Journal of Applied Meteorology and Climatology, 2018
Several months of regional convection-permitting forecasts using two microphysical schemes (WSM6 ... more Several months of regional convection-permitting forecasts using two microphysical schemes (WSM6 and Thompson) are evaluated to determine the accuracy of the simulated convective structure and convective depth and the impact of microphysical scheme on simulated convective properties and biases. Forecasts are evaluated by using concepts from object-based approaches to compare the three-dimensional simulated reflectivity field with the reflectivity field as observed by radar. Results from analysis of both schemes reveals that forecasts generally perform well near the surface but differ considerably aloft both from observations and from each other. Forecasts are found to contain too many convective cores that are individually larger than in the observations, with at least double the number of observed convective cores reaching the midtroposphere (i.e., 4–8 km). Although the number of cores is overpredicted, WSM6 cores typically contain lower simulated reflectivity values than the obser...
During the past three years (2006-2008), a study has been conducted in Mali, located in the centr... more During the past three years (2006-2008), a study has been conducted in Mali, located in the central Sahel region of West Africa, to examine the rainfall characteristics during the summer rainy seasons (~June-October). The main objective of the study has focused on developing a precipitation climatology to better understand the natural variability and the impact on available water resources in the region. The study will examine observations of precipitation using primarily weather radar, rain gauges, and coincident satellite measurements. Radar rainfall estimates will be used to characterize the precipitation spatial variability, intensity, duration, temporal characteristics such as the diurnal cycle, orientation, patterns, frequency of storms, and other attributes to that describe the precipitation patterns in Mali. The observations will be compared with the high resolution (3-h, 0.25 deg) satellite rainfall products (e.g., TMPA, PERSIANN, CMORPH) to determine the relationship of pr...
Observations from the NASA 10 cm polarimetric Doppler weather radar (NPOL) were used to examine s... more Observations from the NASA 10 cm polarimetric Doppler weather radar (NPOL) were used to examine structure, development, and oceanic transition of West African Mesoscale Convective Systems (MCSs) during the NASA African Monsoon Multidisciplinary Analysis (NAMMA) to determine possible indicators leading to downstream tropical cyclogenesis. Characteristics examined from the NPOL data include echo-top heights, maximum radar reflectivity, height of maximum radar reflectivity, and convective and stratiform coverage areas. Atmospheric radiosondes launched during NAMMA were used to investigate environmental stability characteristics that the MCSs encountered while over land and ocean, respectively. Strengths of African Easterly Waves (AEWs) were examined along with the MCSs in order to improve the analysis of MCS characteristics. Mean structural and environmental characteristics were calculated for systems that produced TCs and for those that did not in order to determine differences betwee...
The challenges of monitoring and forecasting flash-flood-producing storm events in data-sparse an... more The challenges of monitoring and forecasting flash-flood-producing storm events in data-sparse and arid regions are explored using the Weather Research and Forecasting (WRF) Model (version 3.5) in conjunction with a range of available satellite, in situ, and reanalysis data. Here, we focus on characterizing the initial synoptic features and examining the impact of model parameterization and resolution on the reproduction of a number of flood-producing rainfall events that occurred over the western Saudi Arabian city of Jeddah. Analysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) data suggests that mesoscale convective systems associated with strong moisture convergence ahead of a trough were the major initial features for the occurrence of these intense rain events. The WRF Model was able to simulate the heavy rainfall, with driving convective processes well characterized by a high-resolution cloud-resolving model. The use of ...
One of the important goals of NASA’s Cirrus Regional Study of Tropical Anvils and Cirrus Layers–F... more One of the important goals of NASA’s Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL-FACE) was to further the understanding of the evolution of tropical anvil clouds generated by deep convective systems. An important step toward understanding the radiative properties of convectively generated anvil clouds is to study their life cycle. Observations from ground-based radar, geostationary satellite radiometers, aircraft, and radiosondes during CRYSTAL-FACE provided a comprehensive look at the generation of anvil clouds by convective systems over South Florida during July 2002. This study focused on the relationship between convective rainfall and the evolution of the anvil cloud shield associated with convective systems over South Florida on 23 July 2002, during the CRYSTAL-FACE experiment. Anvil clouds emanating from convective cells grew downwind (to the southwest), reaching their maximum area at all temperature thresholds 1–2 h afte...
Journal of Atmospheric and Oceanic Technology, 2009
This paper develops a technique for retrieving snowflake size distributions (SSDs) from a vertica... more This paper develops a technique for retrieving snowflake size distributions (SSDs) from a vertically pointing 915-MHz vertical profiler. Drop size distributions (DSDs) have been retrieved from 915-MHz profilers for several years using least squares minimization to determine the best-fit DSD to the observed Doppler spectra. This same premise is used to attempt the retrieval of SSDs. A nonlinear search, the Levenberg–Marquardt (LM) method, is used to search the physically realistic solution space and arrive at a best-fit SSD from the Doppler spectra of the profiler. The best fit is assumed to be the minimum of the squared difference of the log of the observed and modeled spectrum power over the precipitation portion of the spectrum. A snowflake video imager (SVI) disdrometer was collocated with the profiler and provided surface estimates of the SSDs. The SVI also provided estimates of crystal type, which is critical in attempting to estimate the density–size relationship. A method to ...
Journal of Atmospheric and Oceanic Technology, 2009
Herein the authors introduce the Snowflake Video Imager (SVI), which is a new instrument for char... more Herein the authors introduce the Snowflake Video Imager (SVI), which is a new instrument for characterizing frozen precipitation. An SVI utilizes a video camera with sufficient frame rate, pixels, and shutter speed to record thousands of snowflake images. The camera housing and lighting produce little airflow distortion, so SVI data are quite representative of natural conditions, which is important for volumetric data products such as snowflake size distributions. Long-duration, unattended operation of an SVI is feasible because datalogging software provides data compression and the hardware can operate for months in harsh winter conditions. Details of SVI hardware and field operation are given. Snowflake size distributions (SSDs) from a storm near Boulder, Colorado, are computed. An SVI is an imaging system, so SVI data can be utilized to compute diverse data products for various applications. In this paper, the authors present visualizations of frozen particles (i.e., snowflake ag...
Journal of Applied Meteorology and Climatology, 2009
Tropical thunderstorms produce large amounts of cirrus anvil clouds, which have a large effect on... more Tropical thunderstorms produce large amounts of cirrus anvil clouds, which have a large effect on the climate system. Modeling of the cirrus anvil is a very important factor in the driving processes in atmospheric, climate, and radiation budget models. The current research project is focused on determining the relationships between the thunderstorm intensity and cirrus anvil characteristics of storms during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL-FACE). During July 2002, 19 different storms were selected for analysis. A vertical profile of reflectivity was extracted for each cell in which the maximum reflectivity, and maximum 10- and 40-dBZ height were identified. A majority of the thunderstorms in this study were single cells or isolated multicell clusters initiated from outflow boundaries or sea-breeze interactions. The results show that a general thunderstorm life cycle characteristic time sequence was determined, fin...
Journal of Applied Meteorology and Climatology, 2018
Several months of regional convection-permitting forecasts using two microphysical schemes (WSM6 ... more Several months of regional convection-permitting forecasts using two microphysical schemes (WSM6 and Thompson) are evaluated to determine the accuracy of the simulated convective structure and convective depth and the impact of microphysical scheme on simulated convective properties and biases. Forecasts are evaluated by using concepts from object-based approaches to compare the three-dimensional simulated reflectivity field with the reflectivity field as observed by radar. Results from analysis of both schemes reveals that forecasts generally perform well near the surface but differ considerably aloft both from observations and from each other. Forecasts are found to contain too many convective cores that are individually larger than in the observations, with at least double the number of observed convective cores reaching the midtroposphere (i.e., 4–8 km). Although the number of cores is overpredicted, WSM6 cores typically contain lower simulated reflectivity values than the obser...
During the past three years (2006-2008), a study has been conducted in Mali, located in the centr... more During the past three years (2006-2008), a study has been conducted in Mali, located in the central Sahel region of West Africa, to examine the rainfall characteristics during the summer rainy seasons (~June-October). The main objective of the study has focused on developing a precipitation climatology to better understand the natural variability and the impact on available water resources in the region. The study will examine observations of precipitation using primarily weather radar, rain gauges, and coincident satellite measurements. Radar rainfall estimates will be used to characterize the precipitation spatial variability, intensity, duration, temporal characteristics such as the diurnal cycle, orientation, patterns, frequency of storms, and other attributes to that describe the precipitation patterns in Mali. The observations will be compared with the high resolution (3-h, 0.25 deg) satellite rainfall products (e.g., TMPA, PERSIANN, CMORPH) to determine the relationship of pr...
Observations from the NASA 10 cm polarimetric Doppler weather radar (NPOL) were used to examine s... more Observations from the NASA 10 cm polarimetric Doppler weather radar (NPOL) were used to examine structure, development, and oceanic transition of West African Mesoscale Convective Systems (MCSs) during the NASA African Monsoon Multidisciplinary Analysis (NAMMA) to determine possible indicators leading to downstream tropical cyclogenesis. Characteristics examined from the NPOL data include echo-top heights, maximum radar reflectivity, height of maximum radar reflectivity, and convective and stratiform coverage areas. Atmospheric radiosondes launched during NAMMA were used to investigate environmental stability characteristics that the MCSs encountered while over land and ocean, respectively. Strengths of African Easterly Waves (AEWs) were examined along with the MCSs in order to improve the analysis of MCS characteristics. Mean structural and environmental characteristics were calculated for systems that produced TCs and for those that did not in order to determine differences betwee...
The challenges of monitoring and forecasting flash-flood-producing storm events in data-sparse an... more The challenges of monitoring and forecasting flash-flood-producing storm events in data-sparse and arid regions are explored using the Weather Research and Forecasting (WRF) Model (version 3.5) in conjunction with a range of available satellite, in situ, and reanalysis data. Here, we focus on characterizing the initial synoptic features and examining the impact of model parameterization and resolution on the reproduction of a number of flood-producing rainfall events that occurred over the western Saudi Arabian city of Jeddah. Analysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) data suggests that mesoscale convective systems associated with strong moisture convergence ahead of a trough were the major initial features for the occurrence of these intense rain events. The WRF Model was able to simulate the heavy rainfall, with driving convective processes well characterized by a high-resolution cloud-resolving model. The use of ...
One of the important goals of NASA’s Cirrus Regional Study of Tropical Anvils and Cirrus Layers–F... more One of the important goals of NASA’s Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL-FACE) was to further the understanding of the evolution of tropical anvil clouds generated by deep convective systems. An important step toward understanding the radiative properties of convectively generated anvil clouds is to study their life cycle. Observations from ground-based radar, geostationary satellite radiometers, aircraft, and radiosondes during CRYSTAL-FACE provided a comprehensive look at the generation of anvil clouds by convective systems over South Florida during July 2002. This study focused on the relationship between convective rainfall and the evolution of the anvil cloud shield associated with convective systems over South Florida on 23 July 2002, during the CRYSTAL-FACE experiment. Anvil clouds emanating from convective cells grew downwind (to the southwest), reaching their maximum area at all temperature thresholds 1–2 h afte...
Journal of Atmospheric and Oceanic Technology, 2009
This paper develops a technique for retrieving snowflake size distributions (SSDs) from a vertica... more This paper develops a technique for retrieving snowflake size distributions (SSDs) from a vertically pointing 915-MHz vertical profiler. Drop size distributions (DSDs) have been retrieved from 915-MHz profilers for several years using least squares minimization to determine the best-fit DSD to the observed Doppler spectra. This same premise is used to attempt the retrieval of SSDs. A nonlinear search, the Levenberg–Marquardt (LM) method, is used to search the physically realistic solution space and arrive at a best-fit SSD from the Doppler spectra of the profiler. The best fit is assumed to be the minimum of the squared difference of the log of the observed and modeled spectrum power over the precipitation portion of the spectrum. A snowflake video imager (SVI) disdrometer was collocated with the profiler and provided surface estimates of the SSDs. The SVI also provided estimates of crystal type, which is critical in attempting to estimate the density–size relationship. A method to ...
Journal of Atmospheric and Oceanic Technology, 2009
Herein the authors introduce the Snowflake Video Imager (SVI), which is a new instrument for char... more Herein the authors introduce the Snowflake Video Imager (SVI), which is a new instrument for characterizing frozen precipitation. An SVI utilizes a video camera with sufficient frame rate, pixels, and shutter speed to record thousands of snowflake images. The camera housing and lighting produce little airflow distortion, so SVI data are quite representative of natural conditions, which is important for volumetric data products such as snowflake size distributions. Long-duration, unattended operation of an SVI is feasible because datalogging software provides data compression and the hardware can operate for months in harsh winter conditions. Details of SVI hardware and field operation are given. Snowflake size distributions (SSDs) from a storm near Boulder, Colorado, are computed. An SVI is an imaging system, so SVI data can be utilized to compute diverse data products for various applications. In this paper, the authors present visualizations of frozen particles (i.e., snowflake ag...
Journal of Applied Meteorology and Climatology, 2009
Tropical thunderstorms produce large amounts of cirrus anvil clouds, which have a large effect on... more Tropical thunderstorms produce large amounts of cirrus anvil clouds, which have a large effect on the climate system. Modeling of the cirrus anvil is a very important factor in the driving processes in atmospheric, climate, and radiation budget models. The current research project is focused on determining the relationships between the thunderstorm intensity and cirrus anvil characteristics of storms during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL-FACE). During July 2002, 19 different storms were selected for analysis. A vertical profile of reflectivity was extracted for each cell in which the maximum reflectivity, and maximum 10- and 40-dBZ height were identified. A majority of the thunderstorms in this study were single cells or isolated multicell clusters initiated from outflow boundaries or sea-breeze interactions. The results show that a general thunderstorm life cycle characteristic time sequence was determined, fin...
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Papers by Paul Kucera