scholarly journals Contrasting Effect of Soil Moisture on the Daytime Boundary Layer Under Different Thermodynamic Conditions in Summer Over China

2021 ◽  
Vol 48 (3) ◽  
Author(s):  
Zhiqi Xu ◽  
Haishan Chen ◽  
Jianping Guo ◽  
Wanchun Zhang
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Thermodynamic Conditions ◽  
Contrasting Effect

scholarly journals Summer temperature response to extreme soil water conditions in the Mediterranean transitional climate regime

2021 ◽  
Author(s):  
Stefano Materia ◽  
Constantin Ardilouze ◽  
Chloé Prodhomme ◽  
Markus G. Donat ◽  
Marianna Benassi ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Soil Water ◽  
Land Surface ◽  
Heat Waves ◽  
Climate Regime ◽  
Seasonal Forecasts ◽  
Near Surface ◽  
Surface Temperatures ◽  
The Mediterranean

AbstractLand surface and atmosphere are interlocked by the hydrological and energy cycles and the effects of soil water-air coupling can modulate near-surface temperatures. In this work, three paired experiments were designed to evaluate impacts of different soil moisture initial and boundary conditions on summer temperatures in the Mediterranean transitional climate regime region. In this area, evapotranspiration is not limited by solar radiation, rather by soil moisture, which therefore controls the boundary layer variability. Extremely dry, extremely wet and averagely humid ground conditions are imposed to two global climate models at the beginning of the warm and dry season. Then, sensitivity experiments, where atmosphere is alternatively interactive with and forced by land surface, are launched. The initial soil state largely affects summer near-surface temperatures: dry soils contribute to warm the lower atmosphere and exacerbate heat extremes, while wet terrains suppress thermal peaks, and both effects last for several months. Land-atmosphere coupling proves to be a fundamental ingredient to modulate the boundary layer state, through the partition between latent and sensible heat fluxes. In the coupled runs, early season heat waves are sustained by interactive dry soils, which respond to hot weather conditions with increased evaporative demand, resulting in longer-lasting extreme temperatures. On the other hand, when wet conditions are prescribed across the season, the occurrence of hot days is suppressed. The land surface prescribed by climatological precipitation forcing causes a temperature drop throughout the months, due to sustained evaporation of surface soil water. Results have implications for seasonal forecasts on both rain-fed and irrigated continental regions in transitional climate zones.

scholarly journals Soil Moisture-Boundary Layer Feedbacks on the Loess Plateau in China Using Radiosonde Data with 1-D Atmospheric Boundary Layer Model

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1619
Author(s):  
Yingsai Ma ◽  
Xianhong Meng ◽  
Yinhuan Ao ◽  
Ye Yu ◽  
Guangwei Li ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Atmospheric Boundary Layer ◽  
Loess Plateau ◽  
Atmospheric Stability ◽  
Heat Fluxes ◽  
Radiosonde Data ◽  
Atmospheric Conditions ◽  
The Loess Plateau ◽  
The Impact

The Loess Plateau is one land-atmosphere coupling hotspot. Soil moisture has an influence on atmospheric boundary layer development under specific early-morning atmospheric thermodynamic structures. This paper investigates the sensitivity of atmospheric convection to soil moisture conditions over the Loess Plateau in China by using the convective triggering potential (CTP)—humidity index (HIlow) framework. The CTP indicates atmospheric stability and the HIlow indicates atmospheric humidity in the low-level atmosphere. By comparing the model outcomes with the observations, the one-dimensional model achieves realistic daily behavior of the radiation and surface heat fluxes and the mixed layer properties with appropriate modifications. New CTP-HIlow thresholds for soil moisture-atmosphere feedbacks are found in the Loess Plateau area. By applying the new thresholds with long-time scales sounding data, we conclude that negative feedback is dominant in the north and west portion of the Loess Plateau; positive feedback is predominant in the south and east portion. In general, this framework has predictive significance for the impact of soil moisture on precipitation. By using this new CTP-HIlow framework, we can determine under what atmospheric conditions soil moisture can affect the triggering of precipitation and under what atmospheric conditions soil moisture has no influence on the triggering of precipitation.

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

2005 ◽  
Vol 6 (5) ◽  
pp. 670-680 ◽  
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.

Simulation of boundary layer trajectory dispersion sensitivity to soil moisture conditions: MM5 and Noah-based investigation

2009 ◽  
Vol 43 (24) ◽  
pp. 3774-3785 ◽  
Author(s):  
Arturo I. Quintanar ◽  
Rezaul Mahmood ◽  
Monica V. Motley ◽  
Jun Yan ◽  
John Loughrin ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Moisture Conditions

scholarly journals Preferential transport of water and <sup>131</sup>Iodide in a clay loam assessed with TDR-techniques and boundary-layer flow theory

1997 ◽  
Vol 1 (4) ◽  
pp. 813-822 ◽  
Author(s):  
A. Mdaghri Alaoui ◽  
P. Germann ◽  
L. Lichner ◽  
V. Novak
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Boundary Layer Flow ◽  
Preferential Flow ◽  
Flow Theory ◽  
Reaction Type ◽  
Type Iii ◽  
Rapid Flow ◽  
Preferential Transport ◽  
Layer Flow

Abstract. Rapid soil moisture variations were measured with TDR equipment at five depths ranging from 0.1 to 0.9 m during five consecutive infiltration experiments under ponding. Each time, 27 mm of water were applied. The water of the second experiment was spiked with 200 mbq of K131I-tracer. Its activity was recorded as functions of depth and time with Geiger-Müller probes in 12 vertically installed access tubes. The soil moisture variations were classified as showing (i) no reaction, (ii) monotonous increase, and (iii) rapid increase followed by a gradual decrease. Reaction type (iii) was investigated further according to the boundary-layer flow theory and diagnosed as preferential flow. Rapid variations of 131I-activities occurred at all depths showing soil moisture reaction type (iii). However, some of the reaction types (i) and (ii) also included rapid variations of the activities. The approach based on boundary-laver flow theory allows fluxes to be estimated from soil moisture variations. Seven estimated total volumes of rapid flow ranged from 0.15 to 1.1 of the applied volume of water, and in only one case was the total volume badly overestimated by a factor of almost 3. The approach is worth further exploration.

scholarly journals On the Relationship Between Aerosol and Boundary Layer Height in Summer in China Under Different Thermodynamic Conditions

2019 ◽  
Vol 6 (5) ◽  
pp. 887-901 ◽  
Author(s):  
Mengyun Lou ◽  
Jianping Guo ◽  
Lingling Wang ◽  
Hui Xu ◽  
Dandan Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Thermodynamic Conditions ◽  
The Relationship

scholarly journals Climatology of Planetary Boundary Layer Height-Controlling Meteorological Parameters Over the Korean Peninsula

2020 ◽  
Vol 12 (16) ◽  
pp. 2571
Author(s):  
Shaik Allabakash ◽  
Sanghun Lim
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Planetary Boundary Layer ◽  
Korean Peninsula ◽  
Meteorological Parameters ◽  
Weather Forecasting ◽  
High Elevation ◽  
Transport Processes ◽  
Surface Fluxes ◽  
Pollution Transport

Planetary boundary layer (PBL) height plays a significant role in climate modeling, weather forecasting, air quality prediction, and pollution transport processes. This study examined the climatology of PBL-associated meteorological parameters over the Korean peninsula and surrounding sea using data from the ERA5 dataset produced by the European Centre for Medium-range Weather Forecasts (ECMWF). The data covered the period from 2008 to 2017. The bulk Richardson number methodology was used to determine the PBL height (PBLH). The PBLH obtained from the ERA5 data agreed well with that derived from sounding and Global Positioning System Radio Occultation datasets. Significant diurnal and seasonal variability in PBLH was observed. The PBLH increases from morning to late afternoon, decreases in the evening, and is lowest at night. It is high in the summer, lower in spring and autumn, and lowest in winter. The variability of the PBLH with respect to temperature, relative humidity, surface pressure, wind speed, lower tropospheric stability, soil moisture, and surface fluxes was also examined. The growth of the PBLH was high in the spring and in southern regions due to the low soil moisture content of the surface. A high PBLH pattern is evident in high-elevation regions. Increasing trends of the surface temperature and accordingly PBLH were observed from 2008 to 2017.

Soil Moisture Feedbacks on Convection Triggers: The Role of Soil–Plant Hydrodynamics

2009 ◽  
Vol 10 (1) ◽  
pp. 96-112 ◽  
Author(s):  
Mario Siqueira ◽  
Gabriel Katul ◽  
Amilcare Porporato
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Water Vapor ◽  
Negative Feedback ◽  
Stomatal Closure ◽  
Inversion Layer ◽  
Self Regulation ◽  
Surface Fluxes ◽  
Plant Hydraulics ◽  
Wide Range

Abstract The linkages between soil moisture dynamics and convection triggers, defined here as the first crossing between the boundary layer height (hBL) and lifting condensation level (hLCL), are complicated by a large number of interacting processes occurring over a wide range of space and time scales. To progress on this problem, a soil–plant hydrodynamics model was coupled to a simplified ABL budget to explore the feedback of soil moisture on convection triggers. The soil–plant hydraulics formulation accounted mechanistically for features such as root water uptake, root water redistribution, and midday stomatal closure, all known to affect diurnal cycles of surface fluxes and, consequently, ABL growth. The ABL model considered the convective boundary layer as a slab with a discontinuity at the inversion layer. The model was parameterized using the wealth of data already collected for a maturing Loblolly pine plantation situated in the southeastern United States. A 30-day dry-down simulation was used to investigate the possible feedback mechanisms between soil moisture and convective rainfall triggers. Previous studies, which made use of surface flux measurements to drive an ABL model, have postulated that a negative feedback was possible, which could award the ecosystem with some degree of self-regulation of its water status. According to model simulation results here, this negative feedback is unlikely. However, drastic changes in external water sources to the ABL are needed for triggering convection when soil moisture is depleted. The apparent negative feedback originated from a decoupling between the water vapor sources needed to produce convection triggers and surface water vapor fluxes.

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