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Precipitation Periods (precipitation + period)

Distribution by Scientific Domains

Earth and Environmental Science	75%

Selected Abstracts

Kinetics of Calcium Carbonate (CaCO3) Precipitation from a Icel-Yavca Dolomite Leach Solution by a Gas (Carbon Dioxide)/Liquid Reaction

HELVETICA CHIMICA ACTA, Issue 3 2009
Mehmet Yildirim
Abstract The effects of time, CO2 -gas-injection pressure, and bulk temperature on the precipitation of Ca2+ ions as a precipitated calcium carbonate (PCC) from a dolomite leach solution were investigated. Precipitation periods from 1 to 7,min were examined, and experiments were run at CO2 -injection pressures of 200,800,kPa. Effects of bulk temperature were studied in the range from 40 to 70°, and precipitation rates of PCC were determined by measuring the Ca2+ concentrations in the initial and effluent solutions. Influences of these parameters on the subsequent incorporation of Mg2+ ions with the precipitate are discussed in detail. Kinetic analysis of the precipitation was performed by considering the rates as a function of CO -ion concentrations. Results obtained by this process clearly show that Ca2+ ions in the solution can successfully be precipitated as a calcium carbonate product containing 54.70% of CaO and 0.77% MgO, at the rate of 2.01,mM h,1. [source]

A gridded hourly precipitation dataset for Switzerland using rain-gauge analysis and radar-based disaggregation

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2010
Marc Wüest
Abstract Rain gauges and weather radars both constitute important devices for operational precipitation monitoring. Gauges provide accurate yet spotty precipitation estimates, while radars offer high temporal and spatial resolution yet at a limited absolute accuracy. We propose a simple methodology to combine radar and daily rain-gauge data to build up a precipitation dataset with hourly resolution covering a climatological time period. The methodology starts from a daily precipitation analysis, derived from a dense rain-gauge network. A sequence of hourly radar analyses is then used to disaggregate the daily analyses. The disaggregation is applied such as to retain the daily precipitation totals of the rain-gauge analysis, in order to reduce the impact of quantitative radar biases. Hence, only the radar's advantage in terms of temporal resolution is exploited. In this article the disaggregation method is applied to derive a 15-year gridded precipitation dataset at hourly resolution for Switzerland at a spatial resolution of 2 km. Validation of this dataset indicates that errors in hourly intensity and frequency are lower than 25% on average over the Swiss Plateau. In Alpine valleys, however, errors are typically larger due to shielding effects of the radar and the corresponding underestimation of precipitation periods by the disaggregation. For the flatland areas of the Swiss Plateau, the new dataset offers an interesting quantitative description of high-frequency precipitation variations suitable for climatological analyses of heavy events, the evaluation of numerical weather forecasting models and the calibration/operation of hydrological runoff models. Copyright © 2009 Royal Meteorological Society [source]

Erosion predictions with the Wind Erosion Equation (WEQ) using different climatic factors

LAND DEGRADATION AND DEVELOPMENT, Issue 1 2008
J. E. Panebianco
Abstract Little information is available on the performance of the Wind Erosion Equation (WEQ) for estimating wind erosion under differing climatic conditions. The objective of this study was to assess the fitting of measured and WEQ-estimated wind erosion with different climatic C factors. Results showed that WEQ underestimated the annual wind erosion by 45 per cent when loaded with the historic C, obtained with climatic data records between 1981 and 1990. The monthly averaged C factor (monthly C, n,=,12) underestimated the erosion by 29 per cent, the C factors of each one of the six studied years (annual C, n,=,6) underestimated the erosion by 19 per cent, and the C factors of each one of the evaluated months (monthly C, n,=,72) overestimated the erosion by 31 per cent. Precipitation explained most of C factors variability. C factors corresponding to high precipitation periods predicted low erosion amounts in no-till (NT) and conventional tillage (CT). C factors corresponding to low precipitation periods calculated high erosion rates in CT (143,t,ha,1,y,1) and low in NT (2·4,t,ha,1,y,1). The historical C factor predicted no erosion in NT and 7·1,t,ha,1,y,1 in CT. These results indicated that the WEQ should be used with variable C factors in order to assess different climatic scenarios of the semiarid Argentina. Copyright © 2007 John Wiley & Sons, Ltd. [source]