Variation Of Es Research Articles

Understanding the Diurnal Cycle of Midlatitude Sporadic E. The Role of Metal Atoms

AbstractMidlatitude ionosonde observations show that there is a sporadic E (Es) diurnal cycle that starts in higher altitudes at sunrise. This property is labeled as the “Sporadic E sunrise effect.” Given that sporadic E layers are composed of metal ions, the sunrise effect implies that metal atom solar photoionization could play a role in the diurnal variability of sporadic E occurrence. This possibility is endorsed by Arecibo's incoherent scatter radar observations, showing that weak ion layers at lowest E and uppermost D region heights appear at sunrise to live during the daytime, apparently coming out of nighttime metal atom mesospheric layers. The solar photoionization of metal atoms increases the abundance of metal ions available for Es layer generation during the daytime, whereas this effect is absent at nighttime. This can explain why sporadic E layers start or intensify at sunrise all year round and why Es activity maximizes during sunlit hours, as has been reported in many ionosonde and satellite radio occultation studies. The significance of metal atom solar photoionization on the regular diurnal variation of Es went unnoticed, despite existing evidence for a long time. The present paper provides a base for a better physical understanding of the pronounced 24‐hr periodicity in Es layer intensity and places a step toward the improvement of simulation models for the predictions of sporadic E layer characteristics.

Sporadic E morphology based on COSMIC radio occultation data and its relationship with wind shear theory

The S4max data retrieved from the Constellation Observing System for the Meteorology, Ionosphere, and Climate (COSMIC) radio occultation (RO) measurements during 2007 to 2015 is adopted to investigate the global distribution and seasonal variation of the sporadic E (Es) layers in the present work. The long-term and short-term global Es occurrence maps are presented and the spatial and temporal distributions of Es occurrence rates (ORs) are further confirmed and studied. The International Geomagnetic Reference Field model (IGRF12) is used to calculate the horizontal intensity and inclination of the Earth’s magnetic field. The analysis shows that the Earth’s magnetic field is one of the fundamental reasons for the global distribution of the Es layers. In addition, the Horizontal Wind Field model HWM14 and the IGRF12 model were employed to calculate the vertical ion convergence (VIC) to examine the role of neutral wind shear in the global distribution of the Es ORs. The results reveal that the middle latitude distribution of simulated vertical concentration of Fe+ is similar to that of Es ORs, which indicates that the VIC induced by the neutral wind shear is an important factor in determining the geographical distribution, summer maximum (or winter minimum) and diurnal characteristics of Es ORs in middle latitudes. The new findings mainly include the following two aspects: (1) in summer over mid-latitudes, VIC peaks in the morning and afternoon to evening, which explains the semidiurnal behavior of Es ORs; (2) VIC reaches its minimum value in low-altitude (100 km) areas, which is the reason for the significant decrease in Es ORs in low-altitude areas. The disagreements between the VIC and Es ORs indicate that other processes, such as the meteor influx rate, the ionospheric electric fields and atmospheric tides, should also be considered as they may have an important impact on the variation of Es layers.Graphical

Estimating individual- and stand-level stem CO2 efflux in a subalpine forest: assessment of different extrapolation methods

Accurate evaluation of the carbon release by stems is an important objective of many forest carbon cycling studies. However, few studies have assessed the applicability of different extrapolation methods of stem CO2 efflux. Therefore, a reliable estimation method that considers both temporal and vertical variations is required. To overcome this problem, we conducted a field experiment to measure the stem CO2 efflux rate of Abies fabri in subalpine forests, and evaluated the effect of three extrapolation methods (area-based estimation, volume-based estimation and integral method) on accurate estimation of stem respiration at the individual and stand levels. First, we calculated the stem carbon loss at the individual level using the three extrapolation methods, and discovered that the diameter at the breast height (DBH) played a major role in determining the magnitudes of stem respiration. Second, we summarized the relationship between the stem CO2 efflux rate (Es) and the DBH from previous studies. The Es for small diameter stems tended to increase with height, but remained constant in trees with large DBH, implying a role of DBH threshold in determination of the Es effect. Our calculations from three estimation methods supported the hypothesis that a threshold accounted for the different vertical variations in Es. Specifically, the vertical variation of Es primarily presented as two categories: Es decreased with the stem height for small diameters (DBH 60 cm). Based on these trends, we suggest a two-part approach to scale the individual tree stem CO2 efflux, in which a volume-based scaling method is recommended for trees with small DBH (0–30 or 40 cm) and an area-based estimation is suitable for stems with large DBH (> 30 or 40 cm). Using this approach, the annual amount of stem carbon release for an immature forest and a mature forest were estimated as 1.80 and 4.81 t C ha−1 year−1, respectively.

贡嘎山峨眉冷杉树干呼吸空间特征及其对温度的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 贡嘎山峨眉冷杉树干呼吸空间特征及其对温度的响应 DOI: 10.5846/stxb201705160912 作者: 作者单位: 中国科学院水利部成都山地灾害与环境研究所;中国科学院大学,中国科学院水利部成都山地灾害与环境研究所,中国科学院水利部成都山地灾害与环境研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划课题（2017YFC0505004）；中国科学院成都山地所"一三五重点培育项目"；国家自然科学基金项目（41471232） Spatial variations in the stem CO2 efflux rate of Abies fabri and the response to temperature in the Gongga Mountains Author: Affiliation: Institute of Mountain Hazards and Environment,Chinese Academy of Sciences,Chengdu,Institute of Mountain Hazards and Environment,Chinese Academy of Sciences,Chengdu,Institute of Mountain Hazards and Environment,Chinese Academy of Sciences,Chengdu Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用红外线气体分析仪-土壤呼吸气室水平测定法（HOSC）原位监测了贡嘎山东坡峨眉冷杉（Abies fabri）树干CO2释放速率（Es），分析了树干Es与树干温度（Tstem）的关系。贡嘎山峨眉冷杉树干Es和Tstem空间变化格局明显，不同测定高度树干温度为0.3m > 1.3m > 2.3m，以1.3m处Es最大；不同方向Es和Tstem均表现为南面>北面。生长季和非生长季的峨眉冷杉Es分别在0.51-0.99μmol m-2 s-1和0.14-0.22μmol m-2 s-1之间波动。峨眉冷杉树Es变化趋势和Tstem一致，二者具有显著的指数函数关系（P<0.01）。峨眉冷杉非生长季树干呼吸Q10显著高于生长季（P<0.01），其中生长季变幅在1.9-3.0之间，非生长季在4.6-6.8之间，暗示个体或群落水平树干CO2释放通量的估算应充分考虑树干Es空间特征和Q10变化。 Abstract:As an important component of carbon budgets and net ecosystem CO2 exchange in forest ecosystems, stem CO2 efflux rate (Es) plays a crucial role in the global carbon balance. Investigation of spatial variations and the response of Es to temperature, are essential for improving the accuracy of Es estimates at individual and community levels. In this study, the horizontally oriented soil chamber (HOSC) technique was applied to measure the CO2 released by stems. We measured Es in situ in the Abies fabri forest on Gongga Mountain using IRGA with a Li-6400-09 from September to December 2014. Our objectives were to examine the spatial variations in Es of A. fabri and to explore the response of Es to stem temperature (Tstem). Two representative trees in an immature A. fabri forest stand were selected. An opaque PVC collar (10.7cm inside diameter and 5cm high) was cut to match the approximate curvature of the stem with the other end being cut flat. Then the custom-built PVC collar was fastened to the south of the stem at a height of 0.3, 1.3 and 2.3m and to the north at a height of 1.3m, with 100% silicone sealant 24h before the measurement was made. Loose bark and moss were carefully removed from the stem surface curved by the PVC collar using a hairbrush without damaging the underlying cambium before installing the PVC collars. Measurements were made over three cycles at each sampling point, every 2h from 8:00 to 18:00 in the same day of every month. The A. fabri stem Es and Tstem showed an apparent spatial pattern. The Tstem at different heights ranked as follows:0.3 > 1.3 > 2.3m with maximum Es appearing at 1.3m. The Es and Tstem on the south face of the stem were higher than that on the north. The monthly averages Es of the growing season (September and October) and the non-growing season (November and December) was 0.51-0.99 and 0.14-0.22μmol m-2 s-1, respectively. The trend in A. fabri stem Es was consistent with Tstem with a significantly exponential relationship observed. The temperature coefficient (Q10) during the non-growing season (4.6-6.8) was much higher than that in the growing season (1.9-3.0). It was concluded that spatial variations of Es and Q10 should be considered when estimating individual and community stem Es. 参考文献 相似文献 引证文献

Sapflow characteristics of Kandelia obovata and their controlling factors in Zhangjiang estuary, China.

In this study, the Grainer's thermal dissipation probe method was applied to monitor sap flux density (SFD) of a mangrove species Kandelia obovata over a period of one year (2010-10-2011-10) in Zhangjiangkou Mangrove National Nature Reserve, Fujian, China. The results showed that both season and diameter class exerted significant effects on the SFD of K. obovata trees. In summer, when the diameter at breast height (DBH) reached 8-10 cm, the highest SFD was found at a depth of 2 cm with a value of 38.21 g·m-2·s-1, which was comparable with those for other mangrove tree species and forested wetland tree species. The mean whole tree transpiration (i.e. daily water use) of all stem size classes demonstrated large changes from winter to summer, increased from 0.14 to 0.19 kg·d-1 in small trees (S, DBH=2-4 cm), from 0.94 to 1.45 kg·d-1 in medium trees (M, DBH=4-8 cm) and from 1.96 to 3.43 kg·d-1 in large ones (L, DBH=8-10 cm). The daily transpiration of K. obovata stand was calculated by summing all size classes, which was then summed up for entire year to estimate annual transpiration of entire K. obovata forest, which was about 100.38 mm, less than 6% of local annual precipitation. Key environmental factors all had significant effects (all P<0.001) on the stand transpiration rate (Es) of K. obovata forest, and photosynthetically active radiation (PAR) and vapor pressure deficit (VPD) were the main driving factors, which explained 60%-92% seasonal variation of Es. The PAR and VPD had larger effects on the Es in summer than that in winter. In addition, we observed an obvious time lag phenomenon in the relationship between Es and PAR or VPD, which should be taken into account when explaining seasonal variation of Es in K. obovata forest.

Evolution of the elastic moduli of seismogenic Triassic Evaporites subjected to cyclic stressing

Seismic cycles lead to variations in rock physical properties. Quantifying these changes is of key importance in building reliable crustal deformation models. Here we report laboratory measurements of the uniaxial compressive strength (UCS), Young's modulus and Poisson's ratio, both static (Es, νs) and dynamic (Ed, νd) of the seismogenic Triassic Evaporites of the Northern Apennines. Triassic Evaporites are composed of dolostones, anhydrites and gypsum. Gypsum was the weakest lithology, with UCS values ranging from 10 to 26MPa; anhydrite exhibited intermediate values from 52 to 144MPa; and dolostones were the strongest with a maximum UCS of 228MPa.During uniaxial cyclic stressing experiments, we observed complex variations in Es and νs with: large increases are observed in the early cycles (stage 1), followed by essentially constant values (stage 2), before Es decreases and νs increases approaching failure (stage 3). Complementary microseismicity (acoustic emission, AE) data show no significant AE during stage 1, then the stress needed to induce AE remained essentially constant (stages 2 and 3). Integration of mechanical data with microstructural observations suggests a first stage dominated by compaction and strengthening, a second stage characterised by quasi-elastic behaviour associated with the development of randomly oriented microfractures, and a third stage of weakening due to the growth of macrofractures parallel to the direction of the load. Laboratory dynamic elastic moduli are, on average, in agreement with dynamic elastic moduli used in crustal modelling. However static values of Young's modulus are about 50% lower than dynamic ones, and static values of Poisson's ratio are about 40% higher with respect to dynamic values. These observations suggest that the frequency effect on the difference between laboratory and crustal scale dynamic moduli values is rather small and that static values of modulus are more appropriate for crustal deformation modelling than seismically derived values.

Effects of sap velocity on the daytime increase of stem CO2 efflux from stems of Schima superba trees

Stem CO2 efflux (E s) has been estimated from a temperature-related equation, but sap flux often affects measurements of E s, which leads to misunderstanding real stem respiration. In order to observe the relationship between E s and stem temperature and to analyze the effect of sap velocity on E s, stem temperature, E s and sap flux were measured from a subtropical Schima superba plantation in South China on three trees for consecutive 3 days in July and October 2009. Stem temperature, E s and sap velocity were significantly higher in July than in October. Stem temperature could explain 17–41 and 54–75% variations of E s in July and October, respectively. A negative relationship between E s and stem temperature was found during 1800–2300 hours in July. The daytime E s was 9.2, 4.3 and 2.4% higher than the predicted for three trees in July, and this occurred only on Tree 1 in October. Sap velocity was positively correlated with E s for three trees in July, and the increase of E s with the increase of sap velocity was only observed on Tree 1 in October. These results demonstrated that the occurrence of sap flux could account for the increase of daytime E s, and the effect of sap velocity on E s varied with the seasons from the S. superba stem.

An attempt to study long-term variation of sporadic E layers using neural networks

Strong positive correlation between sporadic E layers and the solar activity and the long-term declining trend of Es were found in this paper. Then the feed-forward back propagation neural networks (NNs) were used to simulate the long-term variation of Es at four stations and predict foEs yearly average values. The inputs used for NNs are the yearly mean values of foEs in the daytime of the past ten years and the yearly averaged data of solar 10.7cm radio flux (F107) of the present year, and the output is the present yearly mean value of daytime foEs. The outputs of trained NNs have high correlation with the desired values and the foEs yearly mean values predicted by NNs have good agreement with the observed data. The results indicate that NNs can make full use of the observed data to simulate the long variation rule of Es. Also, the results confirm the effect of solar activity on Es.

Factors affecting monoterpene emission from Chamaecyparis obtusa

Monoterpenes are major compounds emitted by plants and contribute to the formation of photochemical oxidants and secondary organic aerosols in the troposphere. We measured monoterpene emissions from Chamaecyparis obtusa, a major coniferous tree species in Japan, in both the field and the laboratory. Short-term monoterpene emission from C. obtusa was typically dependent on temperature but barely dependent on light intensity. We calculated the basal emission rate Es assuming β = 0.09 in the G93 model. Three individual trees showed similar, but large seasonal variations in Es; e.g., 0.21‐ 5.42 µg gDW ‐1 h ‐1 for a tree showing the highest emission rate. The emission rate was much higher in winter and autumn. Although Es values averaged over 4 seasons indicated that C. obtusa is an intermediate emitter among coniferous trees, our results suggest that the large seasonal variation in Es should be considered in estimating annual monoterpene emission from this species. Furthermore, we found a significant effect of branch-to-branch touching by vibration on monoterpene emission from this species, suggesting that wind effect should be considered in the future for more precise emission estimation.

Possible relations between meteors, enhanced electron density layers, and sporadic sodium layers

In this paper, we studied the possible relations between incoming meteors, sporadic E (Es) layers, and sporadic (or sudden) sodium atom layers (SSLs) using the data from the FORMOSAT‐3/COSMIC constellation, a meteor radar (Wuhan, 31°N, 114°E), and a sodium fluorescent lidar (Hefei, 31.8°N, 117.3°E). From a statistical point of view, a seasonal dependence of SSL correlates well with the annual variation of Es and is also consistent with seasonal meteor deposition except for February and March. It suggests that a “meteor‐Es‐SSL” chain could be reasonable if the recombination process were taken into consideration. Detailed study on the relationship between electron density profiles provided by the COSMIC radio occultation and the observations of SSLs by the University of Science and Technology of China via lidar illustrates that the appearance of Es accompanying SSL (i.e., 56.3%) is three times greater than that in the “normal” sodium layer. It also indicates that tides play an important role in causing the lower SSLs, which might be able to carry the upper dense electrons and ions in the Es layer formed by wind shear to the lower altitudes through downward phase propagations.

Seasonal variation of low-latitude E-region plasma irregularities studied using Gadanki radar and ionosonde

Abstract. In this paper, we present seasonal variation of E region field-aligned irregularities (FAIs) observed using the Gadanki radar and compare them with the seasonal variation of Es observed from a nearby location SHAR. During daytime, FAIs occur maximum in summer and throughout the day, as compared to other seasons. During nighttime, FAIs occur equally in both summer and winter, and relatively less in equinoxes. Seasonal variations of Es (i.e. ftEs and fbEs) show that the daytime activity is maximum in summer and the nighttime activity is maximum in equinoxes. No relation is found between FAIs occurrence/SNR and ftEs/fbEs. FAIs occurrence, however, is found to be related well with (ftEs−fbEs). This aspect is discussed in the light of the present understanding of the mid-latitude Es-FAIs relationship. The seasonal variations of FAIs observed at Gadanki are compared in detail with those of Piura, which show a significant difference in the daytime observations. The observed difference has been discussed considering the factors governing the generation of FAIs.

南九州産スギ材の材質 ＩＩ―オビスギ品種の材質特性―

The information on wood properties of sugi cultivars (Cryptomeria japonica) is very important for efficient use of sugi wood. Obi-sugi is a major group of sugi cultivars planted in Southern Kyusyu. However, the wood properties of Obi-sugi still have remained unclear. Therefore, the wood properties of 33-year-old Obi-sugi (15 cultivars) grown at one stand were determined. Mechanical properties were investigated by dynamic testing method for logs and compression test parallel to the grain for small clear specimens. In addition, basic density, latewood tracheid length and microfibril angle of middle layer in secondary wall (S2) in both earlywood and latewood tracheid were examinedThere were differences in the mechanical and anatomical properties of Obi-sugi among cultivars. The maximum and minimum values of static modulus of elasticity (Es) of the mature wood among the cultivars were 13.0 Gpa and 6.6 Gpa respectively. The patterns of radial variation in Es of the wood from pith to bark were also characterized by the cultivars. It was suggested that these revealed characteristics of the cultivars are quite essential information to decide the suitable end use of Obi-sugi.Both the basic density and the S2 microfibril angle affected the mechanical properties of Obi-sugi. Higher basic density and/or lower S2 microfibril angle were the cause of the higher mechanical performance of mature wood of the cultivars. S2 microfibril angle was also the most effective factor in both mature and juvenile wood.

Measurement and simulation of evaporation from soil in olive orchards

Evaporation from the soil (Es) beneath an olive orchard was characterised in a semi-arid Mediterranean climate (Cordoba, Spain). First, the microlysimeter method was modified to measure accurately Es beneath tree orchards. The variability in irradiance reaching the soil beneath the orchard caused spatial variations in Es during both evaporation stages. In the first days of the drying cycle, Es was higher for high irradiance locations but the opposite occurred the subsequent days, although daily differences in Es between locations progressively declined. For the energy-limiting stage, linear relationships between Es values and incident photosynthetically active radiation were found for different times throughout the season. The slopes of the relationships were similar, but their intercepts differed substantially, showing the importance of a variable aerodynamic component in determining Es. A simple functional model was formulated to estimate Es at daily time steps. During the energy-limiting stage, Es is calculated as the sum of the equilibrium evaporation at the soil surface and an aerodynamic term, derived from the Penman equation. For the falling rate stage, Ritchie's (1972) approach is adopted for the Es calculations. The model was successfully tested in an orchard of 6×6 m spacing, typical of intensive olive orchards, under a wide range of evaporative demand conditions. Trees covered around 36% of the soil surface. The model predicted an average seasonal Es of 286 mm, which represents around one third of the estimated olive evapotranspiration and about 50% of the average seasonal rainfall of the area.

Structure in the seasonal variations of Es at southern latitudes

The diurnal variations of the seasonal characteristics of sporadic- E occurrence have been studied by analyzing a large data set of ionosonde parameters for two southern hemisphere stations. The seasonal patterns are found to display anomalous short-term variations apparently not associated with solar control or the effects of dynamic meteorology.

A study of sporadicEat high latitudes

The diurnal distribution of the occurrence of sporadic E at high latitudes during two periods in 1964 is determined from data provided by six IQSY ionospheric forward scatter paths in the arctic and antarctic regions. The relationship of the diurnal variation of Es to geomagnetic activity is investigated and a transition zone, located between the auroral zone and the region closer to the geomagnetic pole, is found to be characterized by a maximum occurring earlier in the afternoon when Σkp>20 than when Σkp<10. Furthermore, a second maximum appears as geomagnetic activity increases. The diurnal variations at geomagnetically conjugate path midpoints are identical if the data are plotted as a function of geomagnetic time.

SporadicE-layer ionization and sunspot cycle

The correlation between the sunspot cycle and the sporadicE-layer ionization is investigated at middle latitudes. Higher mean values off 0Es occur generally with higher sunspot numbers. Some evidence for a phase-shift between long term time-variation in sunspot numbers andf 0Es is obtained. The solar cycle variation ofEs is somewhat larger over the Far East. Regarding the behaviour of the time-development ofEs events in diurnal variation, an interpretation is proposed.

Statical Studies on the Warping of Enamels

The warping caused by the differential contraction (Δl) between sheet steel and enamel layer was studied. Warping is a phenomenon of bending, so it should be considered that the internal moment of force must exist. The internal stresses, originating from Δl, act as a moment (M1), and on the other hand a moment of resistance (M2) of enameled sheet for warping must occured. From this view point, we could find a fundamental equation of warping under the condition of equilibrium M1=M2, as shown by equation (6) and (9).In the equations, the warping is a function of factors that are differential contraction (Δl), modulus of elasticity of sheet steel (Es) and enamel layer (Ee), thickness of sheet steel (s) and enamel layers (E or u and f), and moment of inertia of enameled sheet. But, by the decision of mechanical section, we can easily calculate the moment of inertia.From the equation, the relation between warping and structural dimensions (S and E or S, u and f) at room temperature with the assumption of Δl=0.001 were calculated minutely within the range of common application shown in the diagrams (Fig. 7-Fig. 10).As the warping is approximately proportional to the Δl, here the results are useful to observe the variations of warping relating with structures and to obtain the value of Δl at room temperature approximately from the data of measurement of warping and sectional dimensions without complicated calculations.Obtaining the variation of warping with the change of temperature by experiment, we can calculate the Δl in the cooling period after firing of enameled sheet, and able to make clear the contractive conditions in cooling, but it is necessary to know the variations of Es and Ee by the change of temperature previousely. Therefore the warping was measured with the change of temperature on several kinds of enamels, and the results are shown in the diagrams (Fig. 13-Fig. 17).With the decision of neutral line of mechanical section we are able to examine the distribution of internal stresses in warping or bending. These examples are shown in the diagrams (Fig. 18-Fig. 21). If we consider the stress and strength of enamel layer, we can find the safety condition of enameled sheet, in case of mechanical dealing is required.