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991.
992.
The global positioning system meteorology (GPS/MET) experiment was the first practical demonstration of global navigation satellite system (GNSS)-based active limb sounding employing the radio occultation technique. This method measures, as principal observable and with millimetric accuracy, the excess phase path (relative to propagation in vacuum) of GNSS-transmitted radio waves caused by refraction during passage through the Earth’s neutral atmosphere and ionosphere in limb geometry. It shows great potential utility for weather and climate system studies in providing an unique combination of global coverage, high vertical resolution and accuracy, long-term stability, and all-weather capability. We first describe our GPS/MET data processing scheme from excess phases via bending angles to the neutral atmospheric parameters refractivity, density, pressure and temperature. Special emphasis is given to ionospheric correction methodology and the inversion of bending angles to refractivities, where we introduce a matrix inversion technique (instead of the usual integral inversion). The matrix technique is shown to lead to identical results as integral inversion but is more directly extendable to inversion by optimal estimation. The quality of GPS/MET-derived profiles is analyzed with an error estimation analysis employing a Monte Carlo technique. We consider statistical errors together with systematic errors due to upper-boundary initialization of the retrieval by a priori bending angles. Perfect initialization and properly smoothed statistical errors allow for better than 1 K temperature retrieval accuracy up to the stratopause. No initialization and statistical errors yield better than 1 K accuracy up to 30 km but less than 3 K accuracy above 40 km. Given imperfect initialization, biases ≫ 2 K propagate down to below 30 km height in unfavorable realistic cases. Furthermore, results of a statistical validation of GPS/MET profiles through comparison with atmospheric analyses of the European Centre for Medium-range Weather Forecasts (ECMWF) are presented. The comparisons indicate the high utility of the occultation data in that very good agreement of upper troposphere/lower stratosphere temperature (better than 1.5 K rms, ≪ 0.5 K bias) is found for a region (Europe+USA) where the ECMWF analyses are known to be good, but poorer agreement for a region (Southern Pacific) where the analyses are known to be degraded. 相似文献
993.
The first attempt is made to evaluate quantitatively the changes of accumulation rates in the South China Sea during the last
glaciation and Holocene, based on the data of 72 sediment cores taken from six areas deeper than 100 m. As shown from the
calculations, the accumulation rate during the last glaciation is much higher than that during the Holocene. The southern
and northern continental slopes are distinguished from other areas by the highest accumulation rates, with different features
of sedimentation for aifferent stages: The Glacial-Holocene contrast in accumulation rate of terrigenous material is more
distinct in the southern slope, while the contrast in biogenic sedimentation rate is more remarkable in the northern slope.
Project supported by the National Natural Science Foundation of China (Grant No. 49576268). 相似文献
994.
青藏高原三维变形运动学的时段划分和新构造分区 总被引:80,自引:3,他引:77
青藏高原形成至今经历了4个互有叠接的构造期。α期以南北缩短和向北推移为主,主要发生在45~35 Ma期间,β期表现为长周期缓慢隆升,在35~5.3 Ma期间占主导地位;γ期为短周期快速隆升阶段,自5.3Ma开始,3.0 Ma以后逐渐达到高峰;δ期以东西向伸展变形为特征,3.0 Ma以前出现在喜马拉雅地区,3.0 Ma以后遍及整个高原.第四纪以后表现为占主导地位的变形运动形式。根据γ期和δ期构造变动在空间和时间上的不均匀性,把青藏高原划分为西藏、羌塘和柴达木3个构造域。 相似文献
995.
In 1876 Blytt proposed a post-glacial climatic classification, maintaining that the then temperature fluctuated 1- 2℃ higher or lower than that today. Lamb (1969) held that in Europe " the axis of the subtropical high pressure belt was generally displaced north by about 10° latitudes" during the Hypsithermal and that the temperature was three to six times higher than that in the postglacial period.In China, there appear relict beachrocks (living fossils) in tropical tidal zones from the Bohai Bay (40° N) to coastal areas in South China. Many relict tropical marine fossils were discovered, such as Ostrea gigas in Tianjin (which is larger than that found today in Hainan), Placuna placenta in Zhejiang and Spondylus sp. in Fujian. In Hebei, Henan and Zhejiang provinces and Guilin of Guangxi, such tropical fossil animals as Elephas maximus and Rhinoceros sp, were discovered, and in Hebei and Jiangsu provinces such fresh water fossils as Unio douglasiae were found. Their living species are still seen in So 相似文献
996.
构造摩擦热的初步研究 总被引:6,自引:0,他引:6
构造摩擦热是地质学中的重要基础理论问题。构造摩擦热可使岩石软化,加速岩石的形变作用,还可导致岩石的变质甚至熔融作用,发生同步的地球化学作用。许多内生矿床的形成,都与构造摩擦热有关。本文通过对构造摩擦热的数学计算和分析,认为构造摩擦热的大小与摩擦面两盘岩石的滑动速度和正压应力相关,且滑动速度是决定因素。摩擦力的大小和破裂面与σ1的夹角θ及外力大小有关。在同一应力场中,摩擦热随着θ角而变化。当σ1=50MPa,μ=1情况下,当θ≈30°时,单位体积大约可产生1~2℃的升温效应。 相似文献
997.
通过14件高温高压实验样品及其原样的电子顺磁共振研究,论述了温度、压力、应力、应变速率和应变强度等是影响变形煤化学结构演化的重要因素,但在不同的煤级中和不同的实验条件下,各因素所起的作用是不同的。变形煤EPR参数的演化与镜质组反射率的变化密切相关,并且具有较好的规律性。说明镜质组反射率是煤化学结构演化的外在反映,是煤田构造研究中极为重要的标志物之一。 相似文献
998.
金牛山金矿床的石英包裹体划分为纯液相包裹体、气液相包裹体和CO2三相包裹体三种类型,均一温度在150~300℃,主成矿温度在190~210℃之间。研究表明成矿热液由南向北运移。 相似文献
999.
东北地区5 000 aB.P.~4 700 aB.P.左右的降温事件及对考古文化的影响 总被引:2,自引:0,他引:2
距今5000年左右世界各地普遍存在一次幅度较大的短期降温气候事件,通过对金川剖面泥炭地层14C测年,孢粉分析,认为东北地区此次降温事件结束的14C年龄在4700aB.P.左右,降温事件出现之前气候温暖湿润,降温事件过后温度持续下降,金川剖面的记录与东北地区其它类型沉积物所记录的降温事件出现的时间基本吻合,降温事件对燕辽地区古文化演变产生了深刻的影响。 相似文献
1000.
The authors conducted a Rn222 survey in wells of the Larderello geothermal field (Italy) and observed considerable variations in concentrations. Simple models show that flow-rate plays an important part in the Rn222 content of each well, as it directly affects the fluid transit time in the reservoirs. Rn222 has been sampled from two wells of the Serrazzano area during flow-rate drawdown tests. The apparent volume of the steam reservoir of each of these two wells has been estimated from the Rn222 concentration versus flow-rate curves.List of symbols
Q
Flow-rate (kg h–1)
-
Decay constant of Rn222 (=7.553×10–3 h–1)
-
Porosity of the reservoir (volume of fluid/volume of rock)
- 1
Density of the fluid in the reservoir (kg m–3)
- 2
Density of the rock in the reservoir (kg m–3)
-
M
Stationary mass of fluid filling the reservoir (kg).
-
E
Emanating power of the rock in the reservoir (nCi kg
rock
–1
h–1).
-
P
Production rate of Rn222 in the reservoir: number of atoms of Rn222 (divided by 1.764×107) transferred by the rock to the mass unit of fluid per unit time (nCi kg
fluid
–1
h–1).
-
N
Specific concentration of Rn222 in the fluid (nCi kg–1)
-
Characteristic time of the steam reservoir at maximum flow-rate (=M/Q) 相似文献