bluuebunny/crossref_metadata_2025 huggingface dataset:
Prescribing Antiplatelet Medicine and Subsequent Events After Intracerebral Hemorrhage
Authors: Flynn Robert W.V. , MacDonald Thomas M. , Murray Gordon D. , MacWalter Ronald S. , Doney Alexander S.F.
Published: October 2010

Background and Purpose—

Antiplatelet medicines are commonly perceived as contraindicated after intracerebral hemorrhage (ICH). Many ICH patients have or will have indications for antiplatelet therapy. This observational study describes the level of antiplatelet prescribing and rate of subsequent events after ICH in Tayside, Scotland.

Methods—

This study used record-linkage of an existing stroke cohort with antiplatelet prescribing data from 1994 to 2005. Patients were followed-up from discharge after index event. The primary outcome was recurrent ICH. Other outcomes were subsequent ischemic stroke and a composite of ischemic stroke or myocardial infarction. Event rates were calculated as the number of events divided by patient-years of exposure. Univariate hazard ratios associated with antiplatelet exposure were derived from a Cox model using a time-dependent covariate.

Results—

There were 417 ICH patients who survived to discharge. Of these, 120 patients were prescribed subsequent antiplatelet medicines (28.8%). The median time from discharge to antiplatelet use was 14.8 months (range, 2 days–7.5 years). Among all survivors, there were 14 recurrent ICH (rate, 9.7 per 1000 patient-years; 95% confidence interval [CI], 5.3–16.4), 29 subsequent ischemic strokes (rate, 20.6; 95% CI, 13.8–29.6), and 40 subsequent ischemic strokes or myocardial infarctions (rate, 28.7; 95% CI, 20.5–39.0). Hazard ratios associated with antiplatelet exposure were 1.07 (95% CI, 0.24–4.84) for recurrent ICH, 0.23 (95% CI, 0.03–1.68) for ischemic stroke, and 0.72 (95% CI, 0.25–2.02) for ischemic strokes or myocardial infarction.

Conclusions—

Antiplatelet prescribing was common after ICH. Subsequent ischemic strokes or myocardial infarctions were more common than recurrent ICH. Antiplatelet prescribing did not appear to have a clinically significant impact on outcomes measured. Despite being contraindicated, antiplatelet use was not a major hazard for recurrent ICH.
Early Intracerebral Hematoma Expansion After Aneurysmal Rupture
Authors: van Asch Charlotte J.J. , Oudendijk Jorine F. , Rinkel Gabriël J.E. , Klijn Catharina J.M.
Published: October 2010

Background and Purpose—

Intracerebral hematomas (ICHs) often increase in size in the initial hours. It is unknown whether expansion of ICHs after aneurysmal rupture in the acute phase is always a sign of rerupture of the original aneurysm.

Methods—

We included patients with an ICH from a ruptured aneurysm who underwent computed tomography imaging within 24 hours of symptom onset and a repeat computed tomography within 48 hours. Hematoma growth was considered present when there was a 33% increase in hematoma volume, as assessed by the ABC/2 method. Clinical and radiologic characteristics were compared between patients with ICH growth, with and without clinical signs of rerupture. Rerupture was defined as a sudden deterioration in the level of consciousness in the absence of ventricular enlargement or a systemic cause.

Results—

Hematoma expansion within 48 hours after onset occurred in 12 of the 49 included patients and was preceded by clinical evidence of rerupture in 6 of these 12 patients. Of the 6 patients without an evident rerupture, 3 had no clinical deterioration, 1 had respiratory failure due to pneumonia, another had temporal brain herniation, and the last had acute hydrocephalus.

Conclusion—

Only half of the patients with early ICH expansion after aneurysmal rupture had clinical signs of rerupture of the aneurysm. Early ICH expansion after aneurysmal rupture can be caused by other mechanisms, which are possibly comparable to those responsible for hematoma expansion in spontaneous ICH.
Thrombolysis Is Associated With Consistent Functional Improvement Across Baseline Stroke Severity
Authors: Mishra Nishant K. , Lyden Patrick , Grotta James C. , Lees Kennedy R.
Published: October 2010

Background and Purpose—

Baseline stroke severity predicts outcomes among thrombolysed patients. The baseline National Institutes of Health Stroke Scale (NIHSS) thresholds are sometimes used to select patients for thrombolysis, clinical trial enrollment, or both. Using data lodged with Virtual International Stroke Trials Archive, we compared adjusted outcomes between thrombolysed and nonthrombolysed patients enrolled in neuroprotection trials (1998–2007) to assess the influence of various levels of baseline NIHSS.

Method—

We assessed the association of treatment with outcome, measured across the modified Rankin scale score distribution, in patients categorized by baseline NIHSS in increments of 4. We used an age and baseline NIHSS adjusted Cochran-Mantel-Haenszel test followed by proportional odds logistic regression analysis. We report the Cochran-Mantel-Haenszel
P
values and estimated odds ratios (OR) for improved modified Rankin scale score distribution with treatment for patients within each baseline NIHSS category.

Results—

Data were available for 5817 patients (1585 thrombolysed and 4232 nonthrombolysed). Baseline severity was greater among thrombolysed than nonthrombolysed (median baseline NIHSS, 14 vs 13;
P
<0.05). An association of treatment with outcome was seen independently and was of similar magnitude within each of the baseline NIHSS categories 5 to 8 (
P
=0.04; OR, 1.25; 95% confidence interval [CI], 1.0–1.6; N=278/934 thrombolysed/nonthrombolysed), 9 to 12 (
P
=0.01; OR, 1.3; 95% CI, 1.1–1.6; N=404/942), 13 to 16 (
P
<0.05; OR, 1.6; 95% CI, 1.3–2.1; N=342/814), 17 to 20 (
P
<0.05; OR, 1.7; 95% CI, 1.3–2.1; N=311/736), and 21 to 24 (
P
<0.05; OR, 1.6; 95% CI, 1.1–2.1; N=178/466). No association was observed within baseline NIHSS categories 1 to 4 (
P
=0.8; OR, 1.1; 95% CI, 0.3–4.4; N=8/161) or ≥25 (
P
=0.08; OR, 1.1; 95% CI, 0.7–1.9; N=64/179).

Conclusions—

In this nonrandomized comparison, outcomes after thrombolysis were significantly better than in untreated comparators across baseline NIHSS 5 to 24. The significant association was lost only at extremes of baseline NIHSS when sample sizes were small and confidence limits were wide.
Acute Basilar Artery Occlusion in the Basilar Artery International Cooperation Study
Authors: Arnold Marcel , Fischer Urs , Compter Annette , Gralla Jan , Findling Oliver , Mattle Heinrich P. , Kappelle L. Jaap , Tanne David , Algra Ale , Schonewille Wouter J.
Published: October 2010

Background and Purpose—

Randomized trials suggested a different benefit of intravenous thrombolysis (IVT) and intra-arterial thrombolysis (IAT) between men and women with anterior circulation stroke because of a worse outcome of women in the control group.

Methods—

We compared outcome and recanalization in men and women with basilar artery occlusion treated with antithrombotic treatment alone, IVT or combined IVT–IAT, or IAT in the Basilar Artery International Cooperation Study.

Results—

Overall, 389 male and 226 female patients were analyzed. In the antithrombotic treatment group, 68 of 111 (61%) men and 47 of 70 (67%) women had a poor outcome defined as a modified Rankin Scale score of 4 to 6 (adjusted risk ratio [aRR], 0.96; 95% CI, 0.75 to 1.24), in the IVT/combined IVT–IAT group, 47 of 77 (61%) men and 24 of 43 (56%) women (aRR, 1.19; 95% CI, 0.89 to 1.60), and in the IAT group, 142 of 185 (77%) men and 71 of 102 (70%) women (aRR, 1.01; 95% CI, 0.88 to 1.17). Mortality was not different between men and women in the antithrombotic treatment group (aRR, 0.80; 95% CI, 0.55 to 1.16), the IVT/combined IVT–IAT group (aRR, 1.11; 95% CI, 0.72 to 1.73), or in the IAT group (aRR, 1.01; 95% CI, 0.75 to 1.36). Insufficient recanalization after combined IVT–IAT or IAT was similar in men and women (23% versus 22%; aRR, 0.92; 95% CI, 0.58 to 1.46).

Conclusions—

In patients with acute basilar artery occlusion, no significant gender differences for outcome and recanalization were observed, regardless of treatment modality.
The Significance of Blood Pressure Variability for the Development of Hemorrhagic Transformation in Acute Ischemic Stroke
Authors: Ko Youngchai , Park Jung Hyun , Yang Mi Hwa , Ko Sang-Bae , Han Moon-Ku , Oh Chang Wan , Lee JiSung , Lee Juneyoung , Bae Hee-Joon
Published: October 2010

Background and Purpose—

Elevated blood pressure (BP) is commonly observed in acute ischemic stroke and is known to be associated with hemorrhagic transformation (HT). However, the effect of BP variability on the development of HT is not known well.

Methods—

A consecutive series of patients with acute ischemic stroke, who were hospitalized within 24 hours of onset and showed no HT on initial gradient echo MRI, were enrolled in this study. BP measurements during the first 72 hours were obtained, and BP variability of each patient was described using various summary parameters: SD, maximum (max), minimum (min), difference between max and min (max−min), average squared difference between successive measurements (sv), and maximum sv (svmax).

Results—

Of 792 patients meeting the eligibility criteria, 70 (8.8%) developed HT. Among BP variability parameters categorized into quartiles, SBP
max
, SBP
min
, SBP
max−min
, SBP
svmax
, DBP
SD
, DBP
max
, DBP
min
, DBP
max−min
, and DBP
svmax
were significantly associated with HT independent of mean SBP, age, interval from onset to arrival, initial stroke severity, diabetes mellitus, stroke subtype, thrombolysis, initial glucose, and total cholesterol (
P
<0.05 on likelihood ratio test of trend). The analyses about the interaction between thrombolysis and variability parameters showed that the effects of BP variability on the development of HT did not differ by whether patients received thrombolysis or not.

Conclusions—

Our study suggests that we may consider not only the absolute level of BP but also its variability to prevent hemorrhagic transformation.
Exertion Fatigue and Chronic Fatigue Are Two Distinct Constructs in People Post-Stroke
Authors: Tseng Benjamin Y. , Billinger Sandra A. , Gajewski Byron J. , Kluding Patricia M.
Published: October 2010

Background and Purpose—

Post-stroke fatigue is a common and neglected issue despite the fact that it impacts daily functions, quality of life, and has been linked with a higher mortality rate because of its association with a sedentary lifestyle. The purpose of this study was to identify the contributing factors of exertion fatigue and chronic fatigue in people post-stroke.

Methods—

Twenty-one post-stroke people (12 males, 9 females; 59.5±10.3 years of age; time after stroke 4.1±3.5 years) participated in the study. The response variables included exertion fatigue and chronic fatigue. Participants underwent a standardized fatigue-inducing exercise on a recumbent stepper. Exertion fatigue level was assessed at rest and immediately after exercise using the Visual Analog Fatigue Scale. Chronic fatigue was measured by the Fatigue Severity Scale. The explanatory variables included aerobic fitness, motor control, and depressive symptoms measured by peak oxygen uptake, Fugl-Meyer motor score, and the Geriatric Depression Scale, respectively.

Results—

Using forward stepwise regression, we found that peak oxygen uptake was an independent predictor of exertion fatigue (
P
=0.006), whereas depression was an independent predictor of chronic fatigue (
P
=0.002).

Conclusion—

Exertion fatigue and chronic fatigue are 2 distinct fatigue constructs, as identified by 2 different contributing factors.
Early Protective Effect of Bone Marrow Mononuclear Cells Against Ischemic White Matter Damage Through Augmentation of Cerebral Blood Flow
Authors: Fujita Youshi , Ihara Masafumi , Ushiki Takashi , Hirai Hideyo , Kizaka-Kondoh Shinae , Hiraoka Masahiro , Ito Hidefumi , Takahashi Ryosuke
Published: October 2010

Background and Purpose—

To investigate the efficacy of bone marrow mononuclear cell (BMMNC) treatment against ischemic white matter (WM) damage in a hypoperfused brain.

Methods—

Mice were administered intravenous treatment of vehicle, spleen-derived marrow mononuclear cells (MNCs), or BMMNCs (5×10
6
cells) obtained from enhanced green fluorescent protein transgenic mice 24 hours after bilateral common carotid artery stenosis (BCAS), and then euthanized at either 1 day or 30 days after treatment.

Results—

Laser speckle perfusion imaging analyses revealed marked recovery of cerebral blood flow (CBF) in the early phase after BMMNC treatment (6 hours after administration), before histological evidence of angiogenesis was assessed by fluorescein-isothiocyanate-dextran perfusion assay. BMMNC treatment induced an increase in vascular endothelial growth factor and Ser1177 phosphorylated endothelial nitric oxide synthase levels in the BCAS-induced mouse brains at 1 day after the treatment. BCAS-induced ischemic WM lesions were significantly improved 30 days after BMMNC treatment despite any evidence of direct structural incorporation of donor BMMNCs into endothelial cells and oligodendrocytes. Instead, enhanced green fluorescent protein-positive donor cells with morphological features of pericytes were observed in the vessel walls. Post-BMMNC administration of an NOS inhibitor abolished early CBF recovery and produced protective effects against ischemic WM damage.

Conclusions—

BMMNC treatment provides marked protection against ischemic WM damage, enhancing CBF in the early phase and in subsequent angiogenesis, both of which involve nitric oxide synthase activation. These findings suggest promise for the application of BMMNCs for subcortical ischemic vascular dementia.
Incidence and Case-Fatality of Stroke on the East Border of the European Union
Authors: Kulesh Sergey D. , Filina Nina A. , Frantava Nataliya M. , Zhytko Natallia L. , Kastsinevich Tatsiana M. , Kliatskova Liudmila A. , Shumskas Mechyslovas S. , Hilz Max J. , Schwab Stefan , Kolominsky-Rabas Peter L.
Published: October 2010

Background and Purpose—

The epidemiology of stroke in Belarus is unclear. Therefore, a population-based register of stroke was set up in western Belarus to determine incidence and case-fatality in a defined urban population.

Methods—

The Grodno Stroke Study is a prospective community-based research among 311 134 residents of the city of Grodno, Belarus. Standard definitions and multiple overlapping sources of ascertainment were used to identify all cases of first-ever-in-a-lifetime strokes in all age groups occurring between January 1, 2001, and December 31, 2003.

Results—

During 3 years, 2069 cases of first-ever-in-a-lifetime strokes were registered. Mean age at stroke onset was 65.8±11.6 years; rate of hospitalization was 89.7%. The crude annual incidence rate of first-ever-in-a-lifetime strokes for the study period was 222 per 100 000 (95% CI, 212 to 233). Incidence adjusted to the European standard population and to the World Health Organization world standard population was 287 per 100 000 (95% CI, 274 to 301) and 220 per 100 000 (95% CI, 210 to 231), respectively. The 28-day case-fatality rate was 26.1%. The prevalence of hypertension among all first-ever-in-a-lifetime stroke patients was 87.5%; 529 (25.6%) were current smokers. A total 23.1% of patients had atrial fibrillation, 19.1% had past myocardial infarction, 14.7% had diabetes mellitus, and 22.1% had hypercholesterolemia.

Conclusions—

High incidence and case-fatality rates determine the considerable burden of stroke in Belarus and might at least partly be related to the high prevalence of risk factors among the population.
Utility of Dysphagia Screening Results in Predicting Poststroke Pneumonia
Authors: Lakshminarayan Kamakshi , Tsai Albert W. , Tong Xin , Vazquez Gabriela , Peacock James M. , George Mary G. , Luepker Russell V. , Anderson David C.
Published: October 2010

Background and Purpose—

Dysphagia screening before oral intake (DS) is a stroke care quality indicator. The value of DS is unproven. Quality adherence and outcome data from the Paul Coverdell National Acute Stroke Registry were examined to establish value of DS.

Methods—

Adherence to the DS quality indicator was examined in patients with stroke discharged from Paul Coverdell National Acute Stroke Registry hospitals between March 1 and December 31, 2009. Patients were classified as unscreened (US), screened and passed (S/P), and screened and failed. Associations between screening status and pneumonia rate were assessed by logistic regression models after adjustment for selected variables.

Results—

A total of 18 017 patients with stroke discharged from 222 hospitals in 6 states were included. A total of 4509 (25%) were US; 8406 (47%) were S/P, and 5099 (28%) were screened and failed. Compared with US patients, screened patients were significantly more impaired. Pneumonia rates were: US 4.2%, S/P 2.0%, and screened and failed 6.8%. After adjustment for demographic and clinical features, US patients were at a higher risk of pneumonia (OR, 2.2; 95% CI, 1.7 to 2.7) compared with S/P patients.

Conclusions—

Data suggest that patients are selectively screened based on stroke severity. Pneumonia rate was higher in US patients compared with S/P patients. Clinical judgment regarding who should be screened is imperfect. S/P patients have a lower pneumonia rate indicating that DS adds accuracy in predicting pneumonia risk. The Joint Commission recently retired DS as a performance indicator for Primary Stroke Center certification. These results suggest the need to implement a DS performance measure for patients with acute stroke.
Triggers of Ischemic Stroke
Authors: Guiraud Vincent , Amor Mejdi Ben , Mas Jean-Louis , Touzé Emmanuel
Published: October 2010

Background and Purpose—Several studies have suggested that exposure to “triggers,” could precipitate the onset of ischemic stroke (IS). We performed a systematic review of the potential triggers of IS.

Methods—Two independent reviewers identified studies published between January 1980 and June 2010 from MEDLINE and Embase. Where appropriate, odds ratios (ORs) were combined.

Results—A total of 26 studies identified 12 potential triggers. Twenty-two studies used a case–control design, and hazard period durations ranged from 2 hours to 3 months. The majority of studies were dedicated to alcohol abuse (n=10) and clinical infection (n=12). There was a significant association between IS and alcohol abuse of >40 to 60 g within the preceding 24 hours (OR=2.66; 95% CI, 1.54 to 4.61) or >150 g within the previous week (OR=2.47; 95% CI, 1.52 to 4.02) and infection within the previous week (OR=2.91; 95% CI, 1.41 to 6.00) or within the previous month (OR=2.41; 95% CI, 1.78 to 3.27). Other triggers have been far less investigated. There was a significant association between IS and anger, heavy eating, negative or positive emotions, sudden posture change in response to a startling event, birthday, and psychological distress and no significant association with drug abuse or heavy physical exertion. Regarding methodological issues, patients were rarely blinded to study objectives, and interviewers were rarely blinded to patient status.

Conclusions—Research on triggers of IS has been mainly focused on acute alcohol abuse and clinical infection. More research is needed on factors such as physical exertion or acute stress. Future studies should use more appropriate designs and examine different hazard periods.
How Does Self-Reported History of Stroke Compare to Hospitalization Data in a Population-Based Survey in New Zealand?
Authors: Carter Kristie , Barber P. Alan , Shaw Caroline
Published: October 2010

Background and Purpose—

There is mixed evidence concerning the validity of self-reported history of stroke in population-based studies. We aimed to examine the validity of self-reported stroke using hospitalization with a primary diagnosis of stroke as the reference group.

Methods—

Self-reported history of stroke was taken from the Survey of Families, Income, and Employment (N=18 950; 2004–2005) and defined as a respondent answering yes to the question, “Have you ever been told by a doctor that you have had a stroke?”. Survey of Families, Income, and Employment respondents consented to link their data to the New Zealand Health Information Service records of publically funded hospitalizations between 1990 and 2006. We calculated positive predictive value, sensitivity, and specificity of self-reported stroke against hospitalization for stroke.

Results—

Approximately 2% of the adult Survey of Families, Income, and Employment population reported they had been told by a doctor that they had a stroke. Only 1% had evidence of hospitalization for stroke since 1990. The sensitivity of self-reported stroke was 73% and specificity was 98%. However, the positive predictive value, people who reported having a stroke with confirmation of hospitalization for stroke, was low at 29%.

Conclusions—

The use of self-reported stroke will most likely overestimate the prevalence of stroke. A combination of methods is required to determine prevalence in population-based studies.
Distributional Memory: A General Framework for Corpus-Based Semantics
Authors: Baroni Marco , Lenci Alessandro
Published: October 2010

Research into corpus-based semantics has focused on the development of ad hoc models that treat single tasks, or sets of closely related tasks, as unrelated challenges to be tackled by extracting different kinds of distributional information from the corpus. As an alternative to this “one task, one model” approach, the Distributional Memory framework extracts distributional information once and for all from the corpus, in the form of a set of weighted word-link-word tuples arranged into a third-order tensor. Different matrices are then generated from the tensor, and their rows and columns constitute natural spaces to deal with different semantic problems. In this way, the same distributional information can be shared across tasks such as modeling word similarity judgments, discovering synonyms, concept categorization, predicting selectional preferences of verbs, solving analogy problems, classifying relations between word pairs, harvesting qualia structures with patterns or example pairs, predicting the typical properties of concepts, and classifying verbs into alternation classes. Extensive empirical testing in all these domains shows that a Distributional Memory implementation performs competitively against task-specific algorithms recently reported in the literature for the same tasks, and against our implementations of several state-of-the-art methods. The Distributional Memory approach is thus shown to be tenable despite the constraints imposed by its multi-purpose nature.
Chinese Foreign Policy under Hu Jintao:The Struggle between Low-Profile Policy and Diplomatic Activism
Authors: Suisheng Zhao
Published: October 2010

This article explores a controversial issue of Chinese foreign policy: whether the Hu leadership has abandoned Deng Xiaoping’s taoguang yanghui policy — hiding one’s capabilities and biding one’s time — and reoriented Chinese foreign policy towards a more assertive, if not more aggressive, direction. This is controversial because while China in public still insists that it follows the taoguang yanghui policy established by Deng in the early 1990s; Chinese diplomacy has become increasingly active and assertive since Hu came to power, particularly since the 2008-2009 global economic crisis. This article argues that as a rising power, an active foreign policy has become a necessity rather than a luxury for China. This diplomatic activism marks a certain departure from the taoguang yanghui policy, but the Hu leadership is still juggling China’s taoguang yanghui policy with its emerging role as a global power. One defining tension in China’s foreign policy agenda is to find a balance between expanding China’s international influence and taking more international responsibility on the one hand and continuing to play down its pretence of being a global power and avoiding confrontation with the United States on the other.
Chinese Diplomacy towards the EU: Grand Vision but Hard to Manage
Authors: Gaenssmantel Frank
Published: October 2010

This article investigates the sudden rise and subsequent slow decline of the European Union (EU) in Chinese diplomacy between 2002 and 2007. China’s decision in 2003 to consider relations with the EU as ‘strategic’ in nature does not reflect a fundamental change of mind but rather a perception of favourable circumstances. China has a long track record of high expectations towards a united Europe. After the World Trade Organization (WTO) negotiations had created a positive image of a united and independent EU, the transatlantic rift over the Iraq War in 2002 and 2003 seemed to present an international environment that was conducive to stronger China‐EU ties. Subsequently, however, the difficulties of engaging with a complex entity like the EU have contributed to souring diplomatic relations. This development is traced for two major cases of Chinese foreign policy towards the EU: the quest for recognition as a market economy; and the push to have the EU’s arms embargo lifted. Over time, Chinese engagement with the EU on these issues has gone through different phases, reflecting repeated attempts to improve the diplomatic approach, to eliminate unsuccessful strategies and to react to EU feedback. China has not yet reached its goal on either issue. The article concludes by pointing to the specific difficulties that have emerged from the evolution of Chinese diplomacy towards the EU on these two cases.
Polarimetric Radar Observation of the Melting Layer in a Convective Rainfall System during the Rainy Season over the East China Sea
Authors: Shusse Yukari , Takahashi Nobuhiro , Nakagawa Katsuhiro , Satoh Shinsuke , Iguchi Toshio
Published: October 2010

During the rainy season over the East China Sea, convective rainfalls often show melting layer (ML) characteristics in polarimetric radar variables. In this research, the appearance ratio of the ML (the ratio of rainfall area accompanied by polarimetric ML signatures) and the variation in height of the level of the ML signature maximum (MLSM level; defined by the level of the ρhv minimum in the ML) in a convective rainfall region in a rainfall system over the East China Sea observed on 2 June 2006 were studied using C-band polarimetric radar (COBRA). For this analysis, a method of rainfall type classification that evaluates the presence of an ML in addition to providing conventional convective–stratiform classification using range–height indicator (RHI) observation data was developed. This rainfall type classification includes two steps: conventional convective–stratiform separation using the horizontal distribution of Zh at 2-km altitude, and ML detection using the vertical profile of ρhv at each horizontal grid point. Using a combination of these two classifications, the following four rainfall types were identified: 1) convective rainfall with an ML, 2) convective rainfall with no ML, 3) stratiform rainfall with an ML, and 4) stratiform rainfall with no ML. An ML was detected in 53.9% of the convective region in the rainfall system. Using the same definition, an ML was detected in 83.1% of the stratiform region. The ML in the convective region showed a marked decrease in ρhv coincident with an increase in ZDR around the ambient 0°C level, as did that in the stratiform region. Melting aggregated snow was the likely cause of the ML signature in the convective region. The average height of the MLSM level in the convective region was 4.64 km, which is 0.46 km higher than that in the stratiform region (4.18 km) and 0.27 km higher than the ambient 0°C level (4.37 km).
Uncertainty Analysis for CloudSat Snowfall Retrievals
Authors: Hiley Michael J. , Kulie Mark S. , Bennartz Ralf
Published: October 2010

A new method to derive radar reflectivity–snow rate (Ze–S) relationships from scattering properties of different ice particle models is presented. Three statistical Ze–i relationships are derived to characterize the best estimate and uncertainties due to ice habit. The derived relationships are applied to CloudSat data to derive near-surface snowfall retrievals. Other uncertainties due to various method choices, such as vertical continuity tests, the near-surface reflectivity threshold used for choosing snowfall cases, and correcting for attenuation, are also explored on a regional and zonally averaged basis. The vertical continuity test in particular is found to have interesting regional effects. Although it appears to be useful for eliminating ground clutter over land, it also masks out potential lake-effect-snowfall cases over the Southern Ocean storm-track region. The choice of reflectivity threshold is found to significantly affect snowfall detection but is insignificant in terms of the mean snowfall rate. The use of an attenuation correction scheme can increase mean snowfall rates by ∼20%–30% in some regions. The CloudSat-collocated Advanced Microwave Scanning Radiometer (AMSR)-derived liquid water path is also analyzed, and significant amounts of cloud liquid water are often present in snowfall cases in which surface temperature is below freezing, illustrating the need to improve the arbitrary model-derived surface temperature criterion used to select “dry” snowfall cases. Precipitation measurements from conventional surface weather stations across Canada are used in an initial attempt to evaluate CloudSat snowfall retrievals. As expected, evaluation with ground-based data is fraught with difficulties. Encouraging results are found at a few stations, however—in particular, those located at very high latitudes.
Future Occurrence of Threshold-Crossing Seasonal Rainfall Totals: Methodology and Application to Sites in Africa
Authors: Siebert Asher B. , Ward M. Neil
Published: October 2010

A statistical simulation framework is developed to explore the future frequencies of threshold-crossing events, focusing here on low seasonal rainfall totals. Global change (GC) is represented by a trend on the seasonal mean rainfall total. Natural decadal to multidecadal variability (MDV) is represented by an autoregressive process. Interannual variability (IV) of seasonal totals is represented by white noise with either a normal or skew normal distribution consistent with parameters observed in the historical record at the location being modeled. Monte Carlo simulations are undertaken for various combinations of the above components, and the authors evaluate the extent to which future event frequencies can be estimated from the statistics of previous years. The sample of four study locations used to illustrate the approach is drawn from the Millennium Villages Project in Africa, where the potential of index insurance as a development and adaptation tool has been considered, thereby bringing a targeted problem setting to the analyses. The simulations highlight a number of general principles. For example, it is shown that a 10% change in the mean rainfall can lead to a change of order times 2 in the number of threshold-crossing low seasonal rainfall totals, even without invoking any change in the characteristics of the IV. The magnitudes of change are also shown to be sensitive to the threshold studied, as well as to site-specific climate features (here, coefficient of variation and skewness). The framework developed permits quantification of how, especially in the near term (of order 30 years), MDV can strongly add to uncertainty about future event frequencies. Therefore, statistical treatment of estimated MDV magnitudes will often be a key input to optimal risk management, with further enhancements expected through explicit MDV forecasts. The results highlight the importance of finding optimal ways to update climate statistics such as event thresholds, in the presence of GC and MDV.
A Modular Optimal Estimation Method for Combined Radar–Radiometer Precipitation Profiling
Authors: Munchak S. Joseph , Kummerow Christian D.
Published: October 2010

Although zonal mean rain rates from the Tropical Rainfall Measuring Mission (TRMM) are in good (<10%) agreement between the TRMM Microwave Imager (TMI) and precipitation radar (PR) rainfall algorithms, significant uncertainties remain in some regions where these estimates differ by as much as 30% over the period of record. Previous comparisons of these algorithms with ground validation (GV) rainfall have shown significant (>10%) biases of differing sign at various GV locations. Reducing these biases is important in the context of developing a database of cloud profiles for passive microwave retrievals that is based upon the PR-measured profiles. A retrieval framework based upon optimal estimation theory is proposed wherein three parameters describing the raindrop size distribution (DSD), ice particle size distribution, and cloud water path (cLWP) are retrieved for each radar profile. The modular nature of the framework provides the opportunity to test the sensitivity of the retrieval to the inclusion of different measurements, retrieved parameters, and models for microwave scattering properties of hydrometeors. The retrieved rainfall rate is found to be strongly sensitive to the a priori constraints in DSD and cLWP; thus, these parameters are tuned to match polarimetric radar estimates of rainfall near Kwajalein, Republic of Marshall Islands. An independent validation against gauge-tuned radar rainfall estimates at Melbourne, Florida, shows agreement within 2%, which exceeds previous algorithms’ ability to match rainfall at these two sites. Errors between observed and simulated brightness temperatures are reduced and climatological features of the DSD, as measured by disdrometers at these two locations, are also reproduced in the output of the combined algorithm.
Indian and Pacific Ocean Influences on Southeast Australian Drought and Soil Moisture
Authors: Ummenhofer Caroline C. , Sen Gupta Alexander , Briggs Peter R. , England Matthew H. , McIntosh Peter C. , Meyers Gary A. , Pook Michael J. , Raupach Michael R. , Risbey James S.
Published: October 2010

The relative influences of Indian and Pacific Ocean modes of variability on Australian rainfall and soil moisture are investigated for seasonal, interannual, and decadal time scales. For the period 1900–2006, observations, reanalysis products, and hindcasts of soil moisture during the cool season (June–October) are used to assess the impacts of El Niño–Southern Oscillation (ENSO) and the Indian Ocean dipole (IOD) on southeastern Australia and the Murray–Darling Basin, two regions that have recently suffered severe droughts. A distinct asymmetry is found in the impacts of the opposite phases of both ENSO and IOD on Australian rainfall and soil moisture. There are significant differences between the dominant drivers of drought at interannual and decadal time scales. On interannual time scales, both ENSO and the IOD modify southeastern Australian soil moisture, with the driest (wettest) conditions over the southeast and more broadly over large parts of Australia occurring during years when an El Niño and a positive IOD event (La Niña and a negative IOD event) co-occur. The atmospheric circulation associated with these responses is discussed. Lower-frequency variability over southeastern Australia, however, including multiyear drought periods, seems to be more robustly related to Indian Ocean temperatures than Pacific conditions. The frequencies of both positive and negative IOD events are significantly different during periods of prolonged drought compared to extended periods of “normal” rainfall. In contrast, the frequency of ENSO events remains largely unchanged during prolonged dry and wet periods. For the Murray–Darling Basin, there appears to be a significant influence by La Niña and both positive and negative IOD events. In particular, La Niña plays a much more prominent role than for more southern regions, especially on interannual time scales and during prolonged wet periods. For prolonged dry (wet) periods, positive IOD events also occur in unusually high (low) numbers.
Global-Scale Comparison of MISR and MODIS Land Surface Albedos
Authors: Pinty Bernard , Taberner Malcolm , Haemmerle Vance R. , Paradise Susan R. , Vermote Eric , Verstraete Michel M. , Gobron Nadine , Widlowski Jean-Luc
Published: October 2010

The Moderate Resolution Imaging Spectroradiometer (MODIS) white-sky surface albedos are compared with similar products generated on the basis of the Multiangle Imaging SpectroRadiometer (MISR) surface bidirectional reflectance factor (BRF) model parameters available for the year 2005. The analysis is achieved using global-scale statistics to characterize the broad patterns of these two independent albedo datasets. The results obtained in M. Taberner et al. have shown that robust statistics can be established and that both datasets are highly correlated. As a result, the slight but consistent biases and trends identified in this paper, derived from statistics obtained on a global basis, should be considered sufficiently reliable to merit further investigation. The present paper reports on the zonal- and seasonal-mean differences retrieved from the analysis of the MODIS and MISR surface albedo broadband products. The MISR − MODIS differences exhibit a systematic positive bias or offset in the range of 0.01–0.03 depending on the spectral domain of interest. Results obtained in the visible domain exhibit a well-marked and very consistent meridional trend featuring a “smile effect” such that the MISR − MODIS differences reach maxima at the highest latitudes in both hemispheres. The analysis of seasonal variations observed in MISR and MODIS albedo products reveals that, in the visible domain, the MODIS albedos generate weaker seasonal changes than MISR and that the differences increase poleward from the equatorial regions. A detailed investigation of MODIS and MISR aerosol optical depth retrievals suggests that this large-scale meridional trend is probably not caused by differences in the aerosol load estimated by each instrument. The scale and regularity of the meridional trend suggests that this may be due to the particular sampling regime of each instrument in the viewing azimuthal planes and/or approximations in the atmospheric correction processes. If this is the case, then either MODIS is underestimating, or MISR overestimating, the surface anisotropy or both.
The Analysis of Sea Surface Imagery for Whitecap Kinematics
Authors: Kleiss Jessica M. , Melville W. Kendall
Published: October 2010

Visible sea surface images are analyzed to determine the distribution of the average length of breaking crests per unit sea surface area per unit speed increment Λ(c). The Λ(c) distribution offers a scale-dependent description of wave breaking that is valuable for understanding wave energy dissipation, momentum flux from the wave field to the surface currents, and air–sea fluxes of gas and sea salt aerosols. Two independent processing techniques for determining Λ(c) from video images are implemented. In particular, the importance of the definition of the velocity of a breaking event is considered, as a single value, as a function of time, or as a function of space and time. The velocity can furthermore be defined as the full translational velocity or as the velocity normal to the breaking front. The Λ(c) distributions resulting from various definitions of velocity, sensitivity to thresholds, observational resolution, and the effect of surface currents and long wave orbital velocity are presented. The appropriateness and limitations of the comparison of the first moment of Λ(c) with the breaking rate are discussed. Two previous field observations of Λ(c) give qualitatively different results: Melville and Matusov found an exponential form for Λ(c), whereas Gemmrich et al. obtained a function that peaks at intermediate speeds and is up to an order of magnitude higher than that of Melville and Matusov. Both results can qualitatively be reproduced using the current dataset by employing the definitions of breaking velocity used in the previous studies. The authors argue that the current optimal interpretation of breaking speed resolves the breaking velocity as a function of both space and time and considers the velocity orthogonal to the breaking crest.
An Ensemble Ocean Data Assimilation System for Seasonal Prediction
Authors: Yin Yonghong , Alves Oscar , Oke Peter R.
Published: October 2010

A new ensemble ocean data assimilation system, developed for the Predictive Ocean Atmosphere Model for Australia (POAMA), is described. The new system is called PEODAS, the POAMA Ensemble Ocean Data Assimilation System. PEODAS is an approximate form of an ensemble Kalman filter system. For a given assimilation cycle, a central forecast is integrated, along with a small ensemble of forecasts that are forced with perturbed surface fluxes. The small ensemble is augmented with multiple small ensembles from previous assimilation cycles, yielding a larger ensemble that consists of perturbed forecasts from the last month. This larger ensemble is used to represent the system’s time-dependent background error covariance. At each assimilation cycle, a central analysis is computed utilizing the ensemble-based covariance. Each of the perturbed ensemble members are nudged toward the central analysis to control the ensemble spread and mean. The ensemble-based covariances generated by PEODAS potentially yield dynamically balanced analysis increments. The time dependence of the ensemble-based covariance yields spatial structures that change for different dynamical regimes, for example during El Niño and La Niña conditions. These differences are explored in terms of the dominant dynamics and the system’s errors. The performance of PEODAS during a 27-yr reanalysis is evaluated through a series of comparisons with assimilated and independent observations. When compared to its predecessor, POAMA version 1, and a simulation with no assimilation of subsurface observations, PEODAS demonstrates a quantitative improvement in skill. PEODAS will form the basis of Australia’s next operational seasonal prediction system.
Influence of the Madden–Julian Oscillation on Forecasts of Extreme Precipitation in the Contiguous United States
Authors: Jones Charles , Gottschalck Jon , Carvalho Leila M. V. , Higgins Wayne
Published: October 2010

Extreme precipitation events are among the most devastating weather phenomena since they are frequently accompanied by loss of life and property. This study uses reforecasts of the NCEP Climate Forecast System (CFS.v1) to evaluate the skill of nonprobabilistic and probabilistic forecasts of extreme precipitation in the contiguous United States (CONUS) during boreal winter for lead times up to two weeks.

The CFS model realistically simulates the spatial patterns of extreme precipitation events over the CONUS, although the magnitudes of the extremes in the model are much larger than in the observations. Heidke skill scores (HSS) for forecasts of extreme precipitation at the 75th and 90th percentiles showed that the CFS model has good skill at week 1 and modest skill at week 2. Forecast skill is usually higher when the Madden–Julian oscillation (MJO) is active and has enhanced convection occurring over the Western Hemisphere, Africa, and/or the western Indian Ocean than in quiescent periods. HSS greater than 0.1 extends to lead times of up to two weeks in these situations. Approximately 10%–30% of the CONUS has HSS greater than 0.1 at lead times of 1–14 days when the MJO is active.

Probabilistic forecasts for extreme precipitation events at the 75th percentile show improvements over climatology of 0%–40% at 1-day lead and 0%–5% at 7-day leads. The CFS has better skill in forecasting severe extremes (i.e., events exceeding the 90th percentile) at longer leads than moderate extremes (75th percentile). Improvements over climatology between 10% and 30% at leads of 3 days are observed over several areas across the CONUS—especially in California and in the Midwest.
Tropical Cyclone–like Vortices Detection in the NCEP 16-Day Ensemble System over the Western North Pacific in 2008: Application and Forecast Evaluation
Authors: Tsai Hsiao-Chung , Lu Kuo-Chen , Elsberry Russell L. , Lu Mong-Ming , Sui Chung-Hsiung
Published: October 2010

An automated technique has been developed for the detection and tracking of tropical cyclone–like vortices (TCLVs) in numerical weather prediction models, and especially for ensemble-based models. A TCLV is detected in the model grid when selected dynamic and thermodynamic fields meet specified criteria. A backward-and-forward extension from the mature stage of the track is utilized to complete the track. In addition, a fuzzy logic approach is utilized to calculate the TCLV fuzzy combined-likelihood value (TFCV) for representing the TCLV characteristics in the ensemble forecast outputs. The primary objective of the TCLV tracking and TFCV maps is for use as an evaluation tool for the operational forecasters. It is demonstrated that this algorithm efficiently extracts western North Pacific TCLV information from the vast amount of ensemble data from the NCEP Global Ensemble Forecast System (GEFS). The predictability of typhoon formation and activity during June–December 2008 is also evaluated. The TCLV track numbers and TFCV averages around the formation locations during the 0–96-h period are more skillful than for the 102–384-h forecasts. Compared to weak tropical cyclones (TCs; maximum intensity ≤ 50 kt), the storms that eventually become stronger TCs do have larger TFCVs. Depending on the specified domain size and the ensemble track numbers to define a forecast event, some skill is indicated in predicting the named TC activity. Although this evaluation with the 2008 typhoon season indicates some potential, an evaluation with a larger sample is necessary to statistically verify the reliability of the GEFS forecasts.
“In the footprint of Iḷā” : An EarIy Image of Sacrificial Cosmology in Vedic Tradition
Authors: Sandness Adéla
Published: October 2010

The poets of the Ṛg-Veda speak of the “navel of the earth,” which is the “footprint of Iḷā.” It is among the oldest expressions available which describe a place of ritual offering to the gods. In this case, it is an impression in the ground thought to have been the footprint of a cow, into which was poured milk and butter. The word padá names the footprint in the Indo-Iranian expression “in the footprint of Iḷā.” Yet padá also means “word” and the etymologically related term pāda means a “stanza” of the sacred poetry sung by the ancient visionary poets as they sang their world into being. The footprints are thus also those of the cow Speech whose “supreme place” is parallel to the place of offering which is the footprint of Iḷā. This paper will track the footprints of Iḷā and those of the cow Speech in the Ṛg-Veda.