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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Near-Coastal Ultrahigh Resolution Scatterometer Winds

Hutchings, Nolan Lawrence 05 December 2019 (has links)
RapidScat 2.5 km ultrahigh resolution (UHR) wind estimation is introduced and validated it in near-coastal regions. In addition, this thesis applies direction interval retrieval techniques and develops a new wind processing method to enhance the performance of RapidScat UHR wind estimation in the nadir region. The new algorithm is validated with L2B wind estimates, Numerical Weather Prediction (NWP) wind products, and buoy measurements. The wind processing improvements produce more spatially consistent UHR winds that compare well with the wind products mentioned above. Hawaii regional climate model (HRCM), QuikSCAT, and ASCAT wind estimates are compared in the lee of the Big Island with the goal of understanding UHR scatterometer wind retrieval capabilities in this area. UHR wind vectors better resolve fine resolution wind speed features compared to L2B, but still do not resolve the expected wind direction features. A comparison of scatterometer measured σ 0 and HRCM and NWP predicted σ 0 suggests that scatterometers can detect a reverse flow in the lee of the island. Differences between scatterometer measured σ 0 and HRCM predicted σ 0 indicate error in the placement of key reverse flow features by the model. Coarse initialization fields and a large fixed size median filter window are also shown to impede UHR wind retrieval in this area.
2

Methane fluxes from the Baltic Sea : A first look at measured fluxes of shallow near-coastal waters using floating chambers

Svensson, Johan, Westerholm, Viktor January 2010 (has links)
<p>Methane is an important green house gas as it is responsible for 15-20 % of the green house effect. Marine environments in general and shallow near-coastal waters specifically may be important contributors of methane emissions but are as of today poorly studied.  In this study we measured total fluxes of methane from shallow near-coastal waters at two sites along the east coast of Sweden. The sea-to-air emissions of methane where captured using floating chambers. This gave measured fluxes as compared to earlier studies of the Baltic Sea where calculated fluxes are often used. Measured fluxes have the merit of not having to rely on several highly varying and complex variables e.g. mean wind speed and piston velocity that vary and give an uncertainty to the results.  The fluxes ranged from -2.14 to 0.37 mg CH4 m-2 d-1 with a mean of 0.05 mg CH4 m-2 d-1. The results show a correlation, however not strong, between depth and methane. No difference in flux between the study sites could be seen. We look forward to further studies using floating chambers on shallow near-coastal waters with longer sampling periods to catch seasonal variations.</p>
3

Methane fluxes from the Baltic Sea : A first look at measured fluxes of shallow near-coastal waters using floating chambers

Svensson, Johan, Westerholm, Viktor January 2010 (has links)
Methane is an important green house gas as it is responsible for 15-20 % of the green house effect. Marine environments in general and shallow near-coastal waters specifically may be important contributors of methane emissions but are as of today poorly studied.  In this study we measured total fluxes of methane from shallow near-coastal waters at two sites along the east coast of Sweden. The sea-to-air emissions of methane where captured using floating chambers. This gave measured fluxes as compared to earlier studies of the Baltic Sea where calculated fluxes are often used. Measured fluxes have the merit of not having to rely on several highly varying and complex variables e.g. mean wind speed and piston velocity that vary and give an uncertainty to the results.  The fluxes ranged from -2.14 to 0.37 mg CH4 m-2 d-1 with a mean of 0.05 mg CH4 m-2 d-1. The results show a correlation, however not strong, between depth and methane. No difference in flux between the study sites could be seen. We look forward to further studies using floating chambers on shallow near-coastal waters with longer sampling periods to catch seasonal variations.

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