CAO Weihong, WANG Shuxin
Cities gathered in Beijing-Tianjin-Hebei region, and regional population is more than 100 million. The regional distribution differences of population are obvious and exit the situation of maldistribution. There has already formed Beijing, Tianjin, Shijiazhuang and Baoding as the population centers. Currently under the planning of coordinated development among Beijing, Tianjin and Hebei Province, city has to face population flowing into others and outflow in the industrial structure adjustment. Climate suitability of urban human settlement will affect population redistribution in Beijing-Tianjin-Hebei region. Evaluation of nature suitability for human settlement is on important premise to spatial distribution and optimization of population, including climate comfort is an important evaluation factors. Based on climate data in the past 63 years (1951-2013), this paper evaluates the climate suitability for urban human settlement of 13 main cities in Beijing-Tianjin-Hebei region, divides the grades of fitness and periodic distribution and analyze the characteristics of climatic environment using the method of THI (temperature humidity index) and K (wind effect index). The calculation results are analyzed comparably, which show that: 1) The average length of climate suitable duration was 7.62 months and unsuitable duration was 4.38 months. Beijing-Tianjin-Hebei region was considered as comfort living climate regions. 2) Most people feeled comfortable in April, may, September and October, and uncomfortable in January, July and August. This indicates that the spring and autumn were suitable periods, and the annual distribution of climate comfort appears "M" type. 3) There were common distinguishing climatic features in these 13 cities. Besides distinctive seasons, long summers and winters, short springs and autumns, wet and dry season clearly and etc., cold dry winter cities have hot summer with heavy falls of rain which is precipitation concentration period. However, the temperature, precipitation, wind speed and other meteorological elements had significant differences, as well as the annual distribution of climate comfortable period. 4) The spatial heterogeneity of climate types is strong, which is demonstrated as follows: the comfort degree showed a decreasing tendency from northeast to southwest. Cities in Hebei province were more comfortable than Tianjin as for Climate suitability, whereas Qinhuangdao, Tangshan, Langfang, Handan were more comfortable than Beijing. The sorting of annual climate comfort degree is as following: Qinhuangdao > Tangshan > Langfang, Handan, Beijing > Chengde > Zhangjiakou > Shijiazhuang, Xingtai, Baoding, Hengshui > Cangzhou, Tianjin. On the premise of coordinated development among Beijing, Tianjin and Hebei Province and positively interacting with one another, the climatic characteristics is helpful to distribute crowded population into cities in addition to Beijing and Tianjin, so as to solve "great urban disease", guiding the crowded population distribution reasonably. These results could provide scientific basis and decision reference for the research of functional partition of population development in Beijing-Tianjin-Hebei region.