Effects of quasi‐stationary large‐scale anomalies on some mesoscale features associated with the 1993 flood: A regional model simulation

Pan, Zaitao; Arritt, Raymond W.; Segal, M.; Chen, Tsing Chang; Weng, Shu Ping

doi:10.1029/2000jd900429

Cited by 7 publications

(6 citation statements)

References 19 publications

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“…[12] In light of the feedback process described herein we conclude that in order to produce accurate projections of changes in the climate of the central U.S. it is necessary to simulate the mesoscale processes that convert converged moisture into rainfall near the northern terminus of southerly LLJs [Augustine and Caracena, 1994]. Regional climate models simulate these processes reasonably well judging from the Project to Intercompare Regional Climate Simulations (PIRCS) experiments, which evaluated 16 such models [Anderson et al, 2003], and our previous studies [Pan et al, 2000]. In contrast current global climate models (GCMs) poorly simulate the link between regional precipitation and LLJs, due in part to their coarse spatial resolution [Ghan et al, 1996].…”

Section: Discussionmentioning

confidence: 81%

Altered hydrologic feedback in a warming climate introduces a “warming hole”

Pan

Arritt

Takle

et al. 2004

Geophysical Research Letters

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[1] In the last 25 years of the 20th century most major land regions experienced a summer warming trend, but the central U.S. cooled by 0.2 -0.8 K. In contrast most climate projections using GCMs show warming for all continental interiors including North America. We examined this discrepancy by using a regional climate model and found a circulation-precipitation coupling under enhanced greenhouse gas concentrations that occurs on scales too small for current GCMs to resolve well. Results show a local minimum of warming in the central U.S. (a ''warming hole'') associated with changes in low-level circulations that lead to replenishment of seasonally depleted soil moisture, thereby increasing late-summer evapotranspiration and suppressing daytime maximum temperatures. These regional-scale feedback processes may partly explain the observed late 20th century temperature trend in the central U.S. and potentially could reduce the magnitude of future greenhouse warming in the region.

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Section: Discussionmentioning

confidence: 81%

Altered hydrologic feedback in a warming climate introduces a “warming hole”

Pan

Arritt

Takle

et al. 2004

Geophysical Research Letters

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199

165

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“…However, they are not independent from the large‐scale environment. Stronger low‐level jets have been correlated with intense upper level zonal flow over the Rockies [ Byerle and Paegle , 2003], and mesoscale convective complexes are favored by a strong low‐level jet and weaker upper tropospheric inertial stability [ Pan et al , 2000].…”

Section: Discussionmentioning

confidence: 99%

Spectral nudging to eliminate the effects of domain position and geometry in regional climate model simulations

2004

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[1] It is well known that regional climate simulations are sensitive to the size and position of the domain chosen for calculations. Here we study the physical mechanisms of this sensitivity. We conducted simulations with the Regional Atmospheric Modeling System (RAMS) for June 2000 over North America at 50 km horizontal resolution using a 7500 km Â 5400 km grid and NCEP/NCAR reanalysis as boundary conditions. The position of the domain was displaced in several directions, always maintaining the U.S. in the interior, out of the buffer zone along the lateral boundaries. Circulation biases developed a large scale structure, organized by the Rocky Mountains, resulting from a systematic shifting of the synoptic wave trains that crossed the domain. The distortion of the large-scale circulation was produced by interaction of the modeled flow with the lateral boundaries of the nested domain and varied when the position of the grid was altered. This changed the large-scale environment among the different simulations and translated into diverse conditions for the development of the mesoscale processes that produce most of precipitation for the Great Plains in the summer season. As a consequence, precipitation results varied, sometimes greatly, among the experiments with the different grid positions. To eliminate the dependence of results on the position of the domain, we used spectral nudging of waves longer than 2500 km above the boundary layer. Moisture was not nudged at any level. This constrained the synoptic scales to follow reanalysis while allowing the model to develop the small-scale dynamics responsible for the rainfall. Nudging of the large scales successfully eliminated the variation of precipitation results when the grid was moved. We suggest that this technique is necessary for all downscaling studies with regional models with domain sizes of a few thousand kilometers and larger embedded in global models.

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“…Evaporation tends to influence precipitation only if the large‐scale conditions are favorable for precipitation [e.g., Barnston and Schikedanz , 1984], as during the summer of 1993. Pan et al [2000] for instance, demonstrate the important contribution of MCC‐like systems to precipitation totals during the summer of 1993. Namias [1991] finds that the large‐scale circulation was not conducive to precipitation during the spring and early summer of 1988.…”

Section: Model Experimentsmentioning

confidence: 94%

“…The UGM simulations presented here are on a 2.2° (latitude) by 2.8° (longitude) horizontal grid and are too coarse to adequately resolve mesoscale features. Pan et al [2000] also concluded that the anomalous, large‐scale environment during summer 1993 created conditions favorable for MCCs. Such interactions occurred in their 30‐day simulations (and verified against observations) in regions away from the simulated boundary‐forcing locations, where MCCs were favored substantially by the large‐scale anomalies.…”

Section: Model Experimentsmentioning

confidence: 98%

“… Pan et al [2000] demonstrated with a mesoscale model that a major contributor to the summer 1993 floods was a continuous generation of mesoscale convective complex (MCC)‐like systems. The UGM simulations presented here are on a 2.2° (latitude) by 2.8° (longitude) horizontal grid and are too coarse to adequately resolve mesoscale features.…”

Section: Model Experimentsmentioning

confidence: 99%

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Modulation of the Great Plains low‐level jet and moisture transports by orography and large‐scale circulations

Byerle

Paegle

2003

J. Geophys. Res.

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[1] This paper describes orographic processes that modulate the Great Plains low-level jet (LLJ) and related hydrology of the Mississippi River basin. Mechanical flow deflection by the Rocky Mountains is diagnosed in 50 years of monthly averaged National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) Reanalysis fields and in a series of integrations using a primitive equation version of the Utah Global Model (UGM). Although the mountain profiles are fixed over periods of short-to medium-range climate changes, their influence on the LLJ is not stationary because evolving ambient flows produce changing LLJ responses. Ensembles of mediumrange forecasts are made for the 1993 U.S. floods and for the 1988 U.S. drought. The forecasts distinguish some of the observed precipitation differences between these years, but the magnitude of the differences is underestimated. Seasonal and longer-term changes of the ambient flow occur on large scales, while the response of the LLJ occurs on smaller scales that may promote cloud generation and precipitation. Month-long simulations with monthly averaged conditions suggest that the Great Plains LLJ is a component of the large-scale circulation associated with the topography of the western United States. Orography thus provides a scale transfer mechanism that focuses global-scale features into the regional-scale responses. These are relevant to precipitation distribution and to moisture budgets of the larger individual river basins comprising the GCIP domain. A theoretical interpretation of the large-scale, mechanical influence of orography on surrounding low-level circulations is proposed.

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Effects of quasi‐stationary large‐scale anomalies on some mesoscale features associated with the 1993 flood: A regional model simulation

Cited by 7 publications

References 19 publications

Altered hydrologic feedback in a warming climate introduces a “warming hole”

Altered hydrologic feedback in a warming climate introduces a “warming hole”

Spectral nudging to eliminate the effects of domain position and geometry in regional climate model simulations

Modulation of the Great Plains low‐level jet and moisture transports by orography and large‐scale circulations

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