Mesoscale model simulation of a severe summer Thunderstorm in The Netherlands: Performance and uncertainty assessment for parameterised and resolved convection
Steeneveld, Gert Jan ; Peerlings, Esther E.M. - \ 2020
Atmosphere 11 (2020)8. - ISSN 2073-4433
Cumulus parameterisation - Grey zone - Mesoscale convective system - The Netherlands - WRF model
On the evening of 23 June 2016 around 18:00 UTC, a mesoscale convective system (MCS) with hail and wind gusts passed the southern province Noord-Brabant in the Netherlands, and caused 675 millions of euros damage. This study evaluates the performance of the Weather Research and Forecasting model with three cumulus parameterisation schemes (Betts-Miller-Janjic, Grell-Freitas and Kain-Fritsch) on a grid spacing of 4 km in the 'grey-zone' and with explicitly resolved convection at 2 and 4 km grid spacing. The results of the five experiments are evaluated against observations of accumulated rainfall, maximum radar reflectivity, the CAPE evolution and wind speed. The results show that the Betts-Miller-Janjic scheme is activated too early and can therefore not predict any MCS over the region of interest. The Grell-Freitas and Kain-Fritsch schemes do predict an MCS, but its intensity is underestimated. With the explicit convection, the model is able to resolve the storm, though with a delay and an overestimated intensity. We also study whether spatial uncertainty in soil moisture is scaled up differently using parameterised or explicitly resolved convection. We find that the uncertainty in soil moisture distribution results in larger uncertainty in convective activity in the runs with explicit convection and the Grell-Freitas scheme, while the Kain-Fritsch and Betts-Miller-Janjic scheme clearly present a smaller variability.
WRF Model Prediction of a Dense Fog Event Occurred During the Winter Fog Experiment (WIFEX)
Pithani, Prakash ; Ghude, Sachin D. ; Chennu, V.N. ; Kulkarni, Rachana G. ; Steeneveld, Gert Jan ; Sharma, Ashish ; Prabhakaran, Thara ; Chate, D.M. ; Gultepe, Ismail ; Jenamani, R.K. ; Madhavan, Rajeevan - \ 2019
Pure and Applied Geophysics 176 (2019)4. - ISSN 0033-4553 - p. 1827 - 1846.
Liquid water content - PBL scheme - vertical level - WIFEX - WRF model
In this study, the sensitivity of the Weather Research and Forecasting (WRF) model to simulate the life cycle of a dense fog event that occurred on 23–24 January 2016 is evaluated using different model configurations. For the first time, intensive observational periods (IOPs) were made during the unique winter fog experiment (WIFEX) that took place over Delhi, India, where air quality is serious during the winter months. The multiple sensitivity experiments to evaluate the WRF model performance included parameters such as initial model and boundary conditions, vertical resolution in the lower boundary layer (BL), and the planetary BL (PBL) physical parameterizations. In addition, the model sensitivity was tested using various configurations that included domain size and grid resolution. Results showed that simulations with a high number of vertical levels within the lower PBL height (i.e., 10 levels below 300 m) simulated the accurate timing of fog formation, development, and dissipation. On the other hand, simulations with less vertical levels in the PBL captured only the mature physical characteristics of the fog cycle. A comparison of six local PBL schemes showed little variation in the onset of fog life cycle in comparison to observations of visibility. However, comparisons of observations with thermodynamical values such as 2-m temperature and longwave radiation showed poor relationships. Overall, quasi-normal scale elimination (QNSE) and MYNN 2.5 PBL schemes simulated the complete fog life cycle correctly with high liquid water content (LWC; 0.5/0.35 g m −3 ), while other schemes only responded during the mature phase.