Interannual and intraseasonal variations of the energy budget over the polar regions and its climatic implications

The atmospheric energy budget is often adopted by previous studies to explore the balance between energy sources/sinks and the divergence of atmospheric energy flux. Because the atmospheric circulation is essentially generated by the energy balance between sources and sinks, a better knowledge of an energy budget will lead to a better understanding of the atmospheric circulation and its variations.;Climatologically, the polar regions are the major sink regions of global energy. The energy in the polar regions undergoes interannual and 30-60 day variations. It was inferred from previous studies dealing with the poleward propagation of angular momentum that energy exhibits a propagating signature, originating from the tropics and extending into the polar regions, on the interannual and 30-60 day timescales. To gain a new perspective on the polar energy change, the polar energy budget was studied in this thesis, based on a hypothesis that the low-latitude atmospheric energy with poleward propagation could indirectly affect the divergence of energy flux, and, in turn, affect the variations of the polar energy budget. In addition, polar climate changes (e.g., precipitation) associated with the energy propagation were also studied.;Results indicated that the energy changes in the polar regions and the tropics are remotely linked through the poleward propagation of energy relay carried out by different types of circulation patterns at different latitudes, as the propagation of angular momentum depicted by previous studies. Analyses have pointed out that the propagation of energy is led by the divergence of energy flux with a horizontal quadrature shift between the former and the latter. After a larger (smaller) energy propagates into the polar regions, the polar energy budget is changed by an increase (decrease) of energy transport into the polar regions. On the other hand, it was found that the increase (decrease) of energy flux converging into the polar regions is balanced by an increase (decrease) of downward surface flux and upward radiation flux at the top of the atmosphere over the polar regions. Associated with this energy balance, the polar climate changes include a reduced (increased) precipitation and an increased (reduced) outgoing longwave radiation. Maintenance of these changes were discussed

Reactive halogen compounds in the marine boundary layer: method developments and field measurements

Reactive halogen compounds are known to play an important role in a wide variety of atmospheric processes such as atmospheric oxidation capacity and coastal new particle formation. In this work, novel analytical approaches combining diffusion denuder/impinger sampling techniques with gas chromatographic–mass spectrometric (GC–MS) determination are developed to measure activated chlorine compounds (HOCl and Cl2), activated bromine compounds (HOBr, Br2, BrCl, and BrI), activated iodine compounds (HOI and ICl), and molecular iodine (I2). The denuder/GC–MS methods have been used to field measurements in the marine boundary layer (MBL). High mixing ratios (of the order of 100 ppt) of activated halogen compounds and I2 are observed in the coastal MBL in Ireland, which explains the ozone destruction observed. The emission of I2 is found to correlate inversely with tidal height and correlate positively with the levels of O3 in the surrounding air. In addition the release is found to be dominated by algae species compositions and biomass density, which proves the “hot-spot” hypothesis of atmospheric iodine chemistry. The observations of elevated I2 concentrations substantially support the existence of higher concentrations of littoral iodine oxides and thus the connection to the strong ultra-fine particle formation events in the coastal MBL.Bei einer Vielzahl an atmosphärischen Prozessen spielen reaktive Halogenverbindungen eine wichtige Rolle, so beeinflussen sie z.B. die Oxidationskapazität der Atmosphäre und die Partikelneubildung in küstennahen Gebieten. In dieser Arbeit wurden neuartige analytische Ansätze zur Messung von aktivierten Chlor- und Bromverbindungen (HOCl, Cl2, HOBr, Br2, BrCl, BrI), sowie von molekularem Iod (I2), entwickelt. Dazu wurden Diffusions-Gasphasenabscheider/Gaswaschflaschen (diffusion denuder/impinger) Probenahmetechniken und Gaschromatographie-Massenspektrometrie (GC-MS) Detektion miteinander verbunden. Die denuder/GC-MS Methoden wurden für Feldmessungen in der marinen Atmosphärengrenzschicht (marine boundary layer, MBL) verwendet. In der küstennahen MBL von Irland konnten große Mischungsverhältnisse (in der Größenordnung von 100 ppt) an reaktiven Halogenverbindungen und I2 gemessen werden, wodurch auch der beobachtete Ozonabbau erklärt werden kann. Die I2-Emission konnte invers zur Höhe des Tidenhubs und positiv zum Ozongehalt der umgebenden Luft korreliert werden. Als zusätzliches Ergebnis kann festgehalten werden, dass die Iodemmision durch die Zusammensetzung der vorhandenen Algenspezies und durch die Biomassedichte dominiert wird, wodurch die „hot-spot“ Hypothese der atmosphärischen Iodchemie bestätigt werden konnte. Durch die Beobachtung von erhöhten Iodkonzentrationen kann im Wesentlichen auf das Vorhandensein erhöhter Konzentrationen an Iodoxiden in der Küstenregion geschlossen werden. Dadurch lässt sich eine Verbindung zu den stark ausgeprägten Partikelneubildungsereignissen von ultrafeinen Partikeln in der küstennahen MBL herstellen