Sökning: "data assimilation"

Visar resultat 16 - 20 av 73 avhandlingar innehållade orden data assimilation.

1. 16. Validation and time series analysis of global stratospheric data sets

   Författare :Ashley Jones; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; OSIRIS; MIPAS; remote sensing; data assimilation; Trend; stratosphere; ozone; linear regression; Odin; validation;

   Sammanfattning : The depletion of ozone from the stratosphere and the impact of global warming have been identified as phenomena caused as a result of anthropogenic activity. Scientists are thus trying to find quicker and more reliable ways to analyse these environmental problems. LÄS MER

3. 17. Data assimilation for numerical weather prediction systems : a 25 year perspective

   Författare :Nils Gustafsson; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; meteorologi; Meteorology;

   Sammanfattning : This thesis deals with the assimilation of meteorological observations in numerical weather prediction models. A selection of research and development contributions by the author during 25 years is included and discussed in the light of international development efforts up to the present time. LÄS MER

4. 18. A Study of Polar Ozone Depletion in the Lower Stratosphere. -Dynamical assimilation of O3 and N2O data from Odin/SMR and ENVISAT/MIPAS

   Författare :JOHN RÖSEVALL; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; SMR; O3; stratosphere; Odin; data assimilation; transport modelling; atmosphere; NO2; ozone depletion; MIPAS;

   Sammanfattning : For more than 20 years, a hole in the ozone layer has formed each spring over Antarctica when sunlight returns to the polar region. Similar albeit far less extensive ozone destruction has also been observed in the Arctic polar vortex after colder than average winters. LÄS MER

5. 19. Graphic Representation and Visualisation as Modelling Support for the Knowledge Acquisition Process

   Författare :Anne Håkansson; Andreas Hamfelt; Harald Kjellin; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Datavetenskap; Artficial Intelligence; Knowledge-Based Systems; Knowledge Acquisition; Graphic Representation; Visualisation; Unified Modelling Language; Modelling Rule-based Systems; Visual programming; Declarative Programming; Information Networks; User-Centered Design; Knowledge Interface; Datavetenskap; Computer science; Datavetenskap; datalogi; Computer Science;

   Sammanfattning : The thesis describes steps taken towards using graphic representation and visual modelling support for the knowledge acquisition process in knowledge-based systems – a process commonly regarded as difficult. The performance of the systems depends on the quality of the embedded knowledge, which makes the knowledge acquisition phase particularly significant. LÄS MER

7. 20. Essays on Microeconometrics and Immigrant Assimilation

   Författare :Alpaslan Akay; Göteborgs universitet; []
   Nyckelord :SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; Average marginal effect; Marginal effect of the average individual; Employment and earnings assimilation; Quasi-fixed effects approach; Initial value problem; Dynamic censored random-effects model; Monte Carlo experiment; Heckman’s approximation; Simple method of Wooldridge; Dynamic random-effects sample-selection model; wage-curve method;

   Sammanfattning : Paper I. Asymptotic bias reduction for a conditional marginal effects estimator in sam- ple selection models. In this article we discuss the di¤erences between the average marginal effect and the mar- ginal effect of the average individual in sample selection models, estimated by the Heck- man procedure. LÄS MER