Chapter 20 Review and intercomparison of operational methods for the determination of the mixing height

2002 ◽  
pp. 569-613 ◽  
Author(s):  
Petra Seibert ◽  
Frank Beyrich ◽  
Sven-Erik Gryning ◽  
Sylvain Joffre ◽  
Alix Rasmussen ◽  
...  
Keyword(s):  
Mixing Height ◽  
Operational Methods

scholarly journals Determination of an effective trace gas mixing height by differential optical absorption spectroscopy (DOAS)

2009 ◽  
Vol 2 (4) ◽  
pp. 1663-1692 ◽  
Author(s):  
B. Zhou ◽  
S. N. Yang ◽  
S. S. Wang ◽  
T. Wagner
Keyword(s):  
Trace Gases ◽  
Mixing Layer ◽  
Correlation Coefficients ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Gas Mixing ◽  
Mixing Height ◽  
Free Atmosphere ◽  
Layer Height

Abstract. A new method for the determination of the Mixing layer Height (MH) by the DOAS technique is proposed in this article. The MH can be retrieved by a combination of active DOAS and passive DOAS observations of atmospheric trace gases; here we focus on observations of NO2. Because our observations are sensitive to the vertical distribution of trace gases, we refer to the retrieved layer height as an ''effective trace gas mixing height'' (ETMH). By analyzing trace gas observations in Shanghai over one year (1017 hourly means in 93 days in 2007), the retrieved ETMH was found to range between 0.1 km and 2.8 km (average is 0.78 km); more than 90% of the measurements yield an ETMH between 0.2 km and 2.0 km. The seasonal and diurnal variation of the ETMH shows good agreement with mixing layer heights derived from meteorological observations. We investigated the relationship of the derived ETMH to temperature and wind speed and found correlation coefficients of 0.65 and 0.37, respectively. Also the wind direction has an impact on the measurement to some extent. Especially in cases when the air flow comes from highly polluted areas and the atmospheric lifetime of NO2 is long (e.g. in winter), the NO2 concentration at high altitudes over the measurement site can be enhanced, which leads to an overestimation of the ETMH. Enhanced NO2 concentrations in the free atmosphere and heterogeneity within the mixing layer can cause additional uncertainties. Our method could be easily extended to other species like e.g. SO2, HCHO or Glyoxal. Simultaneous studies of these molecules could yield valuable information on their respective atmospheric lifetimes.

scholarly journals Characterisation of the mixing height temporal evolution by means of a laser dial system in an urban area – intercomparison results with a model application

2007 ◽  
Vol 25 (10) ◽  
pp. 2119-2124 ◽  
Author(s):  
M. A. García ◽  
M. L. Sánchez ◽  
B. de Torre ◽  
I. A. Pérez
Keyword(s):  
Urban Area ◽  
Lower Layer ◽  
Layer Structure ◽  
Correlation Coefficients ◽  
Temporal Variations ◽  
Mixing Height ◽  
Hysplit Model ◽  
Sensing System ◽  
Early Afternoon

Abstract. Measurements of vertical and temporal variations in ozone and aerosol as extinction over an urban area in Segovia, central Spain, were performed during two summer months in 2004 by means of a commercial Nd:YAG laser DIAL remote sensing system. The Differential Absorption Lidar (DIAL) technique was applied and its description is given. From the profile data, a practical determination of mixing height may be derived. A diurnal evolution for the whole dataset is observed, the highest mean mixing height being reached at 16:00 GMT, 2150 m. The presence of a double-layer structure at night was observed and the layers can be considered residual. On average, the lower layer is formed at 670 m and the upper layer yielded mean heights ranging between 1270 and 1390 m. The estimated mixing heights during the day are also compared with those obtained from the Lagrangian HYSPLIT model. The results show good statistical agreement between both approaches, mainly in the early afternoon, with correlation coefficients around 0.7.

Determination of airports’ atmospheric mixing height boundaries using operational data

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Alper Dalkıran
Keyword(s):  
Design Methodology ◽  
Average Duration ◽  
Data Sets ◽  
Mixing Height ◽  
Content Type ◽  
Aircraft Landing ◽  
Segment Data ◽  
Operational Data ◽  
Practical Implications

Purpose This study aims to determine the distance and duration to reach airports mixing height of 3,000 feet limit. Airport operations significantly contribute to the aircraft landing and take-off (LTO) cycle. Eurocontrol’s SO6 data sets comprise several abutted segment data to analyse the duration and distance for specific flights. Design/methodology/approach Two consequential methods have been used to calculate the distance and destination from the SO6 databases. First, SQL filtering and pivot tables were formed for the required data. Second, over 583,000 data lines for a year of Boeing 747–400 aircraft routes were calculated and filtered for the monthly assessments. Findings LTO cycles’ durations have deviated −24% to 76% from the ICAO assumptions. Distance facts determined for specific airports as 2.57 to 3.66 nm for take-off and 5.02 to 23.25 nm for the landing. The average duration of the aircraft’s in mentioned airport take-off are 66 to 74 s and 40 to 50 s; averages have been calculated as 70 to 44 s. Landing durations have been calculated for four different airports as 173 to 476 s. Practical implications This study provides a re-evaluation chance for the current assumptions and helps for better assessments. Each airport and aircraft combinations have their duration and distance figures. Originality/value This study has calculated the first LTO distances in the literature for the aerodrome. This method applies to all airports, airline fleets and aircraft if the segmented SO6 data are available.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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