Analysis of monthly mean cloud amount for China: 1951--1994

摘要

The distribution of clouds over the globe greatly influences the regimes of other important climatic variables, such as temperature and precipitation. While satellite records of cloudiness are extremely valuable in the study of the earth's climate (spanning now 2--3 decades), the longer records of surface-observed cloudiness for much of the earth's surface are preferred for integration with long-term records of other surface variables in attempting to understand these variables' relationships and trends. As databases of surface-based cloud observations have become available for research use over recent decades, there have been many studies concerned with examining trends in regional cloud cover. Kaiser and Vose (1997) performed a gridded analysis of variations and trends in cloud amount using 187 Chinese weather stations for the period 1954--1990. The main findings were significant decreases in annual mean cloud amount over much of northern China, coupled with corresponding increases in the frequency of occurrence of clear skies. The decreased trends in annual mean cloud amount over northern China were found to be driven by decreasing cloud amount over most months of the year. The current study uses an expanded period of record of China cloud observations (1951--1994) to re-examine trends in cloud amount at individuals stations and over eight regions of China.