scholarly journals Continuous monitoring of the boundary-layer top with lidar

2008 ◽  
Vol 8 (23) ◽  
pp. 7281-7296 ◽  
Author(s):  
H. Baars ◽  
A. Ansmann ◽  
R. Engelmann ◽  
D. Althausen
Keyword(s):  
Boundary Layer ◽  
Weather Forecast ◽  
Forecast Model ◽  
Raman Lidar ◽  
Data Set ◽  
Weather Forecast Model ◽  
One Year ◽  
The One ◽  
Lidar Observations

Abstract. Continuous lidar observations of the top height of the boundary layer (BL top) have been performed at Leipzig (51.3° N, 12.4° E), Germany, since August 2005. The results of measurements taken with a compact, automated Raman lidar over a one–year period (February 2006 to January 2007) are presented. Main goals of the study are (a) to demonstrate that BL top monitoring with lidar throughout the year is possible, (b) to present the required data analysis method that permits an automated, robust retrieval of BL top at all weather situations, and (c) to use this opportunity to compare the lidar-derived BL top data with respective BL tops hourly predicted by the regional weather forecast model COSMO. Four different lidar methods for the determination of the BL top are discussed. The wavelet covariance algorithm is modified so that an automated retrieval of BL depths from lidar data is possible. Three case studies of simultaneous observations with the Raman lidar, a vertical-wind Doppler lidar, and accompanying radiosonde profiling of temperature and humidity are presented to compare the potential and the limits of the four lidar techniques. The statistical analysis of the one-year data set reveals that the seasonal mean of the daytime (about 08:00–20:00 Local Time, LT) maximum BL top is 1400 m in spring, 1800 m in summer, 1200 m in autumn, and 800 m in winter at the continental, central European site. BL top typically increases by 100–300 m per hour in the morning of convective days. The comparison between the lidar-derived BL top heights and the predictions of COSMO yields a general underestimation of the BL top by about 20% by the model.

scholarly journals Continuous monitoring of the boundary-layer top with lidar

2008 ◽  
Vol 8 (3) ◽  
pp. 10749-10790 ◽  
Author(s):  
H. Baars ◽  
A. Ansmann ◽  
R. Engelmann ◽  
D. Althausen
Keyword(s):  
Boundary Layer ◽  
Weather Forecast ◽  
Forecast Model ◽  
Raman Lidar ◽  
Data Set ◽  
Weather Forecast Model ◽  
One Year ◽  
The One ◽  
Lidar Observations

Abstract. Continuous lidar observations of the top height of the boundary layer (BL top) have been performed at Leipzig (51.3° N, 12.4° E), Germany, since August 2005. The results of measurements taken with a compact, automated Raman lidar over a one-year period (February 2006 to January 2007) are presented. Four different methods for the determination of the BL top are discussed. The most promising technique, the wavelet covariance algorithm, is improved by implementing some modifications so that an automated, robust retrieval of BL depths from lidar data is possible. Three case studies of simultaneous observations with the Raman lidar, a vertical-wind Doppler lidar, and accompanying radiosonde profiling of temperature and humidity are discussed to demonstrate the potential and the limits of the four lidar techniques at different aerosol and meteorological conditions. The lidar-derived BL top heights are compared with respective values derived from predictions of the regional weather forecast model COSMO of the German Meteorological Service. The comparison shows a general underestimation of the BL top by about 20% by the model. The statistical analysis of the one-year data set reveals that the seasonal mean of the daytime maximum BL top is 1400 m in spring, 1800 m in summer, 1200 m in autumn, and 800 m in winter at the continental, central European site. BL top typically increases by 100–300 m per hour in the morning of convective days.

Stochastic Models for Actuarial Use: The Equilibrium Modelling of Local Markets

2009 ◽  
Vol 39 (1) ◽  
pp. 339-370 ◽  
Author(s):  
Robert J. Thomson ◽  
Dmitri V. Gott
Keyword(s):  
Local Market ◽  
Market Participants ◽  
Market Portfolio ◽  
One Year ◽  
The One ◽  
Mean Variance ◽  
Annual Time ◽  
Time Subject

AbstractIn this paper, a long-term equilibrium model of a local market is developed. Subject to minor qualifications, the model is arbitrage-free. The variables modelled are the prices of risk-free zero-coupon bonds – both index-linked and conventional – and of equities, as well as the inflation rate. The model is developed in discrete (nominally annual) time, but allowance is made for processes in continuous time subject to continuous rebalancing. It is based on a model of the market portfolio comprising all the above-mentioned asset categories. The risk-free asset is taken to be the one-year index-linked bond. It is assumed that, conditionally upon information at the beginning of a year, market participants have homogeneous expectations with regard to the forthcoming year and make their decisions in mean-variance space. For the purposes of illustration, a descriptive version of the model is developed with reference to UK data. The parameters produced by that process may be used to inform the determination of those required for the use of the model as a predictive model. Illustrative results of simulations of the model are given.

scholarly journals A new Lagrangian in-time particle simulation module (Itpas v1) for atmospheric particle dispersion

2021 ◽  
Vol 14 (4) ◽  
pp. 2205-2220
Author(s):  
Matthias Faust ◽  
Ralf Wolke ◽  
Steffen Münch ◽  
Roger Funk ◽  
Kerstin Schepanski
Keyword(s):  
Boundary Layer ◽  
Particle Transport ◽  
Dispersion Model ◽  
Weather Forecast ◽  
Forecast Model ◽  
Particle Dispersion ◽  
Particle Simulation ◽  
High Temporal Resolution ◽  
Atmospheric Particle ◽  
Trajectory Models

Abstract. Trajectory models are intuitive tools for airflow studies. But in general, they are limited to non-turbulent, i.e. laminar flow, conditions. Therefore, trajectory models are not particularly suitable for investigating airflow within the turbulent atmospheric boundary layer. To overcome this, a common approach is handling the turbulent uncertainty as a random deviation from a mean path in order to create a statistic of possible solutions which envelops the mean path. This is well known as the Lagrangian particle dispersion model (LPDM). However, the decisive factor is the representation of turbulence in the model, for which widely used models such as FLEXPART and HYSPLIT use an approximation. A conceivable improvement could be the use of a turbulence parameterisation approach based on the turbulent kinetic energy (TKE) at high temporal resolution. Here, we elaborated this approach and developed the LPDM Itpas, which is coupled online to the German Weather Service's mesoscale weather forecast model COSMO. It benefits from the prognostically calculated TKE as well as from the high-frequency wind information. We demonstrate the model's applicability for a case study on agricultural particle emission in eastern Germany. The results obtained are discussed with regard to the model's ability to describe particle transport within a turbulent boundary layer. Ultimately, the simulations performed suggest that the newly introduced method based on prognostic TKE sufficiently represents the particle transport.

scholarly journals Some Experimental Lessons on Digital Filtering in the ALADIN-France 3DVAR Based on Near-Ground Examination

2011 ◽  
Vol 139 (3) ◽  
pp. 774-785 ◽  
Author(s):  
Claude Fischer ◽  
Ludovic Auger
Keyword(s):  
Data Assimilation ◽  
Digital Filter ◽  
Three Dimensional ◽  
Weather Forecast ◽  
Forecast Model ◽  
Horizontal Wind ◽  
Screen Level ◽  
Incremental Formulation ◽  
Weather Forecast Model ◽  
Observation Impact

Abstract This paper deals with the characteristics and effects of digital filter initialization, as implemented in the operational three-dimensional variational data assimilation (3DVAR) system of the Aire Limitée Adaptation Dynamique Développement International (ALADIN)-France regional weather forecast model. First, a series of findings on the properties of the initialization of the model are discussed. Examples of initial spinup linked with inertia–gravity wave occurrence are shown, and the major sources for their generation are listed. These experimental results are compared with past and present experiences concerning the use and need for digital filter initialization. Furthermore, the impacts of switching to an incremental formulation of the filter in data assimilation mode are demonstrated. Second, the effects of the filter formulation on the results of an observation impact study are illustrated. The latter consists of implementing screen-level, 10-m horizontal wind information into the ALADIN 3DVAR analysis. There can, indeed, be some delicate interference between observation impact evaluation and the effects of filtering, at least on short-term forecasts. The paper is concluded with some general considerations on the experimental evaluation of spinup and the link between the assimilation system design and model state filtering.

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