Showing papers on "Cloud computing published in 1984"

Global Cloud Climatologies: A Historical Review

Abstract: Accurate global cloud information is required for many climate studies, particularly for validation of climate model simulations. This paper reviews the cloud climatologies currently available, identifying and attempting to explain the differences between various global cloud assessments. The two types of cloud observations used to construct a cloud climatology, conventional surface observations and satellite-derived observations, are contrasted. Meridional profiles of zonally-averaged total cloud amount and the geographic distribution of total cloud amount from 17 cloud data sets are compared. There is at present no unique and/or agreed global cloud climatology. This review emphasizes the uncertainty and inaccuracies associated with the present knowledge of the global cloud distribution. Cloud climatologies constructed from either surface or satellite cloud observations will not be identical. The range of cloud amount available from current cloud climatologies must be noted by all users of globa...

On the parameterization of the radiative properties of broken clouds

Abstract: A one-dimensional radiative transfer scheme is presented which accounts for the effects of broken cloud in the solar and infrared radiation field The fractional cloud amount is explicitly considered in the two-stream model by treating clouds as the boundary condition between two adjacent atmospheric layers The scheme accounts for absorption and scattering by gases and aerosols assuming realistic atmospheres The radiative properties of broken clouds are included in a parameterized form making use of results from three-dimensional radiative transfer models The radiative characteristics of a cloud field are represented by an average finite cloud whose size or optical thickness grows with increasing cloud amount This growth is described by a simple mathematical model, and its use yields qualitative agreement between model results and observations for solar radiation The scheme is then applied to calculate the net radiative effect of broken cloud Since the cloud size growth with cloud amount implies a non-linear relation between the fractional cloud amount and the radiative properties of the cloud field, the net radiative effect of cloud depends on cloud amount The idealized model shows that the albedo effect (increase of solar reflection with cloud amount) of broken cloud is smaller than that of a plane-parallel cloud for cloud amounts less than about 07, while the opposite is true for larger cloud amounts The greenhouse effect (reduction of the outgoing long-wave flux) of broken cloud is larger than that of a plane-parallel cloud for small cloud amount and smaller for large cloud amount An application of the radiation scheme to compute bispectral curves of visible albedo versus thermal brightness temperature shows that broken cloud layers and unbroken layers with variable optical depths show a similar shape of the bispectral curve DOI: 101111/j1600-08701984tb00259x

Solar reflection from interacting and shadowing cloud elements

Abstract: An attempt is made to relate the reflection from a broken cloud field to that from a plane parallel cloud of the same optical properties by using Monte Carlo simulations for a very simple model of an array of regularly spaced, infinitely long bar clouds. Reflection from the array is represented by an effective cloud fraction, and it is shown that for many cases this may be obtained by treating the cloud elements to be noninteracting azimuthally symmetric reflectors. The effective cloud fraction is a function of solar zenith angle, the aspect ratio of the individual cloud elements, and the normal or zenith cloud fraction of the array. Model computations for reflection from an array of randomly distributed identical cylinders are also presented as an example of a possible application of this technique.

Two Case Studies of Wintertime Cloud Systems over the Colorado Rockies

Abstract: The economical importance of the winter snowpack to the Colorado Rocky Mountain region (e.g., weather modification potential, ski industry, avalanche prediction, snow removal, etc.) calls for an understanding of how the mountain environment and synoptic weather systems interact to produce precipitating orographic cloud systems. This may be achieved by recognizing that each cloud system can be broken down into individual cloud components. In each of the case studies, a synoptic cloud component, an orographic cloud component and a convective cloud component were identified through the analysis of rawinsonde data, vertically pointing radar data, and visual observations. This study shows that wintertime cloud systems over mountainous terrain can be thought of as being composed of cloud components that form when vertical velocity components act on different size and time scales (synoptic, orographic, convective). The following atmospheric phenomena are shown to be important factors which contribute to...

On removing cloud interference in remote-sensing images

Abstract: Improvements made to the cloud removal method for landsat MSS images proposed by O.R. Mitchell are presented. A more reasonable mathematical model for the cloud effect has been derived, and a two-stage filtering scheme based on this new model has been proposed. A filtering and a 3-D processing method for landsat MSS image noise cleaning has been developed to implement the scheme. A preliminary experiment shows promising results.

Determination of cloud parameters from infrared sounder data

Abstract: The World Climate Research Programme (WCRP) plan is concerned with the need to develop a uniform global cloud climatology as part of a broad research program on climate processes. The International Satellite Cloud Climatology Project (ISCCP) has been approved as the first project of the WCRP. The ISCCP has the basic objective to collect and analyze satellite radiance data to infer the global distribution of cloud radiative properties in order to improve the modeling of cloud effects on climate. Research is conducted to explore an algorithm for retrieving cloud properties by utilizing the available infrared sounder data from polar-orbiting satellites. A numerical method is developed for computing cloud top heights, amount, and emissivity on the basis of a parameterized infrared radiative transfer equation for cloudy atmospheres. Theoretical studies were carried out by considering a synthetic atmosphere.

GASP cloud- and particle-encounter statistics and their application to LPC aircraft studies. Volume 1: Analysis and conclusions

Abstract: Summary studies are presented for the entire cloud observation archieve from the NASA Global Atmospheric Sampling Program (GASP). Studies are also presented for GASP particle concentration data gathered concurrently with the cloud observations. Cloud encounters are shown on about 15 percent of the data samples overall, but the probability of cloud encounter is shown to vary significantly with altitude, latitude, and distance from the tropopause. Several meteorological circulation features are apparent in the latitudinal distribution of cloud cover, and the cloud encounter statistics are shown to be consistent with the classical mid-latitude cyclone model. Observations of clouds spaced more closely than 90 minutes are shown to be statistically dependent. The statistics for cloud and particle encounter are utilized to estimate the frequency of cloud encounter on long range airline routes, and to assess the probability and extent of laminar flow loss due to cloud or particle encounter by aircraft utilizing laminar flow control (LFC). It is shown that the probability of extended cloud encounter is too low, of itself, to make LFC impractical.

GASP cloud- and particle-encounter statistics and their application to LFC aircraft studies. Volume 2: Appendixes

Abstract: Summary studies are presented for the entire cloud observation archive from the NASA Global Atmospheric Sampling Program (GASP). Studies are also presented for GASP particle-concentration data gathered concurrently with the cloud observations. Cloud encounters are shown on about 15 percent of the data samples overall, but the probability of cloud encounter is shown to vary significantly with altitude, latitude, and distance from the tropopause. Several meteorological circulation features are apparent in the latitudinal distribution of cloud cover, and the cloud-encounter statistics are shown to be consistent with the classical mid-latitude cyclone model. Observations of clouds spaced more closely than 90 minutes are shown to be statistically dependent. The statistics for cloud and particle encounter are utilized to estimate the frequency of cloud encounter on long-range airline routes, and to assess the probability and extent of laminaar flow loss due to cloud or particle encounter by aircraft utilizing laminar flow control (LFC). It is shown that the probability of extended cloud encounter is too low, of itself, to make LFC impractical. This report is presented in two volumes. Volume I contains the narrative, analysis, and conclusions. Volume II contains five supporting appendixes.