Abstract:There are 13 severe convective weather in Shandong in May 2020,including 8 hail processes occurring at 81 stations(65.9％)in 15 cities(93.8％)in total,with a maximum station-hail-hit number of 4 times.There are 10 thunderstorm gales above Beaufort scale 10 and 5 short-time heavy precipitation.The frequency,coverage,intensity,and severity of disasters have been rare over the last decade.The"5·17"convective weather process is the most intense,and its wide range of hail is very rare.The largest hail diameter is 4.5 cm,the maximum wind speed is 36.6 m·s-1(Beaufort scale 12),and the maximum rainfall intensity is 56.9 mm·h-1.Based on ECMWF(European Centre for Medium-Range Weather Forecasts)Reanalysis v5(ERA5)and data of intensive automatic meteorological observation stations,Doppler weather radar,and lightning location,the characteristics of severe convective weather in Shandong in May 2020 and the causes of frequent occurrence are analyzed.Taking the"5·17"severe convective weather process as an example,the characteristics of radar echoes and the vertical motion in the storm are analyzed.The results are shown below.(1)The stronger subtropical high not only favors the southwest warm moist airflow reaching Shandong,but also obstructs the westerly system,resulting in the forward trough getting intensified and maintaining over Shandong for a long time.The cold air carried by the northwest airflow in front of the 500-hPa enormously stronger warm ridge is superimposed over the 850-hPa unusually stronger warm temperature ridge,leading to an unstable atmospheric stratification over Shandong continuously.(2)Under the above favorable weather background,the water vapor over Shandong is abundant,CAPE(convective available potential energy)is large,the cyclonic convergence is strong at the junction of Hebei,Shandong,and Henan provinces,and there is a stable convergence line in the middle region of Shandong,which is easy to trigger severe convective weather,resulting in frequent severe convective weather in Shandong in May.(3)The highly organized convective storm,regional supercell groups,and a strong squall line with its length more than 500 km are the direct causes of"5·17"strong convection.The ascending velocity inside the storm reaches up to 28 m·s-1.

Abstract:By analyzing the difference between the echoes detected by the W-band radar and the cloud echoes detected by Ka-band radar at the same time, the detection capabilities of the W-band radar prototype are verified.The results show that: 1) W-band radar prototype operates reliably.The macro-parameters of clouds including the layer, boundary and thicker, the fine structure of cloud and the change of the microphysics parameters of clouds can be obtained by both the two band radars.Strong echoes, small speed and broad spectrum of ice clouds reveal existence of updrafts and more supercooled water.2) The capabilities to detect fog and haze of W-band radar with enhancement pattern in close to the ground is stronger than that of Ka-band radar.The two cloud radars have the same detection capabilities to thin clouds, but the less thicker, lower cloud top and less echo intensity for precipitation and thick clouds with more water content and multilayer clouds are measured by W-band radar because of the stronger attenuation to W-band radar, and the echo intensity of W-band radar is also reduced in the case of Rayleigh scattering.

Abstract:The selection of methods for extracting crop planting areas is of great significance for agricultural remote sensing monitoring.To explore the differences between optimum phase scheme,time series optical data scheme and optical-SAR(synthetic aperture radar)fusion phase scheme in remote sensing recognition of summer maize planting areas,Shanghe County of Shandong Province is taken as the study area.Based on the Sentinel-1/2 data from the GEE(Google Earth Engine)cloud platform,three datasets are constructed.Combined with ground survey samples,random forest method is used to extract the summer maize planting areas in the study area using three schemes,and the accuracy of each scheme is analyzed.The result shows that all the three schemes can achieve high accuracy in distinguishing summer maize planting areas from other crops.Compared with the optimum phase scheme,the time series optical data scheme improves the overall classification accuracy of summer maize from 83.01％to 89.44％,and the Kappa coefficient increases from 0.77 to 0.86.Compared with the optimum phase scheme and time series optical data scheme,the overall classification accuracy of the optical-SAR fusion phase scheme is the highest,reaching 92.51％,and the Kappa coefficient reaches 0.89.The classification results show that the optical-SAR fusion phase scheme can effectively recognize summer maize planting areas with high accuracy,providing reference for agricultural investigation and management during the growing season.