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.

The Simulation of Moisture Processes in Climate Models and Climate Sensitivity

2005 ◽  
Vol 18 (13) ◽  
pp. 2172-2193 ◽  
Author(s):  
Haijun Hu ◽  
Robert J. Oglesby ◽  
Susan Marshall
Keyword(s):  
Boundary Layer ◽  
General Circulation ◽  
Climate Models ◽  
General Circulation Models ◽  
Atmospheric Moisture ◽  
Model Sensitivity ◽  
Surface Warming ◽  
Wide Range ◽  
Modeling Techniques ◽  
Moisture Performance

Abstract General circulation models (GCMs) designed for projecting climatic change have exhibited a wide range of sensitivity. Therefore, projected surface warming with increasing CO2 varies considerably depending on which model is used. Despite notable advances in computing power and modeling techniques that have occurred over the past decade, uncertainties of model sensitivity have not been reduced accordingly. The sensitivity issue is investigated by examining two GCMs of very different modeling techniques and sensitivity, with attention focused on how moisture processes are treated in these models, how moisture simulations are affected by these processes, and how well these simulations compare to the observed and analyzed moisture field. Both GCMs predict increases of atmospheric moisture with doubled CO2, but the increment predicted by one model is substantially higher (approximately twice) than that predicted by the other. This same difference is seen in responses of the boundary layer diffusive moistening rate. Calculations with a radiative–convective model indicate that the differences in predicted equilibrium atmospheric moisture, including both column amount and vertical distribution, have contributed to the largest differences in model sensitivity between the two models. We argue that in order for climate models to be credible for prediction purposes, they must possess credible skills of simulating surface and boundary layer processes, which likely holds the key to overall moisture performance, its response to external forcing, and in turn to model sensitivity.

scholarly journals The impact of the 1783–1784 AD Laki eruption on global aerosol formation processes and cloud condensation nuclei

2010 ◽  
Vol 10 (2) ◽  
pp. 3189-3228
Author(s):  
A. Schmidt ◽  
K. S. Carslaw ◽  
G. W. Mann ◽  
B. M. Wilson ◽  
T. J. Breider ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Northern Hemisphere ◽  
General Circulation ◽  
Cloud Condensation Nuclei ◽  
General Circulation Models ◽  
Aerosol Formation ◽  
Condensation Nuclei ◽  
Upper Troposphere ◽  
Microphysical Processes ◽  
The Impact

Abstract. The 1783–1784 AD Laki flood lava eruption commenced on 8 June 1783 and released 122 Tg of sulphur dioxide gas over the course of 8 months into the upper troposphere and lower stratosphere above Iceland. Previous studies have examined the impact of the Laki eruption on sulphate aerosol and climate using general circulation models. Here, we study the impact on aerosol microphysical processes, including the nucleation of new particles and their growth to cloud condensation nuclei (CCN) using a comprehensive Global Model of Aerosol Processes (GLOMAP). Total particle concentrations in the free troposphere increase by a factor ~16 over large parts of the Northern Hemisphere in the 3 months following the onset of the eruption. Particle concentrations in the boundary layer increase by a factor 2 to 5 in regions as far away as North America, the Middle East and Asia due to long-range transport of nucleated particles. CCN concentrations (at 0.22% supersaturation) increase by a factor 65 in the upper troposphere with maximum changes in 3-month zonal mean concentrations of ~1400 cm−3 at high northern latitudes. 3-month zonal mean CCN concentrations in the boundary layer at the latitude of the eruption increase by up to a factor 26, and averaged over the Northern Hemisphere, the eruption caused a factor 4 increase in CCN concentrations at low-level cloud altitude. The simulations show that the Laki eruption would have completely dominated as a source of CCN in the pre-industrial atmosphere. The model also suggests an impact of the eruption in the Southern Hemisphere, where CCN concentrations are increased by up to a factor 1.4 at 20° S. Our model simulations suggest that the impact of an equivalent wintertime eruption on upper tropospheric CCN concentrations is only about one-third of that of a summertime eruption. The simulations show that the microphysical processes leading to the growth of particles to CCN sizes are fundamentally different after an eruption when compared to the unperturbed atmosphere, underlining the importance of using a fully coupled microphysics model when studying long-lasting, high-latitude eruptions.

scholarly journals Soil moisture: variable in space but redundant in time

2020 ◽  
Vol 24 (5) ◽  
pp. 2633-2653 ◽  
Author(s):  
Mirko Mälicke ◽  
Sibylle K. Hassler ◽  
Theresa Blume ◽  
Markus Weiler ◽  
Erwin Zehe
Keyword(s):  
Soil Moisture ◽  
Spatial Patterns ◽  
Clustering Algorithm ◽  
Spatial Information ◽  
Soil Conditions ◽  
Catchment Scale ◽  
Significant Information ◽  
Soil Moisture Variability ◽  
Over Time ◽  
Moisture Variability

Abstract. Soil moisture at the catchment scale exhibits a huge spatial variability. This suggests that even a large amount of observation points would not be able to capture soil moisture variability. We present a measure to capture the spatial dissimilarity and its change over time. Statistical dispersion among observation points is related to their distance to describe spatial patterns. We analyzed the temporal evolution and emergence of these patterns and used the mean shift clustering algorithm to identify and analyze clusters. We found that soil moisture observations from the 19.4 km2 Colpach catchment in Luxembourg cluster in two fundamentally different states. On the one hand, we found rainfall-driven data clusters, usually characterized by strong relationships between dispersion and distance. Their spatial extent roughly matches the average hillslope length in the study area of about 500 m. On the other hand, we found clusters covering the vegetation period. In drying and then dry soil conditions there is no particular spatial dependence in soil moisture patterns, and the values are highly similar beyond hillslope scale. By combining uncertainty propagation with information theory, we were able to calculate the information content of spatial similarity with respect to measurement uncertainty (when are patterns different outside of uncertainty margins?). We were able to prove that the spatial information contained in soil moisture observations is highly redundant (differences in spatial patterns over time are within the error margins). Thus, they can be compressed (all cluster members can be substituted by one representative member) to only a fragment of the original data volume without significant information loss. Our most interesting finding is that even a few soil moisture time series bear a considerable amount of information about dynamic changes in soil moisture. We argue that distributed soil moisture sampling reflects an organized catchment state, where soil moisture variability is not random. Thus, only a small amount of observation points is necessary to capture soil moisture dynamics.

scholarly journals Sensitivity in the Overland Reintensification of Tropical Cyclone Erin (2007) to Near-Surface Soil Moisture Characteristics

2011 ◽  
Vol 139 (12) ◽  
pp. 3848-3870 ◽  
Author(s):  
Clark Evans ◽  
Russ S. Schumacher ◽  
Thomas J. Galarneau
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Tropical Cyclone ◽  
Moisture Content ◽  
Tropical Cyclones ◽  
Soil Moisture Content ◽  
Soil Conditions ◽  
Seasonal Signal ◽  
Along Track ◽  
The Impact

Abstract This study investigates the impact of abnormally moist soil conditions across the southern Great Plains upon the overland reintensification of North Atlantic Tropical Cyclone Erin (2007). This is tested by analyzing the contributions of three soil moisture–related signals—a seasonal signal, an along-track rainfall signal, and an early postlandfall rainfall signal—to the intensity of the vortex. In so doing, a suite of nine convection-permitting numerical simulations using the Advanced Research Weather Research and Forecasting model (WRF-ARW) is used. Of the signals tested, soil moisture contributions from the anomalously wet months preceding Erin are found to have the greatest positive impact upon the intensity of the vortex, though this impact is on the order of that from climatological soil moisture conditions. The greatest impact of the early rainfall signal contributions is found when it is added to the seasonal signal. Along-track rainfall during the simulation period has a minimal impact. Variations in soil moisture content result in impacts upon the boundary layer thermodynamic environment via boundary layer mixing. Greater soil moisture content results in weaker mixing, a shallower boundary layer, and greater moisture and instability. Differences in the intensity of convection that develops and its accompanying latent heat release aloft result in greater warm-core development and surface vortex intensification within the simulations featuring greater soil moisture content. Implications of these findings to the tropical cyclone development process are discussed. Given that the reintensification is shown to occur in, apart from land, an otherwise favorable environment for tropical cyclone development and results in a vortex with a structure similar to developing tropical cyclones, these findings provide new insight into the conditions under which tropical cyclones develop.

scholarly journals Indications of Surface and Sub-Surface Hydrologic Properties from SMAP Soil Moisture Retrievals

Hydrology ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 36 ◽  
Author(s):  
Paul Dirmeyer ◽  
Holly Norton
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Soil Column ◽  
Remotely Sensed ◽  
Subsurface Geology ◽  
South Central ◽  
Significant Relationships ◽  
The Impact ◽  
Soil Moisture Variability ◽  
Moisture Variability

Variability and covariability of land properties (soil, vegetation and subsurface geology) and remotely sensed soil moisture over the southeast and south-central U.S. are assessed. The goal is to determine whether satellite soil moisture memory contains information regarding land properties, especially the distribution karst formations below the active soil column that have a bearing on land-atmosphere feedbacks. Local (within a few tens of km) statistics of land states and soil moisture are considered to minimize the impact of climatic variations, and the local statistics are then correlated across the domain to illuminate significant relationships. There is a clear correspondence between soil moisture memory and many land properties including karst distribution. This has implications for distributed land surface modeling, which has not considered preferential water flows through geologic formations. All correspondences are found to be strongest during spring and fall, and weak during summer, when atmospheric moisture demand appears to dominate soil moisture variability. While there are significant relationships between remotely-sensed soil moisture variability and land properties, it will be a challenge to use satellite data for terrestrial parameter estimation as there is often a great deal of correlation among soil, vegetation and karst property distributions.

Evaluation of the impact of rainfall on soil moisture variability

1998 ◽  
Vol 21 (5) ◽  
pp. 375-384 ◽  
Author(s):  
Chulsang Yoo ◽  
Juan B. Valdés ◽  
Gerald R. North
Keyword(s):  
Soil Moisture ◽  
The Impact ◽  
Soil Moisture Variability ◽  
Moisture Variability

scholarly journals The impact of the 1783–1784 AD Laki eruption on global aerosol formation processes and cloud condensation nuclei

2010 ◽  
Vol 10 (13) ◽  
pp. 6025-6041 ◽  
Author(s):  
A. Schmidt ◽  
K. S. Carslaw ◽  
G. W. Mann ◽  
M. Wilson ◽  
T. J. Breider ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Northern Hemisphere ◽  
General Circulation ◽  
Cloud Condensation Nuclei ◽  
General Circulation Models ◽  
Aerosol Formation ◽  
Condensation Nuclei ◽  
Upper Troposphere ◽  
Microphysical Processes ◽  
The Impact

Abstract. The 1783–1784 AD Laki flood lava eruption commenced on 8 June 1783 and released 122 Tg of sulphur dioxide gas over the course of 8 months into the upper troposphere and lower stratosphere above Iceland. Previous studies have examined the impact of the Laki eruption on sulphate aerosol and climate using general circulation models. Here, we study the impact on aerosol microphysical processes, including the nucleation of new particles and their growth to cloud condensation nuclei (CCN) using a comprehensive Global Model of Aerosol Processes (GLOMAP). Total particle concentrations in the free troposphere increase by a factor ~16 over large parts of the Northern Hemisphere in the 3 months following the onset of the eruption. Particle concentrations in the boundary layer increase by a factor 2 to 5 in regions as far away as North America, the Middle East and Asia due to long-range transport of nucleated particles. CCN concentrations (at 0.22% supersaturation) increase by a factor 65 in the upper troposphere with maximum changes in 3-month zonal mean concentrations of ~1400 cm−3 at high northern latitudes. 3-month zonal mean CCN concentrations in the boundary layer at the latitude of the eruption increase by up to a factor 26, and averaged over the Northern Hemisphere, the eruption caused a factor 4 increase in CCN concentrations at low-level cloud altitude. The simulations show that the Laki eruption would have completely dominated as a source of CCN in the pre-industrial atmosphere. The model also suggests an impact of the eruption in the Southern Hemisphere, where CCN concentrations are increased by up to a factor 1.4 at 20° S. Our model simulations suggest that the impact of an equivalent wintertime eruption on upper tropospheric CCN concentrations is only about one-third of that of a summertime eruption. The simulations show that the microphysical processes leading to the growth of particles to CCN sizes are fundamentally different after an eruption when compared to the unperturbed atmosphere, underlining the importance of using a fully coupled microphysics model when studying long-lasting, high-latitude eruptions.

scholarly journals Impact of Shortened Winter Road Access on Costs of Forest Operations

Forests ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 447 ◽  
Author(s):  
Tevfik Z. Kuloglu ◽  
Victor J. Lieffers ◽  
Axel E. Anderson
Keyword(s):  
General Circulation ◽  
Unit Cost ◽  
Weather Conditions ◽  
General Circulation Models ◽  
Forest Harvesting ◽  
Frozen Soil ◽  
Annual Number ◽  
Soil Conditions ◽  
Frozen Ground ◽  
The Impact

A significant portion of the forest harvesting in the cooler regions of North America occurs in the winter when the ground is frozen and can support machine traffic. Climate change may influence the cost of forestry operations by reducing the period of winter access in those cold regions. In this study, we examined the impact of a shortened period of frozen ground conditions on logging operation and costs. To adapt to shorter period of frozen soil conditions, logging contractors might need to provide more machines and labor to complete logging in a shorter period of frozen conditions. The objectives were to calculate the costs of logging operations of a hypothetical forestry company in Alberta, Canada under two conditions: first, when the wood was hauled to the mill directly; and second, when part of the wood was hauled to satellite yards close to the logging area, thereby minimizing the annual number of idle hauling trucks. General Circulation Models were used to predict future winter weather conditions. Using the current type of harvesting machines and hauling directly to the mill, the unit cost of logging operations ($/m3) was projected to increase by an average of 1.6% to 2.5% in 2030s, 2.8% to 5.3% in the 2050s and 4.8% to 10.9% in the 2080s compared to the base year of 2015–2016. With use of satellite yards during the winter logging, the total logging cost will increase over direct haul, by 1.8% to 2.8% in the 2030s, 3.1% to 5.7% in the 2050s and 5.2% to 11.4% in the 2080s. Using satellite yards, however, will provide year-around employment for hauling truckers and more consistent and reliable hauling operations.

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