Brad S. Ferrier

Shipboard Radar Rainfall Patterns within the TOGA COARE IFA

Abstract Radar rainfall measurements over the equatorial western Pacific warm pool were collected by two shipboard Doppler radars as part of the Tropical Oceans Global Atmosphere Coupled Ocean–Atmosphere Response Experiment during the intensive observing period (November 1992–February 1993). A comprehensive dataset of gridded rainfall fields, convective/stratiform identification maps, and vertical structure products has been produced, covering an area approximately 400 km (E–W) by 300 km (N–S) within the Intensive Flux Array (IFA), centered near 2°S, 156°E. The radar rainfall product, which was used as validation for the Third Algorithm Intercomparison Project of the Global Precipitation Climatology Project, indicates an overall average of 4.8 mm day−1; however, correction for range dependence increases the total to 5.4 mm day−1. Rainfall patterns varied considerably during the experiment with isolated convection dominating periods of light winds, while squall lines and organized mesoscale systems were ab...

A Double-Moment Multiple-Phase Four-Class Bulk Ice Scheme. Part II: Simulations of Convective Storms in Different Large-Scale Environments and Comparisons with other Bulk Parameterizations

Abstract Part I of this study described a detailed four-class bulk ice scheme (4ICE) developed to simulate the hydro-meteor profiles of convective and stratiform precipitation associated with mesoscale convective systems. In Part II, the 4ICE scheme is incorporated into the Goddard Cumulus Ensemble (GCE) model and applied without any “tuning” to two squall lines occurring in widely different environments, namely, one over the “Pica) ocean in the Global Atmospheric Research Programs (GARP) Atlantic Tropical Experiment (GATE) and the other over a midlatitude continent in the Cooperative Huntsville Meteorological Experiment (COHMEX). Comparisons were made both with earlier three-class ice formulations and with observations. In both cases, the 4ICE scheme interacted with the dynamics so as to resemble the observations much more closely than did the model runs with either of the three-class ice parameterizations. The following features were well simulated in the COHMEX case: a lack of stratiform rain at the s...

Factors Responsible for Precipitation Efficiencies in Midlatitude and Tropical Squall Simulations

Abstract Different definitions of storm precipitation efficiency were investigated from numerical simulators of convective systems in widely varying ambient conditions using a two-dimensional cloud model with sophisticated ice microphysics. The model results indicate that the vertical orientation of the updrafts, which is controlled by the vertical wind shear, and the ambient moisture content are important in determining storm efficiency. In terms of rainfall divided by condensation, simulated efficiencies ranged from 20%–35% for convective systems that tilted strongly against the low-level shear (upshear), to 40%–50% for erect storms. Changes in environmental moisture produced smaller variations in efficiency that were less than 10%. Upright convection allows for effective collection of cloud condensate by precipitation, whereas lower efficiencies in upshear storms are due to greater evaporation of cloud at middle levels and evaporation of rain at lower levels. Development of trailing stratiform precipit...

Shipborne Dual-Doppler Operations during TOGA COARE: Integrated Observations of Storm Kinematics and Electrification

Abstract Shipborne Doppler radar operations were conducted over the western Pacific warm pool during TOGA COARE using the Massachusetts Institute of Technology and NOAA TOGA C-band Doppler radars. Occasionally the ships carrying these radars were brought to within 50 km of each other to conduct coordinated dual-Doppler scanning. The dual-Doppler operations were considered a test of the logistical and engineering constraints associated with establishing a seagoing dual-Doppler configuration. A very successful dual-Doppler data collection period took place on 9 February 1993 when an oceanic squall line developed, intensified, and propagated through the shipborne dual-Doppler lobes. Later on the same day, NOAA P-3 aircraft sampled a more intense squall line located approximately 400 km to the southeast of the shipborne operations. This study provides an overview of the shipborne dual-Doppler operations, followed by a comparison of the kinematic and precipitation structures of the convective systems sampled b...

The Effect of Melting Processes on the Development of a Tropical and a Midlatitude Squall Line

Abstract Several sensitivity tests are performed to assess the effect of melting processes on the development of a midlatitude continental squall line and a tropical oceanic squall line. It is found that melting processes play an important role in the structure of a midlatitude continental squall system. For the maritime tropical case, squall development is not as sensitive to the presence of melting, due to the dominance of warm rain processes. Melting processes exert an influence on midlatitude cloud system development through the conversion of ice particles to rain. The simulated convective system was found to be much weaker in the absence of evaporative cooling by rain. For a given vertical shear of horizontal wind, cooling by evaporation in the convective region was found to be essential for maintaining a long-lived cloud system. Diabatic cooling by melting played only a secondary role in this respect. In the absence of melting processes, the simulated mildlatitude squall system acquired the characte...

Ice Fog in Arctic During FRAM–Ice Fog Project: Aviation and Nowcasting Applications

Ice fog and frost occur commonly (at least 26% of the time) in the northern latitudes and Arctic regions during winter at temperatures usually less than about –15°C. Ice fog is strongly related to frost formation—a major aviation hazard in the northern latitudes. In fact, it may be considered a more dangerous event than snow because of the stronger aircraft surface adhesion compared to snow particles. In the winter of 2010/11, the Fog Remote Sensing and Modeling–Ice Fog (FRAM-IF) project was organized near Yellowknife International Airport, Northwest Territories, Canada, with the main goals of advancing understanding of ice fog microphysical and visibility characteristics, and improving its prediction using forecast models and remotesensing retrievals. Approximately 40 different sensors were used to measure visibility, precipitation, ice particle spectra, vertical thermodynamic profiles, and ceiling height. Fog coverage and visibility parameters were estimated using both Geostationary Operational Environm...

Rainfall Morphology in Florida Convergence Zones: A Numerical Study

Abstract Central Florida is the ideal test laboratory for studying convergence zone–induced convection. The region regularly experiences sea-breeze fronts and rainfall-induced outflow boundaries. The focus of this study is convection associated with the commonly occurring convergence zone established by the interaction of the sea-breeze front and an outflow boundary. Previous studies have investigated mechanisms primarily affecting storm initiation by such convergence zones. Few have focused on rainfall morphology, yet these storms contribute a significant amount of precipitation to the annual rainfall budget. Low-level convergence and midtropospheric moisture have been shown to be correlated with rainfall amounts in Florida. Using 2D and 3D numerical simulations, the roles of low-level convergence and midtropospheric moisture in rainfall evolution are examined. The results indicate that area- and time-averaged, vertical moisture flux (VMF) at the sea-breeze front–outflow convergence zone is directly and ...

An Ensemble of Convective Systems on 11 February 1993 during TOGA COARE:Morphology, Rainfall Characteristics, and Anvil Cloud Interactions

Abstract An active day during the Coupled Ocean–Atmosphere Response Experiment (COARE) Intensive Observation Period (IOP) is examined in which nine convective systems evolved and moved eastward across the region of shipboard radar coverage in the Intensive Flux Array (IFA) within westerly wind burst conditions. The detailed genesis, morphology, and interactions between these cloud systems are documented from a radar and satellite perspective. One of these systems was a large and complex elliptical cluster, among the largest observed during the Tropical Ocean Global Atmosphere COARE. Multiple, parallel deep convective lines spaced 20–30 km apart and embedded within this system were initially oriented from north-northwest to south-southeast, oblique to the storm motion. Furthermore, the lines underwent counterclockwise realignment as the system moved eastward. The influence of strong lower-tropospheric directional and speed shear on these convective system properties is examined in the context of a dynamic,...

The New England High-Resolution Temperature Program

Abstract The New England High-Resolution Temperature Program seeks to improve the accuracy of summertime 2-m temperature and dewpoint temperature forecasts in the New England region through a collaborative effort between the research and operational components of the National Oceanic and Atmospheric Administration (NOAA). The four main components of this program are 1) improved surface and boundary layer observations for model initialization, 2) special observations for the assessment and improvement of model physical process parameterization schemes, 3) using model forecast ensemble data to improve upon the operational forecasts for near-surface variables, and 4) transfering knowledge gained to commercial weather services and end users. Since 2002 this program has enhanced surface temperature observations by adding 70 new automated Cooperative Observer Program (COOP) sites, identified and collected data from over 1000 non-NOAA mesonet sites, and deployed boundary layer profilers and other special instrum...

Establishing Closer Collaboration to Improve Model Physics for Short-Range Forecasts

AffiliAtions: Wolff—research applications laboratory, national Center for atmospheric research, and developmental testbed Center, boulder, Colorado; ferrier—national Centers for Environmental prediction/Environmental modeling Center, Camp springs, maryland; maSS—University of Washington, seattle, Washington Corresponding Author: Jamie K. Wolff, ral, nCar, p.o. box 3000, boulder, Co 80307-3000 E-mail: jwolff@ucar.edu