scholarly journals On the Realism of the Rain Microphysics Representation of a Squall Line in the WRF Model. Part II: Sensitivity Studies on the Rain Drop Size Distributions

2019 ◽  
Vol 147 (8) ◽  
pp. 2811-2825 ◽  
Author(s):  
Céline Planche ◽  
Frédéric Tridon ◽  
Sandra Banson ◽  
Gregory Thompson ◽  
Marie Monier ◽  
...  
Keyword(s):  
Drop Size ◽  
Wrf Model ◽  
Melting Process ◽  
Squall Line ◽  
Size Distributions ◽  
Line System ◽  
Stratiform Region ◽  
Rain Drop ◽  
Vertical Evolution ◽  
Drop Size Distributions

Abstract A comparison between retrieved properties of the rain drop size distributions (DSDs) from multifrequency cloud radar observations and WRF Model results using either the Morrison or the Thompson bulk microphysics scheme is performed in order to evaluate the model’s ability to predict the rain microphysics. This comparison reveals discrepancies in the vertical profile of the rain DSDs for the stratiform region of the squall-line system observed on 12 June 2011 over Oklahoma. Based on numerical sensitivity analyses, this study addresses the bias at the top of the rain layer and the vertical evolution of the DSD properties (i.e., of Dm and N0*). In this way, the Thompson scheme is used to explore the sensitivity to the melting process. Moreover, using the Thompson and Morrison schemes, the sensitivity of the DSD vertical evolution to different breakup and self-collection parameterizations is studied. Results show that the DSDs are strongly dependent on the representation of the melting process in the Thompson scheme. In the Morrison scheme, the simulations with more efficient breakup reproduce the DSD properties with better fidelity. This study highlights how the inaccuracies in simulated Dm and N0* for both microphysics schemes can impact the evaporation rate, which is systematically underestimated in the model.

scholarly journals Comparison of simultaneous rain drop size distributions estimated from two surface disdrometers and a UHF profiler

2000 ◽  
Vol 27 (12) ◽  
pp. 1763-1766 ◽  
Author(s):  
Christopher R. Williams ◽  
Anton Kruger ◽  
Kenneth S. Gage ◽  
Ali Tokay ◽  
Robert Cifelli ◽  
...  
Keyword(s):  
Drop Size ◽  
Size Distributions ◽  
Rain Drop ◽  
Drop Size Distributions

scholarly journals On the Realism of the Rain Microphysics Representation of a Squall Line in the WRF Model. Part I: Evaluation with Multifrequency Cloud Radar Doppler Spectra Observations

2019 ◽  
Vol 147 (8) ◽  
pp. 2787-2810 ◽  
Author(s):  
Frédéric Tridon ◽  
Céline Planche ◽  
Kamil Mroz ◽  
Sandra Banson ◽  
Alessandro Battaglia ◽  
...  
Keyword(s):  
Quantitative Description ◽  
Wrf Model ◽  
Companion Paper ◽  
Temporal Variations ◽  
Squall Line ◽  
Line System ◽  
Cloud Radar ◽  
Retrieval Technique ◽  
Stratiform Region ◽  
Sensitivity Studies

Abstract This study investigates how multifrequency cloud radar observations can be used to evaluate the representation of rain microphysics in the WRF Model using two bulk microphysics schemes. A squall line observed over Oklahoma on 12 June 2011 is used as a case study. A recently developed retrieval technique combining observations of two vertically pointing cloud radars provides quantitative description of the drop size distribution (DSD) properties of the transition and stratiform regions of the squall-line system. For the first time, the results of this multifrequency cloud radar retrieval are compared to more conventional retrievals from a nearby polarimetric radar, and a supplementary result of this work is that this new methodology provides a much more detailed description of the DSD vertical and temporal variations. While the extent and evolution of the squall line is well reproduced by the model, the 1-h low-reflectivity transition region is not. In the stratiform region, simulations with both schemes are able to reproduce the observed downdraft and the associated significative subsaturation below the melting level, but with a slight overestimation of the relative humidity. Under this subsaturated air, the simulated rain mixing ratio continuously decreases toward the ground, in agreement with the observations. Conversely, the profiles of the mean volume diameter and the concentration parameter of the DSDs are not well reproduced. These discrepancies pinpoint at an issue in the representation of rain microphysics. The companion paper, investigates the sources of the biases in the microphysics processes in the rain layer by performing numerical sensitivity studies.

scholarly journals Intercomparison of simulations using 5 WRF microphysical schemes with dual-Polarization data for a German squall line

2008 ◽  
Vol 16 ◽  
pp. 109-116 ◽  
Author(s):  
W. A. Gallus ◽  
M. Pfeifer
Keyword(s):  
Wrf Model ◽  
Squall Line ◽  
Convective System ◽  
Polarimetric Radar ◽  
Dual Polarization ◽  
Rain Area ◽  
Fine Grid ◽  
Line System ◽  
Stratiform Region ◽  
Microphysical Parameterization

Abstract. Simulations of a squall line system which occurred on 12 August 2004 near Munich, Germany are performed using a fine grid version of the Weather Research and Forecasting (WRF) model with five different microphysical schemes. Synthetic dual polarization observations are created from the model output and compared with detailed observations gathered by the DLR polarimetric radar POLDIRAD located near Munich. Synthetic polarimetric radar scans are derived from the model forecasts employing the polarimetric radar forward operator SynPolRad. Evaluations of the microphysical parameterization schemes are carried out comparing Plan Position Indicator (PPI) and Range Height Indicator (RHI) scans of reflectivity and the spatial distribution of hydrometeor types. The hydrometeor types are derived applying a hydrometeor classification scheme to the observed and simulated polarimetric radar quantities. Furthermore, the Ebert-McBride contiguous rain area method of verification is tested in a variety of ways on the reflectivity output from the simulations. It is found that all five schemes overestimate reflectivity in the domain, particularly in the stratiform region of the convective system. All four schemes including graupel as a hydrometeor type produce too much of it. Differences are seen among the schemes in their depiction of reflectivity in the convective line and their representation of radar bright bands.

scholarly journals Do We Observe Aerosol Impacts on DSDs in Strongly Forced Tropical Thunderstorms?

2011 ◽  
Vol 68 (9) ◽  
pp. 1902-1910 ◽  
Author(s):  
P. T. May ◽  
V. N. Bringi ◽  
M. Thurai
Keyword(s):  
Drop Size ◽  
Probability Distributions ◽  
Size Distributions ◽  
Cloud Properties ◽  
Median Volume ◽  
Rain Drop ◽  
Distribution Parameters ◽  
Radar Measurements ◽  
Ice Multiplication ◽  
Drop Size Distributions

Abstract Rain drop size distributions retrieved from polarimetric radar measurements over regularly occurring thunderstorms over the islands north of Darwin, Australia, are used to test if aerosol contributions to the probability distributions of the drop size distribution parameters (median volume diameter and normalized intercept parameter) are detectable. The observations reported herein are such that differences in cloud properties arising from thermodynamic differences are minimized but even so may be a factor. However, there is a clear signature that high aerosol concentrations are correlated with smaller number concentrations and larger drops. This may be associated with enhanced ice multiplication processes for low aerosol concentration storms or other processes such as invigoration of the updrafts.

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