Carbon dioxide, water vapor, and heat fluxes over agricultural crop field in an arid oasis of Northwest China, as determined by eddy covariance

Abstract. Sodar (SOund Detection And Ranging), eddy-covariance, and tower profile measurements of wind speed and carbon dioxide were performed during 17 consecutive nights in complex terrain in northern Taiwan. The scope of the study was to identify the causes for intermittent turbulence events and to analyze their importance in nocturnal atmosphere–biosphere exchange as quantified with eddy-covariance measurements. If intermittency occurs frequently at a measurement site, then this process needs to be quantified in order to achieve reliable values for ecosystem characteristics such as net ecosystem exchange or net primary production. Fourteen events of intermittent turbulence were identified and classified into above-canopy drainage flows (ACDFs) and low-level jets (LLJs) according to the height of the wind speed maximum. Intermittent turbulence periods lasted between 30 and 110 min. Towards the end of LLJ or ACDF events, positive vertical wind velocities and, in some cases, upslope flows occurred, counteracting the general flow regime at nighttime. The observations suggest that the LLJs and ACDFs penetrate deep into the cold air pool in the valley, where they experience strong buoyancy due to density differences, resulting in either upslope flows or upward vertical winds. Turbulence was found to be stronger and better developed during LLJs and ACDFs, with eddy-covariance data presenting higher quality. This was particularly indicated by spectral analysis of the vertical wind velocity and the steady-state test for the time series of the vertical wind velocity in combination with the horizontal wind component, the temperature, and carbon dioxide. Significantly higher fluxes of sensible heat, latent heat, and shear stress occurred during these periods. During LLJs and ACDFs, fluxes of sensible heat, latent heat, and CO2 were mostly one-directional. For example, exclusively negative sensible heat fluxes occurred while intermittent turbulence was present. Latent heat fluxes were mostly positive during LLJs and ACDFs, with a median value of 34 W m−2, while outside these periods the median was 2 W m−2. In conclusion, intermittent turbulence periods exhibit a strong impact on nocturnal energy and mass fluxes.

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Carbon dioxide, water vapor and sensible heat fluxes over a tallgrass prairie

Boundary-Layer Meteorology ◽

10.1007/bf00118446 ◽

1989 ◽

Vol 46 (1-2) ◽

pp. 53-67 ◽

Cited By ~ 59

Author(s):

Shashi B. Verma ◽

Joon Kim ◽

Robert J. Clement

Keyword(s):

Carbon Dioxide ◽

Water Vapor ◽

Tallgrass Prairie ◽

Heat Fluxes ◽

Sensible Heat

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Measurements of carbon dioxide and heat fluxes during monsoon-2011 season over rural site of India by eddy covariance technique

Journal of Earth System Science ◽

10.1007/s12040-013-0374-z ◽

2014 ◽

Vol 123 (1) ◽

pp. 177-185 ◽

Cited By ~ 9

Author(s):

M N PATIL ◽

T DHARMARAJ ◽

R T WAGHMARE ◽

T V PRABHA ◽

J R KULKARNI

Keyword(s):

Carbon Dioxide ◽

Eddy Covariance ◽

Heat Fluxes ◽

Rural Site ◽

Eddy Covariance Technique

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Tower and Aircraft Eddy Covariance Measurements of Water Vapor, Energy, and Carbon Dioxide Fluxes during SMACEX

Journal of Hydrometeorology ◽

10.1175/jhm457.1 ◽

2005 ◽

Vol 6 (6) ◽

pp. 954-960 ◽

Cited By ~ 64

Author(s):

J. H. Prueger ◽

J. L. Hatfield ◽

T. B. Parkin ◽

W. P. Kustas ◽

L. E. Hipps ◽

...

Keyword(s):

Carbon Dioxide ◽

Water Vapor ◽

Eddy Covariance ◽

Spatial And Temporal Variability ◽

Co2 Fluxes ◽

Sensible Heat ◽

Carbon Dioxide Fluxes ◽

Crop Growth Stage ◽

Aircraft Flux Measurements ◽

Carbon Dioxide Co2

Abstract A network of eddy covariance (EC) and micrometeorological flux (METFLUX) stations over corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] canopies was established as part of the Soil Moisture–Atmosphere Coupling Experiment (SMACEX) in central Iowa during the summer of 2002 to measure fluxes of heat, water vapor, and carbon dioxide (CO2) during the growing season. Additionally, EC measurements of water vapor and CO2 fluxes from an aircraft platform complemented the tower-based measurements. Sensible heat, water vapor, and CO2 fluxes showed the greatest spatial and temporal variability during the early crop growth stage. Differences in all of the energy balance components were detectable between corn and soybean as well as within similar crops throughout the study period. Tower network–averaged fluxes of sensible heat, water vapor, and CO2 were observed to be in good agreement with area-averaged aircraft flux measurements.

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TOTAL EMISSIVITY AND ABSORPTIVITY MODELS FOR CARBON DIOXIDE, WATER VAPOR AND THEIR MIXTURES

Proceeding of International Heat Transfer Conference 8 ◽

10.1615/ihtc8.4140 ◽

1986 ◽

Cited By ~ 2

Author(s):

F. R. Steward ◽

Yasar S. Kocaefe

Keyword(s):

Carbon Dioxide ◽

Water Vapor ◽

Total Emissivity

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Faculty Opinions recommendation of Partitioning evapotranspiration using long-term carbon dioxide and water vapor fluxes.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.727830085.793534790 ◽

2017 ◽

Author(s):

Dennis Baldocchi

Keyword(s):

Carbon Dioxide ◽

Water Vapor

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Ecosystem modeling of methane and carbon dioxide fluxes for boreal forest sites

Canadian Journal of Forest Research ◽

10.1139/x00-164 ◽

2001 ◽

Vol 31 (2) ◽

pp. 208-223 ◽

Cited By ~ 11

Author(s):

Christopher Potter ◽

Jill Bubier ◽

Patrick Crill ◽

Peter Lafleur

Keyword(s):

Carbon Dioxide ◽

Boreal Forest ◽

Land Surface ◽

Net Primary Production ◽

Ground Cover ◽

Methane Flux ◽

Growing Season ◽

Ecosystem Model ◽

Heat Fluxes ◽

Water Levels

Predicted daily fluxes from an ecosystem model for water, carbon dioxide, and methane were compared with 1994 and 1996 Boreal EcosystemAtmosphere Study (BOREAS) field measurements at sites dominated by old black spruce (Picea mariana (Mill.) BSP) (OBS) and boreal fen vegetation near Thompson, Man. Model settings for simulating daily changes in water table depth (WTD) for both sites were designed to match observed water levels, including predictions for two microtopographic positions (hollow and hummock) within the fen study area. Water run-on to the soil profile from neighboring microtopographic units was calibrated on the basis of daily snowmelt and rainfall inputs to reproduce BOREAS site measurements for timing and magnitude of maximum daily WTD for the growing season. Model predictions for daily evapotranspiration rates closely track measured fluxes for stand water loss in patterns consistent with strong controls over latent heat fluxes by soil temperature during nongrowing season months and by variability in relative humidity and air temperature during the growing season. Predicted annual net primary production (NPP) for the OBS site was 158 g C·m2 during 1994 and 135 g C·m2 during 1996, with contributions of 75% from overstory canopy production and 25% from ground cover production. Annual NPP for the wetter fen site was 250 g C·m2 during 1994 and 270 g C·m2 during 1996. Predicted seasonal patterns for soil CO2 fluxes and net ecosystem production of carbon both match daily average estimates at the two sites. Model results for methane flux, which also closely match average measured flux levels of 0.5 mg CH4·m2·day1 for OBS and 2.8 mg CH4·m2·day1 for fen sites, suggest that spruce areas are net annual sinks of about 0.12 g CH4·m2, whereas fen areas generate net annual emissions on the order of 0.30.85 g CH4·m2, depending mainly on seasonal WTD and microtopographic position. Fen hollow areas are predicted to emit almost three times more methane during a given year than fen hummock areas. The validated model is structured for extrapolation to regional simulations of interannual trace gas fluxes over the entire North America boreal forest, with integration of satellite data to characterize properties of the land surface.

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A Positive Feedback Process Related to the Rapid Development of an Extratropical Cyclone over the Kuroshio/Kuroshio Extension

Monthly Weather Review ◽

10.1175/mwr-d-17-0063.1 ◽

2018 ◽

Vol 146 (2) ◽

pp. 417-433 ◽

Cited By ~ 10

Author(s):

Hidetaka Hirata ◽

Ryuichi Kawamura ◽

Masaya Kato ◽

Taro Shinoda

Keyword(s):

Water Vapor ◽

Positive Feedback ◽

Heat Supply ◽

Rapid Development ◽

Kuroshio Extension ◽

Heat Fluxes ◽

Latent Heating ◽

Sensible Heat ◽

Feedback Process ◽

The Kuroshio

Abstract The active roles of sensible heat supply from the Kuroshio/Kuroshio Extension in the rapid development of an extratropical cyclone, which occurred in the middle of January 2013, were examined by using a regional cloud-resolving model. In this study, a control experiment and three sensitivity experiments without sensible and latent heat fluxes from the warm currents were conducted. When the cyclone intensified, sensible heat fluxes from these currents become prominent around the cold conveyor belt (CCB) in the control run. Comparisons among the four runs revealed that the sensible heat supply facilitates deepening of the cyclone’s central pressure, CCB development, and enhanced latent heating over the bent-back front. The sensible heat supply enhances convectively unstable conditions within the atmospheric boundary layer along the CCB. The increased convective instability is released by the forced ascent associated with frontogenesis around the bent-back front, eventually promoting updraft and resultant latent heating. Additionally, the sensible heating leads to an increase in the water vapor content of the saturated air related to the CCB through an increase in the saturation mixing ratio. This increased water vapor content reinforces the moisture flux convergence at the bent-back front, contributing to the activation of latent heating. Previous research has proposed a positive feedback process between the CCB and latent heating over the bent-back front in terms of moisture supply from warm currents. Considering the above two effects of the sensible heat supply, this study revises the positive feedback process.

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