Detection of potentially hazardous convective clouds with a dual-polarized C-band radar

Abstract

Abstract.A method for forecasting very short-term rainfall to detect potentially hazardous convective cloud that produces heavy local rainfall was developed using actual volumetric C-band polarimetric radar data. Because the rainfall estimation algorithm used in this method removed the effect of ice particles based on polarimetric measurements, it was immune to the high reflectivity associated with hail. The reliability of the algorithm was confirmed by comparing the rainfall rate estimated from the polarimetric radar measurements at the lowest elevation angle with that obtained from optical disdrometers on the ground. The rainfall rate estimated from polarimetric data agreed well with the results obtained from the disdrometers, and was much more reliable than results derived from reflectivity alone.Two small cumulus cells were analyzed, one of which developed and later produced heavy rainfall, whereas the other did not. Observations made by polarimetric radar with a volumetric scan revealed that a high vertical maximum intensity of rainfall rate and a vertical area of enhanced differential reflectivity extending above the freezing level, often termed a high Z DR column, were clearly formed about 10 min prior to the onset of heavy rainfall on the ground. The onset time of the heavy rainfall could be estimated in advance from the polarimetric data, which agreed fairly well with observations. These polarimetric characteristics were not observed for the cumulus cell that did not produce heavy rainfall. The results suggest that both the vertical maximum intensity of the rainfall rate and a high Z DR column, estimated from polarimetric measurements, can be used to identify potentially hazardous clouds. Furthermore, this study shows that polarimetric radar measurements with high spatial and temporal resolutions are invaluable for disaster reduction.

Improving Short‐Term Rainfall Forecasts by Assimilating Weather Radar Reflectivity Using Additive Ensemble Perturbations

“…The parent storm associated with this F3 tornado was generated on the western side of the Kanto Plain and moved northeastward. The advanced C‐band solid‐state polarimetric radar (MACS‐POL; Adachi et al, ) of the Meteorological Research Institute has 150‐m radial and 0.7° azimuthal resolutions and observed not only the parent storm but also the mesoscale vortex associated with the F3 tornado (Yamauchi et al, ). Assimilating the MACS‐POL reflectivity data is expected to improve the forecast of this tornadic supercell.…”

Overview: Tropospheric profiling: state of the art and future challenges – introduction to the AMT special issue

“…Several authors pointed out that instrument synergy should be better exploited to overcome intrinsic limitations and reduce the uncertainties of products, such as the PBL height Summa et al, 2013), atmospheric refractivity (Hurter and Maier, 2013), aerosol profiles (Marcos et al, 2013), and rainfall rates (Réchou et al, 2014). The availability of near-real-time data and smart information and communications technology tools is recognized as crucial for applications such as flight trajectory prediction , weather nowcasting (Hurter and Maier, 2013), and hazard early warning (Adachi et al, 2013). On the other hand, Bock et al (2013) noted that long-term historical data sets may be reprocessed with new insight to infer by-products, such as integrated water vapor from astronomical spectrometers available starting at the beginning of the 20th century.…”

“…Therefore, they conclude that the polarized phase is a key parameter to characterize the atmospheric particles of the region -a populated city in a semi-arid area of the earth's dust belt. Adachi et al (2013) present a method using volumetric C-band polarimetric radar data for very short-term forecasting of potentially hazardous convective clouds. The method is immune to the high reflectivity associated with hail as the effect of ice particles is removed based on polarimetric measurements.…”

Observational operators for dual polarimetric radars in variational data assimilation systems (PolRad VAR v1.0)

“…These errors are homogeneous in space, which means observational error covariances are diagonal. The first one was done using NHM-4DVAR with actual radar data from the C-band dual polarimetric radar at the Meteorological Research Institute in Tsukuba, Japan (Yamauchi et al, 2012;Adachi et al, 2013). In this experiment, both radial velocity data and the polarimetric parameters of Z H , Z DR , and K DP were assimilated in FIT, and radial velocity and Q rain derived from K DP were assimilated in KD.…”

“…T. Kawabata et al: PolRad VAR v1.0 1991;Jameson and Caylor, 1994;Ryzhkov and Zrnić, 1995;Anagnostou et al, 2008;Kim et al, 2010;Ryzhkov et al, 2014;Adachi et al, 2015). Because QPE methods using dual polarimetric radar parameters are expected to be better than methods using single polarization radar data, we developed assimilation methods for dual polarimetric radar observations for both WRF Var and NHM-4DVAR.…”