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1.
Observed,reconstructed, and simulated decadal variability of summer precipitation over eastern China 总被引：2，自引：0，他引：2 
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下载免费PDF全文 Jingyun Zheng Maowei Wu Quansheng Ge Zhixin Hao Xuezhen Zhang 《Acta Meteorologica Sinica》2017,31(1):49-60
Based on observations made during recent decades, reconstructed precipitation for the period A.D. 1736–2000, dry–wet index data for A.D. 500–2000, and a 1000-yr control simulation using the Community Earth System Model with fixed pre-industrial external forcing, the decadal variability of summer precipitation over eastern China is studied. Power spectrum analysis shows that the dominant cycles for the decadal variation of summer precipitation are: 22–24 and quasi-70 yr over the North China Plain; 32–36, 44–48, and quasi-70 yr in the Jiang–Huai area; and 32–36 and 44–48 yr in the Jiang–Nan area. Bandpass decomposition from observation, reconstruction, and simulation reveals that the variability of summer precipitation over the North China Plain, Jiang–Huai area, and Jiang–Nan area, at scales of 20–35, 35–50, and 50–80 yr, is not consistent across the entire millennium. We also find that the warm (cold) phase of the Pacific Decadal Oscillation generally corresponds to dry (wet) conditions over the North China Plain, but wet (dry) conditions in the Jiang–Nan area, from A.D. 1800, when the PDO became strengthened. However, such a correspondence does not exist throughout the entire last millennium. Data–model comparison suggests that these decadal oscillations and their temporal evolution over eastern China, including the decadal shifts in the spatial pattern of the precipitation anomaly observed in the late 1970s, early 1990s, and early 2000s, might result from internal variability of the climate system. 相似文献
2.
本文基于高原季风指数和高原涡数据集,利用小波分析等统计方法对高原季风和高原低涡的气候特征进行了统计分析,并探究了两者之间的关系,主要结果有:(1)高原季风夏强冬弱,高原季风的准4年、准6年周期振荡的特征十分明显。(2)30年来高原低涡平均每年生成64.2个,其中有51.2个是暖性高原低涡。高原低涡的强度季节内呈正态分布,高原低涡的生成频数的季节内变化有明显的周期振荡特征。(3)高原季风的周期振荡特征在季节尺度和年际尺度上与高原低涡气候特征有一定的相关性,准4年与准6年周期振荡特征十分明显。通过相关概率统计:高原季风的建立时间与强度都与高原低涡的气候特征有一定的正负相关。 相似文献
3.
This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50–70-yr, 100–120-yr, and 200–250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3℃ and 0.7℃, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870–2000, at a rate of 0.56°± 0.42℃(100 yr)~(-1); however, temperatures recorded in the 20 th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981–1100 and AD1201–70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern: dry south of 25°N, wet from 25°–30°N, and dry to the north of 30°N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20 th century warming can primarily be attributed to a mega El Nino–Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China. 相似文献
4.
Climatic regime shift and decadal anomalous events in China 总被引：15，自引：0，他引：15
Climatic time series from historical documents and instrumental records from China showed temporal and regional patterns in
the last two to three centuries, including two multidecadal oscillations at quasi-20-year and quasi-70-year timescales revealed
by signal analysis from wavelet transform. Climatic anomalous events on the decadal timescale were identified based on the
two oscillations when their positive (or negative) phases coincide with each other to amplify amplitude. The coldest event
occurred in the decade of 1965–1975 in eastern China, while the periods of 1920–1930, 1940–1950, and 1988–2000 appeared to
be warmer in most parts of China. For the precipitation series in northern China, the dry anomalous event was found in the
late 1920s, while the wet anomalous event occurred in the 1950s. A severe drought in 1927–1929 in northern China coincided
with the anomalous warm and dry decade, caused large-scale famine in nine provinces over northern China. Climatic anomalous
events with a warm-dry or cold-wet association in the physical climate system would potentially cause severe negative impacts
on natural ecosystem in the key vulnerable region over northern China. The spatial pattern of summer rainfall anomalies in
the eastern China monsoon region showed an opposite variations in phase between the Yellow River Valley (North China) and
the mid-low Yangtze River Valley as well as accompanied the shift of the northernmost monsoon boundary. Climatic regime shifts
for different time points in the last 200 years were identified. In North China, transitions from dry to wet periods occurred
around 1800, 1875, and 1940 while the transitions from wet to dry periods appeared around 1840, 1910, and the late 1970s.
The reversal transition in these time points can also be found in the lower Yangtze River. Climatic regime shifts in China
were linked to the interaction of mid- and low latitude atmospheric circulations (the westerly flow and the monsoon flow)
when they cross the Tibetan Plateau in East Asia. 相似文献
5.
文中采用时间域的带通滤波方法和合成分析技术,通过对1981年夏季月份OLR资料的准40天和准双周振荡的对比分析得到:(1)南亚季风区普遍存在准40天和准双周振荡,季风的活跃和中断要受其影响。(2)江淮流域到日本地区和南海到西太平洋地区OLR的分布是反位相的,它表明只有当南海季风槽断裂时,热带西南季风才能进入东亚大陆,这时大陆的季风雨较强。(3)OLR的分布表明,东亚大陆和印度北部平原季风雨的活跃与中断,对准40天振荡是同步的,而对准双周振荡是反位相的。(4)东亚大陆季风雨活跃与中断位相的转变,准40天振荡是从南海扰动中分裂出一块向北移动引起,而准双周振荡则是来自印度北部平原的季风扰动有规律的向东移动引起。 相似文献
6.
利用RHtest软件结合台站元数据对广州1908—2019年平均气温进行非均一性检验和订正,结果显示在1912、1928、1942、1988、1995、2004和2010年有7个显著的非均一间断点,订正后升温速率为1.39℃/(100 a),较订正前显著增加,具有准50 a和准3 a的显著周期。运用DB16正交小波分析其多时间尺度变化特征,结果显示方差贡献最大的是趋势分量,其次是准3 a和准6 a周期分量。趋势分量从20世纪40年代开始呈现持续的升温趋势;20世纪80年代中期至20世纪末的快速增暖是准50 a和准20 a周期分量的上升期叠加于趋势分量的结果;1998—2014年增暖停滞特征是准50 a、准20 a和准10 a这3个年代际周期分量的降温位相叠加在趋势分量上引起的。 相似文献
7.
Yan Junyue 《大气科学进展》1997,14(2):277-287
ＯｂｓｅｒｖａｔｉｏｎａｌＳｔｕｄｙｏｎｔｈｅＯｎｓｅｔｏｆｔｈｅＳｏｕｔｈＣｈｉｎａＳｅａＳｏｕｔｈｗｅｓｔＭｏｎｓｏｏｎＹａｎＪｕｎｙｕｅ（阎俊岳）ＮａｔｉｏｎａｌＣｌｉｍａｔｅＣｅｎｔｅｒ，Ｂｅｉｊｉｎｇ１０００８１ＲｅｃｅｉｖｅｄＮｏｖｅｍｂ... 相似文献
8.
该文比较了不同站点分布情况下我国江淮地区梅雨期降水基本空间型态,发现较高分辨率的站点分布能得到更细化的空间型态。1979—2010年我国江淮地区梅雨期降水基本空间型态主要包括南部型、长江型和江淮型。年际变化上,梅雨期降水的南北反位相特征更加明显;而长江型梅雨期降水较其他两个型态而言相对独立。回归分析表明,3种降水型态所对应的东亚夏季风环流子系统的位置、季风经圈环流及梅雨期水汽输送等均存在明显差别,其中东亚太平洋遥相关型 (EAP) 和欧亚遥相关型 (EU) 对南部型降水有显著影响。1979年以来,前期赤道东太平洋海温主要影响我国长江流域和江南地区梅雨期降水,而江淮型梅雨期降水与热带海温没有显著的相关关系。 相似文献
9.
The seasonal variations of the Asian monsoon were explored by applying the atmospheric general circulation model R42L9 that was developed recently at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences (LASG/IAP/CAS). The 20-yr (1979-1998) simulation was done using the prescribed 20-yr monthly SST and sea-ice data as required by Atmospheric Model Intercomparison Project (AMIP)Ⅱ in the model. The monthly precipitation and monsoon circulations were analyzed and compared with the observations to validate the model‘s performance in simulating the climatological mean and seasonal variations of the Asian monsoon. The results show that the model can capture the main features of the spatial distribution and the temporal evolution of precipitation in the Indian and East Asian monsoon areas. The model also reproduced the basic patterns of monsoon circulation. However, some biases exis tin this model. The simulation of the heating over the Tibetan Plateau in summer was too strong. The overestimated heating caused a stronger East Asian monsoon and a weaker Indian monsoon than the observations. In the circulation fields, the South Asia high was stronger and located over the Tibetan Plateau. The western Pacific subtropical high was extended westward, which is in accordance with the observational results when the heating over the Tibetan Plateau is stronger. Consequently, the simulated rainfall around this area and in northwest China was heavier than in observations, but in the Indian monsoon area and west Pacific the rainfall was somewhat deficient. 相似文献
10.
Interdecadal Variability of East Asian Summer Monsoon Precipitation over 220 Years （1777-1997） 总被引：1，自引：1，他引：0
In this study, long-term (1777–1997) precipitation data for Seoul, Korea, wetness indices from eastern China, and modern observations are used to identify the interdecadal variability in East Asian summer monsoon precipitation over the last 220 years. In the East Asian monsoon region, two long-term timescales of dry–wet transitions for the interdecadal variability and quasi-40-and quasi-60-year timescales are dominant in the 220-year precipitation data of Seoul, as well as in the wetness indices over China.... 相似文献
11.
Ashwini Kulkarni Ramesh Kripalani Sudhir Sabade Madhavan Rajeevan 《Climate Dynamics》2011,36(5-6):1005-1021
The day-to-day behavior of Indian summer monsoon rainfall (IMR) is associated with a hierarchy of quasi-periods, namely 3?C7, 10?C20 and the 30?C60?days. These two periods, the 10?C20?days and the 30?C60?days have been related with the active and break cycles of the monsoon rainfall over the Indian sub-continent. The seasonal strength of Indian summer monsoon rainfall may depend on the frequency and duration of spells of break and active periods associated with the fluctuations of the above intra-seasonal oscillations (ISOs). Thus the predictability of the seasonal (June through September) mean Indian monsoon depends on the extent to which the intra-seasonal oscillations could be predicted. The primary objective of this study is to bring out the dynamic circulation features during the pre-monsoon/monsoon season associated with the extreme phases of these oscillations The intense (weak) phase of the 10?C20 (30?C60) days oscillation is associated with anti-cyclonic circulation over the Indian Ocean, easterly flow over the equatorial Pacific Ocean resembling the normal or cold phase (La Nina) of El Nino Southern Oscillation (ENSO) phenomenon, and weakening of the north Pacific Sub-tropical High. On the other hand the weak phase of 10?C20?days mode and the intense phase of 30?C60?days mode shows remarkable opposite flow patterns. The circulation features during pre-monsoon months show that there is a tendency for the flow patterns observed in pre-monsoon months to persist during the monsoon months. Hence some indications of the behavior of these modes during the monsoon season could be foreshadowed from the spring season patterns. The relationship between the intensity of these modes and some of the long-range forecasting parameters used operationally by the India Meteorological Department has also been examined. 相似文献
12.
Interdecadal variability of the relationship between the East Asian winter monsoon and ENSO 总被引：2，自引：0，他引：2
W. Zhou X. Wang T. J. Zhou C. Li J. C. L. Chan 《Meteorology and Atmospheric Physics》2007,98(3-4):283-293
Summary The authors examine relationships between the East Asian winter monsoon and the ENSO, particularly on the interdecadal timescales.
Based on the analyses of SLP data from 1899 to 1997, the East-Asian winter monsoon index (WMI) is defined as the zonal difference
of SLP between ∼120° E and ∼160° E. It is found that 18 out of 28 strong winter monsoon years are either before the development
of an El Ni?o or during the decaying La Ni?a event, 12 out of 28 weak winter monsoon are before the development of a La Ni?a
or during the decaying El Ni?o event. There is a significant positive correlation coefficient value of about 0.49 between
the normalized 11-yr running mean of WMI and ENSO index, however, the WMI-ENSO relationship is not consistently highly correlated.
The temporal evolution of correlation between WMI and ENSO indices in both 11-yr and 21-yr moving window shows that the WMI-ENSO
relationship clearly undergo low-frequency oscillation. Obviously, both observational and IPSL air-sea coupled modeling WMI
index has a near-decadal peak with PDO timescales and internal peaks with ENSO timescales by applying the Multitaper method.
Moreover, the cross wavelet and wavelet coherence analysis of WMI/ENSO indicate that there is a larger significant sections
with an in phase behavior between WMI and ENSO at period of 20–30 yrs, suggesting that the interdecadal variation of the WMI-ENSO
relationship might exist. 相似文献
13.
Francis Joseph Turk Byung-Ju Sohn Hyun-Jong Oh Elizabeth E. Ebert Vincenzo Levizzani Eric A. Smith 《Meteorology and Atmospheric Physics》2009,105(1-2):99-108
In order to properly utilize remotely sensed precipitation estimates in hydrometeorological applications, knowledge of the accuracy of the estimates are needed. However, relatively few ground validation networks operate with the necessary spatial density and time-resolution required for validation of high-resolution precipitation products (HRPP) generated at fine space and time scales (e.g., hourly accumulations produced on a 0.25° spatial scale). In this article, we examine over-land validation statistics for an operationally designed, meteorological satellite-based global rainfall analysis that blends intermittent passive microwave-derived rainfall estimates aboard a variety of low Earth-orbiting satellite platforms with sub-hourly time sampling capabilities of visible and infrared imagers aboard operational geostationary platforms. The validation dataset is comprised of raingauge data collected from the dense, nearly homogeneous, 1-min reporting Automated Weather Station (network of the Korean Meteorological Administration during the June to August 2000 summer monsoon season. The space-time RMS error, mean bias, and correlation matrices were computed using various time windows for the gauge averaging, centered about the satellite observation time. For ±10 min time window, a correlation of 0.6 was achieved at 0.1° spatial scale by averaging more than 3 days; coarsening the spatial scale to 1.8° produced the same correlation by averaging over 1 h. Finer than approximately 24-h and 1° time and space scales, respectively, a rapid decay of the error statistics was obtained by trading-off either spatial or time resolution. Beyond a daily time scale, the blended estimates were nearly unbiased and with an RMS error of no worse than 1 mm day?1. 相似文献
14.
Spatio-Temporal Correlation Analysis of Global Temperature Based on the Correlation Matrix Theory 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 TBased on the NCEP/NCAR reanalysis daily mean temperature data from 1948 to 2005 and random time series of the same size, temperature correlation matrixes (TCMs) and random correlation matrixes (RCMs) are constructed and compared. The results show that there are meaningful true correlations as well as correlation "noises" in the TCMs. The true correlations contain short range correlations (SRCs) among temperature series of neighboring grid points as well as long range correlations (LRCs) among temperature series of different regions, such as the El Ni o area and the warm pool areas of the Pacific, the Indian Ocean, the Atlantic, etc. At different time scales, these two kinds of correlations show different features: at 1-10-day scale, SRCs are more important than LRCs; while at 15-day-or-more scale, the importance of SRCs and LRCs decreases and increases respectively, compared with the case of 1-10-day scale. It is found from the analyses of eigenvalues and eigenvectors of TCMs and corresponding RCMs that most correlation information is contained in several eigenvectors of TCMs with relatively larger eigenvalues, and the projections of global temperature series onto these eigenvectors are able to reflect the overall characteristics of global temperature changes to some extent. Besides, the correlation coefficients (CCs) of grid point temperature series show significant temporal and spatial variations. The average CCs over 1950-1956, 1972 1977, and 1996 2000 axe significantly higher than average while that over the periods 1978-1982 and 1991 1996 are opposite, suggesting a distinctive oscillation of quasi-10-20 yr. Spatially, the CCs at 1- and 15-day scales both show band-like zonal distributions; the zonally averaged CCs at 1-day scale display a better latitudinal symmetry, while they are relatively worse at 15-day scale because of sea-land contrast of the Northern and Southern Hemisphere. However, the meridionally averaged CCs at 15-day scale display a longitudinal quasi-symmetry. 相似文献
15.
Spatial Patterns of Precipitation Anomalies for 30-yr Warm Periods in China During the Past 2000 Years 下载免费PDF全文
下载免费PDF全文 The spatial patterns of precipitation anomalies during five 30-yr warm periods of 691-720, 1231-1260, 1741-1770, 1921-1950, and 1981-2000 were investigated using a dryness/wetness grading dataset covering 48 stations from Chinese historical documents and 22 precipitation proxy series from natural archives. It was found that the North China Plain (approximately 35 -40 N, east of 105 E) was dry in four warm periods within the centennial warm epochs of 600-750, the Medieval Warm Period (about 900-1300) and after 1900. A wet condition prevailed over most of China during 1741-1770, a 30-yr warm peak that occurred during the Little Ice Age (about 1650-1850). The spatial pattern of the precipitation anomaly in 1981-2000 over East China (25 -40 N, east of 105 E) is roughly consistent with that in 1231-1260, but a difference in the precipitation anomaly appeared over the Tibetan Plateau. The spatial patterns of the precipitation anomalies over China varied between all five 30-yr warm periods, which implies that the matching pattern between temperature and precipitation change is multiform, and the precipitation anomaly could be positive or negative when a decadal warm climate occurs in different climate epochs. This result may provide a primary reference for the mechanism detection and climate simulation of the precipitation anomaly of the future warm climate. 相似文献
16.
南海西南季风爆发的气候特征 总被引：56，自引：9，他引：56
利用多年的海洋船舶、岛屿站和沿岸站观测记录及卫星观测的高反射云（ＨＲＣ）资料，揭示南海西南季风爆发和建立时期的环流特征及要素变化。在南海，西南季风爆发的平均时间为５月中旬，北部略早（５月１２日），南部略迟（５月２０日），但年际差别可达一个月左右。伴随着西南季风的爆发，南海云量和降水量增多，对流加强，但海区之间具有很大的不均匀性。西南季风建立以后，强对流区稳定于南海中部，季风雨带没有明显的跳跃现象。西南季风爆发之前，南海表层温度迅速升高，其开始时间较季风爆发约提前一个月，海面水温的升高为季风爆发提供了热量和水汽条件。４—５月，南海海面热交换分量（海面吸收的太阳辐射、潜热输送等）发生明显的改变，特别是潜热交换和蒸发量明显增大，它可能是西南季风首先在南海爆发的原因之一。 相似文献
17.
A nine-member ensemble of simulations with a state-of-the-art atmospheric model forced only by the observed record of sea
surface temperature (SST) over 1930–2000 is shown to capture the dominant patterns of variability of boreal summer African
rainfall. One pattern represents variability along the Gulf of Guinea, between the equator and 10°N. It connects rainfall
over Africa to the Atlantic marine Intertropical Convergence Zone, is controlled by local, i.e., eastern equatorial Atlantic,
SSTs, and is interannual in time scale. The other represents variability in the semi-arid Sahel, between 10°N and 20°N. It
is a continental pattern, capturing the essence of the African summer monsoon, while at the same time displaying high sensitivity
to SSTs in the global tropics. A land–atmosphere feedback associated with this pattern translates precipitation anomalies
into coherent surface temperature and evaporation anomalies, as highlighted by a simulation where soil moisture is held fixed
to climatology. As a consequence of such feedback, it is shown that the recent positive trend in surface temperature is consistent
with the ocean-forced negative trend in precipitation, without the need to invoke the direct effect of the observed increase
in anthropogenic greenhouse gases. We advance plausible mechanisms by which the balance between land–ocean temperature contrast
and moisture availability that defines the monsoon could have been altered in recent decades, resulting in persistent drought.
This discussion also serves to illustrate ways in which the monsoon may be perturbed, or may already have been perturbed,
by anthropogenic climate change. 相似文献
18.
1616-1911年河南省异常洪涝灾害的时空特征及其成因 总被引：1，自引：0，他引：1
通过分类和整理1616-1911年河南省洪涝灾害记录,建立了洪涝灾害等级序列。采用Morlet小波变换、DBSCAN空间聚类等方法研究了河南异常洪涝灾害时空分异规律。探讨了洪涝发生对东亚夏季风和太阳活动变化的响应。结果表明：河南省洪涝灾害的发生存在80 a、30 a、20 a、9 a 4个主周期。在不同冷暖时期,北部地区洪涝灾害强度大于南部地区,且气候冷期洪涝强度和发生区域明显大于气候暖期,这除了与降水分布有关外,可能还与水域分布有关。河南南、北部洪涝强度对东亚夏季风强度的响应存在较大的差异,在东亚夏季风强年,季风系统位置偏北,易引起北部地区多洪涝;在东亚夏季风弱年,季风系统位置偏南,易引起南部地区多洪涝。不同时间尺度上二者相关性有显著差异,在100 a及以下时间尺度上,东亚夏季风对河南南部的洪涝影响显著;在200 a时间尺度上,东亚夏季风对河南北部的洪涝影响更显著。洪涝灾害易出现在太阳黑子数极值年及其附近,出现在极大值M年的频率高于极小值m年。河南北部的洪涝在各种不同时间尺度上对太阳黑子周期长度（SCL）的变化均有显著响应,河南南部的洪涝只在100 a尺度上对SCL的变化有显著响应,即当SCL变长（太阳活动减弱）时,有利于河南北部洪涝的少发;反之有利于洪涝的多发。河南省洪涝的变化可能是太阳活动与东亚夏季风共同作用的结果。进一步揭示历史洪涝发生规律及其成因对于正确预估未来旱涝趋势具有重要意义。 相似文献
19.
北大西洋年代际振荡（AMO）气候影响的研究评述 总被引：6，自引：0，他引：6
北大西洋年代际振荡（theAtlantic Multidecadal Oscillation,AMO）是发生在北大西洋区域空间上具有海盆尺度、时间上具有多十年尺度的海表温度（sea surface temperature,SST）准周期性暖冷异常变化。它具有65～80a周期,振幅为0.4℃。AMO的形成与热盐环流的准周期性振荡有关,它是气候系统的一种自然变率。诸多研究表明,AMO在北大西洋局地气候及全球其他区域气候演变中发挥了重要影响。欧亚大陆的表面气温,美国大陆、巴西东北部、西非以及南亚的降水,北大西洋飓风等都与之密切相关。AMO对东亚季风气候的年代际变化有显著的调制作用,暖位相AMO增强东亚夏季风,减弱冬季风,冷位相则相反。本文总结了这方面的研究进展,讨论了AMO对未来气候预测的意义,认为最近20多年来我国冬季的显著增暖与AMO处于暖位相有关,是人类温室气体强迫与暖位相AMO（自然因子）两种增暖影响相叠加的结果。随着AMO逐渐转入冷位相,我国冬季变暖趋势将放慢,并有望于21世纪20年代中期逆转。 相似文献
20.
1960～2010年湖南雨日的时空变化特征 总被引：1，自引：0，他引：1
采用湖南省的88个地面气象站点逐日降水资料,运用经验正交分解（EOF）、线性回归、小波分析等方法分析了湖南雨日的空间变化特征和气候变化趋势,以及湖南雨日与降水量的关系。结果表明：湖南雨日空间分布大致是南多北少,平原少于山区丘陵区,呈现出2条少雨日带、4个多雨日区;过去51 a湖南大部分地区雨日呈减少趋势,对比雨日的空间分布发现,未来湖南雨日的空间分布差异可能减小;湖南雨日存在明显的年代际变化,1970年代和2000年代分别为近51 a来雨日最多和最少的10 a。湖南雨日的空间分型既有全区一致性,也存在着东南部—西北部、湘中地区与周围地区及东部—西部相反变化的差异。全区一致型雨日呈下降趋势,存在3 a、8 a和21 a周期变化。东南—西北反向型雨日东南（西北）呈下降（上升）趋势,存在3 a、6 a和18 a周期变化。湖南雨日与降水量呈正相关关系,且雨日和降水量的时空变化特征非常相似。 相似文献