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Frederick, J. E.

Publications and source records attributed to Frederick, J. E..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Atmospheric odd oxygen production due to the photodissociation of ordinary and isotopic molecular oxygen

Line-by-line calculations are performed to determine the contributions of the Schumann-Runge bands of ordinary and isotopic oxygen to the photodissociation of these molecules at different altitudes. The contributions to the dissociation rates of the satellite lines and of the first and higher vibrational states of the initial molecular states are found to be insignificant. At 70 km, (O-16)(O-18) is found to produce 10 times as much odd oxygen as would be produced if the isotope did not have selective absorption, and 6 percent of the odd oxygen produced is due to this isotope. It is noted that the excess odd oxygen produced is not enough to explain the excess quantity of ozone observed in the atmosphere, which cannot be accounted for in photochemical models. Comparison with previous results is made.

Omidvar, K.↗
NASA NTRS1986

Instrument characterization for the detection of long-term changes in stratospheric ozone - An analysis of the SBUV/2 radiometer

The scientific objective of unambiguously detecting subtle global trends in upper stratospheric ozone requires that one maintains a thorough understanding of the satellite-based remote sensors intended for this task. The instrument now in use for long term ozone monitoring is the SBUV/2 being flown on NOAA operational satellites. A critical activity in the data interpretation involves separating small changes in measurement sensitivity from true atmospheric variability. By defining the specific issues that must be addressed and presenting results derived early in the mission of the first SBUV/2 flight model, this work serves as a guide to the instrument investigations that are essential in the attempt to detect long-term changes in the ozone layer.

Frederick, J. E.↗
NASA NTRS1985

Dissociation of metastable O2 as a potential source of atmospheric odd oxygen

An analysis of the possible dissociation of metastable oxygen molecules subject ot constraints imposed by selection rules for molecular transitions, airglow observations, and atmospheric chemistry leads to the following conclusions. Dissociation of O2(b1Sigma g +) must produce a negligible number of oxygen atoms at all altitudes in the earth's atmosphere. However, if the dissociation cross section of O2(a1Delta g) has a maximum value in the range 10 to the -20th to 10 to the -19th/sq cm, then the process O2(a1Delta g) + h(nu) yields O2(C3Delta u) yields O(3P) + O(3P) will constitute a significant, and potentially the major, source of odd oxygen in the uppermost stratosphere and mesosphere.

Frederick, J. E.↗
NASA NTRS1985

The detection of long-term changes in stratospheric ozone Scientific requirements and current results from satellite-based measurement systems

The ability to detect subtle trends in upper stratospheric ozone places strict requirements on satellite-based Solar Backscatter Ultraviolet (SBUV) sensors intended for this purpose. Simulation of the long-term change in backscattered radiance indicates trends in the range 1.0-1.6 percent per decade depending on wavelength for an ozone depletion scenario based on chlorofluorocarbon (CFC) chemistry. The maximum percentage change in the measured quantity, as would be sensed by the Nimbus-7 SBUV experiment and future similar instruments, is roughly a factor of two less than the maximum percentage change in ozone, the quantity of geophysical interest. Furthermore, interannual variations, whose magnitude can be estimated from the SBUV data set, could obscure a CFC-related trend in radiance when viewed over a period less than a decade. Even when such atmospheric noise and possible solar cycle variations are neglected, the detection of an ozone trend of the magnitude predicted for CFC-related chemistry requires a set of radiance measurements that are internally consistent to 1 percent or better over a time span of a decade.

Frederick, J. E.↗
NASA NTRS1985

In-situ measurements of nitric oxide in the high latitude upper stratosphere

The vertical profiles of nitric acid were measured over Poker Flat, Alaska, in August 1984 and January and February 1985 using a rocket-launched parachute-deployed chemiluminescence sensor. Results for the altitude range 35-45 km indicate a large seasonal variation, with wintertime mixing ratios being a factor of two above summer values. The winter profiles contain sharp positive vertical gradients persisting through the highest altitudes observed. Above the stratopause, the mixing ratio observed in February increases rapidly and between 52 and 53 km reaches 148.9 ppbv, an order of magnitude greater than typical mid-latitude values measured with this instrument. Such behavior is consistent with the idea that nitric oxide produced at greater altitudes reaches the high-latitude upper stratosphere or lower mesosphere in winter. The results support the existence of a vertical coupling between diverse regions of the atmosphere in the high-latitude winter.

Horvath, J. J.↗
NASA NTRS1985

Satellite observations of the nitric oxide dayglow Implications for the behavior of mesospheric and lower-thermospheric odd nitrogen

The solar backscattered ultraviolet spectral radiometer on the Nimbus 7 satellite routinely measures fluorescence emissions from the nitric oxide (1, 4) gamma band that are imposed on the large Rayleigh-scattered signal in the wavelength range 255-256 nm. The gamma band feature, when isolated from the background radiance, provide information on the seasonal and latitudinal variations in the nitric oxide column abundance over the altitude region from 40 to 45 km upward through the thermosphere. At latitudes from 30 deg to 45 deg in the Northern Hemisphere the measurements show an annual cycle with maximum nitric oxide abundance in summer. The Southern Hemisphere pattern is qualitatively similar to this, although the amplitude of the seasonal variation is substantially smaller. The most prominent feature of the data base is a large maximum in nitric oxide emission that develops poleward of 45 deg latitude in both Hemispheres during late autumn and early winter. These maxima dissipate rapidly as spring approaches and are no longer evident in the data for Northern Hemisphere March and Southern Hemisphere September.

Frederick, J. E.↗
NASA NTRS1985

Measurement Requirements for the Detection of Ozone Trends

The number of measurements and period of collection in order to detect a trend in the vertical distribution of ozone was studied. Specific issues considered include the impact of: (1) short term ozone variability over the measurement site, and (2) the precision of the measuring instrument on the ability to detect trends to a given confidence limit.

Frederick, J. E.↗
NASA NTRS1985

Ozone-temperature relationships in the stratosphere

Utilizing independent estimates of ozone and temperature fields from the SBUV (Nimbus 7) and NOAA operational satellites, respectively, for the period 1978-1981, the coefficient of variation between the two parameters is determined. This coefficient is defined as A = Delta-O3 x (T)/Delta T x (O3) wehre Delta is an incremental change in either temperature or ozone and the bracket is a mean state. In practice, A is determined on a daily basis by regression of ozone mixing ratio versus temperature around a latitude circle during the winter season and the bracket value is the daily zonal average. This has the advantage of keeping the solar zenith angle fixed for a daily value while allowing it to change during the season. This is done at 30, 10, 5, 2, and 1 mb from 20 deg to 60 deg latitude in both hemispheres. The results are summarized and compared with those determined from a one-dimensional photochemical model applied to different latitudes.

Miller, A. J.↗
NASA NTRS1985

Radiative processes

Solar radiation and the processes that control its deposition in the Earth atmosphere are considered. The published data obtained since 1978 define a reference solar spectral irradiance for use in atmospheric chemical and dynamical studies, while long term satellite measurements are now providing information on variations in the output of the Sun over a range of time scales. As concerns absorption of solar radiation in the atmosphere, new cross section data for molecular oxygen and ozone are now available. Line-by-line calculations used to predict infrared flux divergences, both as regards assumptions made in radiative transfer calculations and in the spectroscopic parameters used as inputs are examined. Also examined are the influence of radiative processes on planetary scale wave activity, photochemical acceleration of radiative damping, and the breakdown of local thermodynamic equilibrium at mesospheric altitudes.

Frederick, J. E.↗
NASA NTRS1984

An analysis of the annual cycle in upper stratospheric ozone

The mid-latitude upper stratospheric ozone profiles obtained by the solar backscatter ultraviolet instrument on the Nimbus 7 satellite show a clear annual cycle both in the absolute ozone amounts between 0.98 and 15.6 mbar and in the magnitude of disturbances that reveal themselves as longitudinal structure. At the lowest pressure analyzed a winter maximum in ozone exists, but as one progresses downward in altitude a shift in the temporal phase of the annual cycle occurs in the vicinity of 3 to 4 mbar. Comparison of the observed behavior with the predictions of a one-dimensional photochemical model shows a systematic tendency for calculated ozone amount to be 20-27 percent below the data for pressures less than 7.8 mbar. The chemical model successfully predicts the change in phase of the annual cycle, although at a pressure greater than observed. Diagnosis of model results shows the observed shift to be closely coupled to the magnitude of the ozone column density near 3-4 mbar. The wavelength-dependent attenuation of the solar radiation field by ozone alters the relative magnitude of the molecular oxygen and ozone dissociation rates, leading to a change in the temporal phase of the annual cycle.

Frederick, J. E.↗
NASA NTRS1984

Analysis of upper stratospheric Umkehr ozone profile data for trends and the effects of stratospheric aerosols

The effect of stratospheric aerosols on Umkehr estimates of long-term ozone depletion associated with chlorofluoromethanes (CFMs) is considered in a statistical time series trend analysis. Time series models are estimated using monthly averages of Umkehr measurements made over the last 15 to 20 years. The time series regression models incorporate seasonal, trend and noise factors and an additional factor to account for the effects of atmospheric aerosols on the Umkehr measurements. The analysis indicates a statistically significant relation with atmospheric aerosol transmission in the Umkehr layers and implies that the relation is an important factor in any time series trend analysis of Umkehr data. Taking this relation into account, statistically significant negative trends were found in the Upper Umkehr layers. It is pointed out that upper stratospheric ozone could be sensitive to long-term solar variability as well as other possible influences in addition to CFM-induced effects, and therefore the cause or causes of the estimated trend cannot be unambiguously estimated using current Umkehr data.

Reinsel, G. C.↗
NASA NTRS1983

Nitric oxide in the upper stratosphere - Measurements and geophysical interpretation

A rocket-borne parachute-deployed chemiluminescence instrument has obtained seven new measurements of atmospheric nitric oxide for altitudes between 30 and 50 km at mid-latitudes. These results, when combined with profiles measured by an earlier version of the instrument, cover all four seasons and provide a more comprehensive picture of upper stratospheric nitric oxide than has been available previously. At the highest altitudes studied, the vertical gradient in mixing ratio displays positive and negative values during different observations, with the largest values tending to appear at the greatest heights in summer. Examination of the differences among the profiles, which exceed a factor of 3 near the stratopause, suggests that they arise from the action of transport processes which carry air into the mid-latitude upper stratosphere from regions of the atmosphere that contain widely different odd-nitrogen abundances.

Harvath, J. J.↗
NASA NTRS1983

Atmospheric temperatures near the tropical tropopause Temporal variations, zonal asymmetry and implications for stratospheric water vapor

Analysis of temperature measurements obtained over an eight-year period in the vicinity of the low-latitude tropopause confirms the existence of longitude regions which are consistently colder by approximately 2-3 K than elsewhere in the tropics. These temperature differences, however, are confined to a layer of thickness 3-5 km centered on the tropopause. The lowest monthly mean temperatures observed at the colder stations yield saturation mixing ratios that are consistent with the range of measured stratospheric water vapor. Examination of the daily variations in temperature at a given station reveals a more complex pattern than indicated by the monthly averages. On many days temperatures at the colder longitudes correspond to water vapor abundances that are less than observed in the stratosphere despite the favorable comparison of the monthly means. The results point to the need for a series of water vapor soundings at selected longitudes and times in order to define the extent to which the tropical tropopause controls the stratospheric water vapor abundance.

Frederick, J. E.↗
NASA NTRS1983

MSG-7: Molecular absorption processes related to the penetration of ultraviolet solar radiation into the middle atmosphere

The information presently available on the absorption cross sections of O2 and O3 with attention to the application of these data in middle atmospheric science is reviewed. The cross sections values reported by different groups are intercompared in tabular form where feasible, and specific values are recommended when there is a basis for preferring a particular set of results over other available data. When no such basis exists, the differences among published cross sections then serve to indicate a range of uncertainty. In these cases the need for additional work is indicated. Specific topics addressed are the absorption of molecular oxygen at Lyman alpha, in the Schumann-Runge continuum, in the Schumann-Runge bands, and in the Herzberg continuum. For ozone, the Hartley and Huggins bands are considered.

Frederick, J. E.↗
NASA NTRS1983

The distribution and annual cycle of ozone in the upper stratosphere

Study of the global distribution of upper stratospheric ozone derived from backscatter ultraviolet (BUV/SBUV) instruments on the Nimbus 4 and 7 satellites reveals the following characteristics for the period June 1970 May 1972 plus portions of 1978 and 1979. At pressures less than 5 mbar a local midlatitude maximum in the ozone mixing ratio develops in autumn and persists through the winter season in both hemispheres. However, by a pressure of 10 mbar the seasonal trend has reversed, with midlatitude summer values exceeding those in winter. The largest ozone mixing ratios in a global sense occur at tropical latitudes between pressures of 7 and 9 mbar. The general character of this pattern repeats from year to year, although differences in detail exist, especially in winter. This interannual variability in ozone increases the difficulty in extracting small long-term trends from the available data base. The overall seasonal pattern revealed by the measurements is in accord with photochemical model predictions which include the annual variation in temperature and solar illumination.

Frederick, J. E.↗
NASA NTRS1983

The Delta band dissociation of nitric oxide - A potential mechanism for coupling thermospheric variations to the mesosphere and stratosphere

Depletion of solar radiation at discrete wavelengths by nitric oxide has a significant impact on the dissociation rate of this gas in the delta(0, 0) and delta(1, 0) bands. Inclusion of the opacity provided by a typical NO profile reduces the dissociation rate in the upper stratosphere to 50-75 pct of that predicted when the optical depth calculation omits this contribution. A substantial fraction of the NO column abundance as measured near the stratopause resides in the lower thermosphere where correlations of NO with solar and magnetic activity are well documented. Variations in the thermospheric NO abundance therefore modulate the radiation field at the precise wavelengths absorbed by this molecule in the mesosphere and upper stratosphere. Predicted changes in the dissociation rate arising from a varying thermospheric opacity exceed 8 pct throughout the mesosphere and reach 15 pct between 65 km and 95 km.

Frederick, J. E.↗
NASA NTRS1982

MSG-7: Atmospheric Penetration of Solar Radiation in the Range of Schumann-runge Bands

There have been major efforts in measuring extraterrestrial solar irradiance for use in atmospheric studies. The quantity of immediate relevance to theoretical studies is the number of photons which reach a given altitude in the middle atmosphere. Current models compute the attenuated radiation field but the cross sections available for the major absorbers, O2 and O3, often come from experiments that are now quite old. Balloon measurements show some significant differences between the predicted and observed ultraviolet radiation field between 30 and 40 km. The wavelength region to be studied includes Lyman alpha plus the range 175 nm to the visible. Specific topics to be addressed are as follows: (1) the cross sections of the major absorbers, O2 and O3 including the Schumann-Runge bands as a subset; (2) comparison of the in situ measurements of the attenuated radiation field with calculations; and (3) the relevance of the scattered and reflected radiation fields for middle atmospheric processes.

Frederick, J. E.↗