摘要:

AbstractIn recent years several refinements have been made in the numerical computation of solar atmospheric tides between 30 and 60 km. Although comparisons have been made with winds observed by rockets it has not been possible until now to test these predictions against a globally extensive set of observations. In this paper we describe techniques for obtaining such observations from measurements made by the stratospheric sounding units (SSU) on the TIROS‐N series of satellites. These unique data are compared with calculations of the radiance variations expected from the SSU based on classical tidal theory at equino

ISSN:0035-9009    

DOI:10.1002/qj.49711146502

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractA detailed narrow band model of longwave radiation transfer in a clear‐sky atmosphere is used to study the impact on cooling rate profiles and radiative fluxes of some approximations commonly used in GCM‐type radiation codes.Systematic errors in the results arise when economies are made in the vertical and spectral resolution. A coarse discretization of the vertical profiles of temperature and humidity overestimates atmospheric absorption (by as much as +5 W m−2), as does (by as much as +5 W m−2) the use of mean values of the temperature and humidity in each model layer. Overestimation of the absorption (up to +7 W m−2) also results from the use of the strong line approximation for H2O and CO2, or of the weak line approximation for O3.Decreasing the order of the vertical quadrature used for the vertical integration tends to decrease the absorption. Effects of the water vapour continuum absorption outside the 800‐1250 cm−1window region cannot be neglected, as this absorption accounts respectively for 21 and 8 W m−2of the downward radiation at the surface for a tropical and a subarctic winter atmosphere, and decreases the corresponding outgoing radiation at the top of the atmosphere by 5 and 0.3 W m−2respectively. Neglecting N2O and CH3decreases absorption by about 5 W m−2. Restricting CO2absorption to the 500‐800 cm−1interval, and O3absorption to the 970‐1110 cm−1interval further decreases by 5 W m−2the absorption in the tropical atmosphere.For transmission functions described by statistical models, a widening of the spectral intervals reinforces the influence of the strong lines and leads to an overestimation of the absorption, which is partly compensated by a

ISSN:0035-9009    

DOI:10.1002/qj.49711146503

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe performance of the ECMWF forecasting system in tropical prediction is discussed in terms of objective scores and systematic errors. the temperature, humidity and wind errors appear to be mutually consistent. the forecasts exhibit a cooling in the tropical stratosphere, warming at and below the tropical tropopause and a cooling in the mid and lower tropical troposphere. the analyses appear too humid in the lower troposphere, while the forecasts show a drying. Precipitation and evaporation are both too weak; a new energy balance within the model is slowly established through cooling, this new balance having a reduced total energy (Lq+cqT). the associated wind errors are seen to have a highly baroclinic structure and a meridional extent such as to affect significantly the baroclinicity of the mid‐latitude flow, particularly over the North and South Atlantic. Systematic errors are large compared to the variability of the fields themselves and show a remarkable temporal consistency from month to mont

ISSN:0035-9009    

DOI:10.1002/qj.49711146504

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThe kinematic and thermodynamic structure of a strong cold front over the Gulf of Alaska has been determined using aircraft, dropsonde, and radiosonde data obtained during the Storm Transfer and Response Experiment. Synoptic‐scale analysis using the Sawyer‐Eliassen secondary circulation equation shows that friction and diabatic heating, as well as the geostrophic forcing, are important in accounting for the secondary circulation at the front. A fine‐scale analysis, with horizontal resolution of 700m and vertical resolution of 100 m, shows strong relative inflow of warm boundary layer air toward the front from the east and a weaker inflow of cold air from the west. Updraught velocities of greater than 6 m s−1over a 2 km width were measured at 875 mb near the leading edge of the front. the frontogenetical effects of confluence, turbulent mixing, and tilting of isentropic surfaces are evaluated in the region of the front and compared with the results of previous studies. the high resolution of the thermodynamic fields provides new data for comparison with high resolution numerical

ISSN:0035-9009    

DOI:10.1002/qj.49711146505

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractCloud‐street observations over northern Germany are analysed with respect to wind and temperature profiles obtained from routine radiosonde stations in the area. In nearly all cases the wind profiles on cloudstreet days were characterized by an inflection point in the cross‐wind component with unstable stratification of the boundary layer. the height of the inflection point was found to be related to the convection height on those days, which may suggest the importance of both inflection point and convective instability for explanation of cloud‐street develo

ISSN:0035-9009    

DOI:10.1002/qj.49711146506

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractOn 27 July 1981, as part of the CCOPE experiment, the University of Wyoming King Air research aeroplane made penetrations at six levels ranging from 590mb (‐4.9°C) to 770mb (7.2°C) through a nonprecipitating, unglaciated cumulus cloud whose top was at about 560 mb (‐7°C) and base about 780mb (8°C). the entire flight sequence—from the top downwards—took about six minutes. Principal measurements were of droplet size distributionN(d), number concentrationNand liquid water contentL, measured at 10 Hz (≃10m spatial resolution); drop‐countN′(50Hz, ≃2m); temperatureT. Also we calculated the fractionFof cloud base air in the mixture sampled (1Hz, ≃100m). the cloud was substantially subadiabatic throughout the volume studied. Paluch analyses, the observed air motions near cloud top, buoyancy profiles and the observed distribution ofLandFwith altitude demonstrated that the cloud was diluted principally by entrainment from cloud top. Considerable scatter was found in all microphysical and thermodynamic variables on all spatial scales. Large variations inLwere primarily attributable to fluctuations inNandN′. Bimodal spectra were sometimes found at the interface between statistically smooth and highly variable regions. the breadth of the droplet spectra and the size of the largest droplets in the condensate spectrum were not systematically related to the degree of dilution. Calculations showed that a small fraction of the droplets (≃100 litres−1) exhibited superadiabatic growth of up to 4 m̈m diameter at the intermediate levels, but not near cloud base or cloud top. Support for the idea that droplets in lower concentrations (≃10 litre−1) grew even faster was provided by 1‐D probe measurements of droplets of up to 75 m̈m diameter in the cen

ISSN:0035-9009    

DOI:10.1002/qj.49711146507

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThree days of measurements in stable conditions (Monin‐Obukhov lengthLbetween 15 and 300 m) at the Boulder Atmospheric Observatory tower are presented. Winds came off the Rocky Mountains on two days and off the plains on the other day. Vertical profiles of the mean horizontal velocity and Brunt‐Väisälä frequencyN, and the standard deviation of the vertical component, ow, fluxes, spectra, cospectra, quadspectra, correlations and length scales are examined in this study. the measurements indicate that wave motion was present on all occasions, but which varied in strength, from weak to strong. New theoretical arguments are tested, which suggest that where the Richardson number is less than one, the velocity gradientdU/dzrather thanNdetermines the integral scalesLx(w)of the vertical velocity fluctuations, i.e.Lx(w)≃ ow/(dU/dz).But theory also suggests that it is not this scale, but the larger buoyancy scaleow/Nthat determines the temperature variance and thermal diffusivity. On this basis, dimensionless parameters are developed for plotting the measurements of temperature variance and thermal diffusivity. They are found to be in reasonably good agreement with other observations and with theory, even though the relative strength of wave motion to turbulence varied considerably. Low frequency wave motion appeared to be associated with significant heat flux, a possibility that has been excluded or overlooked in some previous

ISSN:0035-9009    

DOI:10.1002/qj.49711146508

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper describes an extensive series of aerosol experiments conducted from a coastal site on the island of South Uist in the Outer Hebrides. Measurements at this site are shown to be reasonably representative of open ocean conditions. Aerosol size distributions (0.08

ISSN:0035-9009    

DOI:10.1002/qj.49711146509

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractA one‐dimensional model is adopted to describe the energy partition of sparse crops. Theoretical development of this model yields a combination equation which describes evaporation in terms of controlling resistances associated with the plants, and with the soil or water in which they are growing. the equation provides a simple but physically plausible description of the transition between bare substrate and a closed canopy. Although the aerodynamic transfer resistances for incomplete canopies have, as yet, no experimental justification, typical values, appropriate to a specimen agricultural crop and soil, are shown to have limited sensitivity in the model. Processes which require further study if the equation is to be used to calculate evaporation throughout a crop season are also discusse

ISSN:0035-9009    

DOI:10.1002/qj.49711146510

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractConservative properties of steady flow in non‐hydrostatic pressure coordinates are used to formulate theoretical models of deep convection. the pressure coordinate analysis extends the range of analytic solutions previously obtained in height coordinates, because the effect of the variation of density with height is included and is more useful for comparison with observations and the implementation of dynamical cloud models in convective parametrization schemes. Previous models are made more realistic by including a non‐constant thermodynamic lapse rate. In the case of steering‐level convection, this is shown to be a simple reinterpretation of the constant lapse rate model, while for propagating convection there are more fundamental implications; downstream propagating solutions cannot exist if the net work done by the pressure field is zero, while upstream propagation, although dynamically possible, is not obs

ISSN:0035-9009    

DOI:10.1002/qj.49711146511

出版商:John Wiley&Sons, Ltd    

年代:1985

数据来源: WILEY