Variations In Cloudiness Research Articles

Variability of Cloudiness at Airline Cruise Altitudes from GASP Measurements

Additional statistics relating to the climatology of cloud cover at airline cruise altitudes are presented. The data were obtained between 1975 and 1979 from commercial airliners participating in the Global Atmospheric Sampling Program (GASP). The statistics describe the seasonal, latitudinal and altitudinal variation in cloudiness parameters as well as differences in the high-altitude cloud structure attributed to cyclone and convective-cloud generation processes. The latitudinal distribution of cloud cover derived form the GASP data was found to agree with high-altitude satellite observations. The relationships between three different measures of cloudiness and the relative vorticity at high altitudes is also discussed.

Cloudiness over the Eastern Equatorial Pacific for summer 1983 from geostationary satellite data

The extraordinary El-Nino event of 1982–83 started to fade out in the late spring of 1983. However the sea surface temperature of the Eastern Equatorial Pacific still remained warmer than normal in the following summer. To investigate the characteristics of this late transition phase of the 1982–83 El-Nino, the GOES-West satellite data of July and August of 1983 are analyzed. The outgoing longwave radiation field and the distribution of cloudiness, which was derived by using a new threshold technique, are obtained. The longwave radiation field is compared to monthly average climatic indices commonly used at the Climatic Analysis Center. The results of cloud analysis showed some interesting features during the decaying phase of the 1982–83 El-Nino. The diurnal variation of cloudiness indicates that total cloud amounts decrease from 8 GMT to 20 GMT over most of the area. This overall study demonstrates preliminary results of the International Satellite Cloud Climatology Project of the World Climate Research Program.

Statistical estimation of Cloudiness parameters

An attempt has been made to use satellite radiation measurements for the determination of the temporal and spatial variability of two cloudiness parameters, which are closely related with the radiation budget of the Earth-atmosphere system. On the basis of two sets of experimentally determined values of the planetary albedo the monthly mean cloud amount distribution has been estimated in the latitudinal belt between 60°N and 60°S. For this purpose the realistic values of the ground albedo have been used, and the cloud albedo was assumed to be dependent only on the solar zenith angle. A harmonic analysis has been undertaken for the cloud amount distribution over the latitudinal belt from 30°N to 30°S. It has been shown that nine harmonics can be used for an adequate description of the temporal-spatial variability of cloudiness. The mean monthly zonal values of cloud top temperature and of the cloud top height over the tropical oceans have been estimated on the basis of the experimental values of outgoing longwave flux. For this task the monthly mean sea surface temperatures have been used. The transfer of longwave radiation has been described by means of the integral transmission functions for water vapour and carbon dioxide.

Ocean–atmosphere coupling over monsoon regions

In monsoon regions, the seasonal migration of the intertropical convergence zone (ITCZ) is manifested as a seasonal reversal of winds. Most of the summer monsoon rainfall over India occurs owing to synoptic and large-scale convection associated with the continental ITCZ (Fig. 1). We have investigated the interaction between these large-scale convective systems and the ocean over which they are generated1â3, concentrating on the relationship between organized convection over the Indian Ocean and sea surface temperature (SST). We report here that on a monthly basis the degree of cloudiness correlates well with SST for the relatively colder oceans, but when SST is maintained above 28 °C it ceases to be an important factor in determining the variability of cloudiness. Over the major regions of convection east of 70°E, which are warm year after year, the observed cloudiness cannot be correlated with variations in SST.

The influence of the spectral response of satellite sensors on estimates of broadband albedo

AbstractThe radiative impact of cloudiness variations on climate depends on the relative magnitudes of changes in the planetary albedo and the outgoing longwave radiation. R. D. Cess and co‐workers showed in 1982 that the calculated direction of the cloud‐climate feedback (i.e. whether the earth‐atmosphere system warms or cools with changing cloud amount) depended on the satellite data sets used in their analysis. It was suggested that the different spectral resolutions of the satellite sensors might be responsible. This note examines that suggestion. It is shown that the change in planetary albedo measured by the narrow band scanning radiometers on board NOAAs 2 to 5 as a result of cloudiness variation can be an overestimate of the actual change by a factor of up to 1.38 at low latitudes. The overestimate is not sufficient to explain completely the differences amongst the satellite data. Nevertheless, the results indicate that satellite spectral response must be carefully considered if the strength (and possibly even the sign) of the cloud‐climate feedback is to be correctly assessed from narrow band satellite data. Over snow‐covered surfaces it is shown that the NOAA data may underestimate the effect of cloud cover changes by over 70%, and overestimate the planetary albedo by over 0.2.

Variation in United States Cloudiness and Sunshine, 1950–82

The variation in cloudiness and percentage of possible sunshine for the contiguous United States and six regions thereof is examined, based on data from 101 National Weather Service stations for the years 1950–82. Over this 33-year interval, linear regression analysis indicates a 3.7% increase in United States cloudiness significant at the 1% level, but a nonsignificant (at the 5% level) 0.9% decrease in sunshine. This difference in trend magnitude and significance may be related to an increase in cirrus, perhaps partly aircraft-induced. Changes in United States cloudiness during this interval have been greatest in autumn (7.0%) and least in spring (1.7%), and for year-average values greatest in the Southwest (4.7%) and South-Central (4.4%) regions, and least in the North-Central (2.5%) and Northeast (2.8%) regions. There is a highly significant (at the 0.1% level) correlation of −0.92 between year-average United States cloudiness and sunshine, so that dust, smoke and haze have not had a large effect on sunshine duration. There have also been no anomalous changes of sunshine duration relative to cloudiness following the Agung, Mt. St. Helens and El Chichon eruptions. The positive correlations between cloudiness values (and sunshine values) for the most distant regions of the United States show that some of the interannual variations in these quantities are of large spatial extent. There has been an appreciable tendency (though not quite significant at the 5% level), particularly in the Southwest and the North- and South-Central regions, for cloudiness to be above average and sunshine below average in years of warm sea surface temperature (SST) in the equatorial eastern Pacific (El Niño). This tendency was pronounced during the unusually warm SST years of 1972 and 1982, when United States cloudiness was 4.0 and 4.7% above average, respectively, and sunshine 3.5 and 3.1% below average, respectively. There is no evidence for a consistent relationship between the quasi-biennial oscillation in the tropical stratosphere, and United States cloudiness or sunshine. There has, however, been a significant tendency (at the 5% level) for United States cloudiness to be above average and sunshine below average in years when Indian summer-monsoon rainfall is below average, and vice versa, with respective correlations of −0.42 and 0.46. There is no evidence for a relation between Northern Hemisphere surface temperature and United States cloudiness or sunshine in the same year, but there is evidence for a relation with cloudiness and sunshine one year later.

A study of the earth's radiation budget using a general circulation model

AbstractObservations by satellites have shown that the various components of the global mean radiation budget have a significant seasonal variation, the causes of which are not properly understood. Results from an annual cycle integration with the Meteorological Office 5‐level general circulation model have been used to clarify the roles played by clouds and the surface in determining the seasonal variations in the radiation budget. The model uses an interactive radiation scheme with seasonally varying climatological sea surface temperatures, incoming solar radiation and zonal mean climatological cloud amounts. Its simulation of the various components of the earth's radiation compares favourably with results from satellites and it has therefore been possible to use its results to explain some aspects of the observed budgets.Many of the features of the annual cycle of the global mean radiation can be associated with the asymmetry in the distribution of land and sea between the two hemispheres. Variations in the global mean planetary albedo can be attributed partly to the illumination of Antarctica near the solstice and partly to the southwards spread of winter snow cover over the northern hemisphere continents. For the globe as a whole variations in cloudiness have little effect. The main determinants of the global mean outgoing flux appear to be the surface and associated tropospheric temperatures. Since the seasonal change in the surface temperatures of the land masses of the northern hemisphere is greater than that of the extensive oceans of the southern hemisphere, the variation in the global mean outgoing flux is dominated by that in the northern hemisphere. Again the effect of seasonal variations in cloudiness is small.The model results have also been used to estimate the earth's annual mean total energy budget and, in particular, the poleward flux of heat by the oceans. The oceanic heat flux implied by the model compares quite favourably with estimates based on observations, the main differences being at the equator and near the North Pole. The model gives a cross‐equatorial oceanic flux from the southern to the northern hemisphere and a significant flux of heat by the oceans into the Arctic Basin.

A study of the earth's radiation budget using a general circulation model

Observations by satellites have shown that the various components of the global mean radiation budget have a significant seasonal variation, the causes of which are not properly understood. Results from an annual cycle integration with the Meteorological Office 5-level general circulation model have been used to clarify the roles played by clouds and the surface in determining the seasonal variations in the radiation budget. The model uses an interactive radiation scheme with seasonally varying climatological sea surface temperatures, incoming solar radiation and zonal mean climatological cloud amounts. Its simulation of the various components of the earth's radiation compares favourably with results from satellites and it has therefore been possible to use its results to explain some aspects of the observed budgets. Many of the features of the annual cycle of the global mean radiation can be associated with the asymmetry in the distribution of land and sea between the two hemispheres. Variations in the global mean planetary albedo can be attributed partly to the illumination of Antarctica near the solstice and partly to the southwards spread of winter snow cover over the northern hemisphere continents. For the globe as a whole variations in cloudiness have little effect. The main determinants of the global mean outgoing flux appear to be the surface and associated tropospheric temperatures. Since the seasonal change in the surface temperatures of the land masses of the northern hemisphere is greater than that of the extensive oceans of the southern hemisphere, the variation in the global mean outgoing flux is dominated by that in the northern hemisphere. Again the effect of seasonal variations in cloudiness is small. The model results have also been used to estimate the earth's annual mean total energy budget and, in particular, the poleward flux of heat by the oceans. The oceanic heat flux implied by the model compares quite favourably with estimates based on observations, the main differences being at the equator and near the North Pole. The model gives a cross-equatorial oceanic flux from the southern to the northern hemisphere and a significant flux of heat by the oceans into the Arctic Basin.

Towards regional scenarios for a CO2-warmed Earth

Measured and projected increases in carbon dioxide content of the atmosphere point towards a significant global warming. The regional effects of such a warming will be of primary importance in determining the social and economic consequences. Four methods of arriving at tentative regional scenarios are discussed and illustrated by application to Australia and New Zealand. Methods used include numerical modelling, extreme warm and cold year ensembles, dynamical/empirical reasoning and palaeoclimatic reconstructions from the Hypsithermal. A surprising degree of consistency is revealed between the various approaches to a scenario for a CO2-warmed Earth and the climatic conditions which prevailed during the Hypsithermal. The best overall analogy to a CO2-warmed Earth seems to be this epoch, especially as recent evidence suggests it to be one of higher CO2 concentrations. High priority should be given to further investigations using numerical models which include an interactive dynamic ocean and hydrologic cycle including variable cloudiness, as well as more detailed reconstruction of climatic conditions during the Hypsithermal in areas sensitive to any circulation changes.

5338. Effects of variation in cloudiness and stratospheric aerosol scattering upon tropospheric UV flux, photolysis rates, and the ozone urban plume: Gregory L Matloff,Appl Optics,20 (22), 3947–3950

5338. Effects of variation in cloudiness and stratospheric aerosol scattering upon tropospheric UV flux, photolysis rates, and the ozone urban plume: Gregory L Matloff,Appl Optics,20 (22), 3947–3950

Low-Latitude Cloudiness and Climate Feedback: Comparative Estimates from Satellite Data

At low latitudes the seasonal variation in the radiation budget of the earth-atmosphere system is due largely to seasonal variability in cloudiness. Making use of this, we have estimated, from three different sets of satellite data, the relative albedo versus infrared modifications associated with cloudiness variability at low latitudes. Employing satellite data sets due to Ellis and Vonder Haar (1976) and Campbell and Vonder Haar (1980), we find that the albedo modification is somewhat less than that of the infrared. But when use is made of radiation budget data derived from NOAA–NESS scanning radiometer measurements, the albedo modification dominates over that of the infrared by nearly a factor of 2. This obviously suggests that estimates of climate feedback associated with changes in cloudiness are highly dependent on the satellite data set which is employed. It is further suggested that these differences might be in part attributable to the NOAA–NESS data being derived from narrow spectral measurements.

Effects of variation in cloudiness and stratospheric aerosol scattering upon tropospheric UV flux, photolysis rates, and the ozone urban plume

Using a radiative transfer model, the sensitivity of tropospheric UV flux and photolysis rates for NO(2) and HNO(2) to variations in cloudiness and stratospheric aerosol scattering are evaluated. A lumped parameter ozone plume model combining photochemistry and diffusion is then utilized to investigate variations in downwind ozone concentrations caused by variations in cloudiness.

Cloud Cover Archiving on a Global Scale: A Discussion of Principles

Monitoring of climatic variability and climate modeling both require a reliable global cloud data set. Examination is made of the temporal and spatial variability of cloudiness in light of recommendations made by GARP in 1975 (and updated by JOC in 1978 and 1980) for cloud data archiving. An examination of the methods of comparing cloud cover frequency curves suggests that the use of the beta distribution not only facilitates objective comparison, but also reduces overall storage requirements. A specific study of the only current global cloud climatology (the U.S. Air Force's 3-dimensional nephanalysis) over the United Kingdom indicates that discussion of methods of validating satellite-based data sets is urgently required.

Remote detection of nutrient and water deficiencies in sugarcane under variable cloudiness

Spectral measurements were made in a red (0.63–0.69 μm) and an infrared (0.76–0.90 μm) band over sugarcane using a radiometer mounted on a 4-m aluminum pole. Infrared/red ratios measured over a plot with adequate nitrogen, potassium, and water were significantly higher than those measured over a nitrogen-deficient plot at the 1% level, and higher than those over a potassium-deficient plot at the 10% level. In a second experiment, the infrared/red ratios of water-deficient plots were significantly lower than those for plots receiving adequate water. The measurements were made under conditions of variable cloudiness, ranging from full shade to direct sunlight. Although radiance values changed by a factor of 5 from one measurement to the next, changes in the infrared/red ratio were minimal, indicating that this ratio can be adequately measured under variable irradiance conditions for sugarcane when the plants form complete ground cover.

On the Use of Earth Radiation Budget Statistics for Studies of Clouds and Climate

Abstract Daily observations of albedo and outgoing terrestrial radiation derived from NOAA Scanning Radiometer measurements are used to relate cloudiness variations to regional features of the general circulation and to estimate the relative importance of the albedo and infrared effects of clouds on the net radiation balance of the earth on a regional basis. The results indicate that there are clear relationships between the variability in outgoing IR and features of the atmospheric circulation, which appear to be linked to changes in cloudiness. A method requiring only measurements of planetary albedo and total outgoing IR is devised to evaluate the relative importance of the albedo and IR effects of the current distribution of cloud for the net radiation balance of the earth. The results obtained from this method suggest that globally the effect on the radiation balance of the high albedo of clouds is two or more times greater than the effect of clouds in reducing outgoing IR, so that an increase in the...

The sensitivity of an energy balance climate model to variations in the orbital parameters

The responses of a zonally symmetric model of the global energy balance to perturbations in incident solar radiation are analyzed. The model is forced with seasonally varying insolation and incorporates in a simple way the positive feedback due to the high albedo of snow and sea ice. Meridional energy transport due to atmospheric motions is simulated with lateral diffusion of heat. Meridional energy transport by oceanic currents is ignored, as are possible variations in cloudiness. Emphasis is placed on the model's sensitivity to the latitudinal and seasonal redistribution of insolation produced by variations in the obliquity, the eccentricity, and the longitude of perihelion of the earth's orbit. It is found that when albedos are allowed to vary, increased seasonal variation of insolation leads to increased temperature in the northern hemisphere. In all cases considered, the latitudinal extent of perennial snow cover in the northern hemisphere is particularly sensitive to the perturbations, a response suggestive of the large fluctuations of continental glaciers during the Pleistocene. When the model is forced with the orbital variations of the past 150,000 years, its response is qualitatively similar to the geologic record of that period.

The First 18 Months of Planetary Radiation Budget Measurements from the Nimbus 6 ERB Experiment

The Nimbus 6 satellite Earth Radiation Budget (ERB) experiment has continuously monitored the solar radiation input and the reflected shortwave and emitted longwave radiation exitance from the earth-atmosphere system since July 1975. In this paper, the planetary radiation budget parameters observed during the first eighteen months in orbit (July 1975–December 1976) are presented. The results show that the annual mean planetary albedo and longwave radiation flux are 31% and 234 W m−2> (radiative equilibrium temperature of 254 K), respectively. The earth atmosphere system is observed to be in complete radiation balance over a one-year period to within the experimental error of observation. There is an annual cycle of the mean monthly planetary net radiation which is due predominantly to the annual cycle of incoming solar radiation caused by the time variation of earth-sun distance and the sun's declination. Monthly variations in outgoing longwave radiation due to variation in global cloudiness and snow and ice cover are generally compensated by the simultaneous variations in the planetary albedo so that there is generally little monthly variability of the total radiation to space compared to that of the net radiation.

Short-term temperature variation in needles of Pinussilvestris L.

The temperatures of needles of 10- to 15-year-old trees of Pinussilvestris L. growing in a frost hollow in Sweden were measured with an ultraminiature thermocouple. The measurements were made in the spring of 1977, during days of variable cloudiness. During periods of full sun and very low wind speed the temperature of the needles exceeded that of the surrounding air by 12 to 15 °C.

The radiative effect of atmospheric pollution: Latitudinally dependent radiation calculations including cloud contribution

In this paper, we have developed a radiation scheme based on the discrete-ordinate method into which a comparatively thick cloud layer can be incorporated for inhomogeneous aerosol atmospheres. Using the above radiation scheme, we performed calculations of the effect of clouds upon the inhomogeneous aerosol atmospheres, including the effects of optical depth, vertical distribution and extent of cloud layer. Calculations were also carried out for the local albedo, total absorption and diffuse transmission at each latitude belt, considering a land-sea distribution and a latitudinal variation of cloudiness, for six realistic model aerosol atmospheres. A 0.50 μm flux of the solar radiation is used for this study. The main conclusions of the radiative calculations may be summarized as follows. 1. (1) For the same optical thickness, a densely stratified cloud layer within the lower aerosol troposphere is apt to reflect the solar radiation much less effectively than other stratifications of cloud. If cloud layers are present at higher levels, absorption of solar radiation within the atmosphere would decrease considerably. 2. (2) Cloudiness and/or cloud thickness play a very important role upon the global heat balance problems and should never be ignored in studying the effects of increased aerosols upon climate, because contrary to the cloudless condition, heating of the earth-atmosphere system would tend to be induced by an increase of aerosols in the atmosphere where clouds are present. Because of the high surface albedo, an increase of aerosols reduces the reflectivity at the snow-covered high latitude belts, regardless of the effects of cloud. 3. (3) By the perturbation of adding aerosols into the troposphere or the stratosphere the diffuse transmission increases at the ground level. However, this effect is offset by the direct exponential attenuation of solar flux, and as a result, the total solar radiation reaching the ground is somewhat reduced. 4. (4) The absorption of solar radiation within the atmospheres due to aerosols would reach near 10% of incident solar flux for injection of a fairly massive amount of aerosols into the troposphere or the stratosphere due to great volcanic eruptions or man's impact.

The Possibility that Changes in Cloudiness Will Compensate for Changes in Ozone and Lead to Natural Protection Against Ultraviolet Radiation

Sunshine duration and total ozone trends from 1963 to 1975 for the United States are compared. It is found that in winter, spring, and summer sunshine variations correlate well with ozone variations. It is concluded that for those seasons natural cloudiness variations are in the opposite sense to natural ozone variations and tend to give partial compensation by minimizing the changes in sunburning ultraviolet radiation at the ground. In fall there is negative correlation between sunshine variations and ozone variations.