Search Results
You are looking at 1 - 5 of 5 items for
- Author or Editor: D. van de Kamp x
- Refine by Access: All Content x
Abstract
Recently, a mathematical theory has been developed that proves that there are two main components of the solution of the forced dynamical system that describes a mesoscale storm driven by cooling and heating processes. The component that contains most of the energy of the solution (and is therefore called the dominant component) satisfies a simple nonlinear system devoid of gravity and sound waves. The residual component of the solution satisfies a forced gravity wave equation and essentially does not interact with the dominant component. The mathematical theory also provides information about the amplitude, wavelength, and period of the gravity waves. In the paper entitled “Comments on ‘Use of ducting theory in an observed case of gravity waves,”’ Dr. F. M. Ralph has claimed that the new gravity wave theory is not consistent with profiler observations of vertical velocity in his earlier paper entitled “Observations of a mesoscale ducted gravity wave.” Here it is shown that the new theory is completely consistent with profilers that have documented error bounds on the vertical velocity measurements. In the case that the new theory is claimed to be inconsistent with observational data, the data were obtained from a profiler with undocumented accuracy of the vertical velocity measurements in the precipitating case, and the two components of the solution were not properly separated.
Abstract
Recently, a mathematical theory has been developed that proves that there are two main components of the solution of the forced dynamical system that describes a mesoscale storm driven by cooling and heating processes. The component that contains most of the energy of the solution (and is therefore called the dominant component) satisfies a simple nonlinear system devoid of gravity and sound waves. The residual component of the solution satisfies a forced gravity wave equation and essentially does not interact with the dominant component. The mathematical theory also provides information about the amplitude, wavelength, and period of the gravity waves. In the paper entitled “Comments on ‘Use of ducting theory in an observed case of gravity waves,”’ Dr. F. M. Ralph has claimed that the new gravity wave theory is not consistent with profiler observations of vertical velocity in his earlier paper entitled “Observations of a mesoscale ducted gravity wave.” Here it is shown that the new theory is completely consistent with profilers that have documented error bounds on the vertical velocity measurements. In the case that the new theory is claimed to be inconsistent with observational data, the data were obtained from a profiler with undocumented accuracy of the vertical velocity measurements in the precipitating case, and the two components of the solution were not properly separated.
Abstract
No abstract available
Abstract
No abstract available
A brief description is given of NOAA's 404-MHz Wind Profiler Demonstration Network (WPDN), including the radar configuration, sampling strategy, site locations and characteristics, and a discussion of the Doppler power spectrum and its first three spectral moments: signal power (S), radial velocity (Vr ), and velocity variance (σ 2). Evidence is presented showing that 6-min time resolution spectral moment data from the vertically pointing beam of a WPDN wind profiler can be used to identify when precipitation is present above the profiler. Signatures of snow, light and moderate stratiform rain, heavy convective rain, freezing rain, and snow within jet stream cirrus are illustrated and summarized. Although radar reflectivity factor (Z) cannot be determined from WPDN wind profilers, the precipitation rates and fall speeds shown to be observable in the cases documented here are roughly consistent with earlier studies suggesting that precipitation with Z > 0–15 dBZ should typically be observable at 404 MHz, and that precipitation or clouds with Z < 0 dBZ should not be readily distinguishable from clear-air echoes. General signatures common to most precipitation, and characteristics in the data that allow different types of precipitation to be distinguished from one another, are revealed from three case studies. The most useful indicators of stratiform rain are downward Vr > 3–5 m s−1 and σ 2 > 1.0 m2 s−2. Snow is indicated by 2m s−1 > Vr > 0.5–0.9 ms−1 and σ 2< 1.0m2 s−2. Evidence of a melting level in S, Vr , and σ 2 is a very good indicator of stratiform precipitation, and when absent helps identify precipitation as convective when S and σ 2 are large. Because the spectral moment data are regularly archived, this information can be examined in real time and compared with simultaneously measured wind profiles. Such information should be useful in both research and operational meteorology. The ability to infer relationships between precipitation and kinematic features evident in the observed winds is also illustrated.
A brief description is given of NOAA's 404-MHz Wind Profiler Demonstration Network (WPDN), including the radar configuration, sampling strategy, site locations and characteristics, and a discussion of the Doppler power spectrum and its first three spectral moments: signal power (S), radial velocity (Vr ), and velocity variance (σ 2). Evidence is presented showing that 6-min time resolution spectral moment data from the vertically pointing beam of a WPDN wind profiler can be used to identify when precipitation is present above the profiler. Signatures of snow, light and moderate stratiform rain, heavy convective rain, freezing rain, and snow within jet stream cirrus are illustrated and summarized. Although radar reflectivity factor (Z) cannot be determined from WPDN wind profilers, the precipitation rates and fall speeds shown to be observable in the cases documented here are roughly consistent with earlier studies suggesting that precipitation with Z > 0–15 dBZ should typically be observable at 404 MHz, and that precipitation or clouds with Z < 0 dBZ should not be readily distinguishable from clear-air echoes. General signatures common to most precipitation, and characteristics in the data that allow different types of precipitation to be distinguished from one another, are revealed from three case studies. The most useful indicators of stratiform rain are downward Vr > 3–5 m s−1 and σ 2 > 1.0 m2 s−2. Snow is indicated by 2m s−1 > Vr > 0.5–0.9 ms−1 and σ 2< 1.0m2 s−2. Evidence of a melting level in S, Vr , and σ 2 is a very good indicator of stratiform precipitation, and when absent helps identify precipitation as convective when S and σ 2 are large. Because the spectral moment data are regularly archived, this information can be examined in real time and compared with simultaneously measured wind profiles. Such information should be useful in both research and operational meteorology. The ability to infer relationships between precipitation and kinematic features evident in the observed winds is also illustrated.
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 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.
