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Abstract
The net flux of radiation at the top of the atmosphere and associated quantities (albedo and outgoing longwave radiation) were computed for five successive semimonthly periods from measurements of the radiance of emitted longwave radiation and reflected solar radiation obtained over the entire globe from the satellite Nimbus II during the period 16 May–28 July 1966. The anisotropy of the reflection characteristics of the earth-atmosphere system was considered for the first time with gross empirical models derived from airplane and balloon observations.
The global planetary albedo was found to be between 29 and 31%, while the mean planetary temperature ranged between 254 and 255K. Both results deviate from the corresponding values of earlier investigations in such a way as to suggest that in those investigations the cloudiness or its effect on radiative tranfer, especially in the tropics and subtropics, was overestimated. The global averages of the radiation balance indicate a slight deficit of about 0.005 cal cm−2 min−1, when computed with a value of the solar constant of 2.00 cal cm−2 min−1. Seasonal trends and day-to-day variations of the earth's radiation field are also discussed.
Abstract
The net flux of radiation at the top of the atmosphere and associated quantities (albedo and outgoing longwave radiation) were computed for five successive semimonthly periods from measurements of the radiance of emitted longwave radiation and reflected solar radiation obtained over the entire globe from the satellite Nimbus II during the period 16 May–28 July 1966. The anisotropy of the reflection characteristics of the earth-atmosphere system was considered for the first time with gross empirical models derived from airplane and balloon observations.
The global planetary albedo was found to be between 29 and 31%, while the mean planetary temperature ranged between 254 and 255K. Both results deviate from the corresponding values of earlier investigations in such a way as to suggest that in those investigations the cloudiness or its effect on radiative tranfer, especially in the tropics and subtropics, was overestimated. The global averages of the radiation balance indicate a slight deficit of about 0.005 cal cm−2 min−1, when computed with a value of the solar constant of 2.00 cal cm−2 min−1. Seasonal trends and day-to-day variations of the earth's radiation field are also discussed.
Abstract
In this study, data obtained from measurements with a ground-based vertical-pointing 95-GHz polarimetric cloud radar are analyzed. The investigations concentrate on the relationships between the Doppler spectral moments observed in different regions of nonprecipitating cirrostratus and altostratus decks connected with warm fronts approaching the radar site. In some of these cases, a remarkably well-defined relationship between the radar reflectivity and the spectral width is found. It is demonstrated how this relationship can be used to obtain information on the size distributions and the fallspeeds of the particles in the investigated cloud sections. It is found that if single parameters of the size distributions, for example, are parameterized by a lognormal distribution, they cannot be determined with an acceptable accuracy. However, at least the changes of these parameters, such as mean particle diameter and particle concentration, with changing reflectivity as well as the behavior of the corresponding particle fallspeeds, can be described with the help of empirical relations between the Doppler moments. A main result is that significant changes in reflectivity within a cloud section (e.g., of 10 dBZ e ) must correspond with a change in the relation between particle size and fallspeed, most commonly described by empirical power laws, and, therefore, probably with changes in particle shapes. This kind of radar data analysis will help to come to a better understanding of the microphysical and dynamical properties of the investigated cloud types, especially if further information from simultaneous measurements with other remote sensors is available.
Abstract
In this study, data obtained from measurements with a ground-based vertical-pointing 95-GHz polarimetric cloud radar are analyzed. The investigations concentrate on the relationships between the Doppler spectral moments observed in different regions of nonprecipitating cirrostratus and altostratus decks connected with warm fronts approaching the radar site. In some of these cases, a remarkably well-defined relationship between the radar reflectivity and the spectral width is found. It is demonstrated how this relationship can be used to obtain information on the size distributions and the fallspeeds of the particles in the investigated cloud sections. It is found that if single parameters of the size distributions, for example, are parameterized by a lognormal distribution, they cannot be determined with an acceptable accuracy. However, at least the changes of these parameters, such as mean particle diameter and particle concentration, with changing reflectivity as well as the behavior of the corresponding particle fallspeeds, can be described with the help of empirical relations between the Doppler moments. A main result is that significant changes in reflectivity within a cloud section (e.g., of 10 dBZ e ) must correspond with a change in the relation between particle size and fallspeed, most commonly described by empirical power laws, and, therefore, probably with changes in particle shapes. This kind of radar data analysis will help to come to a better understanding of the microphysical and dynamical properties of the investigated cloud types, especially if further information from simultaneous measurements with other remote sensors is available.
Following an overview of the scientific objectives and organization of the French–Russian–German Scanner for Radiation Budget (ScaRaB) project, brief descriptions of the instrument, its ground calibration, and in-flight operating and calibration procedures are given. During the year (24 February 1994–6 March 1995) of ScaRaB Flight Model 1 operation on board Meteor-317, radiometer performance was generally good and well understood. Accuracy of the radiances is estimated to be better than 1% in the longwave and 2% in the shortwave domains. Data processing procedures are described and shown to be compatible with those used for the National Aeronautics and Space Administration's (NASA) Earth Radiation Budget Experiment (ERBE) scanner data, even though time sampling properties of the Meteor-3 orbit differ considerably from the ERBE system orbits. The resulting monthly mean earth radiation budget distributions exhibit no global bias when compared to ERBE results, but they do reveal interesting strong regional differences. The “ERBE-like” scientific data products are now available to the general scientific research community. Prospects for combining data from ScaRaB Flight Model 2 (to fly on board Ressurs-1 beginning in spring 1998) with data from the NASA Clouds and the Earth's Radiant Energy System (CERES) instrument on board the Tropical Rainfall Measurement Mission (TRMM) are briefly discussed.
Following an overview of the scientific objectives and organization of the French–Russian–German Scanner for Radiation Budget (ScaRaB) project, brief descriptions of the instrument, its ground calibration, and in-flight operating and calibration procedures are given. During the year (24 February 1994–6 March 1995) of ScaRaB Flight Model 1 operation on board Meteor-317, radiometer performance was generally good and well understood. Accuracy of the radiances is estimated to be better than 1% in the longwave and 2% in the shortwave domains. Data processing procedures are described and shown to be compatible with those used for the National Aeronautics and Space Administration's (NASA) Earth Radiation Budget Experiment (ERBE) scanner data, even though time sampling properties of the Meteor-3 orbit differ considerably from the ERBE system orbits. The resulting monthly mean earth radiation budget distributions exhibit no global bias when compared to ERBE results, but they do reveal interesting strong regional differences. The “ERBE-like” scientific data products are now available to the general scientific research community. Prospects for combining data from ScaRaB Flight Model 2 (to fly on board Ressurs-1 beginning in spring 1998) with data from the NASA Clouds and the Earth's Radiant Energy System (CERES) instrument on board the Tropical Rainfall Measurement Mission (TRMM) are briefly discussed.
The Baltic Sea Experiment (BALTEX) is one of the five continental-scale experiments of the Global Energy and Water Cycle Experiment (GEWEX). More than 50 research groups from 14 European countries are participating in this project to measure and model the energy and water cycle over the large drainage basin of the Baltic Sea in northern Europe. BALTEX aims to provide a better understanding of the processes of the climate system and to improve and to validate the water cycle in regional numerical models for weather forecasting and climate studies. A major effort is undertaken to couple interactively the atmosphere with the vegetated continental surfaces and the Baltic Sea including its sea ice. The intensive observational and modeling phase BRIDGE, which is a contribution to the Coordinated Enhanced Observing Period of GEWEX, will provide enhanced datasets for the period October 1999–February 2002 to validate numerical models and satellite products. Major achievements have been obtained in an improved understanding of related exchange processes. For the first time an interactive atmosphere–ocean–land surface model for the Baltic Sea was tested. This paper reports on major activities and some results.
The Baltic Sea Experiment (BALTEX) is one of the five continental-scale experiments of the Global Energy and Water Cycle Experiment (GEWEX). More than 50 research groups from 14 European countries are participating in this project to measure and model the energy and water cycle over the large drainage basin of the Baltic Sea in northern Europe. BALTEX aims to provide a better understanding of the processes of the climate system and to improve and to validate the water cycle in regional numerical models for weather forecasting and climate studies. A major effort is undertaken to couple interactively the atmosphere with the vegetated continental surfaces and the Baltic Sea including its sea ice. The intensive observational and modeling phase BRIDGE, which is a contribution to the Coordinated Enhanced Observing Period of GEWEX, will provide enhanced datasets for the period October 1999–February 2002 to validate numerical models and satellite products. Major achievements have been obtained in an improved understanding of related exchange processes. For the first time an interactive atmosphere–ocean–land surface model for the Baltic Sea was tested. This paper reports on major activities and some results.
