bluuebunny/crossref_metadata_2025 huggingface dataset:
Serum Chitotriosidase Activity, a Marker of Activated Macrophages, Predicts New Cardiovascular Events Independently of C-Reactive Protein
Authors: Artieda Marta , Cenarro Ana , Gañán Alberto , Lukic Antonela , Moreno Eva , Puzo José , Pocoví Miguel , Civeira Fernando
Published: February 2007

Background: C-reactive protein (CRP) is a well-established inflammation marker associated with cardiovascular risk. However, its relationship with chitotriosidase activity, a novel marker of activated macrophages highly expressed in human atherosclerotic plaques, is unknown. Therefore, we sought to determine if serum chitotriosidase activity predicts the risk of new coronary events, and to analyze its relationship with CRP. Methods: Chitotriosidase activity and genotype, and high-sensitivity CRP were measured at baseline in 133 middle-aged men with stable coronary heart disease, who were followed for the occurrence of cardiovascular morbidity and mortality for a mean of 4 years. We studied the value of these proteins in predicting the risk of new cardiovascular events. Results: Serum chitotriosidase activity was higher in the group of subjects with a prespecified major event (nonfatal myocardial infarction, nonfatal ischemic stroke, coronary revascularization procedures and death from cardiovascular causes) than in the group of subjects without event, 116 ± 30.9 nmol/ml·h versus 74.2 ± 5.69 nmol/ml·h, respectively (p = 0.042). The baseline values of chitotriosidase activity and CRP did not correlate (R = 0.104, p = 0.266), but both parameters were related to a reduction of event-free survival in the Cox regression analysis, with relative risks of 2.61 (p = 0.060) and 2.56 (p = 0.019), respectively. Chitotriosidase activity seems to be a better marker for new events occurring after 2 years of follow-up than in the first 2 years. Both markers had similar predictive values, and their sensitivity (64%) and negative predictive value (84%) were improved when combined. Conclusions: Our results suggest that serum chitotriosidase activity predicts the risk of new cardiovascular events in the following 4 years. This new cardiovascular risk marker is independent of CRP and, when combined, the prediction of the risk of new cardiovascular events and the identification of a lower risk group seem to improve.
Exercise-Induced Increase in Lipid Peroxidation in Patients with Chronic Heart Failure: Relation to Exercise Intolerance
Authors: Sayar Nurten , Terzi Sait , Yilmaz Hale Yaka , Tangurek Burak , Bilsel Tuba , Cakmak Nazmiye , Orhan Lutfullah , Emre Ayse , Ciloglu Figen , Peker Ismail , Yesilcimen Kemal
Published: February 2007

Background: Little is known about the relationship between exercise intolerance and lipid peroxidation in chronic heart failure (CHF) patients. This study was designed to investigate the relationship between exercise-induced plasma malondialdehyde (MDA) changes in CHF patients and to determine whether there is any association between plasma MDA levels and exercise capacity assessed by cardiopulmonary exercise testing. Methods: Cardiopulmonary exercise testing was applied to 31 CHF patients (16 ischemic, 15 idiopathic) and controls. Rest and peak exercise blood samples were analyzed for MDA. Results: Patients with CHF had elevation of plasma MDA levels during exercise compared with controls (p < 0.001 vs. p = 0.588). MDA change remained significant both in ischemic and idiopathic cardiomyopathy groups (p < 0.05 and p < 0.01, respectively). ΔMDA (peak exercise MDA – rest MDA) showed significant inverse correlation with peak oxygen consumption in patients with CHF. Conclusion: Lipid peroxidation is increased in patients with CHF during exercise regardless of etiology, and this increase is inversely related to oxygen consumption.
A Suggestive Association of Fuchs Heterochromic Cyclitis with Cytotoxic T Cell Antigen 4 Gene Polymorphism
Authors: Spriewald Bernd M. , Lefter Carolina , Huber Ilka , Lauer Birgit , Wenkel Hartmut
Published: February 2007

Background: Fuchs heterochromic cyclitis (FHC) is a chronic inflammatory eye disease, usually presenting as unilateral anterior uveitis. Up to date no disease susceptibility genes have been described for FHC. Methods: The allele frequency of HLA DRB1 and DQB1, polymorphisms of the tumour necrosis factor (TNF) α promoter region (–376, –308, –238), the promoter (–318), first exon (+49) and (AT)n repeat polymorphism of the cytotoxic T cell antigen 4 (CTLA4) gene were analysed in 44 FHC patients and 139 healthy controls. Results: The CTLA4 –318 C/T genotype was increased in FHC patients [odds ratio (OR) 3.0, 95% confidence interval (CI) 1.4–6.5], as well as long CTLA4 (AT)n microsatellite alleles with more than 16 AT repeats (OR 2.6, 95% CI 1.3–5.3). A trend towards the –308 G/A TNF-α genotype was found in the patient cohort, whereas no difference in HLA class II allele distribution was observed. Conclusion:CTLA4 but not TNF-α or HLA class II DRB1 and DQB1 may represent a candidate gene for disease susceptibility in FHC.
Quality of Life in Women with Urinary Stress Incontinence and Evaluation of Tension-Free Vaginal Tape Treatment
Authors: Pozowski Janusz , Sobański Andrzej , Dudkiewicz Dariusz , Michalski Bogdan , Ulman-Włodarz Izabela
Published: February 2007

Objectives: Assessment of quality of life in women stress urinary incontinence (USI) and evaluation of tension-free vaginal tape (TVT) treatment. Material and Methods: The research included a group of 112 women aged 33–78 years. Before as well as 3 and 6 months after the TVT operation, patients were asked to fill in quality of life questionnaires. Results: After 3 months 87.25% of the women reported full regression of USI symptoms, 7.8% an insignificant improvement, and 4.9% did not observe any change. After 6 months 85.71% reported full regression, 9.18% an insignificant improvement, and 5.1% did not observe any change. USI is responsible for a decrease in physical activity. The most uncomfortable symptom is involuntary urine leakage occuring mainly during an effort or sleep. After the TVT procedure, the majority of women confirmed a significant improvement in quality of life. Conclusions: The TVT procedure is an effective method of treating USI in women: it significantly improves quality of life, with a recovery rate of 85–87%, and a low rate of complications.
Feasible Use of Estimated Height for Predicting Outcome by the Geriatric Nutritional Risk Index in Long-Term Care Resident Elderly
Authors: Cereda Emanuele , Limonta Daniela , Pusani Chiara , Vanotti Alfredo
Published: February 2007

Background: The Geriatric Nutritional Risk Index (GNRI) is a new index recently introduced for predicting risk of nutritional-related complications in elderly patients. It combines albumin with information about body weight: GNRI = (1.489 × albumin, g/l) + (41.7 × present/ideal body weight), with ideal weight calculated according to the Lorentz formula. Because standing height (SH) is frequently difficult to obtain in older people, in Lorentz equations this parameter has been replaced by estimated height (EH) from knee height. Though, if EH is well accepted as a valid surrogate for SH, the same might not be expected for its use in ideal body weight calculation, with possible consequences in grading nutritional risk correctly. Objective: The aim of this study was to investigate whether the use of SH rather than EH for the calculation of ideal body weight predicts similar outcomes by GNRI. Methods: Body weight, SH and EH were obtained in 231 long-term care resident elderly (88 males and 143 females, mean age ± SD 80.0 ± 8.4, range 65–97 years). Blood samples were assessed for albumin concentration. Ideal body weight was derived from the Lorentz formula using both SH and EH. According to both ideal weight estimates, nutritional risk was defined by the GNRI score. Results: The Pearson correlation coefficients were high for both EH (with SH; r = 0.90) and estimates of ideal body weight (r = 0.90) and all were highly significant (p < 0.0001). A statistically significant difference was found between SH and EH (p = 0.0265). Similar and expectable differences in significance have also been observed between ideal body weights (p = 0.0271). However, an accordance of 95.2% has been detected (Kendall’s τ test: τ = 0.85, p < 0.0001) in grading nutritional risk by GNRI. Conclusion: The use of EH for ideal body weight calculation and nutritional risk assessment by GNRI is feasible. Thus, GNRI seems to have been designed in the best way and its use is really attractive, particularly when considering the low-grade participation demanded of the patient in the assessment. This simple and valid assessment tool should be taken into greater consideration.
Relation between Bone Mass and Catecholamines in the General Population
Authors: Martín-Escudero Juan Carlos , Pérez-Castrillón José Luis , Blanco Fernando Simal , Arzua-Mouronte Delfín , Bellido Casado Jesús , Martín Javier Mena
Published: February 2007

Background: The relation between the sympathetic nervous system and bone metabolism has been known for some time, although diverse experimental studies do not show uniformity in their evaluation of the different data. The aim of this paper is to determine the relation between urinary catecholamines, as an expression of sympathetic activity, and bone mass among the general population. Methods: A study was made of 274 individuals (124 males and 150 females), who formed part of the Hortega cohort. All underwent measurement of fractionated catecholamines in urine (dopamine, noradrenaline and adrenaline) and calcaneal density, using a Pixi-Lunar (Lunar Corp., Madison, Wisc., USA). Results: The linear correlation study revealed a statistically significant association of dopamine with bone mass (r = 0. 229, p = 0.0001), which was not observed with the other catecholamines. The effect was shown in men (r = 0.184, p = 0.04) and women (r = 0.251, p = 0.002). When a multiple correlation analysis was performed, the effect of the dopamine (p = 0.038) persisted. Conclusions: Our study shows that dopamine is an independent, positive variable for bone mass in men and women in the general population, and for the latter, it is independent of their hormonal state.
Interaction between Poly(ADP-Ribose) Polymerase 1 and Interleukin 1A Genes Is Associated with Alzheimer’s Disease Risk
Authors: Infante Jon , Llorca Javier , Mateo Ignacio , Rodríguez-Rodríguez Eloy , Sánchez-Quintana Coro , Sánchez-Juan Pascual , Fernández-Viadero Carlos , Peña Nicolás , Berciano José , Combarros Onofre
Published: February 2007

Excessive release of proinflammatory cytokines by activated microglia surrounding senile plaques might contribute to the neurodegeneration associated with Alzheimer’s disease (AD). Poly(ADP-ribose) polymerase 1 (PARP-1) is a nuclear protein recently implicated in the initial inflammatory response by modulating expression of inflammation-related genes, like interleukin 1 (IL-1). As PARP-1 overactivity has been shown in the AD brain, we tested the hypothesis that the PARP-1 –410 and –1672 polymorphisms would predispose people to AD due to overexpression of the PARP-1 gene, independently or in concert with the proinflammatory IL-1A –889 polymorphism. So, we performed a case-control study in 263 Spanish AD patients and 293 healthy controls. PARP-1 –410 and PARP-1 –1672 haplotypes were associated with an increased risk for AD (global haplotype association p value = 0.019), and, in addition, PARP-1 haplotypes increased the risk of AD by interaction with the IL-1A –889 allele 2.
Effects of Pioglitazone in Patients With Type 2 Diabetes With or Without Previous Stroke
Authors: Wilcox Robert , Bousser Marie-Germaine , Betteridge D. John , Schernthaner Guntram , Pirags Valdis , Kupfer Stuart , Dormandy John
Published: February 2007

Background and Purpose—

Diabetes is an important risk factor for stroke. We conducted analyses in patients who had entered the PROspective pioglitAzone Clinical Trial In macroVascular Events (PROactive) with a history of stroke or without stroke.

Methods—

The prospective, double-blind PROactive (mean duration, 34.5 months) randomized 5238 patients with type 2 diabetes and a history of macrovascular disease to pioglitazone (titrated to 45 mg) or placebo, in addition to current diabetes and cardiovascular medications. Cardiovascular end-point events were independently adjudicated. This analysis evaluated the risk of stroke and other cardiovascular outcomes in patients with (n=984) and without (n=4254) prior stroke.

Results—

In patients with previous stroke (n=486 in the pioglitazone group and n=498 in the placebo group), there was a trend of benefit with pioglitazone for the primary end point of all-cause death, nonfatal myocardial infarction, acute coronary syndrome, and cardiac intervention (including coronary artery bypass graft or percutaneous coronary intervention), stroke, major leg amputation, or bypass surgery or leg revascularization (hazard ratio[HR]=0.78, event rate=20.2% pioglitazone vs 25.3% placebo; 95% CI=0.60–1.02;
P
=0.0670) and for the main secondary end point of all-cause death, nonfatal myocardial infarction, or nonfatal stroke (HR=0.78, event rate=15.6% pioglitazone vs 19.7% placebo; 95% CI=0.58–1.06;
P
=0.1095). Pioglitazone reduced fatal or nonfatal stroke (HR=0.53, event rate=5.6% pioglitazone vs 10.2% placebo; 95% CI=0.34–0.85;
P
=0.0085) and cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke (HR=0.72, event rate=13.0% pioglitazone vs 17.7% placebo; 95% CI=0.52–1.00;
P
=0.0467). Higher event rates were observed in patients with prior stroke compared with those without prior stroke. In patients without prior stroke, no treatment effect was observed for a first stroke.

Conclusions—

In a subgroup analysis from PROactive, pioglitazone reduced the risk of recurrent stroke significantly in high-risk patients with type 2 diabetes.
Speed of tPA-Induced Clot Lysis Predicts DWI Lesion Evolution in Acute Stroke
Authors: Delgado-Mederos Raquel , Rovira Alex , Alvarez-Sabín José , Ribó Marc , Munuera Josep , Rubiera Marta , Santamarina Esteban , Maisterra Olga , Delgado Pilar , Montaner Joan , Molina Carlos A.
Published: February 2007

Background and Purpose—

We sought to evaluate the impact of the speed of recanalization on the evolution of diffusion- weighted imaging (DWI) lesions and outcome in stroke patients treated with tissue-type plasminogen activator (tPA).

Methods—

We evaluated 113 consecutive stroke patients with a middle cerebral artery occlusion who were treated with intravenous tPA. All patients underwent multiparametric magnetic resonance imaging studies, including DWI and perfusion-weighted imaging before and 36 to 48 hours after administration of a tPA bolus. Patients were continuously monitored with transcranial Doppler during the first 2 hours after tPA administration. The pattern of recanalization on transcranial Doppler was defined as sudden (<1 minute), stepwise (1 to 29 minutes), or slow (>30 minutes).

Results—

During transcranial Doppler monitoring, 13 (12.3%) patients recanalized suddenly, 32 (30.2%) recanalized in a stepwise manner, and 18 (17%) recanalized slowly. Baseline clinical and imaging parameters were similar among recanalization subgroups. At 36 to 48 hours, DWI lesion growth was significantly (
P
=0.001) smaller after sudden (3.23±10.5 cm
3
) compared with stepwise (24.9±37 cm
3
), slow (46.3±38 cm
3
), and no (51.7±34 cm
3
) recanalization. The slow pattern was associated with greater DWI growth (
P
=0.003), lesser degree of clinical improvement (
P
=0.021), worse 3-month outcome (
P
=0.032), and higher mortality (
P
=0.003).

Conclusions—

The speed of tPA-induced clot lysis predicts DWI lesion evolution and clinical outcome. Unlike sudden and stepwise patterns, slow recanalization is associated with greater DWI lesion growth and poorer short- and long-term outcomes.
Recent Climate-Driven Increases in Vegetation Productivity for the Western Arctic: Evidence of an Acceleration of the Northern Terrestrial Carbon Cycle
Authors: Kimball J. S. , Zhao M. , McGuire A. D. , Heinsch F. A. , Clein J. , Calef M. , Jolly W. M. , Kang S. , Euskirchen S. E. , McDonald K. C. , Running S. W.
Published: February 2007

Northern ecosystems contain much of the global reservoir of terrestrial carbon that is potentially reactive in the context of near-term climate change. Annual variability and recent trends in vegetation productivity across Alaska and northwest Canada were assessed using a satellite remote sensing–based production efficiency model and prognostic simulations of the terrestrial carbon cycle from the Terrestrial Ecosystem Model (TEM) and BIOME–BGC (BioGeoChemical Cycles) model. Evidence of a small, but widespread, positive trend in vegetation gross and net primary production (GPP and NPP) is found for the region from 1982 to 2000, coinciding with summer warming of more than 1.8°C and subsequent relaxation of cold temperature constraints to plant growth. Prognostic model simulation results were generally consistent with the remote sensing record and also indicated that an increase in soil decomposition and plant-available nitrogen with regional warming was partially responsible for the positive productivity response. Despite a positive trend in litter inputs to the soil organic carbon pool, the model results showed evidence of a decline in less labile soil organic carbon, which represents approximately 75% of total carbon storage for the region. These results indicate that the regional carbon cycle may accelerate under a warming climate by increasing the fraction of total carbon storage in vegetation biomass and more rapid turnover of the terrestrial carbon reservoir.
A New Look at Stratospheric Sudden Warmings. Part II: Evaluation of Numerical Model Simulations
Authors: Charlton Andrew J. , Polvani Lorenzo M. , Perlwitz Judith , Sassi Fabrizio , Manzini Elisa , Shibata Kiyotaka , Pawson Steven , Nielsen J. Eric , Rind David
Published: February 2007

The simulation of major midwinter stratospheric sudden warmings (SSWs) in six stratosphere-resolving general circulation models (GCMs) is examined. The GCMs are compared to a new climatology of SSWs, based on the dynamical characteristics of the events. First, the number, type, and temporal distribution of SSW events are evaluated. Most of the models show a lower frequency of SSW events than the climatology, which has a mean frequency of 6.0 SSWs per decade. Statistical tests show that three of the six models produce significantly fewer SSWs than the climatology, between 1.0 and 2.6 SSWs per decade. Second, four process-based diagnostics are calculated for all of the SSW events in each model. It is found that SSWs in the GCMs compare favorably with dynamical benchmarks for SSW established in the first part of the study.

These results indicate that GCMs are capable of quite accurately simulating the dynamics required to produce SSWs, but with lower frequency than the climatology. Further dynamical diagnostics hint that, in at least one case, this is due to a lack of meridional heat flux in the lower stratosphere. Even though the SSWs simulated by most GCMs are dynamically realistic when compared to the NCEP–NCAR reanalysis, the reasons for the relative paucity of SSWs in GCMs remains an important and open question.
A New Look at Stratospheric Sudden Warmings. Part I: Climatology and Modeling Benchmarks
Authors: Charlton Andrew J. , Polvani Lorenzo M.
Published: February 2007

Stratospheric sudden warmings are the clearest and strongest manifestation of dynamical coupling in the stratosphere–troposphere system. While many sudden warmings have been individually documented in the literature, this study aims at constructing a comprehensive climatology: all major midwinter warming events are identified and classified, in both the NCEP–NCAR and 40-yr ECMWF Re-Analysis (ERA-40) datasets. To accomplish this a new, objective identification algorithm is developed. This algorithm identifies sudden warmings based on the zonal mean zonal wind at 60°N and 10 hPa, and classifies them into events that do and do not split the stratospheric polar vortex.

Major midwinter stratospheric sudden warmings are found to occur with a frequency of approximately six events per decade, and 46% of warming events lead to a splitting of the stratospheric polar vortex. The dynamics of vortex splitting events is contrasted to that of events where the vortex is merely displaced off the pole. In the stratosphere, the two types of events are found to be dynamically distinct: vortex splitting events occur after a clear preconditioning of the polar vortex, and their influence on middle-stratospheric temperatures lasts for up to 20 days longer than vortex displacement events. In contrast, the influence of sudden warmings on the tropospheric state is found to be largely insensitive to the event type.

Finally, a table of dynamical benchmarks for major stratospheric sudden warming events is compiled. These benchmarks are used in a companion study to evaluate current numerical model simulations of the stratosphere.
Ten Years of Measurements of Tropical Upper-Tropospheric Water Vapor by MOZAIC. Part I: Climatology, Variability, Transport, and Relation to Deep Convection
Authors: Luo Zhengzhao , Kley Dieter , Johnson Richard H. , Smit Herman
Published: February 2007

Ten years (1994–2004) of measurements of tropical upper-tropospheric water vapor (UTWV) by the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) are investigated over three regions—the tropical Atlantic, tropical Africa, and the Asian monsoon region—to determine the UTWV climatology and variability on multiple scales and to understand them in relation to moisture transport and deep convection.

The seasonal migration of upper-tropospheric humidity (UTH) keeps pace with that of the ITCZ, indicating the convective influence on UTH distribution. Some significant regional differences are identified with the tropical Africa and the Asian monsoon regions being moister than the tropical Atlantic. UTH generally increases with height by 10%–20% relative humidity with respect to ice (RHi) from about 300 to 200 hPa, and the differences are larger in the deep Tropics than in the subtropics. The probability density functions of tropical UTH are often bimodal. The two modes stay rather constant; differences in the mean value are largely due to the variations in the proportion of the two modes as opposed to changes in the modes themselves. In the deep Tropics, the moisture level frequently reaches ice supersaturation, the most notable case being the near-equatorial Asian monsoon region during the wet season when ice supersaturation is observed 46% of the time.

Interannual variations are observed in association with the 1997–98 ENSO event. A warming of about 1–2 K is observed for all three regions equatorward of roughly 15°. Specific humidity also increases somewhat for the tropical Atlantic and tropical Africa, but the increase in temperature outweighs the increase in specific humidity such that RH decreases by 5%–15% RHi. In addition to the ENSO-related variation, MOZAIC also sees increases in both RH and specific humidity over tropical Africa from 2000 onward.

Moisture fluxes are computed from MOZAIC data and decomposed into contributions from the mean circulation and from eddies. The flux divergence, which represents the moisture source/sink from horizontal transport, is also estimated. Finally, the MOZAIC climatology and variability are revisited in relation to deep convection obtained from the International Satellite Cloud Climatology Project (ISCCP).
Detection of Human Influence on a New, Validated 1500-Year Temperature Reconstruction
Authors: Hegerl Gabriele C. , Crowley Thomas J. , Allen Myles , Hyde William T. , Pollack Henry N. , Smerdon Jason , Zorita Eduardo
Published: February 2007

Climate records over the last millennium place the twentieth-century warming in a longer historical context. Reconstructions of millennial temperatures show a wide range of variability, raising questions about the reliability of currently available reconstruction techniques and the uniqueness of late-twentieth-century warming. A calibration method is suggested that avoids the loss of low-frequency variance. A new reconstruction using this method shows substantial variability over the last 1500 yr. This record is consistent with independent temperature change estimates from borehole geothermal records, compared over the same spatial and temporal domain. The record is also broadly consistent with other recent reconstructions that attempt to fully recover low-frequency climate variability in their central estimate.

High variability in reconstructions does not hamper the detection of greenhouse gas–induced climate change, since a substantial fraction of the variance in these reconstructions from the beginning of the analysis in the late thirteenth century to the end of the records can be attributed to external forcing. Results from a detection and attribution analysis show that greenhouse warming is detectable in all analyzed high-variance reconstructions (with the possible exception of one ending in 1925), and that about a third of the warming in the first half of the twentieth century can be attributed to anthropogenic greenhouse gas emissions. The estimated magnitude of the anthropogenic signal is consistent with most of the warming in the second half of the twentieth century being anthropogenic.
Dynamics of the West African Monsoon under Mid-Holocene Precessional Forcing: Regional Climate Model Simulations
Authors: Patricola C. M. , Cook K. H.
Published: February 2007

The African Humid Period (AHP), about 14 800 yr ago [14.8–5.5 ka (ka ≡ 1000 yr ago)], was a time of increased humidity over Africa. Paleoclimate evidence suggests that the West African summer monsoon was stronger and more extensive 6 ka than today, and that the Saharan Desert was green. Here, a regional climate model that produces an excellent simulation of today’s climate over northern Africa is used to study the dynamics of the monsoon 6 ka. Changes in insolation, atmospheric CO2, and vegetation are used to impose 6-ka conditions, and the role of each forcing is isolated. Vegetation is not interactive, and the large-scale circulation and SSTs are fixed at present-day values for the 6-ka simulations.

The regional model produces precipitation increases across the Sahel and Sahara that are in good agreement with the paleodata. However, unobserved drying is simulated over the Guinean coast region where paleodata are sparse. Precipitation increases in the Sahel are related to a northward shift of the monsoon, the elimination of the African easterly jet, and an intensification and deepening of the low-level westerly jet on the west coast. The thermal low–Saharan high system of the present-day climate is replaced by a deep thermal low. When this system becomes fully developed in midsummer, cyclonic circulations transport moisture north into the Sahara, and rainfall increases there. Surface temperatures decrease despite the increased solar forcing 6 ka because of an increase in cloudiness. A moist static energy budget analysis shows that increased low-level moisture dominates the cooling to destabilize the vertical column and enhance convection. Even though solar forcing is the ultimate cause of the AHP, the model responds more strongly to the vegetation forcing, especially early in the summer season, emphasizing the importance of vegetation in maintaining the intensified monsoon system.
The Scripps Coupled Ocean–Atmosphere Regional (SCOAR) Model, with Applications in the Eastern Pacific Sector
Authors: Seo Hyodae , Miller Arthur J. , Roads John O.
Published: February 2007

A regional coupled ocean–atmosphere model is introduced. It is designed to admit the air–sea feedbacks arising in the presence of an oceanic mesoscale eddy field. It consists of the Regional Ocean Modeling System (ROMS) and the Regional Spectral Model (RSM). Large-scale forcing is provided by NCEP/DOE reanalysis fields, which have physics consistent with the RSM. Coupling allows the sea surface temperature (SST) to influence the stability of the atmospheric boundary layer and, hence, the surface wind stress and heat flux fields. The system is denominated the Scripps Coupled Ocean–Atmosphere Regional (SCOAR) Model.

The model is tested in three scenarios in the eastern Pacific Ocean sector: tropical instability waves of the eastern tropical Pacific, mesoscale eddies and fronts of the California Current System, and gap winds of the Central American coast. Recent observational evidence suggests air–sea interactions involving the oceanic mesoscale in these three regions. Evolving SST fronts are shown to drive an unambiguous response of the atmospheric boundary layer in the coupled model. This results in significant model anomalies of wind stress curl, wind stress divergence, surface heat flux, and precipitation that resemble the observations and substantiate the importance of ocean–atmosphere feedbacks involving the oceanic mesoscale.
Observed Influence of North Pacific SST Anomalies on the Atmospheric Circulation
Authors: Frankignoul Claude , Sennéchael Nathalie
Published: February 2007

A lagged maximum covariance analysis (MCA) of monthly anomaly data from the NCEP–NCAR reanalysis shows significant relations between the large-scale atmospheric circulation in two seasons and prior North Pacific sea surface temperature (SST) anomalies, independent from the teleconnections associated with the ENSO phenomenon. Regression analysis based on the SST anomaly centers of action confirms these findings. In late summer, a hemispheric atmospheric signal that is primarily equivalent barotropic, except over the western subtropical Pacific, is significantly correlated with an SST anomaly mode up to at least 5 months earlier. Although the relation is most significant in the upper troposphere, significant temperature anomalies are found in the lower troposphere over North America, the North Atlantic, Europe, and Asia. The SST anomaly is largest in the Kuroshio Extension region and along the subtropical frontal zone, resembling the main mode of North Pacific SST anomaly variability in late winter and spring, and it is itself driven by the atmosphere. The predictability of the atmospheric signal, as estimated from cross-validated correlation, is highest when SST leads by 4 months because the SST anomaly pattern is more dominant in the spring than in the summer. In late fall and early winter, a signal resembling the Pacific–North American (PNA) pattern is found to be correlated with a quadripolar SST anomaly during summer, up to 4 months earlier, with comparable statistical significance throughout the troposphere. The SST anomaly changes shape and propagates eastward, and by early winter it resembles the SST anomaly that is generated by the PNA pattern. It is argued that this results via heat flux forcing and meridional Ekman advection from an active coupling between the SST and the PNA pattern that takes place throughout the fall. Correspondingly, the predictability of the PNA-like signal is highest when SST leads by 2 months. In late summer, the maximum atmospheric perturbation at 250 mb reaches 35 m K−1 in the MCA and 20 m K−1 in the regressions. In early winter, the maximum atmospheric perturbation at 250 mb ranges between 70 m K−1 in the MCA and about 35 m K−1 in the regressions. This suggests that North Pacific SST anomalies have a substantial impact on the Northern Hemisphere climate. The back interaction of the atmospheric response onto the ocean is also discussed.
Steric Sea Level Change in the Northern Seas
Authors: Steele Michael , Ermold Wendy
Published: February 2007

Ocean temperature and salinity data over the period 1950–2000 in the Northern Seas, defined here as the North Atlantic Ocean (north of 50°N), North Pacific Ocean (north of 40°N), and Arctic Oceans, are combined to diagnose the steric (i.e., density) contribution to sea level variation. The individual contributions to steric height from temperature (thermosteric height) and salinity (halosteric height) are also analyzed. It is found that during 1950–2000, steric height rose over the study’s domain, mostly as a result of halosteric increases (i.e., freshening). Over a shorter time period (late 1960s to early 1990s) during which climate indices changed dramatically, steric height gradients near the Nordic Seas minimum were reduced by 18%–32%. It is speculated that this may be associated with a local slowing of both the Meridional Overturning Circulation and the southward flow through Fram Strait. However, steric height increases in the North Pacific Ocean during this time imply a possible acceleration of flow through the poorly measured Canadian Arctic. Evidence that the Great Salinity Anomaly of the late 1960s and 1970s had two distinct Arctic Ocean sources is also found: a late 1960s export of sea ice, and a delayed but more sustained 1970s export of liquid (ocean) freshwater. A simple calculation indicates that these Arctic Ocean freshwater sources were not sufficient to create the 1970s freshening observed in the North Atlantic Ocean.
Ice Bridges on the St. Lawrence River as an Index of Winter Severity from 1620 to 1910
Authors: Houle Daniel , Moore Jean-David , Provencher Jean
Published: February 2007

Temperature reconstruction of the last thousand years suggests that an unprecedented warming (+0.6°C) occurred over the globe in the last century. However, regional variations in climate are not resolved by Northern Hemisphere reconstructions. In northeastern North America, past climate and, particularly, past winter variations are poorly known. Here, the authors report on the variation of a winter temperature index during the 1620–1910 period, based on the ice bridge formation (IBF) rate on the Saint Lawrence River at Québec City (Canada), combined with instrumental data (1876–2000). During this 300-yr period, the IBF rate shows that winters in the seventeenth and eighteenth centuries were warmer than those in the nineteenth century. In particular, the IBF rate suggests that winter severity culminated in the 1850–1900 period, while very few ice bridges were reported between 1620 and 1740, presumably because of warmer temperatures and the relative scarcity of historical documents for the 1680–1740 period. These data suggest that winter temperature, particularly between ∼1800 and 1910, was 2.4° to 4.0°C colder than the last 30-yr average. Major volcanic eruptions had a significant positive impact on IBF rates, which is consistent with their role as important climate-forcing events.
Simulations of Arctic Temperature and Pressure by Global Coupled Models
Authors: Chapman William L. , Walsh John E.
Published: February 2007

Simulations of Arctic surface air temperature and sea level pressure by 14 global climate models used in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change are synthesized in an analysis of biases and trends. Simulated composite GCM surface air temperatures for 1981–2000 are generally 1°–2°C colder than corresponding observations with the exception of a cold bias maximum of 6°–8°C in the Barents Sea. The Barents Sea bias, most prominent in winter and spring, occurs in 12 of the 14 GCMs and corresponds to a region of oversimulated sea ice. All models project a twenty-first-century warming that is largest in the autumn and winter, although the rates of the projected warming vary considerably among the models. The across-model and across-scenario uncertainties in the projected temperatures are comparable through the first half of the twenty-first century, but increases in variability associated with the choice of scenario begin to outpace increases in across-model variability by about the year 2070. By the end of the twenty-first century, the cross-scenario variability is about 50% greater than the across-model variability. The biases of sea level pressure are smaller than in the previous generation of global climate models, although the models still show a positive bias of sea level pressure in the Eurasian sector of the Arctic Ocean, surrounded by an area of negative pressure biases. This bias is consistent with an inability of the North Atlantic storm track to penetrate the Eurasian portion of the Arctic Ocean. The changes of sea level pressure projected for the twenty-first century are negative over essentially the entire Arctic. The most significant decreases of pressure are projected for the Bering Strait region, primarily in autumn and winter.
The Isotopic Composition of Present-Day Antarctic Snow in a Lagrangian Atmospheric Simulation*
Authors: Helsen M. M. , Van de Wal R. S. W. , Van den Broeke M. R.
Published: February 2007

The isotopic composition of present-day Antarctic snow is simulated for the period September 1980–August 2002 using a Rayleigh-type isotope distillation model in combination with backward trajectory calculations with 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data as meteorological input. Observed spatial isotopic gradients are correctly reproduced, especially in West Antarctica and in the coastal areas. However, isotopic depletion of snow on the East Antarctic plateau is underestimated, a problem that is also observed in general circulation models equipped with isotope tracers. The spatial isotope–temperature relation varies strongly, which indicates that this widely used relation is not applicable to all sites and temporal scales. Spatial differences in the seasonal amplitude are identified, with maximum values in the Antarctic interior and hardly any seasonal isotope signature in Marie Byrd Land, West Antarctica. The modeled signature of deuterium excess remains largely preserved during the last phase of transport, though the simulated relation of deuterium excess with δ18O suggests that parameterizations of kinetic isotopic fractionation can be improved.
Trends in Southern Hemisphere Circulation in IPCC AR4 Models over 1950–99: Ozone Depletion versus Greenhouse Forcing
Authors: Cai Wenju , Cowan Tim
Published: February 2007

Simulations by the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) models on the Southern Hemisphere (SH) circulation are assessed over the period 1950–99, focusing on the seasonality of the trend and the level of its congruency with the southern annular mode (SAM) in terms of surface zonal wind stress. It is found that, as a group, the models realistically produce the seasonality of the trend, which is strongest in the SH summer season, December–February (DJF). The modeled DJF trend is principally congruent with the modeled SAM trend, as in observations. The majority of models produce a statistically significant positive trend, with decreasing westerlies in the midlatitudes and increasing westerlies in the high latitudes. The trend pattern from an all-experiment mean achieves highest correlation with that from the National Centers for Environmental Prediction (NCEP) data. A total of 48 out of the 71 experiments were run with ozone-depletion forcing, which offers an opportunity to assess the importance of ozone depletion in driving the late-twentieth-century trends. The AR4 model ensemble that contains an ozone-depletion forcing produces an averaged trend that is comparable to the trend from the NCEP outputs corrected by station-based observations. The trend is largely generated after the mid-1970s. Without ozone depletion the trend is less than half of that in the corrected NCEP, although the errors in the observed trend are large. The impact on oceanic circulation is inferred from wind stress curl in the group with ozone-depletion forcing. The result shows an intensification of the southern midlatitude supergyre circulation, including a strengthening East Australian Current flowing through the Tasman Sea. Thus, ozone depletion also plays an important role in the subtropical gyre circulation change over the past decades.
A Multifaceted Climatology of Atmospheric Blocking and Its Recent Linear Trend
Authors: Croci-Maspoli M. , Schwierz C. , Davies H. C.
Published: February 2007

A dynamically based climatology is derived for Northern Hemisphere atmospheric blocking events. Blocks are viewed as large amplitude, long-lasting, and negative potential vorticity (PV) anomalies located beneath the dynamical tropopause. The derived climatology [based on the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40)] provides a concise, coherent, and illuminating description of the main physical characteristics of blocks and the accompanying linear trends. The latitude–longitude distribution of blocking frequency captures the standard bimodal geographical distribution with major peaks over the North Atlantic and eastern North Pacific in all four seasons. The accompanying pattern for the age distribution, the genesis–lysis regions, and the track of blocks reveals that 1) younger blocks (1–4 days) are more prevalent at lower latitudes whereas significantly older blocks (up to 12 days) are located at higher latitudes; 2) genesis is confined predominantly to the two major ocean basins and in a zonal band between 40° and 50°N latitude, whereas lysis is more dispersed but with clear preference to higher latitudes; and 3) the general northeastward–west-northwest movement of blocks in the genesis–lysis phase also exhibits subtle seasonal and intra- and interbasin differences. Examination of the intensity and spatial-scale changes during the blocking life cycle suggests that in the mean a block’s evolution is independent of the genesis region and its eventual duration. A novel analysis of blocking trends reveals significant negative trends in winter over Greenland and in spring over the North Pacific. It is shown that the changes over Greenland are linked to the number of blocking episodes, whereas a neighboring trend signal to the south is linked to higher-frequency anticyclonic systems. Furthermore, evidence is adduced that changes in blocking frequency contribute seminally to tropopause height trends.
Conditional Exceedance Probabilities
Authors: Mason Simon J. , Galpin Jacqueline S. , Goddard Lisa , Graham Nicholas E. , Rajartnam Balakanapathy
Published: February 2007

Probabilistic forecasts of variables measured on a categorical or ordinal scale, such as precipitation occurrence or temperatures exceeding a threshold, are typically verified by comparing the relative frequency with which the target event occurs given different levels of forecast confidence. The degree to which this conditional (on the forecast probability) relative frequency of an event corresponds with the actual forecast probabilities is known as reliability, or calibration. Forecast reliability for binary variables can be measured using the Murphy decomposition of the (half) Brier score, and can be presented graphically using reliability and attributes diagrams. For forecasts of variables on continuous scales, however, an alternative measure of reliability is required. The binned probability histogram and the reliability component of the continuous ranked probability score have been proposed as appropriate verification procedures in this context, but are subject to some limitations. A procedure is proposed that is applicable in the context of forecast ensembles and is an extension of the binned probability histogram. Individual ensemble members are treated as estimates of quantiles of the forecast distribution, and the conditional probability that the observed precipitation, for example, exceeds the amount forecast [the conditional exceedance probability (CEP)] is calculated. Generalized linear regression is used to estimate these conditional probabilities. A diagram showing the CEPs for ranked ensemble members is suggested as a useful method for indicating reliability when forecasts are on a continuous scale, and various statistical tests are suggested for quantifying the reliability.
The Characteristics of Key Analysis Errors. Part I: Dynamical Balance and Comparison with Observations
Authors: Caron Jean-François , Yau M. K. , Laroche Stéphane , Zwack Peter
Published: February 2007

The characteristics of the initial corrections obtained from the Canadian Meteorological Centre (CMC) energy-norm-based key analysis error algorithm that minimizes short-range (24 h) forecast errors were investigated for four specific CMC operational analyses. The results show that both the rotational and the divergent components of the initial corrections are strongly out of balance. Some dispersive modes are also present in the mass component of the initial corrections. The results from one experiment where the initial state errors were known suggest that the current algorithm always selects a set of unbalanced initial corrections with more mass correction than wind correction, regardless of the characteristics of the real initial condition errors. Comparison with observational data showed that the corrected analysis is systematically farther away from the observations than the control analysis even in large forecast error events where most of the forecast errors are believed to have originated from errors in the initial state.
Inferential, Nonparametric Statistics to Assess the Quality of Probabilistic Forecast Systems
Authors: Maia Alinede H. N. , Meinke Holger , Lennox Sarah , Stone Roger
Published: February 2007

Many statistical forecast systems are available to interested users. To be useful for decision making, these systems must be based on evidence of underlying mechanisms. Once causal connections between the mechanism and its statistical manifestation have been firmly established, the forecasts must also provide some quantitative evidence of “quality.” However, the quality of statistical climate forecast systems (forecast quality) is an ill-defined and frequently misunderstood property. Often, providers and users of such forecast systems are unclear about what quality entails and how to measure it, leading to confusion and misinformation. A generic framework is presented that quantifies aspects of forecast quality using an inferential approach to calculate nominal significance levels (p values), which can be obtained either by directly applying nonparametric statistical tests such as Kruskal–Wallis (KW) or Kolmogorov–Smirnov (KS) or by using Monte Carlo methods (in the case of forecast skill scores). Once converted to p values, these forecast quality measures provide a means to objectively evaluate and compare temporal and spatial patterns of forecast quality across datasets and forecast systems. The analysis demonstrates the importance of providing p values rather than adopting some arbitrarily chosen significance levels such as 0.05 or 0.01, which is still common practice. This is illustrated by applying nonparametric tests (such as KW and KS) and skill scoring methods [linear error in the probability space (LEPS) and ranked probability skill score (RPSS)] to the five-phase Southern Oscillation index classification system using historical rainfall data from Australia, South Africa, and India. The selection of quality measures is solely based on their common use and does not constitute endorsement. It is found that nonparametric statistical tests can be adequate proxies for skill measures such as LEPS or RPSS. The framework can be implemented anywhere, regardless of dataset, forecast system, or quality measure. Eventually such inferential evidence should be complemented by descriptive statistical methods in order to fully assist in operational risk management.