Effect of Ocean Surface Heterogeneity on Climate Simulation

Gutowski, William J.; Ötles, Zekai; Chen, Yibin

doi:10.1175/1520-0493(1998)126<1419:eoosho>2.0.co;2

Cited by 4 publications

(4 citation statements)

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“…Thus the model can be used to examine such issues as effects on the regional hydrologic cycle of vegetation distributions that are subgrid in scale relative to the width of the atmospheric column. Earlier work using the atmospheric portion of this model, for example, examined how and when subgrid distributions of sea surface temperature influences air‐sea interaction [ Gutowski et al , 1998]. An important capability of the model in this regard is its ability to perform multiyear runs efficiently so that the model can simulate simultaneously the fast evolution of the atmospheric hydrologic cycle and the slow evolution of subterranean water.…”

Section: Resultsmentioning

confidence: 99%

“…The Coupled Land‐Atmosphere Simulation Program is a single atmospheric column coupled to an underlying terrestrial domain that may encompass one or more watershed subcatchments. Earlier studies have also used similar one‐dimensional (1‐D) atmospheric models to study land‐atmosphere coupling [e.g., Wetzel and Chang , 1988; Koster and Eagleson , 1990] and ocean‐atmosphere coupling [e.g., Gutowski et al , 1998] in the hydrologic cycle. Because the CLASP emulates a grid box of an AGCM, the atmospheric column's horizontal extent, and hence its horizontal resolution, can range from several tens to hundreds of kilometers, depending on the application.…”

Section: Mathematical Modelmentioning

confidence: 99%

“…The ATMOS portion of the model has been described in detail elsewhere [ Gutowski et al , 1998]; we give a brief description here. Behavior of the atmospheric column is determined by conservation laws for momentum, energy, mass, and water.…”

Section: Mathematical Modelmentioning

confidence: 99%

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A Coupled Land‐Atmosphere Simulation Program (CLASP): Calibration and validation

et al. 2002

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[1] We present a model and application designed to study the coupled land-atmosphere hydrologic cycle, following water from its inflow into a region by horizontal atmospheric transport through surface-atmosphere exchange processes and aquifer recharge to outflow as runoff and river discharge. The model includes a two-way water flow among its major reservoirs (atmosphere, vadose zone, groundwater, surface water, river). A unique feature of the model is that phreatophytic interactions are included when the water table intersects the root zone. The model emulates a uniform grid box of an atmospheric general circulation model, but with finer horizontal resolution for the land processes, and forms a test bed for developing continental-scale simulation of the hydrologic cycle. The model is calibrated using the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) observations for 1987 and validated using FIFE observations for 1988 and 1989. Four physical factors emerge as important for simulating the FIFE water cycle: effective relative humidity for initiating stable (large scale) condensation, length of the growing season, amount of available soil water, and cloud cover parameterization. Further evaluation uses water table and river discharge measurements for years up to 1993. The model simulates multiyear behavior in the hydrologic cycle reasonably well. Average differences between FIFE observations and simulated fluxes during the calibration period are only a few percent, including fluxes not specifically calibrated. Model-observation differences in surface sensible and latent heat fluxes are larger during the 1988 drought but recover to relatively small values for 1989, suggesting some difficulty in simulating hydrologic extremes occurring outside the calibration conditions. A model sensitivity study using statistical disaggregation to allow precipitation to fall on only a portion of the landscape indicates that spatial disaggregation of precipitation can have strong impact on groundwater storage and surface discharge, potentially improving agreement between observed and simulated streamflow. Water redistributed through the model's aquifer-river network can at times raise the water table high enough for water to seep back to the vegetation root zone and increase evapotranspiration. During relatively dry periods, up to 33% of monthly evapotranspiration was derived from groundwater-supported evapotranspiration, emphasizing the need to quantify better aquifer-atmosphere interaction. The work also demonstrates the feasibility and utility of fully coupled water budgeting schemes.

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Section: Resultsmentioning

confidence: 99%

Section: Mathematical Modelmentioning

confidence: 99%

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A Coupled Land‐Atmosphere Simulation Program (CLASP): Calibration and validation

et al. 2002

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“…The spatial mean Q c value also decreased but negligibly (~0.05 W/m 2 ) for the very stable MGL3 mission when comparing high‐resolution to low‐resolution patterns. These findings demonstrate that in the surface heat flux estimation of inland water bodies, the errors associated with the area‐averaged LSWT are expected to be higher under near‐neutral conditions (Gutowski et al, ; Mahrt & Hristov, ), a condition that is not common on an annual basis over lakes (Verburg & Antenucci, ; Woolway et al, ). In order to further investigate the effect of the above estimated biases of the calculated surface cooling induced by LSWT subpixel‐scale heterogeneity on the overall heat budget of a large lake such as Lake Geneva, and in particular, in a long‐term analysis, a more extensive data base would be required; this currently does not exist.…”

Section: Resultsmentioning

confidence: 86%

Surface Water Temperature Heterogeneity at Subpixel Satellite Scales and Its Effect on the Surface Cooling Estimates of a Large Lake: Airborne Remote Sensing Results From Lake Geneva

2019

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The dynamics of spatial heterogeneity of lake surface water temperature (LSWT) at subpixel satellite scale O(1 m) and its effect on the surface cooling estimation at typical satellite pixel areas O(1 km 2 ) were investigated using an airborne platform. The measurements provide maps that revealed spatial LSWT variability with unprecedented detail. The cold season data did not show significant LSWT heterogeneity and hence no surface cooling spatial variability. However, based on three selected daytime subpixel-scale maps, LSWT patterns showed a variability of >2°C in the spring and >3.5°C in the summer, corresponding to a spatial surface cooling range of >20 and >40 W/m 2 , respectively. Due to the nonlinear relationship between turbulent surface heat fluxes and LSWT, negatively skewed LSWT distributions resulted in negatively skewed surface cooling patterns under very stable or predominantly unstable atmospheric boundary layer (ABL) conditions and positively skewed surface cooling patterns under predominantly stable ABL conditions. Implementing a mean spatial filter, the effect of area-averaged LSWT on the surface cooling estimation up to a typical satellite pixel was assessed. The effect of the averaging filter size on the mean spatial surface cooling values was negligible, except for predominantly stable ABL conditions. In that situation, a reduction of~3.5 W/m 2 was obtained when moving from high O(1 m) to low O(1 km) pixel resolution.Plain Language Summary Lake surface water temperature (LSWT) is one of the main parameters required for estimating surface cooling at the air-water interface and is also essential for understanding other processes (such as ecosystem dynamics, climate change, and numerical weather prediction) in lakes. Usually, surface cooling is determined from in situ point measurements or satellite images. Satellite thermal images resolve surface areas with a typical pixel resolution of O(1 km). Therefore, satellite data can depict large-scale thermal patterns. But can LSWT spatial variability be significant at subpixel satellite resolution over a large lake? What is the effect of such variability on area-averaged surface cooling estimates? To address these questions, a measurement system, including a balloon-launched airborne platform for thermography and a catamaran for in situ measurements along predefined tracks, was used for LSWT mapping and calibration. Surface cooling patterns were then estimated using a calibrated bulk model. Results showed insignificant LSWT heterogeneity and hence no surface cooling spatial variability during the cold seasons. However, a notable spatial variability of >2°C and > 3.5°C was found in spring and summer, respectively. The effect of LSWT heterogeneity on surface cooling variability was significant, in particular, when air-water temperature differences were close to 0.

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Putting aquifers into atmospheric simulation models: an example from the Mill Creek Watershed, northeastern Kansas

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Gutowski

et al. 2002

Advances in Water Resources

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144

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Aquifer-atmosphere interactions can be important in regions where the water table is shallow (<2 >m). A shallow water table provides moisture for the soil and vegetation and thus acts as a source term for evapotranspiration to the atmosphere. A coupled aquifer-land surface-atmosphere model has been developed to study aquifer-atmosphere interactions in watersheds, on decadal timescales. A single column vertically discretized atmospheric model is linked to a distributed soil-vegetation-aquifer model. This physically based model was able to reproduce monthly and yearly trends in precipitation, stream discharge, and evapotranspiration, for a catchment in northeastern Kansas. However, the calculated soil moisture tended to drop to levels lower than were observed in drier years. The evapotranspiration varies spatially and seasonally and was highest in cells situated in topographic depressions where the water table is in the root zone. Annually, simulation results indicate that from 5-20% of groundwater supported evapotranspiration is drawn from the aquifer. The groundwater supported fraction of evapotranspiration is higher in drier years, when evapotranspiration exceeds precipitation. A long-term (40 year) simulation of extended drought conditions indicated that water table position is a function of groundwater hydrodynamics and cannot be predicted solely on the basis of topography. The response time of the aquifer to drought conditions was on the order of 200 years indicating that feedbacks between these two water reservoirs act on disparate time scales. With recent advances in the computational power of massively parallel supercomputers, it may soon become possible to incorporate physically based representations of aquifer hydrodynamics into general circulation models (GCM) land surface parameterization schemes. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. AbstractAquifer-atmosphere interactions can be important in regions where the water table is shallow (<2 m). A shallow water table provides moisture for the soil and vegetation and thus acts as a source term for evapotranspiration to the atmosphere. A coupled aquifer-land surface-atmosphere model has been developed to study aquifer-atmosphere interactions in watersheds, on decadal timescales. A single column vertically discretized atmospheric model is linked to a distributed soil-vegetation-aquifer model. This physically based model was able to reproduce monthly and yearly trends in precipitation, stream discharge, and evapotranspiration, for a catchment in northeastern Kansas. However, the calculated soil moisture tended to drop to levels lower than were observed in drier years. The evapotranspiration varies spatially and seasonally and was highest in cells situated in topographic depressions where the water table is in the root zone. Annually, simulation results indicate that from 5-20% of groundwater supported evapotranspir...

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Effect of Ocean Surface Heterogeneity on Climate Simulation

Cited by 4 publications

References 36 publications

A Coupled Land‐Atmosphere Simulation Program (CLASP): Calibration and validation

A Coupled Land‐Atmosphere Simulation Program (CLASP): Calibration and validation

Surface Water Temperature Heterogeneity at Subpixel Satellite Scales and Its Effect on the Surface Cooling Estimates of a Large Lake: Airborne Remote Sensing Results From Lake Geneva

Putting aquifers into atmospheric simulation models: an example from the Mill Creek Watershed, northeastern Kansas

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