Research On Near Space Environment Modeling Based On TIMED/SABER Observation

Near space environment is an important part of the upper and middle atmosphere of the earth.It is affected not only by tropospheric activity but also by solar radiation and cosmic rays.These factors interact to make near space environment complicated and changeable.More importantly,near space has a direct impact on the engineering applications of aircraft and human activities in the region.However,due to the limitations of observation and other models,it is necessary to establish a new model of near space atmospheric environment to simulate the characteristics of atmospheric parameters.The analysis of the inflection point temperature is a vital step in this model.Using the grid data from the processed Sounding of the Atmosphere using Broadband Emission Radiometry?SABER?data on Thermosphere Ionosphere Mesosphere Energetics and Dynamics?TIMED?from 2002 to 2017,this paper studies the characteristics analysis of the spatial and temporal distributions of stratopause temperature?Tsp?between 50°S?50°N,which is defined as the maximum vertical temperature between 40km and 60km,and the responding factors.The results show that Tsp has obvious latitudinal and seasonal characteristics.Tsp is higher in the equator and in the summer of the northern or southern hemispheres,while the lowest temperature is near 40°latitude in the winter of northern or southern hemispheres.Using the EOF method,the first mode,which represents 91%of the total Tsp variability,is discussed in our work.Its coefficient has the highest correlation of 0.49with the ozone volume mixing ratio?O₃?VMR?on stratopause,while the correlation with earth-sun distance and solar activity?F10.7,SSN?is about 0.44 and 0.33,respectively.According to the relations,further researches show that Tsp has the opposite latitudinal variations with stratopause O₃?VMR and the opposite seasonal variations with earth-sun distance.Moreover,the annual averaged Tsp varies in a range of 2K from 2002 to 2017,and has a good correlation with F10.7.The best correlation coefficient is 0.74 near 20°S and20°N.The core idea of this model is as follows.Firstly,we establish the mathematical expressions of atmospheric temperature including the changes with latitude,local time,and altitude,by fitting the inflection point temperature?stratopause temperature and20km-temperature?and the atmospheric temperature profile in the area of 20-90 km using the processed TIMED/SABER data from 2002 to 2017.According to the pressure differential equation and the ideal gas equation,we can get the atmospheric temperature,pressure,density,and component densities?including N₂,O₂,Ar,and He?under the certain conditions.Then,based on the semi-annual change,the influence of geomagnetic activity,and the seasonal-latitude change in atmospheric environmental parameters,the model results are modified.Based on J70 model results in the range of 90-120km,the preliminary simulations?NSM model?of near space environmental parameters can be obtained.Moreover,the model results are further calibrated to improve the model accuracy in the way of establishing the partial derivative relationship between the atmospheric elements and the inflection point temperature using the real-time observed data and calculating the optimal correction value of the atmospheric parameters.Finally,a global near space atmospheric environment model?NSDCAM model?with a horizontal resolution of 2.5oand a vertical resolution of 2 km is successfully obtained.This paper also tests the models.Based on the SABER observation data on March 21,June 22,September 23,and December 22 in 2018,the NSDCAM,NRLMSISE-00 and CIRA-86 modeling temperatures are compared.The comparing figure shows that the NSDCAM model can present the temperature changes apparently in altitude and latitude on different seasonal date.At 40km,70km,and 100km,the applicability of the NSM model is also verified using SABER data,atmospheric density results from the NRLMSISE-00 model,and atmospheric pressure results from the CIRA-86 model.Then by calculating the error results of the NSDCAM and USSA-76 models versus the measured data on three altitudes?20km,55km,80km?,the detailed error analysis appears that NSDCAM model has more accurate performance than USSA-76 model.All above,NSM and NSDCAM model can be used to simulate and analyze the near space atmosphere's feature.As an application of the NSM model,taking five stations as examples,which are Beijing,Wuhan,Haikou,Chongqing and Lasa,the atmospheric environment of the"Meridian Project"stations is analyzed.The results show that atmospheric parameters change more significantly on different latitudes than longitudes,and their seasonal variations at different altitudes are also different.