Nitrogen oxides in the arctic stratosphere: Implications for ozone abundances

Thesis (Ph.D.) University of Alaska Fairbanks, 1994In the high latitude winter stratosphere, NO\sb2 sequesters chlorine compounds which are extremely efficient at destroying ozone. During the nighttime, NO\sb2 reacts with ozone to form \rm N\sb2 O\sb5 which acts as a reservoir of NO\sb2. Under heavy aerosol loading, \rm N\sb2O\sb5 may react with water on aerosol surfaces to form HNO\sb3, a reservoir more resistant to photolysis. This heterogeneous reaction results in reduced NO\sb2 concentration when the sun returns at the end of the winter. A spectrograph system has been developed to measure scattered zenith skylight and thereby determine stratospheric NO\sb2 slant column abundance. Conversion of the measured slant column abundance to vertical column abundance requires dividing by the air mass. The air mass is the enhancement in the optical path for the scattered twilight as compared to a vertical path. Air mass values determined using a multiple scattering radiative transfer code have been compared to those derived using a Monte Carlo code and were found to agree to within 6% at a 90\sp\circ solar zenith angle for a stratospheric absorber. Six months of NO\sb2 vertical column abundance measured over Fairbanks during the winter 1992-93 exhibited the daylight diminished and increased as the sunlight hours lengthened. The overall seasonal behavior was similar to high-latitude measurements made in the Southern Hemisphere. The ratios of morning to evening column abundance were consistent with predictions based on gas-phase chemistry. The possible heterogeneous reaction of \rm N\sb2O\sb5 on sulfate aerosols was investigated using Fourier Transform Infrared Spectrometer measurements of \rm HNO\sb3 column abundance and lidar determinations of the aerosol profile. Using an estimated \rm N\sb2O\sb5 column abundance and aerosol profile as input to a simple model, significant \rm HNO\sb3 production was expected. No increase in \rm HNO\sb3 column abundance was measured. From this set of data, it was not possible to determine whether significant amounts of \rm N\sb2O\sb5 were converted to \rm HNO\sb3 by this heterogeneous reaction. Better estimates of the \rm N\sb2O\sb5 and aerosol profile, and a more continuous set of \rm HNO\sb3 measurements, are needed to determine if \rm HNO\sb3 was actually produced

Stalin in October

Originally published in 1987. In March 1917 young Joseph Stalin, already a high-ranking Bolshevik, returned from Siberian exile in search of greatness and power. But his activities during the months leading up to the October Revolution were full of blunders and misjudgments—failures that in later years Stalin obliterated from the historical record. Stalin in October reassembles the history of 1917 and explains why, on the eve of the revolutionaries' seizure of power, Stalin seemingly dropped out of the picture. "He would always be dogged," Slusser writes, "by a nagging sense of having somehow missed the revolution." The lingering shame was crucial to Stalin's development into a Soviet dictator

The Berlin Crisis of 1961

Originally published in 1973. This book uses the Berlin Crisis of 1961 as a starting point to investigate Soviet-American relations in the Kruschev period. The book first chronicles the timeline of the succession of events during the Berlin Crisis and their interrelation. It then turns to the close interaction between Soviet and foreign policy before situating the event into the broader timeline of Soviet history