First, human metabolism uses organic carbon to produce inorganic carbon to realize carbon cycle. Second, the positive effect of human production and life is that increasing the coverage of green plants can improve the inorganic carbon in the ecosystem carbon cycle to achieve a benign carbon cycle, while the negative effect is that the destruction of the coverage of green plants and predatory development lead to the deterioration of the ecosystem carbon cycle and the decline of the ecosystem.
1: In recent years, China is in a period of vigorous development, so the exploitation of coal far exceeds the exploitation speed of thousands of years in history, so human beings have increased the process of coal changing from C to carbon dioxide;
2. Over-exploitation of land by human beings leads to the shrinking of forest area year by year; This led to the greening of the forest; Slow down the conversion of carbon dioxide to oxygen;
Therefore, it leads to the increase of carbon dioxide and the greenhouse effect; The polar icebergs melted; Sea level rise;
With the development of human society, especially the extensive use of fossil fuels, the intensity of human carbon sources is increasing. Human carbon sources mainly include carbon emissions from fossil fuel use and cement production, as well as carbon emissions from land use (such as rice planting), mineral exploitation and groundwater exploitation, among which fossil fuel combustion plays the most important role. The increase of carbon emissions caused by land use change is equivalent to this.
Since humans realized that the increase of greenhouse gas (especially carbon dioxide) concentration would make the global temperature warm, which would bring a series of serious ecological and environmental problems, they began to study the carbon cycle.
Of course, while human activities increase atmospheric carbon dioxide, it is entirely possible to increase the absorption of atmospheric carbon dioxide through positive actions, such as afforestation.
2. Research on carbon cycle
Global carbon cycle is the flow of carbon among the three main reservoirs of atmosphere, ocean and terrestrial ecosystem, and it is an important symbol of biosphere development. The research work of carbon cycle includes the estimation of terrestrial biomass, the influence of land use change on terrestrial carbon, the estimation of terrestrial ecosystem production, carbon cycle simulation and so on. Traditional terrestrial carbon cycle models are based on ground observation and measurement, and many models have only been tested by very limited point observation data. Remote sensing technology provides large-scale observation ability and is an effective means to solve the problem of regional ecosystem model verification.
Remote sensing has the characteristics of short period, high spatial-temporal resolution, wide coverage and convenient data acquisition, and has become an indispensable technical means in the study of global change. Remote sensing technology has unique advantages in obtaining land surface parameters, especially large-scale land surface parameters. Important ecological characteristics and biological growth parameters can be obtained directly from remote sensing images. Besides the macroscopic parameters such as vegetation area, net primary productivity (NPP) and net ecosystem productivity (NEP), leaf area index (LAI), canopy chemical composition, canopy temperature, stomatal conductance and photosynthetic effective radiation (APAR) can also be obtained. These physical parameters obtained from remote sensing inversion are directly used as driving variables or parameters of terrestrial ecosystem model, and the carbon cycle is studied by combining the dynamic information of land cover or vegetation status obtained from remote sensing images.
3. Application of 3.SAR in carbon assessment
SAR is an active microwave remote sensing, which is not limited by time and weather, and can penetrate the atmospheric interference layer similar to clouds and storms. Compared with the vertical shooting of optical sensors, SAR is a side-looking sensor, which means that terrain and target objects have unique responses to radar signals, and SAR data and optical data complement each other.
(1) background
In the past few decades, many countries in the world have begun to solve global environmental problems. One of the main goals is to reduce greenhouse gases and fundamentally solve the problem of global warming. One way is to limit deforestation and forest degradation.
The Earth Observation Organization FCT (Forest Carbon Cycle Earth Observation Group) was established to monitor the changes of ecosystem and land use. Its goal is to prove the feasibility of using remote sensing technology for forest monitoring, and to collect information to serve the future national forest input and carbon monitoring system.
Dr. Anthea Mitchell, a visiting scholar at the Center for Spatial Information Cooperation of the University of New South Wales, Australia, is one of several global investigators sent by GEO FCT. His job is to study the standard methods of data and image processing and generate forest information products for carbon estimation. Finally, Mitchell developed a general image analysis method, which can be widely used in measurement, monitoring and forest change reporting.
(2) Search and rescue solutions
Dr Mitchell's method of monitoring forest change is to estimate the amount of forest change by using optical and synthetic aperture radar images.
SAR can obtain data completely different from optics and show researchers the unique information of the geographical area of interest. Dr Mitchell believes that SAR provides unique three-dimensional structure and water content information on the surface, which is very useful for identifying and mapping different forest types and estimating biomass.
In order to effectively apply SAR data, Dr Mitchell needs a solution, which can not only effectively process and analyze SAR data, but also combine it with optical images. After a lot of comparison and selection, the advanced radar image processing tool SARscape of ENVI company is selected. The software has the unique ability to read, process, analyze and output SAR data. SARscape transforms abstract radar data into meaningful information. At the same time, because SARscape is integrated into ENVI image processing and analysis software, users can use various types of images to extract important information contained in the images.
In order to extract valuable information from SAR data, the data must be read and processed first. Dr Mitchell uses a lot of SAR data sources, and needs software to read all kinds of data correctly. SARscape has easy-to-use tools to input and read SAR data from various data sources.
After reading SAR data in SARscape, Dr. Mitchell did a lot of automatic processing on the image to visualize and analyze the data, including multi-view, registration, speckle noise removal, geocoding, radiation calibration and image mosaic. Because radar images contain a lot of noise, filtering can minimize the noise. In order to compare the data of different phases or sensors, the images are automatically registered, geometrically corrected and radiation corrected.
Figure: ALOS PALSAR data of Tasmania, the result after orthorectification, radiation calibration and mosaic in SARscape.
After data preprocessing, SAR data is analyzed in ENVI environment. Because SARscape is integrated in ENVI, researchers can analyze SAR data without switching software platforms. Dr Mitchell uses the change monitoring tool of ENVI to detect the change area of two images. The process-based change monitoring tool of ENVI can automatically identify the change type and range. Using the change monitoring tool, we can get the areas where the brightness increases and decreases, which indicate the deforestation or regeneration of forests, because the increase of brightness is often caused by the increase of soil or canopy humidity, and the final result can be verified by optical images.
(3) The success of search and rescue
Dr Mitchell has achieved a lot. Processing and analyzing SAR and optical images in SARscape and ENVI can draw forest and non-forest and land cover maps, and reflect the deforestation and regeneration with time. Dr Mitchell developed a standard method for processing and analyzing radar data from different data sources, and used these data to generate forest information products for carbon estimation. In a word, SAR data provides key information for Dr. Mitchell.