bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced airway dilation by positive-pressure inflation of the lungs compared with active deep inspiration in patients with asthma
Authors: Slats Annelies M. , Janssen Kirsten , de Jeu Ronald C. , van der Plas Dirk T. , Schot Robert , van den Aardweg Joost G. , Sterk Peter J.
Published: September 2008

Deep inspiration temporarily reduces induced airways obstruction in healthy subjects. This bronchodilatory effect of deep inspiration is impaired in asthma. Passive machine-assisted lung inflation may augment bronchodilation compared with an active deep inspiration in patients with asthma by either opening closed airways or by reducing fluid flux across the airway wall during deep inspiration, and thereby increasing the tethering forces on the airway wall. We recruited 24 patients with asthma [18–46 yr old, forced expiratory volume in 1 s (FEV1) > 70% predicted; provocative concentration of methacholine inducing a 20% fall in FEV1 (PC20) < 8 mg/ml], with either an impaired ( n = 12) or an intact ( n = 12) bronchodilatory response to deep inspiration. Two methacholine challenges were performed on separate days. At a 50% increase in respiratory resistance (forced oscillation technique at 8 Hz), the change in resistance by a positive-pressure inflation (computer-driven syringe) or an active deep inspiration was measured in randomized order. The reduction in resistance by positive-pressure inflation was significantly greater than by active deep inspiration in the impaired deep inspiration response group (mean change ± SE: −0.6 ± 0.1 vs. −0.03 ± 0.2 cmH2O·l−1·s, P = 0.002). No significant difference was found between positive-pressure inflation and active deep inspiration in the intact deep inspiration response group (−0.6 ± 0.2 vs. −1.0 ± 0.3 cmH2O·l−1·s, P = 0.18). Positive-pressure inflation of the lungs can significantly enhance deep inspiration-induced bronchodilation in patients with asthma.
Fat adaptation followed by carbohydrate restoration increases AMPK activity in skeletal muscle from trained humans
Authors: Yeo Wee Kian , Lessard Sarah J. , Chen Zhi-Ping , Garnham Andrew P. , Burke Louise M. , Rivas Donato A. , Kemp Bruce E. , Hawley John A.
Published: September 2008

We have previously reported that 5 days of a high-fat diet followed by 1 day of high-carbohydrate intake (Fat-adapt) increased rates of fat oxidation and decreased rates of muscle glycogenolysis during submaximal cycling compared with consumption of an isoenergetic high-carbohydrate diet (HCHO) for 6 days (Burke et al. J Appl Physiol 89: 2413–2421, 2000; Stellingwerff et al. Am J Physiol Endocrinol Metab 290: E380–E388, 2006). To determine potential mechanisms underlying shifts in substrate selection, eight trained subjects performed Fat-adapt and HCHO. On day 7, subjects performed 1-h cycling at 70% peak O2uptake. Muscle biopsies were taken immediately before and after exercise. Resting muscle glycogen content was similar between treatments, but muscle triglyceride levels were higher after Fat-adapt ( P < 0.05). Resting AMPK-α1and -α2activity was higher after Fat-adapt ( P = 0.02 and P = 0.05, respectively), while the phosphorylation of AMPK's downstream target, acetyl-CoA carboxylase (pACC at Ser221), tended to be elevated after Fat-adapt ( P = 0.09). Both the respiratory exchange ratio ( P < 0.01) and muscle glycogen utilization ( P < 0.05) were lower during exercise after Fat-adapt. Exercise increased AMPK-α1activity after HCHO ( P = 0.03) but not Fat-adapt. Exercise was associated with an increase in pACC at Ser221for both dietary treatments ( P < 0.05), with postexercise pACC Ser221higher after Fat-adapt ( P = 0.02). In conclusion, compared with HCHO, Fat-adapt increased resting muscle triglyceride stores and resting AMPK-α1and -α2activity. Fat-adapt also resulted in higher rates of whole body fat oxidation, reduced muscle glycogenolysis, and attenuated the exercise-induced rise in AMPK-α1and AMPK-α2activity compared with HCHO. Our results demonstrate that AMPK-α1and AMPK-α2activity and fuel selection in skeletal muscle in response to exercise can be manipulated by diet and/or the interactive effects of diet and exercise training.
Exercise enhances the proliferation of neural stem cells and neurite growth and survival of neuronal progenitor cells in dentate gyrus of middle-aged mice
Authors: Wu Chih-Wei , Chang Ya-Ting , Yu Lung , Chen Hsiun-ing , Jen Chauying J. , Wu Shih-Ying , Lo Chen-Peng , Kuo Yu-Min
Published: September 2008

Aging is an important determinant of adult hippocampal neurogenesis as the proliferation of neural stem/precursor cells (NSCs) declines dramatically before middle age. Contrary to this, physical exercise is known to promote adult hippocampal neurogenesis. The objective of this study is to investigate the effects of mandatory treadmill running (TR) on neurogenesis, including 1) NSCs proliferation, 2) neurite outgrowth of neuronal progenitor cells, and 3) the survival of newborn neurons in dentate area of middle-aged animals. Compared with 3-mo-old mice, numbers of mitotic cells and neuronal progenitor cells decreased dramatically by middle age and remained at low levels after middle age. Five weeks of TR not only increased NSC proliferation and the number of immature neurons but also promoted the maturation and survival of immature neurons in middle-aged mice. The neurogenic and neurotrophic effects of TR were not due to the reduction of the age-related elevation of serum corticosterone. Significantly, 5 wk of TR restored the age-dependent decline of brain-derived neurotrophic factor and its receptor, TrkB, which are known to promote neuronal differentiation and survival. Taken together, mandatory running exercise alters the brain chemistries of middle-aged animals toward an environment that is favorable to NSC proliferation, survival, and maturation.
Age-dependent increase in oxidative stress in gastrocnemius muscle with unloading
Authors: Siu Parco M. , Pistilli Emidio E. , Alway Stephen E.
Published: September 2008

Oxidative stress increases during unloading in muscle from young adult rats. The present study examined the markers of oxidative stress and antioxidant enzyme gene and protein expressions in medial gastrocnemius muscles of aged and young adult (30 and 6 mo of age) Fischer 344 × Brown Norway rats after 14 days of hindlimb suspension. Medial gastrocnemius muscle weight was decreased by ∼30% in young adult and aged rats following suspension. When muscle weight was normalized to animal body weight, it was reduced by 12% and 22% in young adult and aged rats, respectively, after suspension. Comparisons between young adult and aged control animals demonstrated a 25% and 51% decline in muscle mass when expressed as absolute muscle weight and muscle weight normalized to the animal body weight, respectively. H2O2content was elevated by 43% while Mn superoxide dismutase (MnSOD) protein content was reduced by 28% in suspended muscles compared with control muscles exclusively in the aged animals. Suspended muscles had greater content of malondialdehyde (MDA)/4-hydroxyalkenals (4-HAE) (29% and 58% increase in young adult and aged rats, respectively), nitrotyrosine (76% and 65% increase in young adult and aged rats, respectively), and catalase activity (69% and 43% increase in young adult and aged rats, respectively) relative to control muscles. Changes in oxidative stress markers MDA/4-HAE, H2O2, and MnSOD protein contents in response to hindlimb unloading occurred in an age-dependent manner. These findings are consistent with the hypotheses that oxidative stress has a role in mediating disuse-induced and sarcopenia-associated muscle losses. Our data suggest that aging may predispose skeletal muscle to increased levels of oxidative stress both at rest and during unloading.
The Role of Chemokines in Transplant Graft Arterial Disease
Authors: Shimizu Koichi , Mitchell Richard N.
Published: September 2008

Despite the development of effective immunosuppressive therapy, transplant graft arterial disease (GAD) remains the major limitation to long-term graft survival. Multiple immune and nonimmune risk factors contribute to this vasculopathic intimal hyperplastic process. Thus, initial interplay between host inflammatory cells and donor endothelial cells triggers alloimmune responses, whereas alloantigen-independent factors such as prolonged ischemia, surgical manipulation, ischemia-reperfusion injury, and hyperlipidemia enhance the antigen-dependent events. Intrinsic to all stages of this process are chemokines, a family of 8- to 10-kDa proteins mediating directional migration of immune cells to sites of inflammation and injury. Beyond their role in immune-cell chemotaxis, chemokines also contribute to cellular activation, vascular remodeling, and angiogenesis. Expression of chemokines and their cognate receptors in allografts correlates with acute organ rejection, as well as GAD. Moreover, chemokine or chemokine receptor blockade prolongs graft survival and attenuates GAD in experimental models. Further studies will likely confirm a substantial utility for antichemokine therapy in human organ transplantation.
Inhibition of Tumor Necrosis Factor α–Stimulated Monocyte Adhesion to Human Aortic Endothelial Cells by AMP-Activated Protein Kinase
Authors: Ewart Marie-Ann , Kohlhaas Christine F. , Salt Ian P.
Published: September 2008

Objective—

Proatherosclerotic adhesion of leukocytes to the endothelium is attenuated by NO. As AMP-activated protein kinase (AMPK) regulates endothelial NO synthesis, we investigated the modulation of adhesion to cultured human aortic endothelial cells (HAECs) by AMPK.

Methods and Results—

HAECs incubated with the AMPK activator, AICAR, or expressing constitutively active AMPK demonstrated reduced TNFα-stimulated adhesion of promonocytic U-937 cells. Rapid inhibition of TNFα-stimulated U-937 cell adhesion by AICAR was NO-dependent, associated with unaltered cell surface adhesion molecule expression, and reduced MCP-1 secretion by HAECs. In contrast, inhibition of TNFα-stimulated U-937 cell adhesion by prolonged AMPK activation was NO-independent and associated with reduced cell surface adhesion molecule expression.

Conclusions—

AMPK activation in HAECs inhibits TNFα-stimulated leukocyte adhesion by a rapid NO-dependent mechanism associated with reduced MCP-1 secretion and a late NO-independent mechanism whereby adhesion molecule expression, in particular E-selectin, is suppressed.
Function of Ca
2+
Release Channels in Purkinje Cells That Survive in the Infarcted Canine Heart
Authors: Hirose Masanori , Stuyvers Bruno D. , Dun Wen , ter Keurs Henk E.D.J. , Boyden Penelope A.
Published: September 2008

Background—

Triggered Purkinje ectopy can lead to the initiation of serious ventricular arrhythmias in post–myocardial infarction patients. In the canine model, Purkinje cells from the subendocardial border of the healing infarcted heart can initiate ventricular arrhythmias. Intracellular Ca
2+
abnormalities underlie these arrhythmias, yet the subcellular reasons for these abnormalities remain unknown.

Methods and Results—

Using 2D confocal microscopy, we directly quantify and compare typical spontaneous Ca
2+
events in specific subcellular regions of normal Purkinje cells with those Purkinje cells from the subendocardium of the 48-hour infarcted canine heart (IZPCs). The Ca
2+
event rate was higher in the subsarcolemmal region of IZPCs when compared with normal Purkinje cells; IZPC amplitudes were higher, yet the spatial extents of these events were similar. The amplitude of caffeine-releasable Ca
2+
in either the subsarcolemmal or core regions of IZPCs did not differ from normal Purkinje cells, suggesting that Ca
2+
overload was not related to the frequency change. In permeabilized Purkinje cells from both groups, the event rate was related to free [Ca
2+
] in both subsarcolemmal and core, but in IZPCs, this event rate was significantly increased at each free Ca
2+
, suggesting an enhanced sensitivity to Ca
2+
release. Furthermore, decays of wide long lasting Ca
2+
release events in IZPC’s core were significantly accelerated compared with those in normal Purkinje cells. JTV519 (K201) suppressed IZPC cell wide Ca
2+
waves as well as normalized the enhanced event rate and its response to free Ca
2+
.

Conclusions—

Increased spontaneous Ca
2+
release events in IZPCs are due to uniform regionally increased Ca
2+
release channel sensitivity to Ca
2+
without a change in sarcoplasmic reticulum content. In addition, Ca
2+
reuptake in IZPCs is accelerated. These properties would lower the threshold of Ca
2+
release channels, setting the stage for the highly frequent arrhythmogenic cell wide Ca
2+
waves observed in IZPCs.
In a Swine Model, Chest Compressions Cause Ventricular Capture and, By Means of a Long-Short Sequence, Ventricular Fibrillation
Authors: Osorio Jose , Dosdall Derek J. , Robichaux Robert P. , Tabereaux Paul B. , Ideker Raymond E.
Published: September 2008

Background—

During resuscitation, fibrillation often recurs. In swine, we studied refibrillation after long-duration ventricular fibrillation, investigating an association with chest compressions (CCs).

Methods and Results—

In protocol A, 47 episodes of long-duration ventricular fibrillation lasting at least 2.5 minutes were induced in 8 animals. After defibrillation, CCs were required for 35 episodes and delivered with a pneumatic device (Lucas cardiopulmonary resuscitation). In 9 episodes, refibrillation occurred within 2 seconds of CC initiation (group 1) and in 26 episodes, CCs were delivered without refibrillation (group 2). From the ECG and intracardiac electrodes, the RR interval preceding CCs, the shortest cycle length during the first 2 CCs (short), and the preceding cycle length (long) were measured. A similar study was conducted in 3 more animals without intracardiac catheters (protocol B). In protocol A, the mean RR before CC was 665�292 ms in group 1 and 769�316 in group 2. CCs stimulated ventricular beats in all 35 episodes. The short and long intervals were shorter in group 1 (215�31 and 552�210 ms) than in group 2 (402�153 and 699�147 ms) (
P
=0.009 and
P
=0.04, respectively). The prematurity index (short/RR) was lower in group 1 than in group 2 (0.35�0.09 vs 0.58�0.21;
P
<0.01). A short interval <231 ms predicted refibrillation with 88% sensitivity and 91% specificity. In protocol B, CCs were required in 11 episodes, causing ventricular stimulation in all of them and ventricular fibrillation within the first 2 CCs in 3.

Conclusions—

Under some conditions, CC during resuscitation can stimulate the ventricles and initiate ventricular fibrillation by a long-short sequence.
Scleraxis Is Required for Cell Lineage Differentiation and Extracellular Matrix Remodeling During Murine Heart Valve Formation In Vivo
Authors: Levay Agata K. , Peacock Jacqueline D. , Lu Yinhui , Koch Manuel , Hinton Robert B. , Kadler Karl E. , Lincoln Joy
Published: September 2008

Heart valve structures, derived from mesenchyme precursor cells, are composed of differentiated cell types and extracellular matrix arranged to facilitate valve function. Scleraxis (scx) is a transcription factor required for tendon cell differentiation and matrix organization. This study identified high levels of
scx
expression in remodeling heart valve structures at embryonic day 15.5 through postnatal stages using
scx-GFP
reporter mice and determined the in vivo function using mice null for
scx
.
Scx
−/−
mice display significantly thickened heart valve structures from embryonic day 17.5, and valves from mutant mice show alterations in valve precursor cell differentiation and matrix organization. This is indicated by decreased expression of the tendon-related collagen type XIV, increased expression of cartilage-associated genes including
sox9
, as well as persistent expression of mesenchyme cell markers including
msx1
and
snai1
. In addition, ultrastructure analysis reveals disarray of extracellular matrix and collagen fiber organization within the valve leaflet. Thickened valve structures and increased expression of matrix remodeling genes characteristic of human heart valve disease are observed in juvenile
scx
−/−
mice. In addition, excessive collagen deposition in annular structures within the atrioventricular junction is observed. Collectively, our studies have identified an in vivo requirement for scx during valvulogenesis and demonstrate its role in cell lineage differentiation and matrix distribution in remodeling valve structures.
Acceleration of Crossbridge Kinetics by Protein Kinase A Phosphorylation of Cardiac Myosin Binding Protein C Modulates Cardiac Function
Authors: Tong Carl W. , Stelzer Julian E. , Greaser Marion L. , Powers Patricia A. , Moss Richard L.
Published: September 2008

Normal cardiac function requires dynamic modulation of contraction. β1-Adrenergic–induced protein kinase (PK)A phosphorylation of cardiac myosin binding protein (cMyBP)-C may regulate crossbridge kinetics to modulate contraction. We tested this idea with mechanical measurements and echocardiography in a mouse model lacking 3 PKA sites on cMyBP-C, ie, cMyBP-C(t3SA). We developed the model by transgenic expression of mutant cMyBP-C with Ser-to-Ala mutations on the cMyBP-C knockout background. Western blots, immunofluorescence, and in vitro phosphorylation combined to show that non–PKA-phosphorylatable cMyBP-C expressed at 74% compared to normal wild-type (WT) and was correctly positioned in the sarcomeres. Similar expression of WT cMyBP-C at 72% served as control, ie, cMyBP-C(tWT). Skinned myocardium responded to stretch with an immediate increase in force, followed by a transient relaxation of force and finally a delayed development of force, ie, stretch activation. The rate constants of relaxation,
k
rel
(s-1), and delayed force development,
k
df
(s-1), in the stretch activation response are indicators of crossbridge cycling kinetics. cMyBP-C(t3SA) myocardium had baseline
k
rel
and
k
df
similar to WT myocardium, but, unlike WT,
k
rel
and
k
df
were not accelerated by PKA treatment. Reduced dobutamine augmentation of systolic function in cMyBP-C(t3SA) hearts during echocardiography corroborated the stretch activation findings. Furthermore, cMyBP-C(t3SA) hearts exhibited basal echocardiographic findings of systolic dysfunction, diastolic dysfunction, and hypertrophy. Conversely, cMyBP-C(tWT) hearts performed similar to WT. Thus, PKA phosphorylation of cMyBP-C accelerates crossbridge kinetics and loss of this regulation leads to cardiac dysfunction.
Upstream Stimulatory Factor Is Required for Human Angiotensinogen Expression and Differential Regulation by the A−20C Polymorphism
Authors: Dickson Matthew E. , Tian Xin , Liu Xuebo , Davis Deborah R. , Sigmund Curt D.
Published: September 2008

Among naturally occurring polymorphisms in the 5′ flanking region of the human angiotensinogen (AGT) gene, the −20 and −217 polymorphisms have the strongest effects on AGT regulation in AGT-expressing cells derived from liver, kidney, brain, and fat. These polymorphisms may affect allele-specific transcription factor binding, and the high-expressing alleles are both relatively common. We show herein that the −20C allele has higher transcriptional activity than −20A, and the −20A allele confers no additional transactivation potential beyond that of a mutated vector. Gel-shift assays show that upstream stimulatory factor (USF)1 and USF2 preferentially bind the −20C allele, whereas the −20A allele retains a low affinity USF binding site. Plasmid immunoprecipitation assays confirmed preferential association of USF1 with the −20C allele in transfected HepG2 cells. Chromatin immunoprecipitation confirmed that USF1 binds to the endogenous AGT −20C allele in CCF cells, the only cell line tested that carries the −20C allele, and to the human AGT promoter in liver and adipose tissue from transgenic mice. Transduction of AGT-expressing cells with short hairpin RNAs specifically targeting USF1 or USF2, resulted in cell- and allele-specific attenuation of AGT promoter activity. In vivo, knockdown of USF expression in the liver of transgenic mice expressing the −20C allele of AGT resulted in lower AGT expression, a decrease in circulating human AGT protein but no change in expression of GAPDH or hepatocyte nuclear factor-4α. We conclude that USF1 functionally and differentially regulates AGT expression via the −20 polymorphism and that the differential expression exhibited by −20 can be accounted for by differential association with USF1.
Vascular Endothelial Growth Factor-A Specifies Formation of Native Collaterals and Regulates Collateral Growth in Ischemia
Authors: Clayton Jason A. , Chalothorn Dan , Faber James E.
Published: September 2008

The density of native (preexisting) collaterals and their capacity to enlarge into large conduit arteries in ischemia (arteriogenesis) are major determinants of the severity of tissue injury in occlusive disease. Mechanisms directing arteriogenesis remain unclear. Moreover, nothing is known about how native collaterals form in healthy tissue. Evidence suggests vascular endothelial growth factor (VEGF), which is important in embryonic vascular patterning and ischemic angiogenesis, may contribute to native collateral formation and arteriogenesis. Therefore, we examined mice heterozygous for VEGF receptor-1 (VEGFR-1
+/−
), VEGF receptor-2 (VEGFR-2
+/−
), and overexpressing (VEGF
hi/+
) and underexpressing VEGF-A (VEGF
lo/+
). Recovery from hindlimb ischemia was followed for 21 days after femoral artery ligation. All statements below are
P
<0.05. Compared to wild-type mice, VEGFR-2
+/−
showed similar: ischemic scores, recovery of hindlimb perfusion, pericollateral leukocytes, collateral enlargement, and angiogenesis. In contrast, VEGFR-1
+/−
showed impaired: perfusion recovery, pericollateral leukocytes, collateral enlargement, worse ischemic scores, and comparable angiogenesis. Compared to wild-type mice, VEGF
lo/+
had 2-fold lower perfusion immediately after ligation (suggesting fewer native collaterals which was confirmed by angiography) and blunted recovery of perfusion. VEGF
hi/+
mice had 3-fold greater perfusion immediately after ligation, more native collaterals, and improved recovery of perfusion. These differences were confirmed in the cerebral pial cortical circulation where, compared to VEGF
hi/+
mice, VEGF
lo/+
formed fewer collaterals during the perinatal period when adult density was established, and had 2-fold larger infarctions after middle cerebral artery ligation. Our findings indicate VEGF and VEGFR-1 are determinants of arteriogenesis. Moreover, we describe the first signaling molecule, VEGF-A, that specifies formation of native collaterals in healthy tissues.
Ignorance Is Bliss: Attitudinal Aspects of the Judgment according to Works in Matthew 25:31-46
Authors: Grindheim Sigurd
Published: September 2008

This paper argues that the righteous in Matt 25:31-46 stand out not only by their works of mercy, but also by their attitudes. Comparable descriptions of judgment emphasize the self-confidence of the righteous, based on their own knowledge of their good deeds. In contrast, those acquitted in Matt 25:31-46 are characterized by their ignorance of their own righteousness and their overall inability to help themselves. The passage therefore serves as a fitting conclusion to the teaching on discipleship in the Gospel of Matthew, contrasting the true disciples with the hypocrites (cf. 7:21-23) and bringing together the twin Matthean emphases on the faith of the helpless and the works of the righteous.
Text-Critical and Intertextual Remarks on 1 Tim 2:8-10
Authors: Zamfir Korinna , Verheyden Joseph
Published: September 2008

After reassessing the various ways of dealing with the ellipsis in 1 Tim 2:9, it is argued that βoνλoμαι πρoσενχεσαι offers a plausible resolution. Yet the ambiguity of the text suggests that 1 Tim 2:8-15 resulted from using several sources. The intertextual analysis shows that 1 Timothy very likely used as a pre-text the cultic rule found in 1 Cor 11 and its context. A second pre-text consists of a station code tradition and of Neo-Pythagorean exhortations. This complex intertextual enterprise allows 1 Tim to "correct" Paul's more permissive attitude regarding the role men and women can play in public worship.
Gust Factors and Turbulence Intensities for the Tropical Cyclone Environment
Authors: Yu Bo , Gan Chowdhury Arindam
Published: September 2008

Gust factors are used to convert peak wind speeds averaged over a relatively short period (e.g., 3 s) to mean wind speeds averaged over a relatively long reference period (e.g., 1 h) or vice versa. Such conversions are needed for engineering, climatological, or forecasting purposes. In this paper, gust factors in tropical cyclone (TC) winds are estimated from Florida Coastal Monitoring Program (FCMP) observations of near-surface TC wind speeds representative of flow over the sea surface and over open flat terrain in coastal areas. Comparisons are made with gust factors in extratropical winds over open flat terrain that are available in the literature. According to the results of the study, for gust durations of less than 20 s, the Durst model underestimates, and the Krayer–Marshall model overestimates, gust factors of TC winds over surfaces with roughness specified in the American Society of Civil Engineers (ASCE) 7 Standard Commentary as typical of open terrain. Consideration should be given to these findings when updating the gust factors provided in the ASCE 7 Standard Commentary. The study also compares gust factors in TC winds obtained from FCMP data with gust factors in extratropical winds obtained from near-surface wind data collected at eight Automated Surface Observing System (ASOS) stations and concludes that, depending upon terrain roughness, gust factors in TC winds can be higher by about 10%–15% than gust factors in extratropical winds. The study also presents FCMP-based estimates of turbulence intensities and their variability and shows that turbulence intensities in TC winds increase as the terrain roughness increases. The longitudinal turbulence intensity can vary from storm to storm and can exceed its typical value by as much as 20%. It is recommended that future TC wind measurement campaigns obtain temperature data usable for stratification estimation purposes, as well as information on waves and storm surge upwind of the anemometer towers.
A Statistical Downscaling Model for Southern Australia Winter Rainfall
Authors: Li Yun , Smith Ian
Published: September 2008

A technique for obtaining downscaled rainfall projections from climate model simulations is described. This technique makes use of the close association between mean sea level pressure (MSLP) patterns and rainfall over southern Australia during winter. Principal components of seasonal mean MSLP anomalies are linked to observed rainfall anomalies at regional, gridpoint, and point scales. A maximum of four components is sufficient to capture a relatively large fraction of the observed variance in rainfall at most locations. These are used to interpret the MSLP patterns from a single climate model, which has been used to simulate both present-day and future climate. The resulting downscaled values provide 1) a closer representation of the observed present-day rainfall than the raw climate model values and 2) alternative estimates of future changes to rainfall that arise owing to changes in mean MSLP. While decreases are simulated for later this century (under a single emissions scenario), the downscaled values, in percentage terms, tend to be less.
Nonlinear Climate and Hydrological Responses to Aerosol Effects
Authors: Ming Yi , Ramaswamy V.
Published: September 2008

The equilibrium temperature and hydrological responses to the total aerosol effects (i.e., direct, semidirect, and indirect effects) are studied using a modified version of the Geophysical Fluid Dynamics Laboratory atmosphere general circulation model (AM2.1) coupled to a mixed layer ocean model. The treatment of aerosol–liquid cloud interactions and associated indirect effects is based upon a prognostic scheme of cloud droplet number concentration, with an explicit representation of cloud condensation nuclei activation involving sulfate, organic carbon, and sea salt aerosols. Increasing aerosols from preindustrial (1860) to present-day (1990) levels leads to a decrease of 1.9 K in the global annual mean surface temperature. The cooling is relatively strong over the Northern Hemisphere midlatitude land owing to the high aerosol burden there, while being amplified at high latitudes. When being subject to aerosols and radiatively active gases (i.e., well-mixed greenhouse gases and ozone) simultaneously, the model climate behaves nonlinearly; the simulated increase in surface temperature (0.55 K) is considerably less than the arithmetic sum of separate aerosol and gas effects (0.86 K). The thermal responses are accompanied by the nonlinear changes in cloud fields, which are amplified owing to the surface albedo feedback at high latitudes. The two effects completely offset each other in the Northern Hemisphere, while gas effect is dominant in the Southern Hemisphere. Both factors are crucial in shaping the regional responses. Interhemispheric asymmetry in aerosol-induced cooling yields a southward shift of the intertropical convergence zone, thus giving rise to a significant reduction in precipitation north of the equator, and an increase to the south. The simulations show that the change of precipitation in response to the simultaneous increases in aerosols and gases not only largely follows the same pattern as that for aerosols alone, but that it is also substantially strengthened in terms of magnitude south of 10°N. This is quite different from the damping expected from adding up individual responses, and further indicates the nonlinearity in the model’s hydrological response.
Spatial Coherence of Monsoon Onset over Western and Central Sahel (1950–2000)
Authors: Marteau Romain , Moron Vincent , Philippon Nathalie
Published: September 2008

The spatial coherence of boreal monsoon onset over the western and central Sahel (Senegal, Mali, Burkina Faso) is studied through the analysis of daily rainfall data for 103 stations from 1950 to 2000. Onset date is defined using a local agronomic definition, that is, the first wet day (>1 mm) of 1 or 2 consecutive days receiving at least 20 mm without a 7-day dry spell receiving less than 5 mm in the following 20 days. Changing either the length or the amplitude of the initial wet spell, or both, or the length of the following dry spell modifies the long-term mean of local-scale onset date but has only a weak impact either on its interannual variability or its spatial coherence. Onset date exhibits a seasonal progression from southern Burkina Faso (mid-May) to northwestern Senegal and Saharian edges (early August). Interannual variability of the local-scale onset date does not seem to be strongly spatially coherent. The amount of common or covariant signal across the stations is far weaker than the interstation noise at the interannual time scale. In particular, a systematic spatially consistent advance or delay of the onset is hardly observed across the whole western and central Sahel. In consequence, the seasonal predictability of local-scale onset over the western and central Sahel associated, for example, with large-scale sea surface temperatures, is, at best, weak.
Role of Subtropical Precipitation Anomalies in Maintaining the Summertime Meridional Teleconnection over the Western North Pacific and East Asia
Authors: Lu Riyu , Lin Zhongda
Published: September 2008

The meridional teleconnection patterns over the western North Pacific and East Asia (WNP–EA) during summer have a predominant role in affecting East Asian climate on the interannual time scale. A well-known seesaw pattern of tropical–subtropical precipitation is associated with the meridional teleconnection, and the subtropical precipitation anomaly has been previously viewed as a result of anomalous circulations associated with the teleconnection.

In this study, however, the authors suggest that subtropical precipitation anomalies, in turn, can significantly affect large-scale circulations and may be crucial for maintenance of the meridional teleconnection. Diagnosis by using observational and reanalysis data indicates that the meridional teleconnection patterns are clearer in summers when the subtropical rainfall anomalies are greater. The simulated results by a linear baroclinic model indicate that a subtropical heat source, which is equivalent to the diagnosed positive subtropical precipitation anomaly, induces zonally elongated zonal wind anomalies that resemble the diagnosed ones in both the upper and lower troposphere over the extratropical WNP–EA. The simulated results also indicate that the horizontal and vertical structures of circulation responses are insensitive to the locations and shapes of imposed subtropical heat anomalies, which implies the important role of basic flow in circulation responses. This study suggests that, for confidential dynamical seasonal forecasting in East Asia, general circulation models should be required to capture the features of interannual subtropical rainfall variability and basic-state flows in WNP–EA.
Is the Atmosphere Interesting? A Projection Pursuit Study of the Circulation in the Northern Hemisphere Winter
Authors: Christiansen Bo
Published: September 2008

The Northern Hemisphere winter circulation is probed for deviations from Gaussianity. A projection pursuit approach is applied that searches for directions in phase space that maximize an index of interest. Different indices gauging different aspects of non-Gaussianity such as flatness, bimodality, and multimodality are considered. The projection pursuit approach allows high-dimensional data spaces to be investigated and it therefore complements previous studies that usually have been confined to spaces of a few dimensions. Both stratospheric and tropospheric circulations are studied at daily, monthly, and annual time scales.

The statistical significance of the results is considered by a Monte Carlo method where results from the atmospheric data are compared with results from Gaussian distributed surrogate data. The surrogate data are generated so that they have the same temporal structure as the original data. Careful considerations of the statistical significance are of particular importance in studies with exploratory methods such as projection pursuit.

In the stratosphere the moderate evidence for bimodality in the interannual variability of extended winter means is confirmed. On monthly and daily time scales strong evidence for non-Gaussianity but no evidence for bi- or multimodality is found. In the troposphere only evidence for non-Gaussianity is found and mainly on the shortest time scales.

Finally, recent arguments that principal components are prone to Gaussianity are discussed. It is shown that these arguments are based on erroneous use of the central limit theorem.
Air, Sea, and Land Interactions of the Continental U.S. Hydroclimate
Authors: Misra Vasubandhu , Dirmeyer P. A.
Published: September 2008

Multidecadal simulations over the continental United States by an atmospheric general circulation model coupled to an ocean general circulation model is compared with that forced by observed sea surface temperature (SST). The differences in the mean and the variability of precipitation are found to be larger in the boreal summer than in the winter. This is because the mean SST differences in the two simulations are qualitatively comparable between the two seasons. The analysis shows that, in the boreal summer season, differences in moisture flux convergence resulting from changes in the circulation between the two simulations initiate and sustain changes in precipitation between them. This difference in precipitation is, however, further augmented by the contributions from land surface evaporation, resulting in larger differences of precipitation between the two simulations. However, in the boreal winter season, despite differences in the moisture flux convergence between the two model integrations, the precipitation differences over the continental United States are insignificant. It is also shown that land–atmosphere feedback is comparatively much weaker in the boreal winter season.
Observations of the Transition Layer
Authors: Johnston T. M. Shaun , Rudnick Daniel L.
Published: September 2008

The transition layer is the poorly understood interface between the stratified, weakly turbulent interior and the strongly turbulent surface mixed layer. The transition layer displays elevated thermohaline variance compared to the interior and maxima in current shear, vertical stratification, and potential vorticity. A database of 91 916 km or 25 426 vertical profiles of temperature and salinity from SeaSoar, a towed vehicle, is used to define the transition layer thickness. Acoustic Doppler current measurements are also used, when available. Statistics of the transition layer thickness are compared for 232 straight SeaSoar sections, which range in length from 65 to 1129 km with typical horizontal resolution of ∼4 km and vertical resolution of 8 m. Transition layer thicknesses are calculated in three groups from 1) vertical displacements of the mixed layer base and of interior isopycnals into the mixed layer; 2) the depths below the mixed layer depth of peaks in shear, stratification, and potential vorticity and their widths; and 3) the depths below or above the mixed layer depth of extrema in thermohaline variance, density ratio, and isopycnal slope. From each SeaSoar section, the authors compile either a single value or a median value for each of the above measures. Each definition yields a median transition layer thickness from 8 to 24 m below the mixed layer depth. The only exception is the median depth of the maximum isopycnal slope, which is 37 m above the mixed layer base, but its mode is 15–25 m above the mixed layer base. Although the depths of the stratification, shear, and potential vorticity peaks below the mixed layer are not correlated with the mixed layer depth, the widths of the shear and potential vorticity peaks are. Transition layer thicknesses from displacements and the full width at half maximum of the shear and potential vorticity peak give transition layer thicknesses from 0.11× to 0.22× the mean depth of the mixed layer. From individual profiles, the depth of the shear peak below the stratification peak has a median value of 6 m, which shows that momentum fluxes penetrate farther than buoyancy fluxes. A typical horizontal scale of 5–10 km for the transition layer comes from the product of the isopycnal slope and a transition layer thickness suggesting the importance of submesoscale processes in forming the transition layer. Two possible parameterizations for transition layer thickness are 1) a constant of 11–24 m below the mixed layer depth as found for the shear, stratification, potential vorticity, and thermohaline variance maxima and the density ratio extrema; and 2) a linear function of mixed layer depth as found for isopycnal displacements and the widths of the shear and potential vorticity peaks.
Impact of Horizontal Diffusion on the Nonlinear Stability of Thermohaline Circulation in a Modified Box Model
Authors: Wu Xiaogang , Mu Mu
Published: September 2008

This note studies the impact of horizontal diffusion (HD) on the thermohaline circulation (THC) within a modified Stommel’s box model, which was introduced by Longworth et al. HD may arise as a result of mesoscale eddies from the instability of wind-driven gyres. Focuses are on the multi-equilibriums’ existence and nonlinear stability of the THC. A nonlinear approach called conditional nonlinear optimal perturbation (CNOP) is adopted. Both numerical and analytical analyses suggest that there exists a physical mechanism, which makes HD result in more decrement of salinity difference in the meridional direction than that of temperature difference. Consequently, the effects of HD on the thermally and salinity-driven equilibriums of THC are different: HD stabilizes the former but destabilizes the latter.
Numerical Study on the Variability of Mixed Layer Temperature in the North Pacific
Authors: Kako Shin’ichiro , Kubota Masahisa
Published: September 2008

Physical processes important for the interannual variability in mixed layer temperature (MLT) in the North Pacific have been examined by using a three-dimensional bulk mixed layer model. This model was forced by the momentum, heat, and freshwater flux data derived from the NCEP–NCAR reanalysis and geostrophic flow data included in Japanese Ocean Flux datasets with Use of Remote Sensing Observations. The interannual variation in MLT was hindcasted over the course of 11 years from January 1993 to December 2003. The interannual variation in the modeled MLT favorably agreed with that of the available in situ and satellite sea surface temperature (SST) observational data. This agreement depended crucially on whether horizontal heat advection was considered a part of the model dynamics. Although both atmospheric and oceanic processes were required to explain the observed interannual MLT variability, the physical process most important for determining this variability was likely to differ year by year. For example, in the Kuroshio Extension region, it was found that the positive temperature tendency peak in 1997 was attributed to the positive surface thermal forcing, while the temperature tendency in 1998 and 1999 continued to increase in spite of the negative surface thermal forcing. Thus, the abnormal heat loss from the ocean to the atmosphere (hence, the atmospheric circulation change) in 1998–99 was considered to be excited by the ocean dynamics related to the warmer SST. Likewise, it was found that the rapid decrease in SST during 2001–03 was mainly caused by the effect of lateral flux.
Comparison of Envisat ASAR Ocean Wave Spectra with Buoy and Altimeter Data via a Wave Model
Authors: Li Jian-Guo , Holt Martin
Published: September 2008

The Advanced Synthetic Aperture Radar (ASAR) on board the Envisat satellite is an important resource for observation of global ocean surface wave spectra. However, assessment of this valuable dataset is not straightforward as a result of a lack of other independent ocean wave spectral observations. The radar altimeter (RA-2) on board the same satellite measures ocean wave height at the same time as the ASAR but at a location about 200 km distant. A small number of moored buoys produce one-dimensional (1D) ocean wave spectra but few ASAR spectra fall on the buoy positions in a given period. Indirect comparison of the Envisat ASAR 2D wave spectra with the RA-2 wave heights and 1D spectra of three selected buoys from July 2004 to February 2006 is facilitated by a wave model, which provides coherent spatial and temporal links between these observations. In addition to the conventional significant wave height (SWH), four spectral subrange wave heights (SRWHs) are used to illustrate the spectral characteristics of these observations. A comparison of three Envisat ASAR 2D spectra with the closest model and buoy spectra is also attempted to illustrate the qualities of these different observations and to demonstrate the restrictions to their direct comparison. Results indicate that these three independent observations are in good agreement in terms of SWH, though the Envisat ASAR shows the largest variance. Comparison of SRWHs indicates that the ASAR spectra agree well with buoy and model in moderately long waves, but the ASAR instrument does not resolve high-frequency waves, especially along the satellite track.
Sampling Errors in Seasonal Forecasting
Authors: Cusack Stephen , Arribas Alberto
Published: September 2008

The limited numbers of start dates and ensemble sizes in seasonal forecasts lead to sampling errors in predictions. Defining the magnitude of these sampling errors would be useful for end users as well as informing decisions on resource allocation to minimize total system error. A numerical experiment has been designed to measure them, and results indicate that sampling errors are substantial in state-of-the-art seasonal forecast systems. The standard solution of increasing sample sizes is of limited benefit in seasonal forecasting because of restrictions imposed by resource costs and nonstationary observations. Alternative options, based on the postprocessing of forecast and hindcast data, are presented in this paper. The spatial and temporal aggregations of data together with the appropriate use of theoretical distributions can reduce the effect of sampling errors on forecast quantities by an amount equivalent to increasing samples sizes by a factor of 4 of more, with insignificant losses of forecast information. These postprocessing techniques can be viewed as cost-effective methods of reducing the effects of sampling errors in seasonal forecast quantities.
Analysis of a Dryline during IHOP: Implications for Convection Initiation
Authors: Wakimoto Roger M. , Murphey Hanne V.
Published: September 2008

A detailed analysis of a dryline that formed on 22 May 2002 during the International H2O Project (IHOP) is presented. The dryline was classified as a null case since air parcels lifted over the convergence boundary were unable to reach the level of free convection preventing thunderstorms from forming. A secondary dryline associated with a distinct moisture discontinuity developed to the west of the primary dryline. The primary dryline exhibited substantial along-frontal variability owing to the presence of misocyclones. This nonlinear pattern resembled the precipitation core/gap structure associated with cold fronts during one of the analysis times although the misocyclones were positioned within the gap regions. Radar refractivity has been recently shown to accurately retrieve the low-level moisture fields within the convective boundary layer; however, its use in forecasting the initiation of convection has been restricted to qualitative interpretations. This study introduces the total derivative of radar refractivity as a quantitative parameter that may improve nowcasts of convection. Although no storms developed on this day, there was a tendency for maxima of the total derivative to be near regions where cumulus clouds were developing near a convergence boundary.
Improving Incremental Balance in the GSI 3DVAR Analysis System
Authors: Kleist Daryl T. , Parrish David F. , Derber John C. , Treadon Russ , Errico Ronald M. , Yang Runhua
Published: September 2008

The gridpoint statistical interpolation (GSI) analysis system is a unified global/regional three-dimensional variational data assimilation (3DVAR) analysis code that has been under development for several years at the National Centers for Environmental Prediction (NCEP)/Environmental Modeling Center. It has recently been implemented into operations at NCEP in both the global and North American data assimilation systems (GDAS and NDAS, respectively). An important aspect of this development has been improving the balance of the analysis produced by GSI. The improved balance between variables has been achieved through the inclusion of a tangent-linear normal-mode constraint (TLNMC). The TLNMC method has proven to be very robust and effective. The TLNMC as part of the global GSI system has resulted in substantial improvement in data assimilation at NCEP.