Frequency distributions of the mixing height over an urban area from SODAR data

Emeis, Stefan; Türk, Matthias

doi:10.1127/0941-2948/2004/0013-0361

Cited by 40 publications

(39 citation statements)

References 12 publications

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“…According to the observations the backscattered signal S has a secondary maximum at the top of the mixing layer (Beyrich, 1995(Beyrich, , 1997. Emeis and Türk (2004) detected the MH from the sodar data employing two different criteria. According the first criterion a sharp decrease of the acoustic backscatter intensity indicates the top of the turbulent layer; the second criterion diagnoses the (secondary) maxima of the backscatter profile.…”

Section: Introductionmentioning

confidence: 99%

Mixing height determination by ceilometer

et al. 2006

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Abstract.A novel method for estimating the mixing height based on ceilometer measurements is described and tested against commonly used methods for determining mixing height. In this method an idealised backscatter profile is fitted to the observed backscatter profile. The mixing height is one of the idealised backscatter profile parameters.An extensive amount of ceilometer data and vertical soundings data from the Helsinki area in 2002 is utilized to test the applicability of the ceilometer for mixing height determination. The results, including 71 convective and 38 stable cases, show that in clear sky conditions the mixing heights determined from ceilometer based aerosol profiles and BL-height estimates based on sounding data are in a good agreement. Rejected outlier cases corresponded to very low aerosol concentrations in the mixed layer leading to a very weak aerosol backscatter signal in the lowest layer.

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Section: Introductionmentioning

confidence: 99%

Mixing height determination by ceilometer

et al. 2006

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“…This evaluation scheme (Emeis and Türk, 2004) allows distinguishing between super-adiabatic and thermally stable temperature gradients near the surface. The averaged results showed a clear diurnal cycle and an annual cycle of the mixing layer height (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Path-averaging optical measurement techniques (two, some times three DOAS systems) were used continuously at the ground and at building roof level. The meteorological background (vertical profiles of wind and turbulence plus mixing layer height) came from a SODAR system that was positioned about 500 m apart from the street canyon (Emeis, 2004;Emeis and Türk, 2004). The determination of the mixing layer height over an urban area is a subject of ongoing research (Baklanov et al, 2006 1 ;Rotach et al, 2005 www.atmos-chem-phys.net/6/3077/2006/ Three intensive observation periods (IOPs) in different seasons were successfully executed.…”

Section: Methodsmentioning

confidence: 99%

Development and validation of tools for the implementation of european air quality policy in Germany (Project VALIUM)

Schatzmann

Bächlin

Emeis³

et al. 2006

Atmos. Chem. Phys.

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Abstract. In the framework of the German Atmospheric Research Program AFO-2000 a system of consistent coupled numerical models has been developed. The purpose of the model system is to serve as a tool for the execution of European urban air quality regulations. A consortium with the acronym VALIUM was formed, which consisted of German research institutes, environmental consultancies and an environmental agency.A substantial part of the VALIUM program was devoted to the generation of a set of high quality data for the validation of the numerical model system. The validation data are based on a combination of field studies, tracer experiments and corresponding wind tunnel experiments. The field experiments were carried out inside and around a street canyon in a city district of Hanover/Germany. After a brief introduction to the VALIUM project a summary of the main results will be given.

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“…Acoustic detection of MLH Beyrich [9] has listed possible ways to analyze MLH from acoustic backscatter intensities measured by a sodar. This algorithm has been enhanced in [4] by simultaneously using acoustic backscatter intensity and the variance of the vertical velocity component σ w . In [7] the algorithm has been extended for the detection of multiple inversions present simultaneously.…”

Section: Methodsmentioning

confidence: 99%

Long-term observations of the urban mixing-layer height with ceilometers

Emeis¹,

Schäfer²,

Münkel³

2008

IOP Conf. Ser.: Earth Environ. Sci.

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View the article online for updates and enhancements. Abstract. Urban air quality assessment requires the knowledge of the temporal and spatial structure of the mixing-layer height (MLH), because this variable controls the vertical space for rapid mixing of near-surface pollutants. Because MLH is a consequence of vertical temperature and moisture profiles in the lower atmosphere, remote sensing is a suitable tool to monitor MLH. Two ceilometers, a Vaisala LD40 and a Vaisala CL31, have been run for many months in the German city of Augsburg to observe the vertical aerosol distribution. Wind and temperature profile information have been obtained for the same period from sodar observations. This paper compares the MLH determined from the optical backscatter intensity received by the two ceilometers among each other and with the MLH derived from the acoustic backscatter intensity and the variance of the vertical wind component from sodar measurements. Related content IntroductionThe mixing layer height (MLH) is assumed to be a key parameter for the characterisation of air pollution, because this variable controls the vertical space for rapid mixing of near-surface pollutants. The determination and modelling of the MLH has therefore found considerable interest in the recent decade [1], especially in urban meteorology. With today's availability of ground-based remote sensing devices for monitoring the structure of the atmospheric boundary layer (ABL) it has been shown that the ABL sometimes exhibits multiple layering (e.g. internal boundary layers, near-surface inversions and residual layers at night-time and in the morning hours) [2]. It was demonstrated that the lowest stable layer or inversion limits the vertical exchange of primary pollutants emitted at or near the surface [3] and thus controls the near-surface pollutant concentrations. Acoustic remote sensing has also been used to derive climatologic statistics of MLH for towns ([4], [5]) and wind and turbulence profiles over towns [6]. Multiple inversions within a few hundred meters above ground have been detected both with optical and acoustic remote sensing in an Alpine valley [7]. MLH information is also necessary for special kinds of satellite data interpretation, e. g. the retrievals of optical depths for the particle concentration near the surface [8].

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Frequency distributions of the mixing height over an urban area from SODAR data

Cited by 40 publications

References 12 publications

Mixing height determination by ceilometer

Mixing height determination by ceilometer

Development and validation of tools for the implementation of european air quality policy in Germany (Project VALIUM)

Long-term observations of the urban mixing-layer height with ceilometers

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