Analysis Of The Influence Of Terrain On Remote Sensing Atmospheric CO₂ Retrieval

Nowadays researches on the change of global climate is an important study topic for the international community.The greenhouse effect causes global to become warm and induces extreme weather frequently.The high-precision monitoring of carbon dioxide(CO2)on a global scale,which is an important member of greenhouse gases,is of great significance in the climate research,and the formulation and implementation of CO2 emission policies.Although the traditional observations methods have high precision,including the ground-based observation and the air-borne observation,there are disadvantages such as the small number of observation stations and sparse spatial distribution,which makes it impossible to monitor CO2 globally in real time.While satellite observation can obtain stable and continuous global data through data acquisition with high-frequency.Actually,the atmospheric CO2 retrieval process is the approaching process of the simulated spectrum of radiation transmission to the spectrum measured by satellite.The premise of high-precision of CO2 retrieval is the objectivity and accuracy of the simulated process of radiation transmission.To meet the requirements of climate research,the accuracy of CO2 concentration detected by satellite needs to reach 0.3%-0.5%.Objective and accurate simulated process of radiation transmission has something with instrument,surface,and the accuracy of environmental parameters in atmosphere.The surface elevation reflects the length of atmospheric radiation transmission path,which affects the total volume of air.And the changes of field of view of satellite will significantly increase the inaccuracy of the XCO2.In order to improve the retrieval accuracy,it is necessary to analyze the CO2 retrieval error caused by the surface elevation deviation quantitatively.Based on the principle of atmospheric CO2 satellite remote sensing,this paper analyzed the characteristics of surface elevation changes under different terrains and studied their effects on the accuracy of CO2 retrieval.The changes of surface elevation of the three types of surface morphology,including plain,mountainous area and the boundaries between the above two were studied using the SRTM surface elevation data.The results showed that there were pointing deviations during the process of the remote sensing,and the errors caused by different terrains were different.In general,as the degree of fluctuation of the terrain increased,the surface elevation error increased accordingly.Based on the topographic analysis,the effects of surface elevation changes on CO2 concentration were analyzed from the aspects of the radiation transmission simulation and the retrieval of atmospheric CO2 respectively.The simulation results showed that the surface elevation deviation had a great influence on the change of atmospheric CO2 content.For every 100m change,the corresponding change of CO2 column concentration was about 4.248 ppm.During the C02 retrieval process,although some correction actions were taken,the elevation value change of 100 m would cause a deviation of 3.11 ppm.It can be seen that the CO2 deviation caused by topographic changes was very obvious.This paper believed that in the process of CO2 retrieval,the deviation induced by terrain should be overcome as much as possible.Meanwhile,the threshold of the surface elevation error was proposed to be 60 m.To ensure the reliability of the retrieval results,remote sensing data which was more than the threshold should be filtered or used with caution.