Satellite remote sensing detection principles and data applications

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Remote Sensing Satellite (Remote Sensing Satellite) is an artificial satellite used as a remote sensing platform for outer space. Remote sensing technology that uses satellites as a platform is called satellite remote sensing. Typically, remote sensing satellites remain in orbit for several years. The satellite orbit can be determined as needed. Remote sensing satellites can cover the entire earth or any designated area within a specified period of time. When operating along the geosynchronous orbit, they can continuously conduct remote sensing of a designated area on the earth's surface. All remote sensing satellites require remote sensing satellite ground stations. The satellite data obtained from the remote sensing market platform can monitor agriculture, forestry, oceans, land, environmental protection, meteorology and other conditions. Remote sensing satellites mainly include meteorological satellites, land satellites and ocean satellites. Three types.

Principles of remote sensing detection by meteorological satellites

The radiation process of various natural surfaces and the atmosphere itself in the earth's atmospheric system is a very complex issue, which involves the characteristics of each radiation source and objects And many aspects of characteristics such as gas absorption, emission, transmission, target reflection, particle scattering and transmission. As a whole, the earth's atmospheric system must accept incident solar radiation on the one hand, and on the other hand, it must reflect solar radiation and emit infrared radiation based on its own temperature. The radiation measured within its field of view mainly includes:

1) Infrared radiation emitted by the surface and clouds. The infrared cloud image is obtained by converting the radiation measured by the satellite in the atmospheric window channel into an image.

2) The infrared radiation emitted by gases in the atmosphere is absorbed. The radiation emitted by atmospheric gases measured by satellites can be inverted to obtain relevant parameters of the atmosphere. For example, by selecting the radiation emitted by CO2?, the vertical parameters of the atmosphere can be obtained Temperature, water vapor distribution can be obtained from the radiation emitted by H2O?

3) The atmospheric downward infrared radiation reflected by the ground and clouds can be ignored because the ground reflected atmospheric radiation measured by satellites in the infrared band is very small.

4) The ground and cloud surfaces reflect solar radiation, and the visible light cloud image is obtained by measuring the radiation measured by the satellite in the visible-near infrared spectrum band.

5) The scattering radiation of solar radiation by atmospheric molecules and aerosols. The distribution of atmospheric molecules and aerosols can be obtained based on the backscattered radiation of atmospheric molecules and aerosols measured by satellites.

Satellites receive the relative magnitude of radiation emitted by various radiation sources in the Earth's atmosphere in space. For the reflected solar radiation, the satellite mainly measures the solar radiation reflected by clouds, which accounts for 20% of the incident solar radiation. Secondly, The backscattered radiation of air molecules is only 6%, while the ground reflected solar radiation is 4% smaller. The infrared radiation received by satellites is mainly emitted by H2O and CO2, followed by clouds, and a smaller amount is received directly from the ground.

01

Increased and enriched the content and scope of meteorological observations and data in other fields

The establishment of the meteorological satellite observation system has greatly enriched the scope of meteorological observations. The content and scope have brought atmospheric detection technology and meteorological observation into a new price range, breaking through the limitation that humans can only observe the atmosphere at the bottom of the atmosphere. Some data and areas that are difficult to observe can now be obtained from meteorological satellites. Current meteorological satellites can provide the following valuable data:

1. Daily multi-spectrum image data such as visible light, infrared and water vapor;

2. Atmospheric vertical detection data;

3. Microwave detection data;

4. Solar proton, particle data, etc.;

The above data contain a large amount of earth’s atmospheric information. From this information The following various parameters and phenomena in meteorology and other fields can be derived:

1. The range distribution of cloud systems and the location, formation, occurrence and development of various weather systems; the occurrence and development of disastrous weather;

2. Cloud type, cloud amount, cloud top temperature (cloud top height), cloud phase, etc.;

3. Aerosols, sandstorms, blowing sand, floating dust, ice and snow cover, etc. ;

4. Land surface temperature, vegetation distribution, evapotranspiration, soil moisture, ground albedo and other land surface parameters;

5. Vertical distribution of atmospheric temperature and humidity, total water vapor in the atmosphere amount, total ozone;

6. Precipitation and precipitation areas, surface water resources, floods, etc.;

7. Cloud and wind vectors in a given area;

< p> 8. The solar radiation incident on the earth’s atmospheric system and the total radiation reflected by the earth’s atmospheric system, the total amount of long-wave radiation, the radiation budget of the earth’s atmosphere system, etc.;

9. Ocean surface temperature, ocean currents, suspended matter concentration, Chlorophyll concentration and sea ice and other ocean surface conditions;

10. Monitor forest fires and forest growth conditions;

11. Extract vegetation index from visible light and near-infrared cloud images to monitor crop growth, Estimating crop yield;

12. Monitor solar protons, a? particles, electron flux density and energy spectrum, and total particle energy at satellite altitude.

02

An important basis for weather analysis and forecasting

Due to the large observation range of satellites, meteorological data can be obtained in sparsely populated areas such as oceans, plateaus, deserts, etc., which greatly It has greatly improved the accuracy of weather analysis in these areas, deepened the understanding of various weather systems, revealed some new weather facts, and explained previously unexplained weather phenomena. Because satellite cloud images have high spatial and temporal resolution, they can continuously track the formation of cloud systems, the relationship between the development and strengthening of weather systems and precipitation, etc., such as new insights into the occurrence, development and evolution of fronts, upper-altitude troughs and cyclonic cloud systems. knowledge and understanding. Various cloud type characteristics of large-scale cloud system distribution were discovered, and a conceptual model for the evolution of weather-scale cloud systems was proposed, providing a basis for forecasters to accurately predict weather. After using satellite data, weather systems can be discovered early, thereby improving the accuracy of forecasts and extending the timeliness of forecasts. For example, before satellite observations, data on the Tibetan Plateau were scarce, and many weather systems were often missed, resulting in the failure of weather forecasts. After using satellite data, we discovered and mastered the activity patterns of cold, warm fronts, jet streams and other systems on the Tibetan Plateau, which played an important role in predicting precipitation in eastern my country.

03

Monitor disastrous weather systems such as heavy rains and severe thunderstorms

Heavy rains and severe thunderstorms (strong winds and thunder and lightning) are disastrous and dangerous weather systems, which are harmful to people Often causing serious losses to life and property. This type of system has small spatial scale, rapid change, short life, and high intensity. It is difficult to capture it using conventional observation data. Therefore, the analysis and prediction of this type of system has always been an important issue in atmospheric scientific research. Geostationary satellite cloud images can continuously observe a fixed area and have high spatial and temporal resolution. They are a very effective tool for discovering and continuously monitoring heavy rain and severe thunderstorm weather systems. Chinese forecasters use geostationary satellite cloud images to monitor the occurrence of heavy rains and strong convection. Development occurs, and short-term weather forecasts of 0-6 hours and 0-12 hours are produced, which reduces the losses of people's lives and property.

04

Monitoring weather systems such as low pressure and typhoons on the tropical ocean

In tropical ocean areas, meteorological stations are rare and data is in short supply. Conventional Meteorological data are difficult to detect and track the development and movement of ocean surface weather systems. Satellite cloud images are an important tool for monitoring low pressure, typhoons and other weather systems on the tropical ocean. Since the use of satellite cloud images, no typhoon has been missed, and a set of effective methods for using satellite cloud images to forecast station intensity and path have been summarized, which has improved the accuracy of typhoon forecasts, extended the forecast timeliness, ensured the safety of people's lives and property, and reduced economic losses.

05

Improving long-term weather forecasts

Satellite data can provide relevant information on the interaction between circulations in the northern and southern hemispheres and circulations at mid- and low-latitudes. Impacts occur in mid-latitudes over days or weeks, so applying these data can help produce mid- and long-term weather forecasts. In addition, ocean surface temperature, ice and snow cover data on the earth's surface and ocean surface calculated from satellite observation data, and data on the exchange of radiant energy between the earth, the atmosphere and the universe can be used to study air-sea exchanges and climate change.

The atmospheric temperature, humidity distribution and cloud trace wind at each altitude are inverted from the detection data obtained by the high-resolution infrared detector of the NOAA? Meteorological satellite, and are input into the numerical model to provide The initial field of numerical prediction further improves the accuracy of numerical weather prediction.

06

Application in climate research

1) Cloud amount and cloud type

Clouds control the amount of radiation incident on the earth’s surface. Solar radiation and infrared radiation emitted by the earth itself, so clouds have an important impact on the earth's radiation budget, thus playing a direct and important role in the warming and cooling of the earth. Using satellite data to estimate the spatial and temporal distribution of clouds can be used to study: (1) Climate models and validity testing; (2) The impact of clouds on climate: (3) Clouds and the earth's radiation budget: (4) Cloud climatology changes etc.

2) Radiation

The radiation budget at the top of the Earth’s atmosphere determines the energy input of the earth-atmosphere system. The sources and sinks of radiant energy lead to atmospheric circulation and affect the global energy and water cycle. . Satellite observations can determine the radiation budget at the top of the atmosphere, solar radiation incident on the ground, emitted long-wave radiation, total radiation, etc.

3) Precipitation

Using satellite data to estimate precipitation is another new way to measure precipitation, especially the most effective method for estimating large-scale precipitation. Convective precipitation and the latent heat released in the tropics are one of the important forcing mechanisms of atmospheric circulation. Satellite estimation of precipitation is already an important business product and is very useful for studying the relationship between precipitation and climate, water cycle, crop growth, etc.

4) Aerosols and trace gases

CO2, CH4? and N2O, these gases play a greenhouse effect and affect climate change; ozone changes affect human health; SO2 and other harmful Gases cause air pollution.

5) Ice and snow coverage

China is one of the countries with the most mountain glaciers in the middle and low latitudes of the world. Although the glacier area is less than 6% of the country’s area, its melt water accounts for It accounts for 2.0% of the total annual runoff in temples across the country, which is equivalent to the total annual runoff of the Yellow River entering the sea every year. Satellite data can be used to calculate glacier area, glacier changes, etc.

Changes in ice and snow cover are one of the most important signals of climate change. Global climate simulations show that the greenhouse effect is greatest at high latitudes. Once polar ice and snow melt, the ground albedo will change greatly, and the results will be more severe. Conducive to warming. The earth's ice and snow cover consists of three parts: sea ice, snow caps and glaciers. Satellite data can be used to conduct detailed observations of the horizontal distribution of ice and snow coverage, making the analysis of glaciers more systematic and global. NOAA? satellite data can be used to analyze the extent of snow cover, monthly and seasonal snow cover frequency and anomalies; the NOAA-K? satellite 1.6 micron data makes it easier to distinguish snow and clouds, and the depth of snow cover; from the U.S. Defense Meteorological Satellite SSM/I? data analysis of snow depth. Synthetic aperture radar can provide ice range, density, ice age, ice crevices, etc. .

06

Providing meteorological data for agriculture

Meteorological satellites can provide agriculture with information such as sunshine, precipitation, air temperature, land surface temperature, vegetation distribution, evapotranspiration, soil Meteorological parameters and land surface parameters such as humidity and ground albedo can be used to conduct agricultural zoning, monitor crop growth, monitor drought, insect pests, and estimate crop yields. Determine the inverse ecological environment predictor variables.

Vegetation distribution in the northwest region? Vegetation distribution in the middle and lower reaches of the Yangtze River

07

Monitoring forest fires and surface thermal anomalies

Forest fires are commonly used Observation towers and aircraft are established on the ground for observation. The observation range of the observation tower is very limited, and the cost of aircraft observation is very expensive. Satellite observation has high spatial and temporal resolution and can monitor and observe large-scale forest fires. It has low economic cost and is a very effective tool.

Forest fires in Heilongjiang Province

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Application of satellite data in hydrology

(1) Estimating precipitation;

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(2) Monitor flood disasters; floods can cause heavy losses, and near-infrared satellite data can be used to produce flood maps.

(3) Surface water resources. Water is ubiquitous on the ground, but it is also the most variable mineral resource. Monitoring environmental water is one of the difficult and urgent issues. Water is one of the components of all organic objects. Without water, there would be no life. The use of satellite remote sensing data can help find groundwater.

For sparsely populated plateau and other areas, satellite observation of the distribution of water resources is an ideal tool.

09

Providing meteorological data for marine activities

1) Marine meteorological forecast and marine navigation guarantee: the influence of large-scale sea ice and water conditions on the vast oceans around the world Global weather has a major impact. Sea surface temperature, sea ice, and sea surface wind and wave conditions observed by satellites are of great help in making marine weather forecasts. Live weather conditions and weather forecasts provided by satellite cloud images can avoid adverse weather and huge waves on the ocean and improve maritime navigation operations. Another example is the sea ice distribution map produced based on satellite data, which can find the best route for navigable waterways, not only bypassing dangerous huge icebergs at sea, but also saving time and money. For example, in the United States, the annual losses caused by maritime shipping accidents amount to 5 billion US dollars. After using satellite data, the losses can be reduced by 5-10%. Every winter, ice often occurs in the Bohai Bay area of ??my country. Using aircraft or ships to detect the distribution of sea ice is not only expensive, but also cannot meet the requirements. Satellite data can be used to accurately and timely produce sea ice distribution maps, providing useful data for my country's navigation industry.

2) Marine environment monitoring: The use of satellite data can realize environmental monitoring, detect large-scale pollution and red tides on the ocean, and obtain ocean surface conditions such as ocean surface temperature, ocean currents, suspended matter concentration, and chlorophyll concentration; Marine pollution such as oil pollution, thermal pollution and solid waste pollution has great ecological damage, and these can be monitored and detected by satellites.

3) Research on estuaries and coasts: Satellite data can be used to study the morphology of coasts and estuaries and the transport of sediment along the coast. Provide information for seaport construction, coastal protection and shallow sea area construction.

4) Marine fishing: Satellite data can help marine fishing provide marine information, directly or indirectly reflecting the ecological conditions of fish. For example, based on the sea surface temperature provided by satellites, the boundary location of warm and cold ocean currents can be determined, which is the area where fish move. This can predict fish stocks and increase fishing yields.

Distribution of water bodies in the Yellow Sea region

10

Providing flight support for aviation

Before satellite observation, aviation weather conditions were limited due to lack of data. Forecasts are difficult to make accurately. On a route map, it is very difficult to mark where there are strong turbulences, where there are cumulonimbus clouds, where visibility is poor, where there is dangerous weather, etc. Even if it can be marked, the error will be large. After using satellite data, This situation is improved, and the above problems are easily solved, providing guarantee for safe flight of the aircraft. Satellite data can be used to select the best route, such as flying along high-altitude jet streams, which can shorten flight time and save fuel.

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Providing meteorological services to the military

Meteorological satellite data are widely used in military support work, such as air force shooting ranges, landing forecasts, long-range bomber route weather forecasts, Satellite data plays an important role in hazardous weather warnings, special military service support, calculations of ballistic missile systems, calculations of the impact of meteorological parameters on communications and radar systems, etc.

The United States also specially launched the National Defense Meteorological Satellite (DMPS), established a military meteorological satellite system, and obtained meteorological data with a higher resolution than civilian meteorological satellites. Military meteorological satellite data were widely used in the Vietnam War and the Middle East War. played a role. With the development of my country's national defense modernization, space science and cutting-edge weapons, higher and higher requirements have been placed on meteorological support work. For example, the areas where satellites are launched, landed and recovered are sparsely populated and lack meteorological data. Satellites can provide timely and effective data.

In wartime, meteorological satellites can obtain meteorological data in enemy areas to serve the war. At the same time, if the enemy imposes a blockade on us and the source of meteorological information is interrupted, meteorological satellites can play a greater role.

12

Space environment monitoring

The meteorological satellite is equipped with a space environment monitor (SEM) to measure solar protons, electron flow density, alpha particles, and energy spectrum and total particle energy, etc., determine the strength and direction of the magnetic field around the satellite, estimate the solar X-ray flux, detect the solar wind and energy particles in the radiation belt surrounding the earth, and provide data for upper atmospheric physics and space scientific research.