Quantitative Estimates Of Urbanization Effects On Climate Change In Central Yunnan Plateau

Anthropogenic effects and climate fluctuations are important factors affect regional climate. Under the background of the global warming, the effects of rapid urbanizations on regional climate have been attracting more attention in recent years. The Central Yunnan Plateau (CYP) is a place with great economic development and potential that lies in the Yunnan Plateau. So, the CYP plays a key role on potential responses and feedbacks to climate change. It is necessary to analyze the temporal-spatial variation of climate and investigate the urbanization impacts on the regional climate.This research presents the analyses of regional climate change features and the urbanization impacts on temperature and precipitation trends over the CYP during1961to2010. Finally, I conducted path analysis between the computed urban temperature variations and the main factors to create the comprehensive model of the urban temperatures. The main conclusions can be drawn as follows:1. Over the CYP, the mean annual air temperatures have been increasing by0.17℃/decade during the period1961-2010, and the total annual precipitation fluctuated and showed a slight downward trend(-12.6mm/10a). From1961to2010, there was a significant linear ascending tendency both in the annual mean air temperature and the seasonal mean air temperature in most parts of the CYP except in Yuanmou dry-hot valley, and the precipitation significantly decreased in the southeast of the CYP. The mean annual temperature and precipitation fluctuated significantly with the interval of24years, and they tend to be change after an abrupt occurred in1974,1993and1997, respectively. The warming rates during winter (0.31℃/decade) were greater than in other seasons. After2000, there was a decreasing trend of precipitation appeared both in dry and rainy seasons.2. It has been proved that the standardized precipitation evapotranspiration index (SPEI) was feasible and applicable in this area. The SPEI at annual timescale showed a slowly descending tendency during the period1961-2010. The CYP tends to be dryer after an abrupt change in annual mean SPEI occur in1977, especially in southeast area, whereas the hot-dry valley along the Jinsha River showed a wetting and cooling trend during the past five decades. The SPEI at6-month timescale showed a dryer and warmer climate in the dry-season in the whole since1990.3. The trend slope of mean annual air temperature was0.27℃/decade in city stations, and the effect of urbanization has enhanced the increasing trend of mean annual air temperature by an average of47.3%or0.13℃/decade over the period from1961to2010. Warming trend of0.20℃/decade was observed for winter temperature and contributes to41.9%of total warming in city stations. However, the warming contribution caused by urbanization was the greatest in spring, which contributes to58.9%of total warming (0.14℃/decade). Due to urbanization, a considerable increase in precipitation was noticeable at the annual scale, which accounted for about18.5%of the total precipitation variation. It is found that the regional average annual mean air temperature series was impacted by urban warming, and the trend of urban warming was estimated to be0.033℃/decade, which accounted for about20.4%of the regional warming. Urbanization contributions to the long-term trends are less than15%of the regional precipitation variation during the period.4. The urban-induced warming trend in Kunming increased with the biggest ratio (0.32℃/decade), followed by warming trends in Chuxiong (0.20℃/decade) and Yuxi (0.10℃/decade). Since the1990s, the effect of urbanization on mean annual air temperature occurred at these three urban stations. The urban-induced warming trend in the winter and spring was more significant than in the summer and autumn, and the warming contribution caused by urbanization in the spring was greater than in other seasons. The effect of urbanization has some influence on precipitation, but the increasing trend in the precipitation was not obvious in Kunming and Yuxi.5. The influence of human activity on urban heat island intensity was more significant than the effect of climate fluctuations in Kunming and Yuxi, and urban population was the main artificial factor for the increase of urban temperature. The non-agriculture population contributes to29.0%and30.9%of urban heat island intensity in Kunming and Yuxi, respectively. In the meantime, the increase of electric power consumption and gross domestic product, as well as the size of the built-up area also play an important role in the formation of the urban heat island effect of Kunming. The mitigation of urban heat island intensity was possible with the adjustment of non-agriculture population and total industrial output value for Yuxi. Other indicators are subject to non-agriculture population and total industrial output value, indirectly affecting the enhancement of urban heat island effect.