A preliminary cause analysis of extremely less precipitation in Heilongjiang Province in July 2020 was carried out by using the monthly precipitation data at 62 meteorological stations of Heilongjiang Province, reanalysis data from National Center for Environmental Prediction and circulation indices from National Climate Center of China Meteorological Administration, etc. Results are as follows: (1) The precipitation was abnormally less in Heilongjiang in July 2020, and the average precipitation in the whole province was only 75.0 mm, which was the second least since 1961. (2) When the precipitation was abnormally less in Heilongjiang Province in July, the negative phase distribution with East Asia-Pacific teleconnection (EAP) pattern appeared over the East Asian coast from low to high latitude at 500 hPa geopotential height anomaly field in the same period, the position of East Asian subtropical westerly jet (EASWJ) obviously leaned to south, and the anomalous anticyclone-cyclone circulation appeared over northeastern China to near the Yellow Sea at the lower level of troposphere, the integrated water vapor diverged over Heilongjiang Province. The circulation characteristics in July 2020 were similar to those in the same period of less rain years, but the intensity of the jet center and its negative anomaly areas on the north side was significantly stronger than those in less rain years, and the center of the jet moved slightly to the east, the meridional wave train in troposphere over East Asian coast was more clearly. The abnormally southerly EASWJ played an important role on abnormally less precipitation in Heilongjiang Province in July 2020. (3) The atmospheric heat source near the South China Sea in May 2020 was abnormally weak, and the distribution of the North Atlantic Oscillation (NAO) appeared negative phase in July 2020, which caused the EASWJ to move anomalously southward in July through the meridional wave train of EAP teleconnection over East Asian coast and zonal wave train over the middle-high latitude of Eurasia, respectively, and resulted in less precipitation in Heilongjiang Province.
There are some systematic biases in prediction of solar radiation based on numerical models, the AVT method has been verified to reduce the prediction bias effectively. The AVT correction method was used to modify the forecasted solar radiation in two photovoltaic power plants in Hexi area of Gansu Province. The results state: (1) Before correction the forecast bias presented obviously diurnal variation with increase first and then decrease, while it wasn’t obvious after correction. There was a strong linear relationship between forecast deviation of solar radiation and observed values before correction, while it got weak after correction (the correlation coefficient and good fitting degree decreased). (2) There was obviously annual change characteristic of solar radiation with the highest forecast bias in spring, followed by summer, autumn and winter. After correction, its forecast bias was reduced in four seasons, especially in spring and summer.
By using the conventional observation data and NCEP reanalysis data，the shear line rainfall occurred in the central North China on July 16－17，2009 was analyzed．Results demonstrated that:(1)The northern cold air met with southern warm wet air in central North China，which provided the favorable weather background conditions for the heavy rain．(2)The strong rainfall took place on the left front and front side of a low level jet stream and in the vicinity of a shear line．(3)Frontogenesis function showed the gathering intensity of the cold and warm air，which can indicate the rainfall period and rainfall area．(4)By analyzing the temperature advection，there existed dry intrusion phenomena and the strong rainfall occurred during the period of the low level warm advection tilting upwards and the high level cold advection intruding downwards，northern low level cold air acted as"cold cushion"for the process．
The effect of a hail suppression by anti-hail gun which occurred on June 25, 2005 in the east part of the Qilian Mountain was analyzed by using the CINRAD/CC products, including the layer composite reflectivity factors, the maximum values of the vertical reflectivity, echo tops, the horizontal wind field in the hail cell, the vertical structure and the maximum values of VIL, their changes before and after the hail suppression, as well as ground precipitation. Results show: (1) There are two aspects of hail suppression effect by anti-hail gun: The first is that silver iodide crystals sprinkle fleetly around the explosive point, and collide with the surrounding frozen droplets, reducing the average quality and diameter of frozen droplets; the second is that the power from shells exploding suppresses the developing of the updrafts under the explosive point. (2) The hail suppression by anti-hail gun is available for rainfall increase on ground. As for this hail suppression process, assuming that liquid water in the hail cloud falls completely as raindrops to the ground, the precipitation on the ground will increase 4.69%.
The new generation of "the synthetical system of operation and service on the northwest drought monitoring and fore is a synthetical system of operation service which has good physical foundation，stronger monitoring, prcdicting,and service abilities, higher automation degree and local characteristic of the northwest region. Relying on the short一term weather forecasting, this system gathers the weather information collecting, processing and information saving for an integral whole, and takes full advantage of the Internet technique and previous systems, data and information，takes up the systems and pro- ductions of the other sul〕一special subjects in the item，so that it saves the great capacity of computer space，avoids many rc- pcated labor, and it brings into play the positive function in the usually monitoring and forecasting service in recent years.
