The Use of CASES-97 Observations to Assess and Parameterize the Impact of Land-Surface Heterogeneity on Area-Average Surface Heat Fluxes for Large-Scale Coupled Atmosphere-Hydrology Models

NASA Technical Reports Server (NTRS)

Chen, Fei; Yates, David; LeMone, Margaret

2001-01-01

To understand the effects of land-surface heterogeneity and the interactions between the land-surface and the planetary boundary layer at different scales, we develop a multiscale data set. This data set, based on the Cooperative Atmosphere-Surface Exchange Study (CASES97) observations, includes atmospheric, surface, and sub-surface observations obtained from a dense observation network covering a large region on the order of 100 km. We use this data set to drive three land-surface models (LSMs) to generate multi-scale (with three resolutions of 1, 5, and 10 kilometers) gridded surface heat flux maps for the CASES area. Upon validating these flux maps with measurements from surface station and aircraft, we utilize them to investigate several approaches for estimating the area-integrated surface heat flux for the CASES97 domain of 71x74 square kilometers, which is crucial for land surface model development/validation and area water and energy budget studies. This research is aimed at understanding the relative contribution of random turbulence versus organized mesoscale circulations to the area-integrated surface flux at the scale of 100 kilometers, and identifying the most important effective parameters for characterizing the subgrid-scale variability for large-scale atmosphere-hydrology models.

USING A HEAT PULSE TO MEASURE THE FLUX BETWEEN GROUNDWATER AND SURFACE WATER

EPA Science Inventory

EPA estimates that 10 percent of the sediments under the surface waters of the United States are contaminated and approximately 20 percent of the superfund sites include contaminated sediments. The risk associated with these contaminated sediments is directly related to the flux...

Satellite-based Calibration of Heat Flux at the Ocean Surface

NASA Astrophysics Data System (ADS)

Barron, C. N.; Dastugue, J. M.; May, J. C.; Rowley, C. D.; Smith, S. R.; Spence, P. L.; Gremes-Cordero, S.

2016-02-01

Model forecasts of upper ocean heat content and variability on diurnal to daily scales are highly dependent on estimates of heat flux through the air-sea interface. Satellite remote sensing is applied to not only inform the initial ocean state but also to mitigate errors in surface heat flux and model representations affecting the distribution of heat in the upper ocean. Traditional assimilation of sea surface temperature (SST) observations re-centers ocean models at the start of each forecast cycle. Subsequent evolution depends on estimates of surface heat fluxes and upper-ocean processes over the forecast period. The COFFEE project (Calibration of Ocean Forcing with satellite Flux Estimates) endeavors to correct ocean forecast bias through a responsive error partition among surface heat flux and ocean dynamics sources. A suite of experiments in the southern California Current demonstrates a range of COFFEE capabilities, showing the impact on forecast error relative to a baseline three-dimensional variational (3DVAR) assimilation using Navy operational global or regional atmospheric forcing. COFFEE addresses satellite-calibration of surface fluxes to estimate surface error covariances and links these to the ocean interior. Experiment cases combine different levels of flux calibration with different assimilation alternatives. The cases may use the original fluxes, apply full satellite corrections during the forecast period, or extend hindcast corrections into the forecast period. Assimilation is either baseline 3DVAR or standard strong-constraint 4DVAR, with work proceeding to add a 4DVAR expanded to include a weak constraint treatment of the surface flux errors. Covariance of flux errors is estimated from the recent time series of forecast and calibrated flux terms. While the California Current examples are shown, the approach is equally applicable to other regions. These approaches within a 3DVAR application are anticipated to be useful for global and larger regional domains where a full 4DVAR methodology may be cost-prohibitive.

Evaluation of satellite and reanalysis‐based global net surface energy flux and uncertainty estimates

PubMed Central

Allan, Richard P.; Mayer, Michael; Hyder, Patrick; Loeb, Norman G.; Roberts, Chris D.; Valdivieso, Maria; Edwards, John M.; Vidale, Pier‐Luigi

2017-01-01

Abstract The net surface energy flux is central to the climate system yet observational limitations lead to substantial uncertainty. A combination of satellite‐derived radiative fluxes at the top of atmosphere adjusted using the latest estimation of the net heat uptake of the Earth system, and the atmospheric energy tendencies and transports from the ERA‐Interim reanalysis are used to estimate surface energy flux globally. To consider snowmelt and improve regional realism, land surface fluxes are adjusted through a simple energy balance approach at each grid point. This energy adjustment is redistributed over the oceans to ensure energy conservation and maintain realistic global ocean heat uptake, using a weighting function to avoid meridional discontinuities. Calculated surface energy fluxes are evaluated through comparison to ocean reanalyses. Derived turbulent energy flux variability is compared with the Objectively Analyzed air‐sea Fluxes (OAFLUX) product, and inferred meridional energy transports in the global ocean and the Atlantic are also evaluated using observations. Uncertainties in surface fluxes are investigated using a variety of approaches including comparison with a range of atmospheric reanalysis products. Decadal changes in the global mean and the interhemispheric energy imbalances are quantified, and present day cross‐equator heat transports are reevaluated at 0.22 ± 0.15 PW (petawatts) southward by the atmosphere and 0.32 ± 0.16 PW northward by the ocean considering the observed ocean heat sinks. PMID:28804697

Sputter ripples and radiation-enhanced surface kinetics on Cu(001)

NASA Astrophysics Data System (ADS)

Chan, Wai Lun; Chason, Eric

2005-10-01

We have measured the temperature and flux dependence of the wavelength of surface ripples spontaneously formed by low-energy sputtering of a Cu(001) surface. We find that the temperature dependence of the ripple wavelength is non-Arrhenius, with a greater apparent activation at high temperature than at low temperature. Furthermore, the dependence of the wavelength on flux changes significantly with temperature. In the high-temperature regime, the wavelength decreases as the ion flux increases, while at low temperature, the wavelength is essentially independent of flux. We explain these results by a quantitative model that includes the mechanisms controlling the concentration of mobile defects on the surface in the two temperature regimes. At low temperature, mobile defects are induced by the ion beam while at higher temperature, the defects are thermally generated.

Estimation of land surface heat fluxes based on visible infrared imaging radiometer suite data: case study in northern China

NASA Astrophysics Data System (ADS)

Li, Xiaojun; Xin, Xiaozhou; Peng, Zhiqing; Zhang, Hailong; Li, Li; Shao, Shanshan; Liu, Qinhuo

2017-10-01

Evapotranspiration (ET) plays an important role in surface-atmosphere interactions and can be monitored using remote sensing data. The visible infrared imaging radiometer suite (VIIRS) sensor is a generation of optical satellite sensors that provide daily global coverage at 375- to 750-m spatial resolutions with 22 spectral channels (0.412 to 12.05 μm) and capable of monitoring ET from regional to global scales. However, few studies have focused on methods of acquiring ET from VIIRS images. The objective of this study is to introduce an algorithm that uses the VIIRS data and meteorological variables to estimate the energy budgets of land surfaces, including the net radiation, soil heat flux, sensible heat flux, and latent heat fluxes. A single-source model that based on surface energy balance equation is used to obtain surface heat fluxes within the Zhangye oasis in China. The results were validated using observations collected during the HiWATER (Heihe Watershed Allied Telemetry Experimental Research) project. To facilitate comparison, we also use moderate resolution imaging spectrometer (MODIS) data to retrieve the regional surface heat fluxes. The validation results show that it is feasible to estimate the turbulent heat flux based on the VIIRS sensor and that these data have certain advantages (i.e., the mean bias error of sensible heat flux is 15.23 W m-2) compared with MODIS data (i.e., the mean bias error of sensible heat flux is -29.36 W m-2). Error analysis indicates that, in our model, the accuracies of the estimated sensible heat fluxes rely on the errors in the retrieved surface temperatures and the canopy heights.

Heat transfer from an oxidized large copper surface to liquid helium: Dependence on surface orientation and treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iwamoto, A.; Mito, T.; Takahata, K.

Heat transfer of large copper plates (18 x 76 mm) in liquid helium has been measured as a function of orientation and treatment of the heat transfer surface. The results relate to applications of large scale superconductors. In order to clarify the influence of the area where the surface treatment peels off, the authors studied five types of heat transfer surface areas including: (a) 100% polished copper sample, (b) and (c) two 50% oxidized copper samples having different patterns of oxidation, (d) 75% oxidized copper sample, (e) 90% oxidized copper sample, and (f) 100% oxidized copper sample. They observed thatmore » the critical heat flux depends on the heat transfer surface orientation. The critical heat flux is a maximum at angles of 0{degrees} - 30{degrees} and decreases monotonically with increasing angles above 30{degrees}, where the angle is taken in reference to the horizontal axis. On the other hand, the minimum heat flux is less dependent on the surface orientation. More than 75% oxidation on the surface makes the critical heat flux increase. The minimum heat fluxes of the 50 and 90% oxidized Cu samples approximately agree with that of the 100% oxidized Cu sample. Experiments and calculations show that the critical and the minimum heat fluxes are a bilinear function of the fraction of oxidized surface area.« less

High-resolution CO2 and CH4 flux inverse modeling combining GOSAT, OCO-2 and ground-based observations

NASA Astrophysics Data System (ADS)

Maksyutov, S. S.; Oda, T.; Saito, M.; Ito, A.; Janardanan Achari, R.; Sasakawa, M.; Machida, T.; Kaiser, J. W.; Belikov, D.; Valsala, V.; O'Dell, C.; Yoshida, Y.; Matsunaga, T.

2017-12-01

We develop a high-resolution CO2 and CH4 flux inversion system that is based on the Lagrangian-Eulerian coupled tracer transport model, and is designed to estimate surface fluxes from atmospheric CO2 and CH4 data observed by the GOSAT and OCO-2 satellites and by global in-situ networks, including observation in Siberia. We use the Lagrangian particle dispersion model (LPDM) FLEXPART to estimate the surface flux footprints for each observation at 0.1-degree spatial resolution for three days of transport. The LPDM is coupled to a global atmospheric tracer transport model (NIES-TM). The adjoint of the coupled transport model is used in an iterative optimization procedure based on either quasi-Newtonian algorithm or singular value decomposition. Combining surface and satellite data for use in inversion requires correcting for biases present in satellite observation data, that is done in a two-step procedure. As a first step, bi-weekly corrections to prior flux fields are estimated for the period of 2009 to 2015 from in-situ CO2 and CH4 data from global observation network, included in Obspack-GVP (for CO2), WDCGG (CH4) and JR-STATION datasets. High-resolution prior fluxes were prepared for anthropogenic emissions (ODIAC and EDGAR), biomass burning (GFAS), and the terrestrial biosphere. The terrestrial biosphere flux was constructed using a vegetation mosaic map and separate simulations of CO2 fluxes by the VISIT model for each vegetation type present in a grid. The prior flux uncertainty for land is scaled proportionally to monthly mean GPP by the MODIS product for CO2 and EDGAR emissions for CH4. Use of the high-resolution transport leads to improved representation of the anthropogenic plumes, often observed at continental continuous observation sites. OCO-2 observations are aggregated to 1 second averages, to match the 0.1 degree resolution of the transport model. Before including satellite observations in the inversion, the monthly varying latitude-dependent bias is estimated by comparing satellite observations with column abundance simulated with surface fluxes optimized by surface inversion. The bias-corrected GOSAT and OCO-2 data are then used in the inversion together with ground-based observations. Application of the bias correction to satellite data reduces the difference between the flux estimates based on ground-based and satellite observations.

The SURFEXv7.2 land and ocean surface platform for coupled or offline simulation of earth surface variables and fluxes

NASA Astrophysics Data System (ADS)

Masson, V.; Le Moigne, P.; Martin, E.; Faroux, S.; Alias, A.; Alkama, R.; Belamari, S.; Barbu, A.; Boone, A.; Bouyssel, F.; Brousseau, P.; Brun, E.; Calvet, J.-C.; Carrer, D.; Decharme, B.; Delire, C.; Donier, S.; Essaouini, K.; Gibelin, A.-L.; Giordani, H.; Habets, F.; Jidane, M.; Kerdraon, G.; Kourzeneva, E.; Lafaysse, M.; Lafont, S.; Lebeaupin Brossier, C.; Lemonsu, A.; Mahfouf, J.-F.; Marguinaud, P.; Mokhtari, M.; Morin, S.; Pigeon, G.; Salgado, R.; Seity, Y.; Taillefer, F.; Tanguy, G.; Tulet, P.; Vincendon, B.; Vionnet, V.; Voldoire, A.

2013-07-01

SURFEX is a new externalized land and ocean surface platform that describes the surface fluxes and the evolution of four types of surfaces: nature, town, inland water and ocean. It is mostly based on pre-existing, well-validated scientific models that are continuously improved. The motivation for the building of SURFEX is to use strictly identical scientific models in a high range of applications in order to mutualise the research and development efforts. SURFEX can be run in offline mode (0-D or 2-D runs) or in coupled mode (from mesoscale models to numerical weather prediction and climate models). An assimilation mode is included for numerical weather prediction and monitoring. In addition to momentum, heat and water fluxes, SURFEX is able to simulate fluxes of carbon dioxide, chemical species, continental aerosols, sea salt and snow particles. The main principles of the organisation of the surface are described first. Then, a survey is made of the scientific module (including the coupling strategy). Finally, the main applications of the code are summarised. The validation work undertaken shows that replacing the pre-existing surface models by SURFEX in these applications is usually associated with improved skill, as the numerous scientific developments contained in this community code are used to good advantage.

Visualization of particle flux in the human body on the surface of Mars

NASA Technical Reports Server (NTRS)

Saganti, Premkumar B.; Cucinotta, Francis A.; Wilson, John W.; Schimmerling, Walter

2002-01-01

For a given galactic cosmic ray (GCR) environment, information on the particle flux of protons, alpha particles, and heavy ions, that varies with respect to the topographical altitude on the Martian surface, are needed for planning exploration missions to Mars. The Mars Global Surveyor (MGS) mission with its Mars Orbiter Laser Altimeter (MOLA) instrument has been providing precise topographical surface map of the Mars. With this topographical data, the particle flux at the Martian surface level through the CO2 atmospheric shielding for solar minimum and solar maximum conditions are calculated. These particle flux calculations are then transported first through an anticipated shielding of a conceptual shelter with several water equivalent shield values (up to 50 g/cm2 of water in steps of 5 g/cm2) considered to represent a surface habitat, and then into the human body. Model calculations are accomplished utilizing the HZETRN, QMSFRG, and SUM-MARS codes. Particle flux calculations for 12 different locations in the human body were considered from skin depth to the internal organs including the blood-forming organs (BFO). Visualization of particle flux in the human body at different altitudes on the Martian surface behind a known shielding is anticipated to provide guidance for assessing radiation environment risk on the Martian surface for future human missions.

Visualization of particle flux in the human body on the surface of Mars.

PubMed

Saganti, Premkumar B; Cucinotta, Francis A; Wilson, John W; Schimmerling, Walter

2002-12-01

For a given galactic cosmic ray (GCR) environment, information on the particle flux of protons, alpha particles, and heavy ions, that varies with respect to the topographical altitude on the Martian surface, are needed for planning exploration missions to Mars. The Mars Global Surveyor (MGS) mission with its Mars Orbiter Laser Altimeter (MOLA) instrument has been providing precise topographical surface map of the Mars. With this topographical data, the particle flux at the Martian surface level through the CO2 atmospheric shielding for solar minimum and solar maximum conditions are calculated. These particle flux calculations are then transported first through an anticipated shielding of a conceptual shelter with several water equivalent shield values (up to 50 g/cm2 of water in steps of 5 g/cm2) considered to represent a surface habitat, and then into the human body. Model calculations are accomplished utilizing the HZETRN, QMSFRG, and SUM-MARS codes. Particle flux calculations for 12 different locations in the human body were considered from skin depth to the internal organs including the blood-forming organs (BFO). Visualization of particle flux in the human body at different altitudes on the Martian surface behind a known shielding is anticipated to provide guidance for assessing radiation environment risk on the Martian surface for future human missions.

Simulations of Emerging Magnetic Flux. II. The Formation of Unstable Coronal Flux Ropes and the Initiation of Coronal Mass Ejections

NASA Technical Reports Server (NTRS)

Leake, James E.; Linton, Mark G.; Antiochos, Spiro K.

2014-01-01

We present results from three-dimensional magnetohydrodynamic simulations of the emergence of a twisted convection zone flux tube into a pre-existing coronal dipole field. As in previous simulations, following the partial emergence of the sub-surface flux into the corona, a combination of vortical motions and internal magnetic reconnection forms a coronal flux rope. Then, in the simulations presented here, external reconnection between the emerging field and the pre-existing dipole coronal field allows further expansion of the coronal flux rope into the corona. After sufficient expansion, internal reconnection occurs beneath the coronal flux rope axis, and the flux rope erupts up to the top boundary of the simulation domain (approximately 36 Mm above the surface).We find that the presence of a pre-existing field, orientated in a direction to facilitate reconnection with the emerging field, is vital to the fast rise of the coronal flux rope. The simulations shown in this paper are able to self-consistently create many of the surface and coronal signatures used by coronal mass ejection (CME) models. These signatures include surface shearing and rotational motions, quadrupolar geometry above the surface, central sheared arcades reconnecting with oppositely orientated overlying dipole fields, the formation of coronal flux ropes underlying potential coronal field, and internal reconnection which resembles the classical flare reconnection scenario. This suggests that proposed mechanisms for the initiation of a CME, such as "magnetic breakout," are operating during the emergence of new active regions.

Large-Eddy Atmosphere-Land-Surface Modelling over Heterogeneous Surfaces: Model Development and Comparison with Measurements

NASA Astrophysics Data System (ADS)

Shao, Yaping; Liu, Shaofeng; Schween, Jan H.; Crewell, Susanne

2013-08-01

A model is developed for the large-eddy simulation (LES) of heterogeneous atmosphere and land-surface processes. This couples a LES model with a land-surface scheme. New developments are made to the land-surface scheme to ensure the adequate representation of atmosphere-land-surface transfers on the large-eddy scale. These include, (1) a multi-layer canopy scheme; (2) a method for flux estimates consistent with the large-eddy subgrid closure; and (3) an appropriate soil-layer configuration. The model is then applied to a heterogeneous region with 60-m horizontal resolution and the results are compared with ground-based and airborne measurements. The simulated sensible and latent heat fluxes are found to agree well with the eddy-correlation measurements. Good agreement is also found in the modelled and observed net radiation, ground heat flux, soil temperature and moisture. Based on the model results, we study the patterns of the sensible and latent heat fluxes, how such patterns come into existence, and how large eddies propagate and destroy land-surface signals in the atmosphere. Near the surface, the flux and land-use patterns are found to be closely correlated. In the lower boundary layer, small eddies bearing land-surface signals organize and develop into larger eddies, which carry the signals to considerably higher levels. As a result, the instantaneous flux patterns appear to be unrelated to the land-use patterns, but on average, the correlation between them is significant and persistent up to about 650 m. For a given land-surface type, the scatter of the fluxes amounts to several hundred W { m }^{-2}, due to (1) large-eddy randomness; (2) rapid large-eddy and surface feedback; and (3) local advection related to surface heterogeneity.

NITRATE RELEASE BY SALT MARSH PLANTS: AN OVERLOOKED NUTRIENT FLUX MECHANISM

EPA Science Inventory

Salt marshes provide water purification as an important ecosystem service in part by storing, transforming and releasing nutrients. This service can be quantified by measuring nutrient fluxes between marshes and surface waters. Many processes drive these fluxes, including photosy...

Baseline high heat flux and plasma facing materials for fusion

NASA Astrophysics Data System (ADS)

Ueda, Y.; Schmid, K.; Balden, M.; Coenen, J. W.; Loewenhoff, Th.; Ito, A.; Hasegawa, A.; Hardie, C.; Porton, M.; Gilbert, M.

2017-09-01

In fusion reactors, surfaces of plasma facing components (PFCs) are exposed to high heat and particle flux. Tungsten and Copper alloys are primary candidates for plasma facing materials (PFMs) and coolant tube materials, respectively, mainly due to high thermal conductivity and, in the case of tungsten, its high melting point. In this paper, recent understandings and future issues on responses of tungsten and Cu alloys to fusion environments (high particle flux (including T and He), high heat flux, and high neutron doses) are reviewed. This review paper includes; Tritium retention in tungsten (K. Schmid and M. Balden), Impact of stationary and transient heat loads on tungsten (J.W. Coenen and Th. Loewenhoff), Helium effects on surface morphology of tungsten (Y. Ueda and A. Ito), Neutron radiation effects in tungsten (A. Hasegawa), and Copper and copper alloys development for high heat flux components (C. Hardie, M. Porton, and M. Gilbert).

CERES Fast Longwave And SHortwave Radiative Flux (FLASHFlux) Version4A.

NASA Astrophysics Data System (ADS)

Sawaengphokhai, P.; Stackhouse, P. W., Jr.; Kratz, D. P.; Gupta, S. K.

2017-12-01

The agricultural, renewable energy management, and science communities need global surface and top-of-atmosphere (TOA) radiative fluxes on a low latency basis. The Clouds and Earth's Radiant Energy System (CERES) FLASHFlux (Fast Longwave and SHortwave radiative Flux) data products address this need by enhancing the speed of CERES processing using simplified calibration and parameterized model of surface fluxes to provide a daily global radiative fluxes data set within one week of satellite observations. The CERES FLASHFlux provides two data products: 1) an overpass swath Level 2 Single Scanner Footprint (SSF) data products separately for both Aqua and Terra observations, and 2) a daily Level 3 Time Interpolated and Spatially Averaged (TISA) 1o x 1o gridded data that combines Aqua and Terra observations. The CERES FLASHFlux data product is being promoted to Version4A. Updates to FLASHFlux Version4A include a new cloud retrieval algorithm and an improved shortwave surface flux parameterization. We inter-compared FLASHFlux Version4A, FLASHFlux Version3C, CERES Edition 4 Syn1Deg and at the monthly scale CERES Edition4 EBAF (Energy Balanced and Filled) Top-of-Atmosphere and Edition 4 Surface EBAF fluxes to evaluate these improvements. We also analyze the impact of the new inputs and cloud algorithm to the surface shortwave and longwave radiative fluxes using ground sites measurement provided by CAVE (CERES/ARM Validation Experiment).

Heat Flux Sensor

NASA Technical Reports Server (NTRS)

1994-01-01

A heat flux microsensor developed under a NASP Small Business Innovation Research (SBIR) has a wide range of potential commercial applications. Vatell Corporation originally designed microsensors for use in very high temperatures. The company then used the technology to develop heat flux sensors to measure the rate of heat energy flowing in and out of a surface as well as readings on the surface temperature. Additional major advantages include response to heat flux in less than 10 microseconds and the ability to withstand temperatures up to 1,200 degrees centigrade. Commercial applications are used in high speed aerodynamics, supersonic combustion, blade cooling, and mass flow measurements, etc.

Dual-stage trapped-flux magnet cryostat for measurements at high magnetic fields

DOEpatents

Islam, Zahirul; Das, Ritesh K.; Weinstein, Roy

2015-04-14

A method and a dual-stage trapped-flux magnet cryostat apparatus are provided for implementing enhanced measurements at high magnetic fields. The dual-stage trapped-flux magnet cryostat system includes a trapped-flux magnet (TFM). A sample, for example, a single crystal, is adjustably positioned proximate to the surface of the TFM, using a translation stage such that the distance between the sample and the surface is selectively adjusted. A cryostat is provided with a first separate thermal stage provided for cooling the TFM and with a second separate thermal stage provided for cooling sample.

Heat fluxes at the Earth's surface and core-mantle boundary since Pangea formation and their implications for the geomagnetic superchrons

NASA Astrophysics Data System (ADS)

Zhang, Nan; Zhong, Shijie

2011-06-01

The Earth's surface and core-mantle boundary (CMB) heat fluxes are controlled by mantle convection and have important influences on Earth's thermal evolution and geodynamo processes in the core. However, the long-term variations of the surface and CMB heat fluxes remain poorly understood, particularly in response to the supercontinent Pangea — likely the most significant global tectonic event in the last 500 Ma. In this study, we reconstruct temporal evolution of the surface and CMB heat fluxes since the Paleozoic by formulating three-dimensional spherical models of mantle convection with plate motion history for the last 450 Ma that includes the assembly and break-up of supercontinent Pangea. Our models reproduce well present-day observations of the surface heat flux and seafloor age distribution. Our models show that the present-day CMB heat flux is low below the central Pacific and Africa but high elsewhere due to subducted slabs, particularly when chemically dense piles are present above the CMB. We show that while the surface heat flux may not change significantly in response to Pangea assembly, it increases by ~ 16% from 200 to 120 Ma ago as a result of Pangea breakup and then decreases for the last 120 Ma to approximately the pre-200 Ma value. As consequences of the assembly and breakup of Pangea, equatorial CMB heat flux reaches minimum at ~ 270 Ma and again at ~ 100 Ma ago, while global CMB heat flux is a maximum at ~ 100 Ma ago. These extrema in CMB heat fluxes coincide with the Kiaman (316-262 Ma) and Cretaceous (118-83 Ma) Superchrons, respectively, and may be responsible for the Superchrons.

Simulations of Ground and Space-Based Oxygen Atom Experiments

NASA Technical Reports Server (NTRS)

Minton, T. K.; Cline, J. A.; Braunstein, M.

2002-01-01

Fast, pulsed atomic oxygen sources are a key tool in ground-based investigations of spacecraft contamination and surface erosion effects. These technically challenging ground-based studies provide a before and after picture of materials under low-earth-orbit (LEO) conditions. It would be of great interest to track in real time the pulsed flux from the source to the surface sample target and beyond in order to characterize the population of atoms and molecules that actually impact the surface and those that make it downstream to any coincident detectors. We have performed simulations in order to provide such detailed descriptions of these ground-based measurements and to provide an assessment of their correspondence to the actual LEO environment. Where possible we also make comparisons to measured fluxes and erosion yields. To perform the calculations we use a detailed description of a measurement beam and surface geometry based on the W, pulsed apparatus at Montana State University. In this system, a short pulse (on the order of 10 microseconds) of an O/O2 beam impacts a flat sample about 40 cm downstream and slightly displaced &om the beam s central axis. Past this target, at the end of the beam axis is a quadrupole mass spectrometer that measures the relative in situ flux of 0102 to give an overall normalized erosion yield. In our simulations we use the Direct Simulation Monte Carlo (DSMC) method, and track individual atoms within the atomic oxygen pulse. DSMC techniques are typically used to model rarefied (few collision) gas-flows which occur at altitudes above approximately 110 kilometers. These techniques are well suited for the conditions here, and multi-collision effects that can only be treated by this or a similar technique are included. This simulation includes collisions with the surface and among gas atoms that have scattered from the surface. The simulation also includes descriptions of the velocity spread and spatial profiles of the O/O2 beam obtained from separate measurements. These computations use basic engineering models for the gas-gas and gas-surface scattering and focus on the influence of multi-collision effects. These simulations characterize many important quantities of interest including the actual flux of atoms that reach the surface, the energy distribution of this flux, as well as the direction of the velocity of the flux that strikes the surface. These quantities are important in characterizing the conditions which give rise to measured surface erosion. The calculations also yield time- snapshots of the pulse as it impacts and flows around the surface. These snapshots reveal the local environment of gas near the surface for the duration of the pulse. We are also able to compute the flux of molecules that travel downstream and reach the spectrometer, and we characterize their velocity distribution. The number of atoms that reach the spectrometer can in fact be influenced by the presence of the surface due to gas-gas collisions from atoms scattered h m the surface, and it will generally be less than that with the surface absent. This amounts to an overall normalization factor in computing erosion yields. We discuss these quantities and their relationship to the gas-surf$ce interaction parameters. We have also performed similar calculations corresponding to conditions (number densities, temperatures, and velocities) of low-earth orbit. The steady-state nature and lower overall flux of the actual space environment give rise to differences in the nature of the gas-impacts on the surface from those of the ground-based measurements using a pulsed source.

Model predictions and visualization of the particle flux on the surface of Mars.

PubMed

Cucinotta, Francis A; Saganti, Premkumar B; Wilson, John W; Simonsen, Lisa C

2002-12-01

Model calculations of the particle flux on the surface of Mars due to the Galactic Cosmic Rays (GCR) can provide guidance on radiobiological research and shielding design studies in support of Mars exploration science objectives. Particle flux calculations for protons, helium ions, and heavy ions are reported for solar minimum and solar maximum conditions. These flux calculations include a description of the altitude variations on the Martian surface using the data obtained by the Mars Global Surveyor (MGS) mission with its Mars Orbiter Laser Altimeter (MOLA) instrument. These particle flux calculations are then used to estimate the average particle hits per cell at various organ depths of a human body in a conceptual shelter vehicle. The estimated particle hits by protons for an average location at skin depth on the Martian surface are about 10 to 100 particle-hits/cell/year and the particle hits by heavy ions are estimated to be 0.001 to 0.01 particle-hits/cell/year.

Validation and Improvement of CERES Surface Radiation Budget Algorithms: Extension of Dusty and Cloudy Scenes

NASA Technical Reports Server (NTRS)

Ramanathan, V.; Inamdar, Anand K.

2005-01-01

Our main task was to validate and improve the generation of surface long wave fluxes from the CERES TOA window channel flux measurements. We completed this task successfully for the clear sky fluxes in the presence of aerosols including dust during the first year of the project. The algorithm we developed for CERES was remarkably successful for clear sky fluxes and we have no further tasks that need to be performed past the requested termination date of December 31, 2004. We found that the information contained in the TOA fluxes was not sufficient to improve upon the current CERES algorithm for cloudy sky fluxes. Given this development and given our success in clear sky fluxes, we do not see any reason to continue our validation work beyond what we have completed. Specific details are given.

Pyrolytic graphite gauge for measuring heat flux

NASA Technical Reports Server (NTRS)

Bunker, Robert C. (Inventor); Ewing, Mark E. (Inventor); Shipley, John L. (Inventor)

2002-01-01

A gauge for measuring heat flux, especially heat flux encountered in a high temperature environment, is provided. The gauge includes at least one thermocouple and an anisotropic pyrolytic graphite body that covers at least part of, and optionally encases the thermocouple. Heat flux is incident on the anisotropic pyrolytic graphite body by arranging the gauge so that the gauge surface on which convective and radiative fluxes are incident is perpendicular to the basal planes of the pyrolytic graphite. The conductivity of the pyrolytic graphite permits energy, transferred into the pyrolytic graphite body in the form of heat flux on the incident (or facing) surface, to be quickly distributed through the entire pyrolytic graphite body, resulting in small substantially instantaneous temperature gradients. Temperature changes to the body can thereby be measured by the thermocouple, and reduced to quantify the heat flux incident to the body.

Global observations and modeling of atmosphere-surface exchange of elemental mercury: a critical review

NASA Astrophysics Data System (ADS)

Zhu, Wei; Lin, Che-Jen; Wang, Xun; Sommar, Jonas; Fu, Xuewu; Feng, Xinbin

2016-04-01

Reliable quantification of air-surface fluxes of elemental Hg vapor (Hg0) is crucial for understanding mercury (Hg) global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc.) in the past three decades. However, large uncertainties remain due to the complexity of Hg0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere-surface exchange of Hg0. Specifically, the advancement of flux quantification techniques, mechanisms in driving the air-surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O3, radicals, etc.). However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling. We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann-Whitney U test). The spatiotemporal coverage of existing Hg0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia). The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg0 flux observations in East Asia are comparatively larger in magnitude than the rest of the world, suggesting substantial re-emission of previously deposited mercury from anthropogenic sources. The Hg0 exchange over pristine surfaces (e.g., background soil and water) and vegetation needs better constraints for global analyses of the atmospheric Hg budget. The existing knowledge gap and the associated research needs for future measurements and modeling efforts for the air-surface exchange of Hg0 are discussed.

A heat budget for the Stratus mooring in the southeast Pacific

NASA Astrophysics Data System (ADS)

Holte, J.; Straneo, F.; Weller, R. A.; Farrar, J. T.

2012-12-01

The surface layer of the southeast Pacific Ocean (SEP) requires an input of fresh, cold water to balance evaporation and heat gain from incoming solar radiation. Numerous processes contribute to closing the SEP's upper-ocean heat budget, including gyre circulation, Ekman transport and pumping, vertical mixing, and horizontal eddy heat flux divergence. However, there is little consensus on which processes are most important, as many modeling and observational studies have reported conflicting results. To examine how the SEP maintains relatively cool surface temperatures despite such strong surface forcing, we calculate a heat budget for the upper 250 m of the Stratus mooring. The Stratus mooring, deployed at 85(^o)W 20(^o)S since 2000, is in the center of the stratus cloud region. The surface buoy measures meteorological conditions and air-sea fluxes; the mooring line is heavily instrumented, measuring temperature, salinity, and velocity at approximately 15 to 20 depth levels. Our heat budget covers 2004 - 2010. The net air-sea heat flux over this period is 32 W m(^{-2}), approximately 2/3 of the flux over earlier periods. We use Argo profiles, relatively abundant in the region since 2004, to calculate horizontal temperature gradients. These gradients, coupled with the mooring velocity record, are used to estimate the advective heat flux. We find that the cool advective heat flux largely compensates the air-sea heat flux at the mooring; in our calculation this term includes the mean gyre circulation, horizontal Ekman transport, and some contribution from eddies. The passage of numerous eddies is evident in the mooring velocity record, but with the available data we cannot separate the eddy heat flux divergence from the mean heat advection. Vertical mixing and Ekman pumping across the base of the layer are both small.

Numerical Study of Hydrothermal Wave Suppression in Thermocapillary Flow Using a Predictive Control Method

NASA Astrophysics Data System (ADS)

Muldoon, F. H.

2018-04-01

Hydrothermal waves in flows driven by thermocapillary and buoyancy effects are suppressed by applying a predictive control method. Hydrothermal waves arise in the manufacturing of crystals, including the "open boat" crystal growth process, and lead to undesirable impurities in crystals. The open boat process is modeled using the two-dimensional unsteady incompressible Navier-Stokes equations under the Boussinesq approximation and the linear approximation of the surface thermocapillary force. The flow is controlled by a spatially and temporally varying heat flux density through the free surface. The heat flux density is determined by a conjugate gradient optimization algorithm. The gradient of the objective function with respect to the heat flux density is found by solving adjoint equations derived from the Navier-Stokes ones in the Boussinesq approximation. Special attention is given to heat flux density distributions over small free-surface areas and to the maximum admissible heat flux density.

Effect of wakes on land-atmosphere fluxes

NASA Astrophysics Data System (ADS)

Markfort, C. D.; Zhang, W.; Porte-Agel, F.; Stefan, H. G.

2011-12-01

Wakes affect land-atmosphere fluxes of momentum and scalars, including water vapor and trace gases. Canopies and bluff bodies, including forests, buildings and topography, cause boundary layer flow separation, significantly extend flow recovery, and lead to a break down of standard Monin-Obukhov similarity relationships in the atmospheric boundary layer (ABL). Wakes generated by these land surface features persist for significant distances affecting a large fraction of the Earth's terrestrial surface. This effect is currently not accounted for in land-atmosphere modeling, and little is known about how heterogeneity of wake-generating features effect land surface fluxes. Additionally flux measurements, made in wake-affected regions, do not satisfy the homogeneous requirements for the standard eddy correlation (EC) method. This phenomenon often referred to as sheltering has been shown to affect momentum and kinetic energy fluxes into lakes from the atmosphere (Markfort et al. 2010). This presentation will highlight results from controlled wind tunnel experiments of neutral and thermally stratified boundary layers, using PIV and custom x-wire/cold-wire anemometry, designed to understand how the physical structure of upstream bluff bodies or porous canopies and thermal stability affect the separation zone, boundary layer recovery and surface fluxes. We also compare these results to field measurements taken with a Doppler LiDAR in the wake of a canopy and a building. We have found that there is a nonlinear relationship between porosity and flow separation behind a canopy to clearing transition. Results will provide the basis for new parameterizations to account for wake effects on land-atmosphere fluxes and corrections for EC measurements over open fields, lakes, and wetlands.

Calibration of Ocean Forcing with satellite Flux Estimates (COFFEE)

NASA Astrophysics Data System (ADS)

Barron, Charlie; Jan, Dastugue; Jackie, May; Rowley, Clark; Smith, Scott; Spence, Peter; Gremes-Cordero, Silvia

2016-04-01

Predicting the evolution of ocean temperature in regional ocean models depends on estimates of surface heat fluxes and upper-ocean processes over the forecast period. Within the COFFEE project (Calibration of Ocean Forcing with satellite Flux Estimates, real-time satellite observations are used to estimate shortwave, longwave, sensible, and latent air-sea heat flux corrections to a background estimate from the prior day's regional or global model forecast. These satellite-corrected fluxes are used to prepare a corrected ocean hindcast and to estimate flux error covariances to project the heat flux corrections for a 3-5 day forecast. In this way, satellite remote sensing is applied to not only inform the initial ocean state but also to mitigate errors in surface heat flux and model representations affecting the distribution of heat in the upper ocean. While traditional assimilation of sea surface temperature (SST) observations re-centers ocean models at the start of each forecast cycle, COFFEE endeavors to appropriately partition and reduce among various surface heat flux and ocean dynamics sources. A suite of experiments in the southern California Current demonstrates a range of COFFEE capabilities, showing the impact on forecast error relative to a baseline three-dimensional variational (3DVAR) assimilation using operational global or regional atmospheric forcing. Experiment cases combine different levels of flux calibration with assimilation alternatives. The cases use the original fluxes, apply full satellite corrections during the forecast period, or extend hindcast corrections into the forecast period. Assimilation is either baseline 3DVAR or standard strong-constraint 4DVAR, with work proceeding to add a 4DVAR expanded to include a weak constraint treatment of the surface flux errors. Covariance of flux errors is estimated from the recent time series of forecast and calibrated flux terms. While the California Current examples are shown, the approach is equally applicable to other regions. These approaches within a 3DVAR application are anticipated to be useful for global and larger regional domains where a full 4DVAR methodology may be cost-prohibitive.

Studies of the net surface radiative flux from satellite radiances during FIFE

NASA Technical Reports Server (NTRS)

Frouin, Robert

1993-01-01

Studies of the net surface radiative flux from satellite radiances during First ISLSCP Field Experiment (FIFE) are presented. Topics covered include: radiative transfer model validation; calibration of VISSR and AVHRR solar channels; development and refinement of algorithms to estimate downward solar and terrestrial irradiances at the surface, including photosynthetically available radiation (PAR) and surface albedo; verification of these algorithms using in situ measurements; production of maps of shortwave irradiance, surface albedo, and related products; analysis of the temporal variability of shortwave irradiance over the FIFE site; development of a spectroscopy technique to estimate atmospheric total water vapor amount; and study of optimum linear combinations of visible and near-infrared reflectances for estimating the fraction of PAR absorbed by plants.

Using a spatially-distributed hydrologic biogeochemistry model with nitrogen transport to study the spatial variation of carbon stocks and fluxes in a Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Shi, Y.; Eissenstat, D. M.; He, Y.; Davis, K. J.

2017-12-01

Most current biogeochemical models are 1-D and represent one point in space. Therefore, they cannot resolve topographically driven land surface heterogeneity (e.g., lateral water flow, soil moisture, soil temperature, solar radiation) or the spatial pattern of nutrient availability. A spatially distributed forest biogeochemical model with nitrogen transport, Flux-PIHM-BGC, has been developed by coupling a 1-D mechanistic biogeochemical model Biome-BGC (BBGC) with a spatially distributed land surface hydrologic model, Flux-PIHM, and adding an advection dominated nitrogen transport module. Flux-PIHM is a coupled physically based model, which incorporates a land-surface scheme into the Penn State Integrated Hydrologic Model (PIHM). The land surface scheme is adapted from the Noah land surface model, and is augmented by adding a topographic solar radiation module. Flux-PIHM is able to represent the link between groundwater and the surface energy balance, as well as land surface heterogeneities caused by topography. In the coupled Flux-PIHM-BGC model, each Flux-PIHM model grid couples a 1-D BBGC model, while nitrogen is transported among model grids via surface and subsurface water flow. In each grid, Flux-PIHM provides BBGC with soil moisture, soil temperature, and solar radiation, while BBGC provides Flux-PIHM with spatially-distributed leaf area index. The coupled Flux-PIHM-BGC model has been implemented at the Susquehanna/Shale Hills Critical Zone Observatory. The model-predicted aboveground vegetation carbon and soil carbon distributions generally agree with the macro patterns observed within the watershed. The importance of abiotic variables (including soil moisture, soil temperature, solar radiation, and soil mineral nitrogen) in predicting aboveground carbon distribution is calculated using a random forest. The result suggests that the spatial pattern of aboveground carbon is controlled by the distribution of soil mineral nitrogen. A Flux-PIHM-BGC simulation without the nitrogen transport module is also executed. The model without nitrogen transport fails in predicting the spatial patterns of vegetation carbon, which indicates the importance of having a nitrogen transport module in spatially distributed ecohydrologic modeling.

Quantifying the Terrestrial Surface Energy Fluxes Using Remotely-Sensed Satellite Data

NASA Astrophysics Data System (ADS)

Siemann, Amanda Lynn

The dynamics of the energy fluxes between the land surface and the atmosphere drive local and regional climate and are paramount to understand the past, present, and future changes in climate. Although global reanalysis datasets, land surface models (LSMs), and climate models estimate these fluxes by simulating the physical processes involved, they merely simulate our current understanding of these processes. Global estimates of the terrestrial, surface energy fluxes based on observations allow us to capture the dynamics of the full climate system. Remotely-sensed satellite data is the source of observations of the land surface which provide the widest spatial coverage. Although net radiation and latent heat flux global, terrestrial, surface estimates based on remotely-sensed satellite data have progressed, comparable sensible heat data products and ground heat flux products have not progressed at this scale. Our primary objective is quantifying and understanding the terrestrial energy fluxes at the Earth's surface using remotely-sensed satellite data with consistent development among all energy budget components [through the land surface temperature (LST) and input meteorology], including validation of these products against in-situ data, uncertainty assessments, and long-term trend analysis. The turbulent fluxes are constrained by the available energy using the Bowen ratio of the un-constrained products to ensure energy budget closure. All final products are within uncertainty ranges of literature values, globally. When validated against the in-situ estimates, the sensible heat flux estimates using the CFSR air temperature and constrained with the products using the MODIS albedo produce estimates closest to the FLUXNET in-situ observations. Poor performance over South America is consistent with the largest uncertainties in the energy budget. From 1984-2007, the longwave upward flux increase due to the LST increase drives the net radiation decrease, and the decrease in the available energy balances the decrease in the sensible heat flux. These datasets are useful for benchmarking climate models and LSM output at the global annual scale and the regional scale subject to the regional uncertainties and performance. Future work should improve the input data, particularly the temperature gradient and Zilitinkevich empirical constant, to reduce uncertainties.

Exploring the Influence of Topography on Belowground C Processes Using a Coupled Hydrologic-Biogeochemical Model

NASA Astrophysics Data System (ADS)

Shi, Y.; Davis, K. J.; Eissenstat, D. M.; Kaye, J. P.; Duffy, C.; Yu, X.; He, Y.

2014-12-01

Belowground carbon processes are affected by soil moisture and soil temperature, but current biogeochemical models are 1-D and cannot resolve topographically driven hill-slope soil moisture patterns, and cannot simulate the nonlinear effects of soil moisture on carbon processes. Coupling spatially-distributed physically-based hydrologic models with biogeochemical models may yield significant improvements in the representation of topographic influence on belowground C processes. We will couple the Flux-PIHM model to the Biome-BGC (BBGC) model. Flux-PIHM is a coupled physically-based land surface hydrologic model, which incorporates a land-surface scheme into the Penn State Integrated Hydrologic Model (PIHM). The land surface scheme is adapted from the Noah land surface model. Because PIHM is capable of simulating lateral water flow and deep groundwater, Flux-PIHM is able to represent the link between groundwater and the surface energy balance, as well as the land surface heterogeneities caused by topography. The coupled Flux-PIHM-BBGC model will be tested at the Susquehanna/Shale Hills critical zone observatory (SSHCZO). The abundant observations, including eddy covariance fluxes, soil moisture, groundwater level, sap flux, stream discharge, litterfall, leaf area index, above ground carbon stock, and soil carbon efflux, make SSHCZO an ideal test bed for the coupled model. In the coupled model, each Flux-PIHM model grid will couple a BBGC cell. Flux-PIHM will provide BBGC with soil moisture and soil temperature information, while BBGC provides Flux-PIHM with leaf area index. Preliminary results show that when Biome- BGC is driven by PIHM simulated soil moisture pattern, the simulated soil carbon is clearly impacted by topography.

Soil surface CO2 flux in a boreal black spruce fire chronosequence

NASA Astrophysics Data System (ADS)

Wang, Chuankuan; Bond-Lamberty, Ben; Gower, Stith T.

2003-02-01

Understanding the effects of wildfire on the carbon (C) cycle of boreal forests is essential to quantifying the role of boreal forests in the global carbon cycle. Soil surface CO2 flux (Rs), the second largest C flux in boreal forests, is directly and indirectly affected by fire and is hypothesized to change during forest succession following fire. The overall objective of this study was to measure and model Rs for a black spruce (Picea mariana [Mill.] BSP) postfire chronosequence in northern Manitoba, Canada. The experiment design was a nested factorial that included two soil drainage classes (well and poorly drained) × seven postfire aged stands. Specific objectives were (1) to quantify the relationship between Rs and soil temperature for different aged boreal black spruce forests in well-drained and poorly drained soil conditions, (2) to examine Rs dynamics along postfire successional stands, and (3) to estimate annual soil surface CO2 flux for these ecosystems. Soil surface CO2 flux was significantly affected by soil drainage class (p = 0.014) and stand age (p = 0.006). Soil surface CO2 flux was positively correlated to soil temperature (R2 = 0.78, p < 0.001), but different models were required for each drainage class × aged stand combination. Soil surface CO2 flux was significantly greater at the well-drained than the poorly drained stands (p = 0.007) during growing season. Annual soil surface CO2 flux for the 1998, 1995, 1989, 1981, 1964, 1930, and 1870 burned stands averaged 226, 412, 357, 413, 350, 274, and 244 g C m-2 yr-1 in the well-drained stands and 146, 380, 300, 303, 256, 233, and 264 g C m-2 yr-1 in the poorly drained stands. Soil surface CO2 flux during the winter (from 1 November to 30 April) comprised from 5 to 19% of the total annual Rs. We speculate that the smaller soil surface CO2 flux in the recently burned than the older stands is mainly caused by decreased root respiration.

Soil surface CO2 flux in a boreal black spruce fire chronosequence

NASA Astrophysics Data System (ADS)

Wang, Chuankuan; Bond-Lamberty, Ben; Gower, Stith T.

2002-02-01

Understanding the effects of wildfire on the carbon (C) cycle of boreal forests is essential to quantifying the role of boreal forests in the global carbon cycle. Soil surface CO2 flux (Rs), the second largest C flux in boreal forests, is directly and indirectly affected by fire and is hypothesized to change during forest succession following fire. The overall objective of this study was to measure and model Rs for a black spruce (Picea mariana [Mill.] BSP) postfire chronosequence in northern Manitoba, Canada. The experiment design was a nested factorial that included two soil drainage classes (well and poorly drained) × seven postfire aged stands. Specific objectives were (1) to quantify the relationship between Rs and soil temperature for different aged boreal black spruce forests in well-drained and poorly drained soil conditions, (2) to examine Rs dynamics along postfire successional stands, and (3) to estimate annual soil surface CO2 flux for these ecosystems. Soil surface CO2 flux was significantly affected by soil drainage class (p = 0.014) and stand age (p = 0.006). Soil surface CO2 flux was positively correlated to soil temperature (R2 = 0.78, p < 0.001), but different models were required for each drainage class × aged stand combination. Soil surface CO2 flux was significantly greater at the well-drained than the poorly drained stands (p = 0.007) during growing season. Annual soil surface CO2 flux for the 1998, 1995, 1989, 1981, 1964, 1930, and 1870 burned stands averaged 226, 412, 357, 413, 350, 274, and 244 g C m-2 yr-1 in the well-drained stands and 146, 380, 300, 303, 256, 233, and 264 g C m-2 yr-1 in the poorly drained stands. Soil surface CO2 flux during the winter (from 1 November to 30 April) comprised from 5 to 19% of the total annual Rs. We speculate that the smaller soil surface CO2 flux in the recently burned than the older stands is mainly caused by decreased root respiration.

Forcing and Responses of the Surface Energy Budget at Summit, Greenland

NASA Astrophysics Data System (ADS)

Miller, Nathaniel B.

Energy exchange at the Greenland Ice Sheet surface governs surface temperature variability, a factor critical for representing increasing surface melt extent, which portends a rise in global sea level. A comprehensive set of cloud, tropospheric, near-surface and sub-surface measurements at Summit Station is utilized to determine the driving forces and subsequent responses of the surface energy budget (SEB). This budget includes radiative, turbulent, and ground heat fluxes, and ultimately controls the evolution of surface temperature. At Summit Station, clouds radiatively warm the surface in all months with an annual average cloud radiative forcing value of 33 W m -2, largely driven by the occurrence of liquid-bearing clouds. The magnitude of the surface temperature response is dependent on how turbulent and ground heat fluxes modulate changes to radiative forcing. Relationships between forcing terms and responding surface fluxes show that changes in the upwelling longwave radiation compensate for 65-85% (50- 60%) of the total change in radiative forcing in the winter (summer). The ground heat flux is the second largest response term (16% annually), especially during winter. Throughout the annual cycle, the sensible heat flux response is comparatively constant (9%) and latent heat flux response is only 1.5%, becoming more of a factor in modulating surface temperature responses during the summer. Combining annual cycles of these responses with cloud radiative forcing results, clouds warm the surface by an estimated 7.8°C annually. A reanalysis product (ERA-I), operational model (CFSv2), and climate model (CESM) are evaluated utilizing the comprehensive set of SEB observations and process-based relationships. Annually, surface temperatures in each model are warmer than observed with overall poor representation of the coldest surface temperatures. Process-based relationships between different SEB flux terms offer insight into how well a modeling framework represents physical processes and the ability to distinguish errors in forcing versus those in physical representation. Such relationships convey that all three models underestimate the response of surface temperatures to changes in radiative forcing. These results provide a method to expose model deficiencies and indicate the importance of representing surface, sub-surface and boundary-layer processes when portraying cloud impacts on surface temperature variability.

A new solar cycle model including meridional circulation

NASA Technical Reports Server (NTRS)

Wang, Y.-M.; Sheeley, N. R., Jr.; Nash, A. G.

1991-01-01

A kinematic model is presented for the solar cycle which includes not only the transport of magnetic flux by supergranular diffusion and a poleward bulk flow at the sun's surface, but also the effects of turbulent diffusion and an equatorward 'return flow' beneath the surface. As in the earlier models of Babcock and Leighton, the rotational shearing of a subsurface poloidal field generates toroidal flux that erupts at the surface in the form of bipolar magnetic regions. However, such eruptions do not result in any net loss of toroidal flux from the sun (as assumed by Babcock and Leighton); instead, the large-scale toroidal field is destroyed both by 'unwinding' as the local poloidal field reverses its polarity, and by diffusion as the toroidal flux is transported equatorward by the subsurface flow and merged with its opposite hemisphere counterpart. The inclusion of meridional circulation allows stable oscillations of the magnetic field, accompanied by the equatorward progression of flux eruptions, to be achieved even in the absence of a radial gradient in the angular velocity. An illustrative case in which a subsurface flow speed of order 1 m/s and subsurface diffusion rate of order 10 sq km/s yield 22-yr oscillations in qualitative agreement with observations.

A mechanism for the dynamo terms to sustain closed-flux current, including helicity balance, by driving current which crosses the magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jarboe, T. R.; Nelson, B. A.; Sutherland, D. A.

2015-07-15

An analysis of imposed dynamo current drive (IDCD) [T.R. Jarboe et al., Nucl. Fusion 52 083017 (2012)] reveals: (a) current drive on closed flux surfaces seems possible without relaxation, reconnection, or other flux-surface-breaking large events; (b) the scale size of the key physics may be smaller than is often computationally resolved; (c) helicity can be sustained across closed flux; and (d) IDCD current drive is parallel to the current which crosses the magnetic field to produce the current driving force. In addition to agreeing with spheromak data, IDCD agrees with selected tokamak data.

Dependence of the residual surface resistance of superconducting radio frequency cavities on the cooling dynamics around T{sub c}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romanenko, A., E-mail: aroman@fnal.gov; Grassellino, A., E-mail: annag@fnal.gov; Melnychuk, O.

We report a strong effect of the cooling dynamics through T{sub c} on the amount of trapped external magnetic flux in superconducting niobium cavities. The effect is similar for fine grain and single crystal niobium and all surface treatments including electropolishing with and without 120 °C baking and nitrogen doping. Direct magnetic field measurements on the cavity walls show that the effect stems from changes in the flux trapping efficiency: slow cooling leads to almost complete flux trapping and higher residual resistance, while fast cooling leads to the much more efficient flux expulsion and lower residual resistance.

The Role of Surface Water Flow in Gas Fluxes from a Subtropical Rice Field

NASA Astrophysics Data System (ADS)

Huynh, K. T.; Suvocarev, K.; Reavis, C.; Runkle, B.; Variano, E. A.

2016-12-01

Wetlands are the single largest source of methane emissions, but the underlying processes behind this flux are not yet fully understood. Typically, methane fluxes from wetlands have been attributed to ebullition (bubbling) and to transport through vegetation. However, a third major pathway-hydrodynamic transport-has been seen in a temperate wetland in the Sacramento-San Joaquin Delta. We wish to explore whether this additional pathway is also important to a subtropical rice paddy site where the diel thermal cycle is less pronounced than in the temperate site. Measurements in the surface water of a rice field were collected over two weeks. Specific measurements collected included dissolved and atmospheric methane concentration, surface water velocity, and air and water temperature. These were used to augment a long-term dataset of micrometeorology and gas fluxes. Together, these data demonstrate the role that surface water motions play in the fluxes between soil and atmosphere. Data are analyzed to reveal the fraction of total methane flux that is governed by advective/diffusive transport through surface water, and daily cycles in this behavior. Results will be used to advance predictions of atmospheric methane gas concentrations and could be foundational for developing methane management solutions. Closing this gap in knowledge is key to improving calculations of current global greenhouse gas emissions.

Atmospheric responses to sensible and latent heating fluxes over the Gulf Stream

NASA Astrophysics Data System (ADS)

Minobe, S.; Ida, T.; Takatama, K.

2016-12-01

Air-sea interaction over mid-latitude oceanic fronts such as the Gulf Stream attracted large attention in the last decade. Observational analyses and modelling studies revealed that atmospheric responses over the Gulf Stream including surface wind convergence, enhanced precipitation and updraft penetrating to middle-to-upper troposphere roughly on the Gulf Stream current axis or on the warmer flank of sea-surface temperature (SST) front of the Gulf Stream . For these atmospheric responses, oceanic information should be transmitted to the atmosphere via turbulent heat fluxes, and thus the mechanisms for atmospheric responses can be understood better by examining latent and sensible air-sea heat fluxes more closely. Thus, the roles of the sensible and latent heat fluxes are examined by conducting a series of numerical experiments using the IPRC Regional Atmospheric Model over the Gulf Stream by applying SST smoothing for latent and sensible heating separately. The results indicate that the sensible and latent heat fluxes affect the atmosphere differently. Sensible heat flux intensifies surface wind convergence to produce sea-level pressure (SLP) anomaly. Latent heat flux supplies moistures and maintains enhanced precipitation. The different heat flux components cause upward wind velocity at different levels.

Process for reducing series resistance of solar-cell metal-contact systems with a soldering-flux etchant

DOEpatents

Coyle, R.T.; Barrett, J.M.

1982-05-04

Disclosed is a process for substantially reducing the series resistance of a solar cell having a thick film metal contact assembly thereon while simultaneously removing oxide coatings from the surface of the assembly prior to applying solder therewith. The process includes applying a flux to the contact assembly and heating the cell for a period of time sufficient to substantially remove the series resistance associated with the assembly by etching the assembly with the flux while simultaneously removing metal oxides from said surface of said assembly.

Process for reducing series resistance of solar cell metal contact systems with a soldering flux etchant

DOEpatents

Coyle, R. T.; Barrett, Joy M.

1984-01-01

Disclosed is a process for substantially reducing the series resistance of a solar cell having a thick film metal contact assembly thereon while simultaneously removing oxide coatings from the surface of the assembly prior to applying solder therewith. The process includes applying a flux to the contact assembly and heating the cell for a period of time sufficient to substantially remove the series resistance associated with the assembly by etching the assembly with the flux while simultaneously removing metal oxides from said surface of said assembly.

Automated video-microscopic imaging and data acquisition system for colloid deposition measurements

DOEpatents

Abdel-Fattah, Amr I.; Reimus, Paul W.

2004-12-28

A video microscopic visualization system and image processing and data extraction and processing method for in situ detailed quantification of the deposition of sub-micrometer particles onto an arbitrary surface and determination of their concentration across the bulk suspension. The extracted data includes (a) surface concentration and flux of deposited, attached and detached colloids, (b) surface concentration and flux of arriving and departing colloids, (c) distribution of colloids in the bulk suspension in the direction perpendicular to the deposition surface, and (d) spatial and temporal distributions of deposited colloids.

How Well are Recent Climate Variability Signals Resolved by Satellite Radiative Flux Estimates?

NASA Technical Reports Server (NTRS)

Robertson, Franklin R.; Lu, H.-L.

2004-01-01

One notable aspect of Earth s climate is that although the planet appears to be very close to radiative balance at top-of-atmosphere (TOA), the atmosphere itself and underlying surface are not. Profound exchanges of energy between the atmosphere and oceans, land and cryosphere occur over a range of time scales. Recent evidence from broadband satellite measurements suggests that even these TOA fluxes contain some detectable variations. Our ability to measure and reconstruct radiative fluxes at the surface and at the top of atmosphere is improving rapidly. Understanding the character of radiative flux estimates and relating them to variations in other energy fluxes and climate state variables is key to improving our understanding of climate. In this work we will evaluate several recently released estimates of radiative fluxes, focusing primarily on surface estimates. The International Satellite Cloud Climatology Project FD radiative flux profiles are available from rnid-1983 to near present and have been constructed by driving the radiative transfer physics from the Goddard Institute for Space Studies (GISS) global model with ISCCP clouds and HlRS operational soundings profiles. Full and clear sky SW and LW fluxes are produced. A similar product from the NASA/GEWEX Surface Radiation Budget Project using different radiative flux codes and thermodynamics from the NASA/Goddard Earth Observing System assimilation model makes a similar calculation of surface fluxes. However this data set currently extends only through 1995. Several estimates of downward LW flux at the surface inferred from microwave data are also examined. Since these products have been evaluated with Baseline Surface Radiation Network data over land we focus over ocean regions and use the DOE/NOAA/NASA Shipboard Ocean Atmospheric Radiation (SOAR) surface flux measurements to characterize performance of these data sets under both clear and cloudy conditions. Some aspects of performance are stratified according to SST and vertical motion regimes. Comparisons to the TRMM/CERES SRB data in 1998 are also interpreted. These radiative fluxes are then analyzed to determine how surface (and TOA) radiative exchanges respond to interannual signals of ENS0 warm and cold events. Our analysis includes regional changes as well as integrated signals over land, ocean and various latitude bands. Changes in water vapor and cloud forcing signatures are prominent on interannual time scales. Prominent signals are also found in the SW fluxes for the Pinatubo volcanic event. These systematic changes in fluxes are related to changes in large-scale circulations and energy transport in the atmosphere and ocean. Some estimates of signal-to-noise and reliability are discussed to place our results in context.

Solids-based concentrated solar power receiver

DOEpatents

None

2018-04-10

A concentrated solar power (CSP) system includes channels arranged to convey a flowing solids medium descending under gravity. The channels form a light-absorbing surface configured to absorb solar flux from a heliostat field. The channels may be independently supported, for example by suspension, and gaps between the channels are sized to accommodate thermal expansion. The light absorbing surface may be sloped so that the inside surfaces of the channels proximate to the light absorbing surface define downward-slanting channel floors, and the flowing solids medium flows along these floors. Baffles may be disposed inside the channels and oriented across the direction of descent of the flowing solids medium. The channels may include wedge-shaped walls forming the light-absorbing surface and defining multiple-reflection light paths for solar flux from the heliostat field incident on the light-absorbing surface.

ANALYSIS OF WATER AND ENERGY FLUXES USING SATELLITE, ENERGY BALANCE MODELING AND OBSERVATIONS (Invited)

NASA Astrophysics Data System (ADS)

Irmak, A.

2009-12-01

Surface energy fluxes, including net radiation (Rn), sensible heat (H), latent heat (LE), and soil heat flux (G) are critical in surface energy balance of any terrain or landscapes. Estimation or measurement of these energy fluxes is important for completing the water balance in terrestrial ecosystems, and therefore accurately predicting the effects of global climate and land use change. The objectives of this study were to (1) use METRICtm (Mapping Evapotranspiration at high Resolution using Internalized Calibration) model for estimating land surface energy fluxes in Nebraska (NE) by utilizing satellite remote sensing data, (2) identify model bias in energy balance components compared with measurements from Bowen Ratio Energy Balance System (BREBS) in a subsurface drip-irrigated maize field in South-central Nebraska, and (3) understand the partitioning of available energy into latent heat for corn and soybean cropping systems at large scale. A total of 15 Landsat images were processed to estimate instantaneous surface energy fluxes at Landsat overpasses with METRIC model. Results showed that the model predictions of the surface energy fluxes and daily evapotranspiration were correlated well with the BREBS measurements. There is a need, however, to test the performance of the model with in-situ observations in other locations with different dataset before utilizing it for crucial water regulatory and policy decisions. The METRICtm approach illustrated how an ‘off-the-shelf’ model can be applied operationally over a significant time period and how that model behaves. The findings makes considerable contribution to our understanding of estimating land surface energy fluxes using remote sensing approach and experimentally describes the operational characteristics of METRICtm and presents its limitations.

Surface Meteorological Station - ARL 2m, ancillary flux, Prineville - Reviewed Data

DOE Data Explorer

Clawson, Kirk

2017-10-23

These data contain measurements from a four-component net radiometer, as well as 2-m temperature, pressure, and relative humidity. In addition, soil moisture and temperature measurements and soil heat fluxes are included.

Surface Meteorological Station - ARL 2m, ancillary flux, Boardman - Raw Data

DOE Data Explorer

Clawson, Kirk

2017-10-23

These data contain measurements from a four-component net radiometer, as well as 2-m temperature, pressure, and relative humidity. In addition, soil moisture and temperature measurements and soil heat fluxes are included.

Surface Meteorological Station - ARL 2m, ancillary flux, Boardman - Reviewed Data

DOE Data Explorer

Clawson, Kirk

2017-10-23

These data contain measurements from a four-component net radiometer, as well as 2-m temperature, pressure, and relative humidity. In addition, soil moisture and temperature measurements and soil heat fluxes are included.

Are Surface Waters Around Greenland Getting Saltier in a Warming Climate?

NASA Astrophysics Data System (ADS)

Vinogradova, N. T.; Ponte, R. M.; Piecuch, C. G.; Little, C. M.

2016-02-01

During the past two decades, most surface waters around Greenland ice sheet and in the Nordic Seas became significantly saltier. Given the fact that these waters feed the North Atlantic thermohaline circulation, an increase in surface salinity, which can exceed 0.2 psu in places, might have an important impact on the global ocean circulation and on future projections of the climate state. Surface salinification may seem counter-intuitive to the reported long-term increase in freshwater supply to the region from river discharge and ice melting, sparking debates about whether the freshening of the subpolar gyre has ceased, and whether the recent salinification, if continued, will be able to forestall the projected slowdown of the overturning circulation. Here we assess what controls contemporary salinity changes by examining various terms of the salinity budget, including the dilution effect due to air-sea fluxes of freshwater, fluxes of salt due to sea ice formation/melting, and ocean fluxes of salinity associated with advective and diffusive processes. We use an ocean state estimate produced by the ECCO consortium to consider the budgets over the period 1992-2011. ECCO estimates produce salinity fields close to the observations and, crucial for our purposes, permit closed budget diagnostics of salinity and respective fluxes. The budgets are formulated within the entire water column in order to examine three-dimensional structure of freshwater storage and establish a link between the surface and upper-ocean change in near-Greenland waters. Over the past two decades, patterns of change are evident in all budget terms, with ocean fluxes either offsetting or enhancing surface forcing, including the effects of sea ice dynamics. Interpretation is provided within the context of a changing climate, including intensification of the hydrological cycle and weakening of ocean transports and overturning, as well as natural decadal-to-interdacadal variability present in the system.

Dependence of the residual surface resistance of superconducting radio frequency cavities on the cooling dynamics around T c

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romanenko, A.; Grassellino, A.; Melnychuk, O.

We report a strong effect of the cooling dynamics throughmore » $$T_\\mathrm{c}$$ on the amount of trapped external magnetic flux in superconducting niobium cavities. The effect is similar for fine grain and single crystal niobium and all surface treatments including electropolishing with and without 120$$^\\circ$$C baking and nitrogen doping. Direct magnetic field measurements on the cavity walls show that the effect stems from changes in the flux trapping efficiency: slow cooling leads to almost complete flux trapping and higher residual resistance while fast cooling leads to the much more efficient flux expulsion and lower residual resistance.« less

Comparison of Surface Ground Temperature from Satellite Observations and the Off-Line Land Surface GEOS Assimilation System

NASA Technical Reports Server (NTRS)

Yang, R.; Houser, P.; Joiner, J.

1998-01-01

The surface ground temperature (Tg) is an important meteorological variable, because it represents an integrated thermal state of the land surface determined by a complex surface energy budget. Furthermore, Tg affects both the surface sensible and latent heat fluxes. Through these fluxes. the surface budget is coupled with the atmosphere above. Accurate Tg data are useful for estimating the surface radiation budget and fluxes, as well as soil moisture. Tg is not included in conventional synoptical weather station reports. Currently, satellites provide Tg estimates globally. It is necessary to carefully consider appropriate methods of using these satellite data in a data assimilation system. Recently, an Off-line Land surface GEOS Assimilation (OLGA) system was implemented at the Data Assimilation Office at NASA-GSFC. One of the goals of OLGA is to assimilate satellite-derived Tg data. Prior to the Tg assimilation, a thorough investigation of satellite- and model-derived Tg, including error estimates, is required. In this study we examine the Tg from the n Project (ISCCP DI) data and the OLGA simulations. The ISCCP data used here are 3-hourly DI data (2.5x2.5 degree resolution) for 1992 summer months (June, July, and August) and winter months (January and February). The model Tg for the same periods were generated by OLGA. The forcing data for this OLGA 1992 simulation were generated from the GEOS-1 Data Assimilation System (DAS) at Data Assimilation Office NASA-GSFC. We examine the discrepancies between ISCCP and OLGA Tg with a focus on its spatial and temporal characteristics, particularly on the diurnal cycle. The error statistics in both data sets, including bias, will be estimated. The impact of surface properties, including vegetation cover and type, topography, etc, on the discrepancies will be addressed.

Surface energy fluxes in complex terrain

NASA Technical Reports Server (NTRS)

Reiter, E. R.; Sheaffer, J. D.; Bossert, J. E.

1986-01-01

The emphasis of the 1985 NASA project activity was on field measurements of wind data and heat balance data. Initiatives included a 19 station mountaintop monitoring program, testing and refining the surface flux monitoring systems and packing and shipping equipment to the People's Republic of China in preparation for the 1986 Tibet Experiment. Other work included more extensive analyses of the 1984 Gobi Desert and Rocky Mountain observations plus some preliminary analyses of the 1985 mountaintop network data. Details of our field efforts are summarized and results of our data analyses are presented.

Incorporating both physical and kinetic limitations in quantifying dissolved oxygen flux to aquatic sediments

USGS Publications Warehouse

O'Connor, B.L.; Hondzo, Miki; Harvey, J.W.

2009-01-01

Traditionally, dissolved oxygen (DO) fluxes have been calculated using the thin-film theory with DO microstructure data in systems characterized by fine sediments and low velocities. However, recent experimental evidence of fluctuating DO concentrations near the sediment-water interface suggests that turbulence and coherent motions control the mass transfer, and the surface renewal theory gives a more mechanistic model for quantifying fluxes. Both models involve quantifying the mass transfer coefficient (k) and the relevant concentration difference (??C). This study compared several empirical models for quantifying k based on both thin-film and surface renewal theories, as well as presents a new method for quantifying ??C (dynamic approach) that is consistent with the observed DO concentration fluctuations near the interface. Data were used from a series of flume experiments that includes both physical and kinetic uptake limitations of the flux. Results indicated that methods for quantifying k and ??C using the surface renewal theory better estimated the DO flux across a range of fluid-flow conditions. ?? 2009 ASCE.

The Role of Surface Energy Exchange for Simulating Wind Inflow: An Evaluation of Multiple Land Surface Models in WRF for the Southern Great Plains Site Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wharton, Sonia; Simpson, Matthew; Osuna, Jessica

The Weather Research and Forecasting (WRF) model is used to investigate choice of land surface model (LSM) on the near-surface wind profile, including heights reached by multi-megawatt wind turbines. Simulations of wind profiles and surface energy fluxes were made using five LSMs of varying degrees of sophistication in dealing with soil-plant-atmosphere feedbacks for the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Southern Great Plains (SGP) Central Facility in Oklahoma. Surface-flux and wind-profile measurements were available for validation. The WRF model was run for three two-week periods during which varying canopy and meteorological conditions existed. Themore » LSMs predicted a wide range of energy-flux and wind-shear magnitudes even during the cool autumn period when we expected less variability. Simulations of energy fluxes varied in accuracy by model sophistication, whereby LSMs with very simple or no soil-plant-atmosphere feedbacks were the least accurate; however, the most complex models did not consistently produce more accurate results. Errors in wind shear also were sensitive to LSM choice and were partially related to the accuracy of energy flux data. The variability of LSM performance was relatively high, suggesting that LSM representation of energy fluxes in the WRF model remains a significant source of uncertainty for simulating wind turbine inflow conditions.« less

Comparing Multiple Evapotranspiration-calculating Methods, Including Eddy Covariance and Surface Renewal, Using Empirical Measurements from Alfalfa Fields in the Sacramento-San Joaquin River Delta

NASA Astrophysics Data System (ADS)

Clay, J.; Kent, E. R.; Leinfelder-Miles, M.; Lambert, J. J.; Little, C.; Paw U, K. T.; Snyder, R. L.

2016-12-01

Eddy covariance and surface renewal measurements were used to estimate evapotranspiration (ET) over a variety of crop fields in the Sacramento-San Joaquin River Delta during the 2016 growing season. However, comparing and evaluating multiple measurement systems and methods for determining ET was focused upon at a single alfalfa site. The eddy covariance systems included two systems for direct measurement of latent heat flux: one using a separate sonic anemometer and an open path infrared gas analyzer and another using a combined system (Campbell Scientific IRGASON). For these methods, eddy covariance was used with measurements from the Campbell Scientific CSAT3, the LI-COR 7500a, the Campbell Scientific IRGASON, and an additional R.M. Young sonic anemometer. In addition to those direct measures, the surface renewal approach included several energy balance residual methods in which net radiation, ground heat flux, and sensible heat flux (H) were measured. H was measured using several systems and different methods, including using multiple fast-response thermocouple measurements and using the temperatures measured by the sonic anemometers. The energy available for ET was then calculated as the residual of the surface energy balance equation. Differences in ET values were analyzed between the eddy covariance and surface renewal methods, using the IRGASON-derived values of ET as the standard for accuracy.

The impact of standard and hard-coded parameters on the hydrologic fluxes in the Noah-MP land surface model

NASA Astrophysics Data System (ADS)

Cuntz, Matthias; Mai, Juliane; Samaniego, Luis; Clark, Martyn; Wulfmeyer, Volker; Branch, Oliver; Attinger, Sabine; Thober, Stephan

2016-09-01

Land surface models incorporate a large number of process descriptions, containing a multitude of parameters. These parameters are typically read from tabulated input files. Some of these parameters might be fixed numbers in the computer code though, which hinder model agility during calibration. Here we identified 139 hard-coded parameters in the model code of the Noah land surface model with multiple process options (Noah-MP). We performed a Sobol' global sensitivity analysis of Noah-MP for a specific set of process options, which includes 42 out of the 71 standard parameters and 75 out of the 139 hard-coded parameters. The sensitivities of the hydrologic output fluxes latent heat and total runoff as well as their component fluxes were evaluated at 12 catchments within the United States with very different hydrometeorological regimes. Noah-MP's hydrologic output fluxes are sensitive to two thirds of its applicable standard parameters (i.e., Sobol' indexes above 1%). The most sensitive parameter is, however, a hard-coded value in the formulation of soil surface resistance for direct evaporation, which proved to be oversensitive in other land surface models as well. Surface runoff is sensitive to almost all hard-coded parameters of the snow processes and the meteorological inputs. These parameter sensitivities diminish in total runoff. Assessing these parameters in model calibration would require detailed snow observations or the calculation of hydrologic signatures of the runoff data. Latent heat and total runoff exhibit very similar sensitivities because of their tight coupling via the water balance. A calibration of Noah-MP against either of these fluxes should therefore give comparable results. Moreover, these fluxes are sensitive to both plant and soil parameters. Calibrating, for example, only soil parameters hence limit the ability to derive realistic model parameters. It is thus recommended to include the most sensitive hard-coded model parameters that were exposed in this study when calibrating Noah-MP.

Estimation of Land Surface Fluxes and Their Uncertainty via Variational Data Assimilation Approach

NASA Astrophysics Data System (ADS)

Abdolghafoorian, A.; Farhadi, L.

2016-12-01

Accurate estimation of land surface heat and moisture fluxes as well as root zone soil moisture is crucial in various hydrological, meteorological, and agricultural applications. "In situ" measurements of these fluxes are costly and cannot be readily scaled to large areas relevant to weather and climate studies. Therefore, there is a need for techniques to make quantitative estimates of heat and moisture fluxes using land surface state variables. In this work, we applied a novel approach based on the variational data assimilation (VDA) methodology to estimate land surface fluxes and soil moisture profile from the land surface states. This study accounts for the strong linkage between terrestrial water and energy cycles by coupling the dual source energy balance equation with the water balance equation through the mass flux of evapotranspiration (ET). Heat diffusion and moisture diffusion into the column of soil are adjoined to the cost function as constraints. This coupling results in more accurate prediction of land surface heat and moisture fluxes and consequently soil moisture at multiple depths with high temporal frequency as required in many hydrological, environmental and agricultural applications. One of the key limitations of VDA technique is its tendency to be ill-posed, meaning that a continuum of possibilities exists for different parameters that produce essentially identical measurement-model misfit errors. On the other hand, the value of heat and moisture flux estimation to decision-making processes is limited if reasonable estimates of the corresponding uncertainty are not provided. In order to address these issues, in this research uncertainty analysis will be performed to estimate the uncertainty of retrieved fluxes and root zone soil moisture. The assimilation algorithm is tested with a series of experiments using a synthetic data set generated by the simultaneous heat and water (SHAW) model. We demonstrate the VDA performance by comparing the (synthetic) true measurements (including profile of soil moisture and temperature, land surface water and heat fluxes, and root water uptake) with VDA estimates. In addition, the feasibility of extending the proposed approach to use remote sensing observations is tested by limiting the number of LST observations and soil moisture observations.

Dry deposition fluxes and deposition velocities of trace metals in the Tokyo metropolitan area measured with a water surface sampler.

PubMed

Sakata, Masahiro; Marumoto, Kohji

2004-04-01

Dry deposition fluxes and deposition velocities (=deposition flux/atmospheric concentration) for trace metals including Hg, Cd, Cu, Mn, Pb, and Zn in the Tokyo metropolitan area were measured using an improved water surface sampler. Mercury is deposited on the water surface in both gaseous (reactive gaseous mercury, RGM) and particulate (particulate mercury, Hg(p)) forms. The results based on 1 yr observations found that dry deposition plays a significant if not dominant role in trace metal deposition in this urban area, contributing fluxes ranging from 0.46 (Cd) to 3.0 (Zn) times those of concurrent wet deposition fluxes. The deposition velocities were found to be dependent on the deposition of coarse particles larger than approximately 5 microm in diameter on the basis of model calculations. Our analysis suggests that the 84.13% diameter is a more appropriate index for each deposited metal than the 50% diameter in the assumed undersize log-normal distribution, because larger particles are responsible for the flux. The deposition velocities for trace metals other than mercury increased exponentially with an increase in their 84.13% diameters. Using this regression equation, the deposition velocities for Hg(p) were estimated from its 84.13% diameter. The deposition fluxes for Hg(p) calculated from the estimated velocities tended to be close to the mercury fluxes measured with the water surface sampler during the study periods except during summer.

In situ soil temperature and heat flux measurements during controlled surface burns at a southern Colorado forest site

Treesearch

W. J. Massman; J. M. Frank; W. D. Shepperd; M. J. Platten

2003-01-01

This study presents in situ soil temperature measurements at 5-6 depths and heat flux measurements at 2-5 depths obtained during the fall/winter of 2001/ 2002 at seven controlled (surface) fires within a ponderosa pine forest site at the Manitou Experimental Forest in central Colorado. Six of these burns included three different (low, medium, and high) fuel loadings...

Evaluating Surface Flux Results from CERES-FLASHFlux

NASA Technical Reports Server (NTRS)

Wilber, Anne C.; Stackhouse, Paul W., Jr.; Kratz, David P.; Gupta, Shashi K.; Sawaengphokhai, Parnchai K.

2015-01-01

The Fast Longwave and Shortwave Radiative Flux (FLASHFlux) data product was developed to provide a rapid release version of the Clouds and Earth's Radiant Energy System (CERES) results, which could be made available to the research and applications communities within one week of the satellite observations by exchanging some accuracy for speed of processing. Unlike standard CERES products, FLASHFlux does not maintain a long-term consistent record. Therefore the latest algorithm changes and input data can be incorporated into processing. FLASHFlux released Version3A (January 2013) and Version 3B (August 2014) which include the latest meteorological product from Global Modeling and Assimilation Office (GMAO), GEOS FP-IT (5.9.1), the latest spectral response functions and gains for the CERES instruments, and aerosol climatology based on the latest MATCH data. Version 3B included a slightly updated calibration and some changes to the surface albedo over snow/ice. Typically FLASHFlux does not reprocess earlier versions when a new version is released. The combined record of Time Interpolated Space Averaged (TISA) surface flux results from Versions3A and 3B for July 2012 to October 2015 have been compared to the ground-based measurements. The FLASHFlux results are also compared to two other CERES gridded products, SYN1deg and EBAF surface fluxes.

Calculating clear-sky radiative heating rates using the Fu-Liou RTM with inputs from observed and reanalyzed profiles

NASA Astrophysics Data System (ADS)

Dolinar, E. K.; Dong, X.; Xi, B.

2015-12-01

One-dimensional radiative transfer models (RTM) are a common tool used for calculating atmospheric heating rates and radiative fluxes. In the forward sense, RTMs use known (or observed) quantities of the atmospheric state and surface characteristics to determine the appropriate surface and top-of-atmosphere (TOA) radiative fluxes. The NASA CERES science team uses the modified Fu-Liou RTM to calculate atmospheric heating rates and surface and TOA fluxes using the CERES observed TOA shortwave (SW) and longwave (LW) fluxes as constraints to derive global surface and TOA radiation budgets using a reanalyzed atmospheric state (e.g. temperature and various greenhouse gases) from the newly developed MERRA-2. However, closure studies have shown that using the reanalyzed state as input to the RTM introduces some disparity between the RTM calculated fluxes and surface observed ones. The purpose of this study is to generate a database of observed atmospheric state profiles, from satellite and ground-based sources, at several permanent Atmospheric Radiation Measurement (ARM) Program sites, including the Southern Great Plains (SGP), Northern Slope of Alaska (NSA) and Tropical Western Pacific Nauru (TWP-C2), and Eastern North Atlantic (ENA) permanent facilities. Since clouds are a major modulator of radiative transfer within the Earth's atmosphere, we will focus on the clear-sky conditions in this study, which will set up the baseline for our cloudy studies in the future. Clear-sky flux profiles are calculated using the Edition 4 NASA LaRC modified Fu-Liou RTM. The aforementioned atmospheric profiles generated in-house are used as input into the RTM, as well as from reanalyses. The calculated surface and TOA fluxes are compared with ARM surface measured and CERES satellite observed SW and LW fluxes, respectively. Clear-sky cases are identified by the ARM radar-lidar observations, as well as satellite observations, at the select ARM sites.

Role of surface heat fluxes underneath cold pools

PubMed Central

Garelli, Alix; Park, Seung‐Bu; Nie, Ji; Torri, Giuseppe; Kuang, Zhiming

2016-01-01

Abstract The role of surface heat fluxes underneath cold pools is investigated using cloud‐resolving simulations with either interactive or horizontally homogenous surface heat fluxes over an ocean and a simplified land surface. Over the ocean, there are limited changes in the distribution of the cold pool temperature, humidity, and gust front velocity, yet interactive heat fluxes induce more cold pools, which are smaller, and convection is then less organized. Correspondingly, the updraft mass flux and lateral entrainment are modified. Over the land surface, the heat fluxes underneath cold pools drastically impact the cold pool characteristics with more numerous and smaller pools, which are warmer and more humid and accompanied by smaller gust front velocities. The interactive fluxes also modify the updraft mass flux and reduce convective organization. These results emphasize the importance of interactive surface fluxes instead of prescribed flux boundary conditions, as well as the formulation of surface heat fluxes, when studying convection. PMID:27134320

Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps

NASA Astrophysics Data System (ADS)

Litt, Maxime; Sicart, Jean-Emmanuel; Six, Delphine; Wagnon, Patrick; Helgason, Warren D.

2017-04-01

Over Saint-Sorlin Glacier in the French Alps (45° N, 6.1° E; ˜ 3 km2) in summer, we study the atmospheric surface-layer dynamics, turbulent fluxes, their uncertainties and their impact on surface energy balance (SEB) melt estimates. Results are classified with regard to large-scale forcing. We use high-frequency eddy-covariance data and mean air-temperature and wind-speed vertical profiles, collected in 2006 and 2009 in the glacier's atmospheric surface layer. We evaluate the turbulent fluxes with the eddy-covariance (sonic) and the profile method, and random errors and parametric uncertainties are evaluated by including different stability corrections and assuming different values for surface roughness lengths. For weak synoptic forcing, local thermal effects dominate the wind circulation. On the glacier, weak katabatic flows with a wind-speed maximum at low height (2-3 m) are detected 71 % of the time and are generally associated with small turbulent kinetic energy (TKE) and small net turbulent fluxes. Radiative fluxes dominate the SEB. When the large-scale forcing is strong, the wind in the valley aligns with the glacier flow, intense downslope flows are observed, no wind-speed maximum is visible below 5 m, and TKE and net turbulent fluxes are often intense. The net turbulent fluxes contribute significantly to the SEB. The surface-layer turbulence production is probably not at equilibrium with dissipation because of interactions of large-scale orographic disturbances with the flow when the forcing is strong or low-frequency oscillations of the katabatic flow when the forcing is weak. In weak forcing when TKE is low, all turbulent fluxes calculation methods provide similar fluxes. In strong forcing when TKE is large, the choice of roughness lengths impacts strongly the net turbulent fluxes from the profile method fluxes and their uncertainties. However, the uncertainty on the total SEB remains too high with regard to the net observed melt to be able to recommend one turbulent flux calculation method over another.

Surface Meteorological Station - ARL 2m, ancillary flux, Prineville - Raw Data

DOE Data Explorer

Clawson, kirk

2017-10-23

These data contain measurements from a 4-component net radiometer, as well as 2-m temperature, pressure, and relative humidity (RH). Measurements of soil moisture and temperature and soil heat fluxes also are included in the dataset.

Boundary Conditions for Scalar (Co)Variances over Heterogeneous Surfaces

NASA Astrophysics Data System (ADS)

Machulskaya, Ekaterina; Mironov, Dmitrii

2018-05-01

The problem of boundary conditions for the variances and covariances of scalar quantities (e.g., temperature and humidity) at the underlying surface is considered. If the surface is treated as horizontally homogeneous, Monin-Obukhov similarity suggests the Neumann boundary conditions that set the surface fluxes of scalar variances and covariances to zero. Over heterogeneous surfaces, these boundary conditions are not a viable choice since the spatial variability of various surface and soil characteristics, such as the ground fluxes of heat and moisture and the surface radiation balance, is not accounted for. Boundary conditions are developed that are consistent with the tile approach used to compute scalar (and momentum) fluxes over heterogeneous surfaces. To this end, the third-order transport terms (fluxes of variances) are examined analytically using a triple decomposition of fluctuating velocity and scalars into the grid-box mean, the fluctuation of tile-mean quantity about the grid-box mean, and the sub-tile fluctuation. The effect of the proposed boundary conditions on mixing in an archetypical stably-stratified boundary layer is illustrated with a single-column numerical experiment. The proposed boundary conditions should be applied in atmospheric models that utilize turbulence parametrization schemes with transport equations for scalar variances and covariances including the third-order turbulent transport (diffusion) terms.

An Analysis of Inter-annual Variability and Uncertainty of Continental Surface Heat Fluxes

NASA Astrophysics Data System (ADS)

Huang, S. Y.; Deng, Y.; Wang, J.

2016-12-01

The inter-annual variability and the corresponding uncertainty of land surface heat fluxes during the first decade of the 21st century are re-evaluated at continental scale based on the heat fluxes estimated by the maximum entropy production (MEP) model. The MEP model predicted heat fluxes are constrained by surface radiation fluxes, automatically satisfy surface energy balance, and are independent of temperature/moisture gradient, wind speed, and roughness lengths. The surface radiation fluxes and temperature data from Clouds and the Earth's Radiant Energy System and the surface specific humidity data from Modern-Era Retrospective analysis for Research and Applications were used to reproduce the global surface heat fluxes with land-cover data from the NASA Energy and Water cycle Study (NEWS). Our analysis shows that the annual means of continental latent heat fluxes have increasing trends associated with increasing trends in surface net radiative fluxes. The sensible heat fluxes also have increasing trends over most continents except for South America. Ground heat fluxes have little trends. The continental-scale analysis of the MEP fluxes are compared with other existing global surface fluxes data products and the implications of the results for inter-annual to decadal variability of regional surface energy budget are discussed.

Characterizing the Early Impact Bombardment

NASA Technical Reports Server (NTRS)

Bogard, Donald D.

2005-01-01

The early bombardment revealed in the larger impact craters and basins on the moon was a major planetary process that affected all bodies in the inner solar system, including the Earth and Mars. Understanding the nature and timing of this bombardment is a fundamental planetary problem. The surface density of lunar impact craters within a given size range on a given lunar surface is a measure of the age of that surface relative to other lunar surfaces. When crater densities are combined with absolute radiometric ages determined on lunar rocks returned to Earth, the flux of large lunar impactors through time can be estimated. These studies suggest that the flux of impactors producing craters greater than 1 km in diameter has been approximately constant over the past approx. 3 Gyr. However, prior to 3.0 - 3.5 Gyr the impactor flux was much larger and defines an early bombardment period. Unfortunately, no lunar surface feature older than approx. 4 Gyr is accurately dated, and the surface density of craters are saturated in most of the lunar highlands. This means that such data cannot define the impactor flux between lunar formation and approx. 4 Gyr ago.

Temperature and heat flux changes at the base of Laurentide ice sheet inferred from geothermal data (evidence from province of Alberta, Canada)

NASA Astrophysics Data System (ADS)

Demezhko, Dmitry; Gornostaeva, Anastasia; Majorowicz, Jacek; Šafanda, Jan

2018-01-01

Using a previously published temperature log of the 2363-m-deep borehole Hunt well (Alberta, Canada) and the results of its previous interpretation, the new reconstructions of ground surface temperature and surface heat flux histories for the last 30 ka have been obtained. Two ways to adjust the timescale of geothermal reconstructions are discussed, namely the traditional method based on the a priori data on thermal diffusivity value, and the alternative one including the orbital tuning of the surface heat flux and the Earth's insolation changes. It is shown that the second approach provides better agreement between geothermal reconstructions and proxy evidences of deglaciation chronology in the studied region.

Influence of Arctic cloud thermodynamic phase on surface shortwave flux

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lubin, D.; Vogelmann, A.

2010-03-15

As part of the Indirect and Semi-Direct Aerosol Campaign (ISDAC) an Analytical Spectral Devices (ASD, Inc.) spectroradiometer was deployed at the Barrow NSA site during April and May of 2008, and in April-October of 2009. This instrument recorded one-minute averages of surface downwelling spectral flux in the wavelength interval 350-2200 nm, thus sampling the two major near infrared windows (1.6 and 2.2 microns) in which the flux is influenced by cloud microphysical properties including thermodynamic phase and effective particle size. Aircraft in situ measurements of cloud properties show mostly mixed-phase clouds over Barrow during the campaign, but with wide variabilitymore » in relative liquid versus ice water content. At fixed total optical depth, this variability in phase composition can yield of order 5-10 Watts per square meter in surface flux variability, with greater cloud attenuation of the surface flux usually occurring under higher ice water content. Thus our data show that changes in cloud phase properties, even within the 'mixed-phase' category, can affect the surface energy balance at the same order of magnitude as greenhouse gas increases. Analysis of this spectral radiometric data provides suggestions for testing new mixed-phase parameterizations in climate models.« less

Simulating fluxes from heterogeneous land surfaces: Explicit subgrid method employing the biosphere-atmosphere transfer scheme (BATS)

NASA Technical Reports Server (NTRS)

Seth, Anji; Giorgi, Filippo; Dickinson, Robert E.

1994-01-01

A vectorized version of the biosphere-atmosphere transfer scheme (VBATS) is used to study moisture, energy, and momentum fluxes from heterogeneous land surfaces st the scale of an atmospheric model (AM) grid cells. To incorporate subgrid scale inhomogeneity, VBATS includes two important features: (1) characterization of the land surface (vegetation and soil parameters) at N subgrid points within an AM grid cell and (2) explicit distribution of climate forcing (precipitation, clouds, etc.) over the subgrid. In this study, VBATS is used in stand-alone mode to simulate a single AM grid cell and to evaluate the effects of subgrid scale vegetation and climate specification on the surface fluxes and hydrology. It is found that the partitioning of energy can be affected by up to 30%, runoff by 50%, and surface stress in excess of 60%. Distributing climate forcing over the AM grid cell increases the Bowen ratio, as a result of enhanced sensible heat flux and reduced latent heat flux. The combined effect of heterogeneous vegetation and distribution of climate is found to be dependent on the dominat vegetation class in the AM grid cell. Development of this method is part of a larger program to explore the importance of subgrid scale processes in regional and global climate simulations.

Seasonal and Vegetational Variation in Albedo Measured During CERES Ground-Validation Pilot Study

NASA Technical Reports Server (NTRS)

Schuster, G. L.; Whitlock, C. H.; Plant, J. V.; Wheeler, R. J.; Moats, C. D.; Larman, K. T.; Ayers, J. K.; Feldl, E. K.

1997-01-01

The Clouds and the Earth's Radiant Energy System (CERES) satellite is scheduled for launch in the Fall of 1997 aboard the Tropical Rainfall Measuring Mission (TRMM). A surface measurement pilot study has been initiated in a 37-km region near Richmond, VA, for comparison with the CERES surface flux retrievals. Two-minute averaged upwelling and downwelling surface fluxes over a mostly deciduous forest have been recorded daily for the past two years, and show a broadband, shortwave daily albedo increase during the summer months. Evidence is presented that indicates vegetational changes in the forest as the overriding mechanism for this change. Upwelling flux measured over the entire region by helicopter-mounted instrumentation has been processed for four solar seasons. Future plans include the installation of four more albedo surface sites over various types of vegetation throughout the region.

Application of radiometric surface temperature for surface energy balance estimation: John Monteith's contributions

USDA-ARS?s Scientific Manuscript database

Over 25 years ago, Huband and Monteith paper’s investigating the radiative surface temperature and the surface energy balance of a wheat canopy, highlighted the key issues in computing fluxes with radiometric surface temperature. These included the relationship between radiometric and aerodynamic s...

Evaluation of surface energy and radiation balance systems for FIFE

NASA Technical Reports Server (NTRS)

Fritschen, Leo J.; Qian, Ping

1988-01-01

The energy balance and radiation balance components were determined at six sites during the First International Satellite Land Surface Climatology Project Field Experiment (FIFE) conducted south of Manhattan, Kansas during the summer of 1987. The objectives were: to determine the effect of slope and aspect, throughout a growing season, on the magnitude of the surface energy balance fluxes as determined by the Energy Balance Method (EBM); to investigate the calculation of the soil heat flux density at the surface as calculated from the heat capacity and the thermal conductivity equations; and to evaluate the performance of the Surface Energy and Radiation Balance System (SERBS). A total of 17 variables were monitored at each site. They included net, solar (up and down), total hemispherical (up and down), and diffuse radiation, soil temperature and heat flux density, air and wet bulb temperature gradients, wind speed and direction, and precipitation. A preliminary analysis of the data, for the season, indicate that variables including net radiation, air temperature, vapor pressure, and wind speed were quite similar at the sites even though the sites were as much as 16 km apart and represented four cardinal slopes and the top of a ridge.

Using diurnal temperature signals to infer vertical groundwater-surface water exchange

USGS Publications Warehouse

Irvine, Dylan J.; Briggs, Martin A.; Lautz, Laura K.; Gordon, Ryan P.; McKenzie, Jeffrey M.; Cartwright, Ian

2017-01-01

Heat is a powerful tracer to quantify fluid exchange between surface water and groundwater. Temperature time series can be used to estimate pore water fluid flux, and techniques can be employed to extend these estimates to produce detailed plan-view flux maps. Key advantages of heat tracing include cost-effective sensors and ease of data collection and interpretation, without the need for expensive and time-consuming laboratory analyses or induced tracers. While the collection of temperature data in saturated sediments is relatively straightforward, several factors influence the reliability of flux estimates that are based on time series analysis (diurnal signals) of recorded temperatures. Sensor resolution and deployment are particularly important in obtaining robust flux estimates in upwelling conditions. Also, processing temperature time series data involves a sequence of complex steps, including filtering temperature signals, selection of appropriate thermal parameters, and selection of the optimal analytical solution for modeling. This review provides a synthesis of heat tracing using diurnal temperature oscillations, including details on optimal sensor selection and deployment, data processing, model parameterization, and an overview of computing tools available. Recent advances in diurnal temperature methods also provide the opportunity to determine local saturated thermal diffusivity, which can improve the accuracy of fluid flux modeling and sensor spacing, which is related to streambed scour and deposition. These parameters can also be used to determine the reliability of flux estimates from the use of heat as a tracer.

Role of surface heat fluxes underneath cold pools

DOE PAGES

Gentine, Pierre; Garelli, Alix; Park, Seung -Bu; ...

2016-01-05

In this paper, the role of surface heat fluxes underneath cold pools is investigated using cloud–resolving simulations with either interactive or horizontally homogenous surface heat fluxes over an ocean and a simplified land surface. Over the ocean, there are limited changes in the distribution of the cold pool temperature, humidity, and gust front velocity, yet interactive heat fluxes induce more cold pools, which are smaller, and convection is then less organized. Correspondingly, the updraft mass flux and lateral entrainment are modified. Over the land surface, the heat fluxes underneath cold pools drastically impact the cold pool characteristics with more numerousmore » and smaller pools, which are warmer and more humid and accompanied by smaller gust front velocities. The interactive fluxes also modify the updraft mass flux and reduce convective organization. These results emphasize the importance of interactive surface fluxes instead of prescribed flux boundary conditions, as well as the formulation of surface heat fluxes, when studying convection.« less

Characterization of extreme air-sea turbulent fluxes

NASA Astrophysics Data System (ADS)

Gulev, Sergey; Belyaev, Konstantin

2017-04-01

Extreme ocean-atmosphere turbulent fluxes play a critical role in the convective processes in the mid and subpolar latitudes and may also affect a variety of atmospheric processes, such as generation and re-intensification of extreme cyclones in the areas of the mid latitude storm tracks. From the ocean dynamics perspective, specifically for quantifying extreme vertical mixing, characterization of the extreme fluxes requires, besides estimation of the extreme events, also consideration of the relative extremeness of surface fluxes and their timing, e.g. the duration of periods of high surface fluxes. In order to comprehensively characterize extreme turbulent fluxes at sea surface we propose a formalism based upon probability density distributions of surface turbulent fluxes and flux-related variables. Individual absolute flux extremes were derived using Modified Fisher-Tippett (MFT) distribution of turbulent fluxes. Then, we extend this distribution to the fractional distribution, characterizing the fraction of time-integrated turbulent heat flux provided by the fluxes exceeding a given percentile. Finally, we consider the time durations during which fluxes of a given intensity provide extreme accumulations of heat loss from the surface. For estimation of these characteristics of surface fluxes we use fluxes recomputed from the state variables available from modern era reanalyses (ERA-Interim, MERRA and CFSR) for the period from 1979 onwards. Applications of the formalism to the VOS (Voluntary Observing Ship) - based surface fluxes are also considered. We discuss application of the new metrics of mesoscale and synoptic variability of surface fluxes to the dynamics of mixed layer depth in the North Atlantic.

[Characteristics of mercury exchange flux between soil and atmosphere under the snow retention and snow melting control].

PubMed

Zhang, Gang; Wang, Ning; Ai, Jian-Chao; Zhang, Lei; Yang, Jing; Liu, Zi-Qi

2013-02-01

Jiapigou gold mine, located in the upper Songhua River, was once the largest mine in China due to gold output, where gold extraction with algamation was widely applied to extract gold resulting in severe mercury pollution to ambient environmental medium. In order to study the characteristics of mercury exchange flux between soil (snow) and atmosphere under the snow retention and snow melting control, sampling sites were selected in equal distances along the slope which is situated in the typical hill-valley terrain unit. Mercury exchange flux between soil (snow) and atmosphere was determined with the method of dynamic flux chamber and in all sampling sites the atmosphere concentration from 0 to 150 cm near to the earth in the vertical direction was measured. Furthermore, the impact factors including synchronous meteorology, the surface characteristics under the snow retention and snow melting control and the mercury concentration in vertical direction were also investigated. The results are as follows: During the period of snow retention and melting the air mercury tends to gather towards valley bottom along the slope and an obvious deposit tendency process was found from air to the earth's surface under the control of thermal inversion due to the underlying surface of cold source (snow surface). However, during the period of snow melting, mercury exchange flux between the soil and atmosphere on the surface of the earth with the snow being melted demonstrates alternative deposit and release processes. As for the earth with snow covered, the deposit level of mercury exchange flux between soil and atmosphere is lower than that during the period of snow retention. The relationship between mercury exchange flux and impact factors shows that in snow retention there is a remarkable negative linear correlation between mercury exchange flux and air mercury concentration as well as between the former and the air temperature. In addition, in snow melting mercury exchange flux is remarkably negatively linearly correlated to air mercury concentration and positively linearly correlated to air temperature. Furthermore, there is a general positive linear correlation between mercury exchange flux and soil temperature on the surface of earth after snow melting.

THE EFFECT OF CLOUD FRACTION ON THE RADIATIVE ENERGY BUDGET: The Satellite-Based GEWEX-SRB Data vs. the Ground-Based BSRN Measurements

NASA Astrophysics Data System (ADS)

Zhang, T.; Stackhouse, P. W.; Gupta, S. K.; Cox, S. J.; Mikovitz, J. C.; Nasa Gewex Srb

2011-12-01

The NASA GEWEX-SRB (Global Energy and Water cycle Experiment - Surface Radiation Budget) project produces and archives shortwave and longwave atmospheric radiation data at the top of the atmosphere (TOA) and the Earth's surface. The archive holds uninterrupted records of shortwave/longwave downward/upward radiative fluxes at 1 degree by 1 degree resolution for the entire globe. The latest version in the archive, Release 3.0, is available as 3-hourly, daily and monthly means, spanning 24.5 years from July 1983 to December 2007. Primary inputs to the models used to produce the data include: shortwave and longwave radiances from International Satellite Cloud Climatology Project (ISCCP) pixel-level (DX) data, cloud and surface properties derived therefrom, temperature and moisture profiles from GEOS-4 reanalysis product obtained from the NASA Global Modeling and Assimilation Office (GMAO), and column ozone amounts constituted from Total Ozone Mapping Spectrometer (TOMS), TIROS Operational Vertical Sounder (TOVS) archives, and Stratospheric Monitoring-group's Ozone Blended Analysis (SMOBA), an assimilation product from NOAA's Climate Prediction Center. The data in the archive have been validated systemically against ground-based measurements which include the Baseline Surface Radiation Network (BSRN) data, the World Radiation Data Centre (WRDC) data, and the Global Energy Balance Archive (GEBA) data, and generally good agreement has been achieved. In addition to all-sky radiative fluxes, the output data include clear-sky fluxes, cloud optical depth, cloud fraction and so on. The BSRN archive also includes observations that can be used to derive the cloud fraction, which provides a means for analyzing and explaining the SRB-BSRN flux differences. In this paper, we focus on the effect of cloud fraction on the surface shortwave flux and the level of agreement between the satellite-based SRB data and the ground-based BSRN data. The satellite and BSRN employ different measuring methodologies and thus result in data representing means on dramatically different spatial scales. Therefore, the satellite-based and ground-based measurements are not expected to agree all the time, especially under skies with clouds. The flux comparisons are made under different cloud fractions, and it is found that the SRB-BSRN radiative flux discrepancies can be explained to a certain extent by the SRB-BSRN cloud fraction discrepancies. Apparently, cloud fraction alone cannot completely define the role of clouds in radiation transfer. Further studies need to incorporate the classification of cloud types, altitudes, cloud optical depths and so on.

An eddy covariance system to characterize the atmospheric surface layer and turbulent latent heat fluxes over a debris-covered Himalayan glacier.

NASA Astrophysics Data System (ADS)

Litt, Maxime; Steiner, Jakob F.; Stigter, Emmy E.; Immerzeel, Walter; Shea, Joseph Michael

2017-04-01

Over debris-covered glaciers, water content variations in the debris layer can drive significant changes in its thermal conductivity and significantly impact melt rates. Since sublimation and evaporation are favoured in high-altitude conditions, e.g., low atmospheric pressure and high wind speeds, they are expected to strongly influence the water balance of the debris-layer. Dedicated latent heat fluxes measurements at the debris surface are essential to characterize the debris heat conductivity in order to assess underlying ice melt. Furthermore, the contribution of the turbulent fluxes in the surface energy balance over debris covered glacier remains uncertain since they are generally evaluated through similarity methods which might not be valid in complex terrain. We present the first results of a 15-day eddy-covariance experiment installed at the end of the monsoon (September-October) on a 3-m tower above the debris-covered Lirung glacier in Nepal. The tower also included measurements of the 4 radiation components. The eddy covariance measurements allowed for the characterization of the turbulence in the atmospheric surface layer, as well as the direct measurements of evaporation, sublimation and turbulent sensible heat fluxes. The experiment helps us to evaluate the contribution of turbulent fluxes to the surface energy balance over this debris-covered glacier, through a precise characterization of the overlying turbulent atmospheric surface layer. It also helps to study the role of the debris-layer water content changes through evaporation and sublimation and its feedback on heat conduction in this layer. The large observed turbulent fluxes play a significant role in the energy balance at the debris surface and significantly influence debris moisture, conductivity and subsequently underlying ice melt.

Estimating surface fluxes over middle and upper streams of the Heihe River Basin with ASTER imagery

NASA Astrophysics Data System (ADS)

Ma, W.; Ma, Y.; Hu, Z.; Su, B.; Wang, J.; Ishikawa, H.

2009-06-01

Surface fluxes are important boundary conditions for climatological modeling and the Asian monsoon system. Recent availability of high-resolution, multi-band imagery from the ASTER (Advanced Space-borne Thermal Emission and Reflection Radiometer) sensor has enabled us to estimate surface fluxes to bridge the gap between local scale flux measurements using micrometeorological instruments and regional scale land-atmosphere exchanges of water and heat fluxes that are fundamental for the understanding of the water cycle in the Asian monsoon system. A Surface Energy Balance System (SEBS) method based on ASTER data and field observations has been proposed and tested for deriving net radiation flux (Rn), soil heat flux (G0), sensible heat flux (H) and latent heat flux (λ E) over heterogeneous land surface in this paper. As a case study, the methodology was applied to the experimental area of the WATER (Watershed Allied Telemetry Experimental Research), located at the mid-to-upstream sections of the Heihe River, northwest China. The ASTER data of 3 May and 4 June in 2008 was used in this paper for the case of mid-to-upstream sections of the Heihe River Basin. To validate the proposed methodology, the ground-measured land surface heat fluxes (net radiation flux (Rn), soil heat flux (G0), sensible heat flux (H) and latent heat flux (λ E)) were compared to the ASTER derived values. The results show that the derived surface variables and land surface heat fluxes in different months over the study area are in good accordance with the land surface status. It is therefore concluded that the proposed methodology is successful for the retrieval of land surface heat fluxes using the ASTER data and filed observation over the study area.

Measurement of local high-level, transient surface heat flux

NASA Technical Reports Server (NTRS)

Liebert, Curt H.

1988-01-01

This study is part of a continuing investigation to develop methods for measuring local transient surface heat flux. A method is presented for simultaneous measurements of dual heat fluxes at a surface location by considering the heat flux as a separate function of heat stored and heat conducted within a heat flux gage. Surface heat flux information is obtained from transient temperature measurements taken at points within the gage. Heat flux was determined over a range of 4 to 22 MW/sq m. It was concluded that the method is feasible. Possible applications are for heat flux measurements on the turbine blade surfaces of space shuttle main engine turbopumps and on the component surfaces of rocket and advanced gas turbine engines and for testing sensors in heat flux gage calibrators.

Evaluating Surface Flux Results from CERES-FLASHFlux

NASA Astrophysics Data System (ADS)

Wilber, A. C.; Stackhouse, P. W., Jr.; Kratz, D. P.; Gupta, S. K.; Sawaengphokhai, P.

2016-12-01

The Clouds and Earth's Radiant Energy System (CERES) mission provides TOA (Top-of-Atmosphere) and surface radiative flux products for each CERES footprint (Single Scanner Footprint) and also time integrated and spatially averaged (TISA) to provide 1ox1o fluxes at various temporal averages. The CERES TISA products are available to the public within 3-6 months of observation. The CERES Fast Longwave and SHortwave radiative Flux (FLASHFlux) data products were developed to provide a rapid release version of the CERES data products. FLASHFlux data products are made available to the research and applications communities within one week of the satellite observations. Over the last several years, the CERES team has contributed to a section on the variability of radiation budget at the Top-of-Atmosphere in the annual "State of the Climate Report" published in BAMS using CERES TISA and FLASHFlux data products. Recently, the FLASHFlux data were used to investigate the radiative impacts of the intense 2015-2016 El Nino event. In addition FLASHFlux date are routinely used by applied science in energy related and agricultural sectors. The current version of FLASHFlux is being upgraded to FLASHFlux Version4A to improve consistency with the climate quality Edition 4 CERES data products. This presentation will describe the planned changes including the change to the latest meteorological product from Global Modeling and Assimilation Office (GMAO), GEOS FP-IT (5.12.4). GEOS 5.12.4 is an assimilation that is consistent with MERRA-2. We present comparisons of global and regional changes in the TOA and surface radiative fluxes as a result of the upgrade for both longwave (LW) and shortwave (SW) surface fluxes. We also compare the data products against ground measurements using data from the Baseline Surface Radiation Network (BSRN) - including NOAA SURFRAD, Atmospheric Radiation Measurement (ARM) and Ocean buoy measurements from Woods Hole Oceanographic Institute (WHOI).

Using NDACC column measurements of carbonyl sulfide to estimate its sources and sinks

NASA Astrophysics Data System (ADS)

Wang, Yuting; Marshall, Julia; Palm, Mathias; Deutscher, Nicholas; Roedenbeck, Christian; Warneke, Thorsten; Notholt, Justus; Baker, Ian; Berry, Joe; Suntharalingam, Parvadha; Jones, Nicholas; Mahieu, Emmanuel; Lejeune, Bernard; Hannigan, James; Conway, Stephanie; Strong, Kimberly; Campbell, Elliott; Wolf, Adam; Kremser, Stefanie

2016-04-01

Carbonyl sulfide (OCS) is taken up by plants during photosynthesis through a similar pathway as carbon dioxide (CO2), but is not emitted by respiration, and thus holds great promise as an additional constraint on the carbon cycle. It might act as a sort of tracer of photosynthesis, a way to separate gross primary productivity (GPP) from the net ecosystem exchange (NEE) that is typically derived from flux modeling. However the estimates of OCS sources and sinks still have significant uncertainties, which make it difficult to use OCS as a photosynthetic tracer, and the existing long-term surface-based measurements are sparse. The NDACC-IRWG measures the absorption of OCS in the atmosphere, and provides a potential long-term database of OCS total/partial columns, which can be used to evaluate OCS fluxes. We have retrieved OCS columns from several NDACC sites around the globe, and compared them to model simulation with OCS land fluxes based on the simple biosphere model (SiB). The disagreement between the measurements and the forward simulations indicates that (1) the OCS land fluxes from SiB are too low in the northern boreal region; (2) the ocean fluxes need to be optimized. A statistical linear flux model describing OCS is developed in the TM3 inversion system, and is used to estimate the OCS fluxes. We performed flux inversions using only NOAA OCS surface measurements as an observational constraint and with both surface and NDACC OCS column measurements, and assessed the differences. The posterior uncertainties of the inverted OCS fluxes decreased with the inclusion of NDACC data comparing to those using surface data only, and could be further reduced if more NDACC sites were included.

Study of a high performance evaporative heat transfer surface

NASA Technical Reports Server (NTRS)

Saaski, E. W.; Hamasaki, R. H.

1977-01-01

An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open-faced screw thread surfaces. With a groove density of 12.6 cm/1 and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm have been measured along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm was measured with a 37.8 cm/1 hybrid surface.

Surface wave effects on water temperature in the Baltic Sea: simulations with the coupled NEMO-WAM model

NASA Astrophysics Data System (ADS)

Alari, Victor; Staneva, Joanna; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian; Janssen, Peter

2016-08-01

Coupled circulation (NEMO) and wave model (WAM) system was used to study the effects of surface ocean waves on water temperature distribution and heat exchange at regional scale (the Baltic Sea). Four scenarios—including Stokes-Coriolis force, sea-state dependent energy flux (additional turbulent kinetic energy due to breaking waves), sea-state dependent momentum flux and the combination these forcings—were simulated to test the impact of different terms on simulated temperature distribution. The scenario simulations were compared to a control simulation, which included a constant wave-breaking coefficient, but otherwise was without any wave effects. The results indicate a pronounced effect of waves on surface temperature, on the distribution of vertical temperature and on upwelling's. Overall, when all three wave effects were accounted for, did the estimates of temperature improve compared to control simulation. During the summer, the wave-induced water temperature changes were up to 1 °C. In northern parts of the Baltic Sea, a warming of the surface layer occurs in the wave included simulations in summer months. This in turn reduces the cold bias between simulated and measured data, e.g. the control simulation was too cold compared to measurements. The warming is related to sea-state dependent energy flux. This implies that a spatio-temporally varying wave-breaking coefficient is necessary, because it depends on actual sea state. Wave-induced cooling is mostly observed in near-coastal areas and is the result of intensified upwelling in the scenario, when Stokes-Coriolis forcing is accounted for. Accounting for sea-state dependent momentum flux results in modified heat exchange at the water-air boundary which consequently leads to warming of surface water compared to control simulation.

AMOC sensitivity to surface buoyancy fluxes: Stronger ocean meridional heat transport with a weaker volume transport?

NASA Astrophysics Data System (ADS)

Sévellec, Florian; Fedorov, Alexey V.

2016-09-01

Oceanic northward heat transport is commonly assumed to be positively correlated with the Atlantic meridional overturning circulation (AMOC). For example, in numerical "water-hosing" experiments, imposing anomalous freshwater fluxes in the northern Atlantic leads to a slow-down of the AMOC and the corresponding reduction of oceanic northward heat transport. Here, we study the sensitivity of the ocean heat and volume transports to surface heat and freshwater fluxes using a generalized stability analysis. For the sensitivity to surface freshwater fluxes, we find that, while the direct relationship between the AMOC volume and heat transports holds on shorter time scales, it can reverse on timescales longer than 500 years or so. That is, depending on the model surface boundary conditions, reduction in the AMOC volume transport can potentially lead to a stronger heat transport on long timescales, resulting from the gradual increase in ocean thermal stratification. We discuss the implications of these results for the problem of steady state (statistical equilibrium) in ocean and climate GCM as well as paleoclimate problems including millennial climate variability.

AMOC sensitivity to surface buoyancy fluxes: Stronger ocean meridional heat transport with a weaker volume transport?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sevellec, Florian; Fedorov, Alexey V.

Oceanic northward heat transport is commonly assumed to be positively correlated with the Atlantic meridional overturning circulation (AMOC). For example, in numerical "water-hosing" experiments, imposing anomalous freshwater fluxes in the northern Atlantic leads to a slow-down of the AMOC and the corresponding reduction of oceanic northward heat transport. Here, we study the sensitivity of the ocean heat and volume transports to surface heat and freshwater fluxes using a generalized stability analysis. For the sensitivity to surface freshwater fluxes, we find that, while the direct relationship between the AMOC volume and heat transports holds on shorter time scales, it can reversemore » on timescales longer than 500 years or so. That is, depending on the model surface boundary conditions, reduction in the AMOC volume transport can potentially lead to a stronger heat transport on long timescales, resulting from the gradual increase in ocean thermal stratification. Finally, we discuss the implications of these results for the problem of steady state (statistical equilibrium) in ocean and climate GCM as well as paleoclimate problems including millennial climate variability.« less

AMOC sensitivity to surface buoyancy fluxes: Stronger ocean meridional heat transport with a weaker volume transport?

DOE PAGES

Sevellec, Florian; Fedorov, Alexey V.

2016-01-04

Oceanic northward heat transport is commonly assumed to be positively correlated with the Atlantic meridional overturning circulation (AMOC). For example, in numerical "water-hosing" experiments, imposing anomalous freshwater fluxes in the northern Atlantic leads to a slow-down of the AMOC and the corresponding reduction of oceanic northward heat transport. Here, we study the sensitivity of the ocean heat and volume transports to surface heat and freshwater fluxes using a generalized stability analysis. For the sensitivity to surface freshwater fluxes, we find that, while the direct relationship between the AMOC volume and heat transports holds on shorter time scales, it can reversemore » on timescales longer than 500 years or so. That is, depending on the model surface boundary conditions, reduction in the AMOC volume transport can potentially lead to a stronger heat transport on long timescales, resulting from the gradual increase in ocean thermal stratification. Finally, we discuss the implications of these results for the problem of steady state (statistical equilibrium) in ocean and climate GCM as well as paleoclimate problems including millennial climate variability.« less

A THREE-DIMENSIONAL BABCOCK-LEIGHTON SOLAR DYNAMO MODEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miesch, Mark S.; Dikpati, Mausumi, E-mail: miesch@ucar.edu

We present a three-dimensional (3D) kinematic solar dynamo model in which poloidal field is generated by the emergence and dispersal of tilted sunspot pairs (more generally bipolar magnetic regions, or BMRs). The axisymmetric component of this model functions similarly to previous 2.5 dimensional (2.5D, axisymmetric) Babcock-Leighton (BL) dynamo models that employ a double-ring prescription for poloidal field generation but we generalize this prescription into a 3D flux emergence algorithm that places BMRs on the surface in response to the dynamo-generated toroidal field. In this way, the model can be regarded as a unification of BL dynamo models (2.5D in radius/latitude)more » and surface flux transport models (2.5D in latitude/longitude) into a more self-consistent framework that builds on the successes of each while capturing the full 3D structure of the evolving magnetic field. The model reproduces some basic features of the solar cycle including an 11 yr periodicity, equatorward migration of toroidal flux in the deep convection zone, and poleward propagation of poloidal flux at the surface. The poleward-propagating surface flux originates as trailing flux in BMRs, migrates poleward in multiple non-axisymmetric streams (made axisymmetric by differential rotation and turbulent diffusion), and eventually reverses the polar field, thus sustaining the dynamo. In this Letter we briefly describe the model, initial results, and future plans.« less

Documentation for Program SOILSIM: A computer program for the simulation of heat and moisture flow in soils and between soils, canopy and atmosphere

NASA Technical Reports Server (NTRS)

Field, Richard T.

1990-01-01

SOILSIM, a digital model of energy and moisture fluxes in the soil and above the soil surface, is presented. It simulates the time evolution of soil temperature and moisture, temperature of the soil surface and plant canopy the above surface, and the fluxes of sensible and latent heat into the atmosphere in response to surface weather conditions. The model is driven by simple weather observations including wind speed, air temperature, air humidity, and incident radiation. The model intended to be useful in conjunction with remotely sensed information of the land surface state, such as surface brightness temperature and soil moisture, for computing wide area evapotranspiration.

Defining the Magnitude: Patterns, Regularities and Direct TOA-Surface Flux Relationships in the 15-Year Long CERES Satellite Data — Observations, Model and Theory

NASA Astrophysics Data System (ADS)

Zagoni, M.

2017-12-01

Over the past fifteen years, the NASA Clouds and the Earth's Radiant Energy System (CERES) satellite mission has provided the scientific community with the most reliable Earth radiation budget data. This presentation offers quantitative assessment of the published CERES Energy Balanced and Filled (EBAF) Edition 2.8 and Edition 4.0 data products, and reveals several internal patterns, ratios and regularities within the annual global mean flux components of the all-sky and clear-sky surface and atmospheric energy budgets. The found patterns, among others, include: (i) direct relationships between the top-of-atmosphere (TOA) radiative and surface radiative and non-radiative fluxes (contradicting the expectation that TOA and surface fluxes are physically decoupled); (ii) integer ratios and relationships between the absorbed and emitted surface and atmospheric energy flow elements; and (iii) definite connections among the clear-sky and the all-sky shortwave, longwave and non-radiative (turbulent) flux elements and the corresponding greenhouse effect. Comparison between the EBAF Ed2.8 and Ed4.0 SFC and TOA data products and trend analyses of the normalized clear-sky and all-sky greenhouse factors are presented. Longwave cloud radiative effect (LW CRE) proved to be playing a principal role in organizing the found numerical patterns in the surface and atmospheric energy flow components. All of the revealed structures are quantitatively valid within the one-sigma range of uncertainty of the involved individual flux elements. This presentation offers a conceptual framework to interpret the found relationships and shows how the observed CERES fluxes can be deduced from this proposed physical model. An important conclusion drawn from our analysis is that the internal atmospheric and surface energy flow system forms a definite structure and seems to be more constrained to the incoming solar energy than previously thought.

Method and apparatus for maintaining equilibrium in a helical axis stellarator

DOEpatents

Reiman, Allan; Boozer, Allen

1987-01-01

Apparatus for maintaining three-dimensional MHD equilibrium in a plasma contained in a helical axis stellerator includes a resonant coil system, having a configuration such that current therethrough generates a magnetic field cancelling the resonant magnetic field produced by currents driven by the plasma pressure on any given flux surface resonating with the rotational transform of another flux surface in the plasma. Current through the resonant coil system is adjusted as a function of plasma beta.

Method and apparatus for maintaining equilibrium in a helical axis stellarator

DOEpatents

Reiman, A.; Boozer, A.

1984-10-31

Apparatus for maintaining three-dimensional MHD equilibrium in a plasma contained in a helical axis stellarator includes a resonant coil system, having a configuration such that current therethrough generates a magnetic field cancelling the resonant magnetic field produced by currents driven by the plasma pressure on any given flux surface resonating with the rotational transform of another flux surface in the plasma. Current through the resonant coil system is adjusted as a function of plasma beta.

Assessing uncertainty and sensitivity of model parameterizations and parameters in WRF affecting simulated surface fluxes and land-atmosphere coupling over the Amazon region

NASA Astrophysics Data System (ADS)

Qian, Y.; Wang, C.; Huang, M.; Berg, L. K.; Duan, Q.; Feng, Z.; Shrivastava, M. B.; Shin, H. H.; Hong, S. Y.

2016-12-01

This study aims to quantify the relative importance and uncertainties of different physical processes and parameters in affecting simulated surface fluxes and land-atmosphere coupling strength over the Amazon region. We used two-legged coupling metrics, which include both terrestrial (soil moisture to surface fluxes) and atmospheric (surface fluxes to atmospheric state or precipitation) legs, to diagnose the land-atmosphere interaction and coupling strength. Observations made using the Department of Energy's Atmospheric Radiation Measurement (ARM) Mobile Facility during the GoAmazon field campaign together with satellite and reanalysis data are used to evaluate model performance. To quantify the uncertainty in physical parameterizations, we performed a 120 member ensemble of simulations with the WRF model using a stratified experimental design including 6 cloud microphysics, 3 convection, 6 PBL and surface layer, and 3 land surface schemes. A multiple-way analysis of variance approach is used to quantitatively analyze the inter- and intra-group (scheme) means and variances. To quantify parameter sensitivity, we conducted an additional 256 WRF simulations in which an efficient sampling algorithm is used to explore the multiple-dimensional parameter space. Three uncertainty quantification approaches are applied for sensitivity analysis (SA) of multiple variables of interest to 20 selected parameters in YSU PBL and MM5 surface layer schemes. Results show consistent parameter sensitivity across different SA methods. We found that 5 out of 20 parameters contribute more than 90% total variance, and first-order effects dominate comparing to the interaction effects. Results of this uncertainty quantification study serve as guidance for better understanding the roles of different physical processes in land-atmosphere interactions, quantifying model uncertainties from various sources such as physical processes, parameters and structural errors, and providing insights for improving the model physics parameterizations.

Effects of thermal vapor diffusion on seasonal dynamics of water in the unsaturated zone

USGS Publications Warehouse

Milly, Paul C.D.

1996-01-01

The response of water in the unsaturated zone to seasonal changes of temperature (T) is determined analytically using the theory of nonisothermal water transport in porous media, and the solutions are tested against field observations of moisture potential and bomb fallout isotopic (36Cl and 3H) concentrations. Seasonally varying land surface temperatures and the resulting subsurface temperature gradients induce thermal vapor diffusion. The annual mean vertical temperature gradient is close to zero; however, the annual mean thermal vapor flux is downward, because the temperature‐dependent vapor diffusion coefficient is larger, on average, during downward diffusion (occurring at high T) than during upward diffusion (low T). The annual mean thermal vapor flux is shown to decay exponentially with depth; the depth (about 1 m) at which it decays to e−1of its surface value is one half of the corresponding decay depth for the amplitude of seasonal temperature changes. This depth‐dependent annual mean flux is effectively a source of water, which must be balanced by a flux divergence associated with other transport processes. In a relatively humid environment the liquid fluxes greatly exceed the thermal vapor fluxes, so such a balance is readily achieved without measurable effect on the dynamics of water in the unsaturated zone. However, if the mean vertical water flux through the unsaturated zone is very small (<1 mm y−1), as it may be at many locations in a desert landscape, the thermal vapor flux must be balanced mostly by a matric‐potential‐induced upward flux of water. This return flux may include both vapor and liquid components. Below any near‐surface zone of weather‐related fluctuations of matric potential, maintenance of this upward flux requires an increase with depth in the annual mean matric potential; this theoretical prediction is supported by long‐term field measurements in the Chihuahuan Desert. The analysis also makes predictions, confirmed by the field observations, regarding the seasonal variations of matric potential at a given depth. The conceptual model of unsaturated zone water transport developed here implies the possibility of near‐surface trapping of any aqueous constituent introduced at the surface.

Evapotranspiration Cycles in a High Latitude Agroecosystem: Potential Warming Role

PubMed Central

Ruairuen, Watcharee

2015-01-01

As the acreages of agricultural lands increase, changes in surface energetics and evapotranspiration (ET) rates may arise consequently affecting regional climate regimes. The objective of this study was to evaluate summertime ET dynamics and surface energy processes in a subarctic agricultural farm in Interior Alaska. The study includes micrometeorological and hydrological data. Results covering the period from June to September 2012 and 2013 indicated consistent energy fractions: LE/R net (67%), G/R net (6%), H/R net (27%) where LE is latent heat flux, R net is the surface net radiation, G is ground heat flux and H is the sensible heat flux. Additionally actual surface evapotranspiration from potential evaporation was found to be in the range of 59 to 66%. After comparing these rates with those of most prominent high latitude ecosystems it is argued here that if agroecosystem in high latitudes become an emerging feature in the land-use, the regional surface energy balance will significantly shift in comparison to existing Arctic natural ecosystems. PMID:26368123

Evapotranspiration Cycles in a High Latitude Agroecosystem: Potential Warming Role.

PubMed

Ruairuen, Watcharee; Fochesatto, Gilberto J; Sparrow, Elena B; Schnabel, William; Zhang, Mingchu; Kim, Yongwon

2015-01-01

As the acreages of agricultural lands increase, changes in surface energetics and evapotranspiration (ET) rates may arise consequently affecting regional climate regimes. The objective of this study was to evaluate summertime ET dynamics and surface energy processes in a subarctic agricultural farm in Interior Alaska. The study includes micrometeorological and hydrological data. Results covering the period from June to September 2012 and 2013 indicated consistent energy fractions: LE/Rnet (67%), G/Rnet (6%), H/Rnet (27%) where LE is latent heat flux, Rnet is the surface net radiation, G is ground heat flux and H is the sensible heat flux. Additionally actual surface evapotranspiration from potential evaporation was found to be in the range of 59 to 66%. After comparing these rates with those of most prominent high latitude ecosystems it is argued here that if agroecosystem in high latitudes become an emerging feature in the land-use, the regional surface energy balance will significantly shift in comparison to existing Arctic natural ecosystems.

Enhancing surface methane fluxes from an oligotrophic lake: exploring the microbubble hypothesis.

PubMed

McGinnis, Daniel F; Kirillin, Georgiy; Tang, Kam W; Flury, Sabine; Bodmer, Pascal; Engelhardt, Christof; Casper, Peter; Grossart, Hans-Peter

2015-01-20

Exchange of the greenhouse gases carbon dioxide (CO2) and methane (CH4) across inland water surfaces is an important component of the terrestrial carbon (C) balance. We investigated the fluxes of these two gases across the surface of oligotrophic Lake Stechlin using a floating chamber approach. The normalized gas transfer rate for CH4 (k600,CH4) was on average 2.5 times higher than that for CO2 (k600,CO2) and consequently higher than Fickian transport. Because of its low solubility relative to CO2, the enhanced CH4 flux is possibly explained by the presence of microbubbles in the lake’s surface layer. These microbubbles may originate from atmospheric bubble entrainment or gas supersaturation (i.e., O2) or both. Irrespective of the source, we determined that an average of 145 L m(–2) d(–1) of gas is required to exit the surface layer via microbubbles to produce the observed elevated k600,CH4. As k600 values are used to estimate CH4 pathways in aquatic systems, the presence of microbubbles could alter the resulting CH4 and perhaps C balances. These microbubbles will also affect the surface fluxes of other sparingly soluble gases in inland waters, including O2 and N2.

Using a spatially-distributed hydrologic biogeochemistry model to study the spatial variation of carbon processes in a Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Shi, Y.; Eissenstat, D. M.; Davis, K. J.; He, Y.

2015-12-01

Forest carbon processes are affected by soil moisture, soil temperature and solar radiation. Most of the current biogeochemical models are 1-D and represent one point in space. Therefore they can neither resolve topographically driven hill-slope soil moisture patterns, nor simulate the nonlinear effects of soil moisture on carbon processes. A spatially-distributed biogeochemistry model, Flux-PIHM-BGC, has been developed by coupling the Biome-BGC (BBGC) model with a coupled physically-based land surface hydrologic model, Flux-PIHM. Flux-PIHM incorporates a land-surface scheme (adapted from the Noah land surface model) into the Penn State Integrated Hydrologic Model (PIHM). Because PIHM is capable of simulating lateral water flow and deep groundwater, Flux-PIHM is able to represent the link between groundwater and the surface energy balance, as well as the land surface heterogeneities caused by topography. Flux-PIHM-BGC model was tested at the Susquehanna/Shale Hills critical zone observatory (SSHCZO). The abundant observations at the SSHCZO, including eddy covariance fluxes, soil moisture, groundwater level, sap flux, stream discharge, litterfall, leaf area index, aboveground carbon stock, and soil carbon efflux, provided an ideal test bed for the coupled model. Model results show that when uniform solar radiation is used, vegetation carbon and soil carbon are positively correlated with soil moisture in space, which agrees with the observations within the watershed. When topographically-driven solar radiation is used, however, the wetter valley floor becomes radiation limited, and produces less vegetation and soil carbon than the drier hillslope due to the assumption that canopy height is uniform in the watershed. This contradicts with the observations, and suggests that a tree height model with dynamic allocation model are needed to reproduce the spatial variation of carbon processes within a watershed.

Assessing Air-Sea Interaction in the Evolving NASA GEOS Model

NASA Technical Reports Server (NTRS)

Clayson, Carol Anne; Roberts, J. Brent

2015-01-01

In order to understand how the climate responds to variations in forcing, one necessary component is to understand the full distribution of variability of exchanges of heat and moisture between the atmosphere and ocean. Surface heat and moisture fluxes are critical to the generation and decay of many coupled air-sea phenomena. These mechanisms operate across a number of scales and contain contributions from interactions between the anomalous (i.e. non-mean), often extreme-valued, flux components. Satellite-derived estimates of the surface turbulent and radiative heat fluxes provide an opportunity to assess results from modeling systems. Evaluation of only time mean and variability statistics, however only provides limited traceability to processes controlling what are often regime-dependent errors. This work will present an approach to evaluate the representation of the turbulent fluxes at the air-sea interface in the current and evolving Goddard Earth Observing System (GEOS) model. A temperature and moisture vertical profile-based clustering technique is used to identify robust weather regimes, and subsequently intercompare the turbulent fluxes and near-surface parameters within these regimes in both satellite estimates and GEOS-driven data sets. Both model reanalysis (MERRA) and seasonal-to-interannual coupled GEOS model simulations will be evaluated. Particular emphasis is placed on understanding the distribution of the fluxes including extremes, and the representation of near-surface forcing variables directly related to their estimation. Results from these analyses will help identify the existence and source of regime-dependent biases in the GEOS model ocean surface turbulent fluxes. The use of the temperature and moisture profiles for weather-state clustering will be highlighted for its potential broad application to 3-D output typical of model simulations.

How Consistent are Recent Variations in the Tropical Energy and Water Cycle Resolved by Satellite Measurements?

NASA Technical Reports Server (NTRS)

Robertson, F. R.; Lu, H.-I.

2004-01-01

One notable aspect of Earth's climate is that although the planet appears to be very close to radiative balance at top-of-atmosphere (TOA), the atmosphere itself and underlying surface are not. Profound exchanges of energy between the atmosphere and oceans, land and cryosphere occur over a range of time scales. Recent evidence from broadband satellite measurements suggests that even these TOA fluxes contain some detectable variations. Our ability to measure and reconstruct radiative fluxes at the surface and at the top of atmosphere is improving rapidly. One question is 'How consistent, physically, are these diverse remotely-sensed data sets'? The answer is of crucial importance to understanding climate processes, improving physical models, and improving remote sensing algorithms. In this work we will evaluate two recently released estimates of radiative fluxes, focusing primarily on surface estimates. The International Satellite Cloud Climatology Project 'FD' radiative flux profiles are available from mid-1983 to near present and have been constructed by driving the radiative transfer physics from the Goddard Institute for Space Studies (GISS) global model with ISCCP clouds and TOVS (TIROS Operational Vertical Sounder)thermodynamic profiles. Full and clear sky SW and LW fluxes are produced. A similar product from the NASA/GEWEX Surface Radiation Budget Project using different radiative flux codes and thermodynamics from the NASA/Goddard Earth Observing System (GEOS-1) assimilation model makes a similar calculation of surface fluxes. However this data set currently extends only through 1995. We also employ precipitation measurements from the Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measuring Mission (TRMM). Finally, ocean evaporation estimates from the Special Sensor Microwave Imager (SSM/I) are considered as well as derived evaporation from the NCAR/NCEP Reanalysis. Additional information is included in the original extended abstract.

Assessing air-sea interaction in the evolving NASA GEOS model

NASA Astrophysics Data System (ADS)

Clayson, C. A.; Roberts, J. B.

2014-12-01

In order to understand how the climate responds to variations in forcing, one necessary component is to understand the full distribution of variability of exchanges of heat and moisture between the atmosphere and ocean. Surface heat and moisture fluxes are critical to the generation and decay of many coupled air-sea phenomena. These mechanisms operate across a number of scales and contain contributions from interactions between the anomalous (i.e. non-mean), often extreme-valued, flux components. Satellite-derived estimates of the surface turbulent and radiative heat fluxes provide an opportunity to assess results from modeling systems. Evaluation of only time mean and variability statistics, however only provides limited traceability to processes controlling what are often regime-dependent errors. This work will present an approach to evaluate the representation of the turbulent fluxes at the air-sea interface in the current and evolving Goddard Earth Observing System (GEOS) model. A temperature and moisture vertical profile-based clustering technique is used to identify robust weather regimes, and subsequently intercompare the turbulent fluxes and near-surface parameters within these regimes in both satellite estimates and GEOS-driven data sets. Both model reanalysis (MERRA) and seasonal-to-interannual coupled GEOS model simulations will be evaluated. Particular emphasis is placed on understanding the distribution of the fluxes including extremes, and the representation of near-surface forcing variables directly related to their estimation. Results from these analyses will help identify the existence and source of regime-dependent biases in the GEOS model ocean surface turbulent fluxes. The use of the temperature and moisture profiles for weather-state clustering will be highlighted for its potential broad application to 3-D output typical of model simulations.

An Overview of the Naval Research Laboratory Ocean Surface Flux (NFLUX) System

NASA Astrophysics Data System (ADS)

May, J. C.; Rowley, C. D.; Barron, C. N.

2016-02-01

The Naval Research Laboratory (NRL) ocean surface flux (NFLUX) system is an end-to-end data processing and assimilation system used to provide near-real time satellite-based surface heat flux fields over the global ocean. Swath-level air temperature (TA), specific humidity (QA), and wind speed (WS) estimates are produced using multiple polynomial regression algorithms with inputs from satellite sensor data records from the Special Sensor Microwave Imager/Sounder, the Advanced Microwave Sounding Unit-A, the Advanced Technology Microwave Sounder, and the Advanced Microwave Scanning Radiometer-2 sensors. Swath-level WS estimates are also retrieved from satellite environmental data records from WindSat, the MetOp scatterometers, and the Oceansat scatterometer. Swath-level solar and longwave radiative flux estimates are produced utilizing the Rapid Radiative Transfer Model for Global Circulation Models (RRTMG). Primary inputs to the RRTMG include temperature and moisture profiles and cloud liquid and ice water paths from the Microwave Integrated Retrieval System. All swath-level satellite estimates undergo an automated quality control process and are then assimilated with atmospheric model forecasts to produce 3-hourly gridded analysis fields. The turbulent heat flux fields, latent and sensible heat flux, are determined from the Coupled Ocean-Atmosphere Response Experiment (COARE) 3.0 bulk algorithms using inputs of TA, QA, WS, and a sea surface temperature model field. Quality-controlled in situ observations over a one-year time period from May 2013 through April 2014 form the reference for validating ocean surface state parameter and heat flux fields. The NFLUX fields are evaluated alongside the Navy's operational global atmospheric model, the Navy Global Environmental Model (NAVGEM). NFLUX is shown to have smaller biases and lower or similar root mean square errors compared to NAVGEM.

Frequency dependence of trapped flux sensitivity in SRF cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Checchin, M.; Martinello, M.; Grassellino, A.

In this paper, we present the frequency dependence of the vortex surface resistance of bulk niobium accelerating cavities as a function of different state-of-the-art surface treatments. Higher flux surface resistance per amount of trapped magnetic field - sensitivity - is observed for higher frequencies, in agreement with our theoretical model. Higher sensitivity is observed for N-doped cavities, which possess an intermediate value of electron mean-free-path, compared to 120° C and EP/BCP cavities. Experimental results from our study showed that the sensitivity has a non-monotonic trend as a function of the mean-free-path, including at frequencies other than 1.3 GHz, and thatmore » the vortex response to the rf field can be tuned from the pinning regime to flux-flow regime by manipulating the frequency and/or the mean-free-path of the resonator, as reported in our previous studies. The frequency dependence of the trapped flux sensitivity to the amplitude of the accelerating gradient is also highlighted.« less

Frequency dependence of trapped flux sensitivity in SRF cavities

DOE PAGES

Checchin, M.; Martinello, M.; Grassellino, A.; ...

2018-02-13

In this paper, we present the frequency dependence of the vortex surface resistance of bulk niobium accelerating cavities as a function of different state-of-the-art surface treatments. Higher flux surface resistance per amount of trapped magnetic field - sensitivity - is observed for higher frequencies, in agreement with our theoretical model. Higher sensitivity is observed for N-doped cavities, which possess an intermediate value of electron mean-free-path, compared to 120° C and EP/BCP cavities. Experimental results from our study showed that the sensitivity has a non-monotonic trend as a function of the mean-free-path, including at frequencies other than 1.3 GHz, and thatmore » the vortex response to the rf field can be tuned from the pinning regime to flux-flow regime by manipulating the frequency and/or the mean-free-path of the resonator, as reported in our previous studies. The frequency dependence of the trapped flux sensitivity to the amplitude of the accelerating gradient is also highlighted.« less

Similarity scaling of turbulence in small temperate lake: implication for gas flux: implication for gas flux

NASA Astrophysics Data System (ADS)

Tedford, E. W.; MacIntyre, S.; Miller, S. D.; Czikowsky, M. J.

2013-12-01

The actively mixing layer, or surface layer, is the region of the upper mixed layer of lakes, oceans and the atmosphere directly influenced by wind, heating and cooling. Turbulence within the surface mixing layer has a direct impact on important ecological processes. The Monin-Obukhov length scale (LMO) is a critical length scale used in predicting and understanding turbulence in the actively mixed layer. On the water side of the air-water interface, LMO is defined as: LMO=-u*^3/(0.4 JB0) where u*, the shear velocity, is defined as (τ/rho)^0.5 where τ is the shear stress and rho is the density of water and JBO is the buoyancy flux at the surface. Above the depth equal to the absolute value of the Monin-Obukhov length scale (zMO), wind shear is assumed to dominate the production of turbulent kinetic energy (TKE). Below zMO, the turbulence is assumed to be suppressed when JB0 is stabilizing (warming surface waters) and enhanced when the buoyancy flux is destabilizing (cooling surface waters). Our observed dissipations were well represented using the canonical similarity scaling equations. The Monin-Obukhov length scale was generally effective in separating the surface-mixing layer into two regions: an upper region, dominated by wind shear; and a lower region, dominated by buoyancy flux. During both heating and cooling and above a depth equal to |LMO|, turbulence was dominated by wind shear and dissipation followed law of the wall scaling although was slightly augmented by buoyancy flux during both heating and cooling. Below a depth equal to |LMO| during cooling, dissipation was nearly uniform with depth. Although distinguishing between an upper region of the actively mixing layer dominated by wind stress and a lower portion dominated by buoyancy flux is typically accurate the most accurate estimates of dissipation include the effects of both wind stress and buoyancy flux throughout the actively mixed layer. We demonstrate and discuss the impact of neglecting the non-dominant forcing (buoyancy flux above zMO and wind stress below zMO) above and below zMO.

CERES EBAF Info

Atmospheric Science Data Center

2014-01-24

... fluxes, where TOA net flux is constrained to ocean heat storage. - Surface: Computed surface clear-sky and all-sky fluxes consistent with the EBAF-TOA fluxes. Data Products:  EBAF-TOA EBAF-Surface ...

Tropical Ocean Surface Energy Balance Variability: Linking Weather to Climate Scales

NASA Technical Reports Server (NTRS)

Roberts, J. Brent; Clayson, Carol Anne

2013-01-01

Radiative and turbulent surface exchanges of heat and moisture across the atmosphere-ocean interface are fundamental components of the Earth s energy and water balance. Characterizing the spatiotemporal variability of these exchanges of heat and moisture is critical to understanding the global water and energy cycle variations, quantifying atmosphere-ocean feedbacks, and improving model predictability. These fluxes are integral components to tropical ocean-atmosphere variability; they can drive ocean mixed layer variations and modify the atmospheric boundary layer properties including moist static stability, thereby influencing larger-scale tropical dynamics. Non-parametric cluster-based classification of atmospheric and ocean surface properties has shown an ability to identify coherent weather regimes, each typically associated with similar properties and processes. Using satellite-based observational radiative and turbulent energy flux products, this study investigates the relationship between these weather states and surface energy processes within the context of tropical climate variability. Investigations of surface energy variations accompanying intraseasonal and interannual tropical variability often use composite-based analyses of the mean quantities of interest. Here, a similar compositing technique is employed, but the focus is on the distribution of the heat and moisture fluxes within their weather regimes. Are the observed changes in surface energy components dominated by changes in the frequency of the weather regimes or through changes in the associated fluxes within those regimes? It is this question that the presented work intends to address. The distribution of the surface heat and moisture fluxes is evaluated for both normal and non-normal states. By examining both phases of the climatic oscillations, the symmetry of energy and water cycle responses are considered.

Forcing of global ocean ice models using an atmospheric boundary layer model: assessing consequences for the simulation of the AMOC

NASA Astrophysics Data System (ADS)

Abel, R.; Boning, C. W.

2016-02-01

Current practice in ocean-only model simulations is to force the ocean with a prescribed atmospheric state using bulk formulations. This practice provides a strong thermal restoring to the surface ocean with a typical time-scale of one month. In the real ocean a positive feedback (salinity advection) and a negative feedback (temperature advection) are associated with the Atlantic Meridional Overturning Circulation (AMOC). The surface branch of the AMOC transports warm and salty (relative to the mean conditions) to the subpolar North Atlantic and mix with the near-surface waters. A strong AMOC would therefore warm the subpolar North Atlantic, decrease deep water formation and also reduce AMOC strength (negative feedback). This negative feedback is diminished due to the surface forcing formulation and makes the system excessively sensitive to details in the freshwater fluxes . Instead, additional and unrealistic Sea Surface Salinity (SSS) restoring is applied. There have been several suggestions during the last 20 years for at least partially alleviating the problem. This includes some simplified model of the atmospheric mixed layer (AML) (CheapAML; Deremble et al., 2013) with prescribed winds which allows some feedback of SST anomalies on the near-surface air temperature and humidity needed to calculate the turbulent surface fluxes. We show that if the turbulent heat fluxes are modelled by the simple AML model net-fluxes get more realistic. Commonly ocean models experience an AMOC slowdown if SSS restoring is turned off. In the new system (ORCA05 with turbulent fluxes from CheapAML) this slowdown can be eliminated.

CentNet—A deployable 100-station network for surface exchange research

NASA Astrophysics Data System (ADS)

Oncley, S.; Horst, T. W.; Semmer, S.; Militzer, J.; Maclean, G.; Knudson, K.

2014-12-01

Climate, air quality, atmospheric composition, surface hydrology, and ecological processes are directly affected by the Earth's surface. Complexity of this surface exists at multiple spatial scales, which complicates the understanding of these processes. NCAR/EOL currently provides a facility to the research community to make direct eddy-covariance flux observations to quantify surface-atmosphere interactions. However, just as model resolution has continued to increase, there is a need to increase the spatial density of flux measurements to capture the wide variety of scales that contribute to exchange processes close to the surface. NCAR/EOL now has developed the CentNet facility, that is envisioned to have on the order of 100 surface flux stations deployable for periods of months to years. Each station would measure standard meteorological variables, all components of the surface energy balance (including turbulence fluxes and radiation), atmospheric composition, and other quantities to characterize the surface. Thus, CentNet can support observational research in the biogeosciences, hydrology, urban meteorology, basic meteorology, and turbulence. CentNet has been designed to be adaptable to a wide variety of research problems while keeping operations manageable. Tower infrastructure has been designed to be lightweight, easily deployed, and with a minimal set-up footprint. CentNet uses sensor networks to increase spatial sampling at each station. The data system saves every sample on site to retain flexibility in data analysis. We welcome guidance on development and funding priorities as we build CentNet.

Radiocarbon in Ecosystem Respiration and Soil Pore-Space CO2 with Surface Gas Flux, Air Temperature, and Soil Temperature and Moisture, Barrow, Alaska, 2012-2014

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lydia Vaughn; Margaret Torn; Rachel Porras

Dataset includes Delta14C measurements made from CO2 that was collected and purified in 2012-2014 from surface soil chambers, soil pore space, and background atmosphere. In addition to 14CO2 data, dataset includes co-located measurements of CO2 and CH4 flux, soil and air temperature, and soil moisture. Measurements and field samples were taken from intensive study site 1 areas A, B, and C, and the site 0 and AB transects, from specified positions in high-centered, flat-centered, and low centered polygons.

Using Diurnal Temperature Signals to Infer Vertical Groundwater-Surface Water Exchange.

PubMed

Irvine, Dylan J; Briggs, Martin A; Lautz, Laura K; Gordon, Ryan P; McKenzie, Jeffrey M; Cartwright, Ian

2017-01-01

Heat is a powerful tracer to quantify fluid exchange between surface water and groundwater. Temperature time series can be used to estimate pore water fluid flux, and techniques can be employed to extend these estimates to produce detailed plan-view flux maps. Key advantages of heat tracing include cost-effective sensors and ease of data collection and interpretation, without the need for expensive and time-consuming laboratory analyses or induced tracers. While the collection of temperature data in saturated sediments is relatively straightforward, several factors influence the reliability of flux estimates that are based on time series analysis (diurnal signals) of recorded temperatures. Sensor resolution and deployment are particularly important in obtaining robust flux estimates in upwelling conditions. Also, processing temperature time series data involves a sequence of complex steps, including filtering temperature signals, selection of appropriate thermal parameters, and selection of the optimal analytical solution for modeling. This review provides a synthesis of heat tracing using diurnal temperature oscillations, including details on optimal sensor selection and deployment, data processing, model parameterization, and an overview of computing tools available. Recent advances in diurnal temperature methods also provide the opportunity to determine local saturated thermal diffusivity, which can improve the accuracy of fluid flux modeling and sensor spacing, which is related to streambed scour and deposition. These parameters can also be used to determine the reliability of flux estimates from the use of heat as a tracer. © 2016, National Ground Water Association.

Using Ground Measurements to Examine the Surface Layer Parameterization Scheme in NCEP GFS

NASA Astrophysics Data System (ADS)

Zheng, W.; Ek, M. B.; Mitchell, K.

2017-12-01

Understanding the behavior and the limitation of the surface layer parameneterization scheme is important for parameterization of surface-atmosphere exchange processes in atmospheric models, accurate prediction of near-surface temperature and identifying the role of different physical processes in contributing to errors. In this study, we examine the surface layer paramerization scheme in the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) using the ground flux measurements including the FLUXNET data. The model simulated surface fluxes, surface temperature and vertical profiles of temperature and wind speed are compared against the observations. The limits of applicability of the Monin-Obukhov similarity theory (MOST), which describes the vertical behavior of nondimensionalized mean flow and turbulence properties within the surface layer, are quantified in daytime and nighttime using the data. Results from unstable regimes and stable regimes are discussed.

Spatial variability of shortwave radiative fluxes in the context of snowmelt

NASA Astrophysics Data System (ADS)

Pinker, Rachel T.; Ma, Yingtao; Hinkelman, Laura; Lundquist, Jessica

2014-05-01

Snow-covered mountain ranges are a major source of water supply for run-off and groundwater recharge. Snowmelt supplies as much as 75% of surface water in basins of the western United States. Factors that affect the rate of snow melt include incoming shortwave and longwave radiation, surface albedo, snow emissivity, snow surface temperature, sensible and latent heat fluxes, ground heat flux, and energy transferred to the snowpack from deposited snow or rain. The net radiation generally makes up about 80% of the energy balance and is dominated by the shortwave radiation. Complex terrain poses a great challenge for obtaining the needed information on radiative fluxes from satellites due to elevation issues, spatially-variable cloud cover, rapidly changing surface conditions during snow fall and snow melt, lack of high quality ground truth for evaluation of the satellite based estimates, as well as scale issues between the ground observations and the satellite footprint. In this study we utilize observations of high spatial resolution (5-km) as available from the Moderate Resolution Imaging Spectro-radiometer (MODIS) to derive surface shortwave radiative fluxes in complex terrain, with attention to the impact of slopes on the amount of radiation received. The methodology developed has been applied to several water years (January to July during 2003, 2004, 2005 and 2009) over the western part of the United States, and the available information was used to derive metrics on spatial and temporal variability in the shortwave fluxes. It is planned to apply the findings from this study for testing improvements in Snow Water Equivalent (SWE) estimates.

Revisiting the global surface energy budgets with maximum-entropy-production model of surface heat fluxes

NASA Astrophysics Data System (ADS)

Huang, Shih-Yu; Deng, Yi; Wang, Jingfeng

2017-09-01

The maximum-entropy-production (MEP) model of surface heat fluxes, based on contemporary non-equilibrium thermodynamics, information theory, and atmospheric turbulence theory, is used to re-estimate the global surface heat fluxes. The MEP model predicted surface fluxes automatically balance the surface energy budgets at all time and space scales without the explicit use of near-surface temperature and moisture gradient, wind speed and surface roughness data. The new MEP-based global annual mean fluxes over the land surface, using input data of surface radiation, temperature data from National Aeronautics and Space Administration-Clouds and the Earth's Radiant Energy System (NASA CERES) supplemented by surface specific humidity data from the Modern-Era Retrospective Analysis for Research and Applications (MERRA), agree closely with previous estimates. The new estimate of ocean evaporation, not using the MERRA reanalysis data as model inputs, is lower than previous estimates, while the new estimate of ocean sensible heat flux is higher than previously reported. The MEP model also produces the first global map of ocean surface heat flux that is not available from existing global reanalysis products.

Surface energy budget and turbulent fluxes at Arctic terrestrial sites

NASA Astrophysics Data System (ADS)

Grachev, Andrey; Persson, Ola; Uttal, Taneil; Konopleva-Akish, Elena; Crepinsek, Sara; Cox, Christopher; Fairall, Christopher; Makshtas, Alexander; Repina, Irina

2017-04-01

Determination of the surface energy budget (SEB) and all SEB components at the air-surface interface are required in a wide variety of applications including atmosphere-land/snow simulations and validation of the surface fluxes predicted by numerical models over different spatial and temporal scales. Here, comparisons of net surface energy budgets at two Arctic sites are made using long-term near-continuous measurements of hourly averaged surface fluxes (turbulent, radiation, and soil conduction). One site, Eureka (80.0 N; Nunavut, Canada), is located in complex topography near a fjord about 200 km from the Arctic Ocean. The other site, Tiksi (71.6 N; Russian East Siberia), is located on a relatively flat coastal plain less than 1 km from the shore of Tiksi Bay, a branch of the Arctic Ocean. We first analyzed diurnal and annual cycles of basic meteorological parameters and key SEB components at these locations. Although Eureka and Tiksi are located on different continents and at different latitudes, the annual course of the surface meteorology and SEB components are qualitatively similar. Surface energy balance closure is a formulation of the conservation of energy principle. Our direct measurements of energy balance for both Arctic sites show that the sum of the turbulent sensible and latent heat fluxes and the ground (conductive) heat flux systematically underestimate the net radiation by about 25-30%. This lack of energy balance closure is a fundamental and pervasive problem in micrometeorology. We discuss a variety of factors which may be responsible for the lack of SEB closure. In particular, various storage terms (e.g., air column energy storage due to radiative and/or sensible heat flux divergence, ground heat storage above the soil flux plate, energy used in photosynthesis, canopy biomass heat storage). For example, our observations show that the photosynthesis storage term is relatively small (about 1-2% of the net radiation), but about 8-12% of the imbalance magnitude. All turbulent fluxes are highly correlated with net radiation because this balance between solar and longwave radiation is the principal energy source for daytime surface warming, evaporation, and photosynthesis. We find that turbulent fluxes of carbon dioxide and sensible heat are closely linked and, on average, change sign synchronously during the diurnal and annual cycles. The work is supported by the NOAA Climate Program Office, the U.S. National Science Foundation (NSF) with award ARC 11-07428, and by the U.S. Civilian Research & Development Foundation (CRDF) with award RUG1-2976-ST-10.

Wavelet and Fractal Analysis of Remotely Sensed Surface Temperature with Applications to Estimation of Surface Sensible Heat Flux Density

NASA Technical Reports Server (NTRS)

Schieldge, John

2000-01-01

Wavelet and fractal analyses have been used successfully to analyze one-dimensional data sets such as time series of financial, physical, and biological parameters. These techniques have been applied to two-dimensional problems in some instances, including the analysis of remote sensing imagery. In this respect, these techniques have not been widely used by the remote sensing community, and their overall capabilities as analytical tools for use on satellite and aircraft data sets is not well known. Wavelet and fractal analyses have the potential to provide fresh insight into the characterization of surface properties such as temperature and emissivity distributions, and surface processes such as the heat and water vapor exchange between the surface and the lower atmosphere. In particular, the variation of sensible heat flux density as a function of the change In scale of surface properties Is difficult to estimate, but - in general - wavelets and fractals have proved useful in determining the way a parameter varies with changes in scale. We present the results of a limited study on the relationship between spatial variations in surface temperature distribution and sensible heat flux distribution as determined by separate wavelet and fractal analyses. We analyzed aircraft imagery obtained in the thermal infrared (IR) bands from the multispectral TIMS and hyperspectral MASTER airborne sensors. The thermal IR data allows us to estimate the surface kinetic temperature distribution for a number of sites in the Midwestern and Southwestern United States (viz., San Pedro River Basin, Arizona; El Reno, Oklahoma; Jornada, New Mexico). The ground spatial resolution of the aircraft data varied from 5 to 15 meters. All sites were instrumented with meteorological and hydrological equipment including surface layer flux measuring stations such as Bowen Ratio systems and sonic anemometers. The ground and aircraft data sets provided the inputs for the wavelet and fractal analyses, and the validation of the results.

Free convection in the Matian atmosphere

NASA Technical Reports Server (NTRS)

Clow, G. D.; Haberle, R. M.

1990-01-01

The 'free convective' regime for the Martian atmospheric boundary layer (ABL) was investigated. This state occurs when the mean windspeed at the top of the ABL drops below some critical value U(sub c) and positive buoyant forces are present. Such forces can arise either from vertical temperature or water vapor gradients across the atmospheric surface layer. During free convection, buoyant forces drive narrow plumes that ascend to the inversion height with a return circulation consisting of broad slower-moving downdraughts. Horizontal pressure, temperature, windspeed, and water vapor fluctuations resulting form this circulation pattern can be quite large adjacent to the ground (within the surface layer). The local turbulent fluctuations cause non-zero mean surface stresses, sensible heat fluxes, and latent heat fluxes, even when the mean regional windspeed is zero. Although motions above the surface layer are insensitive to the nature of the surface, the sensible and latent heat fluxes are primarily controlled by processes within the interfacial sublayer immediately adjacent to the ground during free convection. Thus the distinction between aerodynamically smooth and rough airflow within the interfacial sublayer is more important than for the more typical situation where the mean regional windspeed is greater than U(sub c). Buoyant forces associated with water vapor gradients are particularly large on Mars at low pressures and high temperatures when the surface relative humidity is 100 percent, enhancing the likelihood of free convection under these conditions. On this basis, Ingersol postulated the evaporative heat losses from an icy surface on Mars at 237 K and current pressures would exceed the available net radiative flux at the surface, thus prohibiting ice from melting at low atmospheric pressures. Schumann has developed equations describing the horizontal fluctuations and mean vertical gradients occurring during free convection. Schumann's model was generalized to include convection driven by water vapor gradients and to include the effects of circulation above both aerodynamically smooth and rough surfaces.

Meteorological factors controlling year-to-year variations in the spring onset of snow melt over the Arctic sea ice

NASA Astrophysics Data System (ADS)

Maksimovich, E.

2010-09-01

The spring onset of snow melt on the Arctic sea ice shows large inter-annual variability. Surface melt triggers positive feedback mechanisms between the albedo, snow properties and thickness, as well as sea ice thickness. Hence, it is important to quantify the factors contributing to inter-annual variability of the melt onset (MO) in various parts of the Arctic Ocean. Meteorological factors controlling surface heat budget and surface melting/freezing are the shortwave and longwave radiative fluxes and the turbulent fluxes of sensible and latent heat. These fluxes depend on the weather conditions, including the radiative impact of clouds, heat advection and wind speed. We make use of SSM/I-based MO time series (Markus, Miller and Stroeve) and the ECMWF ERA Interim reanalysis on the meteorological conditions and surface fluxes, both data sets spanning the period 1989-2008 and covering recent years with a rapid sea ice decline. The advantage is that SSM/I-based MO time series are independent of the ERA-Interim data. Our objective is to investigate if there exists a physically consistent and statistically significant relationship between MO timing and corresponding meteorological conditions. Results based on the regression analysis between the MO timing and seasonal anomalies of surface longwave radiative fluxes reveal strong relationships. Synoptic scale (3-14 days) anomalies in downward longwave radiation are essential in the Western Arctic. Regarding the longer history (20-60 days) the distinct contribution from the downward longwave radiative fluxes is captured within the whole study region. Positive anomalies in the downward longwave radiation dominate over the simultaneous negative anomalies in the downward shortwave radiation. The anomalies in downward radiative fluxes are consistent with the total column water vapor, sea level pressure and 10-m wind direction. Sensible and latent heat fluxes affect surface melt timing in the Beaufort Sea and in the Atlantic sector of the Arctic Basin. Stronger winds strengthen the relationship between the turbulent fluxes and the MO timing. The turbulent surface fluxes in spring are relatively weak, of the order of 1-10W/m2, compared to the downward shortwave and longwave radiative fluxes, which are of the order of 100-150W/m2. As soon as data uncertainties are comparable to the anomaly in turbulent fluxes, statistical relationships found between MO timing and preceding anomaly in turbulent fluxes do not necessarily prove their reasonal-causal relationship. This joint study of SSM/I-based MO record and the ERA-Interim meteorological fields region-wide with a focus on the seasonal transition demonstrates their consistency in time and space. Such result could be regarded as an important indicator that both data sets have the appropriate performance of the surface state in the Arctic Ocean. Nevertheless, an important additional effort is needed for to resolve better the cloud radiative and boundary layer turbulent processes over the sea ice.

Scripps Ocean Modeling and Remote Sensing (SOMARS)

DTIC Science & Technology

1988-09-20

Topics in this brief reports include: Kalman filtering of oceanographic data; Remote sensing of sea surface temperature; Altimetry and Surface heat fluxes; Ocean models of the marine mixed layer; Radar altimetry; Mathematical model of California current eddies.

Estimating surface fluxes over middle and upper streams of the Heihe River Basin with ASTER imagery

NASA Astrophysics Data System (ADS)

Ma, W.; Ma, Y.; Hu, Z.; Su, Z.; Wang, J.; Ishikawa, H.

2011-05-01

Land surface heat fluxes are essential measures of the strengths of land-atmosphere interactions involving energy, heat and water. Correct parameterization of these fluxes in climate models is critical. Despite their importance, state-of-the-art observation techniques cannot provide representative areal averages of these fluxes comparable to the model grid. Alternative methods of estimation are thus required. These alternative approaches use (satellite) observables of the land surface conditions. In this study, the Surface Energy Balance System (SEBS) algorithm was evaluated in a cold and arid environment, using land surface parameters derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. Field observations and estimates from SEBS were compared in terms of net radiation flux (Rn), soil heat flux (G0), sensible heat flux (H) and latent heat flux (λE) over a heterogeneous land surface. As a case study, this methodology was applied to the experimental area of the Watershed Allied Telemetry Experimental Research (WATER) project, located on the mid-to-upstream sections of the Heihe River in northwest China. ASTER data acquired between 3 May and 4 June 2008, under clear-sky conditions were used to determine the surface fluxes. Ground-based measurements of land surface heat fluxes were compared with values derived from the ASTER data. The results show that the derived surface variables and the land surface heat fluxes furnished by SEBS in different months over the study area are in good agreement with the observed land surface status under the limited cases (some cases looks poor results). So SEBS can be used to estimate turbulent heat fluxes with acceptable accuracy in areas where there is partial vegetation cover in exceptive conditions. It is very important to perform calculations using ground-based observational data for parameterization in SEBS in the future. Nevertheless, the remote-sensing results can provide improved explanations of land surface fluxes over varying land coverage at greater spatial scales.

Aerosol-Induced Radiative Flux Changes Off the United States Mid-Atlantic Coast: Comparison of Values Calculated from Sunphotometer and In Situ Data with Those Measured by Airborne Pyranometer

NASA Technical Reports Server (NTRS)

Russell, P. B.; Livingston, J. M.; Hignett, P.; Kinne, S.; Wong, J.; Chien, A.; Bergstrom, R.; Durkee, P.; Hobbs, P. V.

2000-01-01

The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) measured a variety of aerosol radiative effects (including flux changes) while simultaneously measuring the chemical, physical, and optical properties of the responsible aerosol particles. Here we use TARFOX-determined aerosol and surface properties to compute shortwave radiative flux changes for a variety of aerosol situations, with midvisible optical depths ranging from 0.06 to 0.55. We calculate flux changes by several techniques with varying degrees of sophistication, in part to investigate the sensitivity of results to computational approach. We then compare computed flux changes to those determined from aircraft measurements. Calculations using several approaches yield downward and upward flux changes that agree with measurements. The agreement demonstrates closure (i.e. consistency) among the TARFOX-derived aerosol properties, modeling techniques, and radiative flux measurements. Agreement between calculated and measured downward flux changes is best when the aerosols are modeled as moderately absorbing (midvisible single-scattering albedos between about 0.89 and 0.93), in accord with independent measurements of the TARPOX aerosol. The calculated values for instantaneous daytime upwelling flux changes are in the range +14 to +48 W/sq m for midvisible optical depths between 0.2 and 0.55. These values are about 30 to 100 times the global-average direct forcing expected for the global-average sulfate aerosol optical depth of 0.04. The reasons for the larger flux changes in TARFOX include the relatively large optical depths and the focus on cloud-free, daytime conditions over the dark ocean surface. These are the conditions that produce major aerosol radiative forcing events and contribute to any global-average climate effect.

NASA/GEWEX Surface Radiation Budget: Integrated Data Product With Reprocessed Radiance, Cloud, and Meteorology Inputs, and New Surface Albedo Treatment

NASA Technical Reports Server (NTRS)

Cox, Stephen J.; Stackhouse, Paul W., Jr.; Gupta, Shashi K.; Mikovitz, J. Colleen; Zhang, Taiping

2016-01-01

The NASA/GEWEX Surface Radiation Budget (SRB) project produces shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. Spatial resolution is 1 degree. The current release 3.0 (available at gewex-srb.larc.nasa.gov) uses the International Satellite Cloud Climatology Project (ISCCP) DX product for pixel level radiance and cloud information. This product is subsampled to 30 km. ISCCP is currently recalibrating and recomputing their entire data series, to be released as the H product, at 10km resolution. The ninefold increase in pixel number will allow SRB a higher resolution gridded product (e.g. 0.5 degree), as well as the production of pixel-level fluxes. In addition to the input data improvements, several important algorithm improvements have been made. Most notable has been the adaptation of Angular Distribution Models (ADMs) from CERES to improve the initial calculation of shortwave TOA fluxes, from which the surface flux calculations follow. Other key input improvements include a detailed aerosol history using the Max Planck Institut Aerosol Climatology (MAC), temperature and moisture profiles from HIRS, and new topography, surface type, and snow/ice. Here we present results for the improved GEWEX Shortwave and Longwave algorithm (GSW and GLW) with new ISCCP data, the various other improved input data sets and the incorporation of many additional internal SRB model improvements. As of the time of abstract submission, results from 2007 have been produced with ISCCP H availability the limiting factor. More SRB data will be produced as ISCCP reprocessing continues. The SRB data produced will be released as part of the Release 4.0 Integrated Product, recognizing the interdependence of the radiative fluxes with other GEWEX products providing estimates of the Earth's global water and energy cycle (I.e., ISCCP, SeaFlux, LandFlux, NVAP, etc.).

Micrometeorological, evapotranspiration, and soil-moisture data at the Amargosa Desert Research site in Nye County near Beatty, Nevada, 2006-11

USGS Publications Warehouse

Arthur, Jonathan M.; Johnson, Michael J.; Mayers, C. Justin; Andraski, Brian J.

2012-11-13

This report describes micrometeorological, evapotranspiration, and soil-moisture data collected since 2006 at the Amargosa Desert Research Site adjacent to a low-level radio-active waste and hazardous chemical waste facility near Beatty, Nevada. Micrometeorological data include precipitation, solar radiation, net radiation, air temperature, relative humidity, saturated and ambient vapor pressure, wind speed and direction, barometric pressure, near-surface soil temperature, soil-heat flux, and soil-water content. Evapotranspiration (ET) data include latent-heat flux, sensible-heat flux, net radiation, soil-heat flux, soil temperature, air temperature, vapor pressure, and other principal energy-budget data. Soil-moisture data include periodic measurements of volumetric water-content at experimental sites that represent vegetated native soil, devegetated native soil, and simulated waste disposal trenches - maximum measurement depths range from 5.25 to 29.25 meters. All data are compiled in electronic spreadsheets that are included with this report.

Component-specific dynamics of riverine mangrove CO2 efflux in the Florida coastal Everglades

USGS Publications Warehouse

Troxler, Tiffany G.; Barr, Jordan G.; Fuentes, Jose D.; Engel, Victor C.; Anderson, Gordon H.; Sanchez, Christopher; Lagomosino, David; Price, Rene; Davis, Stephen E.

2015-01-01

Carbon cycling in mangrove forests represents a significant portion of the coastal wetland carbon (C) budget across the latitudes of the tropics and subtropics. Previous research suggests fluctuations in tidal inundation, temperature and salinity can influence forest metabolism and C cycling. Carbon dioxide (CO2) from respiration that occurs from below the canopy is contributed from different components. In this study, we investigated variation in CO2 flux among different below-canopy components (soil, leaf litter, course woody debris, soil including pneumatophores, prop roots, and surface water) in a riverine mangrove forest of Shark River Slough estuary, Everglades National Park (Florida, USA). The range in CO2 flux from different components exceeded that measured among sites along the oligohaline-saline gradient. Black mangrove (Avicennia germinans) pneumatophores contributed the largest average CO2 flux. Over a narrow range of estuarine salinity (25–35 practical salinity units (PSU)), increased salinity resulted in lower CO2 flux to the atmosphere. Tidal inundation reduced soil CO2 flux overall but increased the partial pressure of CO2 (pCO2) observed in the overlying surface water upon flooding. Higher pCO2 in surface water is then subject to tidally driven export, largely as HCO3. Integration and scaling of CO2 flux rates to forest scale allowed for improved understanding of the relative contribution of different below-canopy components to mangrove forest ecosystem respiration (ER). Summing component CO2fluxes suggests a more significant contribution of below-canopy respiration to ER than previously considered. An understanding of below-canopy CO2 component fluxes and their contributions to ER can help to elucidate how C cycling will change with discrete disturbance events (e.g., hurricanes) and long-term change, including sea-level rise, and potential impact mangrove forests. As such, key controls on below-canopy ER must be taken into consideration when developing and modeling mangrove forest C budgets.

Edge-localized-modes in tokamaks

DOE PAGES

Leonard, Anthony W.

2014-09-11

Edge-localized-modes (ELMs) are a ubiquitous feature of H-mode in tokamaks. When gradients in the H-mode transport barrier grow to exceed the MHD stability limit the ELM instability grows explosively rapidly transporting energy and particles onto open field lines and material surfaces. Though ELMs provide additional particle and impurity transport through the H-mode transport barrier, enabling steady operation, the resulting heat flux transients to plasma facing surfaces project to large amplitude in future low collisionality burning plasma tokamaks. Measurements of the ELM heat flux deposition onto material surfaces in the divertor and main chamber indicate significant broadening compared to inter-ELM heatmore » flux, with a timescale for energy deposition that is consistent with sonic ion flow and numerical simulation. Comprehensive ELM simulation is highlighting the important physics processes of ELM transport including parallel transport due to magnetic reconnection and turbulence resulting from collapse of the H-mode transport barrier. As a result, encouraging prospects for ELM control and/or suppression in future tokamaks include intrinsic modes of ELM free operation, ELM triggering with frequent small pellet injection and the application of 3D magnetic fields.« less

Edge-localized-modes in tokamaksa)

NASA Astrophysics Data System (ADS)

Leonard, A. W.

2014-09-01

Edge-localized-modes (ELMs) are a ubiquitous feature of H-mode in tokamaks. When gradients in the H-mode transport barrier grow to exceed the MHD stability limit the ELM instability grows explosively, rapidly transporting energy and particles onto open field lines and material surfaces. Though ELMs provide additional particle and impurity transport through the H-mode transport barrier, enabling steady operation, the resulting heat flux transients to plasma facing surfaces project to large amplitude in future low collisionality burning plasma tokamaks. Measurements of the ELM heat flux deposition onto material surfaces in the divertor and main chamber indicate significant broadening compared to inter-ELM heat flux, with a timescale for energy deposition that is consistent with sonic ion flow and numerical simulation. Comprehensive ELM simulation is highlighting the important physics processes of ELM transport including parallel transport due to magnetic reconnection and turbulence resulting from collapse of the H-mode transport barrier. Encouraging prospects for ELM control and/or suppression in future tokamaks include intrinsic modes of ELM free operation, ELM triggering with frequent small pellet injection and the application of 3D magnetic fields.

CERES Monthly Gridded Single Satellite TOA and Surfaces/Clouds (SFC) data in HDF (CER_SFC_TRMM-PFM-VIRS_Beta4)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

The Monthly Gridded TOA/Surface Fluxes and Clouds (SFC) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SFC is also produced for combinations of scanner instruments. All instantaneous shortwave, longwave, and window fluxes at the Top-of-the-Atmosphere (TOA) and surface from the CERES SSF product for a month are sorted by 1-degree spatial regions and by the local hour of observation. The mean of the instantaneous fluxes for a given region-hour bin is determined and recorded on the SFC along with other flux statistics and scene information. These average fluxes are given for both clear-sky and total-sky scenes. The regional cloud properties are column averaged and are included on the SFC. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop_Date=2000-03-31] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=100] [Data_Resolution: Latitude_Resolution=1 degree; Longitude_Resolution=1 degree; Horizontal_Resolution_Range=100 km - < 250 km or approximately 1 degree - < 2.5 degrees; Temporal_Resolution=1 hour; Temporal_Resolution_Range=Hourly - < Daily].

The NASA/GEWEX Surface Radiation Budget: Integrated Data Product With Reprocessed Radiance, Cloud, and Meteorology Inputs

NASA Astrophysics Data System (ADS)

Stackhouse, P. W.; Gupta, S. K.; Cox, S. J.; Mikovitz, J. C.; Zhang, T.

2015-12-01

The NASA/GEWEX Surface Radiation Budget (SRB) project produces shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. Spatial resolution is 1 degree. The current release 3.0 (available at gewex-srb.larc.nasa.gov) uses the International Satellite Cloud Climatology Project (ISCCP) DX product for pixel level radiance and cloud information. This product is subsampled to 30 km. ISCCP is currently recalibrating and recomputing their entire data series, to be released as the H product, at 10km resolution. The ninefold increase in pixel number will allow SRB a higher resolution gridded product (e.g. 0.5 degree), as well as the production of pixel-level fluxes. Other key input improvements include a detailed aerosol history using the Max Planck Institut Aerosol Climatology (MAC), temperature and moisture profiles from HIRS, and new topography, surface type, and snow/ice. At the time of abstract submission, results from the year 2007 have been produced. More years will be added as ISCCP reprocessing occurs. Here we present results for the improved GEWEX Shortwave and Longwave algorithm (GSW and GLW) with new ISCCP data, the various other improved input data sets and the incorporation of many additional internal SRB model improvements. Improvements in GSW include an expansion of the number of wavelength bands from five to eighteen, and the inclusion of ice cloud vs. water cloud radiative transfer. The SRB data produced will be released as part of the Release 4.0 Integrated Product, recognizing the interdependence of the radiative fluxes with other GEWEX products providing estimates of the Earth's global water and energy cycle (I.e., ISCCP, SeaFlux, LandFlux, NVAP, etc.).

Diurnal variation in greenhouse fluxes from a feedyard pen surface

USDA-ARS?s Scientific Manuscript database

Accurate estimation of greenhouse gas (GHG) emissions, including nitrous oxide (N2O) and methane (CH4) from open-lot beef cattle feedlots is an increasing concern given the current and potential future reporting requirements for GHG emissions. Research concerning N2O and CH4 emission fluxes from the...

Reconstruction of flux coordinates from discretized magnetic field maps

NASA Astrophysics Data System (ADS)

Predebon, I.; Momo, B.; Suzuki, Y.; Auriemma, F.

2018-04-01

We provide a simple method to build a straight field-line coordinate system from discretized (Poincaré) magnetic field maps. The method is suitable for any plasma domain with nested flux surfaces, including magnetic islands. Illustrative examples are shown for tokamak, heliotron, and reversed-field-pinch plasmas with m = 1 islands.

Improving Surface Flux Parameterizations in the NRL Coupled Ocean/Atmosphere Mesoscale Prediction System

DTIC Science & Technology

2008-09-30

these days from a suite of instruments were analyzed, including those from rawinsonde launches, acoustic radar, and the 20 m flux tower. The objective...aircraft IR pyrometer in CBLAST-Low on (c) August 18, and (d) August 25, 2003. The NCOM simulation suggests that the high SST variability observed on

Upscaling surface energy fluxes over the North Slope of Alaska using airborne eddy-covariance measurements and environmental response functions

NASA Astrophysics Data System (ADS)

Serafimovich, Andrei; Metzger, Stefan; Hartmann, Jörg; Kohnert, Katrin; Zona, Donatella; Sachs, Torsten

2018-03-01

The objective of this study was to upscale airborne flux measurements of sensible heat and latent heat and to develop high resolution flux maps. In order to support the evaluation of coupled atmospheric/land-surface models we investigated spatial patterns of energy fluxes in relation to land-surface properties. We used airborne eddy-covariance measurements acquired by the POLAR 5 research aircraft in June-July 2012 to analyze surface fluxes. Footprint-weighted surface properties were then related to 21 529 sensible heat flux observations and 25 608 latent heat flux observations using both remote sensing and modelled data. A boosted regression tree technique was used to estimate environmental response functions between spatially and temporally resolved flux observations and corresponding biophysical and meteorological drivers. In order to improve the spatial coverage and spatial representativeness of energy fluxes we used relationships extracted across heterogeneous Arctic landscapes to infer high-resolution surface energy flux maps, thus directly upscaling the observational data. These maps of projected sensible heat and latent heat fluxes were used to assess energy partitioning in northern ecosystems and to determine the dominant energy exchange processes in permafrost areas. This allowed us to estimate energy fluxes for specific types of land cover, taking into account meteorological conditions. Airborne and modelled fluxes were then compared with measurements from an eddy-covariance tower near Atqasuk. Our results are an important contribution for the advanced, scale-dependent quantification of surface energy fluxes and provide new insights into the processes affecting these fluxes for the main vegetation types in high-latitude permafrost areas.

Diurnal Variations of the Flux Imbalance Over Homogeneous and Heterogeneous Landscapes

NASA Astrophysics Data System (ADS)

Zhou, Yanzhao; Li, Dan; Liu, Heping; Li, Xin

2018-05-01

It is well known that the sum of the turbulent sensible and latent heat fluxes as measured by the eddy-covariance method is systematically lower than the available energy (i.e., the net radiation minus the ground heat flux). We examine the separate and joint effects of diurnal and spatial variations of surface temperature on this flux imbalance in a dry convective boundary layer using the Weather Research and Forecasting model. Results show that, over homogeneous surfaces, the flux due to turbulent-organized structures is responsible for the imbalance, whereas over heterogeneous surfaces, the flux due to mesoscale or secondary circulations is the main contributor to the imbalance. Over homogeneous surfaces, the flux imbalance in free convective conditions exhibits a clear diurnal cycle, showing that the flux-imbalance magnitude slowly decreases during the morning period and rapidly increases during the afternoon period. However, in shear convective conditions, the flux-imbalance magnitude is much smaller, but slightly increases with time. The flux imbalance over heterogeneous surfaces exhibits a diurnal cycle under both free and shear convective conditions, which is similar to that over homogeneous surfaces in free convective conditions, and is also consistent with the general trend in the global observations. The rapid increase in the flux-imbalance magnitude during the afternoon period is mainly caused by the afternoon decay of the turbulent kinetic energy (TKE). Interestingly, over heterogeneous surfaces, the flux imbalance is linearly related to the TKE and the difference between the potential temperature and surface temperature, ΔT; the larger the TKE and ΔT values, the smaller the flux-imbalance magnitude.

Sources of Uncertainty in Predicting Land Surface Fluxes Using Diverse Data and Models

NASA Technical Reports Server (NTRS)

Dungan, Jennifer L.; Wang, Weile; Michaelis, Andrew; Votava, Petr; Nemani, Ramakrishma

2010-01-01

In the domain of predicting land surface fluxes, models are used to bring data from large observation networks and satellite remote sensing together to make predictions about present and future states of the Earth. Characterizing the uncertainty about such predictions is a complex process and one that is not yet fully understood. Uncertainty exists about initialization, measurement and interpolation of input variables; model parameters; model structure; and mixed spatial and temporal supports. Multiple models or structures often exist to describe the same processes. Uncertainty about structure is currently addressed by running an ensemble of different models and examining the distribution of model outputs. To illustrate structural uncertainty, a multi-model ensemble experiment we have been conducting using the Terrestrial Observation and Prediction System (TOPS) will be discussed. TOPS uses public versions of process-based ecosystem models that use satellite-derived inputs along with surface climate data and land surface characterization to produce predictions of ecosystem fluxes including gross and net primary production and net ecosystem exchange. Using the TOPS framework, we have explored the uncertainty arising from the application of models with different assumptions, structures, parameters, and variable definitions. With a small number of models, this only begins to capture the range of possible spatial fields of ecosystem fluxes. Few attempts have been made to systematically address the components of uncertainty in such a framework. We discuss the characterization of uncertainty for this approach including both quantifiable and poorly known aspects.

Closing the Seasonal Ocean Surface Temperature Balance in the Eastern Tropical Oceans from Remote Sensing and Model Reanalyses

NASA Technical Reports Server (NTRS)

Roberts, J. Brent; Clayson, Carol A.

2012-01-01

The Eastern tropical ocean basins are regions of significant atmosphere-ocean interaction and are important to variability across subseasonal to decadal time scales. The numerous physical processes at play in these areas strain the abilities of coupled general circulation models to accurately reproduce observed upper ocean variability. Furthermore, limitations in the observing system of important terms in the surface temperature balance (e.g., turbulent and radiative heat fluxes, advection) introduce uncertainty into the analyses of processes controlling sea surface temperature variability. This study presents recent efforts to close the surface temperature balance through estimation of the terms in the mixed layer temperature budget using state-of-the-art remotely sensed and model-reanalysis derived products. A set of twelve net heat flux estimates constructed using combinations of radiative and turbulent heat flux products - including GEWEX-SRB, ISCCP-SRF, OAFlux, SeaFlux, among several others - are used with estimates of oceanic advection, entrainment, and mixed layer depth variability to investigate the seasonal variability of ocean surface temperatures. Particular emphasis is placed on how well the upper ocean temperature balance is, or is not, closed on these scales using the current generation of observational and model reanalysis products. That is, the magnitudes and spatial variability of residual imbalances are addressed. These residuals are placed into context within the current uncertainties of the surface net heat fluxes and the role of the mixed layer depth variability in scaling the impact of those uncertainties, particularly in the shallow mixed layers of the Eastern tropical ocean basins.

Response of water temperature to surface wave effects in the Baltic Sea: simulations with the coupled NEMO-WAM model

NASA Astrophysics Data System (ADS)

Alari, Victor; Staneva, Joanna; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian; Janssen, Peter

2016-04-01

The effects of wind waves on the Baltic Sea water temperature has been studied by coupling the hydrodynamical model NEMO with the wave model WAM. The wave forcing terms that have been taken into consideration are: Stokes-Coriolis force, seastate dependent energy flux and sea-state dependent momentum flux. The combined role of these processes as well as their individual contributions on simulated temperature is analysed. The results indicate a pronounced effect of waves on surface temperature, on the distribution of vertical temperature and on upwellinǵs. In northern parts of the Baltic Sea a warming of the surface layer occurs in the wave included simulations. This in turn reduces the cold bias between simulated and measured data. The warming is primarily caused by sea-state dependent energy flux. Wave induced cooling is mostly observed in near coastal areas and is mainly due to Stokes-Coriolis forcing. The latter triggers effect of intensifying upwellings near the coasts, depending on the direction of the wind. The effect of sea-state dependent momentum flux is predominantly to warm the surface layer. During the summer the wave induced water temperature changes were up to 1 °C.

Spatial and temporal connections in groundwater contribution to evaporation

NASA Astrophysics Data System (ADS)

Lam, A.; Karssenberg, D.; van den Hurk, B. J. J. M.; Bierkens, M. F. P.

2011-08-01

In climate models, lateral terrestrial water fluxes are usually neglected. We estimated the contribution of vertical and lateral groundwater fluxes to the land surface water budget at a subcontinental scale, by modeling convergence of groundwater and surfacewater fluxes. We present a hydrological model of the entire Danube Basin at 5 km resolution, and use it to show the importance of groundwater for the surface climate. Results show that the contribution of groundwater to evaporation is significant, and can locally be higher than 30 % in summer. We demonstrate through the same model that this contribution also has important temporal characteristics. A wet episode can influence groundwater contribution to summer evaporation for several years afterwards. This indicates that modeling groundwater flow has the potential to augment the multi-year memory of climate models. We also show that the groundwater contribution to evaporation is local by presenting the groundwater travel times and the magnitude of groundwater convergence. Throughout the Danube Basin the lateral fluxes of groundwater are negligible when modeling at this scale and resolution. This suggests that groundwater can be adequately added in land surface models by including a lower closed groundwater reservoir of sufficient size with two-way interaction with surface water and the overlying soil layers.

Analysis of uncertainties in GOSAT-inferred regional CO2 fluxes

NASA Astrophysics Data System (ADS)

Ishizawa, M.; Shirai, T.; Maksyutov, S. S.; Yoshida, Y.; Morino, I.; Inoue, M.; Nakatsuru, T.; Uchino, O.; Mabuchi, K.

2016-12-01

Satellite-based CO2 measurements have potential for improving our understanding global carbon cycle because of more spatiotemporal coverage than those from ground-based observations. Since the Greenhouse gases Observing Satellite (GOSAT) was launched in January 2009, it has been measuring the column-average dry air-mole function of CO2 (XCO2) from the space. To utilize the GOSAT XCO2 for better CO2 flux estimates, several challenges should be overcome. Systematic errors (biases) in XCO2 retrievals are a major factor which leads to large differences among inverted CO2 fluxes. Temporally variable data coverage and density are also taken into account when interpreting the estimated surface fluxes. In this study, we employ an atmospheric inverse model to investigate the impacts of retrievals biases and temporally varying global distribution of GOSAT XCO2 on surface CO2 flux estimates. Inversions are performed for 2009-2013, with several subsets of the 5-year record of GOSAT XCO2 (v2.21) and its bias-corrected XCO2. GOSAT XCO2 data consist of three types: H-gain for vegetated lands, M-gain for bright surfaces (desert areas), and sun-glint for ocean surface. The results show that the global spatial distributions of estimated CO2 fluxes depend on the subset of XCO2 used. M-gain XCO2 results in unrealistically high CO2 emissions in and around the Middle East, including the neighboring ocean regions. On the other hand, M-gain XCO2 causes compensating unrealistic uptakes far beyond M-gain regions in low latitudes, also partially contributing on the summer uptake in Europe. The joint inversions with both surface measurements and GOSAT XCO2 data obtain larger flux gradient between the northern extra-tropics and the tropics than the inversion with surface measurements only for the first 2 years. Recently, these North-South gradients seem to be gradually reducing as the tropics become a weaker source or turn into a sink, while the net emission strength in East Asia is increasing. The 5-year XCO2 data allows us detailed analysis of uncertainties in GOSAT-inferred fluxes and assessment of GOSAT XCO2 biases.

Simulation of the Indian Summer Monsoon Using Comprehensive Atmosphere-land Interactions, in the Absence of Two-way Air-sea Interactions

NASA Technical Reports Server (NTRS)

Lim, Young-Kwon; Shin, D. W.; Cocke, Steven; Kang, Sung-Dae; Kim, Hae-Dong

2011-01-01

Community Land Model version 2 (CLM2) as a comprehensive land surface model and a simple land surface model (SLM) were coupled to an atmospheric climate model to investigate the role of land surface processes in the development and the persistence of the South Asian summer monsoon. Two-way air-sea interactions were not considered in order to identify the reproducibility of the monsoon evolution by the comprehensive land model, which includes more realistic vertical soil moisture structures, vegetation and 2-way atmosphere-land interactions at hourly intervals. In the monsoon development phase (May and June). comprehensive land-surface treatment improves the representation of atmospheric circulations and the resulting convergence/divergence through the improvements in differential heating patterns and surface energy fluxes. Coupling with CLM2 also improves the timing and spatial distribution of rainfall maxima, reducing the seasonal rainfall overestimation by approx.60 % (1.8 mm/d for SLM, 0.7 mm/dI for CLM2). As for the interannual variation of the simulated rainfall, correlation coefficients of the Indian seasonal rainfall with observation increased from 0.21 (SLM) to 0.45 (CLM2). However, in the mature monsoon phase (July to September), coupling with the CLM2 does not exhibit a clear improvement. In contrast to the development phase, latent heat flux is underestimated and sensible heat flux and surface temperature over India are markedly overestimated. In addition, the moisture fluxes do not correlate well with lower-level atmospheric convergence, yielding correlation coefficients and root mean square errors worse than those produced by coupling with the SLM. A more realistic representation of the surface temperature and energy fluxes is needed to achieve an improved simulation for the mature monsoon period.

Relating Radiative Fluxes on Arctic Sea Ice Area Using Arctic Observation and Reanalysis Integrated System (ArORIS)

NASA Astrophysics Data System (ADS)

Sledd, A.; L'Ecuyer, T. S.

2017-12-01

With Arctic sea ice declining rapidly and Arctic temperatures rising faster than the rest of the globe, a better understanding of the Arctic climate, and ice cover-radiation feedbacks in particular, is needed. Here we present the Arctic Observation and Reanalysis Integrated System (ArORIS), a dataset of integrated products to facilitate studying the Arctic using satellite, reanalysis, and in-situ datasets. The data include cloud properties, radiative fluxes, aerosols, meteorology, precipitation, and surface properties, to name just a few. Each dataset has uniform grid-spacing, time-averaging and naming conventions for ease of use between products. One intended use of ArORIS is to assess Arctic radiation and moisture budgets. Following that goal, we use observations from ArORIS - CERES-EBAF radiative fluxes and NSIDC sea ice fraction and area to quantify relationships between the Arctic energy balance and surface properties. We find a discernable difference between energy budgets for years with high and low September sea ice areas. Surface fluxes are especially responsive to the September sea ice minimum in months both leading up to September and the months following. In particular, longwave fluxes at the surface show increased sensitivity in the months preceding September. Using a single-layer model of solar radiation we also investigate the individual responses of surface and planetary albedos to changes in sea ice area. By partitioning the planetary albedo into surface and atmospheric contributions, we find that the atmospheric contribution to planetary albedo is less sensitive to changes in sea ice area than the surface contribution. Further comparisons between observations and reanalyses can be made using the available datasets in ArORIS.

Thermal-Hydrology Simulations of Disposal of High-Level Radioactive Waste in a Single Deep Borehole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hadgu, Teklu; Stein, Emily; Hardin, Ernest

2015-11-01

Simulations of thermal-hydrology were carried out for the emplacement of spent nuclear fuel canisters and cesium and strontium capsules using the PFLOTRAN simulator. For the cesium and strontium capsules the analysis looked at disposal options such as different disposal configurations and surface aging of waste to reduce thermal effects. The simulations studied temperature and fluid flux in the vicinity of the borehole. Simulation results include temperature and vertical flux profiles around the borehole at selected depths. Of particular importance are peak temperature increases, and fluxes at the top of the disposal zone. Simulations of cesium and strontium capsule disposal predictmore » that surface aging and/or emplacement of the waste at the top of the disposal zone reduces thermal effects and vertical fluid fluxes. Smaller waste canisters emplaced over a longer disposal zone create the smallest thermal effect and vertical fluid fluxes no matter the age of the waste or depth of emplacement.« less

Marine Atmospheric Surface Layer and Its Application to Electromagnetic Wave Propagation

NASA Astrophysics Data System (ADS)

Wang, Q.

2015-12-01

An important application of the atmospheric surface layer research is to characterize the near surface vertical gradients in temperature and humidity in order to predict radar and radio communication conditions in the environment. In this presentation, we will give an overview of a new research initiative funded under the Office of Naval Research (ONR) Multi-University Research Initiative (MURI): the Coupled Air-Sea Processes and EM Ducting Research (CASPER). The objective is to fully characterize the marine atmospheric boundary layer (MABL) as an electromagnetic (EM) propagation environment with the emphasis of spatial and temporal heterogeneities and surface wave/swell effects, both of which contravene the underlying assumptions of Monin-Obukhov Similarity Theory (MOST) used in coupled environmental forecast models. Furthermore, coastal variability in the inversion atop the MABL presents a challenge to forecast models and also causes practical issues in EM prediction models. These issues are the target of investigation of CASPER. CASPER measurement component includes two major field campaigns: CASPER-East (2015 Duck, NC) and CASPER-West (2018 southern California). This presentation will show the extensive measurements to be made during the CASPER -East field campaign with the focus on the marine atmospheric surface layer measurements with two research vessels, two research aircraft, surface flux buoy, wave gliders, ocean gliders, tethered balloons, and rawinsondes. Unlike previous research on the marine surface layer with the focus on surface fluxes and surface flux parameterization, CASPER field campaigns also emphasize of the surface layer profiles and the validation of the surface layer flux-profile relationship originally derived over land surfaces. Results from CASPER pilot experiment and preliminary results from CASPER-East field campaign will be discussed.

Analytic solution for quasi-Lambertian radiation transfer.

PubMed

Braun, Avi; Gordon, Jeffrey M

2010-02-10

An analytic solution is derived for radiation transfer between flat quasi-Lambertian surfaces of arbitrary orientation, i.e., surfaces that radiate in a Lambertian fashion but within a numerical aperture smaller than unity. These formulas obviate the need for ray trace simulations and provide exact, physically transparent results. Illustrative examples that capture the salient features of the flux maps and the efficiency of flux transfer are presented for a few configurations of practical interest. There is also a fundamental reciprocity relation for quasi-Lambertian exchange, akin to the reciprocity theorem for fully Lambertian surfaces. Applications include optical fiber coupling, fiber-optic biomedical procedures, and solar concentrators.

Plasma surface modification of nanofiltration (NF) thin-film composite (TFC) membranes to improve anti organic fouling

NASA Astrophysics Data System (ADS)

Kim, Eun-Sik; Yu, Qingsong; Deng, Baolin

2011-09-01

Commercial nanofiltration (NF) thin-film composite (TFC) membranes were treated by low-pressure NH3 plasma, and the effects of the plasma treatment were investigated in terms of the membrane hydrophilicity, pure water flux, salt rejection, protein adsorption, and humic acid fouling. Experimental results indicated that the membrane surface hydrophilicity was increased by the plasma treatment, and changes in the hydrophilicity as well as membrane performance including permeate flux and fouling varied with the original membrane characteristics (e.g., roughness and hydrophilicity). Water flux of plasma treated membranes was the highest with 10 min and 90 W of plasma treatment, and salt rejection was mainly affected by the intensity of the plasma power. Results of bovine serum albumin (BSA) adsorption demonstrated that the protein adsorption decreased with increasing plasma treatment time. The plasma treatment that resulted in more negatively charged surfaces could also better prevent Aldrich humic acid (AHA) attachment on the membrane surface.

Correlations Between Sea-Surface Salinity Tendencies and Freshwater Fluxes in the Pacific Ocean

NASA Technical Reports Server (NTRS)

Li, Zhen; Adamec, David

2007-01-01

Temporal changes in sea-surface salinity (SSS) from 21 years of a high resolution model integration of the Pacific Ocean are correlated with the freshwater flux that was used to force the integration. The correlations are calculated on a 1 x10 grid, and on a monthly scale to assess the possibility of deducing evaporation minus precipitation (E-P) fields from the salinity measurements to be taken by the upcoming Aquarius/SAC-D mission. Correlations between the monthly mean E-P fields and monthly mean SSS temporal tendencies are mainly zonally-oriented, and are highest where the local precipitation is relatively high. Nonseasonal (deviations from the monthly mean) correlations are highest along mid-latitude storm tracks and are relatively small in the tropics. The response of the model's surface salinity to surface forcing is very complex, and retrievals of freshwater fluxes from SSS measurements alone will require consideration of other processes, including horizontal advection and vertical mixing, rather than a simple balance between the two.

A modified force-restore approach to modeling snow-surface heat fluxes

Treesearch

Charles H. Luce; David G. Tarboton

2001-01-01

Accurate modeling of the energy balance of a snowpack requires good estimates of the snow surface temperature. The snow surface temperature allows a balance between atmospheric heat fluxes and the conductive flux into the snowpack. While the dependency of atmospheric fluxes on surface temperature is reasonably well understood and parameterized, conduction of heat from...

Biogenic Emission Inventories: Scaling Local Biogenic Measurements to Regions

NASA Astrophysics Data System (ADS)

Lamb, B.; Pressley, S.; Westberg, H.; Guenther, A.

2002-12-01

Biogenic Hydrocarbons, such as isoprene, are important trace gas species that are naturally emitted by vegetation and that affect the oxidative capacity of the atmosphere. Biogenic emissions are regulated by many environmental variables; the most important variables are thought to be temperature and light. Long-term isoprene flux measurements are useful for verifying existing canopy models and exploring other correlations between isoprene fluxes and environmental parameters. Biogenic Emission Models, such as BEIS (Biogenic Emission Inventory System) rely on above canopy environmental parameters and below canopy scaling factors to estimate canopy scale biogenic hydrocarbon fluxes. Other models, which are more complex, are coupled micrometeorological and physiological modules that provide feedback mechanisms present in a canopy environment. These types of models can predict biogenic emissions well, however, the required input is extensive, and for regional applications, they can be cumbersome. This paper presents analyses based on long-term isoprene flux measurements that have been collected since 1999 at the AmeriFlux site located at the University of Michigan Biological Station (UMBS) as part of the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport (PROPHET). The goals of this research were to explore a potential relationship between the surface energy budget (primarily sensible heat flux) and isoprene emissions. Our hypothesis is that the surface energy flux is a better model parameter for isoprene emissions at the canopy scale than temperature and light levels, and the link to the surface energy budget will provide a significant improvement in isoprene emission models. Preliminary results indicate a significant correlation between daily isoprene emissions and sensible heat fluxes for a predominantly aspen/oak stand located in northern Michigan. Since surface energy budgets are an integral part of mesoscale meteorological models, this could potentially be a useful tool for including biogenic emissions into regional atmospheric models. Comparison of measured isoprene fluxes with current BEIS estimates will also be shown as an example of where emission inventories currently stand.

Area-averaged evapotranspiration over a heterogeneous land surface: aggregation of multi-point EC flux measurements with a high-resolution land-cover map and footprint analysis

NASA Astrophysics Data System (ADS)

Xu, Feinan; Wang, Weizhen; Wang, Jiemin; Xu, Ziwei; Qi, Yuan; Wu, Yueru

2017-08-01

The determination of area-averaged evapotranspiration (ET) at the satellite pixel scale/model grid scale over a heterogeneous land surface plays a significant role in developing and improving the parameterization schemes of the remote sensing based ET estimation models and general hydro-meteorological models. The Heihe Watershed Allied Telemetry Experimental Research (HiWATER) flux matrix provided a unique opportunity to build an aggregation scheme for area-averaged fluxes. On the basis of the HiWATER flux matrix dataset and high-resolution land-cover map, this study focused on estimating the area-averaged ET over a heterogeneous landscape with footprint analysis and multivariate regression. The procedure is as follows. Firstly, quality control and uncertainty estimation for the data of the flux matrix, including 17 eddy-covariance (EC) sites and four groups of large-aperture scintillometers (LASs), were carefully done. Secondly, the representativeness of each EC site was quantitatively evaluated; footprint analysis was also performed for each LAS path. Thirdly, based on the high-resolution land-cover map derived from aircraft remote sensing, a flux aggregation method was established combining footprint analysis and multiple-linear regression. Then, the area-averaged sensible heat fluxes obtained from the EC flux matrix were validated by the LAS measurements. Finally, the area-averaged ET of the kernel experimental area of HiWATER was estimated. Compared with the formerly used and rather simple approaches, such as the arithmetic average and area-weighted methods, the present scheme is not only with a much better database, but also has a solid grounding in physics and mathematics in the integration of area-averaged fluxes over a heterogeneous surface. Results from this study, both instantaneous and daily ET at the satellite pixel scale, can be used for the validation of relevant remote sensing models and land surface process models. Furthermore, this work will be extended to the water balance study of the whole Heihe River basin.

Validation of the Martilli's Urban Boundary Layer Scheme with measurements from two mid-latitude European cities

NASA Astrophysics Data System (ADS)

Hamdi, R.; Schayes, G.

2005-07-01

The Martilli's urban parameterization scheme is improved and implemented in a mesoscale model in order to take into account the typical effects of a real city on the air temperature near the ground and on the surface exchange fluxes. The mesoscale model is run on a single column using atmospheric data and radiation recorded above roof level as forcing. Here, the authors validate the Martilli's urban boundary layer scheme using measurements from two mid-latitude European cities: Basel, Switzerland and Marseilles, France. For Basel, the model performance is evaluated with observations of canyon temperature, surface radiation, and energy balance fluxes obtained during the Basel urban boundary layer experiment (BUBBLE). The results show that the urban parameterization scheme is able to reproduce the generation of the Urban Heat Island (UHI) effect over urban area and represents correctly most of the behavior of the fluxes typical of the city center of Basel, including the large heat uptake by the urban fabric and the positive sensible heat flux at night. For Marseilles, the model performance is evaluated with observations of surface temperature, canyon temperature, surface radiation, and energy balance fluxes collected during the field experiments to constrain models of atmospheric pollution and transport of emissions (ESCOMPTE) and its urban boundary layer (UBL) campaign. At both urban sites, vegetation cover is less than 20%, therefore, particular attention was directed to the ability of the Martilli's urban boundary layer scheme to reproduce the observations for the Marseilles city center, where the urban parameters and the synoptic forcing are totally different from Basel. Evaluation of the model with wall, road, and roof surface temperatures gave good results. The model correctly simulates the net radiation, canyon temperature, and the partitioning between the turbulent and storage heat fluxes.

Validation of Martilli's urban boundary layer scheme with measurements from two mid-latitude European cities

NASA Astrophysics Data System (ADS)

Hamdi, R.; Schayes, G.

2007-08-01

Martilli's urban parameterization scheme is improved and implemented in a mesoscale model in order to take into account the typical effects of a real city on the air temperature near the ground and on the surface exchange fluxes. The mesoscale model is run on a single column using atmospheric data and radiation recorded above roof level as forcing. Here, the authors validate Martilli's urban boundary layer scheme using measurements from two mid-latitude European cities: Basel, Switzerland and Marseilles, France. For Basel, the model performance is evaluated with observations of canyon temperature, surface radiation, and energy balance fluxes obtained during the Basel urban boundary layer experiment (BUBBLE). The results show that the urban parameterization scheme represents correctly most of the behavior of the fluxes typical of the city center of Basel, including the large heat uptake by the urban fabric and the positive sensible heat flux at night. For Marseilles, the model performance is evaluated with observations of surface temperature, canyon temperature, surface radiation, and energy balance fluxes collected during the field experiments to constrain models of atmospheric pollution and transport of emissions (ESCOMPTE) and its urban boundary layer (UBL) campaign. At both urban sites, vegetation cover is less than 20%, therefore, particular attention was directed to the ability of Martilli's urban boundary layer scheme to reproduce the observations for the Marseilles city center, where the urban parameters and the synoptic forcing are totally different from Basel. Evaluation of the model with wall, road, and roof surface temperatures gave good results. The model correctly simulates the net radiation, canyon temperature, and the partitioning between the turbulent and storage heat fluxes.

Study on a Dynamic Vegetation Model for Simulating Land Surface Flux Exchanges at Lien-Hua-Chih Flux Observation Site in Taiwan

NASA Astrophysics Data System (ADS)

Yeh, T. Y.; Li, M. H.; Chen, Y. Y.; Ryder, J.; McGrath, M.; Otto, J.; Naudts, K.; Luyssaert, S.; MacBean, N.; Bastrikov, V.

2016-12-01

Dynamic vegetation model ORCHIDEE (Organizing Carbon and Hydrology In Dynamic EcosystEms) is a state of art land surface component of the IPSL (Institute Pierre Simon Laplace) Earth System Model. It has been used world-wide to investigate variations of water, carbon, and energy exchanges between the land surface and the atmosphere. In this study we assessed the applicability of using ORCHIDEE-CAN, a new feature with 3-D CANopy structure (Naudts et al., 2015; Ryder et al., 2016), to simulate surface fluxes measured at tower-based eddy covariance fluxes at the Lien-Hua-Chih experimental watershed in Taiwan. The atmospheric forcing including radiation, air temperature, wind speed, and the dynamics of vertical canopy structure for driving the model were obtained from the observations site. Suitable combinations of default plant function types were examined to meet in-situ observations of soil moisture and leaf area index from 2009 to 2013. The simulated top layer soil moisture was ranging from 0.1 to 0.4 and total leaf area was ranging from 2.2 to 4.4, respectively. A sensitivity analysis was performed to investigate the sensitive of model parameters and model skills of ORCHIDEE-CAN on capturing seasonal variations of surface fluxes. The most sensitive parameters were suggested and calibrated by an automatic data assimilation tool ORCHDAS (ORCHIDEE Data Assimilation Systems; http://orchidas.lsce.ipsl.fr/). Latent heat, sensible heat, and carbon fluxes simulated by the model were compared with long-term observations at the site. ORCHIDEE-CAN by making use of calibrated surface parameters was used to study variations of land-atmosphere interactions on a variety of temporal scale in associations with changes in both land and atmospheric conditions. Ref: Naudts, K., et al.,: A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes, Geoscientific Model Development, 8, 2035-2065, doi:10.5194/gmd-8-2035-2015,2015. Ryder, J., et al. : A multi-layer land surface energy budget model for implicit coupling with global atmospheric simulations, Geoscientific Model Development, 9, 223-245, doi:10.5194/gmd-9-223-2016, 2016.

The Sensitivity of Tropical Squall Lines (GATE and TOGA COARE) to Surface Fluxes: Cloud Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Wang, Yansen; Tao, Wei-Kuo; Simpson, Joanne; Lang, Stephen

1999-01-01

Two tropical squall lines from TOGA COARE and GATE were simulated using a two-dimensional cloud-resolving model to examine the impact of surface fluxes on tropical squall line development and associated precipitation processes. The important question of how CAPE in clear and cloudy areas is maintained in the tropics is also investigated. Although the cloud structure and precipitation intensity are different between the TOGA COARE and GATE squall line cases, the effects of the surface fluxes on the amount of rainfall and on the cloud development processes are quite similar. The simulated total surface rainfall amount in the runs without surface fluxes is about 67% of the rainfall simulated with surface fluxes. The area where surface fluxes originated was categorized into clear and cloudy regions according to whether there was cloud in the vertical column. The model results indicated that the surface fluxes from the large clear air environment are the dominant moisture source for tropical squall line development even though the surface fluxes in the cloud region display a large peak. The high-energy air from the boundary layer in the clear area is what feeds the convection while the CAPE is removed by the convection. The surface rainfall was only reduced 8 to 9% percent in the simulations without surface fluxes in the cloud region. Trajectory and water budget analysis also indicated that most moisture (92%) was from the boundary layer of the clear air environment.

Lunar surface: Changes in 31 months and micrometeoroid flux

NASA Technical Reports Server (NTRS)

Jaffe, L. D.

1972-01-01

A preliminary comparison of Surveyor 3 and Apollo 12 photographs of areas disturbed by the Surveyor is described. About 60 Surveyor pictures taken in April and May 1967 and 20 Apollo photographs including stereo pairs were examined in detail. Only one definite change in the surface, other than those produced by astronauts, was noted. This is a particle about 2 mm in diameter which appears in the Apollo photographs of a Surveyor footpad imprint but which does not appear in the Surveyor photographs. The walls made by Surveyor footpads and surface sampler were still in place, and surface areas darkened by ejected fines during the Surveyor landing still appeared dark. The absence of detectable craters in the footpad imprint implies a very low micrometeorite flux on the lunar surface.

Surface energy fluxes and their representation in CMIP5 models

NASA Astrophysics Data System (ADS)

Wild, M.

2016-12-01

Energy fluxes at the Earth surface play a key role in the determination of surface climate and in the coupling of atmosphere, land and ocean components. Unlike their counterparts at the top of atmosphere (TOA), surface fluxes cannot be directly measured from satellites, but have to be inferred from the space-born observations using additional models to account for atmospheric perturbations, or from the limited number of surface observations. Uncertainties in the energy fluxes at the surface have therefore traditionally been larger than at the TOA, and have limited our knowledge on the distribution of the energy flows within the climate system. Accordingly, current climate models still largely differ in their representation of surface and atmospheric energy fluxes. Since the mid-1990s, accurate flux measurements became increasingly available from surface networks such as BSRN, which allow to better constrain the surface energy fluxes. There is, however, still a lack of flux measurements particularly over oceans. Further, the larger-scale representativeness of the station records needs to be assessed to judge their suitability as anchor sites for gridded flux products inferred from satellites, reanalyses and climate models. In addition, historic records need to be carefully quality-checked and homogeneized. In parallel, satellite-derived products of surface fluxes profit from the great advancement in space-born observations since the turn of the millennium, and from improved validation capabilities with surface observations. Ultimately, it is the combination of surface and space-born observations, reanalyses and modeling approaches that will advance our knowledge on the distribution of the surface energy fluxes. Uncertainties remain in the determination of surface albedo, skin temperatures and the partitioning of surface net radiation into the sensible and latent heat. Climate models over generations up to present day (CMIP5) tend to overestimate the downward shortwave and underestimate the downward longwave radiation. A challenge also remains the consistent representation of the global energy and water cycles. Yet it is shown that those climate models with a realistic surface radiation balance also simulate global precipitation amounts within the uncertainty range of observational estimates.

The Global Energy Balance Archive (GEBA): A database for the worldwide measured surface energy fluxes

NASA Astrophysics Data System (ADS)

Wild, Martin; Ohmura, Atsumu; Schär, Christoph; Müller, Guido; Hakuba, Maria Z.; Mystakidis, Stefanos; Arsenovic, Pavle; Sanchez-Lorenzo, Arturo

2017-02-01

The Global Energy Balance Archive (GEBA) is a database for the worldwide measured energy fluxes at the Earth's surface. GEBA is maintained at ETH Zurich (Switzerland) and has been founded in the 1980s by Prof. Atsumu Ohmura. It has continuously been updated and currently contains around 2500 stations with 500`000 monthly mean entries of various surface energy balance components. Many of the records extend over several decades. The most widely measured quantity available in GEBA is the solar radiation incident at the Earth's surface ("global radiation"). The data sources include, in addition to the World Radiation Data Centre (WRDC) in St. Petersburg, data reports from National Weather Services, data from different research networks (BSRN, ARM, SURFRAD), data published in peer-reviewed publications and data obtained through personal communications. Different quality checks are applied to check for gross errors in the dataset. GEBA is used in various research applications, such as for the quantification of the global energy balance and its spatiotemporal variation, or for the estimation of long-term trends in the surface fluxes, which enabled the detection of multi-decadal variations in surface solar radiation, known as "global dimming" and "brightening". GEBA is further extensively used for the evaluation of climate models and satellite-derived surface flux products. On a more applied level, GEBA provides the basis for engineering applications in the context of solar power generation, water management, agricultural production and tourism. GEBA is publicly accessible over the internet via www.geba.ethz.ch.

Decomposing Shortwave Top-of-Atmosphere Radiative Flux Variability in Terms of Surface and Atmospheric Contributions Using CERES Observations

NASA Astrophysics Data System (ADS)

Loeb, N. G.; Wong, T.; Wang, H.

2017-12-01

Earth's climate is determined by the exchange of radiant energy between the Sun, Earth and space. The absorbed solar radiation (ASR) fuels the climate system, providing the energy required for atmospheric and oceanic motions, while the system cools by emitting outgoing longwave (LW) radiation to space. A central objective of the Clouds and the Earth's Radiant Energy System (CERES) is to produce a long-term global climate data record of Earth's radiation budget along with the associated atmospheric and surface properties that influence it. CERES data products utilize a number of data sources, including broadband radiometers measuring incoming and reflected solar radiation and OLR, polar orbiting and geostationary spectral imagers, meteorological, aerosol and ozone assimilation data, and snow/sea-ice maps based on microwave radiometer data. Here we use simple diagnostic model of Earth's albedo and CERES Energy Balanced and Filled (EBAF) Ed4.0 data for March 2000-February 2016 to quantify interannual variations in SW TOA flux associated with surface albedo and atmospheric reflectance and transmittance variations. Surface albedo variations account for <0.5% of the total SW TOA flux variance over the tropics and 4% globally. Variations in atmospheric reflectance and transmittance account for virtually all of the total SW TOA flux variance over the tropics and only 81% globally. The remaining 15% of the global SW TOA flux variance is explained by the co-variance of surface albedo and atmospheric reflectance/transmittance. Equatorward of 60-degree latitude, the atmospheric contribution exceeds that of the surface by at least an order-of-magnitude. In contrast, the surface and atmospheric variations contribute equally poleward of 60S and surface variations account for twice as much as the atmosphere poleward of 60N. However, as much as 40% of the total SW TOA flux variance poleward of 60N is explained by the covariance of surface albedo and atmospheric reflectance/transmittance, highlighting the tight coupling between sea-ice concentration and cloud properties over the Arctic Ocean.

Simulating the effects of fire disturbance and vegetation recovery on boreal ecosystem carbon fluxes

NASA Astrophysics Data System (ADS)

Yi, Y.; Kimball, J. S.; Jones, L. A.; Zhao, M.

2011-12-01

Fire related disturbance and subsequent vegetation recovery has a major influence on carbon storage and land-atmosphere CO2 fluxes in boreal ecosystems. We applied a synthetic approach combining tower eddy covariance flux measurements, satellite remote sensing and model reanalysis surface meteorology within a terrestrial carbon model framework to estimate fire disturbance and recovery effects on boreal ecosystem carbon fluxes including gross primary production (GPP), ecosystem respiration and net CO2 exchange (NEE). A disturbance index based on MODIS land surface temperature and NDVI was found to coincide with vegetation recovery status inferred from tower chronosequence sites. An empirical algorithm was developed to track ecosystem recovery status based on the disturbance index and used to nudge modeled net primary production (NPP) and surface soil organic carbon stocks from baseline steady-state conditions. The simulations were conducted using a satellite based terrestrial carbon flux model driven by MODIS NDVI and MERRA reanalysis daily surface meteorology inputs. The MODIS (MCD45) burned area product was then applied for mapping recent (post 2000) regional disturbance history, and used with the disturbance index to define vegetation disturbance and recovery status. The model was then applied to estimate regional patterns and temporal changes in terrestrial carbon fluxes across the entire northern boreal forest and tundra domain. A sensitivity analysis was conducted to assess the relative importance of fire disturbance and recovery on regional carbon fluxes relative to assumed steady-state conditions. The explicit representation of disturbance and recovery effects produces more accurate NEE predictions than the baseline steady-state simulations and reduces uncertainty regarding the purported missing carbon sink in the high latitudes.

The effects of sea spray and atmosphere-wave coupling on air-sea exchange during a tropical cyclone

NASA Astrophysics Data System (ADS)

Garg, Nikhil; Kwee Ng, Eddie Yin; Narasimalu, Srikanth

2018-04-01

The study investigates the role of the air-sea interface using numerical simulations of Hurricane Arthur (2014) in the Atlantic. More specifically, the present study aims to discern the role ocean surface waves and sea spray play in modulating the intensity and structure of a tropical cyclone (TC). To investigate the effects of ocean surface waves and sea spray, numerical simulations were carried out using a coupled atmosphere-wave model, whereby a sea spray microphysical model was incorporated within the coupled model. Furthermore, this study also explores how sea spray generation can be modelled using wave energy dissipation due to whitecaps; whitecaps are considered as the primary mode of spray droplets generation at hurricane intensity wind speeds. Three different numerical simulations including the sea- state-dependent momentum flux, the sea-spray-mediated heat flux, and a combination of the former two processes with the sea-spray-mediated momentum flux were conducted. The foregoing numerical simulations were evaluated against the National Data Buoy Center (NDBC) buoy and satellite altimeter measurements as well as a control simulation using an uncoupled atmosphere model. The results indicate that the model simulations were able to capture the storm track and intensity: the surface wave coupling results in a stronger TC. Moreover, it is also noted that when only spray-mediated heat fluxes are applied in conjunction with the sea-state-dependent momentum flux, they result in a slightly weaker TC, albeit stronger compared to the control simulation. However, when a spray-mediated momentum flux is applied together with spray heat fluxes, it results in a comparably stronger TC. The results presented here allude to the role surface friction plays in the intensification of a TC.

Effect of canopy and topography induced wakes on land-atmosphere fluxes of momentum and scalars

NASA Astrophysics Data System (ADS)

Markfort, C. D.; Zhang, W.; Porté-Agel, F.; Stefan, H. G.

2012-04-01

Wakes shed from natural and anthropogenic landscape features affect land-atmosphere fluxes of momentum and scalars, including water vapor and trace gases (e.g. CO2). Canopies and bluff bodies, such as forests, buildings and topography, cause boundary layer flow separation, and lead to a break down of standard Monin-Obukhov similarity relationships in the atmospheric boundary layer (ABL). Wakes generated by these land surface features persist for significant distances (>100 typical length scales) and affect a large fraction of the Earth's terrestrial surface. This effect is currently not accounted for in land-atmosphere models, and little is known about how heterogeneity of wake-generating features affect land surface fluxes. Additionally flux measurements, made in wake-affected regions, do not satisfy the homogeneous flow requirements for the standard eddy correlation (EC) method. This phenomenon, often referred to as wind sheltering, has been shown to affect momentum and kinetic energy fluxes at the lake-atmosphere interface (Markfort et al. 2010). This presentation will highlight results from controlled wind tunnel experiments of neutral and thermally stratified boundary layers, using particle image velocimetry (PIV) and custom x-wire/cold-wire anemometry, to understand how the physical structure of upstream bluff bodies and porous canopies as well as how thermal stability affect the flow separation zone, boundary layer recovery and surface fluxes. We have found that there is a nonlinear relationship between canopy length/porosity and flow separation downwind of a canopy to clearing transition. Results will provide the basis for new parameterizations to account for wake effects on land-atmosphere fluxes and corrections for the EC measurements over open fields, lakes, and wetlands. Key words: Atmospheric boundary layer; Wakes; Stratification; Land-Atmosphere Parameterization; Canopy

An ocean large-eddy simulation of Langmuir circulations and convection in the surface mixed layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skyllingstad, E.D.; Denbo, D.W.

Numerical experiments were performed using a three-dimensional large-eddy simulation model of the ocean surface mixed layer that includes the Craik-Leibovich vortex force to parameterize the interaction of surface waves with mean currents. Results from the experiments show that the vortex force generates Langmuir circulations that can dominate vertical mixing. The simulated vertical velocity fields show linear, small-scale, coherent structures near the surface that extend downwind across the model domain. In the interior of the mixed layer, scales of motion increase to eddy sizes that are roughly equivalent to the mixed-layer depth. Cases with the vortex force have stronger circulations nearmore » the surface in contrast to cases with only heat flux and wind stress, particularly when the heat flux is positive. Calculations of the velocity variance and turbulence dissipation rates for cases with and without the vortex force, surface cooling, and wind stress indicate that wave-current interactions are a dominant mixing process in the upper mixed layer. Heat flux calculations show that the entrainment rate at the mixed-layer base can be up to two times greater when the vortex force is included. In a case with reduced wind stress, turbulence dissipation rates remained high near the surface because of the vortex force interaction with preexisting inertial currents. In deep mixed layers ({approximately}250 m) the simulations show that Langmuir circulations can vertically transport water 145 m during conditions of surface heating. Observations of turbulence dissipation rates and the vertical temperature structure support the model results. 42 refs., 20 figs., 21 tabs.« less

CO2 CH4 flux Air temperature Soil temperature and Soil moisture, Barrow, Alaska 2013 ver. 1

DOE Data Explorer

Margaret Torn

2015-01-14

This dataset consists of field measurements of CO2 and CH4 flux, as well as soil properties made during 2013 in Areas A-D of Intensive Site 1 at the Next-Generation Ecosystem Experiments (NGEE) Arctic site near Barrow, Alaska. Included are i) measurements of CO2 and CH4 flux made from June to September (ii) Calculation of corresponding Gross Primary Productivity (GPP) and CH4 exchange (transparent minus opaque) between atmosphere and the ecosystem (ii) Measurements of Los Gatos Research (LGR) chamber air temperature made from June to September (ii) measurements of surface layer depth, type of surface layer, soil temperature and soil moisture from June to September.

Radiation Climatology of the Greenland Ice Sheet Derived from Greenland Climate Network Data

NASA Technical Reports Server (NTRS)

Steffen, Konrad; Box, Jason

2003-01-01

The magnitude of shortwave and longwave dative fluxes are critical to surface energy balance variations over the Greenland ice sheet, affecting many aspects of its climate, including melt rates, the nature of low-level temperature inversions, the katabatic wind regime and buoyant stability of the atmosphere. Nevertheless, reliable measurements of the radiative fluxes over the ice sheet are few in number, and have been of limited duration and areal distribution (e.g. Ambach, 1960; 1963, Konzelmann et al., 1994, Harding et al., 1995, Van den Broeke, 1996). Hourly GC-Net radiation flux measurements spanning 1995-2001 period have been used to produce a monthly dataset of surface radiation balance components. The measurements are distributed widely across Greenland and incorporate multiple sensors

The impact of land-surface wetness heterogeneity on mesoscale heat fluxes

NASA Technical Reports Server (NTRS)

Chen, Fei; Avissar, Roni

1994-01-01

Vertical heat fluxes associated with mesoscale circulations generated by land-surface wetness discontinuities are often stronger than turbulent fluxes, especially in the upper part of the atmospheric planetary boundary layer. As a result, they contribute significantly to the subgrid-scale fluxes in large-scale atmospheric models. Yet they are not considered in these models. To provide some insights into the possible parameterization of these fluxes in large-scale models, a state-of-the-art mesoscale numerical model was used to investigate the relationships between mesoscale heat fluxes and atmospheric and land-surface characteristics that play a key role in the generation of mesoscale circulations. The distribution of land-surface wetness, the wavenumber and the wavelength of the land-surface discontinuities, and the large-scale wind speed have a significant impact on the mesoscale heat fluxes. Empirical functions were derived to characterize the relationships between mesoscale heat fluxes and the spatial distribution of land-surface wetness. The strongest mesoscale heat fluxes were obtained for a wavelength of forcing corresponding approximately to the local Rossby deformation radius. The mesoscale heat fluxes are weakened by large-scale background winds but remain significant even with moderate winds.

Evaluation of an urban canopy model in a tropical city: the role of tree evapotranspiration

NASA Astrophysics Data System (ADS)

Liu, Xuan; Li, Xian-Xiang; Harshan, Suraj; Roth, Matthias; Velasco, Erik

2017-09-01

A single layer urban canopy model (SLUCM) with enhanced hydrologic processes, is evaluated in a tropical city, Singapore. The evaluation was performed using an 11 month offline simulation with the coupled Noah land surface model/SLUCM over a compact low-rise residential area. Various hydrological processes are considered, including anthropogenic latent heat release, and evaporation from impervious urban facets. Results show that the prediction of energy fluxes, in particular latent heat flux, is improved when these processes were included. However, the simulated latent heat flux is still underestimated by ∼40%. Considering Singapore’s high green cover ratio, the tree evapotranspiration process is introduced into the model, which significantly improves the simulated latent heat flux. In particular, the systematic error of the model is greatly reduced, and becomes lower than the unsystematic error in some seasons. The effect of tree evapotranspiration on the urban surface energy balance is further demonstrated during an unusual dry spell. The present study demonstrates that even at sites with relatively low (11%) tree coverage, ignoring evapotranspiration from trees may cause serious underestimation of the latent heat flux and atmospheric humidity. The improved model is also transferable to other tropical or temperate regions to study the impact of tree evapotranspiration on urban climate.

ON POLAR MAGNETIC FIELD REVERSAL AND SURFACE FLUX TRANSPORT DURING SOLAR CYCLE 24

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Xudong; Todd Hoeksema, J.; Liu, Yang

As each solar cycle progresses, remnant magnetic flux from active regions (ARs) migrates poleward to cancel the old-cycle polar field. We describe this polarity reversal process during Cycle 24 using four years (2010.33-2014.33) of line-of-sight magnetic field measurements from the Helioseismic and Magnetic Imager. The total flux associated with ARs reached maximum in the north in 2011, more than two years earlier than the south; the maximum is significantly weaker than Cycle 23. The process of polar field reversal is relatively slow, north-south asymmetric, and episodic. We estimate that the global axial dipole changed sign in 2013 October; the northernmore » and southern polar fields (mean above 60° latitude) reversed in 2012 November and 2014 March, respectively, about 16 months apart. Notably, the poleward surges of flux in each hemisphere alternated in polarity, giving rise to multiple reversals in the north. We show that the surges of the trailing sunspot polarity tend to correspond to normal mean AR tilt, higher total AR flux, or slower mid-latitude near-surface meridional flow, while exceptions occur during low magnetic activity. In particular, the AR flux and the mid-latitude poleward flow speed exhibit a clear anti-correlation. We discuss how these features can be explained in a surface flux transport process that includes a field-dependent converging flow toward the ARs, a characteristic that may contribute to solar cycle variability.« less

Using model analyses and surface-atmosphere exchange measurements from the Howland AmeriFlux Site in Maine, USA, to improve understanding of forest ecosystem C cycling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hollinger, David Y.; Davidson, Eric A.; Richardson, Andrew D.

2013-03-25

Summary of research carried out under Interagency Agreement DE-AI02-07ER64355 with the USDA Forest Service at the Howland Forest AmeriFlux site in central Maine. Includes a list of publications resulting in part or whole from this support.

EUV mirror based absolute incident flux detector

DOEpatents

Berger, Kurt W.

2004-03-23

A device for the in-situ monitoring of EUV radiation flux includes an integrated reflective multilayer stack. This device operates on the principle that a finite amount of in-band EUV radiation is transmitted through the entire multilayer stack. This device offers improvements over existing vacuum photo-detector devices since its calibration does not change with surface contamination.

Gas and aerosol fluxes. [emphasizing sulfur, nitrogen, and carbon

NASA Technical Reports Server (NTRS)

Martens, C. S.

1980-01-01

The development of remote sensing techniques to address the global need for accurate distribution and flux determinations of both man made and natural materials which affect the chemical composition of the atmosphere, the heat budget of the Earth, and the depletion, of stratospheric ozone is considered. Specifically, trace gas fluxes, sea salt aerosol production, and the effect of sea surface microlayer on gas and aerosol fluxes are examined. Volatile sulfur, carbon, nitrogen, and halocarbon compounds are discussed including a statement of the problem associated with each compound or group of compounds, a brief summary of current understanding, and suggestions for needed research.

Global Intercomparison of 12 Land Surface Heat Flux Estimates

NASA Technical Reports Server (NTRS)

Jimenez, C.; Prigent, C.; Mueller, B.; Seneviratne, S. I.; McCabe, M. F.; Wood, E. F.; Rossow, W. B.; Balsamo, G.; Betts, A. K.; Dirmeyer, P. A.;

The distribution of ion orbit loss fluxes of ions and energy from the plasma edge across the last closed flux surface into the scrape-off layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stacey, Weston M.; Schumann, Matthew T.

A more detailed calculation strategy for the evaluation of ion orbit loss of thermalized plasma ions in the edge of tokamaks is presented. In both this and previous papers, the direct loss of particles from internal flux surfaces is calculated from the conservation of canonical angular momentum, energy, and magnetic moment. The previous result that almost all of the ion energy and particle fluxes crossing the last closed flux surface are in the form of ion orbit fluxes is confirmed, and the new result that the distributions of these fluxes crossing the last closed flux surface into the scrape-off layermore » are very strongly peaked about the outboard midplane is demonstrated. Previous results of a preferential loss of counter current particles leading to a co-current intrinsic rotation peaking just inside of the last closed flux surface are confirmed. Various physical details are discussed.« less

SW radiative effect of aerosol in GRAPES_GFS

NASA Astrophysics Data System (ADS)

Chen, Qiying

2017-04-01

The aerosol particles can scatter and absorb solar radiation, and so change the shortwave radiation absorbed by the atmosphere, reached the surface and that reflected back to outer space at TOA. Since this process doesn't interact with other processes, it is called direct radiation effect. The clear sky downward SW and net SW fluxes at the surface in GRAPES_GFS of China Meteorological Administration are overestimated in Northern multitudes and Tropics. The main source of these errors is the absence of aerosol SW effect in GRAPES_GFS. The climatic aerosol mass concentration data, which include 13 kinds of aerosol and their 14 SW bands optical properties are considered in GRAPES_GFS. The calculated total optical depth, single scatter albedo and asymmetry factor are used as the input to radiation scheme. Compared with the satellite observation from MISER, the calculated total optical depth is in good consistent. The seasonal experiments show that, the summer averaged clear sky radiation fluxes at the surface are improved after including the SW effect of aerosol. The biases in the clear sky downward SW and net SW fluxes at the surface in Northern multitudes and Tropic reduced obviously. Furthermore, the weather forecast experiments also show that the skill scores in Northern hemisphere and East Asia also become better.

Evaluation of surface layer flux parameterizations using in-situ observations

NASA Astrophysics Data System (ADS)

Katz, Jeremy; Zhu, Ping

2017-09-01

Appropriate calculation of surface turbulent fluxes between the atmosphere and the underlying ocean/land surface is one of the major challenges in geosciences. In practice, the surface turbulent fluxes are estimated from the mean surface meteorological variables based on the bulk transfer model combined with the Monnin-Obukhov Similarity (MOS) theory. Few studies have been done to examine the extent to which such a flux parameterization can be applied to different weather and surface conditions. A novel validation method is developed in this study to evaluate the surface flux parameterization using in-situ observations collected at a station off the coast of Gulf of Mexico. The main findings are: (a) the theoretical prediction that uses MOS theory does not match well with those directly computed from the observations. (b) The largest spread in exchange coefficients is shown in strong stable conditions with calm winds. (c) Large turbulent eddies, which depend strongly on the mean flow pattern and surface conditions, tend to break the constant flux assumption in the surface layer.

The hydrological cycle at European Fluxnet sites: modeling seasonal water and energy budgets at local scale.

NASA Astrophysics Data System (ADS)

Stockli, R.; Vidale, P. L.

2003-04-01

The importance of correctly including land surface processes in climate models has been increasingly recognized in the past years. Even on seasonal to interannual time scales land surface - atmosphere feedbacks can play a substantial role in determining the state of the near-surface climate. The availability of soil moisture for both runoff and evapotranspiration is dependent on biophysical processes occuring in plants and in the soil acting on a wide time-scale from minutes to years. Fluxnet site measurements in various climatic zones are used to drive three generations of LSM's (land surface models) in order to assess the level of complexity needed to represent vegetation processes at the local scale. The three models were the Bucket model (Manabe 1969), BATS 1E (Dickinson 1984) and SiB 2 (Sellers et al. 1996). Evapotranspiration and runoff processes simulated by these models range from simple one-layer soils and no-vegetation parameterizations to complex multilayer soils, including realistic photosynthesis-stomatal conductance models. The latter is driven by satellite remote sensing land surface parameters inheriting the spatiotemporal evolution of vegetation phenology. In addition a simulation with SiB 2 not only including vertical water fluxes but also lateral soil moisture transfers by downslope flow is conducted for a pre-alpine catchment in Switzerland. Preliminary results are presented and show that - depending on the climatic environment and on the season - a realistic representation of evapotranspiration processes including seasonally and interannually-varying state of vegetation is significantly improving the representation of observed latent and sensible heat fluxes on the local scale. Moreover, the interannual evolution of soil moisture availability and runoff is strongly dependent on the chosen model complexity. Biophysical land surface parameters from satellite allow to represent the seasonal changes in vegetation activity, which has great impact on the yearly budget of transpiration fluxes. For some sites, however, the hydrological cycle is simulated reasonably well even with simple land surface representations.

The NASA/GEWEX Surface Radiation Budget Release 4 Integrated Product: An Assessment of Improvements in Algorithms and Inputs

NASA Astrophysics Data System (ADS)

Stackhouse, P. W., Jr.; Cox, S. J.; Mikovitz, J. C.; Zhang, T.; Gupta, S. K.

2016-12-01

The NASA/GEWEX Surface Radiation Budget (SRB) project produces, validates and analyzes shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. The current release 3.0/3.1 consists of 1x1 degree radiative fluxes (available at gewex-srb.larc.nasa.gov) and is produced using the International Satellite Cloud Climatology Project (ISCCP) DX product for pixel level radiance and cloud information. This ISCCP DX product is subsampled to 30 km. ISCCP is currently recalibrating and reprocessing their entire data series, to be released as the H product series, with its highest resolution at 10km pixel resolution. The nine-fold increase in number of pixels will allow SRB to produce a higher resolution gridded product (e.g. 0.5 degree or higher), as well as the production of pixel-level fluxes. Other key input improvements include a detailed aerosol history using the Max Planck Institute Aerosol Climatology (MAC), temperature and moisture profiles from HIRS, and new topography, surface type, and snow/ice maps. Here we present results for the improved GEWEX Shortwave and Longwave algorithm (GSW and GLW) with new ISCCP data (for at least 5 years, 2005-2009), various other improved input data sets and incorporation of many additional internal SRB model improvements. We assess the radiative fluxes from new SRB products and contrast these at various resolutions. All these fluxes are compared to both surface measurements and to CERES SYN1Deg and EBAF data products for assessment of the effect of improvements. The SRB data produced will be released as part of the Release 4.0 Integrated Product that shares key input and output quantities with other GEWEX global products providing estimates of the Earth's global water and energy cycle (i.e., ISCCP, SeaFlux, LandFlux, NVAP, etc.).

The impact of standard and hard-coded parameters on the hydrologic fluxes in the Noah-MP land surface model

NASA Astrophysics Data System (ADS)

Thober, S.; Cuntz, M.; Mai, J.; Samaniego, L. E.; Clark, M. P.; Branch, O.; Wulfmeyer, V.; Attinger, S.

2016-12-01

Land surface models incorporate a large number of processes, described by physical, chemical and empirical equations. The agility of the models to react to different meteorological conditions is artificially constrained by having hard-coded parameters in their equations. Here we searched for hard-coded parameters in the computer code of the land surface model Noah with multiple process options (Noah-MP) to assess the model's agility during parameter estimation. We found 139 hard-coded values in all Noah-MP process options in addition to the 71 standard parameters. We performed a Sobol' global sensitivity analysis to variations of the standard and hard-coded parameters. The sensitivities of the hydrologic output fluxes latent heat and total runoff, their component fluxes, as well as photosynthesis and sensible heat were evaluated at twelve catchments of the Eastern United States with very different hydro-meteorological regimes. Noah-MP's output fluxes are sensitive to two thirds of its standard parameters. The most sensitive parameter is, however, a hard-coded value in the formulation of soil surface resistance for evaporation, which proved to be oversensitive in other land surface models as well. Latent heat and total runoff show very similar sensitivities towards standard and hard-coded parameters. They are sensitive to both soil and plant parameters, which means that model calibrations of hydrologic or land surface models should take both soil and plant parameters into account. Sensible and latent heat exhibit almost the same sensitivities so that calibration or sensitivity analysis can be performed with either of the two. Photosynthesis has almost the same sensitivities as transpiration, which are different from the sensitivities of latent heat. Including photosynthesis and latent heat in model calibration might therefore be beneficial. Surface runoff is sensitive to almost all hard-coded snow parameters. These sensitivities get, however, diminished in total runoff. It is thus recommended to include the most sensitive hard-coded model parameters that were exposed in this study when calibrating Noah-MP.

Optimization of Modeled Land-Atmosphere Exchanges of Water and Energy in an Isotopically-Enabled Land Surface Model by Bayesian Parameter Calibration

NASA Astrophysics Data System (ADS)

Wong, T. E.; Noone, D. C.; Kleiber, W.

2014-12-01

The single largest uncertainty in climate model energy balance is the surface latent heating over tropical land. Furthermore, the partitioning of the total latent heat flux into contributions from surface evaporation and plant transpiration is of great importance, but notoriously poorly constrained. Resolving these issues will require better exploiting information which lies at the interface between observations and advanced modeling tools, both of which are imperfect. There are remarkably few observations which can constrain these fluxes, placing strict requirements on developing statistical methods to maximize the use of limited information to best improve models. Previous work has demonstrated the power of incorporating stable water isotopes into land surface models for further constraining ecosystem processes. We present results from a stable water isotopically-enabled land surface model (iCLM4), including model experiments partitioning the latent heat flux into contributions from plant transpiration and surface evaporation. It is shown that the partitioning results are sensitive to the parameterization of kinetic fractionation used. We discuss and demonstrate an approach to calibrating select model parameters to observational data in a Bayesian estimation framework, requiring Markov Chain Monte Carlo sampling of the posterior distribution, which is shown to constrain uncertain parameters as well as inform relevant values for operational use. Finally, we discuss the application of the estimation scheme to iCLM4, including entropy as a measure of information content and specific challenges which arise in calibration models with a large number of parameters.

Using Profiles of Water Vapor Flux to Characterize Turbulence in the Convective Boundary Layer

NASA Astrophysics Data System (ADS)

Weber, Kristy Jane

The 2015 Plains Elevated Convection at Night (PECAN) field campaign sought to increase understanding of mechanisms for nocturnal severe weather in the Great Plains of the United States. A collection of instruments from this field campaign, including a water vapor Differential LiDAR (Light Detection Imaging And Ranging) (DIAL) and 449 MHz radar wind profiler were used to measure water vapor flux in regions between 300 m and the convective boundary layer. Methods to properly sample eddies using eddy-covariance were established, where analysis showed that a 90-minute Reynold's averaging period was optimal to sample most eddies. Additionally, a case study was used to demonstrate the additional atmospheric parameters which can be calculated from profiles of water vapor flux, such as the water vapor flux convergence/divergence. Flux footprints calculated at multiple heights within the convective boundary layer also show how a surface based instrument is sampling a completely different source than one taking measurements above 300 m. This result is important, as it shows how measurements above the surface layer will not be expected to match with those taken within a few meters of the surface, especially if average surface features such as land use type and roughness length are significantly different. These calculated water vapor flux profile measurements provide a new tool to analyze boundary layer dynamics during the PECAN field campaign, and their relationships to PECAN's study areas such as mesoscale convective systems (MCSs), nocturnal low-level jets (NLLJs), elevated convective initiation, and the propagation of bores or wavelike features from nocturnal convective systems.

Investigating spatial variability of vertical water fluxes through the streambed in distinctive stream morphologies using temperature and head data

NASA Astrophysics Data System (ADS)

Wang, Liping; Jiang, Weiwei; Song, Jinxi; Dou, Xinyi; Guo, Hongtao; Xu, Shaofeng; Zhang, Guotao; Wen, Ming; Long, Yongqing; Li, Qi

2017-08-01

Investigating the interaction of groundwater and surface water is key to understanding the hyporheic processes. The vertical water fluxes through a streambed were determined using Darcian flux calculations and vertical sediment temperature profiles to assess the pattern and magnitude of groundwater/surface-water interaction in Beiluo River, China. Field measurements were taken in January 2015 at three different stream morphologies including a meander bend, an anabranching channel and a straight stream channel. Despite the differences of flux direction and magnitude, flux directions based on vertical temperature profiles are in good agreement with results from Darcian flux calculations at the anabranching channel, and the Kruskal-Wallis tests show no significant differences between the estimated upward fluxes based on the two methods at each site. Also, the upward fluxes based on the two methods show similar spatial distributions on the streambed, indicating (1) that higher water fluxes at the meander bend occur from the center of the channel towards the erosional bank, (2) that water fluxes at the anabranching channel are higher near the erosional bank and in the center of the channel, and (3) that in the straight channel, higher water fluxes appear from the center of the channel towards the depositional bank. It is noted that higher fluxes generally occur at certain locations with higher streambed vertical hydraulic conductivity ( K v) or where a higher vertical hydraulic gradient is observed. Moreover, differences of grain size, induced by stream morphology and contrasting erosional and depositional conditions, have significant effects on streambed K v and water fluxes.

Elucidating Carbon Exchange at the Regional Scale Via Airborne Eddy Covariance Flux Measurements

NASA Astrophysics Data System (ADS)

Hannun, R. A.; Wolfe, G. M.; Kawa, S. R.; Newman, P. A.; Hanisco, T. F.; Diskin, G. S.; DiGangi, J. P.; Nowak, J. B.; Barrick, J. D. W.; Thornhill, K. L., II; Noormets, A.; Vargas, R.; Clark, K. L.; Kustas, W. P.

2017-12-01

Direct flux observations from aircraft provide a unique tool for probing greenhouse gas (GHG) sources and sinks on a regional scale. Airborne eddy covariance, which relies on high-frequency, simultaneous measurements of fluctuations in concentration and vertical wind speed, is a robust method for quantifying surface-atmosphere exchange. We have assembled and flown an instrument payload onboard the NASA C-23 Sherpa aircraft capable of measuring CO2, CH4, H2O, and heat fluxes. Flights for the Carbon Airborne Flux Experiment (CARAFE) took place during September 2016 and May 2017 based out of Wallops Flight Facility, VA. Flight tracks covered a variety of ecosystems and land-use types in the Mid-Atlantic, including forests, croplands, and wetlands. Carbon fluxes are derived using eddy covariance and wavelet analysis. Our results show a strong drawdown of CO2 and near-zero CH4 emissions from crops and dry-land forest, but seasonally strong CH4 flux from wetland forest. CARAFE flux data will also be compared with observations from several flux towers along the flight path to complement the airborne measurements. We will further assess the effects of land surface type and seasonal variability in carbon exchange. Regional-scale flux observations from CARAFE supply a useful constraint for improving top-down and bottom up estimates of carbon sources and sinks.

Assessment of clear sky radiative fluxes in CMIP5 climate models using surface observations from BSRN

NASA Astrophysics Data System (ADS)

Wild, M.; Hakuba, M. Z.; Folini, D.; Ott, P.; Long, C. N.

2017-12-01

Clear sky fluxes in the latest generation of Global Climate Models (GCM) from CMIP5 still vary largely particularly at the Earth's surface, covering in their global means a range of 16 and 24 Wm-2 in the surface downward clear sky shortwave (SW) and longwave radiation, respectively. We assess these fluxes with monthly clear sky reference climatologies derived from more than 40 Baseline Surface Radiation Network (BSRN) sites based on Long and Ackermann (2000) and Hakuba et al. (2015). The comparison is complicated by the fact that the monthly SW clear sky BSRN reference climatologies are inferred from measurements under true cloud-free conditions, whereas the GCM clear sky fluxes are calculated continuously at every timestep solely by removing the clouds, yet otherwise keeping the prevailing atmospheric composition (e.g. water vapor, temperature, aerosols) during the cloudy conditions. This induces the risk of biases in the GCMs just due to the additional sampling of clear sky fluxes calculated under atmospheric conditions representative for cloudy situations. Thereby, a wet bias may be expected in the GCMs compared to the observational references, which may induce spurious low biases in the downward clear sky SW fluxes. To estimate the magnitude of these spurious biases in the available monthly mean fields from 40 CMIP5 models, we used their respective multi-century control runs, and searched therein for each month and each BSRN station the month with the lowest cloud cover. The deviations of the clear sky fluxes in this month from their long-term means have then be used as indicators of the magnitude of the abovementioned sampling biases and as correction factors for an appropriate comparison with the BSRN climatologies, individually applied for each model and BSRN site. The overall correction is on the order of 2 Wm-2. This revises our best estimate for the global mean surface downward SW clear sky radiation, previously at 249 Wm-2 infered from the GCM clear sky flux fields and their biases compared to the BSRN climatologies, now to 247 Wm-2 including this additional correction. 34 out of 40 CMIP5 GCMs exceed this reference value. With a global mean surface albedo of 13 % and net TOA SW clear sky flux of 287 Wm-2 from CERES-EBAF this results in a global mean clear sky surface and atmospheric SW absorption of 214 and 73 Wm-2, respectively.

Evaluation of Cloud Fraction and Radiative Fluxes in Recent Reanalyses over the Arctic using Surface and Satellite Observations

NASA Astrophysics Data System (ADS)

Zib, B.; Dong, X.; Xi, B.; Kennedy, A. D.

2010-12-01

Reanalysis datasets can be an essential tool for investigating numerous climate parameters, especially in data-sparse regions like the Arctic. Where long-term continuous data is limited, reanalyses offer a resource for the recognition and analysis of change in a sensitive and complex coupled Arctic climate system. A study focused on the evaluation and intercomparison of four relatively new global reanalysis datasets will be conducted. The four new reanalyses being investigated include: (i) NASA-MERRA, (ii) NCEP-CFS, (iii) NOAA-20CR, and (iv) NCEP-DOE II. In this study, the cloud fraction and TOA radiative fluxes simulated from four reanalyses over the entire Arctic region will be compared with those derived from NASA MODIS and CERES sensors during the period 2000-2008. The surface radiative fluxes derived in each reanalysis will also be compared and validated by the BSRN surface observations during the period 1994-2008. The high latitude BSRN sites used in this study are Barrow, Alaska (BAR) and Ny Alesund, Svalbard, Norway (NYA). BSRN offers high time resolution solar and atmospheric radiation measurements from high accuracy instruments that provide a baseline for validating reanalysis estimates of surface radiation. In addition to downwelling radiation fluxes, cloud fraction from the reanalyses will also be evaluated by the Vaisala ceilometer derived cloud fraction at the Barrow, AK site. The ultimate goal of this study is to quantitatively estimate the uncertainties or biases of cloud fraction and TOA and surface radiative fluxes derived from four different recent reanalyses using highly qualified long-term surface and satellite observations as ground truth over the Arctic region.

Estimation of Surface Heat Flux and Surface Temperature during Inverse Heat Conduction under Varying Spray Parameters and Sample Initial Temperature

PubMed Central

Aamir, Muhammad; Liao, Qiang; Zhu, Xun; Aqeel-ur-Rehman; Wang, Hong

2014-01-01

An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27 mm and thickness (mm) 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2 MPa to 1.8 MPa, while sample initial temperature varied from 600°C to 900°C. Beck's sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF) within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024 MW/m2 was estimated for a thickness of 8.5 mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8 MPa. PMID:24977219

Instantaneous and daily values of the surface energy balance over agricultural fields using remote sensing and a reference field in an arid environment

USGS Publications Warehouse

Kustas, William P.; Moran, M.S.; Jackson, R. D.; Gay, L.W.; Duell, L.F.W.; Kunkel, K.E.; Matthias, A.D.

1990-01-01

Remotely sensed surface temperature and reflectance in the visible and near infrared wavebands along with ancilliary meteorological data provide the capability of computing three of the four surface energy balance components (i.e., net radiation, soil heat flux, and sensible heat flux) at different spatial and temporal scales. As a result, under nonadvective conditions, this enables the estimation of the remaining term (i.e., the latent heat flux). One of the practical applications with this approach is to produce evapotranspiration (ET) maps for agricultural regions which consist of an array of fields containing different crops at varying stages of growth and soil moisture conditions. Such a situation exists in the semiarid southwest at the University of Arizona Maricopa Agricultural Center, south of Phoenix. For one day (14 June 1987), surface temperature and reflectance measurements from an aircraft 150 m above ground level (agl) were acquired over fields from zero to nearly full cover at four times between 1000 MST and 1130 MST. The diurnal pattern of the surface energy balance was measured over four fields, which included alfalfa at 60% cover, furrowed cotton at 20% and 30% cover, and partially plowed what stubble. Instantaneous and daily values of ET were estimated for a representative area around each flux site with an energy balance model that relies on a reference ET. This reference value was determined with remotely sensed data and several meteorological inputs. The reference ET was adjusted to account for the different surface conditions in the other fields using only remotely sensed variables. A comparison with the flux measurements suggests the model has difficulties with partial canopy conditions, especially related to the estimation of the sensible heat flux. The resulting errors for instantaneous ET were on the order of 100 W m-2 and for daily values of order 2 mm day-1. These findings suggest future research should involve development of methods to account for the variability of meteorological parameters brought about by changes in surface conditions and improvements in the modeling of sensible heat transfer across the surface-atmosphere interface for partial canopy conditions using remote sensing information. ?? 1990.

CERES Monthly Gridded Single Satellite TOA and Surfaces/Clouds (SFC) data in HDF (CER_SFC_Terra-FM2-MODIS_Edition2A)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

The Monthly Gridded TOA/Surface Fluxes and Clouds (SFC) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SFC is also produced for combinations of scanner instruments. All instantaneous shortwave, longwave, and window fluxes at the Top-of-the-Atmosphere (TOA) and surface from the CERES SSF product for a month are sorted by 1-degree spatial regions and by the local hour of observation. The mean of the instantaneous fluxes for a given region-hour bin is determined and recorded on the SFC along with other flux statistics and scene information. These average fluxes are given for both clear-sky and total-sky scenes. The regional cloud properties are column averaged and are included on the SFC. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop_Date=2003-12-31] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=100] [Data_Resolution: Latitude_Resolution=1 degree; Longitude_Resolution=1 degree; Horizontal_Resolution_Range=100 km - < 250 km or approximately 1 degree - < 2.5 degrees; Temporal_Resolution=1 hour; Temporal_Resolution_Range=Hourly - < Daily].

CERES Monthly Gridded Single Satellite TOA and Surfaces/Clouds (SFC) data in HDF (CER_SFC_Terra-FM2-MODIS_Edition2C)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

The Monthly Gridded TOA/Surface Fluxes and Clouds (SFC) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SFC is also produced for combinations of scanner instruments. All instantaneous shortwave, longwave, and window fluxes at the Top-of-the-Atmosphere (TOA) and surface from the CERES SSF product for a month are sorted by 1-degree spatial regions and by the local hour of observation. The mean of the instantaneous fluxes for a given region-hour bin is determined and recorded on the SFC along with other flux statistics and scene information. These average fluxes are given for both clear-sky and total-sky scenes. The regional cloud properties are column averaged and are included on the SFC. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop_Date=2005-12-31] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=100] [Data_Resolution: Latitude_Resolution=1 degree; Longitude_Resolution=1 degree; Horizontal_Resolution_Range=100 km - < 250 km or approximately 1 degree - < 2.5 degrees; Temporal_Resolution=1 hour; Temporal_Resolution_Range=Hourly - < Daily].

CERES Monthly Gridded Single Satellite TOA and Surfaces/Clouds (SFC) data in HDF (CER_SFC_Terra-FM1-MODIS_Edition2B)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

The Monthly Gridded TOA/Surface Fluxes and Clouds (SFC) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SFC is also produced for combinations of scanner instruments. All instantaneous shortwave, longwave, and window fluxes at the Top-of-the-Atmosphere (TOA) and surface from the CERES SSF product for a month are sorted by 1-degree spatial regions and by the local hour of observation. The mean of the instantaneous fluxes for a given region-hour bin is determined and recorded on the SFC along with other flux statistics and scene information. These average fluxes are given for both clear-sky and total-sky scenes. The regional cloud properties are column averaged and are included on the SFC. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop_Date=2003-10-31] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=100] [Data_Resolution: Latitude_Resolution=1 degree; Longitude_Resolution=1 degree; Horizontal_Resolution_Range=100 km - < 250 km or approximately 1 degree - < 2.5 degrees; Temporal_Resolution=1 hour; Temporal_Resolution_Range=Hourly - < Daily].

CERES Monthly Gridded Single Satellite TOA and Surfaces/Clouds (SFC) data in HDF (CER_SFC_Aqua-FM3-MODIS_Edition2A)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

The Monthly Gridded TOA/Surface Fluxes and Clouds (SFC) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SFC is also produced for combinations of scanner instruments. All instantaneous shortwave, longwave, and window fluxes at the Top-of-the-Atmosphere (TOA) and surface from the CERES SSF product for a month are sorted by 1-degree spatial regions and by the local hour of observation. The mean of the instantaneous fluxes for a given region-hour bin is determined and recorded on the SFC along with other flux statistics and scene information. These average fluxes are given for both clear-sky and total-sky scenes. The regional cloud properties are column averaged and are included on the SFC. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop_Date=2005-12-31] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=100] [Data_Resolution: Latitude_Resolution=1 degree; Longitude_Resolution=1 degree; Horizontal_Resolution_Range=100 km - < 250 km or approximately 1 degree - < 2.5 degrees; Temporal_Resolution=1 hour; Temporal_Resolution_Range=Hourly - < Daily].

Simulating carbon, water and energy fluxes of a rainforest and an oil palm plantation using the Community Land Model (CLM4.5)

NASA Astrophysics Data System (ADS)

Fan, Yuanchao; Bernoux, Martial; Roupsard, Olivier; Panferov, Oleg; Le Maire, Guerric; Tölle, Merja; Knohl, Alexander

2014-05-01

Deforestation and forest degradation driven by the expansion of oil palm (Elaeis guineensis) plantations has become the major source of GHG emission in Indonesia. Changes of land surface properties (e.g. vegetation composition, soil property, surface albedo) associated with rainforest to oil palm conversion might alter the patterns of land-atmosphere energy, water and carbon cycles and therefore affect local or regional climate. Land surface modeling has been widely used to characterize the two-way interactions between climate and human disturbances on land surface. The Community Land Model (CLM) is a third-generation land model that simulates a wide range of biogeophysical and biogeochemical processes. This project utilizes the land-cover/land-use change (LCLUC) capability of the latest CLM versions 4/4.5 to characterize quantitatively how anthropogenic land surface dynamics in Indonesia affect land-atmosphere carbon, water and energy fluxes. Before simulating land use changes, the first objective is to parameterize and validate the CLM model at local rainforest and oil palm plantation sites through separate point simulations. This entails creation and parameterization of a new plant functional type (PFT) for oil palm, as well as sensitivity analysis and adaptation of model parameters for the rainforest PFTs. CLM modelled fluxes for the selected sites are to be compared with field observations from eddy covariance (EC) flux towers (e.g. a rainforest site in Bariri, Sulawesi; an oil palm site in Jambi, Sumatra). After validation, the project will proceed to parameterize land-use transformation system using remote sensing data and to simulate the impacts of historical LUCs on carbon, water and energy fluxes. Last but not least, the effects of future LUCs in Indonesia on the fluxes and carbon sequestration capacity will be investigated through scenario study. Historical land cover changes, especially oil palm coverage, are retrieved from Landsat or MODIS archival images. Oil palm concession boundaries are used to define and project future land use scenarios. Initial results include outputs from a single-point simulation for the Bariri rainforest site forced with locally measured meteorological data which already showed significant advantage over global forcing data in predicting net ecosystem exchange and latent and sensible heat fluxes. Modeled fluxes are being compared with EC flux observations and with Mixfor-SVAT model outputs from another project at the same site. In the next few months, focus will be on sensitivity analyses of model parameters including PFT optical, morphological and physiological parameters that are necessary to configure the new oil palm PFT and represent rainforest to oil palm conversion. The new parameterization will contribute to the development of the CLM model and its implementation in the modelling of LUC effects in tropical regions will help understanding land-climate interactions.

Surface Heat Budgets and Sea Surface Temperature in the Pacific Warm Pool During TOGA COARE

NASA Technical Reports Server (NTRS)

Chou, Shu-Hsien; Zhao, Wenzhong; Chou, Ming-Dah

1998-01-01

The daily mean heat and momentum fluxes at the surface derived from the SSM/I and Japan's GMS radiance measurements are used to study the temporal and spatial variability of the surface energy budgets and their relationship to the sea surface temperature during the COARE intensive observing period (IOP). For the three time legs observed during the IOP, the retrieved surface fluxes compare reasonably well with those from the IMET buoy, RV Moana Wave, and RV Wecoma. The characteristics of surface heat and momentum fluxes are very different between the southern and northern warm pool. In the southern warm pool, the net surface heat flux is dominated by solar radiation which is, in turn, modulated by the two Madden-Julian oscillations. The surface winds are generally weak, leading to a shallow ocean mixed layer. The solar radiation penetrating through the bottom of the mixed layer is significant, and the change in the sea surface temperature during the IOP does not follow the net surface heat flux. In the northern warm pool, the northeasterly trade wind is strong and undergoes strong seasonal variation. The variation of the net surface heat flux is dominated by evaporation. The two westerly wind bursts associated with the Madden-Julian oscillations seem to have little effect on the net surface heat flux. The ocean mixed layer is deep, and the solar radiation penetrating through the bottom of the mixed layer is small. As opposed to the southern warm pool, the trend of the sea surface temperature in the northern warm pool during the IOP is in agreement with the variation of the net heat flux at the surface.

The environmental heat flux routine, version 4 (EHFR-4) and Multiple Reflections Routine (MRR), volume 1

NASA Technical Reports Server (NTRS)

Dietz, J. B.

1973-01-01

The environmental heat flux routine version 4, (EHFR-4) is a generalized computer program which calculates the steady state and/or transient thermal environments experienced by a space system during lunar surface, deep space, or thermal vacuum chamber operation. The specific environments possible for EHFR analysis include: lunar plain, lunar crater, combined lunar plain and crater, lunar plain in the region of spacecraft surfaces, intervehicular, deep space in the region of spacecraft surfaces, and thermal vacuum chamber generation. The EHFR was used for Extra Vehicular Mobility Unit environment analysis of the Apollo 11-17 missions, EMU manned and unmanned thermal vacuum qualification testing, and EMU-LRV interface environmental analyses.

Advances in the Surface Renewal Flux Measurement Method

NASA Astrophysics Data System (ADS)

Shapland, T. M.; McElrone, A.; Paw U, K. T.; Snyder, R. L.

2011-12-01

The measurement of ecosystem-scale energy and mass fluxes between the planetary surface and the atmosphere is crucial for understanding geophysical processes. Surface renewal is a flux measurement technique based on analyzing the turbulent coherent structures that interact with the surface. It is a less expensive technique because it does not require fast-response velocity measurements, but only a fast-response scalar measurement. It is therefore also a useful tool for the study of the global cycling of trace gases. Currently, surface renewal requires calibration against another flux measurement technique, such as eddy covariance, to account for the linear bias of its measurements. We present two advances in the surface renewal theory and methodology that bring the technique closer to becoming a fully independent flux measurement method. The first advance develops the theory of turbulent coherent structure transport associated with the different scales of coherent structures. A novel method was developed for identifying the scalar change rate within structures at different scales. Our results suggest that for canopies less than one meter in height, the second smallest coherent structure scale dominates the energy and mass flux process. Using the method for resolving the scalar exchange rate of the second smallest coherent structure scale, calibration is unnecessary for surface renewal measurements over short canopies. This study forms the foundation for analysis over more complex surfaces. The second advance is a sensor frequency response correction for measuring the sensible heat flux via surface renewal. Inexpensive fine-wire thermocouples are frequently used to record high frequency temperature data in the surface renewal technique. The sensible heat flux is used in conjunction with net radiation and ground heat flux measurements to determine the latent heat flux as the energy balance residual. The robust thermocouples commonly used in field experiments underestimate the sensible heat flux, yielding results that are less than 50% of the sensible heat flux measured with finer sensors. We present the methodology for correcting the thermocouple signal to avoid underestimating the heat flux at both the smallest and the second smallest coherent structure scale.

An update of Leighton's solar dynamo model

NASA Astrophysics Data System (ADS)

Cameron, R. H.; Schüssler, M.

2017-03-01

In 1969, Leighton developed a quasi-1D mathematical model of the solar dynamo, building upon the phenomenological scenario of Babcock published in 1961. Here we present a modification and extension of Leighton's model. Using the axisymmetric component (longitudinal average) of the magnetic field, we consider the radial field component at the solar surface and the radially integrated toroidal magnetic flux in the convection zone, both as functions of latitude. No assumptions are made with regard to the radial location of the toroidal flux. The model includes the effects of (I) turbulent diffusion at the surface and in the convection zone; (II) poleward meridional flow at the surface and an equatorward return flow affecting the toroidal flux; (III) latitudinal differential rotation and the near-surface layer of radial rotational shear; (iv) downward convective pumping of magnetic flux in the shear layer; and (v) flux emergence in the form of tilted bipolar magnetic regions treated as a source term for the radial surface field. While the parameters relevant for the transport of the surface field are taken from observations, the model condenses the unknown properties of magnetic field and flow in the convection zone into a few free parameters (turbulent diffusivity, effective return flow, amplitude of the source term, and a parameter describing the effective radial shear). Comparison with the results of 2D flux transport dynamo codes shows that the model captures the essential features of these simulations. We make use of the computational efficiency of the model to carry out an extended parameter study. We cover an extended domain of the 4D parameter space and identify the parameter ranges that provide solar-like solutions. Dipole parity is always preferred and solutions with periods around 22 yr and a correct phase difference between flux emergence in low latitudes and the strength of the polar fields are found for a return flow speed around 2 m s-1, turbulent diffusivity below about 80 km2s-1, and dynamo excitation not too far above the threshold (linear growth rate less than 0.1 yr-1).

Assessment of land surface temperature and heat fluxes over Delhi using remote sensing data.

PubMed

Chakraborty, Surya Deb; Kant, Yogesh; Mitra, Debashis

2015-01-15

Surface energy processes has an essential role in urban weather, climate and hydrosphere cycles, as well in urban heat redistribution. The research was undertaken to analyze the potential of Landsat and MODIS data in retrieving biophysical parameters in estimating land surface temperature & heat fluxes diurnally in summer and winter seasons of years 2000 and 2010 and understanding its effect on anthropogenic heat disturbance over Delhi and surrounding region. Results show that during years 2000-2010, settlement and industrial area increased from 5.66 to 11.74% and 4.92 to 11.87% respectively which in turn has direct effect on land surface temperature (LST) and heat fluxes including anthropogenic heat flux. Based on the energy balance model for land surface, a method to estimate the increase in anthropogenic heat flux (Has) has been proposed. The settlement and industrial areas has higher amounts of energy consumed and has high values of Has in all seasons. The comparison of satellite derived LST with that of field measured values show that Landsat estimated values are in close agreement within error of ±2 °C than MODIS with an error of ±3 °C. It was observed that, during 2000 and 2010, the average change in surface temperature using Landsat over settlement & industrial areas of both seasons is 1.4 °C & for MODIS data is 3.7 °C. The seasonal average change in anthropogenic heat flux (Has) estimated using Landsat & MODIS is up by around 38 W/m(2) and 62 W/m(2) respectively while higher change is observed over settlement and concrete structures. The study reveals that the dynamic range of Has values has increased in the 10 year period due to the strong anthropogenic influence over the area. The study showed that anthropogenic heat flux is an indicator of the strength of urban heat island effect, and can be used to quantify the magnitude of the urban heat island effect. Copyright © 2013 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bourham, Mohamed A.; Gilligan, John G.

Safety considerations in large future fusion reactors like ITER are important before licensing the reactor. Several scenarios are considered hazardous, which include safety of plasma-facing components during hard disruptions, high heat fluxes and thermal stresses during normal operation, accidental energy release, and aerosol formation and transport. Disruption events, in large tokamaks like ITER, are expected to produce local heat fluxes on plasma-facing components, which may exceed 100 GW/m{sup 2} over a period of about 0.1 ms. As a result, the surface temperature dramatically increases, which results in surface melting and vaporization, and produces thermal stresses and surface erosion. Plasma-facing componentsmore » safety issues extends to cover a wide range of possible scenarios, including disruption severity and the impact of plasma-facing components on disruption parameters, accidental energy release and short/long term LOCA's, and formation of airborne particles by convective current transport during a LOVA (water/air ingress disruption) accident scenario. Study, and evaluation of, disruption-induced aerosol generation and mobilization is essential to characterize database on particulate formation and distribution for large future fusion tokamak reactor like ITER. In order to provide database relevant to ITER, the SIRENS electrothermal plasma facility at NCSU has been modified to closely simulate heat fluxes expected in ITER.« less

Version 2 Goddard Satellite-Based Surface Turbulent Fluxes (GSSTF2)

NASA Technical Reports Server (NTRS)

Chou, Shu-Hsien; Nelkin, Eric; Ardizzone, Joe; Atlas, Robert M.; Shie, Chung-Lin; Starr, David O'C. (Technical Monitor)

2002-01-01

Information on the turbulent fluxes of momentum, moisture, and heat at the air-sea interface is essential in improving model simulations of climate variations and in climate studies. We have derived a 13.5-year (July 1987-December 2000) dataset of daily surface turbulent fluxes over global oceans from the Special Sensor Mcrowave/Imager (SSM/I) radiance measurements. This dataset, version 2 Goddard Satellite-based Surface Turbulent Fluxes (GSSTF2), has a spatial resolution of 1 degree x 1 degree latitude-longitude and a temporal resolution of 1 day. Turbulent fluxes are derived from the SSM/I surface winds and surface air humidity, as well as the 2-m air and sea surface temperatures (SST) of the NCEP/NCAR reanalysis, using a bulk aerodynamic algorithm based on the surface layer similarity theory.

Empirical retrieval of sea spray aerosol production using satellite microwave radiometry

NASA Astrophysics Data System (ADS)

Savelyev, I. B.; Yelland, M. J.; Norris, S. J.; Salisbury, D.; Pascal, R. W.; Bettenhausen, M. H.; Prytherch, J.; Anguelova, M. D.; Brooks, I. M.

2017-12-01

This study presents a novel approach to obtaining global sea spray aerosol (SSA) production source term by relying on direct satellite observations of the ocean surface, instead of more traditional approaches driven by surface meteorology. The primary challenge in developing this empirical algorithm is to compile a calibrated, consistent dataset of SSA surface flux collected offshore over a variety of conditions (i.e., regions and seasons), thus representative of the global SSA production variability. Such dataset includes observations from SEASAW, HiWASE, and WAGES field campaigns, during which the SSA flux was measured from the bow of a research vessel using consistent and state-of-the-art eddy covariance methodology. These in situ data are matched to observations of the state of the ocean surface from Windsat polarimetric microwave satellite radiometer. Previous studies demonstrated the ability of WindSat to detect variations in surface waves slopes, roughness and foam, which led to the development of retrieval algorithms for surface wind vector and more recently whitecap fraction. Similarly, in this study, microwave emissions from the ocean surface are matched to and calibrated against in situ observations of the SSA production flux. The resulting calibrated empirical algorithm is applicable for retrieval of SSA source term throughout the duration of Windsat mission, from 2003 to present.

On the Interaction between Marine Boundary Layer Cellular Cloudiness and Surface Heat Fluxes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kazil, J.; Feingold, G.; Wang, Hailong

2014-01-02

The interaction between marine boundary layer cellular cloudiness and surface uxes of sensible and latent heat is investigated. The investigation focuses on the non-precipitating closed-cell state and the precipitating open-cell state at low geostrophic wind speed. The Advanced Research WRF model is used to conduct cloud-system-resolving simulations with interactive surface fluxes of sensible heat, latent heat, and of sea salt aerosol, and with a detailed representation of the interaction between aerosol particles and clouds. The mechanisms responsible for the temporal evolution and spatial distribution of the surface heat fluxes in the closed- and open-cell state are investigated and explained. Itmore » is found that the horizontal spatial structure of the closed-cell state determines, by entrainment of dry free tropospheric air, the spatial distribution of surface air temperature and water vapor, and, to a lesser degree, of the surface sensible and latent heat flux. The synchronized dynamics of the the open-cell state drives oscillations in surface air temperature, water vapor, and in the surface fluxes of sensible and latent heat, and of sea salt aerosol. Open-cell cloud formation, cloud optical depth and liquid water path, and cloud and rain water path are identified as good predictors of the spatial distribution of surface air temperature and sensible heat flux, but not of surface water vapor and latent heat flux. It is shown that by enhancing the surface sensible heat flux, the open-cell state creates conditions by which it is maintained. While the open-cell state under consideration is not depleted in aerosol, and is insensitive to variations in sea-salt fluxes, it also enhances the sea-salt flux relative to the closed-cell state. In aerosol-depleted conditions, this enhancement may replenish the aerosol needed for cloud formation, and hence contribute to the perpetuation of the open-cell state as well. Spatial homogenization of the surface fluxes is found to have only a small effect on cloud properties in the investigated cases. This indicates that sub-grid scale spatial variability in the surface flux of sensible and latent heat and of sea salt aerosol may not be required in large scale and global models to describe marine boundary layer cellular cloudiness.« less

Extreme air-sea surface turbulent fluxes in mid latitudes - estimation, origins and mechanisms

NASA Astrophysics Data System (ADS)

Gulev, Sergey; Natalia, Tilinina

2014-05-01

Extreme turbulent heat fluxes in the North Atlantic and North Pacific mid latitudes were estimated from the modern era and first generation reanalyses (NCEP-DOE, ERA-Interim, MERRA NCEP-CFSR, JRA-25) for the period from 1979 onwards. We used direct surface turbulent flux output as well as reanalysis state variables from which fluxes have been computed using COARE-3 bulk algorithm. For estimation of extreme flux values we analyzed surface flux probability density distribution which was approximated by Modified Fisher-Tippett distribution. In all reanalyses extreme turbulent heat fluxes amount to 1500-2000 W/m2 (for the 99th percentile) and can exceed 2000 W/m2 for higher percentiles in the western boundary current extension (WBCE) regions. Different reanalyses show significantly different shape of MFT distribution, implying considerable differences in the estimates of extreme fluxes. The highest extreme turbulent latent heat fluxes are diagnosed in NCEP-DOE, ERA-Interim and NCEP-CFSR reanalyses with the smallest being in MERRA. These differences may not necessarily reflect the differences in mean values. Analysis shows that differences in statistical properties of the state variables are the major source of differences in the shape of PDF of fluxes and in the estimates of extreme fluxes while the contribution of computational schemes used in different reanalyses is minor. The strongest differences in the characteristics of probability distributions of surface fluxes and extreme surface flux values between different reanalyses are found in the WBCE extension regions and high latitudes. In the next instance we analyzed the mechanisms responsible for forming surface turbulent fluxes and their potential role in changes of midlatitudinal heat balance. Midlatitudinal cyclones were considered as the major mechanism responsible for extreme turbulent fluxes which are typically occur during the cold air outbreaks in the rear parts of cyclones when atmospheric conditions provide locally high winds and air-sea temperature gradients. For this purpose we linked characteristics of cyclone activity over the midlatitudinal oceans with the extreme surface turbulent heat fluxes. Cyclone tracks and parameters of cyclone life cycle (deepening rates, propagation velocities, life time and clustering) were derived from the same reanalyses using state of the art numerical tracking algorithm. The main questions addressed in this study are (i) through which mechanisms extreme surface fluxes are associated with cyclone activity? and (ii) which types of cyclones are responsible for forming extreme turbulent fluxes? Our analysis shows that extreme surface fluxes are typically associated not with cyclones themselves but rather with cyclone-anticyclone interaction zones. This implies that North Atlantic and North Pacific series of intense cyclones do not result in the anomalous surface fluxes. Alternatively, extreme fluxes are most frequently associated with blocking situations, particularly with the intensification of the Siberian and North American Anticyclones providing cold-air outbreaks over WBC regions.

Simulation of Surface Energy Fluxes and Snow Interception Using a Higher Order Closure Multi-Layer Soil-Vegetation-Atmospheric Model: The Effect of Canopy Shape and Structure

NASA Astrophysics Data System (ADS)

McGowan, L. E.; Dahlke, H. E.; Paw U, K. T.

2015-12-01

Snow cover is a critical driver of the Earth's surface energy budget, climate change, and water resources. Variations in snow cover not only affect the energy budget of the land surface but also represent a major water supply source. In California, US estimates of snow depth, extent, and melt in the Sierra Nevada are critical to estimating the amount of water available for both California agriculture and urban users. However, accurate estimates of snow cover and snow melt processes in forested area still remain a challenge. Canopy structure influences the vertical and spatiotemporal distribution of snow, and therefore ultimately determines the degree and extent by which snow alters both the surface energy balance and water availability in forested regions. In this study we use the Advanced Canopy-Atmosphere-Soil algorithm (ACASA), a multi-layer soil-vegetation-atmosphere numerical model, to simulate the effect of different snow-covered canopy structures on the energy budget, and temperature and other scalar profiles within different forest types in the Sierra Nevada, California. ACASA incorporates a higher order turbulence closure scheme which allows the detailed simulation of turbulent fluxes of heat and water vapor as well as the CO2 exchange of several layers within the canopy. As such ACASA can capture the counter gradient fluxes within canopies that may occur frequently, but are typically unaccounted for, in most snow hydrology models. Six different canopy types were modeled ranging from coniferous forests (e.g. most biomass near the ground) to top-heavy (e.g. most biomass near the top of the crown) deciduous forests to multi-layered forest canopies (e.g. mixture of young and mature trees). Preliminary results indicate that the canopy shape and structure associated with different canopy types fundamentally influence the vertical scalar profiles (including those of temperature, moisture, and wind speed) in the canopy and thus alter the interception and snow melt dynamics in forested land surfaces. The turbulent transport dynamics, including counter-gradient fluxes, and radiation features including land surface albedo, are discussed in the context of the snow energy balance.

Critical heat flux (CHF) phenomenon on a downward facing curved surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheung, F.B.; Haddad, K.H.; Liu, Y.C.

1997-06-01

This report describes a theoretical and experimental study of the boundary layer boiling and critical heat flux phenomena on a downward facing curved heating surface, including both hemispherical and toroidal surfaces. A subscale boundary layer boiling (SBLB) test facility was developed to measure the spatial variation of the critical heat flux and observe the underlying mechanisms. Transient quenching and steady-state boiling experiments were performed in the SBLB facility under both saturated and subcooled conditions to obtain a complete database on the critical heat flux. To complement the experimental effort, an advanced hydrodynamic CHF model was developed from the conservation lawsmore » along with sound physical arguments. The model provides a clear physical explanation for the spatial variation of the CHF observed in the SBLB experiments and for the weak dependence of the CHF data on the physical size of the vessel. Based upon the CHF model, a scaling law was established for estimating the local critical heat flux on the outer surface of a heated hemispherical vessel that is fully submerged in water. The scaling law, which compares favorably with all the available local CHF data obtained for various vessel sizes, can be used to predict the local CHF limits on large commercial-size vessels. This technical information represents one of the essential elements that is needed in assessing the efficacy of external cooling of core melt by cavity flooding as a severe accident management strategy. 83 figs., 3 tabs.« less

Comparison of sea surface flux measured by instrumented aircraft and ship during SOFIA and SEMAPHORE experiments

NASA Astrophysics Data System (ADS)

Durand, Pierre; Dupuis, HéLèNe; Lambert, Dominique; BéNech, Bruno; Druilhet, Aimé; Katsaros, Kristina; Taylor, Peter K.; Weill, Alain

1998-10-01

Two major campaigns (Surface of the Oceans, Fluxes and Interactions with the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphère, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale (SEMAPHORE)) devoted to the study of ocean-atmosphere interaction were conducted in 1992 and 1993, respectively, in the Azores region. Among the various platforms deployed, instrumented aircraft and ship allowed the measurement of the turbulent flux of sensible heat, latent heat, and momentum. From coordinated missions we can evaluate the sea surface fluxes from (1) bulk relations and mean measurements performed aboard the ship in the atmospheric surface layer and (2) turbulence measurements aboard aircraft, which allowed the flux profiles to be estimated through the whole atmospheric boundary layer and therefore to be extrapolated toward the sea surface level. Continuous ship fluxes were calculated with bulk coefficients deduced from inertial-dissipation measurements in the same experiments, whereas aircraft fluxes were calculated with eddy-correlation technique. We present a comparison between these two estimations. Although momentum flux agrees quite well, aircraft estimations of sensible and latent heat flux are lower than those of the ship. This result is surprising, since aircraft momentum flux estimates are often considered as much less accurate than scalar flux estimates. The various sources of errors on the aircraft and ship flux estimates are discussed. For sensible and latent heat flux, random errors on aircraft estimates, as well as variability of ship flux estimates, are lower than the discrepancy between the two platforms, whereas the momentum flux estimates cannot be considered as significantly different. Furthermore, the consequence of the high-pass filtering of the aircraft signals on the flux values is analyzed; it is weak at the lowest altitudes flown and cannot therefore explain the discrepancies between the two platforms but becomes considerable at upper levels in the boundary layer. From arguments linked to the imbalance of the surface energy budget, established during previous campaigns performed over land surfaces with aircraft, we conclude that aircraft heat fluxes are probably also underestimated over the sea.

Identifying microturbulence regimes in a TCV discharge making use of physical constraints on particle and heat fluxes

DOE PAGES

Mariani, Alberto; Brunner, S.; Dominski, J.; ...

2018-01-17

Reducing the uncertainty on physical input parameters derived from experimental measurements is essential towards improving the reliability of gyrokinetic turbulence simulations. This can be achieved by introducing physical constraints. Amongst them, the zero particle flux condition is considered here. A first attempt is also made to match as well the experimental ion/electron heat flux ratio. This procedure is applied to the analysis of a particular Tokamak à Configuration Variable discharge. A detailed reconstruction of the zero particle flux hyper-surface in the multi-dimensional physical parameter space at fixed time of the discharge is presented, including the effect of carbon as themore » main impurity. Both collisionless and collisional regimes are considered. Hyper-surface points within the experimental error bars are found. In conclusion, the analysis is done performing gyrokinetic simulations with the local version of the GENE code, computing the fluxes with a Quasi-Linear (QL) model and validating the QL results with non-linear simulations in a subset of cases.« less

Evaporation Flux Distribution of Drops on a Hydrophilic or Hydrophobic Flat Surface by Molecular Simulations.

PubMed

Xie, Chiyu; Liu, Guangzhi; Wang, Moran

2016-08-16

The evaporation flux distribution of sessile drops is investigated by molecular dynamic simulations. Three evaporating modes are classified, including the diffusion dominant mode, the substrate heating mode, and the environment heating mode. Both hydrophilic and hydrophobic drop-substrate interactions are considered. To count the evaporation flux distribution, which is position dependent, we proposed an azimuthal-angle-based division method under the assumption of spherical crown shape of drops. The modeling results show that the edge evaporation, i.e., near the contact line, is enhanced for hydrophilic drops in all the three modes. The surface diffusion of liquid molecular absorbed on solid substrate for hydrophilic cases plays an important role as well as the space diffusion on the enhanced evaporation rate at the edge. For hydrophobic drops, the edge evaporation flux is higher for the substrate heating mode, but lower than elsewhere of the drop for the diffusion dominant mode; however, a nearly uniform distribution is found for the environment heating mode. The evidence shows that the temperature distribution inside drops plays a key role in the position-dependent evaporation flux.

Identifying microturbulence regimes in a TCV discharge making use of physical constraints on particle and heat fluxes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mariani, Alberto; Brunner, S.; Dominski, J.

Reducing the uncertainty on physical input parameters derived from experimental measurements is essential towards improving the reliability of gyrokinetic turbulence simulations. This can be achieved by introducing physical constraints. Amongst them, the zero particle flux condition is considered here. A first attempt is also made to match as well the experimental ion/electron heat flux ratio. This procedure is applied to the analysis of a particular Tokamak à Configuration Variable discharge. A detailed reconstruction of the zero particle flux hyper-surface in the multi-dimensional physical parameter space at fixed time of the discharge is presented, including the effect of carbon as themore » main impurity. Both collisionless and collisional regimes are considered. Hyper-surface points within the experimental error bars are found. In conclusion, the analysis is done performing gyrokinetic simulations with the local version of the GENE code, computing the fluxes with a Quasi-Linear (QL) model and validating the QL results with non-linear simulations in a subset of cases.« less

Flux pinning mechanism in codoped-MgB2 with Al2O3 and SiC

NASA Astrophysics Data System (ADS)

Kiafiroozkoohi, Narjess Sadat; Ghorbani, Shaban Reza; Arabi, Hadi

2018-05-01

MgB2 superconductor samples, co-doped with 0.02 wt of Al2O3 and 0.02 wt SiC, have been examined by M-H loop measurements and calculation of the critical current density based on the Bean model. Normalized volume pinning force, f = F/Fmax, as a function of the reduced magnetic field, h = H/Hmax has been obtained at each temperature. Hughochi flux pinning model, which was included the normal point pinning, the normal surface pinning, and the pinning based on spatial variation in the Ginzburg-Landau parameter, was used to study the flux pinning mechanisms. It was found that the Δκ effect and the normal point pinning mechanisms play the main role in the flux pinning at the magnetic field lower than Hmax and the contribution of the Δκ mechanism increases with the increasing temperature, while the contribution of normal point pinning mechanism decreases. At magnetic field larger than Hmax, the only mechanism that acts as the flux pinning was the normal surface pinning mechanism.

Magnetic reconnection process in transient coaxial helicity injection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ebrahimi, F.; Hooper, E. B.; Sovinec, C. R.

The physics of magnetic reconnection and fast flux closure in transient coaxial helicity injection experiments in NSTX is examined using resistive MHD simulations. These simulations have been performed using the NIMROD code with fixed boundary flux (including NSTX poloidal coil currents) in the NSTX experimental geometry. Simulations show that an X point is formed in the injector region, followed by formation of closed flux surfaces within 0.5 ms after the driven injector voltage and injector current begin to rapidly decrease. As the injector voltage is turned off, the field lines tend to untwist in the toroidal direction and magnetic fieldmore » compression exerts a radial J × B force and generates a bi-directional radial E{sub toroidal}×B{sub poloidal} pinch flow to bring oppositely directed field lines closer together to reconnect. At sufficiently low magnetic diffusivity (high Lundquist number), and with a sufficiently narrow injector flux footprint width, the oppositely directed field lines have sufficient time to reconnect (before dissipating), leading to the formation of closed flux surfaces. The reconnection process is shown to have transient Sweet-Parker characteristics.« less

Spatially Distributed Assimilation of Remotely Sensed Leaf Area Index and Potential Evapotranspiration for Hydrologic Modeling in Wetland Landscapes

EPA Science Inventory

Evapotranspiration (ET), a highly dynamic flux in wetland landscapes, regulates the accuracy of surface/sub-surface runoff simulation in a hydrologic model. However, considerable uncertainty in simulating ET-related processes remains, including our limited ability to incorporate ...

Evaluation of Surface Flux Parameterizations with Long-Term ARM Observations

DOE PAGES

Liu, Gang; Liu, Yangang; Endo, Satoshi

2013-02-01

Surface momentum, sensible heat, and latent heat fluxes are critical for atmospheric processes such as clouds and precipitation, and are parameterized in a variety of models ranging from cloud-resolving models to large-scale weather and climate models. However, direct evaluation of the parameterization schemes for these surface fluxes is rare due to limited observations. This study takes advantage of the long-term observations of surface fluxes collected at the Southern Great Plains site by the Department of Energy Atmospheric Radiation Measurement program to evaluate the six surface flux parameterization schemes commonly used in the Weather Research and Forecasting (WRF) model and threemore » U.S. general circulation models (GCMs). The unprecedented 7-yr-long measurements by the eddy correlation (EC) and energy balance Bowen ratio (EBBR) methods permit statistical evaluation of all six parameterizations under a variety of stability conditions, diurnal cycles, and seasonal variations. The statistical analyses show that the momentum flux parameterization agrees best with the EC observations, followed by latent heat flux, sensible heat flux, and evaporation ratio/Bowen ratio. The overall performance of the parameterizations depends on atmospheric stability, being best under neutral stratification and deteriorating toward both more stable and more unstable conditions. Further diagnostic analysis reveals that in addition to the parameterization schemes themselves, the discrepancies between observed and parameterized sensible and latent heat fluxes may stem from inadequate use of input variables such as surface temperature, moisture availability, and roughness length. The results demonstrate the need for improving the land surface models and measurements of surface properties, which would permit the evaluation of full land surface models.« less

Quantifying the Mass Flux, Erosion Rates and Geomorphological Impact of Surging Karakoram Glaciers

NASA Astrophysics Data System (ADS)

Quincey, D. J.; Glasser, N. F.; King, O.

2017-12-01

Surge-type glaciers switch between phases of rapid and slow flow on timescales of a few years to decades. Here, we describe glacier-surface debris changes, surface-elevation changes and velocity changes through surges lasting five to ten years on ten different Karakoram glaciers (Khurdopin, Gasherbrum, Kunyang, Braldu, Chong Khumdan, Qiogeli, Saxintulu, Shakesiga, Skamri and Unnamed). We use these data to characterise their geomorphological imprint on the landscape, calculate a minimum mass flux for each of the surges and provide first-order estimates of bed erosion rates. Surface debris transport through the surges includes widespread rearrangement of surface debris features, folding and the concentration of debris near glacier termini, confluences and margins. Ice and debris-flux is partly dependent on the style of the surge, and in particular whether a surge-front propagates down-glacier during the active phase. Erosion rates also depend on the style and longevity of the surge, but are largely comparable between each of the studied datasets. We conclude by estimating the geomorphic work undertaken during surge events in comparison to work carried out by non-surging glaciers in the same region.

Uncertainties of Large-Scale Forcing Caused by Surface Turbulence Flux Measurements and the Impacts on Cloud Simulations at the ARM SGP Site

NASA Astrophysics Data System (ADS)

Tang, S.; Xie, S.; Tang, Q.; Zhang, Y.

2017-12-01

Two types of instruments, the eddy correlation flux measurement system (ECOR) and the energy balance Bowen ratio system (EBBR), are used at the Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP) site to measure surface latent and sensible fluxes. ECOR and EBBR typically sample different land surface types, and the domain-mean surface fluxes derived from ECOR and EBBR are not always consistent. The uncertainties of the surface fluxes will have impacts on the derived large-scale forcing data and further affect the simulations of single-column models (SCM), cloud-resolving models (CRM) and large-eddy simulation models (LES), especially for the shallow-cumulus clouds which are mainly driven by surface forcing. This study aims to quantify the uncertainties of the large-scale forcing caused by surface turbulence flux measurements and investigate the impacts on cloud simulations using long-term observations from the ARM SGP site.

Effects of Enhanced Thaw Depth on the Composition of Arctic Soil Organic Matter Leachate

NASA Astrophysics Data System (ADS)

Hutchings, J.; Zhang, X.; Bianchi, T. S.; Schuur, E.; Arellano, A. R.; Liu, Y.

2016-12-01

Pan-Arctic permafrost is increasingly susceptible to thaw due to the disproportionally high rate of temperature change in high latitudes. These soils contain a globally significant quantity of organic carbon that, when thawed, interacts with the modern carbon cycle. Current research has focused on atmospheric carbon fluxes and transport by rivers and streams to continental shelves, but has overlooked the lateral flux of carbon within watershed soils, which is the primary link between terrestrial and riverine ecosystems. Understanding the effects of water movement through permafrost soils on dissolved organic carbon is critical to better modelling of lateral carbon fluxes and interpreting the resulting observed riverine carbon fluxes with applications to investigations of the past, present, and future of the pan-Arctic. We conducted a laboratory leaching experiment using active layer soils from the Eight Mile Lake region of interior Alaska. Cores were sampled into surface and deep sections. Surface sections were subjected to a three-stage leaching process using artificial rain, with cores stored frozen overnight between stages (which crudely simulated freeze-thaw mechanisms). Surface leachates were sampled for analysis and the remainder percolated through deep soils using the same three-staged approach. Measurements of surface and deep leachates were selected to characterize transport-related changes to dissolved organic matter and included dissolved organic carbon, fluorescent dissolved organic matter via excitation emission matrices, and molecular composition via Fourier transform ion cyclotron resonance mass spectrometry. Primary findings from the experiment include a net retention of 2.4 to 27% of dissolved organic carbon from surface leachates in deep soils, a net release of fluorescent dissolved organic matter from deep soils that was 43 to 106% greater than surface leachates, increased hydrophobicity during stage three of leaching, and the preferential leaching of lignin- and tannin-like formulas from deep soils, consistent with fluorescence measurements.

A Study of Surface Temperatures, Clouds and Net Radiation

NASA Technical Reports Server (NTRS)

Dhuria, Harbans

1996-01-01

This study focused on the seasonal relationships and interactions of climate parameters such as the surface temperatures, net radiation, long wave flux, short wave flux, and clouds on a global basis. Five years of observations (December 1984 to November 1989) from the Earth Radiation Budget Experiment (ERBE) and the International Satellite Cloud Climatology Program (ISCCP) were used to study both seasonal variations and interannual variations by use of a basic radiation budget equation. In addition, the study was extended to include an analysis of the cloud forcing due El-Nino's impact on the ERBE parameters.

Evaluation of parameterization for turbulent fluxes of momentum and heat in stably stratified surface layers

NASA Astrophysics Data System (ADS)

Sodemann, H.; Foken, Th.

2003-04-01

General Circulation Models calculate the energy exchange between surface and atmosphere by means of parameterisations for turbulent fluxes of momentum and heat in the surface layer. However, currently implemented parameterisations after Louis (1979) create large discrepancies between predictions and observational data, especially in stably stratified surface layers. This work evaluates a new surface layer parameterisation proposed by Zilitinkevich et al. (2002), which was specifically developed to improve energy flux predictions in stable stratification. The evaluation comprises a detailed study of important surface layer characteristics, a sensitivity study of the parameterisation, and a direct comparison to observational data from Antarctica and predictions by the Louis (1979) parameterisation. The stability structure of the stable surface layer was found to be very complex, and strongly influenced fluxes in the surface layer. The sensitivity study revealed that the new parameterisation depends strongly on the ratio between roughness length and roughness temperature, which were both observed to be very variable parameters. The comparison between predictions and measurements showed good agreement for momentum fluxes, but large discrepancies for heat fluxes. A stability dependent evaluation of selected data showed better agreement for the new parameterisation of Zilitinkevich et al. (2002) than for the Louis (1979) scheme. Nevertheless, this comparison underlines the need for more detailed and physically sound concepts for parameterisations of heat fluxes in stably stratified surface layers. Zilitinkevich, S. S., V. Perov and J. C. King (2002). "Near-surface turbulent fluxes in stable stratification: Calculation techniques for use in General Circulation Models." Q. J. R. Meteorol. Soc. 128(583): 1571--1587. Louis, J. F. (1979). "A Parametric Model of Vertical Eddy Fluxes in the Atmosphere." Bound.-Layer Meteor. 17(2): 187--202.

[A review on research of land surface water and heat fluxes].

PubMed

Sun, Rui; Liu, Changming

2003-03-01

Many field experiments were done, and soil-vegetation-atmosphere transfer(SVAT) models were stablished to estimate land surface heat fluxes. In this paper, the processes of experimental research on land surface water and heat fluxes are reviewed, and three kinds of SVAT model(single layer model, two layer model and multi-layer model) are analyzed. Remote sensing data are widely used to estimate land surface heat fluxes. Based on remote sensing and energy balance equation, different models such as simplified model, single layer model, extra resistance model, crop water stress index model and two source resistance model are developed to estimate land surface heat fluxes and evapotranspiration. These models are also analyzed in this paper.

Towards Global Simulation of Irrigation in a Land Surface Model: Multiple Cropping and Rice Paddy in Southeast Asia

NASA Technical Reports Server (NTRS)

Beaudoing, Hiroko Kato; Rodell, Matthew; Ozdogan, Mutlu

2010-01-01

Agricultural land use significantly influences the surface water and energy balances. Effects of irrigation on land surface states and fluxes include repartitioning of latent and sensible heat fluxes, an increase in net radiation, and an increase in soil moisture and runoff. We are working on representing irrigation practices in continental- to global-scale land surface simulation in NASA's Global Land Data Assimilation System (GLDAS). Because agricultural practices across the nations are diverse, and complex, we are attempting to capture the first-order reality of the regional practices before achieving a global implementation. This study focuses on two issues in Southeast Asia: multiple cropping and rice paddy irrigation systems. We first characterize agricultural practices in the region (i.e., crop types, growing seasons, and irrigation) using the Global data set of monthly irrigated and rainfed crop areas around the year 2000 (MIRCA2000) dataset. Rice paddy extent is identified using remote sensing products. Whether irrigated or rainfed, flooded fields need to be represented and treated explicitly. By incorporating these properties and processes into a physically based land surface model, we are able to quantify the impacts on the simulated states and fluxes.

Feedback system for divertor impurity seeding based on real-time measurements of surface heat flux in the Alcator C-Mod tokamak

NASA Astrophysics Data System (ADS)

Brunner, D.; Burke, W.; Kuang, A. Q.; LaBombard, B.; Lipschultz, B.; Wolfe, S.

2016-02-01

Mitigation of the intense heat flux to the divertor is one of the outstanding problems in fusion energy. One technique that has shown promise is impurity seeding, i.e., the injection of low-Z gaseous impurities (typically N2 or Ne) to radiate and dissipate the power before it arrives to the divertor target plate. To this end, the Alcator C-Mod team has created a first-of-its-kind feedback system to control the injection of seed gas based on real-time surface heat flux measurements. Surface thermocouples provide real-time measurements of the surface temperature response to the plasma heat flux. The surface temperature measurements are inputted into an analog computer that "solves" the 1-D heat transport equation to deliver accurate, real-time signals of the surface heat flux. The surface heat flux signals are sent to the C-Mod digital plasma control system, which uses a proportional-integral-derivative (PID) algorithm to control the duty cycle demand to a pulse width modulated piezo valve, which in turn controls the injection of gas into the private flux region of the C-Mod divertor. This paper presents the design and implementation of this new feedback system as well as initial results using it to control divertor heat flux.

Feedback system for divertor impurity seeding based on real-time measurements of surface heat flux in the Alcator C-Mod tokamak.

PubMed

Brunner, D; Burke, W; Kuang, A Q; LaBombard, B; Lipschultz, B; Wolfe, S

2016-02-01

Mitigation of the intense heat flux to the divertor is one of the outstanding problems in fusion energy. One technique that has shown promise is impurity seeding, i.e., the injection of low-Z gaseous impurities (typically N2 or Ne) to radiate and dissipate the power before it arrives to the divertor target plate. To this end, the Alcator C-Mod team has created a first-of-its-kind feedback system to control the injection of seed gas based on real-time surface heat flux measurements. Surface thermocouples provide real-time measurements of the surface temperature response to the plasma heat flux. The surface temperature measurements are inputted into an analog computer that "solves" the 1-D heat transport equation to deliver accurate, real-time signals of the surface heat flux. The surface heat flux signals are sent to the C-Mod digital plasma control system, which uses a proportional-integral-derivative (PID) algorithm to control the duty cycle demand to a pulse width modulated piezo valve, which in turn controls the injection of gas into the private flux region of the C-Mod divertor. This paper presents the design and implementation of this new feedback system as well as initial results using it to control divertor heat flux.

The OceanFlux Greenhouse Gases methodology for deriving a sea surface climatology of CO2 fugacity in support of air-sea gas flux studies

NASA Astrophysics Data System (ADS)

Goddijn-Murphy, L. M.; Woolf, D. K.; Land, P. E.; Shutler, J. D.; Donlon, C.

2015-07-01

Climatologies, or long-term averages, of essential climate variables are useful for evaluating models and providing a baseline for studying anomalies. The Surface Ocean CO2 Atlas (SOCAT) has made millions of global underway sea surface measurements of CO2 publicly available, all in a uniform format and presented as fugacity, fCO2. As fCO2 is highly sensitive to temperature, the measurements are only valid for the instantaneous sea surface temperature (SST) that is measured concurrently with the in-water CO2 measurement. To create a climatology of fCO2 data suitable for calculating air-sea CO2 fluxes, it is therefore desirable to calculate fCO2 valid for a more consistent and averaged SST. This paper presents the OceanFlux Greenhouse Gases methodology for creating such a climatology. We recomputed SOCAT's fCO2 values for their respective measurement month and year using monthly composite SST data on a 1° × 1° grid from satellite Earth observation and then extrapolated the resulting fCO2 values to reference year 2010. The data were then spatially interpolated onto a 1° × 1° grid of the global oceans to produce 12 monthly fCO2 distributions for 2010, including the prediction errors of fCO2 produced by the spatial interpolation technique. The partial pressure of CO2 (pCO2) is also provided for those who prefer to use pCO2. The CO2 concentration difference between ocean and atmosphere is the thermodynamic driving force of the air-sea CO2 flux, and hence the presented fCO2 distributions can be used in air-sea gas flux calculations together with climatologies of other climate variables.

A method for obtaining distributed surface flux measurements in complex terrain

NASA Astrophysics Data System (ADS)

Daniels, M. H.; Pardyjak, E.; Nadeau, D. F.; Barrenetxea, G.; Brutsaert, W. H.; Parlange, M. B.

2011-12-01

Sonic anemometers and gas analyzers can be used to measure fluxes of momentum, heat, and moisture over flat terrain, and with the proper corrections, over sloping terrain as well. While this method of obtaining fluxes is currently the most accurate available, the instruments themselves are costly, making installation of many stations impossible for most campaign budgets. Small, commercial automatic weather stations (Sensorscope) are available at a fraction of the cost of sonic anemometers or gas analyzers. Sensorscope stations use slow-response instruments to measure standard meteorological variables, including wind speed and direction, air temperature, humidity, surface skin temperature, and incoming solar radiation. The method presented here makes use of one sonic anemometer and one gas analyzer along with a dozen Sensorscope stations installed throughout the Val Ferret catchment in southern Switzerland in the summers of 2009, 2010 and 2011. Daytime fluxes are calculated using Monin-Obukhov similarity theory in conjunction with the surface energy balance at each Sensorscope station as well as at the location of the sonic anemometer and gas analyzer, where a suite of additional slow-response instruments were co-located. Corrections related to slope angle were made for wind speeds and incoming shortwave radiation measured by the horizontally-mounted cup anemometers and incoming solar radiation sensors respectively. A temperature correction was also applied to account for daytime heating inside the radiation shield on the slow-response temperature/humidity sensors. With these corrections, we find a correlation coefficient of 0.77 between u* derived using Monin-Obukhov similarity theory and that of the sonic anemometer. Calculated versus measured heat fluxes also compare well and local patterns of latent heat flux and measured surface soil moisture are correlated.

Stability of a two-volume MRxMHD model in slab geometry

NASA Astrophysics Data System (ADS)

Tuen, Li Huey

Ideal MHD models are known to be inadequate to describe various physical attributes of a toroidal field with non-continuous symmetry, such as magnetic islands and stochastic regions. Motivated by this omission, a new variational principle MRXMHD was developed; rather than include an infinity of magnetic flux surfaces, MRxMHD has a finite number of flux surfaces, and thus supports partial plasma relaxation. The model comprises of relaxed plasma regions which are separated by nested ideal MHD interfaces (flux surfaces), and can be encased in a perfectly conducting wall. In each region the pressure is constant, but can jump across interfaces. The field and field pitch, or rotational transform, can also jump across the interfaces. Unlike ideal MHD, MRxMHD plasmas can support toroidally non-axisymmetric confined magnetic fields, magnetic islands and stochastic regions. In toroidally non-axisymmetric plasma, the existence of interfaces in MRxMHD is contingent on the irrationality of the rotational transform of flux surfaces. That is, the KAM theorem shows that invariant tori (flux surfaces) continue to exist for sufficiently small perturbations to an integrable system (which describes flux surfaces), provided that the rotational transform is sufficiently irrational. Building upon the MRxMHD stability model, we study the effects of irrationality of the rotational transform at interfaces in MRxMHD on plasma stability. We present an MRxMHD equilibrium model to investigate the effects of magnetic field pitch within the plasma and across the aforementioned flux surfaces within a chosen geometry. In this model, it is found that the 2D system stability conditions are dependent on the interface and resonant surface magnetic field pitch at minimised energy states, and the stability of a system as a function of magnetic field pitch destabilises at particular values of magnetic field pitch. We benchmark the treatment of a two-volume system, along with the calculations for background and perturbed magnetic fields to existing cylindrical working. An expression is formulated for the stability eigenvalues by creating a model for the slab geometry system. The eigenvalues for system stability at a minimum energy state are found to depend upon the rationality of the magnetic field pitch at resonant surfaces. Various system parameter scans are conducted to determine their affect upon system stability and their implications. While tearing instabilities exist at low order rational resonances, investigating the instability of high-order rationals requires study of pressure-driven instabilities.

Impact of buildings on surface solar radiation over urban Beijing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Bin; Liou, Kuo-Nan; Gu, Yu

The rugged surface of an urban area due to varying buildings can interact with solar beams and affect both the magnitude and spatiotemporal distribution of surface solar fluxes. Here we systematically examine the impact of buildings on downward surface solar fluxes over urban Beijing by using a 3-D radiation parameterization that accounts for 3-D building structures vs. the conventional plane-parallel scheme. We find that the resulting downward surface solar flux deviations between the 3-D and the plane-parallel schemes are generally ±1–10 W m -2 at 800 m grid resolution and within ±1 W m -2 at 4 km resolution. Pairsmore » of positive–negative flux deviations on different sides of buildings are resolved at 800 m resolution, while they offset each other at 4 km resolution. Flux deviations from the unobstructed horizontal surface at 4 km resolution are positive around noon but negative in the early morning and late afternoon. The corresponding deviations at 800 m resolution, in contrast, show diurnal variations that are strongly dependent on the location of the grids relative to the buildings. Both the magnitude and spatiotemporal variations of flux deviations are largely dominated by the direct flux. Furthermore, we find that flux deviations can potentially be an order of magnitude larger by using a finer grid resolution. Atmospheric aerosols can reduce the magnitude of downward surface solar flux deviations by 10–65 %, while the surface albedo generally has a rather moderate impact on flux deviations. The results imply that the effect of buildings on downward surface solar fluxes may not be critically significant in mesoscale atmospheric models with a grid resolution of 4 km or coarser. However, the effect can play a crucial role in meso-urban atmospheric models as well as microscale urban dispersion models with resolutions of 1 m to 1 km.« less

Using Flux Site Observations to Calibrate Root System Architecture Stencils for Water Uptake of Plant Functional Types in Land Surface Models.

NASA Astrophysics Data System (ADS)

Bouda, M.

2017-12-01

Root system architecture (RSA) can significantly affect plant access to water, total transpiration, as well as its partitioning by soil depth, with implications for surface heat, water, and carbon budgets. Despite recent advances in land surface model (LSM) descriptions of plant hydraulics, RSA has not been included because of its three-dimensional complexity, which makes RSA modelling generally too computationally costly. This work builds upon the recently introduced "RSA stencil," a process-based 1D layered model that captures the dynamic shifts in water potential gradients of 3D RSA in response to heterogeneous soil moisture profiles. In validations using root systems calibrated to the rooting profiles of four plant functional types (PFT) of the Community Land Model, the RSA stencil predicts plant water potentials within 2% of the outputs of full 3D models, despite its trivial computational cost. In transient simulations, the RSA stencil yields improved predictions of water uptake and soil moisture profiles compared to a 1D model based on root fraction alone. Here I show how the RSA stencil can be calibrated to time-series observations of soil moisture and transpiration to yield a water uptake PFT definition for use in terrestrial models. This model-data integration exercise aims to improve LSM predictions of soil moisture dynamics and, under water-limiting conditions, surface fluxes. These improvements can be expected to significantly impact predictions of downstream variables, including surface fluxes, climate-vegetation feedbacks and soil nutrient cycling.

A joint data assimilation system (Tan-Tracker) to simultaneously estimate surface CO2 fluxes and 3-D atmospheric CO2 concentrations from observations

NASA Astrophysics Data System (ADS)

Tian, X.; Xie, Z.; Liu, Y.; Cai, Z.; Fu, Y.; Zhang, H.; Feng, L.

2014-12-01

We have developed a novel framework ("Tan-Tracker") for assimilating observations of atmospheric CO2 concentrations, based on the POD-based (proper orthogonal decomposition) ensemble four-dimensional variational data assimilation method (PODEn4DVar). The high flexibility and the high computational efficiency of the PODEn4DVar approach allow us to include both the atmospheric CO2 concentrations and the surface CO2 fluxes as part of the large state vector to be simultaneously estimated from assimilation of atmospheric CO2 observations. Compared to most modern top-down flux inversion approaches, where only surface fluxes are considered as control variables, one major advantage of our joint data assimilation system is that, in principle, no assumption on perfect transport models is needed. In addition, the possibility for Tan-Tracker to use a complete dynamic model to consistently describe the time evolution of CO2 surface fluxes (CFs) and the atmospheric CO2 concentrations represents a better use of observation information for recycling the analyses at each assimilation step in order to improve the forecasts for the following assimilations. An experimental Tan-Tracker system has been built based on a complete augmented dynamical model, where (1) the surface atmosphere CO2 exchanges are prescribed by using a persistent forecasting model for the scaling factors of the first-guess net CO2 surface fluxes and (2) the atmospheric CO2 transport is simulated by using the GEOS-Chem three-dimensional global chemistry transport model. Observing system simulation experiments (OSSEs) for assimilating synthetic in situ observations of surface CO2 concentrations are carefully designed to evaluate the effectiveness of the Tan-Tracker system. In particular, detailed comparisons are made with its simplified version (referred to as TT-S) with only CFs taken as the prognostic variables. It is found that our Tan-Tracker system is capable of outperforming TT-S with higher assimilation precision for both CO2 concentrations and CO2 fluxes, mainly due to the simultaneous estimation of CO2 concentrations and CFs in our Tan-Tracker data assimilation system. A experiment for assimilating the real dry-air column CO2 retrievals (XCO2) from the Japanese Greenhouse Gases Observation Satellite (GOSAT) further demonstrates its potential wide applications.

Evaluating Water and Energy Fluxes across Three Land Cover Types in a Desert Urban Environment through a Mobile Eddy Covariance Platform

NASA Astrophysics Data System (ADS)

Pierini, N.; Vivoni, E. R.; Schreiner-McGraw, A.; Lopez-Castrillo, I.

2015-12-01

The urbanization process transforms a natural landscape into a built environment with many engineered surfaces, leading to significant impacts on surface energy and water fluxes across multiple spatial and temporal scales. Nevertheless, the effects of different urban land covers on energy and water fluxes has been rarely quantified across the large varieties of construction materials, landscaping and vegetation types, and industrial, commercial and residential areas in cities. In this study, we deployed a mobile eddy covariance tower at three different locations in the Phoenix, Arizona, metropolitan area to capture a variety of urban land covers. The three locations each represent a common urban class in Phoenix: 1) a dense, xeric landscape (gravel cover and native plants with drip-irrigation systems near tall buildings); 2) a high-density urban site (asphalt-paved parking lot near a high-traffic intersection); and 3) a suburban mesic landscape (sprinkler-irrigated turf grass in a suburban neighborhood). At each site, we measured meteorological variables, including air temperature and relative humidity at three heights, precipitation and pressure, surface temperature, and soil moisture and temperature (where applicable), to complement the eddy covariance measurements of radiation, energy, carbon dioxide and water vapor fluxes. We evaluated the tower footprint at each site to characterize the contributing surface area to the flux measurements, including engineered and landscaping elements, as a function of time for each deployment. The different sites allowed us to compare how turbulent fluxes of water vapor and carbon dioxide vary for these representative urban land covers, in particular with respect to the role of precipitation events and irrigation. While the deployments covered different seasons, from winter to summer in 2015, the variety of daily conditions allowed quantification of the differential response to precipitation events during the winter, pre-monsoon, and monsoon seasons in relation to irrigation input or lack thereof. As desert urban areas continue to grow worldwide, it is essential to gain an improved understanding of how the energy and water balances vary across the built environment and their implications on urban climate, energy, hydrologic conditions, and air quality.

Spray cooling characteristics of nanofluids for electronic power devices.

PubMed

Hsieh, Shou-Shing; Leu, Hsin-Yuan; Liu, Hao-Hsiang

2015-01-01

The performance of a single spray for electronic power devices using deionized (DI) water and pure silver (Ag) particles as well as multi-walled carbon nanotube (MCNT) particles, respectively, is studied herein. The tests are performed with a flat horizontal heated surface using a nozzle diameter of 0.5 mm with a definite nozzle-to-target surface distance of 25 mm. The effects of nanoparticle volume fraction and mass flow rate of the liquid on the surface heat flux, including critical heat flux (CHF), are explored. Both steady state and transient data are collected for the two-phase heat transfer coefficient, boiling curve/ cooling history, and the corresponding CHF. The heat transfer removal rate can reach up to 274 W/cm(2) with the corresponding CHF enhancement ratio of 2.4 for the Ag/water nanofluids present at a volume fraction of 0.0075% with a low mass flux of 11.9 × 10(-4) kg/cm(2)s.

Computer program determines thermal environment and temperature history of lunar orbiting space vehicles

NASA Technical Reports Server (NTRS)

Head, D. E.; Mitchell, K. L.

1967-01-01

Program computes the thermal environment of a spacecraft in a lunar orbit. The quantities determined include the incident flux /solar and lunar emitted radiation/, total radiation absorbed by a surface, and the resulting surface temperature as a function of time and orbital position.

A Sensitivity Analysis of the Impact of Rain on Regional and Global Sea-Air Fluxes of CO2

PubMed Central

Shutler, J. D.; Land, P. E.; Woolf, D. K.; Quartly, G. D.

2016-01-01

The global oceans are considered a major sink of atmospheric carbon dioxide (CO2). Rain is known to alter the physical and chemical conditions at the sea surface, and thus influence the transfer of CO2 between the ocean and atmosphere. It can influence gas exchange through enhanced gas transfer velocity, the direct export of carbon from the atmosphere to the ocean, by altering the sea skin temperature, and through surface layer dilution. However, to date, very few studies quantifying these effects on global net sea-air fluxes exist. Here, we include terms for the enhanced gas transfer velocity and the direct export of carbon in calculations of the global net sea-air fluxes, using a 7-year time series of monthly global climate quality satellite remote sensing observations, model and in-situ data. The use of a non-linear relationship between the effects of rain and wind significantly reduces the estimated impact of rain-induced surface turbulence on the rate of sea-air gas transfer, when compared to a linear relationship. Nevertheless, globally, the rain enhanced gas transfer and rain induced direct export increase the estimated annual oceanic integrated net sink of CO2 by up to 6%. Regionally, the variations can be larger, with rain increasing the estimated annual net sink in the Pacific Ocean by up to 15% and altering monthly net flux by > ± 50%. Based on these analyses, the impacts of rain should be included in the uncertainty analysis of studies that estimate net sea-air fluxes of CO2 as the rain can have a considerable impact, dependent upon the region and timescale. PMID:27673683

Eddy Current Probe for Surface and Sub-Surface Inspection

NASA Technical Reports Server (NTRS)

Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor)

2014-01-01

An eddy current probe includes an excitation coil for coupling to a low-frequency alternating current (AC) source. A magneto-resistive sensor is centrally disposed within and at one end of the excitation coil to thereby define a sensing end of the probe. A tubular flux-focusing lens is disposed between the excitation coil and the magneto-resistive sensor. An excitation wire is spaced apart from the magneto-resistive sensor in a plane that is perpendicular to the sensor's axis of sensitivity and such that, when the sensing end of the eddy current probe is positioned adjacent to the surface of a structure, the excitation wire is disposed between the magneto-resistive sensor and the surface of the structure. The excitation wire is coupled to a high-frequency AC source. The excitation coil and flux-focusing lens can be omitted when only surface inspection is required.

Air-sea heat exchange, an element of the water cycle

NASA Technical Reports Server (NTRS)

Chahine, M. T.

1984-01-01

The distribution and variation of water vapor, clouds and precipitation are examined. Principal driving forces for these distributions are energy exchange and evaporation at the air-sea interface, which are also important elements of air-sea interaction studies. The overall aim of air-sea interaction studies is to quantitatively determine mass, momentum and energy fluxes, with the goal of understanding the mechanisms controlling them. The results of general circulation simulations indicate that the atmosphere in mid-latitudes responds to changes in the oceanic surface conditions in the tropics. This correlation reflects the strong interaction between tropical and mid-latitude conditions caused by the transport of heat and momentum from the tropics. Studies of air-sea exchanges involve a large number of physica, chemical and dynamical processes including heat flux, radiation, sea-surface temperature, precipitation, winds and ocean currents. The fluxes of latent heat are studied and the potential use of satellite data in determining them evaluated. Alternative ways of inferring heat fluxes will be considered.

Effect of Geomagnetic Storms on Ocean-Atmospheric Interactions over the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Reddy, S.; Karim, R.

There is accumulated evidence from recent past literature to show the possible relation between solar and geomagnetic activity, and meteorological parameters (Pittock, 1978; Reddy et.al. 1979; Bhalme et.al. 1979; Reddy and Karim, 2003). Not many studies have been reported on the relationship between geomagnetic activity and terrestrial weather including ocean-atmospheric interactions that have significant impacts over the large-scale atmospheric circulations. Between the ocean surface and the atmosphere, there is an exchange of heat and moisture that depend in part, on temperature differences between water and air. In winter, when air-water temperature contrasts are greatest, there is a substantial transfer of sensible and latent heat from the ocean surface into the atmosphere. This energy helps to maintain the global airflow. Previous studies (Reddy and Miller, 1997; Reddy et.al. 1998, 1999) have established the relationship between ocean-atmospheric interactions and tropical cyclones/hurricanes over the Gulf of Mexico. In the present study, we investigate the relationship between Geomagnetic Storms and ocean-atmospheric interactions including heat, momentum and moisture fluxes over the Gulf of Mexico during the winter (December to February) for the period, 2001-2003.The data used in this study include, (i) Geomagnetic storms, and (ii) Buoy data (sea surface temperature, air temperature, sea level pressure and wind speed) obtained from National Data Buoy Center (NDBC). The fluxes were computed using standard bulk formulae. The statistical techniques used for data analysis include superposed epoch analysis and student test .The result of the study has pointed out a significant increase in the fluxes 1-3 days after the storm occurrence. The effect of these fluxes on Gulf coast weather is noticed. The study is important for further understanding the climate variability of large-scale circulations including ElNino/Southern Oscillation (ENSO). The results and the possible physical mechanisms for the observed relationships will be presented and discussed. NOAA/Howard University NCAS Grant supports the work

Urban surface energy fluxes based on remotely-sensed data and micrometeorological measurements over the Kansai area, Japan

NASA Astrophysics Data System (ADS)

Sukeyasu, T.; Ueyama, M.; Ando, T.; Kosugi, Y.; Kominami, Y.

2017-12-01

The urban heat island is associated with land cover changes and increases in anthropogenic heat fluxes. Clear understanding of the surface energy budget at urban area is the most important for evaluating the urban heat island. In this study, we develop a model based on remotely-sensed data for the Kansai area in Japan and clarify temporal transitions and spatial distributions of the surface energy flux from 2000 to 2016. The model calculated the surface energy fluxes based on various satellite and GIS products. The model used land surface temperature, surface emissivity, air temperature, albedo, downward shortwave radiation and land cover/use type from the moderate resolution imaging spectroradiometer (MODIS) under cloud free skies from 2000 to 2016 over the Kansai area in Japan (34 to 35 ° N, 135 to 136 ° E). Net radiation was estimated by a radiation budget of upward/downward shortwave and longwave radiation. Sensible heat flux was estimated by a bulk aerodynamic method. Anthropogenic heat flux was estimated by the inventory data. Latent heat flux was examined with residues of the energy budget and parameterization of bulk transfer coefficients. We validated the model using observed fluxes from five eddy-covariance measurement sites: three urban sites and two forested sites. The estimated net radiation roughly agreed with the observations, but the sensible heat flux were underestimated. Based on the modeled spatial distributions of the fluxes, the daytime net radiation in the forested area was larger than those in the urban area, owing to higher albedo and land surface temperatures in the urban area than the forested area. The estimated anthropogenic heat flux was high in the summer and winter periods due to increases in energy-requirements.

The Oceanic Flux Program: A three decade time-series of particle flux in the deep Sargasso Sea

NASA Astrophysics Data System (ADS)

Weber, J. C.; Conte, M. H.

2010-12-01

The Oceanic Flux Program (OFP), 75 km SE of Bermuda, is the longest running time-series of its kind. Initiated in 1978, the OFP has produced an unsurpassed, nearly continuous record of temporal variability in deep ocean fluxes, with a >90% temporal coverage at 3200m depth. The OFP, in conjunction with the co-located Bermuda-Atlantic Time Series (BATS) and the Bermuda Testbed Mooring (BTM) time-series, has provided key observations enabling detailed assessment of how seasonal and non-seasonal variability in the deep ocean is linked with the overlying physical and biogeochemical environment. This talk will focus on the short-term flux variability that overlies the seasonal flux pattern in the Sargasso Sea, emphasizing episodic extreme flux events. Extreme flux events are responsible for much of the year-to-year variability in mean annual flux and are most often observed during early winter and late spring when surface stratification is weak or transient. In addition to biological phenomena (e.g. salp blooms), passage of productive meso-scale features such as eddies, which alter surface water mixing characteristics and surface export fluxes, may initiate some extreme flux events. Yet other productive eddies show a minimal influence on the deep flux, underscoring the importance of upper ocean ecosystem structure and midwater processes on the coupling between the surface ocean environment and deep fluxes. Using key organic and inorganic tracers, causative processes that influence deep flux generation and the strength of the coupling with the surface ocean environment can be identified.

Spotted star light curve numerical modeling technique and its application to HII 1883 surface imaging

NASA Astrophysics Data System (ADS)

Kolbin, A. I.; Shimansky, V. V.

2014-04-01

We developed a code for imaging the surfaces of spotted stars by a set of circular spots with a uniform temperature distribution. The flux from the spotted surface is computed by partitioning the spots into elementary areas. The code takes into account the passing of spots behind the visible stellar limb, limb darkening, and overlapping of spots. Modeling of light curves includes the use of recent results of the theory of stellar atmospheres needed to take into account the temperature dependence of flux intensity and limb darkening coefficients. The search for spot parameters is based on the analysis of several light curves obtained in different photometric bands. We test our technique by applying it to HII 1883.

Evaluation of NASA's Carbon Monitoring System (CMS) Flux Pilot: Terrestrial CO2 Fluxes

NASA Astrophysics Data System (ADS)

Fisher, J. B.; Polhamus, A.; Bowman, K. W.; Collatz, G. J.; Potter, C. S.; Lee, M.; Liu, J.; Jung, M.; Reichstein, M.

2011-12-01

NASA's Carbon Monitoring System (CMS) flux pilot project combines NASA's Earth System models in land, ocean and atmosphere to track surface CO2 fluxes. The system is constrained by atmospheric measurements of XCO2 from the Japanese GOSAT satellite, giving a "big picture" view of total CO2 in Earth's atmosphere. Combining two land models (CASA-Ames and CASA-GFED), two ocean models (ECCO2 and NOBM) and two atmospheric chemistry and inversion models (GEOS-5 and GEOS-Chem), the system brings together the stand-alone component models of the Earth System, all of which are run diagnostically constrained by a multitude of other remotely sensed data. Here, we evaluate the biospheric land surface CO2 fluxes (i.e., net ecosystem exchange, NEE) as estimated from the atmospheric flux inversion. We compare against the prior bottom-up estimates (e.g., the CASA models) as well. Our evaluation dataset is the independently derived global wall-to-wall MPI-BGC product, which uses a machine learning algorithm and model tree ensemble to "scale-up" a network of in situ CO2 flux measurements from 253 globally-distributed sites in the FLUXNET network. The measurements are based on the eddy covariance method, which uses observations of co-varying fluxes of CO2 (and water and energy) from instruments on towers extending above ecosystem canopies; the towers integrate fluxes over large spatial areas (~1 km2). We present global maps of CO2 fluxes and differences between products, summaries of fluxes by TRANSCOM region, country, latitude, and biome type, and assess the time series, including timing of minimum and maximum fluxes. This evaluation shows both where the CMS is performing well, and where improvements should be directed in further work.

What can we learn about ammonia fluxes from open-path eddy covariance measurements?

NASA Astrophysics Data System (ADS)

Pan, D.; Zondlo, M. A.; Benedict, K. B.; Schichtel, B. A.; Ham, J. M.; Shonkwiler, K. B.; Collett, J. L., Jr.

2016-12-01

Ammonia (NH3) is an important component of bio-atmospheric N cycle with implications of regional air quality, human and ecosystem health degradation, and global climate change. NH3 fluxes have high spatiotemporal variability controlled by several factors, such as atmospheric NH3 concentration, meteorological conditions, and compensation point of underlying surfaces. Quantifying NH3 fluxes is further complicated by severe measurement challenges including adsorption to instrument surfaces, low mole fractions, and gas-particle phase partitioning. To overcome these challenges, we have developed an open-path, eddy covariance NH3 instrument that minimizes these sampling issues. Eddy covariance measurements in 2015 and 2016 in the Rocky Mountain National Park (RMNP), Colorado showed the capabilities of the system to measure fluxes in clean and moderate-polluted regions. Interesting patterns of NH3 fluxes and NH3 concentration variations were observed, such as deposition of NH3 associated plumes from urban and agricultural areas and reemission of a similar magnitude when clean free-tropospheric air passing the site. Observed downward fluxes during midnight and upward fluxes in early morning also indicated NH3 fluxes related to dew formation and evaporation events. More details about these patterns and their relationships with ambient temperature, relative humidity, and other fluxes will be presented. These measurements also provided an opportunity to evaluate our current understanding of transport and deposition of NH3. Micrometeorological method, backward trajectory model, and bidirectional NH3 flux model were used to analyze observed variability of NH3 concentrations and fluxes. Implications of these results and how eddy covariance measurements combined with other measurements may provide insights to better quantify NH3 fluxes will be discussed.

Analysis of the surface heat balance over the world ocean

NASA Technical Reports Server (NTRS)

Esbenson, S. K.

1981-01-01

The net surface heat fluxes over the global ocean for all calendar months were evaluated. To obtain a formula in the form Qs = Q2(T*A - Ts), where Qs is the net surface heat flux, Ts is the sea surface temperature, T*A is the apparent atmospheric equilibrium temperature, and Q2 is the proportionality constant. Here T*A and Q2, derived from the original heat flux formulas, are functions of the surface meteorological parameters (e.g., surface wind speed, air temperature, dew point, etc.) and the surface radiation parameters. This formulation of the net surface heat flux together with climatological atmospheric parameters provides a realistic and computationally efficient upper boundary condition for oceanic climate modeling.

NASA/GEWEX Surface Radiation Budget: First Results From The Release 4 GEWEX Integrated Data Products

NASA Astrophysics Data System (ADS)

Stackhouse, Paul; Cox, Stephen; Gupta, Shashi; Mikovitz, J. Colleen; zhang, taiping

2016-04-01

The NASA/GEWEX Surface Radiation Budget (SRB) project produces shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. Spatial resolution is 1 degree. The current release 3 (available at gewex-srb.larc.nasa.gov) uses the International Satellite Cloud Climatology Project (ISCCP) DX product for pixel level radiance and cloud information. This product is subsampled to 30 km. ISCCP is currently recalibrating and recomputing their entire data series, to be released as the H product, at 10km resolution. The ninefold increase in pixel number should help improve the RMS of the existing products and allow for future higher resolution SRB gridded product (e.g. 0.5 degree). In addition to the input data improvements, several important algorithm improvements have been made. Most notable has been the adaptation of Angular Distribution Models (ADMs) from CERES to improve the initial calculation of shortwave TOA fluxes, from which the surface flux calculations follow. Other key input improvements include a detailed aerosol history using the Max Planck Institut Aerosol Climatology (MAC), temperature and moisture profiles from HIRS, and new topography, surface type, and snow/ice. Here we present results for the improved GEWEX Shortwave and Longwave algorithm (GSW and GLW) with new ISCCP data, the various other improved input data sets and the incorporation of many additional internal SRB model improvements. As of the time of abstract submission, results from 2007 have been produced with ISCCP H availability the limiting factor. More SRB data will be produced as ISCCP reprocessing continues. The SRB data produced will be released as part of the Release 4.0 Integrated Product, recognizing the interdependence of the radiative fluxes with other GEWEX products providing estimates of the Earth's global water and energy cycle (I.e., ISCCP, SeaFlux, LandFlux, NVAP, etc.).

Modeling Transport of Turbulent Fluxes in a Heterogeneous Urban Canopy Using a Spatially Explicit Energy Balance

NASA Astrophysics Data System (ADS)

Moody, M.; Bailey, B.; Stoll, R., II

2017-12-01

Understanding how changes in the microclimate near individual plants affects the surface energy budget is integral to modeling land-atmosphere interactions and a wide range of near surface atmospheric boundary layer phenomena. In urban areas, the complex geometry of the urban canopy layer results in large spatial deviations of turbulent fluxes further complicating the development of models. Accurately accounting for this heterogeneity in order to model urban energy and water use requires a sub-plant level understanding of microclimate variables. We present analysis of new experimental field data taken in and around two Blue Spruce (Picea pungens) trees at the University of Utah in 2015. The test sites were chosen in order study the effects of heterogeneity in an urban environment. An array of sensors were placed in and around the conifers to quantify transport in the soil-plant-atmosphere continuum: radiative fluxes, temperature, sap fluxes, etc. A spatial array of LEMS (Local Energy Measurement Systems) were deployed to obtain pressure, surrounding air temperature and relative humidity. These quantities are used to calculate the radiative and turbulent fluxes. Relying on measurements alone is insufficient to capture the complexity of microclimate distribution as one reaches sub-plant scales. A spatially-explicit radiation and energy balance model previously developed for deciduous trees was extended to include conifers. The model discretizes the tree into isothermal sub-volumes on which energy balances are performed and utilizes incoming radiation as the primary forcing input. The radiative transfer component of the model yields good agreement between measured and modeled upward longwave and shortwave radiative fluxes. Ultimately, the model was validated through an examination of the full energy budget including radiative and turbulent fluxes through isolated Picea pungens in an urban environment.

Characterizing energy budget variability at a Sahelian site: a test of NWP model behaviour

NASA Astrophysics Data System (ADS)

Mackie, Anna; Palmer, Paul I.; Brindley, Helen

2017-12-01

We use observations of surface and top-of-the-atmosphere (TOA) broadband radiation fluxes determined from the Atmospheric Radiation Measurement programme mobile facility, the Geostationary Earth Radiation Budget (GERB) and Spinning Enhanced Visible and Infrared Imager (SEVIRI) instruments and a range of meteorological variables at a site in the Sahel to test the ability of the ECMWF Integrated Forecasting System cycle 43r1 to describe energy budget variability. The model has daily average biases of -12 and 18 W m-2 for outgoing longwave and reflected shortwave TOA radiation fluxes, respectively. At the surface, the daily average bias is 12(13) W m-2 for the longwave downwelling (upwelling) radiation flux and -21(-13) W m-2 for the shortwave downwelling (upwelling) radiation flux. Using multivariate linear models of observation-model differences, we attribute radiation flux discrepancies to physical processes, and link surface and TOA fluxes. We find that model biases in surface radiation fluxes are mainly due to a low bias in ice water path (IWP), poor description of surface albedo and model-observation differences in surface temperature. We also attribute observed discrepancies in the radiation fluxes, particularly during the dry season, to the misrepresentation of aerosol fields in the model from use of a climatology instead of a dynamic approach. At the TOA, the low IWP impacts the amount of reflected shortwave radiation while biases in outgoing longwave radiation are additionally coupled to discrepancies in the surface upwelling longwave flux and atmospheric humidity.

Methane emissions from western Canadian peatland lakes: assessing interactive effects of groundwater connectivity and permafrost thaw

NASA Astrophysics Data System (ADS)

Kuhn, M. A.; Riechert, C.; Estop Aragones, C.; Broder, T.; Bastviken, D.; Knorr, K. H.; Olefeldt, D.

2017-12-01

Rising temperatures and the submergence of recently thawed permafrost into lakes has been identified as a major driver of methane (CH4) emissions in northern regions. Lakes on the vast Taiga Plains in western Canada represent a vital unknown with respect to CH4 fluxes and their sensitivity to permafrost thaw. The Taiga Plains has several characteristics that could influence magnitude and controls on lake CH4 emissions in comparison to other regions, including high soil organic carbon stores, distinct permafrost history, and complex groundwater interactions that influence availability of terminal electron acceptor concentrations among lakes. The goal of this research is to describe the similarities and differences in processes governing lake CH4 emissions between western Canada and other northern regions. We carried out biweekly diffusive and ebullition flux measurements and monitored sediment redox profiles from two lakes near the border between Alberta and the Northwest Territories. The two lakes differ in contributions of surface water and groundwater inputs, respectively. Floating chamber-based fluxes were measured leading from the edges to the centers of the lakes from ice-out in early May until ice-cover in the fall. Preliminary redox profile analyses suggest the groundwater-fed lake has extremely high concentrations of sulfides (>200 µmol L-1) down to a depth of 30 cm, while the surface water lake has little to no sulfide, but high concentrations of reduced iron (>200 µmol L-1 ). Despite high sulfide concentrations in the sediments, the groundwater-fed lake had generally higher diffusive fluxes compared to the surface water lake, but there were no differences between the center and along the actively collapsing thermokarst edges. However, ebullition fluxes were highest from a recently thawed lake edge compared to the center of the lake and stable, non-thaw influenced edges. The results of this project will help improve current regional CH4 models by including ground-based methane flux measurements from the vast and previously unstudied region of western Canada.

Comparison of Different Global Information Sources Used in Surface Radiative Flux Calculation: Radiative Properties of the Surface

NASA Technical Reports Server (NTRS)

Zhang, Yuanchong; Rossow, William B.; Stackhouse, Paul W., Jr.

2007-01-01

Direct estimates of surface radiative fluxes that resolve regional and weather-scale variabilty over the whole globe with reasonable accuracy have only become possible with the advent of extensive global, mostly satellite, datasets within the past couple of decades. The accuracy of these fluxes, estimated to be about 10-15 W per square meter is largely limited by the accuracy of the input datasets. The leading uncertainties in the surface fluxes are no longer predominantly induced by clouds but are now as much associated with uncertainties in the surface and near-surface atmospheric properties. This study presents a fuller, more quantitative evaluation of the uncertainties for the surface albedo and emissivity and surface skin temperatures by comparing the main available global datasets from the Moderate-Resolution Imaging Spectroradiometer product, the NASA Global Energy and Water Cycle Experiment Surface Radiation Budget project, the European Centre for Medium-Range Weather Forecasts, the National Aeronautics and Space Administration, the National Centers for Environmental Prediction, the International Satellite Cloud Climatology Project (ISCCP), the Laboratoire de Meteorologie Dynamique, NOAA/NASA Pathfinder Advanced Very High Resolution Radiometer project, NOAA Optimum Interpolation Sea Surface Temperature Analysis and the Tropical Rainfall Measuring Mission (TRMM) Microwave Image project. The datasets are, in practice, treated as an ensemble of realizations of the actual climate such that their differences represent an estimate of the uncertainty in their measurements because we do not possess global truth datasets for these quantities. The results are globally representative and may be taken as a generalization of our previous ISCCP-based uncertainty estimates for the input datasets. Surface properties have the primary role in determining the surface upward shortwave (SW) and longwave (LW) flux. From this study, the following conclusions are obtained. Although land surface albedos in the near near-infrared remain poorly constrained (highly uncertain), they do not cause too much error in total surface SW fluxes; the more subtle regional and seasonal variations associated with vegetation and snow are still on doubt. The uncertainty of the broadband black-sky SW albedo for land surface from this study is about 7%, which can easily induce 5-10 W per square meter uncertainty in (upwelling) surface SW flux estimates. Even though available surface (broadband) LW emissivity datasets differ significantly (3%-5% uncertainty), this disagreement is confined to wavelengths greater than 20 micrometers so that there is little practical effect (1-3 W per square meters) on the surface upwelling LW fluxes. The surface skin temperature is one of two leading factors that cause problems with surface LW fluxes. Even though the differences among the various datasets are generally only 2-4 K, this can easily cause 10-15 W per square meter uncertainty in calculated surface (upwelling) LW fluxes. Significant improvements could be obtained for surface LW flux calculations by improving the retrievals of (in order of decreasing importance): (1) surface skin temperature, (2) surface air and near-surface-layer temperature, (3) column precipitable water amount and (4) broadband emissivity. And for surface SW fluxes, improvements could be obtained (excluding improved cloud treatment) by improving the retrievals of (1) aerosols (from our sensitivity studies but not discussed in this work), and (2) surface (black-sky) albedo, of which, NIR part of the spectrum has much larger uncertainty.

High heat flux measurements and experimental calibrations/characterizations

NASA Technical Reports Server (NTRS)

Kidd, Carl T.

1992-01-01

Recent progress in techniques employed in the measurement of very high heat-transfer rates in reentry-type facilities at the Arnold Engineering Development Center (AEDC) is described. These advances include thermal analyses applied to transducer concepts used to make these measurements; improved heat-flux sensor fabrication methods, equipment, and procedures for determining the experimental time response of individual sensors; performance of absolute heat-flux calibrations at levels above 2,000 Btu/cu ft-sec (2.27 kW/cu cm); and innovative methods of performing in-situ run-to-run characterizations of heat-flux probes installed in the test facility. Graphical illustrations of the results of extensive thermal analyses of the null-point calorimeter and coaxial surface thermocouple concepts with application to measurements in aerothermal test environments are presented. Results of time response experiments and absolute calibrations of null-point calorimeters and coaxial thermocouples performed in the laboratory at intermediate to high heat-flux levels are shown. Typical AEDC high-enthalpy arc heater heat-flux data recently obtained with a Calspan-fabricated null-point probe model are included.

Control of wave-driven turbulence and surface heating on the mixing of microplastic marine debris

NASA Astrophysics Data System (ADS)

Kukulka, T.; Lavender Law, K. L.; Proskurowski, G. K.

2016-02-01

Buoyant microplastic marine debris (MPMD) is a pollutant in the ocean surface boundary layer (OSBL) that is submerged by turbulent transport processes. Langmuir circulation (LC) is a turbulent process driven by wind and surface waves that enhances mixing in the OSBL. Sea surface cooling also contributes to OSBL turbulence by driving convection. On the other hand, sea surface heating stratifies and stabilizes the water column to reduce turbulent motion. We analyze observed MPMD surface concentrations in the Atlantic and Pacific Oceans to reveal a significant increase in MPMD concentrations during surface heating and a decrease during surface cooling. Turbulence resolving large eddy simulations of the OSBL for an idealized diurnal heating cycle suggest that turbulent downward fluxes of buoyant tracers are enhanced at night, facilitating deep submergence of plastics, and suppressed in heating conditions, resulting in surface trapped MPMD. Simulations agree with observations if enhanced mixing due to LC is included. Our results demonstrate the controlling influence of surface heat fluxes and LC on turbulent transport in the OSBL and on vertical distributions of buoyant marine particles.

Modelling of mercury emissions from background soils.

PubMed

Scholtz, M T; Van Heyst, B J; Schroeder, W H

2003-03-20

Emissions of volatile mercury species from natural soils are believed to be a significant contributor to the atmospheric burden of mercury, but only order-of-magnitude estimates of emissions from these sources are available. The scaling-up of mercury flux measurements to regional or global scales is confounded by a limited understanding of the physical, chemical and biochemical processes that occur in the soil, a complex environmental matrix. This study is a first step toward the development of an air-surface exchange model for mercury (known as the mercury emission model (MEM)). The objective of the study is to model the partitioning and movement of inorganic Hg(II) and Hg(0) in open field soils, and to use MEM to interpret published data on mercury emissions to the atmosphere. MEM is a multi-layered, dynamic finite-element soil and atmospheric surface-layer model that simulates the exchange of heat, moisture and mercury between soils and the atmosphere. The model includes a simple formulation of the reduction of inorganic Hg(II) to Hg(0). Good agreement was found between the meteorological dependence of observed mercury emission fluxes, and hourly modelled fluxes, and it is concluded that MEM is able to simulate well the soil and atmospheric processes influencing the emission of Hg(0) to the atmosphere. The heretofore unexplained close correlation between soil temperature and mercury emission flux is fully modelled by MEM and is attributed to the temperature dependence of the Hg(0) Henry's Law coefficient and the control of the volumetric soil-air fraction on the diffusion of Hg(0) near the surface. The observed correlation between solar radiation intensity and mercury flux, appears in part to be due to the surface-energy balance between radiation, and sensible and latent heat fluxes which determines the soil temperature. The modelled results imply that empirical correlations that are based only on flux chamber data, may not extend to the open atmosphere for all weather scenarios.

The inverse Numerical Computer Program FLUX-BOT for estimating Vertical Water Fluxes from Temperature Time-Series.

NASA Astrophysics Data System (ADS)

Trauth, N.; Schmidt, C.; Munz, M.

2016-12-01

Heat as a natural tracer to quantify water fluxes between groundwater and surface water has evolved to a standard hydrological method. Typically, time series of temperatures in the surface water and in the sediment are observed and are subsequently evaluated by a vertical 1D representation of heat transport by advection and dispersion. Several analytical solutions as well as their implementation into user-friendly software exist in order to estimate water fluxes from the observed temperatures. Analytical solutions can be easily implemented but assumptions on the boundary conditions have to be made a priori, e.g. sinusoidal upper temperature boundary. Numerical models offer more flexibility and can handle temperature data which is characterized by irregular variations such as storm-event induced temperature changes and thus cannot readily be incorporated in analytical solutions. This also reduced the effort of data preprocessing such as the extraction of the diurnal temperature variation. We developed a software to estimate water FLUXes Based On Temperatures- FLUX-BOT. FLUX-BOT is a numerical code written in MATLAB which is intended to calculate vertical water fluxes in saturated sediments, based on the inversion of measured temperature time series observed at multiple depths. It applies a cell-centered Crank-Nicolson implicit finite difference scheme to solve the one-dimensional heat advection-conduction equation. Besides its core inverse numerical routines, FLUX-BOT includes functions visualizing the results and functions for performing uncertainty analysis. We provide applications of FLUX-BOT to generic as well as to measured temperature data to demonstrate its performance.

Heat transfer and pressure measurements for the SSME fuel turbine

NASA Technical Reports Server (NTRS)

Dunn, Michael G.; Kim, Jungho

1991-01-01

A measurement program is underway using the Rocketdyne two-stage Space Shuttle Main Engine (SSME) fuel turbine. The measurements use a very large shock tunnel to produce a short-duration source of heated and pressurized gas which is subsequently passed through the turbine. Within this environment, the turbine is operated at the design values of flow function, stage pressure ratio, stage temperature ratio, and corrected speed. The first stage vane row and the first stage blade row are instrumented in both the spanwise and chordwise directions with pressure transducers and heat flux gages. The specific measurements to be taken include time averaged surface pressure and heat flux distributions on the vane and blade, flow passage static pressure, flow passage total pressure and total temperature distributions, and phase resolved surface pressure and heat flux on the blade.

Influence of water table fluctuations on subsurface methane dynamics and surface fluxes in seasonally flooded subtropical pastures.

NASA Astrophysics Data System (ADS)

Chamberlain, S.; Gomez-Casanovas, N.; Boughton, E.; Keel, E.; Walter, M. T.; Groffman, P. M.; Sparks, J. P.

2015-12-01

Seasonally flooded subtropical pastures are major sources of methane (CH4), and periodic flooding drives complex emission dynamics from these ecosystems. Understanding the mechanisms of belowground CH4 dynamics driving soil surface fluxes is needed to better understand emissions from these systems and their response to environmental change. We investigated subsurface CH4 dynamics in relation to net surface fluxes using laboratory water table manipulations and compared these results to eddy covariance-measured fluxes to link within-soil CH4 dynamics to observed ecosystem fluxes. Pronounced hysteresis was observed in ecosystem CH4 fluxes during precipitation driven flooding events. This dynamic was replicated in mesocosm experiments, with maximum CH4 fluxes observed during periods of water table recession. Hysteresis dynamics were best explained by oxygen dynamics during precipitation recharge events and the oxidation of CH4 produced in organic soil horizons during water table recession. We observed distinct CH4 dynamics between surface organic and deeper mineral soil horizons. In surface organic soil horizons, high levels of CH4 production were temporally linked to observed surface emissions. In contrast, high concentrations of CH4 observed in deeper mineral soils did not contribute to surface fluxes. Methane production potentials in surface organic soils were orders of magnitude higher than in mineral soils, suggesting that over longer flooding regimes CH4 produced in mineral horizons is unlikely to be a significant component of net surface emissions. Our results demonstrate that distinct CH4 dynamics may be stratified by depth, and flooding of the near-surface organic soils drives the high magnitude CH4 fluxes observed from subtropical pastures. These results suggest that relatively small changes in pasture water table dynamics can drive large changes in net CH4 emissions if surface organic soils remain saturated over longer time scales.

Quantifying the Impact of Background Atmospheric Stability on Air-Ice-Ocean Interactions the Arctic Ocean During the Fall Freeze-Up

NASA Astrophysics Data System (ADS)

Guest, P. S.; Persson, O. P. G.; Blomquist, B.; Fairall, C. W.

2016-02-01

"Background" stability refers to the effect of vertical virtual temperature variations above the surface layer on fluxes within the surface layer. This is different from the classical surface layer stability quantified by the Obhukhov length scale. In most locations, changes in the background stability do not have a significant direct impact on surface fluxes. However in polar regions, where there is usually a strong low-level temperature inversion capping the boundary layer, changes in background stability can have big impacts on surface fluxes. Therefore, in the Arctic, there is potential for a positive feedback effect between ice cover and surface wind speed (and momentum flux) due to the background stability effects. As the surface becomes more ice free, heat fluxes from the surface weaken the temperature inversion which in turn increases the surface wind speed which further increases the surface turbulent heat fluxes and removes more sea ice by melting or advection. It is not clear how important feedbacks involving the background stability are during the fall freeze up of the Arctic Ocean; that will be the focus of this study. As part of an ONR-sponsored cruise in the fall of 2015 to examine sea state and boundary layer processes in the Beaufort Sea on the R/V Sikuliaq, the authors will perform a variety of surface layer and upper level atmospheric measurements of temperature, humidity and wind vector using ship platform instruments, radiosonde weather balloons, tethered balloons, kites, and miniature quad-rotor unmanned aerial vehicles. In addition, the authors will deploy a full suite of turbulent and radiational flux measurements from the vessel. These measurements will be used to quantify the impact of changing surface conditions on atmospheric structure and vice-versa. The goal is to directly observe how the surface and atmosphere above the surface layer interact and feedback with each other through radiational and turbulent fluxes.

Measurement of a surface heat flux and temperature

NASA Astrophysics Data System (ADS)

Davis, R. M.; Antoine, G. J.; Diller, T. E.; Wicks, A. L.

1994-04-01

The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. It consists of several thin-film layers forming a differential thermopile across a thermal resistance layer. The measured heat flux q is proportional to the temperature difference across the resistance layer q= k(sub g)/delta(sub g) x (t(sub 1) - T(sub 2)), where k(sub g) is the thermal conductivity and delta (sub g) is the thickness of the thermal resistance layer. Because the gages are sputter coated directly onto the surface, their total thickness is less than 2 micrometers, which is two orders of magnitude thinner than previous gages. The resulting temperature difference across the thermal resistance layer (delta is less than 1 micrometer) is very small even at high heat fluxes. To generate a measurable signal many thermocouple pairs are put in series to form a differential thermopile. The combination of series thermocouple junctions and thin-film design creates a gage with very attractive characteristics. It is not only physically non-intrusive to the flow, but also causes minimal disruption of the surface temperature. Because it is so thin, the response time is less than 20 microsec. Consequently, the frequency response is flat from 0 to over 50 kHz. Moreover, the signal of the Heat Flux Microsensor is directly proportional to the heat flux. Therefore, it can easily be used in both steady and transient flows, and it measures both the steady and unsteady components of the surface heat flux. A version of the Heat Flux Microsensor has been developed to meet the harsh demands of combustion environments. These gages use platinum and platinum-10 percent rhodium as the thermoelectric materials. The thermal resistance layer is silicon monoxide and a protective coating of Al2O3 is deposited on top of the sensor. The superimposed thin-film pattern of all six layers is presented. The large pads are for connection with pins used to bring the signal out the back of the ceramic.

Measurement of a surface heat flux and temperature

NASA Technical Reports Server (NTRS)

Davis, R. M.; Antoine, G. J.; Diller, T. E.; Wicks, A. L.

1994-01-01

The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. It consists of several thin-film layers forming a differential thermopile across a thermal resistance layer. The measured heat flux q is proportional to the temperature difference across the resistance layer q= k(sub g)/delta(sub g) x (t(sub 1) - T(sub 2)), where k(sub g) is the thermal conductivity and delta (sub g) is the thickness of the thermal resistance layer. Because the gages are sputter coated directly onto the surface, their total thickness is less than 2 micrometers, which is two orders of magnitude thinner than previous gages. The resulting temperature difference across the thermal resistance layer (delta is less than 1 micrometer) is very small even at high heat fluxes. To generate a measurable signal many thermocouple pairs are put in series to form a differential thermopile. The combination of series thermocouple junctions and thin-film design creates a gage with very attractive characteristics. It is not only physically non-intrusive to the flow, but also causes minimal disruption of the surface temperature. Because it is so thin, the response time is less than 20 microsec. Consequently, the frequency response is flat from 0 to over 50 kHz. Moreover, the signal of the Heat Flux Microsensor is directly proportional to the heat flux. Therefore, it can easily be used in both steady and transient flows, and it measures both the steady and unsteady components of the surface heat flux. A version of the Heat Flux Microsensor has been developed to meet the harsh demands of combustion environments. These gages use platinum and platinum-10 percent rhodium as the thermoelectric materials. The thermal resistance layer is silicon monoxide and a protective coating of Al2O3 is deposited on top of the sensor. The superimposed thin-film pattern of all six layers is presented. The large pads are for connection with pins used to bring the signal out the back of the ceramic. In addition to the heat flux measurement, the surface temperature is measured with a platinum resistance layer (RTS). The resistance of this layer increases with increasing temperature. Therefore, these gages simultaneously measure the surface temperature and heat flux. The demonstrated applications include rocket nozzles, SCRAM jet engines, gas turbine engines, boiling heat transfer, flame experiments, basic fluid heat transfer, hypersonic flight, and shock tube testing. The laboratory involves using one of these sensors in a small combustion flame. The sensor is made on a 2.5 cm diameter piece of aluminum nitride ceramic.

Synergy of the SimSphere land surface process model with ASTER imagery for the retrieval of spatially distributed estimates of surface turbulent heat fluxes and soil moisture content

NASA Astrophysics Data System (ADS)

Petropoulos, George; Wooster, Martin J.; Carlson, Toby N.; Drake, Nick

2010-05-01

Accurate information on spatially explicit distributed estimates of key land-atmosphere fluxes and related land surface parameters is of key importance in a range of disciplines including hydrology, meteorology, agriculture and ecology. Estimation of those parameters from remote sensing frequently employs the integration of such data with mathematical representations of the transfers of energy, mass and radiation between soil, vegetation and atmosphere continuum, known as Soil Vegetation Atmosphere Transfer (SVAT) models. The ability of one such inversion modelling scheme to resolve for key surface energy fluxes and of soil surface moisture content is examined here using data from a multispectral high spatial resolution imaging instrument, the Advanced Spaceborne Thermal Emission and Reflection Scanning Radiometer (ASTER) and SimSphere one-dimensional SVAT model. Accuracy of the investigated methodology, so-called as the "triangle" method, is verified using validated ground observations obtained from selected days collected from nine CARBOEUROPE IP sites representing a variety of climatic, topographic and environmental conditions. Subsequently, a new framework is suggested for the retrieval of two additional parameters by the investigated method, namely the Evaporative (EF) and the Non-Evaporative (NEF) Fractions. Results indicated a close agreement between the inverted surface fluxes and surface moisture availability maps as well as of the EF and NEF parameters with the observations both spatially and temporally with accuracies comparable to those obtained in similar experiments with high spatial resolution data. Inspection of the inverted surface fluxes maps regionally, showed an explainable distribution in the range of the inverted parameters in relation with the surface heterogeneity. Overall performance of the "triangle" inversion methodology was found to be affected predominantly by the SVAT model "correct" initialisation representative of the test site environment, most importantly the atmospheric conditions required in the SVAT model initial conditions. This study represents the first comprehensive evaluation of the performance of this particular methodological implementation at a European setting using the SimSphere SVAT with the ASTER data. The present work is also very timely in that, a variation of this specific inversion methodology has been proposed for the operational retrieval of the soil surface moisture content by National Polar-orbiting Operational Environmental Satellite System (NPOESS), in a series of satellite platforms that are due to be launched in the next 12 years starting from 2012. KEYWORDS: micrometeorology, surface heat fluxes, soil moisture content, ASTER, triangle method, SimSphere, CarboEurope IP

Gradient flux measurements of sea-air DMS transfer during the Surface Ocean Aerosol Production (SOAP) experiment

NASA Astrophysics Data System (ADS)

Smith, Murray J.; Walker, Carolyn F.; Bell, Thomas G.; Harvey, Mike J.; Saltzman, Eric S.; Law, Cliff S.

2018-04-01

Direct measurements of marine dimethylsulfide (DMS) fluxes are sparse, particularly in the Southern Ocean. The Surface Ocean Aerosol Production (SOAP) voyage in February-March 2012 examined the distribution and flux of DMS in a biologically active frontal system in the southwest Pacific Ocean. Three distinct phytoplankton blooms were studied with oceanic DMS concentrations as high as 25 nmol L-1. Measurements of DMS fluxes were made using two independent methods: the eddy covariance (EC) technique using atmospheric pressure chemical ionization-mass spectrometry (API-CIMS) and the gradient flux (GF) technique from an autonomous catamaran platform. Catamaran flux measurements are relatively unaffected by airflow distortion and are made close to the water surface, where gas gradients are largest. Flux measurements were complemented by near-surface hydrographic measurements to elucidate physical factors influencing DMS emission. Individual DMS fluxes derived by EC showed significant scatter and, at times, consistent departures from the Coupled Ocean-Atmosphere Response Experiment gas transfer algorithm (COAREG). A direct comparison between the two flux methods was carried out to separate instrumental effects from environmental effects and showed good agreement with a regression slope of 0.96 (r2 = 0.89). A period of abnormal downward atmospheric heat flux enhanced near-surface ocean stratification and reduced turbulent exchange, during which GF and EC transfer velocities showed good agreement but modelled COAREG values were significantly higher. The transfer velocity derived from near-surface ocean turbulence measurements on a spar buoy compared well with the COAREG model in general but showed less variation. This first direct comparison between EC and GF fluxes of DMS provides confidence in compilation of flux estimates from both techniques, as well as in the stable periods when the observations are not well predicted by the COAREG model.

Estimating regional CO2 and CH4 fluxes using GOSAT XCO2 and XCH4 observations

NASA Astrophysics Data System (ADS)

Fraser, A. C.; Palmer, P. I.; Feng, L.; Parker, R.; Boesch, H.; Cogan, A. J.

2012-12-01

We infer regional monthly surface flux estimates for CO2 and CH4, June 2009-December 2010, from proxy dry-air column-averaged mole fractions of CO2 and CH4 from the Greenhouse gases Observing SATellite (GOSAT) using an ensemble Kalman Filter combined with the GEOS-Chem chemistry transport model. We compare these flux estimates with estimates inferred from in situ surface mole fraction measurements and from combining in situ and GOSAT measurements in order to quantify the added value of GOSAT data above the conventional surface measurement network. We find that the error reduction, a measure of how much the posterior fluxes are being informed by the assimilated data, at least doubles when GOSAT measurements are used versus the surface only inversions, with the exception of regions that are well covered by the surface network at the spatial and temporal resolution of our flux estimation calculation. We have incorporated a new online bias correction scheme to account for GOSAT biases. We report global and regional flux estimates inferred from GOSAT and/or in situ measurements. While the global posterior fluxes from GOSAT and in situ measurements agree, we find significant differences in the regional fluxes, particularly over the tropics. We evaluate the posterior fluxes by comparing them against independent surface mole fraction, column, and aircraft measurements using the GEOS-Chem model as an intermediary.

Impact of water use efficiency on eddy covariance flux partitioning using correlation structure analysis

USDA-ARS?s Scientific Manuscript database

Partitioned land surfaces fluxes (e.g. evaporation, transpiration, photosynthesis, and ecosystem respiration) are needed as input, calibration, and validation data for numerous hydrological and land surface models. However, one of the most commonly used techniques for measuring land surface fluxes,...

Real-time plasma control in a dual-frequency, confined plasma etcher

NASA Astrophysics Data System (ADS)

Milosavljević, V.; Ellingboe, A. R.; Gaman, C.; Ringwood, J. V.

2008-04-01

The physics issues of developing model-based control of plasma etching are presented. A novel methodology for incorporating real-time model-based control of plasma processing systems is developed. The methodology is developed for control of two dependent variables (ion flux and chemical densities) by two independent controls (27 MHz power and O2 flow). A phenomenological physics model of the nonlinear coupling between the independent controls and the dependent variables of the plasma is presented. By using a design of experiment, the functional dependencies of the response surface are determined. In conjunction with the physical model, the dependencies are used to deconvolve the sensor signals onto the control inputs, allowing compensation of the interaction between control paths. The compensated sensor signals and compensated set-points are then used as inputs to proportional-integral-derivative controllers to adjust radio frequency power and oxygen flow to yield the desired ion flux and chemical density. To illustrate the methodology, model-based real-time control is realized in a commercial semiconductor dielectric etch chamber. The two radio frequency symmetric diode operates with typical commercial fluorocarbon feed-gas mixtures (Ar/O2/C4F8). Key parameters for dielectric etching are known to include ion flux to the surface and surface flux of oxygen containing species. Control is demonstrated using diagnostics of electrode-surface ion current, and chemical densities of O, O2, and CO measured by optical emission spectrometry and/or mass spectrometry. Using our model-based real-time control, the set-point tracking accuracy to changes in chemical species density and ion flux is enhanced.

Characterization of Turbulent Latent and Sensible Heat Flux Exchange Between the Atmosphere and Ocean in MERRA

NASA Technical Reports Server (NTRS)

Robert, J. Brent; Robertson, Franklin R.; Clayson, Carol Anne; Bosilovich, Michael G.

2012-01-01

Turbulent fluxes of heat and moisture across the atmosphere-ocean interface are fundamental components of the Earth's energy and water balance. Characterizing both the spatiotemporal variability and the fidelity of these exchanges of heat and moisture is critical to understanding the global water and energy cycle variations, quantifying atmosphere-ocean feedbacks, and improving model predictability. This study examines the veracity of the recently completed NASA Modern-Era Retrospective analysis for Research and Applications (MERRA) product with respect to its representation of the surface turbulent heat fluxes. A validation of MERRA turbulent heat fluxes and near-surface bulk variables at local, high-resolution space and time scales is achieved by making comparisons to a large suite of direct observations. Both in situ and satellite-observed gridded surface heat flux estimates are employed to investigate the spatial and temporal variability of the surface fluxes with respect to their annual mean climatologies, their seasonal covariability of near-surface bulk parameters, and their representation of extremes. The impact of data assimilation on the near-surface parameters is assessed through evaluation of incremental analysis update tendencies produced by the assimilation procedure. It is found that MERRA turbulent surface heat fluxes are relatively accurate for typical conditions but have systematically weak vertical gradients in moisture and temperature and have a weaker covariability between the near-surface gradients and wind speed than found in observations. This results in an underestimate of the surface latent and sensible heat fluxes over the western boundary current and storm track regions. The assimilation of observations mostly acts to bring MERRA closer to observational products by increasing moisture and temperature near the surface and decreasing the near-surface wind speeds. The major patterns of spatial and temporal variability of the turbulent heat fluxes produced by MERRA compare favorably to observationally based estimates. However, MERRA is distinct in terms of amplitude. These results suggest that MERRA is likely to be a valuable resource for a number of research applications though, as with all turbulent flux estimates, systematic issues should be taken into account

Characterization of Turbulent Latent and Sensible Heat Flux Exchange Between the Atmosphere and Ocean in MERRA

NASA Technical Reports Server (NTRS)

Roberts, J. Brent; Robertson, Franklin R.; Clayson, Carol Anne; Bosilovich, Michael G.

2012-01-01

Turbulent fluxes of heat and moisture across the atmosphere-ocean interface are fundamental components of the Earth s energy and water balance. Characterizing both the spatiotemporal variability and the fidelity of these exchanges of heat and moisture is critical to understanding the global water and energy cycle variations, quantifying atmosphere-ocean feedbacks, and improving model predictability. This study examines the veracity of the recently completed NASA Modern-Era Retrospective analysis for Research and Applications (MERRA) product with respect to its representation of the surface turbulent heat fluxes. A validation of MERRA turbulent heat fluxes and near-surface bulk variables at local, high-resolution space and time scales is achieved by making comparisons to a large suite of direct observations. Both in situ and satellite-observed gridded surface heat flux estimates are employed to investigate the spatial and temporal variability of the surface fluxes with respect to their annual mean climatologies, their seasonal covariability of near-surface bulk parameters, and their representation of extremes. The impact of data assimilation on the near-surface parameters is assessed through evaluation of incremental analysis update tendencies produced by the assimilation procedure. It is found that MERRA turbulent surface heat fluxes are relatively accurate for typical conditions but have systematically weak vertical gradients in moisture and temperature and have a weaker covariability between the near-surface gradients and wind speed than found in observations. This results in an underestimate of the surface latent and sensible heat fluxes over the western boundary current and storm track regions. The assimilation of observations mostly acts to bring MERRA closer to observational products by increasing moisture and temperature near the surface and decreasing the near-surface wind speeds. The major patterns of spatial and temporal variability of the turbulent heat fluxes produced by MERRA compare favorably to observationally based estimates. However, MERRA is distinct in terms of amplitude. These results suggest that MERRA is likely to be a valuable resource for a number of research applications though, as with all turbulent flux estimates, systematic issues should be taken into account.

Miniature Convection Cooled Plug-type Heat Flux Gauges

NASA Technical Reports Server (NTRS)

Liebert, Curt H.

1994-01-01

Tests and analysis of a new miniature plug-type heat flux gauge configuration are described. This gauge can simultaneously measure heat flux on two opposed active surfaces when heat flux levels are equal to or greater than about 0.2 MW/m(sup 2). The performance of this dual active surface gauge was investigated over a wide transient and steady heat flux and temperature range. The tests were performed by radiatively heating the front surface with an argon arc lamp while the back surface was convection cooled with air. Accuracy is about +20 percent. The gauge is responsive to fast heat flux transients and is designed to withstand the high temperature (1300 K), high pressure (15 MPa), erosive and corrosive environments in modern engines. This gauge can be used to measure heat flux on the surfaces of internally cooled apparatus such as turbine blades and combustors used in jet propulsion systems and on the surfaces of hypersonic vehicles. Heat flux measurement accuracy is not compromised when design considerations call for various size gauges to be fabricated into alloys of various shapes and properties. Significant gauge temperature reductions (120 K), which can lead to potential gauge durability improvement, were obtained when the gauges were air-cooled by forced convection.

Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement

DOE PAGES

Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.; ...

2018-04-19

Smore » mall 3D perturbations to the magnetic field in DIII-D ( δ B / B ~ 2 × 10 - 4 ) result in large modulations of density fluctuation amplitudes in the pedestal, which are shown using Doppler backscattering measurements to vary by a factor of 2. Helical perturbations of equilibrium density within flux surfaces have previously been observed in the pedestal of DIII-D plasmas when 3D fields are applied and were correlated with density fluctuation asymmetries in the pedestal. These intra-surface density and pressure variations are shown through two fluid MHD modeling studies using the M3D-C1 code to be due to the misalignment of the density and temperature equilibrium iso-surfaces in the pedestal region. This modeling demonstrates that the phase shift between the two iso-surfaces corresponds to the diamagnetic direction of the two species, with the mass density surfaces shifted in the ion diamagnetic direction relative to the temperature and magnetic flux iso-surfaces. Finally, the resulting pedestal density, potential, and turbulence asymmetries within flux surfaces near the separatrix may be at least partially responsible for several poorly understood phenomena that occur with the application of 3D fields in tokamaks, including density pump out and the increase in power required to transition from L- to H-mode.« less

Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.

Smore » mall 3D perturbations to the magnetic field in DIII-D ( δ B / B ~ 2 × 10 - 4 ) result in large modulations of density fluctuation amplitudes in the pedestal, which are shown using Doppler backscattering measurements to vary by a factor of 2. Helical perturbations of equilibrium density within flux surfaces have previously been observed in the pedestal of DIII-D plasmas when 3D fields are applied and were correlated with density fluctuation asymmetries in the pedestal. These intra-surface density and pressure variations are shown through two fluid MHD modeling studies using the M3D-C1 code to be due to the misalignment of the density and temperature equilibrium iso-surfaces in the pedestal region. This modeling demonstrates that the phase shift between the two iso-surfaces corresponds to the diamagnetic direction of the two species, with the mass density surfaces shifted in the ion diamagnetic direction relative to the temperature and magnetic flux iso-surfaces. Finally, the resulting pedestal density, potential, and turbulence asymmetries within flux surfaces near the separatrix may be at least partially responsible for several poorly understood phenomena that occur with the application of 3D fields in tokamaks, including density pump out and the increase in power required to transition from L- to H-mode.« less

Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement

NASA Astrophysics Data System (ADS)

Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.; Sugiyama, L. E.; Ferraro, N. M.; Lyons, B. C.; McKee, G. R.; Paz-Soldan, C.; Wingen, A.; Zeng, L.

2018-05-01

Small 3D perturbations to the magnetic field in DIII-D ( δB /B ˜2 ×10-4 ) result in large modulations of density fluctuation amplitudes in the pedestal, which are shown using Doppler backscattering measurements to vary by a factor of 2. Helical perturbations of equilibrium density within flux surfaces have previously been observed in the pedestal of DIII-D plasmas when 3D fields are applied and were correlated with density fluctuation asymmetries in the pedestal. These intra-surface density and pressure variations are shown through two fluid MHD modeling studies using the M3D-C1 code to be due to the misalignment of the density and temperature equilibrium iso-surfaces in the pedestal region. This modeling demonstrates that the phase shift between the two iso-surfaces corresponds to the diamagnetic direction of the two species, with the mass density surfaces shifted in the ion diamagnetic direction relative to the temperature and magnetic flux iso-surfaces. The resulting pedestal density, potential, and turbulence asymmetries within flux surfaces near the separatrix may be at least partially responsible for several poorly understood phenomena that occur with the application of 3D fields in tokamaks, including density pump out and the increase in power required to transition from L- to H-mode.

Transport driven by eddy momentum fluxes in the Gulf Stream Extension region

NASA Astrophysics Data System (ADS)

Greatbatch, R. J.; Zhai, X.; Claus, M.; Czeschel, L.; Rath, W.

2010-12-01

The importance of the Gulf Stream Extension region in climate and seasonal prediction research is being increasingly recognised. Here we use satellite-derived eddy momentum fluxes to drive a shallow water model for the North Atlantic Ocean that includes the realistic ocean bottom topography. The results show that the eddy momentum fluxes can drive significant transport, sufficient to explain the observed increase in transport of the Gulf Stream following its separation from the coast at Cape Hatteras, as well as the observed recirculation gyres. The model also captures recirculating gyres seen in the mean sea surface height field within the North Atlantic Current system east of the Grand Banks of Newfoundland, including a representation of the Mann Eddy.

On Magnetic Flux Trapping by Surface Superconductivity

NASA Astrophysics Data System (ADS)

Podolyak, E. R.

2018-03-01

The magnetic flux trapping by surface superconductivity is considered. The stability of the state localized at the cylindrical sample surface upon a change in the external magnetic field is tested. It is shown that as the magnetic field decreases, the sample acquires a positive magnetic moment due to magnetic flux trapping; i.e., the magnetization curve of surface superconductivity is "paramagnetic" by nature.

Turbulent Surface Flux Measurements over Snow-Covered Sea Ice

NASA Astrophysics Data System (ADS)

Andreas, E. L.; Fairall, C. W.; Grachev, A. A.; Guest, P. S.; Jordan, R. E.; Persson, P. G.

2006-12-01

Our group has used eddy correlation to make over 10,000 hours of measurements of the turbulent momentum and heat fluxes over snow-covered sea ice in both the Arctic and the Antarctic. Polar sea ice is an ideal site for studying fundamental processes for turbulent exchange over snow. Both our Arctic and Antarctic sites---in the Beaufort Gyre and deep into the Weddell Sea, respectively---were expansive, flat areas with continuous snow cover; and both were at least 300 km from any topography that might have complicated the atmospheric flow. In this presentation, we will review our measurements of the turbulent fluxes of momentum and sensible and latent heat. In particular, we will describe our experiences making turbulence instruments work in the fairly harsh polar, marine boundary layer. For instance, several of our Arctic sites were remote from our main camp and ran unattended for a week at a time. Besides simply making flux measurements, we have been using the data to develop a bulk flux algorithm and to study fundamental turbulence processes in the atmospheric surface layer. The bulk flux algorithm predicts the turbulent surface fluxes from mean meteorological quantities and, thus, will find use in data analyses and models. For example, components of the algorithm are already embedded in our one- dimensional mass and energy budget model SNTHERM. Our fundamental turbulence studies have included deducing new scaling regimes in the stable boundary layer; examining the Monin-Obukhov similarity functions, especially in stable stratification; and evaluating the von Kármán constant with the largest atmospheric data set ever applied to such a study. During this presentation, we will highlight some of this work.

Dry deposition of PM2.5 sulfate above a hilly forest using relaxed eddy accumulation

NASA Astrophysics Data System (ADS)

Matsuda, Kazuhide; Watanabe, Ichiro; Mizukami, Kou; Ban, Satomi; Takahashi, Akira

2015-04-01

Sulfur compounds continue to be an important component of atmospheric deposition in East Asia. In order to better understand the dry deposition of PM2.5 sulfate, which is one of the most significant transboundary air pollutants in this region, we measured the dry deposition flux of PM2.5 sulfate above a hilly forest of the Field Museum Tamakyuryo (FM Tama) site in suburban Tokyo. We used the relaxed eddy accumulation (REA) method and took measurements during the summer, from 26 July to 2 August 2013, and the autumn, from 18 to 22 November 2013. We primarily focused on the evaluation of dry deposition above a forest on complex terrain. The total flux and 80% of the runs showed downward flux. The deposition velocities measured by the REA method during times when the wind direction was from a relatively uniform sloping surface over the forest were more reasonable than those measured when the wind direction was from a more complex surface. Using a resistance model that includes the effect of growth of hygroscopic aerosols, we inferred the deposition velocities during two experimental periods. When the fluxes were averaged for a long time (i.e., about 2 weeks) the inferred fluxes and deposition velocities were in reasonable agreement with the measurements. Although averages over long periods showed good agreement, the measured deposition velocities were distributed in a wider range than those inferred by the model. An increased range of deposition velocities was associated with flux footprints from complex terrain. It is possible that the agreements between measured and inferred fluxes or deposition velocities at the site are because the depositions of sulfate are largely controlled by surface factors rather than aerodynamic resistance.

Characteristics of urban-ecosystem atmosphere fluxes of CO2, CH4, N2O, and et over Denver, Colorado

USGS Publications Warehouse

Anderson, D.E.; Alvarez, C.; Thienelt, T.

2004-01-01

The characteristics of urban ecosystems fluxes of carbon dioxide, methane, nitrous oxide, and evapotranspiration (ET) over Denver, Colorado were discussed. These atmospheric fluxes were measured using a methodology that included a combination of eddy covariance sensors at two levels on a tall tower and chamber measurements at 33 locations on the soil surface. There was both strong temporal and spatial heterogeneity of fluxes owing to characteristics of natural and anthropogenic ecosystem components. Although the urban ecosystem was a net carbon dioxide source, tower-based eddy covariance measurements showed it to be a net vegetative sink during the majority of mid-say summer hours.

Evaluation of different methods to model near-surface turbulent fluxes for a mountain glacier in the Cariboo Mountains, BC, Canada

NASA Astrophysics Data System (ADS)

Radić, Valentina; Menounos, Brian; Shea, Joseph; Fitzpatrick, Noel; Tessema, Mekdes A.; Déry, Stephen J.

2017-12-01

As part of surface energy balance models used to simulate glacier melting, choosing parameterizations to adequately estimate turbulent heat fluxes is extremely challenging. This study aims to evaluate a set of four aerodynamic bulk methods (labeled as C methods), commonly used to estimate turbulent heat fluxes for a sloped glacier surface, and two less commonly used bulk methods developed from katabatic flow models. The C methods differ in their parameterizations of the bulk exchange coefficient that relates the fluxes to the near-surface measurements of mean wind speed, air temperature, and humidity. The methods' performance in simulating 30 min sensible- and latent-heat fluxes is evaluated against the measured fluxes from an open-path eddy-covariance (OPEC) method. The evaluation is performed at a point scale of a mountain glacier, using one-level meteorological and OPEC observations from multi-day periods in the 2010 and 2012 summer seasons. The analysis of the two independent seasons yielded the same key findings, which include the following: first, the bulk method, with or without the commonly used Monin-Obukhov (M-O) stability functions, overestimates the turbulent heat fluxes over the observational period, mainly due to a substantial overestimation of the friction velocity. This overestimation is most pronounced during the katabatic flow conditions, corroborating the previous findings that the M-O theory works poorly in the presence of a low wind speed maximum. Second, the method based on a katabatic flow model (labeled as the KInt method) outperforms any C method in simulating the friction velocity; however, the C methods outperform the KInt method in simulating the sensible-heat fluxes. Third, the best overall performance is given by a hybrid method, which combines the KInt approach with the C method; i.e., it parameterizes eddy viscosity differently than eddy diffusivity. An error analysis reveals that the uncertainties in the measured meteorological variables and the roughness lengths produce errors in the modeled fluxes that are smaller than the differences between the modeled and observed fluxes. This implies that further advances will require improvement to model theory rather than better measurements of input variables. Further data from different glaciers are needed to investigate any universality of these findings.

Reduction of calcium flux from the extracellular region and endoplasmic reticulum by amorphous nano-silica particles owing to carboxy group addition on their surface.

PubMed

Onodera, Akira; Yayama, Katsutoshi; Morosawa, Hideto; Ishii, Yukina; Tsutsumi, Yasuo; Kawai, Yuichi

2017-03-01

Several studies have reported that amorphous nano-silica particles (nano-SPs) modulate calcium flux, although the mechanism remains incompletely understood. We thus analyzed the relationship between calcium flux and particle surface properties and determined the calcium flux route. Treatment of Balb/c 3T3 fibroblasts with nano-SPs with a diameter of 70 nm (nSP70) increased cytosolic calcium concentration, but that with SPs with a diameter of 300 or 1000 nm did not. Surface modification of nSP70 with a carboxy group also did not modulate calcium flux. Pretreatment with a general calcium entry blocker almost completely suppressed calcium flux by nSP70. Preconditioning by emptying the endoplasmic reticulum (ER) calcium stores slightly suppressed calcium flux by nSP70. These results indicate that nSP70 mainly modulates calcium flux across plasma membrane calcium channels, with subsequent activation of the ER calcium pump, and that the potential of calcium flux by nano-SPs is determined by the particle surface charge.

Hierarchical Superhydrophobic Surfaces with Micropatterned Nanowire Arrays for High-Efficiency Jumping Droplet Condensation.

PubMed

Wen, Rongfu; Xu, Shanshan; Zhao, Dongliang; Lee, Yung-Cheng; Ma, Xuehu; Yang, Ronggui

2017-12-27

Self-propelled droplet jumping on nanostructured superhydrophobic surfaces is of interest for a variety of industrial applications including self-cleaning, water harvesting, power generation, and thermal management systems. However, the uncontrolled nucleation-induced Wenzel state of condensed droplets at large surface subcooling (high heat flux) leads to the formation of unwanted large pinned droplets, which results in the flooding phenomenon and greatly degrades the heat transfer performance. In this work, we present a novel strategy to manipulate droplet behaviors during the process from the droplet nucleation to growth and departure through a combination of spatially controlling initial nucleation for mobile droplets by closely spaced nanowires and promoting the spontaneous outward movement of droplets for rapid removal using micropatterned nanowire arrays. Through the optical visualization experiments and heat transfer tests, we demonstrate greatly improved condensation heat transfer characteristics on the hierarchical superhydrophobic surface including the higher density of microdroplets, smaller droplet departure radius, 133% wider range of surface subcooling for droplet jumping, and 37% enhancement in critical heat flux for jumping droplet condensation, compared to the-state-of-art jumping droplet condensation on nanostructured superhydrophobic surfaces. The excellent water repellency of such hierarchical superhydrophobic surfaces can be promising for many potential applications, such as anti-icing, antifogging, water desalination, and phase-change heat transfer.

Hierarchical Superhydrophobic Surfaces with Micropatterned Nanowire Arrays for High-Efficiency Jumping Droplet Condensation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wen, Rongfu; Xu, Shanshan; Zhao, Dongliang

Self-propelled droplet jumping on nanostructured superhydrophobic surfaces is of interest for a variety of industrial applications including self-cleaning, water harvesting, power generation, and thermal management systems. However, the uncontrolled nucleation-induced Wenzel state of condensed droplets at large surface subcooling (high heat flux) leads to the formation of unwanted large pinned droplets, which results in the flooding phenomenon and greatly degrades the heat transfer performance. In this work, we present a novel strategy to manipulate droplet behaviors during the process from the droplet nucleation to growth and departure through a combination of spatially controlling initial nucleation for mobile droplets by closelymore » spaced nanowires and promoting the spontaneous outward movement of droplets for rapid removal using micropatterned nanowire arrays. Through the optical visualization experiments and heat transfer tests, we demonstrate greatly improved condensation heat transfer characteristics on the hierarchical superhydrophobic surface including the higher density of microdroplets, smaller droplet departure radius, 133% wider range of surface subcooling for droplet jumping, and 37% enhancement in critical heat flux for jumping droplet condensation, compared to the-state-of-art jumping droplet condensation on nanostructured superhydrophobic surfaces. The excellent water repellency of such hierarchical superhydrophobic surfaces can be promising for many potential applications, such as anti-icing, antifogging, water desalination, and phase-change heat transfer.« less

Hierarchical Superhydrophobic Surfaces with Micropatterned Nanowire Arrays for High-Efficiency Jumping Droplet Condensation

DOE PAGES

Wen, Rongfu; Xu, Shanshan; Zhao, Dongliang; ...

2017-12-07

Self-propelled droplet jumping on nanostructured superhydrophobic surfaces is of interest for a variety of industrial applications including self-cleaning, water harvesting, power generation, and thermal management systems. However, the uncontrolled nucleation-induced Wenzel state of condensed droplets at large surface subcooling (high heat flux) leads to the formation of unwanted large pinned droplets, which results in the flooding phenomenon and greatly degrades the heat transfer performance. In this work, we present a novel strategy to manipulate droplet behaviors during the process from the droplet nucleation to growth and departure through a combination of spatially controlling initial nucleation for mobile droplets by closelymore » spaced nanowires and promoting the spontaneous outward movement of droplets for rapid removal using micropatterned nanowire arrays. Through the optical visualization experiments and heat transfer tests, we demonstrate greatly improved condensation heat transfer characteristics on the hierarchical superhydrophobic surface including the higher density of microdroplets, smaller droplet departure radius, 133% wider range of surface subcooling for droplet jumping, and 37% enhancement in critical heat flux for jumping droplet condensation, compared to the-state-of-art jumping droplet condensation on nanostructured superhydrophobic surfaces. The excellent water repellency of such hierarchical superhydrophobic surfaces can be promising for many potential applications, such as anti-icing, antifogging, water desalination, and phase-change heat transfer.« less

FLASH_TISA_Terra+Aqua_Version3C

Atmospheric Science Data Center

2018-04-04

... Cloud Particle Phase Cloud Infrared Emissivity Cloud Base Pressure Surface (Radiative) Flux TOA Flux Surface Types Albedo LW Flux Order Data:  Earthdata Search:  Order Data Guide Documents:  ...

CYGNSS Surface Wind Observations and Surface Flux Estimates within Low-Latitude Extratropical Cyclones

NASA Astrophysics Data System (ADS)

Crespo, J.; Posselt, D. J.

2017-12-01

The Cyclone Global Navigation Satellite System (CYGNSS), launched in December 2016, aims to improve estimates of surface wind speeds over the tropical oceans. While CYGNSS's core mission is to provide better estimates of surface winds within the core of tropical cyclones, previous research has shown that the constellation, with its orbital inclination of 35°, also has the ability to observe numerous extratropical cyclones that form in the lower latitudes. Along with its high spatial and temporal resolution, CYGNSS can provide new insights into how extratropical cyclones develop and evolve, especially in the presence of thick clouds and precipitation. We will demonstrate this by presenting case studies of multiple extratropical cyclones observed by CYGNSS early on in its mission in both Northern and Southern Hemispheres. By using the improved estimates of surface wind speeds from CYGNSS, we can obtain better estimates of surface latent and sensible heat fluxes within and around extratropical cyclones. Surface heat fluxes, driven by surface winds and strong vertical gradients of water vapor and temperature, play a key role in marine cyclogenesis as they increase instability within the boundary layer and may contribute to extreme marine cyclogenesis. In the past, it has been difficult to estimate surface heat fluxes from space borne instruments, as these fluxes cannot be observed directly from space, and deficiencies in spatial coverage and attenuation from clouds and precipitation lead to inaccurate estimates of surface flux components, such as surface wind speeds. While CYGNSS only contributes estimates of surface wind speeds, we can combine this data with other reanalysis and satellite data to provide improved estimates of surface sensible and latent heat fluxes within and around extratropical cyclones and throughout the entire CYGNSS mission.

The role of soil weathering and hydrology in regulating chemical fluxes from catchments (Invited)

NASA Astrophysics Data System (ADS)

Maher, K.; Chamberlain, C. P.

2010-12-01

Catchment-scale chemical fluxes have been linked to a number of different parameters that describe the conditions at the Earth’s surface, including runoff, temperature, rock type, vegetation, and the rate of tectonic uplift. However, many of the relationships relating chemical denudation to surface processes and conditions, while based on established theoretical principles, are largely empirical and derived solely from modern observations. Thus, an enhanced mechanistic basis for linking global solute fluxes to both surface processes and climate may improve our confidence in extrapolating modern solute fluxes to past and future conditions. One approach is to link observations from detailed soil-based studies with catchment-scale properties. For example, a number of recent studies of chemical weathering at the soil-profile scale have reinforced the importance of hydrologic processes in controlling chemical weathering rates. An analysis of data from granitic soils shows that weathering rates decrease with increasing fluid residence times and decreasing flow rates—over moderate fluid residence times, from 5 days to 10 years, transport-controlled weathering explains the orders of magnitude variation in weathering rates to a better extent than soil age. However, the importance of transport-controlled weathering is difficult to discern at the catchment scale because of the range of flow rates and fluid residence times captured by a single discharge or solute flux measurement. To assess the importance of transport-controlled weathering on catchment scale chemical fluxes, we present a model that links the chemical flux to the extent of reaction between the soil waters and the solids, or the fluid residence time. Different approaches for describing the distribution of fluid residence times within a catchment are then compared with the observed Si fluxes for a limited number of catchments. This model predicts high solute fluxes in regions with high run-off, relief, and long flow paths suggesting that the particular hydrologic setting of a landscape will be the underlying control on the chemical fluxes. As such, we reinterpret the large chemical fluxes that are observed in active mountain belts, like the Himalaya, to be primarily controlled by the long reactive flow paths created by the steep terrain coupled with high amounts of precipitation.

Sabots, Obturator and Gas-In-Launch Tube Techniques for Heat Flux Models in Ballistic Ranges

NASA Technical Reports Server (NTRS)

Bogdanoff, David W.; Wilder, Michael C.

2013-01-01

For thermal protection system (heat shield) design for space vehicle entry into earth and other planetary atmospheres, it is essential to know the augmentation of the heat flux due to vehicle surface roughness. At the NASA Ames Hypervelocity Free Flight Aerodynamic Facility (HFFAF) ballistic range, a campaign of heat flux studies on rough models, using infrared camera techniques, has been initiated. Several phenomena can interfere with obtaining good heat flux data when using this measuring technique. These include leakage of the hot drive gas in the gun barrel through joints in the sabot (model carrier) to create spurious thermal imprints on the model forebody, deposition of sabot material on the model forebody, thereby changing the thermal properties of the model surface and unknown in-barrel heating of the model. This report presents developments in launch techniques to greatly reduce or eliminate these problems. The techniques include the use of obturator cups behind the launch package, enclosed versus open front sabot designs and the use of hydrogen gas in the launch tube. Attention also had to be paid to the problem of the obturator drafting behind the model and impacting the model. Of the techniques presented, the obturator cups and hydrogen in the launch tube were successful when properly implemented

Gas Flux and Density Surrounding a Cylindrical Aperture in the Free Molecular Flow Regime

NASA Technical Reports Server (NTRS)

Soulas, George C.

2011-01-01

The equations for rigorously calculating the particle flux and density surrounding a cylindrical aperture in the free molecular flow regime are developed and presented. The fundamental equations for particle flux and density from a reservoir and a diffusely reflecting surface will initially be developed. Assumptions will include a Maxwell-Boltzmann speed distribution, equal particle and wall temperatures, and a linear flux distribution along the cylindrical aperture walls. With this information, the equations for axial flux and density surrounding a cylindrical aperture will be developed. The cylindrical aperture will be divided into multiple volumes and regions to rigorously determine the surrounding axial flux and density, and appropriate limits of integration will be determined. The results of these equations will then be evaluated. The linear wall flux distribution assumption will be assessed. The axial flux and density surrounding a cylindrical aperture with a thickness-to-radius ratio of 1.25 will be presented. Finally, the equations determined in this study will be verified using multiple methods.

NAE Twin Otter operations in FIFE 1989

NASA Technical Reports Server (NTRS)

Macpherson, J. I.

1990-01-01

During the summer of 1989, the National Aeronautical Establishment (Canada) Twin Otter Atmospheric Research Aircraft was flow in support of the NASA sponsored First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment called FIFE-89. Airborne measurements of the fluxes of heat, momentum, water vapor and carbon dioxide were made during 16 flow-altitude flights over the FIFE project area in central Kansas. The Twin Otter operations in FIFE are documented and details are included on the instrumentation, software, flight procedures, atmospheric conditions and analysis methods. Comparisons of Twin Otter measured fluxes are made with those determined at several surface sites and with those made by other instrumented aircraft in the FIFE-87 measurements. Airborne flux measurements are related to run length, altitude, and environmental parameters such as vegetation type, temperature, and wind speed. One night flight was run in an attempt to measure the respiration component of the CO2 flux. The use of aircraft was studied for regional observations of fluxes and to relate these to satellite radiance measurements. Run average data are presented for all 285 flux runs flown by the Twin Otter in FIFE-89. This should serve as as a working reference for scientists utilizing Twin Otter data either directly of through the FIFE data archive.

Evaluation of helicity generation in the tropical storm Gonu

NASA Astrophysics Data System (ADS)

Farahani, Majid M.; Khansalari, Sakineh; Azadi, Majid

2017-06-01

Helicity is a valuable dynamical concept for the study of rotating flows. Consequently helicity flux, indicative of the source or sink of helicity, owns comparable importance. In this study, while reviewing the existing methods, a mathematical relation between helicity and helicity-flux is introduced, discussed and examined. The computed values of helicity and helicity fluxes in an actual case, using the classical and this proposed method are compared. The down-stream helicity flux including sources and sinks of helicity is considered for the tropical storm Gonu that occurred over the coasts of Oman and Iran on June 2-7, 2007. Results show that the buoyancy, through the upper troposphere down to a height within boundary layer, is the main source in producing helicity, and surface friction from earth surface up to a height within boundary layer, is the main dissipating element of helicity. The dominance of buoyancy forcing over the dissipative friction forcing results in generation of vortex or enhancement of it after bouncing the land. Furthermore, the increase (decrease) of helicity results in an increase (decrease) in the height of the level in which maximum helicity flux occurs. It is suggested that the maximum helicity flux occurs at the top of the turbulent boundary layer, so that the height of boundary layer could be obtained.

Method for improving performance of high temperature superconductors within a magnetic field

DOEpatents

Wang, Haiyan; Foltyn, Stephen R.; Maiorov, Boris A.; Civale, Leonardo

2010-01-05

The present invention provides articles including a base substrate including a layer of an oriented cubic oxide material having a rock-salt-like structure layer thereon; and, a buffer layer upon the oriented cubic oxide material having a rock-salt-like structure layer, the buffer layer having an outwardly facing surface with a surface morphology including particulate outgrowths of from 10 nm to 500 run in size at the surface, such particulate outgrowths serving as flux pinning centers whereby the article maintains higher performance within magnetic fields than similar articles without the necessary density of such outgrowths.

Validation of the Archived CERES Surface and Atmosphere Radiation Budget (SARB) at SGP

NASA Technical Reports Server (NTRS)

Charlock, Thomas P.; Rose, Fred G.; Rutan, David A.

2003-01-01

The CERES Surface and Atmosphere Radiation Budget (SARB) product (Charlock et al, 2002) includes the vertical profile of broadband SW, broadband LW, and 8-12 micron window (WN) fluxes; upwelling and downwelling at TOA, 70 hPa, 200 hPa, 500 hPa, and the surface; and for all-sky and clear-sky conditions. We test the archived CERES TRMM record of SARB for January-August 1998 and focus on discrepancies with ground-based measurements at SGP. The CERES SARB is generated by a highly modified Fu-Liou radiative transfer code (Fu and Liou, 1993). The most critical inputs for this application are cloud optical properties (fractional area, optical depth, particle size and phase, height of top, and estimate of geometrical thickness Minnis et al., 2002) from the narrowband VIRS imager. Numerous VIRS pixels (approx. 2km resolution at nadir) are matched to each of the large (approx. 20km) CERES broadband footprints (Wielicki et al, 1996). Other inputs include temperature and humidity from ECMWF (Rabier et al, 1998) , NCEP ozone profiles from SBUV and TOVS (Yang et al, 2001), aerosol optical thickness (AOT) from the Model for Atmospheric Transport and Chemistry (MATCH) aerosol assimilation (Collins et al., 2001) or alternately from the VIRS imager (Ignatov and Stowe, 2000). VIRS AOT is available for clear and partly cloudy ocean footprints during daylight; and only when viewing geometry renders a contribution from sunglint as unlikely. For other footprints, AOT is taken from MATCH. AOT is apportioned into fractions of dust (Tegan and Lacis, 1996), sea salt, sulfate, dust, soluble organic, insoluble organic, and soot (Hess et al., 1996) using the 6-hourly MATCH output. Tuned fluxes are retrieved by adjusting inputs to nudge computed TOA fluxes toward CERES observations (Rose et al, 1997). In clear conditions, the fields of humidity, surface skin temperature, surface albedo and AOT are adjusted to produce a closer match of computed and observed fluxes at TOA. When CERES footprints have clouds, the cloud optical thickness, fractional area within the footprint, and temperature of cloud top are adjusted by the tuning algorithm. Both tuned and untuned fluxes are archived, as are the respective adjustments to any parameters at the surface or within the atmosphere.

CONCENTRATIONS AND ESTIMATED LOADS OF NITROGEN CONTRIBUTED BY TWO ADJACENT WETLAND STREAMS WITH DIFFERENT FLOW-SOURCE TERMS IN WATKINSVILLE, GA

EPA Science Inventory

Inorganic, fixed nitrogen from agricultural settings often is introduced to first-order streams via surface runoff and shallow ground-water flow. Best management practices for limiting the flux of fixed N to surface waters often include buffers such as wetlands. However, the eff...

CONCENTRATIONS AND ESTIMATED LOADS OF NITROGEN CONTRIBUTED BY TWO ADJACENT WETLAND STREAMS WITH DIFFERENT FLOW-SOURCE TERMS IN WATKINSVILLE, GEORGIA

EPA Science Inventory

Inorganic, fixed nitrogen from agricultural settings often is introduced to first-order streams via surface runoff and shallow ground-water flow. Best management practices for limiting the flux of fixed N to surface waters often include buffers such as wetlands. However, the eff...

Soil Mesocosm CO2 Emissions after 13C-glucose Addition, Soil Physical and Chemical Characteristics, and Microbial Biomass, Barrow, Alaska, 2014-2016

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lydia Vaughn; Biao Zhu; Carolin Bimueller

Measurements made from a 2014-2016 field glucose addition experiment. Dataset includes measurements of surface trace gas emissions (Delta13C of ecosystem respiration and source-partitioned surface CO2 flux, CH4 flux, and GPP), soil profile information (concentrations of carbon, nitrogen, and soil microbial biomass carbon, Delta13C of soil organic matter and microbial biomass, gravimetric water content, and bulk density), soil mineral nitrogen availability, and field-measured soil temperature, air temperature and soil moisture. Experiment was conducted in a region of high-centered polygons on the BEO. Data will be available Fall 2017.

Numerical Model Studies of the Martian Mesoscale Circulations

NASA Technical Reports Server (NTRS)

Segal, M.; Arritt, R. W.

1996-01-01

Studies concerning mesoscale topographical effects on Martian flows examined low-level jets in the near equatorial latitudes and the dynamical intensification of flow by steep terrain. Continuation of work from previous years included evaluating the dissipation of cold air mass outbreaks due to enhanced sensible heat flux, further sensitivity and scaling evaluations for generalization of the characteristics of Martian mesoscale circulation caused by horizontal sensible heat-flux gradients, and evaluations of the significance that non-uniform surface would have on enhancing the polar CO2 ice sublimation during the spring. The sensitivity of maximum and minimum atmospheric temperatures to changes in wind speed, surface albedo, and deep soil temperature was investigated.

A Simulation Model of Carbon Cycling and Methane Emissions in Amazon Wetlands

NASA Technical Reports Server (NTRS)

Potter, Christopher; Melack, John; Hess, Laura; Forsberg, Bruce; Novo, Evlyn Moraes; Klooster, Steven

2004-01-01

An integrative carbon study is investigating the hypothesis that measured fluxes of methane from wetlands in the Amazon region can be predicted accurately using a combination of process modeling of ecosystem carbon cycles and remote sensing of regional floodplain dynamics. A new simulation model has been build using the NASA- CASA concept for predicting methane production and emission fluxes in Amazon river and floodplain ecosystems. Numerous innovations area being made to model Amazon wetland ecosystems, including: (1) prediction of wetland net primary production (NPP) as the source for plant litter decomposition and accumulation of sediment organic matter in two major vegetation classes - flooded forests (varzea or igapo) and floating macrophytes, (2) representation of controls on carbon processing and methane evasion at the diffusive boundary layer, through the lake water column, and in wetland sediments as a function of changes in floodplain water level, (3) inclusion of surface emissions controls on wetland methane fluxes, including variations in daily surface temperature and of hydrostatic pressure linked to water level fluctuations. A model design overview and early simulation results are presented.

Determination of a Critical Sea Ice Thickness Threshold for the Central Arctic Ocean

NASA Astrophysics Data System (ADS)

Ford, V.; Frauenfeld, O. W.; Nowotarski, C. J.

2017-12-01

While sea ice extent is readily measurable from satellite observations and can be used to assess the overall survivability of the Arctic sea ice pack, determining the spatial variability of sea ice thickness remains a challenge. Turbulent and conductive heat fluxes are extremely sensitive to ice thickness but are dominated by the sensible heat flux, with energy exchange expected to increase with thinner ice cover. Fluxes over open water are strongest and have the greatest influence on the atmosphere, while fluxes over thick sea ice are minimal as heat conduction from the ocean through thick ice cannot reach the atmosphere. We know that turbulent energy fluxes are strongest over open ocean, but is there a "critical thickness of ice" where fluxes are considered non-negligible? Through polar-optimized Weather Research and Forecasting model simulations, this study assesses how the wintertime Arctic surface boundary layer, via sensible heat flux exchange and surface air temperature, responds to sea ice thinning. The region immediately north of Franz Josef Land is characterized by a thickness gradient where sea ice transitions from the thickest multi-year ice to the very thin marginal ice seas. This provides an ideal location to simulate how the diminishing Arctic sea ice interacts with a warming atmosphere. Scenarios include both fixed sea surface temperature domains for idealized thickness variability, and fixed ice fields to detect changes in the ocean-ice-atmosphere energy exchange. Results indicate that a critical thickness threshold exists below 1 meter. The threshold is between 0.4-1 meters thinner than the critical thickness for melt season survival - the difference between first year and multi-year ice. Turbulent heat fluxes and surface air temperature increase as sea ice thickness transitions from perennial ice to seasonal ice. While models predict a sea ice free Arctic at the end of the warm season in future decades, sea ice will continue to transform seasonally during Polar winter. However, despite seasonal sea ice change, if and where its thickness remains below this critical threshold, the Arctic Ocean will continue interacting with the overlying atmosphere and contributing to Arctic amplification during the cold season.

A Numerical Study of Atmospheric Perturbations Induced by Heat From a Wildland Fire: Sensitivity to Vertical Canopy Structure and Heat Source Strength

NASA Astrophysics Data System (ADS)

Kiefer, Michael T.; Zhong, Shiyuan; Heilman, Warren E.; Charney, Joseph J.; Bian, Xindi

2018-03-01

An improved understanding of atmospheric perturbations within and above a forest during a wildland fire has relevance to many aspects of wildland fires including fire spread, smoke transport and dispersion, and tree mortality. In this study, the ARPS-CANOPY model, a version of the Advanced Regional Prediction System (ARPS) model with a canopy parameterization, is utilized in a series of idealized numerical experiments to investigate the influence of vertical canopy structure on the atmospheric response to a stationary sensible heat flux at the ground ("fire heat flux"), broadly consistent in magnitude with the sensible heat flux from a low-intensity surface fire. Five vertical canopy structures are combined with five fire heat flux magnitudes to yield a matrix of 25 simulations. Analyses of the fire-heat-flux-perturbed u component of the wind, vertical velocity, kinetic energy, and temperature show that the spatial pattern and magnitude of the perturbations are sensitive to vertical canopy structure. Both vertical velocity and kinetic energy exhibit an increasing trend with increasing fire heat flux that is stronger for cases with some amount of overstory vegetation than cases with exclusively understory vegetation. A weaker trend in cases with exclusively understory vegetation indicates a damping of the atmospheric response to the sensible heat from a surface fire when vegetation is most concentrated near the surface. More generally, the results presented in this study suggest that canopy morphology should be considered when applying the results of a fire-atmosphere interaction study conducted in one type of forest to other forests with different canopy structures.

Modeling the pyrolysis study of non-charring polymers under reduced pressure environments

NASA Astrophysics Data System (ADS)

Zong, Ruowen; Kang, Ruxue; Hu, Yanghui; Zhi, Youran

2018-04-01

In order to study the pyrolysis of non-charring polymers under reduced pressure environments, a series of experiments based on black acrylonitrile butadiene styrene (ABS) was conducted in a reduced pressure chamber under different external heat fluxes. The temperatures of the top surface and the bottom of the sample and the mass loss during the whole process were measured in real time. A one-dimensional numerical model was developed to predict the top surface and the bottom surface temperatures of ABS during the pyrolysis at different reduced pressures and external heat fluxes, and the model was validated by the experimental data. The results of the study indicate that the profiles of the top surface and the bottom surface temperatures are different at different pressures and heat fluxes. The temperature and the mass loss rate of the sample under a lower heat flux decreased significantly as the pressure was increased. However, under a higher heat flux, the temperature and the mass loss rate showed little sensitivity to the pressure. The simulated results fitted the experimental results better at the higher heat flux than at the lower heat flux.

Surface fluxes and water balance of spatially varying vegetation within a small mountainous headwater catchment

USDA-ARS?s Scientific Manuscript database

Understanding the role of ecosystems in modulating energy, water and carbon fluxes is critical to quantifying the variability in energy, carbon, and water balances across landscapes. This study compares and contrasts the seasonal surface fluxes of sensible heat, latent heat and carbon fluxes measur...

Thermocouple frequency response compensation leads to convergence of the surface renewal alpha calibration

USDA-ARS?s Scientific Manuscript database

Sensible heat flux measurements are used in conjunction with net radiation and ground heat flux measurements to determine the latent heat flux as the energy balance residual. Surface renewal is a relatively inexpensive technique for sensible heat flux estimation because it requires only a fast-resp...

An Investigation of the Mold-Flux Performance for the Casting of Cr12MoV Steel Using a Mold Simulator Technique

NASA Astrophysics Data System (ADS)

Zhou, Lejun; Wang, Wanlin; Xu, Chao; Zhang, Chen

2017-08-01

Mold flux plays important roles in the process of continuous casting. In this article, the performance of mold flux for the casting of Cr12MoV steel was investigated by using a mold simulator. The results showed that the slag film formed in the gap between the initial shell and mold hot surface is thin and discontinuous during the casting process with the Flux BM, due to the absorption of chromic oxide inclusions into the liquid slag, while the slag film formed in the case of the optimized Flux NEW casting process is uniform. The main precipitated crystals in Flux BM slag film are cuspidine (Ca4Si2O7F2) and Cr3O4, but only Ca4Si2O7F2 precipitated in the Flux NEW case. Besides, both the responding temperature and heat flux in the case of Flux BM are relatively higher and fluctuate in a larger amplitude. The surface of the shell obtained in the case of the Flux BM experiment is quite uneven, and many severe depressions, cracks, and entrapped slags are observed in the surface due to the lack of lubrication. However, the obtained shell surface in the case of the Flux NEW shows good surface quality due to the addition of B2O3 and the adjustment of basicity, which can compensate for the negative effects of the mold-flux properties caused by the absorption of chromic oxide during the casting process.

Semianalytical model predicting transfer of volatile pollutants from groundwater to the soil surface.

PubMed

Atteia, Olivier; Höhener, Patrick

2010-08-15

Volatilization of toxic organic contaminants from groundwater to the soil surface is often considered an important pathway in risk analysis. Most of the risk models use simplified linear solutions that may overpredict the volatile flux. Although complex numerical models have been developed, their use is restricted to experienced users and for sites where field data are known in great detail. We present here a novel semianalytical model running on a spreadsheet that simulates the volatilization flux and vertical concentration profile in a soil based on the Van Genuchten functions. These widely used functions describe precisely the gas and water saturations and movement in the capillary fringe. The analytical model shows a good accuracy over several orders of magnitude when compared to a numerical model and laboratory data. The effect of barometric pumping is also included in the semianalytical formulation, although the model predicts that barometric pumping is often negligible. A sensitivity study predicts significant fluxes in sandy vadose zones and much smaller fluxes in other soils. Fluxes are linked to the dimensionless Henry's law constant H for H < 0.2 and increase by approximately 20% when temperature increases from 5 to 25 degrees C.

High-frequency pressure variations in the vicinity of a surface CO2 flux chamber

Treesearch

Eugene S. Takle; James R. Brandle; R. A. Schmidt; Rick Garcia; Irina V. Litvina; William J. Massman; Xinhua Zhou; Geoffrey Doyle; Charles W. Rice

2003-01-01

We report measurements of 2Hz pressure fluctuations at and below the soil surface in the vicinity of a surface-based CO2 flux chamber. These measurements were part of a field experiment to examine the possible role of pressure pumping due to atmospheric pressure fluctuations on measurements of surface fluxes of CO2. Under the moderate wind speeds, warm temperatures,...

Utility of a thermal-based two-source energy balance model for estimating surface fluxes over complex landscapes

USDA-ARS?s Scientific Manuscript database

Many landscapes are comprised of a variety of vegetation types with different canopy structure, rooting depth, physiological characteristics, including response to environmental stressors, etc. Even in agricultural regions, different management practices, including crop rotations, irrigation schedu...

High Resolution Ecosystem Structure, Biomass and Blue Carbon stocks in Mangrove Ecosystems- Methods and Applications of Lidar, radar Interferometry and High Resolution imagery

NASA Astrophysics Data System (ADS)

Lagomasino, D.; Fatoyinbo, T. E.; Lee, S. K.; Feliciano, E. A.; Simard, M.; Trettin, C.

2016-12-01

Earth's climate is determined by the exchange of radiant energy between the Sun, Earth and space. The absorbed solar radiation (ASR) fuels the climate system, providing the energy required for atmospheric and oceanic motions, while the system cools by emitting outgoing longwave (LW) radiation to space. A central objective of the Clouds and the Earth's Radiant Energy System (CERES) is to produce a long-term global climate data record of Earth's radiation budget along with the associated atmospheric and surface properties that influence it. CERES data products utilize a number of data sources, including broadband radiometers measuring incoming and reflected solar radiation and OLR, polar orbiting and geostationary spectral imagers, meteorological, aerosol and ozone assimilation data, and snow/sea-ice maps based on microwave radiometer data. Here we use simple diagnostic model of Earth's albedo and CERES Energy Balanced and Filled (EBAF) Ed4.0 data for March 2000-February 2016 to quantify interannual variations in SW TOA flux associated with surface albedo and atmospheric reflectance and transmittance variations. Surface albedo variations account for <0.5% of the total SW TOA flux variance over the tropics and 4% globally. Variations in atmospheric reflectance and transmittance account for virtually all of the total SW TOA flux variance over the tropics and only 81% globally. The remaining 15% of the global SW TOA flux variance is explained by the co-variance of surface albedo and atmospheric reflectance/transmittance. Equatorward of 60-degree latitude, the atmospheric contribution exceeds that of the surface by at least an order-of-magnitude. In contrast, the surface and atmospheric variations contribute equally poleward of 60S and surface variations account for twice as much as the atmosphere poleward of 60N. However, as much as 40% of the total SW TOA flux variance poleward of 60N is explained by the covariance of surface albedo and atmospheric reflectance/transmittance, highlighting the tight coupling between sea-ice concentration and cloud properties over the Arctic Ocean.

Flux Sampling Errors for Aircraft and Towers

NASA Technical Reports Server (NTRS)

Mahrt, Larry

1998-01-01

Various errors and influences leading to differences between tower- and aircraft-measured fluxes are surveyed. This survey is motivated by reports in the literature that aircraft fluxes are sometimes smaller than tower-measured fluxes. Both tower and aircraft flux errors are larger with surface heterogeneity due to several independent effects. Surface heterogeneity may cause tower flux errors to increase with decreasing wind speed. Techniques to assess flux sampling error are reviewed. Such error estimates suffer various degrees of inapplicability in real geophysical time series due to nonstationarity of tower time series (or inhomogeneity of aircraft data). A new measure for nonstationarity is developed that eliminates assumptions on the form of the nonstationarity inherent in previous methods. When this nonstationarity measure becomes large, the surface energy imbalance increases sharply. Finally, strategies for obtaining adequate flux sampling using repeated aircraft passes and grid patterns are outlined.

Evaluation of Ten Methods for Initializing a Land Surface Model

NASA Technical Reports Server (NTRS)

Rodell, M.; Houser, P. R.; Berg, A. A.; Famiglietti, J. S.

2005-01-01

Land surface models (LSMs) are computer programs, similar to weather and climate prediction models, which simulate the stocks and fluxes of water (including soil moisture, snow, evaporation, and runoff) and energy (including the temperature of and sensible heat released from the soil) after they arrive on the land surface as precipitation and sunlight. It is not currently possible to measure all of the variables of interest everywhere on Earth with sufficient accuracy and space-time resolution. Hence LSMs have been developed to integrate the available observations with our understanding of the physical processes involved, using powerful computers, in order to map these stocks and fluxes as they change in time. The maps are used to improve weather forecasts, support water resources and agricultural applications, and study the Earth"s water cycle and climate variability. NASA"s Global Land Data Assimilation System (GLDAS) project facilitates testing of several different LSMs with a variety of input datasets (e.g., precipitation, plant type).

An analytical expression for ion velocities at the wall including the sheath electric field and surface biasing for erosion modeling at JET ILW

DOE PAGES

Borodkina, I.; Borodin, D.; Brezinsek, S.; ...

2017-04-12

For simulation of plasma-facing component erosion in fusion experiments, an analytical expression for the ion velocity just before the surface impact including the local electric field and an optional surface biasing effect is suggested. Energy and angular impact distributions and the resulting effective sputtering yields were produced for several experimental scenarios at JET ILW mostly involving PFCs exposed to an oblique magnetic field. The analytic solution has been applied as an improvement to earlier ERO modelling of localized, Be outer limiter, RF-enhanced erosion, modulated by toggling of a remote, however magnetically connected ICRH antenna. The effective W sputtering yields duemore » to D and Be ion impact in Type-I and Type-III ELMs and inter-ELM conditions were also estimated using the analytical approach and benchmarked by spectroscopy. The intra-ELM W sputtering flux increases almost 10 times in comparison to the inter-ELM flux.« less

Ground-based Remote Sensing for Quantifying Subsurface and Surface Co-variability to Scale Arctic Ecosystem Functioning

NASA Astrophysics Data System (ADS)

Oktem, R.; Wainwright, H. M.; Curtis, J. B.; Dafflon, B.; Peterson, J.; Ulrich, C.; Hubbard, S. S.; Torn, M. S.

2016-12-01

Predicting carbon cycling in Arctic requires quantifying tightly coupled surface and subsurface processes including permafrost, hydrology, vegetation and soil biogeochemistry. The challenge has been a lack of means to remotely sense key ecosystem properties in high resolution and over large areas. A particular challenge has been characterizing soil properties that are known to be highly heterogeneous. In this study, we exploit tightly-coupled above/belowground ecosystem functioning (e.g., the correlations among soil moisture, vegetation and carbon fluxes) to estimate subsurface and other key properties over large areas. To test this concept, we have installed a ground-based remote sensing platform - a track-mounted tram system - along a 70 m transect in the ice-wedge polygonal tundra near Barrow, Alaska. The tram carries a suite of near-surface remote sensing sensors, including sonic depth, thermal IR, NDVI and multispectral sensors. Joint analysis with multiple ground-based measurements (soil temperature, active layer soil moisture, and carbon fluxes) was performed to quantify correlations and the dynamics of above/belowground processes at unprecedented resolution, both temporally and spatially. We analyzed the datasets with particular focus on correlating key subsurface and ecosystem properties with surface properties that can be measured by satellite/airborne remote sensing over a large area. Our results provided several new insights about system behavior and also opens the door for new characterization approaches. We documented that: (1) soil temperature (at >5 cm depth; critical for permafrost thaw) was decoupled from soil surface temperature and was influenced strongly by soil moisture, (2) NDVI and greenness index were highly correlated with both soil moisture and gross primary productivity (based on chamber flux data), and (3) surface deformation (which can be measured by InSAR) was a good proxy for thaw depth dynamics at non-inundated locations.

Impact of Low Level Clouds on radiative and turbulent surface flux in southern West Africa

NASA Astrophysics Data System (ADS)

Lohou, Fabienne; Kalthoff, Norbert; Dione, Cheikh; Lothon, Marie; Adler, Bianca; Babic, Karmen; Pedruzo-Bagazgoitia, Xabier; Vila-Guerau De Arellano, Jordi

2017-04-01

During the monsoon season in West Africa, low-level clouds form almost every night and break up between 0900 and the middle of the afternoon depending on the day. The break-up of these clouds leads to the formation of boundary-layer cumuli clouds, which can sometimes evolve into deep convection. The low-level clouds have a strong impact on the radiation and energy budget at the surface and consequently on the humidity in the boundary layer and the afternoon convection. During the DACCIWA ground campaign, which took place in June and July 2016, three supersites in Benin, Ghana, and Nigeria were instrumented to document the conditions within the lower troposphere including the cloud layers. Radiative and turbulent fluxes were measured at different places by several surface stations jointly with low-level cloud occurrence during 50 days. These datasets enable the analysis of modifications in the diurnal cycle of the radiative and turbulent surface flux induced by the formation and presence of the low-level clouds. The final objective of this study is to estimate the error made in some NWP simulations when the diurnal cycle of low-level clouds is poorly represented or not represented at all.

Modeling of Dense Water Production and Salt Transport from Alaskan Coastal Polynyas

NASA Technical Reports Server (NTRS)

Signorini, Sergio R.; Cavalieri, Donald J.

2000-01-01

The main significance of this paper is that a realistic, three-dimensional, high-resolution primitive equation model has been developed to study the effects of dense water formation in Arctic coastal polynyas. The model includes realistic ambient stratification, realistic bottom topography, and is forced by time-variant surface heat flux, surface salt flux, and time-dependent coastal flow. The salt and heat fluxes, and the surface ice drift, are derived from satellite observations (SSM/I and NSCAT sensors). The model is used to study the stratification, salt transport, and circulation in the vicinity of Barrow Canyon during the 1996/97 winter season. The coastal flow (Alaska coastal current), which is an extension of the Bering Sea throughflow, is formulated in the model using the wind-transport regression. The results show that for the 1996/97 winter the northeastward coastal current exports 13% to 26% of the salt produced by coastal polynyas upstream of Barrow Canyon in 20 to 30 days. The salt export occurs more rapidly during less persistent polynyas. The inclusion of ice-water stress in the model makes the coastal current slightly weaker and much wider due to the combined effects of surface drag and offshore Ekman transport.

An intercomparison and validation of satellite-based surface radiative energy flux estimates over the Arctic

NASA Astrophysics Data System (ADS)

Riihelä, Aku; Key, Jeffrey R.; Meirink, Jan Fokke; Kuipers Munneke, Peter; Palo, Timo; Karlsson, Karl-Göran

2017-05-01

Accurate determination of radiative energy fluxes over the Arctic is of crucial importance for understanding atmosphere-surface interactions, melt and refreezing cycles of the snow and ice cover, and the role of the Arctic in the global energy budget. Satellite-based estimates can provide comprehensive spatiotemporal coverage, but the accuracy and comparability of the existing data sets must be ascertained to facilitate their use. Here we compare radiative flux estimates from Clouds and the Earth's Radiant Energy System (CERES) Synoptic 1-degree (SYN1deg)/Energy Balanced and Filled, Global Energy and Water Cycle Experiment (GEWEX) surface energy budget, and our own experimental FluxNet / Satellite Application Facility on Climate Monitoring cLoud, Albedo and RAdiation (CLARA) data against in situ observations over Arctic sea ice and the Greenland Ice Sheet during summer of 2007. In general, CERES SYN1deg flux estimates agree best with in situ measurements, although with two particular limitations: (1) over sea ice the upwelling shortwave flux in CERES SYN1deg appears to be underestimated because of an underestimated surface albedo and (2) the CERES SYN1deg upwelling longwave flux over sea ice saturates during midsummer. The Advanced Very High Resolution Radiometer-based GEWEX and FluxNet-CLARA flux estimates generally show a larger range in retrieval errors relative to CERES, with contrasting tendencies relative to each other. The largest source of retrieval error in the FluxNet-CLARA downwelling shortwave flux is shown to be an overestimated cloud optical thickness. The results illustrate that satellite-based flux estimates over the Arctic are not yet homogeneous and that further efforts are necessary to investigate the differences in the surface and cloud properties which lead to disagreements in flux retrievals.

Wind-tunnel experiments of turbulent flow over a surface-mounted 2-D block in a thermally-stratified boundary layer

NASA Astrophysics Data System (ADS)

Zhang, Wei; Markfort, Corey; Porté-Agel, Fernando

2014-11-01

Turbulent flows over complex surface topography have been of great interest in the atmospheric science and wind engineering communities. The geometry of the topography, surface roughness and temperature characteristics as well as the atmospheric thermal stability play important roles in determining momentum and scalar flux distribution. Studies of turbulent flow over simplified topography models, under neutrally stratified boundary-layer conditions, have provided insights into fluid dynamics. However, atmospheric thermal stability has rarely been considered in laboratory experiments, e.g., wind-tunnel experiments. Series of wind-tunnel experiments of thermally-stratified boundary-layer flow over a surface-mounted 2-D block, in a well-controlled boundary-layer wind tunnel, will be presented. Measurements using high-resolution PIV, x-wire/cold-wire anemometry and surface heat flux sensors were conducted to quantify the turbulent flow properties, including the size of the recirculation zone, coherent vortex structures and the subsequent boundary layer recovery. Results will be shown to address thermal stability effects on momentum and scalar flux distribution in the wake, as well as dominant mechanism of turbulent kinetic energy generation and consumption. The authors gratefully acknowledge funding from the Swiss National Foundation (Grant 200021-132122), the National Science Foundation (Grant ATM-0854766) and NASA (Grant NNG06GE256).

Interannual Variability in Surface LW Fluxes Over the Tropical Oceans As Seen in ISCCP-FD and GEWEX SRB Data Sets

NASA Technical Reports Server (NTRS)

Robertson, F. R.; Lu, H.-I.

2005-01-01

One notable aspect of Earth s climate is that although the planet appears to be very close to radiative balance at top-of-atmosphere (TOA), the atmosphere itself and underlying surface are not. Profound exchanges of energy between the atmosphere and oceans, land and cryosphere occur over a range of time scales. Recent evidence from broadband satellite measurements suggests that even these TOA fluxes contain some detectable variations. Our ability to measure and reconstruct radiative fluxes at the surface and at the top of atmosphere is improving rapidly. In this work we will evaluate two recently released estimates of radiative fluxes, focusing primarily on surface estimates. The International Satellite Cloud Climatology Project FD radiative flux profiles are available from mid-1 983 to near present and have been constructed by driving the radiative transfer physics from the Goddard Institute for Space Studies (GISS) global model with ISCCP clouds and TOVS (TIROS Operational Vertical Sounder)thermodynamic profiles. Fu!l and clear sky SW and LW fluxes are produced. A similar product from the NASA/GEWEX Surface Radiation Budget Project using different radiative flux codes and thermodynamics from the NAS/Goddard Earth Observing System (GEOS-1) assimilation model makes a similar calculation of surface fluxes. However this data set currently extends only through 1995. Significant differences in both interannual variability as well as trends are found between among these data sets. For radiative fluxes these differences are traced to TOVS thermodynamic soundings used to drive the ISCCP-FD calculations. Errors in near surface temperature and precipitable water cascade into ISCCP upward and downward IR flux components, demonstrably affecting interannual variability. Revised estimates of clear-sky fluxes over ocean are made using statistical algorithms and water vapor from the (SSM/I) Special Sensor Microwave Imager. These calculations show strong near-surface water vapor feedback over the tropical oceans in association with SST changes. However, it is also shown that ISCCP longwave cloud forcing, common to both the ISCCP-FD and GEWEX SRB retrievals, is the main driver of a long-term decrease in net LW flux to the surface during the near-20 year period covered by these revised estimates.

Towards an purely data driven view on the global carbon cycle and its spatiotemporal variability

NASA Astrophysics Data System (ADS)

Zscheischler, Jakob; Mahecha, Miguel; Reichstein, Markus; Avitabile, Valerio; Carvalhais, Nuno; Ciais, Philippe; Gans, Fabian; Gruber, Nicolas; Hartmann, Jens; Herold, Martin; Jung, Martin; Landschützer, Peter; Laruelle, Goulven; Lauerwald, Ronny; Papale, Dario; Peylin, Philippe; Regnier, Pierre; Rödenbeck, Christian; Cuesta, Rosa Maria Roman; Valentini, Ricardo

2015-04-01

Constraining carbon (C) fluxes between the Earth's surface and the atmosphere at regional scale via observations is essential for understanding the Earth's carbon budget and predicting future atmospheric C concentrations. Carbon budgets have often been derived based on merging observations, statistical models and process-based models, for example in the Global Carbon Project (GCP). However, it would be helpful to derive global C budgets and fluxes at global scale as independent as possible from model assumptions to obtain an independent reference. Long-term in-situ measurements of land and ocean C stocks and fluxes have enabled the derivation of a new generation of data driven upscaled data products. Here, we combine a wide range of in-situ derived estimates of terrestrial and aquatic C fluxes for one decade. The data were produced and/or collected during the FP7 project GEOCARBON and include surface-atmosphere C fluxes from the terrestrial biosphere, fossil fuels, fires, land use change, rivers, lakes, estuaries and open ocean. By including spatially explicit uncertainties in each dataset we are able to identify regions that are well constrained by observations and areas where more measurements are required. Although the budget cannot be closed at the global scale, we provide, for the first time, global time-varying maps of the most important C fluxes, which are all directly derived from observations. The resulting spatiotemporal patterns of C fluxes and their uncertainties inform us about the needs for intensifying global C observation activities. Likewise, we provide priors for inversion exercises or to identify regions of high (and low) uncertainty of integrated C fluxes. We discuss the reasons for regions of high observational uncertainties, and for biases in the budget. Our data synthesis might also be used as empirical reference for other local and global C budgeting exercises.

Water vapour fluxes trends on different time scales and their relationship with weather and soil drivers: a case study from a dehesa site in South Spain

NASA Astrophysics Data System (ADS)

Polo, María José; Egüen, Marta; Andreu, Ana; Carpintero, Elisabet; Gómez-Giráldez, Pedro; Patrocinio González-Dugo, María

2017-04-01

Water vapour fluxes between the soil surface and the atmosphere constitute one of the most important components of the water cycle in the continental areas. Their regime directly affect the availability of water to plants, water storage in surface bodies, air humidity in the boundary layer, snow persistence… among others, and the list of indirectly affected processes comprises a large number of components. Water potential or wetness gradients are some of the main drivers of water vapour fluxes to the atmosphere; soil humidity is usually monitored as key variable in many hydrological and environmental studies, and its estimated series are used to calibrate and validate the modelling of certain hydrological processes. However, such results may differ when water fluxes are used instead of water state variables, such as humidity. This work shows the analysis of high resolution water vapour fluxes series from a dehesa area in South Spain where a complete energy and water fluxes/variables monitoring site has been operating for the last four years. The results include pasture and tree vegetated control points. The daily water budget calculation on both types of sites has been performed from weather and energy fluxes measurements, and soil moisture measurements, and the results have been aggregated on a weekly, monthly and seasonal basis. Comparison between observed trends of soil moisture and calculated trends of water vapour fluxes is included to show the differences arising in terms of the regime of the dominant weather variables in this type of ecosystems. The results identify significant thresholds for each weather variable driver and highlight the importance of the wind regime, which is the somehow forgotten variable in future climate impacts on hydrology. Further work is being carried out to assess water cycle potential trends under future climate conditions and their impacts on the vegetation in dehesa ecosystems.

Bayesian Hierarchical Model Characterization of Model Error in Ocean Data Assimilation and Forecasts

DTIC Science & Technology

2013-09-30

wind ensemble with the increments in the surface momentum flux control vector in a four-dimensional variational (4dvar) assimilation system. The...stability  effects?   surface  stress   Surface   Momentum  Flux  Ensembles  from  Summaries  of  BHM  Winds  (Mediterranean...surface wind speed given ensemble winds from a Bayesian Hierarchical Model to provide surface momentum flux ensembles. 3 Figure 2: Domain of

Calibrator tests of heat flux gauges mounted in SSME blades

NASA Technical Reports Server (NTRS)

Liebert, Curt H.

1989-01-01

Measurements of heat flux to space shuttle main engine (SSME) turbine blade surfaces are being made in the Lewis heat flux calibration facility. Surface heat flux information is obtained from transient temperature measurements taken at points within the gauge. A 100-kW Vortek arc lamp is used as a source of thermal radiant energy. Thermoplugs, with diameters of about 0.190 cm and lengths varying from about 0.190 to 0.320 cm, are being investigated. The thermoplug is surrounded on all surfaces except the active surface by a pocket of air located in the circular annulus and under the back cover. Since the thermoplug is insulated, it is assumed that heat is conducted in a one-dimensional manner from the hot active surface to the cooler back side of the thermoplug. It is concluded that the miniature plug-type gauge concept is feasible for measurement of blade surface heat flux. It is suggested that it is important to measure heat flux near the hub on the suction surface and at the throat on SSME blades rotating in engines because stress and heat transfer coefficients are high in this region.

Solar flux incident on an orbiting surface after reflection from a planet

NASA Technical Reports Server (NTRS)

Modest, M. F.

1980-01-01

Algorithms describing the solar radiation impinging on an infinitesimal surface after reflection from a gray and diffuse planet are derived. The following conditions apply: only radiation from the sunny half of the planet is taken into account; the radiation must fall on the top of the orbiting surface, and radiation must come from that part of the planet that can be seen from the orbiting body. A simple approximate formula is presented which displays excellent accuracy for all significant situations, with an error which is always less than 5% of the maximum possible reflected flux. Attention is also given to solar albedo flux on a surface directly facing the planet, the influence of solar position on albedo flux, and to solar albedo flux as a function of the surface-planet tilt angle.

How well can regional fluxes be derived from smaller-scale estimates?

NASA Technical Reports Server (NTRS)

Moore, Kathleen E.; Fitzjarrald, David R.; Ritter, John A.

1992-01-01

Regional surface fluxes are essential lower boundary conditions for large scale numerical weather and climate models and are the elements of global budgets of important trace gases. Surface properties affecting the exchange of heat, moisture, momentum and trace gases vary with length scales from one meter to hundreds of km. A classical difficulty is that fluxes have been measured directly only at points or along lines. The process of scaling up observations limited in space and/or time to represent larger areas was done by assigning properties to surface classes and combining estimated or calculated fluxes using an area weighted average. It is not clear that a simple area weighted average is sufficient to produce the large scale from the small scale, chiefly due to the effect of internal boundary layers, nor is it known how important the uncertainty is to large scale model outcomes. Simultaneous aircraft and tower data obtained in the relatively simple terrain of the western Alaska tundra were used to determine the extent to which surface type variation can be related to fluxes of heat, moisture, and other properties. Surface type was classified as lake or land with aircraft borne infrared thermometer, and flight level heat and moisture fluxes were related to surface type. The magnitude and variety of sampling errors inherent in eddy correlation flux estimation place limits on how well any flux can be known even in simple geometries.

Seasonal cycle of the mixed-layer heat and freshwater budget in the eastern tropical Atlantic

NASA Astrophysics Data System (ADS)

Rath, Willi; Dengler, Marcus; Lüdke, Jan; Schmidtko, Sunke; Schlundt, Michael; Brandt, Peter; Partners, Preface

2016-04-01

A new seasonal mixed-layer heat flux climatology is used to explore the mechanisms driving seasonal variability of sea surface temperature and salinity in the eastern tropical Atlantic (ETA) with a focus on the eastern boundary upwelling regions. Until recently, large areas at the continental margins of the ETA were not well covered by publically available hydrographic data hampering a detailed understanding of the involved processes. In a collaborative effort between African and European partners within the EU-funded PREFACE program, a new seasonal climatology for different components of the heat and freshwater budget was compiled for the ETA using all publically available hydrographic data sets and a large trove of previously not-publically available hydrographic measurements from the territorial waters of western African countries, either from national programs or from the FAO supported EAF-Nansen program. The publically available data includes hydrographic data from global data repositories including most recent ARGO floats and glider measurements. This data set was complemented by velocity data from surface drifter and ARGO floats to allow determining horizontal heat and freshwater advection. Monthly means of air-sea heat fluxes were derived from the TropFlux climatology while precipitation rates were derived from monthly mean fields of the Global Precipitation Climatology Project. Finally, microstructure data from individual measurement campaigns allow estimating diapycnal heat and salt fluxes for certain regions during specific months. A detailed analysis of the seasonal cycle of mixed-layer heat and freshwater balance in previously poorly covered regions in the eastern tropical Atlantic upwelling is presented. In both eastern boundary upwelling region, off Senegal/Mauritania and off Angola/Namibia, average net surface heat fluxes warm the mixed layer at a rate between 50 and 80 W/m2 with maxima in the respective summer seasons. Horizontal advection contributed to cooling of the mixed layer but a residual cooling term remains in both upwelling regions. A surprising result is that this residual is largest in the Angolan upwelling region, where upwelling-favourable winds are generally weaker than off Namibia and in the north-eastern upwelling region. The contributions of windstress-derived vertical advection and diapycnal heat and freshwater fluxes are discussed. In addition, the TropFlux climatology is evaluated against radiative and turbulent ocean-atmosphere heat and freshwater fluxes derived from ship-board observations.

NASA/GEWEX shortwave surface radiation budget: Integrated data product with reprocessed radiance, cloud, and meteorology inputs, and new surface albedo treatment

NASA Astrophysics Data System (ADS)

Cox, Stephen J.; Stackhouse, Paul W.; Gupta, Shashi K.; Mikovitz, J. Colleen; Zhang, Taiping

2017-02-01

The NASA/GEWEX Surface Radiation Budget (SRB) project produces shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. Spatial resolution is 1 degree. The current Release 3.0 (available at gewex-srb.larc.nasa.gov) uses the International Satellite Cloud Climatology Project (ISCCP) DX product for pixel level radiance and cloud information. This product is subsampled to 30 km. ISCCP is currently recalibrating and recomputing their entire data series, to be released as the H product, at 10km resolution. The ninefold increase in pixel number will allow SRB a higher resolution gridded product (e.g. 0.5 degree), as well as the production of pixel-level fluxes. Other key input improvements include a detailed aerosol history using the Max Planck Institute Aerosol Climatology (MAC), and temperature and moisture profiles from nnHIRS.

Determination of Fluxes and their Source Partitioning from high-resolution Profile Measurements of Wind Speed and Scalars within and above short Canopies

NASA Astrophysics Data System (ADS)

Graf, A.; Ney, P.

2017-12-01

A continuously moving elevator-based system is described to measure vertical profiles of wind speed, temperature, CO2 and H2O within and above short plant canopies with a vertical resolution in the centimeter range. On sample days in 2015 to 2017, we measured profiles from the soil surface to 2 m a.g.l. in a crop rotation including wheat, barley, bare soil, winter catch crops and sugarbeet, with canopy heights of up to 1 m. Profiles over bare soil or very short canopies could be described well by fitting Monin-Obukhov-like profiles, and the derived fluxes of momentum and all three scalars matched well those of a nearby eddy-covariance station. In green canopies during the day, CO2 profiles clearly indicated the plant sink and soil source by a local minimum in the canopy and a maximum at the soil surface. H2O profiles, indicating sources both in the canopy and at the soil surface, did or did not show a local minimum between both, depending on canopy structure and turbulence. Temperature profiles showed various shapes including solar incident angle effects, and often the expected opposing signs of thermal stability between the subcanopy and the roughness sublayer. Finally, we test different existing parametrizations to estimate the vertical source / sink distribution from the measured profiles, compare the resulting vertically integrated fluxes to eddy-covariance based net fluxes, and discuss limitations and needed improvements to quantify subcanopy soil respiration and evaporation from such approaches.

Simulating 3-D radiative transfer effects over the Sierra Nevada Mountains using WRF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Y.; Liou, K. N.; Lee, W. -L.

2012-01-01

A surface solar radiation parameterization based on deviations between 3-D and conventional plane-parallel radiative transfer models has been incorporated into the Weather Research and Forecasting (WRF) model to understand the solar insolation over mountain/snow areas and to investigate the impact of the spatial and temporal distribution and variation of surface solar fluxes on land-surface processes. Using the Sierra-Nevada in the western United States as a testbed, we show that mountain effect could produce up to -50 to + 50 W m -2 deviations in the surface solar fluxes over the mountain areas, resulting in a temperature increase of up tomore » 1 °C on the sunny side. Upward surface sensible and latent heat fluxes are modulated accordingly to compensate for the change in surface solar fluxes. Snow water equivalent and surface albedo both show decreases on the sunny side of the mountains, indicating more snowmelt and hence reduced snow albedo associated with more solar insolation due to mountain effect. Soil moisture increases on the sunny side of the mountains due to enhanced snowmelt, while decreases on the shaded side. Substantial differences are found in the morning hours from 8–10 a.m. and in the afternoon around 3–5 p.m., while differences around noon and in the early morning and late afternoon are comparatively smaller. Variation in the surface energy balance can also affect atmospheric processes, such as cloud fields, through the modulation of vertical thermal structure. Negative changes of up to -40 g m -2 are found in the cloud water path, associated with reductions in the surface insolation over the cloud region. The day-averaged deviations in the surface solar flux are positive over the mountain areas and negative in the valleys, with a range between -12~12 W m -2. Changes in sensible and latent heat fluxes and surface skin temperature follow the solar insolation pattern. Differences in the domain-averaged diurnal variation over the Sierras show that the mountain area receives more solar insolation during early morning and late afternoon, resulting in enhanced upward sensible heat and latent heat fluxes from the surface and a corresponding increase in surface skin temperature. During the middle of the day, however, the surface insolation and heat fluxes show negative changes, indicating a cooling effect. Hence overall, the diurnal variations of surface temperature and surface fluxes in the Sierra-Nevada are reduced through the interactions of radiative transfer and mountains. Finally, the hourly differences of the surface solar insolation in higher elevated regions, however, show smaller magnitude in negative changes during the middle of the day and possibly more solar fluxes received during the whole day.« less

Verification of land-atmosphere coupling in forecast models, reanalyses and land surface models using flux site observations.

PubMed

Dirmeyer, Paul A; Chen, Liang; Wu, Jiexia; Shin, Chul-Su; Huang, Bohua; Cash, Benjamin A; Bosilovich, Michael G; Mahanama, Sarith; Koster, Randal D; Santanello, Joseph A; Ek, Michael B; Balsamo, Gianpaolo; Dutra, Emanuel; Lawrence, D M

2018-02-01

We confront four model systems in three configurations (LSM, LSM+GCM, and reanalysis) with global flux tower observations to validate states, surface fluxes, and coupling indices between land and atmosphere. Models clearly under-represent the feedback of surface fluxes on boundary layer properties (the atmospheric leg of land-atmosphere coupling), and may over-represent the connection between soil moisture and surface fluxes (the terrestrial leg). Models generally under-represent spatial and temporal variability relative to observations, which is at least partially an artifact of the differences in spatial scale between model grid boxes and flux tower footprints. All models bias high in near-surface humidity and downward shortwave radiation, struggle to represent precipitation accurately, and show serious problems in reproducing surface albedos. These errors create challenges for models to partition surface energy properly and errors are traceable through the surface energy and water cycles. The spatial distribution of the amplitude and phase of annual cycles (first harmonic) are generally well reproduced, but the biases in means tend to reflect in these amplitudes. Interannual variability is also a challenge for models to reproduce. Our analysis illuminates targets for coupled land-atmosphere model development, as well as the value of long-term globally-distributed observational monitoring.

Wind-tunnel experiments of scalar transport in aligned and staggered wind farms

NASA Astrophysics Data System (ADS)

Zhang, W.; Markfort, C. D.; Porté-Agel, F.

2012-04-01

Wind energy is the fastest growing renewable energy worldwide, and it is expected that many more large-scale wind farms will be built and will cover a significant portion of land and ocean surfaces. By extracting kinetic energy from the atmospheric boundary layer, wind farms may affect the exchange/transport of momentum, heat and moisture between the atmosphere and land surface. To ensure the long-term sustainability of wind energy, it is important to understand the influence of large-scale wind farms on land-atmosphere interaction. Knowledge of this impact will also be useful to improve parameterizations of wind farms in numerical prediction tools, such as large-scale weather models and large-eddy simulation. Here, we present wind-tunnel measurements of the surface scalar (heat) flux from model wind farms, consisting of more than 10 rows of wind turbines, in a turbulent boundary layer with a surface heat source. Spatially distributed surface heat flux was obtained in idealized aligned and staggered wind farm layouts, having the same turbine distribution density. Measurements, using surface-mounted heat flux sensors, were taken at the 11th out of 12 rows of wind turbines, where the mean flow achieves a quasi-equilibrium state. In the aligned farm, there exist two distinct regions of increased and decreased surface heat flux on either side of turbine columns. The regions are correlated with coherent wake rotation in the turbine-array. On the upwelling side there is decreased flux, while on the downwelling side cool air moves towards the surface causing increased flux. For the staggered farm, the surface heat flux exhibits a relatively uniform distribution and an overall reduction with respect to the boundary layer flow, except in the vicinity of the turbine tower. This observation is also supported by near-surface temperature and turbulent heat flux measured using a customized x-wire/cold-wire. The overall surface heat flux, relative to that of the boundary layer flow without wind turbines, is reduced by approximately 4% in the staggered wind farm and remains nearly the same in the aligned wind farm.

Heat-Flux Sensor For Hot Engine Cylinders

NASA Technical Reports Server (NTRS)

Kim, Walter S.; Barrows, Richard F.; Smith, Floyd A.; Koch, John

1989-01-01

Heat-flux sensor includes buried wire thermocouple and thin-film surface thermocouple, made of platinum and platinum with 13 percent rhodium. Sensor intended for use in ceramic-insulated, low-heat-rejection diesel engine at temperatures of about 1,000 K. Thermocouple junction resists environment in cylinder of advanced high-temperature diesel engine created by depositing overlapping films of Pt and 0.87 Pt/0.13 Rh on iron plug. Plug also contains internal thermocouple.

A multi-model ensemble view of winter heat flux dynamics and the dipole mode in the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Liguori, Giovanni; Di Lorenzo, Emanuele; Cabos, William

2017-02-01

Changes in surface heat fluxes affect several climate processes controlling the Mediterranean climate. These include the winter formation of deep waters, which is the primary driver of the Mediterranean Sea overturning circulation. Previous studies that characterize the spatial and temporal variability of surface heat flux anomalies over the basin reveal the existence of two statistically dominant patterns of variability: a monopole of uniform sign and an east-west dipole of opposite signs. In this work, we use the 12 regional climate model ensemble from the EU-FP6 ENSEMBLES project to diagnose the large-scale atmospheric processes that control the variability of heat fluxes over the Mediterranean Sea from interannual to decadal timescales (here defined as timescales > 6 year). Our findings suggest that while the monopole structure captures variability in the winter-to-winter domain-average net heat flux, the dipole pattern tracks changes in the Mediterranean climate that are connected to the East Atlantic/Western Russia (EA/WR) atmospheric teleconnection pattern. Furthermore, while the monopole exhibits significant differences in the spatial structure across the multi-model ensemble, the dipole pattern is very robust and more clearly identifiable in the anomaly maps of individual years. A heat budget analysis of the dipole pattern reveals that changes in winds associated with the EA/WR pattern exert dominant control through both a direct effect on the latent heat flux (i.e., wind speed) and an indirect effect through specific humidity (e.g., wind advection). A simple reconstruction of the heat flux variability over the deep-water formation regions of the Gulf of Lion and the Aegean Sea reveals that the combination of the monopole and dipole time series explains over 90 % of the heat flux variance in these regions. Given the important role that surface heat flux anomalies play in deep-water formation and the regional climate, improving our knowledge on the dynamics controlling the leading modes of heat flux variability may enhance our predictability of the climate of the Mediterranean area.

`Surface-Layer' momentum fluxes in nocturnal slope flows over steep terrain

NASA Astrophysics Data System (ADS)

Oldroyd, H. J.; Pardyjak, E.; Higgins, C. W.; Parlange, M. B.

2017-12-01

A common working definition for the `surface layer' is the lowest 10% of the atmospheric boundary layer (ABL) where the turbulent fluxes are essentially constant. The latter part of this definition is a critical assumption that must hold for accurate flux estimations from land-surface models, wall models, similarity theory, flux-gradient relations and bulk transfer methods. We present cases from observed momentum fluxes in nocturnal slope flows over steep (35.5 degree), alpine terrain in Val Ferret, Switzerland that satisfy the classical definitions of the surface layer and other cases where no traditional surface layer is observed. These cases broadly fall into two distinct flow regimes occurring under clear-sky conditions: (1) buoyancy-driven, `katabatic flow', characterized by an elevated velocity maximum (katabatic jet peak) and (2) `downslope winds', for which larger-scale forcing prevents formation of a katabatic jet. Velocity profiles in downslope wind cases are quite similar to logarithmic profiles typically observed over horizontal and homogeneous terrain, and the corresponding momentum fluxes roughly resemble a constant-flux surface-layer. Contrastingly, velocity profiles in the katabatic regime exhibit a jet-like shape. This jet strongly modulates the corresponding momentum fluxes, which exhibit strong gradients over the shallow katabatic layer and usually change sign near the jet peak, where the velocity gradients also change sign. However, a counter-gradient momentum flux is frequently observed near the jet peak (and sometimes at higher levels), suggesting strong non-local turbulent transport within the katabatic jet layer. We compare our observations with katabatic flow theories and observational studies over shallow-angle slopes and use co-spectral analyses to better identify and understand the non-local transport dynamics. Finally, we show that because of the counter-gradient momentum fluxes, surface layer stability and even local stability can be difficult to characterize because the counter-gradient momentum flux represents a sink in the shear term of turbulence kinetic energy budget equation. These results have broad implications for stability-based modeling and general definitions and assumptions used for the ABL and so-called `surface layer' over steep terrain.

The Surface Energy Balance at Local and Regional Scales-A Comparison of General Circulation Model Results with Observations.

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Krummel, P. B.; Kowalczyk, E. A.

1993-06-01

Aspects of the mean monthly energy balance at continental surfaces are examined by appeal to the results of general circulation model (GCM) simulations, climatological maps of surface fluxes, and direct observations. Emphasis is placed on net radiation and evaporation for (i) five continental regions (each approximately 20°×150°) within Africa, Australia, Eurasia, South America, and the United States; (ii) a number of continental sites in both hemispheres. Both the mean monthly values of the local and regional fluxes and the mean monthly diurnal cycles of the local fluxes are described. Mostly, GCMs tend to overestimate the mean monthly levels of net radiation by about 15% -20% on an annual basis, for observed annual values in the range 50 to 100 Wm2. This is probably the result of several deficiencies, including (i) continental surface albedos being undervalued in a number of the models, resulting in overestimates of the net shortwave flux at the surface (though this deficiency is steadily being addressed by modelers); (ii) incoming shortwave fluxes being overestimated due to uncertainties in cloud schemes and clear-sky absorption; (iii) land-surface temperatures being under-estimated resulting in an underestimate of the outgoing longwave flux. In contrast, and even allowing for the poor observational base for evaporation, there is no obvious overall bias in mean monthly levels of evaporation determined in GCMS, with one or two exceptions. Rather, and far more so than with net radiation, there is a wide range in values of evaporation for all regions investigated. For continental regions and at times of the year of low to moderate rainfall, there is a tendency for the simulated evaporation to be closely related to the precipitation-this is not surprising. In contrast, for regions where there is sufficient or excessive rainfall, the evaporation tends to follow the behavior of the net radiation. Again, this is not surprising given the close relation between potential evaporation and net radiation, as discussed by Priestley and Taylor. Finally, the introduction into GCMs of an `improved' surface scheme (incorporating more realistic representations of soil and canopy processes and revised albedos) does tend to improve the calculations of both regional net radiation and evaporation.

Derivation of Improved Surface and TOA Broadband Fluxes Using CERES-derived Narrowband-to-Broadband Coefficients

NASA Technical Reports Server (NTRS)

Khaiyer, Mandana M.; Doelling, David R.; Chan, Pui K.; Nordeen, MIchele L.; Palikonda, Rabindra; Yi, Yuhong; Minnis, Patrick

2006-01-01

Satellites can provide global coverage of a number of climatically important radiative parameters, including broadband (BB) shortwave (SW) and longwave (LW) fluxes at the top of the atmosphere (TOA) and surface. These parameters can be estimated from narrowband (NB) Geostationary Operational Environmental Satellite (GOES) data, but their accuracy is highly dependent on the validity of the narrowband-to-broadband (NB-BB) conversion formulas that are used to convert the NB fluxes to broadband values. The formula coefficients have historically been derived by regressing matched polarorbiting satellite BB fluxes or radiances with their NB counterparts from GOES (e.g., Minnis et al., 1984). More recently, the coefficients have been based on matched Earth Radiation Budget Experiment (ERBE) and GOES-6 data (Minnis and Smith, 1998). The Clouds and the Earth's Radiant Energy Budget (CERES see Wielicki et al. 1998)) project has recently developed much improved Angular Distribution Models (ADM; Loeb et al., 2003) and has higher resolution data compared to ERBE. A limited set of coefficients was also derived from matched GOES-8 and CERES data taken on Topical Rainfall Measuring Mission (TRMM) satellite (Chakrapani et al., 2003; Doelling et al., 2003). The NB-BB coefficients derived from CERES and the GOES suite should yield more accurate BB fluxes than from ERBE, but are limited spatially and seasonally. With CERES data taken from Terra and Aqua, it is now possible to derive more reliable NB-BB coefficients for any given area. Better TOA fluxes should translate to improved surface radiation fluxes derived using various algorithms. As part of an ongoing effort to provide accurate BB flux estimates for the Atmospheric Radiation Measurement (ARM) Program, this paper documents the derivation of new NB-BB coefficients for the ARM Southern Great Plains (SGP) domain and for the Darwin region of the Tropical Western Pacific (DTWP) domain.

Laser Measurement Of Convective-Heat-Transfer Coefficient

NASA Technical Reports Server (NTRS)

Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.

1994-01-01

Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.

Upscaling and Downscaling of Land Surface Fluxes with Surface Temperature

NASA Astrophysics Data System (ADS)

Kustas, W. P.; Anderson, M. C.; Hain, C.; Albertson, J. D.; Gao, F.; Yang, Y.

2015-12-01

Land surface temperature (LST) is a key surface boundary condition that is significantly correlated to surface flux partitioning between latent and sensible heat. The spatial and temporal variation in LST is driven by radiation, wind, vegetation cover and roughness as well as soil moisture status in the surface and root zone. Data from airborne and satellite-based platforms provide LST from ~10 km to sub meter resolutions. A land surface scheme called the Two-Source Energy Balance (TSEB) model has been incorporated into a multi-scale regional modeling system ALEXI (Atmosphere Land Exchange Inverse) and a disaggregation scheme (DisALEXI) using higher resolution LST. Results with this modeling system indicates that it can be applied over heterogeneous land surfaces and estimate reliable surface fluxes with minimal in situ information. Consequently, this modeling system allows for scaling energy fluxes from subfield to regional scales in regions with little ground data. In addition, the TSEB scheme has been incorporated into a large Eddy Simulation (LES) model for investigating dynamic interactions between variations in the land surface state reflected in the spatial pattern in LST and the lower atmospheric air properties affecting energy exchange. An overview of research results on scaling of fluxes and interactions with the lower atmosphere from the subfield level to regional scales using the TSEB, ALEX/DisALEX and the LES-TSEB approaches will be presented. Some unresolved issues in the use of LST at different spatial resolutions for estimating surface energy balance and upscaling fluxes, particularly evapotranspiration, will be discussed.

Analysis of Atmosphere-Ocean Surface Flux Feedbacks in Recent Satellite and Model Reanalysis Products

NASA Technical Reports Server (NTRS)

Roberts, J. Brent; Robertson, F. R.; Clayson, C. A.

2010-01-01

Recent investigations have examined observations in an attempt to determine when and how the ocean forces the atmosphere, and vice versa. These studies focus primarily on relationships between sea surface temperature anomalies and the turbulent and radiative surface heat fluxes. It has been found that both positive and negative feedbacks, which enhance or reduce sea surface temperature anomaly amplitudes, can be generated through changes in the surface boundary layer. Consequent changes in sea surface temperature act to change boundary layer characteristics through changes in static stability or turbulent fluxes. Previous studies over the global oceans have used coarse-resolution observational and model products such as ICOADS and the NCEP Reanalysis. This study focuses on documenting the atmosphere ocean feedbacks that exist in recently produced higher resolution products, namely the SeaFlux v1.0 product and the NASA Modern Era Retrospective-Analysis for Research and Applications (MERRA). It has been noted in recent studies that evidence of oceanic forcing of the atmosphere exists on smaller scales than the usually more dominant atmospheric forcing of the ocean, particularly in higher latitudes. It is expected that use of these higher resolution products will allow for a more comprehensive description of these small-scale ocean-atmosphere feedbacks. The SeaFlux intercomparisons have revealed large scatter between various surface flux climatologies. This study also investigates the uncertainty in surface flux feedbacks based on several of these recent satellite based climatologies

Enhancement of surface-atmosphere fluxes by desert-fringe vegetation through reduction of surface albedo and of soil heat flux

NASA Technical Reports Server (NTRS)

Otterman, J.

1987-01-01

Under the arid conditions prevailing at the end of the dry season in the western Negev/northern Sinai region, vegetation causes a sharp increase relative to bare soil in the daytime sensible heat flux from the surface to the atmosphere. Two mechanisms are involved: the increase in the surface absorptivity and a decrease in the surface heat flux. By increasing the sensible heat flux to the atmosphere through the albedo and the soil heat flux reductions, the desert-fringe vegetation increases the daytime convection and the growth of the planetary boundary layer. Removal of vegetation by overgrazing, by reducing the sensible heat flux, tends to reduce daytime convective precipitation, producing higher probabilities of drought conditions. This assessment of overgrazing is based on observations in the Sinai/Negev, where the soil albedo is high and where overgrazing produces an essential bare soil. Even if the assessment for the Sinai/Negev does not quantitatively apply throughout Africa, the current practice in many African countries of maintaining a large population of grazing animals, can contribute through the mesoscale mechanisms described to reduce daytime convective precipitation, perpetuating higher probabilities of drought. Time-of-day analysis of precipitation in Africa appears worthwhile, to better assess the role of the surface conditions in contributing to drought.

Estimating and validating surface energy fluxes at field scale over a heterogeneous land surfaces based on two-source energy balance model (TSEB)

USDA-ARS?s Scientific Manuscript database

Accurate estimation of surface energy fluxes at field scale over large areas has the potential to improve agricultural water management in arid and semiarid watersheds. Remote sensing may be the only viable approach for mapping fluxes over heterogeneous landscapes. The Two-Source Energy Balance mode...

A two-dimensional hydrodynamic model of turbulent transfer of CO2 and H2O over a heterogeneous land surface

NASA Astrophysics Data System (ADS)

Mukhartova, Yu. V.; Krupenko, A. S.; Mangura, P. A.; Levashova, N. T.

2018-01-01

A two-dimensional hydrodynamic model was developed and applied to describe turbulent fluxes of CO2 and H2O within the atmospheric surface layer over a heterogeneous land surface featuring mosaic vegetation and complex topography. Numerical experiments were carried out with a 4.5-km profile that crosses a hilly region in the central part of European Russia, with the diverse land-use patterns (bare soil, crop areas, grasslands, and forests). The results showed very strong variability of the vertical and horizontal turbulent CO2 and H2O fluxes. The standard deviations of the vertical fluxes were estimated for separate profile sections with uniform vegetation cover for daylight conditions in summer, and they were comparable with the mean vertical fluxes for corresponding sections. The highest horizontal turbulent fluxes occurred at the boundaries between different plant communities and at irregularities in surface profile. In some cases, these fluxes reached 10-20% of the absolute values of the mean vertical fluxes for corresponding profile sections. Significant errors in estimating the local and integrated fluxes e.g. when using the eddy covariance technique, can result from ignoring the surface topography, even in the case of relatively large plots with uniform vegetation cover.

Effect of Climate Extremes, Seasonal Change, and Agronomic Practices on Measured Evapotranspiration and CO2 Exchange in Sacramento-San Joaquin River Delta Alfalfa Fields

NASA Astrophysics Data System (ADS)

Clay, J.; Kent, E. R.; Leinfelder-Miles, M.; Paw U, K. T.; Little, C.; Lambert, J. J.

2017-12-01

Evapotranspiration and CO2 exchange was measured in five alfalfa fields in the Sacramento-San Joaquin River Delta region from 2016 to 2017 using eddy covariance and surface renewal methods. Seasonal changes of evapotranspiration and CO2 fluxes were compared between 2016, a drought year, and 2017, a high rainfall year. Additionally, changes in evapotranspiration and CO2 flux were investigated across various agronomic considerations, such as irrigation methods (border-check flood and sub-surface), stand life, and herbicide programs. Components of the energy balance, including net radiation, latent heat, ground heat flux, and sensible heat, were evaluated considering correlations to wind speed measured by three sonic anemometers, irrigation frequency, and crop cutting cycle. Comparisons between two different types of radiometers were also carried out. Under drought conditions, we observed higher amounts of evapotranspiration in a field having a stand life of less than two years of age compared to older stands, and in a sub-surface irrigated field compared to flood irrigated fields.

Effect of Running Parameters on Flow Boiling Instabilities in Microchannels.

PubMed

Zong, Lu-Xiang; Xu, Jin-Liang; Liu, Guo-Hua

2015-04-01

Flow boiling instability (FBI) in microchannels is undesirable because they can induce the mechanical vibrations and disturb the heat transfer characteristics. In this study, the synchronous optical visualization experimental system was set up. The pure acetone liquid was used as the working fluid, and the parallel triangle silicon microchannel heat sink was designed as the experimental section. With the heat flux ranging from 0-450 kW/m2 the microchannel demand average pressure drop-heater length (Δp(ave)L) curve for constant low mass flux, and the demand pressure drop-mass flux (Δp(ave)G) curve for constant length on main heater surface were obtained and studied. The effect of heat flux (q = 188.28, 256.00, and 299.87 kW/m2), length of main heater surface (L = 4.5, 6.25, and 8.00 mm), and mass flux (G = 188.97, 283.45, and 377.94 kg/m2s) on pressure drops (Ap) and temperatures at the central point of the main heater surface (Twc) were experimentally studied. The results showed that, heat flux, length of the main heater surface, and mass flux were identified as the important parameters to the boiling instability process. The boiling incipience (TBI) and critical heat flux (CHF) were early induced for the lower mass flux or the main heater surface with longer length. With heat flux increasing, the pressure drops were linearly and slightly decreased in the single liquid region but increased sharply in the two phase flow region, in which the flow boiling instabilities with apparent amplitude and long period were more easily triggered at high heat flux. Moreover, the system pressure was increased with the increase of the heat flux.

Estimating lake-atmosphere CO2 exchange

USGS Publications Warehouse

Anderson, D.E.; Striegl, Robert G.; Stannard, D.I.; Michmerhuizen, C.M.; McConnaughey, T.A.; LaBaugh, J.W.

1999-01-01

Lake-atmosphere CO2 flux was directly measured above a small, woodland lake using the eddy covariance technique and compared with fluxes deduced from changes in measured lake-water CO2 storage and with flux predictions from boundary-layer and surface-renewal models. Over a 3-yr period, lake-atmosphere exchanges of CO2 were measured over 5 weeks in spring, summer, and fall. Observed springtime CO2 efflux was large (2.3-2.7 ??mol m-2 s-1) immediately after lake-thaw. That efflux decreased exponentially with time to less than 0.2 ??mol m-2 s-1 within 2 weeks. Substantial interannual variability was found in the magnitudes of springtime efflux, surface water CO2 concentrations, lake CO2 storage, and meteorological conditions. Summertime measurements show a weak diurnal trend with a small average downward flux (-0.17 ??mol m-2 s-1) to the lake's surface, while late fall flux was trendless and smaller (-0.0021 ??mol m-2 s-1). Large springtime efflux afforded an opportunity to make direct measurement of lake-atmosphere fluxes well above the detection limits of eddy covariance instruments, facilitating the testing of different gas flux methodologies and air-water gas-transfer models. Although there was an overall agreement in fluxes determined by eddy covariance and those calculated from lake-water storage change in CO2, agreement was inconsistent between eddy covariance flux measurements and fluxes predicted by boundary-layer and surface-renewal models. Comparison of measured and modeled transfer velocities for CO2, along with measured and modeled cumulative CO2 flux, indicates that in most instances the surface-renewal model underpredicts actual flux. Greater underestimates were found with comparisons involving homogeneous boundary-layer models. No physical mechanism responsible for the inconsistencies was identified by analyzing coincidentally measured environmental variables.

Partitioning of Electromagnetic Energy Inputs to the Thermosphere during Geomagnetic Disturbances

DTIC Science & Technology

2012-06-01

boundary of a local flux tube volume is an equipotential . Figure 4 contains maps of Poynting flux normal to a 500 km altitude surface and maps of height...as a cell quantity throughout its computational volume, we are able to generate maps of the Poynting flux, ⃗ ⃗⃗⃗⃗⃗⃗ , on altitude surfaces at...the top of the thermosphere. We used separate modules to integrate the Poynting flux over this surface to compute the total electromagnetic energy

Semiconductor etching by hyperthermal neutral beams

NASA Technical Reports Server (NTRS)

Minton, Timothy K. (Inventor); Giapis, Konstantinos P. (Inventor)

1999-01-01

An at-least dual chamber apparatus and method in which high flux beams of fast moving neutral reactive species are created, collimated and used to etch semiconductor or metal materials from the surface of a workpiece. Beams including halogen atoms are preferably used to achieve anisotropic etching with good selectivity at satisfactory etch rates. Surface damage and undercutting are minimized.

Gravel bar thermal variability and its potential consequences for CO2 evasion from Alpine coldwater streams

NASA Astrophysics Data System (ADS)

Boodoo, Kyle; Battin, Tom; Schelker, Jakob

2017-04-01

Gravel bars (GB) are ubiquitous in-stream structures with relatively large exposed surfaces, capable of absorbing heat and possibly acting as a heat source to the underlying hyporheic zone (HZ). The distinctive mixing of groundwater and surface water within their HZ largely determines its characteristic physical and biogeochemical properties, including temperature distribution. To study thermal variability within GBs and its possible consequences for CO2 evasion fluxes we analysed high frequency spatio-temporal data for a range of stream and atmospheric physical parameters including the vertical GB temperature, in an Alpine cold water stream (Oberer Seebach, Austria) over the course of a year. We found the vertical temperature profiles within the GB to vary seasonally and with discharge. We extended our study to 13 other gravel bars of varying physical characteristics within the surrounding Ybbs and Erlauf catchments, conducting diurnal spot samplings in summer 2016. Temperatures within the observed permanently wetted hyporheic zone (-56 to -100cm depth below GB surface) of the OSB, were warmer than both end members, surface water and groundwater >18% of the year, particularly during summer. There was a general increase in exceedance within the periodically wetted gravel bar sediment toward the gravel bar surface, further evidencing downward heat transfer to the wetted HZ. Average CO2 flux from the GB was significantly higher than that of streamwater during summer and winter, with significantly higher temperatures and CO2 outgassing rates occurring at the GB tail as compared to streamwater and the head and mid of the GB throughout the year. Higher cumulative (over 6 h) GB seasonal temperatures were associated with increased CO2 evasion fluxes within the OSB, particularly during summer. This enhanced CO2 flux may result from the input of warmer CO2-rich groundwater into the HZ in autumn, while downward heat transfer in summer may enhance GB metabolism and therefore CO2 evasion. Furthermore, catchment CO2 outgassing fluxes significantly exceeded that of the stream, with higher diurnal CO2 outgassing fluxes observed for all 13 GBs within the Ybbs and Erlauf catchments as compared to their respective streams. We found DOC concentration did not significantly correlate to CO2 outgassing. But, vertical temperature gradient as a measure of heat flux to the hyporheic zone explained 55% and 69% of the variability in observed CO2 efflux from the OSB gravel bar (seasonal samplings during summer 2015 - winter 2016) and 11 catchment gravel bars (2 GBs excluded due to equipment malfunction) respectively. These results highlight the effect of temperature on physical and biochemical stream processes, particularly in cold-water streams, due to the occurrence of more frequent and intense warm temperature events, as well as altered flow regimes, likely consequences of climatic change.

Soil property effects on wind erosion of organic soils

NASA Astrophysics Data System (ADS)

Zobeck, Ted M.; Baddock, Matthew; Scott Van Pelt, R.; Tatarko, John; Acosta-Martinez, Veronica

2013-09-01

Histosols (also known as organic soils, mucks, or peats) are soils that are dominated by organic matter (OM > 20%) in half or more of the upper 80 cm. Forty two states have a total of 21 million ha of Histosols in the United States. These soils, when intensively cropped, are subject to wind erosion resulting in loss of crop productivity and degradation of soil, air, and water quality. Estimating wind erosion on Histosols has been determined by USDA-Natural Resources Conservation Service (NRCS) as a critical need for the Wind Erosion Prediction System (WEPS) model. WEPS has been developed to simulate wind erosion on agricultural land in the US, including soils with organic soil material surfaces. However, additional field measurements are needed to understand how soil properties vary among organic soils and to calibrate and validate estimates of wind erosion of organic soils using WEPS. Soil properties and sediment flux were measured in six soils with high organic contents located in Michigan and Florida, USA. Soil properties observed included organic matter content, particle density, dry mechanical stability, dry clod stability, wind erodible material, and geometric mean diameter of the surface aggregate distribution. A field portable wind tunnel was used to generate suspended sediment and dust from agricultural surfaces for soils ranging from 17% to 67% organic matter. The soils were tilled and rolled to provide a consolidated, friable surface. Dust emissions and saltation were measured using an isokinetic vertical slot sampler aspirated by a regulated suction source. Suspended dust was sampled using a Grimm optical particle size analyzer. Particle density of the saltation-sized material (>106 μm) was inversely related to OM content and varied from 2.41 g cm-3 for the soil with the lowest OM content to 1.61 g cm-3 for the soil with highest OM content. Wind erodible material and the geometric mean diameter of the surface soil were inversely related to dry clod stability. The effect of soil properties on sediment flux varied among flux types. Saltation flux was adequately predicted with simple linear regression models. Dry mechanical stability was the best single soil property linearly related to saltation flux. Simple linear models with soil properties as independent variables were not well correlated with PM10E values (mass flux). A second order polynomial equation with OM as the independent variable was found to be most highly correlated with PM10E values. These results demonstrate that variations in sediment and dust emissions can be linked to soil properties using simple models based on one or more soil properties to estimate saltation mass flux and PM10E values from organic and organic-rich soils.

The ancient oxygen exosphere of Mars - Implications for atmosphere evolution

NASA Technical Reports Server (NTRS)

Zhang, M. H. G.; Luhmann, J. G.; Bougher, S. W.; Nagy, A. F.

1993-01-01

The paper considers absorption of oxygen (atoms and ions) by the surface as a mechanism for the early Martian atmosphere escape, due to the effect of high EUV flux of the ancient sun. Hot oxygen exosphere densities in ancient atmosphere and ionosphere are calculated for different EUV fluxes and the escape fluxes associated with these exposures. Using these densities, the ion production rate above the ionopause is calculated for different epochs including photoionization, charge exchange, and solar wind electron impact. It is found that, when the inferred high solar EUV fluxes of the past are taken into account, oxygen equivalent to that in several tens of meters of water, planet-wide, should have escaped Martian atmosphere to space over the last 3 Gyr.

The ancient oxygen exosphere of Mars - Implications for atmosphere evolution

NASA Astrophysics Data System (ADS)

Zhang, M. H. G.; Luhmann, J. G.; Bougher, S. W.; Nagy, A. F.

1993-06-01

The paper considers absorption of oxygen (atoms and ions) by the surface as a mechanism for the early Martian atmosphere escape, due to the effect of high EUV flux of the ancient sun. Hot oxygen exosphere densities in ancient atmosphere and ionosphere are calculated for different EUV fluxes and the escape fluxes associated with these exposures. Using these densities, the ion production rate above the ionopause is calculated for different epochs including photoionization, charge exchange, and solar wind electron impact. It is found that, when the inferred high solar EUV fluxes of the past are taken into account, oxygen equivalent to that in several tens of meters of water, planet-wide, should have escaped Martian atmosphere to space over the last 3 Gyr.

Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements

NASA Astrophysics Data System (ADS)

Fraser, A.; Palmer, P. I.; Feng, L.; Boesch, H.; Cogan, A.; Parker, R.; Dlugokencky, E. J.; Fraser, P. J.; Krummel, P. B.; Langenfelds, R. L.; O'Doherty, S.; Prinn, R. G.; Steele, L. P.; van der Schoot, M.; Weiss, R. F.

2013-06-01

We use an ensemble Kalman filter (EnKF), together with the GEOS-Chem chemistry transport model, to estimate regional monthly methane (CH4) fluxes for the period June 2009-December 2010 using proxy dry-air column-averaged mole fractions of methane (XCH4) from GOSAT (Greenhouse gases Observing SATellite) and/or NOAA ESRL (Earth System Research Laboratory) and CSIRO GASLAB (Global Atmospheric Sampling Laboratory) CH4 surface mole fraction measurements. Global posterior estimates using GOSAT and/or surface measurements are between 510-516 Tg yr-1, which is less than, though within the uncertainty of, the prior global flux of 529 ± 25 Tg yr-1. We find larger differences between regional prior and posterior fluxes, with the largest changes in monthly emissions (75 Tg yr-1) occurring in Temperate Eurasia. In non-boreal regions the error reductions for inversions using the GOSAT data are at least three times larger (up to 45%) than if only surface data are assimilated, a reflection of the greater spatial coverage of GOSAT, with the two exceptions of latitudes >60° associated with a data filter and over Europe where the surface network adequately describes fluxes on our model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2 model output to investigate model error on quantifying proxy GOSAT XCH4 (involving model XCO2) and inferring methane flux estimates from surface mole fraction data and show similar resulting fluxes, with differences reflecting initial differences in the proxy value. Using a series of observing system simulation experiments (OSSEs) we characterize the posterior flux error introduced by non-uniform atmospheric sampling by GOSAT. We show that clear-sky measurements can theoretically reproduce fluxes within 10% of true values, with the exception of tropical regions where, due to a large seasonal cycle in the number of measurements because of clouds and aerosols, fluxes are within 15% of true fluxes. We evaluate our posterior methane fluxes by incorporating them into GEOS-Chem and sampling the model at the location and time of surface CH4 measurements from the AGAGE (Advanced Global Atmospheric Gases Experiment) network and column XCH4 measurements from TCCON (Total Carbon Column Observing Network). The posterior fluxes modestly improve the model agreement with AGAGE and TCCON data relative to prior fluxes, with the correlation coefficients (r2) increasing by a mean of 0.04 (range: -0.17 to 0.23) and the biases decreasing by a mean of 0.4 ppb (range: -8.9 to 8.4 ppb).

Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements

NASA Astrophysics Data System (ADS)

Fraser, A.; Palmer, P. I.; Feng, L.; Boesch, H.; Cogan, A.; Parker, R.; Dlugokencky, E. J.; Fraser, P. J.; Krummel, P. B.; Langenfelds, R. L.; O'Doherty, S.; Prinn, R. G.; Steele, L. P.; van der Schoot, M.; Weiss, R. F.

2012-12-01

We use an ensemble Kalman filter (EnKF), together with the GEOS-Chem chemistry transport model, to estimate regional monthly methane (CH4) fluxes for the period June 2009-December 2010 using proxy dry-air column-averaged mole fractions of methane (XCH4) from GOSAT (Greenhouse gases Observing SATellite) and/or NOAA ESRL (Earth System Research Laboratory) and CSIRO GASLAB (Global Atmospheric Sampling Laboratory) CH4 surface mole fraction measurements. Global posterior estimates using GOSAT and/or surface measurements are between 510-516 Tg yr-1, which is less than, though within the uncertainty of, the prior global flux of 529 ± 25 Tg yr-1. We find larger differences between regional prior and posterior fluxes, with the largest changes (75 Tg yr-1) occurring in Temperate Eurasia. In non-boreal regions the error reductions for inversions using the GOSAT data are at least three times larger (up to 45%) than if only surface data are assimilated, a reflection of the greater spatial coverage of GOSAT, with the two exceptions of latitudes > 60° associated with a data filter and over Europe where the surface network adequately describes fluxes on our model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2 model output to investigate model error on quantifying proxy GOSAT XCH4 (involving model XCO2) and inferring methane flux estimates from surface mole fraction data and show similar resulting fluxes, with differences reflecting initial differences in the proxy value. Using a series of observing system simulation experiments (OSSEs) we characterize the posterior flux error introduced by non-uniform atmospheric sampling by GOSAT. We show that clear-sky measurements can theoretically reproduce fluxes within 5% of true values, with the exception of South Africa and Tropical South America where, due to a large seasonal cycle in the number of measurements because of clouds and aerosols, fluxes are within 17% and 19% of true fluxes, respectively. We evaluate our posterior methane fluxes by incorporating them into GEOS-Chem and sampling the model at the location and time of independent surface CH4 measurements from the AGAGE (Advanced Global Atmospheric Gases Experiment) network and column XCH4 measurements from TCCON (Total Carbon Column Observing Network). The posterior fluxes modestly improve the model agreement with AGAGE and TCCON data relative to prior fluxes, with the correlation coefficients (r2) increasing by a mean of 0.04 (range: -0.17, 0.23) and the biases decreasing by a mean of 0.4 ppb (range: -8.9, 8.4 ppb).

Inverse Modeling of Hydrologic Parameters Using Surface Flux and Runoff Observations in the Community Land Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yu; Hou, Zhangshuan; Huang, Maoyi

2013-12-10

This study demonstrates the possibility of inverting hydrologic parameters using surface flux and runoff observations in version 4 of the Community Land Model (CLM4). Previous studies showed that surface flux and runoff calculations are sensitive to major hydrologic parameters in CLM4 over different watersheds, and illustrated the necessity and possibility of parameter calibration. Two inversion strategies, the deterministic least-square fitting and stochastic Markov-Chain Monte-Carlo (MCMC) - Bayesian inversion approaches, are evaluated by applying them to CLM4 at selected sites. The unknowns to be estimated include surface and subsurface runoff generation parameters and vadose zone soil water parameters. We find thatmore » using model parameters calibrated by the least-square fitting provides little improvements in the model simulations but the sampling-based stochastic inversion approaches are consistent - as more information comes in, the predictive intervals of the calibrated parameters become narrower and the misfits between the calculated and observed responses decrease. In general, parameters that are identified to be significant through sensitivity analyses and statistical tests are better calibrated than those with weak or nonlinear impacts on flux or runoff observations. Temporal resolution of observations has larger impacts on the results of inverse modeling using heat flux data than runoff data. Soil and vegetation cover have important impacts on parameter sensitivities, leading to the different patterns of posterior distributions of parameters at different sites. Overall, the MCMC-Bayesian inversion approach effectively and reliably improves the simulation of CLM under different climates and environmental conditions. Bayesian model averaging of the posterior estimates with different reference acceptance probabilities can smooth the posterior distribution and provide more reliable parameter estimates, but at the expense of wider uncertainty bounds.« less

Changes in urban-related precipitation in the summer over three city clusters in China

NASA Astrophysics Data System (ADS)

Zhao, Deming; Wu, Jian

2017-09-01

The impacts of urban surface expansion on the summer precipitations over three city clusters [Beijing-Tianjin-Hebei (BTH), the Yangtze River Delta (YRD), and the Pearl River Delta (PRD)] in eastern China under different monsoonal circulation backgrounds were explored using the nested fifth-generation Penn State/NCAR Mesoscale Model version 3.7 (MM5 V3.7), including the urban-related thermal and dynamical parameters. Ten-year integrations were performed using satellite image data from 2000 and 2010 to represent the urban surface distributions and expansions in China. Changes in the precipitation revealed obvious subregional characteristics, which could be explained by the influences of the vertical wind velocity and moisture flux. With urban-related warming, vertical wind motion generally intensified over urban surface-expanded areas. Meanwhile, the increase in impervious surface areas induced rapid rainwater runoff into drains, and the Bowen ratio increased over urban areas, which further contributed to changes in the local moisture fluxes in these regions. The intensities of the changes in precipitation were inconsistent over the three city clusters, although the changes in vertical motion and local evaporation were similar, which indicates that the changes in precipitation cannot be solely explained by the changes in the local evaporation-related moisture flux. The changes in precipitation were also influenced by the changes in the East Asian summer monsoon (EASM) circulation and the corresponding moisture flux, which are expressed in marked subregional characteristics. Therefore, the influence of urban-related precipitation over the three city clusters in China, for which changes in moisture flux from both the impacted local evaporation and EASM circulation should be considered, varied based on the precipitation changes of only a single city.

Inverse modeling of hydrologic parameters using surface flux and runoff observations in the Community Land Model

NASA Astrophysics Data System (ADS)

Sun, Y.; Hou, Z.; Huang, M.; Tian, F.; Leung, L. Ruby

2013-12-01

This study demonstrates the possibility of inverting hydrologic parameters using surface flux and runoff observations in version 4 of the Community Land Model (CLM4). Previous studies showed that surface flux and runoff calculations are sensitive to major hydrologic parameters in CLM4 over different watersheds, and illustrated the necessity and possibility of parameter calibration. Both deterministic least-square fitting and stochastic Markov-chain Monte Carlo (MCMC)-Bayesian inversion approaches are evaluated by applying them to CLM4 at selected sites with different climate and soil conditions. The unknowns to be estimated include surface and subsurface runoff generation parameters and vadose zone soil water parameters. We find that using model parameters calibrated by the sampling-based stochastic inversion approaches provides significant improvements in the model simulations compared to using default CLM4 parameter values, and that as more information comes in, the predictive intervals (ranges of posterior distributions) of the calibrated parameters become narrower. In general, parameters that are identified to be significant through sensitivity analyses and statistical tests are better calibrated than those with weak or nonlinear impacts on flux or runoff observations. Temporal resolution of observations has larger impacts on the results of inverse modeling using heat flux data than runoff data. Soil and vegetation cover have important impacts on parameter sensitivities, leading to different patterns of posterior distributions of parameters at different sites. Overall, the MCMC-Bayesian inversion approach effectively and reliably improves the simulation of CLM under different climates and environmental conditions. Bayesian model averaging of the posterior estimates with different reference acceptance probabilities can smooth the posterior distribution and provide more reliable parameter estimates, but at the expense of wider uncertainty bounds.

On the performance of surface renewal analysis to estimate sensible heat flux over two growing rice fields under the influence of regional advection

NASA Astrophysics Data System (ADS)

Castellví, F.; Snyder, R. L.

2009-09-01

SummaryHigh-frequency temperature data were recorded at one height and they were used in Surface Renewal (SR) analysis to estimate sensible heat flux during the full growing season of two rice fields located north-northeast of Colusa, CA (in the Sacramento Valley). One of the fields was seeded into a flooded paddy and the other was drill seeded before flooding. To minimize fetch requirements, the measurement height was selected to be close to the maximum expected canopy height. The roughness sub-layer depth was estimated to discriminate if the temperature data came from the inertial or roughness sub-layer. The equation to estimate the roughness sub-layer depth was derived by combining simple mixing-length theory, mixing-layer analogy, equations to account for stable atmospheric surface layer conditions, and semi-empirical canopy-architecture relationships. The potential for SR analysis as a method that operates in the full surface boundary layer was tested using data collected over growing vegetation at a site influenced by regional advection of sensible heat flux. The inputs used to estimate the sensible heat fluxes included air temperature sampled at 10 Hz, the mean and variance of the horizontal wind speed, the canopy height, and the plant area index for a given intermediate height of the canopy. Regardless of the stability conditions and measurement height above the canopy, sensible heat flux estimates using SR analysis gave results that were similar to those measured with the eddy covariance method. Under unstable cases, it was shown that the performance was sensitive to estimation of the roughness sub-layer depth. However, an expression was provided to select the crucial scale required for its estimation.

Drivers of inorganic carbon dynamics in first-year sea ice: A model study

NASA Astrophysics Data System (ADS)

Moreau, Sébastien; Vancoppenolle, Martin; Delille, Bruno; Tison, Jean-Louis; Zhou, Jiayun; Kotovitch, Marie; Thomas, David N.; Geilfus, Nicolas-Xavier; Goosse, Hugues

2015-01-01

Sea ice is an active source or a sink for carbon dioxide (CO2), although to what extent is not clear. Here, we analyze CO2 dynamics within sea ice using a one-dimensional halothermodynamic sea ice model including gas physics and carbon biogeochemistry. The ice-ocean fluxes, and vertical transport, of total dissolved inorganic carbon (DIC) and total alkalinity (TA) are represented using fluid transport equations. Carbonate chemistry, the consumption, and release of CO2 by primary production and respiration, the precipitation and dissolution of ikaite (CaCO3·6H2O) and ice-air CO2 fluxes, are also included. The model is evaluated using observations from a 6 month field study at Point Barrow, Alaska, and an ice-tank experiment. At Barrow, results show that the DIC budget is mainly driven by physical processes, wheras brine-air CO2 fluxes, ikaite formation, and net primary production, are secondary factors. In terms of ice-atmosphere CO2 exchanges, sea ice is a net CO2 source and sink in winter and summer, respectively. The formulation of the ice-atmosphere CO2 flux impacts the simulated near-surface CO2 partial pressure (pCO2), but not the DIC budget. Because the simulated ice-atmosphere CO2 fluxes are limited by DIC stocks, and therefore <2 mmol m-2 d-1, we argue that the observed much larger CO2 fluxes from eddy covariance retrievals cannot be explained by a sea ice direct source and must involve other processes or other sources of CO2. Finally, the simulations suggest that near-surface TA/DIC ratios of ˜2, sometimes used as an indicator of calcification, would rather suggest outgassing.

Drivers of inorganic carbon dynamics in first-year sea ice: A model study

NASA Astrophysics Data System (ADS)

Moreau, Sébastien; Vancoppenolle, Martin; Delille, Bruno; Tison, Jean-Louis; Zhou, Jiayun; Kotovich, Marie; Thomas, David; Geilfus, Nicolas-Xavier; Goosse, Hugues

2015-04-01

Sea ice is an active source or a sink for carbon dioxide (CO2), although to what extent is not clear. Here, we analyze CO2 dynamics within sea ice using a one-dimensional halo-thermodynamic sea ice model including gas physics and carbon biogeochemistry. The ice-ocean fluxes, and vertical transport, of total dissolved inorganic carbon (DIC) and total alkalinity (TA) are represented using fluid transport equations. Carbonate chemistry, the consumption and release of CO2 by primary production and respiration, the precipitation and dissolution of ikaite (CaCO3•6H2O) and ice-air CO2 fluxes, are also included. The model is evaluated using observations from a 6-month field study at Point Barrow, Alaska and an ice-tank experiment. At Barrow, results show that the DIC budget is mainly driven by physical processes, wheras brine-air CO2 fluxes, ikaite formation, and net primary production, are secondary factors. In terms of ice-atmosphere CO2 exchanges, sea ice is a net CO2 source and sink in winter and summer, respectively. The formulation of the ice-atmosphere CO2 flux impacts the simulated near-surface CO2 partial pressure (pCO2), but not the DIC budget. Because the simulated ice-atmosphere CO2 fluxes are limited by DIC stocks, and therefore < 2 mmol m-2 day-1, we argue that the observed much larger CO2 fluxes from eddy covariance retrievals cannot be explained by a sea ice direct source and must involve other processes or other sources of CO2. Finally, the simulations suggest that near surface TA/DIC ratios of ~2, sometimes used as an indicator of calcification, would rather suggest outgassing.

Solution for Minimizing Surface Heating Effect for Fast Open-Path CO2 Flux Measurements in Cold Environments

NASA Astrophysics Data System (ADS)

Hupp, J. R.; Burba, G. G.; McDermitt, D. K.; Anderson, D. J.; Eckles, R. D.

2010-12-01

Open-path design of the high speed gas analyzers is a well-established configuration widely used for measurements of CO2 fluxes and concentrations. This configuration has advantages and deficiencies. Advantages include excellent frequency response, long-term stability, low sensitivity to window contamination, low-power pump-free operation, and infrequent calibration requirements. Deficiencies include susceptibility to precipitation and icing, and a potential need for instrument surface heating correction in extremely cold environments. In spite of the deficiencies, open-path measurements often provide data coverage that would not have been possible using traditional closed-path approach. Data loss from precipitation and icing may not always be prevented for the open-path instruments, while heating effect does not pose a problem for CO2 flux in warm environments. Even in cold environments, the impact of heating on CO2 flux is much smaller than other well-known effects, such as Webb-Pearman-Leuning terms, or frequency response corrections for closed-path analyzers. Nonetheless, instrument surface heating effect in cold environments could be addressed scientifically, via developing the theoretical corrections, and instrumentally, via measuring fast integrated air temperature in the optical path, or via enclosing the open-path instrument into a low-power short-intake design. Here we provide an alternative way to minimize or eliminate open-path heating effect, achieved by minimizing or eliminating the temperature gradient between the instrument surface and ambient air. Open-path low temperature controlled design is discussed in comparison with two other approaches (e.g., traditional open-path design and closed-path design) in terms of their field performance for Eddy Covariance flux measurements in the cold. This study presents field data from a new open-path CO2/H2O gas analyzer, LI-7500A, based on the LI-7500 model modified to produce substantially less heat during extremely cold conditions. Two regiments of the temperature control for internal electronics were examined across a wide range of temperatures: (i) the traditional control temperature of about 30oC, and (ii) new regiment controlling parts of internal electronics at 5oC. When new 5oC regiment was activated, the following changes were observed: heat dissipation from the surface reduced several folds, surface-to-air temperature gradients reduced 2-50 times; and the number of false uptake hours were reduced by 3.5 times, to the same level as a closed-path standard. Significant advantage of the new regiment was also observed in the magnitude of CO2 fluxes, especially in cold weather below -10oC. At such cold temperatures, CO2 fluxes from a 30oC controlled LI-7500 were 19% below those of the closed-path standard, while fluxes from a 5oC controlled LI-7500A were, on average, within 1% of the standard. These are strong experimental evidence that open-path instrument heating can be substantially reduced or eliminated via such simple hardware based solution. This allows continued and expanded use of this ultimately lowest-power remote solution for fast gas measurements.

Quantifying Surface Water, Porewater, and Groundwater Interactions Using Tracers: Tracer Fluxes, Water Fluxes, and End-member Concentrations

NASA Astrophysics Data System (ADS)

Cook, Peter G.; Rodellas, Valentí; Stieglitz, Thomas C.

2018-03-01

Tracer approaches to estimate both porewater exchange (the cycling of water between surface water and sediments, with zero net water flux) and groundwater inflow (the net flow of terrestrially derived groundwater into surface water) are commonly based on solute mass balances. However, this requires appropriate characterization of tracer end-member concentrations in exchanging or discharging water. Where either porewater exchange or groundwater inflow to surface water occur in isolation, then the water flux is easily estimated from the net tracer flux if the end-member is appropriately chosen. However, in most natural systems porewater exchange and groundwater inflow will occur concurrently. Our analysis shows that if groundwater inflow (Qg) and porewater exchange (Qp) mix completely before discharging to surface water, then the combined water flux (Qg + Qp) can be approximated by dividing the combined tracer flux by the difference between the porewater and surface water concentrations, (cp - c). If Qg and Qp do not mix prior to discharge, then (Qg + Qp) can only be constrained by minimum and maximum values. The minimum value is obtained by dividing the net tracer flux by the groundwater concentration, and the maximum is obtained by dividing by (cp - c). Dividing by the groundwater concentration gives a maximum value for Qg. If porewater exchange and groundwater outflow occur concurrently, then dividing the net tracer flux by (cp - c) will provide a minimum value for Qp. Use of multiple tracers, and spatial and temporal replication should provide a more complete picture of exchange processes and the extent of subsurface mixing.

Mapping surface heat fluxes by assimilating GOES land surface temperature and SMAP products

NASA Astrophysics Data System (ADS)

Lu, Y.; Steele-Dunne, S. C.; Van De Giesen, N.

2017-12-01

Surface heat fluxes significantly affect the land-atmosphere interaction, but their modelling is often hindered by the lack of in-situ measurements and the high spatial heterogeneity. Here, we propose a hybrid particle assimilation strategy to estimate surface heat fluxes by assimilating GOES land surface temperature (LST) data and SMAP products into a simple dual-source surface energy balance model, in which the requirement for in-situ data is minimized. The study aims to estimate two key parameters: a neutral bulk heat transfer coefficient (CHN) and an evaporative fraction (EF). CHN scales the sum of surface energy fluxes, and EF represents the partitioning between flux components. To bridge the huge resolution gap between GOES and SMAP data, SMAP data are assimilated using a particle filter to update soil moisture which constrains EF, and GOES data are assimilated with an adaptive particle batch smoother to update CHN. The methodology is applied to an area in the US Southern Great Plains with forcing data from NLDAS-2 and the GPM mission. Assessment against in-situ observations suggests that the sensible and latent heat flux estimates are greatly improved at both daytime and 30-min scale after assimilation, particularly for latent heat fluxes. Comparison against an LST-only assimilation case demonstrates that despite the coarse resolution, assimilating SMAP data is not only beneficial but also crucial for successful and robust flux estimation, particularly when the modelling uncertainties are large. Since the methodology is independent on in-situ data, it can be easily applied to other areas.

Kinetic Monte Carlo simulations of ion-induced ripple formation: Dependence on flux, temperature, and defect concentration in the linear regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chason, E.; Chan, W. L.; Bharathi, M. S.

Low-energy ion bombardment produces spontaneous periodic structures (sputter ripples) on many surfaces. Continuum theories describe the pattern formation in terms of ion-surface interactions and surface relaxation kinetics, but many features of these models (such as defect concentration) are unknown or difficult to determine. In this work, we present results of kinetic Monte Carlo simulations that model surface evolution using discrete atomistic versions of the physical processes included in the continuum theories. From simulations over a range of parameters, we obtain the dependence of the ripple growth rate, wavelength, and velocity on the ion flux and temperature. The results are discussedmore » in terms of the thermally dependent concentration and diffusivity of ion-induced surface defects. We find that in the early stages of ripple formation the simulation results are surprisingly well described by the predictions of the continuum theory, in spite of simplifying approximations used in the continuum model.« less

On the modeling of wave-enhanced turbulence nearshore

NASA Astrophysics Data System (ADS)

Moghimi, Saeed; Thomson, Jim; Özkan-Haller, Tuba; Umlauf, Lars; Zippel, Seth

2016-07-01

A high resolution k-ω two-equation turbulence closure model, including surface wave forcing was employed to fully resolve turbulence dissipation rate profiles close to the ocean surface. Model results were compared with observations from Surface Wave Instrument Floats with Tracking (SWIFTs) in the nearshore region at New River Inlet, North Carolina USA, in June 2012. A sensitivity analysis for different physical parameters and wave and turbulence formulations was performed. The flux of turbulent kinetic energy (TKE) prescribed by wave dissipation from a numerical wave model was compared with the conventional prescription using the wind friction velocity. A surface roughness length of 0.6 times the significant wave height was proposed, and the flux of TKE was applied at a distance below the mean sea surface that is half of this roughness length. The wave enhanced layer had a total depth that is almost three times the significant wave height. In this layer the non-dimensionalized Terray scaling with power of - 1.8 (instead of - 2) was applicable.

Vaporization of a solid surface in an ambient gas

NASA Astrophysics Data System (ADS)

Benilov, M. S.; Jacobsson, S.; Kaddani, A.; Zahrai, S.

2001-07-01

The net flux of vapour from a solid surface in an ambient gas is analysed with the aim to estimate the effect of vaporization cooling on the energy balance of an arc cathode under conditions typical for a high-power current breaker. If the ratio of the equilibrium vapour pressure pv to the ambient pressure p∞ is smaller than unity, the removal of vapour from the surface is due to diffusion into the bulk of the gas. As a consequence, the net flux of the vapour from the surface is much smaller than the emitted flux. An estimate of the diffusion rate under conditions typical for a high-power current breaker indicates that vaporization cooling plays a minor role in the energy balance of the cathode in this case. If ratio pv/p∞ is above unity, the flow of the vapour from the surface appears and the net flux is comparable to the emitted flux. A simple analytical solution has been obtained for this case, which is in a good agreement with results of the Monte Carlo modelling of preceding authors. If pv/p∞ exceeds approximately 4.5, vaporization occurs as into vacuum and the net flux is about 0.82 of the emitted flux.

47 CFR 25.208 - Power flux density limits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... COMMUNICATIONS Technical Standards § 25.208 Power flux density limits. (a) In the band 3650-4200 MHz, the power flux density at the Earth's surface produced by emissions from a space station for all conditions and... and 10.7-11.7 GHz for NGSO FSS space stations, the power flux-density at the Earth's surface produced...

Effects of warming on CO2, N2O and CH4 fluxes and underlying processes from subarctic tundra, Northwest Russia

NASA Astrophysics Data System (ADS)

Voigt, Carolina; Lamprecht, Richard E.; Marushchak, Maija E.; Biasi, Christina; Martikainen, Pertti J.

2014-05-01

Peatlands, especially those located in the highly sensitive arctic and subarctic latitudes, are known to play a major role in the global carbon cycle. Predicted climatic changes - entailing an increase in near-surface temperature and a change in precipitation patterns - will most likely have a serious yet uncertain impact on the greenhouse gas (GHG) balance of these ecosystems. Microbial processes are enhanced by warmer temperatures which may lead to increased trace gas fluxes to the atmosphere. However, the response of ecosystem processes and related GHG fluxes may differ largely across the landscape depending on soil type, vegetation cover, and moisture conditions. In this study we investigate how temperature increase potentially reflects on GHG fluxes (CO2, CH4 and N2O) from various tundra surfaces in the Russian Arctic. These surfaces include raised peat plateau complexes, mineral tundra soils, bare surfaces affected by frost action such as peat circles and thermokarst lake walls, as well as wetlands. Predicted temperature increase and climate change effects are simulated by means of open top chambers (OTCs), which are placed on different soil types for the whole snow-free period. GHG fluxes, gas and nutrient concentrations in the soil profile, as well as supporting environmental parameters are monitored for the full growing season. Aim of the study is not only the quantification of aboveground GHG fluxes from the study area, but the linking of those to underlying biogeochemical processes in permafrost soils. Special emphasis is placed on the interface between active layer and old permafrost and its response to warming, since little is known about the lability of old carbon stocks made available through an increase in active layer depth. Overall goal of the study is to gain a better understanding of C and N cycling in subarctic tundra soils and to deepen knowledge in respect to carbon-permafrost feedbacks in respect to climate.

Micrometeorological observations of carbon, water vapor and heat exchanges on the California Academy of Sciences' living roof using eddy covariance

NASA Astrophysics Data System (ADS)

Lavender, S.; Oliphant, A. J.; Thorp, R.

2014-12-01

Living roofs have very different surface energy, water and carbon budgets than conventional roofs. Since roofs cover approximately one third of the planimetric surface area of cities, they are a significant driver of the urban boundary layer. Living roofs have been thought to be beneficial for reducing the urban heat island through increased latent heat exchange, uptake of atmospheric carbon dioxide and storage in soil and plant matter, building energy conservation through soil heat storage and latent heat fluxes and reduction in runoff. Here we present evidence of some of these through ongoing observations of surface energy, water and carbon budget estimates for the extensive living roof of the California Academy of Sciences building in Golden Gate Park, San Francisco, California. Micrometeorological measurements including the eddy covariance approach are used to estimate CO2, water vapor and both ground and atmospheric heat fluxes. The California Academy's roof encompasses an area of 18,000 m2. Vegetation surveys were conducted in the spring; beach strawberry (Fragaria chiloensis) and California bentgrass (Agrostis) were found to dominate the project footprint out of the 26 species observed. Eddy covariance measurements are made about one meter above the 10-20 cm tall vegetation on the downwind side of the building. Approximately 50% of data are rejected due to less than 80% of the flux source area being contained in the roof or due to low friction velocity. Nevertheless, we are able to develop robust diurnal ensemble fluxes, and will present data from a nine month period. During summer, the roof acted as a carbon sink of approximately 1.5 gC m-2 d-1. Turbulent heat fluxes were dominated by sensible heat flux with a mean Bowen ratio of approximately 1.5 and daily evapotranspiration rates of about 1.8 mm d-1. The role of seasonality and meteorology on surface microclimate characteristics will also be discussed.

Study of the Effect of Nanoparticles and Surface Morphology on Reverse Osmosis and Nanofiltration Membrane Productivity

PubMed Central

Fang, Yuming; Duranceau, Steven J.

2013-01-01

To evaluate the significance of reverse osmosis (RO) and nanofiltration (NF) surface morphology on membrane performance, productivity experiments were conducted using flat-sheet membranes and three different nanoparticles, which included SiO2, TiO2 and CeO2. In this study, the productivity rate was markedly influenced by membrane surface morphology. Atomic force microscopy (AFM) analysis of membrane surfaces revealed that the higher productivity decline rates associated with polyamide RO membranes as compared to that of a cellulose acetate NF membrane was due to the inherent ridge-and-valley morphology of the active layer. The unique polyamide active layer morphology was directly related to the surface roughness, and was found to contribute to particle accumulation in the valleys causing a higher flux decline than in smoother membranes. Extended RO productivity experiments using laboratory grade water and diluted pretreated seawater were conducted to compare the effect that different nanoparticles had on membrane active layers. Membrane flux decline was not affected by particle type when the feed water was laboratory grade water. On the other hand, membrane productivity was affected by particle type when pretreated diluted seawater served as feed water. It was found that CeO2 addition resulted in the least observable flux decline, followed by SiO2 and TiO2. A productivity simulation was conducted by fitting the monitored flux data into a cake growth rate model, where the model was modified using a finite difference method to incorporate surface thickness variation into the analysis. The ratio of cake growth term (k1) and particle back diffusion term (k2) was compared in between different RO and NF membranes. Results indicated that k2 was less significant for surfaces that exhibited a higher roughness. It was concluded that the valley areas of thin-film membrane surfaces have the ability to capture particles, limiting particle back diffusion. PMID:24956946

A one-layer satellite surface energy balance for estimating evapotranspiration rates and crop water stress indexes.

PubMed

Barbagallo, Salvatore; Consoli, Simona; Russo, Alfonso

2009-01-01

Daily evapotranspiration fluxes over the semi-arid Catania Plain area (Eastern Sicily, Italy) were evaluated using remotely sensed data from Landsat Thematic Mapper TM5 images. A one-source parameterization of the surface sensible heat flux exchange using satellite surface temperature has been used. The transfer of sensible and latent heat is described by aerodynamic resistance and surface resistance. Required model inputs are brightness, temperature, fractional vegetation cover or leaf area index, albedo, crop height, roughness lengths, net radiation, air temperature, air humidity and wind speed. The aerodynamic resistance (r(ah)) is formulated on the basis of the Monin-Obukhov surface layer similarity theory and the surface resistance (r(s)) is evaluated from the energy balance equation. The instantaneous surface flux values were converted into evaporative fraction (EF) over the heterogeneous land surface to derive daily evapotranspiration values. Remote sensing-based assessments of crop water stress (CWSI) were also made in order to identify local irrigation requirements. Evapotranspiration data and crop coefficient values obtained from the approach were compared with: (i) data from the semi-empirical approach "K(c) reflectance-based", which integrates satellite data in the visible and NIR regions of the electromagnetic spectrum with ground-based measurements and (ii) surface energy flux measurements collected from a micrometeorological tower located in the experiment area. The expected variability associated with ET flux measurements suggests that the approach-derived surface fluxes were in acceptable agreement with the observations.

A Multiyear Dataset of SSM/I-Derived Global Ocean Surface Turbulent Fluxes

NASA Technical Reports Server (NTRS)

Chou, Shu-Hsien; Shie, Chung-Lin; Atlas, Robert M.; Ardizzone, Joe; Nelkin, Eric; Einaudi, Franco (Technical Monitor)

2001-01-01

The surface turbulent fluxes of momentum, latent heat, and sensible heat over global oceans are essential to weather, climate and ocean problems. Evaporation is a key component of the hydrological cycle and the surface heat budget, while the wind stress is the major forcing for driving the oceanic circulation. The global air-sea fluxes of momentum, latent and sensible heat, radiation, and freshwater (precipitation-evaporation) are the forcing for driving oceanic circulation and, hence, are essential for understanding the general circulation of global oceans. The global air-sea fluxes are required for driving ocean models and validating coupled ocean-atmosphere global models. We have produced a 7.5-year (July 1987-December 1994) dataset of daily surface turbulent fluxes over the global oceans from the Special Sensor microwave/Imager (SSM/I) data. Daily turbulent fluxes were derived from daily data of SSM/I surface winds and specific humidity, National Centers for Environmental Prediction (NCEP) sea surface temperatures, and European Centre for Medium-Range Weather Forecasts (ECMWF) air-sea temperature differences, using a stability-dependent bulk scheme. The retrieved instantaneous surface air humidity (with a 25-km resolution) validated well with that of the collocated radiosonde observations over the global oceans. Furthermore, the retrieved daily wind stresses and latent heat fluxes were found to agree well with that of the in situ measurements (IMET buoy, RV Moana Wave, and RV Wecoma) in the western Pacific warm pool during the TOGA COARE intensive observing period (November 1992-February 1993). The global distributions of 1988-94 seasonal-mean turbulent fluxes will be presented. In addition, the global distributions of 1990-93 annual-means turbulent fluxes and input variables will be compared with those of UWM/COADS covering the same period. The latter is based on the COADS (comprehensive ocean-atmosphere data set) and is recognized to be one of the best climatological analyses of fluxes derived from ship observations.

Incoming Shortwave Fluxes at the Surface--A Comparison of GCM Results with Observations.

NASA Astrophysics Data System (ADS)

Garratt, J. R.

1994-01-01

Evidence is presented that the exam surface net radiation calculated in general circulation models at continental surfaces is mostly due to excess incoming shortwave fluxes. Based on long-term observations from 22 worldwide inland stations and results from four general circulation models the overestimate in models of 20% (11 W m2) in net radiation on an annual basis compares with 6% (9 W m2) for shortwave fluxes for the same 22 locations, or 9% (18 W m2) for a larger set of 93 stations (71 having shortwave fluxes only). For annual fluxes, these differences appear to be significant.

A dynamical stabilizer in the climate system: a mechanism suggested by a simple model

NASA Astrophysics Data System (ADS)

Bates, J. R.

1999-05-01

A simple zonally averaged hemispheric model of the climate system is constructed, based on energy equations for two ocean basins separated at 30° latitude with the surface fluxes calculated explicitly. A combination of empirical input and theoretical calculation is used to determine an annual mean equilibrium climate for the model and to study its stability with respect to small perturbations. The insolation, the mean albedos and the equilibrium temperatures for the two model zones are prescribed from observation. The principal agent of interaction between the zones is the vertically integrated poleward transport of atmospheric angular momentum across their common boundary. This is parameterized using an empirical formula derived from a multiyear atmospheric data set. The surface winds are derived from the angular momentum transport assuming the atmosphere to be in a state of dynamic balance on the climatic timescales of interest. A further assumption that the air sea temperature difference and low level relative humidity remain fixed at their mean observed values then allows the surface fluxes of latent and sensible heat to be calculated. Results from a radiative model, which show a positive lower tropospheric water vapour/infrared radiative feedback on SST perturbations in both zones, are used to calculate the net upward infrared radiative fluxes at the surface. In the model's equilibrium climate, the principal processes balancing the solar radiation absorbed at the surface are evaporation in the tropical zone and net infrared radiation in the extratropical zone. The stability of small perturbations about the equilibrium is studied using a linearized form of the ocean energy equations. Ice-albedo and cloud feedbacks are omitted and attention is focussed on the competing effects of the water vapour/infrared radiative feedback and the turbulent surface flux and oceanic heat transport feedbacks associated with the angular momentum cycle. The perturbation equations involve inter-zone coupling and have coefficients dependent on the values of the equilibrium fluxes and the sensitivity of the angular momentum transport. Analytical solutions for the perturbations are obtained. These provide criteria for the stability of the equilibrium climate. If the evaporative feedback on SST perturbations is omitted, the equilibrium climate is unstable due to the influence of the water vapour/infrared radiative feedback, which dominates over the effects of the sensible heat and ocean heat transport feedbacks. The inclusion of evaporation gives a negative feedback which is of sufficient strength to stabilize the system. The stabilizing mechanism involves wind and humidity factors in the evaporative fluxes that are of comparable magnitude. Both factors involve the angular momentum transport. In including angular momentum and calculating the surface fluxes explicitly, the model presented here differs from the many simple climate models based on the Budyko Sellers formulation. In that formulation, an atmospheric energy balance equation is used to eliminate surface fluxes in favour of top-of-the-atmosphere radiative fluxes and meridional atmospheric energy transports. In the resulting models, infrared radiation appears as a stabilizing influence on SST perturbations and the dynamical stabilizing mechanism found here cannot be identified.

Observations of the Earth's Radiation Budget in relation to atmospheric hydrology. 4: Atmospheric column radiative cooling over the world's oceans

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.; Slingo, Anthony; Webb, Mark J.; Minnett, Peter J.; Daum, Peter H.; Kleinman, Lawrence; Wittmeyer, Ian; Randall, David A.

1994-01-01

This paper introduces a simple method for deriving climatological values of the longwave flux emitted from the clear sky atmosphere to the ice-free ocean surface. It is shown using both theory and data from simulations how the ratio of the surface to top-of-atmosphere (TOA) flux is a simple function of water vapor (W) and a validation of the simple relationship is presented based on a limited set of surface flux measurements. The rms difference between the retrieved surface fluxes and the simulated surface fluxes is approximately 6 W/sq m. The clear sky column cooling rate of the atmosphere is derived from the Earth Radiation Budget Experiment (ERBE) values of the clear sky TOA flux and the surface flux retrieved using Special Scanning Microwave Imager (SSM/I) measurements of w together with ERBE clear sky fluxes. The relationship between this column cooling rate, w, and the sea surface temperature (SST) is explored and it is shown how the cooling rate systematically increases as both w and SST increase. The uncertainty implied in these estmates of cooling are approximately +/- 0.2 K/d. The effects of clouds on this longwave cooling are also explored by placing bounds on the possible impact of clouds on the column cooling rate based on certain assumptions about the effect of clouds on the longwave flux to the surface. It is shown how the longwave effects of clouds in a moist atmosphere where the column water vapor exceeds approximately 30 kg/sq m may be estimated from presently available satellite data with an uncertainty estimated to be approximately 0.2 K/d. Based on an approach described in this paper, we show how clouds in these relatively moist regions decrease the column cooling by almost 50% of the clear sky values and the existence of significant longitudinal gradients in column radiative heating across the equatorial and subtropical Pacific Ocean.

VOC emission rates over London and South East England obtained by airborne eddy covariance.

PubMed

Vaughan, Adam R; Lee, James D; Shaw, Marvin D; Misztal, Pawel K; Metzger, Stefan; Vieno, Massimo; Davison, Brian; Karl, Thomas G; Carpenter, Lucy J; Lewis, Alastair C; Purvis, Ruth M; Goldstein, Allen H; Hewitt, C Nicholas

2017-08-24

Volatile organic compounds (VOCs) originate from a variety of sources, and play an intrinsic role in influencing air quality. Some VOCs, including benzene, are carcinogens and so directly affect human health, while others, such as isoprene, are very reactive in the atmosphere and play an important role in the formation of secondary pollutants such as ozone and particles. Here we report spatially-resolved measurements of the surface-to-atmosphere fluxes of VOCs across London and SE England made in 2013 and 2014. High-frequency 3-D wind velocities and VOC volume mixing ratios (made by proton transfer reaction - mass spectrometry) were obtained from a low-flying aircraft and used to calculate fluxes using the technique of eddy covariance. A footprint model was then used to quantify the flux contribution from the ground surface at spatial resolution of 100 m, averaged to 1 km. Measured fluxes of benzene over Greater London showed positive agreement with the UK's National Atmospheric Emissions Inventory, with the highest fluxes originating from central London. Comparison of MTBE and toluene fluxes suggest that petroleum evaporation is an important emission source of toluene in central London. Outside London, increased isoprene emissions were observed over wooded areas, at rates greater than those predicted by a UK regional application of the European Monitoring and Evaluation Programme model (EMEP4UK). This work demonstrates the applicability of the airborne eddy covariance method to the determination of anthropogenic and biogenic VOC fluxes and the possibility of validating emission inventories through measurements.

Vibration welding system with thin film sensor

DOEpatents

Cai, Wayne W; Abell, Jeffrey A; Li, Xiaochun; Choi, Hongseok; Zhao, Jingzhou

2014-03-18

A vibration welding system includes an anvil, a welding horn, a thin film sensor, and a process controller. The anvil and horn include working surfaces that contact a work piece during the welding process. The sensor measures a control value at the working surface. The measured control value is transmitted to the controller, which controls the system in part using the measured control value. The thin film sensor may include a plurality of thermopiles and thermocouples which collectively measure temperature and heat flux at the working surface. A method includes providing a welder device with a slot adjacent to a working surface of the welder device, inserting the thin film sensor into the slot, and using the sensor to measure a control value at the working surface. A process controller then controls the vibration welding system in part using the measured control value.

New Constraints on Terrestrial Surface-Atmosphere Fluxes of Gaseous Elemental Mercury Using a Global Database.

PubMed

Agnan, Yannick; Le Dantec, Théo; Moore, Christopher W; Edwards, Grant C; Obrist, Daniel

2016-01-19

Despite 30 years of study, gaseous elemental mercury (Hg(0)) exchange magnitude and controls between terrestrial surfaces and the atmosphere still remain uncertain. We compiled data from 132 studies, including 1290 reported fluxes from more than 200,000 individual measurements, into a database to statistically examine flux magnitudes and controls. We found that fluxes were unevenly distributed, both spatially and temporally, with strong biases toward Hg-enriched sites, daytime and summertime measurements. Fluxes at Hg-enriched sites were positively correlated with substrate concentrations, but this was absent at background sites. Median fluxes over litter- and snow-covered soils were lower than over bare soils, and chamber measurements showed higher emission compared to micrometeorological measurements. Due to low spatial extent, estimated emissions from Hg-enriched areas (217 Mg·a(-1)) were lower than previous estimates. Globally, areas with enhanced atmospheric Hg(0) levels (particularly East Asia) showed an emerging importance of Hg(0) emissions accounting for half of the total global emissions estimated at 607 Mg·a(-1), although with a large uncertainty range (-513 to 1353 Mg·a(-1) [range of 37.5th and 62.5th percentiles]). The largest uncertainties in Hg(0) fluxes stem from forests (-513 to 1353 Mg·a(-1) [range of 37.5th and 62.5th percentiles]), largely driven by a shortage of whole-ecosystem fluxes and uncertain contributions of leaf-atmosphere exchanges, questioning to what degree ecosystems are net sinks or sources of atmospheric Hg(0).

Evaluating Clouds in Long-Term Cloud-Resolving Model Simulations with Observational Data

NASA Technical Reports Server (NTRS)

Zeng, Xiping; Tao, Wei-Kuo; Zhang, Minghua; Peters-Lidard, Christa; Lang, Stephen; Simpson, Joanne; Kumar, Sujay; Xie, Shaocheng; Eastman, Joseph L.; Shie, Chung-Lin;

Modelling and analysis of flux surface mapping experiments on W7-X

NASA Astrophysics Data System (ADS)

Lazerson, Samuel; Otte, Matthias; Bozhenkov, Sergey; Sunn Pedersen, Thomas; Bräuer, Torsten; Gates, David; Neilson, Hutch; W7-X Team

2015-11-01

The measurement and compensation of error fields in W7-X will be key to the device achieving high beta steady state operations. Flux surface mapping utilizes the vacuum magnetic flux surfaces, a feature unique to stellarators and heliotrons, to allow direct measurement of magnetic topology, and thereby allows a highly accurate determination of remnant magnetic field errors. As will be reported separately at this meeting, the first measurements confirming the existence of nested flux surfaces in W7-X have been made. In this presentation, a synthetic diagnostic for the flux surface mapping diagnostic is presented. It utilizes Poincaré traces to construct an image of the flux surface consistent with the measured camera geometry, fluorescent rod sweep plane, and emitter beam position. Forward modeling of the high-iota configuration will be presented demonstrating an ability to measure the intrinsic error field using the U.S. supplied trim coil system on W7-X, and a first experimental assessment of error fields in W7-X will be presented. This work has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the US Department of Energy.

Seasonal and annual variation in planktonic foraminiferal fluxes including warm period related El Niño in the northwestern North Pacific

NASA Astrophysics Data System (ADS)

Kuroyanagi, A.; Kawahata, H.; Nishi, H.; Honda, M. C.

2007-12-01

Planktonic foraminifera provide a record of the upper ocean environment through their species assemblage and individual tests. To investigate the relationship between foraminifera and oceanographic conditions and the impact of El Niño on foraminifera, we analyzed foraminiferal fluxes and relative abundances by using sediment trap samples collected biweekly at three sites in the northwestern North Pacific: Site 40N (39 °60'N, 165 °00'E), Site KNOT (43 °58'N, 155 °03'E), and Site 50N (50 °01'N, 165 °02'E) from 1998- 2001, a period that included an El Niño effect. Based on foraminiferal production and assemblage composition, we divided the sampling duration into several periods during which certain characteristic oceanographic properties were observed. These sampling periods were classified into five types (I-V) based upon four factors: 1) the predominant foraminiferal group, 2) total foraminiferal fluxes (TFFs), 3) organic matter (OM) fluxes, and 4) hydrographic conditions, which included sea surface temperature (SST) and thermal structure. Our results suggest that seasonal changes in foraminifera were closely related to water mass properties in addition to SST. If species compositions were the same, then water mass properties were the most important factors affecting the seasonal variation of foraminiferal abundance in the northwestern North Pacific. Although one of the major controlling factors for foraminiferal fluxes is food availability, the controlling factors for each type (types I-V) are different because of specific oceanographic situations, such as phytoplankton blooms, which result in an excess food supply for foraminifera. At Site KNOT in 1998, SST was remarkably high because of El Niño, and high surface temperatures and weak winds would have lowered nutrient supply and intensified water column stratification, resulting in the relatively low fluxes of total foraminifera, N. pachyderma, and G. bulloides, and the high fluxes of N. dutertrei that were observed. The response of foraminifera to El Niño at Site KNOT in 1998 was similar to the response of foraminifera off the coast of Chile during a weak El Niño event in 1991-1992. The impact of El Niño on foraminifera was variable, depending on the strength of the El Niño event and the location, even though some cases showed common patterns of foraminiferal response. At Site KNOT, El Niño conditions affected foraminiferal abundance not only because of higher sea surface temperature, but also through the formation of a stratified water column.

Estimates of Gelatinous Zooplankton Carbon Flux in the Global Oceans

NASA Astrophysics Data System (ADS)

Luo, J. Y.; Condon, R.; Cowen, R. K.

2016-02-01

Gelatinous zooplankton (GZ), which include the cnidarians, ctenophores, and pelagic tunicates, are a common feature of marine ecosystems worldwide, but their contribution to global biogeochemical fluxes has never been assessed. We constructed a carbon-cycle model with a single, annual time-step and resolved to a 5° spatial grid for the three major GZ groups in order to evaluate the GZ-mediated carbon fluxes and export to depth. Biomass inputs (totaling 0.149 Pg C) were based off of Lucas et al. (2014) and updated using the JeDI database (Condon et al. 2015). From the upper ocean, biomass export flux from cnidarians, ctenophores, and tunicates totaled 2.96 ± 2.82 Pg C y-1, though only 0.199 ± 0.023 Pg C y-1 of GZ carbon were transferred to upper trophic levels, roughly amounting to one-quarter of all mesozooplankton production flux. In contrast, GZ fluxes to DOC only comprised ca. 2% of labile DOC flux. Egestion flux from the upper ocean totaled 2.56 ± 3.35 Pg C y-1, with over 80% being fast-sinking tunicate fecal pellets. Due to fast sinking rates of carcasses and fecal pellets, 26% of all C export from the upper ocean reached the seafloor, such that GZ fecal matter is estimated to comprise between 20-30% of global POC surface export and 11-30% of POC seafloor deposition. Finally, results from sensitivity analyses showed no increase in cnidarian and ctenophore export fluxes with increased temperature and jelly biomass, though tunicate export fluxes showed some increase with both temperature and biomass. These results suggest that current estimates of global POC flux from the surface oceans, which range between 8.6 - 12.9 Pg C y-1, may be underestimated by as much as 20 - 25%, implying a definite need to incorporate GZ mediated flux in estimating the biological pump transfer efficiency. Our study represents the first effort to quantify the role of gelatinous zooplankton in the global marine carbon cycle.

First Results of the Land Atmosphere Feedback Experiment

NASA Astrophysics Data System (ADS)

Wulfmeyer, V.; Turner, D. D.

2017-12-01

The Land-Atmosphere Feedback Experiment (LAFE) deployed several state-of-the-art scanning lidar and remote sensing systems to the ARM SGP site during August 2017. A novel synergy of remote sensing systems was applied for simultaneous measurements of land-surface fluxes and horizontal and vertical transport processes in the atmospheric boundary layer (ABL). The impact of spatial inhomogeneities of the soil-vegetation continuum on LA feedback was studied using the scanning capability of the instrumentation as well as soil, vegetation, and surface flux measurements. The synergy of remote sensing and in-situ instruments consisted of three components: 1) The SGP water-vapor and temperature Raman lidar, the SGP Doppler lidar, the University of Hohenheim (UHOH) Doppler lidar, and the NCAR water-vapor DIAL to measure mean profiles and gradients of moisture, temperature, and horizontal wind. Due to their high vertical and temporal resolutions, also profiles of higher-order turbulent moments in the water vapor and wind fields as well as of profiles of the latent heat flux, the sensible heat flux, TKE, and momentum flux were observed. 2) A novel scanning lidar system synergy consisting of the NOAA High-Resolution Doppler lidar, the UHOH water-vapor differential absorption lidar, and the UHOH temperature rotational Raman lidar. These systems performed coordinated range-height indicator (RHI) scans from just above the canopy level to the lower troposphere including the interfacial layer at the ABL top. This component was augmented by three energy balance closure towers of NOAA and one EBC station of UHOH. 3) The University of Wisconsin SPARC and the University of Oklahoma CLAMPS systems operating two vertically pointing atmospheric emitted radiance interferometers and two Doppler lidar systems scanning cross track to the central RHI for determining the surface friction velocity and the horizontal variability of temperature, moisture, and wind. NOAA ARL also provided UAS and aircraft measurements (Navajo Piper) in accordance with the surface scans. Thus, both the variability of surface fluxes and CBL dynamics and thermodynamics over the SGP site was studied for the first time. This is essential for advanced observation and understanding of LA feedback. First results are presented at the conference.

The role of turbulent fluxes in the atmospheric boundary layer above a debris-covered glacier in the Himalayas

NASA Astrophysics Data System (ADS)

Steiner, J. F.; Stigter, E.; Litt, M.; Shea, J.; Bierkens, M. F.; Immerzeel, W. W.

2017-12-01

Debris-covered glaciers play an important role in the water cycle in high altitude catchments in the Himalaya. The melt dynamics of these glaciers are complex as a result of the debris. A thin debris layer (up to a few cm) may act as a facilitator of melt, whereas a thick layer serves primarily as an insulator. The debris cover itself shows a strong diurnal variation in temperature and humidity resulting in a complex interaction with the atmospheric boundary layer (ABL). Energy balance models are a common way to quantify sub-debris melt, but the importance of turbulent fluxes in this energy balance have so far been poorly investigated. We hypothesize that they may play a substantial role during phases of wetting and drying. In this study, ABL characteristics and surface turbulent fluxes are measured using an automatic weather station including an eddy-correlation (EC) system on the debris-covered Lirung glacier in Nepal over a 10 day period in late 2016, during the transition period from monsoon to the drier post-monsoon. The measurements are combined with surface temperature measurements and thermal UAV flights covering the footprint area of the EC tower to quantify the surface fluxes over a larger area. Our results show that turbulent fluxes do play a substantial role in the energy balance of debris-covered glaciers, and need to be accounted for to accurately simulate glacier melt. The EC tower results are subsequently evaluated against a number of different bulk approaches to quantify sensible and latent heat fluxes and are evaluated against turbulence characteristics. If found accurate enough, these approaches require less advanced measurement set-ups and can be applied on a wider scale.

Escape of magnetic toroids from the Sun

NASA Technical Reports Server (NTRS)

Bieber, John W.; Rust, David M.

1995-01-01

Analysis of heliospheric magnetic fields at 1 AU shows that 10(exp 24) Mx of net azimuthal flux escapes from the Sun per solar cycle. This rate is consistent with rates derived from other indicators of flux escape, including coronal mass ejections and filament eruptions. The toroidal flux escape rate is compared with the apparent rate of flux emergence at the solar surface, and it is concluded that escaping toroids will remove at least 20% of the emerging flux, and may remove as much as 100% of emerging flux if multiple eruptions occur on the toroids. The data imply that flux escapes the Sun with an efficiency far exceeding Parker's upper limit estimate of 3%. Toroidal flux escape is almost certainly the source of the observed overwinding of the interplanetary magnetic field spiral. Two mechanisms to facilitate net flux escape are discussed: helicity charging to push open the fields and flux transport with reconnection to close them off. We estimate the Sun will shed approximately 2 x 10(exp 45) of magnetic helicity per solar cycle, leading to a mean helicity density of 100 Mx(exp 2)cm(exp -3) at 1 AU, which agrees well with observations.

Bichromatic Scintillometer Measurements of Sensible and Latent Heat Fluxes over a Boreal Forested Valley

NASA Astrophysics Data System (ADS)

Isabelle, P. E.; Nadeau, D.; Parent, A. C.; Rousseau, A. N.; Jutras, S.; Anctil, F.

2017-12-01

Boreal forest covers roughly 10% of the earth emerged surface, making it one of the world most common type of landscape. There is a large number of studies on the land-atmosphere exchanges of water and energy for this type of forested surfaces. However, few were located in complex terrain, and, to the best of our knowledge, none have looked at continuous regional scale fluxes. Scintillometry is a powerful tool that allows such measurements, but is usually used over flat homogeneous terrain due to its dependency on Monin-Obukhov Similarity Theory. However, some recent studies have applied this method over slopes, measuring fluxes comparable to those using the eddy covariance method. Still, more experiments are needed using scintillometry over sloped surfaces. This study presents bichromatic scintillometer measurements of sensible and latent heat fluxes over a boreal-forested valley. The field site is located in the Montmorency Forest, Québec, Canada (47°17'N; 71°10'W). The instrumented valley is surrounded by ridges at 900 m elevation, with the bottom stream at 785 m, and follows a 300-120° azimuth coinciding with the two main wind direction (up and down-valley, respectively). Vegetation mostly includes balsam firs 6-10 m tall, creating a rough but homogeneous surface. Scintillometer transmitters and receivers are installed on top of the ridges enclosing the valley, making the path 1.35 km long and its effective height 70-m tall. The setup includes a large aperture and a micro-wave scintillometer with crossing paths allowing the use of the bichromatic method. Measurement are taken continuously from August to October 2017. Scintillometer fluxes are compared with those measured by a 15-m eddy covariance tower located 100 m west of the measurement path, on the southern slope of the valley. Net radiation is also measured to assess energy budget closure over the valley. The setup allows us to test the limits of applicability of scintillometer measurements, especially with regards to surface layer height and Monin-Obukhov Similarity Theory. Ultimately, the knowledge collected in this study will further our understanding of land-atmosphere interactions in sloped and forested environments at a critical spatial scale seldom studied before.

Vertical dissolved inorganic nitrogen fluxes in marsh and mudflat areas of the yangtze estuary.

PubMed

Deng, Huanguang; Wang, Dongqi; Chen, Zhenlou; Liu, Jie; Xu, Shiyuan; White, John R

2014-03-01

Nitrogen (N) is a dominant macronutrient in many river-dominated coastal systems, and excess concentrations can drive eutrophication, the effects of which can include hypoxia and algal blooms. The Yangtze River in China transports a large amount of dissolved inorganic N. Therefore, it is important to understand the role of the marsh and mudflat areas within the estuary on processing this exogenous N load. In situ dissolved inorganic nitrogen (DIN) fluxes across the sediment-water interface were determined monthly at Chongming Island at two sites (a vegetated marsh and an unvegetated mudflat) and were compared with rates from a previously published laboratory incubation study by our research group. Results from the in situ study showed that NO flux rates comprised the major component of total DIN flux, ranging from 55 to 97%. No significant difference was observed in the N flux rates between the marsh and mudflat sites. Overall, sediment at both sites served as a sink of DIN from surface water with mean flux rates of -178 μmol m h and -165 μmol m h for the marsh and mudflat, respectively. In general, DIN flux rates were not significantly correlated with DIN concentrations and other measured parameters (temperature, dissolved oxygen, salinity, and pH) of surface water. The in situ measured fluxes of NO and NO in this study were not significantly different from those of our previous laboratory incubation ( > 0.05), whereas NH fluxes in situ were significantly lower than those from the laboratory core incubations ( < 0.05). This result suggests that caution should be used when extrapolating rates from laboratory incubation methods to the field because the rates might not be equivalent. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Methane flux from Minnesota Peatlands

NASA Astrophysics Data System (ADS)

Crill, P. M.; Bartlett, K. B.; Harriss, R. C.; Gorham, E.; Verry, E. S.; Sebacher, D. I.; Madzar, L.; Sanner, W.

1988-12-01

Northern (>40°N) wetlands have been suggested as the largest natural source of methane (CH4) to the troposphere. To refine our estimates of source strengths from this region and to investigate climatic controls on the process, fluxes were measured from a variety of Minnesota peatlands during May, June, and August 1986. Sites included forested and unforested ombrotrophic bogs and minerotrophic fens in and near the U.S. Department of Agriculture Marcell Experimental Forest and the Red Lake peatlands. Late spring and summer fluxes ranged from 11 to 866 mg CH4 m-2 d-1, averaging 207 mg CH4 m-2 d-1 overall. At Marcell Forest, forested bogs and fen sites had lower fluxes (averages of 77 ± 21 mg CH4 m-2 d-1 and 142 ± 19 mg CH4 m-2 d-1) than open bogs (average of 294 ± 30 mg CH4 m-2 d-1). In the Red Lake peatland, circumneutral fens, with standing water above the peat surface, produced more methane than acid bog sites in which the water table was beneath the moss surface (325 ± 31 and 102 ± 13 mg CH4 m-2 d-1, respectively). Peat temperature was an important control. Methane flux increased in response to increasing soil temperature. For example, the open bog in the Marcell Forest with the highest CH4 flux exhibited a 74-fold increase in flux over a three-fold increase in temperature. We estimate that the methane flux from all peatlands north of 40° may be on the order of 70 to 90 Tg/yr though estimates of this sort are plagued by uncertainties in the areal extent of peatlands, length of the CH4 producing season, and the spatial and temporal variability of the flux.

Boiling Visualization and Critical Heat Flux Phenomena In Narrow Rectangular Gap

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. J. Kim; Y. H. Kim; S. J. Kim

2004-12-01

An experimental study was performed to investifate the pool boling critical hear flux (CHF) on one-dimensional inclined rectangular channels with narrow gaps by changing the orientation of a copper test heater assembly. In a pool of saturated water at atmospheric pressure, the test parameters include the gap sizes of 1,2,5, and 10 mm, andthe surface orientation angles from the downward facing position (180 degrees) to the vertical position (90 degress) respectively.

Application of self-preservation in the diurnal evolution of the surface energy budget to determine daily evaporation

NASA Technical Reports Server (NTRS)

Brutsaert, Wilfried; Sugita, Michiaki

1992-01-01

Evaporation from natural land surfaces often exhibits a strong variation during the course of a day, mostly in response to the daily variation of radiative energy input at the surface. This makes it difficult to derive the total daily evaporation, when only one or a few instantaneous estimates of evaporation are available. It is often possible to resolve this difficulty by assuming self-preservation in the diurnal evolution of the surface energy budget. Thus if the relative partition of total incoming energy flux among the different components remains the same, the ratio of latent heat flux and any other flux component can be taken as constant through the day. This concept of constant flux ratios is tested by means of data obtained during the First ISLSCP Field Experiment; the instantaneous evaporation values were calculated by means of the atmospheric boundary layer bulk similarity approach with radiosonde profiles and radiative surface temperatures. Good results were obtained for evaporative flux ratios with available energy flux, with net radiation, and with incoming shortwave radiation.

The potential influence of multiple scattering on longwave flux and heating rate simulations with clouds

NASA Astrophysics Data System (ADS)

Kuo, C. P.; Yang, P.; Huang, X.; Feldman, D.; Flanner, M.; Kuo, C.; Mlawer, E. J.

2017-12-01

Clouds, which cover approximately 67% of the globe, serve as one of the major modulators in adjusting radiative energy on the Earth. Since rigorous radiative transfer computations including multiple scattering are costly, only absorption is considered in the longwave spectral bands in the radiation sub-models of the general circulation models (GCMs). Quantification of the effect of ignoring longwave scattering for flux and heating rate simulations is performed by using the GCM version of the Longwave Rapid Radiative Transfer Model (RRTMG_LW) with an implementation with the 16-stream Discrete Ordinates Radiative Transfer (DISORT) Program for a Multi-Layered Plane-Parallel Medium in conjunction with the 2010 CCCM products that merge satellite observations from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), the CloudSat, the Clouds and the Earth's Radiant Energy System (CERES) and the Moderate Resolution Imaging Spectrometer (MODIS). One-year global simulations show that neglecting longwave scattering overestimates upward flux at the top of the atmosphere (TOA) and underestimates downward flux at the surface by approximately 2.63 and 1.15 W/m2, respectively. Furthermore, when longwave scattering is included in the simulations, the tropopause is cooled by approximately 0.018 K/day and the surface is heated by approximately 0.028 K/day. As a result, the radiative effects of ignoring longwave scattering and doubling CO2 are comparable in magnitude.

Experimental investigation of piston heat transfer under conventional diesel and reactivity-controlled compression ignition combustion regimes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Splitter, Derek A; Hendricks, Terry Lee; Ghandhi, Jaal B

2014-01-01

The piston of a heavy-duty single-cylinder research engine was instrumented with 11 fast-response surface thermocouples, and a commercial wireless telemetry system was used to transmit the signals from the moving piston. The raw thermocouple data were processed using an inverse heat conduction method that included Tikhonov regularization to recover transient heat flux. By applying symmetry, the data were compiled to provide time-resolved spatial maps of the piston heat flux and surface temperature. A detailed comparison was made between conventional diesel combustion and reactivity-controlled compression ignition combustion operations at matched conditions of load, speed, boost pressure, and combustion phasing. The integratedmore » piston heat transfer was found to be 24% lower, and the mean surface temperature was 25 C lower for reactivity-controlled compression ignition operation as compared to conventional diesel combustion, in spite of the higher peak heat release rate. Lower integrated piston heat transfer for reactivity-controlled compression ignition was found over all the operating conditions tested. The results showed that increasing speed decreased the integrated heat transfer for conventional diesel combustion and reactivity-controlled compression ignition. The effect of the start of injection timing was found to strongly influence conventional diesel combustion heat flux, but had a negligible effect on reactivity-controlled compression ignition heat flux, even in the limit of near top dead center high-reactivity fuel injection timings. These results suggest that the role of the high-reactivity fuel injection does not significantly affect the thermal environment even though it is important for controlling the ignition timing and heat release rate shape. The integrated heat transfer and the dynamic surface heat flux were found to be insensitive to changes in boost pressure for both conventional diesel combustion and reactivity-controlled compression ignition. However, for reactivity-controlled compression ignition, the mean surface temperature increased with changes in boost suggesting that equivalence ratio affects steady-state heat transfer.« less

The Surface Radiation Budget over Oceans and Continents.

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Prata, A. J.; Rotstayn, L. D.; McAvaney, B. J.; Cusack, S.

1998-08-01

An updated evaluation of the surface radiation budget in climate models (1994-96 versions; seven datasets available, with and without aerosols) and in two new satellite-based global datasets (with aerosols) is presented. All nine datasets capture the broad mean monthly zonal variations in the flux components and in the net radiation, with maximum differences of some 100 W m2 occurring in the downwelling fluxes at specific latitudes. Using long-term surface observations, both from land stations and the Pacific warm pool (with typical uncertainties in the annual values varying between ±5 and 20 W m2), excess net radiation (RN) and downwelling shortwave flux density (So) are found in all datasets, consistent with results from earlier studies [for global land, excesses of 15%-20% (12 W m2) in RN and about 12% (20 W m2) in So]. For the nine datasets combined, the spread in annual fluxes is significant: for RN, it is 15 (50) W m2 over global land (Pacific warm pool) in an observed annual mean of 65 (135) W m2; for So, it is 25 (60) W m2 over land (warm pool) in an annual mean of 176 (197) W m2.The effects of aerosols are included in three of the authors' datasets, based on simple aerosol climatologies and assumptions regarding aerosol optical properties. They offer guidance on the broad impact of aerosols on climate, suggesting that the inclusion of aerosols in models would reduce the annual So by 15-20 W m2 over land and 5-10 W m2 over the oceans. Model differences in cloud cover contribute to differences in So between datasets; for global land, this is most clearly demonstrated through the effects of cloud cover on the surface shortwave cloud forcing. The tendency for most datasets to underestimate cloudiness, particularly over global land, and possibly to underestimate atmospheric water vapor absorption, probably contributes to the excess downwelling shortwave flux at the surface.

Accurate integration over atomic regions bounded by zero-flux surfaces.

PubMed

Polestshuk, Pavel M

2013-01-30

The approach for the integration over a region covered by zero-flux surface is described. This approach based on the surface triangulation technique is efficiently realized in a newly developed program TWOE. The elaborated method is tested on several atomic properties including the source function. TWOE results are compared with those produced by using well-known existing programs. Absolute errors in computed atomic properties are shown to range usually from 10(-6) to 10(-5) au. The demonstrative examples prove that present realization has perfect convergence of atomic properties with increasing size of angular grid and allows to obtain highly accurate data even in the most difficult cases. It is believed that the developed program can be bridgehead that allows to implement atomic partitioning of any desired molecular property with high accuracy. Copyright © 2012 Wiley Periodicals, Inc.

Mapping Surface Heat Fluxes by Assimilating SMAP Soil Moisture and GOES Land Surface Temperature Data

NASA Astrophysics Data System (ADS)

Lu, Yang; Steele-Dunne, Susan C.; Farhadi, Leila; van de Giesen, Nick

2017-12-01

Surface heat fluxes play a crucial role in the surface energy and water balance. In situ measurements are costly and difficult, and large-scale flux mapping is hindered by surface heterogeneity. Previous studies have demonstrated that surface heat fluxes can be estimated by assimilating land surface temperature (LST) and soil moisture to determine two key parameters: a neutral bulk heat transfer coefficient (CHN) and an evaporative fraction (EF). Here a methodology is proposed to estimate surface heat fluxes by assimilating Soil Moisture Active Passive (SMAP) soil moisture data and Geostationary Operational Environmental Satellite (GOES) LST data into a dual-source (DS) model using a hybrid particle assimilation strategy. SMAP soil moisture data are assimilated using a particle filter (PF), and GOES LST data are assimilated using an adaptive particle batch smoother (APBS) to account for the large gap in the spatial and temporal resolution. The methodology is implemented in an area in the U.S. Southern Great Plains. Assessment against in situ observations suggests that soil moisture and LST estimates are in better agreement with observations after assimilation. The RMSD for 30 min (daytime) flux estimates is reduced by 6.3% (8.7%) and 31.6% (37%) for H and LE on average. Comparison against a LST-only and a soil moisture-only assimilation case suggests that despite the coarse resolution, assimilating SMAP soil moisture data is not only beneficial but also crucial for successful and robust flux estimation, particularly when the uncertainties in the model estimates are large.

Measurement uncertainties in quantifying aeolian mass flux: evidence from wind tunnel and field site data

PubMed Central

Keijsers, Joep G.S.; Maroulis, Jerry; Visser, Saskia M.

2014-01-01

Aeolian sediment traps are widely used to estimate the total volume of wind-driven sediment transport, but also to study the vertical mass distribution of a saltating sand cloud. The reliability of sediment flux estimations from such measurements are dependent upon the specific configuration of the measurement compartments and the analysis approach used. In this study, we analyse the uncertainty of these measurements by investigating the vertical cumulative distribution and relative sediment flux derived from both wind tunnel and field studies. Vertical flux data was examined using existing data in combination with a newly acquired dataset; comprising meteorological data and sediment fluxes from six different events, using three customized catchers at Ameland beaches in northern Netherlands. Fast-temporal data collected in a wind tunnel shows that the median transport height has a scattered pattern between impact and fluid threshold, that increases linearly with shear velocities above the fluid threshold. For finer sediment, a larger proportion was transported closer to the surface compared to coarser sediment fractions. It was also shown that errors originating from the distribution of sampling compartments, specifically the location of the lowest sediment trap relative to the surface, can be identified using the relative sediment flux. In the field, surface conditions such as surface moisture, surface crusts or frozen surfaces have a more pronounced but localized effect than shear velocity. Uncertainty in aeolian mass flux estimates can be reduced by placing multiple compartments in closer proximity to the surface. PMID:25071984

Eddy Covariance Measurements of Methane Flux Using an Open-Path Gas Analyzer

NASA Astrophysics Data System (ADS)

Burba, G.; Anderson, T.; Zona, D.; Schedlbauer, J.; Anderson, D.; Eckles, R.; Hastings, S.; Ikawa, H.; McDermitt, D.; Oberbauer, S.; Oechel, W.; Riensche, B.; Starr, G.; Sturtevant, C.; Xu, L.

2008-12-01

Methane is an important greenhouse gas with a warming potential of about 23 times that of carbon dioxide over a 100-year cycle (Houghton et al., 2001). Measurements of methane fluxes from the terrestrial biosphere have mostly been made using flux chambers, which have many advantages, but are discrete in time and space and may disturb surface integrity and air pressure. Open-path analyzers offer a number of advantages for measuring methane fluxes, including undisturbed in- situ flux measurements, spatial integration using the Eddy Covariance approach, zero frequency response errors due to tube attenuation, confident water and thermal density terms from co-located fast measurements of water and sonic temperature, and remote deployment due to lower power demands in the absence of a pump. The prototype open-path methane analyzer is a VCSEL (vertical-cavity surface-emitting laser)-based instrument. It employs an open Herriott cell and measures levels of methane with RMS noise below 6 ppb at 10 Hz sampling in controlled laboratory environment. Field maintenance is minimized by a self-cleaning mechanism to keep the lower mirror free of contamination. Eddy Covariance measurements of methane flux using the prototype open-path methane analyzer are presented for the period between 2006 and 2008 in three ecosystems with contrasting weather and moisture conditions: (1) Fluxes over a short-hydroperiod sawgrass wetland in the Florida Everglades were measured in a warm and humid environment with temperatures often exceeding 25oC, variable winds, and frequent heavy dew at night; (2) Fluxes over coastal wetlands in an Arctic tundra were measured in an environment with frequent sub-zero temperatures, moderate winds, and ocean mist; (3) Fluxes over pacific mangroves in Mexico were measured in an environment with moderate air temperatures high winds, and sea spray. Presented eddy covariance flux data were collected from a co-located prototype open-path methane analyzer, LI-7500, and sonic anemometer at a 10 Hz rate. Data were processed using EdiRe software following standard FluxNet methodology, including stationarity tests, frequency response, and Webb- Pearman-Leuning density terms. Further details are provided in the extended conference paper at: ftp://ftp.licor.com/public/GBurba/AGU LI- 7700 Paper-2008.pdf

Quantifying the drivers of ocean-atmosphere CO2 fluxes

NASA Astrophysics Data System (ADS)

Lauderdale, Jonathan M.; Dutkiewicz, Stephanie; Williams, Richard G.; Follows, Michael J.

2016-07-01

A mechanistic framework for quantitatively mapping the regional drivers of air-sea CO2 fluxes at a global scale is developed. The framework evaluates the interplay between (1) surface heat and freshwater fluxes that influence the potential saturated carbon concentration, which depends on changes in sea surface temperature, salinity and alkalinity, (2) a residual, disequilibrium flux influenced by upwelling and entrainment of remineralized carbon- and nutrient-rich waters from the ocean interior, as well as rapid subduction of surface waters, (3) carbon uptake and export by biological activity as both soft tissue and carbonate, and (4) the effect on surface carbon concentrations due to freshwater precipitation or evaporation. In a steady state simulation of a coarse-resolution ocean circulation and biogeochemistry model, the sum of the individually determined components is close to the known total flux of the simulation. The leading order balance, identified in different dynamical regimes, is between the CO2 fluxes driven by surface heat fluxes and a combination of biologically driven carbon uptake and disequilibrium-driven carbon outgassing. The framework is still able to reconstruct simulated fluxes when evaluated using monthly averaged data and takes a form that can be applied consistently in models of different complexity and observations of the ocean. In this way, the framework may reveal differences in the balance of drivers acting across an ensemble of climate model simulations or be applied to an analysis and interpretation of the observed, real-world air-sea flux of CO2.

AmeriFlux US-CRT Curtice Walter-Berger cropland

DOE Data Explorer

Chen, Jiquan [University of Toledo / Michigan State University

2016-01-01

This is the AmeriFlux version of the carbon flux data for the site US-CRT Curtice Walter-Berger cropland. Site Description - The conventional cropland site is rain fed and no irrigation is applied. As it is located in a part of the historic Great Black Swamp, drainage tiles are deployed around 0.5–1.0 m beneath the ground surface in order to draw down the water level. The soil is classified as silty clay and silty clay loam. The cultivation practices include minimum tillage and both insect and weed control.  During the study period, the cropland was planted with soybean and winter wheat.

Evaluation of surface renewal and flux-variance methods above agricultural and forest surfaces

NASA Astrophysics Data System (ADS)

Fischer, M.; Katul, G. G.; Noormets, A.; Poznikova, G.; Domec, J. C.; Trnka, M.; King, J. S.

2016-12-01

Measurements of turbulent surface energy fluxes are of high interest in agriculture and forest research. During last decades, eddy covariance (EC), has been adopted as the most commonly used micrometeorological method for measuring fluxes of greenhouse gases, energy and other scalars at the surface-atmosphere interface. Despite its robustness and accuracy, the costs of EC hinder its deployment at some research experiments and in practice like e.g. for irrigation scheduling. Therefore, testing and development of other cost-effective methods is of high interest. In our study, we tested performance of surface renewal (SR) and flux variance method (FV) for estimates of sensible heat flux density. Surface renewal method is based on the concept of non-random transport of scalars via so-called coherent structures which if accurately identified can be used for the computing of associated flux. Flux variance method predicts the flux from the scalar variance following the surface-layer similarity theory. We tested SR and FV against EC in three types of ecosystem with very distinct aerodynamic properties. First site was represented by agricultural wheat field in the Czech Republic. The second site was a 20-m tall mixed deciduous wetland forest on the coast of North Carolina, USA. The third site was represented by pine-switchgrass intercropping agro-forestry system located in coastal plain of North Carolina, USA. Apart from solving the coherent structures in a SR framework from the structure functions (representing the most common approach), we applied ramp wavelet detection scheme to test the hypothesis that the duration and amplitudes of the coherent structures are normally distributed within the particular 30-minutes time intervals and so just the estimates of their averages is sufficient for the accurate flux determination. Further, we tested whether the orthonormal wavelet thresholding can be used for isolating of the coherent structure scales which are associated with flux transport. Finally, we tested whether low-pass filtering in the Fourier domain based on integral length scale can improve estimates of both SR and FV as it supposedly removes the low frequency portion of the signal not related with the investigated fluxes.

Methodology for estimation of time-dependent surface heat flux due to cryogen spray cooling.

PubMed

Tunnell, James W; Torres, Jorge H; Anvari, Bahman

2002-01-01

Cryogen spray cooling (CSC) is an effective technique to protect the epidermis during cutaneous laser therapies. Spraying a cryogen onto the skin surface creates a time-varying heat flux, effectively cooling the skin during and following the cryogen spurt. In previous studies mathematical models were developed to predict the human skin temperature profiles during the cryogen spraying time. However, no studies have accounted for the additional cooling due to residual cryogen left on the skin surface following the spurt termination. We formulate and solve an inverse heat conduction (IHC) problem to predict the time-varying surface heat flux both during and following a cryogen spurt. The IHC formulation uses measured temperature profiles from within a medium to estimate the surface heat flux. We implement a one-dimensional sequential function specification method (SFSM) to estimate the surface heat flux from internal temperatures measured within an in vitro model in response to a cryogen spurt. Solution accuracy and experimental errors are examined using simulated temperature data. Heat flux following spurt termination appears substantial; however, it is less than that during the spraying time. The estimated time-varying heat flux can subsequently be used in forward heat conduction models to estimate temperature profiles in skin during and following a cryogen spurt and predict appropriate timing for onset of the laser pulse.

Intercomparison of oceanic and atmospheric forced and coupled mesoscale simulations. Part I: Surface fluxes

NASA Astrophysics Data System (ADS)

Josse, P.; Caniaux, G.; Giordani, H.; Planton, S.

1999-04-01

A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500 × 500 km2 domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the effect of mesoscale coupling, three simulations are compared: the first one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric fields, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface fluxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface fields with in situ observations reveals that the winds of the fine mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger fluxes. The coupled simulation has the strongest surface heat fluxes: the difference in the net heat budget with the oceanic forced simulation reaches on average 50 Wm-2 over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface fluxes are strongly inhomogeneous over the simulation domain. The amplitude of the flux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat flux patterns indicates that the surface fluxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer to the atmosphere is highly non-local and enhanced in the coupled simulation.

Surface Flux Modeling for Air Quality Applications

EPA Science Inventory

For many gasses and aerosols, dry deposition is an important sink of atmospheric mass. Dry deposition fluxes are also important sources of pollutants to terrestrial and aquatic ecosystems. The surface fluxes of some gases, such as ammonia, mercury, and certain volatile organic c...

How Well Can a Footpoint Tracking Method Estimate the Magnetic Helicity Influx during Flux Emergence?

NASA Astrophysics Data System (ADS)

Choe, Gwangson; Kim, Sunjung; Kim, Kap-Sung; No, Jincheol

2015-08-01

As shown by Démoulin and Berger (2003), the magnetic helicity flux through the solar surface into the solar atmosphere can be exactly calculated if we can trace the motion of footpoints with infinite temporal and spatial resolutions. When there is a magnetic flux transport across the solar surface, the horizontal velocity of footpoints becomes infinite at the polarity inversion line, although the surface integral yielding the helicity flux does not diverge. In practical application, a finite temporal and spatial resolution causes an underestimate of the magnetic helicity flux when a magnetic flux emerges from below the surface, because there is an observational blackout area near a polarity inversion line whether it is pre-existing or newly formed. In this paper, we consider emergence of simple magnetic flux ropes and calculate the supremum of the magnitude of the helicity influx that can be estimated from footpoint tracking. The results depend on the ratio of the resolvable length scale and the flux rope diameter. For a Gold-Hoyle flux rope, in which all field lines are uniformly twisted, the observationally estimated helicity influx would be about 90% of the real influx when the flux rope diameter is one hundred times the spatial resolution (for a large flux rope), and about 45% when it is ten times (for a small flux rope). For Lundquist flux ropes, the errors incurred by observational estimation are smaller than the case of the Gold-Hoyle flux rope, but could be as large as 30% of the real influx. Our calculation suggests that the error in the helicity influx estimate is at least half of the real influx or even larger when small scale magnetic structures (less than 10,000 km) emerge into the solar atmosphere.

Impact of water use efficiency on eddy covariance flux partitioning using correlation structure analysis

NASA Astrophysics Data System (ADS)

Anderson, Ray; Skaggs, Todd; Alfieri, Joseph; Kustas, William; Wang, Dong; Ayars, James

2016-04-01

Partitioned land surfaces fluxes (e.g. evaporation, transpiration, photosynthesis, and ecosystem respiration) are needed as input, calibration, and validation data for numerous hydrological and land surface models. However, one of the most commonly used techniques for measuring land surface fluxes, Eddy Covariance (EC), can directly measure net, combined water and carbon fluxes (evapotranspiration and net ecosystem exchange/productivity). Analysis of the correlation structure of high frequency EC time series (hereafter flux partitioning or FP) has been proposed to directly partition net EC fluxes into their constituent components using leaf-level water use efficiency (WUE) data to separate stomatal and non-stomatal transport processes. FP has significant logistical and spatial representativeness advantages over other partitioning approaches (e.g. isotopic fluxes, sap flow, microlysimeters), but the performance of the FP algorithm is reliant on the accuracy of the intercellular CO2 (ci) concentration used to parameterize WUE for each flux averaging interval. In this study, we tested several parameterizations for ci as a function of atmospheric CO2 (ca), including (1) a constant ci/ca ratio for C3 and C4 photosynthetic pathway plants, (2) species-specific ci/ca-Vapor Pressure Deficit (VPD) relationships (quadratic and linear), and (3) generalized C3 and C4 photosynthetic pathway ci/ca-VPD relationships. We tested these ci parameterizations at three agricultural EC towers from 2011-present in C4 and C3 crops (sugarcane - Saccharum officinarum L. and peach - Prunus persica), and validated again sap-flow sensors installed at the peach site. The peach results show that the species-specific parameterizations driven FP algorithm came to convergence significantly more frequently (~20% more frequently) than the constant ci/ca ratio or generic C3-VPD relationship. The FP algorithm parameterizations with a generic VPD relationship also had slightly higher transpiration (5 Wm-2 difference) than the constant ci/ca ratio. However, photosynthesis and respiration fluxes over sugarcane were ~15% lower with a VPD-ci/ca relationship than a constant ci/ca ratio. The results illustrate the importance of combining leaf-level physiological observations with EC to improve the performance of the FP algorithm.

Analysis of Surface Fluxes at Eureka Climate Observatory in Arctic

NASA Astrophysics Data System (ADS)

Grachev, Andrey; Albee, Robert; Fairall, Christopher; Hare, Jeffrey; Persson, Ola; Uttal, Taneil

2010-05-01

The Arctic region is experiencing unprecedented changes associated with increasing average temperatures (faster than the pace of the globally-averaged increase) and significant decreases in both the areal extent and thickness of the Arctic pack ice. These changes are early warning signs of shifts in the global climate system that justifies increased scientific focus on this region. The increase in atmospheric carbon dioxide has raised concerns worldwide about future climate change. Recent studies suggest that huge stores of carbon dioxide (and other climate relevant compounds) locked up in Arctic soils could be unexpectedly released due to global warming. Observational evidence suggests that atmospheric energy fluxes are a major contributor to the decrease of the Arctic pack ice, seasonal land snow cover and the warming of the surrounding land areas and permafrost layers. To better understand the atmosphere-surface exchange mechanisms, improve models, and to diagnose climate variability in the Arctic, accurate measurements are required of all components of the net surface energy budget and the carbon dioxide cycle over representative areas and over multiple years. In this study we analyze variability of turbulent fluxes including water vapor and carbon dioxide transfer based on long-term measurements made at Eureka observatory (80.0 N, 85.9 W) located near the coast of the Arctic Ocean (Canadian territory of Nunavut). Turbulent fluxes and mean meteorological data are continuously measured and reported hourly at various levels on a 10-m flux tower. Sonic anemometers are located at 3 and 8 m heights while high-speed Licor 7500 infrared gas analyzer (water moisture and carbon dioxide measurements) at 7.5 m height. According to our data, that the sensible heat flux, carbon dioxide and water vapor fluxes exhibited clear diurnal cycles in Arctic summer. This behavior is similar to the diurnal variation of the fluxes in mid-latitudes during the plants growing season, with carbon dioxide uptake from the atmosphere during the day due to photosynthesis, and carbon dioxide loss to the atmosphere due to vegetation respiration during the night. However, at Eureka vegetation was a source of carbon dioxide during sunlit periods. Thus the sign of carbon dioxide flux was controlled by air temperature even during Arctic summer.

Fabrication of Thin Film Heat Flux Sensors

NASA Technical Reports Server (NTRS)

Will, Herbert A.

1992-01-01

Prototype thin film heat flux sensors have been constructed and tested. The sensors can be applied to propulsion system materials and components. The sensors can provide steady state and fast transient heat flux information. Fabrication of the sensor does not require any matching of the mounting surface. Heat flux is proportional to the temperature difference across the upper and lower surfaces of an insulation material. The sensor consists of an array of thermocouples on the upper and lower surfaces of a thin insulating layer. The thermocouples for the sensor are connected in a thermopile arrangement. A 100 thermocouple pair heat flux sensor has been fabricated on silicon wafers. The sensor produced an output voltage of 200-400 microvolts when exposed to a hot air heat gun. A 20 element thermocouple pair heat flux sensor has been fabricated on aluminum oxide sheet. Thermocouples are Pt-Pt/Rh with silicon dioxide as the insulating material. This sensor produced an output of 28 microvolts when exposed to the radiation of a furnace operating at 1000 C. Work is also underway to put this type of heat flux sensor on metal surfaces.

A fundamental study of nucleate pool boiling under microgravity

NASA Technical Reports Server (NTRS)

Ervin, Jamie S.; Merte, Herman, Jr.

1991-01-01

An experimental study of incipient boiling in short-term microgravity and with a/g = +/- 1 for pool boiling was performed. Calibrated thin gold films sputtered on a smoothly polished quartz surface were used simultaneously for thermal resistance measurements and heating of the boiling surface. The gold films were used for both transient and quasi-steady heating surface temperature measurements. Two test vessels were constructed for precise measurement and control of fluid temperature and pressure: a laboratory pool boiling vessel for the a/g = +/- experiments and a pool boiling vessel designed for the 131 m free-fall in the NASA Lewis Research Center Microgravity Research Facility for the microgravity tests. Measurements included the heater surface temperature, the pressure near the heating surface, and the bulk liquid temperatures. High speed photography was used in the experiments. With high quality microgravity and the measured initial temperature of the quiescent test fluid, R113, the temperature distribution in the liquid at the moment of boiling inception resulting from an imposed step in heat flux is known with a certainty not possible previously. The types of boiling propagation across the large flat heating surface are categorized; the conditions necessary for their occurrence are described. Explosive boiling propagation with a striking pattern of small scale protuberances over the entire vapor mass periphery not observed previously at low heat flux levels is described. For the heater surface with a/g = -1, a step in the heater surface temperature of short duration was imposed. The resulting liquid temperature distribution at the moment of boiling inception was different from that obtained with a step in heat flux.

Hydrologically transported dissolved organic carbon influences soil respiration in a tropical rainforest

NASA Astrophysics Data System (ADS)

Zhou, Wen-Jun; Lu, Hua-Zheng; Zhang, Yi-Ping; Sha, Li-Qing; Schaefer, Douglas Allen; Song, Qing-Hai; Deng, Yun; Deng, Xiao-Bao

2016-10-01

To better understand the effect of dissolved organic carbon (DOC) transported by hydrological processes (rainfall, throughfall, litter leachate, and surface soil water; 0-20 cm) on soil respiration in tropical rainforests, we detected the DOC flux in rainfall, throughfall, litter leachate, and surface soil water (0-20 cm), compared the seasonality of δ13CDOC in each hydrological process, and δ13C in leaves, litter, and surface soil, and analysed the throughfall, litter leachate, and surface soil water (0-20 cm) effect on soil respiration in a tropical rainforest in Xishuangbanna, south-west China. Results showed that the surface soil intercepted 94.4 ± 1.2 % of the annual litter leachate DOC flux and is a sink for DOC. The throughfall and litter leachate DOC fluxes amounted to 6.81 and 7.23 % of the net ecosystem exchange respectively, indicating that the DOC flux through hydrological processes is an important component of the carbon budget, and may be an important link between hydrological processes and soil respiration in a tropical rainforest. Even the variability in soil respiration is more dependent on the hydrologically transported water than DOC flux insignificantly, soil temperature, and soil-water content (at 0-20 cm). The difference in δ13C between the soil, soil water (at 0-20 cm), throughfall, and litter leachate indicated that DOC is transformed in the surface soil and decreased the sensitivity indices of soil respiration of DOC flux to water flux, which suggests that soil respiration is more sensitive to the DOC flux in hydrological processes, especially the soil-water DOC flux, than to soil temperature or soil moisture.

Structure of solar coronal streamers

NASA Astrophysics Data System (ADS)

Schultz, C. G.

The present, direct method for the solution of generalized potential problems works outward from an O-point, under an assumption of the existence of flux surfaces. At each flux surface, a Fourier filter is used for the flux surface length variable to prevent numerical error amplifications, and the value of the inverse curvature radius and the normal direction are filtered to avoid the effects of local wrinkles.

BOREAS TF-10 NSA-YJP Tower Flux, Meteorological, and Porometry Data

NASA Technical Reports Server (NTRS)

McCaughey, J. Harry; Liblik, Laura; Hall, Forrest G. (Editor); Huemmrich, K. (Editor)

2000-01-01

The BOREAS TF-10 team collected tower flux and meteorological data at two sites, a fen and a young jack pine forest, near Thompson, Manitoba, Canada, as part of BOREAS. A preliminary data set was assembled in August 1993 while field testing the instrument packages, and at both sites data were collected from 15-Aug to 31-Aug. The main experimental period was in 1994, when continuous data were collected from the young jack pine site from 23-May to 20-Sep. Upon examination of the 1994 data set, it became clear that the behavior of the heat, water, and carbon dioxide fluxes throughout the whole growing season was an important scientific question, and that the 1994 data record was not sufficiently long to capture the character of the seasonal behavior of the fluxes. Thus, the young jack pine site was operated from 08-May to 07-Nov in 1996 in order to collect data from spring melt to autumn freeze-up. All variables are presented as 30-minute averages. Supporting data were also collected to describe the surface#s state and to provide the information, in association with the flux data, to build SVAT models. For the young jack pine site, these supporting data included stomatal conductance measurements. The data are stored in tabular ASCII files.

BOREAS AFM-08 ECMWF Hourly Surface and Upper Air Data for the SSA and NSA

NASA Technical Reports Server (NTRS)

Viterbo, Pedro; Betts, Alan; Hall, Forrest G. (Editor); Newcomer, Jeffrey A.; Smith, David E. (Technical Monitor)

2000-01-01

The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-8 team focused on modeling efforts to improve the understanding of the diurnal evolution of the convective boundary layer over the boreal forest. This data set contains hourly data from the European Center for for Medium-Range Weather Forecasts (ECMWF) operational model from below the surface to the top of the atmosphere, including the model fluxes at the surface. Spatially, the data cover a pair of the points that enclose the rawinsonde sites at Candle Lake, Saskatchewan, in the Southern Study Area (SSA) and Thompson, Manitoba, in the Northern Study Area (NSA). Temporally, the data include the two time periods of 13 May 1994 to 30 Sept 1994 and 01 Mar 1996 to 31 Mar 1997. The data are stored in tabular ASCII files. The number of records in the upper air data files may exceed 20,000, causing a problem for some software packages. The ECMWF hourly surface and upper air data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

Experimental study of the impact of large-scale wind farms on land-atmosphere exchanges

NASA Astrophysics Data System (ADS)

Zhang, wei; Markfort, Corey; Porté-Agel, Fernando

2013-04-01

Wind energy is one of the fastest growing sources of renewable energy world-wide, and it is expected that many more large-scale wind farms will be built and cover a significant portion of land and ocean surfaces. By extracting kinetic energy from the atmospheric boundary layer and converting it to electricity, wind farms may affect the transport of momentum, heat, moisture and trace gases (e.g. CO2) between the atmosphere and the land surface locally and globally. Understanding wind farm-atmosphere interactions and subsequent environmental impacts are complicated by the effects of turbine array configuration, wind farm size, land-surface characteristics and atmospheric thermal stability. In particular, surface scalar flux is influenced by wind farms and needs to be appropriately parameterized in meso-scale and/or high-resolution numerical models. Wind-tunnel experiments of model wind farms with perfectly aligned and staggered configurations, having the same turbine distribution density, were conducted in a neutral turbulent boundary layer with a surface heat source. Turbulent flow and fluxes over and through the wind farm were measured using a custom x-wire/cold-wire anemometer; and surface scalar flux was measured with an array of surface-mounted heat flux sensors within the quasi-developed flow regime. Although the overall surface heat flux change produced by the wind farms was found to be small, with a net reduction of 4% for the staggered wind farm and nearly zero for the aligned wind farm, the highly heterogeneous spatial distribution of the surface heat flux, dependent on wind farm layout, is significant. The difference between the minimum and maximum surface heat fluxes could be up to 12% and 7% in aligned and staggered wind farms, respectively. This finding is important for planning intensive agriculture practices and optimizing agricultural land use with regard to wind energy project development. The well-controlled wind-tunnel experiments presented here also provide a first comprehensive dataset on turbulent flow and scalar transport in wind farms, which can be further used to develop and validate new parameterizations for surface scalar fluxes in numerical models.

Contrasting variations in the surface layer structure between the convective and non-convective periods in the summer monsoon season for Bangalore location during PRWONAM

NASA Astrophysics Data System (ADS)

Reddy, N. Narendra; Rao, Kusuma G.

2018-01-01

An attempt has been made here to examine the contrasting variations in mean surface layer parameters including surface fluxes, and in surface layer stability between the convective and non-convective periods in the southwest monsoon season for the Bangalore experiment location (12.54° N, 77.22° E). The micrometeorological measurements analysed during 2009 and 2010 are from the instrumentation network established during the programme, "Prediction of Regional Weather using Observational meso-Network and Atmospheric Modelling (PRWONAM)". The Short Wave (SW) radiative flux at the surface is observed to be respectively at 799 ± 188 Wm-2 (772 ± 195 Wm-2) and 436 ± 113 Wm-2 (257 ± 101 Wm-2) at 12:00 LT (Local Time, UTC+05:30) during the non-convective and convective periods in 2009 (2010). The significant difference in SW radiative flux is due to the difference of cloud cover between the non-convective and convective periods. This significant reduction of 515 W m-2 at 12:00 LT in SW radiative flux caused maximum cooling in skin temperature (air temperature) by 6.2 °C (3.8 °C) at 12:00 LT (18:30 LT) from 30.8 ± 3.9 °C (27.1 ± 1.4 °C) in the non-convective period. The impact of convection on soil temperature is observed up to 0.2 m deep. The diurnal amplitudes in composites of air temperature are 8.4 °C (8.4 °C) and 5.7 °C (4.7 °C) during the non-convective and convective periods respectively in 2009 (2010); and the amplitudes in relative humidity are 41.5% (39.7%) and 29% (22.8%). Low wind speeds prevailed 63.4% of the time, all through the day and night, in the monsoon season. The diurnal variations in wind speed during the convective period showed higher variability than in non-convective period. The momentum flux varied in accordance with the strength of the wind speed during the monsoon seasons of both the years 2009 and 2010. The peak sensible heat flux in the convective period is noted to be smaller than that in the non-convective period by 128 W m-2 in 2009 and 124 W m-2 in 2010. The moisture flux showed no significant variations between the two periods. Sensible heat and moisture flux peaked up at 334 W m-2 and 258 W m-2 respectively at low wind strong unstable situation.

Flux canceling in three-dimensional radiative magnetohydrodynamic simulations

NASA Astrophysics Data System (ADS)

Thaler, Irina; Spruit, H. C.

2017-05-01

We aim to study the processes involved in the disappearance of magnetic flux between regions of opposite polarity on the solar surface using realistic three-dimensional (3D) magnetohydrodynamic (MHD) simulations. "Retraction" below the surface driven by magnetic forces is found to be a very effective mechanism of flux canceling of opposite polarities. The speed at which flux disappears increases strongly with initial mean flux density. In agreement with existing inferences from observations we suggest that this is a key process of flux disappearance within active complexes. Intrinsic kG strength concentrations connect the surface to deeper layers by magnetic forces, and therefore the influence of deeper layers on the flux canceling process is studied. We do this by comparing simulations extending to different depths. For average flux densities of 50 G, and on length scales on the order of 3 Mm in the horizontal and 10 Mm in depth, deeper layers appear to have only a mild influence on the effective rate of diffusion.

Estimation of surface heat and moisture fluxes over a prairie grassland. I - In situ energy budget measurements incorporating a cooled mirror dew point hygrometer

NASA Technical Reports Server (NTRS)

Smith, Eric A.; Crosson, William L.; Tanner, Bertrand D.

1992-01-01

Attention is focused on in situ measurements taken during FIFE required to support the development and validation of a biosphere model. Seasonal time series of surface flux measurements obtained from two surface radiation and energy budget stations utilized to support the FIFE surface flux measurement subprogram are examined. Data collection and processing procedures are discussed along with the measurement analysis for the complete 1987 test period.

The Validation of the GEWEX SRB Surface Shortwave Flux Data Products Using BSRN Measurements: A Systematic Quality Control, Production and Application Approach

NASA Technical Reports Server (NTRS)

Zhang, Taiping; Stackhouse, Paul W., Jr.; Gupta, Shashi K.; Cox, Stephen J.; Mikovitz, J. Colleen; Hinkelman, Laura M.

2013-01-01

The NASA/GEWEX Surface Radiation Budget (SRB) project has produced a 24.5-year continuous record of global shortwave and longwave radiation fluxes at TOA and the Earth's surface from satellite measurements. The time span of the data is from July 1983 to December 2007, and the spatial resolution is 11 latitude11 longitude. The inputs of the latest version (Release 3.0) include the GEOS Version 4.0.3 meteorological information and cloud properties derived from ISCCP DX data. The SRB products are available on 3-hourly, 3-hourly-monthly, daily and monthly time scales. To assess the quality of the product, we extensively validated the SRB data against 5969 site-months of groundbased measurements from 52 Baseline Surface Radiation Network (BSRN) stations. This paper describes first the characteristics of the BSRN data and the GEWEX SRB data, the methodology for quality control and processing of the shortwave BSRN data, and then the systematic SRB-BSRN comparisons. It is found that, except for occasional extreme outliers as seen in scatter plots, the satellite-based surface radiation data generally agree very well with BSRN measurements. Specifically, the bias/RMS for the daily and monthly mean shortwave fluxes are, respectively, -3.6/35.5 and -5.2/23.3W1 m2 under all-sky conditions.

Eddy covariance measurement of the spatial heterogeneity of surface energy exchanges over Heron Reef, Great Barrier Reef, Australia

NASA Astrophysics Data System (ADS)

MacKellar, M.; McGowan, H. A.; Phinn, S. R.

2011-12-01

Coral reefs cover 2.8 to 6.0 x 105 km2 of the Earth's surface and are warm, shallow regions that are believed to contribute enhanced sensible and latent heat to the atmosphere, relative to the surrounding ocean. To predict the impact of climate variability on coral reefs and their weather and climate including cloud, winds, rainfall patterns and cyclone genesis, accurate parameterisation of air-sea energy exchanges over coral reefs is essential. This is also important for the parameterisation and validation of regional to global scale forecast models to improve prediction of tropical and sub-tropical marine and coastal weather. Eddy covariance measurements of air-sea fluxes over coral reefs are rare due to the complexities of installing instrumentation over shallow, tidal water. Consequently, measurements of radiation and turbulent flux data for coral reefs have been captured remotely (satellite data) or via single measurement sites downwind of coral reefs (e.g. terrestrial or shipboard instrumentation). The resolution of such measurements and those that have been made at single locations on reefs may not capture the spatial heterogeneity of surface-atmosphere energy exchanges due to the different geomorphic and biological zones on coral reefs. Accordingly, the heterogeneity of coral reefs with regard to substrate, benthic communities and hydrodynamic processes are not considered in the characterization of the surface radiation energy flux transfers across the water-atmosphere interface. In this paper we present a unique dataset of concurrent in situ eddy covariance measurements made on instrumented pontoons of the surface energy balance over different geomorphic zones of a coral reef (shallow reef flat, shallow and deep lagoons). Significant differences in radiation transfers and air-sea turbulent flux exchanges over the reef were highlighted, with higher Bowen ratios over the shallow reef flat. Increasing wind speed was shown to increase flux divergence between sites to the extent that under unstable, south-easterly Trade Winds the net flux of heat was positive and negative over different geomorphic zones. The surface drag coefficient ranged from 1 to 2.5 x 10-3, with no significant difference between sites. Results highlight the spatial variation of air-sea energetics across a lagoonal platform reef in response to local meteorology, hydrodynamics and benthic/substrate cover.

Effects of Precipitation on Ocean Mixed-Layer Temperature and Salinity as Simulated in a 2-D Coupled Ocean-Cloud Resolving Atmosphere Model

NASA Technical Reports Server (NTRS)

Li, Xiaofan; Sui, C.-H.; Lau, K-M.; Adamec, D.

1999-01-01

A two-dimensional coupled ocean-cloud resolving atmosphere model is used to investigate possible roles of convective scale ocean disturbances induced by atmospheric precipitation on ocean mixed-layer heat and salt budgets. The model couples a cloud resolving model with an embedded mixed layer-ocean circulation model. Five experiment are performed under imposed large-scale atmospheric forcing in terms of vertical velocity derived from the TOGA COARE observations during a selected seven-day period. The dominant variability of mixed-layer temperature and salinity are simulated by the coupled model with imposed large-scale forcing. The mixed-layer temperatures in the coupled experiments with 1-D and 2-D ocean models show similar variations when salinity effects are not included. When salinity effects are included, however, differences in the domain-mean mixed-layer salinity and temperature between coupled experiments with 1-D and 2-D ocean models could be as large as 0.3 PSU and 0.4 C respectively. Without fresh water effects, the nocturnal heat loss over ocean surface causes deep mixed layers and weak cooling rates so that the nocturnal mixed-layer temperatures tend to be horizontally-uniform. The fresh water flux, however, causes shallow mixed layers over convective areas while the nocturnal heat loss causes deep mixed layer over convection-free areas so that the mixed-layer temperatures have large horizontal fluctuations. Furthermore, fresh water flux exhibits larger spatial fluctuations than surface heat flux because heavy rainfall occurs over convective areas embedded in broad non-convective or clear areas, whereas diurnal signals over whole model areas yield high spatial correlation of surface heat flux. As a result, mixed-layer salinities contribute more to the density differences than do mixed-layer temperatures.

Wake Dynamics in the Atmospheric Boundary Layer Over Complex Terrain

NASA Astrophysics Data System (ADS)

Markfort, Corey D.

The goal of this research is to advance our understanding of atmospheric boundary layer processes over heterogeneous landscapes and complex terrain. The atmospheric boundary layer (ABL) is a relatively thin (˜ 1 km) turbulent layer of air near the earth's surface, in which most human activities and engineered systems are concentrated. Its dynamics are crucially important for biosphere-atmosphere couplings and for global atmospheric dynamics, with significant implications on our ability to predict and mitigate adverse impacts of land use and climate change. In models of the ABL, land surface heterogeneity is typically represented, in the context of Monin-Obukhov similarity theory, as changes in aerodynamic roughness length and surface heat and moisture fluxes. However, many real landscapes are more complex, often leading to massive boundary layer separation and wake turbulence, for which standard models fail. Trees, building clusters, and steep topography produce extensive wake regions currently not accounted for in models of the ABL. Wind turbines and wind farms also generate wakes that combine in complex ways to modify the ABL. Wind farms are covering an increasingly significant area of the globe and the effects of large wind farms must be included in regional and global scale models. Research presented in this thesis demonstrates that wakes caused by landscape heterogeneity must be included in flux parameterizations for momentum, heat, and mass (water vapor and trace gases, e.g. CO2 and CH4) in ABL simulation and prediction models in order to accurately represent land-atmosphere interactions. Accurate representation of these processes is crucial for the predictions of weather, air quality, lake processes, and ecosystems response to climate change. Objectives of the research reported in this thesis are: 1) to investigate turbulent boundary layer adjustment, turbulent transport and scalar flux in wind farms of varying configurations and develop an improved modeling framework for wind farm - atmosphere interaction, 2) to determine how heterogeneous patches of forest affect the structure of the ABL and its interactions with clearings and water bodies, 3) to investigate how landscape heterogeneity, including wakes, may be parameterized in regional-scale weather and climate models to improve the representation of surface fluxes, e.g. from lakes/wetlands and forest clearings. To achieve these objectives, this research employs an interdisciplinary strategy, utilizing concepts and methods from fluid mechanics, micrometeorology, ecosystem ecology and environmental sciences, and combines laboratory and field experiments. In particular, a) wind tunnel experiments of flow through and over model wind farms and model forest canopies were used to improve our fundamental understanding of how wakes affect land-atmosphere coupling, including surface fluxes, after wind farm installation and for heterogeneous landscapes of canopies and clearings or lakes, and b) extensive field studies over lakes and wetlands were undertaken to study the effects of wakes downwind of forest canopies and the effect of wind sheltering on lake stratification dynamics and gas fluxes. These experiments were also used to improve and validate numerical simulation techniques for the atmospheric boundary layer, specifically the large eddy simulation technique, which is used to simulate flow in wind farms and flow over heterogeneous terrain.

The influence of idealized surface heterogeneity on virtual turbulent flux measurements

NASA Astrophysics Data System (ADS)

De Roo, Frederik; Mauder, Matthias

2018-04-01

The imbalance of the surface energy budget in eddy-covariance measurements is still an unsolved problem. A possible cause is the presence of land surface heterogeneity, which affects the boundary-layer turbulence. To investigate the impact of surface variables on the partitioning of the energy budget of flux measurements in the surface layer under convective conditions, we set up a systematic parameter study by means of large-eddy simulation. For the study we use a virtual control volume approach, which allows the determination of advection by the mean flow, flux-divergence and storage terms of the energy budget at the virtual measurement site, in addition to the standard turbulent flux. We focus on the heterogeneity of the surface fluxes and keep the topography flat. The surface fluxes vary locally in intensity and these patches have different length scales. Intensity and length scales can vary for the two horizontal dimensions but follow an idealized chessboard pattern. Our main focus lies on surface heterogeneity of the kilometer scale, and one order of magnitude smaller. For these two length scales, we investigate the average response of the fluxes at a number of virtual towers, when varying the heterogeneity length within the length scale and when varying the contrast between the different patches. For each simulation, virtual measurement towers were positioned at functionally different positions (e.g., downdraft region, updraft region, at border between domains, etc.). As the storage term is always small, the non-closure is given by the sum of the advection by the mean flow and the flux-divergence. Remarkably, the missing flux can be described by either the advection by the mean flow or the flux-divergence separately, because the latter two have a high correlation with each other. For kilometer scale heterogeneity, we notice a clear dependence of the updrafts and downdrafts on the surface heterogeneity and likewise we also see a dependence of the energy partitioning on the tower location. For the hectometer scale, we do not notice such a clear dependence. Finally, we seek correlators for the energy balance ratio in the simulations. The correlation with the friction velocity is less pronounced than previously found, but this is likely due to our concentration on effectively strongly to freely convective conditions.

Effects of Land Surface Heterogeneity on Simulated Boundary-Layer Structures from the LES to the Mesoscale

NASA Astrophysics Data System (ADS)

Poll, Stefan; Shrestha, Prabhakar; Simmer, Clemens

2017-04-01

Land heterogeneity influences the atmospheric boundary layer (ABL) structure including organized (secondary) circulations which feed back on land-atmosphere exchange fluxes. Especially the latter effects cannot be incorporated explicitly in regional and climate models due to their coarse computational spatial grids, but must be parameterized. Current parameterizations lead, however, to uncertainties in modeled surface fluxes and boundary layer evolution, which feed back to cloud initiation and precipitation. This study analyzes the impact of different horizontal grid resolutions on the simulated boundary layer structures in terms of stability, height and induced secondary circulations. The ICON-LES (Icosahedral Nonhydrostatic in LES mode) developed by the MPI-M and the German weather service (DWD) and conducted within the framework of HD(CP)2 is used. ICON is dynamically downscaled through multiple scales of 20 km, 7 km, 2.8 km, 625 m, 312 m, and 156 m grid spacing for several days over Germany and partial neighboring countries for different synoptic conditions. We examined the entropy spectrum of the land surface heterogeneity at these grid resolutions for several locations close to measurement sites, such as Lindenberg, Jülich, Cabauw and Melpitz, and studied its influence on the surface fluxes and the evolution of the boundary layer profiles.

Surface thermocouples for measurement of pulsed heat flux in the divertor of the Alcator C-Mod tokamak

NASA Astrophysics Data System (ADS)

Brunner, D.; LaBombard, B.

2012-03-01

A novel set of thermocouple sensors has been developed to measure heat fluxes arriving at divertor surfaces in the Alcator C-Mod tokamak, a magnetic confinement fusion experiment. These sensors operate in direct contact with the divertor plasma, which deposits heat fluxes in excess of ˜10 MW/m2 over an ˜1 s pulse. Thermoelectric EMF signals are produced across a non-standard bimetallic junction: a 50 μm thick 74% tungsten-26% rhenium ribbon embedded in a 6.35 mm diameter molybdenum cylinder. The unique coaxial geometry of the sensor combined with its single-point electrical ground contact minimizes interference from the plasma/magnetic environment. Incident heat fluxes are inferred from surface temperature evolution via a 1D thermal heat transport model. For an incident heat flux of 10 MW/m2, surface temperatures rise ˜1000 °C/s, corresponding to a heat flux flowing along the local magnetic field of ˜200 MW/m2. Separate calorimeter sensors are used to independently confirm the derived heat fluxes by comparing total energies deposited during a plasma pulse. Langmuir probes in close proximity to the surface thermocouples are used to test plasma-sheath heat transmission theory and to identify potential sources of discrepancies among physical models.

On Averaging Timescales for the Surface Energy Budget Closure Problem

NASA Astrophysics Data System (ADS)

Grachev, A. A.; Fairall, C. W.; Persson, O. P. G.; Uttal, T.; Blomquist, B.; McCaffrey, K.

2017-12-01

An accurate determination of the surface energy budget (SEB) and all SEB components at the air-surface interface is of obvious relevance for the numerical modelling of the coupled atmosphere-land/ocean/snow system over different spatial and temporal scales, including climate modelling, weather forecasting, environmental impact studies, and many other applications. This study analyzes and discusses comprehensive measurements of the SEB and the surface energy fluxes (turbulent, radiative, and ground heat) made over different underlying surfaces based on the data collected during several field campaigns. Hourly-averaged, multiyear data sets collected at two terrestrial long-term research observatories located near the coast of the Arctic Ocean at Eureka (Canadian Archipelago) and Tiksi (East Siberia) and half-hourly averaged fluxes collected during a year-long field campaign (Wind Forecast Improvement Project 2, WFIP 2) at the Columbia River Gorge (Oregon) in areas of complex terrain. Our direct measurements of energy balance show that the sum of the turbulent sensible and latent heat fluxes systematically underestimate the available energy at half-hourly and hourly time scales by around 20-30% at these sites. This imbalance of the surface energy budget is comparable to other terrestrial sites. Surface energy balance closure is a formulation of the conservation of energy principle (the first law of thermodynamics). The lack of energy balance closure at hourly time scales is a fundamental and pervasive problem in micrometeorology and may be caused by inaccurate estimates of the energy storage terms in soils, air and biomass in the layer below the measurement height and above the heat flux plates. However, the residual energy imbalance is significantly reduced at daily and monthly timescales. Increasing the averaging time to daily scales substantially reduces the storage terms because energy locally entering the soil, air column, and vegetation in the morning is released in the afternoon and evening.

Dependence of trapped-flux-induced surface resistance of a large-grain Nb superconducting radio-frequency cavity on spatial temperature gradient during cooldown through T c

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Shichun; Kubo, Takayuki; Geng, R. L.

Recent studies by Romanenko et al. revealed that cooling down a superconducting cavity under a large spatial temperature gradient decreases the amount of trapped flux and leads to reduction of the residual surface resistance. In the present paper, the flux expulsion ratio and the trapped-flux-induced surface resistance of a large-grain cavity cooled down under a spatial temperature gradient up to 80K/m are studied under various applied magnetic fields from 5E-6 T to 2E-5 T. We show the flux expulsion ratio improves as the spatial temperature gradient increases, independent of the applied magnetic field: our results supports and enforces the previousmore » studies. We then analyze all RF measurement results obtained under different applied magnetic fields together by plotting the trapped- flux-induced surface resistance normalized by the applied magnetic field as a function of the spatial temperature gradient. All the data can be fitted by a single curve, which defines an empirical formula for the trapped- flux-induced surface resistance as a function of the spatial temperature gradient and applied magnetic field. The formula can fit not only the present results but also those obtained by Romanenko et al. previously. Furthermore, the sensitivity r fl of surface resistance from trapped magnetic flux of fine-grain and large-grain niobium cavities and the origin of dT/ds dependence of R fl/B a are also discussed.« less

Dependence of trapped-flux-induced surface resistance of a large-grain Nb superconducting radio-frequency cavity on spatial temperature gradient during cooldown through T c

DOE PAGES

Huang, Shichun; Kubo, Takayuki; Geng, R. L.

2016-08-26

Recent studies by Romanenko et al. revealed that cooling down a superconducting cavity under a large spatial temperature gradient decreases the amount of trapped flux and leads to reduction of the residual surface resistance. In the present paper, the flux expulsion ratio and the trapped-flux-induced surface resistance of a large-grain cavity cooled down under a spatial temperature gradient up to 80K/m are studied under various applied magnetic fields from 5E-6 T to 2E-5 T. We show the flux expulsion ratio improves as the spatial temperature gradient increases, independent of the applied magnetic field: our results supports and enforces the previousmore » studies. We then analyze all RF measurement results obtained under different applied magnetic fields together by plotting the trapped- flux-induced surface resistance normalized by the applied magnetic field as a function of the spatial temperature gradient. All the data can be fitted by a single curve, which defines an empirical formula for the trapped- flux-induced surface resistance as a function of the spatial temperature gradient and applied magnetic field. The formula can fit not only the present results but also those obtained by Romanenko et al. previously. Furthermore, the sensitivity r fl of surface resistance from trapped magnetic flux of fine-grain and large-grain niobium cavities and the origin of dT/ds dependence of R fl/B a are also discussed.« less

Evaluation of surface energy and carbon fluxes within a large wind farm during the CWEX-10/11 Crop Wind-energy EXperiments

NASA Astrophysics Data System (ADS)

Rajewski, D. A.; Takle, E. S.; Prueger, J. H.; Oncley, S.; Horst, T. W.; Pfeiffer, R.; Hatfield, J.; Spoth, K. K.; Doorenbos, R.

2012-12-01

The Crop Wind-energy EXperiment conducted in summer 2010 (very moist conditions) and summer 2011 (abnormally dry) included measurements of wind speed, temperature, relative humidity, turbulence kinetic energy, H2O, and CO2 at stations north and south of a line of turbines at the southwest edge of a large-scale 200-turbine wind farm (prevailing wind from the south). In contrast to previous studies that have reported turbine influences on surface wind speed and temperature, this report focuses on scalar fluxes of heat, H2O, and CO2. From previous measurements in agricultural fields we recognize the importance of non-turbine factors in analysis of the flux differences: variability of soil characteristics, moisture content, crop cultivar, management practices, planting dates, etc., which can create differences in what looks like a uniform field of maize (corn). We conceptualize the influences of turbines at canopy height at a given location in the field to arise from (1) wakes of reduced wind speed and turbulence conditions different from ambient that intersect the surface, (2) wakes that are passing overhead and interrupt the ambient turbulence that scales with height, or (3) changes in static pressure upwind and downwind of lines of turbines that create small-scale pressure gradients, localized flows, and changes to the vertical exchange of scalar variables. The turbine SCADA wind speed and wind direction provided by the wind farm operator facilitated our comparison of surface fluxes upwind and downwind as wakes moved laterally throughout the day and night. We report multiple levels of evidence that wind turbines increase vertical exchange of carbon dioxide and water vapor over the canopy. Latent heat and carbon fluxes are responsive to slight changes in the turbine wake position, and the flux differences are maximized when the periphery of the wake edge is above the station. The flux stations north of the turbine line report a larger net ecosystem exchange accumulation over both the 2010 and 2011 measurement periods than for the reference towers south of the turbine line. Future experiments however, must address if and to what extent this enhanced CO2 flux is assimilated to the crop and whether or not the bio-physiological response to this effect among many other turbine-related factors (e.g. higher nighttime temperature and higher daytime transpiration) modifies overall crop yield.

Droplet-surface Impingement Dynamics for Intelligent Spray Design

NASA Technical Reports Server (NTRS)

VanderWal, Randy L.; Kizito, John P.; Tryggvason, Gretar; Berger, Gordon M.; Mozes, Steven D.

2004-01-01

Spray cooling has high potential in thermal management and life support systems by overcoming the deleterious effect of microgravity upon two-phase heat transfer. In particular spray cooling offers several advantages in heat flux removal that include the following: 1. By maintaining a wetted surface, spray droplets impinge upon a thin fluid film rather than a dry solid surface 2. Most heat transfer surfaces will not be smooth but rough. Roughness can enhance conductive cooling, aid liquid removal by flow channeling. 3. Spray momentum can be used to a) substitute for gravity delivering fluid to the surface, b) prevent local dryout and potential thermal runaway and c) facilitate liquid and vapor removal. Yet high momentum results in high We and Re numbers characterizing the individual spray droplets. Beyond an impingement threshold, droplets splash rather than spread. Heat flux declines and spray cooling efficiency can markedly decrease. Accordingly we are investigating droplet impingement upon a) dry solid surfaces, b) fluid films, c) rough surfaces and determining splashing thresholds and relationships for both dry surfaces and those covered by fluid films. We are presently developing engineering correlations delineating the boundary between splashing and non-splashing regions.

Measuring surface fluxes in CAPE

NASA Technical Reports Server (NTRS)

Kanemasu, E. T.; D-Shah, T.; Nie, Dalin

1992-01-01

Two stations (site 1612 and site 2008) were operated by the University of Georgia group from 6 July 1991 to 18 August 1991. The following data were collected continuously: surface energy fluxes (i.e., net radiation, soil heat fluxes, sensible heat flux and latent heat flux), air temperature, vapor pressure, soil temperature (at 1 cm depth), and precipitation. Canopy reflectance and light interception data were taken three times at each site between 6 July and 18 August. Soil moisture content was measured twice at each site.

Seasonal Clear-Sky Flux and Cloud Radiative Effect Anomalies in the Arctic Atmospheric Column Associated with the Arctic Oscillation and Arctic Dipole

NASA Technical Reports Server (NTRS)

Hegyi, Bradley M.; Taylor, Patrick C.

2017-01-01

The impact of the Arctic Oscillation (AO) and Arctic Dipole (AD) on the radiative flux into the Arctic mean atmospheric column is quantified. 3-month-averaged AO and AD indices are regressed with corresponding surface and top-of-atmosphere (TOA) fluxes from the CERES-SFC and CERES-TOA EBAF datasets over the period 2000-2014. An increase in clear-sky fluxes into the Arctic mean atmospheric column during fall is the largest net flux anomaly associated with AO, primarily driven by a positive net longwave flux anomaly (i.e. increase of net flux into the atmospheric column) at the surface. A decrease in the Arctic mean atmospheric column cloud radiative effect during winter and spring is the largest flux anomaly associated with AD, primarily driven by a change in the longwave cloud radiative effect at the surface. These prominent responses to AO and AD are widely distributed across the ice-covered Arctic, suggesting that the physical process or processes that bring about the flux change associated with AO and AD are distributed throughout the Arctic.

Regional Mapping of Coupled Fluxes of Carbon and Water Using Multi-Sensor Fusion Techniques

NASA Astrophysics Data System (ADS)

Schull, M. A.; Anderson, M. C.; Semmens, K. A.; Yang, Y.; Gao, F.; Hain, C.; Houborg, R.

2014-12-01

In an ever-changing climate there is an increasing need to measure the fluxes of water, energy and carbon for decision makers to implement policies that will help mitigate the effects of climate change. In an effort to improve drought monitoring, water resource management and agriculture assessment capabilities, a multi-scale and multi-sensor framework for routine mapping of land-surface fluxes of water and energy at field to regional scales has been established. The framework uses the ALEXI (Atmosphere Land Exchange Inverse)/DisALEXI (Disaggregated ALEXI) suite of land-surface models forced by remotely sensed data from Landsat, MODIS (MODerate resolution Imaging Spectroradiometer), and GOES (Geostationary Operational Environmental Satellite). Land-surface temperature (LST) can be an effective substitute for in-situ surface moisture observations and a valuable metric for constraining land-surface fluxes at sub-field scales. The adopted multi-scale thermal-based land surface modeling framework facilitates regional to local downscaling of water and energy fluxes by using a combination of shortwave reflective and thermal infrared (TIR) imagery from GOES (4-10 km; hourly), MODIS (1 km; daily), and Landsat (30-100 m; bi-weekly). In this research the ALEXI/DisALEXI modeling suite is modified to incorporate carbon fluxes using a stomatal resistance module, which replaces the Priestley-Taylor latent heat approximation. In the module, canopy level nominal light-use-efficiency (βn) is the parameter that modulates the flux of water and carbon in and out of the canopy. Leaf chlorophyll (Chl) is a key parameter for quantifying variability in photosynthetic efficiency to facilitate the spatial distribution of coupled carbon and water retrievals. Spatial distribution of Chl are retrieved from Landsat (30 m) using a surface reflectance dataset as input to the REGularized canopy reFLECtance (REGFLEC) tool. The modified ALEXI/DisALEXI suite is applied to regions of rain fed and irrigated soybean and maize agricultural landscapes within the continental U.S. and flux estimates are compared with flux tower observations.

Using a spatially-distributed hydrologic biogeochemistry model to study the spatial variation of carbon processes in a Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Shi, Y.; Eissenstat, D. M.; Davis, K. J.; He, Y.

2016-12-01

Forest carbon processes are affected by, among other factors, soil moisture, soil temperature, soil nutrients and solar radiation. Most of the current biogeochemical models are 1-D and represent one point in space. Therefore, they cannot resolve the topographically driven hill-slope land surface heterogeneity or the spatial pattern of nutrient availability. A spatially distributed forest ecosystem model, Flux-PIHM-BGC, has been developed by coupling a 1-D mechanistic biogeochemical model Biome-BGC (BBGC) with a spatially distributed land surface hydrologic model, Flux-PIHM. Flux-PIHM is a coupled physically based model, which incorporates a land-surface scheme into the Penn State Integrated Hydrologic Model (PIHM). The land surface scheme is adapted from the Noah land surface model. Flux-PIHM is able to represent the link between groundwater and the surface energy balance, as well as the land surface heterogeneities caused by topography. In the coupled Flux-PIHM-BGC model, each Flux-PIHM model grid couples a 1-D BBGC model, while soil nitrogen is transported among model grids via subsurface water flow. In each grid, Flux-PIHM provides BBGC with soil moisture, soil temperature, and solar radiation information, while BBGC provides Flux-PIHM with leaf area index. The coupled Flux-PIHM-BGC model has been implemented at the Susquehanna/Shale Hills critical zone observatory (SSHCZO). Model results suggest that the vegetation and soil carbon distribution is primarily constrained by nitorgen availability (affected by nitorgen transport via topographically driven subsurface flow), and also constrained by solar radiation and root zone soil moisture. The predicted vegetation and soil carbon distribution generally agrees with the macro pattern observed within the watershed. The coupled ecosystem-hydrologic model provides an important tool to study the impact of topography on watershed carbon processes, as well as the impact of climate change on water resources.

Air Layer Drag Reduction

NASA Astrophysics Data System (ADS)

Ceccio, Steven; Elbing, Brian; Winkel, Eric; Dowling, David; Perlin, Marc

2008-11-01

A set of experiments have been conducted at the US Navy's Large Cavitation Channel to investigate skin-friction drag reduction with the injection of air into a high Reynolds number turbulent boundary layer. Testing was performed on a 12.9 m long flat-plate test model with the surface hydraulically smooth and fully rough at downstream-distance-based Reynolds numbers to 220 million and at speeds to 20 m/s. Local skin-friction, near-wall bulk void fraction, and near-wall bubble imaging were monitored along the length of the model. The instrument suite was used to access the requirements necessary to achieve air layer drag reduction (ALDR). Injection of air over a wide range of air fluxes showed that three drag reduction regimes exist when injecting air; (1) bubble drag reduction that has poor downstream persistence, (2) a transitional regime with a steep rise in drag reduction, and (3) ALDR regime where the drag reduction plateaus at 90% ± 10% over the entire model length with large void fractions in the near-wall region. These investigations revealed several requirements for ALDR including; sufficient volumetric air fluxes that increase approximately with the square of the free-stream speed, slightly higher air fluxes are needed when the surface tension is reduced, higher air fluxes are required for rough surfaces, and the formation of ALDR is sensitive to the inlet condition.

A COUPLED LAND-SURFACE AND DRY DEPOSITION MODEL AND COMPARISON TO FIELD MEASUREMENTS OF SURFACE HEAT, MOISTURE, AND OZONE FLUXES

EPA Science Inventory

We have developed a coupled land-surface and dry deposition model for realistic treatment of surface fluxes of heat, moisture, and chemical dry deposition within a comprehensive air quality modeling system. A new land-surface model (LSM) with explicit treatment of soil moisture...

Siphon flows in isolated magnetic flux tubes. V - Radiative flows with variable ionization

NASA Technical Reports Server (NTRS)

Montesinos, Benjamin; Thomas, John H.

1993-01-01

Steady siphon flows in arched isolated magnetic flux tubes in the solar atmosphere are calculated here including radiative transfer between the flux tube and its surrounding and variable ionization of the flowing gas. It is shown that the behavior of a siphon flow is strongly determined by the degree of radiative coupling between the flux tube and its surroundings in the superadiabatic layer just below the solar surface. Critical siphon flows with adiabatic tube shocks in the downstream leg are calculated, illustrating the radiative relaxation of the temperature jump downstream of the shock. For flows in arched flux tubes reaching up to the temperature minimum, where the opacity is low, the gas inside the flux tube is much cooler than the surrounding atmosphere at the top of the arch. It is suggested that gas cooled by siphon flows contribute to the cool component of the solar atmosphere at the height of the temperature minimum implied by observations of the infrared CO bands at 4.6 and 2.3 microns.

Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection

DOE Data Explorer

Ebrahimi, Fatima [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)] (ORCID:0000000331095367); Raman, Roger [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)] (ORCID:0000000220273271)

2016-01-01

A large-volume flux closure during transient coaxial helicity injection (CHI) in NSTX-U is demonstrated through resistive magnetohydrodynamics (MHD) simulations. Several major improvements, including the improved positioning of the divertor poloidal field coils, are projected to improve the CHI start-up phase in NSTX-U. Simulations in the NSTX-U configuration with constant in time coil currents show that with strong flux shaping the injected open field lines (injector flux) rapidly reconnect and form large volume of closed flux surfaces. This is achieved by driving parallel current in the injector flux coil and oppositely directed currents in the flux shaping coils to form a narrow injector flux footprint and push the injector flux into the vessel. As the helicity and plasma are injected into the device, the oppositely directed field lines in the injector region are forced to reconnect through a local Sweet–Parker type reconnection, or to spontaneously reconnect when the elongated current sheet becomes MHD unstable to form plasmoids. In these simulations for the first time, it is found that the closed flux is over 70% of the initial injector flux used to initiate the discharge. These results could work well for the application of transient CHI in devices that employ super conducting coils to generate and sustain the plasma equilibrium.

Large-volume flux closure during plasmoid-mediated reconnection in coaxial helicity injection

DOE Data Explorer

Ebrahimi, F. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Raman, R. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

2016-04-01

A large-volume flux closure during transient coaxial helicity injection (CHI) in NSTX-U is demonstrated through resistive magnetohydrodynamics (MHD) simulations. Several major improvements, including the improved positioning of the divertor poloidal field coils, are projected to improve the CHI start-up phase in NSTX-U. Simulations in the NSTX-U configuration with constant in time coil currents show that with strong flux shaping the injected open field lines (injector flux) rapidly reconnect and form large volume of closed flux surfaces. This is achieved by driving parallel current in the injector flux coil and oppositely directed currents in the flux shaping coils to form a narrow injector flux footprint and push the injector flux into the vessel. As the helicity and plasma are injected into the device, the oppositely directed field lines in the injector region are forced to reconnect through a local Sweet–Parker type reconnection, or to spontaneously reconnect when the elongated current sheet becomes MHD unstable to form plasmoids. In these simulations for the first time, it is found that the closed flux is over 70% of the initial injector flux used to initiate the discharge. These results could work well for the application of transient CHI in devices that employ super conducting coils to generate and sustain the plasma equilibrium.

An inverse method to estimate stem surface heat flux in wildland fires

Treesearch

Anthony S. Bova; Matthew B. Dickinson

2009-01-01

Models of wildland fire-induced stem heating and tissue necrosis require accurate estimates of inward heat flux at the bark surface. Thermocouple probes or heat flux sensors placed at a stem surface do not mimic the thermal response of tree bark to flames.We show that data from thin thermocouple probes inserted just below the bark can be used, by means of a one-...

Progress in remote sensing of global land surface heat fluxes and evaporations with a turbulent heat exchange parameterization method

NASA Astrophysics Data System (ADS)

Chen, Xuelong; Su, Bob

2017-04-01

Remote sensing has provided us an opportunity to observe Earth land surface with a much higher resolution than any of GCM simulation. Due to scarcity of information for land surface physical parameters, up-to-date GCMs still have large uncertainties in the coupled land surface process modeling. One critical issue is a large amount of parameters used in their land surface models. Thus remote sensing of land surface spectral information can be used to provide information on these parameters or assimilated to decrease the model uncertainties. Satellite imager could observe the Earth land surface with optical, thermal and microwave bands. Some basic Earth land surface status (land surface temperature, canopy height, canopy leaf area index, soil moisture etc.) has been produced with remote sensing technique, which already help scientists understanding Earth land and atmosphere interaction more precisely. However, there are some challenges when applying remote sensing variables to calculate global land-air heat and water exchange fluxes. Firstly, a global turbulent exchange parameterization scheme needs to be developed and verified, especially for global momentum and heat roughness length calculation with remote sensing information. Secondly, a compromise needs to be innovated to overcome the spatial-temporal gaps in remote sensing variables to make the remote sensing based land surface fluxes applicable for GCM model verification or comparison. A flux network data library (more 200 flux towers) was collected to verify the designed method. Important progress in remote sensing of global land flux and evaporation will be presented and its benefits for GCM models will also be discussed. Some in-situ studies on the Tibetan Plateau and problems of land surface process simulation will also be discussed.

Linking atmospheric synoptic transport, cloud phase, surface energy fluxes, and sea-ice growth: observations of midwinter SHEBA conditions

NASA Astrophysics Data System (ADS)

Persson, P. Ola G.; Shupe, Matthew D.; Perovich, Don; Solomon, Amy

2017-08-01

Observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) project are used to describe a sequence of events linking midwinter long-range advection of atmospheric heat and moisture into the Arctic Basin, formation of supercooled liquid water clouds, enhancement of net surface energy fluxes through increased downwelling longwave radiation, and reduction in near-surface conductive heat flux loss due to a warming of the surface, thereby leading to a reduction in sea-ice bottom growth. The analyses provide details of two events during Jan. 1-12, 1998, one entering the Arctic through Fram Strait and the other from northeast Siberia; winter statistics extend the results. Both deep, precipitating frontal clouds and post-frontal stratocumulus clouds impact the surface radiation and energy budget. Cloud liquid water, occurring preferentially in stratocumulus clouds extending into the base of the inversion, provides the strongest impact on surface radiation and hence modulates the surface forcing, as found previously. The observations suggest a minimum water vapor threshold, likely case dependent, for producing liquid water clouds. Through responses to the radiative forcing and surface warming, this cloud liquid water also modulates the turbulent and conductive heat fluxes, and produces a thermal wave penetrating into the sea ice. About 20-33 % of the observed variations of bottom ice growth can be directly linked to variations in surface conductive heat flux, with retarded ice growth occurring several days after these moisture plumes reduce the surface conductive heat flux. This sequence of events modulate pack-ice wintertime environmental conditions and total ice growth, and has implications for the annual sea-ice evolution, especially for the current conditions of extensive thinner ice.

The Estimation of Surface Latent Heat Flux over the Ocean and its Relationship to Marine Atmospheric Boundary Layer (MABL) Structure

NASA Technical Reports Server (NTRS)

Palm, Stephen P.; Schwemmer, Geary K.; Vandemark, Doug; Evans, Keith; Miller, David O.; Demoz, Belay B.; Starr, David OC. (Technical Monitor)

2001-01-01

A new technique combining active and passive remote sensing instruments for the estimation of surface latent heat flux over the ocean is presented. This synergistic method utilizes aerosol lidar backscatter data, multi-channel infrared radiometer data, and microwave scatterometer data acquired onboard the NASA P-313 research aircraft during an extended field campaign over the Atlantic ocean in support of the Lidar In-space Technology Experiment (LITE) in September of 1994. The 10 meter wind speed derived from scatterometers and lidar-radiometer inferred near-surface moisture are used to obtain an estimate of the surface flux of moisture via a bulk aerodynamic formula. The results are compared with the Special Sensor Microwave Imager (SSM/I) daily average latent heat flux and show reasonable agreement. However, the SSM/I values are biased low by about 15 W/sq m. In addition, the Marine Atmospheric Boundary Layer (MABL) height, entrainment zone thickness and integrated lidar backscatter intensity are computed from the lidar data and compared with the magnitude of the surface fluxes. The results show that the surface latent heat flux is most strongly correlated with entrainment zone depth, MABL height and the integrated MABL lidar backscatter, with corresponding correlation coefficients of 0.39, 0.43 and 0.71, respectively.

A DOUBLE-RING ALGORITHM FOR MODELING SOLAR ACTIVE REGIONS: UNIFYING KINEMATIC DYNAMO MODELS AND SURFACE FLUX-TRANSPORT SIMULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munoz-Jaramillo, Andres; Martens, Petrus C. H.; Nandy, Dibyendu

The emergence of tilted bipolar active regions (ARs) and the dispersal of their flux, mediated via processes such as diffusion, differential rotation, and meridional circulation, is believed to be responsible for the reversal of the Sun's polar field. This process (commonly known as the Babcock-Leighton mechanism) is usually modeled as a near-surface, spatially distributed {alpha}-effect in kinematic mean-field dynamo models. However, this formulation leads to a relationship between polar field strength and meridional flow speed which is opposite to that suggested by physical insight and predicted by surface flux-transport simulations. With this in mind, we present an improved double-ring algorithmmore » for modeling the Babcock-Leighton mechanism based on AR eruption, within the framework of an axisymmetric dynamo model. Using surface flux-transport simulations, we first show that an axisymmetric formulation-which is usually invoked in kinematic dynamo models-can reasonably approximate the surface flux dynamics. Finally, we demonstrate that our treatment of the Babcock-Leighton mechanism through double-ring eruption leads to an inverse relationship between polar field strength and meridional flow speed as expected, reconciling the discrepancy between surface flux-transport simulations and kinematic dynamo models.« less

The Estimation of Surface Latent Heat Flux Over the Ocean and its Relationship to Marine Atmospheric Boundary Layer (MABL) Structure

NASA Technical Reports Server (NTRS)

Palm, Stephen P.; Miller, David O.; Schwemmer, Geary

2000-01-01

A new technique combining active and passive remote sensing instruments for the estimation of surface latent heat flux over the ocean is presented. This synergistic method uses aerosol lidar backscatter data, multi-channel infrared radiometer data and microwave scatterometer data acquired onboard the NASA P-3B research aircraft during an extended field campaign over the Atlantic ocean in support of the Lidar In-space Technology Experiment (LITE) in September of 1994. The 10 meter wind speed derived from the scatterometers and the lidar-radiometer inferred near-surface moisture are used to obtain an estimate of the surface flux of moisture via bulk aerodynamic formulae. The results are compared with the Special Sensor Microwave Imager (SSM/I) daily average latent heat flux and show reasonable agreement with an rms error and bias of about 50 and 25 W per square meters, respectively. In addition, the MABL height, entrainment zone thickness and integrated lidar backscatter intensity are computed from the lidar data and compared with the magnitude of the surface fluxes. The results show that the surface latent heat flux is most strongly correlated with entrainment zone top, bottom and the integrated MABL lidar backscatter, with corresponding correlation coefficients of 0.62, 0.67 and 0.61, respectively.

On Laminar to Turbulent Transition of Arc-Jet Flow in the NASA Ames Panel Test Facility

NASA Technical Reports Server (NTRS)

Gokcen, Tahir; Alunni, Antonella I.

2012-01-01

This paper provides experimental evidence and supporting computational analysis to characterize the laminar to turbulent flow transition in a high enthalpy arc-jet facility at NASA Ames Research Center. The arc-jet test data obtained in the 20 MW Panel Test Facility include measurements of surface pressure and heat flux on a water-cooled calibration plate, and measurements of surface temperature on a reaction-cured glass coated tile plate. Computational fluid dynamics simulations are performed to characterize the arc-jet test environment and estimate its parameters consistent with the facility and calibration measurements. The present analysis comprises simulations of the nonequilibrium flowfield in the facility nozzle, test box, and flowfield over test articles. Both laminar and turbulent simulations are performed, and the computed results are compared with the experimental measurements, including Stanton number dependence on Reynolds number. Comparisons of computed and measured surface heat fluxes (and temperatures), along with the accompanying analysis, confirm that that the boundary layer in the Panel Test Facility flow is transitional at certain archeater conditions.

The impact of the fast ion fluxes and thermal plasma loads on the design of the ITER fast ion loss detector

NASA Astrophysics Data System (ADS)

Kocan, M.; Garcia-Munoz, M.; Ayllon-Guerola, J.; Bertalot, L.; Bonnet, Y.; Casal, N.; Galdon, J.; Garcia-Lopez, J.; Giacomin, T.; Gonzalez-Martin, J.; Gunn, J. P.; Rodriguez-Ramos, M.; Reichle, R.; Rivero-Rodriguez, J. F.; Sanchis-Sanchez, L.; Vayakis, G.; Veshchev, E.; Vorpahl, C.; Walsh, M.; Walton, R.

2017-12-01

Thermal plasma loads to the ITER Fast Ion Loss Detector are studied for QDT = 10 burning plasma equilibrium using the 3D field line tracing. The simulations are performed for a FILD insertion 9-13 cm past the port plasma facing surface, optimized for fast ion measurements, and include the worst-case perturbation of the plasma boundary and the error in the magnetic reconstruction. The FILD head is exposed to superimposed time-averaged ELM heat load, static inter-ELM heat flux and plasma radiation. The study includes the estimate of the instantaneous temperature rise due to individual 0.6 MJ controlled ELMs. The maximum time-averaged surface heat load is lesssim 12 MW/m2 and will lead to increase of the FILD surface temperature well below the melting temperature of the materials considered here, for the FILD insertion time of 0.2 s. The worst-case instantaneous temperature rise during controlled 0.6 MJ ELMs is also significantly smaller than the melting temperature of e.g. Tungsten or Molybdenum, foreseen for the FILD housing.

Remote Heat Flux Using a Self Calibration Multiwavelength Pyrometer and a Transparent Material

NASA Technical Reports Server (NTRS)

Ng, Daniel

1998-01-01

A self calibrating multiwavelength pyrometer was used to conduct remote heat flux measurements using a transparent sapphire disk by determining the sapphire disk's front and back surface temperatures. Front surface temperature (Tfs) was obtained from detection of surface emitted radiation at long wavelengths (k = 6 gm). Back surface temperature (Tbs) was obtained from short wavelength (1 to 5 gm) radiation transmitted through the sapphire disk. The thermal conductivity of the sapphire disk and the heat transfer coefficients h, and h2 of its surfaces are determined experimentally. An analysis of the heat flux measurement is presented.

Thermoplastic welding apparatus and method

DOEpatents

Matsen, Marc R.; Negley, Mark A.; Geren, William Preston; Miller, Robert James

2017-03-07

A thermoplastic welding apparatus includes a thermoplastic welding tool, at least one tooling surface in the thermoplastic welding tool, a magnetic induction coil in the thermoplastic welding tool and generally encircling the at least one tooling surface and at least one smart susceptor in the thermoplastic welding tool at the at least one tooling surface. The magnetic induction coil is adapted to generate a magnetic flux field oriented generally parallel to a plane of the at least one smart susceptor.

Symposium on Numerical and Physical Aspects of Aerodynamic Flows

DTIC Science & Technology

1992-01-15

ReT/R. -1 wide range of Mach numbers including pressure gradient, a = - (a*) (10) surface roughness. surface heating and cooling . and surface 9 I + ReT...and specific heat at constant pressure, respectively. Favre equation is then obtained by contracting the Reynolds-stress decomposition is applied to...their near- wall behavior. In other words, if highly cooled -wall flows are to be predicted correctly, heat fluxes should be modeled e = 2ak + 4bky

Estimating Turbulent Surface Fluxes from Small Unmanned Aircraft: Evaluation of Current Abilities

NASA Astrophysics Data System (ADS)

de Boer, G.; Lawrence, D.; Elston, J.; Cassano, J. J.; Mack, J.; Wildmann, N.; Nigro, M. A.; Ivey, M.; Wolfe, D. E.; Muschinski, A.

2014-12-01

Heat transfer between the atmosphere and Earth's surface represents a key component to understanding Earth energy balance, making it important in understanding and simulating climate. Arguably, the oceanic air-sea interface and Polar sea-ice-air interface are amongst the most challenging in which to measure these fluxes. This difficulty results partially from challenges associated with infrastructure deployment on these surfaces and partially from an inability to obtain spatially representative values over a potentially inhomogeneous surface. Traditionally sensible (temperature) and latent (moisture) fluxes are estimated using one of several techniques. A preferred method involves eddy-correlation where cross-correlation between anomalies in vertical motion (w) and temperature (T) or moisture (q) is used to estimate heat transfer. High-frequency measurements of these quantities can be derived using tower-mounted instrumentation. Such systems have historically been deployed over land surfaces or on ships and buoys to calculate fluxes at the air-land or air-sea interface, but such deployments are expensive and challenging to execute, resulting in a lack of spatially diverse measurements. A second ("bulk") technique involves the observation of horizontal windspeed, temperature and moisture at a given altitude over an extended time period in order to estimate the surface fluxes. Small Unmanned Aircraft Systems (sUAS) represent a unique platform from which to derive these fluxes. These sUAS can be small ( 1 m), lightweight ( 700 g), low cost ( $2000) and relatively easy to deploy to remote locations and over inhomogeneous surfaces. We will give an overview of the ability of sUAS to provide measurements necessary for estimating surface turbulent fluxes. This discussion is based on flights in the vicinity of the 1000 ft. Boulder Atmospheric Observatory (BAO) tower, and over the US Department of Energy facility at Oliktok Point, Alaska. We will present initial comparisons between UAS-derived turbulent fluxes and those derived from tower-based instrumentation and discuss differences in the context of sensor technology and flight patterns employed to collect data.

Inventory of File gdas1.t06z.sfluxgrbf06.grib2

Science.gov Websites

hour ave Visible Diffuse Downward Solar Flux [W/m^2] 036 surface NBDSF 0-6 hour ave Near IR Beam Downward Solar Flux [W/m^2] 037 surface NDDSF 0-6 hour ave Near IR Diffuse Downward Solar Flux [W/m^2] 038

Inventory of File gfs.t06z.sfluxgrbf06.grib2

Science.gov Websites

hour ave Visible Diffuse Downward Solar Flux [W/m^2] 036 surface NBDSF 0-6 hour ave Near IR Beam Downward Solar Flux [W/m^2] 037 surface NDDSF 0-6 hour ave Near IR Diffuse Downward Solar Flux [W/m^2] 038

Updated Magmatic Flux Rate Estimates for the Hawaii Plume

NASA Astrophysics Data System (ADS)

Wessel, P.

2013-12-01

Several studies have estimated the magmatic flux rate along the Hawaiian-Emperor Chain using a variety of methods and arriving at different results. These flux rate estimates have weaknesses because of incomplete data sets and different modeling assumptions, especially for the youngest portion of the chain (<3 Ma). While they generally agree on the 1st order features, there is less agreement on the magnitude and relative size of secondary flux variations. Some of these differences arise from the use of different methodologies, but the significance of this variability is difficult to assess due to a lack of confidence bounds on the estimates obtained with these disparate methods. All methods introduce some error, but to date there has been little or no quantification of error estimates for the inferred melt flux, making an assessment problematic. Here we re-evaluate the melt flux for the Hawaii plume with the latest gridded data sets (SRTM30+ and FAA 21.1) using several methods, including the optimal robust separator (ORS) and directional median filtering techniques (DiM). We also compute realistic confidence limits on the results. In particular, the DiM technique was specifically developed to aid in the estimation of surface loads that are superimposed on wider bathymetric swells and it provides error estimates on the optimal residuals. Confidence bounds are assigned separately for the estimated surface load (obtained from the ORS regional/residual separation techniques) and the inferred subsurface volume (from gravity-constrained isostasy and plate flexure optimizations). These new and robust estimates will allow us to assess which secondary features in the resulting melt flux curve are significant and should be incorporated when correlating melt flux variations with other geophysical and geochemical observations.

Kinetically controlled indium surface coverage effects on PAMBE-growth of InN/GaN(0001) quantum well structures

NASA Astrophysics Data System (ADS)

Li, Chen; Maidaniuk, Yurii; Kuchuk, Andrian V.; Shetty, Satish; Ghosh, Pijush; White, Thomas P.; Morgan, Timothy Al.; Hu, Xian; Wu, Yang; Ware, Morgan E.; Mazur, Yuriy I.; Salamo, Gregory J.

2018-05-01

We report the effects of nitrogen (N) plasma and indium (In) flux on the In adatom adsorption/desorption kinetics on a GaN(0001) surface at the relatively high plasma-assisted molecular beam epitaxy-growth temperature of 680 °C. We experimentally demonstrate that under an active N flux, the (√{3 }×√{3 })R 30 ° surface reconstruction containing In and N quickly appears and the dynamically stable In adlayers sitting on this surface exhibit a continuous change from 0 to 2 MLs as a function of In flux. Compared to the bare GaN 1 ×1 surface which is stable during In exposure without an active N flux, we observed a much faster desorption for the bottom In adlayer and the absence of an In flux window corresponding to an In coverage of 1 ML. Moreover, when the In coverage exceeds 2 MLs, the desorption rates become identical for both surfaces. Finally, the importance of In surface coverage before GaN capping was shown by growing a series of InN/GaN multiple quantum well samples. The photoluminescence data show that a consistent quantum well structure is only formed if the surface is covered by excess In droplets before GaN capping.

The Characterization of Atmospheric Boundary Layer Depth and Turbulence in a Mixed Rural and Urban Convective Environment

NASA Astrophysics Data System (ADS)

Hicks, Micheal M.

A comprehensive analysis of surface-atmosphere flux exchanges over a mixed rural and urban convective environment is conducted at Howard University Beltsville, MD Research Campus. This heterogeneous site consists of rural, suburban and industrial surface covers to its south, east and west, within a 2 km radius of a flux sensor. The eddy covariance method is utilized to estimate surface-atmosphere flux exchanges of momentum, heat and moisture. The attributes of these surface flux exchanges are contrasted to those of classical homogeneous sites and assessed for accuracy, to evaluate the following: (I) their similarity to conventional convective boundary layer (CBL) processes and (II) their representativeness of the surrounding environment's turbulent properties. Both evaluations are performed as a function of upwind surface conditions. In particular, the flux estimates' obedience to spectrum power laws and similarity theory relationships is used for performing the first evaluation, and their ability to close the surface energy balance and accurately model CBL heights is used for the latter. An algorithm that estimates atmospheric boundary layer heights from observed lidar extinction backscatter was developed, tested and applied in this study. The derived lidar based CBL heights compared well with those derived from balloon borne soundings, with an overall Pearson correlation coefficient and standard deviation of 0.85 and 223 m, respectively. This algorithm assisted in the evaluation of the response of CBL processes to surface heterogeneity, by deriving high temporal CBL heights and using them as independent references of the surrounding area averaged sensible heat fluxes. This study found that the heterogeneous site under evaluation was rougher than classical homogeneous sites, with slower dissipation rates of turbulent kinetic energy. Flux measurements downwind of the industrial complexes exhibited enhanced efficiency in surface-atmosphere momentum, heat, and moisture transport relative to their similarity theory predictions. In addition, these enhanced heat flux estimates ingested into the CBL slab model overestimated observed CBL heights. More spatial flux observations are needed to better understand the role that the industrial complexes are playing in enhancing the efficiency of turbulent processes, which may have important implications on the role humans are assuming in regional climate change.

The contribution of reactive carbon emissions from vegetation to the carbon balance of terrestrial ecosystems.

PubMed

Guenther, Alex

2002-12-01

About 2.4 Pg (1 Pg = 10(15) g) of carbon is emitted annually into the atmosphere as reactive compounds and most of it is eventually oxidized to CO2. Isoprene, alpha-pinene, methanol, carbon monoxide and other compounds emitted by terrestrial vegetation contribute about half of the total flux and are estimated to produce about 1 Pg C as CO2 per year. The global average for vegetated surfaces is about 7 g C m(-2) per year but could exceed 100 g m(-2) per year at some tropical locations. The magnitude of these fluxes on both the landscape and global scales are small relative to the total carbon emission or deposition but are significant relative to the net fluxes. Reactive carbon fluxes are very sensitive to landcover and climate change and may vary significantly due to future perturbations. This paper summarizes what is known about reactive carbon emissions from vegetation including the magnitude of local, landscape, and global scale fluxes and their contribution to atmospheric CO2. Reasons for including this term in carbon flux models are presented as well as the potential importance on various spatial scales. Past, present and future reactive carbon emissions are expected to differ significantly and the implications of this are discussed.

2D surface temperature measurement of plasma facing components with modulated active pyrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amiel, S.; Loarer, T.; Pocheau, C.

2014-10-01

In nuclear fusion devices, such as Tore Supra, the plasma facing components (PFC) are in carbon. Such components are exposed to very high heat flux and the surface temperature measurement is mandatory for the safety of the device and also for efficient plasma scenario development. Besides this measurement is essential to evaluate these heat fluxes for a better knowledge of the physics of plasma-wall interaction, it is also required to monitor the fatigue of PFCs. Infrared system (IR) is used to manage to measure surface temperature in real time. For carbon PFCs, the emissivity is high and known (ε ~more » 0.8), therefore the contribution of the reflected flux from environment and collected by the IR cameras can be neglected. However, the future tokamaks such as WEST and ITER will be equipped with PFCs in metal (W and Be/W, respectively) with low and variable emissivities (ε ~ 0.1–0.4). Consequently, the reflected flux will contribute significantly in the collected flux by IR camera. The modulated active pyrometry, using a bicolor camera, proposed in this paper allows a 2D surface temperature measurement independently of the reflected fluxes and the emissivity. Experimental results with Tungsten sample are reported and compared with simultaneous measurement performed with classical pyrometry (monochromatic and bichromatic) with and without reflective flux demonstrating the efficiency of this method for surface temperature measurement independently of the reflected flux and the emissivity.« less

Quantum theory of atoms in molecules: results for the SR-ZORA Hamiltonian.

PubMed

Anderson, James S M; Ayers, Paul W

2011-11-17

The quantum theory of atoms in molecules (QTAIM) is generalized to include relativistic effects using the popular scalar-relativistic zeroth-order regular approximation (SR-ZORA). It is usually assumed that the definition of the atom as a volume bounded by a zero-flux surface of the electron density is closely linked to the form of the kinetic energy, so it is somewhat surprising that the atoms corresponding to the relativistic kinetic-energy operator in the SR-ZORA Hamiltonian are also bounded by zero-flux surfaces. The SR-ZORA Hamiltonian should be sufficient for qualitative descriptions of molecular electronic structure across the periodic table, which suggests that QTAIM-based analysis can be useful for molecules and solids containing heavy atoms.

Analysis of longwave radiation for the Earth-atmosphere system

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Venuru, C. S.; Subramanian, S. V.

1983-01-01

Accurate radiative transfer models are used to determine the upwelling atmospheric radiance and net radiative flux in the entire longwave spectral range. The validity of the quasi-random band model is established by comparing the results of this model with those of line-by-line formulations and with available theoretical and experimental results. Existing radiative transfer models and computer codes are modified to include various surface and atmospheric effects (surface reflection, nonequilibrium radiation, and cloud effects). The program is used to evaluate the radiative flux in clear atmosphere, provide sensitivity analysis of upwelling radiance in the presence of clouds, and determine the effects of various climatological parameters on the upwelling radiation and anisotropic function. Homogeneous and nonhomogeneous gas emissivities can also be evaluated under different conditions.

MODELING THE RISE OF FIBRIL MAGNETIC FIELDS IN FULLY CONVECTIVE STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weber, Maria A.; Browning, Matthew K., E-mail: mweber@astro.ex.ac.uk

Many fully convective stars exhibit a wide variety of surface magnetism, including starspots and chromospheric activity. The manner by which bundles of magnetic field traverse portions of the convection zone to emerge at the stellar surface is not especially well understood. In the solar context, some insight into this process has been gleaned by regarding the magnetism as consisting partly of idealized thin flux tubes (TFTs). Here we present the results of a large set of TFT simulations in a rotating spherical domain of convective flows representative of a 0.3 M {sub ⊙} main-sequence star. This is the first studymore » to investigate how individual flux tubes in such a star might rise under the combined influence of buoyancy, convection, and differential rotation. A time-dependent hydrodynamic convective flow field, taken from separate 3D simulations calculated with the anelastic equations, impacts the flux tube as it rises. Convective motions modulate the shape of the initially buoyant flux ring, promoting localized rising loops. Flux tubes in fully convective stars have a tendency to rise nearly parallel to the rotation axis. However, the presence of strong differential rotation allows some initially low-latitude flux tubes of moderate strength to develop rising loops that emerge in the near-equatorial region. Magnetic pumping suppresses the global rise of the flux tube most efficiently in the deeper interior and at lower latitudes. The results of these simulations aim to provide a link between dynamo-generated magnetic fields, fluid motions, and observations of starspots for fully convective stars.« less

Sensitivity of land surface modeling to parameters: An uncertainty quantification method applied to the Community Land Model

NASA Astrophysics Data System (ADS)

Ricciuto, D. M.; Mei, R.; Mao, J.; Hoffman, F. M.; Kumar, J.

2015-12-01

Uncertainties in land parameters could have important impacts on simulated water and energy fluxes and land surface states, which will consequently affect atmospheric and biogeochemical processes. Therefore, quantification of such parameter uncertainties using a land surface model is the first step towards better understanding of predictive uncertainty in Earth system models. In this study, we applied a random-sampling, high-dimensional model representation (RS-HDMR) method to analyze the sensitivity of simulated photosynthesis, surface energy fluxes and surface hydrological components to selected land parameters in version 4.5 of the Community Land Model (CLM4.5). Because of the large computational expense of conducting ensembles of global gridded model simulations, we used the results of a previous cluster analysis to select one thousand representative land grid cells for simulation. Plant functional type (PFT)-specific uniform prior ranges for land parameters were determined using expert opinion and literature survey, and samples were generated with a quasi-Monte Carlo approach-Sobol sequence. Preliminary analysis of 1024 simulations suggested that four PFT-dependent parameters (including slope of the conductance-photosynthesis relationship, specific leaf area at canopy top, leaf C:N ratio and fraction of leaf N in RuBisco) are the dominant sensitive parameters for photosynthesis, surface energy and water fluxes across most PFTs, but with varying importance rankings. On the other hand, for surface ans sub-surface runoff, PFT-independent parameters, such as the depth-dependent decay factors for runoff, play more important roles than the previous four PFT-dependent parameters. Further analysis by conditioning the results on different seasons and years are being conducted to provide guidance on how climate variability and change might affect such sensitivity. This is the first step toward coupled simulations including biogeochemical processes, atmospheric processes or both to determine the full range of sensitivity of Earth system modeling to land-surface parameters. This can facilitate sampling strategies in measurement campaigns targeted at reduction of climate modeling uncertainties and can also provide guidance on land parameter calibration for simulation optimization.

Spray Cooling Trajectory Angle Impact Upon Heat Flux Using a Straight Finned Enhanced Surface

NASA Technical Reports Server (NTRS)

Silk, Eric A.; Kim, Jungho; Kiger, Ken

2005-01-01

Experiments were conducted to study the effects of spray trajectory angles upon heat flux for flat and enhanced surface spray cooling. The surface enhancement consisted of straight fins machined on the top surface of a copper heater block. Spray cooling curves were obtained with the straight fin surface aligned both parallel (axial) and perpendicular (transverse) to the spray axis. Measurements were also obtained on a flat surface heater block for comparison purposes. Each copper block had a cross-sectional area of 2.0 sq cm. A 2x2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed (chamber pressure of 41.4 kPa) conditions. Results show that the maximum CHF in all cases was attained for a trajectory angle of 30' from the surface normal. Furthermore, trajectory angles applied to straight finned surfaces can have a critical heat flux (CHF) enhancement as much as 75% (heat flux value of 140 W/sq cm) relative to the vertical spray orientation for the analogous flat surface case under nominally degassed conditions.

Modeling of Melt Growth During Carbothermal Processing of Lunar Regolith

NASA Technical Reports Server (NTRS)

Balasubramaniam, R.; Gokoglu S.; Hegde, U.

2012-01-01

The carbothermal processing of lunar regolith has been proposed as a means to produce carbon monoxide and ultimately oxygen to support human exploration of the moon. In this process, gaseous methane is pyrolyzed as it flows over the hot surface of a molten zone of lunar regolith and is converted to carbon and hydrogen. Carbon gets deposited on the surface of the melt, and mixes and reacts with the metal oxides in it to produce carbon monoxide that bubbles out of the melt. Carbon monoxide is further processed in other reactors downstream to ultimately produce oxygen. The amount of oxygen produced crucially depends on the amount of regolith that is molten. In this paper we develop a model of the heat transfer in carbothermal processing. Regolith in a suitable container is heated by a heat flux at its surface such as by continuously shining a beam of solar energy or a laser on it. The regolith on the surface absorbs the energy and its temperature rises until it attains the melting point. The energy from the heat flux is then used for the latent heat necessary to change phase from solid to liquid, after which the temperature continues to rise. Thus a small melt pool appears under the heated zone shortly after the heat flux is turned on. As time progresses, the pool absorbs more heat and supplies the energy required to melt more of the regolith, and the size of the molten zone increases. Ultimately, a steady-state is achieved when the heat flux absorbed by the melt is balanced by radiative losses from the surface. In this paper, we model the melting and the growth of the melt zone with time in a bed of regolith when a portion of its surface is subjected to a constant heat flux. The heat flux is assumed to impinge on a circular area. Our model is based on an axisymmetric three-dimensional variation of the temperature field in the domain. Heat transfer occurs only by conduction, and effects of convective heat transport are assumed negligible. Radiative heat loss from the surface of the melt and the regolith to the surroundings is permitted. We perform numerical computations to determine the shape and the mass of the melt at steady state and its time evolution. We first neglect the volume change upon melting, and subsequently perform calculations including it. Predictions from our model are compared to test data to determine the effective thermal conductivities of the regolith and the melt that are compatible with the data

CarbonTracker-Lagrange: A Framework for Greenhouse Gas Flux Estimation at Regional to Continental Scales

NASA Astrophysics Data System (ADS)

Andrews, A. E.

2016-12-01

CarbonTracker-Lagrange (CT-L) is a flexible modeling framework developed to take advantage of newly available atmospheric data for CO2 and other long-lived gases such as CH4 and N2O. The North American atmospheric CO2 measurement network has grown from three sites in 2004 to >100 sites in 2015. The US network includes tall tower, mountaintop, surface, and aircraft sites in the NOAA Global Greenhouse Gas Reference Network along with sites maintained by university, government and private sector researchers. The Canadian network is operated by Environment and Climate Change Canada. This unprecedented dataset can provide spatially and temporally resolved CO2 emissions and uptake flux estimates and quantitative information about drivers of variability, such as drought and temperature. CT-L is a platform for systematic comparison of data assimilation techniques and evaluation of assumed prior, model and observation errors. A novel feature of CT-L is the optimization of boundary values along with surface fluxes, leveraging vertically resolved data available from NOAA's aircraft sampling program. CT-L uses observation footprints (influence functions) from the Weather Research and Forecasting/Stochastic Time-Inverted Lagrangian Transport (WRF-STILT) modeling system to relate atmospheric measurements to upwind fluxes and boundary values. Footprints are pre-computed and the optimization algorithms are efficient, so many variants of the calculation can be performed. Fluxes are adjusted using Bayesian or Geostatistical methods to provide optimal agreement with observations. Satellite measurements of CO2 and CH4 from GOSAT are available starting in July 2009 and from OCO-2 since September 2014. With support from the NASA Carbon Monitoring System, we are developing flux estimation strategies that use remote sensing and in situ data together, including geostatistical inversions using satellite retrievals of solar-induced chlorophyll fluorescence. CT-L enables quantitative investigation of what new measurements would best complement the existing carbon observing system. We are also working to implement multi-species inversions for CO2 flux estimation using CO2 data along with CO, δ13CO2, COS and radiocarbon observations and for CH4 flux estimation using data for various hydrocarbons.

Visualization of Radiation Environment on Mars: Assessment with MARIE Measurements

NASA Technical Reports Server (NTRS)

Saganti, P.; Cucinotta, F.; Zeitlin, C.; Cleghorn, T.; Flanders, J.; Riman, F.; Hu, X.; Pinsky, L.; Lee, K.; Anderson, V.;

Land surface models systematically overestimate the intensity, duration and magnitude of seasonal-scale evaporative droughts

DOE PAGES

Ukkola, A. M.; De Kauwe, M. G.; Pitman, A. J.; ...

2016-10-13

Land surface models (LSMs) must accurately simulate observed energy and water fluxes during droughts in order to provide reliable estimates of future water resources. We evaluated 8 different LSMs (14 model versions) for simulating evapotranspiration (ET) during periods of evaporative drought (Edrought) across six flux tower sites. Using an empirically defined Edrought threshold (a decline in ET below the observed 15th percentile), we show that LSMs simulated 58 Edrought days per year, on average, across the six sites, ~3 times as many as the observed 20 d. The simulated Edrought magnitude was ~8 times greater than observed and twice asmore » intense. Our findings point to systematic biases across LSMs when simulating water and energy fluxes under water-stressed conditions. The overestimation of key Edrought characteristics undermines our confidence in the models' capability in simulating realistic drought responses to climate change and has wider implications for phenomena sensitive to soil moisture, including heat waves.« less

A Multilayer Dataset of SSM/I-Derived Global Ocean Surface Turbulent Fluxes

NASA Technical Reports Server (NTRS)

Chou, Shu-Hsien; Shie, Chung-Lin; Atlas, Robert M.; Ardizzone, Joe; Nelkin, Eric; Einaud, Franco (Technical Monitor)

2001-01-01

A dataset including daily- and monthly-mean turbulent fluxes (momentum, latent heat, and sensible heat) and some relevant parameters over global oceans, derived from the Special Sensor Microwave/Imager (SSM/I) data, for the period July 1987-December 1994 and the 1988-94 annual and monthly-mean climatologies of the same variables is created. It has a spatial resolution of 2.0deg x 2.5deg latitude-longitude. The retrieved surface air humidity is found to be generally accurate as compared to the collocated radiosonde observations over global oceans. The retrieved wind stress and latent heat flux show useful accuracy as verified against research quality measurements of ship and buoy in the western equatorial Pacific. The 1988-94 seasonal-mean wind stress and latent heat flux show reasonable patterns related to seasonal variations of the atmospheric general circulation. The patterns of 1990-93 annual-mean turbulent fluxes and input variables are generally in good agreement with one of the best global analyzed flux datasets that based on COADS (comprehensive ocean-atmosphere data set) with corrections on wind speeds and covered the same period. The retrieved wind speed is generally within +/-1 m/s of the COADS-based, but is stronger by approx. 1-2 m/s in the northern extratropical oceans. The discrepancy is suggested to be mainly due to higher COADS-modified wind speeds resulting from underestimation of anemometer heights. Compared to the COADS-based, the retrieved latent heat flux and sea-air humidity difference are generally larger with significant differences in the trade wind zones and the ocean south of 40degS (up to approx. 40-60 W/sq m and approx. 1-1.5 g/kg). The discrepancy is believed to be mainly caused by higher COADS-based surface air humidity arising from the overestimation of dew point temperatures and from the extrapolation of observed high humidity southward into data-void regions south of 40degS. The retrieved sensible heat flux is generally within +/-5 W/sq m of UWM/COADS, except for some areas in the extratropical oceans, where the differences in wind speed have large impact on the difference in sensible heat flux. The dataset of SSM/I-derived turbulent fluxes is useful for climate studies, forcing of ocean models, and validation of coupled ocean-atmosphere global models.

Relationship between wind, waves and radar backscatter

NASA Technical Reports Server (NTRS)

Katsaros, Kristina B.; Ataktuerk, Serhad S.

1991-01-01

The aim of the research was to investigate the relationship between wind, waves, and radar backscatter from water surface. To this end, three field experiments with periods of 2 to 4 weeks were carried out during summer months in 1988, 1989 and 1990. For these periods, the University of Washington group provided (1) environmental parameters such as wind speed, wind stress, and atmospheric stratification through measurements of surface fluxes (of momentum, sensible heat and latent heat) and of air and water temperatures; and (2) wave height spectra including both the dominant waves and the short gravity-capillary waves. Surface flux measurements were performed by using our well tested instruments: a K-Gill twin propeller-vane anemometer and a fast response thermocouple psychrometer. Wave heights were measured by a resistance wire wave gauge. The University of Kansas group was responsible for the operation of the microwave radars.

Aeroheating Analysis for the Mars Reconnaissance Orbiter with Comparison to Flight Data

NASA Technical Reports Server (NTRS)

Liechty, Derek S.

2007-01-01

The aeroheating environment of the Mars Reconnaissance Orbiter (MRO) has been analyzed using the direct simulation Monte Carlo and free-molecular techniques. The results of these analyses were used to develop an aeroheating database to be used for the preflight planning and the in-flight operations support for the aerobraking phase of the MRO mission. The aeroheating predictions calculated for the MRO include the heat transfer coefficient (CH) over a range of angles-of-attack, sideslip angles, and number densities. The effects of flow chemistry, surface temperature, and surface grid resolution were also investigated to determine the aeroheating database uncertainties. Flight heat flux data has been calculated from surface temperature sensor data returned to Earth from the MRO in orbit around Mars during the aerobraking phase of its mission. The heat flux data have been compared to the aeroheating database and agree favorably.

Diminished mercury emission from waters with duckweed cover

NASA Astrophysics Data System (ADS)

Wollenberg, Jennifer L.; Peters, Stephen C.

2009-06-01

Duckweeds (Lemnaceae) are a widely distributed type of floating vegetation in freshwater systems. Under suitable conditions, duckweeds form a dense vegetative mat on the water surface, which reduces light penetration into the water column and limits gas exchange at the water-air interface by decreasing the area of open water surface. Experiments were conducted to determine whether duckweed decreases mercury emission by limiting gas diffusion across the water-air interface and attenuating light, or, conversely, enhances emission via transpiration of mercury vapor. Microcosm flux chamber experiments indicate that duckweed decreases mercury emission from the water surface compared to open water controls. Fluxes under duckweed were 17-67% lower than in controls, with lower fluxes occurring at higher percent cover. The decrease in mercury emission suggests that duckweed may limit emission through one of several mechanisms, including limited gas transport across the air-water interface, decreased photoreactions due to light attenuation, and plant-mercury interactions. The results of this experiment were applied to a model lake system to illustrate the magnitude of potential effects on mercury cycling. The mercury retained in the lake as a result of hindered emission may increase bioaccumulation potential in lakes with duckweed cover.

High-resolution hot-film measurement of surface heat flux to an impinging jet

NASA Astrophysics Data System (ADS)

O'Donovan, T. S.; Persoons, T.; Murray, D. B.

2011-10-01

To investigate the complex coupling between surface heat transfer and local fluid velocity in convective heat transfer, advanced techniques are required to measure the surface heat flux at high spatial and temporal resolution. Several established flow velocity techniques such as laser Doppler anemometry, particle image velocimetry and hot wire anemometry can measure fluid velocities at high spatial resolution (µm) and have a high-frequency response (up to 100 kHz) characteristic. Equivalent advanced surface heat transfer measurement techniques, however, are not available; even the latest advances in high speed thermal imaging do not offer equivalent data capture rates. The current research presents a method of measuring point surface heat flux with a hot film that is flush mounted on a heated flat surface. The film works in conjunction with a constant temperature anemometer which has a bandwidth of 100 kHz. The bandwidth of this technique therefore is likely to be in excess of more established surface heat flux measurement techniques. Although the frequency response of the sensor is not reported here, it is expected to be significantly less than 100 kHz due to its physical size and capacitance. To demonstrate the efficacy of the technique, a cooling impinging air jet is directed at the heated surface, and the power required to maintain the hot-film temperature is related to the local heat flux to the fluid air flow. The technique is validated experimentally using a more established surface heat flux measurement technique. The thermal performance of the sensor is also investigated numerically. It has been shown that, with some limitations, the measurement technique accurately measures the surface heat transfer to an impinging air jet with improved spatial resolution for a wide range of experimental parameters.

Characteristics of the Surface Turbulent Flux and the Components of Radiation Balance over the Grasslands in the Southeastern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Li, H.; Xiao, Z.; Wei, J.

2016-12-01

Characteristics of the Surface Turbulent Flux and the Components of Radiation Balance over the Grasslands in the Southeastern Tibetan PlateauHongyi Li 1, Ziniu Xiao 2 and Junhong Wei31 China Meteorological Administration Training Centre, Beijing, China2 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China 3Theory of Atmospheric Dynamics and Climate, Institute for Atmospheric and Environmental Sciences, Goethe University of Frankfurt, Campus Riedberg, GermanyAbstract:Based on the field observation data over the grasslands in the southeastern Tibetan Plateau and the observational datasets in Nyingchi weather station for the period from May 20 to July 9, 2013, the variation characteristics of the basic meteorological elements in Nyingchi weather station, the surface turbulent fluxes and the components of radiation balance over the grasslands, as well as their relationships, are analyzed in this paper. The results show that in Nyingchi weather station, the daily variations of relative humidity and average total cloud cover are consistent with that of precipitation, but that those of daily average air temperature, daily average ground temperature, daily average wind speed and daily sunshine duration have an opposite change to that of precipitation. During the observation period, latent heat exchange is greater than sensible heat exchange, and latent heat flux is significantly higher when there is rainfall, but sensible heat flux and soil heat flux are lower. The daily variation of the total solar radiation (DR) is synchronous with that of sensible heat flux, and the daily variations of reflective solar radiation (UR), long wave radiation by earth (ULR), net radiation (Rn) and surface albedo are consistent with DR, but that of the long wave radiation by atmosphere (DLR) has an opposite change. The diurnal variations of sensible heat flux, latent heat flux, soil heat flux and the components of surface radiation balance over the grasslands are characterized by higher values at noon and lower values in the morning and evening. Keywords: surface turbulent flux, components of radiation balance, grasslands, southeastern Tibetan Plateau

The Development and Validation of a New Land Surface Model for Regional and Global Climate Modeling

NASA Astrophysics Data System (ADS)

Lynch-Stieglitz, Marc

1995-11-01

A new land-surface scheme intended for use in mesoscale and global climate models has been developed and validated. The ground scheme consists of 6 soil layers. Diffusion and a modified tipping bucket model govern heat and water flow respectively. A 3 layer snow model has been incorporated into a modified BEST vegetation scheme. TOPMODEL equations and Digital Elevation Model data are used to generate baseflow which supports lowland saturated zones. Soil moisture heterogeneity represented by saturated lowlands subsequently impacts watershed evapotranspiration, the partitioning of surface fluxes, and the development of the storm hydrograph. Five years of meteorological and hydrological data from the Sleepers river watershed located in the eastern highlands of Vermont where winter snow cover is significant were then used to drive and validate the new scheme. Site validation data were sufficient to evaluate model performance with regard to various aspects of the watershed water balance, including snowpack growth/ablation, the spring snowmelt hydrograph, storm hydrographs, and the seasonal development of watershed evapotranspiration and soil moisture. By including topographic effects, not only are the main spring hydrographs and individual storm hydrographs adequately resolved, but the mechanisms generating runoff are consistent with current views of hydrologic processes. The seasonal movement of the mean water table depth and the saturated area of the watershed are consistent with site data and the overall model hydroclimatology, including the surface fluxes, seems reasonable.

NASA's Carbon Monitoring System Flux-Pilot Project: A Multi-Component Analysis System for Carbon-Cycle Research and Monitoring

NASA Technical Reports Server (NTRS)

Pawson, S.; Gunson, M.; Potter, C.; Jucks, K.

2012-01-01

The importance of greenhouse gas increases for climate motivates NASA s observing strategy for CO2 from space, including the forthcoming Orbiting Carbon Observatory (OCO-2) mission. Carbon cycle monitoring, including attribution of atmospheric concentrations to regional emissions and uptake, requires a robust modeling and analysis infrastructure to optimally extract information from the observations. NASA's Carbon-Monitoring System Flux-Pilot Project (FPP) is a prototype for such analysis, combining a set of unique tools to facilitate analysis of atmospheric CO2 along with fluxes between the atmosphere and the terrestrial biosphere or ocean. NASA's analysis system is unique, in that it combines information and expertise from the land, oceanic, and atmospheric branches of the carbon cycle and includes some estimates of uncertainty. Numerous existing space-based missions provide information of relevance to the carbon cycle. This study describes the components of the FPP framework, assessing the realism of computed fluxes, thus providing the basis for research and monitoring applications. Fluxes are computed using data-constrained terrestrial biosphere models and physical ocean models, driven by atmospheric observations and assimilating ocean-color information. Use of two estimates provides a measure of uncertainty in the fluxes. Along with inventories of other emissions, these data-derived fluxes are used in transport models to assess their consistency with atmospheric CO2 observations. Closure is achieved by using a four-dimensional data assimilation (inverse) approach that adjusts the terrestrial biosphere fluxes to make them consistent with the atmospheric CO2 observations. Results will be shown, illustrating the year-to-year variations in land biospheric and oceanic fluxes computed in the FPP. The signals of these surface-flux variations on atmospheric CO2 will be isolated using forward modeling tools, which also incorporate estimates of transport error. The results will be discussed in the context of interannual variability of observed atmospheric CO2 distributions.

A simple hydrologically based model of land surface water and energy fluxes for general circulation models

NASA Technical Reports Server (NTRS)

Liang, XU; Lettenmaier, Dennis P.; Wood, Eric F.; Burges, Stephen J.

1994-01-01

A generalization of the single soil layer variable infiltration capacity (VIC) land surface hydrological model previously implemented in the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation model (GCM) is described. The new model is comprised of a two-layer characterization of the soil column, and uses an aerodynamic representation of the latent and sensible heat fluxes at the land surface. The infiltration algorithm for the upper layer is essentially the same as for the single layer VIC model, while the lower layer drainage formulation is of the form previously implemented in the Max-Planck-Institut GCM. The model partitions the area of interest (e.g., grid cell) into multiple land surface cover types; for each land cover type the fraction of roots in the upper and lower zone is specified. Evapotranspiration consists of three components: canopy evaporation, evaporation from bare soils, and transpiration, which is represented using a canopy and architectural resistance formulation. Once the latent heat flux has been computed, the surface energy balance is iterated to solve for the land surface temperature at each time step. The model was tested using long-term hydrologic and climatological data for Kings Creek, Kansas to estimate and validate the hydrological parameters, and surface flux data from three First International Satellite Land Surface Climatology Project Field Experiment (FIFE) intensive field campaigns in the summer-fall of 1987 to validate the surface energy fluxes.

Seasonal cycle of oceanic mixed layer and upper-ocean heat fluxes in the Mediterranean Sea from in-situ observations.

NASA Astrophysics Data System (ADS)

Houpert, Loïc; Testor, Pierre; Durrieu de Madron, Xavier; Estournel, Claude; D'Ortenzio, Fabrizio

2013-04-01

Heat fluxes across the ocean-atmosphere interface play a crucial role in the upper turbulent mixing. The depth reached by this turbulent mixing is indicated by an homogenization of seawater properties in the surface layer, and is defined as the Mixed Layer Depth (MLD). The thickness of the mixed layer determines also the heat content of the layer that directly interacts with the atmosphere. The seasonal variability of these air-sea fluxes is crucial in the calculation of heat budget. An improvement in the estimate of these fluxes is needed for a better understanding of the Mediterranean ocean circulation and climate, in particular in Regional Climate Models. There are few estimations of surface heat fluxes based on oceanic observations in the Mediterranean, and none of them are based on mixed layer observations. So, we proposed here new estimations of these upper-ocean heat fluxes based on mixed layer. We present high resolution Mediterranean climatology (0.5°) of the mean MLD based on a comprehensive collection of temperature profiles of last 43 years (1969-2012). The database includes more than 150,000 profiles, merging CTD, XBT, ARGO Profiling floats, and gliders observations. This dataset is first used to describe the seasonal cycle of the mixed layer depth on the whole Mediterranean on a monthly climatological basis. Our analysis discriminates several regions with coherent behaviors, in particular the deep water formation sites, characterized by significant differences in the winter mixing intensity. Heat storage rates (HSR) were calculated as the time rate of change of the heat content integrated from the surface down to a specific depth that is defined as the MLD plus an integration constant. Monthly climatology of net heat flux (NHF) from ERA-Interim reanalysis was balanced by the 1°x1° resolution heat storage rate climatology. Local heat budget balance and seasonal variability in the horizontal heat flux are then discussed by taking into account uncertainties, due to errors in monthly value estimation and to intra-annual and inter-annual variability.

The spontaneous concentration of magnetic field in the photosphere of the sun

NASA Technical Reports Server (NTRS)

Parker, E. N.

1981-01-01

The basic physics of magnetic flux tubes in the solar photosphere is reviewed, with areas still open to conjecture pointed out. The question of the concentration of individual small flux tubes to levels of 1-2 kilogauss, when the average solar surface magnetic field is on the order of 10 gauss, by processes of twisting and the formation of flux ropes made up of tubes wound around each other is considered together with the effects of turbulence on the flux tube. Mechanisms for tube compression by the evacuation of the gas contained within a flux tube are then examined, and the possibility of field concentration through the cooling of the gas within the tube in a superadiabatic process is suggested. Attention is then given to possible mechanisms serving to maintain the concentration of flux tubes far below the surface of the sun which gives rise to sunspots and pores as the flux tree emerges through the surface.

An analytical formalism accounting for clouds and other `surfaces' for exoplanet transmission spectroscopy

NASA Astrophysics Data System (ADS)

Bétrémieux, Yan; Swain, Mark R.

2017-05-01

Although the formalism of Lecavelier des Etangs et al. is extremely useful to understand what shapes transmission spectra of exoplanets, it does not include the effects of a sharp change in flux with altitude generally associated with surfaces and optically thick clouds. Recent advances in understanding the effects of refraction in exoplanet transmission spectra have, however, demonstrated that even clear thick atmospheres have such a sharp change in flux due to a refractive boundary. We derive a more widely applicable analytical formalism by including first-order effects from all these 'surfaces' to compute an exoplanet's effective radius, effective atmospheric thickness and spectral modulation for an atmosphere with a constant scaleheight. We show that the effective radius cannot be located below these 'surfaces' and that our formalism matches the formalism of Lecavelier des Etangs et al. in the case of a clear atmosphere. Our formalism explains why clouds and refraction reduce the contrast of spectral features, and why refraction decreases the Rayleigh scattering slope as wavelength increases, but also shows that these are common effects of all 'surfaces'. We introduce the concept of a 'surface' cross-section, the minimum mean cross-section that can be observed, as an index to characterize the location of 'surfaces' and provide a simple method to estimate their effects on the spectral modulation of homogeneous atmospheres. We finally devise a numerical recipe that extends our formalism to atmospheres with a non-constant scaleheight and arbitrary sources of opacity, a potentially necessary step to interpret observations.

Resolving Magnetic Flux Patches at the Surface of the Core

NASA Technical Reports Server (NTRS)

OBrien, Michael S.

1996-01-01

The geomagnetic field at a given epoch can be used to partition the surface of the liquid outer core into a finite number of contiguous regions in which the radial component of the magnetic flux density, B (sub r), is of one sign. These flux patches are instrumental in providing detail to surface fluid flows inferred from the changing geomagnetic field and in evaluating the validity of the frozen-flux approximation on which such inferences rely. Most of the flux patches in models of the modem field are small and enclose little flux compared to the total unsigned flux emanating from the core. To demonstrate that such patches are not required to explain the most spatially complete and accurate data presently available, those from the Magsat mission, I have constructed a smooth core field model that fits the Magsat data but does not possess small flux patches. I conclude that our present knowledge of the geomagnetic field does not allow us to resolve these features reliably at the core-mantle boundary; thus we possess less information about core flow than previously believed.

Downwelling Longwave Fluxes at Continental Surfaces-A Comparison of Observations with GCM Simulations and Implications for the Global Land-Surface Radiation Budget.

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Prata, A. J.

1996-03-01

Previous work suggests that general circulation (global climate) models have excess net radiation at land surfaces, apparently due to overestimates in downwelling shortwave flux and underestimates in upwelling long-wave flux. Part of this excess, however, may be compensated for by an underestimate in downwelling longwave flux. Long term observations of the downwelling longwave component at several land stations in Europe, the United States, Australia, and Antarctica suggest that climate models (four are used, as in previous studies) underestimate this flux component on an annual basis by up to 10 W m2, yet with low statistical significance. It is probable that the known underestimate in boundary-layer air temperature contributes to this, as would low model cloudiness and neglect of minor gases such as methane, nitrogen oxide, and the freons. The bias in downwelling longwave flux, together with those found earlier for downwelling shortwave and upwlling long-wave fluxes, are consistent with the model bias found previously for net radiation. All annually averaged fluxes and biases are deduced for global land as a whole.

Nitrous acid formation in a snow-free wintertime polluted rural area

NASA Astrophysics Data System (ADS)

Tsai, Catalina; Spolaor, Max; Fedele Colosimo, Santo; Pikelnaya, Olga; Cheung, Ross; Williams, Eric; Gilman, Jessica B.; Lerner, Brian M.; Zamora, Robert J.; Warneke, Carsten; Roberts, James M.; Ahmadov, Ravan; de Gouw, Joost; Bates, Timothy; Quinn, Patricia K.; Stutz, Jochen

2018-02-01

Nitrous acid (HONO) photolysis is an important source of hydroxyl radicals (OH) in the lower atmosphere, in particular in winter when other OH sources are less efficient. The nighttime formation of HONO and its photolysis in the early morning have long been recognized as an important contributor to the OH budget in polluted environments. Over the past few decades it has become clear that the formation of HONO during the day is an even larger contributor to the OH budget and additionally provides a pathway to recycle NOx. Despite the recognition of this unidentified HONO daytime source, the precise chemical mechanism remains elusive. A number of mechanisms have been proposed, including gas-phase, aerosol, and ground surface processes, to explain the elevated levels of daytime HONO. To identify the likely HONO formation mechanisms in a wintertime polluted rural environment we present LP-DOAS observations of HONO, NO2, and O3 on three absorption paths that cover altitude intervals from 2 to 31, 45, and 68 m above ground level (a.g.l.) during the UBWOS 2012 experiment in the Uintah Basin, Utah, USA. Daytime HONO mixing ratios in the 2-31 m height interval were, on average, 78 ppt, which is lower than HONO levels measured in most polluted urban environments with similar NO2 mixing ratios of 1-2 ppb. HONO surface fluxes at 19 m a.g.l., calculated using the HONO gradients from the LP-DOAS and measured eddy diffusivity coefficient, show clear upward fluxes. The hourly average vertical HONO flux during sunny days followed solar irradiance, with a maximum of (4.9 ± 0.2) × 1010 molec. cm-2 s-1 at noontime. A photostationary state analysis of the HONO budget shows that the surface flux closes the HONO budget, accounting for 63 ± 32 % of the unidentified HONO daytime source throughout the day and 90 ± 30 % near noontime. This is also supported by 1-D chemistry and transport model calculations that include the measured surface flux, thus clearly identifying chemistry at the ground as the missing daytime HONO source in this environment. Comparison between HONO surface flux, solar radiation, NO2 and HNO3 mixing ratios, and results from 1-D model runs suggest that, under high NOx conditions, HONO formation mechanisms related to solar radiation and NO2 mixing ratios, such as photo-enhanced conversion of NO2 on the ground, are most likely the source of daytime HONO. Under moderate to low NO2 conditions, photolysis of HNO3 on the ground seems to be the main source of HONO.

Stair-Step Particle Flux Spectra on the Lunar Surface: Evidence for Nonmonotonic Potentials?

NASA Technical Reports Server (NTRS)

Collier, Michael R.; Newheart, Anastasia; Poppe, Andrew R.; Hills, H. Kent; Farrell, William M.

2016-01-01

We present examples of unusual "stair-step" differential flux spectra observed by the Apollo 14 Suprathermal Ion Detector Experiment on the lunar dayside surface in Earth's magnetotail. These spectra exhibit a relatively constant differential flux below some cutoff energy and then drop off precipitously, by about an order of magnitude or more, at higher energies. We propose that these spectra result from photoions accelerated on the lunar dayside by nonmonotonic potentials (i.e.,potentials that do not decay to zero monotonically) and present a model for the expected differential flux. The energy of the cutoff and the magnitude of the differential flux are related to the properties of the local space environment and are consistent with the observed flux spectra. If this interpretation is correct, these surface-based ion observations provide a unique perspective that both complements and enhances the conclusions obtained by remote-sensing orbiter observations on the Moon's exospheric and electrostatic properties.

Vadose zone controls on damping of climate-induced transient recharge fluxes in U.S. agroecosystems

NASA Astrophysics Data System (ADS)

Gurdak, Jason

2017-04-01

Understanding the physical processes in the vadose zone that link climate variability with transient recharge fluxes has particular relevance for the sustainability of groundwater-supported irrigated agriculture and other groundwater-dependent ecosystems. Natural climate variability on interannual to multidecadal timescales has well-documented influence on precipitation, evapotranspiration, soil moisture, infiltration flux, and can augment or diminish human stresses on water resources. Here the behavior and damping depth of climate-induced transient water flux in the vadose zone is explored. The damping depth is the depth in the vadose zone that the flux variation damps to 5% of the land surface variation. Steady-state recharge occurs when the damping depth is above the water table, and transient recharge occurs when the damping depth is below the water table. Findings are presented from major agroecosystems of the United States (U.S.), including the High Plains, Central Valley, California Coastal Basin, and Mississippi Embayment aquifer systems. Singular spectrum analysis (SSA) is used to identify quasi-periodic signals in precipitation and groundwater time series that are coincident with the Arctic Oscillation (AO) (6-12 mo cycle), Pacific/North American oscillation (PNA) (<1-4 yr cycle), El Niño/Southern Oscillation (ENSO) (2-7 yr cycle), North Atlantic Oscillation (NAO) (3-6 yr cycle), Pacific Decadal Oscillation (PDO) (15-30 yr cycle), and Atlantic Multidecadal Oscillation (AMO) (50-70 yr cycle). SSA results indicate that nearly all of the quasi-periodic signals in the precipitation and groundwater levels have a statistically significant lag correlation (95% confidence interval) with the AO, PNA, ENSO, NAO, PDO, and AMO indices. Results from HYDRUS-1D simulations indicate that transient water flux through the vadose zone are controlled by highly nonlinear interactions between mean infiltration flux and infiltration period related to the modes of climate variability and the local soil textures, layering, and depth to the water table. Simulation results for homogeneous profiles generally show that shorter-period climate oscillations, smaller mean fluxes, and finer-grained soil textures generally produce damping depths closer to land surface. Simulation results for layered soil textures indicate more complex responses in the damping depth, including the finding that finer-textured layers in a coarser soil profile generally result in damping depths closer to land surface, while coarser-textured layers in coarser soil profile result in damping depths deeper in the vadose zone. Findings from this study improve understanding of how vadose zone properties influences transient recharge flux and damp climate variability signals in groundwater systems, and have important implications for sustainable management of groundwater resources and coupled agroecosystems under future climate variability and change.

The Evolution of the Solar Magnetic Field: A Comparative Analysis of Two Models

NASA Astrophysics Data System (ADS)

McMichael, K. D.; Karak, B. B.; Upton, L.; Miesch, M. S.; Vierkens, O.

2017-12-01

Understanding the complexity of the solar magnetic cycle is a task that has plagued scientists for decades. However, with the help of computer simulations, we have begun to gain more insight into possible solutions to the plethora of questions inside the Sun. STABLE (Surface Transport and Babcock Leighton) is a newly developed 3D dynamo model that can reproduce features of the solar cycle. In this model, the tilted bipolar sunspots are formed on the surface (based on the toroidal field at the bottom of the convection zone) and then decay and disperse, producing the poloidal field. Since STABLE is a 3D model, it is able to solve the full induction equation in the entirety of the solar convection zone as well as incorporate many free parameters (such as spot depth and turbulent diffusion) which are difficult to observe. In an attempt to constrain some of these free parameters, we compare STABLE to a surface flux transport model called AFT (Advective Flux Transport) which solves the radial component of the magnetic field on the solar surface. AFT is a state-of-the-art surface flux transport model that has a proven record of being able to reproduce solar observations with great accuracy. In this project, we implement synthetic bipolar sunspots into both models, using identical surface parameters, and run the models for comparison. We demonstrate that the 3D structure of the sunspots in the interior and the vertical diffusion of the sunspot magnetic field play an important role in establishing the surface magnetic field in STABLE. We found that when a sufficient amount of downward magnetic pumping is included in STABLE, the surface magnetic field from this model becomes insensitive to the internal structure of the sunspot and more consistent with that of AFT.

A Fundamental Study of Nucleate Pool Boiling Under Microgravity

NASA Technical Reports Server (NTRS)

Ervin, Jamie S.; Merte, Herman, Jr.

1996-01-01

An experimental study of incipient boiling in short-term microgravity and with a/g = +/- 1 for pool boiling was performed. Calibrated thin gold films sputtered on a smoothly polished quartz surface were used simultaneously for thermal-resistance measurements and heating of the boiling surface. The gold films were used for both transient and quasi-steady heating surface temperature measurements. Two test vessels were constructed for precise measurement and control of fluid temperature and pressure: a laboratory pool boiling vessel for the a/g = +/- 1 experiments and a pool boiling vessel designed for the 131 m free-fall in the NASA Lewis Research Center Microgravity Research Facility for the microgravity tests. Measurements included the heater surface temperature, the pressure near the heating surface, the bulk liquid temperatures. High speed photography (up to 1,000 frames per second) was used in the experiments. With high quality microgravity and the measured initial temperature of the quiescent test fluid, R113, the temperature distribution in the liquid at the moment of boiling inception resulting from an imposed step in heat flux is known with a certainty not possible previously. The types of boiling propagation across the large flat heating surface, some observed here for the first time, are categorized; the conditions necessary for their occurrence are described. Explosive boiling propagation with a striking pattern of small scale protuberances over the entire vapor mass periphery not observed previously at low heat flux levels (on the order of 5 W/cm(exp 2)) is described. For the heater surface with a/g = -1, a step in the heater surface temperature of short duration was imposed. The resulting liquid temperature distribution at the moment of boiling inception was different from that obtained with a step in heat flux.

FLASH_SSF_Aqua-FM3-MODIS_Version3C

Atmospheric Science Data Center

2018-04-04

... Tool:  CERES Order Tool  (netCDF) Subset Data:  CERES Search and Subset Tool (HDF4 & netCDF) ... Cloud Layer Area Cloud Infared Emissivity Cloud Base Pressure Surface (Radiative) Flux TOA Flux Surface Types TOT ... Radiance SW Filtered Radiance LW Flux Order Data:  Earthdata Search:  Order Data Guide Documents:  ...

FLASH_SSF_Terra-FM1-MODIS_Version3C

Atmospheric Science Data Center

2018-04-04

... Tool:  CERES Order Tool  (netCDF) Subset Data:  CERES Search and Subset Tool (HDF4 & netCDF) ... Cloud Layer Area Cloud Infrared Emissivity Cloud Base Pressure Surface (Radiative) Flux TOA Flux Surface Types TOT ... Radiance SW Filtered Radiance LW Flux Order Data:  Earthdata Search:  Order Data Guide Documents:  ...

Flux Meter Assesses the Effects of Groundwater, Surface Water, and Contaminated Sediment Interactions on Ecosystems

EPA Science Inventory

The slow flow of water between groundwater (GW) and surface water (SW) is often referred to as seepage, or in scientific terms, advective flux. This slow flow at the GW/SW interface presents measurement difficulties. This project was conducted to develop a durable advective flux ...

Application of the Combination Approach for Estimating Evapotranspiration in Puerto Rico

NASA Technical Reports Server (NTRS)

Harmsen, Eric; Luvall, Jeffrey; Gonzalez, Jorge

2005-01-01

The ability to estimate short-term fluxes of water vapor from the land surface is important for validating latent heat flux estimates from high resolution remote sensing techniques. A new, relatively inexpensive method is presented for estimating t h e ground-based values of the surface latent heat flux or evapotranspiration.

Heat flux estimates over vegetation derived using radiometric surface temperatures and a boundary layer model in comparison with sodar-derived values. M.S. Thesis; [Rock Springs Agricultural Research Center, Pennsylvania

NASA Technical Reports Server (NTRS)

Cooper, J. N. (Principal Investigator)

1981-01-01

An attempt was made to validate a method that uses radiometric surface temperatures and a boundary layer model to estimate surface energy budgets and characteristics. Surface temperatures from a hand-held radiometer and sodar data were collected simultaneously on seven days between mid-July and mid-October 1980. The comparison of the RDMS and sodar heat fluxes proved disappointing. Free convection conditions, required to produce sodar-derived heat fluxes, were inhibited by a terrain-induced low level inversion. Only three out of seven cases produced meaningful sodar heat fluxes. Of those three cases, one had good agreement and the other two had sodar heat fluxes 15 to 45 w/sq m lower than the RDMS values. Since the RDMS method is relatively untested, it was impossible to conclusively determine its validity from the results. There was evidence that the true heat flux was not underestimated by the RDMS, so it could be concluded that the Bowen ratios over well-watered vegetation were likely to be quite small.

Mass loading of the Earth's magnetosphere by micron size lunar ejecta. 1: Ejecta production and orbital dynamics in cislunar space

NASA Technical Reports Server (NTRS)

Alexander, W. M.; Tanner, W. G.; Anz, P. D.; Chen, A. L.

1986-01-01

Particulate matter possessing lunar escape velocity sufficient to enhance the cislunar meteroid flux was investigated. While the interplanetary flux was extensively studied, lunar ejecta created by the impact of this material on the lunar surface is only now being studied. Two recently reported flux models are employed to calculate the total mass impacting the lunar surface due to sporadic meteor flux. There is ample evidence to support the contention that the sporadic interplanetary meteoroid flux enhances the meteroid flux of cislunar space through the creation of micron and submicron lunar ejecta with lunar escape velocity.

Flux-fusion anomaly test and bosonic topological crystalline insulators

DOE PAGES

Hermele, Michael; Chen, Xie

2016-10-13

Here, we introduce a method, dubbed the flux-fusion anomaly test, to detect certain anomalous symmetry fractionalization patterns in two-dimensional symmetry-enriched topological (SET) phases. We focus on bosonic systems with Z2 topological order and a symmetry group of the form G=U(1)xG', where G' is an arbitrary group that may include spatial symmetries and/or time reversal. The anomalous fractionalization patterns we identify cannot occur in strictly d=2 systems but can occur at surfaces of d=3 symmetry-protected topological (SPT) phases. This observation leads to examples of d=3 bosonic topological crystalline insulators (TCIs) that, to our knowledge, have not previously been identified. In somemore » cases, these d=3 bosonic TCIs can have an anomalous superfluid at the surface, which is characterized by nontrivial projective transformations of the superfluid vortices under symmetry. The basic idea of our anomaly test is to introduce fluxes of the U(1) symmetry and to show that some fractionalization patterns cannot be extended to a consistent action of G' symmetry on the fluxes. For some anomalies, this can be described in terms of dimensional reduction to d=1 SPT phases. We apply our method to several different symmetry groups with nontrivial anomalies, including G=U(1)×Z T 2 and G=U(1)×Z P 2, where Z T 2 and Z P 2 are time-reversal and d=2 reflection symmetry, respectively.« less

Multi-Scale Observation and Modelling of Energy and Matter Exchange in the Atmospheric Boundary-Layer (ScaleX Campaigns)

NASA Astrophysics Data System (ADS)

Zeeman, M. J.; Wolz, K.; Adler, B.; Brenner, C.; De Roo, F.; Emeis, S.; Kalthoff, N.; Mauder, M.; Schäfer, K.; Wohlfahrt, G.; Zhao, P.

2016-12-01

We investigated biosphere-atmosphere exchange processes in relation to the atmospheric boundary-layer (ABL) flow in a shallow valley. Land-use heterogeneity and topography can force local atmospheric flow patterns, including local circulations. Such flow patterns can impair current techniques for the quantification and source attribution of surface-exchange fluxes due to flux-divergence, advection and decoupling. Wind field, temperature and humidity structures in the ABL were observed in high resolution with spatially distributed observations in a 1 km3 experimental domain. Remote-sensing observations of wind, temperature and particles in the ABL (Raman-lidar; RASS; ceilometer; microwave radiometer; 3D Doppler-lidar) were combined with a high-resolution network of in-situ observations that included vertical and horizontal profiles of wind, temperature, carbon dioxide, methane and water vapor concentrations. The experiments were co-located with the long-term eddy covariance (EC) observatory Fendt (DE-Fen; ICOS, TERENO) and were part of international cooperative efforts in 2015 and 2016 (the ScaleX campaigns). The gathered experimental data offers a scale-transcending insight in local flow patterns in mountainous terrain and their influence on surface-exchange fluxes of energy and matter as observed by EC and flux-gradient methodology. In addition, the data is used for validation of Large-Eddy Simulations in complex terrain using PALM-LES. Within this modelling framework, virtual measurements are conducted to further assess the importance of three-dimensional advective and horizontal turbulent transport terms.

The Joint UK Land Environment Simulator (JULES), model description - Part 2: Carbon fluxes and vegetation dynamics

NASA Astrophysics Data System (ADS)

Clark, D. B.; Mercado, L. M.; Sitch, S.; Jones, C. D.; Gedney, N.; Best, M. J.; Pryor, M.; Rooney, G. G.; Essery, R. L. H.; Blyth, E.; Boucher, O.; Harding, R. J.; Huntingford, C.; Cox, P. M.

2011-09-01

The Joint UK Land Environment Simulator (JULES) is a process-based model that simulates the fluxes of carbon, water, energy and momentum between the land surface and the atmosphere. Many studies have demonstrated the important role of the land surface in the functioning of the Earth System. Different versions of JULES have been employed to quantify the effects on the land carbon sink of climate change, increasing atmospheric carbon dioxide concentrations, changing atmospheric aerosols and tropospheric ozone, and the response of methane emissions from wetlands to climate change. This paper describes the consolidation of these advances in the modelling of carbon fluxes and stores, in both the vegetation and soil, in version 2.2 of JULES. Features include a multi-layer canopy scheme for light interception, including a sunfleck penetration scheme, a coupled scheme of leaf photosynthesis and stomatal conductance, representation of the effects of ozone on leaf physiology, and a description of methane emissions from wetlands. JULES represents the carbon allocation, growth and population dynamics of five plant functional types. The turnover of carbon from living plant tissues is fed into a 4-pool soil carbon model. The process-based descriptions of key ecological processes and trace gas fluxes in JULES mean that this community model is well-suited for use in carbon cycle, climate change and impacts studies, either in standalone mode or as the land component of a coupled Earth system model.

Applications of HCMM satellite data to the study of urban heating patterns

NASA Technical Reports Server (NTRS)

Carlson, T. N. (Principal Investigator)

1980-01-01

A research summary is presented and is divided into two major areas, one developmental and the other basic science. In the first three sub-categories are discussed: image processing techniques, especially the method whereby surface temperature image are converted to images of surface energy budget, moisture availability and thermal inertia; model development; and model verification. Basic science includes the use of a method to further the understanding of the urban heat island and anthropogenic modification of the surface heating, evaporation over vegetated surfaces, and the effect of surface heat flux on plume spread.