Nonlocal Boundary Layer Vertical Diffusion in a Medium-Range Forecast Model

Hong, Song; Pan, Hua-Lu

doi:10.1175/1520-0493(1996)124<2322:nblvdi>2.0.co;2

Cited by 2,013 publications

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“…This LSM does not incorporate any specific urban parametrization but urban areas are identified in the USGS land-use database by a specific flag associated with a specific roughness (80 cm), albedo (15%), emissivity (88% at 9 µm), moisture availability of 10% and thermal inertia of 0.03 cal cm −2 K −1 s −1/2 , which are necessary variables for computing the surface radiative and turbulence fluxes. The planetary boundary layer (PBL) is parametrized using the Hong and Pan (1996) scheme. It is an efficient scheme based on Troen and Mahrt representation of the countergradient term and eddy viscosity profile in the well-mixed PBL, and is suitable for high resolution in the PBL.…”

Section: Mm5 Numerical Modelmentioning

confidence: 99%

Water vapour variability induced by urban/rural surface heterogeneities during convective conditions

Champollion

Drobinski

Haeffelin

et al. 2009

Quart J Royal Meteoro Soc

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Scientific interest in urban meteorology has increased because highly populated areas experience high vulnerability to pollution or heavy rain. However, compared to urban air quality or urban heat island (UHI) processes, the urban water vapour cycle is poorly understood because it has been investigated less due to the lack of upper-air measurements and the high sensitivity of surface measurements to local heterogeneities. In this paper, surface measurements of wind, temperature, pressure and humidity, as well as integrated water vapour (IWV) from GPS and MODIS and numerical simulations, have been used to investigate the urban cycle of water vapour in May and June 2004 during the VAPIC field experiment in the Paris area.The surface data show the typical characteristics of an urban area with the absence of water vapour sources and a UHI of about 6 • C at night. The urban IWV distribution differs completely, with an urban IWV excess on average between 1600 and 0600 UTC (with a maximum of about 1.5 kg m −2 at 0600 and 1700 UTC). No IWV difference between the urban and rural areas is found in the middle of the day. The numerical simulations reproduce accurately the urban IWV anomaly.Shallow surface wind convergence associated with the UHI during nighttime provides moisture from the rural areas. Urban areas are therefore under wind convergence for most of the time. The rural water vapour sources and the depth of the convergence control the amplitude of the urban IWV excess. At about 1200 UTC, entrainment at the top of the urban boundary layer is the key process that inhibits the urban IWV excess observed at night.

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Section: Mm5 Numerical Modelmentioning

confidence: 99%

Water vapour variability induced by urban/rural surface heterogeneities during convective conditions

Champollion

Drobinski

Haeffelin

et al. 2009

Quart J Royal Meteoro Soc

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“…The MM5 model is running operationally at the National Observatory of Athens since 2000 (Kotroni and Lagouvardos, 2004). Concerning the choice of the microphysical and boundary layer schemes, the current operational chain uses the scheme proposed by Schultz (1995) and Hong and Pan (1996), respectively. Indeed, in the study by Akylas et al (2007), the authors have shown that the PBL scheme proposed by Hong and Pan (1996) produces the most consistent results over Greece.…”

Section: Model Setupmentioning

confidence: 99%

“…Concerning the choice of the microphysical and boundary layer schemes, the current operational chain uses the scheme proposed by Schultz (1995) and Hong and Pan (1996), respectively. Indeed, in the study by Akylas et al (2007), the authors have shown that the PBL scheme proposed by Hong and Pan (1996) produces the most consistent results over Greece. For radiation parameterisation, the standard scheme of MM5 that accounts for longwave and shortwave interactions with explicit cloud and clear-air was used.…”

Section: Model Setupmentioning

confidence: 99%

The sensitivity of warm period precipitation forecasts to various modifications of the Kain-Fritsch Convective Parameterization scheme

Mazarakis

Kotroni

Lagouvardos

et al. 2011

Nat. Hazards Earth Syst. Sci.

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Abstract. The sensitivity of quantitative precipitation forecasts to various modifications of the Kain-Fritsch (KF) convective parameterization scheme (CPS) is examined for twenty selected cases characterized by intense convective activity and widespread precipitation over Greece, during the warm period of [2005][2006][2007]. The study is conducted using the MM5 model with a two nested domains strategy, with horizontal grid increments of 24 and 8 km, respectively. Five modifications to the KF CPS, each designed to test the sensitivity of the model to the convective scheme formulation, are discussed. The modifications include: (i) the maximization of the convective scheme precipitation efficiency, (ii) the change of the convective time step, (iii) the forcing of the convective scheme to produce more/less cloud material, (iv) changes to the trigger function and (v) the alteration of the vertical profile of updraft mass flux detrainment.The simulated precipitation from the 8-km grid is verified against raingauge measurements. Although skill scores vary widely among the cases and the precipitation thresholds, model results using the modifications of the convective scheme show improvements in 6-h precipitation totals compared to simulations generated using the unmodified convective scheme. In general, forcing the model to produce less cloud material improves the precipitation forecast for the moderate and high precipitation amounts, while the same modification and the change of the convective time step to 1 min has the same result for the high precipitation thresholds. The increase of convective time step to 15 min, the maximization of precipitation efficiency and the changes to the trigger function give similar results for medium and high precipitation. On the other hand, the forecast for the light Correspondence to: N. Mazarakis (nickmaz@meteo.noa.gr) precipitation is improved by forcing the model to produce more cloud material as well as by the alteration of the vertical profile of updraft mass flux detrainment.

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“…These include upgrades in the parameterization of solar radiation transfer (Hou et al, 1996;Hou et al, 2002), planetary boundary layer (PBL) vertical diffusion (Hong and Pan, 1996), Simplified Arakawa-Schubert (SAS) cumulus convection (Pan and Wu, 1995;Hong and Pan, 1998), and gravity wave drag (Kim and Arakawa, 1995). In addition, cloud condensate is a prognostic variable (Moorthi et al, 2001) with a simple cloud microphysics parameterization (Zhao and Carr, 1997;Sundqvist et al, 1989).…”

Section: Brief Description Of the Gfsmentioning

confidence: 99%

“…The PBL scheme in the GFS is based on the Troen and Mahrt (1986) paper and was implemented by Hong and Pan (1996). The scheme is a first-order vertical diffusion scheme.…”

Section: Brief Description Of the Gfsmentioning

confidence: 99%

Simulation of low clouds in the Southeast Pacific by the NCEP GFS: sensitivity to vertical mixing

Sun¹,

Moorthi²,

Xiao

et al. 2010

Atmos. Chem. Phys.

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Abstract. The NCEP Global Forecast System (GFS) model has an important systematic error shared by many other models: stratocumuli are missed over the subtropical eastern oceans. It is shown that this error can be alleviated in the GFS by introducing a consideration of the low-level inversion and making two modifications in the model's representation of vertical mixing. The modifications consist of (a) the elimination of background vertical diffusion above the inversion and (b) the incorporation of a stability parameter based on the cloud-top entrainment instability (CTEI) criterion, which limits the strength of shallow convective mixing across the inversion. A control simulation and three experiments are performed in order to examine both the individual and combined effects of modifications on the generation of the stratocumulus clouds. Individually, both modifications result in enhanced cloudiness in the Southeast Pacific (SEP) region, although the cloudiness is still low compared to the ISCCP climatology. If the modifications are applied together, however, the total cloudiness produced in the southeast Pacific has realistic values. This nonlinearity arises as the effects of both modifications reinforce each other in reducing the leakage of moisture across the inversion. Increased moisture trapped below the inversion than in the control run without modifications leads to an increase in cloud amount and cloud-top radiative cooling. Then a positive feedback due to enhanced turbulent mixing in the planetary boundary layer by cloud-top radiative cooling leads to and maintains the stratocumulus cover. Although the amount of total cloudiness obtained with both modifications has realistic values, the relative contributions of low, middle, and high layers tend to Correspondence to: R. Sun (ruiyu.sun@noaa.gov) differ from the observations. These results demonstrate that it is possible to simulate realistic marine boundary clouds in large-scale models by implementing direct and physically based improvements in the model parameterizations.

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Nonlocal Boundary Layer Vertical Diffusion in a Medium-Range Forecast Model

Cited by 2,013 publications

References 0 publications

Water vapour variability induced by urban/rural surface heterogeneities during convective conditions

Water vapour variability induced by urban/rural surface heterogeneities during convective conditions

The sensitivity of warm period precipitation forecasts to various modifications of the Kain-Fritsch Convective Parameterization scheme

Simulation of low clouds in the Southeast Pacific by the NCEP GFS: sensitivity to vertical mixing

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