Precipitation Time Series (precipitation + time_series)

Distribution by Scientific Domains

Selected Abstracts

Long-term trend analysis for precipitation in Asian Pacific FRIEND river basins

Z. X. Xu
Abstract In order to analyse the long-term trend of precipitation in the Asian Pacific FRIEND region, records from 30 river basins to represent the large range of climatic and hydrological characteristics in the study area are selected. The long-term trend in precipitation time series and its association with the southern oscillation index (SOI) series are investigated. Application of the nonparametric Mann,Kendall test for 30 precipitation time series has shown that only four of these 30 time series have a long-term trend at the 5% level of significance. Nevertheless, most of the records tend to decrease over the last several decades. The dataset is further divided geographically into northern, middle, and southern zones, with 20°N and 20°S latitude as the dividing lines. The middle zone has the greatest variation and the southern zone the least variation over the past century. Also, the southern zone has greater variation during the past 30 years. The association between precipitation and SOI is investigated by dividing the precipitation records of each station into El Niño, La Niña, and neutral periods. The Wilcoxon rank-sum test showed that differences in precipitation for the three classes were most marked in the southern zone of the study area. The frequencies of below- and above-average precipitation for El Niño, La Niña, and neutral periods are estimated for the 30 precipitation time series as well. The results show that the frequencies of precipitation under each set of conditions, with lower precipitation generally associated with El Niño periods in the southern zone. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A multimodel assessment of future climatological droughts in the United Kingdom,

Jean-Philippe Vidal
Abstract This paper presents a detailed assessment of future rainfall drought patterns over the United Kingdom. Previously developed bias-corrected high-resolution gridded precipitation time series are aggregated to the scale relevant for water resources management, in order to provide 21st-century time series for 183 hydrologic areas, as computed by six General Circulation Models (GCMs) under two emissions scenarios. The control run data are used as a ,learning time series' to compute the Standardized Precipitation Index (SPI) at four different time scales. SPI values for three 30-year future time slices are computed with respect to these learning time series in order to assess the changes in drought frequency. Multimodel results under the A2 scenario show a dramatic increase in the frequency of short-term extreme drought class for most of the country. A decrease of long-term droughts is expected in Scotland, due to the projected increase in winter precipitation. The analysis for two catchment case studies also showed that changes under the B2 scenario are generally consistent with those of the A2 scenario, with a reduced magnitude in changes. The overall increase with time in the spread of individual GCM results demonstrates the utility of multimodel statistics when assessing the uncertainty in future drought indices to be used in long-term water resources planning. Copyright © 2009 Royal Meteorological Society [source]

A comprehensive analysis of changes in precipitation regime in Tuscany

Simone Fatichi
Abstract The analysis of changes in precipitation is nowadays of great interest because rainfall space-time distribution is considered one of the most important indexes in the natural climatic cycle. This study proposes an investigation of precipitation time series recorded in the region of Tuscany (Central Italy) in the period 1916,2003. Forty indexes are defined to evaluate changes in the precipitation patterns and trend detection is performed through statistical tests to assess the significance of temporal and spatial changes in the precipitation regime. The presented analysis does not show strong evidence of nonstationarity. A few indexes in a given number of stations of the analysed territory do show a slight trend, but the significance of those trends is lost once the multiple location testing issue is considered. The complexity of the climate in central Italy, i.e. the presence of numerous feedbacks might in fact distort or remove the consequences of global warming on the precipitation regime. Copyright © 2009 Royal Meteorological Society [source]

Trends in the boreal summer regional Hadley and Walker circulations as expressed in precipitation records from Asia and Africa during the latter half of the 20th century

Hongxu Zhao
Abstract West African summer rainfall, north China summer rainfall and a new climate proxy, snow accumulation from the Dasuopu ice core in the southern Himalaya, have all experienced decreasing trends during the latter half of the 20th century. In this paper, we investigate the existence of a common mechanism that explains these geographically dispersed trends during the boreal summer. In particular, we explore the hypothesis that these trends are related to changes in the regional Hadley and Walker circulations. We show that the divergent circulation in the NCEP reanalysis indicates the existence of trends in these circulations that are consistent with the observed changes in the precipitation records. In addition, the regressions of the divergent circulation in the NCEP reanalysis against these precipitation records indicate that a similar globally coherent signal is associated with the time series and their linear trends while the regressions against the de-trended residuals do not contain statistically significant large-scale signals. These similarities lead us to conclude that the decreasing trends in the three precipitation time series during the latter half of the 20th century are consistent with large-scale changes in the global overturning circulation during the boreal summer. Copyright © 2007 Royal Meteorological Society [source]

Impact of climate variability on Alpine glaciers in northwestern Italy

Sandro Calmanti
Abstract We analyzed glacier snout fluctuation data in Piedmont and Val d'Aosta (Italy) and studied the impact of climate variability on valley glaciers in the western Italian Alps. The study period covered about 70 years in the 20th century; we focused on the last 50 years where a large number of temperature and precipitation time series are available. Superposed onto a general recession trend, we detected strong oscillations on shorter time scales and we showed that they are significantly correlated with fluctuations in winter precipitation rates and average summer temperatures. On the basis of these results, we constructed a simple lagged-linear empirical stochastic model that explained upto 66% of the variance of the snout fluctuation data. The model produces reliable out-of-sample predictions of the impact of climate variability on the glaciers of the western Alps and it can be used to estimate the average response of Alpine glaciers to different scenarios of climate change, provided the morphology of the individual glaciers does not change completely. Copyright © 2007 Royal Meteorological Society [source]

Linking global circulation model synoptics and precipitation for western North America

Suzan Lapp
Abstract Synoptic downscaling from global circulation models (GCMs) has been widely used to develop local and regional-scale future precipitation scenarios under global warming. This paper presents an analysis of the linkages between the Canadian Centre for Climate Modelling and Analysis first version of the Canadian Global Coupled Model (CCCma CGCM1) 2000 model output and local/regional precipitation time series. The GCM 500 hPa geopotential heights were visually classified for synoptic patterns using a geographical information system. The pattern frequencies were statistically compared with historical data from Changnon et al. (1993. Monthly Weather Review121: 633,647) for the winter period 1961,85. The CGCM1 synoptic frequencies compare favourably with the historical data, and they represent a substantial improvement over the 1992 Canadian Climate Centre Global Circulation Model synoptic climatology output. The CGCM1 output was used to forecast future winter precipitation scenarios for five geographically diverse climate stations in western North America. Copyright © 2002 Royal Meteorological Society. [source]

Recent variations in seasonality of temperature and precipitation in Canada, 1976,95

Paul H. Whitfield
Abstract A previously reported analysis of rehabilitated monthly temperature and precipitation time series for several hundred stations across Canada showed generally spatially coherent patterns of variation between two decades (1976,85 and 1986,95). The present work expands that analysis to finer time scales and a greater number of stations. We demonstrate how the finer temporal resolution, at 5 day or 11 day intervals, increases the separation between clusters of recent variations in seasonal patterns of temperature and precipitation. We also expand the analysis by increasing the number of stations from only rehabilitated monthly data sets to rehabilitated daily sets, then to approximately 1500 daily observation stations. This increases the spatial density of data and allows a finer spatial resolution of patterns between the two decades. We also examine the success of clustering partial records, i.e. sites where the data record is incomplete. The intent of this study was to be consistent with previous work and explore how greater temporal and spatial detail in the climate data affects the resolution of patterns of recent climate variations. The variations we report for temperature and precipitation are taking place at different temporal and spatial scales. Further, the spatial patterns are much broader than local climate regions and ecozones, indicating that the differences observed may be the result of variations in atmospheric circulation. Copyright © 2002 Environment Canada. Published by John Wiley & Sons, Ltd. [source]


Mary H. Nichols
ABSTRACT: The climate of Southern Arizona is dominated by summer precipitation, which accounts for over 60 percent of the annual total. Summer and non-summer precipitation data from the USDA-ARS Walnut Gulch Experimental Watershed are analyzed to identify trends in precipitation characteristics from 1956 to 1996. During this period, annual precipitation increased. The annual precipitation increase can be attributed to an increase in precipitation during non-summer months, and is paralleled by an increase in the proportion of annual precipitation contributed during non-summer months. This finding is consistent with previously reported increases in non-summer precipitation in the southwestern United States. Detailed event data were analyzed to provide insight into the characteristics of precipitation events during this time period. Precipitation event data were characterized based on the number of events, event precipitation amount, 30-minute event intensity, and event duration. The trend in non-summer precipitation appears to be a result of increased event frequency since the number of events increased during nonsummer months, although the average amount per event, average event intensity, and average event duration did not. During the summer "monsoon" season, the frequency of recorded precipitation events increased but the average precipitation amount per event decreased. Knowledge of precipitation trends and the characteristics of events that make up a precipitation time series is a critical first step in understanding and managing water resources in semiarid ecosystems. [source]