The research of below-cloud scavengingof rainwater in Guilin City

Ｔｈｅｒｅｓｅａｒｃｈｏｆｂｅｌｏｗ－ｃｌｏｕｄｓｃａｖｅｎｇｉｎｇｏｆｒａｉｎｗａｔｅｒｉｎＧｕｉｌｉｎＣｉｔｙＢａｉＹｕｈｕａ；ＹａｏＲｏｎｇｋｕｉ；ＬｉＸｉｎ；ＴａｎｇＸｉａｏｙａｎ（ＴｈｅＤｅｐａｒｔｍｅｎｔｏｆＴｅｃｈｎｉｃａｌＰｈｙｓｉｅ...     

Climate changes in the past century and radial increment of pine in the Southern Ural steppe

Changes in the main climatic factors (air temperature and total precipitation) and their effect on the radial increment of Scots pine (Pinus sylvestris L.) over the period from 1933 to 2002 were studied in an insular pine forest growing in the steppe zone of the Southern Urals. Evidence for a significant increase in the amount of precipitation and air temperature in the second half of this period was obtained. Functions of response of radial increment indices to climatic parameters were analyzed. Relative contributions of air temperature and precipitation to variation in the radial increment of pine in different time intervals proved to differ in relation to climate changes during the past century.     

湖北省降水分区研究

利用湖北省19个国家级气象台站1956~2009年逐月降水资料,采用分层聚类方法,基于聚类分析碎石图和聚类树状图来探索最适宜的分区方案,对湖北省全年、逐月降水进行了分区,并结合西太平洋副热带高压的移动探讨了分区的合理性,之后逐区进行了自相关分析和趋势分析。结果表明：湖北省全年降水分区为5区,1~12月降水分区分别为3、3、4、3、5、4、3、3、3、4、3、3个区。各月降水分区的差异性与西太平洋副热带高压的南北移动有密切关系,副高脊线在北纬18°以南、北纬20°以北,以及缓慢南退过程中,分区形式有较大差异。自相关分析以及趋势分析结果表明单一气象站不能代表所在分区的气候特点,而所在分区又不能代表湖北省的气候特点,基于不同目的,进行分区和综合,将有助于研究特定区域的气候特点     

Runoff variation affected by precipitation change and human activity in Hailiutu River basin,China

For recent years, runoff generation and hydrological processes in Hailiutu River basin have been greatly changed by climate change and human activity, especially water and soil conservation construction. In this study, the trends in precipitation, evapotranspiration (ET) and river runoff as well as the effects of precipitation change and human activity on runoff variation have been studied. The results showed that during 1960–2000, annual precipitation and river runoff, monthly precipitation and ET in September and October as well as monthly runoff in all months showed a significant decrease. In addition, peak flow and base flow had a large decrease. Under the joint influence of precipitation change and human activity, the mean annual runoff decreased by 35 million m³ from the baseline period (1960–1985) to the change period (1986–2000), which accounted for 60.9% and 39.1% of the total runoff decrease, respectively. Precipitation change played a primary role in the decrease of annual runoff whereas human activity, particularly water and soil conservation construction, also had remarkable impacts on runoff variation.     

中国西南酸雨区降水化学特征研究进展

西南酸雨区为我国主要酸雨沉降区,且是全球三大喀斯特集中分布区之一.本文将该区9个地点的降雨资料进行了总结、整理和分析,数据包括pH值和主离子成分(Cl~-、SO_4~(2-)、NO_3~-、Ca~(2+)、NH_4~+、Mg~(2+)、K~+、Na~+).该地区降雨中的主要阴离子为SO_4~(2-)和NO_3~-,主要阳离子为Ca~(2+)和NH_4~+.与我国其它地区相比,其酸性离子、碱性离子和总离子浓度均普遍高于东南地区、而低于我国北方地区.西南酸雨区主要以pH值为4.5~5.6的弱酸性降雨为主,占总降雨频次的58%左右.根据酸、碱性离子的相关性、中和因子等分析结果,该区雨水中的酸性物质可能受到了碱性离子的中和作用,其中起主要中和作用的离子为Ca~(2+)和NH_4~+.将该区雨水pH值和酸、碱性离子浓度与我国其它地区进行对比研究发现,西南酸雨区降雨受到的中和作用要强于东南地区,但弱于北方地区的降雨.通过对西南酸雨区降雨中主要离子来源的分析和估算,降雨中的酸性离子SO_4~(2-)和NO_3~-主要来自于人为污染;99.7%的Ca~(2+)和84.0%的Mg~(2+)为陆源贡献,这可能与西南地区碳酸盐岩广泛分布有关.     

IS IT REALISTIC TO DEFINE A 100-YEAR DROUGHT FOR WATER MANAGEMENT?1

ABSTRACT: The concept of recurrence interval has been used for years in engineering designs. Can the same concept be applied to the drought analysis? This paper uses the plotting position method to define drought of various recurrence intervals based on stream-flow data. The method of truncation level was applied to the same data to examine the defined drought. Based on the method of truncation level, drought duration and its corresponding flow deficit were investigated. Eighteen flow gage stations from the Scioto River Basin in Ohio were selected for the study. The results show that flows of 100-year droughts using the plotting position method are practically nil. On the other hand, flows of droughts using the truncation method are gradually decreasing with an increase in truncation level, where flows of 95 percent are approximately equal to those of two-year droughts defined by the plotting position. It is also shown that there is a strung correlation between drought duration and deficit.     

Long-term depletion of calcium and other nutrients in eastern US forests

Both harvest removal and leaching losses can deplete nutrient capital in forests, but their combined long-term effects have not been assessed previously. We estimated changes in total soil and biomass N, Ca, K, Mg, and P over 120 years from published data for a spruce-fir site in Maine, two northern hardwood sites in New Hampshire, central hardwood sites in Connecticut and Tennessee, and a loblolly pine site in Tennessee. For N, atmospheric inputs counterbalance the outputs, and there is little long-term change on most sites. For K, Mg, and P, the total pool may decrease by 2%–10% in 120 years depending on site and harvest intensity. For Ca, net leaching loss is 4–16 kg/ha/yr in mature forests, and whole-tree harvest removes 200–1100 kg/ha. Such leaching loss and harvest removal could reduce total soil and biomass Ca by 20%–60% in only 120 years. We estimated unmeasured Ca inputs from rock breakdown, root-zone deepening, and dry deposition; these should not be expected to make up the Ca deficit. Acid precipitation may be the cause of current high leaching of Ca. Although Ca deficiency does not generally occur now in acid forest soils, it seems likely if anthropogenic leaching and intensive harvest removal continue.     

PREDICTING MEASUREMENT ERROR OF AREAL MEAN PRECIPITATION DURING EXTREME EVENTS1

ABSTRACT: The areal mean precipitation (AMP) over a catchment is normally calculated using point measurements at rainfall gages. Error in AMP estimates occurs when an insufficient number of gages are used to sample precipitation which is highly variable in space. AMP error is investigated using historic, severe rainfalls with a set of hypothetical catchments and raingage networks. The potential magnitude of error is estimated for typical gage network densities and arrangements. Possible sources of error are evaluated, and a method is proposed for predicting the magnitude of error using data that are commonly available for severe, historic rainfall.     

四川酸性物湿沉降模式及预测

酸沉降是一复杂的大气物理和化学过程，涉及诸多复杂影响因素。目前，我国酸雨湿沉降模式还仅限于模拟云下洗脱成酸过程，而对云中的成酸过程还未进行深入研究，这不仅在理论上不完善，而且更重要是在许多情况下与我省实际情况不符。本课题针对四川省特定的地理，气象特点和严重的大气污染情况，并借鉴国外研究成果，提出了考虑酸性沉降的云中和云下成酸过程和各种影响因素的综合酸雨湿沉降模式，并根据此模式来估算和预测四川省酸雨     

Watershed factors affecting stream acidification in the White Mountains of New Hampshire,USA

The streams tributary to acidic Cone Pond, pH 4.5–4.8, and circumneutral Black Pond, pH 5.3–6.4, in the White Mountains of New Hampshire, USA, were monitored for a year. The watersheds of these two ponds were characterized in terms of geology and stream hydrology. Chemical gradients and patterns in rock weathering and groundwater discharge explain many of the differences in mineral content and acidity of the streams. The rocks of Black watershed produced an average of ten times the equivalent of basic cations as rocks from Cone watershed. This is on the same order as the difference in acidity of the two streams. Down-stream changes in stream chemistry follow differing patterns, but reflect the same principle of residence time and water path length controlling chemical evolution of streamwater. Watershed and aquatic managers may use these parameters in an inexpensive and simple assessment of the susceptibility of individual streams and ponds to acidification. A method is recommended to determine quickly the potential influence of bedrock type to aquatic chemistry.