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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

A cold air outbreak over the Norwegian Sea observed with the Tiros-N Operational Vertical Sounder (TOVS) and the Special Sensor Microwave/Imager (SSM/I)

Until recently, the scarcity of meteorological observations over polar areas has limited studies of high latitude weather systems, but now data from polar orbiting satellites offer a new opportunity to observe and describe these systems. TOVS data were used successfully for delineating synoptic and subsynoptic systems since they provide the vertical temperature structure of the atmosphere: SSM/I observations have proved valuable for analyzing storms through water vapor and rain determinations. These positive results prompted us to analyze simultaneous TOVS and SSM/I observations obtained during a cold air outbreak over the Norwegian Sea. After a description of the instruments and the retrieval schemes, the mutually supporting information from these two independent instruments is discussed. Implications for the monitoring of polar lows are presented.

Claud, Chantal↗
NASA NTRS1990

Comparisons between TOMS, TOVS and DOBSON observations - Satellite and surface views of total column ozone

The reliability of the ozone retrievals by the TIROS-N Operational Vertical Sounder (TOVS) calculated with the newly developed physical algorithm is investigated by comparing the quality of the TOVS total ozone soundings to the corresponding values obtained by the Nimbus-7 TOMS and by the ground-based DOBSON network. The three-way comparison concentrates on observations during the last 4 months of 1987, the period of the great Antarctic 'ozone hole'. It is shown that each instrument has characteristic strengths and weaknesses, and that each of the three systems makes serious errors under some conditions.

Chesters, Dennis↗
NASA NTRS1992

A cold air outbreak over the Norwegian Sea observed with the Tiros-N Operational Vertical Sounder (TOVS) and the Special Sensor Microwave/Imager (SSM/I)

Until recently, the scarcity of meteorological observations over polar areas has limited studies of high-latitude weather systems, but now data from polar orbiting satellites offer a new opportunity to observe and describe these systems. TOVS data have been used successfully for delineating synoptic and subsynoptic systems, since they provide the vertical temperature structure of the atmosphere; SSM/I observations have proved valuable for analyzing storms through water vapor and rain determinations. These positive results prompted simultaneous analysis of TOVS and SSM/I observations obtained during a cold air outbreak over the Norwegian Sea. After a description of the instruments and the retrieval schemes, the mutually supporting information from these two independent instruments is discussed. Implications for the monitoring of polar lows are presented.

Claud, Chantal↗
NASA NTRS1992

Upper tropospheric water vapor features observed in the 1980's using the 6.7 and 7.2 micron TOVS channels

The NOAA has been preprocessing the TIROS Operational Vertical Sounder (TOVS) IR and microwave channels to correct for cloud amount, spot size, and viewing angle. An examination is now being conducted of the 6-7 micron water vapor band; a preliminary evaluation is here presented of the regional and global features of this large data base on daily, monthly, annual, and decadal time scales. The TOVS archives allow large-scale climatological features to be established.

Chesters, Dennis↗
NASA NTRS1993

Impact of increased TOVS signal on the NMC global spectral model - A tropical-plume case study

Temperature and moisture signals are extracted from operationally available TOVS channel radiances for a tropical plume that developed over the North Pacific in January 1989, and are inserted into the NMC's operational medium-range forecast model. Several 48-h forecasts are made to test the impact of the additional information. It is shown, at least within a single tropical plume event, that there is still unutilized information within operational TOVS satellite observations. This information resides in the moisture channels and within small-amplitude, but horiontally coherent, thermal features. Perturbed upper-tropospheric relative humidity patterns are smoother and more consistent with satellite imagery than is the historical forecast.

Mcguirk, James P.↗
NASA NTRS1999

Longwave Radiative Flux Calculations in the TOVS Pathfinder Path A Data Set

A radiative transfer model developed to calculate outgoing longwave radiation (OLR) and downwelling longwave, surface flux (DSF) from the Television and Infrared Operational Satellite (TIROS) Operational Vertical Sounder (TOVS) Pathfinder Path A retrieval products is described. The model covers the spectral range of 2 to 2800 cm in 14 medium medium spectral bands. For each band, transmittances are parameterized as a function of temperature, water vapor, and ozone profiles. The form of the band transmittance parameterization is a modified version of the approach we use to model channel transmittances for the High Resolution Infrared Sounder 2 (HIRS2) instrument. We separately derive effective zenith angle for each spectral band such that band-averaged radiance calculated at that angle best approximates directionally integrated radiance for that band. We develop the transmittance parameterization at these band-dependent effective zenith angles to incorporate directional integration of radiances required in the calculations of OLR and DSF. The model calculations of OLR and DSF are accurate and differ by less than 1% from our line-by-line calculations. Also, the model results are within 1% range of other line-by-line calculations provided by the Intercomparison of Radiation Codes in Climate Models (ICRCCM) project for clear-sky and cloudy conditions. The model is currently used to calculate global, multiyear (1985-1998) OLR and DSF from the TOVS Pathfinder Path A Retrievals.

Mehta, Amita↗
NASA NTRS1999

Inter-Annual Variability of Atmospheric Water Vapor as seen from the TOVS Pathfinder Path a Data Set

The atmospheric water vapor is a major greenhouse gas and plays a critical role in determining energy and water cycle in the climate system. A new, global, long-term (1985-98) water vapor data set derived from the TIROS Operational Vertical Sounder (TOVS) Path A system will be introduced in the presentation. An assessment of the accuracy of the TOVS Path A water vapor data will he presented. The focus of this oral presentation will be on the inter-annual variability of the water vapor distribution in the atmosphere. Also, water vapor distribution observed during 1997/98 ENSO event will be shown.

Mehta, Amita↗
NASA NTRS2000

Temperature Trends in the TOVS Pathfinder Path A Data Set

TOVS (Tiros Operational Vertical Sounder) is the suite of infra-red and microwave sounding instruments, including HIRS-2 and MSU, that have flown on the NOAA Polar orbiting operational satellites TIROS-N, NOAA 6-14 from November 1978 to the present day. Data has been analyzed for the entire time period using a consistent methodology to produce twice daily per satellite global fields of surface skin temperature, atmospheric temperature-moisture profile, cloud top pressure, and fractional cloud cover, OLR and clear sky OLR, and precipitation. All parameters were found to depend on the orbit time of observation which differed as a function of time both because of differing initial satellite orbits and orbit drift. This must be accounted for before one can attempt to find trends in the data. Methodology to account for orbit drift will be shown. Trends will then be shown, over the 21 year period 1979-1999, for surface skin temperature and atmospheric temperature profile. There has been global warming near the surface which falls off rapidly with height. Trends will also be shown for values of MSU2R and MSU4 which are computed from the soundings. These will be compared to trends of MSU2R and MSU4 observed by Spencer and Christy. There is generally good agreement between Spencer and Christy MSU2R trends and those computed from the TOVS Pathfinder data set, with the largest differences over the tropics.

Susskind, J.↗
NASA NTRS1984

Applications of VAS and TOVS to tropical cyclones

The results of the attempts to use VAS (visible IR spin scan radiometer atmospheric sounder) data for predicting tropical cyclones are reported. VAS, mounted on a GEO platform, has 14 detectors for upwelling radiance. The McIDAS software was, by the 1983 hurricane season, upgraded to providing imagery and mass, motion and moisture patterns using the satellite data, which also permitted determinations of accurate temperature and moisture profiles. Comparisons made between VAS and radiosonde data revealed fairly close agreement of satellite and in-situ conditions during the 1983 season. When combined with data from the Tiros operational vertical sounder (TOVS) to define wind streamlines and predict the path of a hurricane from data fed into numerical models, sufficiently good agreement was obtained to initiate plans to forecast a hurricane trajectory during the 1984 season.

Velden, C. S.↗
NASA NTRS1987

Standard-resolution TOVS observations for the FIRE/SRB Wisconsin experiment region from October 9 through November 2, 1986

Maps and concise tables are presented which show TIROS Operational Vertical Sounder (TOVS) box centroid locations, box size, and vertical sounding products from the NOAA-6 and -9 satellites for the FIRE/SRB (First ISCCP Regional Experiment/Surface Radiation Budget) Wisconsin experiment region during October 9 through November 2, 1986. In addition to the operational standard products, relative reflectance is calculated and presented based on values from HIRS/2 Band 20 measurements.

Whitlock, Charles H.↗
NASA NTRS1987

Analysis and comparison of ozone maps obtained by TOMS and TOVS during the MAP/GLOBUS 1983 campaign

The Nimbus 7 TOMS (UV) and NOAA 7 and NOAA 8 TOVS (IR) data have been specially processed for the MAP/GLOBUS campaign (September 1983, over Europe). Comparison of the ozone results shows a general agreement but also some discrepancies due to clouds, emissivity of the surface, and latitude effects. The variability of the ozone field, closely linked to geopotential height field, may have induced a great change in total ozone along the balloon flights, but fortunately trajectories tend to lie parallel to the total ozone contours, so that the total ozone during each flight is nearly constant.

Muller, S.↗
NASA NTRS1988

High-spatial-resolution TOVS observations for the FIRE/SRB Wisconsin experiment region from October 14 through November 2, 1986

Maps and concise tables are presented which show TOVS (TIROS Operational Vertical Sounder) HIRS/2 (High Resolution Infrared Sounder) data products, resolution size, and sounding location for the FIRE/SRB (First ISCCP Experiment/Surface Radiation Budget) Wisconsin experiment region from October 14 through November 2, 1986. The data presented are the result of a special analysis of the HIRS/2 sounder from the NOAA-9 and -10 satellites.

Whitlock, Charles H.↗
NASA NTRS1990

Intercomparison of standard resolution and high resolution TOVS soundings with radiosonde, lidar, and surface temperature/humidity data

One objective of the FIRE Cirrus IFO is to characterize relationships between cloud properties inferred from satellite observations at various scales to those obtained directly or inferred from very high resolution measurements. Satellite derived NOAA-9 high and standard resolution Tiros Operational Vertical Sounder (TOVS) soundings are compared with directly measured lidar, surface temperature, humidity, and vertical radiosonde profiles associated with the Ft. McCoy site. The results of this intercomparison should be useful in planning future cloud experiments.

Wheeler, R. J.↗
NASA NTRS1991

Satellite observations of polar lows by SSM/I, Geosat and TOVS

Satellite observations in high-latitude regions were used to detect polar lows and track their propagation and evolution. The Special Sensor Microwave/Imager (SSM/I) provided estimates of surface wind speed, integrated cloud liquid water, and water vapor contents over ocean; the Geosat radar altimeter measured surface wind speed and significant wave height; the TIROS-N Operational Vertical Sounder (TOVS) allowed the determination of temperature and humidity profiles in the atmosphere, as well as cloud information (cloud top pressure and temperature). The detection of polar lows at a very early stage, and their development, propagation, and decay is presented for a specific case occurring in the Norwegian Sea on 23-24 January 1988, using a combination of these three instruments, namely a passive and an active microwave sensor, and a vertical sounder (19 infrared, 1 visible, and 4 microwave channels). Advantage is taken of the time and coverage differences between these three satellite sensors for the observation of polar lows. A discussion of the results is given.

Claud, C.↗
NASA NTRS1997

Estimating Surface Radiation Fluxes in the Arctic from TOVS Brightness Temperatures

A new method for estimating downwelling shortwave and longwave radiation fluxes in the Arctic from TOVS brightness temperatures has been developed. The method employs a neural network to bypass computationally intensive inverse and for-ward radiative transfer calculations, Results from two drifting ice camps (CEAREX, LeadEx) and from one coastal station show that downwelling fluxes can be estimated with r.m.s. errors of 20 W/sq m for longwave radiation and 35 W/sq m for shortwave radiation. Mean errors are less than 4 W/sq m and are well within the bounds required for many climate process studies.

Schweiger, A. J.↗
NASA NTRS1998

RADNET: A Neural Network-based Estimation of the Surface Radiation Budget in the Arctic from TOVS Brightness Temperatures

This report summarizes the main accomplishments of the project. Specifics are provided in three journal papers which are enclosed with this report. Two of the journal articles are currently in press, one has already been published. Our work focused on two main areas: (1) RadNet. The main objective of the project was the development of a neural network-based method to compute downwelling shortwave and longwave fluxes directly from TOVS HIRS and MSU brightness temperatures. (2) FlaxNet. A second objective of the project involved the development of neural network-based method for the calculation of surface fluxes based on radiative transfer physics.

Schweiger, Axel↗
NASA NTRS2005

Comparison of Monthly Mean Cloud Fraction and Cloud Optical depth Determined from Surface Cloud Radar, TOVS, AVHRR, and MODIS over Barrow, Alaska

A one year comparison is made of mean monthly values of cloud fraction and cloud optical depth over Barrow, Alaska (71 deg 19.378 min North, 156 deg 36.934 min West) between 35 GHz radar-based retrievals, the TOVS Pathfinder Path-P product, the AVHRR APP-X product, and a MODIS based cloud retrieval product from the CERES-Team. The data sets represent largely disparate spatial and temporal scales, however, in this paper, the focus is to provide a preliminary analysis of how the mean monthly values derived from these different data sets compare, and determine how they can best be used separately, and in combination to provide reliable estimates of long-term trends of changing cloud properties. The radar and satellite data sets described here incorporate Arctic specific modifications that account for cloud detection challenges specific to the Arctic environment. The year 2000 was chosen for this initial comparison because the cloud radar data was particularly continuous and reliable that year, and all of the satellite retrievals of interest were also available for the year 2000. Cloud fraction was chosen as a comparison variable as accurate detection of cloud is the primary product that is necessary for any other cloud property retrievals. Cloud optical depth was additionally selected as it is likely the single cloud property that is most closely correlated to cloud influences on surface radiation budgets.

Uttal, Taneil↗
NASA NTRS1980

Evaluation and use of TOVS retrievals at NMC

In a current analysis procedure at the National Meteorological Center (NMC), a first guess analysis (from the latest 6 or 12 hour forecast) is updated by new data. In the newest analysis procedures, which are based on optimum interpolation, the observational correction depends on the size of preassigned, expected observational errors versus the size of expected errors in the first guess forecast. In the case of Northern Hemisphere ocean temperatures, the latter are around 2 degrees. The infrared satellite retrievals have a similar size "error". If (as assumed) their errors are uncorrelated with the first guess error, they will improve the analysis. The larger errors of the microwave retrievals, however, mean that they will be given little weight in the analysis. An evaluation of the TIROS-N retrievals is currently underway at NMC to determine the impact of satellite derived data within operational analysis schemes, to isolate possible problems within current retrieval methods, and to offer possible solutions for these problems.

Phillips, N. A.↗