Wind Profiler Spectra Research Articles

Removal of Multiple-Radio-Frequency Interference in 1.29 GHz Wind Profiler Spectra

A 1.29 GHz wind profiler was developed under a private–military–government cooperative wind profiler radar development project in the Republic of Korea. During the test operation period, radio frequency interference (RFI) contamination occurred in the spectrum. In addition to the general shape, with a continuous appearance depending on the altitude, the spectrum showed complex shapes, such as discontinuous and overlapping frequencies. The RFI characteristics in the wind profiler spectra were analyzed, and a new algorithm was developed to remove multiple RFI (MRFI). Meteorological and non-meteorological signals were separated by filtering with a spectrum width threshold of 0.1 m/s. A continuity check was performed to determine MRFI in the non-meteorological signal. The number of gates in which the same radial velocity is continuous was determined based on whether the beam was vertical or oblique; a rough continuity test was performed, considering exceptional circumstances for the meteorological signal. For overlapping MRFI, the process was repeated. Spectral contamination by MRFI was removed through filtering and iterated scans; the continuity of wind vectors calculated from the improved spectral radial velocity was verified. Good-quality wind vectors can be produced even in a bad-radio-frequency environment if proper quality control is performed.

Vertical structure and microphysical characteristics of Typhoon Kompasu (2010) at landfall

The vertical structure and microphysics of Typhoon Kompasu that caused a lot of damage associated with strong winds and heavy rainfall over the Seoul metropolitan area on 1∼2 September 2010 were examined primarily from wind profiler measurements. Four different periods that represent a stratiform, outer rainband, inner rainband, and eyewall region during passage of Typhoon Kompasu from 1200 to 2300 UTC 1 September were selected based on bright band intensities and vertical profiles of radar reflectivities and Doppler velocities. The bright band signatures observed in all of these periods indicated that the structure of Kompasu was basically stratiform in a weakening phase. Maximum rainfall rates up to 50 mm hr−1 at the surface and mean wind speeds greater than 30 m s−1 in the 2–4 km layer were observed in the eyewall region. Unlike the other regions that showed nearly zero vertical air motions or weak downdrafts below a melting layer, a mean updraft of ∼1 m s−1 was analyzed only in the eyewall region, which suggests that the updrafts may have enhanced drop growth that led to increasing surface rainfall rates. For each region, the vertical mean characteristics of rainfall parameters retrieved from wind profiler spectra below the melting layer were also examined. The rain properties between the inner and outer rainband were similar although they were apart with a distance of more than 100 km (> 2 hrs in time). The averaged mass-weighted mean diameters within the rainbands were larger than those in the stratiform and eyewall regions. A weaker bright band in the eyewall region suggests the presence of a relatively larger number of rimed particles associated with the updrafts around the melting layer. A stronger bright band was present in the rainbands, which indicates more active aggregation right above the melting layer.

A study of microphysical properties within a precipitation system using wind profiler spectra

This study investigates microphysical properties from wind profiler Doppler spectra observed within a precipitation system that produced high rainfall rates up to 40 mm hr−1 near the southern coast of the Korean Peninsula on 25∼26 June 2010. A 1290-MHz wind profiler located in the National Center for Intensive Observation of Severe Weather at Boseong, Korea, observed a widespread stratiform region and short-lived convective cells from 1850 UTC 25 to 0200 UTC 26 June 2010. By using a spectral model applied to observed profiler spectra, rainfall parameters and raindrop size distributions were retrieved below a melting layer during this period. Three representative periods during precipitation were selected based on intensities of bright band and characteristics in vertical profiles of radar reflectivity and Doppler velocity. During a brief convective period (∼30 min), radar reflectivity tended to be proportional to vertical air motion (positive upward), suggesting that updrafts up to ∼3 m s−1 over a large vertical extent through the melting layer probably contributed to increasing rainfall rates at the surface. In reflectivityrainfall rate distributions, large drop spectra (high reflectivity) were analyzed within downdrafts and small drop spectra (low reflectivity) within updrafts, similar to the large and small drop spectra but found in stratiform and convective regions, respectively, in previous studies. This indicates that the degree of spread between reflectivity and rainfall rate may be strongly dependent on positive and negative magnitudes of vertical air motion. For three categories of vertical air motion (i.e., updrafts, neutral, and downdrafts), physical relations between the retrieved rainfall parameters were examined.

Microphysical retrievals from simultaneous polarimetric and profiling radar observations

Abstract. The character of precipitation detected at the surface is the final product of many microphysical interactions in the cloud above, the combined effects of which may be characterized by the observed drop size distribution (DSD). This necessitates accurate retrieval of the DSD from remote sensing data, especially radar as it offers large areal coverage, high spatial resolution, and rigorous quality control and testing. Combined instrument observations with a UHF wind profiler, an S-band polarimetric weather radar, and a video disdrometer are analyzed for two squall line events occuring during the calendar year 2007. UHF profiler Doppler velocity spectra are used to estimate the DSD aloft, and are complemented by DSDs retrieved from an exponential model applied to polarimetric data. Ground truth is provided by the disdrometer. A complicating factor in the retrieval from UHF profiler spectra is the presence of ambient air motion, which can be corrected using the method proposed by Teshiba et al. (2009), in which a comparison between idealized Doppler spectra calculated from the DSDs retrieved from KOUN and those retrieved from contaminated wind profiler spectra is performed. It is found that DSDs measured using the distrometer at the surface and estimated using the wind profiler and polarimetric weather radar generally showed good agreement. The DSD retrievals using the wind profiler were improved when the estimates of the vertical wind were included into the analysis, thus supporting the method of Teshiba et al. (2009). Furthermore, the the study presents a method of investigating the time and height structure of DSDs.

Evaluation of moments calculated from wind profiler spectra: A comparison between five different processing techniques

A comparison between five different spectra-processing methods for the estimation of the moments of wind profiler radar measurements -is performed. The analysis compares the consensus winds with those measured by the rawinsonde, launched at the same time. The study is performed to select the signal post-processing method that gives the most accurate moments estimation on the used dataset. The moments estimated by the selected post-processing algorithm can then be employed in further work, aiming to improve the retrieval of humidity profile in a combined sensor approach, using wind profiler and radiometer data.

Improving Wind Profiler–Measured Winds Using Coplanar Spectral Averaging

Abstract A method is presented that increases the detectability of weak clear-air signals by averaging Doppler spectra from coplanar wind profiler beams. The method, called coplanar spectral averaging (CSA), is applied to both simulated wind profiler spectra and to 1 yr of archived spectra from a UHF profiler at Christmas Island (1 October 1999–30 September 2000). A collocated 50-MHz wind profiler provides a truth for evaluating the CSA technique. In the absence of precipitation, it was found that CSA, when combined with a fuzzy logic quality control, increases the height coverage of the 1-hourly averaged UHF profiler winds by over 600 m (two range gates). CSA also increased the number of good wind estimates at each observation range by about 10%–25% over the standard consensus method.

Bird identification on 1290-MHz wind profiler data applying neural networks and neurofuzzy systems

Migrating birds can severely affect data from wind profilers operating in the 1000 MHz range. Recent methods for removing bird contamination do not seem to solve the problem satisfactorily. Here, a new method, the Quantum Neurofuzzy Bird Identification and Removal Deck (NEURO-BIRD) is presented. The algorithm has an overall classification rate of over 90 % for birds, clear air returns, and rain echoes for single, one-second wind profiler spectra. Even with very heavy migration, high quality hourly winds can be obtained. Because the source of contamination of the spectra is unambiguously identified, bird data can be supplied for ornithological research. NEURO-BIRD is very fast and well suited for real-time applications.

Multiple peak processing algorithm for identification of atmospheric signals in Doppler radar wind profiler spectra

Multiple peak processing algorithm for identification of atmospheric signals in Doppler radar wind profiler spectra