scholarly journals How vadose zone mass and energy transfer physics affects the ecohydrological dynamics of a Tibetan meadow?

2020 ◽  
Author(s):  
Lianyu Yu ◽  
Yijian Zeng ◽  
Simone Fatichi ◽  
Zhongbo Su
Keyword(s):  
Vadose Zone ◽  
Land Surface ◽  
Ecosystem Functioning ◽  
Vegetation Dynamics ◽  
Process Model ◽  
Environmental Changes ◽  
Model Performance ◽  
Frozen Soil ◽  
The Tibetan Plateau

Abstract. The vadose zone is a sensitive region to environmental changes and exerts a crucial control in ecosystem functioning. While the way in representing the underlying process of vadose zone differs among models, the effect of such differences on ecosystem functioning is seldomly reported. Here, the detailed vadose zone process model STEMMUS was coupled with the ecohydrological model T&C to investigate the role of solving influential physical processes, considering different soil water and heat transfer parameterizations including frozen soils. We tested model performance with the aid of a comprehensive observation dataset collected at a typical meadow ecosystem on the Tibetan Plateau. Results indicated that: i) explicitly considering the frozen soil process significantly improved the soil moisture/temperature (SM/ST) profile simulations and facilitated our understanding of the water transfer processes within the soil-plant-atmosphere continuum; ii) the difference among various complexity of vadose zone physics have an impact on the vegetation dynamics mainly at the beginning of the growing season; iii) models with different vadose zone physics can predict similar interannual vegetation dynamics, and energy, water and carbon exchanges at the land-surface. This research highlights the role of vadose zone models and their underlying physics, in ecosystem functioning and can guide the development and applications of future earth system models.

scholarly journals The role of vadose zone physics in the ecohydrological response of a Tibetan meadow to freeze–thaw cycles

2020 ◽  
Vol 14 (12) ◽  
pp. 4653-4673
Author(s):  
Lianyu Yu ◽  
Simone Fatichi ◽  
Yijian Zeng ◽  
Zhongbo Su
Keyword(s):  
Vadose Zone ◽  
Ecosystem Functioning ◽  
Vegetation Dynamics ◽  
Water Transfer ◽  
The Tibetan Plateau ◽  
Soil System ◽  
Cold Regions ◽  
Freeze Thaw ◽  
The Impact

Abstract. The vadose zone is a zone sensitive to environmental changes and exerts a crucial control in ecosystem functioning and even more so in cold regions considering the rapid change in seasonally frozen ground under climate warming. While the way in representing the underlying physical process of the vadose zone differs among models, the effect of such differences on ecosystem functioning and its ecohydrological response to freeze–thaw cycles are seldom reported. Here, the detailed vadose zone process model STEMMUS (Simultaneous Transfer of Energy, Mass and Momentum in Unsaturated Soil) was coupled with the ecohydrological model Tethys–Chloris (T&C) to investigate the role of influential physical processes during freeze–thaw cycles. The physical representation is increased from using T&C coupling without STEMMUS enabling the simultaneous mass and energy transfer in the soil system (liquid, vapor, ice) – and with explicit consideration of the impact of soil ice content on energy and water transfer properties – to using T&C coupling with it. We tested model performance with the aid of a comprehensive observation dataset collected at a typical meadow ecosystem on the Tibetan Plateau. Results indicated that (i) explicitly considering the frozen soil process significantly improved the soil moisture/temperature profile simulations and facilitated our understanding of the water transfer processes within the soil–plant–atmosphere continuum; (ii) the difference among various representations of vadose zone physics have an impact on the vegetation dynamics mainly at the beginning of the growing season; and (iii) models with different vadose zone physics can predict similar interannual vegetation dynamics, as well as energy, water, and carbon exchanges, at the land surface. This research highlights the important role of vadose zone physics for ecosystem functioning in cold regions and can support the development and application of future Earth system models.

scholarly journals Development of a Unified Land Model for Prediction of Surface Hydrology and Land–Atmosphere Interactions

2011 ◽  
Vol 12 (6) ◽  
pp. 1299-1320 ◽  
Author(s):  
Ben Livneh ◽  
Pedro J. Restrepo ◽  
Dennis P. Lettenmaier
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Climate Models ◽  
A Priori ◽  
Model Performance ◽  
Surface Flux ◽  
Surface Fluxes ◽  
Frozen Soil ◽  
Surface Model ◽  
Soil Moisture Accounting

Abstract A unified land model (ULM) is described that combines the surface flux parameterizations in the Noah land surface model (used in most of NOAA’s coupled weather and climate models) with the Sacramento Soil Moisture Accounting model (Sac; used for hydrologic prediction within the National Weather Service). The motivation was to develop a model that has a history of strong hydrologic performance while having the ability to be run in the coupled land–atmosphere environment. ULM takes the vegetation, snow model, frozen soil, and evapotranspiration schemes from Noah and merges them with the soil moisture accounting scheme from Sac. ULM surface fluxes, soil moisture, and streamflow simulations were evaluated through comparisons with observations from the Ameriflux (surface flux), Illinois Climate Network (soil moisture), and Model Parameter Estimation Experiment (MOPEX; streamflow) datasets. Initially, a priori parameters from Sac and Noah were used, which resulted in ULM surface flux simulations that were comparable to those produced by Noah (Sac does not predict surface energy fluxes). ULM with the a priori parameters had streamflow simulation skill that was generally similar to Sac’s, although it was slightly better (worse) for wetter (more arid) basins. ULM model performance using a set of parameters identified via a Monte Carlo search procedure lead to substantial improvements relative to the a priori parameters. A scheme for transfer of parameters from streamflow simulations to nearby flux and soil moisture measurement points was also evaluated; this approach did not yield conclusive improvements relative to the a priori parameters.

Quantification of the relative role of land-surface processes and large-scale forcing in dynamic downscaling over the Tibetan Plateau

2016 ◽  
Vol 48 (5-6) ◽  
pp. 1705-1721 ◽  
Author(s):  
Yanhong Gao ◽  
Linhong Xiao ◽  
Deliang Chen ◽  
Fei Chen ◽  
Jianwei Xu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Large Scale ◽  
Surface Processes ◽  
The Tibetan Plateau ◽  
Relative Role ◽  
Dynamic Downscaling ◽  
Land Surface Processes

scholarly journals Evaluating the Atibaia River Hydrology using JULES6.1

2021 ◽  
Author(s):  
Hsi-Kai Chou ◽  
Ana Maria Heuminski de Avila ◽  
Michaela Bray
Keyword(s):  
Land Surface ◽  
Environmental Changes ◽  
Water Flux ◽  
Model Performance ◽  
Reanalysis Data ◽  
Agricultural Activity ◽  
Multiple Sources ◽  
Metropolitan Regions ◽  
River Hydrology

Abstract. Land surface models such as the Joint UK Land Environment Simulator (JULES) are increasingly used for hydrological assessments because of their state-of-the-art representation of physical processes and versatility. Unlike statistical models and AI models, the JULES model simulates the physical water flux under given meteorological conditions, allowing us to understand and investigate the cause and effect of environmental processes changes. Here we explore the possibility of this approach using a case study in the Atibaia river basin, which serves as a major water supply for metropolitan regions of Campinas and São Paulo, Brazil. The watershed is suffering increasing hydrological risks, which could be attributed to environmental changes, such as urbanization and agricultural activity. The increasing risks highlight the importance to evaluate the land surface processes of the watershed systematically. We explore the use of local precipitation collection complement with multiple sources of global reanalysis data to simulate the basin hydrology. Our results show that the coarse resolution of rainfall data is the main reason to reduce model performance. Despite this shortcoming, key hydrological fluxes in the basin can be represented by the JULES model simulations.

The Role of Vadose Zone Physics in the Soil Hydrothermal and Ecohydrological Response of a Tibetan Meadow Ecosystem to Freeze-Thaw Cycles

2021 ◽  
Author(s):  
Lianyu Yu ◽  
Yijian Zeng ◽  
Simone Fatichi ◽  
Zhongbo Su
Keyword(s):  
Vadose Zone ◽  
Ecosystem Functioning ◽  
Water Transfer ◽  
Vapor Flow ◽  
Modeling Framework ◽  
Soil System ◽  
Cold Regions ◽  
Freeze Thaw ◽  
The Impact

<p>The vadose zone is a zone sensitive to environmental changes and exerts a crucial control in ecosystem functioning and even more so in cold regions considering the rapid change in the seasonally frozen ground under climate warming. While the way in representing the underlying physical process of the vadose zone differs among models, the effect of such differences on soil hydrothermal regimes, and then ecosystem functioning and its ecohydrological response to freeze–thaw cycles are seldom reported. Here, the detailed vadose zone process modeling framework STEMMUS (Simultaneous Transfer of Energy, Mass and Momentum in Unsaturated Soil) was coupled with the ecohydrological model Tethys–Chloris (T&C) to investigate the role of influential physical processes during freeze-thaw cycles. The physical representation is increased from using T&C coupling without STEMMUS enabling the simultaneous mass and energy transfer in the soil system (liquid, vapor, ice) – and with explicit consideration of the impact of soil ice content on energy and water transfer properties – to using T&C coupling with it. We tested model performance with the aid of a comprehensive observation dataset collected at a typical meadow ecosystem on the Tibetan Plateau. Results indicated that explicitly considering the frozen soil process and vapor flow significantly improved the soil moisture/temperature profile simulations and facilitated our understanding of the water transfer processes within the soil-plant-atmosphere continuum. We further demonstrated the linkage between the vadose zone physics-induced difference in soil hydrothermal regimes and the ecosystem water/carbon cycles. This research highlights the important role of vadose zone physics for ecosystem functioning in cold regions and can support the development and application of future Earth system models.</p>

scholarly journals Plant phenological responses to climate change on the Tibetan Plateau: research status and challenges

2015 ◽  
Vol 2 (4) ◽  
pp. 454-467 ◽  
Author(s):  
Miaogen Shen ◽  
Shilong Piao ◽  
Tsechoe Dorji ◽  
Qiang Liu ◽  
Nan Cong ◽  
...  
Keyword(s):  
Climate Change ◽  
Remote Sensing ◽  
Tibetan Plateau ◽  
Environmental Changes ◽  
The Tibetan Plateau ◽  
Ecosystem Structure ◽  
Positive Role ◽  
Ecosystem Responses ◽  
Research Issues

Abstract Phenology studies the cycle of events in nature that are initiated and driven by an annually recurring environment. Plant phenology is expected to be one of the most sensitive and easily observable natural indicators of climate change. On the Tibetan Plateau (TP), an accelerated warming since the mid-1980s has resulted in significant environmental changes. These new conditions are accompanied by phenological changes that are characterized by considerable spatiotemporal heterogeneity. Satellite remote sensing observed widespread advance in the start of the plant growing season across the plateau during the 1980s and 1990s but substantial delay over 2000–2011 in the southwest although it continued to advance in the northeast regions of the TP. Both observational studies and controlled experiments have revealed, to some extent, the positive role of higher preseason temperature and even more precipitation in advancing the leaf onset and first flowering date of the TP. However, a number of rarely visited research issues that are essential for understanding the role of phenology in ecosystem responses and feedback processes to climate change remain to be solved. Our review recommends that addressing the following questions should be a high priority. How did other phenological events change, such as flowering and fruiting phenology? What are the influences from environmental changes other than temperature and precipitation, including human activities such as grazing? What are the genetic and physiological bases of plants phenological responses? How does phenological change influence ecosystem structure and function at different scales and feedback to the climate system? Investigating these research questions requires, first of all, new data of the associated environmental variables, and consistent and reliable phenological observation using different methodologies (i.e. in situ observations and remote sensing).

scholarly journals A parameterization of sub-grid topographical effects on solar radiation in the E3SM Land Model (version 1.0): implementation and evaluation over the Tibetan Plateau

2021 ◽  
Vol 14 (10) ◽  
pp. 6273-6289
Author(s):  
Dalei Hao ◽  
Gautam Bisht ◽  
Yu Gu ◽  
Wei-Liang Lee ◽  
Kuo-Nan Liou ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Surface Energy ◽  
Surface Temperature ◽  
Snow Cover ◽  
Land Surface ◽  
Spatial Scales ◽  
The Tibetan Plateau ◽  
Topographic Effects ◽  
Earth System

Abstract. Topography exerts significant influences on the incoming solar radiation at the land surface. A few stand-alone regional and global atmospheric models have included parameterizations for sub-grid topographic effects on solar radiation. However, nearly all Earth system models (ESMs) that participated in the Coupled Model Intercomparison Project (CMIP6) use a plane-parallel (PP) radiative transfer scheme that assumes that the terrain is flat. In this study, we incorporated a well-validated sub-grid topographic (TOP) parameterization in the Energy Exascale Earth System Model (E3SM) Land Model (ELM) version 1.0 to quantify the effects of sub-grid topography on solar radiation flux, including the shadow effects and multi-scattering between adjacent terrain. We studied the role of sub-grid topography by performing ELM simulations with the PP and TOP schemes over the Tibetan Plateau (TP). Additional ELM simulations were performed at multiple spatial resolutions to investigate the role of spatial scale on sub-grid topographic effects on solar radiation. The Moderate Resolution Imaging Spectroradiometer (MODIS) data was used to compare with the ELM simulations. The results show that topography has non-negligible effects on surface energy budget, snow cover, snow depth, and surface temperature over the TP. The absolute differences in surface energy fluxes for net solar radiation, latent heat flux, and sensible heat flux between TOP and PP exceed 20, 10, and 5 W m−2, respectively. The differences in land surface albedo, snow cover fraction, snow depth, and surface temperature between TOP and PP exceed 0.1, 0.1, 10 cm, and 1 K, respectively. The magnitude of the sub-grid topographic effects is dependent on seasons and elevations and is also sensitive to the spatial scales. Although the sub-grid topographic effects on solar radiation are larger with more spatial details at finer spatial scales, they cannot be simply neglected at coarse spatial scales. When compared to MODIS data, incorporating the sub-grid topographic effects overall reduces the biases of ELM in simulating surface energy balance, snow cover, and surface temperature, especially in the high-elevation and snow-covered regions over the TP. The inclusion of sub-grid topographic effects on solar radiation parameterization in ELM will contribute to advancing our understanding of the role of the surface topography on terrestrial processes over complex terrain.

scholarly journals Impact of frozen soil processes on soil thermal characteristics at seasonal to decadal scales over the Tibetan Plateau and North China

2020 ◽  
Author(s):  
Qian Li ◽  
Yongkang Xue ◽  
Ye Liu
Keyword(s):  
Tibetan Plateau ◽  
Soil Temperature ◽  
Temperature Profile ◽  
Land Surface ◽  
North China ◽  
Thermal Characteristics ◽  
Frozen Soil ◽  
The Tibetan Plateau ◽  
Soil Processes ◽  
Freeze Thaw

Abstract. Frozen soil processes are of great importance in controlling surface water and energy balances during the cold season and in cold regions. Over recent decades, considerable frozen soil degradation and surface soil warming have been reported over the Tibetan Plateau and North China, but most land surface models have difficulty in capturing the freeze-thaw cycle and few validations focus on the effects of frozen soil processes on soil thermal characteristics in these regions. This paper addresses these issues by introducing a physically more realistic and computationally more stable and efficient frozen soil module (FSM) into a land surface model—the third-generation Simplified Simple Biosphere model (SSiB3-FSM). To overcome the difficulties in achieving stable numerical solutions for frozen soil, a new semi-implicit scheme and a physics-based freezing-thawing scheme were applied to solve the governing equations. The performance of this model, as well as the effects of frozen soil process on the soil temperature profile and soil thermal characteristics, were investigated over the Tibetan Plateau and North China using observation and models. Results show that the SSiB3 model with the FSM produces more realistic soil temperature profile and its seasonal variation than that without FSM during the freezing and thawing periods. The freezing process in soil delays the winter cooling, while the thawing process delays the summer warming. The time lag and amplitude damping of temperature become more pronounced with increasing depth. These processes are well simulated in SSiB3-FSM. The freeze-thaw processes could increase the simulated phase lag days and land memory at different soil depths, as well as the soil memory change with the soil thickness. Furthermore, compared with observations, SSiB3-FSM produces a realistic change of maximum frozen soil depth at decadal scales. This study shows the soil thermal characteristics at seasonal to decadal scales over frozen ground can be greatly improved in SSiB3-FSM and SSiB3-FSM can be used as an effective model for TP and NC simulation during cold reasons.

scholarly journals Biological and environmental drivers of deep-sea benthic ecosystem functioning in Canada’s Laurentian Channel Area of Interest (AOI)

2018 ◽  
Author(s):  
Marta Miatta ◽  
Paul V Snelgrove
Keyword(s):  
Deep Sea ◽  
Ecosystem Functioning ◽  
Environmental Variables ◽  
Environmental Changes ◽  
Marine Ecosystem ◽  
Environmental Drivers ◽  
Biological Traits ◽  
Area Of Interest ◽  
Prokaryotic Abundance

Ongoing environmental changes and accelerating biodiversity loss raise concern and interest about the role of environmental factors and biodiversity in determining marine ecosystem functioning. This study aims to identify the main drivers of benthic ecosystem functioning in deep-sea sedimentary habitats in the Laurentian Channel Area of Interest (AOI), and in particular the role of sea pens (Pennatulacea) as potential keystone species in the area. Using the ROV ROPOS we collected sediment cores and measured environmental variables from 6 stations inside the AOI (depths 348–445m) in September 2017. Through 48-hours incubations and flux measurements (oxygen, inorganic nutrients), we estimated organic matter remineralization, a key benthic function. Preliminary analyses show no significant variation in fluxes among stations, despite significant differences in environmental variables However, the presence/absence of Pennatulacea inside the cores indicated some capability to enhance remineralization and particularly nitrification. Ongoing analyses will address sediment properties, macrofaunal biodiversity, prokaryotic abundance, and biological traits as drivers of remineralization. Shedding new light on the primary drivers of ecosystem functioning in the area will inform the design or monitoring strategies proposed for this AOI and offer new perspectives and tools for MPA design.

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