bluuebunny/crossref_metadata_2025 huggingface dataset:
PERFORMANCE CHARACTERISTICS OF A SIMULTANEOUS HEATING AND COOLING HEAT PUMP IN THE HEAT RECOVERY MODE
Authors: CHOI JONGMIN , CHOUNG HYUN JOON , JOO YOUNGJU , KANG HOON , KIM YONGCHAN
Published: January 2011

The cooling load in winter is significant in buildings and hotels because of the usage of office equipments and the high efficiency of wall insulation. Hence, the development of a multi-heat pump that can cover heating and cooling simultaneously for each indoor unit is required. In this study, the performance of a simultaneous heating and cooling heat pump was investigated in the heat recovery mode (HR mode). The system adopted a variable speed compressor using R-410A with four indoor units and one outdoor unit. In the HR mode, the capacity and COP were improved as compared with those in the cooling or heating mode because the waste heat in the outdoor unit was utilized as useful heat in the indoor units. However, energy imbalance between heating and cooling capacities of each indoor unit was observed in the 2H–1C HR mode. Therefore, the performance of the system in the 2H–1C HR mode was enhanced by controlling refrigerant flow rate through the outdoor unit.
COMPARATIVE ANALYSIS OF SECONDARY CO2 SYSTEMS AND WATER-BASED BRINES IN INDUSTRIAL AND COMMERCIAL REFRIGERATION APPLICATIONS
Authors: MIKHAILOV A. , MATTHIESEN H. O.
Published: January 2011

In this paper, a comparative study of CO2 and water-based brine secondary cooling systems for refrigeration applications is presented. CO2 secondary systems are simple and could prove to be attractive for high temperature (HT) and medium temperature (MT) in industrial and commercial refrigeration applications regardless of climate. Calculations show that CO2 secondary systems give a possibility of energy savings in the range of 10–20% for HT systems and more than 20–30% for MT systems. The design and particular challenges of CO2 systems are discussed. The analysis is illustrated by case studies. Further possibilities to optimized secondary CO2 systems by modulating pressure or applying frequency converters are discussed. The use of secondary CO2 systems in commercial refrigeration installations (supermarket systems) is briefly discussed.
PARAMETRIC STUDY ON TRANSIENT HOT-WIRE METHOD TO MEASURE NANOFLUID CONDUCTIVITIES
Authors: HONG SUNG WOOK , JUNG JUNG-YEUL , KANG YONG TAE , KOO JUNEMO
Published: January 2011

Recently, nanofluid is a hot research topic among thermal engineers to enhance the heat transfer. However, there are deviations between research groups in the effective thermal conductivity measurements by the transient hot-wire method. Since there has been no report for the researchers to select a proper data range of temperature to estimate the thermal conductivities, the deviation could be partly attributed to the poor selection of the temperature data range. In this study, the impacts of the data range selection, the power supplier response delay, the thermal coefficient of resistors, the hot-wire type and test section size on the thermal conductivity measurement using the transient hot-wire method are analyzed.

The proper selection of the temperature data range to be used to estimate the thermal conductivities of fluids using transient hot-wire method is suggested by investigating the impact of it on the measurement by both computationally and experimentally. The thermal coefficient of resistor is found to affect the measurement seriously whereas the type of hot-wire does not. The test section size of the measuring device is compared with the thermal penetration depth.
Loss of Smad5 leads to the disassembly of the apical junctional complex and increased susceptibility to experimental colitis
Authors: Allaire Joannie M. , Darsigny Mathieu , Marcoux Sébastien S. , Roy Sébastien A. B. , Schmouth Jean-Francois , Umans Lieve , Zwijsen An , Boudreau François , Perreault Nathalie
Published: January 2011

The regulation of intestinal epithelial cell adhesion and migratory properties is often compromised in inflammatory bowel disease (IBD). Despite an increasing interest in bone morphogenetic protein (Bmp) signaling in gut pathologies, little is known of the specific roles played by individual Smads in intestinal epithelial functions. In the present study, we generated a mouse model with deletion of Smad5 transcriptional effector of the Bmp signaling pathway exclusively in the intestinal epithelium. Proliferation, migration, and apical junctional complex (AJC) protein expression were analyzed by immunofluorescence and Western blot. Human intestinal biopsies from control and IBD patients were analyzed for SMAD5 gene transcript expression by quantitative PCR (qPCR). Smad5ΔIECand control mice were subjected to dextran sulfate sodium (DSS)-induced experimental colitis, and their clinical and histological symptoms were assessed. Loss of Smad5 led to intestinal epithelial hypermigration and deregulation of the expression of claudin-1 and claudin-2. E-cadherin was found to be equally expressed but displaced from the AJC to the cytoplasm in Smad5ΔIECmice. Analysis of SMAD5 gene expression in human IBD patient samples revealed a significant downregulation of the gene transcript in Crohn's disease and ulcerative colitis samples. Smad5ΔIECmice exposed to experimental DSS colitis were significantly more susceptible to the disease and had impaired wound healing during the recovery phase. Our results support that Smad5 is partly responsible for mediating Bmp signals in intestinal epithelial cells. In addition, deficiency in epithelial Smad5 leads to the deregulation of cell migration by disassembling the AJC with increasing susceptibility to experimental colitis and impairment in wound healing.
Myocardial blood volume and coronary resistance during and after coronary angioplasty
Authors: Indermühle Andreas , Vogel Rolf , Meier Pascal , Zbinden Rainer , Seiler Christian
Published: January 2011

Animal experiments have shown that the coronary circulation is pressure distensible, i.e., myocardial blood volume (MBV) increases with perfusion pressure. In humans, however, corresponding measurements are lacking so far. We sought to quantify parameters reflecting coronary distensibility such as MBV and coronary resistance (CR) during and after coronary angioplasty. Thirty patients with stable coronary artery disease underwent simultaneous coronary perfusion pressure assessment and myocardial contrast echocardiography (MCE) of 37 coronary arteries and their territories during and after angioplasty. MCE yielded MBV and myocardial blood flow (MBF; in ml·min−1·g−1). Complete data sets were obtained in 32 coronary arteries and their territories from 26 patients. During angioplasty, perfusion pressure, i.e., coronary occlusive pressure, and MBV varied between 9 and 57 mmHg (26.9 ± 11.9 mmHg) and between 1.2 and 14.5 ml/100 g (6.7 ± 3.7 ml/100 g), respectively. After successful angioplasty, perfusion pressure and MBV increased significantly ( P < 0.001 for both) and varied between 64 and 118 mmHg (93.5 ± 12.8 mmHg) and between 3.7 and 17.3 ml/100 g (9.8 ± 3.4 ml/100 g), respectively. Mean MBF increased from 31 ± 20 ml·min−1·g−1 during coronary occlusion, reflecting collateral flow, to 121 ± 33 ml·min−1·g−1 ( P < 0.01), whereas mean CR, i.e., the ratio of perfusion pressure and MBF, decreased by 20% ( P < 0.001). In conclusion, the human coronary circulation is pressure distensible. MCE allows for the quantification of CR and MBV in humans.
Pharmacological intervention against bubble-induced platelet aggregation in a rat model of decompression sickness
Authors: Pontier Jean-Michel , Vallée Nicolas , Ignatescu Mihaela , Bourdon Lionel
Published: January 2011

Decompression sickness (DCS) with alterations in coagulation system and formation of platelet thrombi occurs when a subject is subjected to a reduction in environmental pressure. Blood platelet consumption after decompression is clearly linked to bubble formation in humans and offers an index for evaluating DCS severity in animal models. Previous studies highlighted a predominant involvement of platelet activation and thrombin generation in bubble-induced platelet aggregation (BIPA). To study the mechanism of the BIPA in DCS, we examined the effect of acetylsalicylic acid (ASA), heparin (Hep), and clopidogrel (Clo), with anti-thrombotic dose pretreatment in a rat model of DCS. Male Sprague-Dawley rats ( n = 208) were randomly assigned to one experimental group treated before the hyperbaric exposure and decompression protocol either with ASA (3×100 mg·kg−1·day−1, n = 30), Clo (50 mg·kg−1·day−1, n = 60), Hep (500 IU/kg, n = 30), or to untreated group ( n = 49). Rats were first compressed to 1,000 kPa (90 msw) for 45 min and then decompressed to surface in 38 min. In a control experiment, rats were treated with ASA ( n = 13), Clo ( n = 13), or Hep ( n = 13) and maintained at atmospheric pressure for an equivalent period of time. Onset of DCS symptoms and death were recorded during a 60-min observation period after surfacing. DCS evaluation included pulmonary and neurological signs. Blood samples for platelet count (PC) were taken 30 min before hyperbaric exposure and 30 min after surfacing. Clo reduces the DCS mortality risk (mortality rate: 3/60 with Clo, 15/30 with ASA, 21/30 with Hep, and 35/49 in the untreated group) and DCS severity (neurological DCS incidence: 9/60 with Clo, 6/30 with ASA, 5/30 with Hep, and 12/49 in the untreated group). Clo reduced fall in platelet count and BIPA (−4,5% with Clo, −19.5% with ASA, −19,9% with Hep, and −29,6% in the untreated group). ASA, which inhibits the thromboxane A2 pathway, and Hep, which inhibits thrombin generation, have no protective effect on DCS incidence. Clo, a specific ADP-receptor antagonist, reduces post-decompression platelet consumption. These results point to the predominant involvement of the ADP release in BIPA but cannot differentiate definitively between bubble-induced vessel wall injury and bubble-blood component interactions in DCS.
Gap junctions in IL-1β-mediated cell survival response to strain
Authors: Qi Jie , Chi Liqun , Bynum Donald , Banes Albert J.
Published: January 2011

Mechanical stimuli play important roles in proliferation and differentiation of connective tissue cells, and development and homeostatic maintenance of tissues. However, excessive mechanical loading to a tissue can injure cells and disrupt the matrix, as occurs in tendinopathy. Tendinopathy is a common clinical problem in athletes and in many occupational settings due to overuse of the tendon. Moreover, interleukin (IL)-1β is generally considered to be a “bad” cytokine, activating NF-κb and cell death and inducing matrix metalloproteinase (MMPs 1, 2, 3) expression and matrix destruction. However, activated NF-κB can also drive a cell survival pathway. We have reported that cyclic strain induced tenocyte death in three-dimensional (3D) cultures, and IL-1β could promote cell survival under strain. Therefore, it was hypothesized that 1) cyclic strain could induce cell death in tenocytes as observed in pathologic tendons in vivo; 2) a gene expression profile indicative of tendinopathy could be identified; and 3) low-dose IL-1β could protect cells from strain-induced, tendinopathy-like changes. Human tenocytes were cultured in 3D type I collagen hydrogels and subjected to 3.5% elongation at 1 Hz for 1 h/day for up to 5 days with or without IL-1β. Real-time RT-PCR data showed that cyclic strain regulated the expression of tendinopathy marker genes in a manner similar to that found in pathological tendons from patients and that addition of IL-1β reversed the gene expression changes to control levels. Results of further studies showed that IL-1β may modulate cell survival through upregulating the expression of connexin 43, which is involved in the modulation of cell death/survival in a variety of cells and tissues. The elucidation of the mechanisms underlying strain-induced cell death and recovery from strain injury will facilitate our understanding of the pathogenesis of tendinopathy and may lead to the discovery of new molecular targets for early diagnosis and treatment of tendinopathy.
Gait transitions in simulated reduced gravity
Authors: Ivanenko Yuri P. , Labini Francesca Sylos , Cappellini Germana , Macellari Velio , McIntyre Joseph , Lacquaniti Francesco
Published: January 2011

Gravity has a strong effect on gait and the speed of gait transitions. A gait has been defined as a pattern of locomotion that changes discontinuously at the transition to another gait. On Earth, during gradual speed changes, humans exhibit a sudden discontinuous switch from walking to running at a specific speed. To study the effects of altered gravity on both the stance and swing legs, we developed a novel unloading exoskeleton that allows a person to step in simulated reduced gravity by tilting the body relative to the vertical. Using different simulation techniques, we confirmed that at lower gravity levels the transition speed is slower (in accordance with the previously reported Froude number ∼0.5). Surprisingly, however, we found that at lower levels of simulated gravity the transition between walking and running was generally gradual, without any noticeable abrupt change in gait parameters. This was associated with a significant prolongation of the swing phase, whose duration became virtually equal to that of stance in the vicinity of the walk-run transition speed, and with a gradual shift from inverted-pendulum gait (walking) to bouncing gait (running).
VEGFR-1 Expressed by Malignant Melanoma-Initiating Cells Is Required for Tumor Growth
Authors: Frank Natasha Y. , Schatton Tobias , Kim Soo , Zhan Qian , Wilson Brian J. , Ma Jie , Saab Karim R. , Osherov Veronika , Widlund Hans R. , Gasser Martin , Waaga-Gasser Ana-Maria , Kupper Thomas S. , Murphy George F. , Frank Markus H.
Published: January 2011

Melanoma growth is driven by malignant melanoma-initiating cells (MMIC) identified by expression of the ATP-binding cassette (ABC) member ABCB5. ABCB5+ melanoma subpopulations have been shown to overexpress the vasculogenic differentiation markers CD144 (VE-cadherin) and TIE1 and are associated with CD31− vasculogenic mimicry (VM), an established biomarker associated with increased patient mortality. Here we identify a critical role for VEGFR-1 signaling in ABCB5+ MMIC-dependent VM and tumor growth. Global gene expression analyses, validated by mRNA and protein determinations, revealed preferential expression of VEGFR-1 on ABCB5+ tumor cells purified from clinical melanomas and established melanoma lines. In vitro, VEGF induced the expression of CD144 in ABCB5+ subpopulations that constitutively expressed VEGFR-1 but not in ABCB5− bulk populations that were predominantly VEGFR-1−. In vivo, melanoma-specific shRNA-mediated knockdown of VEGFR-1 blocked the development of ABCB5+ VM morphology and inhibited ABCB5+ VM-associated production of the secreted melanoma mitogen laminin. Moreover, melanoma-specific VEGFR-1 knockdown markedly inhibited tumor growth (by >90%). Our results show that VEGFR-1 function in MMIC regulates VM and associated laminin production and show that this function represents one mechanism through which MMICs promote tumor growth. Cancer Res; 71(4); 1474–85. ©2011 AACR.
Mast Cell Activation In Vivo Impairs the Macrophage Reverse Cholesterol Transport Pathway in the Mouse
Authors: Lee-Rueckert Miriam , Silvennoinen Reija , Rotllan Noemi , Judström Ilona , Blanco-Vaca Francisco , Metso Jari , Jauhiainen Matti , Kovanen Petri T. , Escola-Gil Joan Carles
Published: January 2011

Objective—

Chymase released by activated mast cells degrades high-density lipoproteins. We evaluated whether local activation of mast cells would attenuate cholesterol efflux from neighboring macrophage foam cells, thereby disrupting the entire in vivo pathway of macrophage-specific reverse cholesterol transport (RCT).

Methods and Results—

C57Bl/6J mice received intraperitoneal injections of the mast cell-degranulating compound 48/80 to induce peritoneal mast cell activation, human apolipoprotein A-I (apoA-I) to stimulate RCT, and [
3
H]cholesterol-labeled J774 macrophages for measurement of the rate of RCT. After 3 hours,
3
H-radioactivity was measured in the intestinal lumen contents. Activation of mast cells in the peritoneal cavity depleted human apoA-I pre-β-migrating species, impairing the ability of the peritoneal fluid to efficiently promote cholesterol efflux from cultured macrophages. Moreover, intact but not chymase-treated (proteolyzed) apoA-I accelerated the transfer of macrophage-derived
3
H- radioactivity to the intestinal contents. Importantly, stimulation of RCT by human apoA-I was fully blocked by 48/80 in mast cell–competent wild-type C57Bl/6J mice but not in mast cell–deficient W-
sash
c-
kit
mutant mice. The ability of intraperitoneally administered phospholipid vesicles to promote RCT in wild-type mice was not blocked by 48/80, supporting the notion that mast cell–dependent proteolysis of the intraperitoneally administered apoA-I was responsible for RCT inhibition.

Conclusion—

Overall, our results suggest that tissue-specific activation of mast cells with ensuing release of chymase is able to proteolytically inactivate apoA-I in the microenvironment of the activated mast cells, thus locally impairing the initiation of macrophage RCT in vivo.
Prototyping a Generic, Unified Land Surface Classification and Screening Methodology for GPM-Era Microwave Land Precipitation Retrieval Algorithms
Authors: Sudradjat Arief , Wang Nai-Yu , Gopalan Kaushik , Ferraro Ralph R.
Published: January 2011

A prototype generic, unified land surface classification and screening methodology for Global Precipitation Measurement (GPM)-era microwave land precipitation retrieval algorithms by using ancillary datasets is developed. As an alternative to the current radiometer-determined approach, the new methodology is shown to be promising in improving rain detection by providing better surface-cover-type information. The early prototype new surface screening scheme was applied to the current version of the Goddard profiling algorithm that is used for the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (GPROFV6). It has shown improvements in surface-cover-type classification and hence better precipitation retrieval comparisons with TRMM precipitation radar level-2 (L2) (2A25) data and the Global Precipitation Climatology Project (GPCP) version-2.1 (GPCPV2.1) datasets. The new ancillary data approach removes the current dependency of the screening step on relatively different satellite-specific channels and ensures the comparability and continuity of satellite-based precipitation products from different platforms. This is particularly important for advancing the current state of precipitation retrieval over land and for use in merged rainfall products.
Surface Emissivity Impact on Temperature and Moisture Soundings from Hyperspectral Infrared Radiance Measurements
Authors: Yao Zhigang , Li Jun , Li Jinlong , Zhang Hong
Published: January 2011

An accurate land surface emissivity (LSE) is critical for the retrieval of atmospheric temperature and moisture profiles along with land surface temperature from hyperspectral infrared (IR) sounder radiances; it is also critical to assimilating IR radiances in numerical weather prediction models over land. To investigate the impact of different LSE datasets on Atmospheric Infrared Sounder (AIRS) sounding retrievals, experiments are conducted by using a one-dimensional variational (1DVAR) retrieval algorithm. Sounding retrievals using constant LSE, the LSE dataset from the Infrared Atmospheric Sounding Interferometer (IASI), and the baseline fit dataset from the Moderate Resolution Imaging Spectroradiometer (MODIS) are performed. AIRS observations over northern Africa on 1–7 January and 1–7 July 2007 are used in the experiments. From the limited regional comparisons presented here, it is revealed that the LSE from the IASI obtained the best agreement between the retrieval results and the ECMWF reanalysis, whereas the constant LSE gets the worst results when the emissivities are fixed in the retrieval process. The results also confirm that the simultaneous retrieval of atmospheric profile and surface parameters could reduce the dependence of soundings on the LSE choice and finally improve sounding accuracy when the emissivities are adjusted in the iterative retrieval. In addition, emissivity angle dependence is investigated with AIRS radiance measurements. The retrieved emissivity spectra from AIRS over the ocean reveal weak angle dependence, which is consistent with that from an ocean emissivity model. This result demonstrates the reliability of the 1DVAR simultaneous algorithm for emissivity retrieval from hyperspectral IR radiance measurements.
Regional and Large-Scale Influences on Summer Ozone Levels in Southern California
Authors: Agel Laurie , Lopez Vianney , Barlow Mathew , Colby Frank
Published: January 2011

The links between daily ozone levels in Southern California and atmospheric circulation at regional and large scales are examined for July–September 1994–2001. The monitoring station in Pasadena is used as the primary basis for ozone analysis; comparison with other stations validates its representativeness for Southern California. Comparing the 10% of highest-ozone days with the 10% of lowest-ozone days for Pasadena reveals a large regional difference in 700-hPa vertical velocity over Southern California, consistent with changes to the ventilation and depth of the boundary layer. Analysis of the associated changes in midlevel (500 hPa) circulation reveals near-continental-scale differences, with very large modifications in the strength and position of the North American anticyclone. These links between daily ozone levels and regional and large-scale atmospheric circulation features suggest the potential for using currently available medium-range weather forecasts in ozone prediction.
Wind Regimes along the Beaufort Sea Coast Favorable for Strong Wind Events at Tuktoyaktuk
Authors: Small David , Atallah Eyad , Gyakum John
Published: January 2011

The community of Tuktoyaktuk (Northwest Territories, Canada) along the Beaufort Sea experiences dramatic shoreline erosion during storm surge events that tend to occur during persistent northwesterly wind events in the late summer months (July–September) when the sea ice coverage of the Beaufort Sea reaches its annual minimum. This study compiles the climatology of hourly surface wind, low-level geostrophic wind, and static stability to investigate the physical mechanisms responsible for the high frequency of northwesterly winds observed at Tuktoyaktuk during the late summer. The results link the prevalence of westerly to northwesterly winds at the surface to the high frequency of northwesterly geostrophic winds and a tendency for low static stability. With an environment that favors strong northwesterly geostrophic wind and suggests lower static stability, the high frequency of strong northwesterlies observed at the surface appears to be associated with momentum mixing by turbulent eddies. A composite analysis indicates that persistently strong northwesterly winds are associated with anomalously low pressure northeast of Tuktoyaktuk and high pressure over the Bering Sea and eastern Siberia. The high pressure anomalies over the Bering Sea also extend well to the east along the northern edge of the Brooks Range. An apparent topographic modification of the sea level pressure (SLP) field by cold air trapped to the north of mountains produces the pressure gradient favorable for strong westerly to northwesterly geostrophic winds at Tuktoyaktuk. The results suggest that cold-air damming contributes to the wind regime at Tuktoyaktuk by altering the pressure gradient along the Beaufort coast.
Trapped Lee Wave Interference in the Presence of Surface Friction
Authors: Stiperski Ivana , Grubišić Vanda
Published: January 2011

Trapped lee wave interference over double bell-shaped obstacles in the presence of surface friction is examined. Idealized high-resolution numerical experiments with the nonhydrostatic Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) are performed to examine the influence of a frictional boundary layer and nonlinearity on wave interference and the impact of interference on wave-induced boundary layer separation and the formation of rotors.

The appearance of constructive and destructive interference, controlled by the ratio of the ridge separation distance to the intrinsic horizontal wavelength of lee waves, is found to be predicted well by linear interference theory with orographic adjustment. The friction-induced shortening of intrinsic wavelength displays a strong indirect effect on wave interference. For twin peak orography, the interference-induced variation of wave amplitude is smaller than that predicted by linear theory. The interference is found to affect the formation and strength of rotors most significantly in the lee of the downstream peak; destructive interference suppresses the formation and strength of rotors there, whereas results for constructive interference closely parallel those for a single mountain. Over the valley, under both constructive and destructive interference, rotors are weaker compared to those in the lee of a single ridge while their strength saturates in the finite-amplitude flow regime.

Destructive interference is found to be more susceptible to nonlinear effects, with both the orographic adjustment and surface friction displaying a stronger effect on the flow in this state. “Complete” destructive interference, in which waves almost completely cancel out in the lee of the downstream ridge, develops for certain ridge separation distances but only for a downstream ridge smaller than the upstream one.
Extreme Precipitation and Temperature over the U.S. Pacific Northwest: A Comparison between Observations, Reanalysis Data, and Regional Models*
Authors: Dulière Valérie , Zhang Yongxin , Salathé Eric P.
Published: January 2011

Extreme precipitation and temperature indices in reanalysis data and regional climate models are compared to station observations. The regional models represent most indices of extreme temperature well. For extreme precipitation, finer grid spacing considerably improves the match to observations. Three regional models, the Weather Research and Forecasting (WRF) at 12- and 36-km grid spacing and the Hadley Centre Regional Model (HadRM) at 25-km grid spacing, are forced with global reanalysis fields over the U.S. Pacific Northwest during 2003–07. The reanalysis data represent the timing of rain-bearing storms over the Pacific Northwest well; however, the reanalysis has the worst performance at simulating both extreme precipitation indices and extreme temperature indices when compared to the WRF and HadRM simulations. These results suggest that the reanalysis data and, by extension, global climate model simulations are not sufficient for examining local extreme precipitations and temperatures owing to their coarse resolutions. Nevertheless, the large-scale forcing is adequately represented by the reanalysis so that regional models may simulate the terrain interactions and mesoscale processes that generate the observed local extremes and frequencies of extreme temperature and precipitation.
Summer-Season Forecast Experiments with the NCEP Climate Forecast System Using Different Land Models and Different Initial Land States
Authors: Yang Rongqian , Mitchell Kenneth , Meng Jesse , Ek Michael
Published: January 2011

To examine the impact from land model upgrades and different land initializations on the National Centers for Environmental Prediction (NCEP)’s Climate Forecast System (CFS), extensive T126 CFS experiments are carried out for 25 summers with 10 ensemble members using the old Oregon State University (OSU) land surface model (LSM) and the new Noah LSM. The CFS using the Noah LSM, initialized in turn with land states from the NCEP–Department of Energy Global Reanalysis 2 (GR-2), Global Land Data System (GLDAS), and GLDAS climatology, is compared to the CFS control run using the OSU LSM initialized with the GR-2 land states. Using anomaly correlation as a primary measure, the summer-season prediction skill of the CFS using different land models and different initial land states is assessed for SST, precipitation, and 2-m air temperature over the contiguous United States (CONUS) on an ensemble basis.

Results from these CFS experiments indicate that upgrading from the OSU LSM to the Noah LSM improves the overall CONUS June–August (JJA) precipitation prediction, especially during ENSO neutral years. Such an enhancement in CFS performance requires the execution of a GLDAS with the very same Noah LSM as utilized in the land component of the CFS, while improper initializations of the Noah LSM using the GR-2 land states lead to degraded CFS performance. In comparison with precipitation, the land upgrades have a relatively small impact on both of the SST and 2-m air temperature predictions.
Contribution of the Autumn Tibetan Plateau Snow Cover to Seasonal Prediction of North American Winter Temperature
Authors: Lin Hai , Wu Zhiwei
Published: January 2011

Predicting surface air temperature (T) is a major task of North American (NA) winter seasonal prediction. It has been recognized that variations of the NA winter T’s can be associated with El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). This study presents observed evidence that variability in snow cover over the Tibetan Plateau (TP) and its adjacent areas in prior autumn (September–November) is significantly correlated with the first principal component (PC1) of the NA winter T’s, which features a meridional seesaw pattern over the NA continent. The autumn TP snow cover anomaly can persist into the following winter through a positive feedback between snow cover and the atmosphere. A positive TP snow cover anomaly may induce a negative sea level pressure and geopotential height anomaly over the eastern North Pacific, a positive geopotential height anomaly over Canada, and a negative anomaly over the southeastern United States—a structure very similar to the positive phase of the Pacific–North America (PNA) pattern. This pattern usually favors the occurrence of a warm–north, cold–south winter over the NA continent. When a negative snow cover anomaly occurs, the situation tends to be opposite. Since the autumn TP snow cover shows a weak correlation with ENSO, it provides a new predictability source for NA winter T’s.

Based on the above results, an empirical model is constructed to predict PC1 using a combination of autumn TP snow cover and other sea surface temperature anomalies related to ENSO and the NAO. Hindcasts and real forecasts are performed for the 1972–2003 and 2004–09 periods, respectively. Both show a promising prediction skill. As far as PC1 is concerned, the empirical model hindcast performs better than the ensemble mean of four dynamical models from the Canadian Meteorological Centre. Particularly, the real forecast of the empirical model exhibits a better performance in predicting the extreme phases of PC1—that is, the extremely warm winter over Canada in 2009/10—should the model include the autumn TP snow cover impacts. Since all these predictors can be readily monitored in real time, this empirical model provides a real-time forecast tool for NA winter climate.
High-Resolution Coupled Climate Runoff Simulations of Seasonal Snowfall over Colorado: A Process Study of Current and Warmer Climate
Authors: Rasmussen Roy , Liu Changhai , Ikeda Kyoko , Gochis David , Yates David , Chen Fei , Tewari Mukul , Barlage Michael , Dudhia Jimy , Yu Wei , Miller Kathleen , Arsenault Kristi , Grubišić Vanda , Thompson Greg , Gutmann Ethan
Published: January 2011

Climate change is expected to accelerate the hydrologic cycle, increase the fraction of precipitation that is rain, and enhance snowpack melting. The enhanced hydrological cycle is also expected to increase snowfall amounts due to increased moisture availability. These processes are examined in this paper in the Colorado Headwaters region through the use of a coupled high-resolution climate–runoff model. Four high-resolution simulations of annual snowfall over Colorado are conducted. The simulations are verified using Snowpack Telemetry (SNOTEL) data. Results are then presented regarding the grid spacing needed for appropriate simulation of snowfall. Finally, climate sensitivity is explored using a pseudo–global warming approach. The results show that the proper spatial and temporal depiction of snowfall adequate for water resource and climate change purposes can be achieved with the appropriate choice of model grid spacing and parameterizations. The pseudo–global warming simulations indicate enhanced snowfall on the order of 10%–25% over the Colorado Headwaters region, with the enhancement being less in the core headwaters region due to the topographic reduction of precipitation upstream of the region (rain-shadow effect). The main climate change impacts are in the enhanced melting at the lower-elevation bound of the snowpack and the increased snowfall at higher elevations. The changes in peak snow mass are generally near zero due to these two compensating effects, and simulated wintertime total runoff is above current levels. The 1 April snow water equivalent (SWE) is reduced by 25% in the warmer climate, and the date of maximum SWE occurs 2–17 days prior to current climate results, consistent with previous studies.
Evaluation of a Conjunctive Surface–Subsurface Process Model (CSSP) over the Contiguous United States at Regional–Local Scales
Authors: Yuan Xing , Liang Xin-Zhong
Published: January 2011

This study presents a comprehensive evaluation on a Conjunctive Surface–Subsurface Process Model (CSSP) in predicting soil temperature–moisture distributions, terrestrial hydrology variations, and land–atmosphere exchanges against various in situ measurements and synthetic observations at regional–local scales over the contiguous United States. The CSSP, rooted in the Common Land Model (CoLM) with a few updates from the Community Land Model version 3.5 (CLM3.5), incorporates significant advances in representing hydrology processes with realistic surface (soil and vegetation) characteristics. These include dynamic surface albedo based on satellite retrievals, subgrid soil moisture variability of topographic controls, surface–subsurface flow interactions, and bedrock constraint on water table depths. As compared with the AmeriFlux tower measurements, the CSSP and CLM3.5 reduce surface sensible and latent heat flux errors from CoLM by 10 W m−2 on average, and have much higher correlations with observations for daily latent heat variations. The CSSP outperforms the CLM3.5 over the crop, grass, and shrub sites in depicting the latent heat annual cycles. While retaining the improvement for soil moisture in deep layers, the CSSP shows further advantage over the CLM3.5 in representing seasonal and interannual variations in root zones. The CSSP reduces soil temperature errors from the CLM3.5 (CoLM) by 0.2 (0.7) K at 0.1 m and 0.3 (0.6) K at 1 m; more realistically captures seasonal–interannual extreme runoff and streamflow over most regions and snow depth anomalies in high latitude (45°–52°N); and alleviates climatological water table depth systematic bias (absolute error) by about 1.2 (0.4) m. Clearly, the CSSP performance is overall superior to both the CoLM and CLM3.5. The remaining CSSP deficiencies and future refinements are also discussed.
Incorporation of Pacific SSTs in a Time Series Model toward a Longer-Term Forecast for the Great Salt Lake Elevation
Authors: Gillies Robert R. , Chung Oi-Yu , Wang Shih-Yu , Kokoszka Piotr
Published: January 2011

A recent study identified a pronounced lagged relationship between the Great Salt Lake’s (GSL) elevation and the central tropical Pacific sea surface temperatures (SST) at the 10–15-year time scale. Using this relationship, a principal component analysis of historical time series of SST and local precipitation (P) was used in the construction of a lagged regression model to predict first the GSL elevation tendency and, from there, the GSL elevation. The combined principal component–lagged regression model was able to replicate and forecast turnarounds in the GSL elevation—that is, where prolonged increasing trends were followed by persistent decreases and vice versa. The coupling of the two time series is somewhat different from previous nonparametric, nonlinear time series methods developed for shorter-term (1–2 year) forecasts of the GSL volume. Moreover, by not accounting for interannual variability in the model, a forecast out to 6 years was feasible and was shown to intersect the 2009 and 2010 observations of the GSL elevation.
Cold Water Flow and Upper-Ocean Currents in the Bismarck Sea from December 2001 to January 2002
Authors: Hasegawa Takuya , Ando Kentaro , Sasaki Hideharu
Published: January 2011

The authors investigated the upper-ocean currents in the Bismarck Sea and related oceanic thermal changes in the western equatorial South Pacific for December 2001–January 2002; during this period, coastal upwelling occurred along the Papua New Guinea (PNG) coast. Southeastward and northwestward coastal currents toward the central PNG coast appeared along northern and southern PNG, respectively. In addition, westward currents extended toward central PNG in the southern part of the Bismarck Sea. A northeastward outflow toward the equator from the PNG coastal area, which is compensated for by such flows, was also found. Volume budget analysis in the upper ocean showed that, during the analysis period, the northeastward outflow ranged from +1.0 to +2.0 Sv (1 Sv ≡ 106 m3 s−1). This northeastward outflow brought relatively cool coastal water, which is related to PNG coastal upwelling, to the western equatorial South Pacific near PNG during this period. In addition, the upper-ocean temperature in this region showed a cooling tendency in line with a negative heat transport from the PNG coastal region. The present results indicate that northeastward transport of the cold water is related to the complicated upper-ocean currents in the Bismarck Sea and may have strongly affected the upper-ocean thermal change in the western equatorial Pacific near PNG for December 2001–January 2002.
Narrowband Oscillations in the Upper Equatorial Ocean. Part I: Interpretation as Shear Instabilities
Authors: Moum J. N. , Nash J. D. , Smyth W. D.
Published: January 2011

Extended measurements of temperature fluctuations that include the turbulence wavenumber band have now been made using rapidly sampled fast thermistors at multiple depths above the core of the Equatorial Undercurrent on the Tropical Atmosphere Ocean (TAO) mooring at 0°, 140°W. These measurements include the signature of narrowband oscillations as well as turbulence, from which the temperature variance dissipation rate χT and the turbulence energy dissipation rate εχ are estimated.

The narrowband oscillations are characterized by the following:groupiness—packets consist of O(10) oscillations;spectral peaks of up to two orders of magnitude above background;a clear day–night cycle with more intensive activity at night;enhanced mixing rates;frequencies of 1–2 × 10−3 Hz, close to both the local buoyancy and shear frequencies, N/2π and S/2π, which vary slowly in time;high vertical coherence over at least 30-m scales; andabrupt vertical phase change (π/2 over <20 m).The abrupt vertical phase change is consistent with instabilities formed in stratified shear flows. Linear stability analysis applied to measured velocity and density profiles leads to predicted frequencies that match those of the observed oscillations. This correspondence suggests that the observed oscillation frequencies are set by the phase speed and wavelength of instabilities as opposed to the Doppler shifting of internal gravity waves with intrinsic frequency set by the local stratification N.
Time-Dependent Adjustment in a Simple Model of the Mid-Depth Meridional Overturning Cell
Authors: Samelson R. M.
Published: January 2011

A recently proposed reduced-gravity model of the warm-water branch of the middepth meridional overturning circulation in a rectangular basin with a circumpolar connection is extended to include time dependence. The model describes the balance between gain of warm water through northward Ekman advection across the circumpolar current, loss of warm water through eddy fluxes southward across the current, net gain or loss of warm water through diabatic processes north of the current, and changes in the thickness of the warm-water layer. The steady solutions are the same as those found previously, when the previous parameterization of diabatic fluxes is used. Time-dependent solutions are considered for the approach of the solution to a new equilibrium when the forcing or parameters are abruptly changed and then held fixed. An initial adjustment occurs through a combination of boundary and equatorial adjustment, followed by planetary wave propagation. The longer-term adjustment to equilibrium consists primarily of the slow change in eastern boundary thickness of the warm layer, which controls the mean depth of the entire layer. An approximate analytical solution of the time-dependent equations yields an explicit expression for the intrinsic time scale of the long-term adjustment, which depends on the eddy and diabatic flux parameters and on the equilibrium solution toward which the time-dependent solution adjusts. Numerical solutions are also considered with a second, advective–diffusive diabatic flux parameterization. These solutions differ quantitatively but not qualitatively from those with the original parameterization. For the range of parameter values considered, the adjustment time scale has dimensional values of several decades to more than a century, but the meridional flux of warm water may respond to changes in external parameters or forcing much more rapidly than this time scale for equilibration of the eastern boundary thickness and thermocline structure.
A Multiconserving Discretization with Enthalpy as a Thermodynamic Prognostic Variable in Generalized Hybrid Vertical Coordinates for the NCEP Global Forecast System
Authors: Juang Hann-Ming Henry
Published: January 2011

A new vertical discretization used in the atmospheric dynamics of the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) is illustrated, with enthalpy as the thermodynamic prognostic variable to reduce computation in thermodynamic equations while concerning all gas tracers in the model. Mass, energy, entropy, and angular momentum conservations are utilized as constraints to discretize the vertical integration with a finite-difference scheme. A specific definition of a generalized hybrid vertical coordinate, including sigma, isobaric, and isentropic surfaces, is introduced to define pressure at the model levels. Vertical fluxes are obtained by the equation of local changes in variables defined for vertical coordinates at all model layers. The forward-weighting semi-implicit time scheme is utilized to eliminate computational noise for stable integration. Because of time splitting between the dynamic and physics processes, the vertical advection is required both in the model dynamics and model physics, and the semi-implicit time scheme is used both in dynamics and after physics computation.

Three configurations—sigma, sigma pressure, and sigma entropy—from the specific hybrid vertical coordinates with layer definition similar to NCEP operational GFS have been implemented in the NCEP GFS. Results from the sigma-isentropic coordinate show the largest anomaly correlation and the smallest root-mean-square error in tropical wind among all results at all layers, especially the upper layers. The scores from a period of daily forecast up to 5 days with the sigma-isentropic coordinate show the same level of skill as compared to the NCEP operational GFS. The results from the hurricane tracks for the fall of 2005 with sigma-isentropic coordinates show better scores compared with the operational GFS.
Global Angular Momentum Fluxes in Height Coordinates
Authors: Egger Joseph , Hoinka Klaus-Peter
Published: January 2011

While time and zonal mean budgets of axial angular momentum (AAM) have been presented in pressure coordinates and also in isentropic coordinates, AAM budgets in height coordinates have not been published yet. The results of such an analysis on the basis of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) winter data are presented in this paper, which includes explicitly evaluated vertical eddy fluxes of momentum and mass as new features. As expected, AAM fluxes related to the Hadley cell are dominant. Transient vertical AAM fluxes are directed upward at the midlatitudes. Transient mass transports are not negligible, while triple terms are unimportant. Problems with the global balance of torques acting at the surface are discussed as well as those of mass conservation.
Predictability of an Atmospheric Blocking Event that Occurred on 15 December 2005
Authors: Matsueda Mio , Kyouda Masayuki , Toth Zoltan , Tanaka H. L. , Tsuyuki Tadashi
Published: January 2011

Atmospheric blocking occurred over the Rocky Mountains at 1200 UTC 15 December 2005. The operational medium-range ensemble forecasts of the Canadian Meteorological Center (CMC), the Japan Meteorological Agency (JMA), and the National Centers for Environmental Prediction (NCEP), as initialized at 1200 UTC 10 December 2005, showed remarkable differences regarding this event. All of the NCEP members failed to predict the correct location of the blocking, whereas almost all of the JMA members and most of the CMC members were successful in predicting the correct location. The present study investigated the factors that caused NCEP to incorrectly predict the blocking location, based on an ensemble-based sensitivity analysis and the JMA global spectral model (GSM) multianalysis ensemble forecasts with NCEP, regionally amplified NCEP, and globally amplified NCEP analyses.

A sensitive area for the blocking formation was detected over the central North Pacific. In this area, the NCEP control analysis experienced problems in the handling of a cutoff cyclone, and the NCEP initial perturbations were ineffective in reducing uncertainties in the NCEP control analysis. The JMA GSM multianalysis ensemble forecasts revealed that regional amplification of initial perturbations over the sensitive area could lead to further improvements in forecasts over the blocking region without degradation of forecasts over the Northern Hemisphere (NH), whereas the global amplification of initial perturbations could lead to improved forecasts over the blocking region and degraded forecasts over the NH. This finding may suggest that excessive amplification of initial perturbations over nonsensitive areas is undesirable, and that case-dependent rescaling of initial perturbations may be of value compared with climatology-based rescaling, which is widely used in current operational ensemble prediction systems.