Scaling behaviors of precipitation over China

Scaling behaviors in the precipitation time series derived from 1951 to 2009 over China are investigated by detrended fluctuation analysis (DFA) method. The results show that there exists long-term memory for the precipitation time series in some stations, where the values of the scaling exponent α are less than 0.62, implying weak persistence characteristics. The values of scaling exponent in other stations indicate random behaviors. In addition, the scaling exponent α in precipitation records varies from station to station over China. A numerical test is made to verify the significance in DFA exponents by shuffling the data records many times. We think it is significant when the values of scaling exponent before shuffled precipitation records are larger than the interval threshold for 95 % confidence level after shuffling precipitation records many times. By comparison, the daily precipitation records exhibit weak positively long-range correlation in a power law fashion mainly at the stations taking on zonal distributions in south China, upper and middle reaches of the Yellow River, northern part of northeast China. This may be related to the subtropical high. Furthermore, the values of scaling exponent which cannot pass the significance test do not show a clear distribution pattern. It seems that the stations are mainly distributed in coastal areas, southwest China, and southern part of north China. In fact, many complicated factors may affect the scaling behaviors of precipitation such as the system of the east and south Asian monsoon, the interaction between sea and land, and the big landform of the Tibetan Plateau. These results may provide a better prerequisite to long-term predictor of precipitation time series for different regions over China.     

一种概率方法在沿海海岛台风阵风预报中的应用试验

利用2004—2013年浙江影响台风及9个沿海海岛气象站风力资料,分析了各站阵风系数总体特征,及其与站点纬度、海拔高度和海岸线距离等因子的关系。结果表明,随着平均风速的增大,对应的阵风系数有减少趋势;距离海岸线近的站点和海拔高度小的站点其阵风系数也相对要大些。分析台风参数与阵风系数关系,得出阵风系数与台风7级风圈半径和站点离台风中心距离的比值具有最好相关。利用分位数回归方法建立概率预报模型,试报表明大部分站点阵风的50%和90%概率范围的击中率都符合预期,其波动范围一般在3%以内,模型表现比较稳定,对业务有一定的指导价值。     

Recent fluctuations of tropospheric temperature and water vapour content in the tropics

Summary During the last decades the average temperature of the tropical troposphere (200/850 hPa layer) has steadily increased, between 1965 and 1984 by about 0.8°C in the whole equatorial belt. Data series from a section of individual stations verify this trend as seasonally constant, but decreasing from the equator towards both hemispheres. Further evidence is presented by selected mountain stations and glacier retreat in all equatorial mountains.Above the equatorial Pacific, the same stations indicate an increase of moisture content in the middle troposphere (500/700 hPa layer) expressed in precipitable water as well as in relative humidity. This coincides with increasing sea surface temperature in the area around Indonesia and northern Australia. Above Africa the trend is (if real) quite patchy. Due to the short residence time of water vapour in the atmosphere the horizontal (zonal ) distances between its sources and sinks remain near 2000 km, which may explain, in addition to instrumental differences, large regional deviations.With 7 Figures     

我国近百年气温的非趋势波动分析

为研究我国近百年气温的长程相关规律，通过对我国近百年月平均温度序列的非趋势波动分析。初步得出以下几个结论：我国近百年气温存在内在的长程相关性；标度指数a≌0．66；尽管大于18a尺度区间的α与小于18a尺度区间的α有所不同，但可能由于所分析的温度序列长度受到限制，没有足够充分的理由认为18a是个交叉点。     

四川盆地蒸发站网的合理布局探讨

本文采用四川盆地36个台站1980—1984年的逐日蒸发量资料，从统计各季代表月逐日蒸发量的相关函数着手，推算出相对内插标准误差与相关函数的统计关系，并根据内插标准误差不大于观测随机误差的原则，估算出该地区蒸发站网的合理间距。     

Fluctuations of the relationship between ENSO and northeast Australian rainfall

It is well known that during an El Niño-Southern Oscillation (ENSO) warm event, drought occurs in regions of northeastern (NE) Australia, leading to anomalously low annual rainfall. The present study explores fluctuations of this ENSO-rainfall relationship. It is found that the relationship tends to weaken when the linearly detrended global mean temperature is rising or particularly high, as in the period of 1931–45 period and since the late 1970s. Prior to a weakening, a correlation pattern of increased rainfall during El Niño events is seen first in northwestern Australia, then in eastern and southeastern Australia, and eventually in NE Australia. The 1931–45 period was particularly intriguing, when in terms of rainfall variability over NE Australia, the interannual ENSO-rainfall relationship went through a process of weakening, reversal, and rapid recovery. Features associated with the reversal are therefore examined and these features are: (1) the global background anomaly pattern (upon which internnal ENSO events operate) is ENSO-like; (2) ENSO sea surface temperature (SST) anomalies in tropical Pacific are weaker compared with those averaged over all ENSO events, whereas SST anomalies in the mid- to-high latitude Pacific (which have opposing polarity to those in tropical Pacific) are larger; (3) there is strong coherence between ENSO and variability in northern mid- to high-latitudes; and (4) the relationship that an El Niño event contributes to a warming anomaly of global mean SST weakens. Possible interrelationship among these features are discussed.     

Representativeness of wind measurements on a mesoscale grid with station separations of 312 m to 10 km

A field experiment was carried out in which wind speed and direction were measured over flat terrain at a height of 10 m using 13 identical instruments spaced logarithmically along two perpendicular 10 km lines. Station separations ranged from 312 m to 10 km. One-minute data from 11 sampling periods of duration 6 to 10 h were studied. p ]The statistics showed little dependence on whether the line of instruments was oriented along the wind or across the wind. The correlation coefficients between wind fluctuations at two stations separated by distance x were found to vary exponentially with x, with an integral distance scale on the order of 1 km. The integral time scale derived from the variation of the single station variances with averaging time was found to equal several minutes. At a station separation of 10 km, the correlation coefficients between the wind components at the two sites were calculated to be 0.24, 0.37, and 0.47 for averaging times of 1, 10, and 60 min, respectively. These values for the correlation coefficients correspond to root-mean-square differences in wind speed at the two stations of about 1.3, 1.0, and 0.7 m/s, respectively.Exponential formulas based on dimensional analysis are suggested for fitting these observations. It is found that the observations of spatial correlations are best fit if two independent integral distance scales are used — a boundary-layer distance scale of about 300 m that best applies to small station separations and a mesoscale distance scale of about 10 km that applies to larger station separations.     

THE INTERANNUAL OSCILLATION OF RAINFALL OVER CHINA AND ITS RELATION TO THE INTERANNUAL OSCILLATION OF THE AIR-SEA SYSTEM*

The quasi-biennial oscillation(QBO) and 3.5 years quasi-periodic oscillation(named TO hereafter) are exhibited in most of 48 weather stations of China by applying power spectrum analysis to the monthly rainfall data for the period from Jan. 1933 to Dec. 1987. In order to reveal the features of QBO and TO components, another rainfall data set in 160 stations over China for the period from Jan. 1951 to Dec. 1987 was analysed by means of a new method named complex empirical orthogonal function(CEOF). The results show that both QBO and TO modes exhibit two propagation ways:one originates in Northeast China, extends southward, passes through North China and reaches the eastern part of Northwest China and the northern part of Southwest China; the other appears over Guangdong and Fujian, then moves northward and westward respectively to the Huanghe-Huaihe Basin and Southwest China.These two paths of oscillation meet over North China and the area between the Changjiang River and the Huanghe River. A significant correlation exists between the interannual oscillation of the rainfall over China and that of the sea surface temperature(SST) at the equator. Although the correlation between the rainfall over China and the SST over the equatorial eastern Pacific is rather weak, the correlation between their oscillation component is pronounced.     

Evaluation of various root transformations of daily precipitation amounts fitted with a normal distribution for Australia

This paper evaluates the various root transformations (2/3, 7/12, 1/2, 5/12, 1/3, and 1/4) of daily precipitation amounts fitted with a truncated normal distribution model for 189 stations across Australia. The results indicate that all stations used in this study can be identified to have a specific root transformation resulting in a “good” fit with a normal distribution and the minimum correlation coefficients (r) fitted with a normal distribution is 0.9925. The 5/12 power transformation leads to the “best” fit with a normal distribution in 47% of stations across Australia. This conclusion could extend the applications of many statistical testing techniques and methods on daily precipitation studies.     

Retrieving air humidity,global solar radiation,and reference evapotranspiration from daily temperatures: development and validation of new methods for Mexico. Part I: humidity

The occurrence of flood and drought frequency is highly correlated with the temporal fluctuations of streamflow series; understanding of these fluctuations is essential for the improved modeling and statistical prediction of extreme changes in river basins. In this study, the complexity of daily streamflow fluctuations was investigated by using multifractal detrended fluctuation analysis (MF-DFA) in a large heterogeneous lake basin, the Poyang Lake basin in China, and the potential impacts of human activities were also explored. Major results indicate that the multifractality of streamflow fluctuations shows significant regional characteristics. In the study catchment, all the daily streamflow series present a strong long-range correlation with Hurst exponents bigger than 0.8. The q-order Hurst exponent h(q) of all the hydrostations can be characterized well by only two parameters: a (0.354 ≤ a ≤ 0.384) and b (0.627 ≤ b ≤ 0.677), with no pronounced differences. Singularity spectrum analysis pointed out that small fluctuations play a dominant role in all daily streamflow series. Our research also revealed that both the correlation properties and the broad probability density function (PDF) of hydrological series can be responsible for the multifractality of streamflow series that depends on watershed areas. In addition, we emphasized the relationship between watershed area and the estimated multifractal parameters, such as the Hurst exponent and fitted parameters a and b from the q-order Hurst exponent h(q). However, the relationship between the width of the singularity spectrum (Δα) and watershed area is not clear. Further investigation revealed that increasing forest coverage and reservoir storage can effectively enhance the persistence of daily streamflow, decrease the hydrological complexity of large fluctuations, and increase the small fluctuations.     

IMPACT OF SSTA OF SOUTHERN HEMISPHERE ON FLOOD SEASON PRECIPITATION ANOMALIES IN YUNNAN

Based on the reanalysis data of monthly mean global SST and wind from the NCEP/NCAR and the observation data of rain seasons in 124 stations of Yunnan province from 1961 to 2006, we applied the analytical methods of correlation analysis and composite analysis and a significance testing method to two sets of samples of average differences. The goal is to investigate into the influence of the Southern Hemispheric (SH) SST on the summer precipitation in Yunnan from January to May so as to identify the key time and marine regions. Physical mechanisms are obtained by analyzing the influence of sea level wind and the key marine regions on the precipitation during Yunnan’s rain season. Results show that there is indeed significant relationship between the SST in SH and summer precipitation in Yunnan. The key areas for influencing the summer precipitation are mainly distributed in a region called “West Wind Drift” in the SH, including the Southeast Indian, southern Australia, west coast of eastern Pacific off Chile, Peru and the southwest Atlantic Magellan. Besides, the most significant marine region is the west coast of Chile and Peru (cold-current areas of the eastern Pacific). Diagnostic analysis results also showed that monsoons in the Bay of Bengal, a cross-equatorial flow in the Indian Ocean near the equator and southwest monsoon in India weaken during the warm phase of the Peruvian cold current in the eastern Pacific. Otherwise, they strengthen.     

运城市降水集中度和集中期的时空特征分析

利用运城市9个气象站1960—2014年逐候降水资料,运用线性趋势、MannKendall曲线、相关系数和合成分析等方法探讨了运城市近55 a来年降水量、降水集中度(PCD)和集中期(PCP)的时空特征。结果表明:时间上,年降水量呈减少趋势,变化倾向率为-7.94 mm/10 a;PCD年际变化显著,在0.30~0.72,多年平均为0.53;PCP多年平均41.63候,最早与最晚相差13候。空间上,年降水量区域差异明显,由东南向西北递减;PCD从西南向东北递增,有2个大值和2个小值中心,PCP呈现"南早北晚"形势。PCD、PCP与年降水量、汛期降水量、月最大降水量、候最大降水量和日最大降水量之间都存在正相关,表明汛期降水量、月最大降水量、候最大降水量和日最大降水量越大的年份,PCD值就越大,降水就越集中,出现洪涝灾害的可能性就越大;降水集中期出现的越晚。     

Cloudiness fluctuations over Eastern Africa

Summary Based on ESSA-satellite imagery for the period July 1969–June 1970, this study investigates spatial and temporal variations of East African cloudiness. The major results of this work show that the mean annual cloud amounts over East Africa are lower than those in adjacent tropical areas. One of the main reasons for this is the quasi-meridional alignement of the ITCZ over East Africa during the winter months. Within the area itself, the highest mean annual cloud amount values can generally be found in a diagonally oriented zone extending from the eastern Congo Basin to the Ethiopian Highlands. In contrast to the cloudiness north of the equator, which is dominated by oscillation periods in the range of 30–60 days, the cloudiness fluctuations encountered south of the equator show periodicities around 2 days (in the western part) and 20 days (in the eastern part), respectively. The different oscillation patterns, which are roughly separated by the Rift Valley area (longitudinally) and the equator (latitudinally), resemble the signals of the adjacent (African and Asian) monsoon regimes. However, during the winter months oscillation periods around 40 days can be found north of the equator, whereas a quasi-biweekly oscillation appears over the coastal areas in summer. Further details of the seasonal variability of East African cloudiness are discussed.With 8 Figures     

Statistical analysis of the temperature records for the Northern Territory of Australia

The Northern Territory of Australia has a unique situation of an extension larger than France and a population of 200,000, with only three meteorology stations open for more than 40 years, Darwin (DW), Alice Springs (AS) and Tennant Creek, and only two of them, DW and AS, providing data over 100 years, and from 500 to more than 1,000 km separating these stations and the stations in the neighbouring states of Australia. Homogenizations of data in between different measuring sites for the same location as well as the way to derive the missed data to complete at least 100 years from the neighbouring locations are analysed in details and the effects on the temperature trends are straightforwardly investigated. Using properly homogenised data over 130 years and a linear fitting, the warming maximum and minimum temperatures are +0.009 and +0.057 °C/10 years for Alice Springs and ?0.025 and 0.064 °C/10 years for Darwin. With the data available, the only option to produce warming trends is to overweight the cold years in the middle of the 1970s and the subsequent return to warmer temperatures. Starting from 1980, to compute trends, there is still a clear warming in Alice Springs, but also clear cooling in Tennant Creek, and a mixed behaviour with warming maximum temperatures and cooling minimum temperatures in Darwin.     

The Relationship Between some Large-scale Atmospheric Parameters and Rainfall over Southeast Asia: A Comparison with Features over India

Summary Monthly rainfall data for 135 stations for periods varying from 25 to 125 years are utilised to investigate the rainfall climatology over the southeast Asian monsoon regime. Monthly rainfall patterns for the regions north of equator show that maximum rainfall along the west coasts occurs during the summer monsoon period, while the maximum along the east coasts is observed during the northeast monsoon period. Over the Indonesian region (south of the equator) maximum rainfall is observed west of 125 °E during northern winter and east of 125 °E during northern summer. The spatial relationships of the seasonal rainfall (June to September) with the large scale parameters – the Subtropical Ridge (STR) position over the Indian and the west Pacific regions, the Darwin Pressure Tendency (DPT) and the Northern Hemisphere Surface Temperature (NHST) – reveal that within the Asian monsoon regime, not only are there any regions which are in-phase with Indian monsoon rainfall, but there are also regions which are out-of-phase. The spatial patterns of correlation coefficients with all the parameters are similar, with in-phase relationships occurring over the Indian region, some inland regions of Thailand, central parts of Brunei and the Indonesian region lying between 120° to 140 °E. However, northwest Philippines and some southern parts of Kampuchea and Vietnam show an out-of-phase relationship. Even the first Empirical Orthogonal Function of seasonal rainfall shows similar spatial configuration, suggesting that the spatial correlation patterns depict the most dominant mode of interannual rainfall variability. The influence of STR and DPT (NHST) penetrates (does not penetrate) upto the equatorial regions. Possible dynamic causes leading to the observed correlation structure are also discussed. Received October 10, 1996 Revised February 25, 1997     

四川地区降水幂律指数研究

基于四川地区5个站点1960~2004年的日降水观测资料,对其在等级分析的基础上探讨了幂律分布的规律,结果如下:(1)这5个站点日降水存在的一个共同特征—幂律尾分布,且不同等级的降水量对应不同的幂律尾指数,在一定程度上反映了不同雨型具有不同的气候背景和物理机理;(2)小雨幂指数随时间变化很小,中雨幂指数随时间变化较大,从80年代末期开始,四川盆地西部与南部地区中雨幂指数增加,中雨降水减少,川西高原、四川盆地东部与北部地区中雨幂指数减小,中雨降水增加。因此,中雨的变化可能会引起总降水量的变化。      

Spatial prediction model and its application to chemistry of atmospheric precipitation in Jordan

This study is concerned with the spatial variability of some wet atmospheric precipitation parameters such as; pH, conductivity (EC). The study also depicts the spatial variability of some ions (cations and anions) of atmospheric precipitation in Jordan such as, Ca²⁺, Mg²⁺, Na⁺ and K⁺, HCO₃⁻, Cl⁻, NO₃⁻ and SO₄²⁻. The basis of the work is to establish a relationship through the cumulative semivariogram technique between the distance ratios and the spatial dependence structure of the chemical composition of atmospheric precipitation. All semivariogram models are constructed in this study in order to understand the behavior of the spatial distribution. The spatial distributions of rainwater parameters show differences from station to station which is expressed in terms of angle, where the larger the angle the weaker the correlation. The semivariogram (SV) models are constructed to show the variation of the rainfall chemistry in Jordan. The SV models show weak correlation between mountain and leeside mountain stations, i.e. mountain and desert stations. On the other hand, good correlations are observed when transferring from south to north of the country. The larger is the found angle, the weaker is the correlation. For most of the SV model the correlation is found to be very weak between desert and mountainous locality. The Standard Regional Dependence Factor (SRDF) is used for prediction of the distribution of rain fall parameters. It shows the relative error between observed and predicted values of rainwater parameters. The overall regional relative error between the observed and estimated concentrations remains less than 15%.     

甘肃省玉米产量的主成分分析

应用自然正交函数方法将甘肃省玉米产量的趋势产量项(Yt)和气候产量项(Yw) 进行展开，展开后的Yt、Yw第一特征向量都表明了Yt、Yw总趋势的一致性，其大值中心表明产量变率较大。通过对各主成分主要时间系数与各站Yt、Yw进行相关分布分析，筛选出全省玉米产量的八个站点，这些站点基本上代表了本省不同类型的农业气候区域的玉米产量水平和生育状况。     

中国不同地区气溶胶消光特性分析

利用多波段太阳光度计在中国四个点（北京的密云，广东的新丰，青海的瓦里关，西藏的当雄）观测了４５０—９００ ｕｍ范围中多波长气溶胶光学厚度和Ａｎｇｓｔｒｏｍ指数。本文分析了这些参数从１９９８年２月到１９９９年１月这一年中的特点。结果表明，在干旱和半干旱地区，如密云（１７．１２°Ｅ，４０．６５°Ｎ）和瓦里关（１００．９０°Ｅ，３６．２９°Ｎ），春季出现气溶胶光学厚度的最大值，大约是其它季节的２倍。在湿润地区，如新丰（１１４．２°Ｅ，２４．５°Ｎ），虽然春季气溶胶光学厚度值也是最大，但只是比其它季节稍微大一些 瓦里关春季的Ａｎｇｓｔｒｏｍ指数有最小值，约０．１５，表明有比较大的粒子、密云和新丰的Ａｎｇｓｔｒｏｍ指数也有很大的月际变化。但没有明显的季节倾向。这表明，气溶胶的源比较复杂。     

南海季风爆发的年代际转折与东亚副热带夏季降水的关系

利用1979—2016年NCEP再分析资料, 分析了南海季风爆发的年代际转折与东亚副热带夏季降水的关系。结果表明:南海夏季风爆发时间在1993/1994年出现年代际转变, 1979—1993年爆发时间相对偏晚, 夏季华南降水偏少, 长江中下游至日本南部降水偏多; 1994—2016年爆发时间偏早, 夏季华南降水偏多, 长江中下游到日本南部降水偏少。南海季风爆发时间年代际转折与夏季东亚副热带降水关系可能受到菲律宾越赤道气流强度的调控, 季风爆发时间与菲律宾越赤道气流有显著正相关, 且均在1993/1994年间存在年代际转变。在1994—2016(1979—1993)年南海夏季风爆发偏早(晚), 菲律宾越赤道气流偏弱(强), 澳大利亚北部有偏北(南)风异常, 将暖池的热量往赤道输送, 使得赤道对流增强(减弱), 产生异常上升(下沉)运动汇入Hadley环流上升支, 增强(减弱)的Hadley环流导致下沉主体偏北(南), 促使副高脊线偏北(南), 从西北太平洋(孟加拉湾)往华南地区(江淮到日本南部)输送水汽增强, 所以华南(江淮到日本南部)夏季降水偏多。