High-resolution representation of the mechanisms responsible for the initiation of isolated thunderstorms over flat and complex terrains: analysis of CSIP and COPS cases

Khodayar, S.; Kalthoff, Norbert; Wickert, Jens; Kottmeier, C.; Dorninger, Manfred

doi:10.1007/s00703-012-0232-6

Cited by 12 publications

(20 citation statements)

References 21 publications

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“…Regarding this last point, the identification of low‐level wind convergence lines prior to each deep convection episode in the area turned out to be crucial for the initiation and location of convection in the area, which is in agreement with previous investigations in different midlatitude regions (e.g. Khodayar et al, ).…”

Section: Discussionsupporting

confidence: 90%

“…Particularly relevant is the presence of sufficient moisture in the low and mid‐troposphere (e.g. Khodayar et al, ; ). The availability of moisture for precipitation is controlled by a number of processes including mixing on small scales, convective processes on different scales, and advection on the mesoscale and large‐scale.…”

Section: Introductionmentioning

confidence: 99%

“…Chazette et al, ; Lee et al, ). Furthermore, humidity shows large spatial and temporal variability on the mesoscale (Crook, ; Weckwerth et al, ; Weckwerth, ; Lascaux et al, ; Khodayar et al, ; ; ). The small‐scale variations of humidity can directly influence convective initiation (CI), as well as its further development potential (Sherwood et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Multi‐scale observations of atmospheric moisture variability in relation to heavy precipitating systems in the northwestern Mediterranean during HyMeX IOP12

Khodayar

Czajka

Caldas-Álvarez

et al. 2018

Quart J Royal Meteoro Soc

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The deployment of special instrumentation for the Hydrological Cycle in the Mediterranean Experiment (HyMeX) provides a valuable opportunity to investigate the spatio‐temporal variability of atmospheric water vapour across scales in relationship with the occurrence of Heavy Precipitation Systems (HPSs) in the north Western Mediterranean (WMed) during the Intensive Observation Period (IOP12), which is the focus of this investigation. High‐resolution convection‐permitting COSMO simulations complement the observational network and allow the calculation of on‐line trajectories. In addition to the presence of a favourable large‐scale situation and low‐level convergence, atmospheric moisture changes resulting in conditionally unstable air are identified as responsible for convective initiation (CI). All HPSs within the north‐WMed form in periods/areas of maximum integrated water vapour (IWV; 35–45 kg/m2) after an increase of about 10–20 kg/m2. The most intense events receive moisture from different sources simultaneously and show a sudden increase of about 10 kg/m2 between 6 and 12 h prior to the event, whereas in the less intense events the increase is larger, about 20 kg/m2, over a period of at least 24–36 h. Changes in the lower (∼900 hPa) and mid‐troposphere (∼700 hPa) control the evolution of the atmospheric moisture and the instability increase prior to CI. Spatial inhomogeneities in the lower boundary layer determine the timing and location of deep convection, whereas enhanced moisture in the mid‐troposphere favours intensification. Moister and deeper boundary layers, with updraughts reaching up to 2 km are identified in those pre‐convective environments leading to HPS, whereas dry, shallow boundary layers are found everywhere else. The build‐up time and vertical distribution of the moisture changes are found to be crucial for the evolution and severity of the HPSs rather than the amount of total column atmospheric moisture.

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Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multi‐scale observations of atmospheric moisture variability in relation to heavy precipitating systems in the northwestern Mediterranean during HyMeX IOP12

Khodayar

Czajka

Caldas-Álvarez

et al. 2018

Quart J Royal Meteoro Soc

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“…Atmospheric moisture distribution and evolution strongly impact convection, moreover, low‐level moisture significantly determines CAPE, whose presence is necessary (but not sufficient) for the development of convection. In the same vein, CAPE is strongly correlated to the atmospheric equivalent potential temperature, θ e (Parker, ; Kalthoff et al ., ; Khodayar et al ., ). The 50 hPa Mixed Layer (ML) is used from all models.…”

Section: Model Intercomparisonmentioning

confidence: 98%

“…Having shown the impact of model differences on the precipitation field (Figures 8 and 9), we now consider the impact of model differences on the atmospheric stratification of temperature and humidity, which plays a relevant role in the initiation and intensification of convective storms. A high amount of moisture in the lower levels and an unstable atmosphere are necessary ingredients for convection initiation (Doswell et al, 1996), as well as a sufficient amount of moisture in the midtroposphere to favour intensification and deepening of convective storms (Khodayar et al, 2010(Khodayar et al, , 2013. In addition to differences in the representation of atmospheric conditions resulting from the different initial-boundary conditions and grid spacing, the presence of a convection parametrization scheme may influence the relationship between for example the initiation of convection and the boundary-layer conditions (Baldauf et al, 2011).…”

Section: Atmospheric Conditions and Stratificationmentioning

confidence: 99%

A seamless weather–climate multi‐model intercomparison on the representation of a high impact weather event in the western Mediterranean: HyMeX IOP12

Khodayar

Fosser

Berthou

et al. 2016

Quart J Royal Meteoro Soc

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High Impact Weather (HIW), particularly Heavy Precipitation Events (HPE), are common phenomena affecting the western Mediterranean (WMED) especially in the autumn period. Understanding and evaluating the capability to adequately represent such events in model simulations is one of the main goals of the Hydrological cycle in the Mediterranean Experiment (HyMeX) and the main motivation of this investigation. In order to gain a better knowledge of the model representation of HPE and related processes we perform a seamless multi‐model intercomparison at the event scale. Limited‐area model runs (grid spacing from 2 to 20 km) at weather and climate time‐scales are considered, four with parametrized and five with explicit convection. The performance of the nine models is compared by analysing precipitation, as well as convection‐relevant parameters. An Intensive Observation Period (IOP12) from the HyMeX‐SOP1 (Special Observation Period) is used to illustrate the results. During IOP12, HPE affected the northwestern Mediterranean region, from Spain to Italy, as a consequence of Mesoscale Convective Systems (MCSs) which initiated and intensified in the area of investigation. Results show that: (i) the timing of the maximum precipitation seems to be linked to the representation of large‐scale conditions rather than differences among models; (ii) Convection Permitting Models (CPMs) exhibit differences among each other, but better represent the short‐intense convective events. All four convection‐parametrized models produce a large number of weak and long‐lasting events. Regional Climate Models (RCMs) capture the occurrence of the event but produce notably lower precipitation amounts and hourly intensities than CPMs and Numerical Weather Prediction (NWP) models with parametrized convection; (iii) these differences do not seem to come from mean moisture or Convective Available Potential Energy (CAPE) which are in the same range for all models, but rather from differences in the variability and vertical distribution of moisture and the triggering of deep convection.

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A review on regional convection‐permitting climate modeling: Demonstrations, prospects, and challenges

Prein

Langhans

Fosser

et al. 2015

Reviews of Geophysics

1,095

967

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Regional climate modeling using convection‐permitting models (CPMs; horizontal grid spacing <4 km) emerges as a promising framework to provide more reliable climate information on regional to local scales compared to traditionally used large‐scale models (LSMs; horizontal grid spacing >10 km). CPMs no longer rely on convection parameterization schemes, which had been identified as a major source of errors and uncertainties in LSMs. Moreover, CPMs allow for a more accurate representation of surface and orography fields. The drawback of CPMs is the high demand on computational resources. For this reason, first CPM climate simulations only appeared a decade ago. In this study, we aim to provide a common basis for CPM climate simulations by giving a holistic review of the topic. The most important components in CPMs such as physical parameterizations and dynamical formulations are discussed critically. An overview of weaknesses and an outlook on required future developments is provided. Most importantly, this review presents the consolidated outcome of studies that addressed the added value of CPM climate simulations compared to LSMs. Improvements are evident mostly for climate statistics related to deep convection, mountainous regions, or extreme events. The climate change signals of CPM simulations suggest an increase in flash floods, changes in hail storm characteristics, and reductions in the snowpack over mountains. In conclusion, CPMs are a very promising tool for future climate research. However, coordinated modeling programs are crucially needed to advance parameterizations of unresolved physics and to assess the full potential of CPMs.

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High-resolution representation of the mechanisms responsible for the initiation of isolated thunderstorms over flat and complex terrains: analysis of CSIP and COPS cases

Cited by 12 publications

References 21 publications

Multi‐scale observations of atmospheric moisture variability in relation to heavy precipitating systems in the northwestern Mediterranean during HyMeX IOP12

Multi‐scale observations of atmospheric moisture variability in relation to heavy precipitating systems in the northwestern Mediterranean during HyMeX IOP12

A seamless weather–climate multi‐model intercomparison on the representation of a high impact weather event in the western Mediterranean: HyMeX IOP12

A review on regional convection‐permitting climate modeling: Demonstrations, prospects, and challenges

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