Predicting Small-Scale, Short-Lived Downbursts: Case Study with the NWP Limited-Area ALARO Model for the Pukkelpop Thunderstorm

Meutter, Pieter De; Gerard, Luc; Smet, Geert; Hamid, Karim; Hamdi, Rafiq; Degrauwe, Daan; Termonia, Piet

doi:10.1175/mwr-d-14-00290.1

Cited by 30 publications

(31 citation statements)

References 29 publications

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“…Because they occur in central Europe predominantly in the warm summer months, they may pose a significant threat to outdoor activities or open-air concerts. An example of such damage cases is the music festival Pukkelpop (Hasselt, Belgium) in the summer of 2011 with estimated wind speeds of between 29 and 37 m s −1 , at which 5 people died and at least 140 were injured due to a stage collapse (De Meutter et al, 2015). Another recent example is the Pentecost storm of 9 June 2014 connected with an intense bow echo in western Europe with high wind speeds up to 40 m s −1 that caused six fatalities and total losses of EUR 650 million (Barthlott et al, 2017;Mathias et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Statistical characteristics of convective wind gusts in Germany

Mohr

Kunz

Richter

et al. 2017

Nat. Hazards Earth Syst. Sci.

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Abstract. Due to the small-scale and non-stationary nature of the convective wind gusts usually associated with thunderstorms, there is a considerable lack of knowledge regarding their characteristics and statistics. In an effort to remedy this situation, we investigated in this study a set of 110 climate stations of the German Weather Service between 1992 and 2014 to analyze the temporal and spatial distribution, intensity, and occurrence probability of convective gusts.Similar to thunderstorm activity, the frequency of convective gusts decreases gradually from southern to northern Germany. No further spatial structures, such as a relation to orography or climate conditions, can be identified regarding their strength or likelihood. Rather, high wind speeds of above 30 m s −1 can be expected everywhere in Germany with almost similar occurrence probabilities. A comparison of the 20-year return values of convective gusts with those of turbulent gusts demonstrates that the latter have higher frequencies, especially in northern Germany. However, for higher return periods, this effect can be reversed at some stations.The values of the convective gust factors are mainly in a range between 1 and 4 but can even reach values up to 10. Besides the dependency from the averaging time period of the mean wind, the values of the gust factors additionally depend on the event duration and the storm type, respectively.

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Section: Introductionmentioning

confidence: 99%

Statistical characteristics of convective wind gusts in Germany

Mohr

Kunz

Richter

et al. 2017

Nat. Hazards Earth Syst. Sci.

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“…The cold pool is also accompanied by a mesoscale high pressure area (Fujita, 1959) which plays a crucial role in the wind gusts that go with heavy precipitation. For these reasons, it is no surprise that an appropriate representation of the cold pool mechanism is essential in a NWP model (Engerer et al, 2008;De Meutter et al, 2014). Although evaporative cooling is the main cause for a cold pool, a second mechanism may enhance it.…”

Section: Case Study Of a Cold Pool Originating From Heavy Precipitationmentioning

confidence: 99%

Generalization and application of the flux-conservative thermodynamic equations in the AROME model of the ALADIN system

Degrauwe¹,

Seity²,

Bouyssel³

et al. 2016

Geosci. Model Dev.

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Abstract. General yet compact equations are presented to express the thermodynamic impact of physical parameterizations in a NWP or climate model. By expressing the equations in a flux-conservative formulation, the conservation of mass and energy by the physics parameterizations is a builtin feature of the system. Moreover, the centralization of all thermodynamic calculations guarantees a consistent thermodynamical treatment of the different processes. The generality of this physics-dynamics interface is illustrated by applying it in the AROME NWP model. The physics-dynamics interface of this model currently makes some approximations, which typically consist of neglecting some terms in the total energy budget, such as the transport of heat by falling precipitation, or the effect of diffusive moisture transport. Although these terms are usually quite small, omitting them from the energy budget breaks the constraint of energy conservation. The presented set of equations provides the opportunity to get rid of these approximations, in order to arrive at a consistent and energy-conservative model. A verification in an operational setting shows that the impact on monthlyaveraged, domain-wide meteorological scores is quite neutral. However, under specific circumstances, the supposedly small terms may turn out not to be entirely negligible. A detailed study of a case with heavy precipitation shows that the heat transport by precipitation contributes to the formation of a region of relatively cold air near the surface, the so-called cold pool. Given the importance of this cold pool mechanism in the life cycle of convective events, it is advisable not to neglect phenomena that may enhance it.

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“…Results indicate that OI and the EKF have similar gain coefficients and increments. The EKF has been extended to include other observation types, like AMSR-E soil moisture retrievals (Draper et al, 2009), radar precipitation information (Mahfouf and Bliznak, 2011), and ASCAT surface soil moisture (Mahfouf, 2010;de Rosnay et al, 2012).…”

Section: A Duerinckx Et Al: Study Of the Jacobian Of An Extended Kamentioning

confidence: 99%

“…Overall the Jacobians calculated with offline runs seem to be a good and computationally more feasible alternative to the use of the Jacobians calculated with the fully coupled model. In de Rosnay et al (2012) fully coupled forecasts are used to calculate the Jacobian, because the ECMWF does not yet have an externalised version of their LSM (i.e. HTESSEL) at their disposal.…”

Section: A Duerinckx Et Al: Study Of the Jacobian Of An Extended Kamentioning

confidence: 99%

“…In the ALARO model, ALADIN is updated with the ALARO-0 physics package. This parameterisation has been designed to run at resolutions from the mesoscale to the cloud-resolving scales in a scaleaware manner, based on the modelling approach of the Modular Multiscale Microphysics and Transport (3MT) cloud and precipitation scheme of Gerard and Geleyn (2005), Gerard (2007), and Gerard et al (2009), and has been validated up to a spatial resolution of 4 km for NWP (Gerard et al, 2009;De Meutter et al, 2015) and climate (Hamdi et al, , 2014bDe Troch et al, 2013). The ALARO-0 physics package is coupled to the dynamics via a physics-dynamics interface based on a flux-conservative formulation of the equations proposed by Catry et al (2007).…”

Section: The Alaro Atmospheric Modelmentioning

confidence: 99%

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Study of the Jacobian of an extended Kalman filter for soil analysis in SURFEXv5

Duerinckx

Hamdi

Mahfouf³

et al. 2015

Geosci. Model Dev.

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Abstract. An externalised surface scheme like SURFEX allows computationally cheap offline runs. This is a major advantage for surface assimilation techniques such as the extended Kalman filter (EKF), where the offline runs allow a cheaper numerical estimation of the observation operator Jacobian. In the recent past an EKF has been developed within SURFEX for the initialisation of soil water content and soil temperature based on screen-level temperature and relative humidity observations. In this paper we make a comparison of the Jacobian calculated with offline SURFEX runs and with runs coupled to the atmospheric ALARO model. Comparisons are made with respect to spatial structure and average value of the Jacobian, gain values and increments. We determine the optimal perturbation size of the Jacobian for the offline and coupled approaches and compare the linearity of the Jacobian for these cases. Results show that the offline Jacobian approach gives similar results to the coupled approach and that it allows for smaller perturbation sizes that better approximate this linearity assumption. We document a new case of non-linearities that can hamper this linearity assumption and cause spurious 2 t oscillations in small parts of the domain for the coupled as well as offline runs. While these oscillations do not have a detrimental effect on the model run, they can introduce some noise in the Jacobian at the affected locations. The oscillations influence both the surface fluxes and the screen-level variables. The oscillations occur in the late afternoon in summer when a stable boundary layer starts to form near the surface. We propose a filter to remove the oscillations and show that this filter works accordingly.

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Predicting Small-Scale, Short-Lived Downbursts: Case Study with the NWP Limited-Area ALARO Model for the Pukkelpop Thunderstorm

Cited by 30 publications

References 29 publications

Statistical characteristics of convective wind gusts in Germany

Statistical characteristics of convective wind gusts in Germany

Generalization and application of the flux-conservative thermodynamic equations in the AROME model of the ALADIN system

Study of the Jacobian of an extended Kalman filter for soil analysis in SURFEXv5

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