Oxygen Isotope Processes and Transfer Reactions

A unique kinetic isotope effect has been found in the formation process of ozone molecules. Isotope enrichments of about 10% above statistically expected values were first discovered in atmospheric isotopomers ⁴⁹O₃ and ⁵⁰O₃ and later in many other molecular combinations. Most recently the source of this effect was identified through measurement of isotope-specific ozone formation rate coefficients which show a large variability of over 50%. Ozone molecule formation is a complex process since different reaction channels contribute to a specific isotopomer. In addition, fast oxygen isotope exchange reactions determine the abundance of atomic oxygen participating in ozone formation. The isotope enrichments observed are both pressure and temperature-dependent and they decrease at pressures above 100 mbar and toward lower temperatures. Ozone possesses not only one of the most unusual isotope anomalies, it also serves as a mediator by transferring heavy oxygen from the O₂ reservoir to other species. Stratospheric isotope composition of CO₂ has been recently measured with high accuracy and a pronounced isotopic signature was found which shows that ¹⁷O is preferentially transferred from O₃ into CO₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Vertical density and temperature structure over Northern Europe

During the Energy Budget Campaign, several profiles of the density and temperature of the upper atmosphere were obtained. The measurements were made using rocket-borne instrumentation launched from ESRANGE, Sweden and Andoya Rocket Range, Norway during November and December, 1980. The techniques included meteorological temperature sondes, passive falling spheres, accelerometer instrumented falling spheres, density gauges, mass spectrometers and infrared emission experiments. The instruments provided data within the altitude range from 20 km to 150 km. The measurements were made during periods which have been grouped into three categories by level of geomagnetic activity. Analysis has been made to compare the results and to examine the oscillations and fluctuations in the vertical profiles for scales ranging between hundreds of meters and tens of kilometers. Most of the features observed fit qualitatively within the range expected for internal gravity waves. The geomagnetic storm conditions may be associated with enhanced wave activity and heating observed in the lower thermosphere.