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Journal articles on the topic 'Surface fluxes'

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Published: 4 June 2021
Last updated: 6 September 2023

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1

Costa, Vladimir Santos da, and Afonso De Moraes Paiva. "THE IMPACT OF SURFACE HEAT FLUXES ON THE SIMULATION OF THE BRAZIL CURRENT." Revista Brasileira de Geofísica 31, no. 2 (June 1, 2013): 307. http://dx.doi.org/10.22564/rbgf.v31i2.296.

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ABSTRACT. The impact of different formulations of surface heat fluxes (no fluxes, climatological fluxes, restoring of SST towards climatology, climatological fluxes plus SST restoring, and model-computed fluxes via bulk formulas) on the modeling of the Brazil Current is investigated in numerical simulations performed with the Regional Ocean Model (ROMS). While mechanical forcing may be dominant, it is shown that correct upper ocean currents and thermal structure can only be obtained when heat fluxes are implemented, even in regions of strong horizontal advection, and that some form of feedback of the ocean state upon the fluxes is also a necessary condition. This results are of particular importance for ocean modeling developed having operational oceanography in view. Keywords: Brazil Current, surface heat flux, numerical modeling. RESUMO. O impacto de diferentes formulações dos fluxos de calor em superfície (sem fluxos, fluxos climatológicos, relaxamento de TSM para climatologia, fluxos climatológicos mais relaxamento de TSM e fluxos calculados pelo modelo com “bulk formulas”) sobre a modelagem da Corrente do Brasil é investigado em simulações numéricas com o Regional Ocean Model (ROMS). Apesar da forçante mecânica ser dominante, mostra-se que uma correta representação de correntes e da estrutura térmica nas camadas superiores do oceano somente são possíveis quando fluxos de calor são implementados e que algum tipo de retroalimentação da TSM sobre os fluxos é também necessária. Estes resultados são particularmente importantes na modelagem voltada para a oceanografia operacional. Palavras-chave: Corrente do Brasil, fluxos superficial de calor, modelagem numérica.
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2

Su, Z., H. Pelgrum, and M. Menenti. "Aggregation effects of surface heterogeneity in land surface processes." Hydrology and Earth System Sciences 3, no. 4 (December 31, 1999): 549–63. http://dx.doi.org/10.5194/hess-3-549-1999.

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Abstract. In order to investigate the aggregation effects of surface heterogeneity in land surface processes we have adapted a theory of aggregation. Two strategies have been adopted: 1) Aggregation of radiative fluxes. The aggregated radiative fluxes are used to derive input parameters that are then used to calculate the aerodynamic fluxes at different aggregation levels. This is equivalent to observing the same area at different resolutions using a certain remote sensor, and then calculating the aerodynamic fluxes correspondingly. 2) Aggregation of aerodynamic fluxes calculated at the original observation scale to different aggregation levels. A case study has been conducted to identify the effects of aggregation on areal estimates of sensible and latent heat fluxes. The length scales of surface variables in heterogeneous landscapes are estimated by means of wavelet analysis.
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3

Mahrt, L. "Grid-Averaged Surface Fluxes." Monthly Weather Review 115, no. 8 (August 1987): 1550–60. http://dx.doi.org/10.1175/1520-0493(1987)115<1550:gasf>2.0.co;2.

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4

Martin, Eric, and Yves Lejeune. "Turbulent fluxes above the snow surface." Annals of Glaciology 26 (1998): 179–83. http://dx.doi.org/10.1017/s0260305500014774.

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Measurements of sensible- and latent-heat fluxes under stable conditions are rare. In order to obtain indirect measurements of turbulent fluxes, meteorological data measured at the Col de Porte laboratory (1320 m a.s.l, France) under very stable conditions (cold, clear night with low wind) are used. The radiative fluxes are measured, the conduction within the snowpack is calculated using the snow modelCrocusand the turbulent fluxes are determined as a residual term of the surface-energy balance equation. These data were used to fit a new parameterization of the turbulent fluxes for the snow model. The turbulent fluxes are increased as compared to the theory.Crocuswas also applied to the data from the LEADEX92 experiment and the turbulent fluxes calculated by the model were compared to the fluxes measured using sonic anemometers/thermometers on the site.
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5

Martin, Eric, and Yves Lejeune. "Turbulent fluxes above the snow surface." Annals of Glaciology 26 (1998): 179–83. http://dx.doi.org/10.3189/1998aog26-1-179-183.

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Measurements of sensible- and latent-heat fluxes under stable conditions are rare. In order to obtain indirect measurements of turbulent fluxes, meteorological data measured at the Col de Porte laboratory (1320 m a.s.l, France) under very stable conditions (cold, clear night with low wind) are used. The radiative fluxes are measured, the conduction within the snowpack is calculated using the snow model Crocus and the turbulent fluxes are determined as a residual term of the surface-energy balance equation. These data were used to fit a new parameterization of the turbulent fluxes for the snow model. The turbulent fluxes are increased as compared to the theory. Crocus was also applied to the data from the LEADEX92 experiment and the turbulent fluxes calculated by the model were compared to the fluxes measured using sonic anemometers/thermometers on the site.
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6

Xin, X., and Q. Liu. "The two-layer surface energy balance parameterization scheme (TSEBPS) for estimation of land surface heat fluxes." Hydrology and Earth System Sciences Discussions 6, no. 6 (November 4, 2009): 6795–832. http://dx.doi.org/10.5194/hessd-6-6795-2009.

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Abstract. A Two-layer Surface Energy Balance Parameterization Scheme (TSEBPS) is proposed for the estimation of surface heat fluxes using thermal infrared (TIR) data over sparsely vegetated surfaces. TSEBPS is based on the theory of the classical two-layer energy balance model, as well as a set of new formulations derived from assumption of the energy balance at limiting cases. Two experimental data sets are used to assess the reliabilities of TSEBPS. Based on these case studies, TSEBPS has proven to be capable of estimating heat fluxes at vegetation surfaces with acceptable accuracy. The uncertainties in the estimated heat fluxes are comparable to in-situ measurement uncertainties.
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7

Xin, X., and Q. Liu. "The Two-layer Surface Energy Balance Parameterization Scheme (TSEBPS) for estimation of land surface heat fluxes." Hydrology and Earth System Sciences 14, no. 3 (March 12, 2010): 491–504. http://dx.doi.org/10.5194/hess-14-491-2010.

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Abstract. A Two-layer Surface Energy Balance Parameterization Scheme (TSEBPS) is proposed for the estimation of surface heat fluxes using Thermal Infrared (TIR) data over sparsely vegetated surfaces. TSEBPS is based on the theory of the classical two-layer energy balance model, as well as a set of new formulations derived from assumption of the energy balance at limiting cases. Two experimental data sets are used to assess the reliabilities of TSEBPS. Based on these case studies, TSEBPS has proven to be capable of estimating heat fluxes at vegetation surfaces with acceptable accuracy. The uncertainties in the estimated heat fluxes are comparable to in-situ measurement uncertainties.
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8

Egger, Joseph, Klaus-Peter Hoinka, and Thomas Spengler. "Aspects of Potential Vorticity Fluxes: Climatology and Impermeability." Journal of the Atmospheric Sciences 72, no. 8 (August 1, 2015): 3257–67. http://dx.doi.org/10.1175/jas-d-14-0196.1.

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Abstract Some aspects of the dynamics of generalized potential vorticity (PV) density P = ω ⋅ ∇χ are discussed with the main emphasis on P fluxes, where ωa is absolute vorticity and χ is a scalar. The impermeability theorem claims that there is no net P flux across a χ surface. Various forms of the flux are presented that mostly cross χ surfaces. As these fluxes are as dynamically relevant as the one chosen for the theorem, P fluxes through a surface element are inherently multivalued and there is no best choice on physical grounds. Nevertheless, the net P flux is unique for closed surfaces. This point is illustrated by P integrals over the volume between the earth’s surface and an isentropic surface. Reanalysis data are used to present mean advective and some nonadvective P fluxes for χ = θ in height coordinates. The extratropical tropopause appears to be supported by advective P fluxes. A satisfactorily closed P budget cannot, however, be presented.
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9

Kleidon, Axel, and Maik Renner. "An explanation for the different climate sensitivities of land and ocean surfaces based on the diurnal cycle." Earth System Dynamics 8, no. 3 (September 25, 2017): 849–64. http://dx.doi.org/10.5194/esd-8-849-2017.

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Abstract. Observations and climate model simulations consistently show a higher climate sensitivity of land surfaces compared to ocean surfaces. Here we show that this difference in temperature sensitivity can be explained by the different means by which the diurnal variation in solar radiation is buffered. While ocean surfaces buffer the diurnal variations by heat storage changes below the surface, land surfaces buffer it mostly by heat storage changes above the surface in the lower atmosphere that are reflected in the diurnal growth of a convective boundary layer. Storage changes below the surface allow the ocean surface–atmosphere system to maintain turbulent fluxes over day and night, while the land surface–atmosphere system maintains turbulent fluxes only during the daytime hours, when the surface is heated by absorption of solar radiation. This shorter duration of turbulent fluxes on land results in a greater sensitivity of the land surface–atmosphere system to changes in the greenhouse forcing because nighttime temperatures are shaped by radiative exchange only, which are more sensitive to changes in greenhouse forcing. We use a simple, analytic energy balance model of the surface–atmosphere system in which turbulent fluxes are constrained by the maximum power limit to estimate the effects of these different means to buffer the diurnal cycle on the resulting temperature sensitivities. The model predicts that land surfaces have a 50 % greater climate sensitivity than ocean surfaces, and that the nighttime temperatures on land increase about twice as much as daytime temperatures because of the absence of turbulent fluxes at night. Both predictions compare very well with observations and CMIP5 climate model simulations. Hence, the greater climate sensitivity of land surfaces can be explained by its buffering of diurnal variations in solar radiation in the lower atmosphere.
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10

Fraser, A., P. I. Palmer, L. Feng, H. Boesch, A. Cogan, R. Parker, E. J. Dlugokencky, et al. "Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements." Atmospheric Chemistry and Physics Discussions 12, no. 12 (December 3, 2012): 30989–1030. http://dx.doi.org/10.5194/acpd-12-30989-2012.

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Abstract. 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 &amp;pm; 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).
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11

Fraser, A., P. I. Palmer, L. Feng, H. Boesch, A. Cogan, R. Parker, E. J. Dlugokencky, et al. "Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements." Atmospheric Chemistry and Physics 13, no. 11 (June 13, 2013): 5697–713. http://dx.doi.org/10.5194/acp-13-5697-2013.

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Abstract. 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).
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12

Lansø, Anne Sofie, Thomas Luke Smallman, Jesper Heile Christensen, Mathew Williams, Kim Pilegaard, Lise-Lotte Sørensen, and Camilla Geels. "Simulating the atmospheric CO<sub>2</sub> concentration across the heterogeneous landscape of Denmark using a coupled atmosphere–biosphere mesoscale model system." Biogeosciences 16, no. 7 (April 10, 2019): 1505–24. http://dx.doi.org/10.5194/bg-16-1505-2019.

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Abstract. Although coastal regions only amount to 7 % of the global oceans, their contribution to the global oceanic air–sea CO2 exchange is proportionally larger, with fluxes in some estuaries being similar in magnitude to terrestrial surface fluxes of CO2. Across a heterogeneous surface consisting of a coastal marginal sea with estuarine properties and varied land mosaics, the surface fluxes of CO2 from both marine areas and terrestrial surfaces were investigated in this study together with their impact in atmospheric CO2 concentrations by the usage of a high-resolution modelling framework. The simulated terrestrial fluxes across the study region of Denmark experienced an east–west gradient corresponding to the distribution of the land cover classification, their biological activity and the urbanised areas. Annually, the Danish terrestrial surface had an uptake of approximately −7000 GgC yr−1. While the marine fluxes from the North Sea and the Danish inner waters were smaller annually, with about −1800 and 1300 GgC yr−1, their sizes are comparable to annual terrestrial fluxes from individual land cover classifications in the study region and hence are not negligible. The contribution of terrestrial surfaces fluxes was easily detectable in both simulated and measured concentrations of atmospheric CO2 at the only tall tower site in the study region. Although, the tower is positioned next to Roskilde Fjord, the local marine impact was not distinguishable in the simulated concentrations. But the regional impact from the Danish inner waters and the Baltic Sea increased the atmospheric concentration by up to 0.5 ppm during the winter months.
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13

Cui, Wenhui, and Ting Fong May Chui. "Subsurface Lateral Heat Flux within the Heterogeneous Surface of a Subtropical Wetland and Its Potential Contribution to Energy Imbalance." Journal of Hydrometeorology 18, no. 12 (November 30, 2017): 3125–44. http://dx.doi.org/10.1175/jhm-d-17-0006.1.

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Abstract In the eddy covariance technique, lateral heat fluxes in the atmosphere, surfaces, and subsurfaces are often ignored under the assumption of a homogeneous surface. Among lateral heat fluxes, the surface and subsurface fluxes, which might affect the surface energy balance closure over a heterogeneous surface, are less studied. Many wetlands are heterogeneous, with a mix of vegetated areas and shallow open water. This study examined the subsurface lateral heat fluxes between a reed bed and the adjacent water of a subtropical wetland in Hong Kong, China. An array of temperature and water-level sensors was installed in the soil of the reed bed and in the adjacent water. An eddy covariance system was also set up on the reed bed. The subsurface lateral heat fluxes were largest close to the interface of the reed bed and water and decreased as the distance from the interface increased, as expected. However, the subsurface lateral heat fluxes could not account for the energy imbalance because their magnitudes were relatively small and fluctuated in phase with the energy budget residuals during the winter months. The uncertainties of the turbulent fluxes and the lateral heat fluxes were estimated to be 10%–20% and 10%–30%, respectively. This study explored another potential reason behind the energy imbalance of the eddy covariance technique. The results enhance the understanding of water and energy exchanges between a terrestrial biotope and the surrounding water, which might further generate insights into the biochemical processes in wetlands.
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14

Chen, Jiann-Mou, Yih-Chi Tan, and Chu-Hui Chen. "Multidimensional Infiltration with Arbitrary Surface Fluxes." Journal of Irrigation and Drainage Engineering 127, no. 6 (December 2001): 370–77. http://dx.doi.org/10.1061/(asce)0733-9437(2001)127:6(370).

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15

Howell, J. F., and J. Sun. "Surface-Layer Fluxes in Stable Conditions." Boundary-Layer Meteorology 90, no. 3 (March 1999): 495–520. http://dx.doi.org/10.1023/a:1001788515355.

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16

Zhou, Binbin, and Qin Xu. "Computing Surface Fluxes from Mesonet Data." Journal of Applied Meteorology 38, no. 9 (September 1999): 1370–83. http://dx.doi.org/10.1175/1520-0450(1999)038<1370:csffmd>2.0.co;2.

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17

Smirnov, Boris M. "Metal Fluxes from Surface and Plasma." Physica Scripta 64, no. 2 (August 1, 2001): 152–57. http://dx.doi.org/10.1238/physica.regular.064a00152.

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18

Qin, Huiling, and Hiroshi Kawamura. "Surface heat fluxes during hot events." Journal of Oceanography 65, no. 5 (October 2009): 605–13. http://dx.doi.org/10.1007/s10872-009-0051-7.

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19

Claussen, Martin. "Estimation of areally-averaged surface fluxes." Boundary-Layer Meteorology 54, no. 4 (March 1991): 387–410. http://dx.doi.org/10.1007/bf00118868.

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20

Akylas, E., M. Tombrou, D. Lalas, and S. S. Zilitinkevich. "Surface fluxes under shear-free convection." Quarterly Journal of the Royal Meteorological Society 127, no. 574 (April 2001): 1183–97. http://dx.doi.org/10.1002/qj.49712757403.

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21

Sun, Jielun, and L. Mahrt. "Determination of Surface Fluxes from the Surface Radiative Temperature." Journal of the Atmospheric Sciences 52, no. 8 (April 1995): 1096–106. http://dx.doi.org/10.1175/1520-0469(1995)052<1096:dosfft>2.0.co;2.

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22

Acosta, M., D. Janouš, and M. V Marek. "Soil surface CO2 fluxes in a Norway spruce stand." Journal of Forest Science 50, No. 12 (January 11, 2012): 573–78. http://dx.doi.org/10.17221/4659-jfs.

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The measurements of soil CO<sub>2</sub> efflux in a Norway spruce (Picea abies [L.] Karst.) forest stand are reported for a 6-month period (from May 1<sup>st</sup> to October 26<sup>th</sup> 1999). Forest floor CO<sub>2</sub> efflux was measured at four positions using a portable infra-red gas analyser (LI-COR), operating as a closed dynamic system and connected to a portable soil chamber. Soil CO<sub>2</sub> efflux was measured 3&ndash;4 times per month. Soil temperature at a depth of 5 cm was recorded during the whole period with an interval of ten minutes. An exponential regression was used to describe the relationship between soil temperature and soil CO<sub>2</sub> efflux. On the basis of this relationship Q<sub>10</sub> values were calculated. The averaged value of Q<sub>10</sub> for the studied Norway spruce forest stand was 3.74.
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23

Hoek van Dijke, Anne J., Kaniska Mallick, Martin Schlerf, Miriam Machwitz, Martin Herold, and Adriaan J. Teuling. "Examining the link between vegetation leaf area and land–atmosphere exchange of water, energy, and carbon fluxes using FLUXNET data." Biogeosciences 17, no. 17 (September 4, 2020): 4443–57. http://dx.doi.org/10.5194/bg-17-4443-2020.

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Abstract. Vegetation regulates the exchange of water, energy, and carbon fluxes between the land and the atmosphere. This regulation of surface fluxes differs with vegetation type and climate, but the effect of vegetation on surface fluxes is not well understood. A better knowledge of how and when vegetation influences surface fluxes could improve climate models and the extrapolation of ground-based water, energy, and carbon fluxes. We aim to study the link between vegetation and surface fluxes by combining the yearly average MODIS leaf area index (LAI) with flux tower measurements of water (latent heat), energy (sensible heat), and carbon (gross primary productivity and net ecosystem exchange). We show that the correlation of the LAI with water and energy fluxes depends on the vegetation type and aridity. Under water-limited conditions, the link between the LAI and the water and energy fluxes is strong, which is in line with a strong stomatal or vegetation control found in earlier studies. In energy-limited forest we found no link between the LAI and water and energy fluxes. In contrast to water and energy fluxes, we found a strong spatial correlation between the LAI and gross primary productivity that was independent of vegetation type and aridity. This study provides insight into the link between vegetation and surface fluxes. It indicates that for modelling or extrapolating surface fluxes, the LAI can be useful in savanna and grassland, but it is only of limited use in deciduous broadleaf forest and evergreen needleleaf forest to model variability in water and energy fluxes.
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24

Mueller, James A., and Fabrice Veron. "Bulk Formulation of the Heat and Water Vapor Fluxes at the Air–Sea Interface, Including Nonmolecular Contributions." Journal of the Atmospheric Sciences 67, no. 1 (January 1, 2010): 234–47. http://dx.doi.org/10.1175/2009jas3061.1.

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Abstract Accurate prediction of the air–sea sensible and latent heat fluxes is vital for nearly all applications of atmosphere and ocean models. Existing theories of heat transfer over rough surfaces provide a starting point, but they seem incomplete given that recent measurements suggest a departure from these theoretically predicted fluxes at higher wind speeds. Although explicit models of the air–sea heat fluxes are desperately needed, the formulation presented in this paper is an attempt to model the air–sea fluxes without dependence on explicit heat flux components. Using smooth flow limit approximations, theoretical profiles, and a physically based surface stress model, the predicted heat fluxes show reasonable agreement with available data. With increasing wind forcing, modestly increasing heat and moisture exchange coefficients (Stanton and Dalton numbers) are found. Even though wave age strongly influences the surface drag, stratification and temperature effects seem to dominate the wave-age influence on the air–sea heat and moisture fluxes.
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25

Kaniowski, Robert, Robert Pastuszko, Joanna Kowalczyk, and Łukasz Nowakowski. "Bubble departure diameter determination for pool boiling on surface with microchannels." E3S Web of Conferences 70 (2018): 02008. http://dx.doi.org/10.1051/e3sconf/20187002008.

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The paper presents visualization investigations into pool boiling heat transfer for open microchannel surfaces. The experiments were carried out with saturated water, ethanol, FC-72 and Novec-649 at atmospheric pressure. Parallel microchannels fabricated by machining copper sample were about 0.2 to 0.5 mm wide and 0.2 to 0.5 mm deep. The diameter of departing bubble was calculated for the microchannel surface on the basis of buoyancy force and surface tension force balance. The visualization carried out was aimed at determining the diameters of the departing bubbles at various heat fluxes for four working fluids.
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26

Bui, T. D., and V. K. Dhir. "Transition Boiling Heat Transfer on a Vertical Surface." Journal of Heat Transfer 107, no. 4 (November 1, 1985): 756–63. http://dx.doi.org/10.1115/1.3247501.

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Transition boiling heat transfer on a vertical surface in a pool of saturated water is investigated experimentally. Local heat transfer rates are obtained on a 6.3-cm-wide and 10.3-cm-high surface which was machined from a large block of copper. Experiments conducted with water show that even for relatively slow transient cooling rates (|dT/dt| < 11 K/s), the transient maximum heat fluxes are as much as 60 percent lower than the maximum steady-state heat fluxes. It is found that transition boiling heat transfer is very sensitive to the surface condition as well as to the history of the process. Two distinct transition boiling curves are observed during transient heating and cooling of clean surfaces. However, the difference between the two curves diminishes as the wettability of the surface increases. A correlation is developed to relate the transient quenching and steady-state peak heat fluxes for the range of temperature transient rates and surface conditions used in this investigation. Although the transient transition boiling curves obtained during heating and cooling are distinct because of different initial conditions, it is found that they possess the same rate of change of heat transfer coefficient with surface temperature when a correction factor equal to the ratio of steady to transient maximum heat fluxes is used.
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27

Voogt, J. A., and C. S. B. Grimmond. "Modeling Surface Sensible Heat Flux Using Surface Radiative Temperatures in a Simple Urban Area." Journal of Applied Meteorology 39, no. 10 (October 1, 2000): 1679–99. http://dx.doi.org/10.1175/1520-0450-39.10.1679.

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Abstract Sensible heat fluxes over a light industrial area in Vancouver, British Columbia, Canada, are analyzed from observed tower fluxes and modeled using a bulk heat transfer approach. The bulk transfer models are initialized using remotely sensed surface temperatures from both airborne and ground-based observing platforms. The remotely sensed surface temperature, in conjunction with a surface database, is used to create area-weighted temperature estimates representative of the complete urban surface. Sensitivity analyses of the various surface temperature estimates are performed. Estimates of kB−1, the ratio of roughness length of momentum to heat, for this area are in general agreement with theoretical estimates for bluff-rough surfaces and are larger than those documented for vegetated and agricultural surfaces. Back-calculated values do vary depending on the method used to determine surface temperature but vary more with the time of day. Empirical relations derived previously for vegetated surfaces are shown to agree well with the results for a dry urban environment. Approaches based on microscale variability in temperature fields are problematic.
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Ezzahar, Jamal, Salah Er-Raki, Hamid Marah, Said Khabba, Noureddine Amenzou, and Ghani Chehbouni. "Coupling soil-vegetationatmosphere- transfer model with energy balance model for estimating energy and water vapor fluxes over an olive grove in a semi-arid region." Global Meteorology 1, no. 1 (May 21, 2012): 1. http://dx.doi.org/10.4081/gm.2012.e1.

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Simple soil-vegetation-transfer (SVAT) and energy balance models were used to estimate the surface turbulent fluxes (<em>i.e. </em>sensible and latent heat fluxes) over a complex olive grove using thermal infra-red surface temperature (TIRST). This approach used a dual source SVAT model to calculate the sensible heat fluxes from radiometric surface temperature. These fluxes were then used together with the estimates of the available energy also derived from TIRST to estimate the latent heat flux by applying the first law of thermodynamics <em>i.e.</em> the conservation of energy principle. The data used to validate this approach were collected over an irrigated olive grove site located in central Morocco near Marrakech. Mass and energy fluxes, as well as micrometeorological parameters, were continuously measured during the year 2003. The comparison between estimated and measured daily sensible heat fluxes yielded an acceptable agreement in spite of the complexity of the study surface with a correlation coefficient (R<sup>2</sup>=0.86) and root mean square error (RMSE) of 28 Wm<sup>-2</sup>. For the latent heat fluxes, the statistical result for the comparison between estimated and measured daily values showed a larger scatter than that revealed for the sensible heat fluxes (R<sup>2</sup>=0.75; RMSE=31.42 Wm<sup>-2</sup>). However, the correspondence is to be considered acceptable given the difficulty in estimating latent heat flux over such a complex field. Therefore, it can be concluded that, in spite of the simplicity of the proposed approach, it can be considered a suitable tool for estimating the turbulent fluxes using TIRST over complex surfaces.
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Acevedo, Otávio C., Osvaldo L. L. Moraes, Rodrigo da Silva, Vagner Anabor, Daniel P. Bittencourt, Hans R. Zimmermann, Roberto O. Magnago, and Gervásio A. Degrazia. "Surface-to-Atmosphere Exchange in a River Valley Environment." Journal of Applied Meteorology and Climatology 46, no. 8 (August 1, 2007): 1169–81. http://dx.doi.org/10.1175/jam2517.1.

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Abstract Observations of the turbulent exchange between a river surface and the atmosphere in a mountainous area in southern Brazil are presented and discussed. A micrometeorological tower was installed directly above the surface of a 60-m-wide river. This paper describes the observed turbulent fluxes over 12 days of observations at this site. Eddy correlation sensible and latent heat fluxes are directed toward the river during daytime and from the river at night, and they are controlled by differences between water and air temperatures. The magnitude of the vertical fluxes between the river and the atmosphere increases during daytime with increasing temperature gradient up to a threshold, beyond which the increasing stability starts to dampen the fluxes. Water and air temperatures show very little variations across the width of the river, indicating that the measurements taken at one margin may be representative of the mean river exchange. Local scalar budgets show that daytime warming and moistening rates above the river are controlled by local transport from the riverbanks. The main vertical fluxes have a very small magnitude: 0.8 W m−2 for sensible heat and 1.1 W m−2 for latent heat. Events of very large sensible heat fluxes from the river to the atmosphere and very large latent heat fluxes from the atmosphere to the river happened on 3 days, following nights with a very deep fog layer in the valley. These events represented the passage of a warm and dry air mass down the river. A process to explain the occurrence of these large fluxes is suggested that is associated with differential fog dissipation over the valley.
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Loew, A., J. Peng, and M. Borsche. "High resolution land surface fluxes from satellite data (HOLAPS v1.0): evaluation and uncertainty assessment." Geoscientific Model Development Discussions 8, no. 12 (December 21, 2015): 10783–841. http://dx.doi.org/10.5194/gmdd-8-10783-2015.

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Abstract. Surface water and energy fluxes are essential components of the Earth system. Surface latent heat fluxes provide major energy input to the atmosphere. Despite the importance of these fluxes, state-of-the-art datasets of surface energy and water fluxes largely differ. The present paper introduces a new framework for the estimation of surface energy and water fluxes at the land surface, which allows for temporally and spatially high resolved flux estimates at the global scale (HOLAPS). The framework maximizes the usage of existing long-term satellite data records and ensures internally consistent estimates of the surface radiation and water fluxes. The manuscript introduces the technical details of the developed framework and provides results of a comprehensive sensitivity and evaluation study. Overall the results indicate very good agreement with in situ observations when compared against 49 FLUXNET stations worldwide. Largest uncertainties of latent heat flux and net radiation were found to result from uncertainties in the global solar radiation flux obtained from satellite data products.
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31

Güsten, Hans, Günther Heinrich, Erbo Mönnich, Detlev Sprung, Joseph Weppner, Abou Bakr Ramadan, Mohammed R. M. Ezz El-Din, Darwish M. Ahmed, and Galal K. Y. Hassan. "On-line measurements of ozone surface fluxes: Part II. Surface-level ozone fluxes onto the Sahara desert." Atmospheric Environment 30, no. 6 (March 1996): 911–18. http://dx.doi.org/10.1016/1352-2310(95)00270-7.

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Абгарян, В. К., В. Ю. Гидаспов, А. Б. Надирадзе, and А. А. Семенов. "Ионно-электронная рекомбинация и тепловые потоки в высокочастотных ионных двигателях." Письма в журнал технической физики 45, no. 4 (2019): 3. http://dx.doi.org/10.21883/pjtf.2019.04.47325.17576.

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AbstractHeat fluxes emitted from plasma to the surface of structural elements of high-frequency (HF) ion thrusters with perforated electrodes of the ion-optical system have been studied. Radiation fluxes formed during ion–electron recombination on surfaces in contact with plasma are considered taking into account their spatial distribution and partial reflection from surfaces. New expressions for the heat fluxes are obtained that should be used as boundary conditions in numerical models for the calculation of temperature fields in HF ion thrusters.
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33

Sievers, J., T. Papakyriakou, S. E. Larsen, M. M. Jammet, S. Rysgaard, M. K. Sejr, and L. L. Sørensen. "Estimating surface fluxes using eddy covariance and numerical ogive optimization." Atmospheric Chemistry and Physics 15, no. 4 (February 26, 2015): 2081–103. http://dx.doi.org/10.5194/acp-15-2081-2015.

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Abstract. Estimating representative surface fluxes using eddy covariance leads invariably to questions concerning inclusion or exclusion of low-frequency flux contributions. For studies where fluxes are linked to local physical parameters and up-scaled through numerical modelling efforts, low-frequency contributions interfere with our ability to isolate local biogeochemical processes of interest, as represented by turbulent fluxes. No method currently exists to disentangle low-frequency contributions on flux estimates. Here, we present a novel comprehensive numerical scheme to identify and separate out low-frequency contributions to vertical turbulent surface fluxes. For high flux rates (|Sensible heat flux| > 40 Wm−2, |latent heat flux|> 20 Wm−2 and |CO2 flux|> 100 mmol m−2 d−1 we found that the average relative difference between fluxes estimated by ogive optimization and the conventional method was low (5–20%) suggesting negligible low-frequency influence and that both methods capture the turbulent fluxes equally well. For flux rates below these thresholds, however, the average relative difference between flux estimates was found to be very high (23–98%) suggesting non-negligible low-frequency influence and that the conventional method fails in separating low-frequency influences from the turbulent fluxes. Hence, the ogive optimization method is an appropriate method of flux analysis, particularly in low-flux environments.
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Crespo, Juan, Derek Posselt, and Shakeel Asharaf. "CYGNSS Surface Heat Flux Product Development." Remote Sensing 11, no. 19 (October 1, 2019): 2294. http://dx.doi.org/10.3390/rs11192294.

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Ocean surface heat fluxes play a significant role in the genesis and evolution of various marine-based atmospheric phenomena, from the synoptic scale down to the microscale. While in-situ measurements from buoys and flux towers will continue to be the standard in regard to surface heat flux estimates, they commonly have significant gaps in temporal and spatial coverage. Previous and current satellite missions have filled these gaps; though they may not observe the fluxes directly, they can measure the variables needed (wind speed, temperature and humidity) to estimate latent and sensible heat fluxes. However, current remote sensing instruments have their own limitations, such as infrequent coverage, signals attenuated by precipitation or both. The Cyclone Global Navigation Satellite System (CYGNSS) mission overcomes these limitations over the tropical and subtropical oceans by providing improved coverage in nearly all weather conditions. While CYGNSS (Level 2) primarily estimates surface winds, when coupled with observations or estimates of temperature and humidity from reanalysis data, it can provide estimates of latent and sensible heat fluxes along its orbit. This paper describes the development of the Surface Heat Flux Product for the CYGNSS mission, its current results and expected improvements and changes in future releases.
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35

Rodriguez-Puebla, C., R. T. Pinker, and S. Nigam. "Relationship between downwelling surface shortwave radiative fluxes and sea surface temperature over the tropical Pacific: AMIP II models versus satellite estimates." Annales Geophysicae 26, no. 4 (May 13, 2008): 785–94. http://dx.doi.org/10.5194/angeo-26-785-2008.

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Abstract. Incident shortwave radiation at the Earth's surface is the driving force of the climate system. Understanding the relationship between this forcing and the sea surface temperature, in particular, over the tropical Pacific Ocean is a topic of great interest because of possible climatic implications. The objective of this study is to investigate the relationship between downwelling shortwave radiative fluxes and sea surface temperature by using available data on radiative fluxes. We assess first the shortwave radiation from three General Circulation Models that participated in the second phase of the Atmospheric Model Intercomparison Project (AMIP II) against estimates of such fluxes from satellites. The shortwave radiation estimated from the satellite is based on observations from the International Satellite Cloud Climatology Project D1 data and the University of Maryland Shortwave Radiation Budget model (UMD/SRB). Model and satellite estimates of surface radiative fluxes are found to be in best agreement in the central equatorial Pacific, according to mean climatology and spatial correlations. We apply a Canonical Correlation Analysis to determine the interrelated areas where shortwave fluxes and sea surface temperature are most sensitive to climate forcing. Model simulations and satellite estimates of shortwave fluxes both capture well the interannual signal of El Niño-like variability. The tendency for an increase in shortwave radiation from the UMD/SRB model is not captured by the AMIP II models.
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36

Redeker, K. R., A. J. Baird, and Y. A. Teh. "Quantifying wind and pressure effects on trace gas fluxes across the soil–atmosphere interface." Biogeosciences 12, no. 24 (December 17, 2015): 7423–34. http://dx.doi.org/10.5194/bg-12-7423-2015.

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Abstract. Large uncertainties persist in estimates of soil–atmosphere exchange of important trace gases. One significant source of uncertainty is the combined effect of wind and pressure on these fluxes. Wind and pressure effects are mediated by surface topography: few surfaces are uniform and over scales of tenths of a metre to tens of metres, air pressure and wind speed at the ground surface may be very variable. In this paper we consider how such spatial variability in air pressure and wind speed affects fluxes of trace gases. We used a novel nested wind tunnel design comprising a toroidial wind tunnel, in which wind speed and pressure may be controlled, set within a larger, linear wind tunnel. The effects of both wind speed and pressure differentials on fluxes of CO2 and CH4 within three different ecosystems (forest, grassland, peat bog) were quantified. We find that trace gas fluxes are positively correlated with both wind speed and pressure differential near the surface boundary. We argue that wind speed is the better proxy for trace gas fluxes because of its stronger correlation and because wind speed is more easily measured and wind speed measurement methodology more easily standardized. Trace gas fluxes, whether into or out of the soil, increase with wind speed within the toroidal tunnel (+55 % flux per m s−1), while faster, localized surface winds that are external to the toroidal wind tunnel reduce trace gas fluxes (−13 % flux per m s−1). These results are consistent for both trace gases over all ecosystem soil types studied. Our findings support the need for a revised conceptualization of soil–atmosphere gas exchange. We propose a conceptual model of the soil profile that has a "mixed layer", with fluxes controlled by wind speed, wind duration, porosity, water table, and gas production and consumption.
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37

Redeker, K. R., A. J. Baird, and Y. A. Teh. "Quantifying wind and pressure effects on trace gas fluxes across the soil–atmosphere interface." Biogeosciences Discussions 12, no. 6 (March 24, 2015): 4801–32. http://dx.doi.org/10.5194/bgd-12-4801-2015.

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Abstract. Large uncertainties persist in estimates of soil–atmosphere exchange of important trace gases. One significant source of uncertainty is the combined effect of wind and pressure on these fluxes. Wind and pressure effects are mediated by surface topography: few surfaces are uniform and over scales of tenths of a meter to tens of meters, air pressure and wind speed at the ground surface may be very variable. In this paper we consider how such spatial variability in air pressure and wind speed affects fluxes of trace gases. We used a novel nested wind tunnel design, comprising a toroidial wind tunnel in which wind speed and pressure may be controlled, set within a larger, linear wind tunnel. The effects of both wind speed and pressure differentials on fluxes of CO2 and CH4 within three different ecosystems (forest, grassland, peat bog) were quantified. We find that trace gas fluxes are positively correlated with both wind speed and pressure differential near the surface boundary. We argue that wind speed is the better proxy for trace gas fluxes because of its stronger correlation and because wind speed measurement is more easily accomplished and wind speed measurement methodology can be more easily standardized. Trace gas fluxes, whether into or out of the soil, increase with wind speed within the toroidal tunnel (+54% flux per m s−1), while faster, localized surface winds that are external to the toroidal wind tunnel reduce trace gas fluxes (−11% flux per m s−1). These results are consistent for both trace gases over all ecosystem soil types studied. Our findings support the need for a revised conceptualization of soil–atmosphere gas exchange. We propose a conceptual model of the soil profile that has a "mixed layer", with fluxes controlled by wind speed, wind duration, porosity, water table, and gas production and consumption.
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38

Haualand, Kristine F., and Thomas Spengler. "Direct and Indirect Effects of Surface Fluxes on Moist Baroclinic Development in an Idealized Framework." Journal of the Atmospheric Sciences 77, no. 9 (September 1, 2020): 3211–25. http://dx.doi.org/10.1175/jas-d-19-0328.1.

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Abstract The convoluted role of surface sensible and latent heat fluxes on moist baroclinic development demands a better understanding to disentangle their local and remote effects. Including diabatic effects in the Eady model, the direct effects of surface fluxes on the diabatic generation of eddy available potential energy as well as their indirect effects through modifications of the circulation and latent heating are investigated. It is shown that surface sensible heat fluxes have a minor impact, irrespective of their position and parameterization, while latent heating in the region equivalent to the warm conveyor belt is the dominant diabatic source for development. Downward surface sensible heat fluxes in proximity of the warm conveyor belt results in structural modifications that increase the conversion from basic-state available potential energy to eddy available potential energy, while concomitantly weakening the ascent and hence latent heating. The detrimental effects are easily compensated through provision of additional moisture into the warm conveyor belt. Upward surface heat fluxes in the cold sector, on the other hand, are detrimental to growth. When downward (upward) surface sensible heat fluxes are located below the equivalent of the warm conveyor belt, the diabatically induced PV anomaly at the bottom of the latent heating layer becomes dominant (less dominant). Shifting the downward surface sensible heat fluxes away from the warm conveyor belt results in substantial changes in the growth rate, latent heat release, low-level structure, and energetics, where the effect of surface sensible heat fluxes might even be beneficial.
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39

Ma, Yingtao, Rachel T. Pinker, Margaret M. Wonsick, Chuan Li, and Laura M. Hinkelman. "Shortwave Radiative Fluxes on Slopes." Journal of Applied Meteorology and Climatology 55, no. 7 (July 2016): 1513–32. http://dx.doi.org/10.1175/jamc-d-15-0178.1.

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AbstractSnow-covered mountain ranges are a major source of water supply for runoff and groundwater recharge. Snowmelt supplies as much as 75% of the surface water in basins of the western United States. Net radiative fluxes make up about 80% of the energy balance over snow-covered surfaces. Because of the large extent of snow cover and the scarcity of ground observations, use of remotely sensed data is an attractive option for estimating radiative fluxes. Most of the available methods have been applied to low-spatial-resolution satellite observations that do not capture the spatial variability of snow cover, clouds, or aerosols, all of which need to be accounted for to achieve accurate estimates of surface radiative fluxes. The objective of this study is to use high-spatial-resolution observations that are available from the Moderate Resolution Imaging Spectroradiometer (MODIS) to derive surface shortwave (0.2–4.0 μm) downward radiative fluxes in complex terrain, with attention on the effect of topography (e.g., shadowing or limited sky view) on the amount of radiation received. The developed method has been applied to several typical melt seasons (January–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 of shortwave fluxes. Issues of scale in both the satellite and ground observations are also addressed to illuminate difficulties in the validation process of satellite-derived quantities. It is planned to apply the findings from this study to test improvements in estimation of snow water equivalent.
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40

Wang, Xuanji, and Jeffrey R. Key. "Spatial variability of the sea-ice radiation budget and its effect on aggregate-area fluxes." Annals of Glaciology 33 (2001): 248–52. http://dx.doi.org/10.3189/172756401781818130.

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AbstractThe spatial and temporal variability of surface, cloud and radiative properties of sea ice are examined using new satellite-derived products. Downwelling short- and longwave fluxes exhibit temporal correlation over about 180 days, but cloud optical depth and cloud fraction show almost no correlation over time. The spatial variance of surface properties is shown to increase much less rapidly than that of cloud properties. The effect of small-scale inhomogeneity in surface and cloud properties on the calculation of radiative fluxes at ice- and climate-model gridscales is also investigated. Annual mean differences between gridcell fluxes computed from average surface and cloud properties and averages of pixel-by-pixel fluxes are 9.46% for the downwelling shortwave flux and −7.04% for the longwave flux. Therefore, using mean surface and cloud properties to compute surface radiative fluxes in a gridcell results in an overestimate of the shortwave flux and an underestimate of the longwave flux. Model sensitivity studies show that such biases may result in substantial errors in modeled ice thickness. Clearly, the sub-gridscale inhomogeneity of surface and atmospheric properties must be considered when estimating aggregate-area fluxes in sea-ice and climate models.
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41

Zeng, Xubin, and Robert E. Dickinson. "Effect of Surface Sublayer on Surface Skin Temperature and Fluxes." Journal of Climate 11, no. 4 (April 1998): 537–50. http://dx.doi.org/10.1175/1520-0442(1998)011<0537:eossos>2.0.co;2.

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42

Mlynczak, Pamela E., G. Louis Smith, Anne C. Wilber, and Paul W. Stackhouse. "Annual Cycle of Surface Longwave Radiation." Journal of Applied Meteorology and Climatology 50, no. 6 (June 2011): 1212–24. http://dx.doi.org/10.1175/2011jamc2663.1.

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AbstractThe annual cycles of upward and downward longwave fluxes at the earth’s surface are investigated by use of the NASA Global Energy and Water Cycle Experiment (GEWEX) Surface Radiation Budget Dataset. Principal component analysis is used to quantify the annual cycles. Because of the immense difference between the heat capacity of land and ocean, the surface of the earth is partitioned into these two categories. Over land, the first principal component describes over 95% of the variance of the annual cycle of the upward and downward longwave fluxes. Over ocean the first term describes more than 87% of these annual cycles. Empirical orthogonal functions show the corresponding geographical distributions of these cycles. Phase-plane diagrams of the annual cycles of upward longwave fluxes as a function of net shortwave flux show the thermal inertia of land and ocean.
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43

Sørensen, L. L., B. Jensen, R. N. Glud, D. F. McGinnis, M. K. Sejr, J. Sievers, D. H. Søgaard, J. L. Tison, and S. Rysgaard. "Parameterization of atmosphere–surface exchange of CO<sub>2</sub> over sea ice." Cryosphere 8, no. 3 (May 12, 2014): 853–66. http://dx.doi.org/10.5194/tc-8-853-2014.

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Abstract. We suggest the application of a flux parameterization commonly used over terrestrial areas for calculation of CO2 fluxes over sea ice surfaces. The parameterization is based on resistance analogy. We present a concept for parameterization of the CO2 fluxes over sea ice suggesting to use properties of the atmosphere and sea ice surface that can be measured or calculated on a routine basis. Parameters, which can be used in the conceptual model, are analysed based on data sampled from a seasonal fast-ice area, and the different variables influencing the exchange of CO2 between the atmosphere and ice are discussed. We found the flux to be small during the late winter with fluxes in both directions. Not surprisingly we find that the resistance across the surface controls the fluxes and detailed knowledge of the brine volume and carbon chemistry within the brines as well as knowledge of snow cover and carbon chemistry in the ice are essential to estimate the partial pressure of pCO2 and CO2 flux. Further investigations of surface structure and snow cover and driving parameters such as heat flux, radiation, ice temperature and brine processes are required to adequately parameterize the surface resistance.
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44

Gao, Z., D. H. Lenschow, Z. He, M. Zhou, L. Wang, Y. Wang, J. He, and J. Shi. "Seasonal and diurnal variations in moisture, heat and CO<sub>2</sub> fluxes over a typical steppe prairie in Inner Mongolia, China." Hydrology and Earth System Sciences Discussions 6, no. 2 (March 6, 2009): 1939–72. http://dx.doi.org/10.5194/hessd-6-1939-2009.

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Abstract. In order to examine energy partitioning and CO2 exchange over a steppe prairie in Inner Mongolia, China, fluxes of moisture, heat and CO2 in the surface layer from June 2007 through June 2008 were calculated using the eddy covariance method. The study site was homogenous and approximately 1500 m×1500 m in size. Seasonal and diurnal variations in radiation components, energy components and CO2 fluxes are examined. Results show that all four radiation components changed seasonally, resulting in a seasonal variation in net radiation. The radiation components also changed diurnally. Winter surface albedo was higher than summer surface albedo because during winter the snow-covered surface increased the surface albedo. The seasonal variations in both sensible heat and CO2 fluxes were stronger than those of latent heat and soil heat fluxes. This implies that both sensible heat and CO2 fluxes may be more significant climate signals than latent heat and soil fluxes. Sensible heat flux was the main consumer of available energy for the entire experimental period. The energy imbalance problem was encountered and the causes are analyzed.
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45

Nuijens, Louise, and Bjorn Stevens. "The Influence of Wind Speed on Shallow Marine Cumulus Convection." Journal of the Atmospheric Sciences 69, no. 1 (January 1, 2012): 168–84. http://dx.doi.org/10.1175/jas-d-11-02.1.

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Abstract The role of wind speed on shallow marine cumulus convection is explored using large-eddy simulations and concepts from bulk theory. Focusing on cases characteristic of the trades, the equilibrium trade wind layer is found to be deeper at stronger winds, with larger surface moisture fluxes and smaller surface heat fluxes. The opposing behavior of the surface fluxes is caused by more warm and dry air being mixed to the surface as the cloud layer deepens. This leads to little difference in equilibrium surface buoyancy fluxes and cloud-base mass fluxes. Shallow cumuli are deeper, but not more numerous or more energetic. The deepening response is necessary to resolve an inconsistency in the subcloud layer. This argument follows from bulk concepts and assumes that the lapse rate and flux divergence of moist-conserved variables do not change, based on simulation results. With that assumption, stronger winds and a fixed inversion height imply larger surface moisture and buoyancy fluxes (heat fluxes are small initially). The consequent moistening tends to decrease cloud-base height, which is inconsistent with a larger surface buoyancy flux that tends to increase cloud-base height, in order to maintain the buoyancy flux at cloud base at a fixed fraction of its surface value (entrainment closure). Deepening the cloud layer by increasing the inversion height resolves this inconsistency by allowing the surface buoyancy flux to remain constant without further moistening the subcloud layer. Because this explanation follows from simple bulk concepts, it is suggested that the internal dynamics (mixing) of clouds is only secondary to the deepening response.
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46

Gulev, Sergey K., and Konstantin Belyaev. "Probability Distribution Characteristics for Surface Air–Sea Turbulent Heat Fluxes over the Global Ocean." Journal of Climate 25, no. 1 (January 1, 2012): 184–206. http://dx.doi.org/10.1175/2011jcli4211.1.

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Abstract To analyze the probability density distributions of surface turbulent heat fluxes, the authors apply the two-parametric modified Fisher–Tippett (MFT) distribution to the sensible and latent turbulent heat fluxes recomputed from 6-hourly NCEP–NCAR reanalysis state variables for the period from 1948 to 2008. They derived the mean climatology and seasonal cycle of the location and scale parameters of the MFT distribution. Analysis of the parameters of probability distributions identified the areas where similar surface turbulent fluxes are determined by the very different shape of probability density functions. Estimated extreme turbulent heat fluxes amount to 1500–2000 W m−2 (for the 99th percentile) and can exceed 2000 W m−2 for higher percentiles in the subpolar latitudes and western boundary current regions. Analysis of linear trends and interannual variability in the mean and extreme fluxes shows that the strongest trends in extreme fluxes (more than 15 W m−2 decade−1) in the western boundary current regions are associated with the changes in the shape of distribution. In many regions changes in extreme fluxes may be different from those for the mean fluxes at interannual and decadal time scales. The correlation between interannual variability of the mean and extreme fluxes is relatively low in the tropics, the Southern Ocean, and the Kuroshio Extension region. Analysis of probability distributions in turbulent fluxes has also been used in assessing the impact of sampling errors in the Voluntary Observing Ship (VOS)-based surface flux climatologies, allowed for the estimation of the impact of sampling in extreme fluxes. Although sampling does not have a visible systematic effect on mean fluxes, sampling uncertainties result in the underestimation of extreme flux values exceeding 100 W m−2 in poorly sampled regions.
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47

Mihailovic, D. T., Branislava Lalic, Jacek Lesny, and J. Olejnik. "Modeling surface fluxes over a sparse vegetation." Archives of Biological Sciences 64, no. 4 (2012): 1533–42. http://dx.doi.org/10.2298/abs1204533m.

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In this paper some of aspects in modeling over sparse vegetation using the Land-Air Parameterization Scheme (LAPS), including an approach in calculating the turbulent transfer coefficient using ?K-theory? inside a sparse vegetation canopy, were considered. For this purpose, the scheme was run for different sparse agricultural cultivars, i.e., apple orchard, winter wheat and soybean crops, at different sites. The modeled values for surface fluxes, canopy temperature and soil moisture content, were compared with observations.
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48

Muñoz-Criollo, José Javier, Peter John Cleall, and Stephen William Rees. "Modelling thermal fluxes at the soil surface." Environmental Geotechnics 6, no. 6 (September 1, 2019): 393–405. http://dx.doi.org/10.1680/jenge.15.00075.

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49

MURTHY, B. S., and S. SIVARAMAKRISHNAN. "Surface fluxes over Goa during Indian monsoon." MAUSAM 56, no. 1 (January 19, 2022): 251–56. http://dx.doi.org/10.54302/mausam.v56i1.900.

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Variation of surface sensible heat flux over the west coast in the premises of National Center for Antarctic and Ocean Research (NCAOR), Vasco-da-Gama (15° 21' N, 73° 51' E), Goa during Offshore trough (phase-I) and Warm pool campaigns (phase-II) of ARMEX is studied. Sensible heat flux as measured by sonic anemometer at 5 m above surface is -50 to 150 Wm-2 during 13-28 July, 2002 (phase I) and -5 to 350 Wm-2 during 21-24 April, 2003 (phase II). Coastal atmospheric surface layer at Goa during night time is found to be near neutral (nearly zero heat flux) in April 2003 whereas stable (negative heat flux) in July 2002. All components of solar radiation measured by Eppley radiometers at 2 m above surface are used to compute net radiation which is 900 Wm-2 at noon in April 2003. Net solar radiation is nearly equal to incoming short wave radiation during daytime as net long wave radiation (100 Wm-2) compensates the loss due to reflection of short wave radiation (-100 Wm-2) by the ground. High winds in the surface layer are observed during late night hours with calm winds around sunrise and after sunset giving rise to two minima in the diurnal curve. Influence of sea-breeze on the surface layer over land is discussed.
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50

Stull, Roland B. "A Convective Transport Theory for Surface Fluxes." Journal of the Atmospheric Sciences 51, no. 1 (January 1994): 3–22. http://dx.doi.org/10.1175/1520-0469(1994)051<0003:acttfs>2.0.co;2.

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