Association among geomagnetic activity,atmospheric electric field and selected meteorological parameters

The association among the geomagnetic activity (Ap index) and atmospheric electric field, meteorological parameters was investigated using a long series of continuous data set available for Colaba (18o53’N, 72o48’E, 11m ASL) for the period 1936-1966. The meteorological parameters used for the investigation are the surface pressure, temperature, wind velocity and relative humidity. The results of the above study indicate that the atmospheric electric field and the meteorological parameters are associated with the geomagnetic storms with Ap > 100. The atmospheric electric field shows an increasing trend after the geomagnetic storm. The surface pressure dips and surface tempera-tures increase after a geomagnetic storm. The wind velocity shows a decreasing trend and the relative humidity shows an increasing trend after the geomagnetic storm.     

Possible solar influence on atmospheric electric field

A physical hypothesis for the electrical coupling of the troposphere, ionosphere and magnetosphere has been proposed. It is shown that the vertical mass exchange takes place in the troposphere, ionosphere and magnetosphere by the gravity wave feedback mechanism through a chain of eddy systems. The vertical mass exchange gives rise to a vertical aerosol current which is responsible for the generation and mainte-nance of atmospheric electric field and also the variations in the H-component of the geomagnetic field. Any per-turbation in the troposphere would be transmitted to ionosphere and vice versa. A global perturbation in ionosphere, as the one caused by solar variability, is transmitted to troposphere influencing weather systems/geomagnetic/atmospheric electrification processes.The theory relating to the above physical mechanism is discussed. Also, results of analysis of at-mospheric electrical field data for Colaba, Bombay (8°53’ 56”N, 72° 48’ 54”E, 9.8 m ASL) and solar activity indices (Ap index, DST index and MSB crossing dates) for the 31 year period from 1936-1966 which provide statistical evidence for solar influence on atmospheric electrification processes are presented.     

Sea Storms in the Adriatic Sea and the Western Mediterranean during the Last Millennium

Data regarding the frequency andoccurrence of sea storms in the Adriatic Sea and theWestern Mediterranean during the last millennium havebeen extracted from historical written sources. TheAdriatic Sea shows two anomalous periods of high stormfrequency: the first half of the 1500s and the secondhalf of the 1700s. In the 1500s the storms were morefrequent in autumn, while in the late 1700s theyoccurred at high frequency in winter. In the WesternMediterranean, storms had a higher frequency in thefirst half of the 1600s, with two lesser periods ofhigh frequency in the 1400s and at the end of the1700s. Although both records show a maximum frequencyof sea storms during the Spörer Minimum(1416–1534) of solar activity, sunspot series yieldno, or poor, correlation during the other periods oflowest activity, i.e., Oort Minimum (1010–1090), WolfMinimum (1282–1342), and Maunder Minimum (1645–1715),suggesting that a teleconnection between sea stormsand sunspots is improbable or masked in this region.No teleconnection was found either between the ElNiño-Southern Oscillation (ENSO) and surgesflooding Venice or the Western Mediterranean storms orbetween Venice surges and the Northern AtlanticOscillation (NAO).     

Variations in the atmospheric electric field and Meteorological parameters at a Tropical coastal urban station during 1936–40 and 1962–66

Summary The seasonal and diurnal variations in the vertical component of the atmospheric electric field, air temperature, relative humidity and horizontal wind speed were studied using the surface data for the two periods (1936–40) and (1962–66) recorded at the tropical urban station, Colaba, Bombay (18°51N, 72°49E, 11 m ASL), located on the west coast of India.The atmospheric electric field during the latter period (1962–66) is significantly higher (up to 42.3%) than the earlier period (1936–40). This has been attributed to the enhanced particulate concentrations in the atmosphere. The increase noticed in the atmospheric electric field is a maximum during winter and minimum during the monsoon. The atmospheric electric field exhibited a marked semi-diurnal oscillation with peaks at 0900 LST and 2200 LST during winter, premonsoon and post-monsoon seasons of both the periods. During the monsoon season the double oscillation is not marked.The variations noticed in the surface air temperature and the relative humidity are in agreement with those observed in the atmospheric electric field. The horizontal wind speed showed a decrease which has been attributed to the surface roughness resulting from urbanization.With 7 Figures     

The atmospheric electric field in Athens-Greece

Summary In the present study, the daily, annual and seasonal variations of the electric field in Athens-Greece, for all weather as well as for fair weather conditions, for the 16-years period 1965–1980 were examined. The daily variation of the electric field follows a double oscillation. A Fourier analysis was also used for the study of its diurnal variation. The results of the Man-Kendall test showed that the electric field at National Observatory of Athens (NOA), during the 16-years period, is essentially constant. In addition, the influence of the air pollution due to smoke and of wind speed on electric field was examined. It was deduced that an increase of air pollution results in an increase of electric field, while the electric field decreases as the wind speed increases.With 4 figures     

太原市大气电场特征分析

本文主要使用大气电场监测系统资料,分析了太原市大气电场的日变化和年变化,着重分析了高污染地区大气电场值明显高于其他地区的典型特征。在其他不受污染的陆地区域,晴天电场值维持在＋120V左右,而太原市会达到＋600v以上。分析其原因主要是：太原市大气常年污染较严重,主要为气溶胶状态污染物,有粉尘、烟液滴、雾、降尘、飘尘、悬浮物等,导致大气电导率降低,大气电场强度显著增加。日变化为双峰双谷型,主高值出现在傍晚,次高值出现在午前;主低值出现在清晨,次低值出现在午后,与太阳和人类活动保持较好的一致性。年变化为单峰单谷型,极大值出现在冬季,极小值出现在夏季。     

An Experimental Study on the Variation of Atmospheric Magnetic-Field Intensity Related to Dust,Haze, Rain,Snow, and Thunderstorms

Simultaneous measurements of the vertical magnetic field (VMF), three-dimensional electric field, ambient temperature, ambient relative humidity, particle mass concentration, and three-dimensional velocity are conducted during dust, haze, rain, snow, and thunderstorms. The hourly VMF variation (the rate of VMF increment and time increment with a 1-h time interval) is used to evaluate the disturbance level of the atmospheric magnetic field during the abovementioned weather conditions. There is no significant difference in the hourly VMF variations between hazy days and fair weather. However, the hourly VMF variations on dusty, rainy, snowy, and thunderstorm days differ from those in fair weather, implying that these weather conditions significantly affect the atmospheric magnetic field. On hazy days, although the haze particles are charged, the VMF does not change compared with in fair weather, which suggests that the horizontal electric field generated by haze particles is an irrotational field. On dusty and snowy days, the heterogeneity of the charge distribution forms a rotational horizontal electric field, which can induce the VMF to disturb the atmospheric magnetic field. During rain and thunderstorms, the hourly variation in the VMF is larger than in dust and snow, which can be attributed to the rotational horizontal electric field generated by raindrops and clouds. In addition, the hourly variation in the VMF in thunderstorms is one order of magnitude larger than that during days without thunderstorms, indicating that the VMF induced by the cumulonimbus cloud electric field is more significant than that in other weather conditions.

     

2013年“西马仑”台风大气电场特征分析

利用中国气象局提供的台风定位资料和厦门市气象局测得的大气电场等资料,采用对比分析等方法分析了1308号台风"西马仑"登陆后的大气电场变化特征及其与闪电和降水的关系。分析结果表明:测站大气电场、降水和地闪的变化主要受"西马仑"台风后部云系影响。降水强度与负电场强度之间有着较好的对应关系。强降水时段地闪频次较低;地闪活动滞后于大气电场变化5~20min,地闪密集时段也是大气电场跳变最为剧烈的时段。     

Continuing current in multiple channel cloud-to-ground lightning

In this study we analyze the effects of continuing current initiated by strokes following a new channel to ground in multiple stroke flashes using high-speed video records, electric field measurements from a fast antenna and lightning detection network data. We observed that the long continuing current initiated by a stroke that follows a new channel also obeys the pattern in the initiation of long continuing current suggested by Rakov and Uman [Rakov, V.A., Uman, M.A., 2003. Lightning: Physics and Effects, 687pp., Cambridge Univ. Press, New York.]. We also verify that the statement of Rakov and Uman [Rakov, V.A. and Uman, M.A., 1990. Some properties of negative cloud-to-ground lightning flashes versus stroke order, Journal of Geophysical Research. 95, 5447–5453.] reporting that: “...strokes initiating long continuing currents tend to have lower initial electric field peak than regular strokes” is valid for strokes that create a new channel to ground and are followed by long continuing current (CC). Apparently the reduction of peak current value (I_p) when the stroke is followed by a long CC is stronger than the I_p increase that is commonly observed when strokes follow a new channel. We also find that the “exclusion zone” proposed by Saba et al. [Saba, M.M.F., Pinto, O. Jr., Ballarotti, M.G., 2006a. Relation between lightning return stroke peak current and following continuing current, Geophysical Research Letters 33, L23807, doi:10.1029/2006GL027455.] is valid for new channels initiating CC, and finally we verify that a number of strokes in the same channel larger than four or the existence of a long CC current do not always consolidate the channel in a multiple stroke flash.     

北京地区不同天气条件下近地面大气电场特征

利用2004年8月—2005年11月近地面大气电场仪的观测资料, 对北京地区不同天气条件下近地面大气电场特征进行分析。结果表明:北京地区晴天近地面大气电场日变化呈双峰双谷, 谷值分别出现在北京时05:00和12:00, 峰值分别出现在07:00和23:00, 并且表现出一定的季节变化; 晴天大气电场的变化与气溶胶含量的变化有密切关系, 两者呈正相关; 晴天大气电场与绝对湿度之间也表现出很强的相关性, 在一定程度上反应了水汽对大气电场的作用; 沙尘天气下风速均达到一定强度, 近地面大气电场为负值, 并且变化剧烈, 电场强度与PM₁₀之间呈现较强的负相关, 而电场强度与风速之间没有表现出明显的相关性。     

Analysis of the sea surges at Venice from A.D. 782 to 1990

Summary After an accurate search for old documents in Italian archives, the series of the sea surges has been reconstructed for a period of 12 centuries. In addition to written documents, other sources have also been investigated, e.g. the identification marks made by the Venetian Republic at the mean level of the high tides and accurate drawings made in the 18th century by the painterCanaletto with the help of a portable camera obscura. The sea surges at Venice are due to several forcing factors: a low pressure passing over the Mediterranean and generating a Sirocco wind; the barometric effect associated with a gradient of atmospheric pressure over the sea waters; free oscillations in the Adriatic sea; solar and lunar influences; subsidence of the soil. Except for a period which culminated in 1424–1442, when the moon was in perigee and the earth in perihelion, in general the meteorological factors largely dominate over the astronomical ones: the seasonal distribution shows a narrow peak in November–December and the series is important to show the frequency of the anomalies in the atmospheric circulations which determined meridional winds over the Adriatic sea. The analysis of the data shows clearly the 18.6 yr lunar nutation influence and a continuous rise of the sea level despite the cooling of the Little Ice Age. The most perturbed period were respectively: 1914–today, due to anthropogenic factors, i.e. excavating of new canals and underground water pumping; 1500–1550, during the Spörer Minimum of solar activity; 1720–1830; 1250–1350, which was also a stormy period in the North Sea. No apparent links with the Maunder Minimum of solar activity were found.With 7 Figures     

Methane emissions from a landfill measured by eddy correlation using a fast response diode laser sensor

We describe a fast response methane sensor based on the absorption of radiation generated with a near-infrared InGaAsP diode laser. The sensor uses an open path absorption region 0.5 m long; multiple pass optics provide an optical path of 50 m. High frequency wavelength modulation methods give stable signals with detection sensitivity (S/N=1, 1 Hz bandwidth) for methane of 65 ppb at atmospheric pressure and room temperature. Improvements in the optical stability are expected to lower the current detection limit. We used the new sensor to measure, by eddy correlation, the CH₄ flux from a clay-capped sanitary landfill. Simultaneously we measured the flux of CO₂ and H₂O. From seven half-hourly periods of data collected after a rainstorm on November 23, 1991, the average flux of CH₄ was 17 mmol m^–2 hr^–1 (6400 mg CH₄ m^–2 d^–1) with a coefficient of variation of 25%. This measurement may underrepresent the flux by 15% due to roll-off of the sensor response at high frequency. The landfill was also a source of CO₂ with an average flux of 8.1 mmol m^–2 hr^–1 (8550 mg CO₂ m^–2 d^–1) and a coefficient of variation of 26%. A spectral analysis of the data collected from the CH₄, CO₂, and H₂O sensors showed a strong similarity in the turbulent transfer mechanisms.     

Electrical current along balloon rigging line inside thunderstorms

We have designed a new instrument to measure the current flowing along balloon rigging line during flights through thunderstorms. This instrument was tested in a high voltage facility and used to collect line current data during one balloon flight into a thunderstorm. Using these data, worst-case calculations are made; as such, we claim that they are the upper limits of any alteration (to the measured electric field or particle charge) that may occur, and the real number is likely much less. It is postulated the rigging-line current could have two separate effects on the measured electric field: (1) reduction of the field due to emission of corona ions, and (2) enhancement of the field due to the insertion of a long thin ‘conductor.' Even with current as high as 1 μA (the largest measured was around 50–100 nA), these two effects were found to be about −1% and +1%, respectively. Also, the calculated worst-case alteration to charged precipitation measurements is about 0.1 pC. Thus, with proper efforts to make the rigging line as poor a conductor as possible, it seems that we are justified in stating that these effects are negligible.     

The Electric Field During Blowing Snow Events

A model is proposed to determine the electric field strength in blowing snow. To test this model, the electric field strength was measured over an 80-day period during the Canadian Arctic Shelf Exchange Study (CASES) in 2004. The electric field strength at 0.5 m correlates well with the difference between 10-m wind speed and a threshold wind speed, although there is a large amount of variation between the electric fields generated during different blowing snow events. Although the model predicts that the electric field should be proportional to particle number density, the correlation is weak. The correlation of wind speed and electric field strength suggests that particles become charged primarily due to friction-induced temperature difference as they impact upon the surface. The strength of the electric field is likely influenced by a large number of other factors that are difficult to measure. However, the model predicts electric field strengths in excess of 25 kV m⁻¹ near the surface, which would have a significant effect on particle motion.     

The use of dual channel circular-polarization radar observations for remotely sensing storm electrification

Summary Observations of thunderstorms with a dual channel circularpolarization radar have provided dramatic indications of the buildup of the electric field inside the storms and of the sudden collapse of the field at the time of lightning. The indications are obtained by coherently correlating the simultaneous returns in the right- and left-hand circular polarization channels of the radar, and follow up on the pioneering observations of this type by Hendry and McCormick (1976). The correlation is estimated and displayed in real time and the results enable one to predict when a storm has the potential for producing a lightning discharge, and often to anticipate the occurrence of individual discharges. The observations detect the presence of electrically aligned particles, believed to be small ice crystals, which are aligned by the electrostatic field of the storm. The aligned particles cause the radar signal to become progressively depolarized as it propagates through an alignment region, giving rise to correlated right- and left-circular polarization echoes. The alignment direction can be determined from the phase of the correlation and is found to be predominantly vertical, indicating a similar electric field orientation. Weaker horizontal alignment is often observed immediately following lightning discharges, consistent with the idea that the aligned particles are ice platelets which fall with horizontal orientation due to aerodynamic forces. The observations have been found to reveal the onset of strong electrification in developing storms and to indicate when decaying storms no longer have the potential to produce lightning. By compensating for signal-to-noise effects, the variation of the depolarization with range can be determined. This provides detailed pictures of the alignment regions which could be used as tracers of ice crystal populations in storms. The pictures also show the spatial variation of the alignment directions, raising the possibility of remotely mapping the storm electric field structure. Finally, the depolarization rate results readily enable one to distinguish between liquid and solid precipitation in the storms.With 7 Figures     

一个准稳态的全球大气电路模式

本文用一个全球大气电导率模式和一个全球大气电路模式,计算了地形、大气气溶胶及太阳活动对大气电参量的影响,并估算了它们对地面电流密度和电场的分布影响。结果表明:地形的存在使电离层电势增加,雷暴分布的改变对大气电参量平均值无影响;气溶胶浓度与电离层电势及晴天电阻成正相关。宇宙射线与电离层电势及气—地电流成正相关;气溶胶浓度和宇宙射线的变化也会影响到晴天区电场以及雷暴区地面电流密度和电场;太阳质子流的注入使全球地面电场和电流密度增大,电离层电势不变。     

雷电过程中大气电场信号处理方法探究

基于天津市蓟州区大气电场探测数据和闪电定位数据，利用功率谱分析、小波降噪和快速傅里叶变换等信号处理方法，分析了雷电天气过程中地面大气电场变化特征。结果表明，雷电过程中大气电场能量主要集中在低频部分，利用sym5小波函数进行7层或8层分解，提取的低频信号能够反映大气电场的主要变化特征。在首次闪电发生前1小时，大气电场的频谱幅值起伏变化明显，且远高于非雷电天气电场频谱幅值。通过欧氏距离判别法，判断大气电场频谱特征更接近雷电天气还是非雷电天气，可为雷电预报预警提供参考。     

Parameterisation of surface radiation flux at an Antarctic site

During the Antarctic summer 1994/95 the values of downward and upward flux densities of both solar and terrestrial radiation were recorded at 1200 m for a period of 1 month on the Reeves Nevè Glacier (lat 74°39′S, long 161°35′E), near the Italian base of Terra Nova Bay. The relations proposed by Swinbank [Swinbank, W.C., 1963. Long-wave radiation from clear skies. Q. J. R. Meteorol. Soc. 89, 339–348], Idso and Jackson [Idso, S.B., Jackson, R.D., 1969. Thermal radiation from the atmosphere. J. Geophys. Res. 74, 5397–5403] and Deacon [Deacon, E.L., 1970. The derivation of Swinbank's long-wave radiation formula. Q. J. R. Meteorol. Soc. 96, 313–319] associating the long-wave atmospheric radiation flux only to the air temperature at screen level were tested in extreme Antarctic climatological condition. A relation between the long-wave radiation flux and both screen air temperature and cloud cover fraction in accordance to the height of the cloud base was defined using the Kasten and Czeplak relationship that relates the solar radiation flux and the cloud cover index. The study of the incoming short-wave radiation flux from the clear sky and that reflected by the surrounding snow cover allowed for highlighting the role of surface geometry on the albedo measurements.     

西藏羊八井地区近地晴天大气电场周期变化

基于西藏ARGO-YBJ实验,分析了2005年12月-2007年9月期间西藏羊八井地区近地晴天大气电场强度的周期变化,并重点讨论了其太阳日周期的相位变化.结果表明,晴天状态下大气电场强度存在明显的半日周期和太阳日周期变化.太阳日周期的相位变化呈现大陆复杂型(双峰、双谷),日变化曲线随季节变化,在冬季,电场强度水平较高,最大日变化幅度约30%;春、夏季电场强度水平较低,最大日变化幅度约15%.该初步研究结果对了解西藏地区晴天大气电特征具有十分重要的意义.