Engineering topics

Hasler, A. F.

Publications and source records attributed to Hasler, A. F..

At least 37 records · Page 2

NASA NTRS1987

AOIPS/2 - An interactive system to process, analyze, and display meteorological data sets for nowcasting

A description of AOIPS/2, an interactive hardware and software system to process, integrate, and display meteorological data is presented. The AOIPS/2 objectives and functional specifications are given. The hardware system architecture and work stations and the software architecture and special features are described. A summary is given of the software system and its main menu.

Hasler, A. F.↗

NASA NTRS1986

Hurricane structure and wind fields from stereoscopic and infrared satellite observations and radar data

Hurricane cloud and precipitation structure have been studied by means of IR and stereoscopic visual satellite data from synchronized scanning GOES-East and -West, in combination with ground-based radar data for Hurricane Frederico and time-composited airborne radar data for Hurricane Allen. It is noted that stereoscopically measured cloudtop height in these hurricanes is not as closely correlated to radar reflectivity at lower levels as it is in intense thunderstorms over land. This and other results obtained imply that satellite precipitation estimation techniques for tropical cyclones that are based on cloudtop measurements will not be accurate with respect to time and place scales that are less than several hours and a few hundred km, respectively.

Hasler, A. F.↗

NASA NTRS1985

Meteorological data fields 'in perspective'

Perspective display techniques can be applied to meteorological data sets to aid in their interpretation. Examples of a perspective display procedure applied to satellite and aircraft visible and infrared image pairs and to stereo cloud-top height analyses are presented. The procedure uses a sophisticated shading algorithm that produces perspective images with greatly improved comprehensibility when compared with the wire-frame perspective displays that have been used in the past. By changing the 'eye-point' and 'view-point' inputs to the program in a systematic way, movie loops that give the impression of flying over or through the data field have been made. This paper gives examples that show how several kinds of meteorological data fields are more effectively illustrated using the perspective technique.

Hasler, A. F.↗

NASA NTRS1983

Thunderstorm cloud top observations using satellite stereoscopy

The present investigation has as objective to take a detailed look at the intense squall line over Oklahoma on May 2-3, 1979, using GOES stereoscopy combined with GOES infrared data. The synoptic situation and data sources are considered along with the stereoscopically observed cloud top ascent rates. Cloud top observations of intense thunderstorms are discussed, taking into account a contouring technique, the interpretation of infrared cloud top temperature patterns, and small-scale structure and its variability. It is found that GOES IR cloud top temperatures grossly underestimate the actual cloud top height observed stereoscopically, especially for immature storms. It is difficult to define growing storms below about 10 km in the GOES infrared data.

Mack, R. A.↗

NASA NTRS1983

A satellite stereoscopic technique to estimate tropical cyclone intensity

The techniques used to obtain the mean equivalent temperature of the eye wall for Hurricanes Frederic (1979) and Allen (1980) using GOES satellite IR and stereoscopic observations are described. The eye wall is the area of greatest convection near the center of the storm, and is bounded by the inner radius around the eye and the outer radius bounding the area of inner core convection. The stereoscopic capability afforded by the GOES West and East spacecraft permits simultaneous, two-view imagery of a tropical cyclone, yielding height measurement accuracies of 0.5 km and horizontal accuracies as small as 1 km. An airborne lidar unit was used to verify the height measurements made of Hurricane Frederic. At the same time, the GOES East Visible IR Spin Scan Radiometer (VISSR) provided the mean wall temperatures from the release of latent heat. The trials aided in identifying the assumptions and consequent inaccuracies introduced into the temperature sounding data during analysis. The satellite data is concluded useful for monitoring changes in storm intensity.

Rodgers, E. B.↗

NASA NTRS1983

Advances in systems for interactive processing and display of meteorological data

Advances in systems for interactive processing and display of meteorological data are reviewed, with particular attention given to developments in hardware and software, meteorological data base, analysis and display, and systems availability. These developments include inexpensive minicomputers which give the user almost instantaneous results for many types of jobs; image terminals with the capability to enhance, quantify, animate, and compare image and graphical data; accessibility of a large meteorological data base and the capability of merging different types of data; and sophisticated analysis and multidimensional display techniques. Critical problems still to be solved include getting quick access to historical and real time data bases from any system and making it easy to transport software from one system to another.

Hasler, A. F.↗

NASA NTRS1982

Weather satellites: Stereoscopy and Sounding; Proceedings of the Topical Meeting, Ottawa, Canada, May 16-June 2, 1982

Attention is given to the validation of meteorological satellite observing systems and to stereoscopic observations from meteorological satellites. Particular papers are presented on such topics as the comparison of cloud top heights measured by airborne lidar and TIROS-N image data, the determination of surface global radiation using Meteosat images and ground-based visibility measurements, multichannel improvements to satellite-derived global sea surface temperatures, validation of the Stratospheric Sounding Unit, and the international comparison of satellite winds. Also considered is tropical storm structure revealed by stereo photographs from Skylab, stereo imaging from polar orbit and synthetic stereo imaging, simultaneous measurements of sea surface temperature by GMS-1 and GMS-2, and real-time spectroscopic applications using the GOES operational satellites.

Yates, H.↗

NASA NTRS1982

Stereoscopic observations from meteorological satellites

Stereo cloud top height measurements, accurate to within + or - 500 m, have been performed using operational weather satellites. The stereo has been demonstrated using various combinations of GEO and LEO satellites, and the use of synthetic stereo was considered. Stereo can be done over most of the earth (60 deg S to 60 deg N) during the day; at higher latitudes and at night, stereo can be done using two LEOs if the proper coincidences occur. The usefulness of stereo cloud top height measurements has been demonstrated by many studies of convective storm cloud systems. Recommendations relating to short, medium, and long term planning regarding stereo observations from meteorological satellites are outlined.

Hasler, A. F.↗

NASA NTRS1982

Stereoscopic observations of hurricanes and tornadic thunderstorms from geosynchronous satellites

Results are presented which show the application of GOES stereoscopy to the investigation of hurricanes and tornadic thunderstorms. Stereo cloud top height contour maps were constructed to observe the structural evolution of two hurricanes, Frederic on September 12, 1979 and Allen on August 8, 1980, and a tornadic thunderstorm complex over Oklahoma on May 2-3, 1979. Stereo height contours of Hurricane Allen reveal a very intense and symmetric storm with a circular shaped central dense overcast with an average height of 16.5 km. Contours of Hurricane Frederic reveal a preferred region for convection with an explosive exhaust tower attaining a maximum height of 17.8 km. Also presented is a technique for estimating tropical cyclone intensity using GOES stereo height and IR temperature information. Results indicate vertical motions ranging from 4.4 m/s for a moderate storm to 7.7 m/s for an intense storm.

Mack, R.↗

NASA NTRS1982

The use of stereoscopic satellite observation in the determination of the emissivity of cirrus

The feasibility of determining cirrus 'emissivity' from combined stereoscopic and infrared satellite observations in conjunction with radiosounding data is investigated for a particular case study. Simultaneous visible images obtained during SESAME-1979 from two geosynchronous GOES meteorological satellites were processed on the NASA Goddard interactive system (AOIPS) and were used to determine the stereo cloud top height Z sub C as described by Hasler (1981). Iso-contours of radiances were outlined on the corresponding infrared image. Total brightness temperature T sub B and ground surface brightness temperature T sub S were inferred from the radiances. The special SESAME network of radiosoundings was used to determine the cloud top temperature T sub CLD at the level defined by Z sub C. The 'effective cirrus emissivity' NE where N is the fractional cirrus cloudiness and E is the emissivity in a GOES infrared picture element of about 10 km x 10 km is then computed from T sub B, T sub S and T sub CLD.

Szejwach, G.↗

NASA NTRS1981

Artificial stereo presentation of meteorological data fields

The innate capability to perceive three-dimensional stereo imagery has been exploited to present multidimensional meteorological data fields. Variations on an artificial stereo technique first discussed by Pichel et al. (1973) are used to display single and multispectral images in a vivid and easily assimilated manner. Examples of visible/infrared artificial stereo are given for Hurricane Allen and for severe thunderstorms on 10 April 1979. Three-dimensional output from a mesoscale model also is presented. The images may be viewed through the glasses inserted in the February 1981 issue of the Bulletin of the American Meteorological Society, with the red lens over the right eye. The images have been produced on the interactive Atmospheric and Oceanographic Information Processing System (AOIPS) at Goddard Space Flight Center. Stereo presentation is an important aid in understanding meteorological phenomena for operational weather forecasting, research case studies, and model simulations.

Hasler, A. F.↗

NASA NTRS1981

Stereographic observations from geosynchronous satellites - An important new tool for the atmospheric sciences

Observations of cloud geometry using scan-synchronized stereo geostationary satellites having images with horizontal spatial resolution of approximately 0.5 km, and temporal resolution of up to 3 min are presented. The stereo does not require a cloud with known emissivity to be in equilibrium with an atmosphere with a known vertical temperature profile. It is shown that absolute accuracies of about 0.5 km are possible. Qualitative and quantitative representations of atmospheric dynamics were shown by remapping, display, and stereo image analysis on an interactive computer/imaging system. Applications of stereo observations include: (1) cloud top height contours of severe thunderstorms and hurricanes, (2) cloud top and base height estimates for cloud-wind height assignment, (3) cloud growth measurements for severe thunderstorm over-shooting towers, (4) atmospheric temperature from stereo heights and infrared cloud top temperatures, and (5) cloud emissivity estimation. Recommendations are given for future improvements in stereo observations, including a third GOES satellite, operational scan synchronization of all GOES satellites and better resolution sensors.

Hasler, A. F.↗

NASA NTRS1980

Cloud top structure of a tornadic thunderstorm from 3 min interval stereo satellite images compared with radar and other observations

Cloud heights from 3 min interval GOES EAST/GOES WEST stereo pairs are shown to provide an important new tool for studying severe convective storms with potential for the detection of severe local storms. It is possible to use these data for observing cloud top structure as a function of time on a size scale of few kilometers with quantitative height measurements with relative and absolute accuracies on the order of + or - 0.5 km. It is noted that stereo height measurements detect cirrus anvil cloud decks at two altitudes corresponding to a lower stable layer and the main tropopause.

Hasler, A. F.↗

NASA NTRS1979

In situ aircraft verification of the quality of satellite cloud winds over oceanic regions

A 5-year aircraft experiment to verify the quality of satellite cloud winds over oceans using in situ aircraft Inertial Navigation System wind measurements is presented. Cloud motions measured by satellite and aircraft wind measurements that were coincident in time and space, and the results from the experiment are for undisturbed to moderately disturbed oceanic weather regimes. The results show that satellite measured cumulus cloud motions are good estimators of the cloud-base wind for trade wind and subtropical high regions. The average magnitude of the vector differences between the cloud motion and the cloud-base wind was determined; for cumulus clouds near frontal regions, the cloud motions agreed best with the mean cloud layer wind. For a very limited sample, cirrus cloud motions most closely followed the mean wind in the cloud layer.

Hasler, A. F.↗

NASA NTRS1979

Insitu aircraft verification of the quality of satellite cloud winds over oceanic regions

A five year aircraft experiment to verify the quality of satellite cloud winds over oceans using in situ aircraft inertial navigation system wind measurements is presented. The final results show that satellite measured cumulus cloud motions are very good estimators of the cloud base wind for trade wind and subtropical high regions. The average magnitude of the vector differences between the cloud motion and the cloud base wind is given. For cumulus clouds near frontal regions, the cloud motion agreed best with the mean cloud layer wind. For a very limited sample, cirrus cloud motions also most closely followed the mean wind in the cloud layer.

Hasler, A. F.↗

NASA NTRS1979

Four dimensional observations of clouds from geosynchronous orbit using stereo display and measurement techniques on an interactive information processing system

Simultaneous Geosynchronous Operational Environmental Satellite (GOES) 1 km resolution visible image pairs can provide quantitative three dimensional measurements of clouds. These data have great potential for severe storms research and as a basic parameter measurement source for other areas of meteorology (e.g. climate). These stereo cloud height measurements are not subject to the errors and ambiguities caused by unknown cloud emissivity and temperature profiles that are associated with infrared techniques. This effort describes the display and measurement of stereo data using digital processing techniques.

Hasler, A. F.↗

NASA NTRS1979

Meteorological image processing applications

Meteorologists at NASA's Goddard Space Flight Center are conducting an extensive program of research in weather and climate related phenomena. This paper focuses on meteorological image processing applications directed toward gaining a detailed understanding of severe weather phenomena. In addition, the paper discusses the ground data handling and image processing systems used at the Goddard Space Flight Center to support severe weather research activities and describes three specific meteorological studies which utilized these facilities.

Bracken, P. A.↗

NASA NTRS1979

Digital cloud stereography from geostationary orbit

It has been demonstrated that geostationary satellite imagery provides an effective means of extracting two-dimensional cloud motion wind measurements over large areas. The addition of cloud height information is necessary, however, for the proper assignment of altitude to the wind vectors. This paper discusses the methodology and accuracy of extracting multilevel cloud motion measurements from stereo digital imagery acquired from geostationary orbit.

Dalton, J. T.↗