Radar data assimilation for the simulation of mesoscale convective systems

2010 ◽  
Vol 27 (5) ◽  
pp. 1025-1042 ◽  
Author(s):  
Jo-Han Lee ◽  
Hyun-Ha Lee ◽  
Yonghan Choi ◽  
Hyung-Woo Kim ◽  
Dong-Kyou Lee
Keyword(s):  
Data Assimilation ◽  
Radar Data ◽  
Mesoscale Convective Systems ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Radar Data Assimilation

scholarly journals Evaluation of Ensemble Configurations for the Analysis and Prediction of Heavy-Rain-Producing Mesoscale Convective Systems*

2014 ◽  
Vol 142 (11) ◽  
pp. 4108-4138 ◽  
Author(s):  
Russ S. Schumacher ◽  
Adam J. Clark
Keyword(s):  
Data Assimilation ◽  
Real Time ◽  
Great Plains ◽  
Heavy Rain ◽  
The United States ◽  
Mesoscale Convective Systems ◽  
Convective Systems ◽  
Probabilistic Forecasts ◽  
Mesoscale Convective ◽  
Physical Parameterizations

Abstract This study investigates probabilistic forecasts made using different convection-allowing ensemble configurations for a three-day period in June 2010 when numerous heavy-rain-producing mesoscale convective systems (MCSs) occurred in the United States. These MCSs developed both along a baroclinic zone in the Great Plains, and in association with a long-lived mesoscale convective vortex (MCV) in Texas and Arkansas. Four different ensemble configurations were developed using an ensemble-based data assimilation system. Two configurations used continuously cycled data assimilation, and two started the assimilation 24 h prior to the initialization of each forecast. Each configuration was run with both a single set of physical parameterizations and a mixture of physical parameterizations. These four ensemble forecasts were also compared with an ensemble run in real time by the Center for the Analysis and Prediction of Storms (CAPS). All five of these ensemble systems produced skillful probabilistic forecasts of the heavy-rain-producing MCSs, with the ensembles using mixed physics providing forecasts with greater skill and less overall bias compared to the single-physics ensembles. The forecasts using ensemble-based assimilation systems generally outperformed the real-time CAPS ensemble at lead times of 6–18 h, whereas the CAPS ensemble was the most skillful at forecast hours 24–30, though it also exhibited a wet bias. The differences between the ensemble precipitation forecasts were found to be related in part to differences in the analysis of the MCV and its environment, which in turn affected the evolution of errors in the forecasts of the MCSs. These results underscore the importance of representing model error in convection-allowing ensemble analysis and prediction systems.

scholarly journals Precipitation Forecast Characteristics of Radar Data Assimilation Based on Precipitation Types

2021 ◽  
Author(s):  
Jeong-Ho Bae ◽  
Ki-Hong Min
Keyword(s):  
Numerical Model ◽  
Data Assimilation ◽  
Radar Data ◽  
Precipitation Forecast ◽  
Convective System ◽  
Observation Data ◽  
Microphysics Scheme ◽  
Assimilation Experiment ◽  
Mesoscale Convective ◽  
Radar Data Assimilation

Radar observation data with high temporal and spatial resolution are used in the data assimilation experiment to improve precipitation forecast of a numerical model. The numerical model considered in this study is Weather Research and Forecasting (WRF) model with double-moment 6-class microphysics scheme (WDM6). We calculated radar equivalent reflectivity factor using higher resolution WRF and compared with radar observations in South Korea. To compare the precipitation forecast characteristics of three-dimensional variational (3D-Var) assimilation of radar data, four experiments are performed based on different precipitation types. Comparisons of the 24-h accumulated rainfall with Automatic Weather Station (AWS) data, Contoured Frequency by Altitude Diagram (CFAD), Time Height Cross Sections (THCS), and vertical hydrometeor profiles are used to evaluate and compare the accuracy. The model simulations are performed with and with-out 3D-VAR radar reflectivity, radial velocity and AWS assimilation for two mesoscale convective cases and two synoptic scale cases. The radar data assimilation experiment improved the location of precipitation area and rainfall intensity compared to the control run. Especially, for the two convective cases, simulating mesoscale convective system was greatly improved.

scholarly journals Analysis of Strengthening and Dissipating Mesoscale Convective Systems Propagating off the West African Coast

2014 ◽  
Vol 142 (12) ◽  
pp. 4600-4623 ◽  
Author(s):  
Abdou L. Dieng ◽  
Laurence Eymard ◽  
Saidou M. Sall ◽  
Alban Lazar ◽  
Marion Leduc-Leballeur
Keyword(s):  
Radar Data ◽  
West African ◽  
Mesoscale Convective Systems ◽  
The West ◽  
Convective Systems ◽  
Wave Trough ◽  
West African Coast ◽  
African Coast ◽  
Mesoscale Convective ◽  
Tropical Depressions

Abstract A large number of Atlantic tropical depressions are generated in the eastern basin in relation to the African easterly wave (AEW) and embedded mesoscale convective systems (MCSs) coming from the African continent. In this paper, the structures of strengthening and dissipating MCSs evolving near the West African coast are analyzed, including the role of the ocean surface conditions in their evolution. Satellite infrared brightness temperature and meteorological radar data over seven summer seasons between 1993 and 2006 are used to subjectively select 20 cases of strengthening and dissipating MCSs in the vicinity of the Senegal coast. With these observed MCSs, a lagged composite analysis is then performed using Interim ECMWF Re-Analysis (ERA-Interim) and Climate Forecast System Reanalysis (CFSR). It is shown that the strengthening MCS is generally preceded by prior passage of an AEW near the West African coast. This previous wave trough is associated with a convective cyclonic circulation in the low and middle troposphere, which enhances the southwesterly flow and then provides humidity to the strengthening MCS, located in the vicinity of the subsequent AEW trough. This is favored by the contraction of the wavelength associated with the two troughs. The sea surface contributes to the MCS enhancement through surface evaporation flux. But this contribution is found to be less important than advection of humidity from the previous wave trough. These conditions are almost not found in the dissipating MCS cases, which dissipate in a dry environment dominated by a subsident and anticyclonic circulation, with generally no interaction with a previous wave trough.

scholarly journals Modeling the Flash Rate of Thunderstorms. Part I: Framework

2011 ◽  
Vol 139 (10) ◽  
pp. 3093-3111 ◽  
Author(s):  
Johannes M. L. Dahl ◽  
Hartmut Höller ◽  
Ulrich Schumann
Keyword(s):  
Radar Data ◽  
Mesoscale Convective Systems ◽  
New Approach ◽  
Flash Rate ◽  
Convective Systems ◽  
Cloud Properties ◽  
Lightning Detection ◽  
Mesoscale Convective ◽  
Lightning Discharges ◽  
New Framework

Abstract In this study a straightforward theoretical approach to determining the flash rate in thunderstorms is presented. A two-plate capacitor represents the basic dipole charge structure of a thunderstorm, which is charged by the generator current and discharged by lightning. If the geometry of the capacitor plates, the generator-current density, and the lightning charge are known, and if charging and discharging are in equilibrium, then the flash rate is uniquely determined. To diagnose the flash rate of real-world thunderstorms using this framework, estimates of the required relationships between the predictor variables and observable cloud properties are provided. With these estimates, the flash rate can be parameterized. In previous approaches, the lightning rate has been set linearly proportional to the electrification rate (such as the storm’s generator power or generator current), which implies a constant amount of neutralization by lightning discharges (such as lightning energy or lightning charge). This leads to inconsistencies between these approaches. Within the new framework proposed here, the discharge strength is allowed to vary with storm geometry, which remedies the physical inconsistencies of the previous approaches. The new parameterization is compared with observations using polarimetric radar data and measurements from the lightning detection network, LINET. The flash rates of a broad spectrum of discrete thunderstorm cells are accurately diagnosed by the new approach, while the flash rates of mesoscale convective systems are overestimated.

scholarly journals Mesoscale Convective Systems Monitoring on the Basis of MSG Data – Case Studies

2015 ◽  
Vol 50 (2) ◽  
pp. 91-103
Author(s):  
K. Szafranek ◽  
B. Jakubiak ◽  
R. Lech ◽  
M. Tomczuk
Keyword(s):  
System Development ◽  
Weather Conditions ◽  
Radar Data ◽  
Mesoscale Convective Systems ◽  
Temperature Threshold ◽  
The European Union ◽  
Atmospheric Conditions ◽  
Development Fund ◽  
Convective Systems ◽  
Mesoscale Convective

Abstract Analysis described in the paper were made in the frame of the PROZA (Operational decisionmaking based on atmospheric conditions, http://projekt-proza.pl/) project co-financed by the European Union through the European Regional Development Fund. One of its tasks was to develop an operational forecast system, which is going to support different economies branches like forestry or fruit farming by reducing the risk of economic decisions with taking into consideration weather conditions. The main purpose of the paper is to describe the method of the MCSs (Mesoscale Convective Systems) tracking on the basis of the MSG (Meteosat Second Generation) data. Until now several tests were performed. The Meteosat satellite images in selected spectral channels collected for Central Europe Region for May 2010 were used to detect and track cloud systems recognized as MCSs in Poland. The ISIS tracking method was applied here. First the cloud objects are defined using the temperature threshold and next the selected cells are tracked using principle of overlapping position on consecutive images. The main benefit of using a temperature threshold to define cells is its efficiency. During the tracking process the algorithm links the cells of the image at time t to the one of the following image at time t+dt that correspond to the same cloud system. Selected cases present phenomena, which appeared at the territory of Poland. They were compared to the weather radar data and UKMO UM (United Kingdom MetOffice Unified Model) forecasts. The paper presents analysis of exemplary MCSs in the context of near realtime prediction system development and proves that developed tool can be helpful in MCSs monitoring.

scholarly journals Hydrometeor and Latent Heat Nudging for Radar Reflectivity Assimilation: Response to the Model States and Uncertainties

2021 ◽  
Vol 13 (19) ◽  
pp. 3821
Author(s):  
Zhaoyang Huo ◽  
Yubao Liu ◽  
Ming Wei ◽  
Yueqin Shi ◽  
Chungang Fang ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Latent Heat ◽  
Weather Prediction ◽  
Radar Data ◽  
Time Duration ◽  
Convective Systems ◽  
Relaxation Coefficient ◽  
Key Issues ◽  
Assimilation Process ◽  
Radar Data Assimilation

Radar data are essential to convection nowcasting and nudging-based radar data assimilation through diabatic initialization is one of the most effective approaches for forecasting convective systems with numerical weather prediction (NWP) models, used at several advanced global weather centers. It is desired to assess the uncertainty and physical consistency of this assimilation process. This paper investigated impacts of relaxation coefficient, radar data update intervals and continuous assimilation time duration and addressed the key issues and possible solutions of the radar data assimilation based on the WRF hydrometeor and latent heat nudging (HLHN) developed at the National Center for Atmospheric Research (NCAR). It is revealed that excessively large relaxation coefficient forced the model to observations with a tendency greater than the physical terms of the convection, causing the dynamic imbalances and serious convection “ramp-down” right after the free forecast starts. Assimilating high update frequency radar data can make the tendency terms moderate and sustained thereby maintaining the assimilation effect and reducing fortuitous convection. HLHN requires a minimum continuous assimilation duration to contain the initial forced disturbance of the model. For a summer Meiyu precipitation case studied, the minimum duration is ~1 h. Appropriate selection of the HLHN parameters is able to effectively improve the temperature, humidity, and dynamic fields of the model. In addition, several issues still remain to be solved to further enhance HLHN.

scholarly journals Statistical Analysis of the Mesoscale Convective Systems Propagation East of the Rocky Mountains

2021 ◽  
Author(s):  
Yunsung Hwang ◽  
Yanping Li
Keyword(s):  
Rocky Mountains ◽  
Multiple Scales ◽  
Stage Iv ◽  
Radar Data ◽  
Mesoscale Convective Systems ◽  
Observation Data ◽  
Regional Variability ◽  
Time Step ◽  
Convective Systems ◽  
Mesoscale Convective

Abstract In this work, we characterized the occurrences and propagation speeds of Mesoscale Convective Systems (MCSs) east of the Rocky Mountains, using 15 years of radar data. The central United States has a complex topography. The region also has atmospheric environments that initiate and maintain MCSs at multiple scales. The diurnal and regional variability of MCSs based on their longevities was obtained using high-resolution observation data (Stage IV) and an object tracking algorithm MODE-Time Domain (MTD). MTD-determined MCSs in spring and summer were divided into daytime (initiated from 12 to 23 UTC, MCS12) and nighttime MCSs (formed between 00 and 11 UTC, MCS00) and into short lived (less than the 75th percentile) and long lived MCSs (greater or equal to the 75th percentile). Propagation speeds of MCSs were calculated using distances between MCSs’ centroids at each time step. We suggest a novel way to obtain a Hovmoller diagram to indicate average propagation speeds. There were two key results: 1) Spatial and temporal features of propagation speeds vary at each location and time and, 2.) heavy rainfall (rain rates ≥ 5.0 mmhr-1 ) contributed more than lighter rainfall to overall precipitation. In the east during spring, long-lived MCSs occurred more frequently in the spring than in summer. Short-lived daytime MCSs in spring and summer exhibited similar spatial distributions. In summer alone, short-lived nighttime MCSs occurred more frequently that they did in spring. To the east, the average propagation speeds of short-lived MCSs increased in spring and summer, whereas long-lived MCSs indicated decreasing trends.

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