共查询到20条相似文献，搜索用时 15 毫秒
1.
A. B. Bhattacharya 《Annales Geophysicae》1994,12(2-3):232-239
Radar observations of nor’wester (premonsoon thunderstorm) as experienced over the Gangetic West Bengal and the integrated field intensity of atmospherics (IFIA) at 10, 20 and 30 kHz recorded over the tropical station at Calcutta have been analysed. The records of IFIA reveal that, during nor’wester, the enhancement in the signal level occurs in three different stages: (i) gradual rise of atmospherics (GRA), (ii) first sudden enhancement of atmospherics (SEA1) and (iii) second sudden enhancement of atmospherics (SEA2. Their respective occurrences have been found to be prevalent in pre-noon, latenoon and afternoon hours of a day. Of the three stages, GRA and SEA1 have been found to occur before the onset of thunderstorm, while SEA2 may even occur after its onset. A comparative study reveals that the precipitation during premonsoon thunderstorms is associated with the second sudden enhancement, while it is associated with the steady recovery of IFIA during the monsoon and postmonsoon thunderstorms. The characteristics of the first nor’wester of every year have been critically examined with an additional consideration of simultaneous radiosonde records. A probable explanation has been made in terms of the distribution of the effective sources at such times around the observing site. 相似文献
2.
A. B. Bhattacharya S. K. Kar M. K. Chatterjee R. Bhattacharya 《Annales Geophysicae》1998,16(2):183-188
The records of VLF atmospherics over Calcutta and then over Kalyani (West Bengal) during the torrential rainfall, caused by violent monsoon and post-monsoon depressions, exhibit distinct long-period fadings both at day and night. Interesting results obtained from an analysis of round-the-clock atmospherics data and associated meteorological parameters are reported in this paper. A possible correlation between the severe meteorological activity with the solar geophysical phenomena was studied. The results are indicative of an interesting sequence of solar-terrestrial events. A tentative conclusion is reached, suggesting an origin of the fading from atmospheric gravity waves generated in the centre of activity of the depressions concerned.Currently at: Department of Physics, Serampore College, Serampore, 712 201 West Bengal 相似文献
3.
Ivana Nemešová Jaroslava Kalová Martin Dubrovský 《Studia Geophysica et Geodaetica》1999,43(2):201-222
Three-dimensional general circulation models (GCMs) are 'state-of-the-art' tools for projecting possible changes in climate. Scenarios constructed for the Czech Republic are based on daily outputs of the ECHAM-GCM in the central European region. Essential findings, derived from validating, procedures are summarized and changes in variables between the control and perturbed experiments are examined. The resulting findings have been used in selecting the most proper methods of generating climate change projections for assessing possible hydrological and agricultural impacts of climate change in selected exposure units. The following weather variables have been studied: Daily extreme temperatures, daily mean temperature, daily sum of global solar radiation, and daily precipitation amounts. Due to some discrepancies revealed, the temperature series for changed climate conditions (2×CO
2
) have been created with the help of temperature differences between the control and perturbed runs, and the precipitation series have been derived from an incremental scenario based on an intercomparison of the GCMs' precipitation performance in the region. Solar radiation simulated by the ECHAM was not available and, therefore, it was generated using regression techniques relating monthly means of daily extreme temperatures and global radiation sums. The scenarios published in the paper consist of monthly means of all temperatures, their standard deviations, and monthly means of solar radiation and precipitation amounts. Daily weather series, the necessary input to impact models, are created (i) by the additive or multiplicative modification of observed weather daily series or (ii) by generating synthetic time series with the help of a weather generator whose parameters have been modified in accord with the suggested climate change scenarios. 相似文献
4.
Distributed modeling of monthly air temperatures over the rugged terrain of the Yellow River Basin 总被引：1，自引：0，他引：1
Our analyses of the monthly mean air temperature of meteorological stations show that altitude, global solar radiation and
surface effective radiation have a significant impact on air temperature. We set up a physically-based empirical model for
monthly air temperature simulation. Combined the proposed model with the distributed modeling results of global solar radiation
and routine meteorological observation data, we also developed a method for the distributed simulation of monthly air temperatures
over rugged terrain. Spatial distribution maps are generated at a resolution of 1 km×1 km for the monthly mean, the monthly
mean maximum and the monthly mean minimum air temperatures for the Yellow River Basin. Analysis shows that the simulation
results reflect to a considerable extent the macro and local distribution characteristics of air temperature. Cross-validation
shows that the proposed model displays good stability with mean absolute bias errors of 0.19°C–0.35°C. Tests carried out on
local meteorological station data and case year data show that the model has good spatial and temporal simulation capacity.
The proposed model solely uses routine meteorological data and can be applied easily to other regions.
Supported by China Meteorological Administration key Project on New Technique Diffusion (Grant No. CMATG2006Z10) and Jiangsu
Key Laboratory of Meteorological Disasters (Grant No. KLME050102) 相似文献
5.
Seasonal and monthly global patterns of outgoing longwave radiation, albedo, absorbed solar radiation, and net radiation have been derived from scanning radiometer observations aboard the NOAA polar orbiting satellites since June 1974. These patterns, along with patterns of interannual differences in seasonal and monthly heating, are examined for the three summers of 1974–76 over the Eastern Hemisphere in relation to the variations in the summer monsoon and the major circulation features. During portions of the summer of 1975 the monsoon was more active than in 1974 and 1976, as evidenced by increased albedo and decreased longwave radiation over large sections of India, the Indian Ocean, Southeast Asia, and the Western Pacific. The roles of clouds, snow cover, and other surface characteristics in modulating the radiation balance and circulation are discussed. The pre-monsoon radiative heating in spring is examined with respect to monsoon onset and intensity in the three years. 相似文献
6.
M. I. Beloglazov V. I. Kirillov V. V. Pchelkin A. A. Galakhov 《Geomagnetism and Aeronomy》2014,54(2):248-252
Daily variations in the intensities of atmospherics at 600 Hz and 6 kHz detected at the Lovozero observatory from June to December 2012 were studied. Under quiet geomagnetic conditions, daily variations of atmospherics are shown to be determined by both the waveguide parameters of the Earth’s ionosphere and the activity of storm centers. In summer, a broad daytime maximum of atmospherics flow N hr (the number of atmospherics per hour) is detected most likely due to the lightning activity in mid-latitude regions that are nearer to the observatory than the global storm centers. The daily variations in atmospherics mean amplitudes per hour A hr differ appreciably from the daily variations N hr, reflecting largely the changes in lighting conditions along signal propagation paths. The distribution function of the levels of atmospherics can be approximated by the following formula taken from publications: P(X) = [1 + (X/X 50) k ]?1, where k is a parameter that changes from 2.2 to 3.2 at f = 600 Hz and from 1.5 to 2 at f = 6 kHz under quiet geomagnetic conditions. 相似文献
7.
8.
Yu. M. Mikhailova G. I. Druzhin G. A. Mikhailova O. V. Kapustina 《Geomagnetism and Aeronomy》2006,46(6):783-795
Results of studying the thunderstorm activity dynamics during the Pacific hurricanes in August and October 2001, using broadband recording of the time forms of atmospherics on Kamchatka, have been presented. The number of atmospherics per minute at simultaneously determined azimuths of their sources has been used as an example of thunderstorm activity. An analysis of data processing results has indicated (a) in the absence of hurricanes, the maximal atmospheric flux level (10 ± 4 pulse/min) was observed at night, and the daylight level was 3 ± 1 pulse/min; (b) thunderstorm activity increases at the stage of tropical depression regardless of depression development into hurricane; in this case the flux of atmospherics can increase to 250 pulse/min at night and can be widely variable (5–100 pulse/min) in daytime; (c) in the sate of hurricane maturity, the thunderstorm activity level is not higher than the background level. It has been indicated that IGWs in the Earth’s atmosphere and the lower ionosphere are caused by lightning strokes accompanied by shock waves during expansion of the lighning channel. The results obtained are of interest in studying anomalous effects in the natural electromagnetic field in the VLF band during increased seismic activity on Kamchatka. 相似文献
9.
Dr. Ing. Heinz Meinhold 《Pure and Applied Geophysics》1948,12(1-2):14-22
Zusammenfassung Der zeitliche Gang der atmosph?tischen St?rungen ist zwei Einflüssen unterworfen: 1) Der zeitlichen und r?umlichen Verteilung
der St?rquellen, 2) Den jeweiligen Ausbreitungsbedingungen des zu empfangenden Frequenzbandes. Die bei 5,5 MHz durchgeführten
Messungen des atmosph?rischen St?rpegels zeigen den erwarteten Zusammenhang zwischen dem t?glichen Gang und dem Sonnenstand
entsprechend den normalen Ausbreitungsbedingungen im 50 m Band. W?hrend M?gel-Dellinger Effekte nicht festgestellt werden
konnten, ist die Nordlichtst?rung als Folge einer Korpuskularstrahlung der Sonne klar zu erkennen.
Summary The temporal variation of atmospherics is subjected to two facts: 1) The temporal and local distribution of sources of atmospherics, 2) The present conditions of propagation with regard to the just received short-wave band. Measurements of atmospherics in 50 m-band proved the connection between atmospherics and solar-radiation corresponding to the normal conditions of short-wave propagation, showing a minimum at day and a maximum at night. Whilst the Dellinger-effect did not happen, atmospherics disappeard on account of aurora borealis and strong disturbance of the earth's magnetic field, in consequence of corpusculare-radiation of the sun. Monthly distribution of atmospherics in 50 m-band for 2 years measurements are given.相似文献
10.
V. A. Mullayarov L. M. Abzaletdinova V. V. Argunov A. A. Korsakov 《Geomagnetism and Aeronomy》2011,51(6):825-834
The specific features of a method for radiosounding the lower ionosphere over earthquake epicenters using LF electromagnetic
signals of thunderstorm sources (atmospherics) have been considered. The effects of shallow-focus earthquakes with magnitudes
larger than 4.0 and their precursors manifest themselves in amplitude characteristics of atmospherics. It has been assumed
that variations in the signal characteristics are related to disturbances in the lower ionosphere. According to the results
of azimuthal scanning, cross-sectional dimensions of disturbed regions, as a rule, correspond to the dimensions of the first
two Fresnel zones for signals at a frequency of 10 kHz. Azimuthal scanning also indicated that the positions of disturbed
regions during and before earthquakes could have a certain dynamics and differ from the projection onto the earthquake epicenter.
The ratio of the amplitudes of electric and magnetic signal components, in the variations of which seismic effects before
earthquakes can also be observed, has been considered. An analysis of the ratio makes it possible to increase the probability
of predicting earthquakes when using the characteristics of the electromagnetic signals of lightning discharges as an additional
method of complex monitoring of disturbances in the lower ionosphere caused by seismic processes. 相似文献
11.
Summary Measurements of the total solar radiation at normal incidence, undertaken at Helwan Observatory, on every clear day and for a period of 10 years, have been studied in terms of the air mass and the sun's altitude. These measurements together with the data available in the literature on diffuse radiation, have led to the evaluation of the hourly rates of total solar radiation on vertical surfaces and south facing surfaces inclined to the horizontal at different tilt angles. 相似文献
12.
The effects of the solar eclipse of March 29, 2006, in the signals of ULF radio stations, in the intensity of regular radio noise at frequencies of 0.3–10 kHz, and in the number of atmospherics received in Yakutsk mostly from the west have been considered. The observations were performed using a multichannel parallel analyzer-recorder (11 channels in the frequency band 0.47–8.7 kHz), one-point lightning direction and range finder (0.3–100 kHz), narrow-sector radio noise direction-finder (0.3–10 kHz), recorder of signals from VLF radio stations, and broadband radio noise recorder (0.3–100 kHz). A GPS clock was used to synchronize a recorder of signals from VLF radio stations. The effect was observed in radio signals, radio noise, and number of atmospherics from the direction 270° ± 20° counted off clockwise from the north during the last stage of the eclipse (～ 1100–1200 UT), when the lunar shadow approached the line of the nighttime terminator and obscured part of the signal propagation path. The effect was observed as an enhancement of the received signals by a factor of ～1.2, a factor of ～1.4 increase in the number of atmospherics, and a change in the radio station phase values. 相似文献
13.
Abstract Solar radiation, direct and diffuse, is affected by surface characteristics, such as slope, aspect, altitude and shading. The paper examines the effects of topography on radiation, at multiple spatiotemporal scales, using suitable geometric methods for the direct and diffuse components. Two indices are introduced for comparing the direct radiation received by areas at the same and different latitudes. To investigate the profile of direct radiation across the whole of Greece, these are evaluated from an hourly to annual basis, via GIS techniques. Moreover, different approaches are examined for estimating the actual global radiation at operational spatial scales (sub-basin and terrain), according to the available meteorological data. The study indicates that the errors of typical hydrometeorological modelling formulas, which ignore the topographic effects and the seasonal allocation of direct and diffuse radiation, depend on the spatial scale and are non-uniformly distributed in time. In all cases, the estimations are improved by applying the proposed adjustment approaches. In particular, the adjustment of the measured global radiation ensures up to 10% increase of efficiency, while the modified Angström formula achieves slight (i.e. 2–4%) increase of efficiency and notable reduction of bias. Editor Z.W. Kundzewicz Citation Mamassis, N., Efstratiadis, A. and Apostolidou, I.-G., 2012. Topography-adjusted solar radiation indices and their importance in hydrology. Hydrological Sciences Journal, 57 (4), 756–775. 相似文献
14.
Jan Bednář Jaroslava Kalvová Reviewer K. Vaníček 《Studia Geophysica et Geodaetica》1980,24(4):400-413
Summary The statistical treatment of the dependence of monthly sums of global radiation on the monthly sums of sunshine at the stations of Hradec Králové, Bratislava — Koliba and Hurbanovo is presented. The parameters of linear and quadratic regression are derived for the said stations and for the individual months of the year. Drawing on the statistical analysis of the initial data sets, the accuracy and reliability of the mentioned regression relations are critically evaluated. 相似文献
15.
Summary Measurements of the total incoming solar radiation on a horizontal surface have been recorded since 1967 at a network of actinometric stations in Iraq. The instrument used at each of these stations is a bimetallic actinograph of the Robitzsch type. The stations at Mosul, Baghdad and Nasiriya have been selected, to represent respectively the northern, central and southern climatic zones of Iraq.This paper examines from the available records at these stations, until August 1973, the differnt aspects of radiation climatology which are important in solar energy utilizations. The mean annual, monthly and daily radiation; the number of days in which the radiation has exceeded certain given limits and the periods of successive days having radiation less than 100 and 250 cal cm–2 day–1 have been studied and presented in tabular and graphical forms suitable for direct application.To architects and engineers interested in the availability of solar radiation on vertical and inclined surfaces, the hourly radiation values for Baghdad have been studied for the different months of the year and the corresponding isopleths on the horizontal have been drawn. 相似文献
16.
T. C. O'Connor 《Pure and Applied Geophysics》1957,38(1):154-156
Summary The feasibility of using the difference in the evaporation from a black and a white atmometer for the continuous routine measurement of global radiation at a field station was examined. The atmometers were operated continuously for 177 days and the results obtained were compared with measurements of the global radiation for the corresponding period as given by a Bellani pyranometer. Good agreement between the monthly totals of global radiation from both methods was obtained.
Zusammenfassung Es wird die Möglichkeit der Benützung der Differenz der Verdunstung von einem Schwarz- und Weiss-Kugel-Atmometer für fortlaufende Messung der Globalstrahlung an einer Feldstation geprüft. Die Atmometer wurden während 177 Tagen ununterbrochen in Betrieb erhalten und die Resultate mit den Messungen eines Bellani-Pyranometers für den gleichen Beobachtungszeitraum verglichen. Die Monatssummen der Globalstrahlung nach beiden Methoden stimmen gut überein.相似文献
17.
Agricultural production from steep terrain is frequently limited to pasture systems, where forage harvesting is done by grazing animals. Intercepted solar radiation determines the energy available for forage production. A model was developed for estimating potential direct beam radiation in areas with a wide range of aspects, landscape positions, and various shadow sources. The model was applied to a small, steep pasture watershed in central Appalachia to determine the spatial distribution of potential direct beam radiation. Effective horizon was an important parameter affecting the energy budget of the study watershed. A simple means for estimating global radiation from the modelled potential direct beam radiation, given atmospheric transmissivity and cloudiness, was presented. When the proportion of global radiation that was diffuse radiation was increased the effective horizon was less important and the spatial variability of modelled radiation decreased. 相似文献
18.
利用M-K相关分析方法和大通站1950-2000年逐月径流资料,研究了长江下游干流径流的趋势变化.研究结果表明:1950s以来长江下游径流量呈增加趋势,1990s平均径流量(30415.3 m3/s)比所有其他年代平均径流都大,为近50a以来的最大值;就季节和月份而言,秋季径流明显减少;夏、冬两季径流量,增加的趋势明显,尤以冬季枯水季节径流增加最为突出.洪水、枯水季节径流增加明显,但以枯水季节径流增加占优势.冬季枯水径流的增加,可能在一定程度上能够缓解长江口生态环境的巨大压力.1990s径流量的增加与全球变暖、水循环加快、长江流域降水量增加密切相关. 相似文献
19.
K. Kh. Truong T. S. Vo Yu. M. Mikhailov A. L. Kharitonov O. V. Kapustina 《Geomagnetism and Aeronomy》2010,50(5):690-694
The preliminary results of observations of VLF electromagnetic signals (atmospherics) in the mountains of North Vietnam (Dien
Bien Phu, 21°23′50″ N, 103°0′28″ E) are presented. Primarily, signals of typical atmospherics with a maximum in the frequency
range of 4–9 kHz were observed; sometimes they were accompanied by so-called “tails” at frequencies less than 1 kHz, and also
tweeks of usually short duration (about 10 ms) were observed. Several parameters of the ionosphere, as well as the distance
to sources of atmospherics (in accordance to the data of the World Wide Lightning Location Network (TOGA)), were estimated
by spectral-temporal characteristics of tweeks. 相似文献
20.
Summary The technique for evaluating the natural illumination of direct solar radiation introduced byÅngström andDrummond [1]2) has been applied by the authors to the pyrheliometric observations in India and the values of natural illumination derived at eight representative stations are presented in this paper. The dirunal and seasonal variations of the illumination fluxes have been discussed. —In general, illumination fluxes in India show a maximum during summer season except at Madras, where the maximum occurs during winter. The illumination fluxes at various stations vary within the range 80–110 kilolux throughout the year. However, at Calcutta, it varies within a rather narrow range of 65–85 kilolux. Both in summer and winter, the illumination flux during forenoon hours is usually more than that during afternoon hours. An increase in daylight illumination is observed with height of the station above sea level. 相似文献