Search Results

You are looking at 1 - 10 of 91 items for

  • Author or Editor: T. Lee x
  • All content x
Clear All Modify Search
JEAN T. LEE

Abstract

No Abstract Available.

Full access
J. T. LEE

Abstract

No Abstract Available.

Full access
Matthew T. Boehm and Sukyoung Lee

Abstract

This study puts forward a mechanism for the observed upwelling in the tropical upper troposphere and lower stratosphere. In this hypothesis, the tropical upwelling is driven by momentum transport by Rossby waves that are generated by tropical convection. To test this hypothesis, model runs are conducted using an axisymmetric, global, primitive equation model. In these runs, the effect of Rossby waves is included by driving the model with observed fields of large-scale eddy momentum flux convergence. The resulting overturning circulation includes both meridional flow from the intertropical convergence zone (ITCZ) to the equator and rising motion in the tropical tropopause transition layer (TTL). This circulation therefore helps to explain the transport of moisture from the lower portion of the TTL in the ITCZ to the equatorial cold-point tropopause, where tropopause cirrus layers frequently occur.

Full access
Jean T. Lee and Joseph G. Galway

In a previous paper [5] the authors have indicated the observed relationship between the jet at 200 mb, the −60C isotherm at 200 mb and tornado occurrences. The location of this jet has become important in severe local storm forecasting procedures. Often, the lack of a band of strong winds at 500 mb, especially during the summer months, made this level ineffective as an aid in locating the jet some height above. The 20-mb data are not transmitted until more than six hours after time of observation; thus, the formulation of a chart which is not a constant-pressure chart and called by SELS “The JET CHART” was conceived to remedy this situation. The preparation, analysis, and use of this chart in severe local weather forecasting are set forth here.

Full access
D. C. House and J. T. Lee

A study into the possibility of extreme turbulence occurring in a particular synoptic situation is discussed here. The synoptic weather data are reviewed, and the magnitude of turbulence that might be expected is computed by two different methods. The limitations of each method are discussed. While it might be concluded that thunderstorm updraft velocities were of the order of those producing extreme turbulence, the assumptions are so restrictive that it is not possible to assign confidence limits to the computed gust velocities.

Full access
J. T. Lee and Clarence L. David

This paper is a description of the Tornado Research Airplane Project during 1958 and 1959. The instrumentation of the aircraft, as well as the organization of the project, is described. A section on instrument calibration and a description of data reduction and processing are included. The results of a radiosonde comparison test made in 1959 are given, and these results are compared with the results of radiosonde comparison tests made during 1958. A sample of the graphical presentation that is available for each of the flights is shown. For the information of anyone interested in these data, a listing of all operational flights for both 1958 and 1959 is given.

Full access
Jean T. Lee and Joseph G. Galway

In a study of the 200-mb Height Chart and associated jet to determine their usefulness in tornado forecasting, a consistent phenomenon was observed, namely, that the majority of tornadoes investigated occurred along or near the −60°C isotherm at 200-mb. More precisely, the western and southern portions of the −60°C isotherm of the cold “pool” it circumscribed were the favored area. The jet at 200-mb in most cases delineated that portion of the −60°C isotherm under which tornadoes occurred. Further, certain consistencies appeared on the tropopause chart that might be related with tornado occurrence.

Full access
Jean T. Lee and Clarence L. David

Tornado aircraft research data collected during the period 1956 to 1959 have been used to depict a possible mean cross-section of the squall line during three different stages of development. They are the pre-cloud stage, the cumulus stage and the thunderstorm stage. The limitations of the data and the need for further development of the model are indicated.

Full access
Isaac M. Held, Raymond T. Pierrehumbert, and R. Lee Panetta

Abstract

External Rossby waves in vertical shear can be destabilized by thermal damping. They can also be destabilized by damping of potential vorticity if this damping is larger in the lower than in the upper troposphere. Results are described in detail for Charney's model. Implications for the effects of diabatic heating and mixing due to smaller scale transients on equivalent barotropic stationary or quasi-stationary long waves are discussed. It is painted out that energy or potential enstrophy budgets may indicate that transients are damping the long waves while, in fact, their presence is destabilizing these waves.

Full access
J. Turk, J. Vivekanandan, T. Lee, P. Durkee, and K. Nielsen

Abstract

Recent deployments of the National Oceanic and Atmospheric Administration (NOAA) Geostationary Operational Environmental Satellites (GOES-8 and -9) include full-time 3.9-μm imaging capabilities. This shortwave (near infrared) channel has been available at 3.7 μm on the Advanced Very High Resolution Radiometer (AVHRR) instrument aboard the NOAA polar-orbiting satellite systems. In this spectral region, daytime satellite-observed radiances include contributions from both the reflected solar radiation and the emitted thermal emission. In particular, typical stratus and fog clouds posess near-infrared emissivities less than unity, which requires special processing to account for the angular dependence of the solar reflection. In this paper, a side-by-side comparison of time-coincident GOES- and AVHRR-derived near-infrared cloud reflectance is carried out in order to demonstrate the capability of GOES-8 and -9 in both identifying and characterizing the microphysics of stratus and fog clouds during the daytime.

The authors first present the mathematical formalism and then apply the technique to extract the near-infrared reflectances from GOES-8 and -9 data. The technique is applicable for operational usage and requires a lookup table to account for the continuously changing sun-satellite viewing geometry. Near-infrared cloud reflectances are extracted from coincident GOES-9 and AVHRR data from both NOAA-14 and -12 for different times of day and are verified against theoretical reflectances derived from radiative transfer theory and previously published results. A retrieval of the cloud drop size distribution effective radius is demonstrated on satellite data along coastal California during the summer of 1996.

Full access