Intercomparison of CO2 and HCN wave numbers at 800-600 kaysers with a diode laser spectrometer
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Devi, V. M.↗
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Dobson spectrophotometer ozone measurements during international ozone rocketsonde intercomparison
Measurements of the total ozone content of the atmosphere, made with seven ground based instruments at a site near Wallops Island, Virginia, are discussed in terms for serving as control values with which the rocketborne sensor data products can be compared. These products are profiles of O3 concentration with altitude. By integrating over the range of altitudes from the surface to the rocket apogee and by appropriately estimating the residual ozone amount from apogee to the top of the atmosphere, a total ozone amount can be computed from the profiles that can be directly compared with the ground based instrumentation results. Dobson spectrophotometers were used for two of the ground-based instruments. Preliminary data collected during the IORI from Dobson spectrophotometers 72 and 38 are presented. The agreement between the two and the variability of total ozone overburden through the experiment period are discussed.
Parsons, C. L.↗
Long baseline vector determinations and intercomparisons
The East Coast very long baseline interferometry (VLBI) group has performed about 60 experiments over the last 10 years in the process of developing and exploiting advanced VLBI techniques. Of those, the most recent 14 experiments are briefly described.
Knight, C. A.↗
On the VLBI-satellite laser ranging Iron Triangle intercomparison experiment
Simulations were performed to determine the suitability of the proposed station locations. The criterion was a comparison among the possible station configuration of the standard deviations of baseline and Earth rotation parameters estimated from a least squares covariance analysis. Only the relative magnitudes of the standard deviations were addressed in the analysis. Only random errors were assumed and no provision was made for systematic effects. The Iron Triangle, consisting of the stations at Westford (Haystack), Massachusetts, Owens Valley, California, and Ft. Davis, Texas, was regarded as the structure of the proposed network with options to incorporate either the Goldstone, California, or Green Bank, West Virginia, station or both. It was decided to include the Richmond, Florida, station in the analysis since it offered more North-South separation and therefore could strengthen the geometry of the network especially in the recovery of Earth rotation parameters.
Bock, Y.↗
Optical image and laser slope meter intercomparisons of high-frequency waves
Spectral analyses of optical images of the ocean surface, obtained by a digital video system, are presented and compared with wave data measured simultaneously by the JPL Waverider-mounted laser slope meter. The image analyses, which incorporate several new ideas, provide two-dimensional wave number spectra of slope, covering wavelengths from 10 cm to 10 m. These slope spectra are converted to wave height spectra by a new technique which includes the effects of sky radiance gradients. Space-time spectra are also presented for waves whose frequencies are less than 2 Hz. The JPL slope frequency spectra are compared with image wave number spectra which have been converted to frequency spectra by use of the gravity wave dispersion relation. Results of comparisons between the frequency spectra obtained from the two different measurements show reasonable agreement for frequencies less than 3 Hz.
Lubard, S. C.↗
Precise T and F intercomparison via VLF phase measurements
Continuous phase recording of the 16kHz transmission from GBR (UK) are being made and published midday phase data of GBR are received regularly from laboratories in the US, FGR, and UK. The local time scale (UTC, India), at the National Physical Laboratory in New Delhi, and those at the foreign laboratories are intercompared using the VLF phase data. A major factor which limits the accuracy of long term comparison is the seasonal variation in the VLF over delay over long paths. By taking into account the seasonal delay variations in a semiempirical way, the accuracy of time and frequency comparisons can be improved. Over a one year period, accuracy of a few parts in 10 to the 14th power in frequency and 1 to 2 micron sec in time were obtained. The relative frequency offset difference between UTC, (India) and UTC (PTB, Germany) of (7.0 + or - 0.1) x 10 to the -13 power agrees well with that obtained in a satellite experiment.
Gupta, A. S.↗
Production of odd nitrogen in the stratosphere and mesosphere - An intercomparison of source strengths
Galactic cosmic rays (GCRs), nuclear explosions, lightning, solar proton events (SPEs), relativistic electron precipitation, and meteors are related to the oxidation of nitrous oxide by comparing several sources of odd nitrogen (ON) in the stratosphere and mesosphere. Published O3 and N2O data show that ON produced by the reaction of O(1D) with N2O peaks between 25 and 35 km; the GCRs add approximately the same amount of ON as N2O oxidation at the solar minimum for geographic latitudes over 50 deg. Nuclear explosions in 1961-1962 added 1.1 and 2.2 x 10 to the 34th NO molecules each, and SPEs produced greater amounts of ON above 50 deg than N2O oxidation during 1958 through 1960, and in 1972.
Jackman, C. H.↗
I-Xe dating - Intercomparisons of neutron irradiations and reproducibility of the Bjurbole standard
Previously unpublished data from the stepwise heating analysis of the Valecitos 1 (V1) Bjurbole standard are presented together with the results of an isotopic dilution measurement of a KI monitor included in the V1 irradiation package. The results of these analyses are compared with the values observed in other irradiations. Apparent I-Xe 'formation' ages are reproducible for three different samples of Bjurbole, suggesting isotopic homogeneity for initial iodine in the bulk material. The systematics of neutron capture in Xe-135 (produced from U-235 neutron fission) are examined and verified in irradiated BCR-1.
Hohenberg, C. M.↗
Intercomparison of various measurements of thermal plasma densities at and near the plasmapause
Four methods of investigating the thermal plasma density near the plasmapause are intercompared for the period of July 1 to 15, 1972. These methods are whistlers, the double floating probe on Explorer 45, three IMP I plasma wave signatures, and observations made aboard both Prognoz 1 and Prognoz 2. Explorer 45 data have provided new information on the plasmapause bulge which, during this period, occurs at 16 L.T. This displacement from the accepted time of 18 L.T. or even later is substantiated by the Russian satellites. All methods give the result that the plasmapause is found at an electron number density somewhere between 20 and 120 per cu cm or, alternatively, at 60 per cu cm, to within a factor of 2.
Williams, D. V.↗
Session III of the VLBI/Laser intercomparison task of the NASA crustal dynamics project
Baseline vector measurements are reported for a line crossing most of the state of California from Quincy to Mt. Otay near the Mexican border. They were obtained to compare three space geodetic techniques: very long baseline interferometry, satellite laser ranging, and Doppler satellite tracking.
Fliegel, H.↗
Visible infrared spin-scan radiometer atmospheric sounder radiometric calibration - An inflight evaluation from intercomparisons with HIRS and radiosonde measurements
The ability to conduct soundings from a geostationary platform has been demonstrated with the Visible IR spin-scan radiometer Atmospheric Sounder (VAS) aboard GOES-4. While a negative offset reaching 2.0-3.0 C for the upper atmospheric CO2 bands of VAS was observed in comparisons with High Resolution IR Radiation Sounder (HIRS) measurements and analyses of radiosonde data, VAS radiances are consistent with that material. After removing the offset, the temperature profiles derived from VAS radiances agree very well with those observed by radiosondes. Time variations in the atmospheric state are discernible from VAS soundings at three-hour intervals, and were confirmed by radiosonde observations.
Menzel, W. P.↗
Characteristics of space and ground based total ozone observing systems investigated by intercomparison of Nimbus 4 Backscattered Ultraviolet /BUV/ data with Dobson and M-83 results
The Nimbus 4 Backscattered Ultraviolet (BUV) experiment data has been reprocessed to provide a near global data set covering the seven years from 1970 to 1977. The data set is the result of a three year effort by the Ozone Processing Team which included review and correction of the spacecraft ephemeris, instrument calibration, and processing algorithms. The accuracy of the resulting total ozone determinations compares well with that of ground based data. An important application of the global BUV data set is to use it in determining long term trends in global total ozone. However, in order to identify long term trends in ozone, it is necessary to eliminate first long-term drift in the instrument calibration. A follow on experiment, the Solar Backscattered Ultraviolet/Total Ozone Mapping Spectrometer, (SBUV/TOMS), was flown on Nimbus 7 launched in October 1978. The SBUV provides information about both total ozone and vertical ozone profiles for a 200 km square field of view.
Fleig, A. J.↗
Intercomparison of lunar laser and traditional determinations of earth rotation
Since August, 1969, ranges to one or more retroreflector arrays on the lunar surface have been measured by means of a laser procedure. Analysis of these measurements improves determination, not only of the orbit and librations of the moon, but also of the rotational parameters of the earth, including the X and Y coordinates of the terrestrial pole, and the true rotational angle of the earth with respect to atomic or to broadcast time. The considered approach for deriving the Universal Time 1 (UT1) involves two steps. During the first step the parameters of the lunar orbit and librations are solved along with the coordinates of the retroreflectors on the moon and of the observatory. Improved values of the Universal Time 0 (UT0) and range corrections at the observatory are obtained in the second step. Attention is given to lunar laser ranging (LLR), raw data in UT1, an harmonic analysis of the LLR UT1 data, and data obtained in 1980. The results provide UT1 with an accuracy of a factor of 2 or more better than was previously available from conventional astrometric data.
Fliegel, H. F.↗
An intercomparison of NEL and DHL water flow facilities using a twin orifice plate flowmeter assembly
A 205 mm transfer standard orifice plate meter assembly, consisting of two orifice plates in series separated by a length of pipe containing a flow straightener, was calibrated in two water flow facilities. Results show that the agreement in the characteristics of such a differential pressure transfer standard package is within 0.17% over a 10:1 range from flow rates of approximately 8 to 80 l/sec. When the range over which the comparison was made was limited to that for which the calibration graphs gave straight lines, the agreement is 0.1% in 3 of the 4 calibrations (0.17% in the fourth).
Dejong, J.↗
Satellite-in situ measurement intercomparisons at Wallops Island, Virginia
A field program was carried out at Wallops Island, Virginia in which a number of in situ soundings were made during February to May 1980 in conjunction with near overpasses of NOAA-6. A comparison of NOAA-6 measured and derived quantities with those of in situ instruments was made. Positive temperature biases (satellite warmer) were found to appear in the lower troposphere and tropopause regions; negative differences generally were found to appear in the middle and upper stratosphere. Average geopotential height differences were relatively small at all levels, but increasing rms errors showed decreasing reliability with height of satellite geopotential heights. Satellite-derived geostrophic winds were found to have less shear than in situ determined winds. Bias in the directional differences was found to range from less than 5 deg to about 20 deg, with rms differences apparently decreasing near the level of wind speed.
Nestler, M. S.↗
Intercomparison of NIMBUS 7 solar backscattered ultraviolet ozone profiles with rocket, balloon, and Umkehr profiles
A global ozone data set covering the two years from November 1978 until October 1980, with an average of 1200 profiles per day, has been produced and archived from the solar backscattered ultraviolet (SBUV) instrument flown on the NIMBUS 7 spacecraft. The SBUV ozone profiles are compared with measurements from chemical and optical sensors launched on balloons and rockets and with ozone profiles obtained from the ground-based Dobson spectrophotometers using the Umkehr method. The biases between the SBUV results and the balloon and Umkehr results are generally less than 10 percent. These biases are functions of layer height and latitude and are believed to be largely due to inconsistencies in the ozone absorption cross sections used for the various measurement systems. The precision of the SBUV measurements is found to be better than 8 percent for pressures between 1 and 64 mbar and better than 15 percent from 64 to 253 mbar.
Bhartia, P. K.↗
Intercomparison of the Nimbus 7 SBUV/TOMS total ozone data sets with Dobson and M83 results
Two years of SBUV/TOMS (Solar Backscattered Ultraviolet/Total Ozone Mapping Spectrometer) data spanning the period November 1978 to October 1980 have been processed and compared with ground-based ozone measurements made at 62 Dobson spectrophotometer and 18 M83 filter photometer ozone stations. Results show that the satellite ozone values are consistently smaller than those measured by the stations; most of this difference is probably due to an error in the currently accepted ozone absorption cross sections at ultraviolet wavelengths. Dobson-derived ozone amounts agree extremely well with those derived from each of the satellite instruments. Long-term stability of the ozone derived by the two instruments is expected to be better than 0.5 percent per year.
Bhartia, P. K.↗
An intercomparison of SAGE and SBUV ozone observations for March and April 1979
Thirty-eight latitudinal cross sections of stratospheric ozone observed by the SAGE (Stratospheric Aerosol and Gas Experiment) and SBUV (Solar Backscattered Ultraviolet) satellite instruments on the same days in March and April 1979 and at approximately the same latitude are compared. Differences in the zonal-mean mixing ratios are found. At pressures less than 5 mbar, SAGE gives approximately 20 percent larger mixing ratios at tropical latitudes (after a correction has been applied for the expected diurnal variation of ozone). The uncorrelated portion of the SBUV variances are smaller than the SAGE noise variances at altitudes above 10 mbar, which indicates that the SBUV experiment should provide excellent detectability of longitudinal ozone variations.
Cunnold, D. M.↗