ISSN:0148-0227    

DOI:10.1029/JD089iD01p01247

年代:1984

数据来源: WILEY

摘要:

Infrared radiances were simultaneously measured from broken cloud fields over the eastern Pacific Ocean by means of the eastern and western geostationary satellites. The measurements were compared with the results of models that characterized the clouds as black circular cylinders disposed randomly on a plane and as black cuboids disposed in regular and in shifted periodic arrays. The data were also compared with the results obtained from a radiative transfer model that considered emission and scattering by a regular array of periodic cuboidal clouds. It was found that the radiances did not depend significantly on the azimuth angle; this suggested that the observed cloud fields were not regular periodic arrays. However, the dependence on zenith angle suggested that the clouds were not disposed randomly either. The implication of these measurements on the understanding of the transfer of infrared radiances through broken cloud fields is considered.

ISSN:0148-0227    

DOI:10.1029/JD089iD01p01249

年代:1984

数据来源: WILEY

摘要:

If an adequate model of the reflection characteristics of a given scene is available, the reflected solar irradiance from the scene may be determined from radiance measurements made by satellite‐borne scanning radiometers. A theoretical analysis of the reflection functions of broken cloud scenes is presented, using Monte Carlo simulations of the radiative transfer in various three‐dimensional geometries. It is shown that the reflection functions of horizontally extensive (stratiform) and horizontally limited (cumuliform) clouds are generally quite different. The differences are greatest for nadir and limb views, but tend to vanish for reflected radiances with a zenith angle of 60°. Applications to satellite observations suggest potential errors of a factor of 2 in the inferred irradiance are likely due to scene misidentification when the radiances are interpreted indiscriminantly. Selection of preferred satellite viewing directions, however, can significantly reduce this e

ISSN:0148-0227    

DOI:10.1029/JD089iD01p01259

年代:1984

数据来源: WILEY

摘要:

Changes in geography (topography, continental positions and sea level) are one of the most frequently cited mechanisms of climatic change on geologic time scales. The role of geographic variables in paleoclimatology is investigated through a series of climate model sensitivity studies using a version of the National Center for Atmospheric Research spectral GCM and specified Cretaceous (≈ 100 million years ago) geography. The Cretaceous is investigated because it was both a large geographic and climatic contrast from the present day. The model simulations demonstrate that paleogeography was a substantial climatic forcing factor (4.8°K increase in globally averaged surface temperature compared with a present‐day control). However, the warming is insufficient to explain fully the paleoclimatic data. In addition, the model is insensitive to global sea level variations (related to tectonics and not ice volume) which are well correlated with paleoclimatic data. Additional climatic forcing factors, such as increased atmospheric CO2correlated with these sea level variations, may be required to explain the Cretaceous cli

ISSN:0148-0227    

DOI:10.1029/JD089iD01p01267

年代:1984

数据来源: WILEY

摘要:

Three general questions of climate theory are addressed. First, it is shown that climate sensitivity cannot be determined directly from available data, and hence its computation depends on model assumptions. Second, the relationship between energy‐balance models (EBMs), oscillatory climate models, and ice‐sheet models (ISMs) is discussed, and it is shown how EBMs can be obtained as a singular limit of certain oscillatory models. Finally, the physical and mathematical aspects of the oscillations are discussed in further detail and related to the stability question for EBMs and for I

ISSN:0148-0227    

DOI:10.1029/JD089iD01p01280

年代:1984

数据来源: WILEY

摘要:

Thirty years of daily data have been used to estimate the annual cycle of the large‐scale 500‐mbar geopotential height fields. The resulting Fourier coefficients, describing the smooth annual cycle, have been used to study the annual cycle of the planetary‐scale northern hemisphere seasonally forced waves. Monthly mean maps of the first three waves are presented, as well as the annual cycle of the eddy momentum flux caused by these waves. It is shown that, during the winter circulation regime, zonal wave number 2 transports momentum toward the south, while wave numbers 1 and 3 transport momentum toward the north. During the summer circulation regime, the fluxes are weak. It is found that there is a connection between a suddenly increased equatorward momentum flux for zonal wave number 2 in late November and the onset of the winter circulation r

ISSN:0148-0227    

DOI:10.1029/JD089iD01p01285

年代:1984

数据来源: WILEY

摘要:

Analysis of 38 tree ring chronologies yields evidence for enhanced drought conditions every 18.6 years in the North American interior for the past millennium. Cross spectra between a drought area index and 26 temperature records confirm the analysis of Currie (1979, 1981d) as regards a lunar nodal MNterm in these data. Discussion of the MNtidal constituent, which appreciably modulates amplitude and phase of four main constituents (M2, K1, O1, Mf) is presented, and implications for agriculture are surveyed.

ISSN:0148-0227    

DOI:10.1029/JD089iD01p01295

年代:1984

数据来源: WILEY

摘要:

Tropospheric OH radical concentrations were observed at two locations in Germany by long‐path UV absorption spectroscopy. During the summer months, noontime concentrations at sunny days averaged to 1.6×106OH cm−3. The highest concentrations observed so far did not exceed 2.5×106OH cm−3.The highest concentrations observed so far did not exceed 2.5×106OH cm−3. A number of possible spectral interferences by atmospheric trace gases (SO2, CH2O, CS2) were identified, and OH concentrations, as derived after correction for those interferences (if necessary) are reported for 1979 th

ISSN:0148-0227    

DOI:10.1029/JD089iD01p01309

年代:1984

数据来源: WILEY

摘要:

We have measured stratospheric perhydroxyl (HO2) by using a sensitive mm‐wave receiver to obtain spectroscopic line profiles of three rotational emission lines in the vicinity of 265.8 GHz. The observations were carried out over four days in September–October 1982 at Mauna Kea, Hawaii (19.5 N latitude) and yield good agreement with the column density and vertical distribution predicted above ∼35 km by three representative two‐dimensional photochemical models employing JPL 82‐57 reaction rates and chemistry; predictions from the same models using WMO/NASA chemistry yield poor agreement with our observations. Contrasts between current theoretical predictions and previous observations by Anderson et al. are pointed out for HO2in the 28 to 37‐km range, along with the difficulty of joining the latter with our own measurements through a monotonically varying vertical profile for HO2. A possible explanation involving strong temporal and spatial variation in stratospheric water vapor content i

ISSN:0148-0227    

DOI:10.1029/JD089iD01p01321

年代:1984

数据来源: WILEY

摘要:

The visible light spectrometer on board the Solar Mesosphere Explorer spacecraft measures stratospheric NO2in the 20–40 km altitude region and provides accurate daytime NO2density profiles with nearly complete latitudinal coverage over an extended period of time. The instrument and data analysis are discussed in detail, and NO2results for winter/spring 1982 are presented and compared to current theoretical models. Agreement with other measurements is good, and comparison with NOxmodels indicates that although the overall agreement is acceptable, improvements in the models are required before good agreement is reached at all latitudes. The data indicate that NO2has a strong memory of the physical conditions present in the stratosphere over a time period of several day

ISSN:0148-0227    

DOI:10.1029/JD089iD01p01327

年代:1984

数据来源: WILEY