bluuebunny/crossref_metadata_2025 huggingface dataset:
Troglitazone Inhibits Cell Growth and Induces Apoptosis of B-Cell Acute Lymphoblastic Leukemia Cells with t(14;18)
Authors: Takenokuchi M. , Saigo K. , Nakamachi Y. , Kawano S. , Hashimoto M. , Fujioka T. , Koizumi T. , Tatsumi E. , Kumagai S.
Published: June 2006

Peroxisome proliferator-activated receptor-γ (PPARγ), a member of the nuclear receptor superfamily, has been detected in several human leukemia cells. Recent studies reported that PPARγ ligands inhibit cell proliferation and induce apoptosis in both normal and malignant B-lineage cells. We investigated the expression of PPARγ and the effects of PPARγ ligands on UTree-O2, Bay91 and 380, three B-cell acute lymphoblastic leukemia (B-ALL) cell lines with t(14;18), which show a poor prognosis, accompanying c-myc abnormality. Western blot analysis identified expression of PPARγ protein and real-time PCR that of PPARγ mRNA on the three cell lines. Troglitazone (TGZ), a synthetic PPARγ ligand, inhibited cell growth in these cell lines in a dose-dependent manner, which was associated with G1 cell cycle arrest and apoptosis. We also found this effect PPARγ independent since PPARγ antagonists failed to reverse this effect. We assessed the expression of c-myc, an apoptosis-regulatory gene, since c-myc abnormality was detected in most B-ALL cells with t(14;18). TGZ was found to dose-dependently downregulate the expression of c-myc mRNA and c-myc protein in the three cell lines. These results suggest that TGZ inhibits cell growth via induction of G1 cell cycle arrest and apoptosis in these cell lines and that TGZ-induced apoptosis, at least in part, may be related to the downregulation of c-myc expression. Moreover, the downregulation of c-myc expression by TGZ may depend on a PPARγ-independent mechanism. Further studies indicate that PPARγ ligands may serve as a therapeutic agent in B-ALL with t(14;18).
Consequences of Sport-Imposed Weight Restriction in Childhood
Authors: Boisseau Nathalie
Published: June 2006

Today, young competitors undertake training programs including a high level of physical activity from an early age. This intensive training (volume and intensity) increases energy expenditure which has to be compensated by a greater nutritional intake. Ballet dancers, figure skaters, gymnasts or rhythmic gymnasts start training at the age of 5–6 years and most of them practice more than 20–30 h/week. In these activities, as well as for weight-class sports (wrestlers, jockeys, judo or boxing athletes), young elite athletes make conscious decisions to reduce food intakes to maintain the slender, pre-pubertal physique or to ‘make weight’. Adequate energy and micronutrient intakes are essential for growing children, and caloric and fluid restrictions during physical training in childhood or during adolescence could disturb metabolic and hormonal regulations affecting growth, maturation, body composition, menstrual cycle and reproductive capacity, and may increase the risk of injuries such as stress fractures. Furthermore, these strategies may develop eating disorders (anorexia and/or bulimia nervosa), especially during female adolescence, affecting body image, self-image and developing social and emotional maladjustments.
In situ Graft-Trimming Method Using Polyester Vascular Prosthesis for Inferior Vena Cava Reconstruction after Hepatectomy
Authors: Mizuguchi Toru , Katsuramaki Tadashi , Morishita Kiyofumi , Kawamoto Masaki , Nobuoka Takayuki , Imamura Masato , Kimura Yasutoshi , Hirata Koichi
Published: June 2006

Hepatectomy for secondary liver cancer that has invaded the inferior vena cava (IVC) can be the only way to achieve long-term survival. We describe a method for hepatectomy combined with partial IVC resection without venous bypass circulation and an in situ graft-trimming method to avoid graft size mismatch after reconstruction. We carried out left hepatectomy extended to segment 1 with partial IVC resection first. During resection and reconstruction of the IVC, it was clamped below the right hepatic vein and above the inferior right hepatic vein to maintain systemic circulation. The graft was trimmed in situ, after a half running suture of the graft was finished to ensure the correct size. Preservation of both inferior right hepatic vein and right hepatic vein helps to maintain systemic circulation during reconstruction of the IVC. The in situ graft-trimming method is an easy and safe method to ensure the correct graft size after IVC reconstruction.
Limited Impact of the Summer Heat Wave in France (2003) on Hospital Admissions and Relapses for Multiple Sclerosis
Authors: Tataru Nathalia , Vidal Chrystelle , Decavel Pierre , Berger Eric , Rumbach Lucien
Published: June 2006

Patients with multiple sclerosis (MS) often report worsening of symptoms with increased environmental temperature. The aim of this paper was to determine whether or not the heat wave of the summer of 2003 in France was responsible for an increase in hospital admissions and relapses in MS patients. MS patients who were hospitalized between January 1, 2000 and December 31, 2003 were identified, and we established which patients were suffering relapses. Hospitalization and relapse seasonality were examined and analyzed according to ambient temperature variations. We did not observe a greater number of hospital admissions and relapses during the summer of 2003 compared to the previous 3 years. Results showed that MS hospitalizations display a significant trough in the winter season, especially in December, but no significant peak season or month was observed. There was no statistically significant correlation between mean ambient temperature and the number of admissions and relapses. The adverse symptoms associated with high temperatures that are usually observed in MS patients may require rapid rises in ambient temperate or in internal body temperature.
Cognitive Impairment and Carotid Atherosclerosis in a General Italian Midlife and Old Population
Authors: Prati P. , Casaroli M. , Bignamini A. , Scotti S. , Canciani L. , Ruscio M. , Balestrieri M. , Bornstein N. , Zanetti O. , Tosetto A. , Castellani S. , Pantoni L. , Touboul P.J. , Inzitari D.
Published: June 2006

The authors describe the design and the general, ultrasonographic, neuropsychological methodology of an observational epidemiological population survey, named REMEMBER (Registry Evaluation Memory in Buttrio e Remanzacco) conducted in the northeast of Italy in a randomized stratified sample of 1,026 subjects (554 F and 472 M) aged 55–98 years. The study was planned as cross-sectional and longitudinal survey of cognitive impairment, cardiovascular risk factors, carotid atherosclerosis in a midlife and older Italian population sample. The objectives of the first phase are to assess the prevalence of the different types of dementia, the cognitive impairment non-dementia, the cardiovascular risk factors, the carotid intima-media thickness and arterial distensibility, and of depression. The conclusions of this study will make it possible to organize preventive and interventional strategies for these epidemic conditions.
Prevalence of Multiple Sclerosis in Isfahan, Iran
Authors: Etemadifar Masoud , Janghorbani Mohsen , Shaygannejad Vahid , Ashtari Fereshteh
Published: June 2006

Background: The prevalence of multiple sclerosis (MS) shows considerable variability all over the world. According to Kurtzke, Iran is considered to have a low prevalence. Objective: To estimate the period prevalence and risk factors of MS in Isfahan, central part of Iran. Methods: A cross-sectional case register study conducted between 2004 and 2005. In the province of Isfahan, Iran, all patients known to have definite MS during 2004 and 2005, being alive and resident within Isfahan as well as being a member of the Isfahan MS Association were included in the study. Demographic and case-related information was recorded. 1,391 definite MS patients (308 men and 1,083 women) from the Isfahan MS Association, Iran, have been identified. The disease was confirmed using clinical information and MRI findings by a neurologist and radiologist. The patients were evaluated by interview and a questionnaire. Population data were obtained from the year 1999 Iran Census. The mean (SD) age of the participants was 32.5 (9.3) years with a mean (SD) duration of the disease of 6.4 (5.1) years for men and 6.9 (5.3) years for women. Results: The period prevalence of MS was 35.5 per 100,000 [95% confidence interval (CI) 33.6–37.3] in a population of 3,923,255, with a higher rate in women than men [54.5 (95% CI: 51.1–57.8) for women and 14.9 (95% CI: 13.3–16.6) for men]. The female/male ratio was 3.6 (95% CI: 3.2–4.1). The direct age-adjusted period prevalence was 59.5 per 100,000 (95% CI: 44.8–75.2) for women and 17.0 per 100,000 (95% CI: 8.9–25.1) for men. MS rates were highest among 30- to 39-year-olds and decreased with increasing age. Sensory and visual disturbances were the most common initial presentations with a prevalence of 51.1% (95% CI: 48.4–53.7) and 47.0% (95% CI: 44.4–49.7), respectively. Conclusion: Isfahan could be considered as an area with a medium to high risk of MS. This is in sharp contrast with the gradient hypothesis.
Chemokines and Chemokine Receptors in Scleroderma
Authors: Yamamoto Toshiyuki
Published: June 2006

Scleroderma is a connective tissue disease with unknown etiology characterized by excessive deposition of extracellular matrix in the skin. Cellular infiltrates of certain immune cells and proinflammatory mediators are suggested to play a crucial role in cutaneous fibrosis, forming complicated networks between fibroblasts and immune cells via cell-cell communications. Tissue-selective trafficking of leukocytes is mediated by combinations of adhesion molecules and chemokines. Recent studies have shown that an increase in proinflammatory chemokines has been associated with the initiation and/or development of skin fibrosis/sclerosis, suggesting that chemokines and their receptors may be important mediators of inflammation and fibrosis in scleroderma. This review will focus on the roles of chemokines and their receptors during the process of cutaneous sclerosis and will also provide a current insight into the potential mechanisms of scleroderma.
Facioscapulohumeral Muscular Dystrophy and Occurrence of Heart Arrhythmia
Authors: Trevisan Carlo Pietro , Pastorello Ebe , Armani Mario , Angelini Corrado , Nante Giovanni , Tomelleri Giuliano , Tonin Paola , Mongini Tiziana , Palmucci Laura , Galluzzi Giuliana , Tupler Rossella G. , Barchitta Agata
Published: June 2006

Background: Subjects with facioscapulohumeral muscular dystrophy (FSHD) do not generally suffer from significant cardiac symptoms. Although with heterogeneous results, studies reported to date indicate that heart alterations unrelated to cardiomyopathy are possible in FSHD. Patients and Methods: We describe the findings of a multicenter investigation aimed at detecting cardiac abnormalities in 83 FSHD patients, 44 males and 39 females with a mean age of 47 years. All patients underwent clinical heart examination, 12-lead electrocardiography and 24-hour Holter monitoring; echocardiography was also performed on most patients. Results: Among the 83 patients, 62 with no cardiovascular risk factors were identified. Ten of them manifested clinical or subclinical cardiac involvement: 5 reported symptoms represented mostly by frequent palpitations secondary to supraventricular arrhythmia and another 5 exhibited electrocardiographic signs of short runs of supraventricular paroxysmal tachycardia. In the absence of cardiovascular risk factors, we found symptoms or signs of heart involvement of mainly arrhythmic origin in 10 of our 83 FSHD patients (12%). Conclusions: Considering our data and those available in the literature as a whole, arrhythmic alterations seem to be detected more frequently than expected in FSHD patients.
Climatology of Vertical Wind Shear over the Tropical Atlantic
Authors: Aiyyer Anantha R. , Thorncroft Chris
Published: June 2006

The spatiotemporal variability of the 200–850-hPa vertical wind shear over the tropical Atlantic is examined for a period of 46 yr. This work extends and updates past studies by considering a longer data record as well as a tropospheric-deep measure of vertical wind shear. Composite fields are constructed to illustrate the spatial pattern of the large-scale circulation associated with the mean and extreme cases of vertical shear within the tropical Atlantic. The contemporaneous relationship of vertical shear with El Niño–Southern Oscillation (ENSO) and Sahel precipitation are also examined. While the ENSO–shear correlation appears to have slightly strengthened during the past decade, the Sahel–shear correlation has become significantly degraded.

A combined empirical orthogonal function (EOF) analysis of the zonal and meridional components of the vertical shear reveals interannual and multidecadal modes. The leading EOF exhibits mainly interannual variability and is highly correlated with ENSO. The second EOF is associated with a multidecadal temporal evolution and is correlated with Sahel precipitation. Both EOFs correlate at the same level with tropical cyclones in the main development region of the tropical Atlantic.
Specification of Wintertime North American Surface Temperature
Authors: DelSole Timothy , Shukla J.
Published: June 2006

The extent to which wintertime North American surface temperature can be specified based on simultaneous sea surface temperature (SST) is quantified for the period 1982–98. The term specification indicates that the predictor and predictands are not lagged in time, as would be the case for true prediction. Four state-of-the-art general circulation models (GCMs) and linear empirical models with predictors derived from observations and dynamical models are considered. Predictors are derived from model hindcasts using principal component analysis (PCA), canonical correlation analysis (CCA), and discriminant analysis. The last technique has appeared in the climate literature, but its use in the present context appears new. A distinguishing feature of this paper is that several methods and models are compared in a common framework.

The specification skill of GCMs for the period 1982–98 is statistically significant in the northwestern region near Washington State, British Columbia, and central Canada, with some local correlations exceeding 0.6. The specification skill of GCMs is comparable to, or better than, the skill of the best empirical model for the particular 17-yr period examined.

No single specification strategy was found to improve the model hindcast skill in all cases. Predictors derived from discriminant analysis generally lead to larger skill than predictors based on PCA or CCA. The signal-to-noise ratio varies greatly among models and appears to be, if anything, inversely related to the specification skill when discriminants are used as predictors. Predictors based on 500-hPa geopotential height can lead to specification skill at least as good as predictors based on land surface temperature. Evidence is presented for the existence of at least two distinct dynamically predictable components of land surface temperature arising from two distinct “flavors” of SST anomalies associated with El Niño and La Niña.
On North Pacific Multidecadal Climate Variability
Authors: Latif Mojib
Published: June 2006

The multidecadal climate variability in the North Pacific region is investigated by using a 2000-yr-long integration with a coupled ocean–atmosphere general circulation model. It is shown that the multidecadal variability evolves largely independent of the variations in the tropical Pacific, so that this kind of multidecadal variability may be regarded as internal to the North Pacific. The coupled model results suggest that the multidecadal variability can be explained by the dynamical ocean response to stochastic wind stress forcing. Superimposed on the red background variability, a multidecadal mode with a period of about 40 yr is simulated by the coupled model. This mode can be understood through the concept of spatial resonance between the ocean and the atmosphere.
An Improved Land Surface Emissivity Parameter for Land Surface Models Using Global Remote Sensing Observations
Authors: Jin Menglin , Liang Shunlin
Published: June 2006

Because land surface emissivity (ɛ) has not been reliably measured, global climate model (GCM) land surface schemes conventionally set this parameter as simply constant, for example, 1 as in the National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Prediction (NCEP) model, and 0.96 for bare soil as in the National Center for Atmospheric Research (NCAR) Community Land Model version 2 (CLM2). This is the so-called constant-emissivity assumption. Accurate broadband emissivity data are needed as model inputs to better simulate the land surface climate. It is demonstrated in this paper that the assumption of the constant emissivity induces errors in modeling the surface energy budget, especially over large arid and semiarid areas where ɛ is far smaller than unity. One feasible solution to this problem is to apply the satellite-based broadband emissivity into land surface models.

The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument has routinely measured spectral emissivities (ɛλ) in six thermal infrared bands. The empirical regression equations have been developed in this study to convert these spectral emissivities to broadband emissivity (ɛ) required by land surface models. The observed emissivity data show strong seasonality and land-cover dependence. Specifically, emissivity depends on surface-cover type, soil moisture content, soil organic composition, vegetation density, and structure. For example, broadband ɛ is usually around 0.96–0.98 for densely vegetated areas [(leaf area index) LAI > 2], but it can be lower than 0.90 for bare soils (e.g., desert). To examine the impact of variable surface broadband emissivity, sensitivity studies were conducted using offline CLM2 and coupled NCAR Community Atmosphere Models, CAM2–CLM2. These sensitivity studies illustrate that large impacts of surface ɛ occur over deserts, with changes up to 1°–2°C in ground temperature, surface skin temperature, and 2-m surface air temperature, as well as evident changes in sensible and latent heat fluxes.
A Study of Historical Droughts in Southeastern Mexico
Authors: Mendoza Blanca , Velasco Victor , Jáuregui Ernesto
Published: June 2006

A catalog containing an unprecedented amount of historical data in the southeastern part of Mexico covering almost four centuries (1502–1899) is used to construct a drought time series. The catalog records information of agricultural disasters and includes events associated with hydrometeorological phenomena or hazards whose effects were mainly felt in the agricultural sector, such as droughts. An analysis of the historical series of droughts in southeastern Mexico for the period 1502–1899 is performed. The highest drought frequency occurred around the years 1650, 1782, and 1884; no droughts were reported around 1540, between 1630 and 1640, along the largest time lapse of 1672–1714, and between 1740 and 1760. From 1760 until the end of the period of study droughts definitively occur more often than they did from ∼1550 to 1760. In addition, most droughts lasted for 1–2 yr. Analyzing the frequencies of the drought time series it is found that the most conspicuous cycles are ∼3–4 and 7 yr, although cycles of ∼12, 20, 43, and 70 yr are also evident. The relation between droughts and El Niño events indicates that 38% of droughts are associated with El Niño. Sea surface temperature changes, the Southern Oscillation index, and solar activity leave their signals in the southeastern part of Mexico, with the signs in Oaxaca clearer than in the Yucatan Peninsula. However, the dominance of some phenomena over others depends on the time scales considered.
Transient Climate Simulations with the HadGEM1 Climate Model: Causes of Past Warming and Future Climate Change
Authors: Stott Peter A. , Jones Gareth S. , Lowe Jason A. , Thorne Peter , Durman Chris , Johns Timothy C. , Thelen Jean-Claude
Published: June 2006

The ability of climate models to simulate large-scale temperature changes during the twentieth century when they include both anthropogenic and natural forcings and their inability to account for warming over the last 50 yr when they exclude increasing greenhouse gas concentrations has been used as evidence for an anthropogenic influence on global warming. One criticism of the models used in many of these studies is that they exclude some forcings of potential importance, notably from fossil fuel black carbon, biomass smoke, and land use changes. Herein transient simulations with a new model, the Hadley Centre Global Environmental Model version 1 (HadGEM1), are described, which include these forcings in addition to other anthropogenic and natural forcings, and a fully interactive treatment of atmospheric sulfur and its effects on clouds. These new simulations support previous work by showing that there was a significant anthropogenic influence on near-surface temperature change over the last century. They demonstrate that black carbon and land use changes are relatively unimportant for explaining global mean near-surface temperature changes.

The pattern of warming in the troposphere and cooling in the stratosphere that has been observed in radiosonde data since 1958 can only be reproduced when the model includes anthropogenic forcings. However, there are some discrepancies between the model simulations and radiosonde data, which are largest where observational uncertainty is greatest in the Tropics and high latitudes.

Predictions of future warming have also been made using the new model. Twenty-first-century warming rates, following policy-relevant emissions scenarios, are slightly greater in HadGEM1 than in the Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) as a result of the extra forcing in HadGEM1. An experiment in which greenhouse gases and other anthropogenic forcings are stabilized at 2100 levels and held constant until 2200 predicts a committed twenty-second-century warming of less than 1 K, whose spatial distribution resembles that of warming during the twenty-first century, implying that the local feedbacks that determine the pattern of warming do not change significantly.
Summer Moisture Variability across Europe
Authors: van der Schrier G. , Briffa K. R. , Jones P. D. , Osborn T. J.
Published: June 2006

Maps of monthly self-calibrating Palmer Drought Severity Index (SC-PDSI) have been calculated for the period of 1901–2002 for Europe (35°–70°N, 10°W–60°E) with a spatial resolution of 0.5° × 0.5°. The recently introduced SC-PDSI is a convenient means of describing the spatial and temporal variability of moisture availability and is based on the more common Palmer Drought Severity Index. The SC-PDSI improves upon the PDSI by maintaining consistent behavior of the index over diverse climatological regions. This makes spatial comparisons of SC-PDSI values on continental scales more meaningful.

Over the region as a whole, the mid-1940s to early 1950s stand out as a persistent and exceptionally dry period, whereas the mid-1910s and late 1970s to early 1980s were very wet. The driest and wettest summers on record, in terms of the amplitude of the index averaged over Europe, were 1947 and 1915, respectively, while the years 1921 and 1981 saw over 11% and over 7% of Europe suffering from extreme dry or wet conditions, respectively.

Trends in summer moisture availability over Europe for the 1901–2002 period fail to be statistically significant, both in terms of spatial means of the drought index and in the area affected by drought. Moreover, evidence for widespread and unusual drying in European regions over the last few decades is not supported by the current work.
Tropical Intraseasonal Variability in 14 IPCC AR4 Climate Models. Part I: Convective Signals
Authors: Lin Jia-Lin , Kiladis George N. , Mapes Brian E. , Weickmann Klaus M. , Sperber Kenneth R. , Lin Wuyin , Wheeler Matthew C. , Schubert Siegfried D. , Del Genio Anthony , Donner Leo J. , Emori Seita , Gueremy Jean-Francois , Hourdin Frederic , Rasch Philip J. , Roeckner Erich , Scinocca John F.
Published: June 2006

This study evaluates the tropical intraseasonal variability, especially the fidelity of Madden–Julian oscillation (MJO) simulations, in 14 coupled general circulation models (GCMs) participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Eight years of daily precipitation from each model’s twentieth-century climate simulation are analyzed and compared with daily satellite-retrieved precipitation. Space–time spectral analysis is used to obtain the variance and phase speed of dominant convectively coupled equatorial waves, including the MJO, Kelvin, equatorial Rossby (ER), mixed Rossby–gravity (MRG), and eastward inertio–gravity (EIG) and westward inertio–gravity (WIG) waves. The variance and propagation of the MJO, defined as the eastward wavenumbers 1–6, 30–70-day mode, are examined in detail.

The results show that current state-of-the-art GCMs still have significant problems and display a wide range of skill in simulating the tropical intraseasonal variability. The total intraseasonal (2–128 day) variance of precipitation is too weak in most of the models. About half of the models have signals of convectively coupled equatorial waves, with Kelvin and MRG–EIG waves especially prominent. However, the variances are generally too weak for all wave modes except the EIG wave, and the phase speeds are generally too fast, being scaled to excessively deep equivalent depths. An interesting result is that this scaling is consistent within a given model across modes, in that both the symmetric and antisymmetric modes scale similarly to a certain equivalent depth. Excessively deep equivalent depths suggest that these models may not have a large enough reduction in their “effective static stability” by diabatic heating.

The MJO variance approaches the observed value in only 2 of the 14 models, but is less than half of the observed value in the other 12 models. The ratio between the eastward MJO variance and the variance of its westward counterpart is too small in most of the models, which is consistent with the lack of highly coherent eastward propagation of the MJO in many models. Moreover, the MJO variance in 13 of the 14 models does not come from a pronounced spectral peak, but usually comes from part of an overreddened spectrum, which in turn is associated with too strong persistence of equatorial precipitation. The two models that arguably do best at simulating the MJO are the only ones having convective closures/triggers linked in some way to moisture convergence.
Weak Simulated Extratropical Responses to Complete Tropical Deforestation
Authors: Findell Kirsten L. , Knutson Thomas R. , Milly P. C. D.
Published: June 2006

The Geophysical Fluid Dynamics Laboratory atmosphere–land model version 2 (AM2/LM2) coupled to a 50-m-thick slab ocean model has been used to investigate remote responses to tropical deforestation. Magnitudes and significance of differences between a control run and a deforested run are assessed through comparisons of 50-yr time series, accounting for autocorrelation and field significance. Complete conversion of the broadleaf evergreen forests of South America, central Africa, and the islands of Oceania to grasslands leads to highly significant local responses. In addition, a broad but mild warming is seen throughout the tropical troposphere (<0.2°C between 700 and 150 mb), significant in northern spring and summer. However, the simulation results show very little statistically significant response beyond the Tropics. There are no significant differences in any hydroclimatic variables (e.g., precipitation, soil moisture, evaporation) in either the northern or the southern extratropics. Small but statistically significant local differences in some geopotential height and wind fields are present in the southeastern Pacific Ocean. Use of the same statistical tests on two 50-yr segments of the control run show that the small but significant extratropical differences between the deforested run and the control run are similar in magnitude and area to the differences between nonoverlapping segments of the control run. These simulations suggest that extratropical responses to complete tropical deforestation are unlikely to be distinguishable from natural climate variability.
Great Plains Hydroclimate Variability: The View from North American Regional Reanalysis
Authors: Ruiz-Barradas Alfredo , Nigam Sumant
Published: June 2006

Interannual variability of warm-season rainfall over the Great Plains is analyzed using the recently released North American Regional Reanalysis (NARR). The new dataset differs from its global counterparts in the additional assimilation of precipitation and radiances. This along with the use of a more comprehensive land surface model in generation of NARR offers the prospect of obtaining improved estimates of surface hydrologic and near-surface meteorological fields.

NARR’s representation of hydroclimate is used to weigh in on the authors’ recent finding of the dominance of large-scale moisture flux convergence over evaporation in accounting for Great Plains precipitation variations. Evaporation estimates are notoriously uncertain and, while the NARR ones are not assured to be realistic, they are more constrained than those diagnosed before from inline and offline assessments.

NARR’s portrayal of warm-season hydroclimate variability corroborates the importance of remote water sources in generation of Great Plains precipitation variability and supports the authors’ claim that some state-of-the-art atmosphere/land surface models vigorously recycle precipitation, erroneously, at least in context of Great Plains interannual variability. These very models have been key to recent claims of strong coupling between soil moisture and precipitation.
Influences of the Atlantic Warm Pool on Western Hemisphere Summer Rainfall and Atlantic Hurricanes
Authors: Wang Chunzai , Enfield David B. , Lee Sang-ki , Landsea Christopher W.
Published: June 2006

The Atlantic warm pool (AWP) of water warmer than 28.5°C comprises the Gulf of Mexico, the Caribbean Sea, and the western tropical North Atlantic (TNA). The AWP reaches its maximum size around September, with large AWPs being almost 3 times larger than small ones. Although ENSO teleconnections are influential on the AWP, about two-thirds of the large and small AWP variability appears unrelated to ENSO. The AWP is usually geographically different from the TNA; however, the AWP size is correlated with the TNA SST anomalies. During August to October, large AWPs and warm TNA are associated with increased rainfall over the Caribbean, Mexico, the eastern subtropical Atlantic, and the southeast Pacific, and decreased rainfall in the northwest United States, Great Plains, and eastern South America. In particular, rainfall in the Caribbean, Central America, and eastern South America from August to October is mainly related to the size of the AWP. Large (small) AWPs and warm (cold) TNA correspond to a weakening (strengthening) of the northward surface winds from the AWP to the Great Plains that disfavors (favors) moisture transport for rainfall over the Great Plains. On the other hand, large (small) AWPs and warm (cold) TNA strengthen (weaken) the summer regional Atlantic Hadley circulation that emanates from the warm pool region into the southeast Pacific, changing the subsidence over the southeast Pacific and thus the stratus cloud and drizzle there. The large AWP, associated with a decrease in sea level pressure and an increase in atmospheric convection and cloudiness, corresponds to a weak tropospheric vertical wind shear and a deep warm upper ocean, and thus increases Atlantic hurricane activity.
Seasonality of Decadal Sea Surface Temperature Anomalies in the Northwestern Pacific
Authors: Mochizuki Takashi , Kida Hideji
Published: June 2006

The seasonality of the decadal sea surface temperature (SST) anomalies and the related physical processes in the northwestern Pacific were investigated using a three-dimensional bulk mixed layer model. In the Kuroshio–Oyashio Extension (KOE) region, the strongest decadal SST anomaly was observed during December–February, while that of the central North Pacific occurred during February–April. From an examination of the seasonal heat budget of the ocean mixed layer, it was revealed that the seasonal-scale enhancement of the decadal SST anomaly in the KOE region was controlled by horizontal Ekman temperature transport in early winter and by vertical entrainment in autumn. The temperature transport by the geostrophic current made only a slight contribution to the seasonal variation of the decadal SST anomaly, despite controlling the upper-ocean thermal conditions on decadal time scales through the slow Rossby wave adjustment to the wind stress curl.

When averaging over the entire KOE region, the contribution from the net sea surface heat flux was also no longer significantly detected. By examining the horizontal distributions of the local thermal damping rate, however, it was concluded that the wintertime decadal SST anomaly in the eastern KOE region was rather damped by the net sea surface heat flux. It was due to the fact that the anomalous local thermal damping of the SST anomaly resulting from the vertical entrainment in autumn was considerably strong enough to suppress the anomalous local atmospheric thermal forcing that acted to enhance the decadal SST anomaly.
Recent Trends in Land Surface Temperature on the Tibetan Plateau
Authors: Oku Yuichiro , Ishikawa Hirohiko , Haginoya Shigenori , Ma Yaoming
Published: June 2006

The diurnal, seasonal, and interannual variations in land surface temperature (LST) on the Tibetan Plateau from 1996 to 2002 are analyzed using the hourly LST dataset obtained by Japanese Geostationary Meteorological Satellite 5 (GMS-5) observations. Comparing LST retrieved from GMS-5 with independent precipitation amount data demonstrates the consistent and complementary relationship between them. The results indicate an increase in the LST over this period. The daily minimum has risen faster than the daily maximum, resulting in a narrowing of the diurnal range of LST. This is in agreement with the observed trends in both global and plateau near-surface air temperature. Since the near-surface air temperature is mainly controlled by LST, this result ensures a warming trend in near-surface air temperature.
Modeling the Hydrological Effect on Local Gravity at Moxa, Germany
Authors: Hasan Shaakeel , Troch Peter A. , Boll J. , Kroner C.
Published: June 2006

A superconducting gravimeter has observed with high accuracy (to within a few nm s−2) and high frequency (1 Hz) the temporal variations in the earth’s gravity field near Moxa, Germany, since 1999. Hourly gravity residuals are obtained by time averaging and correcting for earth tides, polar motion, barometric pressure variations, and instrumental drift. These gravity residuals are significantly affected by hydrological processes (interception, infiltration, surface runoff, and subsurface redistribution) in the vicinity of the observatory. In this study time series analysis and distributed hydrological modeling techniques are applied to understand the effect of these hydrological processes on observed gravity residuals. It is shown that the short-term response of gravity residuals to medium- to high-rainfall events can be efficiently modeled by means of a linear transfer function. This transfer function exhibits an oscillatory behavior that indicates fast redistribution of stored water in the upper layers (interception store, root zone) of the catchment surrounding the instrument. The relation between groundwater storage and gravity residuals is less clear and varies according to the season. High positive correlation between groundwater and gravity exists during winter months when the freezing of the upper soil layers immobilizes water stored in the unsaturated zone of the catchment. To further explore the spatiotemporal dynamics of the relevant hydrological processes and their relation to observed gravity residuals, a GIS-based distributed hydrological model is applied for the Silberleite catchment. Driven by observed atmospheric forcings (precipitation and potential evapotranspiration), the model allows the authors to compute the variation of water storage in three different layers: the interception store, the snow cover store, and the soil moisture store. These water storage dynamics are then converted to predicted gravity variation at the location of the superconducting gravimeter and compared to observed gravity residuals. During most of the investigated period (January 2000 to January 2004) predictions are in good agreement with the observed patterns of gravity dynamics. However, during some winter months the distributed hydrological model fails to explain the observations, which supports the authors’ conclusion that groundwater variability dominates the hydrological gravity signal in the winter. More hydrogeological research is needed to include groundwater dynamics in the hydrological model.
GEOtop: A Distributed Hydrological Model with Coupled Water and Energy Budgets
Authors: Rigon Riccardo , Bertoldi Giacomo , Over Thomas M.
Published: June 2006

This paper describes a new distributed hydrological model, called GEOtop. The model accommodates very complex topography and, besides the water balance, unlike most other hydrological models, integrates all the terms in the surface energy balance equation. GEOtop uses a discretization of the landscape based on digital elevation data. These digital elevation data are preprocessed to allow modeling of the effect of topography on the radiation incident on the surface, both shortwave (including shadowing) and longwave (accounting for the sky view factor). For saturated and unsaturated subsurface flow, GEOtop makes use of a numerical solution of the 3D Richards’ equation in order to properly model, besides the lateral flow, the vertical structure of water content and the suction dynamics. These characteristics are deemed necessary for consistently modeling hillslope processes, initiation of landslides, snowmelt processes, and ecohydrological phenomena as well as discharges during floods and interstorm periods. An accurate treatment of radiation inputs is implemented in order to be able to return surface temperature. The motivation behind the model is to combine the strengths and overcome the weaknesses of flood forecasting and land surface models. The former often include detailed spatial description and lateral fluxes but usually lack appropriate knowledge of the vertical ones. The latter are focused on vertical structure and usually lack spatial structure and prediction of lateral fluxes. Outlines of the processes simulated and the methods used to simulate them are given. A series of applications of the model to the Little Washita basin of Oklahoma using data from the Southern Great Plains 1997 Hydrology Experiment (SGP97) is presented. These show the model’s ability to reproduce the pointwise energy and water balance, showing that just an elementary calibration of a few parameters is needed for an acceptable reproduction of discharge at the outlet, for the prediction of the spatial distribution of soil moisture content, and for the simulation of a full year’s streamflow without additional calibration.
Impact of Incorrect Model Error Assumptions on the Sequential Assimilation of Remotely Sensed Surface Soil Moisture
Authors: Crow Wade T. , Van Loon Emiel
Published: June 2006

Data assimilation approaches require some type of state forecast error covariance information in order to optimally merge model predictions with observations. The ensemble Kalman filter (EnKF) dynamically derives such information through a Monte Carlo approach and the introduction of random noise in model states, fluxes, and/or forcing data. However, in land data assimilation, relatively little guidance exists concerning strategies for selecting the appropriate magnitude and/or type of introduced model noise. In addition, little is known about the sensitivity of filter prediction accuracy to (potentially) inappropriate assumptions concerning the source and magnitude of modeling error. Using a series of synthetic identical twin experiments, this analysis explores the consequences of making incorrect assumptions concerning the source and magnitude of model error on the efficiency of assimilating surface soil moisture observations to constrain deeper root-zone soil moisture predictions made by a land surface model. Results suggest that inappropriate model error assumptions can lead to circumstances in which the assimilation of surface soil moisture observations actually degrades the performance of a land surface model (relative to open-loop assimilations that lack a data assimilation component). Prospects for diagnosing such circumstances and adaptively correcting the culpable model error assumptions using filter innovations are discussed. The dual assimilation of both runoff (from streamflow) and surface soil moisture observations appears to offer a more robust assimilation framework where incorrect model error assumptions are more readily diagnosed via filter innovations.
Feasibility Test of Multifrequency Radiometric Data Assimilation to Estimate Snow Water Equivalent
Authors: Durand Michael , Margulis Steven A.
Published: June 2006

A season-long, point-scale radiometric data assimilation experiment is performed in order to test the feasibility of snow water equivalent (SWE) estimation. Synthetic passive microwave observations at Special Sensor Microwave Imager (SSM/I) and Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) frequencies and synthetic broadband albedo observations are assimilated simultaneously in order to update snowpack states in a land surface model using the ensemble Kalman filter (EnKF). The effects of vegetation and atmosphere are included in the radiative transfer model (RTM). The land surface model (LSM) was given biased precipitation to represent typical errors introduced in modeling, yet was still able to recover the true value of SWE with a seasonally integrated rmse of only 2.95 cm, despite a snow depth of around 3 m and the presence of liquid water in the snowpack. This ensemble approach is ideal for investigating the complex theoretical relationships between the snowpack properties and the observations, and exploring the implications of these relationships for the inversion of remote sensing measurements for estimating snowpack properties. The contributions of each channel to recovering the true SWE are computed, and it was found that the low-frequency 10.67-GHz AMSR-E channels contain information even for very deep snow. The effect of vegetation thickness on assimilation results is explored. Results from the assimilation are compared to those from a pure modeling approach and from a remote sensing inversion approach, and the effects of measurement error and ensemble size are investigated.
Contribution of Thermal Infrared Remote Sensing Data in Multiobjective Calibration of a Dual-Source SVAT Model
Authors: Coudert Benoit , Ottlé Catherine , Boudevillain Brice , Demarty Jérôme , Guillevic Pierre
Published: June 2006

This study fits within the overall research on the usage of space remote sensing data to constrain land surface models (LSMs) (also called SVAT models for soil–vegetation–atmosphere transfer). The goal of this paper is to analyze the potential of using thermal infrared (TIR) remote sensing data for LSM calibration. LSMs are characterized by a large number of parameters and initial conditions that have to be specified. This model calibration is generally performed at a local scale by minimization between measurements and time series difference. Recent studies have shed light on the use of multiobjective approaches for performing calibration and for analyzing the model’s sensitivity to input parameters. Such an approach has been implemented in the SEtHyS LSM (for “Suivi de l’Etat Hydrique des Sols,” the French acronym for soil moisture monitoring) with the objective of assessing the information contributed by having knowledge of the remote sensing surface brightness temperature. For this purpose, the model calibration was performed in three different cases at field scale corresponding to different calibration design. The analysis of these numerical experiments permits the authors to show the contribution and the limits of TIR remote sensing data for LSM calibration, in various environmental conditions. The perspectives underline the potential of using a dynamic calibration methodology, taking advantage of the time-varying model parameters’ influence.
Real-Time Data Assimilation for Operational Ensemble Streamflow Forecasting
Authors: Vrugt Jasper A. , Gupta Hoshin V. , Nualláin BreanndánÓ , Bouten Willem
Published: June 2006

Operational flood forecasting requires that accurate estimates of the uncertainty associated with model-generated streamflow forecasts be provided along with the probable flow levels. This paper demonstrates a stochastic ensemble implementation of the Sacramento model used routinely by the National Weather Service for deterministic streamflow forecasting. The approach, the simultaneous optimization and data assimilation method (SODA), uses an ensemble Kalman filter (EnKF) for recursive state estimation allowing for treatment of streamflow data error, model structural error, and parameter uncertainty, while enabling implementation of the Sacramento model without major modification to its current structural form. Model parameters are estimated in batch using the shuffled complex evolution metropolis stochastic-ensemble optimization approach (SCEM-UA). The SODA approach was implemented using parallel computing to handle the increased computational requirements. Studies using data from the Leaf River, Mississippi, indicate that forecast performance improvements on the order of 30% to 50% can be realized even with a suboptimal implementation of the filter. Further, the SODA parameter estimates appear to be less biased, which may increase the prospects for finding useful regionalization relationships.
Snow Data Assimilation via an Ensemble Kalman Filter
Authors: Slater Andrew G. , Clark Martyn P.
Published: June 2006

A snow data assimilation study was undertaken in which real data were used to update a conceptual model, SNOW-17. The aim of this study is to improve the model’s estimate of snow water equivalent (SWE) by merging the uncertainties associated with meteorological forcing data and SWE observations within the model. This is done with a view to aiding the estimation of snowpack initial conditions for the ultimate objective of streamflow forecasting via a distributed hydrologic model. To provide a test of this methodology, the authors performed experiments at 53 stations in Colorado. In each case the situation of an unobserved location is mimicked, using the data at any given station only for validation; essentially, these are withholding experiments. Both ensembles of model forcing data and assimilated data were derived via interpolation and stochastic modeling of data from surrounding sources. Through a process of cross validation the error for the ensemble of model forcing data and assimilated observations is explicitly estimated. An ensemble square root Kalman filter is applied to perform assimilation on a 5-day cycle. Improvements in the resulting SWE are most evident during the early accumulation season and late melt period. However, the large temporal correlation inherent in a snowpack results in a less than optimal assimilation and the increased skill is marginal. Once this temporal persistence is removed from both model and assimilated observations during the update cycle, a result is produced that is, within the limits of available information, consistently superior to either the model or interpolated observations.