利用IRS-P5卫星影像生产1：1万地形图的探讨

随着卫星影像处理技术的不断提高,基于立体卫星影像制作1∶1万地形图已成为当前研究热点。本文研究了IRS-P5卫星影像生产1∶1万地形图的工艺流程和相关的技术要求。     

关于青藏高原2485年温度的季节和空间代表性问题

利用树轮宽度重建的青藏高原东北部2485年年均温度曲线一经发表就引起了学界很大关注。本文就该温度曲线的空间代表性问题进行了再次分析,该研究的样本来自青海乌兰和都兰地区,有一定的空间覆盖度。尽管宽度年表用于年均温度重建,但是我们也指出,它与冬半年(上年9月~当年3月)平均温度也显著高相关(r=0.686,p<0.0001)。重建温度曲线不仅与青藏高原东北部地区,而且与我国中北部地区的气象台站同期平均温度记录显著相关。本文进一步通过重建曲线与不同时空尺度CRU TS3.1网格点资料的相关分析,证明2485年年均温度曲线具有一定的全球空间代表性。     

佘山地磁台百年磁暴（一）——太阳周期变化

上海佘山地磁台位于中纬度地区,拥有逾百年的连续地磁场观测资料,非常有利于研究地磁活动的周期规律.本文利用该台站1908至2007年的100年磁暴记录,通过时序叠加、傅里叶分析和小波分析研究了磁暴的周期规律.结果表明：强磁暴具有显著的11年、22年和季节变化;弱中等磁暴没有明显的11年周期,并且季节变化的幅度较小.奇/偶太阳活动周相比,强磁暴的季节变化存在一定的差异,低年季节变化不明显,高年季节变化显著,并且偶数周的变化相对复杂.     

雅鲁藏布江大峡谷地貌响应时间域的定量计算

基岩河道流域地区的地貌演化定量化研究在构造-气候-表面过程关系的探讨中具有十分重要的意义。定量化的分析主要关注气候、构造等外在因素以及河流内在调节机制对地貌演化的影响。本文总结了关于基岩河道流域地貌分析的定量方法和模型的研究进展,并利用DL模型对雅鲁藏布江中下游河段进行了演算,结果显示该地区在稳定状态下地貌演化时间域在0.065～0.420M a之间,反映了该地区快速的地貌演化过程。     

A 28-Year Climatological Analysis of Size Parameters for Northwestern Pacific Tropical Cyclones

A 28-year best track dataset containing size parameters that include the radii of the 15.4 m s^-1 winds （R15） and the 25.7 m s^-1 winds （R26） of tropical cyclones （TCs） in the Northwestern Pacific, the NCEP/ NCAR reanalysis dataset and the Extended Reconstructed Sea Surface Temperature （ERSST） dataset are employed in this study. The climatology of size parameters for the tropical cyclones in the Northwestern Pacific from 1977 to 2004 is investigated in terms of the spatial and temporal distributions. The results show that the major activity of TCs in the Northwestern Pacific is from July to October. A majority of TCs lie over the ocean west of 150°E, and a few TCs can intensify to the Saffir-Simpson （S-S） categories 4, 5. Both R15 and R26 tend to increase as the tropical cyclones intensify. The values of R15 and R26 are larger for intense TCs in the Northwestern Pacific than in the North Atlantic generally. Both R15 and R26 peak in October, and before and after October, R15 and R26 decrease, which is different from the case in the North Atlantic. The smaller R15s and R26s occur in a large range over the Northwestern Pacific, while the larger R15s and R26s mainly lie in the eastern ocean from Taiwan Island to the Philippine Islands where many tropical cyclones develop in intense systems. The tropical cyclones with size parameters of R15 or R26 on average take a longer time to intensify than to weaken, and the weak tropical cyclones have faster weakening rates than intensification rates. From 1977 to 2004, the annual mean values of R15 increase basically with year; during the 28-year period, the value of R15 increases by 52.7 kin, but R26 does not change with year obviously.     

Trend estimation and univariate forecast of the sunspot numbers: Development and comparison of ARMA, ARIMA and Autoregressive Neural Network models

In the present study, a prominent 11-year cycle, supported by the pattern of the autocorrelation function and measures of Euclidean distances, in the mean annual sunspot number time series has been observed by considering the sunspot series for the duration of 1749 to 2007. The trend in the yearly sunspot series, which is found to be non-normally distributed, is examined through the Mann-Kendall non-parametric test. A statistically significant increasing trend is observed in the sunspot series in annual duration. The results indicate that the performance of the autoregressive neural network-based model is much better than the autoregressive moving average and autoregressive integrated moving average-based models for the univariate forecast of the yearly mean sunspot numbers.     

Astronomical time-scale for physical property records from Quaternary sediments of the northern North Atlantic

Deep sea sediment cores taken between 50° and 75°N in the North Atlantic, in water depths varying between 1340 and 3850 m, were examined to provide an astronomically calibrated late Quaternary time-scale based on physical property records. Magnetic susceptibility and gamma ray attenuation porosity evaluator (GRAPE) density changes of these cores revealed significant responses to orbital forcing in the eccentricity (100 kyr), obliquity (41 kyr) and precessional (23, 19 kyr) bands. At 75°N (Greenland Sea), a response to obliquity forcing was weak despite the fact that it should become more pronounced in sediments at high latitudes. Application of bandpass filtering at the obliquity period (41 kyr), however, showed that variance at this period did exist in the magnetic susceptibility record, but at a very low power. At 50°N stacked curves of magnetic susceptibility correlated strongly with the SPECMAP curve for the past 500 ka. Since about 65 ka, dropstone layers are recorded in both magnetic susceptibility and GRAPE data of Rockall Plateau sediments. Although Rockall Plateau sediments show peaks in physical properties that correlate with Heinrich events (H₁, H₂, H₄, H₅, H₆), such a relationship was not readily observed in Norwegian-Greenland Sea records. Heinrich events at Rockall Plateau sites indicate a northward flow of icebergs in the eastern North Atlantic. This flow pattern and the presence of Heinrich events during the past 65 ka raise the questions of whether similar events occurred before this time period, and to what kind of ice sheet dynamics and climatic-oceanographic conditions favoured major iceberg surges from the Laurentide ice sheet to the North Atlantic at 50°N.     

Luni-solar 18.6-year signal in tree-rings from Argentina and Chile

Spectrum analysis of 32 tree-ring chronologies from Argentina and Chile yields evidence for two peaks with periods 19.2±1.6 years (30 out of 32 records) and 10.5±0.4 years in 22 instances. Tests by thet-statistic show that the long-period peak is significant at a confidence level of 99%. This signal is identified as the luni-solar 18.6-year M _n term reported earlier byCurrie (1983) in two treering chronologies from the same region, and later in tree-rings from North America, Tasmania, New Zealand, and South Africa (Currie, 1991a-c). Amplitude and phase of the M _n signal are nonstationary with respect to both time and geography. In particular, abrupt 180° phase changes in wave polarity are often observed.     

The marine dynamics and changing trend off the modern Yellow River mouth

Topography around the Yellow River mouth has changed greatly in recent years, but studies on the current state of ma- rine dynamics off the Yellow River mouth are relatively scarce. This paper uses a two-dimension numerical model(MIKE 21) to reveal the tidal and wave dynamics in 2012, and conducts comparative analysis of the changes from 1996 to 2012. The results show that M2 amphidromic point moved southeastward by 11 km. It further reveals that the tides around the Yellow River mouth are relatively stable due to the small variations in the tidal constituents. Over the study period, there is no noticeable change in the distribution of tidal types and tidal range, and the mean tidal range off the river mouth during the period studied is 0.5–1.1 m. However, the tidal currents changed greatly due to large change in topography. It is observed that the area with strong tidal currents shifted from the old river mouth(1976–1996) to the modern river mouth(1996–present). While the tidal current speeds decreased continually off the old river mouth, they increased off the modern river mouth. The Maximum Tidal Current Speed(MTCS) reached 1.4 m s-1, and the maximum current speed of 50-year return period reached 2.8 m s-1. Waves also changed greatly due to change in topography. The significant wave height(H1/3) of 50-year return period changed proportionately with the water depth, and the ratio of H1/3 to depth being 0.4–0.6. H1/3 of the 50-year return period in erosion zone increased continually with increasing water depth, and the rate of change varied between 0.06 and 0.07 m yr-1. Based on the results of this study, we infer that in the future, the modern river mouth will protrude gradually northward, while the erosion zone, comprising the old river mouth and area between the modern river mouth and the old river mouth(Intermediate region) will continue to erode. As the modern river mouth protrudes towards the sea, there will be a gradual increase in the current speed and decrease in wave height. Conversely, the old river mouth will retreat, with gradual decrease in current speed and increase in wave height. As more coastal constructions spring up around the Yellow River mouth in the future, we recommend that variation in hydrodynamics over time should be taken into consideration when designing such coastal constructions.     

Evaluation of GEV model for frequency analysis of annual maximum water levels in the coast of United States

The three-parameter generalized-extreme-value (GEV) model has been recommended by FEMA [FEMA (Federal Emergency Management Agency of the United States), 2004. Final Draft Guidelines for Coastal Flood Hazard Analysis and Mapping for the Pacific Coast of the United States. http://www.fema.gov/library/viewRecord.do?id=2188] for frequency analysis of annual maximum water levels in the Pacific coast of the United States. Yet, the GEV model's performance in other coastal areas still needs to be evaluated. The GEV model combines three types of probability distributions into one expression. The probability distributions can be defined by one of the three parameters of the GEV model. In this study, annual maximum water levels at nine water-level stations with long history data (more than 70 years) were chosen for analysis in five coastal areas: Pacific, Northeast Atlantic, East Atlantic, Southeast Atlantic, and Gulf of Mexico coasts. Parameters of the GEV model are estimated by the maximum likelihood estimation (MLE) method. Results indicate that probability distributions are characterized by the GEV Type III model at stations in the Pacific, Northeast, and East Atlantic coastal areas, while they are described by GEV Type II in stations of the Southeast Atlantic and Gulf of Mexico coastal areas. GEV model predictions of extreme water levels show good correlation to observations with correlation coefficients of 0.89 to 0.99. For predictions of 10% annual maximum water levels, the GEV model predictions are very good with errors equal to or less than 5% for all nine stations. Comparison of observations and GEV model estimations of annual maximum water levels for the longest recorded return periods, close to 100 years, revealed errors equal to or less than 5% for stations in the Pacific and Northeast Atlantic coastal areas. However, the errors range from 10% to 28% for other stations located in the East and Southeast Atlantic coasts as well as Gulf of Mexico coastal areas. Findings from this study suggest caution regarding the magnitudes of errors in applying the GEV model to the East and Southeast Atlantic coasts and Gulf of Mexico coast for estimating 100-year annual maximum water levels for coastal flood analysis.