This study uses ECMWF fifth-generation reanalysis, ERA5, which extends to the mesopause, to construct the Initial Conditions(IC) for WACCM(Whole Atmosphere Community Climate Model) simulations. Because the biases betw...This study uses ECMWF fifth-generation reanalysis, ERA5, which extends to the mesopause, to construct the Initial Conditions(IC) for WACCM(Whole Atmosphere Community Climate Model) simulations. Because the biases between ERA5 and Sounding of the Atmosphere using Broadband Emission Radiometry(SABER) temperature data are within ±5 K below the lower mesosphere,ERA5 reanalysis is used to construct IC in the lower atmosphere. Four experiments are performed to simulate a Stratospheric Sudden Warming(SSW) event from 5 to 15 February 2016. The simulation using the WACCM default climatic IC cannot represent the sharp meteorological variation during SSW. In contrast, the 0～4 d forecast results driven by ERA5-constructed IC is consistent with ERA5 reanalysis below the middle mesosphere. Comparing with WACCM climatology ICs scheme, the ICs constructing method based on ERA5 reanalysis can obtain 67%, 40%, 22%, 4% and 6% reduction of temperature forecast RMSE at 10 hPa, 1 hPa, 0.1 hPa, 0.01 hPa and 0.001 hPa respectively. However,such improvement is not shown in the lower thermosphere.展开更多
We introduce a new approach,using the International Reference Ionosphere 2007(IRI-2007)model and observations from the Moscow ionosonde station,to analyze the long-term trends of ionospheric foF2.Possible origins,whet...We introduce a new approach,using the International Reference Ionosphere 2007(IRI-2007)model and observations from the Moscow ionosonde station,to analyze the long-term trends of ionospheric foF2.Possible origins,whether natural or manmade, are discussed.A small but significant residual foF2 trend is found,with-0.76 MHz over the past 50 years,but-0.2 MHz after eliminating the most variations caused by solar and geomagnetic activities and the variational earth's magnetic field.We find that this slope depends on local time and seasons.There is a pronounced diurnal negative variation in k(annual mean slope of diurnal variations),with much larger absolute values in the morning than during afternoon or evening;the largest k is about-0.0018 per year in spring,and the smallest trend of about-0.0012 per year occurs in winter.Finally,the evidence of crucial influences of geomagnetic activity and the earth's magnetic field on the observed trends,as emphasized by the IRI-2007 empirical model,is confirmed,and the effect of CO2 contributions to the trend is also discussed,by cooling the thermospheric temperature or recombining the electron density.展开更多
Ionospheric peak value of F2 layer （NmF2） is an important parameter in the ionosphere, which has important applications in short-wave communication, ionospheric modeling and so on. In this paper, the empirical ortho...Ionospheric peak value of F2 layer （NmF2） is an important parameter in the ionosphere, which has important applications in short-wave communication, ionospheric modeling and so on. In this paper, the empirical orthogonal function （EOF） decompo- sition method is used to analyze the NmFz obtained from the occultation data. Daily spatial distribution of NmF2 at the same time is relatively even. Variance of first modal is much larger than the other modals. A local wavelet power spectrum （LWPS） method is applied to analysis the cycle of Flo.7 index and time coefficient of first modal. The result shows that they have simi- lar cycle distribution, indicating that Flo.7 index is the main factor affecting variation of NmF〉 A function is established be- tween the tine coefficient of first modal and F10.7 index, average F10.7 index value of early 81 days fp by least squares method. The results show that contribution coefficient offp is negative which indicates that fp has an inert effect existing in the iono- sphere. Contribution coefficient of F10.7 is positive, which is consistent with the fact that it has an anomaly in winter/spring seasons. In summary, it is feasible to establish a mid-latitude empirical NmF2 model in northern hemisphere based on occulta- tion data and EOF decomposition method.展开更多
The nightly mean mesospheric temperature profiles between 80 and 107 km, observed by Na lidar, over Fort Collins, Colorado （41°N, 105°W） from 1990 to 2010, are employed to research the temporal and spatial...The nightly mean mesospheric temperature profiles between 80 and 107 km, observed by Na lidar, over Fort Collins, Colorado （41°N, 105°W） from 1990 to 2010, are employed to research the temporal and spatial variations and mesopause. We find that the maximum mean temperature is in summer months above 95 kin, but reverse below 95 kin, and there is a cooler region below 185 K around 97 km in August. The largest seasonal variation is 39.2 K at 81 kin, and the minimum is 6.5 K at 96.5 km. The maximum standard derivation in spring and autumn months are larger than other seasons above 105 kin, but the temperatures in March, June and September are lower than the other months between 82 km and 100 km where winter is the largest season. Moreover, the seasonal variations of the temperature are about 36, 8 and 21 K at 85, 95 and 105 km, respectively, winter is colder and summer is warmer above 97.5 km, but reverse below 92 km. The mesopause height is around 102 km in winter, but 84 km in summer, and the mean speed of decreasing or increasing of the mesopause height is about 5 km/month in spring and autumn months which are about 90 km. The lasting time of the mesopause in winter is near 6 months, longer than other seasons, and the mesopause temperature is about 165 K in cool summer, and 185 K in warm winter.展开更多
基金Supported by the National Natural Science Foundation of China(41375105)
文摘This study uses ECMWF fifth-generation reanalysis, ERA5, which extends to the mesopause, to construct the Initial Conditions(IC) for WACCM(Whole Atmosphere Community Climate Model) simulations. Because the biases between ERA5 and Sounding of the Atmosphere using Broadband Emission Radiometry(SABER) temperature data are within ±5 K below the lower mesosphere,ERA5 reanalysis is used to construct IC in the lower atmosphere. Four experiments are performed to simulate a Stratospheric Sudden Warming(SSW) event from 5 to 15 February 2016. The simulation using the WACCM default climatic IC cannot represent the sharp meteorological variation during SSW. In contrast, the 0～4 d forecast results driven by ERA5-constructed IC is consistent with ERA5 reanalysis below the middle mesosphere. Comparing with WACCM climatology ICs scheme, the ICs constructing method based on ERA5 reanalysis can obtain 67%, 40%, 22%, 4% and 6% reduction of temperature forecast RMSE at 10 hPa, 1 hPa, 0.1 hPa, 0.01 hPa and 0.001 hPa respectively. However,such improvement is not shown in the lower thermosphere.
基金supported by the National Natural Science Foundation of China(40890162 and 40505005)the Specialized Research Fund for State Key Laboratories
文摘We introduce a new approach,using the International Reference Ionosphere 2007(IRI-2007)model and observations from the Moscow ionosonde station,to analyze the long-term trends of ionospheric foF2.Possible origins,whether natural or manmade, are discussed.A small but significant residual foF2 trend is found,with-0.76 MHz over the past 50 years,but-0.2 MHz after eliminating the most variations caused by solar and geomagnetic activities and the variational earth's magnetic field.We find that this slope depends on local time and seasons.There is a pronounced diurnal negative variation in k(annual mean slope of diurnal variations),with much larger absolute values in the morning than during afternoon or evening;the largest k is about-0.0018 per year in spring,and the smallest trend of about-0.0012 per year occurs in winter.Finally,the evidence of crucial influences of geomagnetic activity and the earth's magnetic field on the observed trends,as emphasized by the IRI-2007 empirical model,is confirmed,and the effect of CO2 contributions to the trend is also discussed,by cooling the thermospheric temperature or recombining the electron density.
基金supported by the National Natural Science Foundation of China(Grant No.40505005)the Specialized Research Fund for State Key Laboratories(Grant No.Y22612A33S)
文摘Ionospheric peak value of F2 layer （NmF2） is an important parameter in the ionosphere, which has important applications in short-wave communication, ionospheric modeling and so on. In this paper, the empirical orthogonal function （EOF） decompo- sition method is used to analyze the NmFz obtained from the occultation data. Daily spatial distribution of NmF2 at the same time is relatively even. Variance of first modal is much larger than the other modals. A local wavelet power spectrum （LWPS） method is applied to analysis the cycle of Flo.7 index and time coefficient of first modal. The result shows that they have simi- lar cycle distribution, indicating that Flo.7 index is the main factor affecting variation of NmF〉 A function is established be- tween the tine coefficient of first modal and F10.7 index, average F10.7 index value of early 81 days fp by least squares method. The results show that contribution coefficient offp is negative which indicates that fp has an inert effect existing in the iono- sphere. Contribution coefficient of F10.7 is positive, which is consistent with the fact that it has an anomaly in winter/spring seasons. In summary, it is feasible to establish a mid-latitude empirical NmF2 model in northern hemisphere based on occulta- tion data and EOF decomposition method.
基金supported by the National Natural Science Foundation of China(Grant Nos.40505005,41304146)the Specialized Research Fund for State Key Laboratories of China
文摘The nightly mean mesospheric temperature profiles between 80 and 107 km, observed by Na lidar, over Fort Collins, Colorado （41°N, 105°W） from 1990 to 2010, are employed to research the temporal and spatial variations and mesopause. We find that the maximum mean temperature is in summer months above 95 kin, but reverse below 95 kin, and there is a cooler region below 185 K around 97 km in August. The largest seasonal variation is 39.2 K at 81 kin, and the minimum is 6.5 K at 96.5 km. The maximum standard derivation in spring and autumn months are larger than other seasons above 105 kin, but the temperatures in March, June and September are lower than the other months between 82 km and 100 km where winter is the largest season. Moreover, the seasonal variations of the temperature are about 36, 8 and 21 K at 85, 95 and 105 km, respectively, winter is colder and summer is warmer above 97.5 km, but reverse below 92 km. The mesopause height is around 102 km in winter, but 84 km in summer, and the mean speed of decreasing or increasing of the mesopause height is about 5 km/month in spring and autumn months which are about 90 km. The lasting time of the mesopause in winter is near 6 months, longer than other seasons, and the mesopause temperature is about 165 K in cool summer, and 185 K in warm winter.
