with the largest values during the remain important together with the measured concentrations and mask the winter period, especially at high latitude. ground-based and aircraft-borne effect of chemical reactions. In the Above 80 km however, the mixing ratio measurements. mesosphere, however, the chemical time maximum is formed near the summer pole. The BIC, conducted from the National constants are sufficiently short that the Measurements in the region above the Scientific Balloon Facility in Palestine, ozone response to modification of the mesopause (85 km) also show a dramatic Texas, is intended to enable 17 scientific chemical or photochemical parameters daily variation in ozone concentrations, instruments, developed by teams from should be almost immediate and suggesting rapid fluctuations in the atomic Canada, Europe, Japan and the United practically independent of the dynamical oxygen concentration caused by vertical States, to perform almost simultaneous conditions of the atmosphere. Further motions transporting odd oxygen from measurements up to 45 km altitude. more, the mechanisms by which ozone is above. Another campaign, called Global Budget

destroyed (established by Bates and Nicolet The density of nitrogen dioxide (N02) as of Trace Species (GLOBUS), will be held in in 1950) are dependent only on the action of well as the temperature have been inferred September 1983. Its principal objective is the hydrogen compounds H, OH and H02 , from measurements provided by a visible to measure ozone and the nitrogen oxides, 3 which are themselves formed from water light spectrometer. The N02 density using a series of balloons which will be vapour. varies from pole to pole and during the launched from the French base of Aire-sur- The mesosphere therefore constitutes an winter months exhibits considerable vari 1' Ad our. Complementary observations of ideal laboratory for the study of the ability, reflecting the much larger degree of stratospheric ions and aerosols will be chemical balance of ozone. The SME meridional movement of air in the winter performed, and should enable a determin satellite, conceived at the Laboratory for stratosphere. The observations confirm ation of the stratospheric effects of the El Atmospheric and Space Physics of the that the periods of high N02 at high Chichon volcano whose eruption in April University of Colorado, was launched into latitudes occur when air flow is from the 1982 injected a dust cloud very high into the a polar orbit on 6 October 1981. Since then, equator to the pole; low N02 occurs when atmosphere. 0 it has regularly reported data which are the flow is reversed. Oscillations in the Guy Brasseur is at the Belgian Space Aeronomy processed directly at the Boulder control meridional circulation are connected with Institute, B-1180 Brussels, and at the University centre within a few hours. sudden warmings in the spring high of Brussels. The first results of SME are of major latitude Northern Hemisphere. I. Rusch, D.W. eta!. Geophys. Res. Lei/. 10,241 (1983). importance. First, they clearly confirm The SME satellite also carries a spec 2. Thoms, R.J. eta/. Geophys. Res. Lei/. 10,245 (1983). that in the upper stratosphere and lower trometer for measuring variations in the 3. Mount, G.H. eta/. Geophys Res. Leu. 10,265 (1983). 4. Thomas, R.J. et at. Geophys. Res. Leu. 10, 253 (1983). mesosphere, ozone concentration and solar irradiance and a proton alarm system 5. Solomon, S. et at. Geophys. Res. Lett. 10, 249 (1983). temperature are inversely related, as which can detect the precipitation of ener- 6. Solomon, S. et at. Geophys. Res. Lett. 10, 257 (1983).