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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Applications of the AVE-Sesame data sets to mesoscale studies

Data collected by the lightning data concentrator are available for research. The Mark 3 McIDAS capability provides greater flexibility for the Marshall user community and serves as a model of future UW McIDAS to remote computer links. Techniques were investigated for the display of dynamic 3-D data sets. To date the most promising display technology is a polarized two CRT perspective display which allows both dynamic 3-D images and graphics presentations with full color capability. Algorithms were for the preparation and display of conventional and satellite based weather data in 3-D. These include gridding, contouring, and streamlining processors which operate on both real time and case study data bases. An upper air trajectory model was implemented which creates a display of air parcel trajectories in perspective 3-D. A subsystem for the generation of 3-D solid surface display with shading and hidden surface display with shading and hidden surface removal was tested and its products are currently being evaluated. Motion parallax introduced by moving the point of observation during display is an important depth cue, which, when added to the perspective parallax creates a very realistic appearing display.

Suomi, V. E.↗
NASA NTRS1982

A high-resolution model of the planetary boundary layer - Sensitivity tests and comparisons with SESAME-79 data

A one-dimensional, planetary boundary layer (PBL) model is presented and verified using April 10, 1979 SESAME data. The model contains two modules to account for two different regimes of turbulent mixing. Separate parameterizations are made for stable and unstable conditions, with a predictive slab model for surface temperature. Atmospheric variables in the surface layer are calculated with a prognostic model, with moisture included in the coupled surface/PBL modeling. Sensitivity tests are performed for factors such as moisture availability, albedo, surface roughness, and thermal capacity, and a 24 hr simulation is summarized for day and night conditions. The comparison with the SESAME data comprises three hour intervals, using a time-dependent geostrophic wind. Close correlations were found with daytime conditions, but not in nighttime thermal structure, while the turbulence was faithfully predicted. Both geostrophic flow and surface characteristics were shown to have significant effects on the model predictions

Zhang, D.↗
NASA NTRS1982

Initial results from a mesoscale atmospheric simulation system and comparisons with the AVE-SESAME I data set

The development of a comprehensive mesoscale atmospheric simulation system (MASS) is described in detail. The modeling system is designed for both research and real-time forecast applications. The 14-level numerical model, which has a 48 km grid mesh, can be run over most of North America and the adjacent oceanic regions. The model employs sixth-order accurate numerics, generalized similarity theory boundary-layer physics, a sophisticated cumulus parameterization scheme, and state of the art analysis and initialization techniques. Examples of model output on the synoptic and subsynoptic scales are presented for the AVE-SESAME I field experiment on 10-11 April 1979. The model output is subjectively compared to the observational analysis and the LFM II output on the synoptic scale. Subsynoptic model output is compared to analyses generated from the AVE-SESAME I data set.

Kaplan, M. L.↗
NASA NTRS1980

Analysis and prediction of severe storms environment

Using the special data set collected in Project SESAME (1979), an analysis and modeling efforts to test the hypothesis that a unique combination of terrain, boundary layer processes, and synoptic-scale circulations result in a preferred region of latent instability that determines the location of severe thunderstorm outbreaks are described. Because the relevant circulations are large scale, it is hypothesized that a model that contains the necessary physics will be able to predict the location of these severe storms at least 24 h in advance. Through detailed analysis of the SESAME data set and a series of numerical forecasts, the above hypothesis is being tested and it is hoped that quantitative understanding of the processes leading to the development of severe thunderstorms in the midwestern United States will be gained.

Carlson, T. N.↗
NASA NTRS1982

A comparison of adiabatic and kinematic vertical motions using mesoscale data

Results are compared from the adiabatic and kinematic methods of determining vertical motion during a period of severe convective storms when special meso alpha-scale rawinsonde data were available. The two procedures were tested using data from the first regional-scale day of AVE-SESAME '79 which coincided with the Red River Valley tornado outbreak of April 10-11, 1979. At 700 mb, each technique showed good agreement with the weather patterns, but the kinematic procedure gave superior results at 500 mb. The overall goodness of the adiabatic method during this particular case was not solely due to the high-resolution SESAME data since synoptic-scale mechanisms played a major role in creating a storm-conducive environment. With the advent of computer aided analysis systems such as AFOS, forecasters will have quicker access to a greater variety of information. Present results suggest that the adiabatic method can yield useful information for severe storm forecasters, especially in the lower troposphere. An interesting follow-on study would use sounding data from geostationary VAS satellites to compute adiabatic vertical motions at finer time and space resolutions than is now possible using RAOB data alone. Geostrophic winds derived from satellite thermal data probably can be used.

Fuelberg, H. E.↗
NASA NTRS1984

Accuracy of diagnostic heat and moisture budgets using SESAME-79 field data as revealed by observing system simulation experiments

Observing system simulation experiments are used to investigate the accuracy of diagnostic heat and moisture budgets which employ the AVE-SESAME 1979 data. The time-including, four-dimensional data set of a mesoscale model is used to simulate rawinsonde observations from AVE-SESAME 1979. The 5 C/day (heat budget) and 2 g/kg per day (moisture budget) magnitudes of error obtained indicate difficulties in the diagnosis of the heating rate in weak convective systems. The influences exerted by observational frequency, objective analysis, observational density, vertical interpolation, and observational errors on the budget are also studied, and it is found that the temporal and spatial resolution of the SESAME regional network is marginal for diagnosing convective effects on a horizontal time scale of 550 x 550 km.

Kuo, Y.-H.↗
NASA NTRS1986

Application of satellite data to the variational analysis of the three dimensional wind field

The use of a hybrid vertical velocity algorithm, composed of the kinematic and adiabatic methods of Pettersen (1956), to analyze three-dimensional wind fields is studied. The basic principles and advantages and disadvantages of the adiabatic and kinematic techniques are discussed. The adiabatic method is useful in the clear regions and above the tropopause and the kinematic method is applicable near the surface and in cloudy regions. The effects of a finite difference scheme and the objective analysis of Barnes (1973) on a wind field are investigated. The variational algorithm is evaluated by applying it to SESAME data collected in April 1979.

Chance, Barbara A.↗
NASA NTRS1981

Mesoscale aspects of jet streak coupling and implications for the short term forecasting of severe convective storms

An analysis of a tornado outbreak in Wichita Falls, Texas was analyzed. The coupling of upper and lower tropospheric jet streaks, leading to severe storm outbreaks is illustrated. The high resolution SESAME data sets indicate that mass and momentum adjustments which couple upper and lower tropospheric jets occur within a 3 to 6 hr time frame over a 100 to 500 km domain, and establish the role of isallobaric forcing in the storm development. It is suggested that the output rate of data from the existing 12 hr network be increased to provide better temporal resolution of wind, mass and moisture data.

Uccellini, L. W.↗
NASA NTRS1980

AVE-Sesame 3: 25-MB sounding data

The rawinsonde sounding program for the AVE-SESAME 3 experiment is described and tabulated data at 25-mb intervals from the surface to 25 mb for the 23 National Weather Service and 19 special stations participating in the experiment are presented. Soundings were taken at 3 hr intervals beginning at 1200 GMT on April 25, 1979, and ending at 1200 GMT on April 26, 1979 (nine sounding times). The method of processing is discussed briefly, estimates of the rms errors in the data presented, an example of contact data given, reasons given for the termination of soundings below 100 mb, and soundings listed which exhibit abnormal characteristics.

Williams, S. T.↗
NASA NTRS1980

AVE-SESAME IV: 25 mb sounding data

The rawinsonde sounding program for the AVE-SESAME 4 experiment is descirbed and tabulated data at 25 mb for the 23 National Weather Service and 20 special stations participating in the experiment are presented. Soundings were taken at 3 hr intervals beginning at 1200 GMT on May 9, 1979, and ending at 1200 GMT on May 10, 1979 (nine sounding times). The method of processing is discussed, estimates of the rms errors in the data are presented, and an example of contact data is given. Reasons are given for the termination of soundings below 100 mb, and soundings are listed which exhibit abnormal characteristics.

Sienkiewicz, M. E.↗
NASA NTRS1981

AVE-SESAME 6: 25-MB sounding data

The rawinsonde sounding program for the AVE-SESAME 6 experiment is described and tabulated data at 25 mb intervals from the surface to 25 mb for the 23 National Weather Service and 15 special stations participating in the experiment are presented. Soundings were taken at 3 h intervals beginning at 1200 GMT on June 7, 1979, and ending at 1200 GMT on June 8, 1979 (nine sounding times). The method of processing is discussed briefly, estimates of the rms errors in the data presented, an example of contact data given, reasons given for the termination of soundings below 100 mb, and soundings are listed which exhibit abnormal characteristics.

Sienkiewicz, M. E.↗
NASA NTRS1982

Characteristics of ageostrophic flow in the vicinity of a severe weather outbreak - AVE-SESAME I

GOES satellite data was used to examine the ageostrophic flow in the vicinity of severe weather outbreaks along the Red River between Texas and Oklahoma in April 1979. The observations were part of the NASA AVE-SESAME I data on atmospheric states close to severe weather conditions. The Barnes Objective Analysis Technique was employed to analyze the data on a 100 km grid. The ageostrophic wind was defined on a regional scale from satellite data on different levels of cloud wind vectors, with a height change signalling a short-wave system in a long-wave trough. The percentage of deviation of the subgeostrophic winds from the geostrophic wind was calculated, and maximum departure corresponded with the region of greatest storm development. Time cross sections of additions to the ageostrophic flow were made as a function of pressure at 100 mb intervals from 900-100 mb. The ageostrophic acceleration was consistently twice the geostrophic acceleration.

Arnold, J. E.↗
NASA NTRS1980

AVE-SESAME 2: The 25-MB sounding data

The rawinsonde sounding program for the AVE-SESAME II experiment is described. Data at 25 mb intervals from the surface to 25 mb for the 23 National Weather Service and 19 special stations participating in the experiment are presented. Soundings were taken at 3 hr intervals beginning at 1200 GMT on April 19, 1979, and ending at 1200 GMT on April 20, 1979 (nine sounding times). The method of processing is discussed briefly, estimates of the rms errors in the data presented, an example of contact data given, reasons given for the termination of soundings below 100 mb, and soundings listed which exhibit abnormal characteristics.

Williams, S. F.↗
NASA NTRS1984

Initialization of a mesoscale model for April 10, 1979, using alternative data sources

A 35 km grid limited area mesoscale model was initialized with high density SESAME radiosonde data and high density TIROS-N satellite temperature profiles for April 10, 1979. These data sources were used individually and with low level wind fields constructed from surface wind observations. The primary objective was to examine the use of satellite temperature data for initializing a mesoscale model by comparing the forecast results with similar experiments employing radiosonde data. The impact of observed low level winds on the model forecasts was also investigated with experiments varying the method of insertion. All forecasts were compared with each other and with mesoscale observations for precipitation, mass and wind structure. Several forecasts produced convective precipitation systems with characteristics satisfying criteria for a mesoscale convective complex. High density satellite temperature data and balanced winds can be used in a mesoscale model to produce forecasts which verify favorably with observations.

Kalb, M. W.↗
NASA NTRS1983

An interactive Barnes objective map analysis scheme for use with satellite and conventional data

The Barnes (1973) objective map analysis scheme is employed to develop an interactive analysis package for assessing the impact of satellite-derived data on analyses of conventional meteorological data sets. The method permits modification of the values of input parameters in the objective analysis within objectively determined, internally set limits. The effects of the manipulations are rapidly displayed, and methods are included for assimilating the spatially clustered characteristics of satellite data and the various horizontal resolutions of the data types. Data sets from the SESAME rawinsonde wind data with uniform spatial distribution, with the same data set plus satellite cloud motion data, and a data set from the atmospheric sounder radiometer on the GOES satellite were analyzed as examples. The scheme is demonstrated to recover details after two iterations through the data.

Koch, S. E.↗
NASA NTRS1979

AVE-SESAME 1: 25-MB sounding data

Seven atmospheric variability experiments (AVE), two atmospheric variability and severe storms experiments (AVSSE), and six atmospheric variability experiment-severe environmental storm and mesoscale experiments (AVE-SESAME) conducted by NASA are discussed. The dates, observation times, and data reports for each of the experiments for which data was processed are listed. The AVE experiments were conducted primarily to study atmospheric variability with emphasis on spatial and temporal in atmospheric structure that can be detected from soundings taken at 3 hr intervals but not seen in soundings taken at 12 hr intervals. The AVSSE experiments were conducted to study atmospheric structure and variability associated with severe storms combining both rawinsonde and aircraft data to provide information on near storm environments. The method of processing is discussed, estimates of the rms errors in the data are presented, an example of contact data is given, and soundings are listed which exhibited abnormal characteristics.

Gerhard, M. L.↗
NASA NTRS1984

Transverse ageostrophic circulations associated with elevated mixed layers

The nature of the frontogenetically forced transverse ageostrophic circulations connected with elevated mixed layer structure is investigated as a first step toward diagnosing the complex vertical circulation patterns occurring in the vicinity of elevated mixed layers within a severe storm environment. The Sawyer-Eliassen ageostrophic circulation equation is reviewed and applied to the elevated mixed layer detected in the SESAME IV data set at 2100 GMT of May 9, 1979. The results of the ageostrophic circulation diagnosis are confirmed and refined by considering an analytic specification for the elevated mixed layer structure.

Keyser, D.↗
NASA NTRS1981

AVE-SESAME program for the REEDA System

The REEDA system software was modified and improved to process the AVE-SESAME severe storm data. A random access file system for the AVE storm data was designed, tested, and implemented. The AVE/SESAME software was modified to incorporate the random access file input and to interface with new graphics hardware/software now available on the REEDA system. Software was developed to graphically display the AVE/SESAME data in the convention normally used by severe storm researchers. Software was converted to AVE/SESAME software systems and interfaced with existing graphics hardware/software available on the REEDA System. Software documentation was provided for existing AVE/SESAME programs underlining functional flow charts and interacting questions. All AVE/SESAME data sets in random access format was processed to allow developed software to access the entire AVE/SESAME data base. The existing software was modified to allow for processing of different AVE/SESAME data set types including satellite surface and radar data.

Hickey, J. S.↗