八宝河流域土壤温度波动的时空分异（英文）

The Babao River Basin is the "water tower" of the Heihe River Basin. The combination of vulnerable ecosystems and inhospitable natural environments substantially restricts the existence of humans and the sustainable development of society and environment in the Heihe River Basin. Soil temperature(ST) is a critical soil variable that could affect a series of physical, chemical and biological soil processes, which is the guarantee of water conservation and vegetation growth in this region. To measure the temporal variation and spatial pattern of ST fluctuation in the Babao River Basin, fluctuation of ST at various depths were analyzed with ST data at depths of 4, 10 and 20 cm using classical statistical methods and permutation entropy. The study results show the following: 1) There are variations of ST at different depths, although ST followed an obvious seasonal law. ST at shallower depths is higher than at deeper depths in summer, and vice versa in winter. The difference of ST between different depths is close to zero when ST is near 5℃ in March or –5℃ in September. 2) In spring, ST at the shallower depths becomes higher than at deeper depths as soon as ST is above –5℃; this is reversed in autumn when ST is below 5℃. ST at a soil depth of 4 cm is the first to change, followed by ST at 10 and 20 cm, and the time that ST reaches the same level is delayed for 10–15 days. In chilling and warming seasons, September and February are, respectively, the months when ST at various depths are similar. 3) The average PE values of ST for 17 sites at 4 cm are 0.765 in spring 0.764 in summer 0.735 in autumn 0.723 in winter, which implies the complicated degree of fluctuations of ST. 4) For the variation of ST at different depths, it appears that Max, Ranges, Average and the Standard Deviation of ST decrease by depth increments in soil. Surface soil is more complicated because ST fluctuation at shallower depths is more pronounced and random. The average PE value of ST for 17sites are 0.863 at a depth of 4 cm 0.818 at 10 cm 0.744 at 20 cm. 5) For the variation of ST at different elevations, it appears that Max, Ranges, Average, Standard Deviation and ST fluctuation decrease with increasing elevation at the same soil depth. And with the increase of elevation, the decrease rates of Max, Range, Average, Standard Deviation at 4 cm are –0.89℃/100 m, –0.94℃/100 m, –0.43℃/100 m, and –0.25℃/100 m, respectively. In addition, this correlation decreased with the increase of soil depth. 6) Significant correlation between PE values of ST at depths of 4, 10 and 20 cm can easily be found. This finding implies that temperature can easily be transmitted within soil at depths between 4 and 20 cm. 7) For the variation of ST on shady slope and sunny slope sides, it appears that the PE values of ST at 4, 10 and 20 cm for 8 sites located on shady slope side are 0.868, 0.824 and 0.776, respectively, whereas they are 0.858, 0.810 and 0.716 for 9 sites located on sunny slope side.     

北京市不同功能区不透水地表时空变化差异分析（英文）

Impervious surface(IS) is often recognized as the indicator of urban environmental changes. Numerous research efforts have been devoted to studying its spatio-temporal dynamics and ecological effects, especially for the IS in Beijing metropolitan region. However, most previous studies primarily considered the Beijing metropolitan region as a whole without considering the differences and heterogeneity among the function zones. In this study, the subpixel impervious surface results in Beijing within a time series(1991, 2001, 2005, 2011 and 2015) were extracted by means of the classification and regression tree(CART) model combined with change detection models. Then based on the method of standard deviation ellipse, Lorenz curve, contribution index(CI) and landscape metrics, the spatio-temporal dynamics and variations of IS(1991, 2001, 2011 and 2015) in different function zones and districts were analyzed. It is found that the total area of impervious surface in Beijing increased dramatically during the study period, increasing about 144.18%. The deflection angle of major axis of standard deviation ellipse decreased from 47.15° to 38.82°, indicating the major development axis in Beijing gradually moved from northeast-southwest to north-south. Moreover, the heterogeneity of impervious surface's distribution among 16 districts weakened gradually, but the CI values and landscape metrics in four function zones differed greatly. The urban function extended zone(UFEZ), the main source of the growth of IS in Beijing, had the highest CI values. Its lowest CI value was 1.79 that is still much higher than the highest CI value in other function zones. The core function zone(CFZ), the traditional aggregation zone of impervious surface, had the highest contagion index(CONTAG) values, but it contributed less than UFEZ due to its small area. The CI value of the new urban developed zone(NUDZ) increased rapidly, and it increased from negative to positive and multiplied, becoming animportant contributor to the rise of urban impervious surface. However, the ecological conservation zone(ECZ) had a constant negative contribution all the time, and its CI value decreased gradually. Moreover, the landscape metrics and centroids of impervious surface in different density classes differed greatly. The high-density impervious surface had a more compact configuration and a greater impact on the eco-environment.     

基于30m归一化植被指数的近30年三江源高寒草地植被时空变化及气候影响研究（英文）

植被长期变化及其对气候变化的响应一直是生态学研究的热点。本研究应用前期基于Landsat数据融合得到的青藏高原三江源区1990–2018年近30年30 m空间分辨率归一化植被指数(NDVI),以Theil-Sen中值法和线性回归,分析了近30年高寒草地时空变化及气候变化影响。结果表明：(1)研究区NDVI呈从东南到西北逐渐降低的空间格局,全区平均NDVI为0.39,其中澜沧江源NDVI最高(0.43),其次是黄河源(0.38)和长江源(0.23)。(2)研究期间,全区NDVI以0.0031yr^–1的速率呈上升趋势(R²=0.62,P<0.01),后期(2005–2018年)增长速度为0.00649 yr^–1(R²=0.71,P<0.01),是前期(1990–2005年间)速率0.00284 yr^–1(R²=0.31,P<0.01)的近2.3倍,说明后期(2005–2018年)植被变绿加速,且不同流域间增速在2.3至63倍间。(3)NDVI...     

利用TM影像分析天山北坡三工河流域地表反照率的时空变化

下垫面状况是影响地表反照率分布的主要因素之一。利用遥感方法获取地表反照率时空特征是研究地表下垫面状况的有效手段。天山北坡具有典型的山地－绿洲－荒漠景观和山盆地貌格局,这一独特且复杂多样的地表下垫面特征形成了特有的垂直分布的地表反照率。通过对三工河流域TM影像进行地形校正,基于6S(Second Simulation of Satellite Signal in the Solar Spectrum)模型分析地表反照率的时空分布。结果表明:基于中空间分辨率遥感数据的地表反照率反演适合于地表起伏明显的天山北坡地表反照率的分析。由于受到地表覆被类型及地表干湿程度的影响,三工河流域地表反照率呈明显的垂直地带性分布。中山森林带和低山干草原带受地形起伏和阴阳坡作用,其地表反照率表现出有规律的上下波动。绿洲区随着地表覆被类型、作物结构和作物物候的变化,地表反照率波动较大。     

内蒙古草原草本植物萌芽期时空变化（英文）

Phenological modeling is not only important for the projection of future changes of certain phenophases but also crucial for systematically studying the spatiotemporal patterns of plant phenology. Based on ground phenological observations, we used two existing temperature-based models and 12 modified models with consideration of precipitation or soil moisture to simulate the bud-burst date(BBD) of four common herbaceous plants—Xanthium sibiricum, Plantago asiatica, Iris lactea and Taraxacum mongolicum—in temperate grasslands in Inner Mongolia. The results showed that(1) increase in temperature promoted the BBD of all species. However, effects of precipitation and soil moisture on BBD varied among species.(2) The modified models predicted the BBD of herbaceous plants with R~2 ranging from 0.17 to 0.41 and RMSE ranging from 9.03 to 11.97 days, better than classical thermal models.(3) The spatiotemporal pattern of BBD during 1980–2015 showed that species with later BBD, e.g. X. sibiricum(mean: day of year 135.30) exhibited an evidently larger spatial difference in BBD(standard deviation: 13.88 days) than the other species. Our findings suggest that influences of temperature and water conditions need to be considered simultaneously in predicting the phenological response of herbaceous plants to climate change.     

中国天山玛纳斯河流域积雪垂直分布及其与温度的关系（英文）

How snow cover changes in response to climate change at different elevations within a mountainous basin is a less investigated question. In this study we focused on the vertical distribution of snow cover and its relation to elevation and temperature within different elevation zones of distinct climatology, taking the mountainous Manasi River Basin of Xinjiang, Northwest China as a case study. Data sources include MODIS 8-day snow product, MODIS land surface temperature(LST) data from 2001 to 2014, and in situ temperature data observed at three hydrological stations from 2001 to 2012. The results show that:(1) the vertical distribution of snow areal extent(SAE) is sensitive to elevation in low(2100 m) and high altitude(3200 m) regions and shows four different seasonal patterns, each pattern is well correspondent to the variation of temperature.(2) The correlation between vertical changes of the SAE and temperature is significant in all seasons except for winter.(3) The correlation between annual changes of the SAE and temperature decreases with increasing elevation, the negative correlation is significant in area below 4000 m.(4) The snow cover days(SCDs) and its long-term change show visible differences in different altitude range.(5) The long-term increasing trend of SCDs and decreasing trend of winter temperature have a strong vertical relation with elevation below 3600 m. The decreasing trend of SCDs is attributed to the increasing trend of summer temperature in the area above 3600 m.     

过去百年尼泊尔耕地时空变化（英文）

In order to advance land use and land cover change(LUCC) research in Nepal, it is essential to reconstruct both the spatiotemporal distribution of agricultural land cover as well as scenarios that can explain these changes at the national and regional levels. Because of rapid population growth, the status of agricultural land in Nepal has changed markedly over the last 100 years. Historical data is used in this study, encompassing soils, populations, climatic variables, and topography. Data were revised to a series of 30 m grid cells utilized for agricultural land suitability and allocation models and were analyzed using a suite of advanced geographical tools. Our reconstructions for the spatiotemporal distribution of agricultural land in Nepal reveal an increasing trend between 1910 and 2010(from 151.2 × 10~2 km~2 to 438.8 × 10~2 km~2). This expanded rate of increase in agricultural land has varied between different eco, physiographic, and altitudinal regions of the country, significantly driven by population changes and policies over the period of this investigation. The historical dataset presented in this paper fills an existing gap in studies of agricultural land change and can be applied to other carbon cycle and climate modeling studies, as well as to impact assessments of agricultural land change in Nepal.     

三工河流域土地利用/覆被变化的现代绿洲演变过程（英文）

This study investigated oasis evolution and the changes of peripheral desert in the Sangong River Basin since the 1950 s by rebuilding seven land cover maps derived from black-and-white aerial photographs(1958, 1968, and 1978), a color-infrared aerial photograph(1987), Landsat Thematic Mapper(TM) imagery(1998), Satellite Pour l'Observation de la Terre(SPOT) imagery(2004), and Landsat Operational Land Imager(OLI) imagery(2014). The results showed that:(1) Since 1950, the oasis consecutively expanded more than four times from an alluvial fan to an alluvial plain, causing the shrinkage of desert landscapes that were dominated by a Haloxylon ammodendron Bunge community(HBC) and a Tamarix chinensis Lour community(TLC). Furthermore, the primary(1958–1968) and final(2004– 2014) stages were the most important periods, during which agricultural land experienced the most rapid expansion during the period 1958–1968, and the built-up area showed the most rapid expansion after the 2000 s.(2) Two basic management modes, a "local mode" formed by the local governments and a "farm management mode" developed by Xinjiang Production and Construction Corps, together promoted oasis evolution under various land-use and landcover(LULC) stages.(3) The evolution of the modern oasis during the 1950s–2004 showed the general features of an arid oasis, while during the period of 2004–2014 it was characterized by a large-scale inter-basin water diversion or the import of new water sources.(4) The oasis expanded at the expense of desert vegetation, resulting in distinct variation in the structure of the desert plant community, which will make it more difficult to protect the desert ecosystem.     

80年来埃塞俄比亚北部高原土地利用/覆被变化（英文）

Despite many studies on land degradation in the Highlands of Northern Ethiopia, quantitative information regarding long-term changes in land use/cover(LUC) is rare. Hence, this study aims to investigate the LUC changes in the Geba catchment(5142 km2), Northern Ethiopia, over 80 years(1935–2014). Aerial photographs(APs) of the 1930 s and Google Earth(GE) images(2014) were used. The point-count technique was utilized by overlaying a grid on APs and GE images. The occurrence of cropland, forest, grassland, shrubland, bare land, built-up areas and water body was counted to compute their fractions. A multivariate adaptive regression spline was applied to identify the explanatory factors of LUC and to create fractional maps of LUC. The results indicate significant changes of most types, except for forest and cropland. In the 1930 s, shrubland(48%) was dominant, followed by cropland(39%). The fraction of cropland in 2014(42%) remained approximately the same as in the 1930 s, while shrubland significantly dropped to 37%. Forests shrank further from a meagre 6.3% in the 1930 s to 2.3% in 2014. High overall accuracies(93% and 83%) and strong Kappa coefficients(89% and 72%) for point counts and fractional maps respectively indicate the validity of the techniques used for LUC mapping.     

1992–2015全球耕地时空变化（英文）

人口和人均食物需求的增加对全球耕地产生了显著的影响。利用欧空局提供的精度为300m的最新土地覆被产品,文章分析了1992-2015年全球耕地的时空变化趋势和耕地转化特征。结果显示:1)在1992-2004年间全球耕地面积增长迅速,而在2004-2012年间耕地增长缓慢,2012年后耕地有缓慢减少的趋势。2)在洲尺度上,非洲耕地有一直增长的态势,而其他洲耕地都经历了耕地转型,有先增长后下降的趋势;在收入较高的国家,耕地多有下降的趋势。3)全球耕地增长的热点区域主要分布在亚马逊林地、欧亚大草原和撒哈拉沙漠边缘。全球耕地减少的中心从欧洲转移到亚洲。由于迅速的城市化,亚洲耕地扩张侵占了大量农田。     

中国典型自然保护区生境状况时空变化（英文）

Until 2015,China had established 2740 nature reserves with a total area of 1.47million km~2,covering 14.8%of China’s terrestrial land surface.Based on remote sensing inversion,ecological model simulation and spatial analysis methods,we analyzed the spatial and temporal variations of fractional vegetation coverage(FVC),net primary production(NPP),and human disturbance(HD)in habitats of typical national nature reserves(NNRs)during the first 15 years of the 21st century from 2000 to 2015.And then the three indicators were compared between different NNR types and varied climate zones.The results showed that(1)the average 5-year FVC of NNRs increased from 36.3%to 37.1%,and it improved in all types of NNRs to some extent.The annual average FVC increased by 0.11%,0.84%,0.21%,0.09%,0.11%and 0.08%in NNRs of forest ecosystem,plain meadow,inland wetland,desert ecosystem,wild animal and wild plant,respectively.(2)The NPP annually increased by 2.06 g·m~(-2),1.23 g·m~(-2),0.28 g·m~(-2) and 0.4 g·m~(-2) in NNRs of plain meadow,inland wetland,desert ecosystem and wild animal,respectively.However,it decreased by 3.45 g·m~(-2) and2.35 g·m~(-2) in NNRs of forest ecosystem and wild plant respectively.(3)In the past 15 years,besides the slight decreases in the NNRs located at the Qinghai-Tibet Plateau and the south subtropical zone,HD enhanced in most of NNRs,especially HD in the warm temperate humid zone increased from 4.7% to 5.35%.     

伊犁河流域水汽含量时空变化及其和降水量的关系

利用1976-2006年伊宁探空站的实测资料计算了逐月水汽含量,结合地面水汽压建立适合于伊犁河流域的W-e模型,结合DEM重建了1961-2009年伊犁河流域的月均水汽含量,利用EOF和交叉谱方法分析水汽含量和降水量的时空分布特征,并分析夏季干湿年、典型强降水过程中水汽输送特征。结果表明：大气水汽含量在空间分布上表现为西部多于东部、平原多于山地、迎风坡大于背风坡,下游平原及上游河谷地带是高值区,水汽含量在13～15 mm,这与地形和绿洲城镇的分布有关;在850 hPa至700 hPa的高度上存在一个最大水汽含量带,对应海拔约2 000 m。水汽含量年代际变化呈上升趋势,夏季增加明显（0.48 mm/10a）。降水量和水汽含量标准化场EOF分解表明两者的时空分布极为相似,存在气候振动的一致性和河谷南北相反的分布型式。雨季水汽含量源地以热带海洋为主,同时也受北冰洋为源地的西北向水汽输送的影响。     

埃塞俄比亚极端气候时空特征及其对作物产量的潜在影响（英文）

在全球范围内极端气候事件呈现出增加的时空态势,对人类社会和自然生态系统产生严重影响。本研究以埃塞俄比亚为例,分析了1956年至2016年的极端温度和降水,并评估了极端气候对埃塞俄比亚作物产量的潜在影响。研究结果表明极端温度指数在低温事件中呈现下降趋势,但在极端高温事件中呈现出显着上升趋势,且每年暖夜日数(warm nights)的频率比冷昼日数(cold days)增加的程度更大。年总降水量以46 mm/decade的速度显着下降,干旱天数以5.6 d/decade的速度持续增加,降水天数则以1.4 d/decade的速度下降。此外,年降水量与作物产量显著相关,并且极端降水比极端温度对作物产量的年度变化影响更大。结果表明在没有适当气候应对措施的埃塞俄比亚地区,极端的气候变化已经对农作物产量产生了显着的不利影响。     

1982-2014年青藏高原地表蒸散量时空分布及其变化影响因子分析（英文）

蒸散是地球水循环的关键驱动因子,是地表水平衡和能量平衡的重要分量,因而也体现生态系统水文调节局地热调节功能;青藏高原是长江和黄河等重要河流的发源地,该区域水量平衡对区域生态安全具有重要意义。本文对全球尺度发展的遥感蒸散双源模型ARTS,利用涡度相关观测数据进行验证和评价,以空间插值的气象数据,卫星遥感的FPAR和LAI等驱动模型,估测1982-2014年间青藏高原实际蒸散ET,分析其年际和季节动态变化特征,并采用敏感性分析法和多元线性回归分析计算各气象因子变化对蒸散量变化的贡献率,探讨影响青藏高原蒸散量变化的主导因素。结果表明:(1)估测值能解释观测值季节变化的80%以上(复相关系数R~2=0.80,显著性水平P 0.001),表明模型具有较高的估算准确度。(2)近30多年全年、春、夏和秋季影响蒸散年际变化呈显著增加趋势;但变化趋势存在显著的区域分异,全年或夏季藏南河谷地区呈显著降低趋势(每10年降低20 mm以上),而阿里、拉萨河谷、青海海北地区则为增加趋势(每10年增加10 mm以上)。(3)敏感性分析和多元线性回归分析均表明,年际变化趋势的主导因素是气候变暖,其次是降水的不显著增加;但植被变化的影响也较大,与气候因子共同能够解释蒸散趋势的56%(多元线性回归方程R~2=0.56,P0.001);低覆盖草地多年蒸散分别是高、中覆盖度草地的26.9%和21.1%。青藏高原在显著变暖、不显著变湿的气候变化背景下,地表蒸散的增加必以冰川融水为代价而威胁区域生态环境安全,如何保护生态,维持区域社会可持续发展是难题和巨大挑战。     

中国生态效率时空差异和影响因素分析（英文）

经济发展、资源利用和生态保护之间存在着尖锐矛盾,而生态效率概念和评价体系构建为这一问题提供了解决方案。本研究基于超Slacks-BasedMeasure模型,评价了2005–2016年中国大陆30个省份生态效率的时空特征、区域差异性,并利用面板回归模型分析了其影响因素。研究发现:(1)2005–2016年各省份生态效率在研究时段总体呈现上升态势,伴有波峰变化,但各地区生态效率水平及其变化幅度的差异较为显著。东部地区生态效率明显高于中部地区、西部地区和东北部地区。(2)通过变异系数测算表明各省份生态效率差异在逐渐缩小,但空间分布仍不均衡。从区域内差异看,西部省份区域内差异均值最高,其次为东部地区和东北部地区,中部地区区域差异最小。(3)通过生态效率影响因素研究显示,工业结构、对外开放度、城镇化、技术创新和环境规制对生态效率产生积极影响,能源消费、交通对其产生消极影响,而在不同区域生态效率的影响因素呈现不同作用力。据此,提出各地区提升生态效率的相关政策建议,为缩小绿色发展差距及加快促进区域绿色可持续协调发展提供重要的实证参考。     

哈萨克斯坦1982–2015年植被时空变化（英文）

归一化植被指数(NDVI)作为表征植被生长状况的关键性指标,能够有效的提供植被生长状况的信息。本研究基于1982–2015年哈萨克斯坦时间序列的GIMMS/NDVI数据,分析植被)生长的空间格局及变化趋势,研究结果表明:哈萨克斯坦自北向南分布着农田、草地、灌丛这三类主要的植被类型,呈明晰的地带性分布特征;植被指数由北到南逐渐降低,农田、草地和灌丛三类主要植被类型的NDVI均值水平依次为农田草地灌丛;1982–2015年间,NDVI呈现出先增长(1982–1992年)、再降低(1993–2007年)、然后又增长(2008–2015年)的变化趋势。NDVI显著下降的区域占土地总面积的24.0%,主要分布在西北部的农田与草地交错地带以及南部边缘的农田,草地退化面积占草地总面积的23.5%、农田退化面积占农田总面积的48.4%、灌丛退化面积占灌丛总面积的13.7%,植被改善的区域分布在中东部的农田以及农田与草地的交错带,显著提升的面积占土地总面积的11.8%。     

京津冀干旱时空演变规律分析（英文）

Spatio-temporal patterns of drought from 1961 to 2013 over the Beijing-Tianjin-Hebei(BTH) region of China were analyzed using the Palmer Drought Severity index(PDSI) based on 21 meteorological stations. Overall, changes in the mean-state of drought detected in recent decades were due to decreases in precipitation and potential evapotranspiration. The Empirical Orthogonal Functions(EOF) method was used to decompose drought into spatio-temporal patterns, and the first two EOF modes were analyzed. According to the first leading EOF mode(48.5%), the temporal variability(Principal Components, PC1) was highly positively correlated with annual series of PDSI(r=+0.99). The variance decomposition method was further applied to explain the inter-decadal temporal and spatial variations of drought relative to the total variation. We find that 90% of total variance was explained by time variance, and both total and time variance dramatically decreased from 1982 to 2013. The total variance was consistent with extreme climate events at the inter-decadal scale(r=0.71, p0.01). Comparing the influence of climate change on the annual drought in two different long-term periods characterized by dramatic global warming(P1: 1961–1989 and P2: 1990–2013), we find that temperature sensitivity in the P2 was three times more than that in the P1.     

基于温度的天气衍生品指数定价:以埃塞俄比亚巴赫达尔为例（英文）

本文提出了一个基于温度的导数来计算温度指数的日平均温度随机模型,该模型提出了一个季节性均值及其波动率的计算方法,使用均值回归的Ornstein-Uhlenbeck过程来刻画日平均温度的变化。本文还采用连续的三阶自回归过程来模拟去除趋势和季节性影响后的温度演变过程,模型的模拟结果与从埃塞俄比亚国家气象厅获得的2005年1月1日至2015年12月31日11年间埃塞俄比亚Bahir Dar记录的数据非常吻合。验证后的近似公式很容易根据热日和冷日(heating degree days (HDD) and cooling degree days (CDD))等典型温度指数推导期货价格,也给出了数值例子来说明该方法的准确性。结果表明,本文提出的模型比其他模型能更好地预测CDD指数。     

气候与地表覆被变化对梭磨河流域水文影响的分析

分析了1960～1990年长江上游梭磨河流域气候和地表覆被变化及其对流域水文的影响。30年来，流域降水有所增加，有林地面积1957～1974年大幅下降，以后有所回升。有林地每公顷蓄积量由1957年的423m^3下降到1998年的177m^3，40年来林地质量不断下降，流域水文发生了明显的变化；年均流量自1972年以来不断上升，洪水频率、洪峰流量和土壤侵蚀模糊明显增加。     

哈尔滨市中心城区不透水面时空变化及驱动力分析（英文）

Associated with the rapid economic development of China, the level of urbanization is becoming a serious concern. Harbin, the capital city of Heilongjiang Province, China and one of the political, economic, cultural, and transportation centers of the northeastern region of China, has experienced rapid urbanization recently. To examine the spatial patterns of long-term urbanization and explore its driving forces, we employed the impervious surface fraction derived from remote sensing image as a primary indicator. Specifically, urban impervious surface information for the central city of Harbin in 1984, 1993, 2002, and 2010 was extracted from Landsat Thematic Mapper image using a Linear Spectral Mixture Analysis(LMSA). Then, the spatial and temporal variation characteristics and the driving factors of percent impervious surface area(ISA) changes were analyzed throughout this 26-year period(1984 to 2010). Analysis of results suggests that:(1) ISAs in the central city of Harbin constantly increased, particularly from 1993 to 2010, a rapid urbanization period;(2) the gravity center of impervious surface area in the central city was located in Nangang District in 1984, moving southeast from 1984 to 1993, northwest from 1993 to 2002, and continuing toward the southeast from 2002 to 2010; and(3) the urban growth of the central city can be characterized as edge-type growth.