摘要:

A band‐pass filter is used to obtain an estimate of the seasonal CO2cycle at Mauna Loa from monthly mean concentration data. The signal that is extracted shows interannual variations in the amplitude with, as has frequently been noted, a preponderance of larger amplitudes in recent years. An interesting feature of the signal is that abnormally small amplitude peaks in the (northern) spring are almost always followed by small‐amplitude troughs in the following fall but that there is no similar correlation between the amplitudes of peaks in fall and the following spring. This suggests that the amplitude variations reflect changes in individual northern growth seas

ISSN:0148-0227    

DOI:10.1029/JD092iD05p05497

年代:1987

数据来源: WILEY

摘要:

The multilayer energy balance model of Peng et al. (1982) has been further developed to include a simple two‐dimensional advective‐diffusive deep ocean and to allow seasonal variation in order to study long‐term transient climate response to a CO2increase as well as its seasonal pattern. Comparisons between the model‐simulated present climate and conventional and satellite data show that the model can simulate well the annual cycle of the surface temperature and the radiation budget of the atmosphere. In response to a hypothetical step function doubling of atmospheric CO2, the model reaches within 1/eof the equilibrium response of global mean surface temperature (2.6°C) in 9–35 years for the probable range of vertical heat diffusivity in the ocean. This large range of response time underlies the importance of properly using the heat diffusion coefficient in ocean models. In response to a projected CO2trend based on estimates by the Carbon Dioxide Assessment Committee (National Research Council 1983), the model's transient response in annually and globally averaged surface temperature is 60–75% of the corresponding equilibrium response. The disequilibrium increases with increasing oceanic heat diffusivity. When the atmospheric CO2level reaches twice the current level, in about a century, the global mean surface temperature increases by 1.5°–2.0°C, depending on the heat diffusivity of the ocean. Local warming at certain times of the year, however, may be 2–3 times greater than the annual and global average. In the northern high latitudes the response undergoes significant seasonal and latitudinal variations. A maximum occurs in the early winter, and a secondary maximum occurs in the spring. In the southern hemisphere, large responses are confined to a narrow latitude zone bordering Antarctica and occur only in the cold months. The pattern of the seasonal and latitudinal distribution of the transient response remarkably resembles that of the equilibrium response to a doubling of CO2. This agrees with Bryan et al. (1982) and Spelman and Manabe (1984), implying that sensitivity studies of equilibrium climate can be used as a guide for predicting the latitudinal pattern of a warming trend. The abovementioned transient response is obtained by integrating the model from the equilibrium state corresponding to the year 1975. A comparison between this and another numerical integration of the model starting from the equilibrium state corresponding to the CO2level in 1925 shows that the atmospheric CO2increase before 1975 has only a very small effect on the model response a

ISSN:0148-0227    

DOI:10.1029/JD092iD05p05505

年代:1987

数据来源: WILEY

摘要:

A recurrent suggestion in the literature is that the spatial variability of cloud might best be studied through the power spectrum of the cloud field. In this paper this proposal is examined in the context of radiative transfer by broken cloud. Through the analysis of numerical models in one and two dimensions, three conclusions are drawn: (1) Fields with the same power spectrum may transmit different average fluxes, so the power spectrum alone does not determine the radiative transfer. (2) The power spectrum of both the models and real cloud fields (advanced very high resolution radiometer satellite images) oscillate so rapidly that quantitative analysis of the power spectrum is very sensitive to the manner in which the power spectrum is sampled. The most stable analysis of the power spectrum involves integration over all spatial frequencies. It will be shown how this procedure permits the calculation of infrared transfer in a one‐dimensional cloud model. (3) A proposal for a satellite‐mounted optical Fourier analyzer is examined, and it is shown that while such an instrument eliminates aliasing and computational restraints, the need to compress the data by logarithmic sampling of the power spectrum impairs the resolution of the correlation function of the cloud field. Furthermore, the degradation of the resolution increases with the correlation len

ISSN:0148-0227    

DOI:10.1029/JD092iD05p05522

年代:1987

数据来源: WILEY

摘要:

The transfer of long‐wave radiation in a model of broken clouds constructed on the basis of Poisson point flux is investigated. Formulas are obtained for the expected value of the radiance, taking into account the influence of finite horizontal dimensions of clouds on the radiation field. The results of calculations show a differnce of 2–8°K between the mean brightness temperatures of stratus and cumulus clouds in the wide range of variations of optical‐geometric parameters and viewing

ISSN:0148-0227    

DOI:10.1029/JD092iD05p05533

年代:1987

数据来源: WILEY

摘要:

The cloud climatology data obtained from the analysis of the Air Force three‐dimensional nephanalysis (3DNEPH) cloud data base and the broadband radiation budget data derived from the Nimbus 7 earth radiation budget (ERB) measurements, are compared on regional, zonally averaged, and hemispheric scales for January and July 1979. The analyzed cloud climatologies are also compared with existing cloud climatologies and general circulation features. In addition, they are used as input to an IR parameterization model to calculate the emitted IR flux at the top of the atmosphere. These model fluxes are subsequently compared with the ERB flux climatologies. An investigation of the sensitivity, at 1200 and 2400 local time, of the reflected solar, emitted IR, and net radiation to changes in cloud amount on a regional, zonal, and hemispherical basis is then carried out employing the 3DNEPH and ERB data. The daily net radiation sensitivity factors for the northern hemisphere for January and July, with values of −8.1 and −50.9 W m−2, respectively, compare reasonably well with those obtained by other invest

ISSN:0148-0227    

DOI:10.1029/JD092iD05p05540

年代:1987

数据来源: WILEY

摘要:

Differences in the temporal behavior of the ultraviolet irradiance at 205 nm and the 10.7‐cm radio flux, the ultraviolet irradiance at 121.6 nm, model calculations of the 205‐nm irradiance derived from Ca IIKplage emission, and the sunspot‐blocking function are examined during a 5‐year period near the maximum of solar cycle 21. Because of solar rotation the dominant variance in each of these time series occurs at 27 days, but real temporal differences arise because the five solar time series are each formed at different heights within the solar atmosphere and are associated with a variety of solar active region phenomena having different spatial and temporal characteristics on the solar disc. These differences may be important if the ground‐based solar activity time series are used instead of the measured UV irradiances in correlation studies of solar variability with atmospheric parameters such as ozone densities and temperature. Recognizing the presence of autocorrelation in the UV irradiance time series is also important in solar terrestrial correlation studies, since it complicates the use of classical statistical techniques for estimating the significance of th

ISSN:0148-0227    

DOI:10.1029/JD092iD05p05555

年代:1987

数据来源: WILEY

摘要:

Measurements of transmitted urban light through clouds that are provided by nocturnal satellite images yield information regarding the optical parameters of clouds. While the albedo for optically thick clouds becomes insensitive to changes in optical thickness, the fractional change in the zenith‐directed transmission of city light through thick clouds is relatively sensitive to changes in optical thickness. Models are derived and evaluated to compute the radiances from Lambertian point and extended light sources that are transmitted toward zenith through clouds of varying albedos for single scattering, asymmetry factors, cloud heights, and optical thickness. It is shown that radiances from reflected moonlight and transmitted city light may be used to estimate van de Hulst's similarity parameters of clouds above and near citie

ISSN:0148-0227    

DOI:10.1029/JD092iD05p05565

年代:1987

数据来源: WILEY

摘要:

We report the results of an ozone measurement campaign conducted at Natal, Brazil (5.9°S, 35.2°W) from March 25 to April 15, 1985. Seven profiles were obtained during this period, using ROCOZ‐A and electrochemical concentration cell ozonesondes, standard U.S. meteorological radiosondes, and Super‐Loki datasondes. Complete profiles of ozone, pressure, and temperature were obtained from the ground to 52 km, and all of the profiles correspond with site overpasses by ozone instruments on NASA and National Oceanic and Atmospheric Administration satellites. The profiles from this measurement series show reasonable agreement with established satellite climatologies. Stratospheric ozone variability was 2% or less during the 3 weeks of the measurement campaign, with stratospheric temperature and pressure variabilities half that amount. Low variability at a single location for this period implies comparable uniformity for ozone profiles over a large area around the measurement site. This condition at Natal removes the requirement of exact concurrence between satellite and local ozone measurements, allowing comparisons of larger sets of profiles and improving the precision of the intercomparisons. Regional ozone stability also allows an overall intercomparison of ozone measurements among the four satellites without the need for zonal mean averages. The auxiliary pressure and temperature profiles presented here allow the use of this data set as a transfer standard between satellite instruments with different fundamental ozone measurements. Finally, the low ozone variability in the stratosphere at Natal during this measurement series should provide an opportunity for high‐quality intercomparisons of measured and modeled ozone concentrations in the equatorial stratosphere and lower mesosphere as well as a consistency check among satellite ozone measu

ISSN:0148-0227    

DOI:10.1029/JD092iD05p05573

年代:1987

数据来源: WILEY

摘要:

Contemporary solar and infrared radiative codes have been used with satellite derived distributions of ozone, water vapor, and temperature to calculate the stratospheric solar, infrared, and net radiative heating on a monthly basis. Heating/cooling rates have been Calculated from pole to pole and from 13 to 61 km for each of 12 months. Vertical resolution is 1.5 km. Results are interpolated to surfaces of constant potential temperature, and divergence‐free, zonally averaged, advective fields are diagnosed using the calculated diabatic heating (net radiative heating). Associated stream functions are also derived. Based upon these advective fields, trajectory studies have been carried out in the meridional plane and used to elucidate further the stratospheric transport of inert tracers. Analysis of the presently diagnosed advective fields suggests the following: (1) Entry into the mid to upper stratosphere of tropospheric air is principally from a latitude region of ±10° at the equatorial tropopause. Smaller contributions to the stratosphere come from the polar mesosphere. (2) At latitudes poleward of ±15°, tracers transported from the troposphere into the stratosphere are subsequently transported toward the pole (with little ascending motion) and then downward and out of the stratosphere at the higher latitudes. (3) The nearly continuous presence of cells of net cooling in the lower stratospheric polar regions are important in establishing these regions as continuous vents for polar stratospheric air. (4) Based upon these advective fields, residence times for stratospheric air with given entry points are as follows: for equatorial entry, 3–4 years; for entry from the polar mesosphere, 1–1.5 years; and for entry from the troposphere at extratropical latitudes, ≈1 year. Using heating and advection fields derived from Limb Infrared Monitor of the Stratosphere (LIMS) data, an approximate measure of the interannual variability of the diabatic circulation is obtained. Ramifications of these findings are discussed. The heating rates, the derived advective fields, and the data base used in their calculation are available from the authors u

ISSN:0148-0227    

DOI:10.1029/JD092iD05p05585

年代:1987

数据来源: WILEY

摘要:

Possible dynamical influences on the diurnal behavior of ozone are investigated. A time dependent one‐dimensional photochemical model is developed for this purpose. All model calculations are made at 70°N during summer, because of available data on turbulence and zonal winds at Poker Flat, Alaska, and ozone observations from the Solar Mesosphere Explorer (SME) satellite. The model includes vertical diffusion induced by breaking gravity waves, as parameterized by Lindzen (1981). We show that the vertical diffusion can vary as much as 1 order of magnitude within a day as a result of large changes in the zonal wind induced by atmospheric thermal tides. It is found that by introducing a dissipation time scale for turbulence produced by breaking gravity waves, the agreement with Poker Flat echo data is improved. Comparisons of results from photochemical model calculations where the vertical diffusion is a function of height only with those in whichKzzis changing in time show large differences in the diurnal behavior of ozone between 70 and 90 km. By including the dynamical effect, much better agreement with the SME data is obtained. The results are, however, sensitive to the background zonally averaged wind. The influence of including time‐varyingKzzon the OH densities is also large, especially between 80 and 90 km. This suggests that dynamical effects are important in determining the diurnal behavior of the airglow emission from the Meinel b

ISSN:0148-0227    

DOI:10.1029/JD092iD05p05609

年代:1987

数据来源: WILEY