Abstract
Cloud water is an important geophysical quantity that connects the hydrological and radiation characteristics of climate systems and plays an essential role in the global circulation of the atmosphere, water, and energy. However, compared to the contribution of water vapor to precipitation, the understanding of cloud-precipitation transformation and its climate feedback mechanism remains limited. Based on precipitation and temperature datasets of the National Meteorological Observatory and MODIS (Moderate Resolution Imaging Spectroradiometer) satellite remote sensing products, the evolution characteristics of cloud water resources in China over the last twenty years of the 21st century were evaluated. Significant decreasing trends of −3.3 and −4.89 g/m2 decade−1 were found for both the liquid and ice water path. In humid areas with high precipitation, the cloud water path decreased fast. In semiarid areas with an annual precipitation ranging from 500–800 mm, the decreasing trend of the cloud water path was the lowest. The cloud-water period was calculated to represent the relative changes in clouds and precipitation. The national average cloud-water period in China is approximately 12.4 h, with obvious seasonal changes. Over the last 20 years, the cloud water path in dry regions decreased more slowly than that in wet regions, and the cloud-precipitation efficiency significantly increased, which narrowed the climate difference between the dry and wet regions. Finally, the mechanism of the cloud-water period evolution in the different regions were examined from the perspectives of the dynamic and thermal contributions, respectively. Due to the overall low upward moisture flux (UMF) in the dry region, the response of the cloud-water period to the lower tropospheric stability (LTS) mainly first increased and then decreased, which was the opposite in the wet region. The increase in cloud-precipitation efficiency in the dry region of Northwest China is accompanied by a continuous decrease in LTS. The different configurations of regional UMF and LTS play a crucial role in the evolution of cloud-precipitation, which can be used as a diagnostic basis to predict changes in the precipitation intensity to a certain extent.
Highlights
This study provides a reference to better understand the response of cloud precipitation under global warming and the rational development, utilization, and improvement of cloud water resources
We consider the ratio of the cloud water path to the precipitation rate (PR), which is the inverse of the precipitation efficiency, to represent the cloud-water period (CWP_lifetime)
Tribution of the cloud water path is not exactly the same as that of precipitation, with highthe distribution of the cloud water path is not exactly the same as that of precipitation, with value centers concentrated in the Yangtze River basin, and the difference between the high-value centers concentrated in the Yangtze River basin, and the difference between the north and south extremes is not as large as that between the precipitation extremes
Summary
The atmospheric water cycle includes processes such as evapotranspiration, water vapor transportation, uplift and condensation into clouds, and aggregation of cloud particles to form rain and ice/mixed-phase particles that fall to the ground, among which the cloudprecipitation process is the most active segment in the global water cycle [1,2]. The driving mechanism of the water cycle is climate change. Cloud-precipitation processes within the context of global warming bear the brunt of the observed unprecedented changes and are critical to the study of climate feedbacks [3,4,5]. Atmospheric cloud water resource refers to the hydrometeors in the clouds that can be used by human through artificial precipitation enhancement and other means.
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