Global Climatic Classification Based on Seasonal Distribution of Non-Precipitation Areas

Precipitation is an important climatic element to clarify the world climate, but the precise global distribution of precipitation in less than a month has not been analyzed. The authors take notice of the non-precipitation area (NPA) and intend to clarify the intra-seasonal fluctuation and seasonal difference of global precipitation distribution using 10-day data generated from daily drecipitation data during the First GARP Global Experiment (FGGE). We also intend to present a map of climatic classification based on the seasonal distribution of the non-precipitation areas, and to discuss the climatic boundaries between the east and west of each continent.<br> On the basis of the seasonal composite map of non-precipitation areas (NPAs), we define three NPAs, i.e. Min-NPA, Mean-NPA, and Max-NPA. In the Northern Hemisphere, during DJF season (from December to February), the Mean-NPA widely extends between the northern part of Africa and the Tibetan Plateau. While during JJA season (from June 11 to August 20), it is distributed in the northern part of Africa and in West Asia. In the Southern Hemisphere, during DJF season the Mean-NPAs are limited along the west coasts of each continent. Whereas, during JJA season they extend widely in each continent, and the Min-NPA appears in the northeastern part of South America. The intra-seasonal fluctuation of NPAs is large in the northern part of North America and Australia during DJF season.<br> Based on the distribution of NPAs during two seasons, we define four kinds of seasonal NPAs, i.e. winter and summer Min-NPA (mNPA), winter and summer Mean-NPA (wsNPA), winter Mean-NPA (wNPA), and summer Mean-NPA (sNPA). In the western part of each continent, the mNPA and wsNPA are widely extended and all NPA types are zonally distributed. In the western part of each continent, each seasonal NPA well corresponds to the climatic types of ALisov and KÖPPEN. In the eastern part of each continent, however, only wNPAs, if any, appear, which are not well consistent with ALIsoy's or KÖPPEN's climatic types. The climatic boundaries between the western and eastern parts of each continent are located at the western foot of the highest mountain ranges in each continent, on the basis of the distribution of non-precipitation areas.