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961.
Rafael Moniz Caixeta Diniz Tamantini Ribeiro João Felipe Coimbra Leite Costa Péricles Lopes Machado 《Natural Resources Research》2017,26(2):213-221
Multiple Random Walk Simulation consists of a methodology adapted to run fast simulations if close-spaced data are abundant (e.g., short-term mining models). Combining kriging with the simulation of random walks attempts to approximate traditional simulation algorithm results but at a computationally faster way when there is a large amount of conditioning samples. This paper presents this new algorithm illustrating the situations where the method can be used properly. A synthetic study case is presented in order to illustrate the Multiple Random Walk Simulation and to analyze the speed and goodness of its results against the ones from using Turning Bands Simulation and Sequential Gaussian Simulation. 相似文献
962.
Derek?Weber Bertha?A.?Marquez Charnise?Taylor Paul?Raya Paul?Contreras David?Howard Ikenna?Nwachuku Katie?Fusco Fernanda?Morales Lambert?A.?DoezemaEmail author 《Journal of Atmospheric Chemistry》2017,74(3):339-356
Geologic seepage of methane and light (C2-C5) alkanes was measured at the La Brea Tar Pits in Los Angeles. Samples were collected using flux chambers with stainless steel canisters and analyzed using gas chromatography. Average seepage rates from individual seepage sites were 970 ± 330 mg/h of methane, 14.0 ± 5.5 mg/h of ethane, 9.1 ± 3.7 mg/h of propane, 3.7 ± 1.6 mg/h of i-butane, 0.33 ± 0.16 mg/h of n-butane, 260 ± 120 μg/h of i-pentane, and 5.3 ± 1.9 μg/h of n-pentane, while maximum seepage rates exceeded 17 g/h of methane, 270 mg/h of ethane, 190 mg/h of propane, 95 mg/h of i-butane, 10 mg/h of n-butane, 7 mg/h of i-pentane, and 0.1 mg/h of n-pentane. These absolute fluxes have an additional unknown amount of error associated with them due to sampling methodology, and should be taken as the lower limit of emissions. Samples collected revealed generally dry gas, with high methane emissions relative to the light alkanes. Overall emissions from the tar pits were found to come not only from the active geologic seepage, but also from the outgassing of the standing asphalt at the site. Using the gas ratios, which are negligibly affected by errors introduced by sampling methodology, observed in this study, daily emissions of C2 – C5 alkanes from the La Brea area were estimated to be 4.7 ± 1.6 Mg, which represents 2–3 % of total emissions in the entire Los Angeles region. 相似文献
963.
María?CazorlaEmail authorView authors OrcID profile 《Journal of Atmospheric Chemistry》2017,74(3):377-398
In this paper we present first-time measurements of ozone profiles from a high altitude station in Quito, Ecuador (0.19°S, 78.4°W, and 2391 masl) taken from June 2014 to September 2015. We interpret ozone observations in the troposphere, tropopause, and stratosphere through a zonal comparison with data from stations in the Atlantic and Pacific (Natal and San Cristobal from the SHADOZ network). Tropospheric ozone concentrations above the Andes are lower than ozone over San Cristobal and Natal for similar time periods. Ozone variability and pollution layers are also reduced in the troposphere above the Andes. We explain these differences in terms of reduced contributions from the boundary layer and from horizontal transport. In the tropical tropopause layer, ozone is well-mixed up to near the cold point tropopause level. In this regard, our profiles do not show constraints to deep mixing above 14 km, as has been consistently observed at other tropical stations. Total column ozone and stratospheric column ozone are comparable among the three sites. However, the contribution of tropospheric column ozone to total column ozone is significantly lower above the Andes. Our comparisons provide a connection between observations from tropical stations in equatorial South America separated by the wide continental mass. Identified differences in ozone throughout the atmospheric column demonstrate the global benefit of having an ozone sounding station at the equatorial Andes in support of global monitoring networks. 相似文献
964.
This study focuses on the spatial distribution of mean annual and monthly precipitation in a small island (1128 km2) named Martinique, located in the Lesser Antilles. Only 35 meteorological stations are available on the territory, which has a complex topography. With a digital elevation model (DEM), 17 covariates that are likely to explain precipitation were built. Several interpolation methods, such as regression-kriging (????????, ????????, and ????????) and external drift kriging (??????) were tested using a cross-validation procedure. For the regression methods, predictors were chosen by established techniques whereas a new approach is proposed to select external drifts in a kriging which is based on a stepwise model selection by the Akaike Information Criterion (AIC). The prediction accuracy was assessed at validation sites with three different skill scores. Results show that using methods with no predictors such as inverse distance weighting (??????) or universal kriging (????) is inappropriate in such a territory. ?????? appears to outperform regression methods for any criteria, and selecting predictors by our approach improves the prediction of mean annual precipitation compared to kriging with only elevation as drift. Finally, the predicting performance was also studied by varying the size of the training set leading to less conclusive results for ?????? and its performance. Nevertheless, the proposed method seems to be a good way to improve the mapping of climatic variables in a small island. 相似文献
965.
Jamaludin?SuhailaEmail author Zulkifli?Yusop 《Theoretical and Applied Climatology》2017,127(1-2):229-240
The paper analyzes equivalent data for a low density meteorological station network (spatially discontinuous data) and poor temporal homogeneity of thunderstorm observational data. Due to that, a Regional Climate Model (RegCM) dataset was tested. The Most Unstable Convective Available Potential Energy index value (MUCAPE) above the 200 J kg?1 threshold was selected as a predictor describing favorable conditions for the occurrence of thunderstorms. The quality of the dataset was examined through a comparison between model results and soundings from several aerological stations in Central Europe. Good, statistically significant (0.05 significance level) results were obtained through correlation analysis; the value of Pearson’s correlation coefficient was above 0.8 in every single case. Then, using methods associated with gridded climatology, data series for 44 weather stations were derived and an analysis of correlation between RegCM modeled data and in situ thunderstorm observations was conducted with coefficients in the range of 0.75–0.90. The possibility of employing the dataset in thunderstorm climatology analysis was checked via a few examples by mapping monthly, seasonal, and annual means. Moreover, long-term variability and trend analysis along with modeled MUCAPE data were tested. As a result, the RegCM modeled MUCAPE gridded dataset was proposed as an easily available, suitable, and valuable predictor for thunderstorm climatology analysis and mapping. Finally, some limitations are discussed and recommendations for further improvements are given. 相似文献
966.
Cailin?Wang Xuehui?RenEmail author Ying?Li 《Theoretical and Applied Climatology》2017,127(1-2):169-185
Rainfall in New South Wales (NSW), located in the southeast of the Australian continent, is known to be influenced by four major climate drivers: the El Niño/Southern Oscillation (ENSO), the Interdecadal Pacific Oscillation (IPO), the Southern Annular Mode (SAM) and the Indian Ocean Dipole (IOD). Many studies have shown the influences of ENSO, IPO modulation, SAM and IOD on rainfall in Australia and on southeast Australia in particular. However, only limited work has been undertaken using a multiple regression framework to examine the extent of the combined effect of these climate drivers on rainfall. This paper analysed the role of these combined climate drivers and their interaction on the rainfall in NSW using Bayesian Model Averaging (BMA) to account for model uncertainty by considering each of the linear models across the whole model space which is equal to the set of all possible combinations of predictors to find the model posterior probabilities and their expected predictor coefficients. Using BMA for linear regression models, we are able to corroborate and confirm the results from many previous studies. In addition, the method gives the ranking order of importance and the probability of the association of each of the climate drivers and their interaction on the rainfall at a site. The ability to quantify the relative contribution of the climate drivers offers the key to understand the complex interaction of drivers on rainfall, or lack of rainfall in a region, such as the three big droughts in southeastern Australia which have been the subject of discussion and debate recently on their causes. 相似文献
967.
Jiangbo?GaoEmail author Wenjuan?Hou Yongkang?Xue Shaohong?Wu 《Theoretical and Applied Climatology》2017,127(1-2):241-257
This work aims, as a first step, to analyze rainfall variability in Northern Algeria, in particular extreme events, during the period from 1940 to 2010. Analysis of annual rainfall shows that stations in the northwest record a significant decrease in rainfall since the 1970s. Frequencies of rainy days for each percentile (5th, 10th, 25th, 50th, 75th, 90th, 95th, and 99th) and each rainfall interval class (1–5, 5–10, 10–20, 20–50, and ≥50 mm) do not show a significant change in the evolution of daily rainfall. The Tenes station is the only one to show a significant decrease in the frequency of rainy days up to the 75th percentile and for the 10–20-mm interval class. There is no significant change in the temporal evolution of extreme events in the 90th, 95th, and 99th percentiles. The relationships between rainfall variability and general atmospheric circulation indices for interannual and extreme event variability are moderately influenced by the El Niño-Southern Oscillation and Mediterranean Oscillation. Significant correlations are observed between the Southern Oscillation Index and annual rainfall in the northwestern part of the study area, which is likely linked with the decrease in rainfall in this region. Seasonal rainfall in Northern Algeria is affected by the Mediterranean Oscillation and North Atlantic Oscillation in the west. The ENSEMBLES regional climate models (RCMs) are assessed using the bias method to test their ability to reproduce rainfall variability at different time scales. The Centre National de Recherches Météorologiques (CNRM), Czech Hydrometeorological Institute (CHMI), Eidgenössische Technische Hochschule Zürich (ETHZ), and Forschungszentrum Geesthacht (GKSS) models yield the least biased results. 相似文献
968.
Julian?WittmerEmail author Cornelius?ZetzschEmail author 《Journal of Atmospheric Chemistry》2017,74(2):187-204
The photochemical activation of chlorine by dissolved iron in artificial sea-salt aerosol droplets and by highly dispersed iron oxide (Fe2O3) aerosol particles (mainly hematite, specific surface ~150 m2 g?1) exposed to gaseous HCl, was investigated in humidified air in a Teflon simulation chamber. Employing the radical-clock technique, we quantified the production of gaseous atomic chlorine (Cl) from the irradiated aerosol. When the salt aerosol contained Fe2O3 at pH 6, no significant Cl production was observed, even if the dissolution of iron was forced by “weathering” (repeatedly freezing and thawing for five times). Adjusting the pH in the stock suspension to 2.6, 2.2, and 1.9 and equilibrating for one week resulted in a quantifiable amount of dissolved iron (0.03, 0.2, and 0.6 mmol L?1, respectively) and in gaseous Cl production rates of ~1.6, 6, and 8?×?1021 atoms cm?2 h?1, respectively. In a further series of experiments, the pure Fe2O3 aerosol was exposed to various levels of gaseous hydrogen chloride (HCl). The resulting Cl production rates ranged from 8?×?1020 Cl atoms cm?2 h?1 (at ~4 ppb HCl) to 5?×?1022 Cl atoms cm?2 h?1 (at ~350 ppb HCl) and confirmed the uptake and conversion of HCl to atomic Cl (at HCl to Cl conversion yields of 2–5 %, depending on the relative humidity). The Fe2O3 experiments indicate that iron-induced Cl formation may be important for highly soluble combustion-aerosol particles in marine environments in the presence of gaseous HCl. 相似文献
969.
Katherine?M.?PrimmEmail author Gregory?P.?Schill Daniel?P.?Veghte Miriam?Arak?Freedman Margaret?A.?Tolbert 《Journal of Atmospheric Chemistry》2017,74(1):55-69
Mineral dust particles are known to be efficient ice nuclei in the atmosphere. Previous work has probed heterogeneous ice nucleation on various laboratory dust samples including Arizona Test Dust, kaolinite, montmorillonite, and illite as atmospheric dust surrogates. However, it has recently been suggested that NX illite may be a better representation of atmospheric dust. Hiranuma et al. (2015) performed a laboratory comparison for immersion ice nucleation on NX illite, but here we focus on depositional ice nucleation because of its importance in low temperature cirrus cloud formation. A Raman microscope setup was used to examine the ice-nucleating efficiency of NX illite. Organic coatings on the NX illite particles were also investigated using a mixture of 5 dicarboxylic acids (M5). The ratio of NX illite to M5 was varied from 1:10 to 100:1. It was found that NX illite efficiently nucleates ice with Sice = 1.07 ± 0.01 at ?47 °C, with Sice slightly increasing at lower temperatures. In contrast, pure M5 is a poorer ice nucleus with Sice = 1.30 ± 0.02 at ?40 °C, relatively independent of temperature. Further, it was found that M5 coatings on the order of several monolayers thick hindered the ice nucleating ability of NX illite. Optical images suggest that at colder temperatures (< ?50 °C) 1:1 NX illite:M5 particles and pure M5 particles nucleate ice depositionally, while at warmer temperatures (> ?50 °C) subsaturated immersion ice nucleation dominates. These experiments suggest that mineral dust particles may become less active towards ice nucleation as they age in the atmosphere. 相似文献
970.
Ali?AhmadalipourEmail author Arun?Rana Hamid?Moradkhani Ashish?Sharma 《Theoretical and Applied Climatology》2017,128(1-2):71-87
Climate change is expected to have severe impacts on global hydrological cycle along with food-water-energy nexus. Currently, there are many climate models used in predicting important climatic variables. Though there have been advances in the field, there are still many problems to be resolved related to reliability, uncertainty, and computing needs, among many others. In the present work, we have analyzed performance of 20 different global climate models (GCMs) from Climate Model Intercomparison Project Phase 5 (CMIP5) dataset over the Columbia River Basin (CRB) in the Pacific Northwest USA. We demonstrate a statistical multicriteria approach, using univariate and multivariate techniques, for selecting suitable GCMs to be used for climate change impact analysis in the region. Univariate methods includes mean, standard deviation, coefficient of variation, relative change (variability), Mann-Kendall test, and Kolmogorov-Smirnov test (KS-test); whereas multivariate methods used were principal component analysis (PCA), singular value decomposition (SVD), canonical correlation analysis (CCA), and cluster analysis. The analysis is performed on raw GCM data, i.e., before bias correction, for precipitation and temperature climatic variables for all the 20 models to capture the reliability and nature of the particular model at regional scale. The analysis is based on spatially averaged datasets of GCMs and observation for the period of 1970 to 2000. Ranking is provided to each of the GCMs based on the performance evaluated against gridded observational data on various temporal scales (daily, monthly, and seasonal). Results have provided insight into each of the methods and various statistical properties addressed by them employed in ranking GCMs. Further; evaluation was also performed for raw GCM simulations against different sets of gridded observational dataset in the area. 相似文献