摘要:近年来川中丘陵区季节性干旱频繁发生,对四川省农业生产造成严重影响。根据川中丘陵区8个气象站点1960年―2011年的逐日气象资料,选用国家标准中相对湿润度指数作为干旱指标,采用线性趋势法、morlet小波及反距离加权插值法,研究川中丘陵区季节性干旱频率和强度的时空分布特征。研究结果表明:川中丘陵区不同季节干旱频率和强度差异大,春冬两季的干旱频率和强度显著大于夏秋两季,干旱发生主要集中在春冬两季;时间上,春旱和秋旱呈加重趋势,夏旱和冬旱呈减轻趋势,其中春旱有3个周期演变规律,冬旱有2个周期演变规律;空间上,春夏两季川中丘陵区中部为干旱高发区,秋冬两季川中丘陵区北部为干旱高发区。该研究可为川中丘陵区制定防旱减灾措施提供理论依据。 关键词:川中丘陵区;相对湿润指数;干旱;时空分布;小波变换 中图分类号:S42 文献标志码:A 文章编号:16721683(2015)06104506 Abstract:In recent years,seasonal droughts occur frequently in the hilly area of central Sichuan,resulting in serious impacts on the agricultural production in Sichuan.According to the daily meteorological data of eight meteorological stations from 1960 to 2011 in this area,the relative humidity index in the national standards was selected as the drought index,and linear trend method,Morlet wavelet,and inverse distance weighting interpolation method were used to investigate the spatial and temporal distribution of seasonal drought frequency and intensity.The results indicated that (1) drought frequency and intensity have large differences in different seasons,and they are significantly higher in spring and winter than those in summer and autumn,and drought occurs mainly in spring and winter;(2) on the temporal distribution,drought in spring and autumn tends to be worse while drought in summer and winter alleviates.Drought in spring has three cycle evolutions while drought in winter has 2 cycle evolutions;and (3) on the spatial distribution,the central hilly area of central Sichuan has high incidence of drought in spring and summer,while the northern hilly area of central Sichuan has the high incidence of drought in autumn and winter.This study can provide a theoretical basis for the drought control and mitigation measures in the hilly area of central Sichuan. Key words:hilly area of central Sichuan;relative moisture index;drought;spatial and temporal distribution;wavelet transform 1 研究背景 干旱是影响我国农业生产的主要气象限制因子之一[1]。四川省是我国重要的农业种植区,但随着全球气候的变暖,年内降水时空分布不均,省内季节性干旱发生频率高、影响范围广、经济损失大[2]。例如2006年川渝地区百年特大伏旱 [3]、2009年秋至2010年春西南地区秋冬连旱等[4],因此季节性干旱已严重制约了四川省的农业发展。 目前,国内学者对干旱已经做了大量的研究,干旱的研究方法和评价指标已逐渐趋于完善。任培贵等[5]利用SPEI干旱指标分析了西北地区的气象干旱变化趋势,发现西北地区普遍存在干旱现象;张振伟等[6]采用帕默尔干旱指数(PDSI)研究甘肃省的干旱时空变化特征,发现甘肃全省旱情地域差别较大,呈现微弱缓解趋势;李红英等[7]计算CI干旱指数分析宁夏干旱致灾因子特征,研究发现近30年宁夏干旱频率和干旱强度均呈增加趋势;翟禄新等[8]采用SPI干旱指标分析了西北地区气候干湿变化,发现西北地区干旱发生的地域持续在改变,但干旱频次总体呈下降的趋势。 总体而言,干旱研究主要集中在中国北方干旱、半干旱地区[510],而西南的川中丘陵区是我国重要的农业种植区,全面系统地分析其季节性干旱时空分布特征的研究相对较少。由于干旱的影响因素多,形成原因复杂[11],本文采用综合考虑降水与蒸发气象因子的相对湿润度指数作为干旱评价指标[12],系统分析四川省川中丘陵区季节性干旱时空演变特征,对当地科学制定防旱减灾措施具有重要意义。 计算各站点不同季节的相对湿润度指数的多年平均值表示干旱强度,然后利用ArcGis进行空间插值,以此来研究川中丘陵区干旱强度的空间分布特征。 (1)春旱。图6(a)所示,川中丘陵区春季干旱强度空间分布与春季干旱频率空间分布不一致。北部的达县、巴中和阆中,中部的遂宁和内江,南部的宜宾春季相对湿润度指数在-0.4以下,表示干旱以轻旱为主。此外,高坪和泸州地区的相对湿润度指数在-0.4以上,干旱以轻度偏弱为主。 (2)夏旱。图6(b)所示,夏季干旱强度空间分布与夏季干旱频率空间分布基本一致,呈显著的集中性分布。中部的遂宁和高坪地区相对湿润度指数较小,北部的宜宾和泸州地区相对湿润度指数次之,都在-0.4以下,干旱以轻旱为主。其他地区的相对湿润度指数都在-0.4以上,干旱以轻度偏弱为主。 (3)秋旱。图6(c)所示,秋季干旱强度呈显著的北高南低分布,北部的内江地区相对湿润度指数最小在-0.4以上,干旱以轻度偏弱为主。除此之外,其他地区的秋季相对湿润度指数都在-0.4以下,表明干旱以轻旱为主。 (4)冬旱。图6(d)所示,冬季干旱强度空间分布与冬季干旱频率空间分布一致,也就是说干旱频率高的地方,干旱强度也高,且冬季相对湿润度指数为四季中最小,表明冬季干旱最为严重。其中,北部的达县地区相对湿润度指数在-0.65以下,表示干旱以重旱为主。阆中、宜宾、巴中、遂宁和内江地区的相对湿润度指数在-0.5以下,干旱以中旱为主。此外,泸州和高坪地区的相对湿润度指数在-0.4以下,干旱以轻旱为主。 4 结论 (1)在干旱频率方面,冬旱频率最高,高发区主要在川中丘陵区北部的达县附近;春旱频率次高,高发区主要在北部的阆中和中部的内江附近;秋旱频率较低,多发区与冬旱类似,但频率和范围都不及冬旱;夏旱频率最低,高发区主要集中在川中丘陵区中部的高坪和北部的达县附近。 (2)在干旱强度方面,冬旱强度最高且与干旱频率空间分布一致,周期性强,其中12 a为第一主周期;夏旱强度最小,与干旱频率空间分布基本一致;春秋两季干旱强度介于夏旱和冬旱强度之间,其中,春旱强度周期性强,8 a为第一主周期。 (3)秋旱发生频率和强度在四季中次之,但从年际变化来看,秋季相对湿润度指数呈显著的下降趋势,年际变化率为-0.11/(10a),对冬旱强度有增加的趋势。从冬旱发生频率和强度来看,达县为川中丘陵区干旱最为严重的地区,相关部门应加强意识,采取积极防旱措施。 本文仅从气候角度分析川中丘陵区季节性干旱时空分布特征,农业生产中干旱是否发生还与地形地势、土壤状况及作物种类等多种因子有关,需要综合研究。 参考文献(References): [1]王东,张勃,安美玲,等.基于SPEI的西南地区近53 a干旱时空特征分析[J].自然资源学报,2014,29(6):10031016.(WANG Dong,ZHANG Bo,AN 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摘要:近年来川中丘陵区季节性干旱频繁发生,对四川省农业生产造成严重影响。根据川中丘陵区8个气象站点1960年―2011年的逐日气象资料,选用国家标准中相对湿润度指数作为干旱指标,采用线性趋势法、morlet小波及反距离加权插值法,研究川中丘陵区季节性干旱频率和强度的时空分布特征。研究结果表明:川中丘陵区不同季节干旱频率和强度差异大,春冬两季的干旱频率和强度显著大于夏秋两季,干旱发生主要集中在春冬两季;时间上,春旱和秋旱呈加重趋势,夏旱和冬旱呈减轻趋势,其中春旱有3个周期演变规律,冬旱有2个周期演变规律;空间上,春夏两季川中丘陵区中部为干旱高发区,秋冬两季川中丘陵区北部为干旱高发区。该研究可为川中丘陵区制定防旱减灾措施提供理论依据。 关键词:川中丘陵区;相对湿润指数;干旱;时空分布;小波变换 中图分类号:S42 文献标志码:A 文章编号:16721683(2015)06104506 Abstract:In recent years,seasonal droughts occur frequently in the hilly area of central Sichuan,resulting in serious impacts on the agricultural production in Sichuan.According to the daily meteorological data of eight meteorological stations from 1960 to 2011 in this area,the relative humidity index in the national standards was selected as the drought index,and linear trend method,Morlet wavelet,and inverse distance weighting interpolation method were used to investigate the spatial and temporal distribution of seasonal drought frequency and intensity.The results indicated that (1) drought frequency and intensity have large differences in different seasons,and they are significantly higher in spring and winter than those in summer and autumn,and drought occurs mainly in spring and winter;(2) on the temporal distribution,drought in spring and autumn tends to be worse while drought in summer and winter alleviates.Drought in spring has three cycle evolutions while drought in winter has 2 cycle evolutions;and (3) on the spatial distribution,the central hilly area of central Sichuan has high incidence of drought in spring and summer,while the northern hilly area of central Sichuan has the high incidence of drought in autumn and winter.This study can provide a theoretical basis for the drought control and mitigation measures in the hilly area of central Sichuan. Key words:hilly area of central Sichuan;relative moisture index;drought;spatial and temporal distribution;wavelet transform 1 研究背景 干旱是影响我国农业生产的主要气象限制因子之一[1]。四川省是我国重要的农业种植区,但随着全球气候的变暖,年内降水时空分布不均,省内季节性干旱发生频率高、影响范围广、经济损失大[2]。例如2006年川渝地区百年特大伏旱 [3]、2009年秋至2010年春西南地区秋冬连旱等[4],因此季节性干旱已严重制约了四川省的农业发展。 目前,国内学者对干旱已经做了大量的研究,干旱的研究方法和评价指标已逐渐趋于完善。任培贵等[5]利用SPEI干旱指标分析了西北地区的气象干旱变化趋势,发现西北地区普遍存在干旱现象;张振伟等[6]采用帕默尔干旱指数(PDSI)研究甘肃省的干旱时空变化特征,发现甘肃全省旱情地域差别较大,呈现微弱缓解趋势;李红英等[7]计算CI干旱指数分析宁夏干旱致灾因子特征,研究发现近30年宁夏干旱频率和干旱强度均呈增加趋势;翟禄新等[8]采用SPI干旱指标分析了西北地区气候干湿变化,发现西北地区干旱发生的地域持续在改变,但干旱频次总体呈下降的趋势。 总体而言,干旱研究主要集中在中国北方干旱、半干旱地区[510],而西南的川中丘陵区是我国重要的农业种植区,全面系统地分析其季节性干旱时空分布特征的研究相对较少。由于干旱的影响因素多,形成原因复杂[11],本文采用综合考虑降水与蒸发气象因子的相对湿润度指数作为干旱评价指标[12],系统分析四川省川中丘陵区季节性干旱时空演变特征,对当地科学制定防旱减灾措施具有重要意义。 计算各站点不同季节的相对湿润度指数的多年平均值表示干旱强度,然后利用ArcGis进行空间插值,以此来研究川中丘陵区干旱强度的空间分布特征。 (1)春旱。图6(a)所示,川中丘陵区春季干旱强度空间分布与春季干旱频率空间分布不一致。北部的达县、巴中和阆中,中部的遂宁和内江,南部的宜宾春季相对湿润度指数在-0.4以下,表示干旱以轻旱为主。此外,高坪和泸州地区的相对湿润度指数在-0.4以上,干旱以轻度偏弱为主。 (2)夏旱。图6(b)所示,夏季干旱强度空间分布与夏季干旱频率空间分布基本一致,呈显著的集中性分布。中部的遂宁和高坪地区相对湿润度指数较小,北部的宜宾和泸州地区相对湿润度指数次之,都在-0.4以下,干旱以轻旱为主。其他地区的相对湿润度指数都在-0.4以上,干旱以轻度偏弱为主。 (3)秋旱。图6(c)所示,秋季干旱强度呈显著的北高南低分布,北部的内江地区相对湿润度指数最小在-0.4以上,干旱以轻度偏弱为主。除此之外,其他地区的秋季相对湿润度指数都在-0.4以下,表明干旱以轻旱为主。 (4)冬旱。图6(d)所示,冬季干旱强度空间分布与冬季干旱频率空间分布一致,也就是说干旱频率高的地方,干旱强度也高,且冬季相对湿润度指数为四季中最小,表明冬季干旱最为严重。其中,北部的达县地区相对湿润度指数在-0.65以下,表示干旱以重旱为主。阆中、宜宾、巴中、遂宁和内江地区的相对湿润度指数在-0.5以下,干旱以中旱为主。此外,泸州和高坪地区的相对湿润度指数在-0.4以下,干旱以轻旱为主。 4 结论 (1)在干旱频率方面,冬旱频率最高,高发区主要在川中丘陵区北部的达县附近;春旱频率次高,高发区主要在北部的阆中和中部的内江附近;秋旱频率较低,多发区与冬旱类似,但频率和范围都不及冬旱;夏旱频率最低,高发区主要集中在川中丘陵区中部的高坪和北部的达县附近。 (2)在干旱强度方面,冬旱强度最高且与干旱频率空间分布一致,周期性强,其中12 a为第一主周期;夏旱强度最小,与干旱频率空间分布基本一致;春秋两季干旱强度介于夏旱和冬旱强度之间,其中,春旱强度周期性强,8 a为第一主周期。 (3)秋旱发生频率和强度在四季中次之,但从年际变化来看,秋季相对湿润度指数呈显著的下降趋势,年际变化率为-0.11/(10a),对冬旱强度有增加的趋势。从冬旱发生频率和强度来看,达县为川中丘陵区干旱最为严重的地区,相关部门应加强意识,采取积极防旱措施。 本文仅从气候角度分析川中丘陵区季节性干旱时空分布特征,农业生产中干旱是否发生还与地形地势、土壤状况及作物种类等多种因子有关,需要综合研究。 参考文献(References): [1]王东,张勃,安美玲,等.基于SPEI的西南地区近53 a干旱时空特征分析[J].自然资源学报,2014,29(6):10031016.(WANG Dong,ZHANG Bo,AN 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