Growing-Season Synoptic and Phenological Controls on Heat Fluxes over Forest and Cropland Sites in the Midwest U.S. Corn Belt

2020 ◽  
Vol 59 (3) ◽  
pp. 381-400
Author(s):  
Mikael P. Hiestand ◽  
Andrew M. Carleton
Keyword(s):  
Land Use ◽  
Deciduous Forest ◽  
Growing Season ◽  
Heat Fluxes ◽  
Corn Belt ◽  
Sensible Heat ◽  
Convective Rainfall ◽  
Mesoscale Circulations ◽  
Synoptic Weather ◽  
South Central

AbstractSpatial variations in land use/land cover (LULC) in the Midwest U.S. Corn Belt—specifically, deciduous forest and croplands—have been suggested as influencing convective rainfall through mesoscale circulations generated in the atmosphere’s boundary layer. However, the contributing role of latent and sensible heat fluxes for these two LULC types, and their modulation by synoptic weather systems, have not been determined. This study compares afternoon averages of convective fluxes at two AmeriFlux towers in relation to manually determined synoptic pressure patterns covering the nine growing seasons (1 May–30 September) of 1999–2007. AmeriFlux tower U.S.-Bo1 in eastern Illinois represents agricultural land use—alternating between maize and soybean crops—and AmeriFlux tower U.S.-MMS in south-central Indiana represents deciduous forest cover. Phenologically, the latent and sensible heat fluxes vary inversely across the growing season, and the greatest flux differences between cropland and deciduous forest occur early in the season. Differences in the surface heat fluxes between crop and forest LULC types vary in magnitude according to synoptic type. Moreover, statistically significant differences in latent and sensible heat between the forest and cropland sites occur for the most frequently occurring synoptic pattern of a low pressure system to the west and high pressure to the east of the Corn Belt. The present study lays the groundwork for determining the physical mechanisms of enhanced convection in the Corn Belt, including how LULC-induced mesoscale circulations might interact with synoptic weather patterns to enhance convective rainfall.

The role of soil characteristics on measured and modelled carbon dioxide and energy fluxes for Arctic dwarf shrub tundra sites

2020 ◽  
Author(s):  
Gesa Meyer ◽  
Elyn Humphreys ◽  
Joe Melton ◽  
Peter Lafleur ◽  
Philip Marsh ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Growing Season ◽  
Cold Season ◽  
Soil Characteristics ◽  
Heat Fluxes ◽  
Dwarf Shrub ◽  
The Arctic ◽  
Sensible Heat ◽  
Shrub Tundra ◽  
Tundra Ecosystems

<p>Four years of growing season eddy covariance measurements of net carbon dioxide (CO<sub>2</sub>) and energy fluxes were used to examine the similarities/differences in surface-atmosphere interactions at two dwarf shrub tundra sites within Canada’s Southern Arctic ecozone, separated by approximately 1000 km. Both sites, Trail Valley Creek (TVC) and Daring Lake (DL1), are characterised by similar climate (with some differences in radiation due to latitudinal differences), vegetation composition and structure, and are underlain by continuous permafrost, but differ in their soil characteristics. Total atmospheric heating (the sum of latent and sensible heat fluxes) was similar at the two sites. However, at DL1, where the surface organic layer was thinner and mineral soil coarser in texture, latent heat fluxes were greater, sensible heat fluxes were lower, soils were warmer and the active layer thicker. At TVC, cooler soils likely kept ecosystem respiration relatively low despite similar total growing season productivity. As a result, the 4-year mean net growing season ecosystem CO<sub>2 </sub>uptake (May 1 - September 30) was almost twice as large at TVC (64 ± 19 g C m<sup>-2</sup>) compared to DL1 (33 ± 11 g C m<sup>-2</sup>). These results highlight that soil and thaw characteristics are important to understand variability in surface-atmosphere interactions among tundra ecosystems.</p><p>As recent studies have shown, winter fluxes play an important role in the annual CO<sub>2</sub> balance of Arctic tundra ecosystems. However, flux measurements were not available at TVC and DL1 during the cold season. Thus, the process-based ecosystem model CLASSIC (the Canadian Land Surface Scheme including biogeochemical Cycles, formerly CLASS-CTEM) was used to simulate year-round fluxes. In order to represent the Arctic shrub tundra better, shrub and sedge plant functional types were included in CLASSIC and results were evaluated using measurements at DL1. Preliminary results indicate that cold season CO<sub>2</sub> losses are substantial and may exceed the growing season CO<sub>2</sub> uptake at DL1 during 2010-2017. The joint use of observations and models is valuable in order to better constrain the Arctic CO<sub>2</sub> balance.  </p>

scholarly journals Roles of spatially varying vegetation on surface fluxes within a small mountainous catchment

2010 ◽  
Vol 7 (1) ◽  
pp. 593-619
Author(s):  
G. N. Flerchinger ◽  
D. Marks ◽  
M. L. Reba ◽  
Q. Yu ◽  
M. S. Seyfried
Keyword(s):  
Water Balance ◽  
Latent Heat ◽  
Populus Tremuloides ◽  
Sensible Heat Flux ◽  
Growing Season ◽  
Carbon Fluxes ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Area Index

Abstract. 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 measured over different vegetation in a rangeland mountainous environment within the Reynolds Creek Experimental Watershed. Eddy covariance systems were used to measure surface fluxes over low sagebrush (Artemesia arbuscula), aspen (Populus tremuloides) and the understory of grasses and forbs beneath the aspen canopy. Peak leaf area index of the sagebrush, aspen, and aspen understory was 0.77, 1.35, and 1.20, respectively. The sagebrush and aspen canopies were subject to similar meteorological forces, while the understory of the aspen was sheltered from the wind. Estimated cumulative evapotranspiratation from the sagebrush, aspen understory, and aspen trees were 399 mm, 205 mm and 318 mm. A simple water balance of the catchment indicated that of the 700 mm of areal average precipitation, 442 mm was lost to evapotranspiration, and 254 mm of streamflow was measured from the catchment; water balance closure for the catchment was within 7 mm. Fluxes of latent heat and carbon for all sites were minimal through the winter. Growing season fluxes of latent heat and carbon were consistently higher above the aspen canopy than from the other sites. While growing season carbon fluxes were very similar for the sagebrush and aspen understory, latent heat fluxes for the sagebrush were consistently higher. Higher evapotranspiration from the sagebrush was likely because it is more exposed to the wind. Sensible heat flux from the aspen tended to be slightly less than the sagebrush site during the growing season when the leaves were actively transpiring, but exceeded that from the sagebrush in May, September and October when the net radiation was offset by evaporative cooling. Results from this study illustrate the influence of vegetation on the spatial variability of surface fluxes across mountainous rangeland landscapes.

On the influence of climate and land use change on monthly baseflow across the U.S. Midwest

2020 ◽  
Author(s):  
Jessica Ayers ◽  
Gabriele Villarini ◽  
Keith Schilling ◽  
Chris Jones
Keyword(s):  
Land Use ◽  
Water Availability ◽  
Statistical Models ◽  
Goodness Of Fit ◽  
Cross Validation ◽  
Growing Season ◽  
Corn Belt ◽  
Snow Melt ◽  
The U.S

<p>This study examines the role played by changes in the climate system and land use in the observed monthly baseflow records (1966-2015) for 458 U. S. Geological Survey sites across the U.S. Midwest. We developed parsimonious statistical models in which monthly baseflow is related to any combination of four predictors (precipitation, temperature, antecedent wetness, and agriculture). We found that precipitation and antecedent wetness were the strongest predictors for all months, pointing to the role of water availability and infiltration in driving baseflow. Temperature was an important factor in the winter and spring where snow-melt processes are the most relevant. Agriculture was selected in the Corn Belt region during the growing season (from April to August) indicating that corn and soybean production in the Midwest promote baseflow discharge to streams. Overall, the goodness-of-fit for our models and cross validation strongly support our modeling results for all months. Differences in model selection reported here can aid water managers in decision making for water availability, food security and economic growth.</p>

scholarly journals Influences of a Winter Wheat Belt on the Evolution of the Boundary Layer

2005 ◽  
Vol 133 (8) ◽  
pp. 2178-2199 ◽  
Author(s):  
Renee A. McPherson ◽  
David J. Stensrud
Keyword(s):  
Boundary Layer ◽  
Land Use ◽  
Heat Flux ◽  
Soil Moisture ◽  
Winter Wheat ◽  
Latent Heat ◽  
Planetary Boundary Layer ◽  
Heat Fluxes ◽  
Scale Transformation ◽  
Sensible Heat

Abstract Evidence exists that a large-scale alteration of land use by humans can cause changes in the climatology of the region. The largest-scale transformation is the substitution of native landscape by agricultural cropland. This modeling study examines the impact of a direct substitution of one type of grassland for another—in this case, the replacement of tallgrass prairie with winter wheat. The primary difference between these grasses is their growing season: native prairie grasses of the U.S. Great Plains are warm-season grasses whereas winter wheat is a cool-season grass. Case study simulations were conducted for 27 March 2000 and 5 April 2000—days analyzed in previous observational studies. The simulations provided additional insight into the physical processes involved and changes that occurred throughout the depth of the planetary boundary layer. Results indicate the following: 1) with the proper adjustment of vegetation parameters, land-use type, fractional vegetation coverage, and soil moisture, the numerical simulations were able to capture the overall patterns measured near the surface across a growing wheat belt during benign springtime conditions in Oklahoma; 2) the impacts of the mesoscale belt of growing wheat included increased values of latent heat flux and decreased values of sensible heat flux over the wheat, increased values of atmospheric moisture near the surface above and downstream of the wheat, and a shallower planetary boundary layer (PBL) above and downstream of the wheat; 3) in the sheared environments that were examined, a shallower PBL that resulted from growing wheat (rather than natural vegetation) led to reduced entrainment of higher momentum air into the PBL and, thus, weaker winds within the PBL over and downwind from the growing wheat; 4) for the cases studied, gradients in sensible heat were insufficient to establish an unambiguous vegetation breeze or its corresponding mesoscale circulation; 5) the initialization of soil moisture within the root zone aided latent heat fluxes from growing vegetation; and 6) reasonable specification of land surface parameters was required for the correct simulation and prediction of surface heat fluxes and resulting boundary layer development.

scholarly journals An Application of the Variational Method to Computation of Sensible Heat Flux over a Deciduous Forest

2005 ◽  
Vol 44 (1) ◽  
pp. 144-152 ◽  
Author(s):  
Zuohao Cao ◽  
Jianmin Ma
Keyword(s):  
Heat Flux ◽  
Variational Method ◽  
Forest Canopy ◽  
Deciduous Forest ◽  
Sensible Heat Flux ◽  
Meteorological Conditions ◽  
Heat Fluxes ◽  
Eddy Correlation ◽  
Sensible Heat ◽  
Variance Method

Abstract A variational method is employed to compute surface sensible heat fluxes over a deciduous forest using observed temperature, temperature variance, and wind. Because the variational approach is able to take into account comprehensive observational meteorological conditions over a heterogeneous surface, it is applicable to the computations of sensible heat flux over a forest canopy in which the conventional flux-variance method is difficult to use. Verifications using the direct eddy-correlation measurements over a deciduous forest during the fully leafed summer of 1988 and the leafless winter of 1990 show that the variational method yields very good agreements between the computed and the measured sensible heat fluxes. It is also shown that the variational method is much more accurate than the flux-variance method in computations of sensible heat flux over a forest canopy.

Scaling leaf photosynthesis to canopy in a mixed deciduous forest. I. model description

1997 ◽  
Vol 62 ◽  
Author(s):  
R. Samson ◽  
S. Follens ◽  
R. Lemeur
Keyword(s):  
Temperature Dependence ◽  
Quercus Robur ◽  
Deciduous Forest ◽  
Growing Season ◽  
Model Description ◽  
Canopy Photosynthesis ◽  
Leaf Photosynthesis ◽  
Layer Model ◽  
Mixed Deciduous Forest ◽  
Leaf Level

A  multi-layer model (FORUG) was developed, to simulate the canopy  photosynthesis of a mixed deciduous forest during the growing season.  Measured photosynthesis parameters, for beech (Fagus  sylvatica), oak (Quercus  robur) and ash (Fraxinus  excelsior), were used as input to the model. This  information at the leaf level is then scaled up to the level of the canopy,  taking into account the radiation profiles (diffuse and direct PAR) in the  canopy, the vertical LAI distribution, the evolution of the LAI and the  photosynthesis parameters during the growing season, and the temperature  dependence of the latter parameters.

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

2001 ◽  
Vol 31 (2) ◽  
pp. 208-223 ◽  
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 Ecosystem–Atmosphere 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·m–2 during 1994 and 135 g C·m–2 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·m–2 during 1994 and 270 g C·m–2 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·m–2·day–1 for OBS and 2.8 mg CH4·m–2·day–1 for fen sites, suggest that spruce areas are net annual sinks of about –0.12 g CH4·m–2, whereas fen areas generate net annual emissions on the order of 0.3–0.85 g CH4·m–2, 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.

scholarly journals Fire, land cover, and temperature drivers of bat activity in winter

Fire Ecology ◽  
2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Marcelo H. Jorge ◽  
Sara E. Sweeten ◽  
Michael C. True ◽  
Samuel R. Freeze ◽  
Michael J. Cherry ◽  
...  
Keyword(s):  
Land Cover ◽  
Habitat Management ◽  
Deciduous Forest ◽  
Pinus Palustris ◽  
Growing Season ◽  
Early Spring ◽  
Bat Activity ◽  
White Nose Syndrome ◽  
Dormant Season ◽  
Wind Energy Development

Abstract Background Understanding the effects of disturbance events, land cover, and weather on wildlife activity is fundamental to wildlife management. Currently, in North America, bats are of high conservation concern due to white-nose syndrome and wind-energy development impact, but the role of fire as a potential additional stressor has received less focus. Although limited, the vast majority of research on bats and fire in the southeastern United States has been conducted during the growing season, thereby creating data gaps for bats in the region relative to overwintering conditions, particularly for non-hibernating species. The longleaf pine (Pinus palustris Mill.) ecosystem is an archetypal fire-mediated ecosystem that has been the focus of landscape-level restoration in the Southeast. Although historically fires predominately occurred during the growing season in these systems, dormant-season fire is more widely utilized for easier application and control as a means of habitat management in the region. To assess the impacts of fire and environmental factors on bat activity on Camp Blanding Joint Training Center (CB) in northern Florida, USA, we deployed 34 acoustic detectors across CB and recorded data from 26 February to 3 April 2019, and from 10 December 2019 to 14 January 2020. Results We identified eight bat species native to the region as present at CB. Bat activity was related to the proximity of mesic habitats as well as the presence of pine or deciduous forest types, depending on species morphology (i.e., body size, wing-loading, and echolocation call frequency). Activity for all bat species was influenced positively by either time since fire or mean fire return interval. Conclusion Overall, our results suggested that fire use provides a diverse landscape pattern at CB that maintains mesic, deciduous habitat within the larger pine forest matrix, thereby supporting the diverse bat community at CB during the dormant season and early spring.

scholarly journals Land-Use Improvements in the Weather Research and Forecasting Model over Complex Mountainous Terrain and Comparison of Different Grid Sizes

2021 ◽  
Author(s):  
Alessio Golzio ◽  
Silvia Ferrarese ◽  
Claudio Cassardo ◽  
Gugliemina Adele Diolaiuti ◽  
Manuela Pelfini
Keyword(s):  
Boundary Layer ◽  
Land Use ◽  
Land Cover ◽  
Mixing Layer ◽  
Local Area ◽  
Heat Fluxes ◽  
Weather Research And Forecasting ◽  
Forecasting Model ◽  
Mountainous Terrain ◽  
Weather Research

AbstractWeather forecasts over mountainous terrain are challenging due to the complex topography that is necessarily smoothed by actual local-area models. As complex mountainous territories represent 20% of the Earth’s surface, accurate forecasts and the numerical resolution of the interaction between the surface and the atmospheric boundary layer are crucial. We present an assessment of the Weather Research and Forecasting model with two different grid spacings (1 km and 0.5 km), using two topography datasets (NASA Shuttle Radar Topography Mission and Global Multi-resolution Terrain Elevation Data 2010, digital elevation models) and four land-cover-description datasets (Corine Land Cover, U.S. Geological Survey land-use, MODIS30 and MODIS15, Moderate Resolution Imaging Spectroradiometer land-use). We investigate the Ortles Cevadale region in the Rhaetian Alps (central Italian Alps), focusing on the upper Forni Glacier proglacial area, where a micrometeorological station operated from 28 August to 11 September 2017. The simulation outputs are compared with observations at this micrometeorological station and four other weather stations distributed around the Forni Glacier with respect to the latent heat, sensible heat and ground heat fluxes, mixing-layer height, soil moisture, 2-m air temperature, and 10-m wind speed. The different model runs make it possible to isolate the contributions of land use, topography, grid spacing, and boundary-layer parametrizations. Among the considered factors, land use proves to have the most significant impact on results.

scholarly journals Midwinter melts in the Canadian prairies: energy balance and hydrological effects

2019 ◽  
Vol 23 (4) ◽  
pp. 1867-1883 ◽  
Author(s):  
Igor Pavlovskii ◽  
Masaki Hayashi ◽  
Daniel Itenfisu
Keyword(s):  
Surface Runoff ◽  
Hydrological Cycle ◽  
Remote Sensing Data ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Net Radiation ◽  
Present Climate ◽  
Canadian Prairies ◽  
Energy Inputs ◽  
Hydrological Effects

Abstract. Snowpack accumulation and depletion are important elements of the hydrological cycle in the Canadian prairies. The surface runoff generated during snowmelt is transformed into streamflow or fills numerous depressions driving the focussed recharge of groundwater in this dry setting. The snowpack in the prairies can undergo several cycles of accumulation and depletion in a winter. The timing of the melt affects the mechanisms of snowpack depletion and their hydrological implications. The effects of midwinter melts were investigated at four instrumented sites in the Canadian prairies. Unlike net radiation-driven snowmelt during spring melt, turbulent sensible heat fluxes were the dominant source of energy inputs for midwinter melt occurring in the period with low solar radiation inputs. Midwinter melt events affect several aspects of hydrological cycle with lower runoff ratios than subsequent spring melt events, due to their role in the timing of the focussed recharge. Remote sensing data have shown that midwinter melt events regularly occur under the present climate throughout the Canadian prairies, indicating applicability of the study findings throughout the region.

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