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

Observation Data ◽

Regional Variability ◽

Time Step ◽

Convective Systems ◽

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.

A high-resolution unified observational data product of mesoscale convective systems and isolated deep convection in the United States for 2004–2017

Earth System Science Data ◽

10.5194/essd-13-827-2021 ◽

2021 ◽

Vol 13 (2) ◽

pp. 827-856

Author(s):

Jianfeng Li ◽

Zhe Feng ◽

Yun Qian ◽

L. Ruby Leung

Keyword(s):

United States ◽

High Resolution ◽

Atmospheric Chemistry ◽

Rocky Mountains ◽

Deep Convection ◽

The United States ◽

Convective Systems ◽

Data Product ◽

Abstract. Deep convection possesses markedly distinct properties at different spatiotemporal scales. We present an original high-resolution (4 km, hourly) unified data product of mesoscale convective systems (MCSs) and isolated deep convection (IDC) in the United States east of the Rocky Mountains and examine their climatological characteristics from 2004 to 2017. The data product is produced by applying an updated Flexible Object Tracker algorithm to hourly satellite brightness temperature, radar reflectivity, and precipitation datasets. Analysis of the data product shows that MCSs are much larger and longer-lasting than IDC, but IDC occurs about 100 times more frequently than MCSs, with a mean convective intensity comparable to that of MCSs. Hence both MCS and IDC are essential contributors to precipitation east of the Rocky Mountains, although their precipitation shows significantly different spatiotemporal characteristics. IDC precipitation concentrates in summer in the Southeast with a peak in the late afternoon, while MCS precipitation is significant in all seasons, especially for spring and summer in the Great Plains. The spatial distribution of MCS precipitation amounts varies by season, while diurnally, MCS precipitation generally peaks during nighttime except in the Southeast. Potential uncertainties and limitations of the data product are also discussed. The data product is useful for investigating the atmospheric environments and physical processes associated with different types of convective systems; quantifying the impacts of convection on hydrology, atmospheric chemistry, and severe weather events; and evaluating and improving the representation of convective processes in weather and climate models. The data product is available at https://doi.org/10.25584/1632005 (Li et al., 2020).

A high-resolution unified observational data product of mesoscale convective systems and isolated deep convection in the United States for 2004–2017

10.5194/essd-2020-151 ◽

2020 ◽

Author(s):

Jianfeng Li ◽

Zhe Feng ◽

Yun Qian ◽

L. Ruby Leung

Keyword(s):

United States ◽

High Resolution ◽

Atmospheric Chemistry ◽

Rocky Mountains ◽

Deep Convection ◽

The United States ◽

Convective Systems ◽

Data Product ◽

Abstract. Deep convection possesses markedly distinct properties at different spatiotemporal scales. We present an original high-resolution (4 km, hourly) unified data product of mesoscale convective systems (MCSs) and isolated deep convection (IDC) in the United States east of the Rocky Mountains and examine their climatological characteristics from 2004 to 2017. The data product is produced by applying an updated FLEXTRKR (Flexible Object Tracker) algorithm to hourly satellite brightness temperature, radar reflectivity, and precipitation datasets. Analysis of the data product shows that MCSs are much larger and longer-lasting than IDC, but IDC occurs about 100 times more frequently than MCSs, with a mean convective intensity comparable to that of MCSs. Hence both MCS and IDC are essential contributors to precipitation east of the Rocky Mountains, although their precipitation shows significantly different spatiotemporal characteristics. IDC precipitation concentrates in summer in the Southeast with a peak in the late afternoon, while MCS precipitation is significant in all seasons, especially for spring and summer in the Great Plains. The spatial distribution of MCS precipitation amounts varies by seasons, while diurnally, MCS precipitation generally peaks during nighttime except in the Southeast. Potential uncertainties and limitations of the data product are also discussed. The data product is useful for investigating the atmospheric environments and physical processes associated with different types of convective systems, quantifying the impacts of convection on hydrology, atmospheric chemistry, and severe weather events, and evaluating and improving the representation of convective processes in weather and climate models. The data product is available at https://doi.org/10.25584/1632005 (Li et al., 2020).

Spatiotemporal Characteristics and Large-Scale Environments of Mesoscale Convective Systems East of the Rocky Mountains

Journal of Climate ◽

10.1175/jcli-d-19-0137.1 ◽

2019 ◽

Vol 32 (21) ◽

pp. 7303-7328 ◽

Cited By ~ 18

Author(s):

Zhe Feng ◽

Robert A. Houze ◽

L. Ruby Leung ◽

Fengfei Song ◽

Joseph C. Hardin ◽

...

Keyword(s):

Great Plains ◽

Rocky Mountains ◽

Large Scale ◽

Rain Area ◽

Stratiform Rain ◽

Convective Systems ◽

Mesoscale Convective ◽

The U.S ◽

Mcs Genesis

ABSTRACT The spatiotemporal variability and three-dimensional structures of mesoscale convective systems (MCSs) east of the U.S. Rocky Mountains and their large-scale environments are characterized across all seasons using 13 years of high-resolution radar and satellite observations. Long-lived and intense MCSs account for over 50% of warm season precipitation in the Great Plains and over 40% of cold season precipitation in the southeast. The Great Plains has the strongest MCS seasonal cycle peaking in May–June, whereas in the U.S. southeast MCSs occur year-round. Distinctly different large-scale environments across the seasons have significant impacts on the structure of MCSs. Spring and fall MCSs commonly initiate under strong baroclinic forcing and favorable thermodynamic environments. MCS genesis frequently occurs in the Great Plains near sunset, although convection is not always surface based. Spring MCSs feature both large and deep convection, with a large stratiform rain area and high volume of rainfall. In contrast, summer MCSs often initiate under weak baroclinic forcing, featuring a high pressure ridge with weak low-level convergence acting on the warm, humid air associated with the low-level jet. MCS genesis concentrates east of the Rocky Mountain Front Range and near the southeast coast in the afternoon. The strongest MCS diurnal cycle amplitude extends from the foothills of the Rocky Mountains to the Great Plains. Summer MCSs have the largest and deepest convective features, the smallest stratiform rain area, and the lowest rainfall volume. Last, winter MCSs are characterized by the strongest baroclinic forcing and the largest MCS precipitation features over the southeast. Implications of the findings for climate modeling are discussed.

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

Monthly Weather Review ◽

10.1175/mwr-d-13-00388.1 ◽

2014 ◽

Vol 142 (12) ◽

pp. 4600-4623 ◽

Cited By ~ 6

Author(s):

Abdou L. Dieng ◽

Laurence Eymard ◽

Saidou M. Sall ◽

Alban Lazar ◽

Marion Leduc-Leballeur

Keyword(s):

Radar Data ◽

West African ◽

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.

Modeling the Flash Rate of Thunderstorms. Part I: Framework

Monthly Weather Review ◽

10.1175/mwr-d-10-05031.1 ◽

2011 ◽

Vol 139 (10) ◽

pp. 3093-3111 ◽

Cited By ~ 15

Author(s):

Johannes M. L. Dahl ◽

Hartmut Höller ◽

Ulrich Schumann

Keyword(s):

Radar Data ◽

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.

Radar data assimilation for the simulation of mesoscale convective systems

Advances in Atmospheric Sciences ◽

10.1007/s00376-010-9162-8 ◽

2010 ◽

Vol 27 (5) ◽

pp. 1025-1042 ◽

Cited By ~ 10

Author(s):

Jo-Han Lee ◽

Hyun-Ha Lee ◽

Yonghan Choi ◽

Hyung-Woo Kim ◽

Dong-Kyou Lee

Keyword(s):

Data Assimilation ◽

Radar Data ◽

Convective Systems ◽

Mesoscale Convective ◽

Radar Data Assimilation

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

Artificial Satellites ◽

10.1515/arsa-2015-0007 ◽

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 ◽

Temperature Threshold ◽

The European Union ◽

Atmospheric Conditions ◽

Development Fund ◽

Convective Systems ◽

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.