Spring Precipitation (spring + precipitation)

Distribution by Scientific Domains

Selected Abstracts

Nutritional quality of semi-arid grassland in western Spain over a 10-year period: changes in chemical composition of grasses, legumes and forbs

From 1987 to 1996, the nutritional quality of the main botanical components (grasses, legumes and forbs) in semi-arid grasslands in the dehesa ecosystem in western Spain was analysed. Herbage samples were collected at the end of spring, in 30 locations, at two different topographic positions (upper and lower slope zones). Herbage mass over 2 cm and proportion of botanical components were estimated and samples were analysed for crude protein, neutral-detergent fibre (NDF), hemicellulose, cellulose, lignin and in vitro dry matter digestibility (DMD). Analysis of variance revealed a significant effect of sampling year on the herbage mass, proportion of botanical components and their nutritional quality. The three botanical groups, grasses, legumes and forbs, followed similar year-to-year trends in their crude protein, cellulose and lignin contents and in vitro DMD. Herbage mass was not significantly related to any meteorological variables, suggesting that interannual variation in biomass production of botanically complex pastures cannot be explained by a single factor. However, annual precipitation was significantly related to the proportion of the botanical group that was dominant at each slope zone: grasses in the lower zone and forbs in the upper zone. In the upper zone, spring precipitation explained part of the interannual variation in the NDF, cellulose, lignin contents and in vitro DMD of the botanical components. [source]

Simulation of seasonal precipitation and raindays over Greece: a statistical downscaling technique based on artificial neural networks (ANNs)

K. Tolika
Abstract A statistical downscaling technique based on artificial neural network (ANN) was employed for the estimation of local changes on seasonal (winter, spring) precipitation and raindays for selected stations over Greece. Empirical transfer functions were derived between large-scale predictors from the NCEP/NCAR reanalysis and local rainfall parameters. Two sets of predictors were used: (1) the circulation-based 500 hPa and (2) its combination along with surface specific humidity and raw precipitation data (nonconventional predictor). The simulated time series were evaluated against observational data and the downscaling model was found efficient in generating winter and spring precipitation and raindays. The temporal evolution of the estimated variables was well captured, for both seasons. Generally, the use of the nonconventional predictors are attributed to the improvement of the simulated results. Subsequently, the present day and future changes on precipitation conditions were examined using large-scale data from the atmospheric general circulation model HadAM3P to the statistical model. The downscaled climate change signal for both precipitation and raindays, partly for winter and especially for spring, is similar to the signal from the HadAM3P direct output: a decrease of the parameters is predicted over the study area. However, the amplitude of the changes was different. Copyright 2006 Royal Meteorological Society [source]

Preliminary reconstructions of spring precipitation in southwestern Turkey from tree-ring width

Ramzi Touchan
Abstract Two reconstructions of spring (May,June) precipitation have been developed for southwestern Turkey. The first reconstruction (1776,1998) was developed from principal components of nine chronologies of Cedrus libani, Juniperus excelsa, Pinus brutia, and Pinus nigra. The second reconstruction (1339,1998) was derived from principal components of three J. excelsa chronologies. Calibration and verification statistics of both reconstructions indicate reasonably accurate reconstruction of spring precipitation for southwestern Turkey, and show clear evidence of multi-year to decadal variations in spring precipitation. The longest period of reconstructed spring drought, defined as consecutive years with less than 80% of normal May,June precipitation, was 4 years (1476,79). Only one drought event of this duration has occurred during the last six centuries. Monte Carlo analysis indicates a less than 33% probability that southwestern Turkey has experienced spring drought longer than 5 years in the past 660 years. Apart from the 1476,79 extended dry period, spring droughts of 3 years in length have only occurred from 1700 to the present. The longest reconstructed wet period, defined as consecutive years with more than 120% of normal May,June precipitation, was 4 years (1532,35). The absence of extended spring drought during the 16th and 17th centuries and the occurrence of extended wet spring periods during these centuries suggest a possible regime shift in climate. Preliminary analysis of links between large-scale climatic variation and these climate reconstructions shows that there is a relationship between extremes in spring precipitation and anomalous atmospheric circulation in the region. Copyright 2003 Royal Meteorological Society. [source]

Seasonal prediction of European spring precipitation from El Nio,Southern Oscillation and Local sea-surface temperatures

Benjamin Lloyd-Hughes
Abstract The extent to which European seasonal precipitation is predictable is a topic of scientific and societal importance. Although the potential for seasonal prediction is much less over Europe than in the tropics, it is not negligible. Previous studies suggest that European seasonal precipitation skill may peak in the spring (March,April,May) period, this being the season when El Nio,Southern Oscillation (ENSO) teleconnections to the North Atlantic and European sector are at their strongest. Examination of the correlation significance and temporal stability of contemporaneous and lagged ENSO links to European and North African precipitation over 98 years confirms this to be the case. The strongest ENSO links are found across the central European region (45N,55N,35E,5W). These links are symmetric with the sign of ENSO. Using a linear statistical model employing temporally stable lagged ENSO and lagged local North Atlantic sea surface temperatures as predictors, we compute the forecast skill and significance of central European spring precipitation over 30 independent years. For early March forecasts our model skill is 14,18% better than climatology, which is significant at the 95% level. Copyright 2002 Royal Meteorological Society [source]

Earlywood vessel size of oak as a potential proxy for spring precipitation in mesic sites

Patrick Fonti
Abstract Aim, In this study, we evaluate the importance of the mean earlywood vessel size of oaks as a potential proxy for climate in mesic areas. Location, The study was conducted in Switzerland at three forest sites dominated by oak (Quercus petraea and Q. pubescens). The three sites were in different climatic zones, varying mainly in terms of precipitation regime. Methods, Three 50-year-long site chronologies of mean earlywood vessel size and tree-ring widths were obtained at each site and related to monthly meteorological records in order to identify the main variables controlling growth. The responses of mean vessel size to climate were compared with those of the width variables to evaluate the potential climatic information recorded by the earlywood vessels. Results, The results show that the mean vessel size has a different and stronger response to climate than ring-width variables, although its common signal and year-to-year variability are lower. This response is better in particular at mesic sites, where it is linked to precipitation during spring, i.e. at the time of vessel formation, and is probably related to the occurrence of only a few processes controlling vessel growth, whereas radial increment is controlled by multiple and varying factors. Main conclusions, The mean earlywood vessel size of oak appears to be a promising proxy for future climate reconstructions of mesic sites, where radial growth is not controlled by a single limiting factor. [source]

Long-term study of dry matter allocation and rhizome growth in Anemone nemorosa

Abstract The rhizome system of Anemone nemorosa in a beech forest in Denmark was studied to determine how resources (dry matter) are allocated to segments of different age, and how rhizome growth is influenced by temperature and precipitation in the spring. The allocation pattern was studied by regular sampling and by experiments. In early spring, almost all movable resources in 1,4-year-old rhizome segments are used for development of leaves and flowers. Later, photosynthetic products from the above-ground parts are used for the growth of new segments (one-third to one-quarter of the resources allocated to the rhizome) or stored in segments from previous years (two-thirds to three-quarters of the resources). Thus, A. nemorosa uses the rhizome tissue for storage several times. Maximum and minimum dry weight per unit length (DWUL) was remarkably constant in 1,4-year-old rhizome segments. The DWUL of the current year's segments was half as high as that of the older segments. The differences in dry matter production across years were expressed in differences in segment length and branching, not in the DWUL of rhizomes. Unusually severe drought in the spring had a negative effect on rhizome growth, although a significant correlation between spring precipitation and rhizome growth was not detected. We found a negative correlation between the length of the growing period in spring and segment length, suggesting that a future increase in winter temperatures may cause an increase in rhizome growth. [source]