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Brill, K. F.

Publications and source records attributed to Brill, K. F..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Ozone, jet streaks, and severe weather

Data obtained with the total ozone mapping spectrometer (TOMS) onboard the Nimbus-7 satellite are presented. An attempt is made to relate and synthesize TOMS data with conventional radiosonde analyses and with midtropospheric moisture data available from the VISSR onboard the GOES. Case studies are described which relate the potential vorticity structure of the upper troposphere to the total ozone distribution as measured by TOMS. Cyclogenesis, frontogenesis, and the formation of severe weather outbreaks are then related to jet streaks and their characteristic ozone signature. It is shown that the primary maxima of ozone and potential vorticity are associated with cold advection and subsidence in the main upper-air trough as suggested earlier. The secondary maxima of the three quantities diagnosed in the present work appear in the left front quadrant of a jet streak, revealing the importance of transverse, secondary motions induced by a jet streak above the level of maximum winds in further modifying the potential vorticity and ozone structures.

Sechrist, F. S.↗
NASA NTRS1985

Synoptic scale forecast skill and systematic errors in the MASS 2.0 model

The synoptic scale performance characteristics of MASS 2.0 are determined by comparing filtered 12-24 hr model forecasts to same-case forecasts made by the National Meteorological Center's synoptic-scale Limited-area Fine Mesh model. Characteristics of the two systems are contrasted, and the analysis methodology used to determine statistical skill scores and systematic errors is described. The overall relative performance of the two models in the sample is documented, and important systematic errors uncovered are presented.

Koch, S. E.↗
NASA NTRS1985

Numerical simulations of a transverse indirect circulation and low-level jet in the exit region of an upper-level jet

A numerical study was performed of a severe weather event (tornado) which occurred on May 10, 1973 in the Ohio region. The situation was modeled with a primitive equation mesoscale dynamic formulation. Account was taken of precipitation, the planetary boundary layer parameters as bulk quantities, the vertical pressure gradient, and lateral boundary conditions based on radiosonde data. Two 12-hr simulations, adiabatic and nondivergent, respectively, were analyzed for relationships between upper and lower level jets. In the adiabatic formulation, a transverse circulation with a low level jet formed at the exit region of the upper level jet. The nondivergent situation led to similar, but weaker, phenomena. Both forms suggest that indirect circulation in the exit zone of an upper level jet is strongly influenced by the initial structure of the jet.

Brill, K. F.↗
NASA NTRS1985

The Presidents' Day cyclone of 18-19 February 1979 - Influence of upstream trough amplification and associated tropopause folding on rapid cyclogenesis

The Presidents' Day cyclone of 18-19 February, 1979 is analyzed based on conventional radiosonde data, infrared and visible satellite imagery, water vapor images and ozone measurement. The well-known synoptic-scale characteristics of the PJ-trough system are described, and evidence for the development of the tropopause fold are presented. Processes contributing to the formation of the fold are discussed in terms of an evaluation of the Sawyer-Eliassen circulation equation and a diagnostic evaluation of the ageostrophic winds and vertical motion near the polar jet streak. The documentation of stratospheric extrusions and their possible role in cyclogenesis is reviewed, and Eulerian and Lagrangian diagnostics are used to establish a connection between the tropopause fold associated with the polar jet streak and rapid cyclogenesis along the East Coast. Conservation of potential vorticity expressed in isentropic coordinates is used as a constraint from which to view cyclogenesis.

Uccellini, L. W.↗
NASA NTRS1984

The Presidents' Day cyclone of 18-19 February 1979 - Synoptic overview and analysis of the subtropical jet streak influencing the pre-cyclogenetic period

A detailed examination is undertaken of the subtropical jet (STJ) streak revealed by an analysis of the Presidents' Day cyclone of February 18-19, 1979. During its 24 h period, the STJ's flow became increasingly supergeostrophic and apparently unbalanced, while ageostrophic wind speeds increased to more than 30 m/sec in association with a significant cross-contour component, directed toward lower values of the Montgomery streamfunction, as the flow along the STJ became more divergent with time. These phenomena are linked to the increasing confluence in the entrance region of the jet streak and the decreasing wavelength of the trough-ridge system in which the jet streak was embedded. The upper level divergence and upward vertical motion near the axis of the STJ are found to be important factors in the development of the cyclone's first area of heavy snow.

Uccellini, L. W.↗
NASA NTRS1984

The President's Day cyclone of 18-19 February 1979 - Influence of a tropopause fold on rapid cyclogenesis

The surface and satellite imagery data from the cyclone of February 18-19, 1979 are analyzed. Operational radiosonde data are utilized to study the tropopause fold associated with the polar jet streak. Patterns of vertical motion compatible with the tropopause fold are calculated by the diagnostic ageostrophic circulation equation of Sawyer (1956) and Eliassen (1962); the verification of the calculated patterns is described. The relationship between the stratospheric extrusion and the folded tropopause is determined by examining the potential vorticity and ozone concentrations. The influence of the stratospheric extrusion within the folded tropopause on the development of the cyclone is investigated by analyzing the potential vorticity, static stability, and absolute vorticity from the Eulerian and Lagrangian perspective.

Uccellini, L. W.↗
NASA NTRS1983

An evaluation of the synoptic- and mesoscale predictability of the Mesoscale Atmospheric Simulation System (MASS 2.0) model

A report is presented regarding the synoptic- and mesoscale predictive capabilities of a regional-scale numerical weather prediction model known as the Mesoscale Atmospheric Simulation System (MASS, Version 2.0). The development of this model has been discussed by Kaplan et al. (1982). An evaluation of the performance of MASS 2.0 is based on the study of a sample of approximately thirty 12 h and 24 h forecasts of atmospheric flow patterns over the U.S. during spring and early summer of 1982. A description of model systems is provided, and synoptic-scale evaluation methods are considered along with aspects of mesoscale evaluation methodology, examples of coherent mesoscale information provided by MASS 2.0, the results of a diagnostic study of mesoscale convective systems (MCS), and the results of a limited real-time forecast experiment.

Koch, S. E.↗