The relation between solar radiation and hours of bright sunshine at some tropical stations

Pure and Applied Geophysics - The relationship between (Q) total solar radiation, as measured by a solarimeter, and hours of bright sunshine (n), as measured by a Campbell-Stokes recorder, has been...     

The thermal diffusivity of soil at tropical stations in southern hemisphere

Summary The study of heat transfer or temperature changes in the surface layers of the soil are important in agricultural science at tropical latitudes. The quantity, thermal diffusivity largely determines the temperature changes produced in the layer of the soil when heat is conducted there from an adjacent layer. Therefore, the authors have determined the thermal diffusivity of the soil at the sites Arapongas (23.5°S, 51.7°W) and São José dos Campos (23.3°S, 45.8°W), in Brazil (South America), in accordance with the simple theory of periodic heat flow in a one dimensional, semiinfinite, homogeneous medium. The diffusivity increases with the increase of moisture content in the surface layers of the soil. The results of diffusivity obtained from these methods agree well with those of past workers obtained by other techniques.     

Studies on precipitable water over tropical stations in relation to monsoon flow

Summary The mean monthly precipitable water at four tropical stations Madras (13°00N, 80°11E), Waltair (17°42N, 83°18E), Bombay (18°54N, 72°49E) and Nagpur (21°06N, 79°03E) are evaluated for the layer surface to 500 mb (0–5.4 km) of the atmosphere using radiosonde data available for seven years period (1959–1965). The mean monthly precipitable water for the above four stations is also estimated from dew point temperature.The precipitable water in the air column at any station is examined in relation to monsoon flow. The higher values of precipitable water are found to occur over the regions when there is good supply of moisture by the monsoon flow as well as low level convergence. These studies are believed to provide useful information in forecasting the monsoon circulation over the country.     

Atmospheric turbidity at athens observatory

Summary In this study, values of the Ångström turbidity coefficient () determined from Solar radiation observations at the National Observatory of Athens over the period 1955–1972 are analysed. Mean daily turbidity lies between 0.020–0.100. Turbidity is higher in summer than in winter. The main factor determining the turbidity is the air mass type. The scavenging by rainfall probably has a considerable effect in determining this distribution. There is some evidence of a trend of increasing turbidity during the period.     

Oscillation of wind temperature humidity in the atmospheric surface layer over tropical semi-arid stations

Analysis of wind, air temperature, humidity and rainfall data from Land Surface Processes Experiment (LASPEX) in the surface layer at Anand (22°35′N, 72°55′E) and Khandha (22°02′N, 73°11′E) during January to December 1997 is presented. Wind and temperature at various levels showed prominent diurnal variation. Progression of daily wind and temperature revealed the intra-seasonal, quasi-biweekly and 6–9 day oscillations indicated large-scale convection, transport of heat and water vapor from Arabian Sea towards these stations.Power spectrum of wind and humidity corroborated the planetary scale Madden–Julian oscillation in the surface layer. Periodic oscillations of 21, 6–9, 1 day and 12 h were prominent in the spectrum of all variables. Low-frequency spectral peaks showed the energy in wind is 2–3 times higher over Khandha than at Anand whereas temperature is 3 times higher at Anand than Khandha.     

Atmospheric electric potential gradient at Vishakapatnam

Atmospheric electric potential gradient measurments were made near the ground at Vishakapatnam (17°42N, 83°18E). The diurnal variation of potential gradient during fair weather has been studied. The characteristic pattern of potential gradient in different months, different seasons and its annual variation are examined.     

Surface energy balance at a tropical station

Summary Studies of various fluxes, namely net radiation, soil heat, sensible heat and latent heat observed at a tropical station are presented in this paper. The time variation of these fluxes are examined in relation to various meteorological parameters and atmospheric conditions. The turbulent transfer coefficients have been evaluated to examine the applicability of the classical theory or the non-equivalence theory for eddy transport in the lower layers of the atmosphere. The energy balance at a tropical station is evaluated. It is found over year there is a net surplus of 94,000 ly. A detailed discussion of the disposal of this energy by various consuming processes is given.Symbols and notation All the quantities represented by symbols in the text of the paper are defined below C _p specific heat at constant pressure in cal. g^–1 °K - E evaporation in g cm^–2 hr^–1 - E ^* evaporative heat flux cal. cm^–2 sec^–1 (in Eq. 10) - e vapour pressure in millibars - e _z ,e _2z vapour pressure at heightsz and 2z - g acceleration due to gravity - H sensible heat flux cal cm^–2 sec^–1 (in Eq. 12) - K _M ,K _H ,K _W coefficients of eddy diffusivities of momentum, heat, and water vapour respectively in cm² sec^–1 - k von Karman' constant=0.4 - L Monin-Obukhov length (according to Monin and Obukhov [53] the structure of the turbulent boundary layer is determined by the non-dimensional variableZ/L whereL is defined byL=–(u _* ³ C _p T)/(kgH) - ly langleys - Q _c Q—sensible heat flux in langleys (in Eqs. 3 and 4) - Q _e E—latent heat flux in langleys (in Eqs. 3 and 4) - Q _s S—soil heat flux in langleys (in Eqs. 3 and 4) - Q _i Q _c +Q _e +Q _s whenK _M K _H K _W , (in Eq. 6) - Q' _i Q' _c +Q' _e +Q _s whenK _M =K _H =K _W (in Eq. 7) - qq mean specific humidity g kg^–1     

宽频带流动地震台站中地震计浅井式安装研究

在井下地震观测中,各种地表背景噪声具有显著衰减作用,针对中国地震科学台阵现有大量非专用浅井式设计的Guralp CMG系列地震计,以及目前多个新获批项目在高背景噪声区域的观测需求,设计一种野外实用浅井观测方式,在北京国家地球观象台进行不同深度、不同井壁材质的观测对比实验,分析研究观测数据的背景噪声功率谱密度,结果表明,随着浅井深度的增加,地震背景噪声在垂直、水平向得到改善,改善程度随频率变化有所不同。分析认为,在华北现有地质环境下,6 m浅井是较为经济的观测方式,性价比高、占地小、施工简便,可用于后续多个项目的宽频带流动地震台阵观测。     

Ionospheric response to magnetic activity at low and mid-latitude stations

The F2-layer response to the moderate storm of 5–7 April 2010 was investigated using data from two equatorial stations (Ilorin: lat. 8.5°N, 4.5°E; Kwajalein: lat. 9°N, long. 167.2°E) and mid-latitude (San Vito: lat. 40.6°N, long. 17.8°E; Pruhonice: lat. 50°N, long. 14.6°E). Before storm commencement, enhancement, and depletion of NmF2 values were observed in the equatorial and mid-latitude stations, respectively, indicating the latitudinal dependence of the pre-storm event. All the stations with the exception of Kwajalein show positive phase in NmF2 response at the storm onset stage. Positive phase in NmF2 continues over Ilorin and appears on the daytime ionosphere of Kwajalein on 6 April, whereas negative phase suppressed the positive feature in Pruhonice and San Vito until the recovery condition. The differences in the response of F2-layer to the storm for the two equatorial stations were attributed to their longitudinal differences. On the average, both the AE and D _st indices revealed poor correlation relationship. More studies are required to ascertain this finding.     

On geophysical explanation of some irregular variations of the mean latitudes of latitude stations

Mean latitude variations computed by Orlovs or other filters have some irregular variations in addition to secular ones. These are of the order of ±0.05 to ±0.1, they can last several years and sometimes show regional similarities. In looking for an explanation of such latitude variations several physical mechanisms have been investigated. The most probable one is the mechanism of stress propagation in the lithosphere and asthenosphere. The consequent gravitational and deformational effects could explain both the magnitude and the time dependance of the irregular latitude variations.     

Studies on radiation balance at a tropical station

Summary Studies of various radiation fluxes, namely solar radiation, albedo (reflection coefficient), long-wave radiation of the earth and the atmosphere and net radiation observed at a tropical station are presented in this paper. The time variation of these fluxes are examined in relation to various meteorological parameters and atmospheric conditions.The constants of the general radiation balance equation are determined. The calculated radiation balance equation with new constants for the station isR=0.86 (1–)S–4.2. A high correlation coefficient 0.99 is obtained between net short-wave radiation (1–)S and net radiationR. The radiation balance at a tropical station is evaluated. It is found over a year there is a net surplus of 94 kilo-langleys.     

地下流体台站观测室内化学元素分析

对庐江地震台化学实验室内不同季节空气中氡和汞含量进行测量、分析,得出影响观测室内空气中氡值的主要因素为,标定仪器和空气流通情况,并与国家环境控制标准做对比,得出庐江地震台化学实验室内空气质量符合国家环境控制标准要求。同时,对如何降低室内空气中氡、汞的含量,提出相应的预防措施。     

Radium and barium at GEOSECS stations in the Atlantic and Pacific

²²⁶Ra and Ba show a general linear correlation in the oceanic water column within the uncertainties of the data: the slope of the line is about 4.6 nanomoles (nmoles) Ra/mole Ba, the intercept being at about 4 nmoles Ba/kg. This demonstrates the usefulness of Ba as a “chemical analogue” of Ra. Box-model calculations indicate that the average deep-water excess of Ra over Ba should be about 10% relative to the surface. This is consistent with the observations outside the deep northeast Pacific. However, the uncertainties in the data are such that the regional variation in the primary input cannot be resolved. In the deep waters of the North Pacific there is in fact a large excess of Ra relative to Ba. The one detailed profile presently available (204) can be explained consistently by a simple vertical advection-diffusion model.     

Diurnal variation of surface currents at a tropical station

The surface measurements of different atmospheric electrical and meteorological parameters made at a tropical station were analyzed, to study their diurnal variation pattern with specific emphasis on convection current and the meteorological conditions responsible for its generation. The analysis shows that most of the time the displacement current is very small. The convection current is positive for most of the time of the day indicating transport of negative charge to the earth by convection. In spite of very low winds during night, the convection current is found to be more during night than during day. Large space charge density gradient near the earth's surface during stable and stratified atmosphere at night may be a reason for large convection current during that time. This study demonstrates that eddy diffusion during day time and large space charge gradient during night time are responsible for generation of convection current at this location.     

The weathering rates of some sandstone cliffs central Weald,England

Short-term (1-30 months) weathering rates were obtained for steep cliffs of Cretaceous Ardingly Sandstone in southern England, using a new photographic method. Mean rates for an exposed and a sheltered outcrop were 0.11 and 0.033 mm a^?1 respectively. Significant (p < 0.1) positive correlations were obtained with illumination and algal biomass and a significant negative correlation (p < 0.05) with slope angle. There was no correlation with grain size, porosity, or mean surface temperature. Highest weathering rates were observed on south- and west-facing exposed cliffs. The results are discussed with reference to algal growth, climate, and wind direction.     

Relation between microseisms recorded at seismic stations Praha and Průhonice

Summary In order to compare the course of microseisms recorded at the seismic stations of Praha and Prhonice, the relation between Praha (Wiechert astatic inverted pendulum) and Prhonice (Kirnos — electromagnetic seismographs) amplitudes was derived, using data from the time interval September 1967 — June 1968. It was found that the amplitudes at both stations are almost parallel in time with three almost simultaneous local maxima. In addition corresponding relations have also been found to be valid for the periods.