Land-Atmosphere Interactions

Geography ◽  
2020 ◽  
Author(s):  
Geoffrey M. Henebry ◽  
Nathan J. Moore ◽  
Jiquan Chen
Keyword(s):  
Heat Flux ◽  
Water Vapor ◽  
Solar Radiation ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface ◽  
Longwave Radiation ◽  
Coupled Processes ◽  
Shortwave Radiation ◽  
Ground Heat Flux

Land-atmosphere interactions encompass a multitude of processes that link the land surface with the atmospheric boundary layer. Interactions are bidirectional, include energy and material exchanges, and can include feedbacks that can amplify or attenuate coupled processes. Shortwave radiation drives most of the biogeophysical processes at the land surface. Photosynthetically active radiation (PAR) is the subset of shortwave radiation (400–700 nanometers) and is critical for most life on the planet. Thermal infrared is the more energetic subset of terrestrial radiation that results primarily from interactions of solar radiation with the land surface. Microwaves are an important subset of terrestrial radiation that facilitate monitoring both atmosphere and land surface. Net radiation is the energy left over after accounting for incoming direct and indirect solar radiation less outgoing solar radiation reflected by the surface, plus incoming longwave radiation (from water vapor and other gases in the atmosphere and terrestrial materials within view of the surface), less outgoing longwave radiation from the land surface. This radiation remaining at an “ideal surface” can be simply partitioned into energy transferred into the surface (ground heat flux) plus energy transferred to heat the atmosphere above the surface (sensible heat flux) plus energy transferred via evapotranspiration (latent heat flux) to moisten the atmosphere. Additionally, objects on the surface can absorb radiation and later radiate this stored heat. Photosynthesis uses only a small portion of incident energy. Precipitation on the surface may (1) return to the atmosphere as water vapor (latent heat flux), (2) move as liquid laterally to another surface point (runoff), (3) move as liquid below the surface (drainage), (4) be retained at or below the surface, including in the soil (storage), (5) be transported away, if frozen, from the surface by wind (advection), or combinations of these. Material exchanges between surface and atmosphere include mineral dust, organic particles, biota, and biological materials such as pollen, seeds, combustion products, volcanic ash and ejecta, trace gas emissions, and anthropogenic emissions from stationary and mobile sources. Interactions between the land surface and lower portion of the atmosphere at various time scales from seconds to centuries are influenced by the amount and type of incident sunlight, radiative characteristics of the materials at the surface, amount of moisture at and below the surface, vegetation amount and type, soils and substrate, vertical structures at the surface that affect wind, land cover type and arrangement, atmospheric constituents, and recent weather. Here we focus on interactions moving from land to the atmosphere.

Energy management in dry canopy starts with efficient leaf-scale heat exchange

2020 ◽  
Author(s):  
Jonathan D. Müller ◽  
Eyal Rotenberg ◽  
Fedor Tatarinov ◽  
Itay Oz ◽  
Efrat Schwartz ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Exchange ◽  
Energy Management ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Sensible Heat Flux ◽  
Longwave Radiation ◽  
Shortwave Radiation ◽  
Wave Radiation ◽  
Sensible Heat

<p>Dry forests are expected to heat up considerably more than adjacent shrubland areas due to lower albedo and reduced latent heat flux. Paradoxically, the forest surface at our research site was observed to be cooler than the non-forested neighbouring areas during drought. This reflected the control over canopy temperature through the sensible heat flux, i.e. a 'convector effect'. Our objective was to examine how the efficient non-evaporative energy management, critical to protect the biological functioning of dryland ecosystems, develops at the small, leaf scale. </p><p>We developed a novel system to continuously measure the energy balance and heat dissipation mechanisms on a leaf scale under field conditions. It allows the measurement of emitted leaf and background longwave radiation, and estimating the incoming, absorbed and reflected shortwave radiation using PAR measurements and full spectrum models.  Latent heat exchange and photosynthetic activity were measured with branch chambers. The system was deployed during the long summer drought (>8 months) in drought-exposed and irrigated plots in our semi-arid research Aleppo Pine forest site in southern Israel (mean daytime temperature of >30°C).</p><p>Preliminary results showed that in spite of a x10 higher transpiration rate in the irrigated plot compared with the control plots, leaf temperature remains within 1-2°C of air temperature on average in both plots during direct exposure to sunlight at midday. These results suggest an effective leaf to air heat transfer which prevents overheating independent of the latent heat flux. Under the high radiation load, the midday summer value of incoming shortwave radiation was >800 W·m<sup>-2</sup> (mostly absorbed by the low albedo leaves), and background longwave radiation was >500 W·m<sup>-2</sup>. In turn, the energy dissipation in the drought-exposed trees was dominated by sensible heat flux of >500 W·m<sup>-2</sup>, while the long-wave radiation balance was near neutral (~50 W m<sup>-2</sup>), and the residual latent heat flux was <50 W·m<sup>-2</sup>. We demonstrated a system that provided new insights to leaf and canopy energy management under drought, which is a basis for the evolution of the convector effect.</p>

scholarly journals Estimation of surface energy fluxes under complex terrain of Mt. Qomolangma over the Tibetan Plateau

2013 ◽  
Vol 17 (4) ◽  
pp. 1607-1618 ◽  
Author(s):  
X. Chen ◽  
Z. Su ◽  
Y. Ma ◽  
K. Yang ◽  
B. Wang
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Solar Radiation ◽  
Surface Energy ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Surface Energy Balance ◽  
Sensible Heat ◽  
Balance System ◽  
Ground Heat Flux

Abstract. Surface solar radiation is an important parameter in surface energy balance models and in estimation of evapotranspiration. This study developed a DEM based radiation model to estimate instantaneous clear sky solar radiation for surface energy balance system to obtain accurate energy absorbed by the mountain surface. Efforts to improve spatial accuracy of satellite based surface energy budget in mountainous regions were made in this work. Based on eight scenes of Landsat TM/ETM+ (Thematic Mapper/Enhanced Thematic Mapper+) data and observations around the Qomolangma region of the Tibetan Plateau, the topographical enhanced surface energy balance system (TESEBS) was tested for deriving net radiation, ground heat flux, sensible heat flux and latent heat flux distributions over the heterogeneous land surface. The land surface energy fluxes over the study area showed a wide range in accordance with the surface features and their thermodynamic states. The model was validated by observations at QOMS/CAS site in the research area with a reasonable accuracy. The mean bias of net radiation, sensible heat flux, ground heat flux and latent heat flux is lower than 23.6 W m−2. The surface solar radiation estimated by the DEM based radiation model developed by this study has a mean bias as low as −9.6 W m−2. TESEBS has a decreased mean bias of about 5.9 W m−2 and 3.4 W m−2 for sensible heat and latent heat flux, respectively, compared to the Surface Energy Balance System (SEBS).

Scanning 10-W Water Vapor DIAL for the Investigation of Atmospheric Turbulence and Land-Atmosphere Feedback

2021 ◽  
Author(s):  
Andreas Behrendt ◽  
Florian Spaeth ◽  
Volker Wulfmeyer
Keyword(s):  
Heat Flux ◽  
Water Vapor ◽  
Latent Heat ◽  
Atmospheric Turbulence ◽  
Latent Heat Flux ◽  
Climate Models ◽  
Weather Forecast ◽  
Surface Characteristics ◽  
Scanning System ◽  
Forecast Models

<p>We will present recent measurements made with the water vapor differential absorption lidar (DIAL) of University of Hohenheim (UHOH). This scanning system has been developed in recent years for the investigation of atmospheric turbulence and land-atmosphere feedback processes.</p><p>The lidar is housed in a mobile trailer and participated in recent years in a number of national and international field campaigns. We will present examples of vertical pointing and scanning measurements, especially close to the canopy. The water vapor gradients in the surface layer are related to the latent heat flux. Thus, with such low-elevation scans, the latent heat flux distribution over different surface characteristics can be monitored, which is important to verify and improve both numerical weather forecast models and climate models.</p><p>The transmitter of the UHOH DIAL consists of a diode-pumped Nd:YAG laser which pumps a Ti:sapphire laser. The output power of this laser is up to 10 W. Two injection seeders are used to switch pulse-to-pulse between the online and offline signals. These signals are then either directly sent into the atmosphere or coupled into a fiber and guided to a transmitting telescope which is attached to the scanner unit. The receiving telescope has a primary mirror with a dimeter of 80 cm. The backscatter signals are recorded shot to shot and are typically averaged over 0.1 to 1 s.</p>

The Effect of Soil on the Summertime Surface Energy Budget of a Humid Subarctic Tundra in Northern Quebec, Canada

2021 ◽  
Vol 22 (10) ◽  
pp. 2547-2564
Author(s):  
Georg Lackner ◽  
Daniel F. Nadeau ◽  
Florent Domine ◽  
Annie-Claude Parent ◽  
Gonzalo Leonardini ◽  
...  
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface ◽  
Sensible Heat Flux ◽  
Arctic Region ◽  
Heat Fluxes ◽  
Surface Energy Budget ◽  
Turbulent Heat ◽  
Turbulent Heat Fluxes

AbstractRising temperatures in the southern Arctic region are leading to shrub expansion and permafrost degradation. The objective of this study is to analyze the surface energy budget (SEB) of a subarctic shrub tundra site that is subject to these changes, on the east coast of Hudson Bay in eastern Canada. We focus on the turbulent heat fluxes, as they have been poorly quantified in this region. This study is based on data collected by a flux tower using the eddy covariance approach and focused on snow-free periods. Furthermore, we compare our results with those from six Fluxnet sites in the Arctic region and analyze the performance of two land surface models, SVS and ISBA, in simulating soil moisture and turbulent heat fluxes. We found that 23% of the net radiation was converted into latent heat flux at our site, 35% was used for sensible heat flux, and about 15% for ground heat flux. These results were surprising considering our site was by far the wettest site among those studied, and most of the net radiation at the other Arctic sites was consumed by the latent heat flux. We attribute this behavior to the high hydraulic conductivity of the soil (littoral and intertidal sediments), typical of what is found in the coastal regions of the eastern Canadian Arctic. Land surface models overestimated the surface water content of those soils but were able to accurately simulate the turbulent heat flux, particularly the sensible heat flux and, to a lesser extent, the latent heat flux.

Sensitivity of Latent Heat Flux from PILPS Land-Surface Schemes to Perturbations of Surface Air Temperature

1998 ◽  
Vol 55 (11) ◽  
pp. 1909-1927 ◽  
Author(s):  
Weiqing Qu ◽  
A. Henderson-Sellers ◽  
A. J. Pitman ◽  
T. H. Chen ◽  
F. Abramopoulos ◽  
...  
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Air Temperature ◽  
Land Surface ◽  
Surface Air Temperature

scholarly journals Simulation of Land Surface Climate over China with RegCM4.5: Verification and Analysis

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Minghao Yang ◽  
Ruiting Zuo ◽  
Liqiong Wang ◽  
Xiong Chen
Keyword(s):  
Heat Flux ◽  
Soil Moisture ◽  
Surface Temperature ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface Temperature ◽  
South China ◽  
Land Surface ◽  
Reanalysis Data ◽  
Surface Evaporation

The ability of RegCM4.5 using land surface scheme CLM4.5 to simulate the physical variables related to land surface state was investigated. The NCEP-NCAR reanalysis data for the period 1964–2003 were used to drive RegCM4.5 to simulate the land surface temperature, precipitation, soil moisture, latent heat flux, and surface evaporation. Based on observations and reanalysis data, a few land surface variables were analyzed over China. The results showed that some seasonal features of land surface temperature in summer and winter as well as its magnitude could be simulated well. The simulation of precipitation was sensitive to region and season. The model could, to a certain degree, simulate the seasonal migration of rainband in East China. The overall spatial distribution of the simulated soil moisture was better in winter than in summer. The simulation of latent heat flux was also better in winter. In summer, the latent heat flux bias mainly arose from surface evaporation bias in Northwest China, and it primarily arose from vegetation evapotranspiration bias in South China. In addition, the large latent heat flux bias in South China during summer was probably due to less precipitation generated in the model and poor representation of vegetation cover in this region.

Land–Atmosphere Interaction in Tropical Africa

2020 ◽  
Author(s):  
Cathy Hohenegger
Keyword(s):  
Heat Flux ◽  
Soil Moisture ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Surface State ◽  
Land Surface ◽  
Large Scale ◽  
Moisture Distribution ◽  
Sahel Region ◽  
The Impact

Even though many features of the vegetation and of the soil moisture distribution over Africa reflect its climatic zones, the land surface has the potential to feed back on the atmosphere and on the climate of Africa. The land surface and the atmosphere communicate via the surface energy budget. A particularly important control of the land surface, besides its control on albedo, is on the partitioning between sensible and latent heat flux. In a soil moisture-limited regime, for instance, an increase in soil moisture leads to an increase in latent heat flux at the expanse of the sensible heat flux. The result is a cooling and a moistening of the planetary boundary layer. On the one hand, this thermodynamically affects the atmosphere by altering the stability and the moisture content of the vertical column. Depending on the initial atmospheric profile, convection may be enhanced or suppressed. On the other hand, a confined perturbation of the surface state also has a dynamical imprint on the atmospheric flow by generating horizontal gradients in temperature and pressure. Such gradients spin up shallow circulations that affect the development of convection. Whereas the importance of such circulations for the triggering of convection over the Sahel region is well accepted and well understood, the effect of such circulations on precipitation amounts as well as on mature convective systems remains unclear. Likewise, the magnitude of the impact of large-scale perturbations of the land surface state on the large-scale circulation of the atmosphere, such as the West African monsoon, has long been debated. One key issue is that such interactions have been mainly investigated in general circulation models where the key involved processes have to rely on uncertain parameterizations, making a definite assessment difficult.

scholarly journals Evaluation of functional properties of various types of vegetation cover using remotely sensed data analysis

2010 ◽  
Vol 4 (Special Issue 2) ◽  
pp. S49-S58 ◽  
Author(s):  
J. Brom ◽  
J. Procházka ◽  
A. Rejšková
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface ◽  
Hydrological Cycle ◽  
Sensible Heat Flux ◽  
Sensible Heat ◽  
Remotely Sensed Data ◽  
Mean Values

The dissipation of solar energy and consequently the formation of the hydrological cycle are largely dependent on the structural and optical characteristics of the land surface. In our study, we selected seven units with different types of vegetation in the Mlýnský and Horský catchments (South-Eastern part of the Šumava Mountains, Czech Republic) for the assessment of the differences in their functioning expressed through the surface temperature, humidity, and energy dissipation. For our analyses, we used Landsat 5 TM satellite data from June 25<SUP>th</SUP>, 2008. The results showed that the microclimatic characteristics and energy fluxes varied in different units according to their vegetation characteristics. A cluster analysis of the mean values was used to divide the vegetation units into groups according to their functional characteristics. The mown meadows were characterised by the highest surface temperature and sensible heat flux and the lowest humidity and latent heat flux. On the contrary, the lowest surface temperature and sensible heat flux and the highest humidity and latent heat flux were found in the forest. Our results showed that the climatic and energetic features of the land surface are related to the type of vegetation. We state that the spatial distribution of different vegetation units and the amount of biomass are crucial variables influencing the functioning of the landscape.

scholarly journals Latent Heat Flux Profiles from Collocated Airborne Water Vapor and Wind Lidars during IHOP_2002

2007 ◽  
Vol 24 (4) ◽  
pp. 627-639 ◽  
Author(s):  
C. Kiemle ◽  
G. Ehret ◽  
A. Fix ◽  
M. Wirth ◽  
G. Poberaj ◽  
...  
Keyword(s):  
Heat Flux ◽  
Water Vapor ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Deep Convection ◽  
Minor Role ◽  
Flux Divergence ◽  
Convective Boundary ◽  
Budget Analysis ◽  
Wind Lidar

Abstract Latent heat flux profiles in the convective boundary layer (CBL) are obtained for the first time with the combination of the Deutsches Zentrum für Luft- und Raumfahrt (DLR) water vapor differential absorption lidar (DIAL) and the NOAA high resolution Doppler wind lidar (HRDL). Both instruments were integrated nadir viewing on board the DLR Falcon research aircraft during the International H2O Project (IHOP_2002) over the U.S. Southern Great Plains. Flux profiles from 300 to 2500 m AGL are computed from high spatial resolution (150 m horizontal and vertical) two-dimensional water vapor and vertical velocity lidar cross sections using the eddy covariance technique. Three flight segments on 7 June 2002 between 1000 and 1300 LT over western Oklahoma and southwestern Kansas are analyzed. On two segments with strong convection, the latent heat flux peaks at (700 ± 200) W m−2 in the entrainment zone and decreases linearly to (200 ± 100) W m−2 in the lower CBL. A water vapor budget analysis reveals that this flux divergence [(0.9 ± 0.4) g kg−1 h−1] plus the advection (0.3 g kg−1 h−1) are nearly balanced by substantial CBL drying [(1.5 ± 0.2) g kg−1 h−1] observed by airborne and surface in situ instruments, within the limits of the overall budget rms error of 0.5 g kg−1 h−1. Entrainment of dry air from aloft and net upward humidity transport caused the CBL drying and finally inhibited the initiation of deep convection. All cospectra show significant contributions to the flux between 1- and 10-km wavelength, with peaks between 2 and 6 km, originating from large eddies. The main flux uncertainty is due to low sampling (55% rmse at mid-CBL), while instrument noise (15%) and systematic errors (7%) play a minor role. The combination of a water vapor and a wind lidar on an aircraft appears as an attractive new tool that allows measuring latent heat flux profiles from a single overflight of the investigated area.

scholarly journals Mesoscale Simulations of the Land Surface Effects of Historical Logging in a Moist Continental Climate Regime

2008 ◽  
Vol 47 (8) ◽  
pp. 2166-2182 ◽  
Author(s):  
Nicholas P. Klingaman ◽  
Jason Butke ◽  
Daniel J. Leathers ◽  
Kevin R. Brinson ◽  
Elsa Nickl
Keyword(s):  
Climate Change ◽  
Heat Flux ◽  
Land Cover ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface ◽  
Climate Regime ◽  
Clear Cut ◽  
Atmosphere System ◽  
Regional Climates

Abstract An enhanced knowledge of the feedbacks from land surface changes on regional climates is of great importance in the attribution of climate change. To explore the effects of deforestation on a midlatitude climate regime, two sets of two five-member ensembles of 28-day simulations were conducted using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) coupled to the “Noah” land surface model. The four ensembles represented conditions in summer (August) and winter (February) across the northern mid-Atlantic United States before and after extensive late-nineteenth-century logging of hardwood forests in central and northern Pennsylvania. Prelogging ensembles prescribed a vegetative cover of an evergreen needleleaf forest; postlogging ensembles prescribed sparse vegetation and bare soil to simulate clear-cut deforestation. The results of the MM5 experiments showed a decided seasonality in the response of the land surface–atmosphere system to deforestation, with much stronger effects arising in summer. In August, deforestation caused a repartitioning of the surface energy budget, beginning with a decrease in the latent heat flux of more than 60 W m−2 across the land cover–forcing area, representing almost one-half of the latent heat flux under prelogging land cover. Concomitant with this decrease in evapotranspiration, mean 2-m air temperatures warmed by at least 1.5°C. Increases in sensible heat flux led to a 150-m mean increase in the height of the atmospheric boundary layer over the deforested area. Low-level atmospheric mixing ratios and total precipitation decreased under clear-cut conditions. Mean soil moisture increased in all model levels to 150 cm because of a decrease in vegetative uptake of water, except at the 5-cm level at which such decreases were effectively balanced by greater soil evaporation and less precipitation. A strong diurnal variation in the response to deforestation of ground and lower-atmosphere temperatures and heat fluxes was also identified for the summer season. The February simulations showed the effects of deforestation during low-insolation months to be small and variable. The strong response of the summer land surface–atmosphere system to deforestation shown here suggests that land cover changes can appreciably affect regional climates. Thus, the role of human-induced and naturally occurring land cover variability should not be ignored in the attribution of climate change.

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