The impacts of solar activity on climate are explored in this two-part study. Based on the principles of atmospheric dynamics, Part I propose an amplifying mechanism of solar impacts on winter climate extremes through...The impacts of solar activity on climate are explored in this two-part study. Based on the principles of atmospheric dynamics, Part I propose an amplifying mechanism of solar impacts on winter climate extremes through changing the atmospheric circulation patterns. This mechanism is supported by data analysis of the sunspot number up to the predicted Solar Cycle 24, the historical surface temperature data, and atmospheric variables of NCEP/NCAR Reanalysis up to the February 2011 for the Northern Hemisphere winters. For low solar activity, the thermal contrast between the low- and high-latitudes is enhanced, so as the mid-latitude baroclinic ultra-long wave activity. The land-ocean thermal contrast is also enhanced, which amplifies the topographic waves. The enhanced mid-latitude waves in turn enhance the meridional heat transport from the low to high latitudes, making the atmospheric "heat engine" more efficient than normal. The jets shift southward and the polar vortex is weakened. The Northern Annular Mode (NAM) index tends to be negative. The mid-latitude surface exhibits large-scale convergence and updrafts, which favor extreme weather/climate events to occur. The thermally driven Siberian high is enhanced, which enhances the East Asian winter monsoon (EAWM). For high solar activity, the mid-latitude circulation patterns are less wavy with less meridional transport. The NAM tends to be positive, and the Siberian high and the EAWM tend to be weaker than normal. Thus the extreme weather/climate events for high solar activity occur in different regions with different severity from those for low solar activity. The solar influence on the mid- to high-latitude surface temperature and circulations can stand out after removing the influence from the E1 Nifio-Southern Oscillation. The atmospheric amplifying mechanism indicates that the solar impacts on climate should not be simply estimated by the magnitude of the change in the solar radiation over solar cycles when it is compared with other external radiative forcings that do not influence the climate in the same way as the sun does.展开更多
研究长白山气候舒适期的变化,可以为其旅游业发展规划提供科学依据。基于1961—2018年长白山二道气象站逐日观测资料和NCEP/NCAR(National Centers for Environmental Prediction/Na⁃tional Center for Atmospheric Research)再分析资料...研究长白山气候舒适期的变化,可以为其旅游业发展规划提供科学依据。基于1961—2018年长白山二道气象站逐日观测资料和NCEP/NCAR(National Centers for Environmental Prediction/Na⁃tional Center for Atmospheric Research)再分析资料,分析长白山地区气候舒适期特征及其与大气环流的关系,并利用综合舒适指数对长白山气候舒适度进行评价。结果表明:长白山地区5—9月为气候舒适期,4月和10月为气候较舒适期。稳定气候舒适初日整体呈提前趋势[1.9 d·(10 a)^(-1)];稳定气候舒适终日整体呈推迟趋势[2.3 d·(10 a)^(-1)],且在1988年前后发生突变,由偏早转为偏晚。稳定气候舒适期平均为177 d,整体呈增长趋势[4.2 d·(10 a)^(-1)],其中1960—1980年代初期为偏短期,1980—1990年代中期为平稳期,1990年代中期以后转变为偏长期,并存在3~5 a周期。当东亚地区春季500 hPa高度场正异常,有利于稳定气候舒适初日异常偏早,反之异常偏晚;当东亚—西北太平洋地区500 hPa高度场存在负异常,有利于稳定气候舒适终日异常偏早,反之异常偏晚。展开更多
The laser-guided bomb(LGB)is an air-to-ground pre-cision-guided weapon that offers high hit rates,great power,and ease of use.LGBs are guided by semi-active laser ground-seek-ing technology,which means that atmospheri...The laser-guided bomb(LGB)is an air-to-ground pre-cision-guided weapon that offers high hit rates,great power,and ease of use.LGBs are guided by semi-active laser ground-seek-ing technology,which means that atmospheric conditions can affect their accuracy.The spatial release region(SRR)of LGBs is difficult to calculate precisely,especially when there is a poor field of view.This can result in a lower real hit probability.To increase the hit probability of LGBs in tough atmospheric situa-tions,a novel method for calculating the SRR has been pro-posed.This method is based on the transmittance model of the 1.06μm laser in atmospheric species and the laser diffuse reflection model of the target surface to determine the capture target time of the laser seeker.Then,it calculates the boundary ballistic space starting position by ballistic model and gets the spatial scope of the spatial release region.This method can determine the release region of LGBs based on flight test data such as instantaneous velocity,altitude,off-axis angle,and atmospheric visibility.By more effectively employing aircraft release conditions,atmospheric visibility and other factors,the SRR calculation method can improve LGB hit probabi-lity by 9.2%.展开更多
This paper numerically investigates the radio wave scattering by the artificial acoustic disturbance in the atmospheric boundary layer. The numerical model is based on the finitedifference time-domain（FDTD） method f...This paper numerically investigates the radio wave scattering by the artificial acoustic disturbance in the atmospheric boundary layer. The numerical model is based on the finitedifference time-domain（FDTD） method for radio wave propagation and fluid simulation for atmospheric disturbance by acoustics waves. The characteristics of radio wave scattering propagation in the artificial acoustic perturbations are investigated by this numerical model. The numerical simulation results demonstrate that the radio wave propagation scattered by acoustic scatterer has the characteristic of forward tropospheric scatter. When the radio waves are scattered, they distribute in all directions; a majority of radio waves continues to propagate along the original direction, and only a small part of the energy is scattered. For the same acoustic scatterer, if we merely change the radio wave emission elevation, the horizontal spans of forward scattering radio wave packets centers gradually decrease with the increasing of emission elevations; and the energy of wave packets increases firstly and then decreases with launching elevation, reaching the maximum at a certain angle. If we merely change the wave emitting position, the horizontal spans decrease with the increasing of emission positions, and the energy of wave packets also increases firstly and then decreases with launch position, reaching the maximum at a certain position. This approach can be very promising for atmospheric scatter communications.展开更多
Electron density profiles of Venus＇ ionosphere are inverted from the Venus Express （VEX） one-way open-loop radio occultation experiments carried out by the Shanghai 25 m antenna from November 2011 to January 2012 a...Electron density profiles of Venus＇ ionosphere are inverted from the Venus Express （VEX） one-way open-loop radio occultation experiments carried out by the Shanghai 25 m antenna from November 2011 to January 2012 at solar maximum conditions and by the New Norcia 35 m antenna from August 2006 to June 2008 at solar intermediate conditions. The electron density profile （from 110 km to 400 km）, retrieved from the X-band egress observation at the Shanghai station, shows a single peak near 147 km with a peak density of about 2 × 10^4 cm-3 at a solar zenith angle of 94° As a comparison, the VEX radio science （VeRa） observations at the New Norcia station were also examined, including S- and X-band and dual-frequency data in the ingress mode. The results show that the electron density profiles retrieved from the S-band data are more analogous to the dual-frequency data in terms of the profile shape, compared with the X-band data. Generally, the S-band results slightly underestimate the magnitude of the peak density, while the X-band results overestimate it. The discrepancy in the X-band profile is probably due to the relatively larger unmod- eled orbital errors. It is also expected that the ionopause height is sensitive to the solar wind dynamical pressure in high and intermediate solar activities, usually in the range of 200-1000 km on the dayside and much higher on the nightside. Structural variations （＂bulges＂ and fluctuations） can be found in the electron density profiles during intermediate solar activity, which may be caused by the interaction of the solar wind with the ionosphere. Considerable ionizations can be observed in Venus＇ nightside ionosphere, which are unexpected for the Martian nightside ionosphere in most cases.展开更多
The high ridge in the northern branch of the subtropical westerly （hereafter referred to as northern branch ridge） extends from the north of the Tibetan Plateau to the north of Barr Kashmir Lake （32.5°-47.5...The high ridge in the northern branch of the subtropical westerly （hereafter referred to as northern branch ridge） extends from the north of the Tibetan Plateau to the north of Barr Kashmir Lake （32.5°-47.5°N, 70°-95°E） during wintertime. The intensity index and zonal position index of the wintertime northern branch ridge （WNBR） are defined in this study by using the NCEP-NCAR reanalysis data and precipitation and temperature observations at 160 stations in China. Interannual variation features of the WNBR and its relation with precipitation and surface air temperature in China are discussed based on wavelet analysis, correlation analysis, and composite analysis. The results indicate that the intensity and zonal position of the WNBR exhibit significant interannual variability. The intensity of the WNBR gradually weakens and varies in periodic cycles of 4-6, quasi-2, and quasi-16 yr. Its zonal position shifts westward slightly and varies in periodic cycles of quasi-8 and quasi-16 yr. The WNBR is highly correlated with precipitation and surface air temperature in China. When the WNBR is strong （weak） and its zonal position shifts eastward （westward）, winter precipitation in Northeast China and the northern region of Northwest China increases （decreases）, whereas precipitation decreases in central China, South China, and eastern regions of Northwest and Southwest China. Meanwhile, surface air temperatures in most areas of China are higher （lower） than normal. Further investigation has revealed that the two indexes are closely related to variations in general atmospheric circulation, which explains why there exists a close linkage between the variation of the WNBR and climate in China. It is believed that the WNBR is also tied to the Rossby wave, the North Atlantic Oscillation, the East Asian trough, and the North Pacific jet stream.展开更多
基金provided by the LASG State Key Laboratory Special Fund for this research project
文摘The impacts of solar activity on climate are explored in this two-part study. Based on the principles of atmospheric dynamics, Part I propose an amplifying mechanism of solar impacts on winter climate extremes through changing the atmospheric circulation patterns. This mechanism is supported by data analysis of the sunspot number up to the predicted Solar Cycle 24, the historical surface temperature data, and atmospheric variables of NCEP/NCAR Reanalysis up to the February 2011 for the Northern Hemisphere winters. For low solar activity, the thermal contrast between the low- and high-latitudes is enhanced, so as the mid-latitude baroclinic ultra-long wave activity. The land-ocean thermal contrast is also enhanced, which amplifies the topographic waves. The enhanced mid-latitude waves in turn enhance the meridional heat transport from the low to high latitudes, making the atmospheric "heat engine" more efficient than normal. The jets shift southward and the polar vortex is weakened. The Northern Annular Mode (NAM) index tends to be negative. The mid-latitude surface exhibits large-scale convergence and updrafts, which favor extreme weather/climate events to occur. The thermally driven Siberian high is enhanced, which enhances the East Asian winter monsoon (EAWM). For high solar activity, the mid-latitude circulation patterns are less wavy with less meridional transport. The NAM tends to be positive, and the Siberian high and the EAWM tend to be weaker than normal. Thus the extreme weather/climate events for high solar activity occur in different regions with different severity from those for low solar activity. The solar influence on the mid- to high-latitude surface temperature and circulations can stand out after removing the influence from the E1 Nifio-Southern Oscillation. The atmospheric amplifying mechanism indicates that the solar impacts on climate should not be simply estimated by the magnitude of the change in the solar radiation over solar cycles when it is compared with other external radiative forcings that do not influence the climate in the same way as the sun does.
基金This work was supported by the major research projects within the military-international class(JY2021B077).
文摘The laser-guided bomb(LGB)is an air-to-ground pre-cision-guided weapon that offers high hit rates,great power,and ease of use.LGBs are guided by semi-active laser ground-seek-ing technology,which means that atmospheric conditions can affect their accuracy.The spatial release region(SRR)of LGBs is difficult to calculate precisely,especially when there is a poor field of view.This can result in a lower real hit probability.To increase the hit probability of LGBs in tough atmospheric situa-tions,a novel method for calculating the SRR has been pro-posed.This method is based on the transmittance model of the 1.06μm laser in atmospheric species and the laser diffuse reflection model of the target surface to determine the capture target time of the laser seeker.Then,it calculates the boundary ballistic space starting position by ballistic model and gets the spatial scope of the spatial release region.This method can determine the release region of LGBs based on flight test data such as instantaneous velocity,altitude,off-axis angle,and atmospheric visibility.By more effectively employing aircraft release conditions,atmospheric visibility and other factors,the SRR calculation method can improve LGB hit probabi-lity by 9.2%.
基金supported by the National Natural Science Foundation of China(412041114157414641774162)
文摘This paper numerically investigates the radio wave scattering by the artificial acoustic disturbance in the atmospheric boundary layer. The numerical model is based on the finitedifference time-domain（FDTD） method for radio wave propagation and fluid simulation for atmospheric disturbance by acoustics waves. The characteristics of radio wave scattering propagation in the artificial acoustic perturbations are investigated by this numerical model. The numerical simulation results demonstrate that the radio wave propagation scattered by acoustic scatterer has the characteristic of forward tropospheric scatter. When the radio waves are scattered, they distribute in all directions; a majority of radio waves continues to propagate along the original direction, and only a small part of the energy is scattered. For the same acoustic scatterer, if we merely change the radio wave emission elevation, the horizontal spans of forward scattering radio wave packets centers gradually decrease with the increasing of emission elevations; and the energy of wave packets increases firstly and then decreases with launching elevation, reaching the maximum at a certain angle. If we merely change the wave emitting position, the horizontal spans decrease with the increasing of emission positions, and the energy of wave packets also increases firstly and then decreases with launch position, reaching the maximum at a certain position. This approach can be very promising for atmospheric scatter communications.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11103063 and 11178008)the National Key Basic Research Program of China (Grant No. 2015CB857101)partly supported by the Key Laboratory of Planetary Sciences, Chinese Academy of Sciences (Grant No. PSL15 04)
文摘Electron density profiles of Venus＇ ionosphere are inverted from the Venus Express （VEX） one-way open-loop radio occultation experiments carried out by the Shanghai 25 m antenna from November 2011 to January 2012 at solar maximum conditions and by the New Norcia 35 m antenna from August 2006 to June 2008 at solar intermediate conditions. The electron density profile （from 110 km to 400 km）, retrieved from the X-band egress observation at the Shanghai station, shows a single peak near 147 km with a peak density of about 2 × 10^4 cm-3 at a solar zenith angle of 94° As a comparison, the VEX radio science （VeRa） observations at the New Norcia station were also examined, including S- and X-band and dual-frequency data in the ingress mode. The results show that the electron density profiles retrieved from the S-band data are more analogous to the dual-frequency data in terms of the profile shape, compared with the X-band data. Generally, the S-band results slightly underestimate the magnitude of the peak density, while the X-band results overestimate it. The discrepancy in the X-band profile is probably due to the relatively larger unmod- eled orbital errors. It is also expected that the ionopause height is sensitive to the solar wind dynamical pressure in high and intermediate solar activities, usually in the range of 200-1000 km on the dayside and much higher on the nightside. Structural variations （＂bulges＂ and fluctuations） can be found in the electron density profiles during intermediate solar activity, which may be caused by the interaction of the solar wind with the ionosphere. Considerable ionizations can be observed in Venus＇ nightside ionosphere, which are unexpected for the Martian nightside ionosphere in most cases.
基金Supported by the National Natural Science Foundation of China(41275079,41305077,41405069,91537214,and 41505078)Scientific Research Fund for the Young Academic Leaders,Chengdu University of Information Technology(J201518 and J201516)
文摘The high ridge in the northern branch of the subtropical westerly （hereafter referred to as northern branch ridge） extends from the north of the Tibetan Plateau to the north of Barr Kashmir Lake （32.5°-47.5°N, 70°-95°E） during wintertime. The intensity index and zonal position index of the wintertime northern branch ridge （WNBR） are defined in this study by using the NCEP-NCAR reanalysis data and precipitation and temperature observations at 160 stations in China. Interannual variation features of the WNBR and its relation with precipitation and surface air temperature in China are discussed based on wavelet analysis, correlation analysis, and composite analysis. The results indicate that the intensity and zonal position of the WNBR exhibit significant interannual variability. The intensity of the WNBR gradually weakens and varies in periodic cycles of 4-6, quasi-2, and quasi-16 yr. Its zonal position shifts westward slightly and varies in periodic cycles of quasi-8 and quasi-16 yr. The WNBR is highly correlated with precipitation and surface air temperature in China. When the WNBR is strong （weak） and its zonal position shifts eastward （westward）, winter precipitation in Northeast China and the northern region of Northwest China increases （decreases）, whereas precipitation decreases in central China, South China, and eastern regions of Northwest and Southwest China. Meanwhile, surface air temperatures in most areas of China are higher （lower） than normal. Further investigation has revealed that the two indexes are closely related to variations in general atmospheric circulation, which explains why there exists a close linkage between the variation of the WNBR and climate in China. It is believed that the WNBR is also tied to the Rossby wave, the North Atlantic Oscillation, the East Asian trough, and the North Pacific jet stream.
