The path delay between a GPS satellite and a ground based GPS receiver depends, after elimination of ionospheric effects using a combination of the two GPS frequencies, on the integral effect of the densities of dry air and water vapour along the signal path. The total delay in the signal from each satellite is known as the slant delay as the path is most likely to be non-azimuthal. The slant paths are then transferred into the vertical (or zenith) by an elevation mapping function, and this new parameter is known as the Zenith Total Delay or ZTD. ZTD gives a measure for the integrated tropospheric condition and is now widely accepted as a standard product from a network of dual frequency GPS receivers. With further calculation, taking into account surface pressure and temperature, we can then convert a portion of the ZTD into an estimate of the Integrated Water Vapour content of the atmosphere (IWV). As IWV may potentially change rapidly on a very short timescale, it is the speed at which IWV can be calculated which is of critical importance to short term meteorological forecasting. Often, rapid changes in IWV are associated with high humidity conditions caused by extreme weather events such as thunderstorms. Extreme weather events such as these are typically difficult to predict and track under current operational meteorological systems and, as they have the potential to cause great damage, it is in the interests to both the public and Met Services to significantly improve nowcasting wherever possible. As such the requirement for dense near real-time GPS networks for meteorological applications becomes apparent. Furthermore water vapour is one of the most important constituents of the atmosphere as moisture and latent heat are primarily transmitted through the water vapour phase. As well as this, water vapour is one of the most important greenhouse gases, and as such accurate monitoring of water vapour is of great importance to climatological research. This thesis assesses the quality of GPS water vapour estimates by comparison against a number of other remote sensing instruments to determine what the true value of the water vapour is and how well GPS water vapour estimates accurately represent real atmospheric fluctuations. Through these comparisons we can derive site specific bias corrections and thus, reconstruct a bias corrected time series of data for climate applications. Furthermore to ensure all biases associated with GPS processing changes are removed, a long time series of raw GPS data has been reprocessed under a consistent processing routine to again identify any climate trends in the data. Finally, this thesis addresses the question of whether near real-time GPS derived tropospheric estimates are of sufficient quality for climate applications without the need for time consuming reprocessing.

There is growing interest in quantifying the impact of climate change on extreme hydrologic events where failing to integrate the effect of climate change in rainfall estimation will underestimate the severity of the events and the adequacy of current hydraulic structure designs. The purpose of this study aims is to assess the rainfall trend and frequency analysis with impact from climate change in Peninsular Malaysia using statistical methods. The thesis consists of two sections, where the statistics of rainfall trend are assessed by Mann-Kendall (MK) test and non-stationary tests while the frequency analysis illustrates the changes in distribution functions that fit full series and sub-series of annual maximum rainfall. The study area is delineated into five regions according to their distance to the nearest coast (the different extents of the influence of monsoon to the study area) to examine the spatial characteristic of the rainfall series. The MK test has detected changes for each delineated region during different monsoon seasons. At the same time, the result of non-stationary tests reveal that changes in rainfall trend have developed around year 1995 in most of the stations (41% to 50% annual rainfall over the west coast regions; more than 50% of the short duration annual maximum rainfall in the central west region have shown non-stationarity). Among the regions, the short duration rainfall in central west region show most significant increasing trend by both the MK test and the non-stationary tests. Thus, year 1995 served as trend change-point to split full series data into two sub-series data and frequency analyses are performed on these data sets. From the outcomes of the frequency analysis using two sub-series data sets, the estimated quantiles from most of the regions have increased when the sub-series posterior to 1995 is used compared to full series data, implying an overall upward rainfall trend. The results also indicate that the combination of Generalised Extreme Value distribution function and L-moments for parameters estimation (GEV-LM) outperforms the other choices. The GEV-LM is able to fit well to all regions for short-duration rainfall and three regions for long-duration rainfall. This study demonstrates the importance of incorporating climate change in rainfall assessment. There are two-fold implications of this study. First, there is considerable variability of rainfall patterns due to climate change and hence, it is important to divide the study area into regions based on the results of the MK trend and non-stationary tests. Then, the best fitted distribution function and parameter estimation method combination for frequency analysis should be tested for every region. Second, it is important to appreciate the non-stationarity of rainfall series due to climate change and the impact on how frequency analysis shall be carried out. As the warming trends in Peninsular Malaysia started around year 1995, rainfall series have shown significance upward trend, while the results of the frequency analysis (estimated quantiles) reflects the changes in the rainfall characteristics as well. Hence, in this case, it is important to concern the non-stationarity in data to achieve better estimation performance using frequency analysis.

Data from the National Oceanic and Atmospheric Administration wind profiling radar network for the period 2002 2005 were used to investigate the effects of precipitation, topography and gravity waves on the measurements of winds by wind profilers, and to study the climatology and sources of atmospheric gravity waves. The comparison of the profiler winds to the NCAR/NCEP reanalysis and MM5 model winds revealed that monthly averaged wind profiler vertical velocities are strongly affected by precipitation in the lowest 3 km of the troposphere, both directly by hydrometeor velocity and indirectly via gravity wave activity produced by convection. We have determined that presence of downward wind velocities with magnitudes larger than 0.25 m/s is the sign of precipitation-affected data. This velocity threshold was used for identifying and correcting the contaminated data. The characteristics of the gravity waves in three period bands (6 min - 1 hour, 1 - 3 hours and 3 - 12 hours) and three orthogonal spatial components were obtained using spectral analysis of the profiler winds. The most kinetic energy was found to be associated with the low-frequency horizontal component of gravity waves. A consistent seasonal pattern and geographical distribution of kinetic gravity wave energy were observed in the troposphere, with maxima reaching ~25 J/kg in winter at 8 - 10 km altitude. A technique for quantifying the topography variance near the measurement sites was developed and applied to evaluate the effects of topography on gravity wave generation. We have determined that topography is an important source of the medium- and high-frequency waves in the middle troposphere. Correlation and regression analyses were used to study sources of the gravity waves. Convection was found to explain a significant part of the vertical component of the kinetic gravity wave energy throughout the troposphere and total kinetic energy in the lower troposphere, while vertical shear of the zonal wind was the predominant source in the upper troposphere. The results of this study are important for interpreting the wind measurements by wind profiling radars and for improving gravity wave parameterizations in global circulation models.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. Doron Nof, Florida State University, College of Arts and Sciences, Dept. of Oceanography. Title and description from dissertation home page (viewed Oct. 6, 2003). Includes bibliographical references.

Annual Report / Grant Number E-88-67(G) / Environmental Science Services Administration / January 10, 1968 / Modern statistical innovations have been incorporated into several recent analyses of tree -ring growth as related to climate. For example, Fritts (1962) used stepwise multiple regression techniques to study the systematic relationship of ring widths to climatic parameters in the southwestern United States; Bryson and Dutton (1962) have utilized power and cross -power spectral analyses in analyzing tree-ring records for periodicities; Mitchell (1967) applied factorial analysis; and Julian and Fritts (1967) introduced digital filter techniques as a means of appraising the systematic relations of tree growth to climatic variables. None of these studies, however, has attempted to analyze the joint occurrence of specific ring widths with certain climatic types so that probability statements could be made about climate from ring widths. This present study analyzes the joint occurrence of climate and relative width of tree rings for the state of Arizona. Conditional probabilities of occurrence are used to establish quantitative relevance of state -wide tree -ring growth from 1900 through 1957 to recorded climate for 1899 through 1957. The results are then used to make probability estimates of climate for the period 1650 through 1899.

No description available.

Seasonal ice cover off Canada's east coast was examined in relation to synoptic scale atmospheric events. Ice concentration information derived from Nimbus-7 scanning multichannel microwave radiometer (SMMR) measurements of surface brightness temperatures, supplemented by AES composite ice charts, provided timely coverage of the study area during the 1971/72, 1980/81 and 1984/85 ice seasons, 1971/72 and 1984/85 seasons with high ice concentrations and 1980/81 a season with low concentrations. / Atmospheric variability was monitored using the 850 hPa height at three upper air stations along the western edge of the study region. Additional information was drawn from storm track records, providing an indication of surface variability. Properties of specific storm events were obtained from the storm track data, permitting evaluation of the ice response to passing synoptic disturbances. / Results of this investigation indicate that, (1) passive microwave-derived ice information can be used to monitor high frequency variability in the marginal ice, (2) despite short time series, spectral relationships between ice concentration variability and 850 hPa pressure height indicate a strong association between the two at synoptic frequencies zone, and (3) variability in ice cover extent and concentration can be related to the passage of individual synoptic events.

The purpose of this thesis is to understand the applications and limitations of the Climatological Dispersion Model (CDM), and to explain the role of dispersion modeling within the framework of urban and regional planning. In order to reach the first objective, a detailed study study of the mechanics of the CDM was conducted. Completion of this task provided the necessary foundation for a discussion of the assets and limitations of the model. Conclusions and recommendations are made concerning the utility of the CDM for an urban area.The second objective focuses on the practical applications of dispersion modeling and is divided into four areas; the role of dispersion modeling in air quality management, the practical applications of dispersion modeling from a community view, the incorporation of dispersion modeling into the planning process, and the effectiveness and future direction of dispersion modeling. / Department of Urban Planning

The estimation of the irradiance of sloping surfaces from standard meteorological measurements requires knowledge of the geometrical distribution of scattered radiation from the sky. Measurements of the radiance distribution of cloudless skies were made with a Linke-Feussner actinometer. When measurements of sky radiance N were expressed relative to the diffuse irradiance D of a horizontal surface, the angular distributions of N/D were remarkably independent of atmospheric turbidity. Standard distributions of N/D, drawn up for different solar zenith angles, were used to estimate the diffuse irradiance of slopes under cloudless skies. A new actinometer was designed for the measurement of the radiance of cloudy skies. A theoretical analysis of the energy budget of a thermopile in relation to the actinometer design is presented. Nine actinometers were used to measure mean distributions of radiance for partly cloudy and overcast skies. Results for overcast conditions indicated that the mean radiance near the horizon was larger than the value predicted by the 'Standard Overcast Sky' formula, but the increase in estimated irradiance of vertical surfaces was only about 2/16. A computer model was formulated for estimating the global irradiance of slopes using the new results for diffuse radiation. The model was applied to climatological mean radiation data from the Meteorological Office for Kew, Eskdalemuir, Aberporth and Lerwick.