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## A bulk model for the atmospheric planetary boundary layer

### Boundary-Layer Meteorology (1979-12-01) 17: 411-427 , December 01, 1979

The integrated momentum and thermodynamic equations through the planetary boundary layer (PBL) are solved numerically to predict the mean changes of wind and potential temperature from which surface fluxes are computed using bulk transfer coefficients of momentum and heat. The second part of the study involves a formulation and testing of a PBL height model based on the turbulent energy budget equation where turbulent fluxes of wind and heat are considered as the source of energy. The model exhibits capability of predicting the PBL height development for both stable and unstable regimes of observed conditions. Results of the model agree favourably with those of Deardorff's (1974a) and Tennekes' (1973) models in convective conditions.

## On the relation between ozone storage in the residual layer and daily variation in near-surface ozone concentration — A case study

### Boundary-Layer Meteorology (1994-05-01) 69: 221-247 , May 01, 1994

### Summary

Numerous tethered balloon soundings which measured meteorological parameters and ozone concentration during the POLLUMET field experiments are investigated. They give indications of the influence of ozone conservation in the nocturnal residual layer (RL) on the development of the near surface ozone concentration of the next day. Mixing down from the RL to the surface is simulated by a simple model based on transilient turbulence theory, using measured profiles as initial values or model verification. The cases investigated show that the ozone mixed down from the RL contributes 50–70% to the maximum concentration near the surface on the following day, the rest coming from chemical production and possibly advection. Various features of exchange characteristics between the RL and the nocturnal boundary layer, (NBL) are described by the analysis of the soundings. It can be shown that the vertical exchange situation during the night can have a considerable influence on the ozone concentration of the following day.

## Relating Urban Surface-layer Structure to Upwind Terrain for the Salford Experiment (Salfex)

### Boundary-Layer Meteorology (2008-05-01) 127: 173-191 , May 01, 2008

Profiles of wind and turbulence over an urban area evolve with fetch in response to surface characteristics. Sodar measurements, taken on 22 April 2002 during the Salford Experiment in the UK (Salfex), are here related to upstream terrain. A logarithmic layer up to *z* = 65m was observed in all half-hour averaged profiles. Above this height the profile showed a different vertical gradient, suggesting a change in surface cover upstream. The drag coefficient varied by a factor of two over only a 20° direction change. Turbulence intensity (*σ*_{x}) for each wind component (*x*) decreased with height, but the ratio suggested an underestimate of *σ*_{u} compared to previous results. Mean urban and suburban cover fraction within the source area for each height decreased sharply between *z* = 20 and 50m, increasing slightly above. The near-convergence of cover fractions thus occured for source areas of minimum length ≈ 2,200 m. In comparison, the mean length scale of heterogeneity *L*_{P} was calculated from surface cover data to be 1,284 m, and the corresponding mean blending height *h*_{b} was 175 m. Finally, the mean streamline angle, α, was negative and the magnitude decreased with height. An exponential fit to α for *z* ≤ 65m gave an e-folding height scale of 159 m. A simple relationship between this height scale and *L*_{P} was assumed, giving *L*_{P} ≈ 1,080 m, which is in reasonable agreement with the estimate from surface cover type. The results suggest that more emphasis is required on modelling and measuring surface-layer flow over heterogeneous urban canopies.

## Modelling dust distributions in the atmospheric boundary layer on Mars

### Boundary-Layer Meteorology (2007-11-01) 125: 305-328 , November 01, 2007

A time and height dependent eddy diffusion model is used to investigate possible scenarios for the size distribution of dust in the lower atmosphere of Mars. The dust is assumed to either have been advected from a distant source or to have originated locally. In the former case, the atmosphere is assumed to initially contain dust particles with sizes following a modified gamma distribution. Larger particles are deposited relatively rapidly while small particles are well mixed up to the maximum height of the afternoon boundary layer and are deposited more slowly. In other cases, a parameterization of the dust source at the surface is proposed. Model results show that smaller particles are rapidly mixed within the Martian boundary layer, while larger particles (r > 10 μm) are concentrated near the ground with a stronger diurnal cycle. In all simulations we assume that the initial concentration or surface source depend on a modified gamma function distribution. For small particles (cross- sectional area weighted mean radius, r_{eff} = 1.6 μm) distributions retain essentially the same form, though with variations in the mean and variance of the area-weighted radius, and the gamma function can be used to represent the particle size distribution reasonably well at most heights within the boundary layer. In the case of a surface source of larger particles (mean radius 50 μm) the modified gamma function does not fit the resulting particle size distribution. All results are normalised by a scaling factor that can be adjusted to correspond to an optical depth for assumed particle optical scattering properties.

## A SENSITIVITY STUDY OF A COUPLED SOIL-VEGETATION BOUNDARY-LAYER SCHEME FOR USE IN ATMOSPHERIC MODELING

### Boundary-Layer Meteorology (1997-02-01) 82: 283-315 , February 01, 1997

During the last two decades, several land surface schemes foruse in climate, regional and/or mesoscale, hydrological and ecologicalmodels have been designed. For all of them, of great importance isa correct parameterization of the energy and momentum transportfrom the surface. Mainly, the land-surface schemes have beendeveloped in order to parameterize land-surface variations both ondaily and annual time scales. In this paper we describe the Land AirParameterization Surface Scheme (LAPS) designed for use inatmospheric models and mainly for use in simulations of thermalcirculations. It has two modules for parameterizing the processes atthe boundary-layer interface: one for a bare surface and one for avegetated one.

Incorrect parameterization of land-surface processes andprescription of the surface parameters in atmospheric modeling, canresult in artificial changes of horizontal gradient of the sensible heatflux. Thus, an error in horizontal temperature gradient within thelower atmosphere may be introduced. Of course, the reliability of themodel depends on the quality of boundary-layer scheme implementedand its sensitivity to the bare soil and vegetation parameters.

In this study, the sensitivity of the LAPS scheme toparameterization of bare soil processes, ground roughness length,vegetation parameters (stomatal resistance, leaf area index and canopyheight) and albedo, has been examined. Tests based on timeintegrations using real data were performed. For sensitivity tests withthe non-plant module the data sets for June 3, 1981; June 4, 1982;June 11, 1982 and June 24, 1982 from the experimental site atRimski Šančevi (Yugoslavia) were used. The performance of thevegetation module was tested by employing the data set forSeptember 8, 1988 measured at the experimental site of DeSinderhoeve (The Netherlands). The computed latent heat flux andthe ground temperature outputs were compared with the observations.Finally, the sensitivity of the LAPS scheme to the prescribedparameters was examined by using a simple statistical analysis.

## Similarity theory and calculation of turbulent fluxes at the surface for the stably stratified atmospheric boundary layer

### Boundary-Layer Meteorology (2007-11-01) 125: 193-205 , November 01, 2007

In this paper we revise the similarity theory for the stably stratified atmospheric boundary layer (ABL), formulate analytical approximations for the wind velocity and potential temperature profiles over the entire ABL, validate them against large-eddy simulation and observational data, and develop an improved surface flux calculation technique for use in operational models.

## Sensitivity of PBL model predictions to model design and uncertainties in environmental inputs

### Boundary-Layer Meteorology (1993-07-01) 65: 137-158 , July 01, 1993

A simple time-dependent one-dimensional model of the planetary boundary layer (PBL) is described and used to examine the degree to which model design decisions affect model output variables. The model's sensitivity to changes in the environmental conditions is also explored. Averages of the surface fluxes, near-ground wind speeds and other PBL properties from 48 h simulations are compared to control runs. The model-calculated surface fluxes are most sensitive, in decreasing order of importance, to the vertical grid spacing, the form of closure between the surface temperature and the atmosphere, the use of vertical diffusivity smoothing, the choice of maximum time step and choice of turbulence closure scheme. These fluxes are relatively insensitive to mixing-length scaling or choice of implicit time step weighting factor. Sensitivity to changes in soil type exceeds any of the design criteria tested. The modeled fluxes are moderately sensitive to small variations in the horizontal pressure gradient, to unsteadiness in the geostrophic wind and to variations in surface roughness. They are relatively insensitive to uncertainties in local vertical velocities and small (25%) variations applied separately to soil thermal diffusivity or heat capacity. The sensitivity of the average PBL depth (*Z*_{i}) to model and environmental changes are similar to those of surface fluxes except that*Z*_{i} is more sensitive to changes in mixing length, albedo and imposed vertical velocity then are the surface fluxes.

## A three-component sonic anemometer/thermometer system for general micrometeorological research

### Boundary-Layer Meteorology (1983-09-01) 27: 27-42 , September 01, 1983

A three-component sonic anemometer/thermometer system has been developed. It employs single switched transducer pairs and the inverse timed pulse method to yield an absolute calibration. Microprocessor control and use of newly developed transducers give a very small parts cost. The path length of the instrument can be varied from 10 to 15 cm; output is available in digital or analog form. Temperature sensing, via a 5 Μm tungsten resistance element, is integrated into the digital system. Wind tunnel and field results have confirmed the success of the prototype and a set of operational instruments has been constructed.

## Role of land-surface temperature feedback on model performance for the stable boundary layer

### Boundary-Layer Meteorology (2007-11-01) 125: 361-376 , November 01, 2007

At present a variety of boundary-layer schemes is in use in numerical models and often a large variation of model results is found. This is clear from model intercomparisons, such as organized within the GEWEX Atmospheric Boundary Layer Study (GABLS). In this paper we analyze how the specification of the land-surface temperature affects the results of a boundary-layer scheme, in particular for stable conditions. As such we use a well established column model of the boundary layer and we vary relevant parameters in the turbulence scheme for stable conditions. By doing so, we can reproduce the outcome for a variety of boundary-layer models. This is illustrated with the original set-up of the second GABLS intercomparison study using prescribed geostrophic winds and land-surface temperatures as inspired by (but not identical to) observations of CASES-99 for a period of more than two diurnal cycles. The model runs are repeated using a surface temperature that is calculated with a simple land-surface scheme. In the latter case, it is found that the range of model results in stable conditions is reduced for the sensible heat fluxes, and the profiles of potential temperature and wind speed. However, in the latter case the modelled surface temperatures are rather different than with the original set-up, which also impacts on near-surface air temperature and wind speed. As such it appears that the model results in stable conditions are strongly influenced by non-linear feedbacks in which the magnitude of the geostrophic wind speed and the related land-surface temperature play an important role.