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Suomi, V. E.

Publications and source records attributed to Suomi, V. E..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Cloud motions on Neptune from Voyager 2 images

The puzzle presented by Neptune's circulation is evidenced by its wide spectrum of wind speeds and differences between the drift rate of its longest lived features and its finer scale cloud forms, unlike Jupiter or Saturn. Neptune's clouds appear dynamic and show strong evidence of atmospheric waves, making cloud motion measurements somewhat difficult and requiring some departures from the methods which have been traditionally used to determine atmospheric circulations. New measurements of cloud motions of Neptune that confirm the general characteristics reported by Smith et al. (1989) are presented below. Besides greater number of measurements from a higher time resolution data set, the new results reveal the shape of the westerly jet at 72 deg S latitude.

Limaye, S. S.↗
NASA NTRS1985

The meteorological interactive data display system

During FY-85 the data gathering process was completed. This gave researchers a reasonably complete picture of the Shuttle's operational weather support units and requirements. They expanded on the site visits of FY-84 with telephone follow-up. They finalized recommendations and wrote the final report. The final report was accepted by NASA and has been published as NASA Contractor Report CR-171418.

Suomi, V. E.↗
NASA NTRS1985

A design study for a three-dimensional display computer terminal for meteorological information

The software developed on this project in FY-84 was put into final form and documented for McIDAS user access. The various users have been asked to utilize the techniques and to provide feedback to the developers. Researchers have received limited feedback to date, but nearly all has been helpful and generally favorable. The stereo display has been used by most of the operational users of McIDAS or its progenies. Specifically, the National Hurricane Center, the National Severe Storm Forecast Center, the National Meteorological Center, and the Cape Canaveral Forecast Facility have all made use of the 4-D display techniques to help evaluate meteorological situations on various occasions.

Suomi, V. E.↗
NASA NTRS1985

Temperature structure in the lower atmosphere of Venus - New results derived from Pioneer Venus entry probe measurements

The Pioneer Venus Small-Probe Net Flux Radiometer temperature sensor and its calibration, the thermal model of the sensor head, the procedure for deriving atmospheric temperature from the sensor temperatures, and the new temperature results for each entry probe are reported. The new results are compared with those of the Small-Probe Atmospheric Structure experiment and with simple models of diurnal and latitudinal temperature contrasts. A dynamical inconsistency between these results and low-latitude measurements by the Sounder probe is described, and possible ways to resolve it are considered.

Sromovsky, L. A.↗
NASA NTRS1985

Net thermal radiation in the atmosphere of Venus

Estimates of the true atmospheric net fluxes at the four Pioneer Venus entry sites are presently obtained through corrections of measured values that are relatively small for the case of the clouds, but generally large deeper in the atmosphere. The correction procedure for both the small and large probe fluxes used model results near 14 km to establish the size of the correction. The thermal net fluxes obtained imply that the contribution of mode 3 particles to the IR opacity of the middle and lower clouds is smaller than indicated by the Pioneer Venus cloud particle spectrometer measurements, and the day probe results favor a reduction of only about 50 percent. The fluxes at all sites imply that a yet-undetermined source of considerable opacity is present in the upper cloud. Beneath the clouds, the thermal net fluxes generally increase with increasing latitude.

Revercomb, H. E.↗
NASA NTRS1985

New atmospheric temperature results from the Pioneer Venus entry probes

A new independent determination of Venus atmospheric temperatures, derived from auxiliary engineering measurements of the Small Probe Net Flux Radiometer (SNFR) instruments on board the three small Pioneer Venus entry probes, is presented. The temperature-measurement system and the thermal model needed to convert the raw measurements to atmospheric temperatures are described. The vertical temperature structure and horizontal temperature contrast results are compared graphically measured by the SAS instrument (Seiff et al., 1980), showing a high degree of agreement.

Sromovsky, L. A.↗
NASA NTRS1985

Thermal net flux measurements on the Pioneer Venus entry probes

Corrected thermal net (upward minus downward flux) radiation data from four Pioneer Venus probes at latitudes of 4 deg and 60 deg N, and 27 deg and 31 deg S, are presented. Comparisons of these fluxes with radiative transfer calculations were interpreted in terms of cloud properties and the global distribution of water vapor in the lower atmosphere of Venus. The presence of an as yet undetected source of IR opacity is implied by the fluxes in the upper cloud range. It was also shown that beneath the clouds the fluxes at a given altitude increase with latitude, suggesting greater IR cooling below the clouds at high latitudes and a decrease of the water vapor mixing ratios toward the equator.

Revercomb, H. E.↗
NASA NTRS1985

Net Thermal Radiation in the Atmosphere of Venus

The four entry probes of the Pioneer Venus mission measured the radiative net flux in the atmosphere of Venus at latitudes of 60 deg N, 31 deg S, 27 deg S, and 4 deg N. The three higher latitude probes carried instruments (small probe net flux radiometers; SNFR) with external sensors. The measured SNFR net fluxes are too large below the clouds, but an error source and correction scheme have been found. The near-equatorial probe carried an infrared radiometer (LIR) which viewed the atmosphere through a window in the probe. The LIR measurements are reasonable in the clouds, but increase to physically unreasonable levels shortly below the clouds. The probable error source and a correction procedure are identified. Three main conclusions can be drawn from comparisons of the four corrected flux profiles with radiative transfer calculations: (1) thermal net fluxes for the sounder probe do not require a reduction in the Mode 3 number density as has been suggested, but the probe measurements as a whole are most consistent with a significantly reduced mode 3 contribution to the cloud opacity; (2) at all probe sites, the fluxes imply that the upper cloud contains a yet undetected source of IR opacity; and (3) beneath the clouds the fluxes at a given altitude increase with latitude, suggesting greater IR cooling below the clouds at high latitudes and water vapor mixing ratios of about 2-5 x 10(exp -5) near 60 deg, 2-5 x 10(exp -4) near 30 deg, and greater than 5 x 10(exp -4) near the equator. The suggested latitudinal variation of IR cooling is consistent with descending motions at high latitudes, and it is speculated that it could provide an important additional drive for the general circulation.

Sromovsky, L. A.↗
NASA NTRS1985

Net Thermal Radiation in the Atmosphere of Venus

The four entry probes of the Pioneer Venus mission measured the radiative net flux in the atmosphere of Venus at latitudes of 60 deg. N, 31 deg. S, 27 deg. S, and 4 deg. N. The three higher latitude probes carried instruments (small probe net flux radiometers; SNFR) with external sensors. The measured SNFR net fluxes are too large below the clouds, but an error source and correction scheme have been found (H. E. Revercomb, L. A. Sromovsky, and V. E. Suomi, 1982, Icarus 52, 279-300). The near-equatorial probe carried an infrared radiometer (LIR) which viewed the atmosphere through a window in the probe. The LIR measurements are reasonable in the clouds, but increase to physically unreasonable levels shortly below the clouds. The probable error source and a correction procedure are identified. Three main conclusions can be drawn from comparisons of the four corrected flux profiles with radiative transfer calculations: (1) thermal net fluxes for the sounder probe do not require a reduction in the Mode 3 number density as has been suggested by O.B. Toon, B. Ragent, D. Colburn, J. Blamont, and C. Cot (1964. Icarus 37, 143-160), but the probe measurements as a whole are most consistent with a significantly reduced mode 3 contribution to the cloud opacity; (2) at all probe sites, the fluxes imply that the upper cloud contains a yet undetected source of IR opacity; and (3) beneath the clouds the fluxes at a given altitude increase with latitude, suggesting greater IR cooling below the clouds a( high latitudes and water vapor mixing ratios of about 2-5 x 10(exp -5) near 6 deg., 2-5 x 10(exp -11) near 30 deg., and less than 5 x 10(exp -4 ) near the equator. The suggested latitudinal variation of IR cooling is consistent with descending motions at high latitudes, and it is speculated that it could provide an important additional drive for the general circulation.

Revercomb, H. E.↗
NASA NTRS1984

Cloud and ice in the planetary scale circulation and in climate

The roles of the cryosphere, and of cloud-radiative interactions are investigated. The effects clouds and ice have in the climate system are examined. The cloud radiation research attempts explain the modes of interaction (feedback) between raditive transfer, cloud formation, and atmospheric dynamics. The role of sea ice in weather and climate is also discussed. Models are used to describe the ice and atmospheric dynamics under study.

Herman, G. F.↗
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 NTRS1983

Voyager 2 observations of Saturn's northern mid-latitude cloud features - Morphology, motions, and evolution

Voyager 2 images provide a basis for detailed study of the morphology and circulation of Saturn's northern midlatitudes. Both Saturn's large-scale cloud bands and the distribution of its local cloud features have a characteristic zonal organization. The region between 30 N and 45 N contains two oppositely directed jets in close proximity, with many bright, active features in the westward jet, and an unusual ribbonlike wave feature encircling the planet in the eastward jet. Several of the smaller features within the westward jet do not remain at fixed latitudes and interact with each other. One group of v-shaped features is found to have periods of high activity correlated with the passage of a cyclonic bright spot. The ribbon wave was Fourier analyzed to determine its spectral composition. The greatest power is near wave number 9, with significant additional peaks appearing at planetary wave numbers 19, 25-27, 35-38, and 47-51. The phase velocity increases with wave number but is not well described by a Rossby-Haurwitz dispersion relation. The curvature of the mean wind profile obtained from cloud tracking indicates that the westward jet exceeds the standard barotropic instability condition, while the eastward jet marginally exceeds the deep-circulation instability condition of Ingersoll and Pollard (1982). The rms eddy velocities on Saturn are less than half as large as those observed on Jupiter.

Sromovsky, L. A.↗
NASA NTRS1983

McIDAS III - A modern interactive data access and analysis system

A powerful facility for meteorological analysis called the Man Computer Interactive Data Access System (McIDAS) was designed and implemented in the early 1970's at the Space Science and Engineering Center of the University of Wisconsin-Madison. Hardware and software experience gained via extensive use of that facility and its derivatives have led to a newer implementation of McIDAS on a larger computer with significant enhancements to the supporting McIDAS software. McIDAS allows remote and local access to a wide range of data from satellites and conventional observations, time lapse displays of imagery data, overlaid graphics, and current and past meteorological data. Available software allows one to perform analysis of a wide range of digital images as well as temperature and moisture sounding data obtained from satellites. McIDAS can generate multicolor composites of conventional and satellite weather data, radar and forecast data in a wide variety of two- and three-dimensional displays as well as time lapse movies of these analyses. These and other capabilities are described in this paper.

Suomi, V. E.↗
NASA NTRS1982

Reassessment of net radiation measurements in the atmosphere of Venus

An analysis was performed of the possible error mechanisms which degraded the IR net flux measurements made by the three small atmospheric probes dispatched from the Pioneer Venus spacecraft. The larger errors began below 30 km, and caused the data to be inconsistent with previous estimates of the atmospheric opacity. Evaluations were made of the possible radiation field perturbations behind each probe, cloud particle deposition on the sensor windows, and thermal disturbances within the sensors because of gas flow through the window retainers. The gas flow through the retainers was identified as the most likely error source, and was demonstrated in laboratory tests. A strong Reynolds number dependence was also found. Radiative transfer calculations were performed to account for the errors, using the constraints defined by the tests. Upper and lower bounds were calculated for the true net flux for both day and night conditions.

Revercomb, H. E.↗
NASA NTRS1982

Jovian winds from Voyager 2. I - Zonal mean circulation

Independent measurements of Jovian cloud motions confirm previously published results on the general structure of Jupiter's zonal mean circulation. The new results are based on Voyager 2 images and measurement techniques which are different from those used in previous studies. The latitudes of the zonal jets agree with previous results, but there are some differences in the measured speed of the jets which exceed uncertainty estimates. These differences may be due to differences in sampling strategies. The structure of the zonal mean meridional velocity profile has still not been clearly resolved: mean meridional velocities generally differ from zero by no more than their estimated uncertainty. An analysis of successive measurements of the same cloud targets shows that most of the variance of individual velocity measurements is due to true variability of the winds.

Limaye, S. S.↗
NASA NTRS1982

Jovian winds from Voyager 2. Part II - Analysis of eddy transports

Previous Voyager 1 and 2 Jovian circulation measurements exhibit a large positive correlation between eddy momentum transports and the meridional shear of the zonal wind component, implying a very large rate of conversion of eddy kinetic energy of the zonal jets. Examination of the vectors mainly responsible for the correlation in our recent Voyager 2 global measurements indicates that it is probably caused by a biased sampling of prominent cloud features associated with circulating eddies. Intensive diagnostic measurements with more nearly uniform spatial sampling show no significant correlation in regions where our original measurements showed strong correlations. If the sampling bias mechanism is fully accounted for in all Jovian circulation measurements, the estimated eddy-to-mean-flow kinetic energy conversion rate may be reduced significantly.

Sromovsky, L. A.↗
NASA NTRS1981

Implications of Titan's north-south brightness asymmetry

Voyager 1 images of Titan, when normalized to remove limb darkening, reveal an axially symmetric brightness pattern with significant north-south asymmetry. This interhemispheric contrast seems to be a response to seasonal solar heating variations resulting from Titan's inclined spin axis. The contrast significantly lags the solar forcing, indicating that its production involves the atmosphere well below the unit optical depth level. The contrast has a significant effect on Titan's disk-integrated brightness as seen from earth, and probably accounts for most of the observed long term variation, with solar UV variations accounting for the remainder.

Sromovsky, L. A.↗