On the Opportunistic use of Commercial Ku and Ka Band Satcom Networks for Rain Rate Estimation: Potentials and Critical Issues

AbstractIn this study, methods of convective/stratiform precipitation classification and surface rain-rate estimation based on the Atmospheric Radiation Measurement Program (ARM) cloud radar measurements were developed and evaluated. Simultaneous and collocated observations of the Ka-band ARM zenith radar (KAZR), two scanning precipitation radars [NCAR S-band/Ka-band Dual Polarization, Dual Wavelength Doppler Radar (S-PolKa) and Texas A&M University Shared Mobile Atmospheric Research and Teaching Radar (SMART-R)], and surface precipitation during the Dynamics of the Madden–Julian Oscillation/ARM MJO Investigation Experiment (DYNAMO/AMIE) field campaign were used. The motivation of this study is to apply the unique long-term ARM cloud radar observations without accompanying precipitation radars to the study of cloud life cycle and precipitation features under different weather and climate regimes. The resulting convective/stratiform classification from KAZR was evaluated against precipitation radars. Precipitation occurrence and classified convective/stratiform rain fractions from KAZR compared favorably to the collocated SMART-R and S-PolKa observations. Both KAZR and S-PolKa radars observed about 5% precipitation occurrence. The convective (stratiform) precipitation fraction is about 18% (82%). Collocated disdrometer observations of two days showed an increased number concentration of small and large raindrops in convective rain relative to dominant small raindrops in stratiform rain. The composite distributions of KAZR reflectivity and Doppler velocity also showed distinct structures for convective and stratiform rain. These evidences indicate that the method produces physically consistent results for the two types of rain. A new KAZR-based, two-parameter [the gradient of accumulative radar reflectivity Ze (GAZ) below 1 km and near-surface Ze] rain-rate estimation procedure was developed for both convective and stratiform rain. This estimate was compared with the exponential Z–R (reflectivity–rain rate) relation. The relative difference between the estimated and surface-measured rainfall rates showed that the two-parameter relation can improve rainfall estimation relative to the Z–R relation.

Download Full-text

Estimating Rain Rates from Tipping-Bucket Rain Gauge Measurements

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2007jtecha895.1 ◽

2008 ◽

Vol 25 (1) ◽

pp. 43-56 ◽

Cited By ~ 59

Author(s):

Jianxin Wang ◽

Brad L. Fisher ◽

David B. Wolff

Keyword(s):

Rain Rate ◽

Tropical Rainfall Measuring Mission ◽

Rain Gauge ◽

Radar Reflectivity ◽

Time Shift ◽

Estimation Errors ◽

Rate Estimation ◽

Reflectivity Data ◽

Rain Rates ◽

Event Definition

Abstract This paper describes the cubic spline–based operational system for the generation of the Tropical Rainfall Measuring Mission (TRMM) 1-min rain-rate product 2A-56 from tipping-bucket (TB) gauge measurements. A simulated TB gauge from a Joss–Waldvogel disdrometer is employed to evaluate the errors of the TB rain-rate estimation. These errors are very sensitive to the time scale of rain rates. One-minute rain rates suffer substantial errors, especially at low rain rates. When 1-min rain rates are averaged over 4–7-min intervals or longer, the errors dramatically reduce. Estimated lower rain rates are sensitive to the event definition whereas the higher rates are not. The median relative absolute errors are about 22% and 32% for 1-min rain rates higher and lower than 3 mm h−1, respectively. These errors decrease to 5% and 14% when rain rates are used at the 7-min scale. The radar reflectivity–rain-rate distributions drawn from the large amount of 7-min rain rates and radar reflectivity data are mostly insensitive to the event definition. The time shift due to inaccurate clocks can also cause rain-rate estimation errors, which increase with the shifted time length. Finally, some recommendations are proposed for possible improvements of rainfall measurements and rain-rate estimations.

Download Full-text

Automated rain rate estimates using the Ka-band ARM zenith radar (KAZR)

Atmospheric Measurement Techniques ◽

10.5194/amt-8-3685-2015 ◽

2015 ◽

Vol 8 (9) ◽

pp. 3685-3699 ◽

Cited By ~ 13

Author(s):

A. Chandra ◽

C. Zhang ◽

P. Kollias ◽

S. Matrosov ◽

W. Szyrmer

Keyword(s):

Rain Rate ◽

Tropical Indian Ocean ◽

Rain Gauge ◽

Signal Attenuation ◽

Ka Band ◽

Automated Algorithm ◽

Atmospheric Radiation Measurement ◽

Microphysical Processes ◽

The Tropics ◽

Rain Rates

Abstract. The use of millimeter wavelength radars for probing precipitation has recently gained interest. However, estimation of precipitation variables is not straightforward due to strong signal attenuation, radar receiver saturation, antenna wet radome effects and natural microphysical variability. Here, an automated algorithm is developed for routinely retrieving rain rates from the profiling Ka-band (35-GHz) ARM (Atmospheric Radiation Measurement) zenith radars (KAZR). A 1-dimensional, simple, steady state microphysical model is used to estimate impacts of microphysical processes and attenuation on the profiles of radar observables at 35-GHz and thus provide criteria for identifying situations when attenuation or microphysical processes dominate KAZR observations. KAZR observations are also screened for signal saturation and wet radome effects. The algorithm is implemented in two steps: high rain rates are retrieved by using the amount of attenuation in rain layers, while low rain rates are retrieved from the reflectivity–rain rate (Ze–R) relation. Observations collected by the KAZR, rain gauge, disdrometer and scanning precipitating radars during the DYNAMO/AMIE field campaign at the Gan Island of the tropical Indian Ocean are used to validate the proposed approach. The differences in the rain accumulation from the proposed algorithm are quantified. The results indicate that the proposed algorithm has a potential for deriving continuous rain rate statistics in the tropics.

Download Full-text

Dual-wavelength radar technique development for snow rate estimation: a case study from GCPEx

Atmospheric Measurement Techniques ◽

10.5194/amt-12-1409-2019 ◽

2019 ◽

Vol 12 (2) ◽

pp. 1409-1427 ◽

Cited By ~ 3

Author(s):

Gwo-Jong Huang ◽

Viswanathan N. Bringi ◽

Andrew J. Newman ◽

Gyuwon Lee ◽

Dmitri Moisseev ◽

...

Keyword(s):

Particle Size ◽

Power Law ◽

Radar Reflectivity ◽

Dual Wavelength ◽

Hydrodynamic Theory ◽

Estimation Methods ◽

Fall Velocity ◽

Large Variability ◽

Ka Band ◽

Rate Estimation

Abstract. quantitative precipitation estimation (QPE) of snowfall has generally been expressed in power-law form between equivalent radar reflectivity factor (Ze) and liquid equivalent snow rate (SR). It is known that there is large variability in the prefactor of the power law due to changes in particle size distribution (PSD), density, and fall velocity, whereas the variability of the exponent is considerably smaller. The dual-wavelength radar reflectivity ratio (DWR) technique can improve SR accuracy by estimating one of the PSD parameters (characteristic diameter), thus reducing the variability due to the prefactor. The two frequencies commonly used in dual-wavelength techniques are Ku- and Ka-bands. The basic idea of DWR is that the snow particle size-to-wavelength ratio is falls in the Rayleigh region at Ku-band but in the Mie region at Ka-band. We propose a method for snow rate estimation by using NASA D3R radar DWR and Ka-band reflectivity observations collected during a long-duration synoptic snow event on 30–31 January 2012 during the GCPEx (GPM Cold-season Precipitation Experiment). Since the particle mass can be estimated using 2-D video disdrometer (2DVD) fall speed data and hydrodynamic theory, we simulate the DWR and compare it directly with D3R radar measurements. We also use the 2DVD-based mass to compute the 2DVD-based SR. Using three different mass estimation methods, we arrive at three respective sets of Z–SR and SR(Zh, DWR) relationships. We then use these relationships with D3R measurements to compute radar-based SR. Finally, we validate our method by comparing the D3R radar-retrieved SR with accumulated SR directly measured by a well-shielded Pluvio gauge for the entire synoptic event.

Download Full-text

Rain rate estimation by simplified method using UHF wind profiler measurement at KMITL

10.1117/12.410625 ◽

2000 ◽

Author(s):

Chaiwat Somboonlarp ◽

Nipha Leelaruji ◽

Narong Hemmakorn ◽

Apinan Manyanon ◽

Yuichi Ohno

Keyword(s):

Rain Rate ◽

Wind Profiler ◽

Rate Estimation ◽

Simplified Method ◽

Uhf Wind Profiler

Download Full-text

Application of X- and S-band radars for rain rate estimation over an urban area

Physics and Chemistry of the Earth ◽

10.1016/s0079-1946(97)00141-9 ◽

1997 ◽

Vol 22 (3-4) ◽

pp. 259-264 ◽

Cited By ~ 7

Author(s):

R. Uijlenhoet ◽

J.N.M. Stricker ◽

H.W.J. Russchenberg

Keyword(s):

Urban Area ◽

Rain Rate ◽

Rate Estimation

Download Full-text

Characterization of Rain Specific Attenuation and Frequency Scaling Method for Satellite Communication in South Korea

International Journal of Antennas and Propagation ◽

10.1155/2017/8694748 ◽

2017 ◽

Vol 2017 ◽

pp. 1-16 ◽

Cited By ~ 7

Author(s):

Sujan Shrestha ◽

Dong-You Choi

Keyword(s):

South Korea ◽

Satellite Communication ◽

Rain Rate ◽

Rain Attenuation ◽

Frequency Scaling ◽

Scaling Method ◽

Ka Band ◽

Specific Attenuation ◽

Rain Specific Attenuation ◽

Attenuation Models

The attenuation induced by rain is prominent in the satellite communication at Ku and Ka bands. The paper studied the empirical determination of the power law coefficients which support the calculation of specific attenuation from the knowledge of rain rate at Ku and Ka band for Koreasat 6 and COMS1 in South Korea that are based on the three years of measurement. Rain rate data was measured through OTT Parsivel which shows the rain rate of about 50 mm/hr and attenuation of 10.7, 11.6, and 11.3 dB for 12.25, 19.8, and 20.73 GHz, respectively, for 0.01% of the time for the combined values of rain rate and rain attenuation statistics. Comparing with the measured data illustrates the suitability for estimation of signal attenuation in Ku and Ka band whose validation is done through the comparison with prominent rain attenuation models, namely, ITU-R P.618-12 and ITU-R P. 838-3 with the use of empirically determined coefficient sets. The result indicates the significance of the ITU-R recommended regression coefficients of rain specific attenuation. Furthermore, the overview of predicted year-wise rain attenuation estimation for Ka band in the same link as well as different link is studied which is obtained from the ITU-R P. 618-12 frequency scaling method.

Download Full-text

Application of Synthetic Storm Technique for Diurnal and Seasonal Variation of Slant Path Ka-Band Rain Attenuation Time Series over a Subtropical Location in South Africa

International Journal of Antennas and Propagation ◽

10.1155/2015/474397 ◽

2015 ◽

Vol 2015 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

J. S. Ojo ◽

P. A. Owolawi

Keyword(s):

South Africa ◽

Time Series ◽

Seasonal Variation ◽

Diurnal Variation ◽

Rain Rate ◽

Rain Attenuation ◽

Series Data ◽

Band Frequency ◽

Ka Band ◽

Slant Path

As technology advances and more demands are on satellite services, rain-induced attenuation still creates one of the most damaging effects of the atmosphere on the quality of radio communication signals, especially those operating above 10 GHz. System designers therefore require statistical information on rain-induced attenuation over the coverage area in order to determine the appropriate transmitter and receiver characteristics to be adopted. This paper presents results on the time-varying rain characterization and diurnal variation of slant path rain attenuation in the Ka-band frequency simulated with synthetic storm techniques over a subtropical location in South Africa using 10-year rain rate time-series data. The analysis is based on the CDF of one-minute rain rate; time-series seasonal variation of rain rate observed over four time intervals: 00:00–06:00, 06:00–12:00, 12:00–18:00, and 18:00–24:00; diurnal fades margin; and diurnal variation of rain attenuation. Comparison was also made between the synthesized values and measured attenuation data. The predicted statistics are in good agreement with those obtained from the propagation beacon measurement in the area. The overall results will be needed for an acceptable planning that can effectively reduce the fade margin to a very low value for an optimum data communication over this area.

Download Full-text