A change in the atmospheric inventory of a greenhouse gas produces a radiative forcing on the atmosphere which results in climatic change. Thus to understand climate change resulting from perturbations to atmospheric greenhouse gas concentrations it is necessary to quantify the radiative forcing. Here, radiative forcings are presented for large changes in atmospheric CO2, CH4, and N2O in the modern atmosphere and large changes in atmospheric CO2, CH4 and 18 other gases for the Archean atmosphere. For the modern Earth, I present new calculations of radiative forcing at very high concentrations of CO2, CH4, and N2O, relevant to extreme anthropogenic climate change and paleoclimate studies. CO2 forcing is calculated over the range 100 ppmv to 50,000 ppmv. CH4, and N2O forcings are calculated over the range 100 ppbv to 100 ppmv. The sensitivity of these calculations to spatial averaging and tropopause definition are examined. I compare our results with the ``simplified expressions'' reported by IPCC, and find significant differences at high greenhouse gas concentrations. I provide new simplified expressions which agree much better with the calculated forcings, and suggest that these expressions be used in place of the IPCC expressions. Additionally, I provide meridionally resolved forcings which may be used to force simple and intermediate complexity climate models. For the Archean Earth, I present new calculations of radiative forcing for CO2 (10^-6 - 1 bar), CH4 (500 ppbv - 10,000 ppmv) and 18 other gases (10 ppbv - 10 ppmv). I aim to provide a set of radiative forcing and overlap calculations which can be used as a standard for comparisons. Radiative forcings are calculated for atmospheres with various N2 inventories (0.5, 1, and 2 bar). The effect of overlap and atmospheric pressure on radiative forcing are examined. The CO2 radiative forcings are consistent with previous work, however, I find significantly more shortwave absorption by CH4 than previously reported which may limit warming above 100 ppmv. For the 18 other gases, I find that significant radiative forcings result from low concentrations (<1 ppmv). These forcings are compared to those given in the literature. / Graduate / 0756 / 0608 / 0725 / bbyrne@uvic.ca

A change in the atmospheric inventory of a greenhouse gas produces a radiative forcing on the atmosphere which results in climatic change. Thus to understand climate change resulting from perturbations to atmospheric greenhouse gas concentrations it is necessary to quantify the radiative forcing. Here, radiative forcings are presented for large changes in atmospheric CO2, CH4, and N2O in the modern atmosphere and large changes in atmospheric CO2, CH4 and 18 other gases for the Archean atmosphere. For the modern Earth, I present new calculations of radiative forcing at very high concentrations of CO2, CH4, and N2O, relevant to extreme anthropogenic climate change and paleoclimate studies. CO2 forcing is calculated over the range 100 ppmv to 50,000 ppmv. CH4, and N2O forcings are calculated over the range 100 ppbv to 100 ppmv. The sensitivity of these calculations to spatial averaging and tropopause definition are examined. I compare our results with the ``simplified expressions'' reported by IPCC, and find significant differences at high greenhouse gas concentrations. I provide new simplified expressions which agree much better with the calculated forcings, and suggest that these expressions be used in place of the IPCC expressions. Additionally, I provide meridionally resolved forcings which may be used to force simple and intermediate complexity climate models. For the Archean Earth, I present new calculations of radiative forcing for CO2 (10^-6 - 1 bar), CH4 (500 ppbv - 10,000 ppmv) and 18 other gases (10 ppbv - 10 ppmv). I aim to provide a set of radiative forcing and overlap calculations which can be used as a standard for comparisons. Radiative forcings are calculated for atmospheres with various N2 inventories (0.5, 1, and 2 bar). The effect of overlap and atmospheric pressure on radiative forcing are examined. The CO2 radiative forcings are consistent with previous work, however, I find significantly more shortwave absorption by CH4 than previously reported which may limit warming above 100 ppmv. For the 18 other gases, I find that significant radiative forcings result from low concentrations (<1 ppmv). These forcings are compared to those given in the literature. / Graduate / 0756 / 0608 / 0725 / bbyrne@uvic.ca

Thesis (D. Min.)--Liberty Baptist Theological Seminary, 2000. / Includes bibliographical references.

In astronomy, the Sun has an important role. It keeps the solar-system together and is thesource for life, heat, light and energy to Earth. As any other star or planet, the Sun has amagnetic field. The magnetic field of the Sun has a great impact on the Sun itself as well asits surrounding. The magnetic field shapes solar wind, causes flares and drives coronal massejections radiating towards the Earth (and other planets). The Sun's magnetic field is still notfully understood, and therefore it is useful to study other stars with properties similar to theSun. So by studying young solar-type stars, the evolution of the Sun can be more easilyunderstood. The aim of this project is to study the surface magnetic field in a youngsolar-type star, π1 UMa to see how the magnetic field is distributed and if there are anypatterns like polarity reversals. Magnetic field generates polarisation and with Stokes vector Iand V, polarisation can be described. Earlier measurements from two time-epochs (2014 and2015) of Stokes I and V have been obtained from the spectropolarimeter NARVAL. To getthe desired mean polarisation profiles of the star, a technique called least squaredeconvolution was applied which increases the signal-to-noise level. To reconstruct themagnetic topology the Zeeman-Doppler imaging technique was used. Then we obtained thesurface magnetic field maps of both measurements. No change of the polarity of magneticfield at the visible stellar pole was found. Most of the magnetic field energy was contained inthe spherical harmonic modes with angular degrees l=1-3. The star shows dominance in thetoroidal component so the study seem to agree with the previously established trend thatyounger and faster rotating stars have predominantly toroidal magnetic fields and older starswith slower rotation rate, like the Sun, have predominantly poloidal field. Looking at themagnetic field plots, the star show dominance in the azimuthal field component, and themean magnetic field strength is similar to one found in the previous study. The results of thesurface magnetic field in our study thus agrees with previous study of the same star. With thiswe can conclude that the Sun's magnetic field probably been different when it was younger, and possibly similar to the star analyzed in this study.