The Spatial/Temporal Analyses Of The Climatic Resources For The Winter Crop Production Over Guangxi Based On The Empirical Orthogonal Function

Developing the production of winter crop is an important approach to exert the local advantages and techniques over the South China region. Guangxi locates at the tropical monsoon area over the south of China. The local heat condition is plentiful for developing agriculture. However, in the recent years, the climate change featured by global warming has changed the distribution of the winter climate resources over Guangxi. The increases in winter heat/water conditions have provided a certain advantage for developing the winter crop productions. However, the anomalies of the general circulation caused by climate change have affected the development of winter crop production. This study investigates the historical spatial/temporal distribution of climatic factor during the winter crop season under the climate change condition, based on the observed data from 89 meteorological observatories over Guangxi. The Empirical Orthogonal Function (EOF) and the Geographical Information System are used to explicitly diagnose different modes that indicate different spatial/temporal characteristic of climatic factor. The results include:(1) The first EOF mode reflects the mean climatological distribution, which shows a relatively warm area over the southwest and relatively cold area over the northeast. The analysis of the altitude, slope and aspect indicates that the distribution of the seasonal mean temperature in winter is not only related to the climate background but also associated with the topographic distribution;(2) The monthly mean temperature of the coldest month (MMTCM) and the extreme of the lowest daily temperature (LDT) reflect the heat resource distributions under the impacts of different types of chilling damage. The first EOF mode of the MMTCM indicates more heat resource at south slope than that at northern slope, implying an impacts from the advection type of chilling damage. The temperature at northern slope is relatively low, while the northern slope is comparatively warmer and contains more heat resource compared with the that at southern slope. Moreover, the first EOF mode of LDT shows the northern mountainous area has more heat resource compared with the southern area with a low altitude. This indicates an impact of the radiation type of frost. The high altitude area is warmer and contains more heat resource compared with the low altitude area;(3) The first EOF mode of winter precipitation shows a positive meridional gradient of winter precipitation distribution. The east of Guangxi has relatively plentiful water resources. However, the rain-snow freezing disaster over this area is relatively frequent and requires disaster preventions. Also, the western area is relatively dry and requires drought prevention and water retaining measures.(4) The second mode of EOF is consistent with the climatological linear trend and indicating the changes in variables under the climate change impacts. The second mode of EOF of temperature shows an obvious increased trend in temperature over the east, implying a warmer winter over this area. However, the western area including the valley of You revier over Baise shows a decreased trend in temperature. This may be explained by the weakening of descend and weaker Foehn wind over the east of the Yunnan-Guihou Plateau due to the weakening of westerlies under the climate change impacts.(5) The second EOF mode of precipitation indicates an increase in precipitation over the east. This may be due to the increased water vapor condition under warming.(6) The distributions of altitude, slope and aspect are closely associated with the changes in the distributions of winter climate and heat/water resources.