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Variability Patterns (variability + pattern)
Selected AbstractsVariability patterns and positively selected sites at the gametophytic self-incompatibility pollen SFB gene in a wild self-incompatible Prunus spinosa (Rosaceae) populationNEW PHYTOLOGIST, Issue 3 2006Maria D. S. Nunes Summary ,,Current models for the generation of new gametophytic self-incompatibility specificities require that neutral variability segregates within specificity classes. Furthermore, one of the models predicts greater ratios of nonsynonymous to synonymous substitutions in pollen than in pistil specificity genes. All models assume that new specificities arise by mutation only. ,,To test these models, 21 SFB (the pollen S -locus) alleles from a wild Prunus spinosa (Rosaceae) population were obtained. For seven of these, the corresponding S -haplotype was also characterized. The SFB data set was also used to identify positively selected sites. Those sites are likely to be the ones responsible for defining pollen specificities. ,,Of the 23 sites identified as being positively selected, 21 are located in the variable (including a new region described here) and hypervariable regions. Little variability is found within specificity classes. There is no evidence for selective sweeps being more frequent in pollen than in pistil specificity genes. The S-RNase and the SFB genes have only partially correlated evolutionary histories. ,,None of the models is compatible with the variability patterns found in the SFB and the S -haplotype data. [source] Estimating diurnal to annual ecosystem parameters by synthesis of a carbon flux model with eddy covariance net ecosystem exchange observationsGLOBAL CHANGE BIOLOGY, Issue 2 2005Bobby H. Braswell Abstract We performed a synthetic analysis of Harvard Forest net ecosystem exchange of CO2 (NEE) time series and a simple ecosystem carbon flux model, the simplified Photosynthesis and Evapo-Transpiration model (SIPNET). SIPNET runs at a half-daily time step, and has two vegetation carbon pools, a single aggregated soil carbon pool, and a simple soil moisture sub-model. We used a stochastic Bayesian parameter estimation technique that provided posterior distributions of the model parameters, conditioned on the observed fluxes and the model equations. In this analysis, we estimated the values of all quantities that govern model behavior, including both rate constants and initial conditions for carbon pools. The purpose of this analysis was not to calibrate the model to make predictions about future fluxes but rather to understand how much information about process controls can be derived directly from the NEE observations. A wavelet decomposition enabled us to assess model performance at multiple time scales from diurnal to decadal. The model parameters are most highly constrained by eddy flux data at daily to seasonal time scales, suggesting that this approach is not useful for calculating annual integrals. However, the ability of the model to fit both the diurnal and seasonal variability patterns in the data simultaneously, using the same parameter set, indicates the effectiveness of this parameter estimation method. Our results quantify the extent to which the eddy covariance data contain information about the ecosystem process parameters represented in the model, and suggest several next steps in model development and observations for improved synthesis of models with flux observations. [source] Intercomparison of global cloud cover fields over oceans from the VOS observations and NCEP/NCAR reanalysisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2007Ernst Bedacht Abstract The paper inter-compares the total cloud cover over the World Ocean from marine visual observations assimilated in the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) and National Centers of Environmental Prediction/National Center of Atmospheric Research (NCEP-NCAR) reanalysis. The Intercomparison covers the period from 1948 to 2002. NCEP-NCAR reanalysis shows about 10% of fractional cloud cover smaller than the visual observations do. The largest differences are observed in the mid and sub-polar latitudes. In the tropics, NCEP-NCAR data show slightly higher cloud cover then ICOADS. These systematic differences are quite persistent through the year with somewhat stronger differences in summer. Comparison of the characteristics of inter-annual variability shows little consistency between visually observed total cloud cover and total cloudiness diagnosed by the reanalysis. Linear trends are primarily positive in the ICOADS cloud data, while in the NCEP-NCAR reanalysis they show downward trends in the tropics and upward tendencies in the mid and high latitudes. Analysis of the effect of sampling in ICOADS shows that sampling inhomogeneity cannot fully explain the disagreements observed. At the same time, the major climate variability patterns such as North Atlantic Oscillation (NAO) and El-Nino,Southern Oscillation (ENSO) are well captured in both ICOADS and NCEP-NCAR cloud cover data sets. Copyright © 2007 Royal Meteorological Society [source] Signals of anthropogenic influence on European warming as seen in the trend patterns of daily temperature varianceINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2005A. M. G. Klein Tank Abstract Signals of anthropogenic warming over Europe are searched for in the spatial trend patterns for the variance and skewness (expressed by the 10th and 90th percentiles) of the distribution of daily mean temperature. Comparisons are made between these patterns in the station records of the European Climate Assessment dataset for the 1976,99 period, the patterns associated with natural variability in the observations (which were empirically derived from the observations in the 1946,75 period), and the patterns of future warming and natural variability as simulated by the National Center for Atmospheric Research Community Climate System Model in the Challenge ensemble experiment. The results indicate that, on the basis of the patterns for the variance, a distinction can be made between temperature change due to natural variability and temperature change due to changes in external forcing. The observed variance trend patterns for the spring (March,May) and summer (June,August) warming 1976,99 are clearly different from the patterns for the change in variance associated with a warming due to natural variability in the observations. This led us to conclude that a change in an external forcing has to be invoked to explain the observed spring and summer warming. From the evaluation of the greenhouse and natural variability patterns in the climate model simulations, we infer that the observed spring and summer variance trend patterns contain imprints consistent with anthropogenic warming. The analysis of the variance trend patterns for the winter (December,February) season is inconclusive about identifying causes of the observed warming for that season. Unlike the other three seasons, the autumn (September,November) is for Europe a period of cooling in recent decades. The observed variance trend pattern for this season closely resembles the estimated pattern for the change in variance associated with a cooling due to natural variability, indicating that the observed autumn cooling can be ascribed to random weather variations in the period under consideration. Copyright © 2005 Royal Meteorological Society [source] The spatial and temporal behaviour of the lower stratospheric temperature over the Southern Hemisphere: the MSU view.INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2001Part I: data, methodology, temporal behaviour Abstract The lower stratosphere monthly temperature anomalies over the Southern Hemisphere derived from soundings made by the Microwave Sounding Unit (MSU) between 1979 and 1997 are analysed. Specifically MSU channel 4 temperature retrievals are considered. Principal component (PC) analysis with the S-mode approach is used in order to isolate grid points that covary in a similar manner and to determine the main features of their temporal behaviour. The first six PCs explain 81.3% of the variance and represent the different time variability patterns observed over the Southern Hemisphere for the ten area clusters determined by the method. The most important feature is common to all the PC score pattern,time series and corresponds to a negative linear trend present in almost all the Southern Hemisphere except over New Zealand and surrounding areas. The negative trend is largest over Antarctica. The remaining features of the temporal variability are different for each PC score and therefore for each cluster region over the Southern Hemisphere. The first PC score pattern shows the impact of the Chichón and Mt Pinatubo eruptions that each produced a 2-year warming over the tropical and sub-tropical lower stratosphere. This variability is orthogonal with the behaviour present over Antarctica. There are different anomalies between 1987 (El Niño) and 1988 (La Niña). This second PC does not show any evidence whatsoever of the volcanic eruptions. The semi-annual wave is present in the anomaly recurrence at mid to high latitudes. Over very low latitudes, close to the Equator, the Quasi-Biennial Oscillation (QBO) band of frequency is also present. Copyright © 2001 Royal Meteorological Society [source] Dynamics of the Polychaetes Desdemona ornata and Perinereis cultrifera and Their Resources of Food in a Mediterranean MudflatMARINE ECOLOGY, Issue 4 2002Francesca Rossi Abstract. Availability of food in the sediment can play an important role in determining the dynamics of deposit feeders. Generally the abundance of deposit feeders during winter and spring is related to an increase in the nutritive value of the sediment due to the concurrent microalgal peaks. This work investigated, in 1998, the seasonal variability patterns in the nutritive value of the sediment and in the abundance of two polychaetes, Desdemona ornata (Sabellidae: Fabriicinae) and Perinereis cultrifera (Nereididae), that probably feed on benthic microalgae. Previously, in 1997, these two species were abundant in winter and spring. During that winter, the amount of chlorophyll a in the sediment was quite variable due to grazing activities. Three manipulative field experiments were carried out in winter and spring (January, March and April 1998) to test the hypothesis that increasing the amount of chlorophyll a increases the nutritional value of the sediment and the abundance of Perinereis cultrifera and Desdemona ornata. The results indicated that the patterns of variability for these species and for chlorophyll a were similar to those observed in 1997. In plots where microalgal growth was stimulated experimentally, Perinereis cultrifera increased in January and Desdemona ornata increased in January and March. The role of food in regulating the abundances of Perinereis cultrifera and Desdemona ornata is discussed. [source] Spectroscopic study of the long-period dust-producing WC7pd+O9 binary HD 192641MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2005L. Lefèvre ABSTRACT We present the results of an optical spectroscopic study of the massive Wolf,Rayet (WR) binary HD 192641 = WR 137. These 1986,2000 data cover the dust-formation maximum in 1997. Combining all available measurements of radial velocities, we derive, for the first time, a spectroscopic orbit with period 4766 ± 66 d (13.05 ± 0.18 yr). The resulting masses, adopting i= 67 °, are MO= 20 ± 2 M, for the O component and MWR= 4.4 ± 1.5 M, for the WR component. These appear, respectively, approximately normal and on the low side for the given spectral types. Analysis of the intense multisite spectroscopic monitoring in 1999 shows that the C iii,5696 and C iv,,5802/12 lines have the highest intrinsic variability levels. The periodogram analysis yields a small-amplitude modulation in the absorption troughs of the C iv,,5802/12 and He i,5876 lines with a period of 0.83 d, which could be related either to pulsations or large-scale rotating structures as seen in the WN4 star EZ Canis Majoris (WR 6). Wavelet analysis of the strong emission lines of C iii,5696 and C iv,,5802/12 enabled us to isolate and follow for several hours small structures (emission subpeaks) associated with density enhancements within the wind of the Wolf,Rayet star. Cross-correlating the variability patterns seen in different lines, we find a weak but significant correlation between the variability in emission lines with different ionization potentials, i.e. in lines formed at different distances from the WR stellar core. Adopting a , wind-velocity law, from the motion of individual subpeaks we find ,, 5, which is significantly larger than the canonical value ,, 1 found in O star winds. [source] Variability patterns and positively selected sites at the gametophytic self-incompatibility pollen SFB gene in a wild self-incompatible Prunus spinosa (Rosaceae) populationNEW PHYTOLOGIST, Issue 3 2006Maria D. S. Nunes Summary ,,Current models for the generation of new gametophytic self-incompatibility specificities require that neutral variability segregates within specificity classes. Furthermore, one of the models predicts greater ratios of nonsynonymous to synonymous substitutions in pollen than in pistil specificity genes. All models assume that new specificities arise by mutation only. ,,To test these models, 21 SFB (the pollen S -locus) alleles from a wild Prunus spinosa (Rosaceae) population were obtained. For seven of these, the corresponding S -haplotype was also characterized. The SFB data set was also used to identify positively selected sites. Those sites are likely to be the ones responsible for defining pollen specificities. ,,Of the 23 sites identified as being positively selected, 21 are located in the variable (including a new region described here) and hypervariable regions. Little variability is found within specificity classes. There is no evidence for selective sweeps being more frequent in pollen than in pistil specificity genes. The S-RNase and the SFB genes have only partially correlated evolutionary histories. ,,None of the models is compatible with the variability patterns found in the SFB and the S -haplotype data. [source] | ||||||||||