scispace - formally typeset
Search or ask a question
Author

D. Etling

Bio: D. Etling is an academic researcher from Leibniz University of Hanover. The author has contributed to research in topics: Planetary boundary layer & Water cycle. The author has an hindex of 3, co-authored 3 publications receiving 466 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: Roll vortices may be loosely defined as quasi-two-dimensional organized large eddies with their horizontal axis extending through the whole planetary boundary layer (PBL), and their indirect manifestation is most obvious in so-called cloud streets as can be seen in numerous satellite pictures as mentioned in this paper.
Abstract: Roll vortices may be loosely defined as quasi two-dimensional organized large eddies with their horizontal axis extending through the whole planetary boundary layer (PBL). Their indirect manifestation is most obvious in so-called cloud streets as can be seen in numerous satellite pictures. Although this phenomenon has been known for more than twenty years and has been treated in a review by one of us (R.A.Brown) in 1980, there has been a recent resurgence in interest and information. The interest in ocena/land-atmosphere interactions in the context of climate modeling has led to detailed observational and modeling efforts on this problem. The presence of rolls can have a large impact on flux modelling in the PBL. Hence, we shall review recent advances in our understanding of organized large eddies in the PBL and on their role in vertical transport of momentum, heat, moisture and chemical trace substances within the lowest part of the atmosphere.

477 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compare 1D and 2D models using different local and non-local first-order closure methods for the case of an idealized cold air outbreak (CAO).
Abstract: Numerical experiments have shown that large-eddy-simulation models (LES) are able to reproduce the common features of convective boundary layers (CBL) quite well. Models which cannot resolve the convective motions due to their grid structure (1D-models or models with coarse horizontal and/or vertical resolution) have to take into account the effects of large eddies within their subgrid diffusion terms. Turbulent fluxes are frequently parameterized through first-order-closure methods (K-theory). Recently, non-local closure schemes have also been developed. In this paper we compare 1D-and 2D-models using different local and non-local first-order closure methods. The analysis is carried out for the case of an idealized cold air outbreak (CAO). One of the non-local closures is based on the so-called transilient turbulence theory. The reference states are given by a bulk-model and a 2D-model which resolves the large eddies explicitly. A comparison of the results is presented for characteristic quantities such as evolution of boundary-layer height and surface heat flux as well as mean wind and temperature profiles. It is found that simple local first-order closure does not give good agreement with the reference models. The results of the transilient turbulence model shows that a non-local closure is able to parameterize the effects of the large eddies. Comparable results are produced by a local closure where eddy diffusivities are parameterized by dimensionless gradient-functions.

23 citations

Journal ArticleDOI
TL;DR: The success of weather forecasting and climate prediction essentially depends on our ability to understand and describe the energy and water cycles at various spatial and temporalscales as discussed by the authors, which is one of the major research activities within the framework of the World Climate Research Programme.
Abstract: The success of weather forecasting and climate prediction essentially depends on our ability to understand and describe the energy and water cycles at various spatial and temporalscales.ThishasbeenrecognisedbytheWMOininitiatingtheGlobalEnergy and Water Cycle Project (GEWEX) as one of the major research activities within the framework of the World Climate Research Programme (WCRP). GEWEX covers measurements and modelling activities from the local up to the global scale and also provides an umbrella for a number of so-called continental-scale experiments (CSEs) that focus on the investigation of various aspects of the energy and water cycles in different geographic and climate regions of the earth. Recently, the efforts from the different CSEs have been brought together during a two-year Coordinated Enhanced Observation Period (CEOP) by combining long-term observations at a number of globally distributed reference sites, the analysis of global satellite data products and global climate model simulations in a number of the leading climate research centres of the world (Lawford et al. 2004). TheinternationalBalticSeaExperiment(BALTEX)astheEuropeancontribution to GEWEX is intended to describe and quantify the energy and water budget over the Baltic Sea Drainage Basin, an area of about 2 × 10 6 km 2 covering large parts of

9 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: In this paper, the authors compared the TM model and the K-profile model of the planetary boundary layer (PBL) and found that the TM models gave too high PBL heights in the PBL with strong shear, and too low heights for the convection-dominated PBL, which caused unrealistic heat flux profiles.
Abstract: Modifications of the widely used K-profile model of the planetary boundary layer (PBL), reported by Troen and Mahrt (TM) in 1986, are proposed and their effects examined by comparison with large eddy simulation (LES) data. The modifications involve three parts. First, the heat flux from the entrainment at the inversion layer is incorporated into the heat and momentum profiles, and it is used to predict the growth of the PBL directly. Second, profiles of the velocity scale and the Prandtl number in the PBL are proposed, in contrast to the constant values used in the TM model. Finally, non-local mixing of momentum was included. The results from the new PBL model and the original TM model are compared with LES data. The TM model was found to give too high PBL heights in the PBL with strong shear, and too low heights for the convection-dominated PBL, which causes unrealistic heat flux profiles. The new PBL model improves the predictability of the PBL height and produces profiles that are more realistic. Moreover, the new PBL model produces more realistic profiles of potential temperature and velocity. We also investigated how each of these three modifications affects the results, and found that explicit representation of the entrainment rate is the most critical.

695 citations

Journal ArticleDOI
TL;DR: Roll vortices may be loosely defined as quasi-two-dimensional organized large eddies with their horizontal axis extending through the whole planetary boundary layer (PBL), and their indirect manifestation is most obvious in so-called cloud streets as can be seen in numerous satellite pictures as mentioned in this paper.
Abstract: Roll vortices may be loosely defined as quasi two-dimensional organized large eddies with their horizontal axis extending through the whole planetary boundary layer (PBL). Their indirect manifestation is most obvious in so-called cloud streets as can be seen in numerous satellite pictures. Although this phenomenon has been known for more than twenty years and has been treated in a review by one of us (R.A.Brown) in 1980, there has been a recent resurgence in interest and information. The interest in ocena/land-atmosphere interactions in the context of climate modeling has led to detailed observational and modeling efforts on this problem. The presence of rolls can have a large impact on flux modelling in the PBL. Hence, we shall review recent advances in our understanding of organized large eddies in the PBL and on their role in vertical transport of momentum, heat, moisture and chemical trace substances within the lowest part of the atmosphere.

477 citations

Journal ArticleDOI
TL;DR: In this paper, the characteristics of urban heat island (UHI) and boundary layer structures in the Beijing area, China, are analyzed using conventional and Moderate Resolution Imaging Spectroradiometer (MODIS) observations.
Abstract: In this paper, the characteristics of urban heat island (UHI) and boundary layer structures in the Beijing area, China, are analyzed using conventional and Moderate Resolution Imaging Spectroradiometer (MODIS) observations. The Weather Research and Forecasting (WRF) model coupled with a single-layer urban canopy model (UCM) is used to simulate these urban weather features for comparison with observations. WRF is also used to test the sensitivity of model simulations to different urban land use scenarios and urban building structures to investigate the impacts of urbanization on surface weather and boundary layer structures. Results show that the coupled WRF/Noah/UCM modeling system seems to be able to reproduce the following observed features reasonably well: 1) the diurnal variation of UHI intensity; 2) the spatial distribution of UHI in Beijing; 3) the diurnal variation of wind speed and direction, and interactions between mountain–valley circulations and UHI; 4) small-scale boundary layer conv...

439 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review possible mechanisms by which global climate variability and change may influence the wind energy resource and operating conditions, summarize some of the tools that are being employed to quantify these effects and the sources of uncertainty in making such projections, and discuss results of studies conducted to date.
Abstract: Expansion of wind energy installed capacity is poised to play a key role in climate change mitigation. However, wind energy is also susceptible to global climate change. Some changes associated with climate evolution will likely benefit the wind energy industry while other changes may negatively impact wind energy developments, with such ‘gains and losses’ depending on the region under consideration. Herein we review possible mechanisms by which global climate variability and change may influence the wind energy resource and operating conditions, summarize some of the tools that are being employed to quantify these effects and the sources of uncertainty in making such projections, and discuss results of studies conducted to date. We present illustrative examples of research from northern Europe. Climate change analyses conducted for this region, which has shown considerable penetration of wind energy, imply that in the near-term (i.e. to the middle of the current century) natural variability exceeds the climate change signal in the wind energy resource and extreme wind speeds, but there will likely be a decline in icing frequency and sea ice both of which will tend to benefit the wind energy industry. By the end of the twenty-first century there is evidence for small magnitude changes in the wind resource (though the sign of the change remains uncertain), for increases in extreme wind speeds, and continued declines in sea ice and icing frequencies. Thus the current state-of-the-art suggests no detectable change in the wind resource or other external conditions that could jeopardize the continued exploitation of wind energy in northern Europe, though further research is needed to provide greater confidence in these projections.

397 citations

Book
S. A. Thorpe1
01 Jan 2005
TL;DR: The Turbulent Ocean as discussed by the authors describes the principal dynamic processes that control the distribution of turbulence, its dissipation of kinetic energy and its effects on the dispersion of properties such as heat, salinity, and dissolved or suspended matter in the deep ocean, the shallow coastal and the continental shelf seas.
Abstract: The subject of ocean turbulence is in a state of discovery and development with many intellectual challenges. This book describes the principal dynamic processes that control the distribution of turbulence, its dissipation of kinetic energy and its effects on the dispersion of properties such as heat, salinity, and dissolved or suspended matter in the deep ocean, the shallow coastal and the continental shelf seas. It focuses on the measurement of turbulence, and the consequences of turbulent motion in the oceanic boundary layers at the sea surface and near the seabed. Processes are illustrated by examples of laboratory experiments and field observations. The Turbulent Ocean provides an excellent resource for senior undergraduate and graduate courses, as well as an introduction and general overview for researchers. It will be of interest to all those involved in the study of fluid motion, in particular geophysical fluid mechanics, meteorology and the dynamics of lakes.

380 citations