Quantitative Relationship Between Cloud Amount and Precipitation in Summer over China and its Causes
One of the requirements for producing rainfall is cloud formation,and clouds and precipitation have a very intricate and intimate relationship.First,we used databases from conventional stations and ISCCP(International Satellite Cloud Climatology Project)to evaluate the spatial and temporal relationships between the variation of several characteristic features of clouds and the variance in summertime precipitation over China.According to the station dataset's findings,there is a significant positive correlation between the anomalous percentage of total cloud cover,low cloud cover,and precipitation across the entire nation.For stations that pass the 0.05 level significance test,the linear relationships between the anomalous percentage of clouds and precipitation are particularly obvious.For every 1.00%increase in total cloud cover,precipitation increases by 2.23%,and for every 1.00%increase in low cloud cover,precipitation increases by 0.46%.The ISCCP dataset results demonstrate very strong positive connections between abnormal percentages of cloud amount,optical thickness,cloud-water path,cirrus and deep convective cloud amount in high clouds,and that of precipitation.Second,China was divided into nine climate zones using the k-means cluster analysis method and with reference to the geoclimatic distribution of China.Then wavelet coherence analysis and cross wavelet analysis were used to further investigate the relationship in the time-frequency domain between the anomalous percentage of cloud amounts and precipitation in each climate zone.The findings demonstrate substantial coherence and resonance cycles at the scales of 2 to 4 years and 5 to 8 years,and a positive correlation phase for the anomalous percentage of total and low cloud quantities and daytime precipitation in summer throughout the nine climate zones.In both time-space distributions and time-frequency domains,there are extremely significant positive correlations between the anomalous percentage of cloud amounts(especially the low cloud amount)and precipitation in summer over China.The strong coherence and resonance period between anomalous percentage of cloud amounts and precipitation are the reasons for the positive correlation between them.
国家科技期刊平台
NSTL
万方数据
