我国平均降水相对变率和降水量统计关系的研究

许多研究结果指出,降水量愈少,降水相对变率愈大。亦即降水相对变率与降水量之间存在着某种反相关的关系。关于降水相对变率和降水量间的这种反相关关系,康拉德(V.Conrad)早在40年代就作了研究。他根据世界各地384个台站资料分组统计求得年平均降水相对变率(y)与年降水量(x)之间具有三次抛物线的近似关系:     

轮台县1961-2008年降水变化特征

利用轮台县气象局1961-2008年的年、季降水资料,采用气候倾向率和降水相对变率统计方法,研究了近48a轮台县年、季降水量、降水相对变率及降水日数的年际、年代际变化趋势特征。结果表明：年降水量平均以10．7mm／10a的速率增加;各季降水量平均以0．6-6．5mm／10a的速率增加;年降水相对变率以-6％／10a的速率减小;年降水日数以2．6d／10a的速率增加,各季降水日数以（0．1～1．2）d／10a的速率增加。     

铜仁西部不同时间尺度温度降水变率分析

采用气候统计方法,从年、季、月、旬、候时间尺度分析了铜仁西部近地面平均温度和降水绝对变率及相对变率,结果显示：年平均温度绝对变率在0．3-0．4℃之间,相对变率在1．5％-2．3％之间,年降水绝对变率在120．1-170．5mm之间,相对变率在10．8％-16．1％之间。气温在旬、月尺度上的变率大小与该地区春节前后要么持续低温雨雪,要么持续艳阳高照以及7月下旬一8月上旬间常年持续高温热浪的实际相吻合;降水在月、旬、候尺度上的绝对变率年内变化曲线与多年平均降水量年内变化曲线升降趋势大体一致,呈显著的正相关,而相对变率则与降水量呈反相关。     

黔南近30a夏季降水变化特征及旱涝关系分析

根据改革开放后近30 a(1979—2008年)来黔南自治州降水资料和干旱、洪涝资料,利用数理统计方法对该州夏季(6—8月)的降水变化特征进行统计并结合灾情资料进行分析,结果表明:该州各站夏季降水量变化趋势较为一致,夏季降水量占全年降水量的百分率均有所提高,降水更加集中于夏季,但各地夏季降水变率较大,降水相对变率≥20%时易发生干旱或洪涝灾害,而降水相对变率≥30%时会发生显著的旱涝灾害。     

江门地区降水气候及特征分析

采用1962～2006年的江门地区的5个气象站（新会、鹤山、开平、恩平、台山）降水和气温资料，通过对降水的相对变率、各年份旱涝类型、降水保证率和年、月、季的降水变化规律进行分析，为江门地区预防洪涝、合理蓄水和用水提供科学依据。     

衢州地区降水变率与降水变化规律分析

采用1971~2000年的衢州地区降水资料,通过对年、季降水相对变率和年、季、月的降水变化规律分析,为衢州地区合理蓄水和用水提供科学依据。     

中国6个CMIP5模式对全球降水年际-年代际变率模拟的定量评估

本文利用美国全球降水气候中心(GPCC)的降水资料和中国参加国际第五阶段耦合模式比较计划(CMIP5)的6个气候模式[BCC_CSM1.1、BCC_CSM1.1(m)、BNU-ESM、FGOALS-s2、FGOALS-g2和FIO-ESM]的历史模拟试验的降水数据,采用可以表征降水变率相对和绝对量级的方法,定量评估了6个模式对降水年际-年代际变率的模拟能力。研究表明,观测降水的年际变率一般占总方差的65%~80%,年代际变率占总方差的10%~35%。在CMIP5历史试验中,6个模式平均的降水年际分量方差对总方差的贡献(超过70%)较观测偏强,模拟降水年代际分量的方差对总方差的贡献较小(约为10%~20%)。模式总体低估了全球平均总降水、年际降水和年代际降水的变率,但是高估了年际降水对总降水的贡献、低估了年代际降水对总降水的贡献。与观测相比,6个模式对东亚和澳大利亚地区的年代际降水的模拟都比较好,模拟与观测年代际降水方差的比值为1左右。在非洲、南美洲和海洋性大陆,BCC_CSM1.1模式模拟的降水年代际变率最接近观测;在欧亚和北美,BNU-ESM模式模拟的降水年代际变率与观测最接近。在欧亚大陆上,BCC_CSM1.1模式模拟的降水年际分量与年代际分量的方差比最接近观测;在非洲和美洲,FGOALS-s2模式模拟的降水年际分量与年代际分量的方差比最接近观测。本文的研究结果有助于理解中国当前气候模式对降水年际-年代际变率的模拟能力,以及未来改进模式。     

甘肃雨季的气候特征

根据全省主要气象台站1951—1990年旬降水相对系数,确定了雨季的起讫日期,分析了雨季的稳定程度和变化规律。结果表明:甘肃雨季比较明显,来临较迟,起讫日期不稳定,大部分地方降水变率大,特别是河西东部和中部8月降水变率大于7月,更易出现旱涝。且3年周期振动显著,是个比较重要的气候特征。     

近百年黑龙江省气候变化特征

用黑龙江省8个地面气象观测站的1909～2002年气温和降水资料，对年及冬、夏季气温和年及春、夏季降水进行线性趋势、气候基本态及变率进行了分析，得到气温变化总趋势是上升的，降水变化总趋势是减少的；目前年及冬、夏季气温均处在高气温基本态高变率状态，春季降水处在少降水基本态高变率状态，年及夏季降水处于少降水基本态低变率状态；并对黑龙江省气候变化进行了多时间尺度分析，发现黑龙江省气候变化具有明显的阶段性和突变性，气温经历了冷、暖、冷、暖 4个阶段，现在处于暖阶段，降水经历了干、湿、干、湿、干 5个阶段，目前处在干期；又分析了黑龙江省异常冷暖冬、冷热夏及春、夏季降水事件出现的规律和特征。     

青藏高原及其邻近地区降水变率的研究

本文根据我国西部地区1951—80年期间147个台站的降水变率资料,对青藏高原及其邻近地区的降水变率分布特征作了分析,发现年降水变率低值带和高值带分别对应于高原边缘的多雨带和高原外围的少雨带;冬、夏半年降水变率分布分别由西风带活动和高原季风环流系统及低值天气系统所决定;降水变率月际变化最大梯度出现月份的后延趋势与高原季风的建立,撤退过程有较好的一致性:降水变率随降水量呈幂函数变化。     

Wavelet entropy-based investigation into the daily precipitation variability in the Yangtze River Delta, China, with rapid urbanizations

In this paper, the daily precipitation data measured at 58 meteorological stations were used, and the spatial and temporal variability of daily precipitation and precipitation extrema in the Yangtze River Delta (YRD) during 1958–2007 was investigated using the indicator of discrete wavelet entropy; then, the urbanization effects were further analyzed. Results indicate that the daily precipitation variability in YRD, especially in the mid YRD with highly urbanized city clusters, is determined by the comprehensive impacts of atmospheric circulation, urbanizations, and the Taihu Lake. Compared with the results in 1958–1985, the variability of daily precipitation and precipitation extrema becomes more complex in 1986–2007, and daily precipitation variability is more complex in the mid YRD relative to the north and south. The precipitation extrema with bigger magnitudes show more complex variability. Urbanizations cause more complexity and fluctuations of daily precipitation in the mid YRD in 1986–2007, reflecting more uncertainty of daily precipitation variability, while the urbanization effects vary with regions and precipitation magnitudes. The variability of precipitation extrema with maximum values is mainly determined by natural atmospheric circulation but has little relationship with urbanizations; however, the variability of those precipitation extrema with general values is determined by both urbanizations and the Taihu Lake in YRD over the last three decades.     

Quantifying atmosphere and ocean origins of North American precipitation variability

How atmospheric and oceanic processes control North American precipitation variability has been extensively investigated, and yet debates remain. Here we address this question in a 50 km-resolution flux-adjusted global climate model. The high spatial resolution and flux adjustment greatly improve the model’s ability to realistically simulate North American precipitation, the relevant tropical and midlatitude variability and their teleconnections. Comparing two millennium-long simulations with and without an interactive ocean, we find that the leading modes of North American precipitation variability on seasonal and longer timescales exhibit nearly identical spatial and spectral characteristics, explained fraction of total variance and associated atmospheric circulation. This finding suggests that these leading modes arise from internal atmospheric dynamics and atmosphere-land coupling. However, in the fully coupled simulation, North American precipitation variability still correlates significantly with tropical ocean variability, consistent with observations and prior literature. We find that tropical ocean variability does not create its own type of atmospheric variability but excites internal atmospheric modes of variability in midlatitudes. This oceanic impact on North American precipitation is secondary to atmospheric impacts based on correlation. However, relative to the simulation without an interactive ocean, the fully coupled simulation amplifies precipitation variance over southwest North America (SWNA) during late spring to summer by up to 90%. The amplification is caused by a stronger variability in atmospheric moisture content that is attributed to tropical Pacific sea surface temperature variability. Enhanced atmospheric moisture variations over the tropical Pacific are transported by seasonal mean southwesterly winds into SWNA, resulting in larger precipitation variance.

     

中国降水的年代际变化及全球变暖、太平洋年代际振荡、大西洋多年代际振荡对其的相对贡献

虽然中国降水以年际变化为主,但可利用奇异谱分析辨析出10—20 a、20—50 a 年代际变化的显著性区域以及>50 a 的长期趋势的显著性区域。本研究通过奇异值分解、多元线性回归等方法探究了1934—2018年不同海洋模态对6—8月（夏季）和12月—翌年2月（冬季）中国陆地降水趋势以及年代际振荡的相对贡献。通过对中国降水及中低纬度地区海温进行奇异值分解发现,不论冬夏,影响中国降水的主要模态是全球变暖,其次是太平洋年代际振荡。利用多元线性回归模型定量评估全球变暖、太平洋年代际振荡、大西洋多年代际振荡对中国不同区域降水的方差贡献及各因子的相对贡献,结果表明:夏季,三者可以解释西北和华北大约30%的年代际降水,其中全球变暖的相对贡献最大、太平洋年代际振荡次之;冬季,三者可以解释东北42%、西北和华北30%左右的年代际降水,东北和西北以全球变暖的相对贡献为主、大西洋多年代际振荡为辅,华北仍以全球变暖的影响为主、太平洋年代际振荡为辅。      

Trend analysis of precipitation time series in Greece and their relationship with circulation using surface and satellite data: 1955–2001

Summary In this study, the trends of annual and seasonal precipitation time series were examined on the basis of measurements of 22 surface stations in Greece for the period 1955–2001, and satellite data during the period 1980–2001. For this purpose, two statistical tests based on the least square method and one based on the Mann-Kendall test, which is also capable of detecting the starting year of possible climatic discontinuities or changes, are applied. Greece, in general, presents a clear significant downward trend in annual precipitation for the period 1955–2001, which is determined by the respective decreasing trend in winter precipitation. Both winter and annual series exhibit a downward trend with a starting year being 1984. Satellite-derived precipitation time series could be an alternative means for diagnosing the variability of precipitation in Greece and detecting trends provided that they have been adjusted by surface measurements in the wider area of interest. The relationship between precipitation variability in Greece and atmospheric circulation was also examined using correlation analysis with three circulation indices: the well-known North Atlantic Oscillation Index (NAOI), a Mediterranean Oscillation Index (MOI) and a new Mediterranean Circulation Index (MCI). NAOI is the index that presented the most interesting correlation with winter, summer and annual precipitation in Greece, whereas the MOI and MCI were found to explain a significant proportion of annual and summer precipitation variability, respectively. The observed downward trend in winter and annual precipitation in Greece is linked mainly to a rising trend in the hemispheric circulation modes of the NAO, which are connected with the Mediterranean Oscillation Index.     

Relationship between South China Sea precipitation variability and tropical Indo-Pacific SST anomalies in IPCC CMIP5 models during spring-to-summer transition

The present study evaluates the precipitation variability over the South China Sea (SCS) and its relationship to tropical Indo-Pacific SST anomalies during spring-to-summer transition (April-May-June, AMJ) simulated by 23 Intergovernmental Panel on Climate Change Coupled Model Intercomparison Project Phase 5 coupled models. Most of the models have the capacity to capture the AMJ precipitation variability in the SCS. The precipitation and SST anomaly (SSTA) distribution in the SCS, tropical Pacific Ocean (TPO), and tropical Indian Ocean (TIO) domains is evaluated based on the pattern correlation coefficients between model simulations and observations. The analysis leads to several points of note. First, the performance of the SCS precipitation anomaly pattern in AMJ is model dependent. Second, the SSTA pattern in the TPO and TIO is important for capturing the AMJ SCS precipitation variability. Third, a realistic simulation of the western equatorial Pacific (WEP) and local SST impacts is necessary for reproducing the AMJ SCS precipitation variability in some models. Fourth, the overly strong WEP SST impacts may disrupt the relationship between the SCS precipitation and the TPO-TIO SST. Further work remains to be conducted to unravel the specific reasons for the discrepancies between models and observations in various aspects.     

Impact of sub-grid variability of precipitation and canopy water storage on hydrological processes in a coupled land–atmosphere model

The impact of sub-grid variability of precipitation and canopy water storage is investigated by applying a new canopy interception scheme into the Community Atmosphere Model version 3 (CAM3) coupled with the Community Land Model version 3 (CLM3). Including such sub-grid variability alters the partitioning of net radiation between sensible heat flux and latent heat flux on land surface, which leads to changes in precipitation through various pathways/mechanisms. The areas with most substantial changes are Amazonia and Central Africa where convective rain is dominant and vegetation is very dense. In these areas, precipitation during December–January–February is increased by up to 2 mm/day. This increase is due to the enhanced large-scale circulation and atmospheric instability caused by including the sub-grid variability. Cloud feedback plays an important role in modifying the large-scale circulation and atmospheric instability. Turning off cloud feedback mitigates the changes in surface convergence and boundary layer height caused by inclusion of sub-grid variability of precipitation and water storage canopy, which moderate the effect on precipitation.     

夏季印度洋MJO活跃时间对中国长江流域降水日数的影响

利用1980—2020年中国753站逐日降水资料、NCEP/NCAR大气再分析资料以及哈得来中心的海表温度资料和实时多变量Madden-Julian振荡（ MJO）指数,研究了MJO在印度洋地区（1—3位相）活跃日数对长江流域夏季降水日数的影响。结果表明两者存在显著的统计联系,在MJO活跃日数偏多的年份,MJO相关的西北太平洋反气旋环流异常有利于向长江中下游地区输送水汽,进而导致长江流域中下游范围内降水日数的增加,且这种影响主要体现在降水等级为大雨（25 mm/d）及以上强度的日数上。进一步研究发现,MJO在印度洋活跃日数与长江中下游夏季降水日数的关系存在年代际变化,两者显著的联系仅出现在2000年之后,之前的时段两者联系则较弱。这种关系的转变可能与印度洋海表温度变率减弱的背景有关,印度洋海洋年际变率变弱导致其对于长江中下游地区的影响减弱,进而使得MJO的调控作用凸显出来。夏季季节平均的印度洋MJO活跃日数可以对长江中下游的大雨以上的降水日数产生影响,且两者的关系在大约2000年之后变得尤为显著。      

The MGO climate model for Siberia

Validation results of the MGO regional climate model (RCM) with 50-km resolution for Siberia are discussed. For the specification of side boundary conditions, the reanalysis data are used. It is shown that the model satisfactorily simulates the sea-level pressure and temperature fields for all seasons and the year as a whole. The lowest computational errors in the simulation of regional surface temperature arise in the fall and winter; in spring and summer, the temperature errors are slightly higher. The model slightly underestimates the variability of daily mean temperature in winter relative to the reanalysis data. In summer, on the contrary, the RCM-simulated variability exceeds the variability in reanalysis. In winter, the space distribution of model precipitation is in qualitative agreement with the data of observational analysis; in summer, the space variability of model precipitation is significantly higher than that of precipitation in the reanalysis, especially in the mountains. Agreement between time changes in precipitation and temperature anomalies in RCM and in the reanalysis is better in the areas with a relatively large number of weather stations. The model can be used for estimation of future climate changes in the above-mentioned region.     

Precipitation interannual variability in South America from the WCRP-CMIP3 multi-model dataset

The ability of coupled climate models from the WCRP-CMIP3 multi-model dataset to reproduce the interannual seasonal variability of precipitation in South America and the influence of the Southern Annular Mode (SAM) and El Niño-Southern Oscillation (ENSO) on such variability is examined. Models are able to reproduce the northward migration of the precipitation variability maximum during autumn and winter and its later return towards the south during spring and summer as well as the high variability throughout the year in southern Chile. Nevertheless, most of them have problems in representing accurately the variability associated with the South Atlantic convergence zone during summer and the typical maximum of variability in the subtropical continent during autumn and winter. The annular-like structure characteristic of the SAM influence on the Southern Hemisphere circulation is basically simulated by all models, but they have serious deficiencies in representing the observed relationship between SAM and both precipitation and circulation anomalies in South America. In addition, most of the models are not able to reproduce the typical wavetrains observed in the circulation anomalies in the Southern Hemisphere associated to ENSO. Only few models, previously identified as those with reasonable ENSO representation at the equatorial Pacific, have evidences of such wavetrains. Coherently, they exhibit the best representation of the ENSO signal in the South American precipitation. Results show that considerable improvement in the model representation of the climate variability in South America and in the associated large-scale teleconnections is still needed.     

A tree-ring reconstruction of East Anglian (UK) hydroclimate variability over the last millennium

We present an annually resolved reconstruction of spring-summer precipitation variability in East Anglia, UK (52–53°N, 0–2°E) for the period AD 900–2009. A continuous regional network of 723 living (AD 1590–2009) and historical (AD 781–1790) oak (Quercus sp.) ring-width series has been constructed and shown to display significant sensitivity to precipitation variability during the March-July season. The existence of a coherent common growth signal is demonstrated in oaks growing across East Anglia, containing evidence of near-decadal aperiodic variability in precipitation throughout the last millennium. Positive correlations are established between oak growth and precipitation variability across a large region of northwest Europe, although climate-growth relationships appear time transgressive with correlations significantly weakening during the early twentieth century. Examination of the relationship between oak growth, precipitation, and the North Atlantic Oscillation (NAO), reveals no evidence that the NAO plays any significant role in the control of precipitation or tree growth in this region. Using Regional Curve Standardisation to preserve evidence of low-frequency growth variability in the East Anglian oak chronology, we produce a millennial length reconstruction that is capable of explaining 32–35% of annual-to-decadal regional-scale precipitation variance during 1901–2009. The full length reconstruction indicates statistically significant anomalous dry conditions during AD 900–1100 and circa-1800. An apparent prolonged wetter phase is estimated for the twelfth and thirteen centuries, whilst precipitation fluctuates between wetter and drier phases at near centennial timescales throughout the fourteenth to seventeenth centuries. Above average precipitation reconstructed for the twenty-first century is comparable with that reproduced for the 1600s. The main estimated wet and dry phases reconstructed here appear largely coherent with an independent tree-ring reconstruction for southern-central England.