‘A Case Study on a Polar Cold Air Outbreak over Fram Strait using a Mesoscale Weather Prediction Model’

2005 ◽  
Vol 117 (2) ◽  
pp. 301-336 ◽  
Author(s):  
Ulrike Wacker ◽  
K. V. Jayaraman Potty ◽  
Christof Lüpkes ◽  
Jörg Hartmann ◽  
Matthias Raschendorfer
Keyword(s):  
Prediction Model ◽  
Weather Prediction ◽  
Fram Strait ◽  
Cold Air ◽  
Cold Air Outbreak

scholarly journals On the utility of individual tendency output: Revealing interactions between parameterised processes during a marine cold air outbreak

2021 ◽  
Author(s):  
Marvin Kähnert ◽  
Harald Sodemann ◽  
Wim C. de Rooy ◽  
Teresa M. Valkonen
Keyword(s):  
Prediction Models ◽  
Weather Prediction ◽  
Specific Humidity ◽  
Shallow Convection ◽  
Cold Air ◽  
Cold Air Outbreak ◽  
Order Of Magnitude ◽  
Underlying Causes ◽  
The Individual

AbstractForecasts of marine cold air outbreaks critically rely on the interplay of multiple parameterisation schemes to represent sub-grid scale processes, including shallow convection, turbulence, and microphysics. Even though such an interplay has been recognised to contribute to forecast uncertainty, a quantification of this interplay is still missing. Here, we investigate the tendencies of temperature and specific humidity contributed by individual parameterisation schemes in the operational weather prediction model AROME-Arctic. From a case study of an extensive marine cold air outbreak over the Nordic Seas, we find that the type of planetary boundary layer assigned by the model algorithm modulates the contribution of individual schemes and affects the interactions between different schemes. In addition, we demonstrate the sensitivity of these interactions to an increase or decrease in the strength of the parameterised shallow convection. The individual tendencies from several parameterisations can thereby compensate each other, sometimes resulting in a small residual. In some instances this residual remains nearly unchanged between the sensitivity experiments, even though some individual tendencies differ by up to an order of magnitude. Using the individual tendency output, we can characterise the subgrid-scale as well as grid-scale responses of the model and trace them back to their underlying causes. We thereby highlight the utility of individual tendency output for understanding process-related differences between model runs with varying physical configurations and for the continued development of numerical weather prediction models.

scholarly journals Instability indices and forecasting thunderstorms: the case of 30 April 2009

2012 ◽  
Vol 12 (2) ◽  
pp. 403-413 ◽  
Author(s):  
S. Tajbakhsh ◽  
P. Ghafarian ◽  
F. Sahraian
Keyword(s):  
Relative Humidity ◽  
Prediction Model ◽  
Numerical Weather Prediction ◽  
Vertical Velocity ◽  
Weather Prediction ◽  
Numerical Weather Prediction Model ◽  
Weather Station ◽  
Using Data ◽  
Instability Indices

Abstract. In this paper, one meteorological case study for two Iranian airports are presented. Attempts have been made to study the predefined threshold amounts of some instability indices such as vertical velocity and relative humidity. Two important output variables from a numerical weather prediction model have been used to survey thunderstorms. The climatological state of thunder days in Iran has been determined to aid in choosing the airports for the case studies. The synoptic pattern, atmospheric thermodynamics and output from a numerical weather prediction model have been studied to evaluate the occurrence of storms and to verify the threshold instability indices that are based on Gordon and Albert (2000) and Miller (1972). Using data from the Statistics and Data Center of the Iran Meteorological Organization, 195 synoptic stations were used to study the climatological pattern of thunderstorm days in Iran during a 15-yr period (1991–2005). Synoptic weather maps and thermodynamic diagrams have been drawn using data from synoptic stations and radiosonde data. A 15-km resolution version of the WRF numerical model has been implemented for the Middle East region with the assistance of global data from University Corporation for Atmospheric Research (UCAR). The Tabriz airport weather station has been selected for further study due to its high frequency of thunderstorms (more than 35 thunderstorm days per year) and the existence of an upper air station. Despite the fact that storms occur less often at the Tehran weather station, the station has been chosen as the second case study site due to its large amount of air traffic. Using these two case studies (Tehran at 00:00 UTC, 31 April 2009 and Tabriz at 12:00 UTC, 31 April 2009), the results of this research show that the threshold amounts of 30 °C for KI, −2 °C for LI and −3 °C for SI suggests the occurrence and non-occurrence of thunderstorms at the Tehran and Tabriz stations, respectively. The WRF model output of vertical velocity and relative humidity are the two most important indices for examining storm occurrence, and they have a numerical threshold of 1 m s−1 and 80%, respectively. These results are comparable to other studies that have examined thunderstorm occurrence.

scholarly journals Characterizing the Local and Intense Water Cycle during a Cold Air Outbreak in the Nordic Seas

2018 ◽  
Vol 146 (11) ◽  
pp. 3567-3588 ◽  
Author(s):  
Lukas Papritz ◽  
Harald Sodemann
Keyword(s):  
Water Cycle ◽  
Weather Prediction ◽  
Active Regions ◽  
Numerical Weather Prediction Model ◽  
Limited Area ◽  
Nordic Seas ◽  
Cold Air ◽  
Cold Air Outbreak ◽  
Local Water ◽  
Heat And Moisture

Abstract Air masses in marine cold air outbreaks (CAOs) at high latitudes undergo a remarkable diabatic transformation because of the uptake of heat and moisture from the ocean surface, and the formation of precipitation. In this study, the fundamental characteristics of the water cycle during an intense and persistent, yet archetypal basinwide CAO from Fram Strait into the Nordic seas are analyzed with the aid of the tracer-enabled mesoscale limited-area numerical weather prediction model COSMO. A water budget of the CAO water cycle is performed based on tagged water tracers that follow moisture picked up by the CAO at various stages of its evolution. The atmospheric dynamical factors and boundary conditions that shape this budget are thereby analyzed. The water tracer analysis reveals a highly local water cycle associated with the CAO. Rapid turnover of water vapor results in an average residence time of precipitating waters of about one day. Approximately one-third of the total moisture taken up by the CAO falls as precipitation by convective overturning in the marine CAO boundary layer. Furthermore, precipitation efficiency increases as the CAO air mass matures and is exposed to warmer waters in the Norwegian Sea. These properties of the CAO water cycle are in strong contrast to situations dominated by long-range moisture transport that occur in the dynamically active regions of extratropical cyclones. It is proposed that CAOs in the confined Nordic seas provide a natural laboratory for studying local characteristics of the water cycle and evaluating its representation in models.

The impact of Secondary Ice Processes on a stratocumulus-to-cumulus transition during a Cold-Air Outbreak

2021 ◽  
Author(s):  
Michail Karalis ◽  
Georgia Sotiropoulou ◽  
Steven J. Abel ◽  
Elissavet Bossioli ◽  
Paraskevi Georgakaki ◽  
...  
Keyword(s):  
Prediction Models ◽  
Weather Prediction ◽  
Cumulus Clouds ◽  
Cold Air ◽  
Atmospheric Sciences ◽  
Boundary Layer Clouds ◽  
Cold Air Outbreak ◽  
Stratocumulus Clouds ◽  
Break Up ◽  
The Impact

<p>The representation of boundary layer clouds during marine Cold-Air Outbreaks (CAO) remains a great challenge for weather prediction models. Recent studies have shown that the representation of the transition from stratocumulus clouds to convective cumulus open cells largely depends on microphysical and precipitation processes, while Abel et al. (2017) further suggested that Secondary Ice Processes (SIP) may play a crucial role in the evolution of the cloud fields. In this study we use the Weather Research Forecasting model to investigate the impact of the most well-known SIP mechanisms (rime-splintering or Hallet-Mossop, mechanical break-up upon collisions between ice particles and drop-shattering) on a CAO case observed north of UK in 2013. While Hallet-Mossop is the only SIP process extensively implemented in atmospheric models, our results indicate that collisional break-up is also important in these conditions.</p><p> </p><p>Abel, S. J., Boutle, I. A., Waite, K., Fox, S., Brown, P. R. A., Cotton, R., Lloyd, G., Choularton, T. W., & Bower, K. N. (2017). The Role of Precipitation in Controlling the Transition from Stratocumulus to Cumulus Clouds in a Northern Hemisphere Cold-Air Outbreak, Journal of the Atmospheric Sciences, 74(7), 2293-2314. Retrieved Jan 9, 2021, from https://journals.ametsoc.org/view/journals/atsc/74/7/jas-d-16-0362.1.xml</p>

scholarly journals Numerical Prediction of a Cold-Air Outbreak: A Case Study with Ensemble Forecasts

1999 ◽  
Vol 127 (7) ◽  
pp. 1538-1550 ◽  
Author(s):  
Stephen J. Colucci ◽  
David P. Baumhefner ◽  
Charles E. Konrad
Keyword(s):  
Numerical Prediction ◽  
Ensemble Forecasts ◽  
Cold Air ◽  
Cold Air Outbreak

scholarly journals Verification of the BOLAM weather prediction model over the area of Cyprus

2010 ◽  
Vol 23 ◽  
pp. 93-100
Author(s):  
K. Savvidou ◽  
K. Lagouvardos ◽  
S. Michaelides ◽  
V. Kotroni ◽  
P. Constantinides
Keyword(s):  
Prediction Model ◽  
Mean Absolute Error ◽  
Weather Prediction ◽  
Absolute Error ◽  
Probability Of Detection ◽  
Precipitation Event ◽  
Verification Period ◽  
The Mean ◽  
Observing Systems

Abstract. The purpose of this study is the verification of the BOLAM weather prediction model over the area of Cyprus. The verification period spans from 1 January 2007 till 31 December 2007 and the parameters studied are: temperature, wind and precipitation. The model forecasts are compared to the observations recorded at three locations on the island, where Automatic Weather Observing Systems are operated by the Meteorological Service of Cyprus, namely, those of Larnaka and Paphos Airports and at Athalassa. The statistical analysis includes calculation of the mean error, the mean absolute error and the standard deviation. Based on the construction of a contingency table, the probability of detection of a precipitation event and the false alarm rate are calculated. Finally, an example of BOLAM forecasts for a case study of a low pressure affecting Cyprus during winter is presented and discussed.

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