Effects of temporal scales and space mismatches on the TRMM 3B42 v7 precipitation product in a remote mountainous area

The accurate measurement of precipitation is essential to understanding regional hydrological processes and hydrological cycling. Quantification of precipitation over remote regions such as the Tibetan Plateau is highly unreliable because of the scarcity of rain gauges. The objective of this study is to evaluate the performance of the satellite precipitation product of tropical rainfall measuring mission (TRMM) 3B42 v7 at daily, weekly, monthly, and seasonal scales. Comparison between TRMM grid precipitation and point‐based rain gauge precipitation was conducted using nearest neighbour and bilinear weighted interpolation methods. The results showed that the TRMM product could not capture daily precipitation well due to some rainfall events being missed at short time scales but provided reasonably good precipitation data at weekly, monthly, and seasonal scales. TRMM tended to underestimate the precipitation of small rainfall events (less than 1 mm/day), while it overestimated the precipitation of large rainfall events (greater than 20 mm/day). Consequently, TRMM showed better performance in the summer monsoon season than in the winter season. Through comparison, it was also found that the bilinear weighted interpolation method performs better than the nearest neighbour method in TRMM precipitation extraction.     

1961—2019年青藏高原中东部夏季强降水与大尺度环流的关系

采用一元线性回归、合成分析等方法对1961—2019年青藏高原中东部71个站点夏季强降水与大尺度环流进行了分析,研究结果表明,近年来青藏高原中东部强降水呈增加趋势。在强降水高值年时,青藏高原中东部水汽辐合加强,中纬度西风和热带地区东风带向极移动加强,高层辐散流场、水汽输送以及上升运动条件,共同作用导致了强降水的产生。在强降水低值年时,青藏高原中东部大部水汽异常辐散,区域内的季风水汽输送减弱,西风带和东风带均向赤道移动减弱,高层为气旋式环流异常。通过风暴轴、波作用通量和E-P通量进一步分析发现,当北大西洋地区风暴轴偏强（偏弱）时,瞬变扰动作用加强（减弱）,使得北大西洋地区高纬度西风加速（减弱）,急流出口区的不稳定能量激发了欧洲西北部的异常反气旋（异常气旋）,并通过Rossby波列调控季风输送,导致了青藏高原中东部地区强降水的变化。     

利用树轮宽度资料重建天山中段南坡巴仑台地区过去645年来的降水变化

在分析树木生长对气候要素响应的基础上,利用采自天山中段南坡夫斯坦沟的雪岭云杉树轮宽度年表,重建了巴仑台地区1360~2004A.D.当年7月至次年6月的降水量序列,方差解释量达53%(调整自由度后为52%)。交叉检验结果表明重建方程稳定可信。过去645a以来,巴仑台地区的降水量变化存在12个偏少阶段和12个偏多阶段。巴仑台地区降水量重建序列存在10.7~11、6.7和2.1a的显著准周期及16.5~17.2和2.4~6.6a的较显著准周期,并且在1496A.D.前后发生了降水量由少向多的突变。     

Soil erosion and its response to the changes of precipitation and vegetation cover on the Loess Plateau

Soil erosion is a major threat to our terrestrial ecosystems and an important global environmental problem. The Loess Plateau in China is one of the regions that suffered more severe soil erosion and undergoing climate warming and drying in the past decades. The vegetation restoration named Grain-to-Green Program has now been operating for more than 10 years. It is necessary to assess the variation of soil erosion and the response of precipita- tion and vegetation restoration to soil erosion on the Loess Plateau. In the study, the Revised Universal Soil Loss Equation （RUSLE） was applied to evaluate annual soil loss caused by water erosion. The results showed as follows. The soil erosion on the Loess Plateau between 2000 and 2010 averaged for 15.2 t hm-2 a 1 and was characterized as light for the value less than 25 t hm-2 a-1. The severe soil erosion higher than 25 t hm-2 a-~ was mainly distributed in the gully and hilly regions in the central, southwestern, and some scattered areas of earth-rocky mountainous areas on the Loess Plateau. The soil erosion on the Loess Plateau showed a deceasing trend in recent decade and reduced more at rates more than 1 t hm 2 a 1 in the areas suffering severe soil loss. Benefited from the improved vegetation cover and ecological construction, the soil erosion on the Loess Plateau was significantly declined, es- pecially in the east of Yulin, most parts of Yah＇an prefectures in Shaanxi Province, and the west of Luliang and Linfen prefectures in Shanxi Province in the hilly and gully regions. The variation of vegetation cover responding to soil erosion in these areas showed the relatively higher contribution than the precipitation. However, most areas in Qingyang and Dingxi pre- fectures in Gansu Province and Guyuan in Ningxia Hui Autonomous Region were predomi- nantly related to precipitation.     

长江沿江地区化工产业空间格局演化及影响因素

基于企业数据和空间计量方法,探讨了长江沿江地区2000—2013年化工产业空间格局演化及影响因素。结果表明：化工产业主要分布在上海市和江苏沿江地区;中上游部分地区化工产业呈现明显的增长势头,由3个主要热点区发展到20余个不同规模大小的分布热点,成为化工产业新兴“增长极”;城市主城区化工产业减少而远郊区县增加,分布热点变化也反映了化工产业“郊区化”“园区化”的过程;相对低端基础的行业呈现集聚趋势,其中肥料业集聚明显;相对高端精细的行业呈现扩散趋势,其中合成材料业分散化明显;地区化工产业增长受到环境规制、外商投资、交通区位等因素显著影响,外商投资和交通区位具有显著的促进作用,而环境规制呈现显著的抑制效果。     

层状云中飞机人工增雨作业间距的研究

利用数值试验方法, 设计了4 km, 8 km和20 km 三种飞机增雨播云间距方案, 研究了不同间距对有效区域的影响.从结果分析发现, 实际形成的播云线受水平风场输送作用, 与设计的航线产生了偏离; 不同播云间距形成的投影有效面积、有效作用时段不同, 其时空分布及投影有效面积所对应的地面位置也不尽相同.另外, 提出了增雨效益的数学表达式.效益分析表明, 在相同作业条件下, 8 km间距的增雨效益比20 km间距提高31%, 比4 km间距提高了23%, 4 km间距比20 km间距提高6%, 其物理原因主要是并合作用.最后, 针对交叉和平行播云方案, 提出了设计最佳播云间距的数学表达式.     

“7·21”北京特大暴雨成因分析(I): 天气特征、层结与水汽条件

利用常规、加密自动气象站以及NCEP1°×1°再分析资料,对北京“7.21”特大暴雨过程天气特征和环境条件进行了初步分析。结果表明：1) 降水过程由锋前暖区和锋面降水组成。暖区降水持续时间长,小时雨量大,具有典型的“列车效应”,是造成特大暴雨的主要降水过程。2) 中高层低涡东移、副热带高压北抬、中低层低涡暖式切变线影响是暴雨主要形势特征,暴雨发生在低层低涡右前部暖式切变和高空强辐散气流下方。3) 暴雨过程开始前对流层中低层存在双层湿暖盖。位势不稳定层结的建立机制主要与低层增湿和中层变干的湿度差动平流有关,而低层增湿和中层变干过程与中低层风向转变相关联。4) 暴雨发生前0 — 6 h对流层整层不断增湿,且对流层中高层比低层增湿效应更加明显。与普通暴雨增湿过程和水汽主要集中在对流层中下层不同,深厚的湿度层次,较低的凝结高度和自由对流高度是其显著特征。     

辽宁降水分区变化特征及夏季降水影响因子分析

根据1961—2000年辽宁地区降水资料,将辽宁地区降水划分为4个区,分析各分区降水的年际、年代际、季节变化以及周期特征。结果表明:辽宁南部和东南部地区降水明显减少;自20世纪90年代开始,东南部和南部地区降水显著减少,而中部地区降水增加;东南部地区的夏冬季和南部地区的冬季降水减少,西部地区春季降水增多。周期特征为春季和冬季周期为2 a或4 a,夏季和秋季为10 a。各分区夏季降水的影响因子不同,辽南地区多雨年东亚槽明显加深,东南区多雨年东亚槽略有加深并且偏东;南部和东南部夏季降水与副热带高压系统相关显著;各区夏季降水与太阳黑子负相关较好,其中8月相关显著,南部和中部相关性均好于东南部和西部地区。     

岱海的"中世纪暖期"

内蒙古岱海沉积物近2200a来Rb/Sr比值、CaCO3和有机碳含量的变化展现了包括中世纪暖期（MWP）及小冰期（LIA）等典型气候事件在内的环境演化过程,总体表现为暖期的沉积物Rb/Sr比值低,冷期的则高：CaCO3和有机碳含量则相反。这里,以单一流域化学风化记录表明我国北方存在明显的中世纪暖期,发生时间约900－1200aB.P..主要环境特征表现为流域化学风化的显著增强（低Rb/Sr比值）、生物生产力逐步提高（高有机碳）、湖泊水位大幅度抬升的湖泊沉积记录,其间经历的化学风化是近两千年内最强的,并且其发生时间与全球其他地区基本一致。     

Spatial distribution pattern of seafloor hydrothermal vents to the southeastern Kueishan Tao offshore Taiwan Island

Investigations of the diffusion activities both within and outside the seafloor hydrothermal vents, as well as related mineral genesis, have been one of the key focuses of ocean biogeochemistry studies. Many hydrothermal vents are distributed close to the southern Okinawa Trough on the less-than-30-m deep shallow seafloor off Kueishan Tao, northeast of Taiwan Island. Investigations of temperature, pH and Eh at four depths of hydrothermal plume were carried out near Kueishan Tao at the white(24.83°N, 121.96°E) and yellow(24.83°N, 121.96°E) vents. An 87 h of temperature time series observation-undertaken near the white vent showed that tide is the main factor affecting the background environment. Based on the observed data, 3-dimensional sliced diffusion fields were obtained and analyzed. It was concluded that the plume diffused mainly from north to south due to ebb tide. The yellow vent's plume could effect as far as the white vent surface. From the temperature diffusion field, the vortices of the plume were observed. The Eh negative abnormality was a better indicator to search for hydrothermal plumes and locate hydrothermal vents than high temperature and low pH abnormalities.