Abstract:This paper compares a number of one-dimensional closure models for the planetary boundary layer (PBL) that are currently in use in large-scale atmospheric models. Using the results of a large-eddy simulation (LES) model as the standardof comparison, the PBL models are evaluatedover a range of stratifications from free convective to neutral and a range of surface shear stresses. Capping inversion strengths for the convective cases range from weakly to strongly capped. Six prototypical PBL models are evaluated i… Show more
“…Insufficient entrainment flux under convective conditions by the Mellor-Yamada level 2.5 scheme and other local closure schemes has been found in some onedimensional tests (Holtslag et al 1995;Ayotte et al 1996;Pagowski 2004). Simulated PBL growth and structure have been shown to be sensitive to the entrainment flux by Ayotte et al (1996), Betts et al (1997), andNoh et al (2003).…”
Section: Fig 5 Mean Diurnal Variation Of (A) Surface Sensible Hfx mentioning
confidence: 90%
“…Simulated PBL growth and structure have been shown to be sensitive to the entrainment flux by Ayotte et al (1996), Betts et al (1997), andNoh et al (2003). The nonlocal ACM2 and YSU schemes both were designed for their entrainment flux to better match results from large-eddy simulations.…”
Section: Fig 5 Mean Diurnal Variation Of (A) Surface Sensible Hfx mentioning
Accurate depiction of meteorological conditions, especially within the planetary boundary layer (PBL), is important for air pollution modeling, and PBL parameterization schemes play a critical role in simulating the boundary layer. This study examines the sensitivity of the performance of the Weather Research and Forecast (WRF) model to the use of three different PBL schemes [Mellor-Yamada-Janjic (MYJ), Yonsei University (YSU), and the asymmetric convective model, version 2 (ACM2)]. Comparison of surface and boundary layer observations with 92 sets of daily, 36-h high-resolution WRF simulations with different schemes over Texas in July-September 2005 shows that the simulations with the YSU and ACM2 schemes give much less bias than with the MYJ scheme. Simulations with the MYJ scheme, the only local closure scheme of the three, produced the coldest and moistest biases in the PBL. The differences among the schemes are found to be due predominantly to differences in vertical mixing strength and entrainment of air from above the PBL. A sensitivity experiment with the ACM2 scheme confirms this diagnosis.
“…Insufficient entrainment flux under convective conditions by the Mellor-Yamada level 2.5 scheme and other local closure schemes has been found in some onedimensional tests (Holtslag et al 1995;Ayotte et al 1996;Pagowski 2004). Simulated PBL growth and structure have been shown to be sensitive to the entrainment flux by Ayotte et al (1996), Betts et al (1997), andNoh et al (2003).…”
Section: Fig 5 Mean Diurnal Variation Of (A) Surface Sensible Hfx mentioning
confidence: 90%
“…Simulated PBL growth and structure have been shown to be sensitive to the entrainment flux by Ayotte et al (1996), Betts et al (1997), andNoh et al (2003). The nonlocal ACM2 and YSU schemes both were designed for their entrainment flux to better match results from large-eddy simulations.…”
Section: Fig 5 Mean Diurnal Variation Of (A) Surface Sensible Hfx mentioning
Accurate depiction of meteorological conditions, especially within the planetary boundary layer (PBL), is important for air pollution modeling, and PBL parameterization schemes play a critical role in simulating the boundary layer. This study examines the sensitivity of the performance of the Weather Research and Forecast (WRF) model to the use of three different PBL schemes [Mellor-Yamada-Janjic (MYJ), Yonsei University (YSU), and the asymmetric convective model, version 2 (ACM2)]. Comparison of surface and boundary layer observations with 92 sets of daily, 36-h high-resolution WRF simulations with different schemes over Texas in July-September 2005 shows that the simulations with the YSU and ACM2 schemes give much less bias than with the MYJ scheme. Simulations with the MYJ scheme, the only local closure scheme of the three, produced the coldest and moistest biases in the PBL. The differences among the schemes are found to be due predominantly to differences in vertical mixing strength and entrainment of air from above the PBL. A sensitivity experiment with the ACM2 scheme confirms this diagnosis.
“…Nevertheless, even most of state-of-the-art non-local mixing schemes have difficulties to represent the entrainment processes at the top of even the cloudless boundary layer (Ayotte et al, 1996;Siebesma and Holtslag, 1996;McFarlane, 1997, 1999;Mironov et al, 1999).…”
Section: Rationale Of Non-local and High-order Modellingmentioning
Abstract.A high-order modelling approach to interpret "continental-type" particle formation bursts in the anthropogenically influenced convective boundary layer (CBL) is proposed. The model considers third-order closure for planetary boundary layer turbulence, sulphur and ammonia chemistry as well as aerosol dynamics. In Paper I of four papers, previous observations of ultrafine particle evolution are reviewed, model equations are derived, the model setup for a conceptual study on binary and ternary homogeneous nucleation is defined and shortcomings of process parameterisation are discussed. In the subsequent Papers II, III and IV simulation results, obtained within the framework of a conceptual study on the CBL evolution and new particle formation (NPF), will be presented and compared with observational findings.
“…Since these mechanisms regulate the vertical transport of energy, moisture, trace gases, and pollutants, they play a significant role in climate. Yet while numerous laboratory [Deardorff et al, 1980], observational [Nelson et al, 1989;Lenschow et al, 1999;Bretherton et al, 1995;Faloona et al, 2005;Träumner et al, 2011], and modeling [Sullivan et al, 1998;Brooks and Fowler, 2012] studies have investigated shallow convection and entrainment and their role in transporting material vertically, simulated climates remain sensitive to the choice of model parameterization [Ayotte et al, 1996;Stevens, 2002;Hu et al, 2010]. Such sensitivities suggest bulk features of vertical moisture exchange are still not fully understood.…”
[1] The subtropical convective boundary layer (CBL) plays a critical role in climate by regulating the vertical exchange of moisture, energy, trace gases, and pollutants between the ocean surface and free troposphere. Yet bulk features of this exchange are poorly constrained in climate models. To improve our understanding of moisture transport between the boundary layer and free troposphere, paired measurements of water vapor mixing ratio and the stable isotope ratio 18 O/ 16 O are used to evaluate moist convective mixing and entrainment processes near the Big Island of Hawaii. Profile data from the island's east side are consistent with moist adiabatic processes below the trade wind temperature inversion. In contrast, profiles on the west side follow moist adiabatic lapse rates within discrete stable layers, suggesting moist convection sets the humidity structure of even the unsaturated regions around the island. Above the trade wind inversion, the transition from well-mixed boundary layer to free troposphere is characterized by a simple mixing line analysis, so long as the thermodynamic properties of the air mass at CBL top are known. Deviations from the mixing line identify thermodynamic boundaries in the atmospheric profile, which can persist from one day to the next. These findings indicate residual layers form during strong mixing events and regulate vertical moisture transport for multiple days at a time. Basic assumptions that synoptic-scale transport controls isotope ratios at CBL top are therefore not sufficient for describing moisture exchange between the boundary layer and free troposphere in the subtropics.Citation: Bailey, A., D. Toohey, and D. Noone (2013), Characterizing moisture exchange between the Hawaiian convective boundary layer and free troposphere using stable isotopes in water,
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