Impacts of large-scale oscillations on pan-Arctic terrestrial net primary production

Analyses of regional climate oscillations and satellite remote sensing derived net primary production (NPP) and growing season dynamics for the pan-Arctic region indicate that the oscillations influence NPP by regulating seasonal patterns of low temperature and moisture constraints to photosynthesis. Early-spring (Feb–Apr) patterns of the Arctic Oscillation (AO) are proportional to growing season onset (r = −0.653; P = 0.001), while growing season patterns of the Pacific Decadal Oscillation (PDO) are proportional to plant-available moisture constraints to NPP (Im) (r = −0.471; P = 0.023). Relatively strong, negative PDO phases from 1988–1991 and 1998–2002 coincided with prolonged regional droughts indicated by a standardized moisture stress index. These severe droughts resulted in widespread reductions in NPP, especially for relatively drought prone boreal forest and grassland/cropland ecosystems. The influence of AO and PDO patterns on northern vegetation productivity appears to be decreasing and increasing, respectively, as low temperature constraints to plant growth relax and NPP becomes increasingly limited by available water supply under a warming climate

Surface plasmons at single nanoholes in Au-films

The generation of surface plasmon polaritons (SPP's) at isolated nanoholes in 100 nm thick Au films is studied using near-field scanning optical microscopy (NSOM). Finite-difference time-domain calculations, some explicitly including a model of the NSOM tip, are used to interpret the results. We find the holes act as point-like sources of SPP's and demonstrate that interference between SPP's and a directly transmitted wave allows for determination of the wavelength, phase, and decay length of the SPP. The near-field intensity patterns can be manipulated by varying the angle and polarization of the incident beam.Comment: 12 pages, 3 figure

SAGA: A project to automate the management of software production systems

The project to automate the management of software production systems is described. The SAGA system is a software environment that is designed to support most of the software development activities that occur in a software lifecycle. The system can be configured to support specific software development applications using given programming languages, tools, and methodologies. Meta-tools are provided to ease configuration. Several major components of the SAGA system are completed to prototype form. The construction methods are described

Intra-abdominal hypertension and abdominal compartment syndrome in pancreatitis, paediatrics, and trauma

Intra-abdominal hypertension (IAH) is an important contributor to early organ dysfunction in trauma and sepsis. However, relatively little is known about the impact of intra-abdominal pressure (IAP) in general internal medicine, pregnant patients, and those with obesity or burns. The aim of this paper is to review the pathophysiologic implications and treatment options for IAH in these specific situations. A MEDLINE and PubMed search was performed and the resulting body-of-evidence included in the current review on the basis of relevance and scientific merit. There is increasing awareness of the role of IAH in different clinical situations. Specifically, IAH will develop in most (if not all) severely burned patients, and may contribute to early mortality. One should avoid over-resuscitation of these patients with large volumes of fluids, especially crystalloids. Acute elevations in IAP have similar effects in obese patients compared to non-obese patients, but the threshold IAP associated with organ dysfunction may be higher. Chronic elevations in IAP may, in part, be responsible for the pathogenesis of obesity-related co-morbid conditions such as hypertension, pseudotumor cerebri, pulmonary dysfunction, gastroesophageal reflux disease, and abdominal wall hernias. At the bedside, measuring IAP and considering IAH in all critical maternal conditions is essential, especially in preeclampsia/eclampsia where some have hypothesized that IAH may have an additional role. IAH in pregnancy must take into account the precautions for aorto-caval compression and has been associated with ovarian hyperstimulation syndrome. Recently, IAP has been associated with the cardiorenal dilemma and hepatorenal syndrome, and this has led to the recognition of the polycompartment syndrome. In conclusion, IAH and ACS have been associated with several patient populations beyond the classical ICU, surgical, and trauma patients. In all at risk conditions the focus should be on the early recognition of IAH and prevention of ACS. Patients at risk for IAH should be identified early through measurements of IAP. Appropriate actions should be taken when IAP increases above 15 mm Hg, especially if pressures reach above 20 mm Hg with new onset organ failure. Although non-operative measures come first, surgical decompression must not be delayed if these fail. Percutaneous drainage of ascites is a simple and potentially effective tool to reduce IAP if organ dysfunction develops, especially in burn patients. Escharotomy may also dramatically reduce IAP in the case of abdominal burns

Evaluating the role of land cover and climate uncertainties in computing gross primary production in Hawaiian Island ecosystems

Gross primary production (GPP) is the Earth’s largest carbon flux into the terrestrial biosphere and plays a critical role in regulating atmospheric chemistry and global climate. The Moderate Resolution Imaging Spectrometer (MODIS)-MOD17 data product is a widely used remote sensing-based model that provides global estimates of spatiotemporal trends in GPP. When the MOD17 algorithm is applied to regional scale heterogeneous landscapes, input data from coarse resolution land cover and climate products may increase uncertainty in GPP estimates, especially in high productivity tropical ecosystems. We examined the influence of using locally specific land cover and high-resolution local climate input data on MOD17 estimates of GPP for the State of Hawaii, a heterogeneous and discontinuous tropical landscape. Replacing the global land cover data input product (MOD12Q1) with Hawaii-specific land cover data reduced statewide GPP estimates by ~8%, primarily because the Hawaii-specific land cover map had less vegetated land area compared to the global land cover product. Replacing coarse resolution GMAO climate data with Hawaii-specific high-resolution climate data also reduced statewide GPP estimates by ~8% because of the higher spatial variability of photosynthetically active radiation (PAR) in the Hawaii-specific climate data. The combined use of both Hawaii-specific land cover and high-resolution Hawaii climate data inputs reduced statewide GPP by ~16%, suggesting equal and independent influence on MOD17 GPP estimates. Our sensitivity analyses within a heterogeneous tropical landscape suggest that refined global land cover and climate data sets may contribute to an enhanced MOD17 product at a variety of spatial scales

Satellite assessment of land surface evapotranspiration for the pan-Arctic domain

Regional evapotranspiration (ET), including water loss from plant transpiration and soil evaporation, is essential to understanding interactions between land-atmosphere surface energy and water balances. Vapor pressure deficit (VPD) and surface air temperature are key variables for stomatal conductance and ET estimation. We developed an algorithm to estimate ET using the Penman-Monteith approach driven by Moderate Resolution Imaging Spectroradiometer (MODIS)-derived vegetation data and daily surface meteorological inputs including incoming solar radiation, air temperature, and VPD. The model was applied using alternate daily meteorological inputs, including (1) site level weather station observations, (2) VPD and air temperature derived from the Advanced Microwave Scanning Radiometer (AMSR-E) on the EOS Aqua satellite, and (3) Global Modeling and Assimilation Office (GMAO) reanalysis meteorology-based surface air temperature, humidity, and solar radiation data. Model performance was assessed across a North American latitudinal transect of six eddy covariance flux towers representing northern temperate grassland, boreal forest, and tundra biomes. Model results derived from the three meteorology data sets agree well with observed tower fluxes (r \u3e 0.7; P \u3c 0.003; root mean square error of latent heat flux \u3c30 W m−2) and capture spatial patterns and seasonal variability in ET. The MODIS-AMSR-E–derived ET results also show similar accuracy to ET results derived from GMAO, while ET estimation error was generally more a function of algorithm parameterization than differences in meteorology drivers. Our results indicate significant potential for regional mapping and monitoring daily land surface ET using synergistic information from satellite optical IR and microwave remote sensing

Satellite observations of annual variability in terrestrial carbon cycles and seasonal growing seasons at high northern latitudes

Global satellite remote sensing records show evidence of recent vegetation greening and an advance in the onset of the growing season at high latitudes. We apply a terrestrial net primary production (NPP) model driven by satellite observations of vegetation properties and daily surface meteorology from an atmospheric GCM to assess spatial patterns, annual variability, and recent trends in vegetation productivity across Alaska and northwest Canada. We compare these results with regional observations of the timing of growing season onset derived from satellite passive microwave remote sensing measurements from the Special Sensor Microwave Imager, SSM/I. Our results show substantial variability in annual NPP for the region that appears to be driven largely by variations in canopy photosynthetic leaf area and average summer air temperatures. Variability in maximum canopy leaf area and NPP also correspond closely to remote sensing observations of the timing of the primary seasonal thaw event in spring. Relatively early spring thawing appears to enhance NPP, while delays in seasonal thawing and growing season onset reduce annual vegetation productivity. Our results indicate that advances in seasonal thawing and spring and summer warming for the region associated with global change are promoting a general increase in NPP

Sensitivity of Pan-Arctic Terrestrial Net Primary Productivity Simulations to Daily Surface Meterology From NCEP-NCAR and ERA-40 Reanalyses

We applied a terrestrial net primary production (NPP) model driven by satellite remote sensing observations of vegetation properties and daily surface meteorology from the 45-year ECMWF Re-Analysis (ERA-40) and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP-NCAR) reanalysis (NNR) to assess NPP spatial and temporal variability for the pan-Arctic basin and Alaska from 1982 to 2000. Sensitivity analysis of the production efficiency model (PEM) to uncertainties in surface meteorological inputs indicate that ERA-40 solar radiation and NNR solar radiation and surface temperatures are the primary sources of PEM-based NPP uncertainty for the region. Considerable positive bias in solar radiation inputs relative to surface observation networks resulted in overprediction of annual NPP by approximately 35.2 and 61.6% using ERA-40 and NNR inputs, respectively. Despite these uncertainties, both reanalysis products captured the major annual anomalies and trends in surface meteorology for the domain. The two reanalysis products also produced similar NPP spatial patterns for 74.7% of the domain, and similar annual anomalies and temporal trends, though there were significant regional differences particularly for Eurasia. A simple correction method based on a sensitivity experiment between reanalysis and surface station meteorological measurements produced generally consistent NPP results that were considerably smaller than PEM simulations derived from uncorrected reanalysis drivers. The results of this study identify major sources of uncertainty in reanalysis-based surface meteorology, and associated impacts on regional NPP simulations of the northern high latitudes