Assimilating snow observations to snow interception process simulations

Snow interception is a crucial hydrological process in cold regions needleleaf forests, but is rarely measured directly. Indirect estimates of snow interception can be made by measuring the difference in the increase in snow accumulation between the forest floor and a nearby clearing over the course of a storm. Pairs of automatic weather stations with acoustic snow depth sensors provide an opportunity to estimate this, if snow density can be estimated reliably. Three approaches for estimating fresh snow density were investigated: weighted post-storm density increments from the physically based Snobal model, fresh snow density estimated empirically from air temperature (Hedstrom, N. R., et al. [1998]. Hydrological Processes, 12, 1611–1625), and fresh snow density estimated empirically from air temperature and wind speed (Jordan, R. E., et al. [1999]. Journal of Geophysical Research, 104, 7785–7806). Automated snow depth observations from adjacent forest and clearing sites and estimated snow densities were used to determine snowstorm snow interception in a subalpine forest in the Canadian Rockies, Alberta, Canada. Then the estimated snow interception and measured interception information from a weighed, suspended tree and a time-lapse camera were assimilated into a model, which was created using the Cold Regions Hydrological Modelling platform (CRHM), using Ensemble Kalman Filter or a simple rule-based direct insertion method. Interception determined using density estimates from the Hedstrom-Pomeroy fresh snow density equation agreed best with observations. Assimilating snow interception information from automatic snow depth measurements improved modelled snow interception timing by 7% and magnitude by 13%, compared to an open loop simulation driven by a numerical weather model; its accuracy was close to that simulated using locally observed meteorological data. Assimilation of tree-measured snow interception improved the snow interception simulation timing and magnitude by 18 and 19%, respectively. Time-lapse camera snow interception information assimilation improved the snow interception simulation timing by 32% and magnitude by 7%. The benefits of assimilation were greatly influenced by assimilation frequency and quality of the forcing data.     

三种统计预报模型在江苏省道路低温预警中的应用

为了更好地开展道路交通低温灾害的预警,减轻道路结冰给车辆行驶造成的危害,本文利用2012—2016年江苏省高速公路网AWMS系统交通气象观测数据,在对路面低温发生规律进行分析的基础上,结合多元线性回归、朴素贝叶斯以及支持向量机3种统计预报方法,开展了路面低温预警的统计建模与预报试验。结果表明:(1)江苏全省高速公路网路面温度出现0℃以下、-2℃以下、-5℃以下的低温频率均呈"北高南低"分布。(2)全省高速公路网路面温度出现0℃以下的低温时次大多在15:00到次日06:00之间。(3)在对京沪高速M9308站的单站建模与预报试验中发现,路面低温预报因子组合中以13:00气温、13:00—18:00气温变温、13:00路面温度、13:00—18:00路面变温、13:00路基温度、13:00—18:00路基变温、18:00相对湿度和18:00风速U分量为自变量组合的预报方程效果最好,3种方法中以朴素贝叶斯模型的预报准确率最高;(4)就全省高速公路网而言,3种统计预报模型的路面低温预报准确率均超过75%,通过对全路网路面低温预报的试验结果对比发现,多元线性回归方法对江苏省北部路网的预报效果最好,预报准确率大多在85%以上;而支持向量机模型对江苏省南部路网的预报效果最好,大部分站点的低温预报准确率达95%以上。     

VP型垂直摆倾斜仪观测频带的分析及改进

从仪器原理、传递函数和观测数据等方面分析目前在网进行1 Hz采样的VP型垂直摆倾斜仪在2~60 s周期内的频率特性,认为该仪器可以观测到频带内的信号变化,但因处于过渡带,观测幅度较真实幅度削弱约20~40 dB。对VP型垂直摆倾斜仪观测频带进行拓展,使2~60 s周期内的观测信号由之前的过渡带进入到仪器的通频带,结果与相同采样率的其他定点形变仪器的观测效果相同,将地倾斜观测量转换为加速度表达后,其幅频特性符合全球地震背景噪声模型。改进后的VP型垂直摆倾斜仪对于远距离震级不大的同震体波震相记录效果略优于改进前,但受地脉动影响,在识别非地脉动信号时需要采用更精细的方法和手段来提高识别效果。     

持续光照下光强对北极海域芬迪亚历山大藻生长及产毒的影响

以格陵兰岛西部、冰岛沿海和楚科奇海的芬迪亚历山大藻为受试对象,并以缅因湾的芬迪亚历山大藻藻株做为参照,从沉积物或海水中的休眠孢囊或营养细胞中分离到12株目标藻种,并在实验室建立纯培养系。然后对这些地域的藻种在不同光照下生长特性的比较、对毒素含量进行研究,发现芬迪亚历山大藻在持续光照条件下最适的生长光强范围是38—91μmol×m~(–2)×s~(–1)。另外,在所有分离到的12株藻细胞中均未检测到脱氨甲酰基膝沟藻毒素2(dc GTX2),大部分藻细胞都在光强较强时,即生长速率低时表现出更高的细胞毒素含量和毒性。     

Late Pleistocene - Holocene slip history of the Langshan-Seertengshan piedmont fault (Inner Mongolia,northern China) from cosmogenic <Superscript>10</Superscript>Be dating on a bedrock fault scarp

Offset geomorphic features and deformed late Quaternary strata indicate active deformation along the Langshan-Seertengshan piedmont fault (LSPF), one of the most active faults in the Hetao fault zone in Inner Mongolia, North China. The widespread occurrence of bedrock fault scarps along the LSPF offers excellent opportunity to examine the faulting history. Using cosmogenic ¹⁰Be exposure dating, we measured the exposure ages of the western Langshankou scarp, located in the middle segment of the LSPF. Our data revealed at least two earthquakes that occurred at 22.2±3.3 ka and 7.2±2.4 ka, respectively. These events are consistent with previous paleoseismic trench studies. The regression of the relationship between the age and sampling height along the scarp yield a fault slip rate of 0.10 +0.05/-0.06 mm/yr, which is significantly lower than the average post-late Pleistocene fault slip rate of ~1 mm/yr, as estimated from the offset of the T2 terraces by previous studies. This indicates that the slip of the LSPF may have been accommodated by other fault branches.     

Retrieve sea surface salinity using principal component regression model based on SMOS satellite data

The sea surface salinity(SSS) is a key parameter in monitoring ocean states. Observing SSS can promote the understanding of global water cycle. This paper provides a new approach for retrieving sea surface salinity from Soil Moisture and Ocean Salinity(SMOS) satellite data. Based on the principal component regression(PCR) model, SSS can also be retrieved from the brightness temperature data of SMOS L2 measurements and Auxiliary data. 26 pair matchup data is used in model validation for the South China Sea(in the area of 4?–25?N, 105?–125?E). The RMSE value of PCR model retrieved SSS reaches 0.37 psu(practical salinity units) and the RMSE of SMOS SSS1 is 1.65 psu when compared with in-situ SSS. The corresponding Argo daily salinity data during April to June 2013 is also used in our validation with RMSE value 0.46 psu compared to 1.82 psu for daily averaged SMOS L2 products. This indicates that the PCR model is valid and may provide us with a good approach for retrieving SSS from SMOS satellite data.     

Petroleum accumulation conditions of the Paleogene Shahejie formation in Qingdong Sag of Bohai Bay Basin,Eastern China

Qingdong Sag is a potential area for oil and gas exploration in Bohai Bay Basin of Northern China. In order to find a direction for the subsequent exploration of Jiyang Depression, oil and gas accumulation conditions of Qingdong Sag are studied in details by using geochemistry, sequence stratigraphy, sedimentology, and petroleum geology methods, integrated with geological, seismic, and testing data. The results show that the Shahejie Formation in the Qingdong Sag was mainly deposited in deltaic and lacustrine settings. The upper part of member 4 of the Shahejie Formation formed in delta, beach bar, low stand fan, and submarine fan. Three tectonic settings (extensional, strike-slip, and extension and strike-slip compound) were recognized. Accumulation of oil and gas in Qingdong Sag is influenced by structures and reservoir and cap rock conditions. Six oil and gas accumulation systems were found, which are north fault terrace-north subdepression oil and gas accumulation system, west slope belt and gas accumulation system, middle Horst oil and gas accumulation system, south Horst oil and gas accumulation system, drape structural belt of Qingdong 2 well oil and gas accumulation system, and Qingnan area oil and gas accumulation system. Members 3 and 4 of the Shahejie Formation are the main target of hydrocarbon source rocks because the organic matter abundance is up to the standard of good hydrocarbon source rocks. The north of the Qingdong Sag and second slope-break belt should be the key objectives of exploration in the future.     

A rock fall of the north Zhongtiao Shan fault and the Yongji earthquake in 793, Shanxi Province,North China

Earthquake is the main driving factor of landslides, and a large number of empirical formulas for seismic parameters have been proposed. This article studies a rock avalanche triggered by a paleoearthquake and two trial trenches in Yongji, Shanxi Province. Six quartz samples were collected from different parts on the top of the boulder, and the youngest ¹⁰Be exposure age is 1173 ± 123 years, which is considered as the occurrence time of the rock fall. The trenches excavated near the boulder infer that there was an earthquake between 2000 ± 110 and 465 ± 45 cal a bp in the north Zhongtiao Shan (NZS) fault with a maximum vertical displacement of 1.5 m and the surface rupture length (SRL) of ~35 km corresponding to a magnitude (M _S) of 6.70 ± 0.12 based on the displacement. Taking into account the occurrence time and minimum magnitude triggering the rock fall, the latest paleoearthquake revealed by trenches may be the forcing factor. Furthermore, according to historical records of Yongji, the earthquake of magnitude 6 in ad 793 is in consistency with the occurrence time and magnitude of the earthquake triggering the landslide. Therefore, the rock fall is related to the paleoearthquake revealed by the trenches, which may be the 793 Yongji earthquake.     

A WOE method for urban growth boundary delineation and its applications to land use planning

The aim of this study is to develop a new approach for delineating urban growth boundaries (UGBs) by applying the weight of evidence (WOE) method to land suitability assessments. Rapid urbanization is causing urban areas to encroach on agricultural land in China, posing a threat to national food security. Land use planning with clear delineation of UGBs is an effective method for controlling urban expansion. However, existing methods for delineating UGBs are typically complex or involve arbitrary decision-making. To address these drawbacks, we introduced the WOE method to develop a new UGB delineation approach, and applied this approach to a case study in the city of Jinan, China. This application achieved satisfactory accuracy; therefore, we concluded that the WOE method was an objective and effective approach to land use suitability assessments and UGB delineation. Land use planning could be benefitted considerably from the application of this method to land allocation and other planning decisions.