Cloud is an important part of the earth-atmosphere system, and its macrophysical characteristics are not only closely related to radiation energy budget and regional climate change, but also affect directly the accuracy of cloud precipitation process prediction. In this paper, the occurrence frequency and vertical structure of clouds in the Inner Mongolia section of the Yellow River Basin are analyzed by using the observation data of the milliwave cloud radar in Hohhot from August 2020 to July 2021. The results show that Hohhot is mostly dominated by clear skies, whose profiles exceed 70.00% of total sampling profiles of cloud radar. In comparison, the occurrence frequency of cloud is relatively small, and the highest value in June is only 43.84%. The clouds are mainly medium cloud and high cloud, with base height mostly from 3.00 km to 4.00 km. The occurrence frequency is highest for clouds with a thickness from 0.50 km to 1.00 km, which are relatively thin. The macrophysical properties of clouds have obvious seasonal and diurnal variation. In spring and summer, the occurrence frequency of cloud is higher, with 39.71% and 35.77%, respectively, while that in winter is lowest. For the diurnal variation, the occurrence frequency of cloud in the afternoon is higher than that in the morning of spring, summer and autumn.

different level rainy days and its homologous precipitation quantity are obtained by using the daily precipitation data from
May to September ( 1960 － 2004) of 17 stations in the Qilian Mountain area，thus，we know the daily precipitation intensity of light
rainfall and moderate rainfall( and more) at each station． Based on regional mean value of the different level rainy days and rainfall intensity
in Qilian Mountain area，the tendency of the different level rainy days and rainfall intensity was analyzed using linear trend coefficient
and 5 levels main value function． The results show that both precipitation and different level rainy days from May to September
in Qilian Mountain area presented more in the west side and less in the east side in the same latitude area，and more in the east and
less in the west part of Qilian Mountain． In recent 45 years，the light rainfall days was descending，but the moderate rainfall days was
ascending． The precipitation intensity of light rainfall and moderate rainfall ( and more) presented ascending trend too from May to September
in Qilian Mountain area． The morlet wave analysis show that the light rainfall days had a period of five years，but the period of the moderate rainfall ( and more) days was more complex．

Based on the summarization of the former similar researches about land surface dewfall, this article systematically discusses dewfall’s formation mechanism and analyzes the relation between dewfall and climatic aswell as environmental factors, such as temperature, humidity, windspeed, cloud, topography, and so on. The ecological and climatic effects and biochemics effects about land surface dewfall are discoursed also, and some p roblems in the p resent research on dewfall are pointed out finally.Key words: dewfall; formation mechanism; ecological and climatic effects

By using meteorological data of Dingxi region and EOS／MODIS data，some basic surface parameters and the net radiation of earth’ssurface in the dry-farming region in Northwest China are derived，moreover，the seasonal variety of the net radiation ofearth’s surface is analyzed.The results show that the derived value is close to the observed value，the relative error is less than 16%，which means the derived value may reflect the factin stance；the seasonal variety of the net radiation is least in winter and most in summer and spring，and there is a symmetrical feature of its distribution in different seasons，its frequency distribution range is also
wide in this dry-farming region