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- Author or Editor: D. A. Merritt x
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Abstract
We computed the monthly average backscattered power over a five-year period for the Fleming 50 MHz wind profiler, which is proportional to CN 2. We found that in addition to seasonal cycle in CN 2 below the tropopause, there was a year-to-year variation as well. Above the tropopause, the seasonal variations were almost gone; however, there were significant changes with periods longer than one year. We examined a shorter back-scattered power record from the Stapleton wind profiler and found similar longer-term trends. These long-term trends will affect the performance of wind profilers.
Abstract
We computed the monthly average backscattered power over a five-year period for the Fleming 50 MHz wind profiler, which is proportional to CN 2. We found that in addition to seasonal cycle in CN 2 below the tropopause, there was a year-to-year variation as well. Above the tropopause, the seasonal variations were almost gone; however, there were significant changes with periods longer than one year. We examined a shorter back-scattered power record from the Stapleton wind profiler and found similar longer-term trends. These long-term trends will affect the performance of wind profilers.
Abstract
The maximum height performance of the 50, 405 nd 915 MHz Colorado wind profiles is computed from the wind profiler database. Results show that even though the 50 MHz profiler has the largest seasonal variation in the maximum height coverage, it also has the greatest height coverage. In addition, it also has a greater increase in height for the same increase in sensitivity. On the basis of thew measurements we predict the height coverage of the 405 MHz wind profiler for the proposed wind profiler network.
Abstract
The maximum height performance of the 50, 405 nd 915 MHz Colorado wind profiles is computed from the wind profiler database. Results show that even though the 50 MHz profiler has the largest seasonal variation in the maximum height coverage, it also has the greatest height coverage. In addition, it also has a greater increase in height for the same increase in sensitivity. On the basis of thew measurements we predict the height coverage of the 405 MHz wind profiler for the proposed wind profiler network.
Abstract
The design, construction, and first results are presented of a 915-MHz Doppler wind profiler that may be mounted on a moving platform such as a mobile land vehicle, ocean buoy, or a ship. The long dwell times in multiple beam directions, required for the detection of weak atmospheric radar echoes, are obtained by a passive phased array antenna, controlled by a motion control and monitoring (MCM) computer that acquires platform motion measurements and compensates in real time for the platform rotations. The platform translational velocities are accounted for in the signal processing system (SPS) before the calculation of the wind velocity profiles. The phased array antenna, MCM, and SPS are described, and radar-derived wind profiles are compared with those from rawinsonde balloons released during the first test cruise of the system, as the NOAA R/V Ronald H. Brown performed ship maneuvers.
Abstract
The design, construction, and first results are presented of a 915-MHz Doppler wind profiler that may be mounted on a moving platform such as a mobile land vehicle, ocean buoy, or a ship. The long dwell times in multiple beam directions, required for the detection of weak atmospheric radar echoes, are obtained by a passive phased array antenna, controlled by a motion control and monitoring (MCM) computer that acquires platform motion measurements and compensates in real time for the platform rotations. The platform translational velocities are accounted for in the signal processing system (SPS) before the calculation of the wind velocity profiles. The phased array antenna, MCM, and SPS are described, and radar-derived wind profiles are compared with those from rawinsonde balloons released during the first test cruise of the system, as the NOAA R/V Ronald H. Brown performed ship maneuvers.
Abstract
Horizontal winds in the presence of precipitation were measured routinely with a UHF (405 MHz) Wind Profiler. The profiler had five beam-pointing positions so independent measurements of horizontal winds could be compared to determine relative accuracy and precision. Large precipitation fall speeds are shown to cause very large errors (on the order of tens of meters per second) in the horizontal wind estimates when those fall speeds are not properly included in the estimates. But when the precipitation fall speeds are properly included, the errors are much smaller (2–4 m s−1), approaching those of clear air (1 m s−1). The decrease in the precision in precipitation is attributed largely to horizontal nonuniformity in precipitation from one antenna beam to another. A 4- or 5-beam profiler can detect conditions of horizontal inhomogeneity by virtue of its ability to make independent measurements of the winds from horizontally separated scattering volumes.
Abstract
Horizontal winds in the presence of precipitation were measured routinely with a UHF (405 MHz) Wind Profiler. The profiler had five beam-pointing positions so independent measurements of horizontal winds could be compared to determine relative accuracy and precision. Large precipitation fall speeds are shown to cause very large errors (on the order of tens of meters per second) in the horizontal wind estimates when those fall speeds are not properly included in the estimates. But when the precipitation fall speeds are properly included, the errors are much smaller (2–4 m s−1), approaching those of clear air (1 m s−1). The decrease in the precision in precipitation is attributed largely to horizontal nonuniformity in precipitation from one antenna beam to another. A 4- or 5-beam profiler can detect conditions of horizontal inhomogeneity by virtue of its ability to make independent measurements of the winds from horizontally separated scattering volumes.
Abstract
Two independent wind profiles were measured every hour during February 1986 with a five-beam, UHF (405 MHz) wind Profiler at Platteville, Colorado. Our analysis of the horizontal wind components over all heights for the entire month gave a standard deviation of about 1.3 m s−1 for the measurement errors one can expect for three-beam Profilers in clear air. This study demonstrated that it is important to include the effects of large vertical motion (caused by gravity waves or precipitation in the horizontal wind component measurements. These vertical motions were large enough to raise the error in the horizontal wind components to 1.7 m s−1 in two-beam configurations where no corrections are made for the vertical motion.
Abstract
Two independent wind profiles were measured every hour during February 1986 with a five-beam, UHF (405 MHz) wind Profiler at Platteville, Colorado. Our analysis of the horizontal wind components over all heights for the entire month gave a standard deviation of about 1.3 m s−1 for the measurement errors one can expect for three-beam Profilers in clear air. This study demonstrated that it is important to include the effects of large vertical motion (caused by gravity waves or precipitation in the horizontal wind component measurements. These vertical motions were large enough to raise the error in the horizontal wind components to 1.7 m s−1 in two-beam configurations where no corrections are made for the vertical motion.
Abstract
Remote sensing instrumentation has advanced to the point where serious consideration is being given to a next-generation tropospheric sounding system that uses radars and radiometers to provide profiles of tropospheric variables continuously and automatically. A network of five wind-profiling radars has been constructed in Colorado. This network represents a significant step in the development of a new observing system for operational and research meteorology. The radars and their capabilities and limitations are described.
Abstract
Remote sensing instrumentation has advanced to the point where serious consideration is being given to a next-generation tropospheric sounding system that uses radars and radiometers to provide profiles of tropospheric variables continuously and automatically. A network of five wind-profiling radars has been constructed in Colorado. This network represents a significant step in the development of a new observing system for operational and research meteorology. The radars and their capabilities and limitations are described.
Abstract
The National Oceanic and Atmospheric Administration/Earth System Research Laboratory/Chemical Sciences Division (NOAA/ESRL/CSD) has developed a versatile, airborne lidar system for measuring ozone and aerosols in the boundary layer and lower free troposphere. The Tunable Optical Profiler for Aerosol and Ozone (TOPAZ) lidar was deployed aboard a NOAA Twin Otter aircraft during the Texas Air Quality Study (TexAQS 2006) and the California Research at the Nexus of Air Quality and Climate Change (CalNex 2010) field campaigns. TOPAZ is capable of measuring ozone concentrations in the lower troposphere with uncertainties of several parts per billion by volume at 90-m vertical and 600-m horizontal resolution from an aircraft flying at 60 m s−1. The system also provides uncalibrated aerosol backscatter profiles at 18-m vertical and 600-m horizontal resolution. TOPAZ incorporates state-of-the-art technologies, including a cerium-doped lithium calcium aluminum fluoride (Ce:LiCAF) laser, to make it compact and lightweight with low power consumption. The tunable, three-wavelength UV laser source makes it possible to optimize the wavelengths for differing atmospheric conditions, reduce the interference from other atmospheric constituents, and implement advanced analysis techniques. This paper describes the TOPAZ lidar, its components and performance during testing and field operation, and the data analysis procedure, including a discussion of error sources. The performance characteristics are illustrated through a comparison between TOPAZ and an ozonesonde launched during the TexAQS 2006 field campaign. A more comprehensive set of comparisons with in situ measurements during TexAQS 2006 and an assessment of the TOPAZ accuracy and precision are presented in a companion paper.
Abstract
The National Oceanic and Atmospheric Administration/Earth System Research Laboratory/Chemical Sciences Division (NOAA/ESRL/CSD) has developed a versatile, airborne lidar system for measuring ozone and aerosols in the boundary layer and lower free troposphere. The Tunable Optical Profiler for Aerosol and Ozone (TOPAZ) lidar was deployed aboard a NOAA Twin Otter aircraft during the Texas Air Quality Study (TexAQS 2006) and the California Research at the Nexus of Air Quality and Climate Change (CalNex 2010) field campaigns. TOPAZ is capable of measuring ozone concentrations in the lower troposphere with uncertainties of several parts per billion by volume at 90-m vertical and 600-m horizontal resolution from an aircraft flying at 60 m s−1. The system also provides uncalibrated aerosol backscatter profiles at 18-m vertical and 600-m horizontal resolution. TOPAZ incorporates state-of-the-art technologies, including a cerium-doped lithium calcium aluminum fluoride (Ce:LiCAF) laser, to make it compact and lightweight with low power consumption. The tunable, three-wavelength UV laser source makes it possible to optimize the wavelengths for differing atmospheric conditions, reduce the interference from other atmospheric constituents, and implement advanced analysis techniques. This paper describes the TOPAZ lidar, its components and performance during testing and field operation, and the data analysis procedure, including a discussion of error sources. The performance characteristics are illustrated through a comparison between TOPAZ and an ozonesonde launched during the TexAQS 2006 field campaign. A more comprehensive set of comparisons with in situ measurements during TexAQS 2006 and an assessment of the TOPAZ accuracy and precision are presented in a companion paper.
Abstract
The first wind profiler for a demonstration network of wind profilers recently passed the milestone of 300 h of continuous operation. The horizontal wind component measurements taken during that period are compared with the WPL Platteville wind profiler and the NWS Denver rawinsonde. The differences between the network and WPL wind profilers have standard deviations of 2.30 m s−1 and 2.16 m s−1 for the u- and v-components, respectively. However, the WPL wind profiler ignores vertical velocity, whereas the network radar measures it and removes its effects from the u- and v-component measurements. The differences between the network wind profiler and the NWS rawinsonde (separated spatially by about 50 km) have standard deviations of 3.65 m s−1 and 3.06 m s−1 for the u- and v-components, respectively. These results are similar to those found in earlier comparison studies. Finally, the new network wind profiler demonstrates excellent sensitivity, consistently reporting measurements at all heights msl from 2 to nearly 18 km with very few outages.
Abstract
The first wind profiler for a demonstration network of wind profilers recently passed the milestone of 300 h of continuous operation. The horizontal wind component measurements taken during that period are compared with the WPL Platteville wind profiler and the NWS Denver rawinsonde. The differences between the network and WPL wind profilers have standard deviations of 2.30 m s−1 and 2.16 m s−1 for the u- and v-components, respectively. However, the WPL wind profiler ignores vertical velocity, whereas the network radar measures it and removes its effects from the u- and v-component measurements. The differences between the network wind profiler and the NWS rawinsonde (separated spatially by about 50 km) have standard deviations of 3.65 m s−1 and 3.06 m s−1 for the u- and v-components, respectively. These results are similar to those found in earlier comparison studies. Finally, the new network wind profiler demonstrates excellent sensitivity, consistently reporting measurements at all heights msl from 2 to nearly 18 km with very few outages.
Abstract
Winds measured with 915- and 404-MHz wind profilers are frequently found to have nonrandom errors as large as 15 m s−1 when compared to simultaneously measured rawinsonde winds. Detailed studies of these errors which occur only at night below about 4 km in altitude and have a pronounced seasonal pattern, indicate that they are due to the wind profilers' detection of migrating songbirds (passerines). Characteristics of contaminated data at various stages of data processing are described, including raw time series, individual spectra, averaged spectra, 30- or 60-s moments, 3- or 6-min winds, and hourly averaged winds. An automated technique for the rejection of contaminated data in historical datasets, based on thresholding high values of rnoment-level reflectivity and spectral width, is shown to be effective. Techniques designed for future wind profiter data acquisition systems are described that show promise for rejecting bird echoes, with the additional capability of being able to retrieve the true wind velocity in many instances. Finally, characteristics of bird migration revealed by wind profilers are described, including statistics of the spring (March–May) 1993 migration season determined from the 404-MHz Wind Profiler Demonstration Network (WPDN). During that time, contamination of moment data occurred on 43% of the nights monitored.
Abstract
Winds measured with 915- and 404-MHz wind profilers are frequently found to have nonrandom errors as large as 15 m s−1 when compared to simultaneously measured rawinsonde winds. Detailed studies of these errors which occur only at night below about 4 km in altitude and have a pronounced seasonal pattern, indicate that they are due to the wind profilers' detection of migrating songbirds (passerines). Characteristics of contaminated data at various stages of data processing are described, including raw time series, individual spectra, averaged spectra, 30- or 60-s moments, 3- or 6-min winds, and hourly averaged winds. An automated technique for the rejection of contaminated data in historical datasets, based on thresholding high values of rnoment-level reflectivity and spectral width, is shown to be effective. Techniques designed for future wind profiter data acquisition systems are described that show promise for rejecting bird echoes, with the additional capability of being able to retrieve the true wind velocity in many instances. Finally, characteristics of bird migration revealed by wind profilers are described, including statistics of the spring (March–May) 1993 migration season determined from the 404-MHz Wind Profiler Demonstration Network (WPDN). During that time, contamination of moment data occurred on 43% of the nights monitored.
Abstract
A remote-sensing system for continuously profiling the troposphere is discussed; the prototype Profiler utilizes radio wavelengths, thereby achieving essentially all-weather operation. Designed for unattended operation, the Profiler employs radiometric and Doppler radar technology. Design, construction and calibration of the instruments composing the Profiler system are described along with some of the physics and mathematics upon which their operation is based. Examples of profiles and other variables of meteorological interest are given, and comparisons are made with simultaneous data from colocated operational (NWS) sondes. An algorithm based on climatological statistics of measurements by radiosonde is used in the radiometric retrieval process, but there is no reliance of the products of the Profiler upon any current radiosonde data. The role of the Profiler in mesoscale and synoptic weather forecasting and its relationship to systems employing sounders on satellite platforms are also discussed.
Abstract
A remote-sensing system for continuously profiling the troposphere is discussed; the prototype Profiler utilizes radio wavelengths, thereby achieving essentially all-weather operation. Designed for unattended operation, the Profiler employs radiometric and Doppler radar technology. Design, construction and calibration of the instruments composing the Profiler system are described along with some of the physics and mathematics upon which their operation is based. Examples of profiles and other variables of meteorological interest are given, and comparisons are made with simultaneous data from colocated operational (NWS) sondes. An algorithm based on climatological statistics of measurements by radiosonde is used in the radiometric retrieval process, but there is no reliance of the products of the Profiler upon any current radiosonde data. The role of the Profiler in mesoscale and synoptic weather forecasting and its relationship to systems employing sounders on satellite platforms are also discussed.
