scholarly journals Using Commercial Aircraft Meteorological Data to Assess the Heat Budget of the Convective Boundary Layer Over the Santiago Valley in Central Chile

2022 ◽  
Author(s):  
Ricardo C. Muñoz ◽  
C. David Whiteman ◽  
René D. Garreaud ◽  
José A. Rutllant ◽  
Jacqueline Hidalgo
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Heat Budget ◽  
Meteorological Data ◽  
Sonic Anemometer ◽  
Sensible Heat Flux ◽  
Lower Troposphere ◽  
Commercial Aircraft ◽  
Convective Boundary ◽  
Central Chile

AbstractThe World Meteorological Organization Aircraft Meteorological Data Relay (AMDAR) programme refers to meteorological data gathered by commercial aircraft and made available to weather services. It has become a major source of upper-air observations whose assimilation into global models has greatly improved their performance. Near busy airports, AMDAR data generate semi-continuous vertical profiles of temperature and winds, which have been utilized to produce climatologies of atmospheric-boundary-layer (ABL) heights and general characterizations of specific cases. We analyze 2017–2019 AMDAR data for Santiago airport, located in the centre of a $$40\times 100$$ 40 × 100  km$$^2$$ 2 subtropical semi-arid valley in central Chile, at the foothills of the Andes. Profiles derived from AMDAR data are characterized and validated against occasional radiosondes launched in the valley and compared with routine operational radiosondes and with reanalysis data. The cold-season climatology of AMDAR temperatures reveals a deep nocturnal inversion reaching up to 700 m above ground level (a.g.l.) and daytime warming extending up to 1000 m a.g.l. Convective-boundary-layer (CBL) heights are estimated based on AMDAR profiles and the daytime heat budget of the CBL is assessed. The CBL warming variability is well explained by the surface sensible heat flux estimated with sonic anemometer measurements at one site, provided advection of the cool coastal ABL existing to the west is included. However, the CBL warming accounts for just half of the mean daytime warming of the lower troposphere, suggesting that rather intense climatological diurnal subsidence affects the dynamics of the daytime valley ABL. Possible sources of this subsidence are discussed.

scholarly journals A Method for Estimating the Turbulent Kinetic Energy Dissipation Rate from a Vertically Pointing Doppler Lidar, and Independent Evaluation from Balloon-Borne In Situ Measurements

2010 ◽  
Vol 27 (10) ◽  
pp. 1652-1664 ◽  
Author(s):  
Ewan J. O’Connor ◽  
Anthony J. Illingworth ◽  
Ian M. Brooks ◽  
Christopher D. Westbrook ◽  
Robin J. Hogan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Sonic Anemometer ◽  
Horizontal Wind ◽  
Inertial Subrange ◽  
Doppler Velocity ◽  
Doppler Lidar ◽  
Convective Boundary ◽  
Dissipation Rates

Abstract A method of estimating dissipation rates from a vertically pointing Doppler lidar with high temporal and spatial resolution has been evaluated by comparison with independent measurements derived from a balloon-borne sonic anemometer. This method utilizes the variance of the mean Doppler velocity from a number of sequential samples and requires an estimate of the horizontal wind speed. The noise contribution to the variance can be estimated from the observed signal-to-noise ratio and removed where appropriate. The relative size of the noise variance to the observed variance provides a measure of the confidence in the retrieval. Comparison with in situ dissipation rates derived from the balloon-borne sonic anemometer reveal that this particular Doppler lidar is capable of retrieving dissipation rates over a range of at least three orders of magnitude. This method is most suitable for retrieval of dissipation rates within the convective well-mixed boundary layer where the scales of motion that the Doppler lidar probes remain well within the inertial subrange. Caution must be applied when estimating dissipation rates in more quiescent conditions. For the particular Doppler lidar described here, the selection of suitably short integration times will permit this method to be applicable in such situations but at the expense of accuracy in the Doppler velocity estimates. The two case studies presented here suggest that, with profiles every 4 s, reliable estimates of ε can be derived to within at least an order of magnitude throughout almost all of the lowest 2 km and, in the convective boundary layer, to within 50%. Increasing the integration time for individual profiles to 30 s can improve the accuracy substantially but potentially confines retrievals to within the convective boundary layer. Therefore, optimization of certain instrument parameters may be required for specific implementations.

Characteristics of the secondary circulations in the convective boundary layer over two-dimensional heterogeneous surfaces

2020 ◽  
Author(s):  
Zixuan Xiang ◽  
Jianning Sun ◽  
Jun Zou
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Coriolis Force ◽  
Convective Boundary Layer ◽  
Sensible Heat Flux ◽  
Two Dimensional ◽  
Background Wind ◽  
Convective Boundary ◽  
Boundary Layer Height ◽  
Secondary Circulations

<p>Large-eddy simulations are performed to investigate the effects of background wind on the secondary circulations (SCs) in the convective boundary layer. Heterogeneities are produced by a prescribed two-dimensional surface sensible heat flux pattern of chessboard-type and have a size which is a bit larger than the boundary layer height.</p><p>When the wind blows along the diagonal of the chessboard-like pattern, the roll-like SCs are observed even when the background wind speed is as large as 10m/s, with whose axes are oriented along the diagonal of the pattern. Another case with wind direction along neither the diagonal nor the side of the chessboard-like pattern and weak wind speed shows the roll-like SCs still exist but lack symmetry. The SCs become much weaker and change their axes orientation when the wind speed increases.</p><p>Meanwhile, the results are different when the Coriolis force is considered. When the background wind is weak, the asymmetry of the SCs become more significant with the development of boundary layer when the Coriolis force is considered, while the SCs tend to be symmetrical without the Coriolis force. When the background wind strengthens, the SCs are more difficult to maintain in the case of Coriolis force.</p><p>Further analysis through rotational and divergent decomposition suggests which part contributes more to the maintenance of the SCs.</p><p></p>

scholarly journals Effects of Spatial and Temporal Variations in PBL Depth on a GCM

2007 ◽  
Vol 20 (18) ◽  
pp. 4717-4732 ◽  
Author(s):  
Sun-Hee Shin ◽  
Kyung-Ja Ha
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
East Asian Monsoon ◽  
East Asian ◽  
Sensible Heat Flux ◽  
Lower Troposphere ◽  
Lower Atmosphere ◽  
Convective Boundary ◽  
Stable Conditions ◽  
The Impact

Abstract The effect of variations in planetary boundary layer (PBL) height on a GCM was investigated using the Yonsei University (YONU) AGCM. This GCM assumes a convective boundary layer constrained to the two lowest model levels. As a consequence of this fixed PBL height, the model tends to produce excessive mixing. In this study the authors focuse on the impact of spatially and temporally varying PBL height. In addition to stability-dependent eddy diffusivity, the model adopts both bulk mixing due to the surface heat flux and z-less mixing under stable conditions. The variable-depth PBL strongly suppressed excessive mixing so that the model bias was reduced over stable regions such as the Antarctic continent. On the other hand, vertical mixing over continents in the summer hemisphere was stronger than for the fixed-PBL version, resulting in greater rising motion and warming effects in the lower atmosphere. The variable-PBL height reduces excess precipitation over the western Pacific and East Asian monsoon region. Based on the improved PBL parameterization, widespread decreases in surface sensible heat flux and rising motion in the lower troposphere occurred simultaneously over the East Asian continent. This implies that the precipitation simulation is very sensitive to PBL processes.

scholarly journals Parameterization of Inversion Breakup in Idealized Valleys. Part I: The Adjustable Model Parameters

2006 ◽  
Vol 45 (4) ◽  
pp. 600-608 ◽  
Author(s):  
N. M. Zoumakis ◽  
G. A. Efstathiou
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Convective Boundary Layer ◽  
Sensible Heat Flux ◽  
Layer Growth ◽  
Heat Fluxes ◽  
Future Research ◽  
Model Parameters ◽  
Sensible Heat ◽  
Convective Boundary

Abstract The factors that affect the atmospheric energy budget approach used in the thermodynamic valley inversion destruction model of Whiteman and McKee are investigated theoretically. The height at which the sinking inversion top meets the rising convective boundary layer to destroy valley inversions can be uniquely determined by the topographic characteristics of the valley and an adjustable model parameter, relating to the fraction of sensible heat flux going to convective boundary layer growth, through a simple parabolic relationship. The time required to break a temperature inversion can be expressed with very good approximation as a simple power-law function of the topographic parameters and the fraction of extraterrestrial solar flux that is partitioned to sensible heat flux in the valley atmosphere. The theoretical estimates compare very favorably to predictions from the bulk thermodynamic model of Whiteman and McKee. A new approach to handle time-dependent sensible heat fluxes is outlined. The paper ends with recommendations for future research.

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