Probabilistic forecasting of drought: a hidden Markov model aggregated with the RCP 8.5 precipitation projection

The creeping characteristics of drought make it possible to mitigate drought’s effects with accurate forecasting models. Drought forecasts are inevitably plagued by uncertainties, making it necessary to derive forecasts in a probabilistic framework. In this study, we proposed a new probabilistic scheme to forecast droughts that used a discrete-time finite state-space hidden Markov model (HMM) aggregated with the Representative Concentration Pathway 8.5 (RCP) precipitation projection (HMM-RCP). The standardized precipitation index (SPI) with a 3-month time scale was employed to represent the drought status over the selected stations in South Korea. The new scheme used a reversible jump Markov chain Monte Carlo algorithm for inference on the model parameters and performed an RCP precipitation projection transformed SPI (RCP-SPI) weight-corrected post-processing for the HMM-based drought forecasting to perform a probabilistic forecast of SPI at the 3-month time scale that considered uncertainties. The point forecasts which were derived as the HMM-RCP forecast mean values, as measured by forecasting skill scores, were much more accurate than those from conventional models and a climatology reference model at various lead times. We also used probabilistic forecast verification and found that the HMM-RCP provided a probabilistic forecast with satisfactory evaluation for different drought categories, even at long lead times. In a drought event analysis, the HMM-RCP accurately predicted about 71.19 % of drought events during the validation period and forecasted the mean duration with an error of less than 1.8 months and a mean severity error of <0.57. The results showed that the HMM-RCP had good potential in probabilistic drought forecasting.     

Using a global reference sample set and a cropland map for area estimation in China

A technically transparent and freely available reference sample set for validation of global land cover mapping was recently established to assess the accuracies of land cover maps with multiple resolutions. This sample set can be used to estimate areas because of its equal-area hexagon-based sampling design. The capabilities of these sample set-based area estimates for cropland were investigated in this paper. A 30-m cropland map for China was consolidated using three thematic maps (cropland, forest and wetland maps) to reduce confusion between cropland and forest/wetland. We compared three area estimation methods using the sample set and the 30 m cropland map. The methods investigated were: (1) pixel counting from a complete coverage map, (2) direct estimation from reference samples, and (3) model-assisted estimation combining the map with samples. Our results indicated that all three methods produced generally consistent estimates which agreed with cropland area measured from an independent national land use dataset. Areas estimated from the reference sample set were less biased by comparing with a National Land Use Dataset of China (NLUD-C). This study indicates that the reference sample set can be used as an alternative source to estimate areas over large regions.     

Key preprocessing technology and its application for CBM AVO analysis

The hazards of amplitude versus offset (AVO) technique mostly applied in seismic explorations for predicting coalbed methane (CBM) content mainly derive from multi-stage amplitude modifications during seismic signal preprocessing. The modifications are undoubtedly necessitated by improving high signal-to-noise ratio (SNR) and high resolution, and achieve high fidelity to some extent; and nevertheless lead to an unfavorable possibility to implement CBM AVO analysis. Similar to sandstone reservoir with gas, AVO analysis preprocessing for CBM reservoir strictly abides by a relative amplitude preserved (RAP) principle and particularly emphasizes on preserving the evanescent class IV AVO anomaly. As for those indispensable dealings with linear noise attenuations, near-surface variety compensations and time/depth spatial imaging, the key technologies adapted to CBM AVO preprocessing should use radial trace (RT) filter, refined surface-consistent amplitude compensation (SCAC), and RAP Kirchhoff prestack time migration (PSTM). The theoretical analysis and one real 3D example in this paper demonstrate that three key technologies compliant to RAP principle in CBM AVO preprocessing can preserve the class IV AVO anomaly and benefit an operation of CBM AVO analysis and an improvement of CBM evaluation.     

全面禁止核试验条约组织(CTBTO)筹备委员会核查工作组(B组)会议相关的技术名词解释

参与全面禁止核试验条约组织（CTBTO）筹备委员会核查工作组（B组）会议,以及相关的技术交流活动、核查系统建设等工作,涉及到较为复杂的技术系统和专业技术。为便于从事相关管理和技术工作的专家参考,本文系统地编译了相关技术名词,以供参考。     

Distribution and evolution of water chemistry in Heihe River basin

Surface- vs. ground-water chemistry in the Heihe River basin, assessed through field sampling of precipitation, surface water and groundwater, allowed geographical zones and chemical types to be differentiated. The geographical zones included: alpine ice-snow (>3,900 m), alpine meadow (3,400–3,900 m), mountain forest and shrub (2,600–3,400 m), mountain grassland (1,900–2,600 m) and desert grassland (1,500–1,900 m). Groundwater chemical types included: (1) mountain fissure and piedmont gravel, bicarbonate, (2) piedmont diluvial, alluvial and lacustrine plain, sulphate, and (3) desert salt-accumulating depression, chloride. Since the 1960s, large volumes of river water diverted for irrigation have been found to re-emerge as spring water at the edge of alluvial fans and then reintegrate the Heihe River. After a number of reuses and re-emergences in the middle reaches, the rivers level of mineralization has doubled. Hydrological changes have resulted in the marked degradation of aquatic habitats, and caused substantial, and expanding, land salinization and desertification. Solving these largely anthropogenic problems requires concerted, massive and long-term efforts.     

呼和浩特市大气污染与天气气候的关系

利用1990～2002年呼和浩特市区空气污染物TSP、SO2、NOx浓度的实际监测数据,分析了呼和浩特市大气污染物浓度变化的时空分布特征、大气污染与天气条件的关系。呼和浩特市市区主要以煤烟型污染为主,冬、春季比夏、秋季污染严重,采暖期比非采暖期污染严重,市区中心污染最严重。污染物的排放量及大气的稳定度状态是城市大气污染的主要影响因子,天气变化是城市大气污染物浓度变化的主导因素,局地环流是决定城市污染物分布的关键因素。因此,不同季节排污量的变化、天气条件是制作呼和浩特市大气污染预报的主要依据。     

地面臭氧的变化规律和计算方法的初步研究Ⅰ.紫外波段

通过对广州鼎湖山近地面O3、NOx、太阳辐射、气象参数等项目的观测和理论分析,研究了地面O3与NOx等微量气体及太阳辐射的变化规律,详细讨论了紫外波段、不同天气条件地面O3与NOx,光化学反应、气溶胶、光化辐射等之间复杂的关系.用光能量传输与守恒的观点来考虑大气中与紫外辐射有关的主要过程,并以此来研究大气光化学过程中所遵循的能量规律,建立了一个简单、实用、省时的统计模式,用于计算地面O3浓度.结果表明,不同情况下计算值与观测值均吻合较好.     

内蒙古冬季主要极端气候事件的环流影响因素分析

过去的几十年中,内蒙古冬季(11月至次年2月)出现极端气候事件的年份并不多。对于极端低温事件的发生,在中西部地区极少出现,多数发生在锡林郭勒盟中部及以东地区。特别是自1986年气候转暖以来,在暖的大背景下,更是较少出现极端低温事件;极端降水事件在冬季各月中也有发生,每个月有其各自的特点。文章着重研究分析11月的极端降水事件。通过对海温、大气环流的异常进行分析和研究,找出影响内蒙古冬季极端降水、极端低温的关键性因子,对今后的极端气候事件预测工作有所帮助和借鉴。     

辽东五龙与青城子矿集区成矿和保存条件对比及其深部找矿意义

位于辽东地区的青城子与五龙矿集区尽管成矿大地构造背景相似,但其成矿时代、赋矿围岩及控矿构造却有明显的差别.根据对青城子矿集区金-多金属矿床及五龙矿集区五龙金矿床和四道沟金矿床成矿大地构造背景、赋矿围岩、岩浆活动时代及产状、控矿及容矿构造、成矿时代和剥蚀程度新数据及已有资料的综合分析,认为青城子矿集区金多金属矿床及五龙矿...