Operational Forecasting and Detection of Mesoscale Gravity Waves

Koch, Steven E.; O'Handley, Christopher

doi:10.1175/1520-0434(1997)012<0253:ofadom>2.0.co;2

Cited by 75 publications

(45 citation statements)

References 40 publications

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“…(1) has been shown previously to represent flow imbalance associated with strong divergence seen in rawinsonde data (Moore and Abeling, 1988) and has also been employed with mesoscale model fields for the purpose of analysing the degree of flow imbalance. Most importantly, in those studies (Zack and Kaplan, 1987;Koch and O'Handley, 1997;Koch et al, 1998;Zhang et al, 2001) a region of large NBE residual was found to occur within the generation region of gravity waves.…”

Section: Reanalysis Data Of the Ecmwfmentioning

confidence: 90%

Gravity‐wave‐induced perturbations in marine stratocumulus

Allen

Vaughan

Toniazzo

et al. 2012

Quart J Royal Meteoro Soc

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We discuss the role of atmospheric gravity waves in modulating cloud radiative and dynamical properties over the southeast Pacific. Satellite imagery and satelliteretrieved cloud properties during October 2008 illustrate three distinct episodes of horizontal propagation of gravity wave trains across the large-scale stratocumulus (Sc) cloud deck capping the local marine boundary layer. In one period, 7-9 October 2008, the waves modulated cloud-top-height by up to 400 m peak-to-trough, propagating perpendicular to the synoptic boundary layer flow with phase speed 15.3 m s −1 , period ∼1 h and horizontal wavelength 55 km. The gravity waves were observed to be non-dispersive. These waves were first evident in the cloud deck near 30• S, 85• W during a 24 h period beginning at midday on 7 October 2008, and propagated northeastward toward the Peruvian coast for the following 48 h. During this time they induced both reversible and non-reversible changes in cloud-radiative and cloud-dynamic properties, such that areas of clear sky developed in the troughs of passing wave-fronts. These pockets of open cells persisted long after the passage of the gravity waves, advecting northwestward with the background wind. Using the analysis fields of the European Centre for Medium-Range Weather Forecasts in conjunction with infrared and microwave satellite imagery, we show that these gravity waves emerged from a disturbed subtropical jet stream. The radiant of the waves was coincident in all cases with centres of large negative residuals in nonlinear balance, suggesting that geostrophic readjustment of sharply divergent flows associated with the disturbed jet provided a source for the wave energy. Conversely, gravity waves were not observed in more quiescent jet conditions. This case study highlights the important and irreversible effects that gravity waves propagating in the troposphere can have on cloud radiative properties (and hence surface radiation budgets) over a very wide area. It also highlights the importance of synoptic influence on Sc-covered marine boundary layers.

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Section: Reanalysis Data Of the Ecmwfmentioning

confidence: 90%

Gravity‐wave‐induced perturbations in marine stratocumulus

Allen

Vaughan

Toniazzo

et al. 2012

Quart J Royal Meteoro Soc

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“…Figure 2a depicts the meteorological situation on 27 July at 12:00 UTC derived from operational ECMWF analyses, which represents a typical jet streak. Ucellini and Koch (1987) and Koch and O'Handley (1997) produced similar charts to depict the synoptic environment of jet streak typical occurrences of mesoscale GWs at the exit region of the upper-level jet streak. Isohypses on a 500 hPa meteorological chart visualise the synoptic pattern with a strong minimum of geopotential heights located at 45 • N latitude and 15 • W longitude, which strengthens the jet wind field.…”

Section: Synoptic Situation On 27 July 2013mentioning

confidence: 97%

“…From a climatological survey of such synoptic patterns, Uccellini and Koch (1987) showed the existence of mesoscale GW disturbances, which can have a large influence on the weather conditions. For operational forecasting and detection of such GWs, Koch and O'Handley (1997) proposed a conceptual model with location of GW occurrence in a diffluent region bounded by the 300 hPa ridge axis to the north-east and the 300 hPa inflection axis to the south-west. The southern boundary of the wave region is defined by the location of a surface warm front.…”

Section: Synoptic Situation On 27 July 2013mentioning

confidence: 99%

Gravity-wave effects on tracer gases and stratospheric aerosol concentrations during the 2013 ChArMEx campaign

Ming¹,

Vignelles²,

Jégou³

et al. 2016

Atmos. Chem. Phys.

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Abstract. Coupled balloon-borne observations of Light Optical Aerosol Counter (LOAC), M10 meteorological global positioning system (GPS) sondes, ozonesondes, and GPS radio occultation data, are examined to identify gravity-wave (GW)-induced fluctuations on tracer gases and on the vertical distribution of stratospheric aerosol concentrations during the 2013 ChArMEx (Chemistry-Aerosol Mediterranean Experiment) campaign. Observations reveal signatures of GWs with short vertical wavelengths less than 4 km in dynamical parameters and tracer constituents, which are also correlated with the presence of thin layers of strong local enhancements of aerosol concentrations in the upper troposphere and the lower stratosphere. In particular, this is evident from a case study above Ile du Levant (43.02 • N, 6.46 • E) on 26-29 July 2013. Observations show a strong activity of dominant mesoscale inertia GWs with horizontal and vertical wavelengths of 370-510 km and 2-3 km respectively, and periods of 10-13 h propagating southward at altitudes of 13-20 km during 27-28 July. The European Centre for Medium-Range Weather Forecasts (ECMWF) analyses also show evidence of mesoscale inertia GWs with similar horizontal characteristics above the eastern part of France. Raytracing experiments indicate the jet-front system as the main source of observed GWs. Using a simplified linear GW theory, synthetic vertical profiles of dynamical parameters with large stratospheric vertical wind maximum oscillations of ±40 mms −1 are produced for the dominant mesoscale GW observed at heights of 13-20 km. Parcel advection method reveals signatures of GWs in the ozone mixing ratio and the tropospheric-specific humidity. Simulated vertical wind perturbations of the dominant GWs and small-scale perturbations of aerosol concentration (aerosol size of 0.2-0.7 µm) are revealed to be in phase in the lower stratosphere. Present results support the importance of vertical wind perturbations in the GW-aerosol relationship. Observed mesoscale GWs induce a strong modulation of the amplitude of tracer gases and the stratospheric aerosol background.

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“…Small-scale topographic barriers can also have a profound impact on precipitation distributions downstream due to rain-shadowing effects (Ralph et al 2003) and gravity waves (Koch and O'Handley 1997). Although the general nature of such factors is appreciated, the precise means through which precipitation is produced and altered under such conditions are still uncertain, because it requires understanding both the moist dynamics and microphysics within orographic clouds.…”

Section: Use Of Observationsmentioning

confidence: 99%

Meeting Summaries

Lee¹,

Hong

2005

Bull. Amer. Meteor. Soc.

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THE NEXT-GENERATION NWP MODELS.The meeting provided a good opportunity for various scientists to describe recent modeling improvements. At the Japan Meteorological Agency (JMA), the improved nonhydrostatic model has led to the better prediction of heavy rainfall in Japan. That was the conclusion of Kazuo Saito of the Meteoro- PROBLEMATIC ISSUES. Problems with physics parameterizations in the models that emerged during the workshop include the following: resolution dependency of each physical process, deterministic versus stochastic approaches, and use of observations.Resolution dependency of physics. Physical parameterization schemes developed at one scale may no longer be valid at smaller scales, because computer power increases and grid sizes decrease. Cumulus schemes are a current example, and PBL schemes may be another in the future. Chun stated that GWDC was needed in mesoscale models as long as the need for a cumulus parameterization scheme was valid. Hong stated that parameterized convection could still be useful even at grid sizes of a few kilometers because it helps initiate mesoscale circulation. Dudhia and Lee stated that 4-km grid spacing could be sufficient for microphysics alone in strongly forced midlatitude convective systems. Even with 5-km grid spacing, a convective parameterization is required to properly simulate convective rains and keep radiation and convection in equilibrium. Based on the CRM results and data assimilation issues in high resolutions, Tao argued that 3 km might be the cutoff for cumulus schemes. Hong stated that PBL and shallow convection might be valid with a coarser resolution than is needed for LES. Work at NCAR has shown that the PBL scheme might still give reasonable results at 50-250-m grid sizes by suppressing resolved eddies, thereby eliminating the problem of double counting. Tao said we should separately decide which schemes to apply at various scales (5, 3 km, etc.), while Chen pointed out the need to develop new schemes that gradually change with scale.Deterministic versus ensemble versus stochastic approaches. Deterministic approaches to modeling imply refinement of parameterizations, addition of complexity, and superparameterization, whereas an ensemble approach can be based on uncertainties in initial conditions or physics schemes. Meanwhile, stochastic approach incorporates randomness, such as Grell's ensemble cumulus approach, the PDF approach, or random number uses. For a given computing resource the choice can be as simple as deciding whether to use high-resolution deterministic or lower-resolution ensemble approaches. A recent convection workshop (Tao et al. 2003) found a need to improve ID schemes, a need for multimoment approaches in these schemes, and considered superparameterization a promising approach. Hong pointed out that ensemble means produce better large-scale patterns (such as 500-hPa height), but deterministic method produces better precipitation, such as heavy rain. Hong stated that a stochastic approach might be able to combine advantages ...

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Operational Forecasting and Detection of Mesoscale Gravity Waves

Cited by 75 publications

References 40 publications

Gravity‐wave‐induced perturbations in marine stratocumulus

Gravity‐wave‐induced perturbations in marine stratocumulus

Gravity-wave effects on tracer gases and stratospheric aerosol concentrations during the 2013 ChArMEx campaign

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