Based on the insensitivity of the specific differential phase (KDP) to path-integrated attenuation (PIA), partial beam blockage (PBB), and wet radome (WR) issues, the bias of reflectivity (ZH) is corrected for X-band gap-filling radars. TheKDP-ZHrelationship established using the raindrop size distribution (DSD) data collected by local disdrometers is considered in the correction procedure. The practical performance of this correction procedure is extensively evaluated during a severe rainfall event. The results show that (i) this correction methodology can simultaneously address the PIA, PBB, and WR effects onZHmeasurements at X-band frequency, and the correctedZHat X-band agrees very well with DSD-derivedZHand its C-and S-band counterparts; (ii) radar quantitative precipitation estimates (QPE) based onZHare significantly improved after the correction in both the PBB-affeceted and PBB-unaffected areas. The applications of correctedZHand the improved radar QPE can improve the gap-filling capability of X-band radars for surrounding C- and S-band radar observations.

The microphysical processes' spatial variety and temporal evolution tendency during super typhoon Leima is investigated through measurements from an S-band polarimetric radar and six disdrometers. The results show that collision-coalescence/the collision-breakup occurred near/around the center of the typhoon, deduced from radar-measured and DSD-derived ZDR. In the vertical time-series view of ZDR, the collision-breakup may transition to the collision-breakup near the surface around the altitude of 0.9 km, and the collision-coalescence, collision-breakup, and coalescence-breakup balance may dominate during different periods of typhoon precipitation.

The unique network consisting of three different wavelength (C-, S- and X-band) radar in Eastern China is utilized to demonstrate their coordination capability of better coverage of low atmospheric layers in convective situations. After correcting attenuation effects on horizontal reflectivity (ZH) of all three wavelength radars based on the self-consistency approach, X-band radar exhibits even larger ZHthan S- and C-band, which exactly captures the severe developing convective rainbands on the lower atmospheric layer. In this sense, the X-band radar effectively plays a gap-filling coordination role in this S- and C-band radar network in convective situations.

Partial beam blockage (PBB) correction is necessary in complex terrain for radar quantitative applications. Regional KDP-ZHrelationship is established from in situ raindrop size distribution (DSD) measurements and is then utilized to mitigate the PBB effects through combining an attenuation correction approach. The practical performance of this PBB correction technique is evaluated through evaluating the spatial continuity of reflectivity ($Z_{\mathrm{H}}$}) measurements and rainfall estimates based on$R(Z_{\mathrm{H}})$and$R(K_{\text{DP}})$. The results show that with the developed attenuation and PBB correction schemes (i) the spatial continuity of$Z_{\mathrm{H}}$measurements can effectively be enhanced; (ii) rainfall estimates based on$R(Z_{\mathrm{H}})$in the PBB-affected area are incrementally improved with better spatial continuity and its performance tends to be more comparable with$R(K_{\text{DP}})$.

A water-logging disaster occurred in Eastern China on 1 June 2016 was utilized to investigate the practical performance of six radar rainfall estimators based on horizontal reflectivity ($Z_{\mathrm{H}}$), specific attenuation ($A_{\mathrm{H}}$), specific differential phase ($K_{\text{DP}}$), and multi-variable estimators that integrate differential reflectivity ($Z_{\text{DR}}$), namely$R(Z_{\mathrm{H}},\, Z_{\text{DR}}), R(K_{\text{DP}}, Z_{\text{DR}})$and$R(A_{\mathrm{H}}, Z_{\text{DR}})$. Detailed evaluation with a local rain gauge network and drop size distribution (DSD) measurements shows that (i)$R(A_{\mathrm{H}},\, Z_{\text{DR}})$underestimates the light rain pattern, but it achieves the best scores and performs the best among the various estimators; (ii) each radar rainfall estimator can outperform other estimators at a certain period of time determined by the rainfall patterns; (iii) both the optimal radar rainfall relationship and high calibration accuracy are required to obtain accurate rainfall estimates; (iv) the contamination of melting solid hydrometeors on$A_{\mathrm{H}} \text{and}/\text{or}K_{\text{DP}}$may make them less effective than$Z_{\mathrm{H}}$. In addition, with appropriate adjustment of$\alpha$coefficient,$R(A_{\mathrm{H}})$can perform better than$R(K_{\text{DP}})$.

Ground-based microwave radiometer could provide continuous thermodynamic profiles which are crucial to weather services. But further efforts should be made to improve the accuracy of measurements. In this study, quality control (QC) procedures have been applied to temperature and absolute humidity profiles obtained from a ground-based microwave radiometer (January 2012 to May 2014) at Shanghai Expo Station and thousands of doubtful profiles are flagged. Temporal distributions and possible causes of these doubtful profiles are further investigated. Results show that the doubtful profiles are closely related to specific weather conditions. The doubtful temperature profiles might be caused by various weather conditions, such as precipitation, frost, extreme high temperature, etc. The majority of doubtful humidity profiles are results of precipitation impacts.

A torrential flood event occurred over the complex terrain in Zhejiang on 23 June 2015 is investigated utilizing the first routinely operational C-band polarimetric radar in China. The polarimetric radar quantitative precipitation estimation (QPE) performance is verified using a local rain gauge network, and the microphysical characteristics of the rainstorm are revealed based on polarimetric radar variables. The results show that (i) radar QPE estimator based on KDP performs the best among all estimators; (ii) the rainstorm upon the rainfall center area was dominated by small-moderate sized raindrops with mean volume diameter less than 2 mm, but high raindrop concentration with log10(Nw) exceeding 5 mm-1m-3, resulting in rather high liquid water content; (iii) small hailstones were falling and melting upon the intense rainfall area between gauge stations, which compounded the complex precipitation structure and enhanced raindrop concentration.

Effective utilization of the changing precipitation microphysics in real-time radar quantitative precipitation estimation (QPE) is challenging, which requires dynamic adjustment of the radar reflectivity (Z) and rain rate (R) relations. This article develops and demonstrates two dynamic radar rainfall approaches using 16 Doppler weather radars and 4579 surface rain gauges deployed over the Eastern Jiang Huai River Basin (EJRB) in China. Both approaches are derived based on the radar-gauge feedback mechanism. Although the Z-R relations in both approaches are dynamically adjusted within a precipitation system, one is using a single global optimum (SGO) Z-R relation, while the other is using different Z-R relations for different storm cells identified by a storm cell identification and tracking (SCIT) algorithm. Four precipitation events featured by different rainfall characteristics are investigated to evaluate the performances of various QPE methodologies. In addition, the shortterm vertical profile of reflectivity (VPR) clusters is extensively analyzed to resolve the storm-scale characteristics of different storm cells. The evaluation results based on independent gauge observations show that both rainfall approaches with dynamic Z-R relations perform much better than the fixed Z-R relations. The adaptive approach incorporating the SCIT algorithm and real-time gauge measurements has the best performance since it can better capture the spatial variability and evolution of precipitation.

Quantitative Precipitation Estimation (QPE) is one of the most important applications of weather radars. However, it is difficult to obtain an optimal Z-R relation that can represent the local variability in precipitation microphysics. This study implements an adaptive radar QPE scheme based on the Storm Cell Identification and Tracking (SCIT) algorithm for Doppler radar and rain gauge measurements from Southwest China. The performance of this innovative QPE system is demonstrated using four precipitation events featured by different meteorological characteristics. Evaluation results show that the SCIT-based rainfall approach performs better than conventional Z-R based algorithms.