scholarly journals Air-Traffic Restrictions at the Madeira International Airport Due to Adverse Winds: Links to Synoptic-Scale Patterns and Orographic Effects

Atmosphere ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1257
Author(s):  
Margarida Belo-Pereira ◽  
João A. Santos
Keyword(s):  
Mesoscale Model ◽  
Low Frequency ◽  
Eastern Coast ◽  
Synoptic Scale ◽  
Orographic Effects ◽  
International Airport ◽  
Downslope Winds ◽  
Flow Splitting ◽  
Azores High ◽  
Level Inversion

The Madeira International Airport (MIA) lies on the island’s south-eastern coast and it is known to be exposed to wind hazards. A link between these adverse winds at MIA and the synoptic-scale circulation is established using a weather type (WT) classification. From April to September (summer period), five WTs prevail, cumulatively representing nearly 70% of days. These WTs reflect the presence of well-established Azores high, with some variations on location and strength. Although with a low frequency of occurrence (<5%), this anticyclone occasionally strengthens and extends towards Iberia, inducing anomalously strong NNE/NE up to 3–5 km over Madeira. The most severe and longer-lasting wind conditions at the MIA, with a higher frequency of gusts above 35 kt, are driven by this synoptic-scale pattern and are more common in summer. An episode of adverse winds at the MIA is analysed, illustrating the occurrence of upstream stagnation, flow splitting, and lee wake formation. The upstream conditions include a low-level inversion, strong NNE/NE winds near and above the inversion and a Froude number less than 1. The AROME (Application of Research to Operations at Mesoscale) model predicted the occurrence of downslope winds, in association with a large-amplitude mountain wave. At this time, the strongest wind gusts were registered and one aircraft executed a missed approach. The wind regime in different places of the island suggests that these conditions are relatively frequent, mostly in summer. Finally, objective verification of AROME wind forecast, for a three-year period and from June to August, is discussed.

Air-traffic restrictions at the Madeira International Airport due to adverse winds: links to synoptic-scale patterns and mountain wave phenomena

2021 ◽  
Author(s):  
Margarida Belo-Pereira ◽  
João Santos
Keyword(s):  
Low Frequency ◽  
Eastern Coast ◽  
Synoptic Scale ◽  
Mountain Wave ◽  
International Airport ◽  
Downslope Winds ◽  
Flow Splitting ◽  
Azores High ◽  
Wave Phenomena ◽  
Level Inversion

&lt;p&gt;The Madeira International Airport (MIA) lies on the island south-eastern coast and it is known to be exposed to wind hazards. A link between these adverse winds at MIA and the synoptic-scale circulation is established using a weather type (WT) classification. From April to September (summer period), five WTs prevail, cumulatively representing nearly 70% of days. These WTs reflect the presence of well-established Azores high, with some variations on location and strength. Although with a low frequency of occurrence (&lt;5%), this anticyclone occasionally strengthens and extends towards Iberia, inducing anomalously strong NNE/NE up to 3-5 km over Madeira. The most severe and longer-lasting wind conditions at the MIA, with a higher frequency of gusts above 35 kt, are driven by this synoptic-scale pattern and are more common in summer. An episode of adverse winds at the MIA is analyzed, illustrating the occurrence of upstream stagnation, flow splitting, and lee wake formation. The upstream conditions include a low-level inversion, strong NNE/NE winds near and above the inversion and a Froude number less than 1. AROME model predicted the occurrence of downslope winds, in association with a large-amplitude mountain wave. At this time, the strongest wind gusts were registered and a missed approach occurred. The wind regime in different places of the island suggests that these conditions are relatively frequent, mostly in summer. Lastly, this study provides an objective verification of the AROME wind forecasts, for a 3-year period and from June to August.&lt;/p&gt;

scholarly journals Initial-Condition Sensitivities and the Predictability of Downslope Winds

2009 ◽  
Vol 66 (11) ◽  
pp. 3401-3418 ◽  
Author(s):  
Patrick A. Reinecke ◽  
Dale R. Durran
Keyword(s):  
Wave Breaking ◽  
Initial Conditions ◽  
Static Stability ◽  
Synoptic Scale ◽  
Wind Speeds ◽  
Downslope Winds ◽  
First Case ◽  
Downslope Wind ◽  
The Difference ◽  
Strong Winds

Abstract The sensitivity of downslope wind forecasts to small changes in initial conditions is explored by using 70-member ensemble simulations of two prototypical windstorms observed during the Terrain-Induced Rotor Experiment (T-REX). The 10 weakest and 10 strongest ensemble members are composited and compared for each event. In the first case, the 6-h ensemble-mean forecast shows a large-amplitude breaking mountain wave and severe downslope winds. Nevertheless, the forecasts are very sensitive to the initial conditions because the difference in the downslope wind speeds predicted by the strong- and weak-member composites grows to larger than 28 m s−1 over the 6-h forecast. The structure of the synoptic-scale flow one hour prior to the windstorm and during the windstorm is very similar in both the weak- and strong-member composites. Wave breaking is not a significant factor in the second case, in which the strong winds are generated by a layer of high static stability flowing beneath a layer of weaker mid- and upper-tropospheric stability. In this case, the sensitivity to initial conditions is weaker but still significant. The difference in downslope wind speeds between the weak- and strong-member composites grows to 22 m s−1 over 12 h. During and one hour before the windstorm, the synoptic-scale flow exhibits appreciable differences between the strong- and weak-member composites. Although this case appears to be more predictable than the wave-breaking event, neither case suggests that much confidence should be placed in the intensity of downslope winds forecast 12 or more hours in advance.

scholarly journals Dynamics of Eddy-Driven Low-Frequency Dipole Modes. Part I: A Simple Model of North Atlantic Oscillations

2007 ◽  
Vol 64 (1) ◽  
pp. 3-28 ◽  
Author(s):  
Dehai Luo ◽  
Anthony R. Lupo ◽  
Han Wan
Keyword(s):  
Life Cycle ◽  
Theoretical Model ◽  
North Atlantic ◽  
Low Frequency ◽  
Positive Phase ◽  
Negative Phase ◽  
Synoptic Scale ◽  
Planetary Scale ◽  
The North ◽  
The North Atlantic Oscillation

Abstract A simple theoretical model is proposed to clarify how synoptic-scale waves drive the life cycle of the North Atlantic Oscillation (NAO) with a period of nearly two weeks. This model is able to elucidate what determines the phase of the NAO and an analytical solution is presented to indicate a high similarity between the dynamical processes of the NAO and zonal index, which is not derived analytically in previous theoretical studies. It is suggested theoretically that the NAO is indeed a nonlinear initial-value problem, which is forced by both preexisting planetary-scale and synoptic-scale waves. The eddy forcing arising from the preexisting synoptic-scale waves is shown to be crucial for the growth and decay of the NAO, but the preexisting low-over-high (high-over-low) dipole planetary-scale wave must be required to match the preexisting positive-over-negative (negative-over-positive) dipole eddy forcing so as to excite a positive (negative) phase NAO event. The positive and negative feedbacks of the preexisting dipole eddy forcing depending upon the background westerly wind seem to dominate the life cycle of the NAO and its life period. An important finding in the theoretical model is that negative-phase NAO events could be excited repeatedly after the first event has decayed, but for the positive phase downstream isolated dipole blocks could be produced after the first event has decayed. This is supported by observed cases of the NAO events presented in this paper. In addition, a statistical study of the relationship between the phase of the NAO and blocking activity over Europe in terms of the seasonal mean NAO index shows that blocking events over Europe are more frequent and long-lived for strong positive-phase NAO years, indicating that the positive-phase NAO favors the occurrence of European blocking events.

scholarly journals Lightning characteristics observed by a VLF/LF lightning detection network (LINET) in Brazil, Australia, Africa and Germany

2009 ◽  
Vol 9 (2) ◽  
pp. 6061-6146 ◽  
Author(s):  
H. Höller ◽  
H.-D. Betz ◽  
K. Schmidt ◽  
R. V. Calheiros ◽  
P. May ◽  
...  
Keyword(s):  
Low Frequency ◽  
Sea Breeze ◽  
Warm Pool ◽  
Tropical Convection ◽  
Australian Monsoon ◽  
Orographic Effects ◽  
Lightning Detection ◽  
Vertical Distributions ◽  
Field Campaigns ◽  
The Tropics

Abstract. This paper describes lightning characteristics as obtained in four sets of lightning measurements during recent field campaigns in different parts of the world from mid-latitudes to the tropics by the novel VLF/LF (very low frequency/low frequency) lightning detection network (LINET). The paper gives a general overview on the approach, and a synopsis of the statistical results for the observation periods as a whole and for one special day in each region. The focus is on the characteristics of lightning which can specifically be observed by this system like intra-cloud and cloud-to-ground stroke statistics, vertical distributions of intra-cloud strokes or peak current distributions. Some conclusions regarding lightning produced NOx are also presented as this was one of the aims of the tropical field campaigns TROCCINOX (Tropical Convection, Cirrus and Nitrogen Oxides Experiment) and TroCCiBras (Tropical Convection and Cirrus Experiment Brazil) in Brazil during January/February 2005, SCOUT-O3 (Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere) and TWP-ICE (Tropical Warm Pool – International Cloud Experiment) during November/December 2005 and January/February 2006, respectively, in the Darwin area in N-Australia, and of AMMA (African Monsoon Multidisciplinary Analyses) in W-Africa during June–November 2006. Regional and temporal characteristics of lightning are found to be dependent on orographic effects (e.g. S-Germany, Brazil, Benin), land-sea breeze circulations (N-Australia) and especially the evolution of the monsoons (Benin, N-Australia). Large intra-seasonal variability in lightning occurrence was found for the Australian monsoon between the strong convection during build-up and break phases and the weak wet monsoon phase with only minor lightning activity. Total daily lightning rates can be of comparable intensity in all regions with the heaviest events found in Germany and N-Australia. The frequency of occurrence of such days was by far the largest in N-Australia. In accordance with radar observed storm structures, the intra-cloud stroke mean emission heights were found distinctly different in Germany (8 km) as compared to the tropics (up to 12 km in N-Australia). The fraction of intra-cloud strokes (compared to all strokes) was found to be relatively high in Brazil and Australia (0.83 and 0.74, respectively) as compared to Benin and Germany (0.67 and 0.69, respectively). Using stroke peak currents and vertical location information, lightning NOx (LNOx) production under defined standard conditions can be compared for the different areas of observation. LNOx production per standard stroke was found to be most efficient for the N-Australian and S-German thunderstorms whereas the yield from Brazilian and W-African strokes was nearly 40% less. On the other hand, the main NO contribution in Brazil was from intra-cloud (IC) strokes whereas in Benin it was due to cloud-to-ground (CG) components. For the German and Australian strokes both stroke types contributed similar amounts to the total NO outcome.

scholarly journals A Barotropic Envelope Rossby Soliton Model for Block–Eddy Interaction. Part III: Wavenumber Conservation Theorems for Isolated Blocks and Deformed Eddies

2005 ◽  
Vol 62 (11) ◽  
pp. 3839-3859 ◽  
Author(s):  
Dehai Luo
Keyword(s):  
Low Frequency ◽  
Phase Speed ◽  
Vortex Pair ◽  
Synoptic Scale ◽  
Low Frequency Oscillation ◽  
Soliton Theory ◽  
Eddy Activity ◽  
Synoptic Eddy ◽  
Synoptic Eddies ◽  
Interactive Relationship

Abstract In a series of previous papers, an envelope Rossby soliton theory was formulated to investigate the interaction between a preexisting planetary wave and synoptic-scale eddies leading to a typical blocking flow. In this paper, numerical and analytical studies are presented in order to examine the interactive relationship between an isolated vortex pair block and deformed synoptic-scale eddies during their interaction. The deformed blocked flow and eddies are found to satisfy the wavenumber conservation theorem. It is shown that the feedback by a blocked flow on the preexisting synoptic eddies gives rise to two types of eddies: one is the Z-type eddies with a meridional monopole structure that appears at the middle of the channel and the other is the M-type eddies with a meridional tripole structure that have long wavelength and large amplitude. Both the total wavenumber of the blocked flow and M-type eddies and the total wavenumber of the Z- and M-type eddies are conserved. The M- and Z-type eddies are compressed and elongated, respectively, as the blocked flow is elongated zonally during its onset phase, but the reverse is observed during the decay phase. The zonally elongated Z-type eddies are found to counteract the compressed M-type eddies in the blocking region, but strengthen the M-type eddies upstream, causing the split of eddies around the blocking region. In addition, it is also verified theoretically that the blocked flow and synoptic-eddy activity are symbiotically dependent upon one another. The deformed (Z and M type) eddies also display a low-frequency oscillation in amplitude, wavenumber, group velocity, and phase speed, consistent with the blocked flow by the eddy forcing. Thus, it appears that the low-frequency eddy forcing is responsible for the low-frequency variability of the blocked flow and synoptic-eddy activity.

scholarly journals Using Mesoscale Simulations to Train Statistical Models of Tropical Cyclone Intensity over Land

2010 ◽  
Vol 138 (6) ◽  
pp. 2058-2073 ◽  
Author(s):  
Augustin Colette ◽  
Nadja Leith ◽  
Vincent Daniel ◽  
Enrica Bellone ◽  
David S. Nolan
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Statistical Models ◽  
Mesoscale Model ◽  
Low Frequency ◽  
Historical Record ◽  
Tropical Cyclone Intensity ◽  
Cyclone Intensity ◽  
Key Factor ◽  
Mesoscale Simulations

Abstract The decay of tropical cyclones after landfall is a key factor in estimating the extent of the hazard overland. Yet our current understanding of this decay is challenged by the low frequency of past events. Consequently, one cannot rely solely upon the historical record when attempting to quantify robustly the inland penetration of tropical cyclones. Thus, a framework designed to complement the historical record of landfalling storms by means of numerical modeling is introduced. Historical meteorological situations that could potentially have led to a landfall on the coast of the Gulf of Mexico are targeted and, using a bogus vortex technique in conjunction with a mesoscale model, a large number of landfalling hurricanes are simulated. The numerical ensemble constitutes a more comprehensive sample of possible landfalling hurricanes: it encompasses the range of events observed in the past but is not constrained to it. This allows us to revisit existing statistical models of the decay of tropical cyclones after landfall. A range of statistical models trained on the numerical ensemble of storms are evaluated on their ability to reproduce the inland decay of historical storms. These models have more skill at predicting tropical cyclone intensity over land than similar models trained exclusively on historical data.

scholarly journals Synoptic-Scale Environmental Features of the Long-Lasting Ice Pellet Event in Northern Japan on 10 April 2005

2017 ◽  
Vol 145 (3) ◽  
pp. 899-907 ◽  
Author(s):  
Nobuhiro Nagumo ◽  
Yasushi Fujiyoshi
Keyword(s):  
Mesoscale Model ◽  
Lapse Rate ◽  
Japan Meteorological Agency ◽  
Back Trajectory ◽  
Synoptic Scale ◽  
Environmental Features ◽  
Back Trajectory Analysis ◽  
Scale Structures ◽  
Surrounding Areas ◽  
Northern Japan

An extremely long ice pellet event with extensive episodic ice pellet falls occurred over northern Japan on 10 April 2005. The synoptic-scale environmental features of this event were examined based on Japan Meteorological Agency (JMA) mesoscale model (MSM) datasets. A synoptic-scale dry environment was formed under the melting layer ahead of the surface warm front by an intense secondary circulation. Back-trajectory analysis suggested that dry air was located to the south of the precipitating area and was conveyed to the precipitating area by strong geostrophic winds. The surface air at Sapporo, Japan, originated from the ocean surface to the southeast and was cooled to almost the same temperature as that of the sea surface (+3°C); that is, the minimum temperature at 600 m progressively decreased to −3°C at the dry adiabatic lapse rate, during the ice pellet event. Sapporo and its surrounding areas, which were at the southern edge of the precipitating area until the passage of the low pressure center and continued to experience midlevel dry and low-level cold inflows maintained by persistent synoptic-scale structures, were identified as the favorable locations for long-lasting ice pellets.

scholarly journals Evaluation of large-eddy simulations forced with mesoscale model output for a multi-week period during a measurement campaign

2017 ◽  
Vol 17 (11) ◽  
pp. 7083-7109 ◽  
Author(s):  
Rieke Heinze ◽  
Christopher Moseley ◽  
Lennart Nils Böske ◽  
Shravan Kumar Muppa ◽  
Vera Maurer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Mesoscale Model ◽  
Large Eddy Simulations ◽  
Model Output ◽  
Synoptic Scale ◽  
High Definition ◽  
Shallow Cumulus ◽  
Large Eddy ◽  
Lidar Measurements ◽  
The Mean

Abstract. Large-eddy simulations (LESs) of a multi-week period during the HD(CP)2 (High-Definition Clouds and Precipitation for advancing Climate Prediction) Observational Prototype Experiment (HOPE) conducted in Germany are evaluated with respect to mean boundary layer quantities and turbulence statistics. Two LES models are used in a semi-idealized setup through forcing with mesoscale model output to account for the synoptic-scale conditions. Evaluation is performed based on the HOPE observations. The mean boundary layer characteristics like the boundary layer depth are in a principal agreement with observations. Simulating shallow-cumulus layers in agreement with the measurements poses a challenge for both LES models. Variance profiles agree satisfactorily with lidar measurements. The results depend on how the forcing data stemming from mesoscale model output are constructed. The mean boundary layer characteristics become less sensitive if the averaging domain for the forcing is large enough to filter out mesoscale fluctuations.

scholarly journals Synoptic-Scale Influences on Tropical Cyclone Formation within the Western North Pacific Monsoon Trough

2015 ◽  
Vol 143 (9) ◽  
pp. 3421-3433 ◽  
Author(s):  
Huijun Zong ◽  
Liguang Wu
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Low Frequency ◽  
Vertical Wind Shear ◽  
Monsoon Trough ◽  
Core Area ◽  
Convective Heating ◽  
Synoptic Scale ◽  
The Core

Abstract Tropical cyclones (TCs) always develop from synoptic-scale disturbances. While early studies suggested that the presence of synoptic-scale disturbances may enhance large-scale conditions for TC formation, recent studies argued that TC-precursor disturbances can establish a rotation-dominant area, which can play a crucial role in organizing convective activity and converting convective heating to rotational energy for storm-scale intensification. To demonstrate the synoptic-scale influence of TC-precursor disturbances, 91 TC formation events within the monsoon trough over the western North Pacific during 2000–10 were examined by separating TC-precursor disturbances from the low-frequency background. The composite analysis shows that the synoptic disturbances indeed enhance the mid- and low-level relative vorticity and convergence, but contribute little to reducing vertical wind shear. The dynamic composite that is conducted with respect to disturbance centers indicates that TC-precursor disturbances within the monsoon trough establish a rotation-dominant region with a radius of less than 550 km. The cyclonic rotation increases with time 72 h prior to TC formation and nearly all air particles keep recirculating in the core area with a radius of about 220 km. Analysis of a specific case suggests that vorticity increase occurs through the merger of mesoscale convective systems in the rotation-dominant area. The enhancing rotation in the core area may efficiently convert diabatic heating to kinetic energy for TC formation. Thus, it is suggested that the important role of TC-precursor disturbances in TC formation is the establishment of a limited, rotation-dominant area.

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