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- Author or Editor: JAMES D. McFADDEN x
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Abstract
Following the passage of hurricane Betsy (1965) through the Gulf of Mexico two flights were made five days apart aboard a research aircraft to collect sea-surface temperatures with an infrared radiometer. The purpose was to study the effects of a hurricane on the sea-surface temperatures field. Data from the first flight, which occurred one to two days after the hurricane passage, showed two cores of colder water to the right of the storm's track and very little structure to the left. The flight made five days later still showed a core of colder water to the right, but by this time its shape had been badly distorted by the surface current system. These results are compared with the findings of other investigators, and the value of real-time synoptic coverage with the use of aircraft is pointed out. The plan for an experiment utilizing aircraft and airborne oceanographic techniques to provide a 3-dimensional picture of the ocean temperature structure prior to and following a hurricane is also presented.
Abstract
Following the passage of hurricane Betsy (1965) through the Gulf of Mexico two flights were made five days apart aboard a research aircraft to collect sea-surface temperatures with an infrared radiometer. The purpose was to study the effects of a hurricane on the sea-surface temperatures field. Data from the first flight, which occurred one to two days after the hurricane passage, showed two cores of colder water to the right of the storm's track and very little structure to the left. The flight made five days later still showed a core of colder water to the right, but by this time its shape had been badly distorted by the surface current system. These results are compared with the findings of other investigators, and the value of real-time synoptic coverage with the use of aircraft is pointed out. The plan for an experiment utilizing aircraft and airborne oceanographic techniques to provide a 3-dimensional picture of the ocean temperature structure prior to and following a hurricane is also presented.
Abstract
The feasibility and preliminary testing of a low cost, remote-sensing air-borne, double bolometer technique for inferring atmospheric water vapor is illustrated. To deduce the water vapor profile with commercially available equipment, the radiative transfer equation is solved for the water vapor transmissivity employing an input data remote radiometer-measured upward irradiances obtained at aircraft holding levels. Radiometers sensitive in two separate spectral bands are used. The primary radiometer covers the 4.39 to 20.83µ, broad atmospheric radiation band, and the second, for surface temperature deduction, covers the atmospheric window region, 7.35 to 13.16µ.
The transfer solution results are acquired from computer programs developed specifically for this purpose. Results indicate an accuracy for inferred total tropospheric water vapor and mixing ratio profiles close to that of the standard sounding electrical hygrometer. The absolute accuracy of the radiosonde hygrometer, considering surface calibration procedures, and for a single ascent, is not better than ±12 percent. The absolute accuracy is greatest for “dry” soundings where the largest changes in irradiance occur for given changes in moisture.
Specifically, tests for a vertical profile averaging 6.00 gm./kg. of water vapor produce an average error of 0.70 gm./kg. in the inferred mixing ratio. The average error in mixing ratio obtained by this technique for profiles averaging 2.3 gm./kg. is 0.05 gm./kg. The implications for use on high-flying aircraft or on rockets with highly sensitive radiometers are obvious. The primary purpose in reporting this research is to suggest a technique and illustrate its use. It is clear that with more sensitive bolometer radiometers with selective band pass filters a considerable increase in accuracy can be achieved.
Abstract
The feasibility and preliminary testing of a low cost, remote-sensing air-borne, double bolometer technique for inferring atmospheric water vapor is illustrated. To deduce the water vapor profile with commercially available equipment, the radiative transfer equation is solved for the water vapor transmissivity employing an input data remote radiometer-measured upward irradiances obtained at aircraft holding levels. Radiometers sensitive in two separate spectral bands are used. The primary radiometer covers the 4.39 to 20.83µ, broad atmospheric radiation band, and the second, for surface temperature deduction, covers the atmospheric window region, 7.35 to 13.16µ.
The transfer solution results are acquired from computer programs developed specifically for this purpose. Results indicate an accuracy for inferred total tropospheric water vapor and mixing ratio profiles close to that of the standard sounding electrical hygrometer. The absolute accuracy of the radiosonde hygrometer, considering surface calibration procedures, and for a single ascent, is not better than ±12 percent. The absolute accuracy is greatest for “dry” soundings where the largest changes in irradiance occur for given changes in moisture.
Specifically, tests for a vertical profile averaging 6.00 gm./kg. of water vapor produce an average error of 0.70 gm./kg. in the inferred mixing ratio. The average error in mixing ratio obtained by this technique for profiles averaging 2.3 gm./kg. is 0.05 gm./kg. The implications for use on high-flying aircraft or on rockets with highly sensitive radiometers are obvious. The primary purpose in reporting this research is to suggest a technique and illustrate its use. It is clear that with more sensitive bolometer radiometers with selective band pass filters a considerable increase in accuracy can be achieved.
Abstract
On June 16, 1966, an experiment was performed off the east coast of Florida that involved two research aircraft, one from the Naval Oceanographic Office and one from ESSA's Research Flight Facility, and the USCGSS Peirce, aboard which were two scientists from ESSA's Sea Air Interaction Laboratory, and the Weather Bureau Airport Station at Jacksonville, Fla. The purpose of this investigation was to determine the comparability of data for air-sea interaction research as determined by aircraft temperature, humidity, pressure, and wind sensors; airborne IR radiometers; a tethered boundary layer instrument package, radiosondes, rawinsondes, and dropsondes. Results showed generally good agreement (within listed instrumental accuracies) between comparisons of aircraft and radiosonde temperature and humidity observations, fair agreement of wind observations, and very poor comparisons between dropsondes and radiosondes. The sea surface temperature readings obtained by the airborne radiation thermometer aboard the Navy aircraft were well within ±0.4° C. operational accuracy of the instrument when compared with bucket temperature measurements taken aboard the Peirce. Whether the accuracies of these presently available instruments are good enough for mesoscale and macroscale ocean-atmosphere interaction investigations now being planned will have to await studies of the environments in which these experiments will take place.
Abstract
On June 16, 1966, an experiment was performed off the east coast of Florida that involved two research aircraft, one from the Naval Oceanographic Office and one from ESSA's Research Flight Facility, and the USCGSS Peirce, aboard which were two scientists from ESSA's Sea Air Interaction Laboratory, and the Weather Bureau Airport Station at Jacksonville, Fla. The purpose of this investigation was to determine the comparability of data for air-sea interaction research as determined by aircraft temperature, humidity, pressure, and wind sensors; airborne IR radiometers; a tethered boundary layer instrument package, radiosondes, rawinsondes, and dropsondes. Results showed generally good agreement (within listed instrumental accuracies) between comparisons of aircraft and radiosonde temperature and humidity observations, fair agreement of wind observations, and very poor comparisons between dropsondes and radiosondes. The sea surface temperature readings obtained by the airborne radiation thermometer aboard the Navy aircraft were well within ±0.4° C. operational accuracy of the instrument when compared with bucket temperature measurements taken aboard the Peirce. Whether the accuracies of these presently available instruments are good enough for mesoscale and macroscale ocean-atmosphere interaction investigations now being planned will have to await studies of the environments in which these experiments will take place.
Specially instrumented aircraft of the Environmental Science Services Administration (ESSA), Research Flight Facility (RFF) have supported environmental research efforts for more than a decade. In 1969 the RFF participated in the Barbados Oceanographic and Meteorological Experiment (BOMEX) providing, in addition to approximately 1000 flight hours during the field operating periods of the program (May through July), flights designed to develop operational patterns, test, calibrate and compare sensor derived data.
While the three participating RFF research aircraft accomplished 146 missions, for a total of approximately 1138 hours of flying time, they collected about three million digitally recorded meteorological observations, numerous sea-surface temperature and water vapor flux measurements, two million cloud and radar photographs, and other special data.
A brief description of the scientific objectives of the program, aircraft and instrumentation systems employed, sample tracks, data collected and subsequent procedures are presented.
Specially instrumented aircraft of the Environmental Science Services Administration (ESSA), Research Flight Facility (RFF) have supported environmental research efforts for more than a decade. In 1969 the RFF participated in the Barbados Oceanographic and Meteorological Experiment (BOMEX) providing, in addition to approximately 1000 flight hours during the field operating periods of the program (May through July), flights designed to develop operational patterns, test, calibrate and compare sensor derived data.
While the three participating RFF research aircraft accomplished 146 missions, for a total of approximately 1138 hours of flying time, they collected about three million digitally recorded meteorological observations, numerous sea-surface temperature and water vapor flux measurements, two million cloud and radar photographs, and other special data.
A brief description of the scientific objectives of the program, aircraft and instrumentation systems employed, sample tracks, data collected and subsequent procedures are presented.
Abstract
Analysis of the frequency response of the input parameters of a gust probe system, which measures the turbulent flow of air, is presented. The results show that the system is very sensitive to noise created by aircraft structural and power plant vibrations. This noise appears in the form of discrete frequencies in the range 10 to 50 Hz. The noise may account for as much as 97% of the total power output by certain sensors. Since the usual range of interest for the measurement of fluctuations of meteorological parameters is 0 to 10 Hz, aliasing of these discrete frequencies may become a problem. This analysis is intended to characterize the noise so that some justification may be given to eliminate it from useful, significant data.
Abstract
Analysis of the frequency response of the input parameters of a gust probe system, which measures the turbulent flow of air, is presented. The results show that the system is very sensitive to noise created by aircraft structural and power plant vibrations. This noise appears in the form of discrete frequencies in the range 10 to 50 Hz. The noise may account for as much as 97% of the total power output by certain sensors. Since the usual range of interest for the measurement of fluctuations of meteorological parameters is 0 to 10 Hz, aliasing of these discrete frequencies may become a problem. This analysis is intended to characterize the noise so that some justification may be given to eliminate it from useful, significant data.
