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 whi...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-decrease 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展开更多
Through respectively adding June tide and December tide at the low boundary of the GCITEM-IGGCAS model (Global CoupledIonosphere–Thermosphere–Electrodynamics Model, Institute of Geology and Geophysics, Chinese Acade...Through respectively adding June tide and December tide at the low boundary of the GCITEM-IGGCAS model (Global CoupledIonosphere–Thermosphere–Electrodynamics Model, Institute of Geology and Geophysics, Chinese Academy of Sciences), we simulate theinfluence of atmospheric tide on the annual anomalies of the zonal mean state of the ionospheric electron density, and report that thetidal influence varies with latitude, altitude, and solar activity level. Compared with the density driven by the December tide, the June tidemainly increases lower ionospheric electron densities (below roughly the height of 200 km), and decreases electron densities in thehigher ionosphere (above the height of 200 km). In the low-latitude ionosphere, tides affect the equatorial ionization anomaly structure(EIA) in the relative difference of electron density, which suggests that tides affect the equatorial vertical E×B plasma drifts. Although thetide-driven annual anomalies do not vary significantly with the solar flux level in the lower ionosphere, in the higher ionosphere theannual anomalies generally decrease with solar activity.展开更多
Variation in length of day of the Earth (LOD, equivalent to the Earth's rotation rate) versus change in atmospheric geopotential height fields and astronomical parameters were analyzed for the years 1962-2006. This...Variation in length of day of the Earth (LOD, equivalent to the Earth's rotation rate) versus change in atmospheric geopotential height fields and astronomical parameters were analyzed for the years 1962-2006. This revealed that there is a 27.3-day and an average 13.6-day periodic oscillation in LOD and atmospheric pressure fields following lunar revolution around the Earth. Accompanying the alternating change in celestial gravitation forcing on the Earth and its atmosphere, the Earth's LOD changes from minimum to maximum, then to minimum, and the atmospheric geopotential height fields in the tropics oscillate from low to high, then to low. The 27.3-day and average 13.6-day periodic atmospheric oscillation in the tropics is proposed to be a type of strong atmospheric tide, excited by celestial gravitation forcing. A formula for a Tidal Index was derived to estimate the strength of the celestial gravitation forcing, and a high degree of correlation was found between the Tidal Index determined by astronomical parameters, LOD, and atmospheric geopotential height. The reason for the atmospheric tide is periodic departure of the lunar orbit from the celestial equator during lunar revolution around the Earth. The alternating asymmetric change in celestial gravitation forcing on the Earth and its atmosphere produces a "modulation" to the change in the Earth's LOD and atmospheric pressure fields.展开更多
An informal review is presented of recent developments in numerical simulation of the global atmospheric circulation with very fine numerical resolution models, The focus is on results obtained recently with versions ...An informal review is presented of recent developments in numerical simulation of the global atmospheric circulation with very fine numerical resolution models, The focus is on results obtained recently with versions of the GFDL SKYHI model and the Atmospheric Model for the Earth Simulator (AFES) global atmospheric models. These models have been run with effective horizontal grid resolution of -10-40 km and fine vertical resolution. The results presented demonstrate the utility of such models for the study of a diverse range of phenomena, Specifically the models are shown to simulate the development of tropical cyclones with peak winds and minimum central pressures comparable to those of the most intense hurricanes actually observed, More fundamentally, the spectrum of energy content in the mesoscale in the flow can be reproduced by these models down to near the smallest explicitly-resolved horizontal scales, in the middle atmosphere it is shown that increasing horizontal resolution can lead to significantly improved overall simulation of the global-scale circulation, The application of the models to two specific problems requiring very fine resolution global will be discussed, The spatial and temporal variability of the vertical eddy flux of zonal momentum associated with gravity waves near the tropopause is evaluated in the very fine resolution AFES model, This is a subject of great importance for understanding and modelling the flow in the middle atmosphere, Then the simulation of the small scale variations of the semidiurnal surface pressure oscillation is analyzed, and the signature of significant topographic modulation of the semidiurnal atmospheric tide is identified.展开更多
Previous studies suggest that tidal friction gives rise to the secular deceleration of the Earth rotation by a quantity of about 2.25 ms/cy. Here we just consider additional contributions to the secular Earth rotation...Previous studies suggest that tidal friction gives rise to the secular deceleration of the Earth rotation by a quantity of about 2.25 ms/cy. Here we just consider additional contributions to the secular Earth rotation deceleration. Atmospheric solar semi-diurnal tide has a small amplitude and certain amount of phase lead. This periodic global air-mass excess distribution exerts a quasi-constant torque to accelerate the Earth's spin rotation. Using an updated atmospheric tide model, we re-estimate the amounts of this atmospheric acceleration torque and corresponding energy input, of which the associated change rate in LOD(length of day) is-0.1 ms/cy. In another aspect, evidences from space-geodesy and sea level rise observations suggest that Earth expands at a rate of 0.35 mm/yr in recent decades, which gives rise to the increase of LOD at rate of 1.0 ms/cy. Hence, if the previous estimate due to the tidal friction is correct, the secular Earth rotation deceleration due to tidal friction and Earth expansion should be 3.15 ms/cy.展开更多
Based on the tide gravity observations recorded with LCR-ET20 spring gravimeter at Wuhan international fundamental tidal gravity station, the characteristics of ET20 and atmospheric and oceanic gravity signals are stu...Based on the tide gravity observations recorded with LCR-ET20 spring gravimeter at Wuhan international fundamental tidal gravity station, the characteristics of ET20 and atmospheric and oceanic gravity signals are studied systematically by using international standard data pre-processing and analysis methods and by comparing the results with those obtained by superconducting gravimeter (SG) at the same station. The numerical results indicate that the identical tidal gravity parameters are the same as those with the SG, the instrument can be effectively used to record temporal change of the gravity field, though the ET20 accuracy is one order lower than that of the SG, and has the large drift induced by the spring creep character.展开更多
文摘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-decrease 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
基金This work is supported by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA17010201),the National Natural Science Foundation of China(41674158,41874179,41621063,41427901,41474133,41322030)the Youth Innovation Promotion Association CAS(2014057)and the Opening Funding of Chinese Academy of Sciences dedicated for the Chinese Meridian Project.
文摘Through respectively adding June tide and December tide at the low boundary of the GCITEM-IGGCAS model (Global CoupledIonosphere–Thermosphere–Electrodynamics Model, Institute of Geology and Geophysics, Chinese Academy of Sciences), we simulate theinfluence of atmospheric tide on the annual anomalies of the zonal mean state of the ionospheric electron density, and report that thetidal influence varies with latitude, altitude, and solar activity level. Compared with the density driven by the December tide, the June tidemainly increases lower ionospheric electron densities (below roughly the height of 200 km), and decreases electron densities in thehigher ionosphere (above the height of 200 km). In the low-latitude ionosphere, tides affect the equatorial ionization anomaly structure(EIA) in the relative difference of electron density, which suggests that tides affect the equatorial vertical E×B plasma drifts. Although thetide-driven annual anomalies do not vary significantly with the solar flux level in the lower ionosphere, in the higher ionosphere theannual anomalies generally decrease with solar activity.
基金supported by the National Science Foundation of China (Grant No 40675031)
文摘Variation in length of day of the Earth (LOD, equivalent to the Earth's rotation rate) versus change in atmospheric geopotential height fields and astronomical parameters were analyzed for the years 1962-2006. This revealed that there is a 27.3-day and an average 13.6-day periodic oscillation in LOD and atmospheric pressure fields following lunar revolution around the Earth. Accompanying the alternating change in celestial gravitation forcing on the Earth and its atmosphere, the Earth's LOD changes from minimum to maximum, then to minimum, and the atmospheric geopotential height fields in the tropics oscillate from low to high, then to low. The 27.3-day and average 13.6-day periodic atmospheric oscillation in the tropics is proposed to be a type of strong atmospheric tide, excited by celestial gravitation forcing. A formula for a Tidal Index was derived to estimate the strength of the celestial gravitation forcing, and a high degree of correlation was found between the Tidal Index determined by astronomical parameters, LOD, and atmospheric geopotential height. The reason for the atmospheric tide is periodic departure of the lunar orbit from the celestial equator during lunar revolution around the Earth. The alternating asymmetric change in celestial gravitation forcing on the Earth and its atmosphere produces a "modulation" to the change in the Earth's LOD and atmospheric pressure fields.
基金National Science Foundation Grant ATM- 02-19120the Japan Agency for Marine-Earth ScienceTechnology (JAMSTEC) through its sponsorship of the International Pacific Research Center.
文摘An informal review is presented of recent developments in numerical simulation of the global atmospheric circulation with very fine numerical resolution models, The focus is on results obtained recently with versions of the GFDL SKYHI model and the Atmospheric Model for the Earth Simulator (AFES) global atmospheric models. These models have been run with effective horizontal grid resolution of -10-40 km and fine vertical resolution. The results presented demonstrate the utility of such models for the study of a diverse range of phenomena, Specifically the models are shown to simulate the development of tropical cyclones with peak winds and minimum central pressures comparable to those of the most intense hurricanes actually observed, More fundamentally, the spectrum of energy content in the mesoscale in the flow can be reproduced by these models down to near the smallest explicitly-resolved horizontal scales, in the middle atmosphere it is shown that increasing horizontal resolution can lead to significantly improved overall simulation of the global-scale circulation, The application of the models to two specific problems requiring very fine resolution global will be discussed, The spatial and temporal variability of the vertical eddy flux of zonal momentum associated with gravity waves near the tropopause is evaluated in the very fine resolution AFES model, This is a subject of great importance for understanding and modelling the flow in the middle atmosphere, Then the simulation of the small scale variations of the semidiurnal surface pressure oscillation is analyzed, and the signature of significant topographic modulation of the semidiurnal atmospheric tide is identified.
基金partly supported by National 973 Project China(2013CB733305)NSFC(41174011,41210006,41504019)supported by a fund from Korea Astronomy and Space Science Institute(2016 Space Geodesy Project about Atmospheric/Ocean Tidal Effects)
文摘Previous studies suggest that tidal friction gives rise to the secular deceleration of the Earth rotation by a quantity of about 2.25 ms/cy. Here we just consider additional contributions to the secular Earth rotation deceleration. Atmospheric solar semi-diurnal tide has a small amplitude and certain amount of phase lead. This periodic global air-mass excess distribution exerts a quasi-constant torque to accelerate the Earth's spin rotation. Using an updated atmospheric tide model, we re-estimate the amounts of this atmospheric acceleration torque and corresponding energy input, of which the associated change rate in LOD(length of day) is-0.1 ms/cy. In another aspect, evidences from space-geodesy and sea level rise observations suggest that Earth expands at a rate of 0.35 mm/yr in recent decades, which gives rise to the increase of LOD at rate of 1.0 ms/cy. Hence, if the previous estimate due to the tidal friction is correct, the secular Earth rotation deceleration due to tidal friction and Earth expansion should be 3.15 ms/cy.
基金National Outstanding Youth Foundation of China (49925411) the Knowledge Innovation Foundation,Chinese Academy of Sciences (KZCX2-SW-131).
文摘Based on the tide gravity observations recorded with LCR-ET20 spring gravimeter at Wuhan international fundamental tidal gravity station, the characteristics of ET20 and atmospheric and oceanic gravity signals are studied systematically by using international standard data pre-processing and analysis methods and by comparing the results with those obtained by superconducting gravimeter (SG) at the same station. The numerical results indicate that the identical tidal gravity parameters are the same as those with the SG, the instrument can be effectively used to record temporal change of the gravity field, though the ET20 accuracy is one order lower than that of the SG, and has the large drift induced by the spring creep character.