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Understanding climate change impact on Intensity-Frequency-Duration (IFD) design rainfall is of critical importance to hydrological design and flood risk management. This thesis presents the first ever assessment of the design rainfall derived from high resolution Regional Climate Model (RCM) simulations, offering methods that would be of considerable interest in similar studies across the world. These are a few of the questions this thesis seeks to answer. The first question focuses on the change in the point-to-area design rainfall ratios, known as the Area Reduction Factors (ARFs), for a warmer climate. This thesis proposes a new approach to enable the estimation of ARFs from high resolution RCM simulations with the absence of the point rainfall. It is found that ARFs are likely to increase for short duration events but to decrease for long duration events. The next question addresses the need for a procedure to correct systematic biases in extreme rainfalls simulated by RCMs, that makes better use of the physical mechanisms the model bases its simulations on. A method is developed that utilizes large-scale atmospheric circulation patterns, which are simulated effectively by RCMs, to establish the link with rainfall extremes. Biases in different types of extreme rainfalls are adjusted separately. The results are found to be significantly different from those obtained from conventional bias correction methods. The third question is which method to choose to estimate future daily IFDs and what the implications are if an alternative method is adopted. This thesis compares the nine methods in estimating design rainfalls for the current climate and the potential changes in the future. It is found that applying bias correction to the annual maximum rainfall coupled with regional frequency analysis produces the IFDs closest to the observations for the current climate; and that the most commonly used method projects a lower increase in IFDs than the other methods. The fourth question is how to extend the third question to the sub-daily scale, where there are not sufficient data available. Sixteen methods following two methodological paths are compared, and the skill of each method is assessed through a cross-validation framework. The optimal method varies with the path chosen according to the cross-validation results, and it generally gives a more conservative estimate to the future changes in sub-daily design rainfall depths.

Channel temperature determinations of AlGaN/GaN high electron mobility transistors (HEMTs) by high spectral resolution micro-Raman spectroscopy are proposed. The temperature dependence of the E2 phonon frequency of GaN material is calibrated by using a JYT-64000 micro-Raman system. By using the Lorentz fitting method, the measurement uncertainty for the Raman phonon frequency of ±0.035 cm−1 is achieved, corresponding to a temperature accuracy of ±3.2 °C for GaN material, which is the highest temperature resolution in the published works. The thermal resistance of the tested AlGaN/GaN HEMT sample is 22.8 °C/W, which is in reasonably good agreement with a three dimensional heat conduction simulation. The difference among the channel temperatures obtained by micro-Raman spectroscopy, the pulsed electrical method and the infrared image method are also investigated quantificationally.