IJERT-Characterization Of Dual-Beam MST Radar For The Analysis Of Atmospheric Turbulence And Instrumental Noise (original) (raw)
Related papers
2006
We present an investigation on the correlation between slant wet delays in different directions using two radiometers. A scaling factor for the atmospheric turbulence is estimated on a daily basis using data from one single or both radiometers. The result agree at the ~30% level. We also make tests by increasing the integration in order to decrease the radiometer noise. We show that the retrieved atmospheric variability does not significantly depend on the integration time
In this paper, a brief experiment is conducted for a certain period of time to test the dual-beam width method of estimating the turbulence kinetic energy (TKE) of the MST Atmospheric Radar. An elliptical beam was used with a modified dual beam-width analysis. The dual-beam width method employs the spectral widths measured simultaneously with two different beam-widths and the ratio of the magnitudes of the beam-widths is used under the assumption that the TKE is the same in the sample volumes viewed by both beam widths. The dualbeam width method can be used only at a small number of radar sites that have dual-beam width capability. The wet atmospheric delay of radio signals of earth satellite links can be inferred from ground-based microwave radiometry. Hence it is possible to use microwave radiometers to test models. We present results using data from two colocated radiometers. This gives us a variety of different combinations of data from the radiometers in order to derive parameters for atmospheric turbulence and instrumental noise. A scaling factor for the atmospheric turbulence is estimated using data from one single or both radiometers. We have also experimented with the impact of reduction in noise by increasing the Integration time of the Radiometer.
TOPEX microwave radiometer performance evaluation, 1992-1998
IEEE Transactions on Geoscience and Remote Sensing, 2000
The stability and accuracy of the TOPEX Microwave Radiometer (TMR) measurement of the atmospheric path delay due to water vapor is assessed over the interval from launch (August 1992) through June 1998. Detailed global comparisons are made with path delays derived from the Special Sensor Microwave Imager (SSM/I) instruments and a network of 15 island radiosondes. The results provide consistent evidence that the TMR path delay measurements included an instrument-related downward drift of 1.0-1.5 mm/yr between October 1992 and December 1996. The four-year drift correlates with an upward drift seen in the coldest TMR 18 GHz brightness temperature time series and is further supported by independent comparisons of TMR with ERS-1 and 2, GPS, and the Harvest Platform water vapor radiometer measurements. From January 1997 through June 1998 no significant relative path delay drift between TMR and SSM/I is seen in the comparison data, although anomalies do appear in early 1998. In terms of accuracy, both the SSM/I and radiosonde comparisons indicate no significant ( > 2%) scale error in the TMR path delay. An overall bias < 10 mm may be present, but the comparisons are not consistent in this determination.
Collocating satellite-based radar and radiometer measurements – methodology and usage examples
Atmospheric Measurement Techniques, 2010
Collocations between two satellite sensors are occasions where both sensors observe the same place at roughly the same time. We study collocations between the Microwave Humidity Sounder (MHS) onboard NOAA-18 and the Cloud Profiling Radar (CPR) onboard the CloudSat CPR. First, a simple method is presented to obtain those 5 collocations and this method is compared with a more complicated approach found in literature. We present the statistical properties of the collocations, with particular attention to the effects of the differences in footprint size. For 2007, we find approximately two and a half million MHS measurements with CPR pixels close to their centrepoints. Most of those collocations contain at least ten CloudSat pixels and image relatively 10 homogeneous scenes. In the second part, we present three possible applications for the collocations. Firstly, we use the collocations to validate an operational Ice Water Path (IWP) product from MHS measurements, produced by the National Environment Satellite, Data and Information System (NESDIS) in the Microwave Surface and Precipitation Products System (MSPPS). IWP values from the CloudSat CPR are found 15 to be significantly larger than those from the MSPPS. Secondly, we compare the relation between IWP and MHS channel 5 (190.311 GHz) brightness temperature for two datasets: the collocated dataset, and an artificial dataset. We find a larger variability in the collocated dataset. Finally, we use the collocations to train an Artificial Neural Network and describe how we can use it to develop a new MHS-based IWP product. We also study the effect of adding measurements from the High Resolution Infrared Radiation Sounder (HIRS), channels 8 (11.11 µm) and 11 (8.33 µm). This shows a small improvement in the retrieval quality. The collocations described in the article are available for public use. 3, 2010
Meteorologische Zeitschrift, 2009
Thermodynamic and dynamic quantities, such as the K-index and GUSTEX (a wind gust estimate), are commonly used in the nowcasting of intense convective weather. In the past, they were derived from conventional upper-air ascent measurements, which were normally only available twice a day. In the tropics, the thermodynamic property of the troposphere could change rapidly in rain episodes and the conventional upper-air ascent data alone are not sufficient for nowcasting purposes. This paper discusses the use of a multi-wavelength, ground-based microwave radiometer to provide frequently updated (once every 5 minutes) thermodynamic profiles of the troposphere up to 10 km for the nowcasting of severe convective weather during a field experiment in Hong Kong in 2004. The accuracy of the radiometer's measurements is first established by comparing with the temperature and humidity profiles of upper-air ascents and the integrated water vapour of Global Positioning System (GPS) receivers. The humidity profile and K-index from the radiometer in a number of rainstorm cases are then studied. They are found to give useful indications of the accumulation of water vapour and the increasing degree of instability of the troposphere before the occurrence of the heavy rain. The continuous availability of the thermodynamic profiles from the radiometer also makes it possible to study the correlation between K-index and the degree of instability of the troposphere. In this study, the tropospheric instability is expressed in terms of the total number and the rate of lightning strikes within 20 km or so from the radiometer. It is found to have good correlation with the time-averaged K-index from the radiometer during the heavy rain episodes in the field experiment period. Furthermore, the feasibility of combining the thermodynamic profiles from the radiometer and wind profiles given by radar wind profilers in the continuous estimation of wind gusts is studied. The estimated and the actual gusts are reasonably well correlated. The wind gusts so estimated are found to provide better indications of the strength of squalls, with a lead time of about one hour, compared with those based on radiosonde measurements. Overall speaking, the microwave radiometer is able to provide very useful data in the nowcasting of intense convective weather.
Radio Science, 1993
This study concerns the predicted performance of multifrequency ground-based radiometers in estimating atmospheric moisture and the corresponding attenuation and wet path delay on an Earth-space path. The analysis of the performance is based on a numerical simulation using possible combinations of radiometric channels at 10 microwave frequencies below 100 GHz. We first discuss the accuracy of retrievals of both integrated atmospheric vapor and cloud liquid from noisy radiometric measurements carried out at two frequencies and investigate the improvement attainable by using more than two radiometric channels. Then we focus on the problem of predicting attenuation and wet path delay at several frequencies in the millimeter wave range for a vertical Earth-space path from radiometric data. Examples of possible combinations of two and three frequencies are presented, ranked according to their capability, first in retrieving vapor and liquid, then in predicting attenuation and wet path delay for two different climatologies.
2005
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