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Abstract
It is pointed out that the anomalous seasonal variation in the worldwide ozone concentration above 40 km deduced from Umkehr measurements is opposite to the seasonal variation in atmospheric turbidity. The maximum and minimum seasonal variation in turbidity is used to estimate a haze correction to an Umkehr observation. From a comparison of ozone concentration deduced from corrected and uncorrected Umkehrs it is noted that 1) increased turbidity reduces the ozone concentration at 45 km, and 2) the maximum seasonal change in turbidity can nearly, if not entirely, account for the maximum seasonal change (about 2 μmb) in ozone concentration at 45 km.
Abstract
It is pointed out that the anomalous seasonal variation in the worldwide ozone concentration above 40 km deduced from Umkehr measurements is opposite to the seasonal variation in atmospheric turbidity. The maximum and minimum seasonal variation in turbidity is used to estimate a haze correction to an Umkehr observation. From a comparison of ozone concentration deduced from corrected and uncorrected Umkehrs it is noted that 1) increased turbidity reduces the ozone concentration at 45 km, and 2) the maximum seasonal change in turbidity can nearly, if not entirely, account for the maximum seasonal change (about 2 μmb) in ozone concentration at 45 km.
Abstract
The optimum statistical inversion technique is applied to the evaluation of Umkehr observations from Arosa (46.5N, 9.4E), Aspendale (38.0S, 145.IE) and Tallahassee (30.2N, 84.2W). A Priori statistical information on the vertical ozone distribution is obtained from 511 balloon-sounding profiles at Boulder (40.0N, 105.1W). These latter data are also used to develop a regression method for obtaining a first guess at the O2 distribution, using total O2 as the independent variable. The ozone profiles inferred from the statistical method, when compared with concurrent direct measurements, display a significant improvement over profiles derived by the method in use at the World Ozone Data Center, Most of this improvement is attributable to the better first guess based on the total O2 regression. It is concluded that the utility of Umkehr observations is mainly restricted to estimation of the high-level O2 distribution above the main O2 maximum. For inferences about the ozone distribution at and below the maximum, effort should be directed toward regression techniques using total ozone as the independent variable.
Abstract
The optimum statistical inversion technique is applied to the evaluation of Umkehr observations from Arosa (46.5N, 9.4E), Aspendale (38.0S, 145.IE) and Tallahassee (30.2N, 84.2W). A Priori statistical information on the vertical ozone distribution is obtained from 511 balloon-sounding profiles at Boulder (40.0N, 105.1W). These latter data are also used to develop a regression method for obtaining a first guess at the O2 distribution, using total O2 as the independent variable. The ozone profiles inferred from the statistical method, when compared with concurrent direct measurements, display a significant improvement over profiles derived by the method in use at the World Ozone Data Center, Most of this improvement is attributable to the better first guess based on the total O2 regression. It is concluded that the utility of Umkehr observations is mainly restricted to estimation of the high-level O2 distribution above the main O2 maximum. For inferences about the ozone distribution at and below the maximum, effort should be directed toward regression techniques using total ozone as the independent variable.
This paper describes a new radiation monitoring program, the Integrated Surface Irradiance Study (ISIS), that builds upon and takes over from earlier NOAA networks monitoring components of solar radiation [both the visible component (SOLRAD) and the shortwave component that causes sunburn, UV-B] across the continental United States. ISIS is implemented in two levels. Level 1 addresses incoming radiation only, and level 2 addresses the surface radiation balance. Level 2 also constitutes the SURFRAD (Surface Radiation) program of the NOAA Office of Global Programs, specifically intended to provide radiation data to support large-scale hydrologic studies that will be conducted under the Global Energy and Water Cycle Experiment. Eventually, it is planned for level 2 sites to monitor all components of the surface energy balance. Both levels of ISIS will eventually measure both visible and UV radiation components. At present, there are nine sites that are considered to be at ISIS level 1 standard and an additional four level 2 SURFRAD sites. A 10th level 1 site will be in operation soon. Plans call for an increase in the number of sites of both kinds, up to about 15 ISIS sites, of which 6 will be at the SURFRAD level. Data are available via FTP at ftp.atdd.noaa.gov/pub/isis or at http://www.srrb.noaa.gov (level 2).
This paper describes a new radiation monitoring program, the Integrated Surface Irradiance Study (ISIS), that builds upon and takes over from earlier NOAA networks monitoring components of solar radiation [both the visible component (SOLRAD) and the shortwave component that causes sunburn, UV-B] across the continental United States. ISIS is implemented in two levels. Level 1 addresses incoming radiation only, and level 2 addresses the surface radiation balance. Level 2 also constitutes the SURFRAD (Surface Radiation) program of the NOAA Office of Global Programs, specifically intended to provide radiation data to support large-scale hydrologic studies that will be conducted under the Global Energy and Water Cycle Experiment. Eventually, it is planned for level 2 sites to monitor all components of the surface energy balance. Both levels of ISIS will eventually measure both visible and UV radiation components. At present, there are nine sites that are considered to be at ISIS level 1 standard and an additional four level 2 SURFRAD sites. A 10th level 1 site will be in operation soon. Plans call for an increase in the number of sites of both kinds, up to about 15 ISIS sites, of which 6 will be at the SURFRAD level. Data are available via FTP at ftp.atdd.noaa.gov/pub/isis or at http://www.srrb.noaa.gov (level 2).
A surface radiation budget observing network (SURFRAD) has been established for the United States to support satellite retrieval validation, modeling, and climate, hydrology, and weather research. The primary measurements are the downwelling and upwelling components of broadband solar and thermal infrared irradiance. A hallmark of the network is the measurement and computation of ancillary parameters important to the transmission of radiation. SURFRAD commenced operation in 1995. Presently, it is made up of six stations in diverse climates, including the moist subtropical environment of the U.S. southeast, the cool and dry northern plains, and the hot and arid desert southwest. Network operation involves a rigorous regimen of frequent calibration, quality assurance, and data quality control. An efficient supporting infrastructure has been created to gather, check, and disseminate the basic data expeditiously. Quality controlled daily processed data files from each station are usually available via the Internet within a day of real time. Data from SURFRAD have been used to validate measurements from NASA's Earth Observing System series of satellites, satellite-based retrievals of surface erythematogenic radiation, the national ultraviolet index, and real-time National Environmental Satellite, Data, and Information Service (NESDIS) products. It has also been used for carbon sequestration studies, to check radiative transfer codes in various physical models, for basic research and instruction at universities, climate research, and for many other applications. Two stations now have atmospheric energy flux and soil heat flux instrumentation, making them full surface energy balance sites. It is hoped that eventually all SURFRAD stations will have this capability. A surface radiation budget observing network (SURFRAD) has been established for the United States to support satellite retrieval validation, modeling, and climate, hydrology, and weather research. The primary measurements are the downwelling and upwelling components of broadband solar and thermal infrared irradiance. A hallmark of the network is the measurement and computation of ancillary parameters important to the transmission of radiation. SURFRAD commenced operation in 1995. Presently, it is made up of six stations in diverse climates, including the moist subtropical environment of the U.S. southeast, the cool and dry northern plains, and the hot and arid desert southwest. Network operation involves a rigorous regimen of frequent calibration, quality assurance, and data quality control. An efficient supporting infrastructure has been created to gather, check, and disseminate the basic data expeditiously. Quality controlled daily processed data files from each station are usually available via the Internet within a day of real time. Data from SURFRAD have been used to validate measurements from NASA's Earth Observing System series of satellites, satellite-based retrievals of surface erythematogenic radiation, the national ultraviolet index, and real-time National Environmental Satellite, Data, and Information Service (NESDIS) products. It has also been used for carbon sequestration studies, to check radiative transfer codes in various physical models, for basic research and instruction at universities, climate research, and for many other applications. Two stations now have atmospheric energy flux and soil heat flux instrumentation, making them full surface energy balance sites. It is hoped that eventually all SURFRAD stations will have this capability.
A surface radiation budget observing network (SURFRAD) has been established for the United States to support satellite retrieval validation, modeling, and climate, hydrology, and weather research. The primary measurements are the downwelling and upwelling components of broadband solar and thermal infrared irradiance. A hallmark of the network is the measurement and computation of ancillary parameters important to the transmission of radiation. SURFRAD commenced operation in 1995. Presently, it is made up of six stations in diverse climates, including the moist subtropical environment of the U.S. southeast, the cool and dry northern plains, and the hot and arid desert southwest. Network operation involves a rigorous regimen of frequent calibration, quality assurance, and data quality control. An efficient supporting infrastructure has been created to gather, check, and disseminate the basic data expeditiously. Quality controlled daily processed data files from each station are usually available via the Internet within a day of real time. Data from SURFRAD have been used to validate measurements from NASA's Earth Observing System series of satellites, satellite-based retrievals of surface erythematogenic radiation, the national ultraviolet index, and real-time National Environmental Satellite, Data, and Information Service (NESDIS) products. It has also been used for carbon sequestration studies, to check radiative transfer codes in various physical models, for basic research and instruction at universities, climate research, and for many other applications. Two stations now have atmospheric energy flux and soil heat flux instrumentation, making them full surface energy balance sites. It is hoped that eventually all SURFRAD stations will have this capability. A surface radiation budget observing network (SURFRAD) has been established for the United States to support satellite retrieval validation, modeling, and climate, hydrology, and weather research. The primary measurements are the downwelling and upwelling components of broadband solar and thermal infrared irradiance. A hallmark of the network is the measurement and computation of ancillary parameters important to the transmission of radiation. SURFRAD commenced operation in 1995. Presently, it is made up of six stations in diverse climates, including the moist subtropical environment of the U.S. southeast, the cool and dry northern plains, and the hot and arid desert southwest. Network operation involves a rigorous regimen of frequent calibration, quality assurance, and data quality control. An efficient supporting infrastructure has been created to gather, check, and disseminate the basic data expeditiously. Quality controlled daily processed data files from each station are usually available via the Internet within a day of real time. Data from SURFRAD have been used to validate measurements from NASA's Earth Observing System series of satellites, satellite-based retrievals of surface erythematogenic radiation, the national ultraviolet index, and real-time National Environmental Satellite, Data, and Information Service (NESDIS) products. It has also been used for carbon sequestration studies, to check radiative transfer codes in various physical models, for basic research and instruction at universities, climate research, and for many other applications. Two stations now have atmospheric energy flux and soil heat flux instrumentation, making them full surface energy balance sites. It is hoped that eventually all SURFRAD stations will have this capability.
Abstract
A simple two-channel solar radiometer and analysis technique have been developed for setting atmospheric water vapor via differential solar transmission measurements in and adjacent to the 940-nm water vapor absorption band. A prototype solar radiometer developed for the National Oceanic and Atmospheric Administration (NOAA)/Environmental Research Laboratory underwent trial measurements near Boulder, Colorado, and during the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment Phase II cirrus intensive field observation program (Coffeyville, Kansas). These measurements provided the convenient opportunity to compare solar radiometer water vapor retrievals with those obtained using NOAA microwave radiometers. The solar radiometer and microwave radiometer retrievals were found to agree to within 0.1 cm most of the time and to within 0.05 cm the majority of the time, yielding a percent difference in the retrievals generally within 10%. Radiosonde soundings, when available, were also found to generally agree with the microwave and solar radiometer retrievals within 0.1 cm.
Abstract
A simple two-channel solar radiometer and analysis technique have been developed for setting atmospheric water vapor via differential solar transmission measurements in and adjacent to the 940-nm water vapor absorption band. A prototype solar radiometer developed for the National Oceanic and Atmospheric Administration (NOAA)/Environmental Research Laboratory underwent trial measurements near Boulder, Colorado, and during the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment Phase II cirrus intensive field observation program (Coffeyville, Kansas). These measurements provided the convenient opportunity to compare solar radiometer water vapor retrievals with those obtained using NOAA microwave radiometers. The solar radiometer and microwave radiometer retrievals were found to agree to within 0.1 cm most of the time and to within 0.05 cm the majority of the time, yielding a percent difference in the retrievals generally within 10%. Radiosonde soundings, when available, were also found to generally agree with the microwave and solar radiometer retrievals within 0.1 cm.
Abstract
Although most measurements of total downwelling shortwave irradiance are made with pyranometers, the World Climate Research Program’s Baseline Surface Radiation Network has recommended the use of the summation of shortwave components in which the direct normal irradiance is measured and multiplied by the cosine of the solar zenith angle and then added to the diffuse horizontal irradiance measured by a pyranometer that is shaded from direct solar radiation by a disk. The nonideal angular response of most pyranometers limits their accuracy to about 3%, or 20–30 W m−2, for instantaneous clear-sky measurements. An intensive study of 21 separate measurements of total horizontal irradiance was conducted during extreme winter conditions of low sun and cold temperatures over 12 days at the National Oceanic and Atmospheric Administration’s Climate Monitoring and Diagnostics Laboratory. The experiment showed that the component sum methodology could lower the uncertainty by a factor of 2 or 3. A clear demonstration of this improvement was realized in a separate experiment conducted at the Atmospheric Radiation Measurement Southern Great Plains Cloud and Radiation Testbed site during April 1996. Four independent measurements of downwelling shortwave irradiance using the component sum technique showed typical differences at solar noon of about 10 W m−2. The mean of these summed measurements at solar noon was lower than the mean of the most-well-calibrated pyranometer measurements, acquired simultaneously, by about 30 W m−2, which is consistent with the typical angular response of many pyranometers.
Abstract
Although most measurements of total downwelling shortwave irradiance are made with pyranometers, the World Climate Research Program’s Baseline Surface Radiation Network has recommended the use of the summation of shortwave components in which the direct normal irradiance is measured and multiplied by the cosine of the solar zenith angle and then added to the diffuse horizontal irradiance measured by a pyranometer that is shaded from direct solar radiation by a disk. The nonideal angular response of most pyranometers limits their accuracy to about 3%, or 20–30 W m−2, for instantaneous clear-sky measurements. An intensive study of 21 separate measurements of total horizontal irradiance was conducted during extreme winter conditions of low sun and cold temperatures over 12 days at the National Oceanic and Atmospheric Administration’s Climate Monitoring and Diagnostics Laboratory. The experiment showed that the component sum methodology could lower the uncertainty by a factor of 2 or 3. A clear demonstration of this improvement was realized in a separate experiment conducted at the Atmospheric Radiation Measurement Southern Great Plains Cloud and Radiation Testbed site during April 1996. Four independent measurements of downwelling shortwave irradiance using the component sum technique showed typical differences at solar noon of about 10 W m−2. The mean of these summed measurements at solar noon was lower than the mean of the most-well-calibrated pyranometer measurements, acquired simultaneously, by about 30 W m−2, which is consistent with the typical angular response of many pyranometers.
Abstract
In the United States, there are several federal agencies interested in the effects of UV radiation, which has resulted in the establishment of UV monitoring programs each with their own instrumentation and sites designed to address their specific needs. In 1993, participating agencies of the U.S. Global Change Research Program organized a UV Panel for coordinating the different agencies’ programs in order to ensure that UV data are intercalibrated, have common quality assurance and control procedures, and that the efforts among agencies are not duplicated.
In order to achieve these goals, in 1994 the UV Panel recommended formation of the U.S. Central UV Calibration Facility (CUCF), which is operated by the Surface Radiation and Research Branch of the Air Resources Laboratory of National and Oceanic Atmospheric Administration. The CUCF is responsible for characterizing and calibrating UV measuring instruments from several U.S. federal agencies. Part of this effort is to calibrate UVB broadband radiometers from these agencies. The CUCF has three Yankee Environmental Systems (YES UVB-1) and three Solar Light (SL 501A) broadband radiometers as reference standards that are routinely calibrated. For the past three years, clear-sky erythema calibration factors were determined for these standard UVB broadband radiometers by using simultaneously measured erythema-weighted irradiance determined during the annual North American Intercomparison. Comparisons between erythemally weighted irradiance calculated spectra supplied by spectroradiometers typically agreed better than ±2% for solar zenith angles less than 60°. The spectroradiometers were participating in an intercomparison event organized by the National Institute of Standards and Technology and the CUCF.
In this article, the calibration methodology is described for transferring the calibration from the spectroradiometers to the CUCF’s standard broadband radiometers. The CUCF standard broadband radiometers are used to calibrate UVB broadband radiometers from several U.S. UV monitoring networks. Erythemal calibration factors for the CUCF’s YES UVB-1 standard broadband radiometer triad are reported for 1994, 1995, and 1996. Erythemal calibration factors for CUCF’s SL 501A standard broadband radiometer triad are reported for 1996.
Abstract
In the United States, there are several federal agencies interested in the effects of UV radiation, which has resulted in the establishment of UV monitoring programs each with their own instrumentation and sites designed to address their specific needs. In 1993, participating agencies of the U.S. Global Change Research Program organized a UV Panel for coordinating the different agencies’ programs in order to ensure that UV data are intercalibrated, have common quality assurance and control procedures, and that the efforts among agencies are not duplicated.
In order to achieve these goals, in 1994 the UV Panel recommended formation of the U.S. Central UV Calibration Facility (CUCF), which is operated by the Surface Radiation and Research Branch of the Air Resources Laboratory of National and Oceanic Atmospheric Administration. The CUCF is responsible for characterizing and calibrating UV measuring instruments from several U.S. federal agencies. Part of this effort is to calibrate UVB broadband radiometers from these agencies. The CUCF has three Yankee Environmental Systems (YES UVB-1) and three Solar Light (SL 501A) broadband radiometers as reference standards that are routinely calibrated. For the past three years, clear-sky erythema calibration factors were determined for these standard UVB broadband radiometers by using simultaneously measured erythema-weighted irradiance determined during the annual North American Intercomparison. Comparisons between erythemally weighted irradiance calculated spectra supplied by spectroradiometers typically agreed better than ±2% for solar zenith angles less than 60°. The spectroradiometers were participating in an intercomparison event organized by the National Institute of Standards and Technology and the CUCF.
In this article, the calibration methodology is described for transferring the calibration from the spectroradiometers to the CUCF’s standard broadband radiometers. The CUCF standard broadband radiometers are used to calibrate UVB broadband radiometers from several U.S. UV monitoring networks. Erythemal calibration factors for the CUCF’s YES UVB-1 standard broadband radiometer triad are reported for 1994, 1995, and 1996. Erythemal calibration factors for CUCF’s SL 501A standard broadband radiometer triad are reported for 1996.
Abstract
On 30 September 1970, the National Center for Atmospheric Research (NCAR) obtained data on the vertical distribution of particulate material over Boulder, Colo., from laser radar soundings and simultaneous airborne particle collections. A layer of particulate material at about 13 km was of special interest. Particles in this layer differed from normal tropospheric particles and were probably fly ash created by forest fires in California during the previous week. A technique for determining the complex index of refraction of atmospheric particles has been applied to the 13-km data. By assuming the real part of the refractive index to be 1.55, the imaginary part (the absorption parameter) is estimated to be 0.044±0.011.
Abstract
On 30 September 1970, the National Center for Atmospheric Research (NCAR) obtained data on the vertical distribution of particulate material over Boulder, Colo., from laser radar soundings and simultaneous airborne particle collections. A layer of particulate material at about 13 km was of special interest. Particles in this layer differed from normal tropospheric particles and were probably fly ash created by forest fires in California during the previous week. A technique for determining the complex index of refraction of atmospheric particles has been applied to the 13-km data. By assuming the real part of the refractive index to be 1.55, the imaginary part (the absorption parameter) is estimated to be 0.044±0.011.
Abstract
Two separate datasets both of which provide measurements of net downward shortwave radiation have been combined, so as to provide a means of critically examining methods for transferring satellite measurements to the surface. This is further facilitated through interfacing the two datasets with an atmospheric shortwave-radiation model. One dataset comprises near-surface measurements made at the Boulder Atmospheric Observatory Tower while the other consists of collocated satellite pixel measurements from the Earth Radiation Budget Experiment.
This study amplifies previous suggestions that surface-shortwave absorption is a more meaningful quantity, for climate studies, than is surface insolation. The former should not, however, be evaluated from the latter through use of a surface albedo, since surface albedo is not solely a surface property nor can it easily be evaluated from satellite measurements. It is further demonstrated that a direct evaluation of surface shortwave absorption can be more accurately obtained from satellite measurements than can surface insolation. Specifically, a linear slope-offset relationship exists between surface and surface-atmosphere shortwave absorption, and an algorithm is suggested for transferring satellite shortwave measurements to surface-shortwave absorption. The present study is directed solely at clear-sky conditions because the clear-sky top-to-surface transfer serves as a necessary prerequisite towards treating both clear and overcast conditions.
Abstract
Two separate datasets both of which provide measurements of net downward shortwave radiation have been combined, so as to provide a means of critically examining methods for transferring satellite measurements to the surface. This is further facilitated through interfacing the two datasets with an atmospheric shortwave-radiation model. One dataset comprises near-surface measurements made at the Boulder Atmospheric Observatory Tower while the other consists of collocated satellite pixel measurements from the Earth Radiation Budget Experiment.
This study amplifies previous suggestions that surface-shortwave absorption is a more meaningful quantity, for climate studies, than is surface insolation. The former should not, however, be evaluated from the latter through use of a surface albedo, since surface albedo is not solely a surface property nor can it easily be evaluated from satellite measurements. It is further demonstrated that a direct evaluation of surface shortwave absorption can be more accurately obtained from satellite measurements than can surface insolation. Specifically, a linear slope-offset relationship exists between surface and surface-atmosphere shortwave absorption, and an algorithm is suggested for transferring satellite shortwave measurements to surface-shortwave absorption. The present study is directed solely at clear-sky conditions because the clear-sky top-to-surface transfer serves as a necessary prerequisite towards treating both clear and overcast conditions.
Abstract
Recent data from the Earth Radiation Budget Experiment (ERBE) have raised the question as to whether or not the addition of clouds to the atmospheric column can decrease the top-of-the-atmosphere (TOA) albedo over bright snow-covered surfaces. To address this issue, ERBE shortwave pixel measurements have been collocated with surface insolation measurements made at two snow-covered locations: the South Pole and Saskatoon, Saskatchewan. Both collocated datasets show a negative correlation (with solar zenith angle variability removed) between TOA albedo and surface insulation. Because increased cloudiness acts to reduce surface insulation, these negative correlations demonstrate that clouds increase the TOA albedo at both snow-covered locations.
Abstract
Recent data from the Earth Radiation Budget Experiment (ERBE) have raised the question as to whether or not the addition of clouds to the atmospheric column can decrease the top-of-the-atmosphere (TOA) albedo over bright snow-covered surfaces. To address this issue, ERBE shortwave pixel measurements have been collocated with surface insolation measurements made at two snow-covered locations: the South Pole and Saskatoon, Saskatchewan. Both collocated datasets show a negative correlation (with solar zenith angle variability removed) between TOA albedo and surface insulation. Because increased cloudiness acts to reduce surface insulation, these negative correlations demonstrate that clouds increase the TOA albedo at both snow-covered locations.
