bluuebunny/crossref_metadata_2025 huggingface dataset:
A Push Toward Equality: Processes Among Dual‐Career Newlywed Couples in Collectivist Culture
Authors: Mui‐Teng Quek Karen , Knudson‐Martin Carmen
Published: January 2006

This study examines gender construction among dual‐career newlywed couples in a collectivist culture. A qualitative analysis of in‐depth interviews with 20 heterosexual Singaporean couples reveals aspects of the collectivist norms (e.g., doing family, we‐consciousness, marrying one's equal) that are favorable toward the development of gender equality. Additionally, as couples respond to the political and social pulls of economic development, they begin to organize their relationship around both careers. Incorporating egalitarian values becomes a pragmatic move carried out through five direct processes: (a) career as central to the relationship, (b) flexible allocation of household duties, (c) open dialogue regarding conflict, (d) equal say in decision making, and (e) internal self‐reflection. Implications for future research are addressed.
The Political Values and Choices of Husbands and Wives
Authors: Kan Man Yee , Heath Anthony
Published: January 2006

This article applies theoretical ideas in the literature on the household division of labor to the analysis of partners’ political preferences. We regress men's and women's political party preferences on their own and their partners’ characteristics using data from the 1991 British Household Panel Survey (N =2,846). We find a symmetrical pattern of influence: Men and women both give greatest weight to their own political values but also accord some significant weight to their partners’ values. Economically dependent men, however, place virtually no emphasis on their partners’ political values. Apart from this, we suggest that there may be a process of mutual accommodation within couples regarding political preferences that leads to greater concordance in the partners’ preferences over time.
Parents and Peers in Relation to Early Adolescent Problem Behavior
Authors: Buehler Cheryl
Published: January 2006

Concurrent and prospective associations between parent‐youth dyadic hostility and adolescent externalizing and internalizing problem behavior were examined in a sample of 416 families. Parenting control, parents’ well‐being, and youths’ affiliation with deviant peers were included as integral covariates. Information from multiple sources was analyzed using structural equation modeling. Concurrently, youth externalizing problems were associated with dyadic hostility, deviant peers, inadequate parenting control, and fathers’ well‐being (inversely). Internalizing problems were associated with inadequate parenting control and lower levels of fathers’ well‐being. Prospectively, some of these relations continued over 2 years, with a few new associations emerging. A process model is proposed in which parent‐youth dyadic hostility during early adolescence influences parenting, peer relations, and parents’ well‐being over time.
Family Structure, Father Involvement, and Adolescent Behavioral Outcomes
Authors: Carlson Marcia J.
Published: January 2006

Research has shown that living away from one's biological father is associated with a greater risk of adverse child and adolescent outcomes; yet, the role of the father‐child relationship in understanding this association has not been directly investigated. This study uses data on biological fathers’ relationships with their children from the 1979 National Longitudinal Survey of Youth (N = 2,733) to assess whether father involvement mediates the relationship between family structure (i.e., father absence) and four measures of adolescent behavior. Differences in father involvement are shown to account for a sizeable fraction of the variance in outcomes by family structure. Father involvement does not affect boys and girls differently but is more beneficial when the father lives with the adolescent.
Under Pressure: Gender Differences in the Relationship Between Free Time and Feeling Rushed
Authors: Mattingly Marybeth J. , Sayer Liana C.
Published: January 2006

Free time has the potential to reduce time pressures, yet previous studies paradoxically report increases in free time concurrent with increases in feeling rushed. Using U.S. time diary data from 708 individuals in 1975 and 964 individuals in 1998, we review the evidence on trends in free time and subjective perceptions of feeling rushed, and reexamine the relationship between free time and time pressure. We find that women's time pressure increased significantly between 1975 and 1998 but men's did not. In addition, the effects of objective time constraints vary by gender. Whereas more free time reduces men's perceptions of feeling rushed at both time points, among women, free time marginally reduced time pressure in 1975 but no longer reduced time pressure in 1998. Our findings suggest that persistent inequality in gendered time‐use patterns is paralleled by gendered experiences of time pressure.
Feeling Caught Between Parents: Adult Children's Relations With Parents and Subjective Well‐Being
Authors: Amato Paul R. , Afifi Tamara D.
Published: January 2006

Research on divorce has found that adolescents’ feelings of being caught between parents are linked to internalizing problems and weak parent‐child relationships. The present study estimates the effects of marital discord, as well as divorce, on young adult offspring's feelings of being caught in the middle (N =632). Children with parents in high‐conflict marriages were more likely than other children to feel caught between parents. These feelings were associated with lower subjective well‐being and poorer quality parent‐child relationships. Offspring with divorced parents were no more likely than offspring with continuously married parents in low‐conflict relationships to report feeling caught. Feelings of being caught appeared to fade in the decade following parental divorce. These results suggest that, unlike children of divorce, children with parents in conflicted marriages (who do not divorce) may be unable to escape from their parents’ marital problems—even into adulthood.
Racial Differences in Sexual and Fertility Attitudes in an Urban Setting
Authors: Browning Christopher R. , Burrington Lori A.
Published: January 2006

Using data from the Project on Human Development in Chicago Neighborhoods (neighborhood N= 77; individual N= 951), we consider the extent to which African American youth maintain sexual and fertility‐related norms that support early sexual activity and childbearing and examine the robustness of racial differences in sexual attitudes to controls for neighborhood, family, and individual characteristics. At a minimum, neighborhood economic disadvantage accounts for 26% of the baseline increased likelihood of holding attitudes that encourage early sexual activity among African American youth when compared with Whites. Neighborhood‐, family‐, and individual‐level factors account for 67% of the race difference in sexual attitudes. Implications for contextual and race‐based theories of sexual and fertility norms are discussed.
The Relationship Between Private Safety Nets and Economic Outcomes Among Single Mothers
Authors: Harknett Kristen
Published: January 2006

This article examines the relationship between private safety nets and economic outcomes among 2,818 low‐income single mothers in three U.S. counties in the 1990s. I define private safety nets as the potential to draw upon family and friends for material or emotional support if needed. Using a combination of survey and administrative records data collected for the National Evaluation of Welfare‐to‐Work Strategies, I find that human capital deficits, depressive symptoms, and low self‐efficacy are associated with having less private safety net support, suggesting that social network disadvantages compound individual‐level disadvantages. I also find that mothers with strong private safety nets worked more, earned more, and were less reliant on welfare compared with mothers with more meager private safety nets.
THE RELATIONSHIP BETWEEN LABOUR MARKET DYNAMICS AND HIV/AIDS PREVALENCE IN SOUTH AFRICA ‐ A LITERATURE REVIEW1
Authors: VASS JOCELYN
Published: January 2006

The aim of this literature review is to analyse the contribution of current research and literature to an understanding of the relationship between labour market dynamics and HIV/AIDS prevalence in South Africa. It highlights and assesses the extent to which those factors that are regarded as determinants of HIV susceptibility, AIDS vulnerability and prevalence, interact with differentiation in the labour market. The conclusion is that current research studies do not sufficiently consider a more nuanced relationship between complex labour market dynamics and socio‐economic risk factors driving HIV/AIDS susceptibility and vulnerability.
POVERTY AND LABOUR MARKET MARKERS OF HIV POSITIVE HOUSEHOLDS IN SOUTH AFRICA: AN EXPLORATORY METHODOLOGICAL ANALYSIS
Authors: SHAIKH NAJMA , BHORAT HAROON
Published: January 2006

This study, through an exploratory, but promising methodology, provides a tentative analysis of the relationship between HIV, poverty and labour markets. This was undertaken through the use of the October Household Survey of 1999 and the Antenatal Clinic Survey of 1998. It is clear from the paper that the relationship between poverty, labour markets and HIV is not homogeneous but multi‐dimensional in character. The analysis examines these interrelationships at both the household and individual level. The preliminary key finding from the analysis is that imputed HIV positive women come from poorer households than imputed negative women, but this observed difference is small. It is suggested that the analysis be repeated using larger samples of data, such as that now available from Census 2001
BUDGETING FOR HIV/AIDS IN SOUTH AFRICA: AN ANALYSIS OF PROVINCIAL HEALTH BUDGETS
Authors: HICKEY ALISON , NDLOVU NHLANHLA
Published: January 2006

What is the best way to deliver funds to the provinces for HIV/AIDS interventions? This article analyses HIV/AIDS conditional grant (CG) spending and assesses the success of the new funding approach introduced in 2002/3 which channels HIV/AIDS funds to the provinces via the equitable share grant. Our research shows that on the whole provinces are improving their spending on the HIV/AIDS conditional grants and provinces are also beginning to allocate substantial funds from their own provincial budgets for HIV/AIDS interventions in the health sector. Special emphasis is placed on (a) provinces' initiative to allocate additional funds to HIV/AIDS from their own budgets; (b) variances in per capita spending on HIV‐positive and AIDS sick populations across provinces; and (c) whether prioritisation of HIV/AIDS in health budgets might be squeezing out spending on other health services.
Measurement of gluconeogenesis by deuterated water: the effect of equilibration time and fasting period
Authors: Allick Gideon , van der Crabben Saskia N. , Ackermans Mariette T. , Endert Erik , Sauerwein Hans P.
Published: January 2006

Fasting gluconeogenesis (GNG) is often quantified using the 2H2O technique, which is based on plasma 2H2O enrichment and ensuing enrichment of plasma glucose at the C5 and C2 positions. Fractional (fr)GNG can be calculated using the ratio of C5 to C2 enrichment or the ratio of C5 to plasma 2H2O enrichment. For the latter, equilibration of 2H2O and C2 is required. The optimal equilibration period of 2H2O and C2 remains to be elucidated. In six healthy male subjects fasted for 18 h, we studied the effects of 3-, 5-, and 15-h 2H2O incubation periods on 1) the equilibration of plasma 2H2O and C2 glucose enrichment, 2) the measurement of frGNG, and 3) C5 labeling of hepatic glycogen after 1 mg of glucagon administration. After 3-h 2H2O incubation, plasma 2H2O and C2 were not equilibrated, frGNG C5/2H2O and C5/C2 were also different as was gluconeogenesis calculated with C5/2H2O and C5/C2. After 5- and 15-h 2H2O incubation, plasma 2H2O and C2 were equilibrated, and frGNG C5/2H2O and C5/C2 were similar, as was GNG calculated with C5/2H2O and C5/C2. After glucagon administration, no difference of C5 enrichment was found between 3, 5, and 15 h of 2H2O incubation. In conclusion, for reliable measurement of GNG in healthy subjects with C5/2H2O incubation periods longer than 3 h are required. After 5- and 15-h 2H2O incubation, GNG can be reliably measured with C5/2H2O. Gluconeogenetic labeling of glycogen did not affect the results after 3, 5, or 15 h of 2H2O incubation.
Red blood cells increase secretion of matrix metalloproteinases from human lung fibroblasts in vitro
Authors: Fredriksson K. , Liu X. D. , Lundahl J. , Klominek J. , Rennard S. I. , Skold C. M.
Published: January 2006

Tissue remodeling is an important process in many inflammatory and fibrotic lung disorders. RBC may in these conditions interact with extracellular matrix (ECM). Fibroblasts can produce and secrete matrix components, matrix-degrading enzymes (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Imbalance in matrix synthesis/degradation may result in rearrangement of tissue architecture and lead to diseases such as emphysema or fibrosis. Neutrophil elastase (NE), a protease released by neutrophils, is known to activate MMP. We hypothesized that RBC can stimulate secretion of MMPs from human lung fibroblasts and that NE can augment this effect. Human fetal lung fibroblasts were cultured in floating collagen gels with or without RBC. After 4 days, the culture medium was analyzed with gelatin zymography, Western blot, and ELISA for MMP-1, -2, -3 and TIMP-1, -2. RBC augmented NE-induced fibroblast-mediated collagen gel contraction compared with NE alone (18.4 ± 1.6%, 23.7 ± 1.4% of initial gel area, respectively). A pan-MMP inhibitor (GM-6001) completely abolished the stimulating effect of NE. Gelatin zymography showed that RBC stimulated MMP-2 activity and that NE enhanced conversion to the active form. Addition of GM-6001 completely inhibited MMP-2 activity in controls, whereas it only partially altered RBC-induced MMP activity. Western blot confirmed the presence of MMP-1 and MMP-3 in fibroblasts stimulated with RBC, and ELISA confirmed increased concentrations of pro-MMP-1. We conclude that stimulation of MMP secretion by fibroblasts may explain the ability of RBC to augment fibroblast-mediated collagen gel contraction. This might be a potential mechanism by which hemorrhage in inflammatory conditions leads to ECM remodeling.
Identification and function of hypoxia-response genes in Drosophila melanogaster
Authors: Liu Guowen , Roy Julianne , Johnson Eric A.
Published: January 2006

Hypoxia, an insufficient level of oxygen in the cell, occurs during normal activity and also in pathological conditions such as ischemia and tumorigenesis. Although many hypoxia-response genes have been identified, an understanding of the functional role for these genes in the living animal is lacking. Here we present a genome-wide study of gene expression changes during hypoxia and then functionally test a subset of these genes for roles in survival and recovery from hypoxia. We found 79 genes with increased mRNA levels when adult flies were treated with 0.5% O2 for 6 h. A subset of these genes had detectably increased levels in as short as 1 h of low-oxygen treatment. Mild hypoxia levels resulted in an increase in transcription levels for only 20 genes. Viability during hypoxia and recovery time from hypoxia-induced paralysis was examined in flies with a reduction in activity in hypoxia-response genes. The observed decreased viability and increased recovery time from paralysis in many of the lines demonstrate that the increased transcript levels seen after hypoxia are important for the response to low oxygen.
D
3
Dopamine Receptor Directly Interacts With D
1
Dopamine Receptor in Immortalized Renal Proximal Tubule Cells
Authors: Zeng Chunyu , Wang Zheng , Li Hewang , Yu Peiying , Zheng Shaopeng , Wu Lijuan , Asico Laureano D. , Hopfer Ulrich , Eisner Gilbert M. , Felder Robin A. , Jose Pedro A.
Published: January 2006

D
3
receptors act synergistically with D
1
receptors to inhibit sodium transport in renal proximal tubules; however, the mechanism by which this occurs is not known. Because dopamine receptor subtypes can regulate and interact with each other, we studied the interaction of D
3
and D
1
receptors in rat renal proximal tubule (RPT) cells. The D
3
agonist PD128907 increased the immunoreactive expression of D
1
receptors in a concentration- and time-dependent manner; these effects were blocked by the D
3
antagonist U99194A. PD128907 also transiently (15 minutes) increased the amount of cell surface membrane D
1
receptors. Laser confocal immunofluorescence microscopy showed that D
3
receptor and D
1
receptor colocalized in RPT cells more distinctly in Wistar-Kyoto rats than in spontaneously hypertensive rats (SHRs). In addition, D
3
and D
1
receptors could be coimmunoprecipitated, and this interaction was increased after D
3
receptor agonist stimulation for 24 hours in Wistar-Kyoto rats but not in SHRs. We propose that the synergistic effects of D
3
and D
1
receptors may be caused by a D
3
receptor–mediated increase in total, as well as cell surface membrane D
1
receptor expression, and direct D
3
and D
1
receptor interaction, both of which are impaired in SHRs.
Sensory Neurons With Afferents From Hind Limbs
Authors: Linz Peter , Amann Kerstin , Freisinger Wolfgang , Ditting Till , Hilgers Karl F. , Veelken Roland
Published: January 2006

Sensory nerve fibers from the dorsal root ganglia (DRG) may contribute to the regulation of peripheral vascular resistance. Axons of DRG neurons of the lower thoracic cord project mainly to resistance vessels in the lower limbs, likely opposing the vasoconstrictor effects of the sympathetic activity. This mechanism might be of importance in hypertension with increased sympathetic activity. We tested the hypothesis that sensory neurons of the DRG in the lower thoracic cord show an altered sensitivity to mechanical stimuli in hypertension. Neurons from DRG (T11 to L1) of rats with hypertension (2 kidney-1 clip hypertensive rats and 5 of 6 nephrectomized rats) were cultured on coverslips. Current time relationships were established with whole-cell patch recordings. Cells were characterized under control conditions and after exposure to hypoosmotic solutions to induce mechanical stress. Neurons with projections to the kidney were studied for comparison. The hypoosmotic extracellular medium induced a significant change in conductance of the cells in all of the groups of rats. In hypertensive rats, responses of cells with hindlimb axons were significantly different from controls: (2 kidney-1 clip hypertensives: δ−351±52 pA and 5 of 6 nephrectomized rats: δ−372±43 pA versus controls: δ−190±25 pA;
P
<0.05). Responses of DRG cells with renal afferents to mechanical stress were unaffected. Neurons from DRG in the lower thoracic cord with projections to the lower limbs exhibited an increased sensitivity to mechanical stress. We speculate that this observation may indicate an increased activity of these neurons, their axons, and neurotransmitters in the control of resistance vessels in hypertension.
Enhanced Superoxide Activity Modulates Renal Function in NO-Deficient Hypertensive Rats
Authors: Kopkan Libor , Majid Dewan S.A.
Published: January 2006

An enhancement of superoxide (O
2
−
) activity was shown to contribute to the development of hypertension induced by NO deficiency. To better understand the mechanistic role of O
2
−
in this NO-deficient hypertension, we evaluated the renal responses to acute intraarterial administration of an O
2
−
scavenger, tempol (50 μg/min per 100 g of body weight) in anesthetized male Sprague-Dawley rats treated with NO synthase inhibitor nitro-
l
-arginine methyl ester (15 mg/kg per day in drinking water, n=7) for 4 weeks, which caused increases in mean arterial pressure (146±3 versus 124±2 mm Hg) compared with normotensive control rats (n=6). Hypertensive rats had higher renal vascular resistance (29±2 versus 20±1 mm Hg/mL per minute per gram), as well as lower renal blood flow (5.2±0.3 versus 6.3±0.2 mL/min per gram; cortical blood flow, 153±13 versus 191±8 perfusion units; medullary blood flow, 43±2 versus 51±3 perfusion units) and glomerular filtration rate (0.69±0.04 versus 0.90±0.05 mL/min per gram) without a significant difference in urinary sodium excretion (0.81±0.07 versus 0.86±0.12 μmol/min per gram) compared with normotensive rats. Urinary 8-isoprostane excretion rate (6.8±0.7 versus 4.5±0.3 pg/min per gram) was higher in hypertensive than normotensive rats. Intraarterial infusion of tempol did not alter renal function in normotensive rats. However, tempol significantly decreased renal vascular resistance by 12±2% and urinary 8-isoprostane excretion rate by 24±4% and increased renal blood flow by 10±2%, cortical blood flow by 9±2%, medullary blood flow by 15±6%, glomerular filtration rate by 11±3%, and urinary sodium excretion by 19±5% in hypertensive rats. These data indicate that enhanced O
2
−
activity modulates renal hemodynamics and excretory function during reduced NO production and, thus, contributes to the pathophysiology of the NO-deficient form of hypertension.
Aortic Stiffness, Living Donors, and Renal Transplantation
Authors: Bahous Sola Aoun , Stephan Antoine , Blacher Jacques , Safar Michel E.
Published: January 2006

In subjects with renal disease, reduced renal function and increased arterial stiffness are significantly associated in cross-sectional studies. The relationship is independent of age, blood pressure (BP), and atherosclerosis. Because both variables are independent predictors of cardiovascular risk, time-dependent relationships between them are important to determine. Aortic pulse wave velocity was measured noninvasively by comparison with healthy volunteers in 101 living kidney donors and their 101 corresponding recipients. Healthy volunteers were divided into 2 groups: one was recipient related through familial links and the other was nonrecipient related. Independently of age, gender, and BP, pulse wave velocity was significantly elevated in donors and recipients by comparison with the 2 groups of healthy volunteers. Pulse wave velocity was significantly higher in the recipient-related than in the nonrecipient-related group. Whereas in healthy volunteers, pulse wave velocity was exclusively related to age, gender, and BP, in donors and recipients, it was rather associated with a cluster of cardiovascular risk factors, including smoking habits and plasma glucose. Major factors related to pulse wave velocity were renal: time since nephrectomy (donation date) in donors, in whom pulse pressure was specifically associated with proteinuria, and renal rejection in recipients. Plasma creatinine doubling secondary to chronic allograft nephropathy was significantly associated with renal rejection and donor pulse wave velocity, independent of age. Our findings strongly suggest consistent interactions (including familial factors) between kidney function and arterial stiffness. Assessment of cause–effect relationships and implication of biochemical and/or genetic factors warrant additional studies.
Sustained Reverse Left Ventricular Structural Remodeling With Cardiac Resynchronization at One Year Is a Function of Etiology
Authors: St John Sutton Martin G. , Plappert Ted , Hilpisch Kathryn E. , Abraham William T. , Hayes David L. , Chinchoy Edward
Published: January 2006

Background—

Cardiac resynchronization therapy (CRT) is an effective therapy for patients with moderate to severe heart failure and prolonged QRS duration. The purpose of this study was to determine whether reverse left ventricular (LV) remodeling and symptomatic benefit from CRT were sustained at 12 months, and if so, in what proportion of patients this occurred.

Methods and Results—

Serial Doppler echocardiograms were obtained at baseline and 6 and 12 months after CRT in 228 patients enrolled in the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) trial. Measurements were made of LV end-diastolic (EDV) and end-systolic (ESV) volumes, ejection fraction, LV mass, severity of mitral regurgitation (MR), peak transmitral velocities during early (E wave) and late (A wave) diastolic filling, and myocardial performance index. At both 6 and 12 months, respectively, CRT was associated with reduced LV EDV (
P
<0.0001 and
P
=0.007) and LV ESV (
P
<0.0001 and
P
<0.0001), improved ejection fraction (
P
<0.0001 and
P
<0.0001), regression of LV mass (
P
=0.012 and
P
<0.0001), and reduced MR (
P
<0.0001 and
P
<0.0001). LV filling time, transmitral E/A ratio, and myocardial performance index all improved at 12 months compared with baseline (
P
<0.001,
P
=0.031, and
P
<0.0001). Reverse LV remodeling with CRT occurred in more patients at 6 than at 12 months (74% versus 60%, respectively;
P
<0.05) and was greater in patients with a nonischemic than an ischemic etiology.

Conclusions—

Reverse LV remodeling and symptom benefit with CRT are sustained at 12 months in patients with New York Heart Association class III/IV heart failure but occur to a lesser degree in patients with an ischemic versus a nonischemic etiology, most likely owing to the inexorable progression of ischemic disease.
Intake of Fish and n3 Fatty Acids and Risk of Coronary Heart Disease Among Japanese
Authors: Iso Hiroyasu , Kobayashi Minatsu , Ishihara Junko , Sasaki Satoshi , Okada Katsutoshi , Kita Yoshikuni , Kokubo Yoshihiro , Tsugane Shoichiro
Published: January 2006

Background—

Once- or twice-weekly consumption of fish (or a small amount of fish intake) reduces the risk of coronary heart disease and sudden cardiac death in Western countries. It is uncertain whether a high frequency or large amount of fish intake, as is the case in Japan, further reduces the risk.

Methods and Results—

To examine an association between high intake of fish and n3 polyunsaturated fatty acids and the risk of coronary heart disease, a total of 41 578 Japanese men and women aged 40 to 59 years who were free of prior diagnosis of cardiovascular disease and cancer and who completed a food frequency questionnaire were followed up from 1990–1992 to 2001. After 477 325 person-years of follow-up, 258 incident cases of coronary heart disease (198 definite and 23 probable myocardial infarctions and 37 sudden cardiac deaths) were documented, comprising 196 nonfatal and 62 fatal coronary events. The multivariable hazard ratios (HRs) and 95% confidence intervals in the highest (8 times per week, or median intake=180 g/d) versus lowest (once a week, or median intake=23 g/d) quintiles of fish intake were 0.63 (0.38 to 1.04) for total coronary heart disease, 0.44 (0.24 to 0.81) for definite myocardial infarction, and 1.14 (0.36 to 3.63) for sudden cardiac death. The reduced risk was primarily observed for nonfatal coronary events (HR=0.43 [0.23 to 0.81]) but not for fatal coronary events (HR=1.08 [0.42 to 2.76]). Strong inverse associations existed between dietary intake of n3 fatty acids and risk of definite myocardial infarction (HR=0.35 [0.18 to 0.66]) and nonfatal coronary events (HR=0.33 [0.17 to 0.63]).

Conclusions—

Compared with a modest fish intake of once a week or &20 g/d, a higher intake was associated with substantially reduced risk of coronary heart disease, primarily nonfatal cardiac events, among middle-aged persons.
Statistical Modeling of the Temperatures in the Northern Hemisphere Using Fractional Integration Techniques
Authors: Gil-Alana Luis A.
Published: January 2006

The temperatures in the Northern Hemisphere from 1854 to 1999 have been analyzed in this article by means of a testing procedure that permits one to consider fractional degrees of integration. The tests are valid under general forms of serial correlation and deterministic trends and do not require estimation of the fractional differencing parameter. The results show that the series follows a fractionally integrated process with the order of integration higher than zero and thus implying long memory behavior. The series was decomposed into four different subsamples, and it was observed that the degree of dependence between the observations substantially increased during the twentieth century.
Impact of Sea Surface Temperature and Soil Moisture on Seasonal Rainfall Prediction over the Sahel
Authors: Thiaw Wassila M. , Mo Kingtse C.
Published: January 2006

The ensemble rainfall forecasts over the Sahel for July–September (JAS) from the NCEP Coupled Forecast System (CFS) were evaluated for the period 1981–2002. The comparison with the gauge-based precipitation analysis indicates that the predicted Sahel rainfall is light and exhibits little interannual variability. The rain belt is shifted about 4° southward.

One major source of rainfall errors comes from the erroneous sea surface temperature (SST) forecasts. The systematic SST error pattern has positive errors in the North Pacific and the North Atlantic and negative errors in the tropical Pacific and the southern oceans. It resembles the decadal SST mode, which has a significant influence on rainfall over the Sahel. Because the systematic SST errors were not corrected during the forecasts, persistent errors serve as an additional forcing to the atmosphere.

The second source of error is from the soil moisture feedback, which contributes to the southward shift of rainfall and dryness over West Africa. This was demonstrated by the comparison between simulations (SIMs) and the Atmospheric Model Intercomparison Project (AMIP) run. Both are forced with observed SSTs. The SIMs initialized at the end of June have realistic soil moisture and do not show the southward shift of rainfall. The AMIP, which predicts soil moisture, maintains the dryness through the summer over the Sahel. For AMIP, the decreased rainfall is contributed by the decreased evaporation (E) due to the dry soil and the shift of the large temperature gradients southward. In response, the African easterly jet (AEJ) shifts southward. Since this jet is the primary source of energy for the African waves and their associated mesoscale convective systems, these too shift southward. This negative feedback contributes to increased dryness over the Sahel.
Surface Contribution to Planetary Albedo Variability in Cryosphere Regions
Authors: Qu Xin , Hall Alex
Published: January 2006

Climatological planetary albedo obtained from the International Satellite Cloud Climatology Project (ISCCP) D-series flux dataset is broken down into contributions from the surface and atmosphere in cryosphere regions. The atmosphere accounts for much more of climatological planetary albedo (≥75%) than the surface at all times of the year. The insignificance of the surface contribution over highly reflective cryosphere regions is attributed mostly to the damping effect of the atmosphere. The overlying atmosphere attenuates the surface’s contribution to climatological planetary albedo by reducing the number of solar photons initially reaching the surface and the number of photons initially reflected by the surface that actually reach the top of the atmosphere.

The ISCCP datasets were also used to determine the relative contributions of the surface and atmosphere to seasonal and interannual planetary albedo variability in cryosphere regions. Even damped by the atmosphere to the same degree as in the climatological case, the surface contribution dominates the variability in planetary albedo on seasonal and interannual time scales. The surface accounts for about 75% of the change in climatological planetary albedo from one season to another with similar zenith angle and more than 50% of its interannual variability at nearly all times of the year, especially during seasons with extensive snow and sea ice extent. The dominance of the surface in planetary albedo variability is because surface albedo variability associated with snow and ice fluctuations is significantly larger than atmospheric albedo variability due to cloud fluctuations. The large effect of snow and ice variations on planetary albedo variability suggests that if cloud fields do not change much in a future warmer climate, a retreat of snow cover or sea ice would lead to a significant increase in net incoming solar radiation, resulting in an enhancement of high-latitude climate sensitivity.
Climatology and Interannual Variability of North Atlantic Hurricane Tracks
Authors: Xie Lian , Yan Tingzhuang , Pietrafesa Leonard J. , Morrison John M. , Karl Thomas
Published: January 2006

The spatial and temporal variability of North Atlantic hurricane tracks and its possible association with the annual hurricane landfall frequency along the U.S. East Coast are studied using principal component analysis (PCA) of hurricane track density function (HTDF). The results show that, in addition to the well-documented effects of the El Niño–Southern Oscillation (ENSO) and vertical wind shear (VWS), North Atlantic HTDF is strongly modulated by the dipole mode (DM) of Atlantic sea surface temperature (SST) as well as the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). Specifically, it was found that Atlantic SST DM is the only index that is associated with all top three empirical orthogonal function (EOF) modes of the Atlantic HTDF. ENSO and tropical Atlantic VWS are significantly correlated with the first and the third EOF of the HTDF over the North Atlantic Ocean. The second EOF of North Atlantic HTDF, which represents the “zonal gradient” of North Atlantic hurricane track density, showed no significant correlation with ENSO or with tropical Atlantic VWS. Instead, it is associated with the Atlantic SST DM, and extratropical processes including NAO and AO. Since for a given hurricane season, the preferred hurricane track pattern, together with the overall basinwide hurricane activity, collectively determines the hurricane landfall frequency, the results provide a foundation for the construction of a statistical model that projects the annual number of hurricanes striking the eastern seaboard of the United States.
North Atlantic Oscillation Response to Anomalous Indian Ocean SST in a Coupled GCM
Authors: Bader Jürgen , Latif Mojib
Published: January 2006

The dominant pattern of atmospheric variability in the North Atlantic sector is the North Atlantic Oscillation (NAO). Since the 1970s the NAO has been well characterized by a trend toward its positive phase. Recent atmospheric general circulation model studies have linked this trend to a progressive warming of the Indian Ocean. Unfortunately, a clear mechanism responsible for the change of the NAO could not be given. This study provides further details of the NAO response to Indian Ocean sea surface temperature (SST) anomalies. This is done by conducting experiments with a coupled ocean–atmosphere general circulation model (OAGCM). The authors develop a hypothesis of how the Indian Ocean impacts the NAO.
Reorganization of Tropical Climate during El Niño: A Weak Temperature Gradient Approach
Authors: Lintner Benjamin R. , Chiang John C. H.
Published: January 2006

The applicability of a weak temperature gradient (WTG) formulation for the reorganization of tropical climate during El Niño–Southern Oscillation (ENSO) events is investigated. This idealized dynamical framework solves for the divergent portion of the tropical circulation by assuming a spatially homogeneous perturbation temperature profile and a mass balance constraint applied over the tropical belt. An intermediate-level complexity model [the Quasi-Equilibrium Tropical Circulation Model (QTCM)] configured with the WTG assumptions is used to simulate El Niño conditions and is found to yield an appropriate level of tropospheric warming, a plausible pattern of precipitation anomalies in the tropical Pacific source region of El Niño, and a gross precipitation deficit over the Tropics outside the Pacific (hereafter the “remote Tropics”). Additional tests of the WTG framework with La Niña forcing conditions and enhanced greenhouse gas concentrations support its applicability. However, the ENSO response under the WTG framework fails in some respects when compared to the standard QTCM: in particular, some regional features of the anomalous precipitation response, especially in the remote Tropics, differ markedly between the two model versions. These discrepancies appear to originate in part from the lack of anomalous tropospheric temperature gradients (and circulations) in the framework presented here. Nevertheless, the WTG approach appears to be a useful lowest-order model for the tropical climate adjustment to ENSO. The WTG framework is also used to argue that El Niño may not represent a good proxy for tropical rainfall changes under greenhouse gas warming scenarios because the large-scale subsidence occurring with the tropospheric warming in the El Niño scenario has an effect on rainfall that is distinct from the effect of increased tropospheric temperatures common to both the greenhouse gas warming and El Niño scenarios.
Why Are There Tropical Warm Pools?
Authors: Clement Amy C. , Seager Richard , Murtugudde Raghu
Published: January 2006

Tropical warm pools appear as the primary mode in the distribution of tropical sea surface temperature (SST). Most previous studies have focused on the role of atmospheric processes in homogenizing temperatures in the warm pool and establishing the observed statistical SST distribution. In this paper, a hierarchy of models is used to illustrate both oceanic and atmospheric mechanisms that contribute to the establishment of tropical warm pools. It is found that individual atmospheric processes have competing effects on the SST distribution: atmospheric heat transport tends to homogenize SST, while the spatial structure of atmospheric humidity and surface wind speeds tends to remove homogeneity. The latter effects dominate, and under atmosphere-only processes there is no warm pool. Ocean dynamics counter this effect by homogenizing SST, and it is argued that ocean dynamics is fundamental to the existence of the warm pool. Under easterly wind stress, the thermocline is deep in the west and shallow in the east. Because of this, poleward Ekman transport of water at the surface, compensated by equatorward geostrophic flow below and linked by equatorial upwelling, creates a cold tongue in the east but homogenizes SST in the west, creating a warm pool. High clouds may also homogenize the SST by reducing the surface solar radiation over the warmest water, but the strength of this feedback is quite uncertain. Implications for the role of these processes in climate change are discussed.
Intercomparison of Near-Surface Temperature and Precipitation Extremes in AMIP-2 Simulations, Reanalyses, and Observations
Authors: Kharin Viatcheslav V. , Zwiers Francis W. , Zhang Xuebin
Published: January 2006

The extremes of near-surface temperature and 24-h and 5-day mean precipitation rates are examined in simulations performed with atmospheric general circulation models (AGCMs) participating in the second phase of the Atmospheric Model Intercomparison Project (AMIP-2). The extremes are evaluated in terms of 20-yr return values of annual extremes. The model results are validated against the European Centre for Medium-Range Weather Forecasts and National Centers for Environmental Prediction reanalyses and station data. Precipitation extremes are also validated against the pentad dataset of the Global Precipitation Climatology Project, which is a blend of rain gauge observations, satellite data, and model output.

On the whole, the AGCMs appear to simulate temperature extremes reasonably well. Model disagreements are larger for cold extremes than for warm extremes, particularly in wet and cloudy regions, and over sea ice and snow-covered areas. Many models exhibit an exaggerated clustering behavior for temperatures near the freezing point of water. Precipitation extremes are less reliably reproduced by the models and reanalyses. The largest disagreements are found in the Tropics where the parameterizations of deep convection affect the simulated daily precipitation extremes.
Tropical–North Pacific Climate Linkages over the Past Four Centuries*
Authors: D’Arrigo Rosanne , Wilson Rob , Deser Clara , Wiles Gregory , Cook Edward , Villalba Ricardo , Tudhope Alexander , Cole Julia , Linsley Braddock
Published: January 2006

Analyses of instrumental data demonstrate robust linkages between decadal-scale North Pacific and tropical Indo-Pacific climatic variability. These linkages encompass common regime shifts, including the noteworthy 1976 transition in Pacific climate. However, information on Pacific decadal variability and the tropical high-latitude climate connection is limited prior to the twentieth century. Herein tree-ring analysis is employed to extend the understanding of North Pacific climatic variability and related tropical linkages over the past four centuries. To this end, a tree-ring reconstruction of the December–May North Pacific index (NPI)—an index of the atmospheric circulation related to the Aleutian low pressure cell—is presented (1600–1983). The NPI reconstruction shows evidence for the three regime shifts seen in the instrumental NPI data, and for seven events in prior centuries. It correlates significantly with both instrumental tropical climate indices and a coral-based reconstruction of an optimal tropical Indo-Pacific climate index, supporting evidence for a tropical–North Pacific link extending as far west as the western Indian Ocean. The coral-based reconstruction (1781–1993) shows the twentieth-century regime shifts evident in the instrumental NPI and instrumental tropical Indo-Pacific climate index, and three previous shifts. Changes in the strength of correlation between the reconstructions over time, and the different identified shifts in both series prior to the twentieth century, suggest a varying tropical influence on North Pacific climate, with greater influence in the twentieth century. One likely mechanism is the low-frequency variability of the El Niño–Southern Oscillation (ENSO) and its varying impact on Indo-Pacific climate.
Twentieth-Century Drought in the Conterminous United States
Authors: Andreadis Konstantinos M. , Clark Elizabeth A. , Wood Andrew W. , Hamlet Alan F. , Lettenmaier Dennis P.
Published: January 2006

Droughts can be characterized by their severity, frequency and duration, and areal extent. Depth–area–duration analysis, widely used to characterize precipitation extremes, provides a basis for the evaluation of drought severity when storm depth is replaced by an appropriate measure of drought severity. Gridded precipitation and temperature data were used to force a physically based macroscale hydrologic model at 1/2° spatial resolution over the continental United States, and construct a drought history from 1920 to 2003 based on the model-simulated soil moisture and runoff. A clustering algorithm was used to identify individual drought events and their spatial extent from monthly summaries of the simulated data. A series of severity–area–duration (SAD) curves were constructed to relate the area of each drought to its severity. An envelope of the most severe drought events in terms of their SAD characteristics was then constructed. The results show that (a) the droughts of the 1930s and 1950s were the most severe of the twentieth century for large areas; (b) the early 2000s drought in the western United States is among the most severe in the period of record, especially for small areas and short durations; (c) the most severe agricultural droughts were also among the most severe hydrologic droughts, however, the early 2000s western U.S. drought occupies a larger portion of the hydrologic drought envelope curve than does its agricultural companion; and (d) runoff tends to recover in response to precipitation more quickly than soil moisture, so the severity of hydrologic drought during the 1930s and 1950s was dampened by short wet spells, while the severity of the early 2000s drought remained high because of the relative absence of these short-term phenomena.
A Comparison of the Triangle Retrieval and Variational Data Assimilation Methods for Surface Turbulent Flux Estimation
Authors: Margulis Steven A. , Kim Jongyoun , Hogue Terri
Published: January 2006

Future operational frameworks for estimating surface turbulent fluxes over the necessary spatial and temporal scales will undoubtedly require the use of remote sensing products. Techniques used to estimate surface fluxes from radiometric surface temperature generally fall into two categories: retrieval-based and data assimilation approaches. Up to this point, there has been little comparison between retrieval- and assimilation-based techniques. In this note, the triangle retrieval method is compared to a variational data assimilation approach for estimating surface turbulent fluxes from radiometric surface temperature observations. Results from a set of synthetic experiments and an application using real data from the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) site indicate that the assimilation approach performs slightly better than the triangle method because of the robustness of the estimation to measurement errors and parsimony of the system model, which leads to fewer sources of structural model errors. Future comparison work using retrieval and data assimilation algorithms will provide more insight into the optimal approach for diagnosis of land surface fluxes using remote sensing observations.
Probabilistic and Ensemble Representations of the Uncertainty in an IR/Microwave Satellite Precipitation Product
Authors: Bellerby Timothy J. , Sun Jizhong
Published: January 2006

While current satellite techniques are theoretically capable of producing precipitation estimates to image pixel resolutions, significant uncertainty is present in such high-resolution products. This uncertainty is frequently difficult to characterize using scalar measures of additive error. This paper describes the development of a methodology to more fully represent the uncertainty in satellite precipitation retrievals. The methodology derives conditional probability distribution functions of rainfall on a pixel-by-pixel basis. This array of distribution functions is then combined with a simple model of the spatiotemporal covariance structure of the uncertainty in the precipitation field to stochastically generate an ensemble precipitation product. Each element of the ensemble represents an equiprobable realization of the precipitation field that is consistent with the original satellite data while containing a random element commensurate with the uncertainty in that field. The technique has been tested using data from the Tropical Rainfall Measuring Mission (TRMM) Texas and Florida Underflight Experiment (TEFLUN-B) field campaign.