Carbon Footprint Flux Analysis Of Urban Underlying Surface

CO₂ flux is one of the hot researches in the meteorological environment.More and more scholars have conducted in-depth studies on it from the uniform ecosystem of the underlying surface to the complex ecosystem of the underlying surface,from the CO₂ flux dynamic characteristics to the CO₂ flux.Spatial dynamics,from CO₂ flux source area to CO₂ flux footprint contribution et al.Not only contribute to carbon cycle research,but also provide advice on the implementation of relevant policies.Moreover,obtaining CO₂ flux details of various types of urban settlements is an important basis for pushing the results of various observation stations to the urban scale,but such studies are rare.In view of this,this article uses the measured data of the covariance system in the university city of Fengxian District in Shanghai to develop the specific analysis and research of the time-frequency characteristics of carbon flux,and based on the space of the underlying surface.Differentiating,using the Art Footprint model,the CO₂ flux footprints and contribution rates of different types of underlying surface cover types were studied in turn,and related studies were conducted on the management differences of vegetation CO₂ flux.Specific conclusions include:（1）During the study period,CO₂ fluxes showed regular changes in different seasons,different months and different days.the annual CO₂ flux is mainly concentrated between-10μmolm^-2s^-1-7μmolm^-2s^-11 and the daily flux of carbon sinks is greater than The flux point of the carbon source.The typical seasonal variation map shows a double-peak single-valley phenomenon,the trough is between 10:00-13:00,and the two peaks are at 0:00-8:00 and 17:00-24:00.The maximum summer carbon sink value is-13.4μmolm^-2s^-1,and the maximum carbon source value in winter is7.5μmolm^-2s^-1.The maximum carbon sink intensity in July is July,which is-16.4μmolm^-2s^-1.In January,the carbon source intensity was the highest at 10.7μmolm^-2s^-1;in July,the maximum difference was 11.4μmolm^-2s^-1,and in December the difference was 3.1μmolm^-2s^-1;the typical day CO₂ flux The volume change characteristic map shows that the carbon sink time in summer is longer than that in winter,and the average carbon sink time is 7 hours.（2）During the study period,wind speeds prevailed throughout the year,and the prevailing wind direction in the growing period and the prevailing wind speed in the non-growing period are different.Annual prevailing wind direction is southerly wind and southeast wind,followed by the east wind,with less northerly winds,almost no westerlies,and the main wind direction is The study area accounted for 54%,and the non-mainstream wind direction accounted for 46%.Regardless of the main wind direction or non-main wind direction,the percentage of wind speed between 2-4m/s was the largest,and the main wind direction percentage was greater than the non-main wind direction.During the growing season,the east wind and southeast wind prevail,and the maximum wind speed can reach 7m/s,of which the frequency of 2-3m/s is the largest;the non-growth season prevails in the northwest wind,and the maximum wind speed can reach 9m/s,among which the maximum wind speed is 3-4m/s.（3）The source area and flux contribution rate for different types of underlying surface are different during the study.The flux source area is a circular area of 850m from the observation station.There are 7 kinds of building types in the source area.The flux contribution rate from small to large is Science and Technology Museum<Indoor Basketball Hall<Laboratory<Library<Teaching The contribution rate of the carbon flux of the restaurant is less than 200 times that of the carbon flux of the science and technology museum.There are 9 main roads,4 secondary roads and 6branch roads,and 9 main roads.The flux contribution rate is positively related to the road area as a whole.The growth rate of the flux contribution rate when the road area is less than 8000m² is greater than that when the road area more than 8000m²,and the average flux contribution rate is 12.4%.The area average flux contribution rate is16.8%;the source area in the stable and non-growth seasons under atmospheric stability is much larger than the source area under atmospheric instability.In the steady state of the atmosphere,the upwind windward source area ranges during the growing season<Non-growth season Windward windward source area,vertical wind source area of growing season more thanVertical wind direction source area of non-growth season;under unstable atmosphere,upwind windward source area range less than Non-growth season at atmospheric upwind wind source area,the vertical wind direction during the growing season Region ranges from more than direction perpendicular to the source region of non-growth season range.（4）Different Man-made Management Differences in CO₂ Fluxes.Unmanaged vegetation areas always exhibited carbon sinks,and with the increase of area,they showed a phenomenon of enhanced carbon sinks.Some managed vegetation areas showed an inverted“V”shape,and vegetation areas with an area of less than 3000 m²represented carbon sinks.When the area is more than 3000m²,it is expressed as a carbon source.When the area equal 8000 m²,it begins to show a decrease in the strength of the carbon source;the maximum CO₂ flux can reach 1.5μmolm^-2s^-1,and when it reaches 12000m²,it turns into a carbon sink.