天津市夏季降水日变化特征

利用1954－2007年天津市夏季逐时自记降水资料,分析了天津市夏季降水（包括逐小时降水量、降水频次、降水强度以及不同持续时间降水）日变化规律。结果表明：天津市一日内不同时次的多年累积降水量具有显著的日变化特征,呈明显的双峰型,高值分别出现在午后17时和午夜02时。逐小时降水强度与降水量的变化特征非常一致,而多年累积降水频次在凌晨02时至08时较高,之后至11时逐步降低,11时至24时变化不大。降水量与降水频次及降水强度的关系均达到显著性水平（P < 0.001）,但逐小时降水强度与降水量相关性明显高于降水频次,表明降水量变化与降水强度有直接的关系,而降水频次对累积降水量的贡献占较小的权重。持续不同时间降水事件的发生次数在一日内的变化特征明显不同,长时性降水峰值集中在清晨,而短时性降水尤其是1-3 h降水主要以午后为主。     

不同选样方法对Pilgrim&Cordery设计暴雨雨型的对比研究

采用宜昌市主城区国家基本站长序列的逐分钟降雨过程资料,利用PilgrimCordery法(简称"PC法")比较通过自然降雨过程和最大历时过程两种降雨场次样本选样方法推求的设计暴雨雨型,并分析结果差异。结果表明:基于自然降雨过程和最大历时过程选样,利用PC法推求的宜昌市主城区短历时设计暴雨雨型基本都为单峰型,且雨峰均出现在整场降雨过程的前1/3时段。两种选样方法推求的短历时设计暴雨雨型的雨量分配比例存在较大差异,自然降雨过程选样推求的雨型雨峰峰值占总雨量的比例相较于最大历时过程的数值偏大,更为突出。实际工程设计中,设计师应当根据最大历时过程的选样规则进行推求,结合一定重现期下各个历时的降雨量值,进而得到各历时时程分配的具体雨强;计算得到宜昌市主城区重现期2a历时60、120、180 min的雨峰时段雨强分别为1.16、0.86、0.72 mm/min。     

Warm season heavy rainfall events over the Huaihe River Valley and their linkage with wintertime thermal condition of the tropical oceans

Warm season heavy rainfall events over the Huaihe River Valley (HRV) of China are amongst the top causes of agriculture and economic loss in this region. Thus, there is a pressing need for accurate seasonal prediction of HRV heavy rainfall events. This study improves the seasonal prediction of HRV heavy rainfall by implementing a novel rainfall framework, which overcomes the limitation of traditional probability models and advances the statistical inference on HRV heavy rainfall events. The framework is built on a three-cluster Normal mixture model, whose distribution parameters are sampled using Bayesian inference and Markov Chain Monte Carlo algorithm. The three rainfall clusters reflect probability behaviors of light, moderate, and heavy rainfall, respectively. Our analysis indicates that heavy rainfall events make the largest contribution to the total amount of seasonal precipitation. Furthermore, the interannual variation of summer precipitation is attributable to the variation of heavy rainfall frequency over the HRV. The heavy rainfall frequency, in turn, is influenced by sea surface temperature anomalies (SSTAs) over the north Indian Ocean, equatorial western Pacific, and the tropical Atlantic. The tropical SSTAs modulate the HRV heavy rainfall events by influencing atmospheric circulation favorable for the onset and maintenance of heavy rainfall events. Occurring 5 months prior to the summer season, these tropical SSTAs provide potential sources of prediction skill for heavy rainfall events over the HRV. Using these preceding SSTA signals, we show that the support vector machine algorithm can predict HRV heavy rainfall satisfactorily. The improved prediction skill has important implication for the nation’s disaster early warning system.     

Statistical characteristics of environmental parameters for warm season short-duration heavy rainfall over central and eastern China

Water vapor content,instability,and convergence conditions are the key to short-duration heavy rainfall forecasting.It is necessary to understand the large-scale atmospheric environment characteristics of shortduration heavy rainfall by investigating the distribution of physical parameters for different hourly rainfall intensities.The observed hourly rainfall data in China and the NCEP final analysis（FNL）data during 1May and 30 September from 2002 to 2009 are used.NCEP FNL data are 6-hourly,resulting in sample sizes of 1573370,355346,and 11401 for three categories of hourly rainfall（P）of no precipitation(P<0.1 mm h^-1),ordinary precipitation(0.1≤P<20 mm h^-1),and short-duration heavy rainfall(P≥20.0 mm h^-1),respectively,by adopting a temporal matching method.The results show that the total precipitable water（PWAT）is the best parameter indicating the hourly rainfall intensity.A PWAT of 28 mm is necessary for any short-duration heavy rainfall.The possibility of short-duration heavy rainfall occurrence increases with PWAT,and a PWAT of 59 mm is nearly sufficient.The specific humidity is a better indicator than relative humidity.Both 700-and 850-hPa relative humidity greater than 80%could be used to determine whether or not it is going to rain,but could not be used to estimate the rainfall intensity.Temperature and potential pseudo-equivalent temperature are also reasonable indicators of short-duration heavy rainfall.Among the atmospheric instability parameters,the best lifted index（BLI）performs best on the shortduration rainfall discrimination;the next best is the K index（KI）.The three rainfall categories are not well recognized by total totals（TT）or the temperature difference between 850 and 500 hPa（DT85）.Threequarters of short-duration heavy rainfall occurred with BLI less than-0.9,while no short-duration heavy rainfall occurred when BLI was greater than 2.6.The minimum threshold of KI was 28.1 for short-duration heavy rainfall.The importance of dynamic conditions was well demonstrated by the 925-and 850-hPa divergence.The representativeness of 925-hPa divergence is stronger than that of 850 hPa.Three-quarters of short-duration heavy rainfall occurred under a negative divergence environment.However,both the best convective potential energy（BCAPE）and vertical wind shear were unable to discriminate the hourly rainfall intensities.     

夏季中国中东部不同历时降水时空分布特征

利用1961~2012年台站逐时降水资料,分析了夏季中国中东部不同历时降水的主要气候分布和长期变化特征,为深入认识其时空变化规律和形成机理奠定基础。分析结果表明,降水事件的平均历时由南向北呈"短—长—短"分布型,华南和北方地区以6 h以下的短历时降水为主;而中部地区(28°N~37°N)6 h以上长历时降水占总降水量60%以上。随着降水历时的增加,小雨事件(0.1~1.0 mm/h)的发生概率降低,中雨事件(1.1~10.0 mm/h)的发生概率升高;大雨、暴雨事件(10.0 mm/h)更易出现在35°N以南历时偏短的降水事件中。1961~2012年,中国中东部总降水量呈"南升北降"的趋势分布,夏季南方大部分地区降水强度、时数和事件数均呈上升趋势;而北方地区降水时数和事件数显著减少,不过降水强度呈增强趋势。中东部降水历时总体呈上升趋势,尤其以我国长江与黄河之间的中部地区变化最为显著。同时,该地区短历时(1~6 h)降水无显著的年代际转折,长历时(6 h)降水的年代际增加是20世纪70年代末至20世纪90年代初降水增多的主要原因。20世纪90年代初期以来,南方地区降水的年代际增多则是长、短降水共同作用的结果,但超过6 h降水的影响范围更广,且影响中心较短历时降水偏北。     

南京地区雨滴谱参数的详细统计分析及其在天气雷达探测中的应用

雨滴谱包含了降雨的丰富信息,不仅能反映雨滴群的微物理特性,也能反映降雨类型、降雨强度等宏观特性,并且在雷达气象领域也有重要的价值。论文对2015和2016年度南京地区32次降雨过程的雨滴谱资料进行了处理、并对多种雨滴参数进行了详细的统计和分析,拟合了层状云降雨、对流云降雨以及积层混合云降雨的雨滴谱Gamma分布参数。另外,还基于雨滴谱数据拟合了雷达反射率因子Z与降雨强度R的Z-R关系,计算了差分反射率Z_DR、相位常数K_DP以及衰减参数,并利用衰减参数进行了C波段雷达回波的衰减订正试验。结果表明:（1）层状云降雨的各微物理参数比较稳定,积雨云的变化剧烈;层云降雨和积层混合云降雨的中雨滴、积雨云降雨的大雨滴对雷达反射率因子的贡献最大。（2）积雨云降雨的滴谱最宽,层状云降雨的最窄。（3）利用依据雨滴谱数据拟合的三类降雨Z-R关系,可以一定程度地提高雷达估测降雨的精度。（4）利用基于雨滴谱数据拟合的衰减系数,有效地进行了C波段双偏振雷达回波强度的衰减订正,体现了统计参数和拟合参数准确性。     

Climate change and implications for agriculture in Niger

Five-year moving averages of annual rainfall for 21 locations in Niger showed a decline in the annual rainfall after 1960. Correlation coefficients of the moving averages of monthly rainfall with annual rainfall showed significant correlations between the decline in the annual rainfall with decreased rainfall in August. Analysis of daily rainfall data for rainy season parameters of interest to agriculture suggested that from 1965 there was a significant decrease in the amount of rainfall and in the number of rainy days in the months of July and August, resulting in a decreased volume of rainfall for each rainstorm. In comparison to the period 1945–64, major shifts have occurred in the average dates of onset and ending of rains during 1965–88. The length of the growing season was reduced by 5–20 days across different locations in Niger. The standard deviation for the onset and ending of the rains as well as the length of the growing season has increased, implying that cropping has become more risky. Water balance calculations also demonstrated that the probability of rainfall exceeding potential evapotranspiration decreased during the growing season. The implications of these changes for agriculture in Niger are discussed using field data.     

一个区域气候模式对ENSO衰减年夏季中国东部降水的模拟

The performance of the Climate version of the Regional Eta-coordinate Model (CREM), a regional climate model developed by State Key Laboratory of Nu- merical modeling for Atmospheric Science and Geophysical Fluid Dynamics/Institute of Atmospheric Physics (LASG/IAP), in simulating rainfall anomalies during the ENSO decaying summers from 1982 to 2002 was evaluated. The added value of rainfall simulation relative to reanalysis data and the sources of model bias were studied. Results showed that the model simulated rainfall anomalies moderately well. The model did well at capturing the above-normal rainfall along the Yangtze River valley (YRV) during El Nio decaying summers and the below and above-normal rainfall centers along the YRV and the Huaihe River valley (HRV), respectively, during La Nia decaying summers. These features were not evident in rainfall products derived from the reanalysis, indicating that rainfall simulation did add value. The main limitations of the model were that the simulated rainfall anomalies along the YRV were far stronger and weaker in magnitude than the observations during El Nio decaying summers and La Nia decaying summers, respectively. The stronger magnitude above-normal rainfall during El Nio decaying summers was due to a stronger northward transport of water vapor in the lower troposphere, mostly from moisture advection. An artificial, above-normal rainfall center was seen in the region north to 35°N, which was associated with stronger northward water vapor transport. Both lower tropospheric circulation bias and a wetter model atmosphere contributed to the bias caused by water vapor transport. There was a stronger southward water vapor transport from the southern boundary of the model during La Nia decaying summers;less remaining water vapor caused anomalously weaker rainfall in the model as compared to observations.     

诱发哈萨克斯坦夏季强降水的环流结构特征

采用FNL1°×1°和CPC0.5°×0.5°再分析资料,通过对比分析夏季哈萨克斯坦不同区域的3次强降水过程的环流特征,揭示了诱发强降水的环流结构。结果表明：哈萨克斯坦各区域出现强降水时,西部和东部的强降水中心位于高空急流带入口区右侧,北部位于出口区左侧,辐散抽吸作用利于上升运动发展;强降水的影响系统主要为500 hPa低涡,强降水中心位于低涡槽线前部西南气流带上,中层温度平流对强降水发生有促进作用,西部和北部强降水中心位于低层冷平流大值区,东部则位于东北冷平流南侧的气旋性辐合区;除哈萨克斯坦东部强降水受地形影响地面系统尺度较小外,西部和北部强降水时地面有明显的冷锋,并存在气旋性的辐合切变,冷暖汇合形成的辐合线是强降水的主要中尺度触发系统;哈萨克斯坦强降水的水汽源地主要为地中海、黑海、波斯湾和北冰洋,经长途输送在强降水区形成强的水汽辐合,辐合值＞40×10-6 g?cm-1?s-1。     

Simulated changes in daily rainfall intensity due to the enhanced greenhouse effect: implications for extreme rainfall events

In this study we present rainfall results from equilibrium 1 ×– and 2 × CO₂ experiments with the CSIRO 4-level general circulation model. The 1 × CO₂ results are discussed in relation to observed climate. Discussion of the 2 × CO₂ results focuses upon changes in convective and non-convective rainfall as simulated in the model, and the consequences these changes have for simulated daily rainfall intensity and the frequency of heavy rainfall events. In doing this analysis, we recognize the significant shortcomings of GCM simulations of precipitation processes. However, because of the potential significance of any changes in heavy rainfall events as a result of the enhanced greenhouse effect, we believe a first examination of relevant GCM rainfall results is warranted. Generally, the model results show a marked increase in rainfall originating from penetrative convection and, in the mid-latitudes, a decline in largescale (non-convective) rainfall. It is argued that these changes in rainfall type are a consequence of the increased moisture holding capacity of the warmer atmosphere simulated for 2 × CO₂ conditions. Related to changes in rainfall type, rainfall intensity (rain per rain day) increases in the model for most regions of the globe. Increases extend even to regions where total rainfall decreases. Indeed, the greater intensity of daily rainfall is a much clearer response of the model to increased greenhouse gases than the changes in total rainfall. We also find a decrease in the number of rainy days in the middle latitudes of both the Northern and Southern Hemispheres. To further elucidate these results daily rainfall frequency distributions are examined globally and for four selected regions of interest. In all regions the frequency of high rainfall events increases, and the return period of such events decreases markedly. If realistic, the findings have potentially serious practical implications in terms of an increased frequency and severity of floods in most regions. However, we discuss various important sources of uncertainty in the results presented, and indicate the need for rainfall intensity results to be examined in enhanced greenhouse experiments with other GCMs.     

Relationship between Indian and East Asian Summer Rainfall Variations

The Indian and East Asian summer monsoons are two components of the whole Asian summer monsoon system.Previous studies have indicated in-phase and out-of-phase variations between Indian and East Asian summer rainfall.The present study reviews the current understanding of the connection between Indian and East Asian summer rainfall.The review covers the relationship of northern China,southern Japan,and South Korean summer rainfall with Indian summer rainfall;the atmospheric circulation anomalies connecting Indian and East Asian summer rainfall variations; the long-term change in the connection between Indian and northern China rainfall and the plausible reasons for the change; and the influence of ENSO on the relationship between Indian and East Asian summer rainfall and its change.While much progress has been made about the relationship between Indian and East Asian summer rainfall variations,there are several remaining issues that need investigation.These include the processes involved in the connection between Indian and East Asian summer rainfall,the non-stationarity of the connection and the plausible reasons,the influences of ENSO on the relationship,the performance of climate models in simulating the relationship between Indian and East Asian summer rainfall,and the relationship between Indian and East Asian rainfall intraseasonal fluctuations.     

甘肃雨养农业区降雨概率特征研究

利用甘肃雨养农业区 19个代表站点的 4 0a降雨量资料 ,结合weibull、gringorfen等概率统计分析的方法 ,对这一地区的降雨概率特征进行了研究 ,结果表明 ,甘肃雨养农业区各站年降雨量与其概率对数相关显著 ,可以利用所得关系式计算任一概率下的降雨量 ;各站年降雨量服从正态分布 ,也可用正态法求算任一概率下的降雨量 ;甘肃雨养农业区年平均有效降雨量理论上可以满足小麦生育期的作物需水量。     

Calibration of TRMM rainfall climatology over Saudi Arabia during 1998–2009

The short-term rainfall climatology regime over Saudi Arabia is obtained from the Tropical Rainfall Measuring Mission (TRMM) data for the period 1998–2009. The TRMM rainfall amounts are calibrated with respect to the rain-gauge data recorded at 29 stations across the country. Day-to-day rainfall comparisons show that the TRMM rainfall trends are very similar to the observed data trends, even if a general overestimation in the satellite products must be highlighted. Besides, especially during the wet season, some of the TRMM algorithm runs tend to underestimate the retrieved rainfalls. The TRMM rainfall data also closely follow the observed annual cycle on a monthly scale. The correlation coefficient for rainfall between the TRMM and the rain-gauge data is about 0.90, with a 99% level of significance on the monthly scale.The spatio-temporal distributions of rainfall over Saudi Arabia are analyzed. Besides the four conventional seasons, this analysis consider the wet (November–April) and dry (June–September) seasons, based on the rainfall amounts recorded. Spring is the highest and winter is the second highest rainfall-occurring season, resulting in large amounts of rainfall during the wet season over most of the country. Regional variations in the rainfall climatology over Saudi Arabia are studied through defining four regions. The false alarm ratio, probability of detection, threat score, and skill score are calculated to evaluate the TRMM performance. The country's average annual rainfall measured by the TRMM is 89.42 mm, whereas the observed data is 82.29 mm. Thus, the rainfall in Saudi Arabia is suggested as being the TRMM value multiplied by 0.93 plus 0.04. After this calibration, the TRMM-measured rainfall is almost 100% of the observed data, thereby confirming that TRMM data may be used in a variety of water-related applications in Saudi Arabia.     

Inter-decadal variability of summer rainfall in Eastern China detected by the Lepage test

On the basis of the latest observational datasets, the inter-decadal changes of summer rainfall in East China in the past 50?years are analyzed using the Lepage test. The two traditional methods moving t-test and Mann-Kendall test are also performed on the rainfall data as a comparison. Results indicate four inter-decadal abrupt changes of summer rainfall that occurred near 1979, 1983, 1993, and 1999, and each of them is characterized by remarkable regional features. The abrupt change of summer rainfall around 1979 is accompanied by significant rainfall increase in Yangtze?CHuai River Valley and a decrease in its flank. The one near 1983 shows similar structures of the rainfall changes to that near 1979, but with more significant changes in the South China and Northeast China (NEC). The inter-decadal change around 1993 brings a notable increase of summer rainfall to the South China; and the abrupt shift near 1999 exhibits significant decrease in summer rainfall over a large part of North China and NEC. The spatial?Ctemporal features of the inter-decadal changes in summer rainfall are also investigated. Consistent results are observed. Moreover, results indicate that, on the inter-decadal scale, the rainfall variability mode changes from typical tripole to dipole structure since the early 1990s.     

Interannual and long-term variability in the North Atlantic Oscillation and Indian Summer monsoon rainfall

Summary The interannual and decadal scale variability in the North Atlantic Oscillation (NAO) and its relationship with Indian Summer monsoon rainfall has been investigated using 108 years (1881–1988) of data. The analysis is carried out for two homogeneous regions in India, (Peninsular India and Northwest India) and the whole of India. The analysis reveals that the NAO of the preceding year in January has a statistically significant inverse relationship with the summer monsoon rainfall for the whole of India and Peninsular India, but not with the rainfall of Northwest India. The decadal scale analysis reveals that the NAO during winter (December–January–February) and spring (March–April–May) has a statistically significant inverse relationship with the summer monsoon rainfall of Northwest India, Peninsular India and the whole of India. The highest correlation is observed with the winter NAO. The NAO and Northwest India rainfall relationship is stronger than that for the Peninsular and whole of India rainfall on climatological and sub-climatological scales.Trend analysis of summer monsoon rainfall over the three regions has also been carried out. From the early 1930s the Peninsular India and whole of India rainfall show a significant decreasing trend (1% level) whereas the Northwest India rainfall shows an increasing trend from 1896 onwards.Interestingly, the NAO on both climatological and subclimatological scales during winter, reveals periods of trends very similar to that of Northwest Indian summer monsoon rainfall but with opposite phases.The decadal scale variability in ridge position at 500 hPa over India in April at 75° E (an important parameter used for the long-range forecast of monsoon) and NAO is also investigated.With 4 Figures     

Multi-decadal scale variability in autumn-winter rainfall in south-western Australia since 1655 AD as reconstructed from tree rings of Callitris columellaris

We present the first tree-ring based reconstruction of rainfall for the Lake Tay region of southern Western Australia. We examined the response of Callitris columellaris to rainfall, the southern oscillation index (SOI), the southern annular mode (SAM) and surface sea temperature (SST) anomalies in the southern Indian Ocean. The 350-year chronology was most strongly correlated with rainfall averaged over the autumn-winter period (March–September; r = ?0.70, P < 0.05) and SOI values averaged over June–August (r = 0.25, P < 0.05). The chronology was not correlated with SAM or SSTs. We reconstructed autumn-winter rainfall back to 1655, where current and previous year tree-ring indices explained 54% of variation in rainfall over the 1902–2005 calibration period. Some variability in rainfall was lost during the reconstruction: variability of actual rainfall (expressed as normalized values) over the calibration period was 0.78, while variability of the normalized reconstructed values over the same period was 0.44. Nevertheless, the reconstruction, combined with spectral analysis, revealed that rainfall naturally varies from relatively dry periods lasting to 20–30 years to 15-year long periods of above average rainfall. This variability in rainfall may reflect low-frequency variation in the El Niño-Southern Oscillation rather than the effect of SAM or SSTs.     

Projections of Extreme Rainfall in Hong Kong in the 21st Century

The possible changes in the frequency of extreme rainfall events in Hong Kong in the 21st century wereinvestigated by statistically downscaling 30 sets of the daily global climate model projections (involvinga combination of 12 models and 3 greenhouse gas emission scenarios,namely,A2,A1B,and B1) of theFourth Assessment Report of the Intergovernmental Panel on Climate Change.To cater for the intermittentand skewed character of the daily rainfall,multiple stepwise logistic regression and multiple stepwise linearregression were employed to develop the downscaling models for predicting rainfall occurrence and rainfallamount,respectively.Verification of the simulation of the 1971-2000 climate reveals that the models ingeneral have an acceptable skill in reproducing past statistics of extreme rainfall events in Hong Kong.Theprojection results suggest that,in the 21st century,the annual number of rain days in Hong Kong is expectedto decrease while the daily rainfall intensity will increase,concurrent with the expected increase in annualrainfall.Based on the multi-model scenario ensemble mean,the annual number of rain day is expected todrop from 104 days in 1980-1999 to about 77 days in 2090-2099.For extreme rainfall events,about 90% ofthe model-scenario combinations indicate an increase in the annual number of days with daily rainfall 100mm (R100) towards the end of the 21st century.The mean number of R100 is expected to increase from 3.5days in 1980-1999 to about 5.3 days in 2090-2099.The projected changes in other extreme rainfall indicesalso suggest that the rainfall in Hong Kong in the 21st century may also become more extreme with moreuneven distributions of wet and dry periods.While most of the model-emission scenarios in general projectconsistent trends in the change of rainfall extremes in the 21st century,there is a large divergence in theprojections among different model/emission scenarios.This reflects that there are still large uncertainties inmodel simulations of future extreme rainfall events.     

Effects of the southern oscillation on the probability for climatic categories of monthly rainfall, in a semi-arid region in the southern mid-latitudes

In many regions of the world, planning agricultural and water management activities is usually done based on probabilities for monthly rainfall, taking on values on specified intervals of values. These intervals of monthly rainfall amounts are commonly grouped into three categories: drought, normal rainfall, and abundant rainfall. Changes in the probabilities for occurrence of monthly rainfall amounts within these climatic rainfall categories will influence the decisions farmers and water managers will take (for example, crops to cultivate, flood preparedness, and operations of water reservoirs). This research explores the changes produced by the SO (Southern Oscillation) on the probability that the areal average of monthly rainfall (AAvMR) takes on values belonging to specified climatic rainfall categories. The semi-arid region under study is a major agricultural region in central Argentina; weather effects on agriculture in this region influence the world market of several crops. The evolution of the Southern Oscillation was divided into three phases: LSOI (low Southern Oscillation index phase, that includes ENSO events), NSOI (neutral SOI phase), and HSOI (high SOI phase that includes La Niña–SO events). The following are the criteria defining the three phases of the SO: (1) low SOI (ENSO), where the five-month moving average of the SO index, SOI, is less than −0.5 standard deviation during at least five consecutive months, and is equal to or less than −1 standard deviation during at least one month; (2) high SOI (La Niña–SO), where the SOI is greater than 0.5 standard deviation during at least five consecutive months, and is equal to or greater than 1 standard deviation during at least one month; and (3) neutral SOI (transition between extremes), where the SOI does not correspond to low SOI nor to high SOI. It was found that the Southern Oscillation influences the probability distribution of monthly rainfall only in four months of the year. Findings show that monthly rainfall has a complex response to the evolution of the SO. The response is not restricted to higher probability for occurrence of abundant rainfall or drought categories during low SOI (ENSO) or high SOI (La Niña–SO) episodes, respectively. The LSOI (ENSO) phase influences the AAvMR in several ways: depending on the month, it increases or decreases the probability of the abundant rainfall category. LSOI (ENSO) also increases or decreases, depending on the month, the probability of the normal rainfall category. It also decreases the probability that AAvMR takes on values in the drought category. A similar kind of complex response of monthly rainfall amounts occurs when the active phase is the HSOI (La Niña–SO). The responses are: (1) the probability of the category `drought' increases only in three months of the year, (2) increase or decrease of the probability of the normal rainfall category, depending on the month, and (3) decrease of the probability of the abundant rainfall category. Finally, the effects of NSOI (neutral phase of the SO) are not negligible. Depending on the month, NSOI episodes increase or decrease the probability of drought, or abundant rainfall, or normal rainfall categories.     

大降雨型滑坡临界雨量及潜势预报模型研究

通过对湖北省1975～2002年发生的194次滑坡个例进行分析发现：滑坡时间主要发生在5-8月,占全年总次数的80％左右,与多年月平均雨量分布比较一致;滑坡区域主要位于湖北西部山地,高频中心在三峡库区;滑坡与前期降雨尤其是大降雨关系非常密切,大降雨型滑坡占滑坡总次数的63．1％。利用实效雨量计算方法,确定了大降雨型滑坡临界雨量,以此为依据建立了潜势预报模型。     

How effective is the new generation of GPM satellite precipitation in characterizing the rainfall variability over Malaysia?

We investigated the potential of the new generation of satellite precipitation product from the Global Precipitation Mission (GPM) to characterize the rainfall in Malaysia. Most satellite precipitation products have limited ability to precisely characterize the high dynamic rainfall variation that occurred at both time and scale in this humid tropical region due to the coarse grid size to meet the physical condition of the smaller land size, sub-continent and islands. Prior to the status quo, an improved satellite precipitation was required to accurately measure the rainfall and its distribution. Subsequently, the newly released of GPM precipitation product at half-hourly and 0.1° resolution served an opportunity to anticipate the aforementioned conflict. Nevertheless, related evidence was not found and therefore, this study made an initiative to fill the gap. A total of 843 rain gauges over east (Borneo) and west Malaysia (Peninsular) were used to evaluate the rainfall the GPM rainfall data. The assessment covered all critical rainy seasons which associated with Asian Monsoon including northeast (Nov. - Feb.), southwest (May - Aug.) and their subsequent inter-monsoon period (Mar. - Apr. & Sep. - Oct.). The ability of GPM to provide quantitative rainfall estimates and qualitative spatial rainfall patterns were analysed. Our results showed that the GPM had good capacity to depict the spatial rainfall patterns in less heterogeneous rainfall patterns (Spearman’s correlation, 0.591 to 0.891) compared to the clustered one (r = 0.368 to 0.721). Rainfall intensity and spatial heterogeneity that is largely driven by seasonal monsoon has significant influence on GPM ability to resolve local rainfall patterns. In quantitative rainfall estimation, large errors can be primarily associated with the rainfall intensity increment. 77% of the error variation can be explained through rainfall intensity particularly the high intensity (> 35 mm d^-1). A strong relationship between GPM rainfall and error was found from heavy (~35 mm d^-1) to violent rain (160 mm d^-1). The output of this study provides reference regarding the performance of GPM data for respective hydrology studies in this region.