Statistical post-processing techniques are used to remove systematic biases in modeled data. Models have shortcomings in the physical parameterization of weather events and have the inability to handle sub-grid phenomena successfully. The accuracy of forecasts interpolated to station points is limited by the horizontal resolution of the model. The magnitude of the bias at a station point depends upon geographical location and season. A neural network (NN) is a statistical downscaling method that seeks to model the linear or non-linear relationship between a set of different predictors and the predictand. NN’s have a training rule whereby the weights of connections between predictors and the predictand, are adjusted on the basis of the data. NN systems have been developed by using as input, different model variables from the NCEP Ensemble Prediction System (EPS) and Eta model to forecast minimum/maximum temperature and rainfall (Quantitative Precipitation Forecast (QPF) and Probability of Precipitation (PoP)), respectively. Results show some potential for improved NN forecasts over the forecast generated by the Numerical Weather Prediction (NWP) models. The implementation of a NN system can serve as a guidance tool in operational forecasting but with one difficulty that the NWP model has to be frozen, meaning no upgrades or changes on the model. / Dissertation (MSc)--University of Pretoria, 2009. / Geography, Geoinformatics and Meteorology / Unrestricted

This study of precipitation is based on data in the 1955 Climate of British Columbia concerning the network of 106 stations which have been operated in the Fraser River Basin, Emphasis is on the description of precipitation characteristics, with cartographic representation of the data forming the basis of the explanations and discussion in the The first portion of the study concerns the concentration of annual and seasonal precipitation throughout the Basin, followed by a similar examination of mean annual and seasonal snowfall with observations concerning the proportion of annual snowfall in each season and the proportion of seasonal precipitation which occurs as snow. A parallel discussion of proportions for total precipitation, with emphasis on seasons and months of maximum and minimum, is concluded by an analysis of precipitation regimes in various parts of the Basin. The effect of the gaps in the Coast Mountains resulting in continental or coastal characteristics of precipitation, dependent on station location, is noted repeatedly throughout the thesis. Considerations of variability as well as the value and methods of checking homogeneity of station records are included with observations concerning years in which heavy or light precipitation was general in large parts of the Basin. An examination of all topics as they affect the thirteen sub-basins of the Fraser concludes the study. / Arts, Faculty of / Geography, Department of / Graduate

MENVSC / Department of Geography and Geo-Information Sciences / Many South African nature reserves, like the Kruger National Park (KNP) suffer from monthly below average rainfall that puts pressure in the diversity of wildlife animals in the park. Very little attention has been given to the behaviour of zebra population during period of low rainfall in KNP. Hence, this thesis seeks to examine the role of rainfall in the distribution of burchell’s zebra population from 1983 to 2012. Previous work has failed to explain the abundance of zebras in areas of low rainfall resulting from a long period of no rainfall in the area. Readily available data on rainfall and zebra population distribution was acquired from the KNP. The semi-logarithmic model was also proposed to estimate the probability of rainfall in the Kruger National Park. Three periods of low rainfall period were estimated from the graph and the years were further used to make comparison of how zebra behaves during periods when rainfall is low, medium or highest. GIS tools (spline and kernel) were used to analyse the trend between the years of zebras in relation to rainfall availability in Kruger National Park and a map was created with these tools. The study was based on a hypothesis that there exist a relationship between rainfall and the zebra population. The study advances our understanding of what determines the movement of burchell’s zebra in the park. The findings from the research show that the impact of rainfall on zebra distribution is more complex than previously assumed. The findings based on mapping were able to indicate that rainfall variability does not influence the distribution of zebra, rather more zebras were found in areas with sparse vegetation and avoid dense vegetation as much as possible. / NRF

Cotton production came to a halt in Southern Illinois in 1974 after the last crop was harvested. Many factors went into the death of cotton in Southern Illinois. My dissertation addresses the factors that halted cotton production in 1974, and new technologies that will enable farmers to grow cotton again in 2019. Temperature and rainfall are two important factors that affect the growth of cotton. Once cotton is re-introduced into Southern Illinois, an infrastructure with a well-trained workforce will need to be in place to sustain this new industry. This study was motivated by three research goals and questions: (1) Have Southern Illinois temperatures increased or decreased over the last 50 years? Specifically has Growing Degree Days or Heat Units increased over the last 50 years creating a more suitable environment for cotton production in Southern Illinois? (2) Was rainfall a limiting factor in the death of cotton in 1974 and the revival in 2018? How has rainfall changed in Southern Illinois over the last 50 years? (3) What impact would the cotton industry have on the Southern Illinois workforce? Specifically, what would education and training for a new cotton industry entail?

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Cotton (Gossipium hiristum, L) is a warm season perennial with indeterminant growth habit. In 1995, 42,500 and 300,000 hectares were grown in Virginia and North Carolina, respectively. Soil physical and chemical properties may limit cotton yields. The objective of this study was to; 1) determine influences of soil physical and chemical properties on yield, 2) validate existing preharvest yield estimators, and 3) determine the effect of subsoiling and/or subsurface liming on cotton development and root growth. Two hundred sites were sampled across the Coastal Plain of Virginia and North Carolina to a depth of 92 cm representing 5 major soil series. Soil samples were analyzed for selected physical and chemical properties from each horizon. Boll and plant counts were obtained while harvesting a 3-meter length of row at each site to determine yield for the 1996 and 1997 growing season. Cotton was grown in the greenhouse on 30 cm diameter cores of a soil with low subsoil pH and a hard pan to determine the effects of subsoiling and/or subsurface liming. Ninety days after planting, the cotton plants were harvested and the above ground biomass and rootmass were analyzed. Physical and chemical properties explained 52% of yield variability in 1996 and 27% in 1997. Physical and chemical properties that were significant to yield were surface bulk density, available water holding capacity, depth of the water table and Bt horizon, Mg, K, Ca, and Al content. Soil analysis for nutrient status at depths up to 45 cm were better indicators of cotton yield. Subsoiling with or without subsurface liming increased rooting depth over the untreated check. The subsurface liming reached first flower 11 days prior to the other treatments. The additional period for flowering and boll set in Virginia and North Carolina could increase potential yield. / Ph. D.

Approved for public release; distribution is unlimited / This thesis presents a statistical analysis of the monthly rainfall for the Monterey Peninsula and the Carmel Valley in Central California. The analysis begins with the simple first-order autoregressive Markov model, which is found to be weak. Next, 2X2 contingency tables are used to identify predictors, one of which is found to be January rainfall. Finally, logistic analysis is used to quantify the predictive ability of January. This paper attempts to analyze rainfall time series in the statistical sense. No attempt is made to provide a physical explanation of the findings from the point of view of a meteorologist. / http://archive.org/details/statisticalanaly00davi / Captain, United States Army

A new model of the erosion by water of cohesive soils is developed using physical principles. The theoretical framework which is developed recognises the changing nature of the eroding surface of a soil. Raindrop impact and overland flow are considered to act upon a soil surface so removing soil from the cohesive original (or parent) soil. Once this soil enters the overland flow, either as aggregates or primary particles, it is considered to return to the soil bed, from which it may be re-removed. The development of a deposited layer makes it necessary to distinguish between processes removing sediment from the original soil and those processes removing the deposited layer. This layer, being formed by the relatively gentle action of deposition during the current erosion event, is presumed cohesionless. The physical properties of the original soil and the deposited layer are considered to be very different. The development of two experimental apparatus, a rainfall/runoff simulator and a settling tube for the measurement of aggregate settling velocities, is first described. Experimental investigations, using these apparatus, and field observations to inform the description of the erosion and deposition processes, are then presented. The processes by which rainfall impact removes sediment from the original soil and the deposited layer are termed rainfall detachment and rainfall re-detachment respectively. Initially, descriptions of these processes in the presence of deposition, are combined in a model describing net rainfall detachment when removal of sediment from the flow bed by overland flow is not occurring. The developriient of the deposited layer is considered both quantitatively and qualitatively. The solution of the equation describing mass conservation is then given for the equilibrium situation when the mass of the deposited layer, and therefore the sediment concentration, is constant with respect to time. The processes by which overland flow removes sediment from the original soil and the deposited layer are termed entrainment and re-entrainment. The work done by the process of entrainment is considered to be done wholly against the cohesive strength of the original soil. In contrast to the process of entrainment, the work done in re-entraining sediment from the deposited layer is considered only to be done against gravity. The resulting description of these processes is then combined with the previous descriptions of rainfall detachment, rainfall re-detachment and deposition and with the equation describing the conservation of mass of sediment within any arbitary number of size (or settling velocity) classes. A plane geometry model Is developed in which the surface water flow is considered to be uniformily distributed across a plane slope on which all processes act. When the mass of the deposited layer is steady, two possible forms of equilibrium are shown to exist. When the coverage of the original soil by deposited layer is partial, the sediment concentration is limited by the removal of the cohesive original soil by entrainment and rainfall detachment, in the presence of deposition. This situation is termed 'source limiting' and is shown to provide a lower limit to sediment concentration. When the coverage of the deposited layer is complete so that entrainment and rainfall detachment of the original soil are considered not to occur, then the ability of the erosive agents to re-entrain and re-detach sediment in the presence of deposition limits sediment concentration. This situation, termed 'transport limiting', is shown to provide a practical upper limit to sediment concentration. This plane geometry flow model is followed by a revised model in which all processes are considered to occur but the flow of water on a plane surface is modified by the formation of rills. In this 'detailed geometry model' the spatial distribution of the erosive agents is shown to have a marked influence on the resulting processes and sediment concentrations. A potential description of the sediment transport across a change in land slope is also developed. Finally, a discussion of this new modelling approach is presented in which the conceptual developments of this thesis are considered and future developments are suggested. This discussion also includes a comparison of the outcomes of this new work with similar erosion models.