Environmental Sciences Commons^™

Diatoms In Castor Lake (North-Central Washington, Usa) – Proxies Of Climate And Hydrologic Variation, Kelly D. Hollingshead

Electronic Thesis and Dissertation Repository

This research provides a high temporal resolution (1 sample / 2-3 years) record of hydrologic variation for the last 2,000 years using a lake sediment record from Castor Lake, a closed-basin system in Washington, USA. The core was dated using ¹³⁷Cs, ¹⁴C, and tephrochronology. Approximately 600 diatoms were identified and enumerated in 198 samples from a Castor Lake freeze core and Livingstone-piston core. A diatom-inference model for salinity was applied to reconstruct fossil diatom salinity. Diatom-inferred salinity for the last century tracked Palmer Drought Severity Index, indicating diatom community composition tracks effective moisture and can be used to …

Ozone Measurements And Transport, Mohammed Kedir Osman

Electronic Thesis and Dissertation Repository

Ozone intrusions from the stratosphere to the troposphere occur as part of the Brewer-Dobson circulation, but the details of the microphysics of the process are unresolved. This research mainly focuses on near-tropopause regions, and examines stratospheric ozone intrusions into the troposphere across this stable zone. My research objective is to identify the small-scale atmospheric dynamical features responsible for the intrusion of stratospheric ozone into the troposphere, and to determine their relative importance from case to case.

Windprofiler radars, together with frequent ozonesonde launches, have been used to detect stratospheric ozone intrusions. This work has been supplemented by numerical simulation via …