In order to provide a quantitative method to describe artificial precipitation demand, taking Zhiyan reservoir in Lanxi as the research object, based on precipitation, runoff and water level data, the percentile threshold of monthly water level index (WLI) with different grades of the reservoir was derived from real sample probability distribution of water level, the drought index (DI) was constructed by using the entropy weight method combined with the standardized precipitation index (SPI) and the standardized streamflow index (SSI), then WLI was integrated with DI to generate the demand level index (DLI) to describe artificial precipitation demand of reservoir objectively. The temporal characteristics of WLI, DI and DLI were studied, the applicability of DLI was analyzed based on the reservoir history records, the main conclusions are as follows: (1) The constructed percentile threshold of monthly WLI with different grades was able to reflect the water shortage of the reservoir precisely in different periods of a year. (2) There was no significant change in meteorological drought from 1990 to 2019, meanwhile hydrological drought showed an increasing trend, and the increasing trend was most obvious in spring. (3) The total occurrence frequency of meteorological (hydrological) drought in summer and autumn was 33.9% (35.0%), it is higher than that （30.0% (28.3%)） in winter and spring. The occurrence frequency of severe and extreme drought in spring was the highest, and meteorological and hydrological drought accounted for 11.2% and 10.0% respectively in spring. Hydrological drought did not lag behind and had a more serious effect than meteorological drought. (4) The inter-annual distribution of DLI was similar to that of WLI, and the seasonal distribution of DLI was similar to that of DI. Artificial precipitation demand appeared more frequently and last longer in the years after 2004 than before 2004. Demand occurred most frequently in summer, accounting for 40.0%, however the demand of high and very high level occurred most frequently in spring, accounting for 14.4%. (5) The integrated DLI grades could well reflect the actual demand of the reservoir, and when DLI grade was greater than or equal to 4 for several months, the reservoir might be short of water and emergency measures required to be taken.

Based on rainfall enhancement operation records in Zhejiang Province and Doppler radar data, sounding data and hourly rainfall observations from automatic stations as well as MICAPS weather chart from June to November of 2018-2020, the indexes of Doppler radar echo for rainfall enhancement in summer and autumn in Zhejiang Province were researched with the inverse method after evaluation of rainfall enhancement effect in order to guide cloud seeding operation more scientific and reasonable. The results show that the shear line, upper trough and typhoon are the most favorable weather systems for artificial rainfall enhancement in Zhejiang Province, accounting for 28.6%, 21.4% and 21.4%, respectively. According to radar echo and precipitation characteristics, cloud types can be divided into stratiform cloud, cumuliform cloud, mixed cloud giving priority to stratiform cloud and mixed cloud giving priority to cumuliform cloud. Mixed cloud is the most common type for rainfall enhancement, accounting for up to 82.5%. The number of samples with obvious rainfall enhancement effect is small, only accounting for 13.4%. Radar echo intensity, radar echo top, vertical integrated liquid water and thickness of negative temperature layer are valid criteria for operating conditions. The indexes of Doppler radar echo for rainfall enhancement are different in different seasons and for different cloud types. So the indexes of Doppler radar echo and the discriminant equation of operating conditions should be established separately. Unreasonable operation was the main reason why we failed to get positive effect of rainfall enhancement, which accounted for 49.2% of all the samples. Many other reasons leading to failure of rainfall enhancement included but not limited to inappropriate time, position and object. The indexes of Doppler radar echo for rainfall enhancement established in this article are scientific and easy-to-use. These studies have evident significance to command cloud seeding operation.

Based on CLDAS grid temperature data from National Meteorological Information Center of China, SCMOC grid temperature forecast data from Central Meteorological Observatory of China and temperature observation data at weather stations of Shanxi Province, the applicability of CLDAS temperature in Shanxi Province was evaluated comprehensively by using non-independence test method. And on this basis, based on CLDAS grid temperature data, the objective correction of SCMOC temperature forecast field was studied by using the sliding training period scheme. The results are as follows: (1) The complex terrain in Shanxi Province had a certain influence on the accuracy of CLDAS temperature, and the maximum temperature of CLDAS exhibited a better accuracy than the minimum temperature of CLDAS, which indicated that the influence of terrain on deviation of the minimum temperature was more significant, and the deviation of the minimum temperature in high altitude areas was negative generally, while that in low altitude areas was positive. (2) The deviation of CLDAS grid temperature had a continuity of time in space. After the simple deviation correction, the accuracy of the maximum and minimum temperature of CLDAS promoted by 1.1% and 9.7%, respectively, the revised temperatures were more consistent with observation. (3) Based on improved CLDAS grid temperature, the accuracy rate of SCMOC temperature forecast improved significantly by using the sliding deviation correction scheme. Compared to SCMOC, the accuracy rate of the 24-hour maximum and minimum temperature forecast in Shanxi Province in 2019 respectively increased by 2.7% and 4.7% after the sliding deviation correction. The quality of short-term temperature forecast after the sliding deviation correction had greatly improved, and it was superior to the subjective forecast of forecasters.

The effects of drought stress at different levels on photosynthetic characteristics, dry matter production and yield of winter wheat at flowering stage were examined in a common garden with rainout shelter during 2016－2017 growing season taking the winter wheat variety ‘Qi Mai 2’ as the test material. The experiment was consisted of five moisture treatments including T1 (an appropriate moisture level) and T2, T3, T4, T5 (one-time replenishment in accordance with the annual precipitation decrease of 20%, 50%, 75% and 100% in the critical period of winter wheat) and one rain-fed contrast test. The results indicate that under drought stress, chlorophyll-a content, photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), plant height, leaf area and total dry weight of aerial parts of winter wheat showed a decreasing trend at flowering stage, and the more serious the drought stress, the greater the decrease. The content of chlorophyll-a, Pn, Gs and Tr, plant height, leaf area and the total dry weight above ground under T5 treatment were reduced by 33.6%, 67.4%, 90.9%, 84.6%, 43.9%, 19.1% and 33.3%, compared with those of T1 test. With intensification of drought stress, the leaf water use efficiency (WUE) of winter wheat at flowering stage first increased and then decreased, and reached the highest under light drought stress. Drought stress could promote the transfer of plant nutrients to leaves and sheaths, and reduce nutrient supply to stems and ears, which was detrimental to the increase of winter wheat yield. In addition, drought stress at flowering stage also caused decrease of filling rate and increase of sterile ear rate of winter wheat, which made the theoretical yield of winter wheat reduce.

The advantages of lidar on detecting aerosols and the methods for solution to Mie lidar equation were summarily introduced in this paper. The major studies and the remaining problems on detecting aerosols with Mie lidar in recent two decades were also discussed.

Based on the natural environmental characteristics of Gannan Tibetan Autonomous Prefecture and Construction features of the highway G213，the influence of the highway Construction on the grassland eco一environment there is analyzed in this paper. Results show that the negative influence on vegetation during Construc;tion periods is severe. The soil environment is disturbed greatly in Certain areas rainfall erosion is the main factor in soil erosion and the loss volume of soil and water is 68 866. 7 t，63 060. 5 t of which is the lncrease. Finally  some   proposal  and   suggested  In  terms  Of  the  probable  environment  problems   In  the construetion.

 According to the investigation of Uahai一Gecha National Nature Reserves，the influence of weather disaster, climate warming and creeping environmental problems on its eco-environment  is analyzed and the corresponding protection arc shown in this paper,  It shows that weather disaster can make vegetation drought climate warming and drying, average annual temperature increased 0. }  C and rainfall 1990一1999，which compared with those during the period of 1960一1979.  As a result rated，part of the grassland degraded，the damage by rats have seriously threatened，
Or endure mechanical damage. mcasrcs With the decreased 87.5 mm during the period of ，the ato cco一environment has hccn dctcrio resources reduced and the biologic diversity has been destroyed.  Creeping environmental problems, such as the construction of the highway U213，has some influ cncc on as cco一cnv}ronmcnt.