摘要:

We estimate the trends in Dobson total ozone records from 1970 through 1983, using ozone data from 1964 through 1983. These estimates range from −0.31%/decade ± 0.49%/decade (1σ) for unadjusted data to −1.10%/decade ± 0.47%/decade for data adjusted for instrument interventions and the solar cycle. The negative trends are primarily the result of abnormally low total ozone values in the northern hemisphere during earl

ISSN:0148-0227    

DOI:10.1029/JD091iD02p02675

年代:1986

数据来源: WILEY

摘要:

The net vertical tracer flux in the stratosphere is due primarily to advection by the global‐scale mean meridional circulation, not to diffusion by turbulent eddies. Using a simple model of this circulation, it is shown that the net flux can be approximated by a flux‐gradient relationship in which the vertical “eddy transport” coefficient is proportional to the square of the diabatic heating rate and inversely proportional to the rate at which meridional tracer gradients are destroyed by horizontal eddy mixing and chemical damping. Thus the transport coefficient will differ for tracers with differing chemical lifetimes. Profiles computed for various source gases (CH4, N2O, CF2Cl2, and CFCl3) show that this parameterization provides an improvement over conventional formulations that utilize a single transport coefficient for all

ISSN:0148-0227    

DOI:10.1029/JD091iD02p02681

年代:1986

数据来源: WILEY

摘要:

The Geophysical Fluid Dynamics Laboratory (GFDL) three‐dimensional general circulation/tracer model has been used to investigate the stratospheric behavior of N2O under a range of photodestruction hypotheses. A comparison of observations with these simulations shows that the atmospheric N2O lifetime lies between 100 and 130 years. For the three experiments conducted, it was found that the model‐derived global one‐dimensional eddy diffusion coefficientsKzfor one experiment are appropriate for the other two experiments as well. In addition, the meridional slopes of N2O mixing ratio isolines are virtually identical in the lower stratosphere for all three experiments. The generality of these two results was explored with a simple “two‐slab” model. In this model the equilibrium meridional slopes of trace gas isolines andKzvalues are solved directly. The model predicts that long‐lived gases with weak photodestruction rates should have similar meridional slopes, but the effect of faster destruction is to flatten the meridional slopes. The simple model also predicts thatKzdepends upon chemical processes through a direct dependence upon the meridional slope for a given gas as well as upon the intensity with which upward propagating tropospheric disturbances force the stratospheric zonal winds. The three N2O experiments have been compared against detailed observational analyses. These analyses show that the model meridional N2O slopes are too flat by about 30%. The simple two‐slab model indicates that this results from a somewhat weak forcing of the model stratospheric zonal winds. A comparison of the temporal variability of model N2O against the “Δ” statistics of Ehhalt et al. (1983) shows good agreement. Another simple theoretical model is proposed that shows why Δ statistics are so useful and predicts the circumstances under which different destruction chemistries should lead to different Δ statistics. These results have allowed a very general extrapolation of the three N2O numerical experiments to predicted structure for a wide class of long‐lived trace gases. Specifically, the supporting theoretical developments allow predictions for the effect of chemistry on the global (one‐dimensional) behavior, meridional‐height (two‐dimensional) structure, and local temporal variability. Finally, some examples of transient behavior are presented through model time series at points corresponding to available measurements. These time series, with the support of horizontal N2O charts, show complex behavior, including pronounced seasonal cycles, transport‐produced N2O “inversions,” and detailed meridional transport events associated with

ISSN:0148-0227    

DOI:10.1029/JD091iD02p02687

年代:1986

数据来源: WILEY

摘要:

Results of several recent reports on the role of ocean mixing in the transient response to a CO2doubling are analyzed and compared. Wigley and Schlesinger (1985) obtained an analytical solution to a one‐dimensional box‐diffusion (BD) ocean model in which the mixed layere‐folding time τe∝ ƒ02KΔTeq2, where ƒ0is the planetary ocean fraction,Kis the ocean diffusivity, and ΔTeqis the equilibrium temperature response. The dependence of τeobtained by Wigley and Schlesinger is compared with that obtained using simple land‐sea resolved and box‐advection‐diffusion (BAD) models. For a BAD model the dependence of τeon bothKand ΔTeqis significantly less than for a BD model. A comparison of the transient response of BD and BAD models using the same effectiveKindicates that the behavior of the BAD model cannot be captured using a BD model, except during the first few decades of the transient response. Schlesinger et al. (1985) estimated atmospheric and mixed layer values of τefor their coupled atmosphere‐ocean general circulation model (A/O GCM) by fitting a BD model to the first 16 years of their A/O GCM transient response and then integrating the BD model for 200 years. However, Schlesinger et al. appear to have overestimated values of τefor their long‐term A/O GCM by fitting their short‐term A/O GCM transient response to a model in which the equilibrium globally averaged atmospheric and mixed layer temperature responses are equal, whereas this is apparently not true for their A/O GCM. Hansen et al. (1984) estimated τeby modeling three‐dimensional ocean mixing as a series of isolated BD models, one below each horizontal grid point, and by using tritium‐based diffusion coefficients, which probably are too large when applied to heat and probably lead t

ISSN:0148-0227    

DOI:10.1029/JD091iD02p02709

年代:1986

数据来源: WILEY

摘要:

The temporal and spatial characteristics of short‐term fluctuations in the stratosphere are studied using 30 months of ozone, solar UV, and temperature data from the Nimbus 7 solar backscattered ultraviolet (SBUV) and the stratosphere and mesosphere sounder (SAMS) experiments. It is shown that the stratosphere is in a continuous state of oscillation, with periods varying between 3 to 7 weeks. These oscillations are manifestations of dynamically induced perturbations in the winter hemisphere and the 27‐day modulation of the solar UV radiation. Dynamically induced oscillations are global in extent and appear to be independent of solar activity. They are strongest at high latitudes during the fall‐spring epoch of each hemisphere. When the seasonal differences of the two hemispheres are taken into account, the high‐latitude oscillations in each hemisphere show significant negative correlation with lower latitudes which extends far beyond the tropics into the opposite hemisphere. Their phase shows the characteristics of meridional waves with poleward and equatorward propagations above and below 10 mbar, respectively. Both the multiple regression and cross‐spectral analyses of ozone, temperature, and solar flux data show the ozone mixing ratio to be much more sensitive to dynamically induced changes in temperature than to changes in solar UV flux. The solar‐induced changes in ozone are detectable only under favorable circumstances, that is, at low latitudes during periods of high solar activity. The estimated change in ozone mixing ratio in the upper stratosphere is about 3% over a solar cycle. This is comparable to a temperature‐induced change of about 2 K of dyn

ISSN:0148-0227    

DOI:10.1029/JD091iD02p02719

年代:1986

数据来源: WILEY

摘要:

Absolute infrared line intensities of several ClO lines in the rotational‐vibrational (1–0) band were measured using infrared heterodyne spectroscopy near 12 μm. A measurement technique using combined ultraviolet absorption and infrared line measurements near 9.5 μm and 12 μm permitted an accurate determination of the column densities of O3and ClO in the absorption cell and thus improved ClO line intensities. Results indicate ClO line and band intensities ∼2.4 times lower than previous experimental results. Effects of possible failure of local thermodynamic equilibrium conditions in the absorption cell and the implication of the results for stratospheric ClO measurements in the infrared are d

ISSN:0148-0227    

DOI:10.1029/JD091iD02p02735

年代:1986

数据来源: WILEY

摘要:

A theory is presented which explains the universal nature of one‐dimensional vertical wave number,k, power spectral densities (PSDs) of horizontal winds as measured in the atmosphere and predicted by VanZandt. The theory is that the PSD amplitude at any given wave number (greater than a certain minimum,k*) is determined by its saturation value due either to shear instability (i.e., critical Richardson Number) or, more likely, to convective instability. This explains why the PSD amplitudes observed do not grow exponentially with increasing altitude. This saturation theory assumption plus other considerations leads to a PSD of the formN2/kn, wherenis in the range of about 2.5 to 3 andNis the Brunt frequency. A simplified model involving superimposed narrow bands of gravity waves as well as a model based merely on dimensional arguments both lead ton= 3. The full model not only explains the observed spectral slopes but also predicts the PSD amplitude in the troposphere to be 3.5 times smaller than in the stratosphere. The derivation of the model is based on the saturation condition that ∫k2PSD(k)dk=N2. The model may also apply to the ocean and explain the Garrett‐Munk vertical wave number spe

ISSN:0148-0227    

DOI:10.1029/JD091iD02p02742

年代:1986

数据来源: WILEY

摘要:

We present simultaneous in situ measurements of a long‐period inertio‐gravity wave and of clear air turbulence events associated with wave propagation. The energy budget of the wave‐turbulence interaction shows that a wave of long period and of short vertical wavelength may propagate upward over several wavelengths close to the shear instability conditions. This result allows one to interpret the spatiotemporal structure of CAT layers as reported in the literature and in particular their horizontal and vertical extent, their thickness, and their persis

ISSN:0148-0227    

DOI:10.1029/JD091iD02p02749

年代:1986

数据来源: WILEY

摘要:

The limb radiance inversion radiometer (LRIR) and limb infrared monitor of the stratosphere (LIMS) experiments aboard the Nimbus 6 and 7 spacecraft have made observations of infrared emission by CO2, O3, H2O, HNO3, and NO2at the earth's limb. This paper describes a method by which such measurements can be inverted to give vertical distributions of temperature and mixing ratios as functions of pressure. The simple and efficient approach was successfully applied to the LRIR data and subsequently in the initial assessment of the LIMS data. Inversion of synthetic data indicates the size of the errors to be expected as a result of the assumptions and instrumental errors. Retrievals of measured LIMS radiances are shown as examples and compared to in situ observations. The differences are comparable to those obtained with the more complex retrieval scheme used to process the LIMS archival products. Some problems are noted.

ISSN:0148-0227    

DOI:10.1029/JD091iD02p02757

年代:1986

数据来源: WILEY

摘要:

An analysis using Stratospheric Aerosol and Gas Experiment (SAGE) data for the period February 1979 to November 1981 was performed to determine the spatial extent and frequency of occurrence of cirrus clouds over a large portion of the earth's surface. The effective field of view corresponding to the determined frequency was 100 km2. A by‐product of the study reveals the statistics of tropospheric observational opportunities for a limb‐sounding satellite sensor by determining the percentage of times of successful penetration to a given height or depth below the tropopause.The results of the analysis showed that optically thick cirrus clouds form most often in the midlatitudes and over the tropics, with distinct minima near latitude bands of 20°–30° north and south. The zonally averaged latitudinal distributions of cirrus clouds observed by SAGE compared very well with the Nimbus 5 selective chopper radiometer (SCR) observations in shape but not in magnitude. SAGE showed about twice the magnitude of the SCR results. The percentage of tropospheric observational opportunities down to 7 km was as high as 60% in the upper latitudes. A geographical presentation of the SAGE results showed the growth and seasonal movement of high‐cloud features were in good agreement with previou

ISSN:0148-0227    

DOI:10.1029/JD091iD02p02775

年代:1986

数据来源: WILEY