Xi'an Atmospheric Co <sub> 2 </ Sub> Spatial And Temporal Distribution,

Global warming is the most severe issue that human beings encounter, which has also become an issue of widest concern. The core of climate change is greenhouse gas CO2 emissions, researches on greenhouse gases has become one of the most thriving branches of atmospheric science and environmental science, study on CO2 conservation change and behavior in the atmosphere, etc. will help us understand. predict, and enhance the earth's climate change process. Studies on source and sink of CO2 in urban atmosphere serve as theoretical premise for the construction of Low Carbon Cities and steer the strategic direction of energy conservation and emission reduction.In four inconsecutive days in autumn, four different monitoring spots were chosen in Xi'an to constantly supervise and control daily change of CO2 concentration in atmosphere with infrared co -2 analyzer and meteorological data and other synchronous data were collected. Through analyzing the observations of daily variation trend, days and holiday differentiation, changes in variables of meteorological data and CO2 concentration, regional differences, the CO2 vertical distribution in Ground Layer atmospheric characteristics, the source and sink pattern of CO2 in urban atmosphere of Xi'an is analyzed and meteorological factors driving atmospheric CO2 concentration variation is studied. Finally, the conclusions and knowing concluded are as follows:(1)Through a double-peak model analysis of the daily change of atmospheric CO2 concentration, the major forces causing daily changes of atmospheric CO2 concentration are identified, which are as the day and night alternate of plants'physiological and atmospheric change brought by solar radiation and other natural factors. The periodical appearance of temporary wave crest of atmospheric CO2 concentration, typically during six am to seven am,8 am to 11 am.7 pm to 11 pm in urban areas it bond up with the daily routine of urban citizens, which is caused by the emission of point source and linear source. The difference in climate change determines the density of atmospheric CO2 concentration. During cloudy days with lower atmosphere or overcast days, the atmospheric CO2 concentration is higher; while sunny days with higher atmosphere, the atmospheric CO2 concentration is lower. Speeding up wind can dilute atmospheric CO2 while in long periods of windless weather, the atmospheric CO2 accumulate and increase.(2) The difference of atmospheric CO2 concentration between work days and holidays is specially analyzed, a conclusion is that fuel discharge from factories plays an important role in the atmospheric CO2 concentration of Xi'an. Specifically, during the national holiday, the atmospheric CO2 concentration is 5～10ppm lower compared with usual for the amount of fuel discharge decreases when factories stop production.(3) After comparing and analyzing regional differences in terms of atmospheric CO2 concentration in different monitoring spots. a conclusion is drawn that In the daytime, farms anc plantations serve as the source of CO2 (Mainly manifested as source), while serve as sink in the nigh Contrasted with the suburb, they serve the urban area mainly as source in a day. The composite efforts of changes in concentration of course and sink and atmospheric condition in the functional areas where monitoring spots locate can explain characteristic peak of the two curves of average value of atmospheric CO2 concentration. which is the consequence of emission from humar activities.(4) After tentative researches about the vertical distribution of CO2 concentration in ground layer of urban areas and daily changes, findings are as follows:the average atmospheric density decreases as the altitude increase. which accounts that the urban ground surface serves as the primary origin of atmospheric CO2 in Xi'an. In the daytime, the vertical distribution of atmospheric concentration falls with the rise of altitude. By comparison, there is little change in the CO2 concentration on all levels of altitude, it remains steady, which is led by changes in the extent of constancy resulting from different atmospheric physical properties. In daybreak and dusk, there is an obvious fluctuation in the vertical distribution of atmospheric concentration in monitoring spots, which is because that instantaneous the emission of point source and lateral source strengthen the force of source strength on the underlying surface, combined with the effect of neutral stratification of atmosphere in the two time periods.(5) After comparison and contrast between observation outcomes in two altitudes in farms located in monitoring spots, a regulation is found that:in the daytime, the atmospheric concentration of atmosphere 20 cm far above the farm is lower than that of 110cm far above the farm, while the contrary is true in the night, this distribution is due to the fact that the atmosphere 20cm far above the farm is more affected by the respiration of earth.