scholarly journals Soil moisture-atmosphere feedbacks mitigate declining water availability in drylands

2021 ◽  
Author(s):  
Sha Zhou ◽  
A. Park Williams ◽  
Benjamin Lintner ◽  
Alexis Berg ◽  
Yao Zhang ◽  
...  
Keyword(s):  
Global Warming ◽  
Soil Moisture ◽  
Surface Water ◽  
Negative Feedback ◽  
Water Availability ◽  
Moisture Transport ◽  
Atmospheric Moisture ◽  
Underlying Mechanisms ◽  
Empirical Approaches ◽  
Improve Representation

<p><strong>Global warming alters surface water availability (precipitation minus evapotranspiration, P-E) and hence freshwater resources. However, the influence of land-atmosphere feedbacks on future P-E changes and the underlying mechanisms remain unclear. Here we demonstrate that soil moisture (SM) strongly impacts future P-E changes, especially in drylands, by regulating evapotranspiration and atmospheric moisture inflow. Using modeling and empirical approaches, we find a consistent negative SM feedback on P-E, which may offset ~60% of the decline in dryland P-E otherwise expected in the absence of SM feedbacks. The negative feedback is not caused by atmospheric thermodynamic responses to declining SM, but rather reduced SM, in addition to limiting evapotranspiration, regulates atmospheric circulation and vertical ascent to enhance moisture transport into drylands. This SM effect is a large source of uncertainty in projected dryland P-E changes, underscoring the need to better constrain future SM changes and improve representation of SM-atmosphere processes in models.</strong></p>

scholarly journals Soil moisture-atmosphere feedbacks mitigate declining water availability in drylands

2020 ◽  
Author(s):  
Sha Zhou ◽  
A. Park Williams ◽  
Benjamin R. Lintner ◽  
Alexis M. Berg ◽  
Yao Zhang ◽  
...  
Keyword(s):  
Global Warming ◽  
Soil Moisture ◽  
Surface Water ◽  
Negative Feedback ◽  
Water Availability ◽  
Moisture Transport ◽  
Atmospheric Moisture ◽  
Underlying Mechanisms ◽  
Empirical Approaches ◽  
Improve Representation

Abstract Global warming alters surface water availability (precipitation minus evapotranspiration, P-E) and hence freshwater resources. However, the influence of land-atmosphere feedbacks on future P-E changes and the underlying mechanisms remain unclear. Here we demonstrate that soil moisture (SM) strongly impacts future P-E changes, especially in drylands, by regulating evapotranspiration and atmospheric moisture inflow. Using modeling and empirical approaches, we find a consistent negative SM feedback on P-E, which may offset ~60% of the decline in dryland P-E otherwise expected in the absence of SM feedbacks. The negative feedback is not caused by atmospheric thermodynamic responses to declining SM, but rather reduced SM, in addition to limiting evapotranspiration, regulates atmospheric circulation and vertical ascent to enhance moisture transport into drylands. This SM effect is a large source of uncertainty in projected dryland P-E changes, underscoring the need to better constrain future SM changes and improve representation of SM-atmosphere processes in models.

scholarly journals Changes in Normalized Difference Vegetation Index in the Orinoco and Amazon River Basins: Links to Tropical Atlantic Surface Temperatures

2020 ◽  
Vol 33 (19) ◽  
pp. 8537-8559
Author(s):  
Paola A. Arias ◽  
J. Alejandro Martínez ◽  
Juan David Mejía ◽  
María José Pazos ◽  
Jhan Carlo Espinoza ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Atlantic Ocean ◽  
Moisture Transport ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Dominant Role ◽  
Atmospheric Moisture ◽  
Moisture Recycling ◽  
Surface Temperatures ◽  
Atmospheric Moisture Transport

AbstractWe analyze the observed relationship between sea surface temperatures (SSTs) over the Atlantic Ocean and the normalized difference vegetation index (NDVI) in the Orinoco and Amazon basins. Monthly correlations between anomalies of NDVI and SSTs are computed for different regions of the Atlantic Ocean. We also use a mixture of observations and reanalysis products to analyze lagged correlations. Our results show that during August–September (i.e., the dry-to-wet transition season), changes in NDVI in the central Amazon and the so-called Arc of Deforestation are associated with precedent changes in the SSTs of the tropical North Atlantic (TNA) and the Caribbean (CABN) during March–June. Anomalous warming of the CABN and TNA generates changes in surface winds and atmospheric moisture transport in the region, decreasing precipitation, with consequent decreases of soil moisture, moisture recycling, and NDVI. An increase in TNA and CABN SSTs during March–June is also associated with an increase of NDVI over the northern Orinoco during June (i.e., the wet season). Unlike in the southern Amazon, precipitation and soil moisture in the Orinoco basin do not exhibit significant changes associated with SSTs. By contrast, atmospheric moisture recycling and transport increase with warmer SSTs in the TNA. Therefore, for the Orinoco, the link between SSTs and NDVI appears to be related not to changes in precipitation but to changes in moisture recycling. However, the causality between these changes needs to be further explored. These findings highlight the contrasting responses of the Amazon and Orinoco basins to Atlantic temperatures and the dominant role of atmospheric moisture transport linking these responses.

scholarly journals Influence of the Background Wind on the Local Soil Moisture–Precipitation Feedback

2014 ◽  
Vol 71 (2) ◽  
pp. 782-799 ◽  
Author(s):  
Paul Froidevaux ◽  
Linda Schlemmer ◽  
Juerg Schmidli ◽  
Wolfgang Langhans ◽  
Christoph Schär
Keyword(s):  
Soil Moisture ◽  
Negative Feedback ◽  
Environmental Parameters ◽  
Modeling Framework ◽  
Negative Feedback Loops ◽  
Local Soil ◽  
Positive And Negative Feedback ◽  
Underlying Mechanisms ◽  
Convective Cells ◽  
Open Question

Abstract The importance of soil moisture anomalies on airmass convection over semiarid regions has been recognized in several studies. The underlying mechanisms remain partly unclear. An open question is why wetter soils can result in either an increase or a decrease of precipitation (positive or negative soil moisture–precipitation feedback, respectively). Here an idealized cloud-resolving modeling framework is used to explore the local soil moisture–precipitation feedback. The approach is able to replicate both positive and negative feedback loops, depending on the environmental parameters. The mechanism relies on horizontal soil moisture variations, which may develop and intensify spontaneously. The positive expression of the feedback is associated with the initiation of convection over dry soil patches, but the convective cells then propagate over wet patches where they strengthen and preferentially precipitate. The negative feedback may occur when the wind profile is too weak to support the propagation of convective features from dry to wet areas. Precipitation is then generally weaker and falls preferentially over dry patches. The results highlight the role of the midtropospheric flow in determining the sign of the feedback. A key element of the positive feedback is the exploitation of both low convective inhibition (CIN) over dry patches (for the initiation of convection) and high CAPE over wet patches (for the generation of precipitation).

Surface water availability, Pickens County, Alabama

1975 ◽  
Author(s):  
Marvin E. Davis ◽  
Alfred L. Knight
Keyword(s):  
Surface Water ◽  
Water Availability

scholarly journals Variation in Soil Properties Regulate Greenhouse Gas Fluxes and Global Warming Potential in Three Land Use Types on Tropical Peat

Atmosphere ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 465 ◽  
Author(s):  
Kiwamu Ishikura ◽  
Untung Darung ◽  
Takashi Inoue ◽  
Ryusuke Hatano
Keyword(s):  
Global Warming ◽  
Soil Moisture ◽  
Groundwater Level ◽  
Global Warming Potential ◽  
C:N Ratio ◽  
Co2 Flux ◽  
Nitrate Content ◽  
N2o Flux ◽  
Ch4 Flux ◽  
In The Beginning

This study investigated spatial factors controlling CO2, CH4, and N2O fluxes and compared global warming potential (GWP) among undrained forest (UDF), drained forest (DF), and drained burned land (DBL) on tropical peatland in Central Kalimantan, Indonesia. Sampling was performed once within two weeks in the beginning of dry season. CO2 flux was significantly promoted by lowering soil moisture and pH. The result suggests that oxidative peat decomposition was enhanced in drier position, and the decomposition acidify the peat soils. CH4 flux was significantly promoted by a rise in groundwater level, suggesting that methanogenesis was enhanced under anaerobic condition. N2O flux was promoted by increasing soil nitrate content in DF, suggesting that denitrification was promoted by substrate availability. On the other hand, N2O flux was promoted by lower soil C:N ratio and higher soil pH in DBL and UDF. CO2 flux was the highest in DF (241 mg C m−2 h−1) and was the lowest in DBL (94 mg C m−2 h−1), whereas CH4 flux was the highest in DBL (0.91 mg C m−2 h−1) and was the lowest in DF (0.01 mg C m−2 h−1), respectively. N2O flux was not significantly different among land uses. CO2 flux relatively contributed to 91–100% of GWP. In conclusion, it is necessary to decrease CO2 flux to mitigate GWP through a rise in groundwater level and soil moisture in the region.

scholarly journals Soil Moisture Dynamics in Response to Precipitation and Thinning in a Semi-Dry Forest in Northern Mexico

Water ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 105
Author(s):  
Argelia E. Rascón-Ramos ◽  
Martín Martínez-Salvador ◽  
Gabriel Sosa-Pérez ◽  
Federico Villarreal-Guerrero ◽  
Alfredo Pinedo-Alvarez ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Forest Management ◽  
Water Availability ◽  
Dry Forest ◽  
Rainfall Events ◽  
Rainfall Characteristics ◽  
Northern Mexico ◽  
The Difference ◽  
The Impact ◽  
Moisture Dynamics

Understanding soil moisture behavior in semi-dry forests is essential for evaluating the impact of forest management on water availability. The objective of the study was to analyze soil moisture based in storm observations in three micro-catchments (0.19, 0.20, and 0.27 ha) with similar tree densities, and subject to different thinning intensities in a semi-dry forest in Chihuahua, Mexico. Vegetation, soil characteristics, precipitation, and volumetric water content were measured before thinning (2018), and after 0%, 40%, and 80% thinning for each micro-catchment (2019). Soil moisture was low and relatively similar among the three micro-catchments in 2018 (mean = 8.5%), and only large rainfall events (>30 mm) increased soil moisture significantly (29–52%). After thinning, soil moisture was higher and significantly different among the micro-catchments only during small rainfall events (<10 mm), while a difference was not noted during large events. The difference before–after during small rainfall events was not significant for the control (0% thinning); whereas 40% and 80% thinning increased soil moisture significantly by 40% and 53%, respectively. Knowledge of the response of soil moisture as a result of thinning and rainfall characteristics has important implications, especially for evaluating the impact of forest management on water availability.

Multi-model ensemble projections of soil moisture drought over North Africa and the Sahel region under 1.5, 2, and 3 °C global warming

2021 ◽  
Vol 167 (3-4) ◽  
Author(s):  
Ahmed Elkouk ◽  
Zine El Abidine El Morjani ◽  
Yadu Pokhrel ◽  
Abdelghani Chehbouni ◽  
Abdelfattah Sifeddine ◽  
...  
Keyword(s):  
Global Warming ◽  
Soil Moisture ◽  
North Africa ◽  
Model Ensemble ◽  
Sahel Region ◽  
Ensemble Projections

Potential impacts of global warming on water resources in southern California

2003 ◽  
Vol 47 (7-8) ◽  
pp. 165-168 ◽  
Author(s):  
M. Beuhler
Keyword(s):  
Global Warming ◽  
Surface Water ◽  
Water Resources ◽  
Southern California ◽  
Salt Water ◽  
Scenario Planning ◽  
Potential Range ◽  
Water Supplies ◽  
Sea Levels ◽  
Rising Sea Levels

Global warming will have a significant impact on water resources within the 20 to 30-year planning period of many water projects. Arid and semi-arid regions such as Southern California are especially vulnerable to anticipated negative impacts of global warming on water resources. Long-range water facility planning must consider global climate change in the recommended mix of new facilities needed to meet future water requirements. The generally accepted impacts of global warming include increased temperature, rising sea levels, more frequent and severe floods and droughts, and a shift from snowfall to rain. Precipitation changes are more difficult to predict. For Southern California, these impacts will be especially severe on surface water supplies. Additionally, rising sea levels will exacerbate salt-water intrusion into freshwater and impact the quality of surface water supplies. Integrated water resources planning is emerging as a tool to develop water supplies and demand management strategies that are less vulnerable to the impacts of global warming. These tools include water conservation, reclamation, conjunctive use of surface and groundwater and desalination of brackish water and possibly seawater. Additionally, planning for future water needs should include explicit consideration of the potential range of global warming impacts through techniques such as scenario planning.

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