scholarly journals The response of tropical precipitation to Earth's precession: The role of fluxes and vertical stability

2018 ◽  
Author(s):  
Chetankumar Jalihal ◽  
Joyce Helena Catharina Bosmans ◽  
Jayaraman Srinivasan ◽  
Arindam Chakraborty
Keyword(s):  
Surface Energy ◽  
Bay Of Bengal ◽  
Heat Fluxes ◽  
Energy Fluxes ◽  
Surface Energy Fluxes ◽  
Tropical Precipitation ◽  
Vertical Stability ◽  
Stability Change ◽  
The Tropics

Abstract. The changes in Earth's precession have an impact on tropical precipitation. These changes have been ascribed to the changes in solar radiation at the top of the atmosphere, but this cannot explain the variations in precipitation over oceans. Using energy and moisture budget equations we have shown that the surface energy fluxes, as well as vertical stability, have to be taken into consideration along with insolation, to explain these changes in precipitation. Energy fluxes explain most of the changes in precipitation, when looking at the mean response over the tropics. However, there are regions like the Arabian sea and Africa where stability change is the main cause of change in precipitation. Hence, insolation cannot be thought of as the sole driver of precipitation on orbital timescales, but surface energy and vertical stability should also be considered when looking at oceans or smaller land regions. The decrease in precipitation over the Bay of Bengal, with higher summer insolation, has been shown to be due to the decrease in surface latent heat fluxes. This is a consequence of the remote response of the atmosphere to the enhanced latent heating to the west of Bay of Bengal. This leads to a decrease in wind speed over the Bay of Bengal and hence reduces the total column energy available for convection.

scholarly journals The response of tropical precipitation to Earth's precession: the role of energy fluxes and vertical stability

2019 ◽  
Vol 15 (2) ◽  
pp. 449-462 ◽  
Author(s):  
Chetankumar Jalihal ◽  
Joyce Helena Catharina Bosmans ◽  
Jayaraman Srinivasan ◽  
Arindam Chakraborty
Keyword(s):  
Bay Of Bengal ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Convective Heating ◽  
Energy Fluxes ◽  
Tropical Precipitation ◽  
Vertical Stability ◽  
Final Response ◽  
Precipitation Changes

Abstract. The changes in Earth's precession have an impact on the tropical precipitation. This has been attributed to the changes in seasonal solar radiation at the top of the atmosphere. The primary mechanism that has been proposed is the change in thermal gradient between the two hemispheres. This may be adequate to understand the zonal mean changes, but cannot explain the variations between land and oceans. We have used a simple model of the intertropical convergence zone (ITCZ) to unravel how precipitation changes with precession. Our model attributes the changes in precipitation to the changes in energy fluxes and vertical stability. We include the horizontal advection terms in this model, which were neglected in the earlier studies. The final response of the land and oceans is a result of complex feedbacks triggered by the initial changes in the insolation. We find that the changes in precipitation over the land are mainly driven by changes in insolation, but over the oceans, precipitation changes on account of changes in surface fluxes and vertical stability. Hence insolation can be a trigger for changes in precipitation on orbital timescales, but surface energy and vertical stability play an important role too. The African monsoon intensifies during a precession minimum (higher summer insolation). This intensification is mainly due to the changes in vertical stability. The precipitation over the Bay of Bengal decreases for minimum precession. This is on account of a remote response to the enhanced convective heating to the west of the Bay of Bengal. This weakens the surface winds and thus leads to a decrease in the surface latent heat fluxes and hence the precipitation.

scholarly journals Evapotranspiration and Surface Energy Fluxes Estimation Using the Landsat-7 Enhanced Thematic Mapper Plus Image over a Semiarid Agrosystem in the North-West of Algeria

2017 ◽  
Vol 32 (4) ◽  
pp. 691-702 ◽  
Author(s):  
Nehal Laounia ◽  
Hamimed Abderrahmane ◽  
Khaldi Abdelkader ◽  
Souidi Zahira ◽  
Zaagane Mansour
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Heat Fluxes ◽  
Actual Evapotranspiration ◽  
Semiarid Region ◽  
Energy Fluxes ◽  
North West ◽  
Surface Energy Fluxes ◽  
Landsat 7 ◽  
Energy Balance Approach

Abstract Monitoring evapotranspiration and surface energy fluxes over a range of spatial and temporal scales is crucial for many agroenvironmental applications. Different remote sensing based energy balance models have been developed, to estimate evapotranspiration at both field and regional scales. In this contribution, METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration), has been applied for the estimation of actual evapotranspiration in the Ghriss plain in Mascara (western Algeria), a semiarid region with heterogeneous surface conditions. Four images acquired during 2001 and 2002 by the Landsat-7 satellite were used. The METRIC model followed an energy balance approach, where evapotranspiration is estimated as the residual term when net radiation, sensible and soil heat fluxes are known. Different moisture indicators derived from the evapotranspiration were then calculated: reference evapotranspiration fraction, Priestley-Taylor parameter and surface resistance to evaporation. The evaluation of evapotranspiration and surface energy fluxes are accurate enough for the spatial variations of evapotranspiration rather satisfactory than sophisticated models without having to introduce an important number of parameters in input with difficult accessibility in routine. In conclusion, the results suggest that METRIC can be considered as an operational approach to predict actual evapotranspiration from agricultural areas having limited amount of ground information.

scholarly journals Impacts of grid resolution on surface energy fluxes simulated with an integrated surface-groundwater flow model

2015 ◽  
Vol 12 (7) ◽  
pp. 6437-6466
Author(s):  
P. Shrestha ◽  
M. Sulis ◽  
C. Simmer ◽  
S. Kollet
Keyword(s):  
Soil Moisture ◽  
Surface Energy ◽  
Groundwater Flow ◽  
Soil Temperature ◽  
System Modeling ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Grid Resolution ◽  
Energy Fluxes ◽  
Surface Energy Fluxes

Abstract. The hydrological component of the Terrestrial System Modeling Platform (TerrSysMP) which includes integrated surface-groundwater flow, was used to investigate the grid resolution dependence of simulated soil moisture, soil temperature, and surface energy fluxes over a sub-catchment of the Rur, Germany. The investigation was motivated by the recent developments of new earth system models, which include 3-D physically based groundwater models for the coupling of land–atmosphere interaction and subsurface hydrodynamics. Our findings suggest that for grid resolutions between 100 and 1000 m, the non-local controls of soil moisture are highly grid resolution dependent. Local vegetation, however, strongly modulates the scaling behavior especially for surface fluxes and soil temperature, which depends on the radiative transfer property of the canopy. This study also shows that for grid-resolutions above a few 100 m, the variation of spatial and temporal pattern of sensible and latent heat fluxes may significantly affect the resulting atmospheric mesoscale circulation and boundary layer evolution in coupled runs.

scholarly journals Impacts of grid resolution on surface energy fluxes simulated with an integrated surface-groundwater flow model

2015 ◽  
Vol 19 (10) ◽  
pp. 4317-4326 ◽  
Author(s):  
P. Shrestha ◽  
M. Sulis ◽  
C. Simmer ◽  
S. Kollet
Keyword(s):  
Soil Moisture ◽  
Surface Energy ◽  
Groundwater Flow ◽  
Soil Temperature ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Grid Resolution ◽  
Energy Fluxes ◽  
Spatial And Temporal Patterns ◽  
Surface Energy Fluxes

Abstract. The hydrological component of the Terrestrial Systems Modeling Platform (TerrSysMP), which includes integrated surface-groundwater flow, was used to investigate the grid resolution dependence of simulated soil moisture, soil temperature, and surface energy fluxes over a sub-catchment of the Rur, Germany. The investigation was motivated by the recent developments of new earth system models, which include 3-D physically based groundwater models for the coupling of land–atmosphere interaction and subsurface hydrodynamics. Our findings suggest that for grid resolutions between 100 and 1000 m, the non-local controls of soil moisture are highly grid resolution dependent. Local vegetation, however, strongly modulates the scaling behavior, especially for surface fluxes and soil temperature, which depends on the radiative transfer property of the canopy. This study also shows that for grid resolutions above a few 100 m, the variation of spatial and temporal patterns of sensible and latent heat fluxes may significantly affect the resulting atmospheric mesoscale circulation and boundary layer evolution in coupled runs.

scholarly journals The role of surface energy fluxes in pan-Arctic snow cover changes

2011 ◽  
Vol 6 (3) ◽  
pp. 035204 ◽  
Author(s):  
Xiaogang Shi ◽  
Pavel Ya Groisman ◽  
Stephen J Déry ◽  
Dennis P Lettenmaier
Keyword(s):  
Surface Energy ◽  
Snow Cover ◽  
Energy Fluxes ◽  
Surface Energy Fluxes

scholarly journals Comparison of FASST and SNTHERM in Three Snow Accumulation Regimes

2008 ◽  
Vol 9 (6) ◽  
pp. 1443-1463 ◽  
Author(s):  
Susan Frankenstein ◽  
Anne Sawyer ◽  
Julie Koeberle
Keyword(s):  
Surface Energy ◽  
Single Layer ◽  
Soil Strength ◽  
Snow Accumulation ◽  
Dynamic State ◽  
Energy Fluxes ◽  
One Dimensional ◽  
Surface Energy Fluxes ◽  
Snow Model ◽  
Surface Ice

Abstract Numerical experiments of snow accumulation and depletion were carried out as well as surface energy fluxes over four Cold Land Processes Experiment (CLPX) sites in Colorado using the Snow Thermal model (SNTHERM) and the Fast All-Season Soil Strength model (FASST). SNTHERM is a multilayer snow model developed to describe changes in snow properties as a function of depth and time, using a one-dimensional mass and energy balance. The model is intended for seasonal snow covers and addresses conditions found throughout the winter, from initial ground freezing in the fall to snow ablation in the spring. It has been used by many researchers over a variety of terrains. FASST is a newly developed one-dimensional dynamic state-of-the-ground model. It calculates the ground’s moisture content, ice content, temperature, and freeze–thaw profiles as well as soil strength and surface ice and snow accumulation/depletion. Because FASST is newer and not as well known, the authors wanted to determine its use as a snow model by comparing it with SNTHERM, one of the most established snow models available. It is demonstrated that even though FASST is only a single-layer snow model, the RMSE snow depth compared very favorably against SNTHERM, often performing better during the accumulation phase. The surface energy fluxes calculated by the two models were also compared and were found to be similar.

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