Predicting RUSLE (Revised Universal Soil Loss Equation) Monthly Erosivity Index from Readily Available Rainfall Data in Mediterranean Area

Summary Seasonal rainerosivity is important in the structure and dynamics of Mediterranean ecosystems. The present paper contributes to the quantitative assessment of RUSLE's monthly erosion index in a data-scarce Mediterranean region. Therefore, a regionalized relationship for estimating monthly erosion index (EI_30-month) from only three rainfall parameters has been obtained. Knowledge of the seasonal and annual distribution of erosivity index, permit soil and water conservationists to make improved designs for erosion control, water harvesting or small hydraulic structures. Although a few long data sets were used in the analysis, validation with established monthly erosivity index values from other Italian locations, suggest that the model presented (r² = 0.973) is robust. It is recommended to monthly erosivity estimates when experimental data-scarce rainfall become available.     

绵阳市大气降水pH值时空分布及酸雨成因研究

通过对绵阳市9个测点1998－1999年大气降水监测数据的统计分析，并结合历史数据，对大气降水pH值的时空分布及酸雨成因进行了研究。结果表明：绵阳市大气降水酸化严重，除主要受本地区大气污染影响外，还受大气中、长距离输送的影响。     

HEAVY RAINSTORMS IN CHICAGO: INCREASING FREQUENCY,ALTERED IMPACTS,AND FUTURE IMPLICATIONS1

ABSTRACT: Operations of a dense raingage network in the Chicago area since 1989 provided data to assess the temporal and spatial distributions of heavy rainstorms. The 12‐year average was 4.4 storms per year, 40 percent more than in the 1948 to 1980 period, reflecting an ongoing Midwestern increase in heavy rains. The total rainfall from the 53 heavy rainstorms maximized over the city, reflecting previous observations that the influence of the city and Lake Michigan on the atmosphere causes an increase in heavy rains. Impacts from the record high number of eight storms in 2001 revealed that efforts to control flooding including the Deep Tunnel system, had reduced street and basement flooding in the moderate intensity storms, but the two most intense storms, each with 100‐year rainfall values, led to excessive flooding and a need to release flood waters into Lake Michigan. Results suggest continuing increases in the number of heavy rainstorms in future years, which has major implications for water managers in Chicago and elsewhere.     

Not by nutrients alone: a call to broaden the soil fertility initiative

The article discusses agricultural practices in sub-Saharan Africa, especially in terms of maintaining soil fertility. It disagrees with alarmist tendencies in the current debate, exaggerating the state of soil impoverishment in the African region. Nor does it subscribe to the idea that the remedy lies primarily in a massive influx of chemical fertilisers, especially phosphorus.
Instead, the article advocates a more balanced approach, where soil nutrient replenishment, as an improvement in natural capital, is but one part of the investment African agriculture needs. To achieve sustainable rural livelihoods, other forms of capital are also required, such as physical capital, i.e. infrastructure (roads, means of communication); financial capital in the form of credit and savings schemes; and human- and social capital, especially improved access to information and knowledge for farmers as well as improved local organisation and empowerment.
The article reviews nine case studies, taken from different climate zones in the region and representing different soil conditions. All case studies were projects using the participatory learning and action research (PLAR) method, which is discussed in detail.     

PROBABLE MAXIMUM PRECIPITATION FOR THE LOWER RIO GRANDE1

To aid in planning and design of additional flood protection on the Lower Rio Grande, the Hydroraeteorological Branch prepared a probable maximum precipitation study for the International Boundary and Water Commission (United States and Mexico) and the Republic of Mexico. Five drainages from 2,000 to over 17,000 square miles in area between Falcon and Anzalduas Dams including Rio San Juan and Rio Alamo in Mexico are the areas of concern. The great rains of hurricane Beulah, September 19–24, 1967 verified that additional protection is needed. Procedures for estimating probable maximum precipitation (PMP) are described. A particular problem was to estimate rainfall potential for the Sierra Madre Oriental in Rio San Juan and Alamo drainages. These mountains form a north-south windward-facing slope and barrier of over 7000 feet in elevation. A detailed study was made of rains from hurricane Beulah. The storm produced the greatest known rain depths in North America for 50,000 square miles or greater, and durations longer than 48 hours.     

POTENTIAL EFFECTS OF CHANGED CLIMATES ON HEAVY RAINFALL FREQUENCIES IN TIlE MIDWEST1

ABSTRACT: An important question posed by potential future shifts in climate relates to possible shifts in heavy rainfall events (intensity and/or frequency) used to design hydraulic structures. Heavy rain events were defined as those producing amounts having average recurrence intervals of two years or longer for a specific storm period at a given location. Estimates of such heavy rainfall shifts in the humid continental climate of the midwest were derived by using spatial and temporal analogs. Comparisons in areas of relatively warm, wet conditions were made with those having measurably cooler, drier average conditions. The spatial-temporal analogs provided comparative differences in precipitation and temperature similar to the magnitude of changes obtained from GCM estimates. Spatial analogs/analyses indicated 10 to 15 percent increases in the frequency distribution of rain events having recurrence intervals of 5 to 50 years. Two periods of notably drier and warmer conditions during the past 90 years revealed 5 to 15 percent decreases in the number of 2- to 10-year heavy rain events. The suppression percentages showed a strong tendency to increase with increasing recurrence interval from 2 to 10 years.     

北京沙尘天气与源地气象条件的关系

本介绍了影响北京地区沙尘天气的沙尘源地,沙尘暴发生的条件和传输路径,分析了沙尘暴源地的气候要素特征及其对北京地区沙尘天气的影响,说明了北京沙尘天气发生和加剧的原因,影响北京地区沙尘天气的境外源地主要位于哈萨克斯坦,俄罗斯以及蒙古国境内,境内源地主要位于内蒙古和新疆,以及甘肃和青海的部分地区,沙尘天气发生必须具备三个条件：沙源,大风,气流辐合（垂直对流）,有沙源不一定起沙,但无沙源一定不起沙,沙尘暴源地的气候特征主要表现为冬季寒冷,夏季炎热,全年降水稀水,影响北京的沙尘传输路径,最主要的有两条,即西路传输和北路传输,北京沙尘天气与沙尘暴源地的春季降水比较结果表明,北京地区沙尘暴和浮尘天气发生次数与沙尘源区春季大气降水量有比较显的负相关关系,北京扬沙天气的发生与沙源区冬春季降水量相关关系不显,说明北京扬沙天气起因与源区降水没有明显的关系,北京扬沙天气主要受本地的自然条件和人为活动的影响。     

The Volta Lake and Declining Rainfall and Streamflows in the Volta River Basin

This paper looks at the rainfall and streamflow patterns over two distinct time periods, i.e., 1950–1970 and 1971–1991 within the two most prominent catchments in the Volta river system – White Volta and the Oti basins. The first period (1950–1970) represents relatively vegetated catchments and low population whilst the latter (1971–1990) represents intense land use practices resulting from increased population that have severely degraded the environment. These two catchments are among the most significant contributors to the Volta lake. The Volta lake, which was formed between 1962 and 1966 in Ghana and created primarily for hydroelectric power generation, will probably be one of the greatest man-made lakes for a long time. It produces 912MW of electricity at its maximum operating capacity. Recently, there have been declines in the lake levels resulting most probably from inadequate rainfall and/or runoff from the river catchments that feed the lake. Comparisons of runoffs for the two time periods show reductions in mean streamflows of 32.5% at Saboba on the Oti and 23.1% at Nawuni on the White Volta.     

地震作用下结构失稳诱发的塌陷和地裂缝机理分析

分析了地震诱发的地表塌陷和地裂缝机制。通过地裂缝微观机理分析研究发现:(1)地震造成了大量的地裂缝和塌陷,这些破坏的出现与地震发生时造成的瞬间应力变化和结构破坏密切相关;(2)利用结构突变失稳理论来研究岩土体内部结构是可行的。当应力状态满足孔隙结构失稳判别式时,结构元的变形状态将产生一个“跳跃”;(3)地震情况下岩土体颗粒之间有效接触力的增加,使得结构的变形能增大;同时导致颗粒间连接刚度的降低,导致结构的失稳,这些变化又是在瞬间发生和完成的,这就造成了在地震发生时总是伴随着大量的裂缝和塌陷的出现。     

印度夏季风降水周期性研究

印度夏季风降水(ISMR)在南亚气候系统中是一个非常重要的内容,近年来对它的研究日益受到人们的重视。为了深入认识ISMR的变化特征,主要利用Scargle周期图和小波变换研究了1871-2004年间ISMR变化的周期性。结果表明,ISMR的周期性波动非常复杂,相应的周期参数具有明显的时变特征。文中还简单讨论了ISMR周期时变的可能原因。