Climatic Distribution and Trend Characteristics of Global Cloud Water Content

Based on the monthly cloud water content of the 20th-century reanalysis version 2c dataset, mathematical-statistical methods are employed to analyze the distribution and variation characteristics of the global cloud water content, including oceans and land from 1960 to 2014, and their relationships with water vapor flux. Results show that: 1) The global cloud water content is unevenly distributed spatially, with the oceans having a higher content than the land at a ratio of approximately 4﹕3. Variations in the trend of cloud water content over the middle and low latitude oceans and land are approximately 0.07 g m⁻² (10 a)⁻¹ and −0.04 g m⁻² (10 a)⁻¹, respectively. Seasonal differences are reflected mainly as high cloud water content in the Tropical Convergence Zone and the Southern Hemisphere oceans in summer, and the Northern Hemisphere oceans and the Southern Hemisphere land in winter. 2) South America, with the highest cloud water content, has the fastest increasing trend of 0.46 g m⁻² (10 a)⁻¹ whereas Africa, with the lowest cloud water content, has the fastest decreasing trend of −0.59 g m⁻² (10 a)⁻¹, as shown by a comparison of six continents. 3) The convergence and divergence zones of the water vapor flux divergence field in the middle and lower layers correspond to the high and low-value zones of cloud water content. The variation in the cloud water content and water vapor flux divergence presents a negative correlation, with a correlation coefficient of −0.44. The negative correlation is significant at low latitudes near the equator. Herein, the temporal and spatial patterns of the distribution and change in the cloud water content under the background of global warming are revealed, providing a reference for model parameterization and future climate prediction.