bluuebunny/crossref_metadata_2025 huggingface dataset:
True Malignant Histiocytosis with Trisomy 9 following Primary Mediastinal Germ Cell Tumor
Authors: Suenaga Mitsuhiro , Matsushita Kakushi , Kawamata Nakaaki , Kukita Toshimasa , Hamakawa Yuji , Gejima Kentaro , Onodera Reiri , Sato Tetsuo , Yamaguchi Akihiko , Inoue Hirosaka , Arimura Kosei , Arima Naomichi , Yoshida Hiroki , Tei Chuwa
Published: June 2006

A 24-year-old Japanese man was admitted due to bloody phlegm in May 2002. A diagnosis of mediastinal germ cell tumor, mixed type involving seminoma, immature teratoma and embryonal carcinoma, was made by transthoracic needle biopsy. Three months later, his complete blood counts revealed pancytopenia with high fever. Examination of bone marrow revealed increased atypical large histiocytes (5.6%) with hemophagocytosis, and thus, hemophagocytic syndrome related to germ cell tumor was diagnosed. In addition, chromosomal analysis of the bone marrow cells revealed a 47, XY, +9 genotype. Chemotherapies for germ cell tumor and hemophagocytic syndrome were performed without any improvement, and he died of diffuse alveolar damage. Autopsy revealed diffuse infiltration of immature histiocytes with hemophagocytosis in the liver, spleen and bone marrow. The atypical histiocytes were positive for CD68 and lysozyme and negative for lymphoid markers, and the diagnosis of true malignant histiocytosis associated with mediastinal germ cell tumor was made. The rare chromosomal abnormality of trisomy 9, a marker for benzene-related leukemia, was seen in the present case without apparent benzene exposure.
Muscular System Is the Driver of Skeletal Development
Authors: Schoenau Eckhard
Published: June 2006

This review focuses on methodological concepts in the evaluation of skeletal muscle function and bone adaptation. It is now thought that the critical property of bone is strength rather than weight, and that control of bone strength is mainly exercised through the effect of the mechanical loads brought to bear on bone. Muscle contraction places the greatest physiological load on bone, and so the stability of bone must be adapted to muscle strength (the functional muscle-bone unit). The described suggestions and recommendations outline a new concept: bone mass and strength should not be related to age. There is now more and more evidence that bone mass and strength should be related to muscle function. Thus analyzed, there is no such entity as a ‘peak bone mass’. Many studies are currently under way to evaluate whether these novel approaches increase the sensitivity and specificity of fracture prediction in an individual. Furthermore, the focus of many bone researchers is shifting away from bone mass to bone geometry or bone strength and their relationship to the driving muscle system.
Puberty and Athletic Sports in Female Adolescents
Authors: Klentrou Panagiota (Nota)
Published: June 2006

The increasing involvement of young children in intense physical training over the past several decades has generated concerns as to its potential effects on children’s growth and maturation. Puberty in humans is characterized by large hormonal changes resulting in both physical and sexual maturation. Since intense training prior to puberty, together with the potential metabolic effects of dieting, can alter hypothalamic-pituitary function, the time at which athletic training is initiated has been implicated as a factor in delayed menarche and sexual maturation in female athletes. On the other hand, some studies have suggested that delayed menarche is likely due to genetic factors. Girls who mature later often self-select or are recruited by coaches into sports that favor small or very lean bodies. Body composition has also been used to explain both delayed menarche and menstrual irregularities observed among elite athletes. A higher prevalence of menstrual dysfunction has been reported for adolescent athletes participating in weight-dependent sports as compared to that observed in other sports. However, as recently suggested, there is no direct cause-effect association between fatness and reproduction and, in actual fact, energy availability, and not body fat, regulates reproductive function in females. More research is warranted to further investigate this interaction between short-term changes in fuel availability and athletic amenorrhea in female adolescents. It is concluded that, given the many factors that have been shown to influence menarche and menstruation, the role played by physical training alone as a causative factor in the later onset of puberty and menstrual irregularities in active young females is still unclear. Research involving longitudinally designed studies is required to identify whether the maturity differences observed between female athletes and non-athletes are the result of nature or nurture, and what the balance between the two factors is.
Cardiac Arrest and Ventricular Tachycardia in Japanese-Type Apical Hypertrophic Cardiomyopathy
Authors: Ridjab Denio , Koch Matthias , Zabel Markus , Schultheiss Heinz-Peter , Morguet Andreas J.
Published: June 2006

Apical hypertrophic cardiomyopathy (HCM) is a specific variant of HCM. This disease has been first described in Japan where the prevalence is much higher than in the western world. The prognosis of apical HCM with regard to sudden cardiac death is believed to be better than that of common HCM. We present, however, two male caucasian patients with apical HCM and malignant arrhythmias. Both patients had marked apical hypertrophy on echocardiography, ‘giant’ negative T-waves on the ECG and spade-like configuration of the left ventricle on angiography. The first patient had been succesfully recussitated from cardiac arrest at the age of 52 years. The second patient had a syncope at the age of 42 years and had non-sustained ventricular tachycardia. In both cases, a cardioverter-defibrillator was implanted and treatment with verapamil was initiated. These observations suggest that the risk of sudden cardiac death might be increased not only in common HCM, but also in Japanese-type apical HCM.
Variant in Promoter Region of Platelet-Derived Growth Factor Receptor-α (PDGFRα) Gene Is Associated with the Severity and Allergic Status of Childhood Asthma
Authors: Wu Lawrence Shih-Hsin , Tan Choon-Yee , Wang Ling-Mei , Lin Cherry Guan-Ju , Wang Jiu-Yao
Published: June 2006

Background: Upregulation of the platelet-derived growth factor receptor-α (PDGFRα) in airway myofibroblast cells is one of the mechanisms of airway remodeling. The genetic association between PDGFRα promoter polymorphism and severity of childhood asthma was examined. Methods: Five single nucleotide polymorphisms (SNPs) at the promoter regions of the PDGFRα gene were genotyped in 277 unrelated allergic and nonallergic asthmatic children and 93 age-matched controls. Promoter haplotypes were constructed using SNP genotyping data. The serum level of PDGF-AA, the ligand for PDGFRα, was assayed by ELISA kits. Results: The genotype distribution of SNP rs1800810 (–1171G/C) in nonallergic asthma was significantly different from controls (p = 0.038), as well as its allele distribution (p = 0.028). Using haplotype analysis, the combination frequency of the low expression of H1 homozygous and heterozygous genotype (H1/H1 + H1/H2) was significantly higher in nonallergic asthma as compared to controls (OR = 1.94, CI = 1.11–3.39, p < 0.02). The frequency of H2/H2 homozygous was higher in persistent asthma than in intermittent asthma (p = 0.008, OR = 2.625). In addition, the PDGF-AA serum level in H2/H2 homozygous haplotype was significantly lower as compared to non-H2/H2 homozygous haplotype both in asthmatic (138.1 ± 62.9 vs. 249.7 ± 97.1 ng/ml, p < 0.05) and nonallergic asthmatic children (113.8 ± 38.0 vs. 256.6 ± 58.3 ng/ml, p < 0.05). Conclusions: The developmental deficiency due to the low expression of PDGFRα may be one of the susceptible factors for nonallergic asthmatic children. There was also an autocrine effect of lower PDGF-AA and higher PDGFRα expression that might lead to airway remodeling causing the severity of asthma.
Unsuspected Lupin Allergens Hidden in Food
Authors: Rojas-Hijazo B. , Garcés M.M. , Caballero M.L. , Alloza P. , Moneo I.
Published: June 2006

Background: Lupin is a herbaceous plant from the legume family whose seed allergens usually have cross-reaction with peanut. Lupin flour is used in human nutrition because of its high nutritional and functional qualities. Aims: The aim of this work was to detect non-specified lupin proteins contained in several manufactured foods. Methods: Serum from a patient suffering anaphylactic episodes after ingestion of a certain brand of cookies and with oral allergy syndrome after eating chicken bouillon was used as a tracer. Lupin seeds and commercial food extracts were analyzed by SDS-PAGE, immunoblotting and immunoblotting inhibition. Lupin extract allergenicity after thermal processing was also analyzed. Results: A lupin allergen with a molecular weight close to 14 kDa was detected in extracts from cookies, a chicken bouillon cube and a chicken dehydrated soup. Conclusions: The presence of unsuspected, hidden non-specified lupin sources in food labeling was demonstrated. According to the results of this study, it is important for food-allergic patients that food labels should declare all the components irrespective of their quantity.
Sensitization due to Gum Arabic (Acacia senegal): The Cause of Occupational Allergic Asthma or Crossreaction to Carbohydrates?
Authors: Sander Ingrid , Raulf-Heimsoth Monika , Wiemer Kai , Kespohl Sabine , Brüning Thomas , Merget Rolf
Published: June 2006

Background: A pharmaceutical industry worker was exposed to dust of gum arabic in the tablet coating plant and complained of work-related shortness of breath, chest tightness, runny nose, itching and redness of the eyes. This case was investigated for allergy to gum arabic and compared with a control group. The aim of the study was to identify the IgE-binding components responsible for the work-related symptoms. Methods: Skin prick tests (SPTs)and specific IgE (sIgE) measurements with environmental and occupational allergens, spirometry and a specific bronchial challenge with gum arabic were performed. One hundred and nineteen control subjects underwent SPT with gum arabic and 43 controls were tested for sIgE. Crossreactivity between gum arabic and horse radish peroxidase was investigated by IgE CAP inhibition. A combined procedure of immunoblotting and periodate treatment was applied to identify the epitope nature of gum arabic. Results: Allergy to gum arabic was shown by SPT, presence of sIgE and a positive bronchial challenge with gum arabic. Sensitization to gum arabic was demonstrated by SPT or sIgE in 7 and 5 controls, respectively. The results of inhibition with horse radish peroxidase, immunoblotting and periodate treatment suggest that gum arabic sIgE of the patient and 1 SPT-positive control subject were directed to the polypeptide chains of gum arabic. In contrast, gum arabic sIgE of the other controls reacted to carbohydrate components. Conclusions: Sensitization to gum arabic carbohydrate structures occurs casually in atopic patients with pollen sensitization without obvious exposure to gum arabic. This study suggests that allergy to gum arabic is mediated preferentially by IgE antibodies directed to polypeptide chains of gum arabic.
Autoimmunity: Basic Mechanisms and Implications in Endocrine Diseases
Authors: Ballotti S. , Chiarelli F. , de Martino M.
Published: June 2006

Autoimmunity implies disturbances at several levels of the immune control. Self-tolerance and discrimination between self and non-self synergize to avoid the development of autoimmunity. Negative selection in the thymus, the transcription factor AIRE, CD4+CD25+ regulatory T cells, and dendritic cells cooperate to produce and maintain tolerance. Cytokines modulate deriving immune processes and influence the local micro-environment. Multiple mechanisms are involved in tolerance breakdown: genetic factors (major histocompatibility complex haplotypes, polymorphisms in the cytotoxic T lymphocyte antigen gene and epigenetic alterations), environmental factors (mainly infections), impaired apoptosis, and the emergence of autoreactive naive lymphocytes. These events may be involved in the pathogenesis of endocrine diseases at several levels.
Autoimmunity: Basic Mechanisms and Implications in Endocrine Diseases
Authors: Ballotti S. , Chiarelli F. , de Martino M.
Published: June 2006

Regulation of the immune response to self-antigens is a complex process that involves maintaining self-tolerance while preserving the capacity to exert an effective immune response. The primary mechanism that leads to self-tolerance is central tolerance. However, potential pathogenic autoreactive lymphocytes are normally present in the periphery of all individuals. This suggests the existence of mechanisms of peripheral tolerance that prevent the initiation of autoimmune diseases by limiting the activation of autoreactive lymphocytes. If these mechanisms of peripheral tolerance are impaired, the autoreactive lymphocytes may be activated and autoimmune diseases can develop. Several processes are involved in the maintenance of peripheral tolerance: the active suppression mediated by regulatory T cell populations, the different maturation state of antigen-presenting cells presenting the autoantigen to autoreactive lymphocytes, inducing tolerance instead of cell activation, the characteristics of B cell populations. A deeper comprehension of these mechanisms may lead to important therapeutic applications, such as the development of cellular vaccines for organ-specific autoimmune diseases. In addition, autoimmunity does not always have pathological consequences, but may exert a protective function, as suggested by several observations on the beneficial role of autoreactive T cells in central nervous system injury.
An Unusual Patient with Hypercalciuria, Recurrent Nephrolithiasis, Hypomagnesemia and G227R Mutation of Paracellin-1
Authors: Kutluturk Faruk , Temel Berna , Uslu Bora , Aral Ferihan , Azezli Adil , Orhan Yusuf , Konrad Martin , Ozbey Nese
Published: June 2006

A 19-year-old female patient with hypercalciuria and recurrent nephrolithiasis/urinary tract infection unresponsive to thiazide type diuretics is presented. The patient first experienced nephrolithiasis at the age of 4 years. Afterwards, recurrent passages of stones and urinary tract infection occurred. On diagnostic evaluation at the age of 19 years, she also had hypocitraturia and hypomagnesemia. Her serum calcium concentrations were near the lower limit of normal (8.5–8.8 mg/dl; normal range: 8.5–10.5), her serum magnesium concentrations were 1.15–1.24 mg/dl (normal range: 1.4–2.5) and urinary calcium excretion was 900 mg/24 h. PTH concentrations were increased (110–156 pg/ml; normal range: 10–65). We tried to treat the patient with hydrochlorothiazide at a dose of 50 mg/day. During treatment with thiazide diuretics, PTH concentration remained high and the patient had recurrent urinary tract infections and passages of stones. Serum magnesium concentration did not normalize even under the parenteral magnesium infusion. Her mother had a history of nephrolithiasis 20 years ago. Severe hypomagnesemia in association with hypercalciuria/urinary stones is reported as a rare autosomal recessive disorder caused by impaired reabsorption of magnesium and calcium in the thick assending limp of Henle’s loop. Recent studies showed that mutations in the CLDN16 gene encoding paracellin-1 cause the disorder. In exon 4, a homozygous nucleotide exchange (G679C) was identified for the patient. This results in a point mutation at position Glycine227, which is replaced by an Arginine residue (G227R). The mother was heterozygous for this mutation. G227 is located in the fourth transmembrane domain and is highly conserved in the claudin gene family. This case indicates the pathogenetic role of paracellin-1 mutation in familial hypomagnesemia with hypercalciuria and nephrocalcinosis and further underlines the risk of stone formation in heterozygous mutation carriers.
Allergenic Extracts for Specific Immunotherapy: To Mix or Not to Mix?
Authors: Mari Adriano , Scala Enrico
Published: June 2006

Immunotherapy for allergic diseases give rise to questions about when a decision must be taken to define the number of extracts to be used in a single treatment. This represents a long-lasting matter of debate between American and European allergists, which seems to be without real solution. Through the use of extract-based versus molecule-based diagnostic approaches we suggest a possible solution to this controversial issue. We used four model patients previously tested with allergenic extracts and later on selected on the basis of a panel of available allergenic molecules. Their reactivity patterns in term of extracts and molecules were compared and the decision for allergenic extract immunotherapy was made choosing either the ‘classical’ approach or the molecular approach. From our study it seems that molecules could offer the solution to the ‘mixing’ issue of allergenic extracts. This innovative approach seems to provide a solution for both the American and the European approach.
Interleukin-10-Treated Dendritic Cells Do Not Inhibit Th2 Immune Responses in Ovalbumin/Alum-Sensitized Mice
Authors: Bellinghausen Iris , Sudowe Stephan , König Bettina , Reske-Kunz Angelika B. , Knop Jürgen , Saloga Joachim
Published: June 2006

Background: It is well known that the immunoregulatory cytokine interleukin (IL)-10 inhibits the accessory function of human dendritic cells (DC) in vitro. Recently, we have shown that these IL-10 DC inhibit the production of T helper cell 1 (Th1) and T helper cell 2 (Th2) cytokines by T cells from atopic individuals in vitro. The current study was set out to analyze whether IL-10 DC also exert inhibitory effects in vivo in a murine model of allergy to ovalbumin adsorbed to the adjuvant aluminium hydroxide (OVA/alum). Methods: OVA-pulsed or unpulsed bone marrow-derived DC, treated with IL-10 or left untreated during generation, were injected intravenously into BALB/c mice prior to and during OVA/alum sensitization, and sera and immune responses of mesenterial lymph node cells were analyzed. Additionally, bronchoalveolar lavage was performed after intranasal challenge with OVA. Results: Treatment of BALB/c mice with OVA-pulsed DC led to a significantly enhanced proliferation as well as Th2 (IL-4, IL-5), Th1 (interferon-γ) and IL-10 cytokine production after restimulation of lymph node cells with OVA in vitro compared with OVA immunization alone. In contrast, using OVA-pulsed IL-10 DC for transfer, proliferation and cytokine production by lymph node cells were not enhanced. OVA-specific immunoglobulin G1 (IgG1) and IgG2a production were significantly increased after transfer of OVA-pulsed DC and OVA-pulsed IL-10 DC, respectively, whereas anti-OVA IgE production and airway eosinophilia remained unchanged. Conclusions: Our data indicate that IL-10 treatment of DC decreases the Th1 and Th2 stimulatory capacity of DC but does not actually inhibit systemic (IgE) and local (airway inflammation) allergen-specific immune responses in a murine model of allergy.
Regulation of Anaphylactic IgG1 Antibody Production by IL-4 and IL-10
Authors: Silva Aldacilene S. , Cavalcante Leuridan T. , Faquim-Mauro Eliana L. , Macedo Mahasti S.
Published: June 2006

Background: Different cytokines have been implicated in the regulation of isotype expression in primary and secondary antibody responses. The aim of this study was to assess the regulation of anaphylactic IgG1 and IgE antibodies by IL-4, IL-10 and IFN-γ at different time points of the antibody response against PI, an immunosuppressive fraction of Ascaris suum extract, and ovalbumin (OVA). Methods: Wild-type or cytokine-deficient C57BL/6 or BALB/c mice were immunized with PI or OVA in different adjuvants. Twenty days later, they were boosted with the respective antigen. IgG1 and IgE antibodies produced during primary and secondary responses were measured by passive cutaneous anaphylaxis. Results: PI induced low levels of anaphylactic IgG1 antibodies in the primary response and moderate levels after the antigenic booster, which were IL-4-dependent. In the absence of IL-10 and IFN-γ, PI-specific IgG1 and IgE enhanced significantly, indicating that these cytokines downregulated antibody production in primary and secondary responses. The IgG1 response to OVA in aluminium hydroxide or complete Freund’s adjuvant was IL-4-dependent in the beginning of the primary response. Later on, it became only partially regulated by IL-4 in C57BL/6 mice and IL-4-independent in Th2-prone BALB/c mice. In contrast, IgE antibodies depended exclusively upon IL-4 during the entire time course. Conclusions:These results indicate, first, that the IL-4 dependency of anaphylactic IgG1 antibody production, mainly in the secondary response, varies among mouse strains, and, second, that the nature of the antigen determines whether IL-10 and IFN-γ limit the potential to make large amounts of anaphylactic IgG1 and IgE.
Expression of IL-1β, IL-1 Receptor Type I and IL-1 Receptor Antagonist in Human Aortic Smooth Muscle Cells: Effects of all-trans-Retinoic Acid
Authors: Wågsäter Dick , Jatta Ken , Ocaya Pauline , Dimberg Jan , Sirsjö Allan
Published: June 2006

The proinflammatory cytokine interleukin (IL)-1β and the IL-1 receptor antagonist are expressed by atherosclerotic plaques and may be linked to the development of atherosclerosis. Existing evidence shows that retinoids and their receptors are involved in inflammatory response and that they are found in atherosclerotic plaques. In all-trans-retinoic acid (atRA)-treated human aortic smooth muscle cells (AOSMC), significant increases in IL-1β levels were observed, compared with untreated cells. Examination of IL-1 receptor antagonist and IL-1 receptor type I levels did not show any difference between atRA-treated and -untreated AOSMC. The results show that atRA-treated AOSMC express both the precursor (33 kDa) and the active form (17 kDa) of the IL-1β protein. atRA-treated carotid lesions showed significantly elevated IL-1β mRNA levels (2.9 ± 2.33) compared with untreated lesions (2.0 ± 1.77; p < 0.05). These results support the role of atRA as a regulator of inflammation such as in atherosclerosis.
Prediction Models for Annual U.S. Hurricane Counts
Authors: Elsner James B. , Jagger Thomas H.
Published: June 2006

The authors build on their efforts to understand and predict coastal hurricane activity by developing statistical seasonal forecast models that can be used operationally. The modeling strategy uses May–June averaged values representing the North Atlantic Oscillation (NAO), the Southern Oscillation index (SOI), and the Atlantic multidecadal oscillation to predict the probabilities of observing U.S. hurricanes in the months ahead (July–November). The models are developed using a Bayesian approach and make use of data that extend back to 1851 with the earlier hurricane counts (prior to 1899) treated as less certain relative to the later counts. Out-of-sample hindcast skill is assessed using the mean-squared prediction error within a hold-one-out cross-validation exercise. Skill levels are compared to climatology. Predictions show skill above climatology, especially using the NAO + SOI and the NAO-only models. When the springtime NAO values are below normal, there is a heightened risk of U.S. hurricane activity relative to climatology. The preliminary NAO value for 2005 is −0.565 standard deviations so the NAO-only model predicts a 13% increase over climatology of observing three or more U.S. hurricanes.
Simulation of the North American Monsoon by the NCAR CCM3 and Its Sensitivity to Convection Parameterization
Authors: Collier J. Craig , Zhang Guang J.
Published: June 2006

Two 9-yr runs of the NCAR Community Climate Model version 3 (CCM3) are compared in their simulations of the North American summer monsoon. In a control simulation, the Zhang–McFarlane deep convection scheme is used. For an experimental simulation, the following modifications to the scheme are implemented. The closure is based on the large-scale forcing of virtual temperature, and a relative humidity threshold on convective parcels lifted from the boundary layer is applied. The sensitivity to these modifications for simulating the North American monsoon is investigated. Model validation relies on hourly precipitation rates from surface gauges over the United States, hourly precipitation rates derived from the combination of microwave and radar measurements from NASA’s Tropical Rainfall Measuring Mission (TRMM) satellite over Mexico, and CAPE values as calculated from temperature, specific humidity, and pressure fields from the NCEP–NCAR reanalysis. Results show that the experimental run improves the timing of the monsoon onset and peak in the regions of core monsoon influence considered here, though it increases a negative bias in the peak monsoon intensity in one region of northern Mexico. Sensitivity of the diurnal cycle of precipitation to modifications in the convective scheme is highly geographically dependent. Using a combination of gauge-based rainfall rates and reanalysis-based CAPE, it is found that improvements in the simulated diurnal cycle are confined to a convective regime in which the diurnal evolution of precipitation is observed to lag that of CAPE. For another regime, in which CAPE is observed to be approximately in phase with precipitation, model phase biases increase nearly everywhere. Some of the increased phase biases in the latter regime are primarily because of application of the relative humidity threshold.
Greenland Ice Sheet Surface Mass Balance Variability (1988–2004) from Calibrated Polar MM5 Output*
Authors: Box Jason E. , Bromwich David H. , Veenhuis Bruce A. , Bai Le-Sheng , Stroeve Julienne C. , Rogers Jeffrey C. , Steffen Konrad , Haran T. , Wang Sheng-Hung
Published: June 2006

Regional climate model runs using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesocale Model modified for use in polar regions (Polar MM5), calibrated by independent in situ observations, demonstrate coherent regional patterns of Greenland ice sheet surface mass balance (SMB) change over a 17-yr period characterized by warming (1988–2004). Both accumulation and melt rates increased, partly counteracting each other for an overall negligible SMB trend. However, a 30% increase in meltwater runoff over this period suggests that the overall ice sheet mass balance has been increasingly negative, given observed meltwater-induced flow acceleration. SMB temporal variability of the whole ice sheet is best represented by ablation zone variability, suggesting that increased melting dominates over increased accumulation in a warming scenario. The melt season grew in duration over nearly the entire ablation zone by up to 40 days, 10 days on average. Accumulation area ratio decreased by 3%. Albedo reductions are apparent in five years of the Moderate Resolution Imaging Spectroradiometer (MODIS) derived data (2000–04). The Advanced Very High Resolution Radiometer (AVHRR)-derived albedo changes (1988–99) were less consistent spatially. A conservative assumption as to glacier discharge and basal melting suggests an ice sheet mass loss over this period greater than 100 km3 yr−1, framing the Greenland ice sheet as the largest single glacial contributor to recent global sea level rise. Surface mass balance uncertainty, quantified from residual random error between model and independent observations, suggests two things: 1) changes smaller than approximately 200 km3 yr−1 would not satisfy conservative statistical significance thresholds (i.e., two standard deviations) and 2) although natural variability and model uncertainty were separated in this analysis, the magnitude of each were roughly equivalent. Therefore, improvements in model accuracy and analysis of longer periods (assuming larger changes) are both needed for definitive mass balance change assessments.
Contributions of External Forcings to Southern Annular Mode Trends
Authors: Arblaster Julie M. , Meehl Gerald A.
Published: June 2006

An observed trend in the Southern Hemisphere annular mode (SAM) during recent decades has involved an intensification of the polar vortex. The source of this trend is a matter of scientific debate with stratospheric ozone losses, greenhouse gas increases, and natural variability all being possible contenders. Because it is difficult to separate the contribution of various external forcings to the observed trend, a state-of-the-art global coupled model is utilized here. Ensembles of twentieth-century simulations forced with the observed time series of greenhouse gases, tropospheric and stratospheric ozone, sulfate aerosols, volcanic aerosols, solar variability, and various combinations of these are used to examine the annular mode trends in comparison to observations, in an attempt to isolate the response of the climate system to each individual forcing. It is found that ozone changes are the biggest contributor to the observed summertime intensification of the southern polar vortex in the second half of the twentieth century, with increases of greenhouse gases also being a necessary factor in the reproduction of the observed trends at the surface. Although stratospheric ozone losses are expected to stabilize and eventually recover to preindustrial levels over the course of the twenty-first century, these results show that increasing greenhouse gases will continue to intensify the polar vortex throughout the twenty-first century, but that radiative forcing will cause widespread temperature increases over the entire Southern Hemisphere.
Daily Mean Sea Level Pressure Reconstructions for the European–North Atlantic Region for the Period 1850–2003
Authors: Ansell T. J. , Jones P. D. , Allan R. J. , Lister D. , Parker D. E. , Brunet M. , Moberg A. , Jacobeit J. , Brohan P. , Rayner N. A. , Aguilar E. , Alexandersson H. , Barriendos M. , Brandsma T. , Cox N. J. , Della-Marta P. M. , Drebs A. , Founda D. , Gerstengarbe F. , Hickey K. , Jónsson T. , Luterbacher J. , Nordli Ø. , Oesterle H. , Petrakis M. , Philipp A. , Rodwell M. J. , Saladie O. , Sigro J. , Slonosky V. , Srnec L. , Swail V. , García-Suárez A. M. , Tuomenvirta H. , Wang X. , Wanner H. , Werner P. , Wheeler D. , Xoplaki E.
Published: June 2006

The development of a daily historical European–North Atlantic mean sea level pressure dataset (EMSLP) for 1850–2003 on a 5° latitude by longitude grid is described. This product was produced using 86 continental and island stations distributed over the region 25°–70°N, 70°W–50°E blended with marine data from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS). The EMSLP fields for 1850–80 are based purely on the land station data and ship observations. From 1881, the blended land and marine fields are combined with already available daily Northern Hemisphere fields. Complete coverage is obtained by employing reduced space optimal interpolation. Squared correlations (r 2) indicate that EMSLP generally captures 80%–90% of daily variability represented in an existing historical mean sea level pressure product and over 90% in modern 40-yr European Centre for Medium-Range Weather Forecasts Re-Analyses (ERA-40) over most of the region. A lack of sufficient observations over Greenland and the Middle East, however, has resulted in poorer reconstructions there. Error estimates, produced as part of the reconstruction technique, flag these as regions of low confidence. It is shown that the EMSLP daily fields and associated error estimates provide a unique opportunity to examine the circulation patterns associated with extreme events across the European–North Atlantic region, such as the 2003 heat wave, in the context of historical events.
Changes in the 300-mb North Circumpolar Vortex, 1963–2001
Authors: Angell James K.
Published: June 2006

The mean monthly polar stereographic map analyses of the Free University of Berlin terminated at the end of 2001. This paper summarizes the changes in size of the 300-mb north circumpolar vortex, and quadrants, for the full period of record, 1963–2001, where the size has been defined by planimetering the area poleward of contours in the jet stream core. A contracted vortex has tended to be a deep vortex in winter but a shallow vortex in summer. During 1963–2001 there was a statistically significant decrease in vortex size of 1.5% per decade, the decrease in size of Western Hemisphere quadrants being twice that of Eastern Hemisphere quadrants. A significant increase in Arctic Oscillation (AO) index accompanies the significant decrease in vortex size, but since the vortex contracts appreciably in all four seasons, whereas the positive trend in the AO index is mainly in winter, the vortex cannot serve as a proxy for the AO index. The evidence for vortex contraction at the time of the 1976–77 regime shift is not conclusive, but there is good evidence for a 6% increase in vortex size due to the 1991 Pinatubo eruption. There is little change in vortex size following the 1982 El Chichon eruption, however. Because on average there is a significant 4% contraction of the vortex following an El Niño, it is proposed that the vortex expansion to be expected following the 1982 El Chichon eruption has been contravened by the contraction following the strong 1982–83 El Niño. There is little relation between vortex size and phase of the quasi-biennial oscillation (QBO), and the evidence for a contracted vortex near 11-yr sunspot maxima is tenuous because the vortex record extends through only three full sunspot cycles. There is a highly significant tendency for opposite vortex quadrants 0°–90°E and 90°W–180° to vary in size together, indicating either a pulsating polar vortex or the propagation of planetary wavenumber 2.
The Termination of the 1997–98 El Niño. Part II: Mechanisms of Atmospheric Change
Authors: Vecchi Gabriel A.
Published: June 2006

The mechanisms that drove zonal wind stress (τx) changes in the near-equatorial Pacific at the end of the extreme 1997–98 El Niño event are explored using a global atmospheric general circulation model. The analysis focuses on three features of the τx evolution between October 1997 and May 1998 that were fundamental in driving the oceanic changes at the end of this El Niño event: (i) the southward shift of near-date-line surface zonal wind stress (τx) anomalies beginning November 1997, (ii) the disappearance of the easterly τx from the eastern equatorial Pacific (EEqP) in February 1998, and (iii) the reappearance of easterly τx in the EEqP in May 1998. It is shown that these wind changes represent the deterministic response of the atmosphere to the observed sea surface temperature (SST) field, resulting from changes in the meridional structure of atmospheric convective anomalies in response to the seasonally phase-locked meridional movement of the warmest SST.

The southward shift of the near-date-line τx anomalies at the end of this El Niño event was controlled by the seasonal movement of the warmest SST south of the equator, which—both directly and through its influence on the atmospheric response to changes in SST anomaly—brought the convective anomalies from being centered about the equator to being centered south of the equator. The disappearance (reappearance) of easterly EEqP τx has only been evident in extreme El Niño events and has been associated with the development (northward retreat) of an equatorial intertropical convergence zone (ITCZ). The disappearance/return of EEqP easterly τx arises in the AGCM as the deterministic response to changes in the SST field, tied principally to the changes in climatological SST (given time-invariant extreme El Niño SSTA) and not to changes in the underlying SSTA field. The disappearance (return) of EEqP easterly τx in late boreal winter (late boreal spring) is a characteristic atmospheric response to idealized extreme El Niño SST anomalies; this suggests that the distinctive termination of the 1997–98 El Niño event is that to be expected for extreme El Niño events.
Improvement of Modeled Soil Wetness Conditions and Turbulent Fluxes through the Assimilation of Observed Discharge
Authors: Pauwels Valentijn R. N. , De Lannoy Gabriëlle J. M.
Published: June 2006

The objective of this paper is to improve the performance of a hydrologic model through the assimilation of observed discharge. Since an observation of discharge at a certain time is always influenced by the catchment wetness conditions and meteorology in the past, the assimilation method will have to modify both the past and present soil wetness conditions. For this purpose, a bias-corrected retrospective ensemble Kalman filter has been used as the assimilation algorithm. The assimilation methodology takes into account bias in the forecast state variables for the calculation of the optimal estimates. A set of twin experiments has been developed, in which it is attempted to correct the model results obtained with erroneous initial conditions and strongly over- and underestimated precipitation data. The results suggest that the assimilation of observed discharge can correct for erroneous model initial conditions. When the precipitation used to force the model is underestimated, the assimilation of observed discharge can reduce the bias in the modeled turbulent fluxes by approximately 50%. This is due to a correction of the modeled soil moisture. In the case of an overestimation of the precipitation, an improvement in the modeled wetness conditions is also obtained after data assimilation, but this does not lead to a significant improvement in the modeled energy balance. The results in this paper indicate that there is potential to improve the estimation of hydrologic states and fluxes through the assimilation of observed discharge data.
Mixtures of Gaussians for Uncertainty Description in Bivariate Latent Heat Flux Proxies
Authors: Wójcik R. , Troch Peter A. , Stricker H. , Torfs P. , Wood E. , Su H. , Su Z.
Published: June 2006

This paper proposes a new probabilistic approach for describing uncertainty in the ensembles of latent heat flux proxies. The proxies are obtained from hourly Bowen ratio and satellite-derived measurements, respectively, at several locations in the southern Great Plains region in the United States. The novelty of the presented approach is that the proxies are not considered separately, but as bivariate samples from an underlying probability density function. To describe the latter, the use of Gaussian mixture density models—a class of nonparametric, data-adaptive probability density functions—is proposed. In this way any subjective assumptions (e.g., Gaussianity) on the form of bivariate latent heat flux ensembles are avoided. This makes the estimated mixtures potentially useful in nonlinear interpolation and nonlinear probabilistic data assimilation of noisy latent heat flux measurements. The results in this study show that both of these applications are feasible through regionalization of estimated mixture densities. The regionalization scheme investigated here utilizes land cover and vegetation fraction as discriminatory variables.
Computational Issues for Large-Scale Land Surface Data Assimilation Problems
Authors: McLaughlin Dennis , Zhou Yuhua , Entekhabi Dara , Chatdarong Virat
Published: June 2006

Land surface data assimilation problems are often limited by the high dimensionality of states created by spatial discretization over large high-resolution computational grids. Yet field observations and simulation both confirm that soil moisture can have pronounced spatial structure, especially after extensive rainfall. This suggests that the high dimensionality of the problem could be reduced during wet periods if spatial patterns could be more efficiently represented. After prolonged drydown, when spatial structure is determined primarily by small-scale soil and vegetation variability rather than rainfall, the original high-dimensional problem can be effectively replaced by many independent low-dimensional problems that can be solved in parallel with relatively little effort. In reality, conditions are continually varying between these two extremes. This is confirmed by a singular value decomposition of the replicate matrix (covariance square root) produced in an ensemble forecasting simulation experiment. The singular value spectrum drops off quickly after rainfall events, when a few leading modes dominate the spatial structure of soil moisture. The spectrum is much flatter after a prolonged drydown period, when spatial structure is less significant. Deterministic reduced-rank Kalman filters can achieve significant computational efficiency by focusing on the leading modes of a system with large-scale spatial structure. But these methods are not well suited for land surface problems with complex uncertain inputs and rapidly changing spectra. Local ensemble Kalman filters are suitable for such problems during dry periods but give less accurate results after rainfall. The most promising option for achieving computational efficiency and accuracy is to develop generalized localization methods that dynamically aggregate states, reflecting structural changes in the ensemble.
Data Assimilation for Estimating the Terrestrial Water Budget Using a Constrained Ensemble Kalman Filter
Authors: Pan Ming , Wood Eric F.
Published: June 2006

A procedure is developed to incorporate equality constraints in Kalman filters, including the ensemble Kalman filter (EnKF), and is referred to as the constrained ensemble Kalman filter (CEnKF). The constraint is carried out as a two-step filtering approach, with the first step being the standard (ensemble) Kalman filter. The second step is the constraint step carried out by another Kalman filter that optimally redistributes any imbalance from the first step. The CEnKF is implemented over a 75 000 km2 domain in the southern Great Plains region of the United States, using the terrestrial water balance as the constraint. The observations, consisting of gridded fields of the upper two soil moisture layers from the Oklahoma Mesonet system, Atmospheric Radiation Measurement Program Cloud and Radiation Testbed (ARM-CART) energy balance Bowen ratio (EBBR) latent heat estimates, and U.S. Geological Survey (USGS) streamflow from unregulated basins, are assimilated into the Variable Infiltration Capacity (VIC) land surface model. The water balance was applied at the domain scale, and estimates of the water balance components for the domain are updated from the data assimilation step so as to assure closure.
Effects of the Near-Surface Soil Moisture Profile on the Assimilation of L-band Microwave Brightness Temperature
Authors: Wilker Henning , Drusch Matthias , Seuffert Gisela , Simmer Clemens
Published: June 2006

The impact of model and observation errors in the European Land Data Assimilation System (ELDAS) data assimilation system on the analyzed surface variables has been studied using the Southern Great Plains Hydrology Experiment (SGP) 1997 and 1999 datasets. The model error for soil moisture was derived from an error propagation experiment based on perturbed rainfall forcing data. It was found that the errors for the top three model layers are 0.010, 0.010, and 0.0015 m3 m−3, respectively. Data assimilation experiments based on screen-level variables (2-m temperature and humidity) and L-band brightness temperature observations from SGP97 with this error distribution result in improved soil moisture forecasts when compared to model runs with a vertically constant model error of 0.005 m3 m−3. In the second part of this study, the effect of the vertical soil moisture distribution—which can hardly be resolved by large-scale hydrological models—in the assimilation system has been quantified using SGP99 data. The vertical profile has a significant impact on the modeled brightness temperatures. Based on the time elapsed between a rainfall event and the observation, a correction scheme has been developed that can be applied in observation space. The assimilation of brightness temperatures led to more accurate predictions of soil moisture and surface fluxes when the correction scheme was used.
Impact of Watershed Geomorphic Characteristics on the Energy and Water Budgets
Authors: Bertoldi Giacomo , Rigon Riccardo , Over Thomas M.
Published: June 2006

The GEOtop model makes it possible to analyze the short- and long-term effects of geomorphic variation on the partitioning of the lateral surface and subsurface water and surface energy fluxes. The topography of the Little Washita basin (Oklahoma) and of the Serraia basin (Trentino, Italy) have been used as base topographies from which virtual topographies with altered slopes and elevations have been created with corresponding modifications of the soil thickness and the extension of the channel network, according to applicable geomorphological theories, in order to quantify the contribution of these topographic features to the spatial and temporal variability of energy and water fluxes. Simulation results show that both a more extended channel network and more accentuated slopes cause an increase in the discharge balanced by a diminution of the evapotranspiration. The diminution of the latent heat flux is balanced by the increase in the sensible heat flux. Net radiation shows a minor sensitivity to topography. Evaporative fraction, on the contrary, is shown to be strongly dependent on geomorphic characteristics. The results confirm the importance of including an adequate treatment of topography in large-scale land surface models.
Simulation of Water Sources and Precipitation Recycling for the MacKenzie, Mississippi, and Amazon River Basins
Authors: Bosilovich Michael G. , Chern Jiun-Dar
Published: June 2006

An atmospheric general circulation model simulation for 1948–97 of the water budgets for the MacKenzie, Mississippi, and Amazon River basins is presented. In addition to the water budget, passive tracers are included to identify the geographic sources of water for the basins, and the analysis focuses on the mechanisms contributing to precipitation recycling in each basin. While each basin’s precipitation recycling has a strong dependency on evaporation during the mean annual cycle, the interannual variability of the recycling shows important relationships with the atmospheric circulation. The MacKenzie River basin recycling has only a weak interannual correspondence with evaporation, where the variations in zonal moisture transport from the Pacific Ocean can affect the basin water cycle. On the other hand, the Mississippi River basin precipitation and recycling have strong interannual correlation on evaporation. The evaporation is related to the moist and shallow planetary boundary layer that provides moisture for convection at the cloud base. At global scales, high precipitation recycling is also found to be partly correlated to warm SSTs in the tropical Pacific Ocean. The Amazon River basin evaporation exhibits small interannual variations, so the interannual variations of precipitation recycling are related to atmospheric moisture transport from the tropical South Atlantic Ocean. Increasing SSTs over the 50-yr period are causing increased easterly transport across the basin. As moisture transport increases, the Amazon precipitation recycling decreases (without real-time varying vegetation changes). In addition, precipitation recycling from a bulk diagnostic method is compared to the passive tracer method used in the analysis. While the mean values of the different recycling methods are different, the interannual variations are comparable between each method. The methods also exhibit similar relationships to the terms of the basin-scale water budgets.