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1.
Engdahl M.E. Pulliainen J.T. Hallikainen M.T. 《Geoscience and Remote Sensing Letters, IEEE》2004,1(3):228-231
The performance of interferometric synthetic aperture radar (INSAR)-based boreal forest stem volume retrieval is strongly affected by weather conditions around the time of the SAR image acquisitions. Since weather conditions cannot be controlled, the suitability of a particular interferometric pair for stem volume retrieval can only be assessed afterward. In this letter, four objective measures based on observed forest coherence were compared in assessing the suitability of interferometric pairs for stem volume retrieval. These suitability measures can be used to identify the best and worst pairs, i.e., the ones with the most and least favorable weather conditions. Stem volume retrievals were performed using single European Remote Sensing (ERS-1/2) Tandem interferometric pairs by inverting a backscattering-coherence model for boreal forests. A total of 14 ERS Tandem image pairs acquired in varying weather conditions were studied, and the stem volume retrieval performance was assessed against ground-based stem volume estimates on 134 boreal forest stands. Stem volume retrieval performance as measured by R/sup 2/-values between INSAR-estimated stem volumes and ground truth was found to be directly proportional to boreal forest coherence. The interferometric coherence-contrast (ICC), i.e., the difference in coherence between sparsest and densest boreal forest stands was found to be the best of the four studied suitability measures. The ICC could be used as a suitability parameter in the selection of the best interferometric pairs for operational boreal forest stem volume retrieval. 相似文献
2.
Martti Lehtinen 《Contributions to Mineralogy and Petrology》1974,47(3):223-230
Unit-cell parameters, c */b* ratios, Δbc values (Stewart and Ribbe, 1969), Or contents and the positions of two of the characteristic infared absorption bands are presented for 16 K-rich and for 5 Na-rich alkali feldspar samples. A more specific interpretation is given for the characteristic absorption bands. It is shown that the position of one of the infrared absorption bands depends on the degree of Al/Si order whereas the other depends both on the degree of Al/Si order and to a lesser degree on chemical composition. It is recommended that a combination of X-ray and infrared data is useful in studying certain mineralogical and petrogenetic problems associated with the alkali feldspars. 相似文献
3.
Th. G. Sahama Martti Lehtinen Pentti Rehtijärvi 《Contributions to Mineralogy and Petrology》1973,39(2):171-174
Single crystals of boehmite, up to 0.1 mm in size, were found in open cavities inside a corundum crystal from the Ratnapura area gem gravels in Ceylon. The unit cell parameters are (X-ray powder pattern): a
0=3.695 Å b
0=12.212 Å, c
0=2.867 Å. The crystallographic orientation is based on X-ray single-crystal precession photographs. The crystals show the faces (it010), (001), (101), and (221). Systematic extinctions agree with the space group Amam. Optical orientation: a, b, c. Refractive indices are given. The mineral is optically positive with a large optic axial angle. 相似文献
4.
Theoretical and experimental studies of ultra-high-frequency (UHF) and microwave radiometry to sense remotely the thickness and other characteristics of low-salinity (less than one per mille) sea ice are described. The experimental studies used a 600-MHz and a multichannel, multibeam, 4.7-GHz radiometer carried by a helicopter to measure the brightness temperature of different types of sea ice in the Gulf of Bothnia in 1975 and 1976.The developed theory and experiments show that the brightness temperature of low-salinity sea ice oscillates as a function of ice thickness at UHF frequencies. Due to higher attenuation, the oscillations quickly die away at 4.7 GHz and the brightness temperature reaches an almost constant value when the thickness exceeds a few decimetres. By using a three-channel UHF radiometer with suitably selected center frequencies, the oscillations can be reduced and the effective brightness temperature will grow more linearly with the ice thickness.Experiments show that ice ridges appear as thick ice at 600 MHz and as thinner ice at 4.7 GHz, thus allowing them to be detected by radio techniques. 相似文献
5.
Matson CW Franson JC Hollmén T Kilpi M Hario M Flint PL Bickham JW 《Marine pollution bulletin》2004,49(11-12):1066-1071
Common eiders nesting in the Baltic Sea are exposed to generally high levels of contaminants including potentially genotoxic polycyclic aromatic hydrocarbons and organochlorines. Blood samples were collected from eiders at eight sites in the Baltic Sea and two sites in the Beaufort Sea. DNA content variation was estimated using the flow cytometric method, and subsequently utilized as a biomarker of genetic damage. We observed no significant differences in genetic damage among populations within either the Baltic or Beaufort Seas. However, eider populations from the Baltic Sea had significantly elevated estimates of genetic damage compared to populations from the Beaufort Sea. 相似文献
6.
Lathrap introduced the concept of lateral channel migration of the meandering rivers as a potential factor for human community dynamics in the Upper Amazon. Nevertheless, the dynamics considered by Lathrap is restricted to particular floodplains. He payed no attention to a large scale fluvial phenomenom: the sudden river relocations (avulsion), which also profoundly affected the Upper Amazon cultures. We present here a historical case study analyzing a river floodplain avulsion at the Middle Ucayali River during the late 1700s, causing the abandonment of a settlement called San Miguel de Cunibos and probably leading to the massive migration of the Cunibos Indians. Furthermore, we argue that similar situations have frequently occurred during the human history of the Upper Amazon, and thus these fluvial phenomena should be taken into consideration in future archaeological and ethnohistorical studies. © 1996 John Wiley & Sons, Inc. 相似文献
7.
The effect of the four major surface types in Finland (forests, boglands, farmlands, and water (ice)) on the microwave brightness temperature of snow-covered areas is investigated. Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) data are employed to derive the response of each surface type. An algorithm to retrieve the water equivalent of snow cover from Nimbus-7 SMMR data is tested in different dry snow conditions. 相似文献
8.
Latent Heat Flux from Small Sheltered Lakes 总被引：1，自引：0，他引：1
The dependency of the latent heat flux on the over-water fetch on lakes surrounded by tall, dense forest was studied by making use of measurements made on two different-sized lakes. The measurements were made during the NOPEX (Northern Hemisphere Climate-Processes Land Surface Experiment) field campaign. It was found that, in the case of a typical Scandinavian lake with a size of less than 10 km2, the latent heat flux will increase as a function of over-water fetch due to the increase of wind speed and in spite of the increased air humidity. This also has implications on area-averaged fluxes: when two lakes having similar shorelines, lake water temperatures and solar radiation conditions are compared, then the evaporation per unit area is smaller from the smaller lake. When the lakes are large, with fetches of several kilometres, then the significance of sheltering is small. If point measurements are used for the estimation of area-averaged latent heat fluxes from lakes with short fetches and forested shorelines then the distance of the measuring site from the shoreline should be taken into account, otherwise errors of tens of percent may occur. 相似文献
9.
Parmanne R Hallikainen A Isosaari P Kiviranta H Koistinen J Laine O Rantakokko P Vuorinen PJ Vartiainen T 《Marine pollution bulletin》2006,52(2):149-161
The concentrations and composition profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls, polybrominated diphenyl ethers and polychlorinated naphthalenes were determined in herring individuals collected from the commercial catches of the Bothnian Sea, northern Baltic. The median age of herring was 5.0 years and in the muscle the median toxic equivalent concentration of PCDD/Fs was 5.6 WHO(PCDD/F)-TEQ pg/g fresh weight (fw) and that of PCBs 2.7 WHO(PCB)-TEQ pg/g fw. The median sum concentration of PBDEs was 1.4 ng/g fw and that of PCNs 0.1 ng/g fw. Differences in age-dependent accumulation between the organohalogen groups and individual congeners were major. In the Bothnian Sea the content of organohalogen compounds in herring is obviously elevated due to the availability and large proportion of Mysis crustaceans in their diet. More intensive fishing could reduce the concentrations of organohalogens, including the abundant, accumulative and toxic 2,3,4,7,8-PeCDF congener in the Baltic herring catch. 相似文献
10.
Kainulainen J. Rautiainen K. Tauriainen S. Auer T. Kettunen J. Hallikainen M. 《Geoscience and Remote Sensing Letters, IEEE》2007,4(2):241-245
The Helsinki University of Technology has recently finished the construction of a 2-D airborne aperture synthesis radiometer and conducted a successful test flight with the complete instrument. During the test flight, a number of different brightness temperature sources were measured to examine the instrument's stability, electromagnetic compatibility issues, calibration methods, and image reconstruction algorithm. A set of images from this first test flight is presented, and their main features are discussed 相似文献