The evolution of an MCS over southern England. Part 1: Observations

Clark, Peter A.; Browning, K. A.; Morcrette, C. J.; Blyth, Alan; Forbes, R. M.; Brooks, Barbara; Perry, Felicity

doi:10.1002/qj.2138

Cited by 10 publications

(5 citation statements)

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“…The broad geographic coverage at ;70-km horizontal resolution afforded by the pseudogridded USArray TA over the eastern United States during the 2010-14 period provides an excellent dataset for case-study analysis of large-amplitude gravity wave propagation dynamics within this region. These large-amplitude gravity waves (both solitary and wave packets) are known to propagate several hundred kilometers at speeds of 10-35 m s 21 (Adams-Selin and Johnson 2010; Ruppert and Bosart 2014;Clark et al 2014), which extends beyond the geographic range of previous moderate-density pressure networks that have been used to study large-amplitude gravity waves (e.g., Koch and Siedlarz 1999;Jewett et al 2003). The capability for researchers to examine individual as well as sets of large pressure perturbations within temporal bands (meso-, subsynoptic, and synoptic scales) or simply from the unfiltered pressure time series is an important outcome of this study.…”

Section: Summary and Discussionmentioning

confidence: 99%

Central and Eastern U.S. Surface Pressure Variations Derived from the USArray Network

Jacques

Horel

Crosman

et al. 2015

Monthly Weather Review

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Large-magnitude pressure signatures associated with a wide range of atmospheric phenomena (e.g., mesoscale gravity waves, convective complexes, tropical disturbances, and synoptic storm systems) are examined using a unique set of surface pressure sensors deployed as part of the National Science Foundation EarthScope USArray Transportable Array. As part of the USArray project, approximately 400 seismic stations were deployed in a pseudogrid fashion across a portion of the United States for 1-2 yr, then retrieved and redeployed farther east. Surface pressure observations at a sampling frequency of 1 Hz were examined during the period when the seismic array was transitioning from the central to eastern continental United States. Surface pressure time series at over 900 locations were bandpass filtered to examine pressure perturbations on three temporal scales: meso-(10 min-4 h), subsynoptic (4-30 h), and synoptic (30 h-5 days) scales.Case studies of strong pressure perturbations are analyzed using web tools developed to visualize and track tens of thousands of such events with respect to archived radar imagery and surface wind observations. Seasonal assessments of the bandpass-filtered variance and frequency of large-magnitude events are conducted to identify prominent areas of activity. Large-magnitude mesoscale pressure perturbations occurred most frequently during spring in the southern Great Plains and shifted northward during summer. Synopticscale pressure perturbations are strongest during winter in the northern states with maxima located near the East Coast associated with frequent synoptic development along the coastal storm track.

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Section: Summary and Discussionmentioning

confidence: 99%

Central and Eastern U.S. Surface Pressure Variations Derived from the USArray Network

Jacques

Horel

Crosman

et al. 2015

Monthly Weather Review

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“…This article is a companion to Clark et al (2013), hereafter referred to as Part 1, which describes observations made during the Convective Storm Initiation Project (CSIP; Browning et al, 2007) Intensive Observation Period (IOP) 18, on 25 August 2005 of a Mesoscale Convective System (MCS). As discussed in Part 1, forecasting the occurrence of severe convective storms is of considerable importance for the protection of people and property.…”

Section: Introductionmentioning

confidence: 99%

The evolution of an MCS over southern England. Part 2: Model simulations and sensitivity to microphysics

Clark

Browning

Forbes

et al. 2013

Quart J Royal Meteoro Soc

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ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Simulations using the Met Office Unified Model at 1 km horizontal grid spacing of a Mesoscale Convective System (MCS) with a cold pool which propagated across southern England on 25 August 2005 are validated using detailed observations from the Convective Storm Initiation Project (CSIP). Early organisation of the system is not especially well treated, but the model goes on to form a system which developed qualitative and quantitative features remarkably similar to the observations.A sensitivity study suggests that the initial linear system is driven by the position of a low-level 'lid' and upper-level instability, the linear organisation being promoted by a weak rear-inflow jet forced by the upper-level warm anomaly in the cloud anvil. A weak cold pool develops in the absence of ice-phase processes, but this does not promote system propagation. Strengthening and descent of the rear-inflow jet, and acceleration of the system, is promoted by the additional heating through glaciation and cooling through snow evaporation. The surface cold pool and gust front are further strengthened by snow melting and rainfall evaporation. With ice-phase processes present, the cold pool strengthens as a result of the system development and its strength is broadly correlated with system propagation speed during the middle phase of the system's lifetime. Propagation enables the convective band to 'sweep up' any convective cells which trigger ahead of the system. The differing scales of microphysical processes means that it is difficult to form a steady-state system. The observed transition phase corresponds to an increase in the slantwise nature of the flow in the storm and in the low-level cooling by rainfall evaporation near the gust front, combined with a change in ambient conditions (advection over the sea) which eventually enable the cold pool to propagate ahead of the system. Key Words: convection; precipitation; cold pool; rear-inflow jet; cloud microphysics; mesoscale model

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“…; Clark et al . ). It is likely that the shallower‐than‐observed stable layer in our simulations was susceptible to penetration by downdraughts (Horgan et al .…”

Section: Discussionmentioning

confidence: 99%

Simulations of an observed elevated mesoscale convective system over southern England during CSIP IOP 3

White

Blyth

Marsham

2016

Quart J Royal Meteoro Soc

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Simulations of an elevated mesoscale convective system (MCS) observed over southern England during the Convective Storm Initiation Project (CSIP) provide the first detailed modelling study of a case of elevated convection occurring in the UK. The study shows that many factors can influence the maintenance of elevated deep convection, from large‐scale flow through to surface heating processes and diabatic cooling within the convective system. It is also shown that interactions and feedback mechanisms between a stable layer and the storm can act to maintain deep convection. The simulation successfully reproduced an elevated MCS above a low‐level stable undercurrent, with a wave in the undercurrent linked to a rear‐inflow jet (RIJ). Convection was fed from an elevated (840 hPa) source layer with CAPE of about 350 J kg−1. The undercurrent in the simulation was approximately 1 km deep, about half that observed. Unlike the observed MCS, a transition from elevated to surface‐based convection occurred in the simulation due to the combined effects of a pre‐existing large‐scale θe gradient, advection and surface heating causing the system to encounter increasingly unstable low‐level air and a shallower stable layer that was more susceptible to penetration by downdraughts. The transition to surface‐based convection was accompanied by the development of cold‐pool outflow and an increase in system velocity from about 6 to 10 m s−1. Diabatic cooling from microphysical processes in the simulation enhanced the undercurrent and strengthened the RIJ. This strengthened the wave in the undercurrent and led to more extensive convection. The existence of a positive feedback process between the convection, RIJ and stable layer is discussed. Uncertainty in the synoptic scale generating errors in the undercurrent is shown to be a major source of error for convective‐scale forecasts.

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The evolution of an MCS over southern England. Part 1: Observations

Cited by 10 publications

References 50 publications

Central and Eastern U.S. Surface Pressure Variations Derived from the USArray Network

Central and Eastern U.S. Surface Pressure Variations Derived from the USArray Network

The evolution of an MCS over southern England. Part 2: Model simulations and sensitivity to microphysics

Simulations of an observed elevated mesoscale convective system over southern England during CSIP IOP 3

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