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1.
—The 4-season (12-month) running means of temperatures at five atmospheric levels (surface, 850–300 mb, 300–100 mb, 100–50 mb, 100–30 mb) and seven climatic zones (60°N–90°N, 30°N–60°N, 10°N–30°N, 10°N–10°S, 10°S–30°S, 30°S–60°S, 60°S–90°S) showed QBO (Quasi-biennial Oscillation), QTO (Quasi-triennial Oscillation) and larger periodicities. For stratosphere and tropopause, the temperature variations near the equator and North Pole somewhat resembled the 50mb low latitude zonal winds, mainly due to prominent QBO. For troposphere and surface, the temperature variations, especially those near the equator, resemble those of eastern equatorial Pacific sea-surface temperatures, mainly due to prominent QTO. In general, the temperature trends in the last 35 years show stratospheric cooling and tropospheric warming. But the trends are not monotonic. For example, the surface trends were downward during 1960–70, upward during 1970–82, downward during 1982–85 and upward thereafter. Models of green-house warming should take these non-uniformities into account.  相似文献   

2.
Mesoscale convective systems(MCSs) around the second-step terrain(106°–113°E, 28°–35°N), along the middle reaches of the Yangtze River, were detected, tracked and classified using a black body temperature(TBB) dataset during May to August 2000–2016(except 2005). The MCSs were divided into eastward-propagating(EP) and quasi-stationary(QS) types, to compare their spatial and temporal distributions and convective intensities, and to identify the favorable synoptic conditions for the formation and evolution of EP MCSs. The results showed that both MCS types occurred most often in July. The EP MCSs were mainly initiated over the eastern regions of the study area, while the QS type mainly originated in the western regions of the study area. Both MCS types mainly formed in the afternoon, but a second peak occurred in the early morning for QS MCSs. The EP MCSs had a larger cloud area at their mature stage and a lower cloud brightness temperature, indicating more intense convection. Additionally, the longer lifetime and further eastward propagation of the EP MCSs meant that they had a great influence on the precipitation over the middle and lower reaches of the Yangtze River. Synoptic circulation analysis demonstrated that the combination of the mid-level low trough east of the Tibetan Plateau(TP), and the western pacific subtropical high(WPSH), favored the formation and eastward propagation of EP MCSs. The positive vertical relative vorticity and stronger vertical wind shear provided dynamic conditions favorable for convective organization and development. Furthermore, a stronger low level jet imported warm and moist air to the eastern edge of, and the regions east of, the second-step terrain. The substantial convergence of water vapor promoted the development and long-lived maintenance of the EP MCSs.  相似文献   

3.
The results of the paleomagnetic investigation of the sediments pertaining to the Silasinskaya Formation of the Kiselevka–Manoma terrane within the Sikhote Alin orogenic belt are presented. The ancient prefolding magnetization component is revealed: Decs = 271.7°, Incs = 52.2°, Ks = 13.5, and a 95s = 5.1° (positive fold and reversal tests); and the coordinates of the corresponding paleomagnetic pole for ~103 ± 10 Ma are calculated: Plat = 26.3°, Plong = 70.5°, dp = 4.8°, and dm = 7.0°. As a result of this study, the geodynamical settings and paleolatitudes of the formation of three objects in the northern part of Sikhote Alin orogen are established: (a) the Kiselevskaya Formation of the Kiselevka–Manoma terrane was formed 133 Ma ago at 19° N under the seamount condition on the Izanagi Plate; (b) the Silasinskaya Formation of the Kiselevka–Manoma terrane was formed 103 Ma ago at 35° N under the oceanic island arc conditions; and (c) the Utitskaya Formation of the Zhuravlevsk–Amur terrane was formed 95 Ma ago at 54° N in the active continental margin conditions. It is found that the transform continental margin of Eurasia developed in the time interval from 105 to 65 Ma ago in the regime of a left-lateral submeridional shear from 30° to 60° N. The complete attachment of the studied rocks of the Kiselevka–Manoma terrane to the Eurasia’s margin (to the Zhuravlevsk–Amur terrane) occurred at the boundary of 60–70 Ma. Simultaneously, the sense of the displacement in the submeridional shears changed from left-lateral to right-lateral with the formation of pullapart type basins (Lake Udyl’).  相似文献   

4.
The major sudden stratospheric warming (SSW) events of 2003–04 and 2005–06 are considered to investigate changes in equatorial convection due to circulation changes associated with the SSW events. It is observed that the SSW events are accompanied by a considerable decrease in Outgoing Longwave Radiation (OLR), a proxy for tropical convection, over equatorial latitudes (15°N–15°S) in the Indonesian sector (90°E–150°E). However, unlike noted by earlier observations, the zonal mean OLR does not show any notable relationship with the SSW events. It can be explained from the latitude–longitude map of potential vorticity (PV) at 100 hPa, which shows a tongue of high PV emanating from high latitudes towards equator and converges in the longitude band of 90°E–150°E on the day of peak warming at 1 hPa in the case of 2003–04 and 10 hPa in the case of 2005–06. The latitude-height map of Eliassen–Palm (EP) vector and its divergence show convergence of EP flux in the upper troposphere at latitudes even lower than 20°N on these days. Further, vertical winds computed from the convergence of momentum flux are upward indicating convective activity at low-latitudes and downward at mid-latitudes.  相似文献   

5.
A geophysical study was conducted over the Mid-Atlantic Ridge between 32–39°N and 30–40°W. A particularly deep fracture was observed which offset the ridge crest 110 km in the vicinity of 33°N. A pole of relative motion between the North American and African plates was deduced from this fracture zone as being at 63.1°N, 17°W.  相似文献   

6.
Results of a paleomagnetic study carried out on the exposed volcanic rocks on the western side of the South Kenya Rift Valley are presented. Nine stratigraphic groups ranging in age from Miocene to Pleistocene were sampled. The rocks consist of basalts, trachytes, nephelinites, melanephelinites, olivine melanephelinites and ignimbrites. Paleomagnetic poles obtained for different age ranges are as follows: Period I (0.64–0.72 Ma), 116°E, 85°N (A95 = 6°); Period II (1.6–6.9 Ma), 297°E, 84°N (A95 = 4°); Period III (12.0–15.0 Ma), 34°E, 80°N (A95 = 9°). The results for Period II show large secular variations which are in disagreement with the model predictions for near-equatorial sites.  相似文献   

7.
A statistical analysis is made for the eastern part of Turkey in the beginning of 2009 by studying the phenomenon of seismic quiescence as a potential precursor of the main shocks. The results produced four areas having seismic quiescence in the beginning of 2009. These areas are observed to be centered at 39.96°N–40.69°E (around A?kale, Erzurum), 39.36°N–39.74°E (around Ovac?k, Tunceli), 39.02°N–40.52°E (including Elaz?? and Bingöl), and 38.45°N–42.94°E (Van Lake). Based on the recent results showing 5 ± 1.5 years quiescence before the occurrence of an earthquake in this region, the future earthquake would be expected between 2009.5 and 2010.5. The future earthquake occurrence may reach 2012 if we consider the standard deviation of average seismic quiescence as ±1.5 years. We have found that the M W = 6.0 Elaz?? earthquake on 8 March 2010, followed a seismic quiescence starting about 5 years before the main shock. Thus, special interest should be given to the other regions where the seismic quiescence is observed.  相似文献   

8.
The spatial dynamics of geomagnetic variations and pulsations, auroras, and riometer absorption during the development of the main phase of the extremely strong magnetic storm of November 7–8, 2004, has been studied. It has been indicated that intense disturbances were observed in the early morning sector of auroral latitudes rather than in the nighttime sector, as usually takes place during magnetic storms. The unusual spatial dynamics was revealed at the beginning of the storm main phase. A rapid poleward expansion of disturbances from geomagnetic latitudes of 65°–66° to 74°–75° and the development of the so-called polar cap substorm with a negative bay amplitude of up to 2500 nT, accompanied by precipitation of energetic electrons (riometer absorption) and generation of Pi2–Pi3 pulsations, were observed when IMF B z was about ?45 nT. The geomagnetic activity maximum subsequently sharply shifted equatorward to 60°–61°. The spatial dynamics of the westward electrojet, Pi2–Pi3 geomagnetic pulsations, and riometer absorption was similar, which can indicate that the source of these phenomena is common.  相似文献   

9.
Equatorial spread-F (ESF) backscatter plumes are often observed in radar range-time-intensity (RTI) maps at low latitude. Except case studies, few statistical investigations on the onset locations of scintillation-producing ESF plumes at given sites have been conducted. In this study, a statistical analysis is carried out on onset locations of ESF backscatter plumes observed at a low-latitude location Sanya (18.4°N, 109.6°E; dip lat 12.8°N) during equinoctial months of 2013. By employing a tracing method to locate backscatter plumes, we estimate the onset longitudes of periodic plumes obtained from the Sanya VHF radar five-beam steering measurements. The results show that the inter-plume distances (in longitude) are mostly confined within 200–600 km, and the ESF plumes producing ionospheric scintillations over Sanya are almost exclusively generated at the longitudes of 94°–110°E. The results indicate the necessity to monitor ESF plume initial generation in the longitude region of 94°–110°E to better understand the day-to-day variability in the occurrence of ionospheric scintillations over Sanya.  相似文献   

10.
The zonally averaged UK Meteorological Office (UKMO) zonal mean temperature and zonal winds for the latitudes 8.75°N and 60°N are used to investigate the low-latitude dynamical response to the high latitude sudden stratospheric warming (SSW) events that occurred during winter of the years 1998–1999, 2003–2004 and 2005–2006. The UKMO zonal mean zonal winds at 60°N show a short-term reversal to westward winds in the entire upper stratosphere and lower mesosphere and the low-latitude winds (8.75°N) show enhanced eastward flow in the upper stratosphere and strong westward flow in the lower mesosphere during the major SSW events at high latitudes. The mesosphere and lower thermosphere (MLT) zonal winds acquired by medium frequency (MF) radar at Tirunelveli (8.7°N, 77.8°E) show a change of wind direction from eastward to westward several days before the onset of SSW events and these winds decelerate and weak positive (eastward) winds prevail during the SSW events. The time variation of zonal winds over Tirunelveli is nearly similar to the one reported from high latitudes, except that the latter shows intense eastward winds during the SSW events. Besides, the comparison of daily mean meridional winds over Tirunelveli with those over Collm (52°N, 15°E) show that large equatorial winds are observed over Tirunelveli during the 2005–2006 event and over Collm during the 1998–1999 events. The variable response of MLT dynamics to different SSW events may be explained by the variability of gravity waves.  相似文献   

11.
The Intensive Field Phase of Indian Ocean Experiment (INDOEX, IFP-99) was carried onboard Oceanic Research Vessel Sagar Kanya during January 20–March 12, 1999 over the latitudinal range 15°N–20°S and the longitudinal range 63°E–77°E. The present study deals with the spatial variation of air–sea fluxes over the Indian Ocean during the INDOEX, IFP-99 campaign. Drag coefficient (C_D), and sensible heat (CH) and water vapor (CE) exchange coefficients are determined using an iterative scheme. The estimated values of these coefficients are utilized for the computation of air–sea fluxes using the bulk aerodynamic method. The variations of air–sea flux estimates are studied with respect to the variation of wind speed.  相似文献   

12.
The spatial distribution of the aerosol optical depth during the northern winter, along the West coast of India and over the oceanic environments of the Arabian Sea and the South-West Indian Ocean (between 60°E–78°E and 15°N–20°S), has been investigated using co-ordinated ground-based and ship-borne measurements carried out during January–March of 1998 and 1999 under the Indian Ocean Experiment (INDOEX). In this paper apart from the expected results, an interesting observation is presented of enhanced aerosol activity in the mid Arabian Sea, far removed from the continent. Its implications are discussed.  相似文献   

13.
We describe the parallel algorithms for studying the structural features of the anomalies in the gravity and magnetic fields of the lithosphere, which are based on the height transformations of the data. The algorithms are numerically implemented on the Uran supercomputer. The suggested computer technology is used for constructing the maps of the regional and local anomalies of the magnetic and gravity fields for the northeastern sector of Europe within an area confined between 48°–62° E and 60°–68° N.  相似文献   

14.
The distribution of U in volcanic rocks from two transects across the Central Andes (latitudes 27°–28° S and 16°–18° S, respectively) differs from that of K. For a given SiO2, content of the rocks, K systematically increases with the distance from the trench, while the highest U abundances are found in the rocks overlying the thickest segments of the continental crust, which are situated in the middle parts of the transects. It is suggested that this variation of U reflects crustal contamination.  相似文献   

15.
Following a previous attempt to reproduce miniature sorted patterns on a level surface, we report the results of a full‐scale laboratory simulation on frost sorting produced by needle ice activity on inclined surfaces. Four models, with different slope gradients (5°, 7°, 9°, 11°), were designed. Stones 6 mm in diameter placed in a grid covered 20% of the surface of frost‐susceptible water‐saturated soil. These models were subjected to 20–40 freeze–thaw cycles between 10°C and ?5°C in 12 hours. The evolution of surface patterns was visually traced by photogrammetry. Needle ice growth and collapse induced downslope movement and concentrations of stones. A model produced incipient sorted circles on a 5° slope, whereas it resulted in three distinct sorted stripes on a 7° slope. The average diameter or spacing of these forms is 9.7–19.4 cm, comparable to those in the field dominated by diurnal freeze–thaw cycles. Surface parallel displacements of stone markers were traced with motion analysis software. The observed downslope stone displacements agree with those expected assuming that surface soil and stones move by repeated heaving perpendicular to the surface and vertical settlement due to gravity, although the growth of curved needle adds complexity to the overall displacements. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

16.
Yong-Feng  Zhu  Hans-Joachim  Massonne  Thomas  Theye 《Island Arc》2007,16(4):508-535
Abstract Four phengite‐bearing eclogites, taken from different depths of the Chinese continental scientific drilling (CCSD) borehole in the Sulu ultrahigh pressure terrane, eastern China, were studied with the electron microprobe. The compositional zonations of garnet and omphacite are moderate, whereas phengite compositions generally vary significantly in a single sample from core to rim by decrease of the Si content. Various geothermobarometric methods were applied to constrain the P‐T conditions of these eclogites on the basis of the compositional variability of the above minerals. The constrained P‐T path for sample B218 is characterized by pressure decrease from ca 3.0 GPa (ca 600°C) to 1.3 GPa (ca 550°C). Eclogite B310 yielded P‐T conditions of 3.0 GPa and 750°C. The path for eclogite B1008 starts at about 650°C and 3.6–3.9 GPa (stage I) followed by a pressure decrease to 2.8–3.0 GPa and a significant temperature rise (stages II and IIIa, 750–810°C). Afterwards, this rock cooled down to 620–660°C at still high pressures (2.5–2.7 GPa, stage IIIb). Retrograde conditions were about 670°C and 1.3 GPa (stage IV). Eclogite B1039 yielded a P‐T path starting at ca 600°C and 3.3–3.9 GPa (stage I). A pressure decrease to about 3.0 GPa (stage II, 590–610°C) and then a moderate isobaric temperature increase to ca 630°C (stage III) followed. Stage IV is characterized by temperatures of 650°C at pressures close to 1.3 GPa. During and after this stage (hydrous) fluids partially rich in potassium penetrated the rocks causing minor changes. Relatively high oxygen fugacities led to andradite and magnetite among the newly formed minerals. We think that the above findings can be best explained by mass flow in a subduction channel. Thus, we conclude that the assembly of UHP rocks of the CCSD site, eclogites, quartzofeldspathic rocks, and peridotites, cannot represent a crustal section that was already coherent at UHP conditions as it is the common belief currently. The coherency was attained after significant exhumation of these UHP rocks.  相似文献   

17.
Climate change analysis is essential, considering the numerous economic and ecological implications of this critical global environmental issue. This paper analyzes the spatial and temporal trends of mean air temperature in Romania’s most important agricultural area, the south and south-eastern region, between 1961 and 2009. In this respect, multiannual (the entire period) and multidecadal (1961–1990, 1971–2000, 1981–2009) trends were analyzed using the Mann–Kendall test and Sen’s slope method at 23 weather stations, annually, seasonally and for the growing season of the region’s main agricultural crops (maize and wheat). Multiannually, the results showed statistically significant temperature increases, on all temporal scales (maximum rate of 0.06 °C/year recorded in summer, equivalent to a net temperature rise of 2.82 °C), except for the autumn season (cooling without statistical significance). Multidecadally, the 1961–1990 period is marked by a general cooling, especially in autumn (maximum values of ?0.07 °C/year or over 2 °C net cooling). In the 1971–2000 and 1981–2009 periods, a general warming was observed (maximum in summer for both multidecades, when positive rates peaked at 0.09 °C/year, or 2.5–3 °C net warming), but the warming of the last three decades is the most prominent in terms of spatial average magnitude and trend significance. Upon analysis of the impact of climate warming on agricultural yields (maize) through linear regression, in the 1991–2000 decade, considered as case study, it was found that in 32 % of the total analyzed area there are evident relationships between the two variables (p value <0.05). In this case, a dependency of 33–50 % (40 %, on average) of maize to climate was found, and a sensitivity (loss) ranging between 0.9 and 1.5 t/ha/year (1.2 t/ha/year, on average) for a 1 °C temperature rise. At the same time, significant losses (of up to 1.7 t/ha/year) of maize for a 1 °C temperature rise were identified in 51 % of the area, but with little p value significance (between 0.05 and 0.1). It is however necessary to analyse the agro-climatic results cautiously, considering that only one decade of climate-agriculture relationship was studied. The results can be useful first and foremost for mitigating the climate change impact on agricultural systems, by prioritizing future adaptation strategies enforced by policy makers.  相似文献   

18.
Weathering microforms associated with exfoliation were investigated on 40 granitic spheroidal boulders identified on Pricopan Ridge (M?cin Mountains) in order to establish a spatial distribution pattern. Continuous thermal monitoring allowed the frequency and intensity distribution assessment of short‐term temperature changes triggered by summer storms, of intense day–night amplitudes and frost cycles across a uniform rounded boulder. Rock strength estimated by Schmidt hammer tests differentiates a significantly weaker resistance on the southern face of the boulders (rebound values of 27 to 33) in comparison with the northern face (43–50). The lowest resistance of the north–south cross‐boulder profile corresponds to the southern gentle slopes (0°–45°) thus defining the most susceptible area to exfoliation and other weathering processes. It is argued that this low‐resistant sector fits well with the maximum frequency and intensity of thermal processes recorded on the low and mid slopes (0°–45°) of the boulders south side, with small differences from one process to another, whilst the sector of 20° to 30° south corresponds to the peak activity of all. In accordance, the overlay map of exfoliated surfaces places the high frequency area on a spherical cap developed similarly (between 5° north and 45° south). The smallest exfoliated surfaces normally appear around 30° south and are inferred to extend in time both to the boulder top and downslope. The correlations between the frequency/intensity maps of thermal processes and the frequency map of exfoliated surfaces point to a complementary action in the exfoliated surfaces development of the short‐term temperature changes and diurnal cooling and heating due to the directional insolation effect, as similarly inferred in the development of meridional cracks. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

19.
The preliminary results of solar filaments distinguished in daily H-alpha observations at Kodaikanal (1912–2002) are presented. To mark the boundaries of solar filaments, methods based on automated procedures of marking low-contrast objects on the solar disk, as well as editing of the marked boundaries in a semiautomated manner, were developed. The characteristics of solar filaments were analyzed. Latitudinal diagrams of filaments number in 15–23 activity cycles were constructed. As is shown, one maximum in the filament latitudinal distribution may be clearly distinguished during activity cycles in both hemispheres. This maximum is located slightly higher (θ ~ 25°–30°) than the sunspot distribution maximum (θ ~ 14°–17°). However, there are no other local maxima related to the zonal structure of the large-scale magnetic field (Makarov and Sivaraman, 1989).  相似文献   

20.
Two large earthquakes occurred in the western part of China in 2008, one of them being the Yutian (35.6°N, 81.6°E) M7.3 earthquake that occurred on March 21 (BJT) and the other the Wenchuan (31.0°N, 103.4°E) M8.0 earthquake that occurred on May 12 (BJT). In this paper, the West Continental China (included in 20.0°–50.0°N, 70.0°–110.0°E region) was the study region for verifyong the predictability of the pattern informatics (PI) method using the receiver-operating characteristic curve (ROC) test and R score test. Different forecasting maps with different calculating parameters were obtained. The calculating parameters were the grid size Δx, base time t b, reference interval t b to t 1, change interval t 1 to t 2, and forecasting interval t 2 to t 3. In this paper, the base time t b fixed to June 1, 1971, the ending forecast time t 3 fixed to June 1, 2008, and the forecasting interval t 2 to t 3 changed from 1 to 10 years, and the grid sizes were chosen as 1° × 1° and 2° × 2°, respectively. The results show that the PI method could forecast the Yutian M7.3 and Wenchuan M8.0 earthquakes only using suitable parameters. Comparing the forecast results of grid sizes 1° × 1° and 2° × 2°, the models with 2° × 2° grids were better. Comparing the forecast results with different forecasting windows from 1 to 10 years, the models with forecasting windows of 4–8 years were better using the ROC test, and the models with forecasting windows of 7–10 years were better using the R score test. The forecast efficiency of the model with a grid size of 2° × 2° and forecast window of 8 years was the best one using either the ROC test or the R score test.  相似文献   

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