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Composite Analyses (composite + analysis)
Selected AbstractsSnow disappearance in Eastern Siberia and its relationship to atmospheric influencesINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2007Yoshihiro Iijima Abstract In the present study, we examine the climatological features and interannual variations in snow disappearance within the Lena River Basin, Eastern Siberia, during a recent 15-year period (1986,2000), and the relationship of snow disappearance to atmospheric conditions. According to the climatology of the day of the year on which snow disappears, the boundary of snow disappearance within the Lena River Basin migrates rapidly northward from mid-April until early June, with minimum interannual variation occurring in the middle part of the basin. In addition, the preceding snow disappearance is apparent in the central Lena River Basin. Melting of snow within the Lena River Basin commonly occurs within 30 days of complete snow disappearance under certain atmospheric conditions: daily mean air temperature in excess of , 10 °C, greater than 2 hPa of water vapor pressure, and, hence, more than 170 W m,2 of downward longwave radiation under clear sky conditions. Composite analysis using a reanalysis dataset demonstrates that the increase in air temperature and water vapor that accompanies snow melting is due to wet (and warm) air advection in conjunction with enhanced water vapor convergence over the central Lena River Basin during the 30-day period prior to snow disappearance. Copyright © 2006 Royal Meteorological Society. [source] Regime-dependent streamflow sensitivities to Pacific climate modes cross the Georgia,Puget transboundary ecoregionHYDROLOGICAL PROCESSES, Issue 24 2007Sean W. Fleming Abstract The Georgia Basin,Puget Sound Lowland region of British Columbia (Canada) and Washington State (USA) presents a crucial test in environmental management due to its combination of abundant salmonid habitat, rapid population growth and urbanization, and multiple national jurisdictions. It is also hydrologically complex and heterogeneous, containing at least three streamflow regimes: pluvial (rainfall-driven winter freshet), nival (melt-driven summer freshet), and hybrid (both winter and summer freshets), reflecting differing elevation ranges within various watersheds. We performed bootstrapped composite analyses of river discharge, air temperature, and precipitation data to assess El Niño,Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) impacts upon annual hydrometeorological cycles across the study area. Canadian and American data were employed from a total of 21 hydrometric and four meteorological stations. The surface meteorological anomalies showed strong regional coherence. In contrast, the seasonal impacts of coherent modes of Pacific circulation variability were found to be fundamentally different between streamflow regimes. Thus, ENSO and PDO effects can vary from one stream to the next within this region, albeit in a systematic way. Furthermore, watershed glacial cover appeared to complicate such relationships locally; and an additional annual streamflow regime was identified that exhibits climatically driven non-linear phase transitions. The spatial heterogeneity of seasonal flow responses to climatic variability may have substantial implications to catchment-specific management and planning of water resources and hydroelectric power generation, and it may also have ecological consequences due to the matching or phase-locking of lotic and riparian biological activity and life cycles to the seasonal cycle. The results add to a growing body of literature suggesting that assessments of the streamflow impacts of ocean,atmosphere circulation modes must accommodate local hydrological characteristics and dynamics. Copyright © 2007 John Wiley & Sons, Ltd. The copyright in Paul H. Whitfield's contribution belongs to the Crown in right of Canada and such copyright material is reproduced with the permission of Environment Canada. [source] Effects of the El Niño,southern oscillation on temperature, precipitation, snow water equivalent and resulting streamflow in the Upper Rio Grande river basinHYDROLOGICAL PROCESSES, Issue 6 2004Songweon Lee Abstract Snowmelt runoff dominates streamflow in the Upper Rio Grande (URG) basin of New Mexico and Colorado. Annual variations in streamflow timing and volume at most stations in the region are strongly influenced by the El Niño,southern oscillation (ENSO) through its modulation of the seasonal cycles of temperature and precipitation, and hence on snow accumulation and melting. After removing long-term trends over the study period (water years 1952,99), the dependence of monthly temperature, precipitation, snow water equivalent (SWE) at snowcourse stations, and streamflow throughout the URG on ENSO was investigated using composite analyses of the detrended residuals and through dependence of the residuals on the Climate Prediction Center southern oscillation index during the preceding summer and fall. The climate of La Niña years was found to differ significantly from either El Niño or neutral years. Moreover, significant climatological ENSO-related effects are confined to certain months, predominantly at the beginning and end of the winter season. In particular, March of La Niña years is significantly warmer and drier than during either El Niño or neutral years, and November of El Niño years is significantly colder and wetter. Differences in temperature and precipitation lead to significant differences in SWE and streamflow in the URG between the three ENSO phases. Copyright © 2004 John Wiley & Sons, Ltd. [source] Variability of the recent climate of eastern AfricaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2004Carl J. Schreck III Abstract The primary objective of this study is to investigate the recent variability of the eastern African climate. The region of interest is also known as the Greater Horn of Africa (GHA), and comprises the countries of Burundi, Djibouti, Eritrea, Ethiopia, Kenya, Rwanda, Somalia, Sudan, Uganda, and Tanzania. The analysis was based primarily on the construction of empirical orthogonal functions (EOFs) of gauge rainfall data and on CPC Merged Analysis of Precipitation (CMAP) data, derived from a combination of rain-gauge observations and satellite estimates. The investigation is based on the period 1961,2001 for the ,short rains' season of eastern Africa of October through to December. The EOF analysis was supplemented by projection of National Centers for Environmental Prediction wind data onto the rainfall eigenmodes to understand the rainfall,circulation relationships. Furthermore, correlation and composite analyses have been performed with the Climatic Research Unit globally averaged surface-temperature time series to explore the potential relationship between the climate of eastern Africa and global warming. The most dominant mode of variability (EOF1) based on CMAP data over eastern Africa corresponds to El Niño,southern oscillation (ENSO) climate variability. It is associated with above-normal rainfall amounts during the short rains throughout the entire region, except for Sudan. The corresponding anomalous low-level circulation is dominated by easterly inflow from the Indian Ocean, and to a lesser extent the Congo tropical rain forest, into the positive rainfall anomaly region that extends across most of eastern Africa. The easterly inflow into eastern Africa is part of diffluent outflow from the maritime continent during the warm ENSO events. The second eastern African EOF (trend mode) is associated with decadal variability. In distinct contrast from the ENSO mode pattern, the trend mode is characterized by positive rainfall anomalies over the northern sector of eastern Africa and opposite conditions over the southern sector. This rainfall trend mode eluded detection in previous studies that did not include recent decades of data, because the signal was still relatively weak. The wind projection onto this mode indicates that the primary flow that feeds the positive anomaly region over the northern part of eastern Africa emanates primarily from the rainfall-deficient southern region of eastern Africa and Sudan. Although we do not assign attribution of the trend mode to global warming (in part because of the relatively short period of analysis), the evidence, based on our results and previous studies, strongly suggests a potential connection. Copyright © 2004 Royal Meteorological Society. [source] Seasonal modulation of the El Niño,southern oscillation relationship with sea level pressure anomalies over the North Atlantic in October,March 1873,1996INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2003V. Moron Abstract The seasonal modulation of the relationship between the sea-level pressure anomalies (SLPAs) over the North Atlantic region (100°W,50°E; 20,70°N) and the sea surface temperature anomalies (SSTAs) in the tropical Pacific (120,290°E; 20°N,20°S) is investigated in the northern winter (October to March) from 1873 to 1996, using singular-value decomposition and composite analyses. Both methods show that the pattern of the North Atlantic SLPA associated with the tropical Pacific SSTA in November,December is different from that found in January,March. The surface covered by a significant SLPA is larger in November,December and February,March than in January. In November,December, the warm El Niño,southern oscillation (ENSO) events are associated with negative SLPAs extending from the Hudson Bay to Scandinavia and positive SLPAs over the Azores high. The cold ENSO events are associated with a positive SLPA between Greenland and western Europe. In January, and mainly in February,March, the warm ENSO events are associated with a positive SLPA north of 50°N and a negative SLPA extending from the southeastern USA toward western and central Europe. The cold ENSO events exhibit almost reversed SLPA patterns. The change between November,December and January,March is also observed at the hemispheric scale. In November,December, the SLPAs associated with the warm minus cold ENSO composite form a hemispheric north,south dipole pattern with positive (negative) anomalies south (north) of 40,45°N. In January,March, the SLPA pattern associated with the warm minus cold ENSO composite is close to the tropical Northern-Hemisphere pattern. Copyright © 2003 Royal Meteorological Society. [source] OBSERVATION WELL NETWORK DESIGN FOR PUMPING TESTS IN UNCONFINED AQUIFERS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 1 2003Xunhong Chen ABSTRACT: This paper presents a method for determining locations of observation wells to be used in conducting pumping tests in unconfined aquifers. Sensitivity coefficients, the distribution of relative errors, and the correlation coefficients between four aquifer parameters (horizontal and vertical hydraulic conductivities Kr and Kz, storage coefficient S, and specific yield Sy) are used as the criteria for the design of observation well networks and the interpretation of pumping tests. The contours of the relative errors over a vertical profile are very useful in selecting the "best" location of an observation well. Results from theoretical analyses suggest that a wide range of locations is suitable for the determination of Kr and that good locations for the determination of Kz and S may be poorly suited for the determination of Sy. Consideration must be given to the position and lengths of the pumping well screen in the selection of observation well locations. For a given location, the quality of test data can be improved by using high pumping rates and frequent sampling of drawdowns. We found that a minimum of two and preferably three observation locations are needed along a given transect. Results of the four parameters from a single well analysis may contain higher uncertainties. However, composite analyses of multiple observation wells can reduce the correlation between the four aquifer parameters, particularly between Kr and Sy, thus, improving the quality of parameter estimation. Results from two pumping tests conducted at sites located in Nebraska were examined with regard to the proposed methodology. [source] The dynamics of NAO teleconnection pattern growth and decayTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 589 2003Steven B. Feldstein Abstract This investigation performs both diagnostic analyses with NCEP/NCAR re-analysis data and forced, barotropic model calculations to examine the dynamical mechanisms associated with the growth and decay of the North Atlantic Oscillation (NAO) teleconnection pattern. The diagnostic calculations include projection and composite analyses of each term in the stream-function-tendency equation. The results of the analyses reveal a complete life cycle of growth and decay within approximately two weeks. The positive NAO phase is found to develop after anomalous wavetrain propagation across the North Pacific to the east coast of North America. This contrasts with the negative NAO phase which appeared to develop in situ. Both high-frequency (period <10 days) and low-frequency (period >10 days) transient eddy fluxes drive the NAO growth. After the NAO anomaly attains its maximum amplitude, the high-frequency transient eddy fluxes continue to drive the NAO anomaly in a manner that is consistent with a positive feedback process. The decay of the NAO occurs through both the divergence term and the low-frequency transient eddy fluxes. The temporal and spatial properties of the divergence term are found to be consistent with Ekman pumping. These results illustrate many important differences between the NAO and Pacific/North American (PNA) teleconnection patterns, perhaps most striking being that the NAO life cycle is dominated by nonlinear processes, whereas the PNA evolution is primarily linear, In addition, the relation between the NAO and the zonal index is discussed. Copyright © 2003 Royal Meteorological Society [source] Fundamental mechanisms of the growth and decay of the PNA teleconnection patternTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 581 2002Steven B. Feldstein Abstract This investigation performs diagnostic analyses on NCEP/NCAR re-analysis data, and also does forced, nonlinear, barotropic model calculations to examine the dynamical mechanisms associated with the growth and decay of the Pacific/North American teleconnection pattern (PNA). The diagnostic calculations include projection and composite analyses of each term in the stream-function-tendency equation. The results of the diagnostic analyses and model calculations reveal a PNA life cycle that is complete within approximately 2 weeks and is dominated by linear processes. The growth of the two upstream PNA anomaly centres is found to be by barotropic conversion from the zonally asymmetric climatological flow, and the two downstream PNA anomaly centres by linear dispersion. The PNA anomaly growth eventually ceases because of changes in the spatial structure of the anomaly. An analysis of the role of Ekman pumping is performed with a very simple model. The results, although qualitative, suggest that the decay of the PNA may be through Ekman pumping. An examination of the role of transient eddy vorticity fluxes indicates that they play an important role during some stages of the PNA life cycle. Lastly, the model calculations also reveal a crucial role played by the divergence term in maintaining the PNA anomaly in a quasi-fixed position. Copyright © 2002 Royal Meteorological Society. [source] Relationship between snow cover variability and Arctic oscillation index on a hierarchy of time scalesINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2003A. S. Bamzai Abstract Based on satellite-derived global snow cover data on weekly time scales, the climatology and interannual variability of snow onset day-of-year, snowmelt day-of-year and number of snow-free days in a year are presented. Trends for snow onset day-of-year, snowmelt day-of-year and number of snow-free days in a year indicate that there has been an increase in number of snow-free days in recent decades. The relationship between snow cover and the Arctic oscillation (AO) index is examined on a hierarchy of time scales using lagged correlation and composite analysis. On weekly time scales, composite snow extent anomalies are maximum when AO leads snow cover by 1 week. These composite differences are maintained several weeks thereafter, particularly in the negative phase of the AO. Maps of composite snow cover anomalies when AO leads snow cover by 1 week delineate the spatial structure of these snow anomalies. On monthly time scales, lead,lag correlation between monthly snow cover and AO index indicates that the AO index during January, February and March is significantly correlated with snow cover in concurrent and subsequent spring months, particularly over Eurasia. Finally, on seasonal time scales, it is shown that winter season AO and winter/spring season snow cover are significantly correlated. Copyright © 2003 Royal Meteorological Society. [source] Observations on the presence of E domain variants of estrogen receptor-, in the breast tumorsJOURNAL OF SURGICAL ONCOLOGY, Issue 4 2006Vijay L. Kumar PhD Abstract Background and Objectives Estrogen receptor-, (ER-,) that exists as multiple splice variants, has been widely used as a prognostic marker in the management of breast cancer. Here we have analyzed the hormone binding E domain splice variants of ER-, in the breast tumors with reference to the immunoreactive receptor. Methods Thirty breast cancer patients undergoing surgery at the All India Institute of Medical Sciences, New Delhi, were analyzed for the splice variants of E domain by RT-PCR. The ER level was determined by ELISA and the samples were considered positive if the receptor levels were ,,15 fmol/mg protein. Results Our results show that exon 4 and 5 deletions were prevalent in both ER-positive and ER-negative categories. While most ER-positive cases expressed wild-type (wt) exon 6,+,7, nearly 40% of ER-negative cases showed deletion of exon 6,+,7. Therefore, deletion of exon 6,+,7 or masking of epitopes could lead to underestimation of ER by ELISA. All the metastasis and recurrence cases had undetectable levels of ER. A significant number of node-positive cases expressed immunoreactive ER and wt exon 6,+,7 (r,=,0.509, P,<,0.37). Conclusions Estimation of ER levels combined with composite analysis of ER variants may be a better prognostic marker for breast cancer. J. Surg. Oncol. 2006;94:332,337. © 2006 Wiley-Liss, Inc [source] An integrated serum proteomic approach capable of monitoring the low molecular weight proteome with sequencing of intermediate to large peptidesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2009Karen Merrell The low-abundance, low molecular weight serum proteome has high potential for the discovery of new biomarkers using mass spectrometry (MS). Because the serum proteome is large and complex, defining relative quantitative differences for a molecular species between comparison groups requires an approach with robust separation capability, high sensitivity, as well as high mass resolution. Capillary liquid chromatography (cLC)/MS provides both the necessary separation technique and the sensitivity to observe many low-abundance peptides. Subsequent identification of potential serum peptide biomarkers observed in the cLC/MS step can in principle be accomplished by in series cLC/MS/MS without further sample preparation or additional instrumentation. In this report a novel cLC/MS/MS method for peptide sequencing is described that surpasses previously reported size limits for amino acid sequencing accomplished by collisional fragmentation using a tandem time-of-flight MS instrument. As a demonstration of the approach, two low-abundance peptides with masses of ,4000,5000,Da were selected for MS/MS sequencing. The multi-channel analyzer (MCA) was used in a novel way that allowed for summation of 120 fragmentation spectra for each of several customized collision energies, providing more thorough fragmentation coverage of each peptide with improved signal to noise. The peak list from this composite analysis was submitted to Mascot for identification. The two index peptides, 4279,Da and 5061,Da, were successfully identified. The peptides were a 39 amino acid immunoglobulin G heavy chain variable region fragment and a 47 amino acid fibrin alpha isoform C-terminal fragment. The method described here provides the ability both to survey thousands of serum molecules and to couple that with markedly enhanced cLC/MS/MS peptide sequencing capabilities, providing a promising technique for serum biomarker discovery. Copyright © 2009 John Wiley & Sons, Ltd. [source] The climatology of small-scale orographic precipitation over the Olympic Mountains: Patterns and processesTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 633 2008Justin R. Minder Abstract The climatology of small-scale patterns of mountain precipitation is poorly constrained, yet important for applications ranging from natural hazard assessment to understanding the geologic evolution of mountain ranges. Synthesizing four rainy seasons of high-resolution precipitation observations and mesoscale model output (from the Penn State/NCAR MM5), reveals a persistent small-scale pattern of precipitation over the ,10 km wide, ,800 m high ridges and valleys of the western Olympic Mountains, Washington State, USA. This pattern is characterized by a 50,70% excess accumulation over the ridge crests relative to the adjacent valleys in the annual mean. While the model shows excellent skill in simulating these patterns at seasonal time-scales, major errors exist for individual storms. Investigation of a range of storm events has revealed the following mechanism for the climatological pattern. Regions of enhanced condensation of cloud water are produced by ascent in stable flow over the windward slopes of major ridges. Synoptically generated precipitation grows by collection within these clouds, leading to enhanced precipitation which is advected by the prevailing winds. Instances of atypical patterns of precipitation suggest that under certain conditions (during periods with a low freezing level, or convective cells) fundamental changes in small-scale patterns may occur. However, case-studies and composite analysis suggest that departures from the pattern of ridge-top enhancement are rare; the basic patterns and processes appear robust to changes in temperature, winds, and background rainfall rates. Copyright © 2008 Royal Meteorological Society [source] Evolution and dynamics of summertime blocking over the Far East and the associated surface Okhotsk highTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 599 2004Hisashi Nakamura Abstract Time evolution and dynamics of an upper-level blocking ridge over the Far East and the associated surface high over the Sea of Okhotsk that give rise to abnormal summertime coolness over eastern Japan are investigated through a composite analysis applied to distinct surface high events. The formation mechanism and vertical structure of the blocking differ fundamentally between May and July, attributable to seasonal changes in the jet structure, storm-track activity over the Far East and the land,sea thermal contrast within the Okhotsk region. In May, forcing from migratory eddies is strong enough for precursory anticyclonic anomalies retrograding slowly over the North Pacific to develop into a blocking ridge. The ridge remains equivalent barotropic under the weak land,sea thermal contrast in the Okhotsk region. In contrast, the eddy forcing is no longer the primary factor for the blocking formation in July, in the presence of the weakened and split westerlies. Rather, the propagation of a stationary Rossby wave packet that has emanated from precursory anticyclonic anomalies over northern Europe stagnates over the Far East, and the subsequent local breaking of the packet leads to the blocking formation. In a particular case in July 1993, a wave packet involved in blocking formation could be traced back as far upstream as the east coast of North America over the two previous weeks. Acting on the strong thermal contrast in July between the cool sea surface and a warm land mass to the west, the anomalous surface easterlies induced by the blocking ridge can build up a cold surface anticyclone through cold advection, rendering the blocking anomalies distinctly baroclinic. Copyright © 2004 Royal Meteorological Society [source] | |||||||||||||