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1.
Sayang Mohd Deni Abdul Aziz Jemain Kamarulzaman Ibrahim 《Theoretical and Applied Climatology》2009,97(1-2):109-121
The analysis of the daily rainfall occurrence behavior is becoming more important, particularly in water-related sectors. Many studies have identified a more comprehensive pattern of the daily rainfall behavior based on the Markov chain models. One of the aims in fitting the Markov chain models of various orders to the daily rainfall occurrence is to determine the optimum order. In this study, the optimum order of the Markov chain models for a 5-day sequence will be examined in each of the 18 rainfall stations in Peninsular Malaysia, which have been selected based on the availability of the data, using the Akaike’s (AIC) and Bayesian information criteria (BIC). The identification of the most appropriate order in describing the distribution of the wet (dry) spells for each of the rainfall stations is obtained using the Kolmogorov-Smirnov goodness-of-fit test. It is found that the optimum order varies according to the levels of threshold used (e.g., either 0.1 or 10.0 mm), the locations of the region and the types of monsoon seasons. At most stations, the Markov chain models of a higher order are found to be optimum for rainfall occurrence during the northeast monsoon season for both levels of threshold. However, it is generally found that regardless of the monsoon seasons, the first-order model is optimum for the northwestern and eastern regions of the peninsula when the level of thresholds of 10.0 mm is considered. The analysis indicates that the first order of the Markov chain model is found to be most appropriate for describing the distribution of wet spells, whereas the higher-order models are found to be adequate for the dry spells in most of the rainfall stations for both threshold levels and monsoon seasons. 相似文献
2.
Summary Wet and dry spell properties of monthly rainfall series at five meteorology stations in Turkey are examined by plotting successive
wet and dry month duration versus their number of occurrences on the double-logarithmic paper. Straight line relationships
on such graphs show that power-laws govern the pattern of successive persistent wet and dry monthly spells. Functional power
law relationships between the number of dry and wet spells for a given monthly period are derived from the available monthly
precipitation data. The probability statements for wet and dry period spells are obtained from the power law expressions.
Comparison of power-law behaviours at five distinct sites in Turkey provides useful interpretation about the temporal and
spatial rainfall pattern. As in temperate areas such as Turkey the rainfall amounts change mostly due to one-month-long dry
or wet spells.
Received August 29, 1995 Revised November 9, 1995 相似文献
3.
Modelling Wet and Dry Spells with Mixture Distributions 总被引：1，自引：0，他引：1
Summary The object of the study is to develop a discrete precipitation model which is able to simulate local, daily series of precipitation
occurrences. The model is fitted to the observed data of two stations, Szeged and Szombathely, in Hungary (1951–1995), with
pronounced attention to the reproduction of long dry periods, as characteristic features of the climate in Central Europe.
The point of the approach is to model the duration of consecutive dry and wet series, i.e., spells, instead of individual
wet or dry days. After having comparisons of three different aspects performed, the selected precipitation threshold is 0.1 mm.
This threshold keeps the duration of dry and wet periods more or less balanced, whereas the value of the threshold does not
fundamentally influence either the conditional distribution of macrocirculation types or the local weather statistics related
to the so defined wet or dry days. The duration of both wet and dry spells are found to be independent of the length of either
the preceding (opposite) or the last, but one (identical) state. It is also demonstrated that mixed distributions fairly fit
to the wet and dry spells, whereas the simple geometric does not, especially due to the erroneous lack of long dry sequences.
Weighted sum of two geometric distributions, as well as that of one geometric and one Poisson distribution exhibits good fitting
for the dry spells, whereas only the latter one can be advised to employ for the wet periods. Parameters of the distributions
obviously depend on the season and the site, in question.
Received June 30, 1999 Revised February 3, 2000 相似文献
4.
Statistical modeling of CMIP5 projected changes in extreme wet spells over China in the late 21st century 总被引：1，自引：0，他引：1
The observed intensity, frequency, and duration (IFD) of summer wet spells, defined here as extreme events with one or more consecutive days in which daily precipitation exceeds a given threshold (the 95th percentile), and their future changes in RCP4.5 and RCP8.5 in the late 21st century over China, are investigated by using the wet spell model (WSM) and by extending the point process approach to extreme value analysis. Wet spell intensity is modeled by a conditional generalized Pareto distribution, frequency by a Poisson distribution, and duration by a geometric distribution, respectively. The WSM is able to realistically model summer extreme rainfall spells during 1961–2005, as verified with observations at 553 stations throughout China. To minimize the impact of systematic biases over China in the global climate models (GCMs) of the Coupled Model Intercomparison Project Phase 5 (CMIP5), five best GCMs are selected based on their performance to reproduce observed wet spell IFD and average precipitation during the historical period. Furthermore, a quantile–quantile scaling correction procedure is proposed and applied to produce ensemble projections of wet spell IFD and corresponding probability distributions. The results show that in the late 21st century, most of China will experience more extreme rainfall and less low-intensity rainfall. The intensity and frequency of wet spells are projected to increase considerably, while the duration of wet spells will increase but to a much less extent. The IFD changes in RCP8.5 are in general much larger than those in RCP4.5. 相似文献
5.
6.
Ashwini Ranade A. K. Mitra Nityanand Singh Swati Basu 《Meteorology and Atmospheric Physics》2014,125(1-2):43-61
Evaluation of weather forecasting systems and assessment of existing verification procedures are essential to achieve desirable seamless rainfall prediction. Prediction of wet and dry spells is quite useful in agriculture and hydrology but very few attempts have been made so far to resolve the issue using numerical model output. Performance of five state-of-the-art global atmospheric general circulation models and their ensemble mean has been examined in predicting the parameters of wet and dry spells (WSs/DSs) during monsoon period of 2008–2011 over seven subzones of the Indian region. The number of WSs across the region is found to be underestimated, while total duration and rainfall amount of WSs (DSs) overestimated (underestimated). Start of the first WS is late and ends of the last WS early in the model forecast. More uncertainty is noticed in the prediction of DS rainfall and its duration than that of the WS. The percentage area of India under wet conditions (rainfall amount over each grid is more than its daily mean monsoon rainfall) and rainwater over the wet area is overestimated by about 59 and 32 %, respectively, in all models. 相似文献
7.
A deficit in precipitation may impact greatly on soil moisture, snowpack, streamflow, groundwater and reservoir storage. Among the several approaches available to investigate this phenomenon, one of the most applied is the analysis of dry spells. In this study, a non-homogeneous Poisson model has been applied to a set of high-quality daily rainfall series, recorded in southern Italy (Calabria region) during the period 1981–2010, for the stochastic analysis of dry spells. Firstly, some statistical details of the Poisson models were presented. Then, the proposed model has been applied to the analysis of long dry spells. In particular, a Monte Carlo technique was performed to reproduce the characteristics of the process. As a result, the main characteristics of the long dry spells have shown patterns clearly related to some geographical features of the study area, such as elevation and latitude. The results obtained from the stochastic modelling of the long dry spells proved that the proposed model is useful for the probability evaluation of drought, thus improving environmental planning and management. 相似文献
8.
Statistical distributions of annual extreme (AE) series and partial duration (PD) series for dry-spell event are analyzed for a database of daily rainfall records of 50 rain-gauge stations in Peninsular Malaysia, with recording period extending from 1975 to 2004. The three-parameter generalized extreme value (GEV) and generalized Pareto (GP) distributions are considered to model both series. In both cases, the parameters of these two distributions are fitted by means of the L-moments method, which provides a robust estimation of them. The goodness-of-fit (GOF) between empirical data and theoretical distributions are then evaluated by means of the L-moment ratio diagram and several goodness-of-fit tests for each of the 50 stations. It is found that for the majority of stations, the AE and PD series are well fitted by the GEV and GP models, respectively. Based on the models that have been identified, we can reasonably predict the risks associated with extreme dry spells for various return periods. 相似文献
9.
Neural network based daily precipitation generator (NNGEN-P) 总被引：1，自引：0，他引：1
Jean-Philippe Boulanger Fernando Martinez Olga Penalba Enrique Carlos Segura 《Climate Dynamics》2007,28(2-3):307-324
Daily weather generators are used in many applications and risk analyses. The present paper explores the potential of neural network architectures to design daily weather generator models. Focusing this first paper on precipitation, we design a collection of neural networks (multi-layer perceptrons in the present case), which are trained so as to approximate the empirical cumulative distribution (CDF) function for the occurrence of wet and dry spells and for the precipitation amounts. This approach contributes to correct some of the biases of the usual two-step weather generator models. As compared to a rainfall occurrence Markov model, NNGEN-P represents fairly well the mean and standard deviation of the number of wet days per month, and it significantly improves the simulation of the longest dry and wet periods. Then, we compared NNGEN-P to three parametric distribution functions usually applied to fit rainfall cumulative distribution functions (Gamma, Weibull and double-exponential). A data set of 19 Argentine stations was used. Also, data corresponding to stations in the United States, in Europe and in the Tropics were included to confirm the results. One of the advantages of NNGEN-P is that it is non-parametric. Unlike other parametric function, which adapt to certain types of climate regimes, NNGEN-P is fully adaptive to the observed cumulative distribution functions, which, on some occasions, may present complex shapes. On-going works will soon produce an extended version of NNGEN to temperature and radiation. 相似文献
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12.
Robert Monjo Guillem Chust Vicente Caselles 《Theoretical and Applied Climatology》2014,117(1-2):317-329
A parametric quantile–quantile transformation is used to correct the systematic errors of precipitation projected by regional climate models. For this purpose, we used two new probability distributions: modified versions of the Gumbel and log-logistic distributions, which fit to the precipitation of both wet and dry days. With these tools, the daily probability distribution of seven regional climate models was corrected: Aladin-ARPEGE, CLM-HadCM3Q0, HIRHAM-HadCM3Q0, HIRHAM-BCM, RECMO-ECHAM5-rt3, REMO-ECHAM-rt3 and PROMES-HadCM3Q0. The implemented method presents an error less than 5 % in the simulation of the average precipitation and 1 % in the simulation of the number of dry days. For the study area, an intensification of daily and subdaily precipitation is expected under the A1B scenario throughout the 21st century. This intensification is interpreted as a consequence of the process of ‘mediterraneanisation’ of the most southern ocean climate. 相似文献
13.
Understanding variations in precipitation from a variety of aspects is important for the utilization of water resources. Based on daily precipitation records at 98 meteorological stations in Sichuan province, southwestern China, the spatial and temporal changes in wet/dry spells were investigated by using 14 precipitation indices. The Mann–Kendall trend test is used to detect trends in the index series. Results suggest that the decrease of precipitation in central and eastern Sichuan was significant in terms of decreasing tendencies of wet spell indices. However, the decreasing trend of dry spell indices suggested an increase in precipitation in western Sichuan province. A higher risk of droughts can be expected in autumn and wet spell indices in winter and spring are increasing, implying obvious seasonality and seasonal shifts of change in precipitation within this province. Wet/dry spells with short duration were accounted for a large proportion of spells in Sichuan. The occurrence and fractional contribution of short-duration wet spells were increasing. The same trend was found in dry spells with short and moderate duration in Sichuan 相似文献
14.
Spatial and temporal characteristics of wet spells in Greece 总被引：7，自引：1，他引：6
Summary This study examines the characteristics of wet spells in Greece, using daily rainfall gauge data, over a 40-year period (1958–1997). The longest wet spells, computed for two different thresholds (0.1mm and 1mm), were observed in Western Greece and Crete, whereas the shortest ones were found in the central and south Aegean. A detailed analysis of the wet spells, dividing them into three classes, shows that on an annual basis their highest frequencies were observed in Western and Northwestern Greece. The seasonal results are also quite similar. The trends and the variability of the mean length of the wet spells were also analyzed. Negative trends were found in the case of the year-to-year analysis and during winter. Finally, this study presents an evaluation of two theoretical distribution models; the second order Markov Chains (MC2) and the Negative Binomial Distribution (NBD), by their adjustment to the empirical data. Both models can be used in the future for an estimation of the wet spells in the area under study. 相似文献
15.
Aifang Cheng Qi Feng Guobin Fu Jiankai Zhang Zongxing Li Meng Hu Gang Wang 《大气科学进展》2015,32(10):1391-1406
Changes in rainfall extremes pose a serious and additional threat to water resources planning and management, natural and artificial oasis stability, and sustainable development in the fragile ecosystems of arid inland river basins. In this study, the trend and temporal variation of extreme precipitation are analyzed using daily precipitation datasets at 11 stations over the arid inland Heihe River basin in Northwest China from 1960 to 2011. Eight indices of extreme precipitation are studied. The results show statistically significant and large-magnitude increasing and decreasing trends for most indices, primarily in the Qilian Mountains and eastern Hexi Corridor. More frequent and intense rainfall extremes have occurred in the southern part of the desert area than in the northern portion. In general, the temporal variation in precipitation extremes has changed throughout the basin. Wet day precipitation and heavy precipitation days show statistically significant linear increasing trends and step changes in the Qilian Mountains and Hexi Corridor. Consecutive dry days have decreased obviously in the region in most years after approximately the late 1980s, but meanwhile very long dry spells have increased, especially in the Hexi Corridor. The probability density function indicates that very long wet spells have increased in the Qilian Mountains. The East Asian summer monsoon index and western Pacific subtropical high intensity index possess strong and significant negative and positive correlations with rainfall extremes, respectively. Changes in land surface characteristics and the increase in water vapor in the wet season have also contributed to the changes in precipitation extremes over the river basin. 相似文献
16.
P. D. Tyson 《Climatic change》1980,2(4):363-371
Annual rainfall anomalies over Africa south of 22° are shown to have exhibited a striking degree of organisation in both time and space during the period of meteorological record. Since the beginning of the twentieth century eight regularly alternating wet and dry spells of nine to ten years duration are shown to have occurred in association with a widespread quasi 20-year rainfall oscillation; before the turn of the century at least three spells occurred and more may have. For each wet or dry spell the spatial variation of rainfall over southern Africa is presented.Visiting from the University of the Witwatersrand, Johannesburg. 相似文献
17.
Uncertainty analysis of statistical downscaling models using Hadley Centre Coupled Model 总被引：2，自引：2，他引：0
S. Samadi Catherine A. M. E. Wilson Hamid Moradkhani 《Theoretical and Applied Climatology》2013,114(3-4):673-690
Regression-based statistical downscaling is a method broadly used to resolve the coarse spatial resolution of general circulation models. Nevertheless, the assessment of uncertainties linked with climatic variables is essential to climate impact studies. This study presents a procedure to characterize the uncertainty in regression-based statistical downscaling of daily precipitation and temperature over a highly vulnerable area (semiarid catchment) in the west of Iran, based on two downscaling models: a statistical downscaling model (SDSM) and an artificial neural network (ANN) model. Biases in mean, variance, and wet/dry spells are estimated for downscaled data using vigorous statistical tests for 30 years of observed and downscaled daily precipitation and temperature data taken from the National Center for Environmental Prediction reanalysis predictors for the years of 1961 to 1990. In the case of daily temperature, uncertainty is estimated by comparing monthly mean and variance of downscaled and observed daily data at a 95 % confidence level. In daily precipitation, downscaling uncertainties were evaluated from comparing monthly mean dry and wet spell lengths and their confidence intervals, cumulative frequency distributions of monthly mean of daily precipitation, and the distributions of monthly wet and dry days for observed and modeled daily precipitation. Results showed that uncertainty in downscaled precipitation is high, but simulation of daily temperature can reproduce extreme events accurately. Finally, this study shows that the SDSM is the most proficient model at reproducing various statistical characteristics of observed data at a 95 % confidence level, while the ANN model is the least capable in this respect. This study attempts to test uncertainties of regression-based statistical downscaling techniques in a semiarid area and therefore contributes to an improvement of the quality of predictions of climate change impact assessment in regions of this type. 相似文献
18.
Frequency, intensity, areal extent (AE) and duration of rain spells during summer monsoon exhibit large intra-seasonal and inter-annual variations. Important features of the monsoon period large-scale wet spells over India have been documented. A main monsoon wet spell (MMWS) occurs over the country from 18 June to 16 September, during which, 26.5 % of the area receives rainfall 26.3 mm/day. Detailed characteristics of the MMWS period large-scale extreme rain events (EREs) and spatio-temporal EREs (ST-EREs), each concerning rainfall intensity (RI), AE and rainwater (RW), for 1 to 25 days have been studied using 1° gridded daily rainfall (1951–2007). In EREs, ‘same area’ (grids) is continuously wet, whereas in ST-EREs, ‘any area’ on the mean under wet condition for specified durations is considered. For the different extremes, second-degree polynomial gave excellent fit to increase in values from distribution of annual maximum RI and RW series with increase in duration. Fluctuations of RI, AE, RW and date of occurrence (or start) of the EREs and the ST-EREs did not show any significant trend. However, fluctuations of 1° latitude–longitude grid annual and spatial maximum rainfall showed highly significant increasing trend for 1 to 5 days, and unprecedented rains on 26–27 July 2005 over Mumbai could be a realization of this trend. The Asia–India monsoon intensity significantly influences the MMWS RW. 相似文献
19.
Paraclimatic statistics and the study of climate change: the case of the cork region in the 1750s 总被引：1，自引：1，他引：0
John G. Tyrrell 《Climatic change》1995,29(2):231-245
20.
A comparison of three multi-site statistical downscaling models for daily rainfall in the North China Plain 总被引：1，自引：1，他引：0
Wenbin Liu Guobin Fu Changming Liu Stephen P. Charles 《Theoretical and Applied Climatology》2013,111(3-4):585-600
Three statistical downscaling methods (conditional resampling statistical downscaling model: CR-SDSM, the generalised linear model for daily climate time series: GLIMCLIM, and the non-homogeneous hidden Markov model: NHMM) for multi-site daily rainfall were evaluated and compared in the North China Plain (NCP). The comparison focused on a range of statistics important for hydrological studies including rainfall amount, extreme rainfall, intra-annual variability, and spatial coherency. The results showed that no single model performed well over all statistics/timescales, suggesting that the user should chose appropriate methods after assessing their advantages and limitations when applying downscaling methods for particular purposes. Specifically, the CR-SDSM provided relatively robust results for annual/monthly statistics and extreme characteristics, but exhibited weakness for some daily statistics, such as daily rainfall amount, dry-spell length, and annual wet/dry days. GLIMCLIM performed well for annual dry/wet days, dry/wet spell length, and spatial coherency, but slightly overestimated the daily rainfall. Additionally, NHMM performed better for daily rainfall and annual wet/dry days, but slightly underestimated dry/wet spell length and overestimated the daily extremes. The results of this study could be applied when investigating climate change impact on hydrology and water availability for the NCP, which suffers from intense water shortages due to climate change and human activities in recent years. 相似文献