Variations in the Atmospheric Electric Field at Tropical Station during 1930-1987

The variations noticed in the atmospheric electric field recorded at Pune (18°32'N, 73°51'E, 559 m ASL), a tropical inland station located in Dcccan Plateau, India, during the period 1930-1987, have been examined in relation to the variations observed in the Angstrom turbidity coefficient (β) and selected meteorological parameters. The monthly and annual mean values of the atmospheric electric field. Angstrom turbidity coefficient (β), rainfall, temperature and relative humidity for the years 1930-1938, 1957-1958, 1964-1965, 1973-1974 and 1987 were considered in the study.The results of the above study indicated gradual increases in the atmospheric electric field over the period of study (1930-1987) which is statistically significant at less than 5%level. The increases noticed during different periods varied from 30 to 109%. The increase noticed during the period (1930-1938) and (1973-1974) was maximum (109%). The Angstrom turbidity coefficient also showed systematic increases during the period of s     

Estimation and Long-term Trend Analysis of Surface Solar Radiation in Antarctica: A Case Study of Zhongshan Station

Long-term,ground-based daily global solar radiation (DGSR) at Zhongshan Station in Antarctica can quantitatively reveal the basic characteristics of Earth’s surface radiation balance and validate satellite data for the Antarctic region.The fixed station was established in 1989,and conventional radiation observations started much later in 2008.In this study,a random forest (RF) model for estimating DGSR is developed using ground meteorological observation data,and a highprecision,long-term DGSR dataset is constructed.Then,the trend of DGSR from 1990 to 2019 at Zhongshan Station,Antarctica is analyzed.The RF model,which performs better than other models,shows a desirable performance of DGSR hindcast estimation with an R~2 of 0.984,root-mean-square error of 1.377 MJ m~(-2),and mean absolute error of 0.828 MJ m~(-2).The trend of DGSR annual anomalies increases during 1990–2004 and then begins to decrease after 2004.Note that the maximum value of annual anomalies occurs during approximately 2004/05 and is mainly related to the days with precipitation (especially those related to good weather during the polar day period) at this station.In addition to clouds and water vapor,bad weather conditions (such as snowfall,which can result in low visibility and then decreased sunshine duration and solar radiation) are the other major factors affecting solar radiation at this station.The high-precision,longterm estimated DGSR dataset enables further study and understanding of the role of Antarctica in global climate change and the interactions between snow,ice,and atmosphere.     

A Study of Linke Turbidity Factor over Qena / Egypt

Data on instantaneous atmospheric Linke turbidity factor TL (m) are reported for clear days at Qena/Egypt in the period from June 1992 to May 1993.TL(m) is determined using the values of irradiance of direct solar radiation (I),which are calculated from global (G) and diffuse (D) - solar radiation measurements.Monthly and seasonally variations of both diurnal and daily average values of TL (m) increases steadily in the direction of sunset in the months from June to December 1992 as well as Summer and Autumn seasons,while it falls generally in this direction for the months from January to March and Winter season.In April and May,TL (m) fluctuates obviously through the day hours,it is also shown that the average values of TL(m) are particularly large during Summer months compared to other months of the year.This behavior of TL(m) is discussed in view of the variations of some weather elements,which affect the content of water vapor and dust particle in the atmosphere of the study region.It seems t be of s     

Interannual and Interdecadal Variations in Atmospheric Circulation Factors and Rainfall in China and Their Relationship

Wavelet analysis is used to study the interannual and interdecadal variations of rainfall in China and atmospheric circulation factors, including the key atmospheric oscillations, W, C, E patterns and subtropical high. Regression analysis and correlation analysis are both used to study the relationship of atmospheric circulation factors and China rainfall on different time scale and spatial scale. The results are as follows: (1) The variations of atmospheric circulation and rainfall in China are characterized by interannual and interdecadal scales. The variations of atmospheric circulation and rainfall are composed of interannual and interdecadal variations. It is necessary to separate those two time scales when climate changes and forecast are studied. (2) The variations of China rainfall are due to the interaction of multi-factors rather than single factors. The marked factors which influence the interannual and interdecadal variations are various. Subtropical high is one of the marked factors which influence interannual variations of rainfall, while AO, NAO, and NPO are one of the marked factors which influence interdecadal variations of rainfall. (3) The longer the time scale is, and the larger the spatial scale is, and the more remarkable the relationships between atmospheric circulation and rainfall are.     

Some aspects of the diurnal and semidiurnal tidal wind field in meteor zone

The diurnal and semidiurnal tidal wind field variations in the altitudes between 80 and 100 km of the earth’s atmosphere over a mid-latitude station are studied by means of the phases of the zonal and meridional wind measurements made at Atlanta (34oN, 84oW). The rotation of diurnal tidal wind vector is seen to be clockwise at lower heights (80-86 km), swinging between clockwise and unti-clockwise at intermediate heights (88-96 km) and anti-clockwise at higher-heights (96- 100 km). The senses of rotation of diurnal and semidiurnal tidal wind vectors are compared between the stations located in the same and opposite hemispheres. The results are consistent with the tidal theory in the case of Atlanta and Adelaide (35oS, 139oE) whereas in the case of other stations considered in the present study, they showed marked variations.     

RESEARCH ON SURFACE O_3 WITH METEOROLOGICAL CONDITIONS UNDER ATMOSPHERIC BACKGROUND CONDITIONS IN NORTHEAST CHINA

Surface O_3 concentration and its precursors have been observed at Longfengshan station,Heilongjiang Province for a period of one year from August 13,1994 to July 30,1995.Relationship between surface O_3 and the meteorological conditions during this period is analyzed inthis study.Observation results show that diurnal variation of surface O_3 follows a pattern ofdouble-peaks with amplitude of 27—28 ppb under fine days in summer and autumn.Although thediurnal variation is small(14 ppb),it is still detectable when it is overcast.Diurnal variation of O_3is irregular under rainy days.Surface O_3 concentration rises when wind speed starts to increase at0800 BT(Beijing Time)from 0 to 6 m s~(-1)in autumn,winter and summer.Relative high surfaceO_3 concentration is noticed frequently when S,SSW,SW and WSW wind are encountered at thestation during all seasons.At 0800 BT and 1400 BT the surface O_3 concentration increases with theincrease of global radiation accordingly during fine days in winter,spring and autumn.During finedays average peak of O_3 concentration in summer is 20 ppb higher than that in winter while theaverage peak of global radiation in summer is almost twice as high as that in winter.The averagesurface O_3 concentration under fine days in autumn at Longfengshan station is 14 ppb lower incomparison to the observation results from Lin'an station where Lin'an is at about the samelongitude and lower latitude,with same environment,which is mainly caused by the difference ofglobal radiation due to different latitudes in these two areas(difference of average peak globalradiation about 100 W m~(-2)).     

Lunar phases and atmospheric electric field

The association between the lunar phases and the atmospheric electric field has been investigated from the superposed epoch analysis of the lone series of continuous data of the vertical electric field for Colaba, Bombay (18o53’N, 73o48’E 11 mASL) for the period 1947-1966. Also the periodicities in the atmospheric electric field have been studied from the spectral analysis of the data. The study has indicated that when the full moon is within 4o of the ecliptic plane i. e., Bf 4o, the electric field peaks on the day of the full moon followed by a steep fall in the field val-ues up to 4 days following the full moon day and there after it showed a steep increase. Also, the electric field has exhibited 5-9 day periodicity and its multiples are nearly always present. The periodicity in the electric field corresponds with the average time interval between the successive magnetic sector boundary (MSB) crossings i.e., 7 days. On most of the occasions, the MSB crossing day is associated with a maximum of one or more of the wavelengths derived from the spectral analysis of the atmospheric electric field.     

STUDY ON THE MAIN CLIMATE MODES OF SHANDONG PRECIPITATION AND THEIR RELATIONS WITH THE EAST ASIAN WESTERLY JET

Summer precipitation patterns of Shandong Province are relatively independent with regard to the whole eastern China region.To study the rules and causes of precipitation variations,three main climate modes-on the annual,seasonal,and climatic intra-seasonal oscillation(CISO) scales-are extracted using a harmonic analysis method based on daily precipitation of Shandong during 1965-2009 and multi-year averaged pentad precipitation at 722 stations in China during 1971-2000.Among the three precipitation climate modes,the annual mode is closely related to the annual cycle of Earth-Atmosphere thermal system,which is characterized by the periodic dry and wet seasons.The seasonal mode reflects the monsoon effect on precipitation and the main flood season’s contribution to annual precipitation variations.As an important climatic signal,the CISO mode is more evident during summer monsoon.The gradual modulations of the CISO mode,seasonal mode,and annual mode control the annual variation of precipitation.To study the relationship between precipitation climate modes and atmospheric circulations,an East Asian Westerly Jet Index(EAWJI) is defined in this paper.It is revealed that precipitation of Shandong is closely related to EAWJI in all climate modes.A wet or dry phase of each climate mode corresponds to a specific atmospheric circulation pattern.The phase of the annual mode is reverse to that of EAWJI.During the wet phase of the seasonal mode(weak phase of EAWJI),the atmospheric circulation in and around Shandong is characterized by upper-level divergence and low-level convergence.A reversed atmospheric circulation exists for the dry phase(strong phase for EAWJI).In the summer wet phase of CISO mode(strong phase of EAWJI),Shandong is controlled by upper-level divergence and low-level convergence.Again,the dry phase is corresponding to a reversed circulation structure.The methodology employed in this research,i.e.studying the precipitation climatic variations in terms of independent components of different temporal scales,provides a new approach for annual and seasonal precipitation prediction.     

Lunar Phases and Atmospheric Electric Field

The association between the lunar phases and the atmospheric electric field has been investigated from the superposed epoch analysis of the long series of continuous data of the vertical electric field for Colaba, Bombay (18 ° 53'N, 73 ° 48'E 11 mASL) for the period 1947-1966. Also the periodicities in the atmospheric electric field have been studied from the spectral analysis of the data. The study has indicated that when the full moon is within 4 of the ecliptic plane i.e.,Bf 4 ° , the electric field peaks on the day of the full moon followed by a steep fall in the field values up to 4 days following the full moon day and there after it showed a steep increase. Also, the electric field has exhibited 5-9 day periodicity and its multiples are nearly always present. The periodicity in the electric field corresponds with the average time interval between the successive magnetic sector boundary (MSB ) crossings i.e., 7 days. On most of the occasions, the MSB crossing day is associated with a maximum of     

Characteristic Study of the Boundary Layer Parameters over the Arabian Sea and the Bay of Bengal Using the QuikSCAT Dataset

The marine atmospheric boundary layer (MABL) plays a vital role in the transport of momentum and heat from the surface of the ocean into the atmosphere. A detailed study on the MABL characteristics was carried out using high-resolution surface-wind data as measured by the QuikSCAT (Quick scatterometer) satellite. Spatial variations in the surface wind, frictional velocity, roughness parameter and drag coefficient for the different seasons were studied. The surface wind was strong during the southwest monsoon season due to the modulation induced by the Low Level Jetstream. The drag coefficient was larger during this season, due to the strong winds and was lower during the winter months. The spatial variations in the frictional velocity over the seas was small during the post-monsoon season (～0.2 m s-1). The maximum spatial variation in the frictional velocity was found over the south Arabian Sea (0.3 to 0.5 m s-1) during the southwest monsoon period, followed by the pre-monsoon over the Bay of Bengal (0.1 to 0.25 m s-1). The mean wind-stress curl during the winter was positive over the equatorial region, with a maximum value of 1.5×10-7N m-3, but on either side of the equatorial belt, a negative wind-stress curl dominated. The area average of the frictional velocity and drag coefficient over the Arabian Sea and Bay of Bengal were also studied. The values of frictional velocity shows a variability that is similar to the intraseasonal oscillation (ISO) and this was confirmed via wavelet analysis. In the case of the drag coefficient, the prominent oscillations were ISO and quasi-biweekly mode (QBM). The interrelationship between the drag coefficient and the frictional velocity with wind speed in both the Arabian Sea and the Bay of Bengal was also studied.     

Variations of Atmospheric Carbon Dioxide Concentration and Greenhouse Effect at Syowa Station (69°00''''S, 39°35''''E), Antarctica

On the basis of the analysis of atmospheric carbon dioxide concentration variations and the annual mean air temperature at Syowa Station, Antarctica in the period of 1984-1988, the following results are easily obtained:(1) The annual mean values of the atmospheric carbon dioxide concentration are gradually increased and equal to 342.59, 343.80, 345.15, 346.83 and 348.82 ppmv for 1984, 1985, 1986, 1987 and 1988, respectively. Its annual increase rates are 1.21, 1.35, 1.68 and 1.99 ppmv/yr. For 1984-1985, 1985-1986, 1986-1987 and 1987-1988, respectively and are raised year by year.The seasonal variations are observed and the maximum concentration is in spring and the minimum one is in late-summer or early-autumn.(2)The increasing tendency of the concentration of the atmospheric carbon dioxide is consistent with that of the a.ir temperature.     

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.     

Recent Advances in Predictability Studies in China （1999-2002）

Since the last International Union of Geodesy and Geophysics (IUGG) General Assembly (1999), the predictability studies in China have made further progress during the period of 1999-2002. Firstly, three predictability sub-problems in numerical weather and climate prediction are classified, which are concerned with the maximum predictability time, the maximum prediction error, and the maximum allowable initial error, and then they are reduced into three nonlinear optimization problems. Secondly, the concepts of the nonlinear singular vector (NSV) and conditional nonlinear optimal perturbation (CNOP) are proposed,which have been utilized to study the predictability of numerical weather and climate prediction. The results suggest that the nonlinear characteristics of the motions of atmosphere and oceans can be revealedby NSV and CNOP. Thirdly, attention has also been paid to the relations between the predictability and spatial-temporal scale, and between the model predictability and the machine precision, of which the investigations disclose the importance of the spatial-temporal scale and machine precision in the study of predictability. Also the cell-to-cell mapping is adopted to analyze globally the predictability of climate,which could provide a new subject to the research workers. Furthermore, the predictability of the summer rainfall in China is investigated by using the method of correlation coefficients. The results demonstrate that the predictability of summer rainfall is different in different areas of China. Analysis of variance, which is one of the statistical methods applicable to the study of predictability, is also used to study the potential predictability of monthly mean temperature in China, of which the conclusion is that the monthly mean temperature over China is potentially predictable at a statistical significance level of 0.10. In addition,in the analysis of the predictability of the T106 objective analysis/forecasting field, the variance and the correlation coefficient are calculated to explore the distribution characteristics of the mean-square errors.Finally, the predictability of short-term climate prediction is investigated by using statistical methods or numerical simulation methods. It is demonstrated that the predictability of short-term climate in China depends not only on the region of China being investigated, but also on the time scale and the atmospheric internal dynamical process.     

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 maintenance of atmospheric electric field and also the variations in the H-component of the geomagnetic field. Any perturbation 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 atmospheric electrical field data for Colaba, Bombay (8°53' 56" N, 72° 48' 54" E, 9.8 m ASL) and solar activity indices (Ap index,     

Some Aspects of the Diurnal and Semidiurnal Tidal Wind Field in Meteor Zone

The diurnal and semidiurnal tidal wind field variations in the altitudes between 80 and 100 km of the earth's atmosphere over a mid-latitude station are studied by means of the phases of the zonal and meridional wind measurements made at Atlanta (34 ° N, 84 ° W). The rotation of diurnal tidal wind vector is seen to be clockwise at lower heights (80-86 km), swinging between clockwise and anti-clockwise at intermediate heights (88-96 km) and anti-clockwise at higher heights (96-100 km). The senses of rotation of diurnal and semidiurnal tidal wind vectors are compared between the stations located in the same and opposite hemispheres. The results are consistent with the tidal theory in the case of Atlanta and Adelaide (35°S, 139 ° E) whereas in the case of other stations considered in the present study, they showed marked variations.     

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.     

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 tor Colaba (18 ° 53'N, 72 ° 48'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 temperatures increase after a geomagnetic storm. The wind velocity shows a decreasing trend and the relative humidity shows an increasing trend after the geomagnetic storm.     

SEASONAL VARIATION OF LIDAR-DERIVED AEROSOL CONTENT IN THE LOWER LAYERS OF THE ATMOSPHERE

Results of the study of seasonal variation of total column content of aerosols in the 50—1100 m heightregion are presented,The columnar content of aerosols is computed by integrating the height profiles ofnighttime aerosol number density estimated from the Argon ion lidar observations collected at the ⅡTM,Pune for the one year period from October 1986 to September 1987.The results of the study indicated thatthe aerosol content was higher during winter than during monsoon months by over 78% with an annualmean columnar aerosol content of 1.66×10~8 cm~(-2).The observed seasonal variaticn of aerosol content wasfound to be associated with that of surface wind,temperature,relative humidity(R.H.)and rainfall datarecorded for the above one year period at the station.     

Variation Characteristics of Ultraviolet Radiation over the North China Plain简

In situ measured data of broadband solar radiation （Rs） and ultraviolet （Uv） radiation were used to investigate the spa- tiotemporal variation properties of Uv radiation and the ratio of Uv radiation to Rs over the North China Plain （NCP）. Based on the analysis, an empirical model for estimating Uv radiation under all weather conditions in this region was developed. The results showed that the annual Uv radiation over the NCP ranges from 0.38-0.52 MJ m^-2 d^-1. The highest value during the study period was recorded at the Changwu site, which is located near the margin of the Loess Plateau, while the lowest value appeared at the station in Beijing. The seasonal variation pattern of the ratio of Uv radiation to Rs is similar to that of Uv radiation; namely, the highest value appears in August and then decreases gradually until the lowest value appears in November. A small increasing trend in the Uv radiation levels and the ratio of Uv radiation to Rs was observed over the NCP. The evaluation results showed that the empirical estimation model can be widely used to estimate Uv radiation under all atmospheric conditions. The relative error between the modeled and measured daily values were within ± 15%.     

27.3-day and 13.6-day atmospheric tide and lunar forcing on atmospheric circulation

An analysis of time variations of the earth‘s length of day (LOD) versus atmospheric geopotential height fields and lunar phase is presented. A strong correlation is found between LOD and geopotential height from which a close relationship is inferred and found between atmospheric circulation and the lunar cycle around the earth. It is found that there is a 27.3-day and 13.6-day east-west oscillation in the atmospheric circulation following the lunar phase change. The lunar revolution around the earth strongly influences the atmospheric circulation. During each lunar cycle around the earth there is, on average, an alternating change of 6.8-day-decrease, 6.8-day-increase, 6.8-day-deerease and 6.8-day-increase in atmospheric zonal wind, atmospheric angular momentum and LOD. The dominant factor producing such an oscillation in atmospheric circulation is the periodic change of lunar declination during the lunar revolution around the earth. The 27.3- day and 13.6-day atmospheric oscillatory phenomenon is akin to a strong atmospheric tide, which is different from the weak atmospheric tides, diurnal and semidiurnal, previously documented in the literature. Also it is different from the tides in the ocean in accordance with their frequency and date of occurrence. Estimation shows that the 27.3-day lunar forcing produces a 1-2 m s^-1 change in atmospheric zonal wind. Therefore, it should be considered in models of atmospheric circulation and short and middle term weather forecasting. The physical mechanism and dynamic processes in lunar forcing on atmospheric circulation are discussed.