Cold‐pool formation in a narrow valley

Vosper, Simon; Hughes, John; Lock, A. P.; Sheridan, Peter F.; Ross, Andrew; Jemmett-Smith, Bradley; Brown, Andrew R.

doi:10.1002/qj.2160

Cited by 51 publications

(96 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This supports the validity of earlier COLPEX work (e.g. Vosper et al, 2013b) and also suggests that the missing data periods in the long-term simulation do not undermine the analysis presented here. Figure 6 shows the frequency distribution of biases in the daily minimum and maximum model screen-level (1.5 m) air temperature from the long-term simulation at the main observation sites, Duffryn (valley site) and Spring Hill (hilltop site; see Fig.…”

Section: Impact Of Spinning Up the Model Statesupporting

confidence: 78%

“…Previous COLPEX studies have focused on clear-sky cases, since this is a prerequisite for strong cold pool formation (e.g. Vosper et al, 2013b); however, Fig. 7 shows that a more general evaluation of the modeling setup should include other cases.…”

Section: Model Temperature Biasmentioning

confidence: 99%

“…The results show that the high horizontal and vertical resolution is required in order to sufficiently resolve the orography and obtain a good level of agreement between the simulated and observed temperature variations across the cold pools in clear-sky cases. Subsequently, Vosper et al (2013b) focused in detail on a single intensive observation period (IOP) that took place on the night of 4 March 2010 (IOP 16). The latter study demonstrated the skill of the MetUM in reproducing the observed temperatures across the valley and provided a detailed analysis of the heat budget within the cold pool.…”

Section: Introductionmentioning

confidence: 99%

“…A number of short simulations have been completed, corresponding to IOPs, some of which have been the focus of previous analysis (Sheridan et al, 2013;Vosper et al, 2013b). In addition to these, an extended simulation has been completed, for the period 17 August to 15 October 2009 (the long-term simulation).…”

Section: The Simulationsmentioning

confidence: 99%

See 3 more Smart Citations

Assessment of valley cold pools and clouds in a very high-resolution numerical weather prediction model

et al. 2015

Self Cite

View full text Add to dashboard Cite

Abstract. The formation of cold air pools in valleys under stable conditions represents an important challenge for numerical weather prediction (NWP). The challenge is increased when the valleys that dominate cold pool formation are on scales unresolved by NWP models, which can lead to substantial local errors in temperature forecasts. In this study a 2-month simulation is presented using a nested model configuration with a finest horizontal grid spacing of 100 m. The simulation is compared with observations from the recent COLd air Pooling Experiment (COLPEX) project and the model's ability to represent cold pool formation, and the surface energy balance is assessed. The results reveal a bias in the model long-wave radiation that results from the assumptions made about the sub-grid variability in humidity in the cloud parametrization scheme. The cloud scheme assumes relative humidity thresholds below 100 % to diagnose partial cloudiness, an approach common to schemes used in many other models. The biases in radiation, and resulting biases in screen temperature and cold pool properties are shown to be sensitive to the choice of critical relative humidity, suggesting that this is a key area that should be improved for very high-resolution modeling.

show abstract

Section: Impact Of Spinning Up the Model Statesupporting

confidence: 78%

Section: Model Temperature Biasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: The Simulationsmentioning

confidence: 99%

See 2 more Smart Citations

Assessment of valley cold pools and clouds in a very high-resolution numerical weather prediction model

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…Nakamura and Mahrt (2006) analyzed the heat budget of the air near the surface and contrasted the role of the inferred temperature advection between sites. Vosper et al (2013) numerically simulated flow in an instrumented valley and found important complex advection of temperature.…”

Section: Introductionmentioning

confidence: 99%

Heat Flux in the Strong-Wind Nocturnal Boundary Layer

Mahrt

2016

Boundary-Layer Meteorol

View full text Add to dashboard Cite

Sonic anemometer measurements are analyzed from two primary field programs and 12 supplementary sites to examine the behaviour of the turbulent heat flux near the surface with high wind speeds in the nocturnal boundary layer. On average, large downward heat flux is found for high wind speeds for most of the sites where some stratification is maintained in spite of relatively intense vertical mixing. The stratification for high wind speeds is found to be dependent on wind direction, suggesting the importance of warm-air advection, even for locally homogenous sites. Warm-air advection is also inferred from a large imbalance of the heat budget of the air for strong winds. Shortcomings of our study are noted.

show abstract

The role of forest cover and valley geometry in cold‐air pool evolution

Kiefer

Zhong

2015

JGR Atmospheres

View full text Add to dashboard Cite

This study utilizes a version of the Advanced Regional Prediction System (ARPS) with a canopy submodel (ARPS‐CANOPY) to evaluate the sensitivity of cold‐air pool evolution to forest canopy density and valley geometry and elucidate the underlying processes. Numerical experiments are conducted with forest canopy structures spanning from bare ground to dense canopies and terrain configurations ranging from small, shallow valleys to broad, deep valleys. In a set of experiments in which forest canopy density is varied, the minimum potential temperature in the cold‐air pool is found to be as much as 15 K warmer with a dense canopy than with no canopy. Analysis of the thermodynamic budget reveals weaker cooling rates in the dense canopy case than the sparse canopy case, with differences in cooling rates persisting through the duration of the simulation. An additional experiment in which cooling of canopy elements and the influence of the canopy on the ground radiation budget are neglected highlights the important role the canopy plays in limiting radiative loss from the ground surface along the sidewall and valley floor. In experiments in which valley geometry is varied, the cold‐air pool is found to be strongest in a medium valley (10 km wide, 187.5 m deep) and weakest in a small valley (2 km wide, 37.5 m deep). Analysis of along‐slope buoyancy suggests that downslope flow‐driven cooling in a medium valley is more efficient than in a large valley (30 km wide, 500 m deep).

show abstract

Cold‐pool formation in a narrow valley

Cited by 51 publications

References 34 publications

Assessment of valley cold pools and clouds in a very high-resolution numerical weather prediction model

Assessment of valley cold pools and clouds in a very high-resolution numerical weather prediction model

Heat Flux in the Strong-Wind Nocturnal Boundary Layer

The role of forest cover and valley geometry in cold‐air pool evolution

Contact Info

Product

Resources

About