Composing the diurnal cycle of mixing height from simultaneous sodar and wind profiler measurements

Self Cite

The Evaporation at Grid/Pixel Scale (EVA_GRIPS) project was realised in order to determine the area-averaged evaporation over a heterogeneous land surface at the scale of a grid box of a regional numerical weather prediction or climate model, and at the scale of a pixel of a satellite image. EVA_GRIPS combined surface-based and airborne measurements, satellite data analysis, and numerical modelling activities. A mesoscale field experiment, LITFASS-2003, was carried out in the heterogeneous landscape around the Meteorological Observatory Lindenberg (MOL) of the German Meteorological Service in May and June, 2003. The experiment was embedded in the comprehensive, operational measurement program of the MOL. Experimental determination of surface fluxes on a variety of spatial scales was achieved by employing micrometeorological flux stations, scintillometers, a combination of ground-based remote sensing instruments, and the Helipod, a turbulence probe carried by a helicopter. Surface energy fluxes were also derived from satellite data. Modelling work included the use of different Soil-Vegetation-Atmosphere Transfer schemes, a large-eddy simulation model and three mesoscale atmospheric models. The paper gives an overview on the background of EVA_GRIPS, and on the measurements and meteorological conditions during LITFASS-2003. A few general results are discussed.

Section: Meteorological Conditionsmentioning

confidence: 99%

Evaporation over a Heterogeneous Land Surface: EVA_GRIPS and the LITFASS-2003 Experiment—An Overview

Beyrich

Mengelkamp²

2006

Self Cite

“…As indicated in the previous section, the surface-layer depth is defined as 10 % of the boundary-layer depth. The boundary-layer depth is determined from a wind profiler (LAP 3000) following Beyrich and Görsdorf (1995) and Klein and Holtslag (1997). At 3 m (located in the ASL the entire time) all data under unstable conditions are selected (w T 3m > 0).…”

Section: Research Strategymentioning

confidence: 99%

On Monin–Obukhov Scaling in and Above the Atmospheric Surface Layer: The Complexities of Elevated Scintillometer Measurements

Braam

Bosveld

Moene

2012

In scintillometry Monin-Obukhov similarity theory (MOST) is used to calculate the surface sensible heat flux from the structure parameter of temperature (C T 2 ). In order to prevent saturation a scintillometer can be installed at an elevated level. However, in that case the observation level might be located outside the atmospheric surface layer (ASL) and thus the validity of MOST questioned. Therefore, we examine two concepts to determine the turbulent surface sensible heat flux from the structure parameter at elevated levels with data obtained at 60-m height on the Cabauw tower (the Netherlands). In the first concept (MOSTs) C T 2 is still scaled with the surface flux, whereas in the second (MOSTl) C T 2 is scaled with the local sensible heat flux. The C T 2 obtained from both concepts is compared with direct observations of C T 2 using a sonic anemometer/thermometer. In the afternoon (when the measurement height is located within the ASL) both concepts give results that are comparable to the directly observed values of C T 2 . In the morning (data outside the ASL), our data do not unequivocally support either of the two concepts. First, the peak in C T 2 that occurs when the measurement height is located in the entrainment zone disqualifies the use of MOST. Second, during the morning transition, local scaling shows the correct pattern (zero flux and a minimum in C T 2 ) but underestimates C T 2 by a factor of ten. Third, from the best linear fit a we found that the slope of MOSTl gave better results, whereas the offset is closer to zero for MOSTs. Further, the correlation between the direct observations and MOST-scaled results is low and similar for the two concepts. In the end, we conclude that MOST is not applicable for the morning hours when the observation level is above the ASL.

“…lidars, sodars, and wind profilers) that can operate continuously have been used for estimating h (Beyrich and Görsdorf 1995;Beyrich 1997;Emeis et al 2004;Nielsen-Gammon et al 2008). However, sometimes the interpretation of remotely-sensed structures used to estimate h can be ambiguous, and a comparison with sounding data can help to identify remotely-sensed structures in the ABL (Emeis et al 2004).…”

Section: Introductionmentioning

confidence: 99%

“…However, sometimes the interpretation of remotely-sensed structures used to estimate h can be ambiguous, and a comparison with sounding data can help to identify remotely-sensed structures in the ABL (Emeis et al 2004). Therefore, rawinsonde-based h estimates are often used as a standard for evaluating ABL heights obtained from remote sensing data (Coulter 1979;Van Pul et al 1994;Beyrich and Görsdorf 1995;Marsik et al 1995;Beyrich 1997;Dupont et al 1999;Bianco and Wilczak 2002;Lokoshchenko 2002;Hennemuth and Lammert 2006;Sicard et al 2006;Martucci et al 2007;Nielsen-Gammon et al 2008). In order to improve ABL height detection from profiles, we have carried out a systematic evaluation of profile methods to understand their limitations and identify appropriate criteria for their application.…”

Section: Introductionmentioning

confidence: 99%

Determining Boundary-Layer Height from Aircraft Measurements

Dai

Wang

Kalogiros

et al. 2014

The height of the atmospheric boundary layer (ABL) is an important variable in both observational studies and model simulations. The most commonly used measurement for obtaining ABL height is a rawinsonde profile. Mesoscale or regional scale models use a bulk Richardson number based on profiles of the forecast variables. Here we evaluate the limitations of several frequently-used approaches for defining ABL height from a single profile, and identify the optimal threshold value for each method if profiles are the only available measurements. Aircraft measurements from five field projects are used, representing a variety of ABL conditions including stable, convective, and cloud-topped boundary layers over different underlying surfaces. ABL heights detected from these methods were validated against the 'true' value determined from aircraft soundings, where ABL height is defined as the top of the layer with significant turbulence. A detection rate was defined to denote how often the ABL height was correctly diagnosed with a particular method. The results suggest that the temperature gradient method provides the most reasonable estimates, although the detection rate and suitable detection criteria vary for different types of ABL. The Richardson number method, on the other hand, is in most cases inadequate or inferior to the other methods that were tried. The optimal range of the detection criteria is given for all ABL types examined in this study.