摘要
气象灾害中影响最深远、最严重、最具有破坏力的灾害是旱灾,在全球气候变化背景下,干旱出现的频率更加频繁。而要研究和了解不同区域干旱的发生规律,干旱指标是干旱监测、预警、评估中的关键参数。因此,本研究旨在寻找江苏省干旱监测、预警的可靠指标,指导全省防旱抗旱,减轻旱灾损失,为保障江苏工农业生产和社会和谐发展提供科学依据。
本研究根据江苏省54个气象站资料,利用FAO推荐的Penman-Monteith公式计算了该地区1960-2009年逐日潜在蒸散量,采用国家标准(BG/T20481-2006)《气象干旱等级》推荐的相对湿润度指数(MI)对全省进行干湿状况评价,分析相对湿润度指数的时空分布和变化规律。结果表明：(1)空间分布：江苏省干燥区与湿润区各占一半。(2)年际变化：PE的年际波动与温度的变化相一致。(3)季节变化：春季相对湿润度值由北向南依次增大；夏季全省属于湿润区；秋季除苏南部分站点外均属于半干旱区；冬季相对湿润度值呈显著的纬向分布。(4)受降水和蒸散的共同影响,全省平均MI全年内波动变化特征显著。
根据江苏省54个气象台站1960～2009年实测气象资料,利用综合气象干旱指数(CI)对江苏省近50a的干旱特征进行了时空分析。通过计算各站历年逐日的CI指数值,统计近50a各站点出现的干旱过程,分析江苏省各地区干旱发生的频率、范围和强度,揭示了江苏省干旱发生的时空分布规律。研究结果表明：(1)江苏省全年和各季干旱发生频率都是北高南低,四季中,冬旱发生频率最高,夏旱发生频率最低,秋旱南北差异不显著。(2)冬季江苏省干旱大范围发生的年份最多,夏季最少；近50a来,全年和四季干旱覆盖范围的线性变化趋势不明显。(3)这50a中,江苏省逐年干旱持续日数和干旱强度虽然存在着明显的年际波动,但线性变化趋势不明显。(4)在年代际尺度上,江苏省全年和四季干旱均存在极显著的10～12a周期；而在年际变化尺度上2～4a周期最为显著。(5)江苏省各等级干旱日数总体上呈现冬季多夏季少、北部多南部少的规律。
选取2006年10～11月覆盖全省的一次严重秋旱事件作为典型个例,收集54个气象台站的逐日气象观测资料,计算逐日综合气象干旱指数CI值,以此为基础统计干旱发生的开始日期、结束日期、持续日数和逐日旱强；选取不同地区的典型站点,研究全省和各地区的旱情生消和演变特征；选用MODIS产品数据,利用植被供水指数法,反演干旱发展过程;利用实测土壤相对湿度数据,在ArcGIS9.3中采用反距离权重插值法,分析干旱事件中土壤湿度的空间变化特征。研究结果表明：(1)在这一典型秋旱事件中,由CI指数、VWSI指数和土壤湿度反映的大气、植被、土壤干旱的生消和演变过程基本一致。(2)干旱的发生是由西北到东南逐渐扩展蔓延,结束则由东南向西北逐渐收缩消失,持续天数从北向南递减。(3)旱情总体上北重南轻,但不同地区因大气背景和自然地理条件不同发展过程差异较大。(4)利用CI指数、VSWI指数和土壤湿度可以较全面而系统地监测干旱过程的生消、演变和强度变化。
Drought, as one of the most severe and destructible meteorological disasters, has a most far-reaching side-effect on economic and social development. In recent decades the occurrence of droughts was more and more frequent under the background of the global climate warming. In order to ascertain the occurrence patterns of droughts in different regions,the drought index as a key paramenter of drought monitoring、forewarning and assessment play an important role in the prevention from drought and the mitgation of disaster loss. Therefore, this study was designed to seek some reliable indices for drought monitoring and forewarning in Jiangsu Province. The purpose was guiding the prevention from droughts, reducing the loss of droughts so as to ensure the safety of the industrial and agricultural production and provide scientific basis for the harmonious development of the society in Jiangsu Province.
Based on the climate data of 54 meteorological stations in Jiangsu Province, the daily potential evapotranspiration (ET0) during 1960 to 2009 in the area was calculated by the Penman-Monteith formulation. According to the Chinese Meteorological Drought Grades in the National Standard BG/T20481-2006 in China, MI, a relative index of climate dryness and wetness, was used to evaluate the arid and moist conditions of the climates in different regions of Jiangsu Province. The analysis on the spatial-temporal distribution and variation pattern of MI in the province were displayed as follows:(1) In space, the relative dry and the relative wet climate area half of each in Jiangsu province. (2)Interannual variability:Annual fluctuations of PE was consistent with the change of the temperature.(3) Seasonal change:The MI was in turn increase from north to south in spring, the whole province belonged to wet period in summer, Autumn was semiarid area except a part of south Jiangsu, the MI was a significant zonally distribution in winter. (4) To the meteorological droughts of Jiangsu Province, in the decade scale, the droughts of the whole year and all seasons have been existing a obvious cycle of 10 to 12 years and the cycle of 2 to 4 years was most remarkable on the inter-annual variation. (5) The drought lasting days of different grades in Jiangsu Province were reducing from north to south in general. The drought lasting days of different grades were most in winter and least in summer.
In this paper, the observed meteorological data of 54 meteorological stations from 1960 to 2009 in Jiangsu Province of China were collected and a composite index (CI) of meteorological drought was used to analyze the temporal and spatial characteristics of droughts in the province. Based on the daily CI values of each station in 50 years, the drought processes of each station was confirmed one by one and the occurred frequencies, scopes and severities of the meteorological droughts in the different regions of Jiangsu Province were computed and analyzed to reveal the temporal and spatial occurrence pattern of the meteorological droughts in Jiangsu Province. The results were showed as follows:(1) The annual and seasonal occurrence frequencies of the meteorological drought in Jiangsu Province transferred high to low from north to south. In all seasons, the occurred frequency of the winter droughts was highest, the summer droughts occurred least and the difference of the autumn droughts between the north part and south part of the Province was the least in the occurrence frequency. (2) The years of the drought occurred in a large scope (more than 90% of total area of the Province) was most in winter and least in summer. (3) In the recent 50 years, there was an notable inter-annual wave of the annual average lasting days and the annual average occurrence severities of meteorological droughts in the whole Province but their linear change tendencies were not obvious. (4) The drought lasting days of different grades in Jiangsu Province were reducing from north to south in general. The drought lasting days of different grades were most in winter and least in summer.
In order to understand the engendering, disappearing and evolving pattern, in this paper, a serious autumn drought event when occurred in from October to November in 2006 and covered the whole Jiangsu Province was selected as a typical case and the daily composite meteorological drought index was calculated after the daily observed data of 54 meteorological stations were collected. Based on it, the beginning date, ending date, lasting days and daily drought severity for every station were determined and the drought engendering, disappearing and evolving characteristics of the whole province and each region in this drought event were discussed. A monitoring data production of MODIS Satellite remote sensing was merged into a vegetation water supply index and was used to reflect the evolving pattern of this drought process. The inverse distance weighted interpolation in ArcGIS9.3, a software of geographic information system, was applied in the temporary and spatial analysis of the drought development combined with the observed soil moisture data of 16 agro-meteorological observation stations in Jiangsu Province. The results were showed as follows:(1) In this typical autumn drought event, the engendering, disappearing and evolving pattern of the atmospheric, vegetation and soil drought reflected by the composite drought index, vegetation water supply index and soil moisture were consistent essentially. (2) The engendering of the drought event expanded and spread gradually from the northwestern part to the southeastern part of the province and its ending shrank and disappeared little by little from the southeastern part to the northwestern part of the province and the lasting days decreased successively from the northern part to the southern part of Jiangsu Province. (3) The drought severity in the northern part of the province was heavier than the southern part. Because of the different atmospheric backgrounds and natural geographic conditions, there was a obvious divergence of the evolving processes in the different regions. (4) Composite drought index, vegetation water supply index and soil moisture could be used to monitoring the engendering, developing, disappearing, and severity variations characteristics of a drought process in an all-round and systematic way.
引文
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