Precipitation response to extreme soil moisture conditions over the Mediterranean

AbstractThe intimate link between soil moisture and precipitation makes it a “chicken-and-egg situation” that challenges climate studies of the continental water cycle. This association is particularly acute over the Mediterranean, increasingly exposed to droughts with climate change. This study aims at deciphering the impact of spring soil moisture state in the Mediterranean on subsequent warm season precipitation. In an idealized setup, two distinct climate models are used to generate extreme dry or wet soil conditions, and run climate simulations initialized and/or forced by these conditions. Changes in precipitation distribution and persistence are analyzed and where applicable compared to composites from a reanalysis. Spring soil moisture anomalies are found to be very persistent, but the precipitation response is largely model dependent. Overall, dry soils lead to a reduction of precipitation for early summer months and conversely for wet soils although with a fainter and less robust signal. On the other hand, wet soils tend to favor the persistence of precipitation throughout summer over several sub-regions. Our results highlight the stringent need to reduce the wide array of uncertainties associated to soil moisture, land-atmosphere coupling and convection in climate models, before ascertaining that soil moisture initialization could provide more skillful sub-seasonal to seasonal precipitation prediction.

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Multimodel assessment of climate change-induced hydrologic impacts for a Mediterranean catchment

Hydrology and Earth System Sciences ◽

10.5194/hess-22-4125-2018 ◽

2018 ◽

Vol 22 (7) ◽

pp. 4125-4143 ◽

Cited By ~ 9

Author(s):

Enrica Perra ◽

Monica Piras ◽

Roberto Deidda ◽

Claudio Paniconi ◽

Giuseppe Mascaro ◽

...

Keyword(s):

Climate Change ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Climate Models ◽

Actual Evapotranspiration ◽

Soil Conditions ◽

Hydrologic Models ◽

The Future ◽

The Mediterranean

Abstract. This work addresses the impact of climate change on the hydrology of a catchment in the Mediterranean, a region that is highly susceptible to variations in rainfall and other components of the water budget. The assessment is based on a comparison of responses obtained from five hydrologic models implemented for the Rio Mannu catchment in southern Sardinia (Italy). The examined models – CATchment HYdrology (CATHY), Soil and Water Assessment Tool (SWAT), TOPographic Kinematic APproximation and Integration (TOPKAPI), TIN-based Real time Integrated Basin Simulator (tRIBS), and WAter balance SImulation Model (WASIM) – are all distributed hydrologic models but differ greatly in their representation of terrain features and physical processes and in their numerical complexity. After calibration and validation, the models were forced with bias-corrected, downscaled outputs of four combinations of global and regional climate models in a reference (1971–2000) and future (2041–2070) period under a single emission scenario. Climate forcing variations and the structure of the hydrologic models influence the different components of the catchment response. Three water availability response variables – discharge, soil water content, and actual evapotranspiration – are analyzed. Simulation results from all five hydrologic models show for the future period decreasing mean annual streamflow and soil water content at 1 m depth. Actual evapotranspiration in the future will diminish according to four of the five models due to drier soil conditions. Despite their significant differences, the five hydrologic models responded similarly to the reduced precipitation and increased temperatures predicted by the climate models, and lend strong support to a future scenario of increased water shortages for this region of the Mediterranean basin. The multimodel framework adopted for this study allows estimation of the agreement between the five hydrologic models and between the four climate models. Pairwise comparison of the climate and hydrologic models is shown for the reference and future periods using a recently proposed metric that scales the Pearson correlation coefficient with a factor that accounts for systematic differences between datasets. The results from this analysis reflect the key structural differences between the hydrologic models, such as a representation of both vertical and lateral subsurface flow (CATHY, TOPKAPI, and tRIBS) and a detailed treatment of vegetation processes (SWAT and WASIM).

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Earthworms are little affected by reduced soil tillage methods in vineyards

Plant Soil and Environment ◽

10.17221/160/2017-pse ◽

2017 ◽

Vol 63 (No. 6) ◽

pp. 257-263 ◽

Cited By ~ 8

Author(s):

Faber Florian ◽

Wachter Elisabeth ◽

Zaller Johann G

Keyword(s):

Soil Moisture ◽

Soil Temperature ◽

Soil Tillage ◽

Soil Conditions ◽

Reduced Tillage ◽

No Tillage ◽

Dry Soil ◽

The Impact ◽

Tillage Methods ◽

Erosion Prevention

Inter-rows in vineyards are commonly tilled in order to control weeds and/or to conserve water. While impacts of tillage on earthworms are well studied in arable systems, very little is known from vineyards. In an experimental vineyard, the impact of four reduced tillage methods on earthworms was examined: rotary hoeing, rotary harrowing, grubbing and no tillage. According to an erosion prevention programme, tillage was applied every other inter-row only while alternating rows retained vegetated. Earthworms were extracted from the treated inter-rows 10, 36, 162 and 188 days after tillage. Across dates, tillage methods had no effect on overall earthworm densities or biomass. Considering each sampling date separately, earthworm densities were affected only at day 36 after tillage leading to lower densities under rotary hoeing (150.7 ± 42.5 worms/m2) and no tillage (117.3 ± 24.8 worms/m2) than under rotary harrowing (340.0 ± 87.4 worms/m2) and grubbing (242.7 ± 43.9 worms/m2). Time since tillage significantly increased earthworm densities or biomass, and affected soil moisture and temperature. Across sampling dates, earthworm densities correlated positively with soil moisture and negatively with soil temperature; individual earthworm mass increased with increasing time since tillage. It was concluded that reduced tillage in vineyards has little impact on earthworms when applied in spring under dry soil conditions.

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Weak Land–Atmosphere Coupling Strength in HadAM3: The Role of Soil Moisture Variability

Journal of Hydrometeorology ◽

10.1175/jhm445.1 ◽

2005 ◽

Vol 6 (5) ◽

pp. 670-680 ◽

Cited By ~ 35

Author(s):

David M. Lawrence ◽

Julia M. Slingo

Keyword(s):

Boundary Layer ◽

Soil Moisture ◽

Coupling Strength ◽

General Circulation ◽

General Circulation Models ◽

Soil Conditions ◽

Wide Range ◽

The Impact ◽

Soil Moisture Variability ◽

Moisture Variability

Abstract A recent model intercomparison, the Global Land–Atmosphere Coupling Experiment (GLACE), showed that there is a wide range of land–atmosphere coupling strengths, or the degree that soil moisture affects the generation of precipitation, amongst current atmospheric general circulation models (AGCMs). Coupling strength in the Hadley Centre atmosphere model (HadAM3) is among the weakest of all AGCMs considered in GLACE. Reasons for the weak HadAM3 coupling strength are sought here. In particular, the impact of pervasive saturated soil conditions and low soil moisture variability on coupling strength is assessed. It is found that when the soil model is modified to reduce the occurrence of soil moisture saturation and to encourage soil moisture variability, the soil moisture–precipitation feedback remains weak, even though the relationship between soil moisture and evaporation is strengthened. Composites of the diurnal cycle, constructed relative to soil moisture, indicate that the model can simulate key differences in boundary layer development over wet versus dry soils. In particular, the influence of wet or dry soil on the diurnal cycles of Bowen ratio, boundary layer height, and total heat flux are largely consistent with the observed influence of soil moisture on these properties. However, despite what appears to be successful simulation of these key aspects of the indirect soil moisture–precipitation feedback, the model does not capture observed differences for wet and dry soils in the daily accumulation of boundary layer moist static energy, a crucial feature of the feedback mechanism.

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Soil moisture and the water cycle in the UK Climate Projections

10.5194/egusphere-egu2020-8852 ◽

2020 ◽

Author(s):

Jennifer Pirret ◽

Fai Fung ◽

John. F.B. Mitchell ◽

Rachel McInnes

Keyword(s):

Soil Moisture ◽

Plant Growth ◽

Water Balance ◽

Land Surface ◽

Climate Models ◽

Water Cycle ◽

Future Climate ◽

Future Climate Change ◽

Climate Projections ◽

Plant Cultivation

Soil moisture is a key environmental factor for plant cultivation: too little and plant growth is restricted due to drought conditions; too much and soil becomes water-logged. It is important to understand how well climate models can represent current soil moisture processes as well as how soil moisture will respond to a changing climate, to inform adaptation of plant cultivation to future climate change. We explore current and future climate soil moisture conditions alongside water cycle processes such as evaporation and run-off in the latest UK Climate Projections (UKCP). Three model ensembles are available: UKCP Global, Regional and Local, with horizontal resolutions of 60km, 12km and 2.2km respectively. These each contain the Joint UK Land Environment Simulator (JULES) model as their land surface component. This suite of models offers the opportunity to understand the effects of parameter uncertainty and spatial resolution. Firstly, we assess the performance of the Global and Regional simulations by evaluating results from the baseline period (1981-2010) in terms of soil moisture (and the overall water balance) by comparing it to observations and to JULES driven by observations. Secondly, we assess how the water balance responds to a high future greenhouse gas concentration pathway. We find that soil moisture is likely to be lower in the summer and early autumn and spends a longer time below levels optimal for plant growth. The potential drivers of this change are explored, including future changes in precipitation and evaporation.

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Soil water drying and recharge rates as affected by tillage under continuous barley and barley-canola cropping systems in northwestern Canada

Canadian Journal of Soil Science ◽

10.4141/s00-029 ◽

2001 ◽

Vol 81 (1) ◽

pp. 45-52 ◽

Cited By ~ 14

Author(s):

R H Azooz ◽

M A Arshad

Keyword(s):

Soil Moisture ◽

Soil Water ◽

Sandy Loam ◽

Time Domain Reflectometry ◽

Sandy Loam Soil ◽

Soil Conditions ◽

Silt Loam ◽

Silt Loam Soil ◽

Loam Soil ◽

The Impact

In areas of the northwestern Canadian Prairies, barley and canola are grown in a short growing season with high rainfall variability. Excessively dry soil in conventional tillage (CT) in dry periods and excessively wet soil in no-tillage (NT) in wet periods could cause a significant decrease in crop production by influencing the availability of soil water. The effects of CT, NT and NT with a 7.5-cm residue-free strip on the planting rows (NTR) on soil water drying (–dW/dt) and recharge (dW/dt) rates were studied in 1992 and 1993 during wet and dry periods to evaluate the impact of NTR, NT and CT systems on soil moisture condition. The soils, Donnelly silt loam and Donnelly sandy loam (both Gray Luvisol) were selected and soil water content by depth was measured by time domain reflectometry. Water retained at 6 matric potentials from –5 to –160 kPa were observed. In the field study, –dW/dt was significantly greater in CT than in NT in the silt loam for the 0- to 30-cm layer during the first 34 d after planting in 1992. The 0- to 30-cm soil layer in CT and NTR dried faster than in NT during a period immediately following heavy rainfall in the silt loam in 1993. The drying coefficient (–Kd ) was significantly greater in CT and NTR than in NT in the silt loam soil in 1993 and in the sandy loam soil in 1992 in the top 30-cm depth. The recharge coefficient (Kr) was significantly greater in NT and NTR than in CT for the silt loam soil. The NTR system increased the –dW/dt by 1.2 × 10-2 to 12.1 × 10-2 cm d-1 in 1992 and 1993 in the silt loam soil and by 10.2 × 10-2 cm d-1 in 1993 in the sandy loam soil as compared with NT. The dW/dt was 8.1 × 10-2 cm d-1 greater in NTR in 1992 and 1993 in the silt loam soil and was 1.9 × 10-2 greater in NTR in 1992 than in CT in the sandy loam soil. The laboratory study indicated that NT soils retained more water than the CT soils. The NTR practice maintained better soil moisture conditions for crop growth than CT in dry periods than NT in wet periods. Compared with NT, the NTR avoided prolonged near-saturated soil conditions with increased soil drying rate under extremely wet soil. Key words: Water drying, water recharge, water depletion, wet and drying periods, hydraulic properties, soil capacity to retain water

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Potential Predictability of Long-Term Drought and Pluvial Conditions in the U.S. Great Plains

Journal of Climate ◽

10.1175/2007jcli1741.1 ◽

2008 ◽

Vol 21 (4) ◽

pp. 802-816 ◽

Cited By ~ 54

Author(s):

Siegfried D. Schubert ◽

Max J. Suarez ◽

Philip J. Pegion ◽

Randal D. Koster ◽

Julio T. Bacmeister

Keyword(s):

Soil Moisture ◽

Great Plains ◽

General Circulation ◽

Storm Track ◽

Warm Season ◽

Circulation Model ◽

Skewed Distribution ◽

Soil Conditions ◽

Unexpected Result ◽

Potential Predictability

Abstract This study examines the predictability of seasonal mean Great Plains precipitation using an ensemble of century-long atmospheric general circulation model (AGCM) simulations forced with observed sea surface temperatures (SSTs). The results show that the predictability (intraensemble spread) of the precipitation response to SST forcing varies on interannual and longer time scales. In particular, this study finds that pluvial conditions are more predictable (have less intraensemble spread) than drought conditions. This rather unexpected result is examined in the context of the physical mechanisms that impact precipitation in the Great Plains. These mechanisms include El Niño–Southern Oscillation’s impact on the planetary waves and hence the Pacific storm track (primarily during the cold season), the role of Atlantic SSTs in forcing changes in the Bermuda high and low-level moisture flux into the continent (primarily during the warm season), and soil moisture feedbacks (primarily during the warm season). It is found that the changes in predictability are primarily driven by changes in the strength of the land–atmosphere coupling, such that under dry conditions a given change in soil moisture produces a larger change in evaporation and hence precipitation than the same change in soil moisture would produce under wet soil conditions. The above changes in predictability are associated with a negatively skewed distribution in the seasonal mean precipitation during the warm season—a result that is not inconsistent with the observations.

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Is Missing Orographic Gravity Wave Drag near 60°S the Cause of the Stratospheric Zonal Wind Biases in Chemistry–Climate Models?

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-11-0159.1 ◽

2012 ◽

Vol 69 (3) ◽

pp. 802-818 ◽

Cited By ~ 97

Author(s):

Charles McLandress ◽

Theodore G. Shepherd ◽

Saroja Polavarapu ◽

Stephen R. Beagley

Keyword(s):

Gravity Wave ◽

Zonal Wind ◽

Climate Models ◽

Middle Atmosphere ◽

Wave Drag ◽

Early Summer ◽

Systematic Bias ◽

Stratospheric Polar Vortex ◽

Column Ozone ◽

The Impact

Abstract Nearly all chemistry–climate models (CCMs) have a systematic bias of a delayed springtime breakdown of the Southern Hemisphere (SH) stratospheric polar vortex, implying insufficient stratospheric wave drag. In this study the Canadian Middle Atmosphere Model (CMAM) and the CMAM Data Assimilation System (CMAM-DAS) are used to investigate the cause of this bias. Zonal wind analysis increments from CMAM-DAS reveal systematic negative values in the stratosphere near 60°S in winter and early spring. These are interpreted as indicating a bias in the model physics, namely, missing gravity wave drag (GWD). The negative analysis increments remain at a nearly constant height during winter and descend as the vortex weakens, much like orographic GWD. This region is also where current orographic GWD parameterizations have a gap in wave drag, which is suggested to be unrealistic because of missing effects in those parameterizations. These findings motivate a pair of free-running CMAM simulations to assess the impact of extra orographic GWD at 60°S. The control simulation exhibits the cold-pole bias and delayed vortex breakdown seen in the CCMs. In the simulation with extra GWD, the cold-pole bias is significantly reduced and the vortex breaks down earlier. Changes in resolved wave drag in the stratosphere also occur in response to the extra GWD, which reduce stratospheric SH polar-cap temperature biases in late spring and early summer. Reducing the dynamical biases, however, results in degraded Antarctic column ozone. This suggests that CCMs that obtain realistic column ozone in the presence of an overly strong and persistent vortex may be doing so through compensating errors.

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Estimates of tree root water uptake from soil moisture profile dynamics

10.5194/bg-2019-466 ◽

2019 ◽

Author(s):

Conrad Jackisch ◽

Samuel Knoblauch ◽

Theresa Blume ◽

Erwin Zehe ◽

Sibylle K. Hassler

Keyword(s):

Time Series ◽

Soil Moisture ◽

Water Uptake ◽

Sap Flow ◽

Water Cycle ◽

Xylem Sap ◽

Root Water Uptake ◽

Soil Conditions ◽

Diurnal Changes ◽

Moisture Profile

Abstract. Root water uptake (RWU) as one important process in the terrestrial water cycle can help to better understand the interactions in the soil water plant system. We conducted a field study monitoring soil moisture profiles in the rhizosphere of beech trees at two sites with different soil conditions. We infer RWU from step-shaped, diurnal changes in soil moisture. While this approach is a feasible, easily implemented method during wet and moderate conditions, limitations were identified during drier states and for more heterogeneous soil settings. A comparison with time series of xylem sap velocity reveals that RWU and sap flow are complementary measures of the transpiration process. The high correlation between the sap flow time series of the two sites, but lower correlation between the RWU time series, suggests that the trees adapt RWU to soil heterogeneity and site differences.

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Measuring and modeling water-related soil–vegetation feedbacks in a fallow plot

Hydrology and Earth System Sciences ◽

10.5194/hess-18-1105-2014 ◽

2014 ◽

Vol 18 (3) ◽

pp. 1105-1118 ◽

Cited By ~ 13

Author(s):

N. Ursino ◽

G. Cassiani ◽

R. Deiana ◽

G. Vignoli ◽

J. Boaga

Keyword(s):

Soil Moisture ◽

Water Balance ◽

Vegetation Cover ◽

Water Cycle ◽

Geophysical Methods ◽

Vegetation Feedback ◽

Weed Growth ◽

Local Soil ◽

Soil Saturation ◽

The Impact

Abstract. Land fallowing is one possible response to shortage of water for irrigation. Leaving the soil unseeded implies a change of the soil functioning that has an impact on the water cycle. The development of a soil crust in the open spaces between the patterns of grass weed affects the soil properties and the field-scale water balance. The objectives of this study are to test the potential of integrated non-invasive geophysical methods and ground-image analysis and to quantify the effect of the soil–vegetation interaction on the water balance of fallow land at the local- and plot scale. We measured repeatedly in space and time local soil saturation and vegetation cover over two small plots located in southern Sardinia, Italy, during a controlled irrigation experiment. One plot was left unseeded and the other was cultivated. The comparative analysis of ERT maps of soil moisture evidenced a considerably different hydrologic response to irrigation of the two plots. Local measurements of soil saturation and vegetation cover were repeated in space to evidence a positive feedback between weed growth and infiltration at the fallow plot. A simple bucket model captured the different soil moisture dynamics at the two plots during the infiltration experiment and was used to estimate the impact of the soil vegetation feedback on the yearly water balance at the fallow site.

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The Effect of the Dry Line and Convective Initiation on Drought Evolution over Oklahoma during the 2011 Drought

Advances in Meteorology ◽

10.1155/2017/8430743 ◽

2017 ◽

Vol 2017 ◽

pp. 1-16 ◽

Cited By ~ 3

Author(s):

Paul X. Flanagan ◽

Jeffrey B. Basara ◽

Bradley G. Illston ◽

Jason A. Otkin

Keyword(s):

Soil Moisture ◽

Large Scale ◽

Warm Season ◽

Convective Initiation ◽

Model Simulations ◽

Variable Surface ◽

Oklahoma Mesonet ◽

Dry Conditions ◽

Moisture Conditions ◽

The Impact

Observations from the Oklahoma Mesonet and high resolution Weather Research and Forecasting model simulations were used to evaluate the effect that the dry line and large-scale atmospheric patterns had on drought evolution during 2011. Mesonet observations showed that a “dry” and “wet” pattern developed across Oklahoma due to anomalous atmospheric patterns. The location of the dry line varied due to this “dry” and “wet” pattern, with the average dry line location around 1.5° longitude further to the east than climatology. Model simulations were used to further quantify the impact of variable surface conditions on dry line evolution and convective initiation (CI) during April and May 2011. Specifically, soil moisture conditions were altered to depict “wet” and “dry” conditions across the domain by replacing the soil moisture values by each soil category’s porosity or wilting point value. Overall, the strength of the dry line boundary, its position, and subsequent CI were dependent on the modification of soil moisture. The simulations demonstrated that modifying soil moisture impacted the nature of the dry line and showed that soil moisture conditions during the first half of the warm season modified the dry line pattern and influenced the evolution and perpetuation of drought over Oklahoma.

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