bluuebunny/crossref_metadata_2025 huggingface dataset:
Ambiguous relation between physical workload and low back pain: a twin control study
Authors: Hartvigsen J , Kyvik K O , Leboeuf-Yde C , Lings S , Bakketeig L
Published: January 2003

Aims:To examine the association between self reported physical workload and low back pain (LBP) in younger twins. To investigate whether genetic factors interact with physical workload in relation to LBP.

Methods:A twin control study was performed within a population based twin register using 1910 complete monozygotic (MZ) and same sexed dizygotic (DZ) twin pairs aged 25–42 and discordant for LBP. LBP in the affected twins was divided into two groups: “LBP for ≤30 days during the past year”, and “LBP for >30 days during the past year”. Physical workload was divided into four categories: “sitting”, “sitting/walking”, “light physical”, and “heavy physical”. Data were analysed in a matched design using conditional logistic regression. MZ and DZ twins were analysed separately and together in order to determine possible genetic influences in relation to physical workload and LBP.

Results:Statistically significant graded relations were found for increasing workload and LBP of longer duration but not for LBP of shorter duration (≤30 days during the past year). In both LBP groups the “sitting” and “sitting/walking” groups were not statistically different. MZ and DZ twins did not differ significantly with respect to LBP in the various workload groups.

Conclusions:There is evidence for a dose-response relation between physical workload and LBP of longer duration. Attention to clinically relevant subgroups based on duration, for example, is necessary in epidemiological studies dealing with LBP. Physical workload might be more important than genetic factors in LBP.
Follow up study of haematological effects in workers exposed to 2-methoxyethanol
Authors: Shih T-S , Hsieh A-T , Chen Y-H , Liao G-D , Chen C-Y , Chou J-S , Liou S-H
Published: January 2003

Aims:To examine the association between 2-methoxyethanol (2-ME) exposure and haematological effects, as well as the recovery from these haematological effects with continuous reduction in exposure to 2-ME.

Methods:Twenty nine exposed and 90 non-exposed workers were recruited. Haematological parameters, eight hour full shift personal exposure to 2-ME, and urinary 2-methoxyacetic acid (MAA) were repeatedly measured in three consecutive surveys within six months.

Results:Results of haematological examination in the first exposure survey showed that haemoglobin, packed cell volume, and red blood cell count in the male exposed workers were significantly lower than those in the comparison workers. The frequency of anaemia in the exposed group (42%) was significantly higher than that in the comparison group (3%). The haematological effects were significantly associated with the urinary MAA of exposed workers. The haematological effects had returned to normal in the first follow up survey 2.5 months later, when a reduction in 2-ME exposure was noted. Haematological results of the second follow up examination six months later remained normal. The mean airborne exposure of 2-ME in the three surveys dropped from 35.7 to 2.65, then to 0.55 ppm. The mean urinary MAA of exposed workers in the three surveys was reduced from 57.7 to 24.6, then to 13.5 mg/g creatinine (n = 29). The reduction in exposure through both inhalation and potential dermal contact with 2-ME might account for the haematological recovery.

Conclusion:2-ME is a haematological toxin which leads to anaemia in exposed workers. However, the toxic haematological effects of 2-ME persist for only a short period of time after cessation or reduction of exposure.
Acute effects of winter air pollution on respiratory function in schoolchildren in southern England
Authors: Peacock J L , Symonds P , Jackson P , Bremner S A , Scarlett J F , Strachan D P , Anderson H R
Published: January 2003

Aim:To investigate the acute health effects of winter outdoor air pollution (nitrogen dioxide (NO2), ozone (O3), sulphur dioxide (SO2), sulphate (SO42−) ,and particles (PM10)) on schoolchildren in an area of southern England where levels of SO2had been reported to be high.

Methods:A total of 179 children, aged 7–13, from three schools (two urban and one rural location), were included. Peak expiratory flow rate (PEFR) and presence or absence of upper respiratory infections were recorded on 63 school days from 1 November 1996 to 14 February 1997. Air pollution and meteorological data were taken from monitors at each school site. The analysis regressed daily PEFR on pollutant level adjusting for confounders and serial correlation and calculated a weighted pooled estimate of effect overall for each pollutant. In addition, large decrements in PEFR were analysed as a binary outcome. Same day, lag 1, lag 2, and a five day average of pollutant levels were used.

Results:There were no clear effects of any pollutant on mean PEFR. In addition, we analysed large PEFR decrements (a binary outcome), observing consistent negative associations with NO2, SO42−, and PM10, although few lag/pollutant combinations were significant: odds ratios (95% CI) for five day average effect: NO224 h average 1.043 (1.000 to 1.089), SO42−1.090 (0.898 to 1.322), PM101.037 (0.992 to 1.084). The observed effects of PM10(only) were stronger in wheezy children (1.114 (1.057 to 1.174)). There were no consistent negative associations between large decrements and ozone or SO2.

Conclusions:There is no strong evidence for acute effects of winter outdoor air pollution on mean PEFR overall in this area, but there is evidence for negative effects on large PEFR decrements.
LANDAU–GINZBURG TYPE EQUATIONS IN THE SUBCRITICAL CASE
Authors: HAYASHI NAKAO , KAIKINA ELENA I. , NAUMKIN PAVEL I.
Published: January 2003

We study the Cauchy problem for the nonlinear Landau–Ginzburg equation [Formula: see text] where α, β ∈ C with dissipation condition ℜα > 0. We are interested in the subcritical case [Formula: see text]. We assume that θ = | ∫ u0(x) dx| ≠ 0 and ℜδ (α, β) > 0, where [Formula: see text] Furthermore we suppose that the initial data u0 ∈ L1 are such that (1+|x|)au0 ∈ L1, with sufficiently small norm ε = ‖(1 + |x|)a u0 ‖1, where a ∈ (0,1). Also we assume that σ is sufficiently close to [Formula: see text]. Then there exists a unique solution of the Cauchy problem (*) such that [Formula: see text] satisfying the following time decay estimates for large t > 0[Formula: see text] Note that in comparison with the corresponding linear case the decay rate of the solutions of (*) is more rapid.
MODULI SPACES OF STABLE BUNDLES ON K3 FIBERED CALABI–YAU THREEFOLDS
Authors: NAKASHIMA TOHRU
Published: January 2003

In this paper we study stable rank two bundles on a Calabi–Yau threefold. For hypersurfaces in a ℙ3-bundle over ℙ1, we show that their moduli spaces have irreducible components which are birational to projective spaces.
DECAY OF SOLUTIONS OF THE SYSTEM OF THERMOELASTICITY OF TYPE III
Authors: ZHANG XU , ZUAZUA ENRIQUE
Published: January 2003

This paper is devoted to analyzing the long time behavior of solutions of the system of thermoelasticity of type III in a bounded domain of ℝn (n = 1,2,3) and in the whole space ℝn. For the first case, we introduce a decoupled system that allows to reduce the problem of the asymptotic behavior for the original system to a suitable observability inequality for the Lamé system. In this way most of the existing results for the classical system of thermoelasticity are shown to hold for this system too. In particular, we show that: (1) For most domains the energy of the system does not decay uniformly; (2) Under suitable conditions on the domain that may be described in terms of Geometric Optics, the energy of the system decays exponentially; and (3) For most domains in two space dimensions, the energy of smooth solutions decays polynomially. For the problem in the whole space ℝn, first, based on Fourier analysis and Lyapunov's second method, we show that the energy of longitudinal and thermal waves of the system decays as that of the classical heat equation (while that of the transversal wave component is conservative). Then, by means of a careful spectral analysis, we give a sharp description on the decay rate of the high frequency longitudinal and thermal waves of the system.
BOUNDS FOR THE SPECTRUM OF ANALYTIC QUASINORMAL OPERATOR PENCILS
Authors: GIL' M. I.
Published: January 2003

We consider a class of pencils (operator valued functions of a complex argument) in a separable Hilbert space. Bounds for the λ-nonlinear spectrum are suggested. Applications to differential operators, integral operators with delay and infinite matrix pencils are also discussed.
ON THE SHAPE OF THE SOLUTIONS OF SOME SEMILINEAR ELLIPTIC PROBLEMS
Authors: GROSSI MASSIMO , MOLLE RICCARDO
Published: January 2003

This paper deals with semilinear elliptic problems of Dirichlet type, in star shaped domains. An abstract result is stated, which gives sufficient conditions for a positive solution of the problem to have strictly star shaped superlevels. Moreover, it turns out that the maximum point is the only critical point for these solutions.

Then we apply the result to the "single-peak" solutions of some widely studied problems. First a nonlinear and subcritical elliptic equation is considered, when the nonlinearity approaches the critical one. Then Schrödinger type problems are studied. Finally, the case when the potential is constant is also analyzed, on a bounded domain.
ON ARRANGEMENTS OF A PLANE REAL QUINTIC CURVE WITH RESPECT TO A PAIR OF LINES
Authors: KORCHAGIN ANATOLY B. , POLOTOVSKII GRIGORY M.
Published: January 2003

In this paper the isotopy classification of unions of an M-curve of degree 5 and two lines in ℝP2 satisfying some conditions of maximality and general position is obtained. This classification consists of 20 isotopy types of such unions.
Xanthine Oxidase Inhibition Reverses Endothelial Dysfunction in Heavy Smokers
Authors: Guthikonda Sashi , Sinkey Christine , Barenz Therese , Haynes William G.
Published: January 2003

Background—

Cigarette smoking causes endothelial dysfunction, possibly through increased oxidant stress. The enzyme xanthine oxidase produces oxidative free radicals. We tested the hypothesis that xanthine oxidase contributes to endothelial dysfunction in cigarette smokers by administering the inhibitor allopurinol.

Methods and Results—

Fourteen cigarette smokers (31±4 pack years) and 14 age- and sex-matched healthy non-smoking control subjects participated in a single-blinded, randomized, 2-phase crossover study. All subjects had no other risk factors for atherosclerosis. Inhibition of xanthine oxidase was achieved by a single oral dose of 600 mg of allopurinol on the day of the study. Stimulated nitric oxide endothelial responses were assessed by forearm blood flow responses to intraarterial administration of acetylcholine and bradykinin 4 to 7 hours later; basal nitric oxide was assessed using the nitric oxide synthase inhibitor NG-monomethyl-
l
-arginine (L-NMMA); and nitroprusside was used to assess sensitivity to nitric oxide. Dilatation produced by acetylcholine was significantly less in smokers (254±57%) than healthy controls (390±55%) (
P
=0.009). Allopurinol reversed endothelial dysfunction in smokers (acetylcholine, 463±78%,
P
=0.001) without affecting responses in non-smokers (401±80%). Bradykinin responses were also impaired in smokers (
P
=0.003), and improved with allopurinol, though not significantly (
P
=0.06). Responses to nitroprusside and L-NMMA were not significantly different between smokers and controls and were not altered by allopurinol.

Conclusions—

Smoking-induced endothelial dysfunction of resistance vessels is rapidly reversed with oral allopurinol. These data suggest that xanthine oxidase contributes importantly to endothelial dysfunction caused by cigarette smoking.
Long-Term Results After the Glycoprotein IIb/IIIa Inhibitor Abciximab in Unstable Angina
Authors: Ottervanger J.P. , Armstrong P. , Barnathan E.S. , Boersma E. , Cooper J.S. , Ohman E.M. , James S. , Topol E. , Wallentin L. , Simoons M.L.
Published: January 2003

Background—

This study was designed to investigate long-term effects of the glycoprotein IIb/IIIa inhibitor abciximab in patients with acute coronary syndrome without ST elevation who were not scheduled for coronary intervention.

Methods and Results—

A total of 7800 patients were included with an acute coronary syndrome without ST elevation, documented by either elevated cardiac troponin or transient or persistent ST-segment depression. They were randomized to abciximab bolus and 24-hour infusion, abciximab bolus and 48-hour infusion, or matching placebo. The overall 1-year mortality rate was 8.3% (649 patients). One-year mortality was 7.8% in the placebo group and 8.2% in the 24-hour and 9.0% in the 48-hour abciximab infusion group. Compared with placebo, the hazard ratio for the 24-hour infusion of abciximab was 1.1 (95% CI 0.86 to 1.29), and for the 48-hour infusion, it was 1.2 (95% CI 0.95 to 1.41). The lack of benefit of abciximab was observed in every subgroup studied. Patients with negative troponin or elevated C-reactive protein had a higher mortality rate after treatment with abciximab for 48 hours than with placebo: 8.5% versus 5.8% in those with negative troponin (
P
=0.02), 16.3% versus 12.1% in those with elevated C-reactive protein (
P
=0.04).

Conclusions—

Compared with placebo, abciximab did not provide any survival benefit at 1 year in patients admitted with an acute coronary syndrome with ST depression and/or elevated troponin who were not scheduled to undergo early coronary revascularization. In subgroups of patients, in particular those with low cardiac troponin or elevated C-reactive protein, abciximab was associated with excess mortality.
Should Volume Standards for Cardiovascular Surgery Focus Only on High-Risk Patients?
Authors: Goodney Philip P. , Lucas F.L. , Birkmeyer John D.
Published: January 2003

Background—

Payers and policy makers are attempting to concentrate selected cardiovascular procedures in high-volume centers. A recent analysis of coronary artery bypass grafting (CABG), however, suggests that volume-based referral initiatives should focus only on high-risk patients.

Methods and Results—

Using the national Medicare database (1994 to 1999), we studied the operative mortality in patients undergoing 4 cardiovascular procedures (CABG, aortic valve replacement, mitral valve replacement, and elective abdominal aortic aneurysm repair). We defined 2 categories of patient risk: high-risk (patients in the highest 25th percentile of predicted risk on the basis of a logistic regression model) and low-risk (patients in the lowest 75th percentile). We then compared operative mortality in patients undergoing surgery at very-high volume hospitals (VHVH, highest 20th percentile of procedure volume) and very-low volume hospitals (VLVH, lowest 20th percentile of procedure volume). Absolute differences in operative mortality between VLVH and VHVH were somewhat larger in high-risk patients. However, volume-related differences in mortality were also significant for low-risk patients undergoing one of the 4 procedures. In relative terms, the effect of hospital volume was similar in both high- and low-risk patients. For high- and low-risk patients, the relative risk (RR) of mortality between VHVH and VLVH were nearly equal for CABG (RR=0.78 for low-risk patients, RR=0.77 for high risk patients), aortic valve replacement (0.73 versus 0.76), mitral valve replacement (0.73 versus 0.74), and abdominal aortic aneurysm repair (0.51 versus 0.54).

Conclusions—

Although the merits of volume-based referral initiatives can be debated on many grounds, there seems to be little rationale for restricting these initiatives to high-risk patients.
Protective Role of Uncoupling Protein 2 in Atherosclerosis
Authors: Blanc J. , Alves-Guerra M.C. , Esposito B. , Rousset S. , Gourdy P. , Ricquier D. , Tedgui A. , Miroux B. , Mallat Z.
Published: January 2003

Background—

Uncoupling protein 2 (UCP2) regulates the production of reactive oxygen species in macrophages. However, its role in atherosclerosis is unknown.

Methods and Results—

Irradiated low-density lipoprotein receptor deficient mice (LDLR-/-) were transplanted with bone marrow from either UCP2 deficient mice (
Ucp2
-/-) or wild type mice (
Ucp2
+/+). Mice were fed an atherogenic diet for 7 weeks. Engraftment of bone marrow cells was confirmed by the presence of UCP2 protein expression in spleen cell mitochondria of
Ucp2
+/+ transplanted mice and its absence in
Ucp2
-/- transplanted mice. Leukocyte counts and plasma cholesterol levels were comparable in both groups. We found a marked increase in atherosclerotic lesion size in the thoracic aorta of
Ucp2
-/- transplanted mice compared with control
Ucp2
+/+ transplanted mice (8.3±0.9% versus 4.3±0.4%, respectively;
P
<0.005), as well as in the aortic sinus (150 066±12 388 μm
2
versus 105 689±9 727 μm
2
, respectively;
P
<0.05). This was associated with increased nitrotyrosine staining, which suggests enhanced oxidative stress. Analysis of plaque composition revealed a significant increase in macrophage accumulation (
P
<0.05) and apoptosis (
P
<0.05), along with a decrease in collagen content (
P
<0.05), suggesting a potentially more vulnerable phenotype.

Conclusion—

These results suggest a protective role for UCP2 against atherosclerosis.
C-Reactive Protein Increases Plasminogen Activator Inhibitor-1 Expression and Activity in Human Aortic Endothelial Cells
Authors: Devaraj Sridevi , Xu Dan Yan , Jialal Ishwarlal
Published: January 2003

Background—

Inflammation plays a pivotal role in atherosclerosis. In addition to being a risk marker for cardiovascular disease, much recent data suggest that C-reactive protein (CRP) promotes atherogenesis via effects on monocytes and endothelial cells. The metabolic syndrome is associated with significantly elevated levels of CRP. Plasminogen activator inhibitor-1 (PAI-1), a marker of atherothrombosis, is also elevated in the metabolic syndrome and in diabetes, and endothelial cells are the major source of PAI-1. However, there are no studies examining the effect of CRP on PAI-1 in human aortic endothelial cells (HAECs).

Methods and Results—

Incubation of HAECs with CRP results in a time- and dose-dependent increase in secreted PAI-1 antigen, PAI-1 activity, intracellular PAI-1 protein, and PAI-1 mRNA. CRP stabilizes PAI-1 mRNA. Inhibitors of endothelial NO synthase, blocking antibodies to interleukin-6 and an endothelin-1 receptor blocker, fail to attenuate the effect of CRP on PAI-1. CRP additionally increased PAI-1 under hyperglycemic conditions.

Conclusions—

This study makes the novel observation that CRP induces PAI-1 expression and activity in HAECs and thus has implications for both the metabolic syndrome and atherothrombosis. (Circulation. 2003;107:398-404.)
C-Reactive Protein, the Metabolic Syndrome, and Risk of Incident Cardiovascular Events
Authors: Ridker Paul M , Buring Julie E. , Cook Nancy R. , Rifai Nader
Published: January 2003

Background—

The metabolic syndrome describes a high-risk population having 3 or more of the following clinical characteristics: upper-body obesity, hypertriglyceridemia, low HDL, hypertension, and abnormal glucose. All of these attributes, however, are associated with increased levels of C-reactive protein (CRP).

Methods and Results—

We evaluated interrelationships between CRP, the metabolic syndrome, and incident cardiovascular events among 14 719 apparently healthy women who were followed up for an 8-year period for myocardial infarction, stroke, coronary revascularization, or cardiovascular death; 24% of the cohort had the metabolic syndrome at study entry. At baseline, median CRP levels for those with 0, 1, 2, 3, 4, or 5 characteristics of the metabolic syndrome were 0.68, 1.09, 1.93, 3.01, 3.88, and 5.75 mg/L, respectively (
P
trend
<0.0001). Over the 8-year follow-up, cardiovascular event-free survival rates based on CRP levels above or below 3.0 mg/L were similar to survival rates based on having 3 or more characteristics of the metabolic syndrome. At all levels of severity of the metabolic syndrome, however, CRP added prognostic information on subsequent risk. For example, among those with the metabolic syndrome at study entry, age-adjusted incidence rates of future cardiovascular events were 3.4 and 5.9 per 1000 person-years of exposure for those with baseline CRP levels less than or greater than 3.0 mg/L, respectively. Additive effects for CRP were also observed for those with 4 or 5 characteristics of the metabolic syndrome. The use of different definitions of the metabolic syndrome had minimal impact on these findings.

Conclusions—

These prospective data suggest that measurement of CRP adds clinically important prognostic information to the metabolic syndrome.
Wearable Force Display Using a Particle Mechanical Constraint
Authors: Mitsuda Takashi , Kuge Sachiko , Wakabayashi Masato , Kawamura Sadao
Published: January 2003

A particle mechanical constraint (PMC) is a soft vinyl tube containing Styrofoam beads. It can be freely compressed, elongated, bent, twisted, or otherwise manipulated in all degrees of freedom. Evacuation of the air inside the tube makes the PMC rigid so that it maintains whatever shape it has been given. The stiffness of the PMC is proportional to the reduction in internal pressure below atmospheric pressure. Viscosity is also controlled virtually by changing the inside air pressure in proportion to the speed of transformation of the PMC. We used a PMC to develop a wearable force display that provides the sensation of coming into contact with a wall or of moving in water with viscosity, in addition to that of moving in air. PMC is an inherently passive device that never exerts excessive force if it were to malfunction. In short, it is suitable as a wearable human interface because it is light, soft, and safe.
Estrogen Receptor (ER)-β Reduces ERα-Regulated Gene Transcription, Supporting a “Ying Yang” Relationship between ERα and ERβ in Mice
Authors: Lindberg Marie K. , Movérare Sofia , Skrtic Stanko , Gao Hui , Dahlman-Wright Karin , Gustafsson Jan-Åke , Ohlsson Claes
Published: January 2003

Estrogen is of importance for the regulation of adult bone metabolism. The aim of the present study was to determine the role of estrogen receptor-β (ERβ) in vivo on global estrogen-regulated transcriptional activity in bone. The effect of estrogen in bone of ovariectomized mice was determined using microarray analysis including 9400 genes. Most of the genes (95% = 240 genes) that were increased by estrogen in wild-type (WT) mice were also increased by estrogen in ERβ-inactivated mice. Interestingly, the average stimulatory effect of estrogen on the mRNA levels of these genes was 85% higher in ERβ-inactivated than in WT mice, demonstrating that ERβ reduces estrogen receptor-α (ERα)-regulated gene transcription in bone. The average stimulatory effect of estrogen on estrogen-regulated bone genes in ERα-inactivated mice was intermediate between that seen in WT and ERαβ double-inactivated mice. Thus, ERβ inhibits ERα-mediated gene transcription in the presence of ERα, whereas, in the absence of ERα, it can partially replace ERα. In conclusion, our in vivo data indicate that an important physiological role of ERβ is to modulate ERα-mediated gene transcription supporting a “Ying Yang” relationship between ERα and ERβ in mice.
Impact of flow through the Canadian Archipelago and Bering Strait on the North Atlantic and Arctic circulation: An ocean modelling study
Authors: Wadley Martin R. , Bigg Grant R.
Published: January 2003

An ocean general‐circulation model with an orthogonal curvilinear grid is presented, with the grid north pole over Greenland to achieve improved resolution in the Greenland and Labrador Seas. The model is integrated for 4500 years in five different experiments, with open and closed connections to the Arctic via the Bering Strait (BS) and Canadian Archipelago (CA). When the BS and CA connections are open the Atlantic overturning circulation has a realistic strength (20 Sv), whereas there is stronger overturning with either (25–31 Sv) or both (39 Sv) the connections closed due to additional deep‐water formation in the Labrador Sea. The volume fluxes across the Greenland–Iceland–Scotland ridge are reasonably close to those observed with the two connections either open or closed. With only the BS closed, low‐salinity waters leave the Arctic via the CA, giving a weak East Greenland Current, whereas with only the CA closed deep‐water formation in the Nordic Seas is weak due to the passage of excess low‐salinity water originating from the Pacific via the BS. The simulations suggest that both the CA and BS connections to the Arctic Influence the North Atlantic circulation. Closing the BS reduces the effective freshwater input to the Arctic, leading to a strong Atlantic overturning circulation. Closing the CA leads to increased salinity in the Labrador Sea, and additional deep‐water formation. It is therefore recommended that both these seaways should be represented in ocean general‐circulation models. Copyright © 2002 Royal Meteorological Society
Large‐scale organization of tropical convection in two‐dimensional explicit numerical simulations: Effects of interactive radiation
Authors: Grabowski Wojciech W. , Moncrieff Mitchell W.
Published: January 2003

We examine interactions among radiative processes, water vapour, clouds, and the multi‐scale organization of tropical convection in two‐dimensional idealized cloud‐resolving simulations using planetary‐scale horizontal domains. We extend our earlier study where radiative cooling was prescribed. Therein, deep convection spontaneously organized into two primary scales: westward travelling mesoscale convective systems on a scale of a few hundred kilometres and the eastward‐propagating envelopes of convection spanning thousands of kilometres. These envelopes represented large‐scale convectively coupled gravity waves, two‐dimensional non‐rotating analogues of equatorially trapped Kelvin waves.

Interactive radiation introduces a new mechanism of large‐scale convective organization. Weak overturning circulations, steered by the mean wind and of a few thousand kilometres in scale, gradually develop. This overturning is a manifestation of the baroclinic response to horizontal gradients of radiative heating established between the moist and dry regions, which causes a spontaneous positive feedback among large‐scale dynamics, water vapour, clouds, and radiation. The mechanism is as follows: the convective systems maintain the humidity (vapour and cloud) in the ascending branch which, in turn, maintains the differential radiative heating. Conversely, the large‐scale overturning provides the large‐scale dynamical forcing that maintains the deep convection. This quantifies recent idealized studies that applied convective parametrizations. The radiatively driven overturning and the deep convection are modulated by large‐scale convectively coupled gravity waves responsible for the large‐scale envelopes reported earlier. A series of sensitivity tests, including the effects of environmental shear, demonstrate the robustness of these results. Copyright © 2002 Royal Meteorological Society
Measurements of the near‐surface flow over a hill
Authors: Vosper S. B. , Mobbs S. D. , Gardiner B. A.
Published: January 2003

The near‐surface flow over a hill with moderate slope and height comparable with the boundary‐layer depth is investigated through field measurements of the mean flow (at 2 m), surface pressure, and turbulent momentum flux divergence between 8 and 15 m. The measurements were made along an east–west transect across the hill Tighvein (height 458 m, approximate width 8 km) on the Isle of Arran, south‐west Scotland, during two separate periods, each of around three‐weeks duration. Radiosonde ascents are used to determine the variation of a Froude number, FL=U/NL, where U is the wind speed at the middle‐layer height, hm, N is the mean Brunt–Väisälä frequency below this height and L is a hill length‐scale. Measurements show that for moderately stratified flows (for which FL≳0.25) a minimum in the hill‐induced surface‐pressure perturbation occurs across the summit and this is accompanied by a maximum in the near‐surface wind speed. In the more strongly stratified case FL≲0.25 the pressure field is more asymmetric and the lee‐slope flow is generally stronger than on the windward slope. Such a flow pattern is qualitatively consistent with that predicted by stratified linear boundary‐layer and gravity‐wave theories. The near‐surface momentum budget is analysed by evaluating the dominant terms in a Bernoulli equation suitable for turbulent flow. Measurements during periods of westerly flow are used to evaluate the dominant terms, and the equation is shown to hold to a reasonable approximation on the upwind slope of the hill and also on the downwind slope, away from the summit. Immediately downwind of the summit, however, the Bernoulli equation does not hold. Possible reasons for this, such as non‐separated sheltering and flow separation, are discussed. Copyright © 2002 Royal Meteorological Society
Retrieval of temperature, water vapour and ozone profiles from airborne interferometric measurements
Authors: Grippa M. , Peckham G. E.
Published: January 2003

The Airborne Research Interferometer Evaluation System (ARIES), flying on board the Meteorological Research Flight C130 aircraft, measures infrared radiance spectra from which tropospheric temperature and composition profiles can be determined by solving an inverse ill‐posed problem. We have derived a new regularization scheme for the linearized problem based on the idea that, in a stable atmosphere, the temperature lapse rate never exceeds its adiabatic value, so that a constraint may be applied to the temperature retrievals. The retrieval method is validated by means of an extensive simulation and by analysis of the ARIES data. Water vapour is retrieved simultaneously with temperature, putting particular emphasis on the linearization of the forward model and on the evaluation of the linearization pseudo‐noise associate with it. Preliminary results indicating the potential of ARIES measurements to retrieve tropospheric ozone profiles are also presented. Copyright © 2002 Royal Meteorological Society
Tropical convective variability in the CAPE phase space
Authors: Roff Gregory L. , Yano Jun‐Ichi
Published: January 2003

The relationship between pseudo‐adiabatic and reversible convective available potential energy (CAPE) in the tropical atmosphere is examined using the Tropical Ocean–Global Atmosphere programme (TOGA) Coupled Ocean–Atmosphere Response Experiment (COARE) radiosonde dataset. The effect of the ice phase and the dependence of the various CAPE quantities on surface variabilities is also examined.

CAPE distribution is qualitatively different for the regimes with positive and negative reversible CAPE (rCAPE). The former is characterized by a strong linear relationship (synchronic line) with a slightly weaker increase of rCAPE than that of pseudo‐adiabatic CAPE, with its evolution primarily dictated by the surface moisture. This synchronic line also penetrates into the negative rCAPE regime, where CAPE distributes diffusively between this synchronic line and a line with zero reversible CAPE. These more complex distributions of CAPE in the negative rCAPE regime are explained by their dependence on the level of neutral buoyancy. Copyright © 2002 Royal Meteorological Society
Ice nucleation characteristics of an isolated wave cloud
Authors: Cotton R. J. , Field P. R.
Published: January 2003

This paper reports on a series of simulations of a single isolated gravity‐wave cloud measured during the Interaction of Aerosol and Cold Clouds campaign. Using a parcel model with explicit liquid‐ and ice‐phase microphysics, a number of different heterogeneous nucleation modes have been tested. It has been impossible for the model to reproduce, using any of the usual nucleation modes, both the observed peak ice number concentration and the ice water content, while not affecting the liquid‐water part of the cloud. The key to simulating both of these simultaneously appears to lie in most ice nucleation occurring very rapidly at a critical time coincident with evaporation of the liquid droplets in the downdraught of the lee wave. © Crown copyright, 2002. Royal Meteorological Society
Variational retrieval of cloud profile from ATOVS observations
Authors: Chevallier F. , Bauer P. , Mahfouf J.‐F. , Morcrette J.‐J.
Published: January 2003

Radiation observations such as those from the Advanced Tiros Operational Vertical Sounder (ATOVS) on board the National Oceanic and Atmospheric Administration satellites provide information about cloud systems. However, like the other cloud observations they are not used in global data assimilation systems.

As an essential step towards the assimilation of such data, a fast infrared and microwave radiation model and its linearized version (tangent linear and adjoint operators) have been developed for the computation of model‐equivalent cloud‐affected satellite radiances. They are used in a global one‐dimensional variational (1DVar) analysis of ATOVS radiances over open oceans. In non‐precipitating areas, it is shown that the 1D‐Var can remove, create and modify the cloud variables in each model layer to fit the observed radiances. The retrieved profiles have a degree of realism that will improve with better background constraint. This study is a first step towards the assimilation of clouds by variational analysis of clouds and dynamics at once, and will be further continued. Copyright © 2002 Royal Meteorological Society
Impact of new measurements of oxygen collision‐induced absorption on estimates of short‐wave atmospheric absorption
Authors: Chagas J. C. S. , Newnham D. A. , Smith K. M. , Shine K. P.
Published: January 2003

A new set of laboratory measurements of the 1.06 µm and 1.27 µm collision‐induced bands of gaseous oxygen is presented. Absorption by pure oxygen and mixtures of oxygen with nitrogen and argon was observed using a Fourier transform spectrometer for temperatures between 230 and 295 K and pressures between 1 and 5 bar. Binary cross‐sections derived from the measurements were used to estimate the impacts on estimates of clear‐sky climatological absorption of solar irradiance. Monthly climatological atmospheric profiles averaged over 10° latitude belts were used to study the temporal and annual variation of the impacts. The global‐ and annual‐mean clear‐sky extra‐absorption was 0.58 W m−2 (about 1% of the absorption by water vapour and ozone), 0.42 W m−2 due to the 1.27 µm band and 0.16 W m−2 due to the 1.06 µm band. If estimates for other oxygen collision‐induced bands taken from previous studies are added, an overall impact of about 1 W m−2 results. Copyright © 2002 Royal Meteorological Society
Entropy as a basis for comparing and blending forecasts
Authors: Delsole Timothy
Published: January 2003

The use of Shannon's entropy for comparing forecasts, and for blending the forecasts into a single forecast with higher skill, is discussed. The basic idea is to examine the difference in the entropy of the error distributions. A particularly appealing approach is to decompose the entropy difference into a complete set of vectors in phase space that maximize or minimize the entropy difference. This decomposition identifies the patterns that the first model predicts with less error variance than the second, and those that the second model predicts with less error variance than the first. A ‘blended’ forecast with higher skill than either of the original forecasts can be constructed by an appropriate superposition of these patterns. In contrast to a linear regression correction, which minimizes only the total mean square error, the blended forecast predicts every pattern, and every local region, with less (or equal) error variance than either of the original forecasts. A filtering procedure is introduced to deal with the problem that, at long lead times, error variance fails to be an appropriate measure of skill.

The above procedure is used to compare the 1 to 8‐day forecast skill of 500 hPa geopotential height predicted by the National Centers for Environmental Prediction (NCEP) reanalysis forecast model over a 40‐year period, against the forecast skill of a 200‐variable linear inverse model. The results show that the NCEP model predicts virtually every pattern with less error variance than the linear inverse model, provided that the pattern can be predicted with skill by at least one of the models. The best predicted patterns of each model (in an error variance sense) also have the longest decorrelation times, suggesting a strong relation between predictability and persistence. Copyright © 2002 Royal Meteorological Society
Empirical predictability study of October–December East African rainfall
Authors: Philippon N. , Camberlin P. , Fauchereau N.
Published: January 2003

Relationships between September atmospheric dynamics over the global tropics and the East Africa short rains over the domain 4°S–4°N,30–39°E were investigated to define a seasonal rainfall forecasting scheme. From total and partial correlation analyses over the period 1968–97, three major and useful signals appear in September.

Precursor components of the October–December east–west circulation cell appear over the equatorial Indian Ocean (EIO). They were discovered through various indices of sea‐surface temperature (SST), zonal wind, vertical velocity and moist static energy computed over the western, central and eastern parts of the EIO. Principal component analyses were applied to these indices to form two synthetic indices which discriminate ocean–atmosphere variability in the eastern and western parts of the basin.

The Indian monsoon dynamics control the SSTs off the Somalia coast which are known to play an important role in the variability of the short rains.

Ridge–trough systems develop off South Africa which, when persistent enough, drive SST anomalies in the eastern tropical and equatorial Atlantic; these in turn are associated with anomalies in the middle levels over an equatorial band ranging from the Guinea Gulf to the western Indian Ocean.

The three September signals used as predictors in a multiple linear regression model explain 64% of the rainfall variance; a comparable efficiency is also achieved with a linear discriminant analysis model. Copyright © 2002 Royal Meteorological Society
A note on the occurrence of cloud in meteorologically sensitive areas and the implications for advanced infrared sounders
Authors: McNally A. P.
Published: January 2003

The geographical distribution and persistence of meteorologically sensitive areas (derived using adjoint forecast‐error tracking techniques) are investigated with respect to the occurrence of cloud. Using sensitivity patterns and cloud structures simulated from the ECMWF forecast model a high degree of correlation is found which, if realistic, could limit the ability of space‐based advanced infrared sounders to measure important meteorological features. The result underlines the need to develop techniques to use infrared sounder observations in the presence of cloud. Copyright © 2002 Royal Meteorological Society
A two‐dimensional numerical study of effects of vertical diffusion in frontal zones
Authors: Håkansson Måns
Published: January 2003

Parametrization of vertical diffusion tends to cause excessive smoothing of free‐troposphere frontal‐zone gradients in several forecast models. It has been observed that these models produce frontal structures that are diffuse, and that the dynamic stability of the frontal zones is higher in forecasts than in the corresponding analyses. Because of their inherent characteristics, frontal zones are sensitive to the way turbulent diffusion is parametrized in the model calculations. In several models, the estimation of vertical diffusion is based on the theory for mixing within boundary layers, assuming that the free‐tropospheric turbulent exchanges may be determined by an extension of boundary‐layer theory. This is an unrealistic assumption and consequently the observed model deficiency in describing upper frontal zones may to some significant degree be attributed to the crudeness of the vertical‐diffusion scheme. To address the problem, and in an effort to achieve further understanding of instabilities and turbulent fluxes associated with frontal dynamics, a two‐dimensional, semi‐geostrophic, nearly adiabatic model describing a vertical cross‐section through an idealized frontal zone is presented. The model utilizes the same kind of vertical‐diffusion scheme as numerous operational forecast models. Different types of instability generated in the model's interpretation of the frontogenesis process are presented and discussed in the context of vertical diffusion. Results show that turbulent diffusion as described by the parametrization scheme plays an important role in smoothing the frontal gradients, especially within the shear zone below the jet stream. Furthermore, the scheme shows sensitivity to the choice of parameters. Extreme values of wind shear and temperature gradient in frontal zones are likely to be weakened by the parametrized turbulent fluxes. These effects impact on short‐range forecasts but may also affect the results when modelling future climatological scenarios. Copyright © 2002 Royal Meteorological Society
Comparison of an axisymmetric hurricane model with the corresponding slab‐symmetric ITCZ model
Authors: Ulrich Wolfgang , Smith Roger K. , Chi Mai Nguyen
Published: January 2003

We examine the difference between the evolution of a hurricane‐like vortex in an axisymmetric model and that of an intertropical convergence‐zone‐ like disturbance in a slab‐symmetric model, starting from an initial disturbance with the same lateral structure. The main calculations are carried out using a hurricane model similar to that formulated by DeMaria and Pickle (1988), supplemented by a few calculations using a recently developed model by Nguyen et al. (2002). We show that, although the two flow configurations have many similarities, the slab‐symmetric model does not provide a dynamical surrogate for the hurricane. The main difference can be attributed to a geometrical factor in the formula for the conservation of absolute angular momentum in the axisymmetric model, which for an inward‐moving air parcel permits much larger tangential wind speeds to be attained than in the slab‐symmetric model. As a result, the sea‐surface latent‐heat flux, which is wind‐speed dependent, is much larger in the axisymmetric model, providing a larger energy supply to the growing disturbance per unit area than in the slab‐symmetric case. A further geometrical effect is that for the same inflow velocity profile in the boundary layer, there is larger convergence in the axisymmetric model. Because this convergence determines the deep cumulus mass flux in the DeMaria and Pickle model, the cumulus heating is larger in the axisymmetric configuration. The non‐development of the slab‐symmetric perturbation is a feature also of calculations using the Nguyen et al. (2002) model, even though two of the closures on the deep‐cumulus mass flux used do not depend on the mass convergence in the boundary layer. A few numerical details of the main model are described, including the method of solution, which differs from that used by DeMaria and Pickle (1988). Copyright © 2002 Royal Meteorological Society
Micrometeorological measurements of particle deposition velocities to moorland vegetation
Authors: Nemitz Eiko , Gallagher Martin W. , Duyzer Jan H. , Fowler David
Published: January 2003

Size‐segregated particle number flux measurements using a micrometeorological technique, over the diameter (dp) range 0.1 to 3 µm and total particle number fluxes (dp>11 nm), are reported for Scottish moorland vegetation. Mean particle deposition velocities (Vd) range from 0.3 mm s−1 for 0.1 µm particles to more than 10 mm s−1 for 3 µm particles. On average, the measured size‐dependence of Vd is almost identical with the prediction by the widely used Slinn model, using the original parameters derived from wind‐tunnel studies. Within each size‐band Vd increased linearly with the friction velocity (u*). Total particle number fluxes measured with a condensation particle counter are dominated by the high concentration of small particles; therefore, this provides the first estimate of Vd for particles smaller than those that can be sized by optical techniques, for short vegetation. Values of Vd ranged from 0.2 to 0.6 mm s−1 as u* increased from 0.15 to 0.55 m s−1. These deposition rates are one order of magnitude smaller than have been observed for a pine forest stand. The analysis shows that, at least for super‐micron particles, the emission fluxes that were frequently observed at the study site need to be included in the computation of average values. At this site, upward fluxes are therefore more likely to be an artefact due to statistical constraints than a systematic physical phenomenon. Copyright © 2002 Royal Meteorological Society
Synoptic‐scale variability of the polar and subpolar tropopause: Data analysis and idealized PV inversions
Authors: Zängl G. , Wirth V.
Published: January 2003

The synoptic‐scale variability of the polar and subpolar tropopause is investigated based on radiosonde and European Centre for Medium‐Range Weather Forecasts Reanalysis data in combination with idealized potential vorticity (PV) inversions. A regression analysis is performed to examine the relationship between the relative vorticity at tropopause level, the tropopause displacement, the static stability above the tropopause, and the anomalies of tropopause temperature and potential temperature. The results are compared with regression coefficients computed from a large number of PV inversions. Generally, a cyclonically influenced tropopause is lower, warmer and potentially colder than average, and the static stability above the tropopause is reduced. The opposite is true under anticyclonic influence. Typically, a cyclonic vorticity of 10−5s−1 is associated with a decrease of the tropopause height by 150–200 m. Correspondingly, the mean vertical temperature gradient in the lowermost 2 km above the tropopause decreases by 0.2– 0.3 K km−1. Moreover, an increase of the tropopause height by 1 km is associated with a temperature decrease by 3–5 K and an increase of the potential temperature by 6–8 K. Except for the last one, these values do not depend significantly on the strength and the sign of the tropopause anomaly. Distinct annual cycles are observed in parts of the polar regions. Most of the relations found in the data can be reproduced with the PV inversions, except for the observed linearity for large tropopause displacements which is not always reproduced very well. The annual cycles can be partly explained with the aid of the PV inversions. Copyright © 2002 Royal Meteorological Society