scholarly journals An Intercomparison of Simulated Rainfall and Evapotranspiration Associated with a Mesoscale Convective System over West Africa

2010 ◽  
Vol 25 (1) ◽  
pp. 37-60 ◽  
Author(s):  
Françoise Guichard ◽  
Nicole Asencio ◽  
Christophe Peugeot ◽  
Olivier Bock ◽  
Jean-Luc Redelsperger ◽  
...  
Keyword(s):  
West Africa ◽  
Land Surface ◽  
Mesoscale Convective System ◽  
Precipitable Water ◽  
Horizontal Resolution ◽  
Surface Energy Budget ◽  
Convective System ◽  
Land Surface Modeling ◽  
Multidisciplinary Analysis ◽  
Mesoscale Convective

Abstract An evaluation of precipitation and evapotranspiration simulated by mesoscale models is carried out within the African Monsoon Multidisciplinary Analysis (AMMA) program. Six models performed simulations of a mesoscale convective system (MCS) observed to cross part of West Africa in August 2005. Initial and boundary conditions are found to significantly control the locations of rainfall at synoptic scales as simulated with either mesoscale or global models. When initialized and forced at their boundaries by the same analysis, all models forecast a westward-moving rainfall structure, as observed by satellite products. However, rainfall is also forecast at other locations where none was observed, and the nighttime northward propagation of rainfall is not well reproduced. There is a wide spread in the rainfall rates across simulations, but also among satellite products. The range of simulated meridional fluctuations of evapotranspiration (E) appears reasonable, but E displays an overly strong zonal symmetry. Offline land surface modeling and surface energy budget considerations show that errors in the simulated E are not simply related to errors in the surface evaporative fraction, and involve the significant impact of cloud cover on the incoming surface shortwave flux. The use of higher horizontal resolution (a few km) enhances the variability of precipitation, evapotranspiration, and precipitable water (PW) at the mesoscale. It also leads to a weakening of the daytime precipitation, less evapotranspiration, and smaller PW amounts. The simulated MCS propagates farther northward and somewhat faster within an overall drier atmosphere. These changes are associated with a strengthening of the links between PW and precipitation.

scholarly journals A mesoscale convective system trapped along the Spanish Mediterranean Coast

2006 ◽  
Vol 7 ◽  
pp. 153-156 ◽  
Author(s):  
J. M. Sánchez-Laulhé
Keyword(s):  
Convective Instability ◽  
Heavy Rainfall ◽  
Vertical Wind Shear ◽  
Mesoscale Convective System ◽  
Precipitable Water ◽  
Mediterranean Coast ◽  
Convective System ◽  
Convective Storm ◽  
Low Level ◽  
Mesoscale Convective

Abstract. This paper describes the evolution of a mesoscale convective system (MCS) developed over the Alboran Sea on 7 February 2005, using surface, upper-air stations, radar and satellite observations, and also data from an operational numerical model. The system developed during the night as a small convective storm line in an environment with slight convective instability, low precipitable water and strong low-level vertical wind shear near coast. The linear MCS moved northwards reaching the Spanish coast. Then it remained trapped along the coast for more than twelve hours, following the coast more than five hundred kilometres. The MCS here described had a fundamental orographic character due to: (1) the generation of a low-level storm inflow parallel to the coast, formed by blocking of the onshore flow by coastal mountains and (2) the orientation of both the mesoscale ascent from the sea towards the coastal mountains and the midlevel rear inflow from the coastal mountains to the sea. The main motivation of this work was to obtain a better understanding of the mechanisms relevant to the formation of heavy rainfall episodes occurring at Spanish Mediterranean coast associated with this kind of stationary or slowly moving MCSs.

Impact of vegetation changes on a mesoscale convective system in West Africa

2010 ◽  
Vol 107 (3-4) ◽  
pp. 109-122 ◽  
Author(s):  
D. Lauwaet ◽  
N. P. M. van Lipzig ◽  
N. Kalthoff ◽  
K. De Ridder
Keyword(s):  
West Africa ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Vegetation Changes ◽  
Mesoscale Convective

Convergence zones and their impact on the initiation of a mesoscale convective system in West Africa

2011 ◽  
Vol 138 (665) ◽  
pp. 950-963 ◽  
Author(s):  
Vera Klüpfel ◽  
Norbert Kalthoff ◽  
Leonhard Gantner ◽  
Christopher M. Taylor
Keyword(s):  
West Africa ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Mesoscale Convective ◽  
Convergence Zones

scholarly journals Comparison of Airborne and Spaceborne 95-GHz Radar Reflectivities and Evaluation of Multiple Scattering Effects in Spaceborne Measurements

2008 ◽  
Vol 25 (11) ◽  
pp. 1983-1995 ◽  
Author(s):  
Dominique Bouniol ◽  
Alain Protat ◽  
Artemio Plana-Fattori ◽  
Manuel Giraud ◽  
Jean-Paul Vinson ◽  
...  
Keyword(s):  
Multiple Scattering ◽  
Mesoscale Convective System ◽  
Supercooled Liquid ◽  
Convective System ◽  
Convective Systems ◽  
Multidisciplinary Analysis ◽  
Mesoscale Convective ◽  
Ice Water Content ◽  
Radar Calibration ◽  
Ice Water

Abstract This paper provides an evaluation of the level 1 (reflectivity) CloudSat products by making use of coincident measurements collected by an airborne 95-GHz radar during the African Monsoon Multidisciplinary Analysis (AMMA) experiment that took place in summer 2006 over West Africa. In a first step the airborne radar calibration is assessed. Collocated measurements of the spaceborne and airborne radars within the ice anvil of a mesoscale convective system are then compared. Several aspects are interesting in this comparison: First, both instruments exhibit attenuation within the ice part of the convective system, which suggests either the presence of a significant amount of supercooled liquid water above the melting layer or the presence of wet and very dense ice. Second, from the differences in the observed reflectivity values, a multiple scattering enhancement of at least 2.5 dB in the CloudSat reflectivities at flight altitude is estimated. The main conclusion of this paper is that in such thick anvils of mesoscale convective systems the CloudSat measurements have to be corrected for this effect, if one wants to derive accurate level 2 products such as the ice water content from radar reflectivity. This effect is expected to be much smaller in nonprecipitating clouds though.

Ensemble Probabilistic Prediction of a Mesoscale Convective System and Associated Polarimetric Radar Variables Using Single-Moment and Double-Moment Microphysics Schemes and EnKF Radar Data Assimilation

2017 ◽  
Vol 145 (6) ◽  
pp. 2257-2279 ◽  
Author(s):  
Bryan J. Putnam ◽  
Ming Xue ◽  
Youngsun Jung ◽  
Nathan A. Snook ◽  
Guifu Zhang
Keyword(s):  
Mesoscale Convective System ◽  
Radar Data ◽  
Convective Precipitation ◽  
Convective System ◽  
Ensemble Forecasts ◽  
Verification Methods ◽  
Probabilistic Forecasts ◽  
Mesoscale Convective ◽  
Single Moment ◽  
Double Moment

Abstract Ensemble-based probabilistic forecasts are performed for a mesoscale convective system (MCS) that occurred over Oklahoma on 8–9 May 2007, initialized from ensemble Kalman filter analyses using multinetwork radar data and different microphysics schemes. Two experiments are conducted, using either a single-moment or double-moment microphysics scheme during the 1-h-long assimilation period and in subsequent 3-h ensemble forecasts. Qualitative and quantitative verifications are performed on the ensemble forecasts, including probabilistic skill scores. The predicted dual-polarization (dual-pol) radar variables and their probabilistic forecasts are also evaluated against available dual-pol radar observations, and discussed in relation to predicted microphysical states and structures. Evaluation of predicted reflectivity (Z) fields shows that the double-moment ensemble predicts the precipitation coverage of the leading convective line and stratiform precipitation regions of the MCS with higher probabilities throughout the forecast period compared to the single-moment ensemble. In terms of the simulated differential reflectivity (ZDR) and specific differential phase (KDP) fields, the double-moment ensemble compares more realistically to the observations and better distinguishes the stratiform and convective precipitation regions. The ZDR from individual ensemble members indicates better raindrop size sorting along the leading convective line in the double-moment ensemble. Various commonly used ensemble forecast verification methods are examined for the prediction of dual-pol variables. The results demonstrate the challenges associated with verifying predicted dual-pol fields that can vary significantly in value over small distances. Several microphysics biases are noted with the help of simulated dual-pol variables, such as substantial overprediction of KDP values in the single-moment ensemble.

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