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Calibration of weather radar is the foundation of data quality. Internal calibration, weekly maintenance, monthly maintenance and yearly maintenance ensure that stations of weather radar keep long-term stability. In fact, it shows that the echo intensity is not same between different stations of weather radar for same target, since the parameters obtained from the method of traditional calibration via theoretical calculation and measurement of radar subsystem. According to echo intensity calculation of weather radar equation, radar constant includes some parameters such as transmitted power, pulse width, antenna gain, beam width, system loss and so on. Accumulation of error from radar measurement causes the error between different weather radar stations. This paper researches a method that far-field calibration of weather radar based on the combination of objective truth value and simulating target, which combines far-field test, echo intensity calibration of standard metal ball, and calibration of simulating target. This method uses a device in far-field to receive radar signal to measure some parameters such as beam width, transmitted power, transmitter pulse width and so on; using the character of objective truth value of standard metal ball accurately calibrate that echo intensity and simulating target; and meanwhile, using simulating target generate an accurate and controlled signal in far-field to calibrate weather radar echo intensity, velocity, spectrum width, differential reflectivity factor, and differential propagation phase shift to make calibration of weather radar objectively and accurately.

According to X-band dual-polarized radar data from Beijing area, the authors analyzed the radar echo characteristics of a strong convective hail cloud which used the algorithm for identifying hail and polarization characteristics. The results show that the convective cloud has a distinct V- shaped gap, and the vertex of the gap is facing the radar station. The strong echo structure at the vertex of the gap is compact. The echo top is 13 km, and the maximum reflectivity factor is 57.5 dBZ. Around the V-shaped gap, the differential reflectance factors which are far from the radar station show negative value, indicating that this area is a hail area; the differential reflectance factors which are near the radar station show positive value, indicating that this area has a heavy raindrop. The reflectivity factors at 19:18, 19:48, 20:09, and 20:30 were selected, and the vertical profile was made along the lower inflow direction and the core of strongest reflectance factor. The vertical profile exhibits typical echo characteristics such as WER, BWER and echo overhang. The differential reflectivity factors and correlation coefficients have obvious stratification characteristics, which reflect the precipitation particles within clouds rising continually under the influence of low-level inflow airflow and the upper ice particles moving to the right side of the WER with the upper horizontal airflow and then dropping gradually. This process verifies the evolution of hail rising and falling.

With the rapid socioeconomic development of China, mega-cities with a population of more than 10 million have gradually emerged, with frequent urban floods and atmospheric pollution as well as other disasters. For better weather forecast and disaster prevention and mitigation in mega-cities, in 2016, China Meteorological Administration organized the " MegaCity Experiment On Integrated Meteorological Observation in China (MEMO)", in which continuous and quantitative observation of aerosol profiles in mega-cities by aerosol lidar is one of the important parts. To ensure the quantitative comparability of the aerosol lidar data, the Meteorological Observation Center of China Meteorological Administration launched the first calibration experiment of aerosol lidar network in MEMO at the Beijing Southern Suburb Observatory in September 2017. 6 lidars participated in the calibration and statistical analysis was used for the calibration of key subsystems such as transmit/receive channel, data acquisition. After calibration, the relative standard deviation of backscattering coefficient in 532nm channel is reduced from 90.8% to 20.4% in height range of 1-2 km, and from 244.3% to 35.9% in height range of 2-5 km.

In 2016, the China Meteorological Administration organized the “Megacity Experiment on integrated Meteorological Observation in China” to realize the continuous quantitative observation of aerosol profiles in megacities by using aerosol lidar. In order to ensure the quantitative comparability of the observed data of aerosol lidar, in September 2017, the CMA Meteorological Observation Centre carried out the first megacity experiment in the South suburb Observatory of Beijing. In the calibration test of aerosol lidar, the hardware system calibration of six lidars and the calibration of 2km-5km are completed by using the method of statistical analysis. This is the second aerosol calibration test of the Megacity Experiment in 2018. For the first time, the standard aerosol lidar developed by the University of Naples in Europe is introduced as the standard source, and 10 lidars from different manufacturers participating in the joint test are calibrated and compared at the same site at the same time. The results show that: REAL LIDAR as a reference source is equivalent to the calibration results using statistical methods. In the future, REAL LIDAR can be used as a standard to calibrate other lidar by means of quantum transfer. In this paper, the system deviation and standard deviation of backscatter coefficient of 1-8 km are obtained, and the results meet the calibration requirements of European EARLINET. This work promotes the improvement of the data quality of aerosol lidar, ensures the reliability and consistency of the data when multiple lidar network observation, and provides the basis for lidar to enter the real-time business NET.

In 2019 CMA is still working on upgrading the weather radars to dual polarization as scheduled, dozens of polarimetric radar have been deployed and put into operation, but proper ZDR bias calibration procedures for operational radar are still absent. The accuracy of quantitative precipitation estimators(QPE) and hydrometeor classification algorithm depends heavily on the accurate estimation of ZDR. Continuously monitoring and measurement of system ZDR bias is the key calibration technique for polarization radar, and it’s also one of the biggest challenges in radar operation and maintenance. In order to solve the key technical problems of ZDR calibration for operational radar, this paper proposes a method of ZDR deviation monitoring and calibration using light rain echoes from volume scan data. Both theorical analysis and observation prove that the intrinsic ZDR of light rain is between 0.25-0.35dB. We select light rain echo from every volume scan filtered by range, elevation, signal-to-noise ratio(SNR), correlation coefficient(phv) and the melting layer height.After several volume scans, the system ZDR bias is estimated and calibrated in real time through statistical analysis of light rain ZDR distribution mode. Two precipitation processes in 2016 and 2017 are used to verify and evaluate this method, we can conclude from the test data: (1) the histogram of ZDR is more reasonable after filtered. With the change of ZDR, the change of sample data is close to normal distribution, which proves the rationality of data screening.(2) the system bias ZDR estimated from two precipitation processes is between 0.3-0.5dB, the 0.2dB error meets the accuracy requirements of ZDR (0.1-0.2dB).(3) The new method can estimate and calibrate the ZDR bias along with routing volume scan, which is suitable for operational radar.

Since 2015, the first batch of domestic dual polarization radars have been upgraded and put into operation in Yangjiang, Meizhou, Shaoguan and Guangzhou. In the early stage of polarization radar operation, due to the limitation of technology level, the polarization parameters are not stable, so it is necessary to make a preliminary analysis of the polarization parameters before using data. In this paper, the correlations of reflectivity (ZH), Signal-to-noise ratio(SNR), correlation coefficient (CC), differential reflectivity (ZDR), specific differential phase shift rate (KDP) are quantitatively evaluated by statistics and analysis of a typical stratiform cloud precipitation process observed by dual polarization radar. The results show that: (1) The system ZDR bias by using light rain is stable at about 0.1dB, which meets the accuracy requirements of ZDR (0.1-0.2dB) (2) When SNR 40 dBZ, ZDR and ZH have a positive correlation; (4) when ZH 40 dBZ, KDP has a strong sensitivity, and its growth rate is faster, which shows that KDP can better reflect the characteristics of heavy rainfall. Finally, three typical processes are analyzed according to the above characteristics. Compared with traditional weather radar, dual polarization radar:(1) It is more intuitive and accurate to recognize the echo type with dual polarization radar; (2) it can directly and effectively judge the hail area in the cloud; (3)The corresponding relationship between KDP and rainstorm warning level can be established. These preliminary analysis and results can better reflect the detection performance advantage and data quality of polarization radar, and have certain reference significance for the application of S-band dual polarization radar data.

For a variety of interference exists in the collected real-time traffic images at the scene, and affects the traffic images of authenticity, we de-noise the traffic images with wavelet threshold. In order to verify the effect of de-noising, we add noise to the images, and then de-noise them in the method by hard threshold. The simulation experiments show that the de-noising effect is obvious and can meet the design requirements. Then de-noise the collected traffic images by suitable determine the decomposition levels and appropriate threshold, and do the inverse wavelet transform, we can obtain the much clearer de-noised traffic image.

The cDNA of DREB transcription factor named OjDREB1 was obtained from Lilyturf (Ophiopogon japonicus) under the drought stress of 12h by RT-PCR method. Sequence analysis showed that cDNA of OjDREB1 is 1779 bp long, the open reading frame is 1062bp.The predicted protein has 353 amino acids with an estimated molecular mass of 38.69 kDa and an isoelectric point of 6.46. The deduced primary structure of OjDREB1 contains a single AP2 domain and shows the typical characteristics of DREB gene family. Homological analysis showed that 73% amino acids in the sequences is similar to Asparagus officinalis DREB3. The OjDREB1 gene was cloned into the PBI121 vector to obtain plant expression vector.