Thesis (M.S.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 90-93). Also available via World Wide Web.

Thesis (doctoral)--Königl. Westfäl. Wilhelms-Universität zu Münster i. W., 1910. / "Die Abhandlung erscheint auch in den Veröffentlichungen der Deutschen Seewarte in Hamburg: Aus dem Archiv der Deutschen Seewarte XXXIII. Jahrgang 1910"--T.p. verso. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. [63]-73).

Beamfilling error is one of the main error sources for microwave oceanic rainfall retrieval. An accurate beamfilling correction can improve the rainfall retrieval accuracy significantly. Quantitative understanding of the uncertainty of the Beamfilling Correction Factor (BCF) is very important for the understanding of the accuracy of microwave passive rainfall retrieval. Refinement of the calculation of the BCF and the estimation of BCF uncertainty are the main purposes of this thesis. The characteristic of rainfall distribution is investigated. Quantitative understanding of the statistical characteristics of rainfall distribution provides an indication of the beamfilling error and the uncertainty of BCF in many ways. Some refinements to the traditional BCF calculation algorithm are provided in this thesis. Scattering is included in the new algorithm. Also the BCF calculation only considers the cases within the useful dynamic range. These refinements make the BCF calculation closer to how it is used in the retrieval algorithm. The BCF based on the new algorithm should be more accurate. The global BCF uncertainty and the local BCF uncertainty are estimated using the available A/C radar data. The results show that the uncertainty of BCF is much smaller than expected, and also show that the BCF derived from a specific set of data can be used globally.

A jet madel of cumulus is studied assuming steadystate conditions and horizontally uniform cross-sections of cloud and environment. Numerical solutions, assuming an entrainment rate inversely proportional to cloud radius, show that for a given ambient lapse rate the cloud thickness depends mainly on (i) mass flux at cloud base and (ii) relative humidity in lower levels. [...]

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The area chosen for this study is the Central Elburz of Iran surrounding the southern end of the Caspian Sea. It includes an important rainfall dependent agricultural area and merges into the semi arid zone with a well defined boundary. From social and agricultural points of view rainfall is by far the most important climatic factor in many tropical and subtropical countries. An important aspect in the development of agriculture in the Central Elburz is the determination of the seasonal rainfall patterns. This thesis should be considered as a contribution to the study of the seasonal rainfall regime of Iran, with direct value to agriculture in the region. The purpose of this thesis is to examine the pattern of rainfall especially in relation to the growing season both in time and spatially. Also the thesis describes the variation in the availability of moisture for growth throughout this region. The thesis examines annual, monthly and seasonal rainfall over the region. Multivariate analysis has demonstrated that the study area can be divided into three rainfall regions. Before considering any analysis which could allow prediction on probability of future rainfall amounts, it is important to consider whether or not there on trends or fluctuations. The result of this analysis is that, few stations show positive trends, others negative trends. Rainfall variability has been quantified by the coefficient of variation index and analysed in a similar way to that of rainfall distribution. The results for most stations shown a relationship between variability indices and rainfall amounts. In relation to the study of variability, an assessment of rainfall probability and reliability has been considered with reference to rainfall critical for crops. Probability has a particular value in its application to agriculture. In this study 90% probability is examined and this is related to the economy of the agriculture units in the Central Elburz. Also 80 and 75 percent probability are presented. These spatial patterns of probability thus provide maps of agricultural potential. Rainfall records are analysed to provide estimates, percentage points of rainfall totals, variation in the start, and end of the rainy season and or the probability of dry spells within the rainy season. The estimation of potential evapotranspiration which are discussed and explained in this study are based on the Blaney- Criddle and Pan evaporation methods. The water balance approach provides the most rational method of analysing seasonal pattern since it considers characteristics of the dominant crops in this area, wheat and citrus, and it examines effectiveness of rainfall for these crops. Blaney- Criddle and Pan evaporation have been used to estimate potential evaporation for wheat and citrus and compared to actual evapotranspiration to give potential water deficit. The adoption of probability analysis of potential water deficit provides a valuable description of water availability for crops in this region of variable rainfall.

It is argued that for many regions of the earth, ground based remote sensing techniques for rainfall measurement are impractical due to their cost and limited range of coverage. Global rainfall estimates must therefore be provided largely by satellites, particularly those exploiting atmospheric windows in the visible/IR and microwave regimes. / A 2-D pattern matching technique using visible and IR data is proposed and its accuracy investigated. Because these wavelengths respond primarily to cloud and not rain sized drops, significant accuracy may be achieved in rain areas, but not directly in amounts. However, when long term average rain rates for raining areas are used, errors of (TURN) (+OR-) 49% for 10('5) km('2) are achieved. This compares favorably with other techniques based on cloud life histories. / Microwave radiometer-based techniques are also investigated and are found to be fundamentally limited in accuracy ((TURN) (+OR-) 70%) by the large variations in the (unknown) effective rain layer height. However, useful accuracy ((TURN) (+OR-) 20%) may be obtained over large areas ((TURN) 10('5) km('2)), provided that the long term average effective rain layer height is known. It is argued that a once or twice daily satellite rain estimate is insufficient for either accurate estimates of daily accumulation or for samples of climatological rain rates. A hybrid microwave satellite-vis/IR technique is therefore proposed in order to solve the temporal resolution problem without the necessity of orbiting many microwave radiometers. This technique would take advantage of the high ( 1/2 hour) temporal resolution of the vis/IR data and could achieve accuracies of (TURN) (+OR-) 20% for 12 hour accumulations over 10('5) km('2) provided that the mean effective rain layer height is known. The practical implementation of such a technique will ultimately depend on the relative difficulty of measuring the mean effective rain layer height, and the mean rain rate for raining areas as well as the availability of appropriate sensor platforms.