摘要:

During the Structure and Atmospheric Turbulence Environment (STATE) campaign in June 1983, three small rockets (Super Arcas) containing dc probes to measure electron density irregularities with high spatial resolution were launched at Poker Flat, Alaska. The rockets were launched at three different times when the nearby MST (mesospheric, stratospheric, and tropospheric) radar showed intense regions of backscatter in the mesosphere. The first and third flights (STATE 1 and STATE 3) were perfectly successful, providing high‐quality electron density measurements; STATE 2 did not produce any useful results. When the electron density measurements are compared with the radar echo power as a function of altitude for STATE 1 and 3, large fluctuations and strong gradients in the electron density profiles are observed in the region of most intense backscatter. The electron density profiles show different characteristics in the peak scattering region with respect to altitude, electron density gradients, and irregularities. Power spectra of the electron density spatial fluctuations were derived from the measured electron densities for the region from approximately 65 to 90 km for several height intervals, with the smallest being approximately 100 m. In the region of most intense backscatter, the spectral power over the entire frequency range increases by almost 3 orders of magnitude for both rocket data sets. For STATE 1 a linear fit to the log‐log power spectral plots between 1.0–80 Hz (i.e., spatial scales from about 500 to 5 m) can be approximated by a power law with an index of about –(5/3), as would be expected in an inertial subrange of homogeneous, isotropic turbulence. The spectra, moreover, show a continuous steepening of the spectral slope in the viscous subrange at frequencies above 100 Hz (approximately 4.5–0.5 m), giving a much higher spectral index. The STATE 3 spectra, on the other hand, show a steeper spectral index near −2.0 in the inertial subrange but steepening at the higher frequencies, as do the STATE 1 data. A detailed intercomparison of the probe data is presented, followed by an absolute comparison between the radar and rocket measurements. Reasonable agreement is seen between the observed echo power profile and the profile calculated using the 3‐m electron density fluctuations obtained from th

ISSN:0148-0227    

DOI:10.1029/JD093iD06p06989

年代:1988

数据来源: WILEY

摘要:

The electron density fluctuation spectra measured during the first and third flights of the STATE experiments (STATE 1 and STATE 3) are compared to present theories for the structuring of mesospheric electrons by neutral atmospheric turbulence. The STATE 1 electron turbulence occurs in a region of vertical electron density gradient just above the mesopause. The spectra show a nearly classic spectral form with evidence for buoyancy, inertial, and viscous subranges. A close inspection, however, reveals that the electron gas is characterized by a much smaller microscale than can reasonably be expected for neutral turbulence. Although at first very surprising, it is important to note that the very existence of the observed intense summer polar mesospheric 50‐MHz radar backscatter virtually requires such a result. We explain the extension of electron structure to smaller scales than the neutral gas by invoking a high effective Schmidt number for the passive scalar electrons. This dimensionless number is the ratio of the kinematic viscosity of the neutrals to the diffusion coefficient of the electrons and can only be significantly larger than unity ifDis anomalously small. We suggest that these conditions may occur and may be due to heavily hydrated positive ions near the region of extremely low temperature at the polar mesopause. The maximum in the STATE 1 electron density fluctuation strength was found just above the mesopause and seemed to be organized with a vertical scale of several hundred meters. This variation in fluctuation spectral density correlates with the outer scale of the electron density profile itself. This suggests that the turbulence in this case was dependent on the phase of a wavelike neutral gas disturbance. The STATE 3 turbulence, on the other hand, was centered on a deep electron density “bite‐out” and was correlated in strength with the steep gradients in that region. The STATE 3 spectrum does not display a classic inertial subrange, but it does have a viscous range which is nearly identical to the STATE 3 data. Both data sets imply neutral density fluctuations of the orde

ISSN:0148-0227    

DOI:10.1029/JD093iD06p07001

年代:1988

数据来源: WILEY

摘要:

Estimates of turbulence energy dissipation rates and inner scale sizes have been obtained at altitudes of 80∼90 km, using simultaneous rocket and radar data from the STATE experiments. Spectral widths from radar Doppler spectra and the rocket‐derived temperatures were used to calculate the turbulence energy dissipation rate as a function of height; values generally ranged from 0.05 to 0.15 m2s−3, with a long term average about 0.1 m2s−3. The maximum observed energy dissipation rate was about 1.0 m2s−3, but these occasional intense levels of turbulence lasted only a few minutes. The kinematic viscosity has been calculated from the rocket data, which was then used with the energy dissipation rates to estimate the turbulence microscale (η) as a function of height; values of about 1.5∼2.0 m were obtained from 80 to 87 km, with η increasing rapidly for heights above about 87 km. The inner scale for neutral turbulence is approximately 13 times η, which therefore possibly ranges from 20 to 26 m, which is in approximate agreement with other estimates for the mesosphere. This result shows that the 3‐m scattering wavelength for the Poker Flat Radar is well within the viscous subrange for neutral turbulence and raises questions as to why such large backscatterd signals are detected in the polar mesosphere. A companion paper (Kelley and Ulwick, this issue) discusses this within the context of the electron density fluctuation spectra measured during th

ISSN:0148-0227    

DOI:10.1029/JD093iD06p07009

年代:1988

数据来源: WILEY

摘要:

This study utilizes the unique data set obtained during the Structure and Atmospheric Turbulence Environment (STATE) experiment, conducted during June 1983 at Poker Flat, Alaska, to examine the structure and characteristics of the wave field near the summer mesopause. It is shown that the rocket and radar data together permit a much more detailed specification of wave parameters than would be possible using either data set alone. The results of this analysis suggest that the wave field near the summer mesopause is composed, in general, of a superposition of wave motions which act collectively to produce regions in which the wave field is convectively or dynamically unstable. These regions are found to correlate well with zones of enhanced turbulence and small‐scale wave activity, suggesting the processes and effects of wave field saturatio

ISSN:0148-0227    

DOI:10.1029/JD093iD06p07015

年代:1988

数据来源: WILEY

摘要:

We have compared seasonal variations of semidiurnal tides in the upper middle atmosphere observed by the Kyoto meteor radar and the Saskatoon medium‐frequency (partial reflection) radar in 1983–1985. Amplitudes of semidiurnal tides are generally larger at Saskatoon than at Kyoto. Seasonal variations of phases at 90 km agree fairly well for both zonal and meridional components between Kyoto and Saskatoon. The seasonal variation is mainly composed of two fundamental states appearing in summer‐centered (April/May–September/October) and winter‐centered months (November–February/March), which are characterized by long and relatively short vertical wavelengths, respectively. Clear transitions between the two states occur in equinoxes (February–April and October–November). Using determinations at Kyoto and Saskatoon with 4‐ to 5‐day observation intervals, we have studied the behavior of semidiurnal tides during the transitions in October–November in 1983–1985 and February–April in 1985. Precise comparisons have shown that the transitions are slightly delayed at Saskatoon in both vernal and autumnal equinoxes. Abrupt changes in phases of semidiurnal tides coincide with reduction and pulsating fluctuations of their amplitudes, suggesting the existence of interference between fundamental and higher modes which are dominant in summerlike and winter

ISSN:0148-0227    

DOI:10.1029/JD093iD06p07027

年代:1988

数据来源: WILEY

摘要:

Most studies of the climatic effects of nuclear war have used atmospheric models with simple representations of important physical processes. In this work, a model is used which treats the diurnal cycle of insolation, and includes surface and boundary layer parameterizations which take into account static stability and a four‐layer soil model. Three idealized experiments are described in which a band of smoke is prescribed over northern mid‐latitudes in July. In the first experiment, the standard model is used, in the second the effect of deep soil layers is ignored and in the third the stability dependence in the surface and boundary layer processes is removed. It is found that the inclusion of deep soil layers decreases the surface cooling by about 20%, whereas the inclusion of stability effects increases the cooling by about the same amount, though conclusions will depend to some extent on the model u

ISSN:0148-0227    

DOI:10.1029/JD093iD06p07037

年代:1988

数据来源: WILEY

摘要:

A hierarchy of line‐by‐line, narrow‐band and broadband infrared radiation models are discussed for ozone, a radiatively important atmospheric trace gas. It is shown that the narrow‐band (Malkmus) model is in near‐precise agreement with the line‐by‐line model, thus providing a means of testing narrow‐band Curtis‐Godson scaling, and it is found that this scaling procedure leads to errors in atmospheric fluxes of up to 10%. Moreover, this is a direct consequence of the altitude dependence of the ozone mixing ratio. Somewhat greater flux errors arise with use of the broadband model, due to both a lesser accuracy of the broadband scaling procedure and to inherent errors within the broadband model, despite the fact that this model has been tuned to the l

ISSN:0148-0227    

DOI:10.1029/JD093iD06p07047

年代:1988

数据来源: WILEY

摘要:

We have measured the134Cs,137Cs, and210Pb vertical distributions in a lake sediment core. A value of 0.042 Bq cm−2has been estimated for the atmospheric137Cs fallout originating in Chernobyl release on the Alpine area: it represents 15% of the residual137Cs activity due to nuclear tests. Mixing process and sedimentation rate have been deduced from134Cs and210Pb distribution. Distribution of137Cs has been simulated for slow and rapid mixing processes and for various mixing thicknesses. Comparison with the experimental distribution indicates values of mixing thickness and sedimentation rate in agreement with the previously measured one

ISSN:0148-0227    

DOI:10.1029/JD093iD06p07055

年代:1988

数据来源: WILEY

摘要:

The rotational transitionsJ= 35/2 → 33/2 andJ= 37/2 → 35/2 of35ClO at 21.663 cm−1(649.45 GHz) and 22.898 cm−1(686.45 GHz), respectively, have been identified in stratospheric emission spectra measured with a limb‐sounding Fourier transform spectrometer during balloon flights in April 1979 and October 1982. The measurements provide information on the ClO concentration at altitudes around 28 km. The fit of the observation with the theoretical ClO profile by Ko and Sze (1984) gives, in the case of the afternoon measurements obtained in 1979, a scaling factor of 0.85 (+0.67, −0.64), and in the case of the afternoon and early morning measurements obtained in 1982 flight, a scaling factor of 0.88 (+0.18, −0.08). A day to night variatio

ISSN:0148-0227    

DOI:10.1029/JD093iD06p07063

年代:1988

数据来源: WILEY

摘要:

The technique of spectral least squares fitting has been used to analyze a 0.02 cm−1resolution 3‐ to 4‐μm solar spectrum recorded from the south pole on December 3, 1986. The analysis has resulted in information on the total column amounts of several atmospheric gases. The retrieved total vertical column amounts (in molecules per square centimeter) are 2.4±0.4×1021for H216O; 4.5±0.5×1018for H218O; 3.9±0.4 × 1017for HDO; 2.1±0.2×1019for CH4; 5.1±0.5×1021for CO2; 3.9±0.4×1018for N2O; and 3.7±0.5×1015for C2H6. Identification of12CH3D absorption features and a search for H2CO absorption in the spectral dat

ISSN:0148-0227    

DOI:10.1029/JD093iD06p07069

年代:1988

数据来源: WILEY