Satellite Meteorology An Introduction Pdf Download [2021]
Chieko Aldana
Meteorology, like every other science, relies on careful and precise measurement of its subject. Meteorologists observe the atmosphere using two basic methods.
Direct methods, also called in situ for "in place," measure the properties of the air that are in contact with the instrument being used.
Indirect methods, also referred to as remote sensing, obtain information without coming into physical contact with the region of the atmosphere being measured. Launching satellites into space equipped with remote sensing instruments allows us to continuosly monitor planet Earth from afar.
China is developing a new generation of geostationary meteorological satellites called Fengyun-4 (FY-4), which is planned for launch beginning in 2016. Following upon the current FY-2 satellite series, FY-4 will carry four new instruments: the Advanced Geosynchronous Radiation Imager (AGRI), the Geosynchronous Interferometric Infrared Sounder (GIIRS), the Lightning Mapping Imager (LMI), and the Space Environment Package (SEP). The first satellite of the FY-4 series launched on 11 December 2016 is experimental, and the following four or more satellites will be operational.
On 7 September 1988, the Long March rocket carried the Fengyun-1A (FY-1A) polar-orbiting satellite into orbit, marking the start of the Chinese Fengyun (FY; meaning wind and cloud in Chinese) meteorological satellite observing systems program. On 10 June 1997, the FY-2A geostationary satellite was successfully launched and the Chinese meteorological satellite program took a large step toward its goal of establishing both polar-orbiting and geostationary observational systems. Over time the Fengyun satellites have become increasingly important for protecting lives and property from natural disasters in China.
The Chinese FY satellites are launched as a series. The odd numbers denote the polar-orbiting satellite series, and the even numbers denote the geostationary satellite series. After launch, a letter is appended to indicate the order in the satellite series; for instance, FY-2F is the sixth satellite that has been launched in the first generation of the Chinese geostationary satellites (FY-2). The FY-2, the first generation of the Fengyun geostationary weather satellite series, includes seven satellites launched since 1997; another will follow around 2017 to conclude the FY-2 mission. The Chinese geostationary weather satellite system operates two satellites located at 86.5E (FY-2 West) and 105E (FY-2 East); they provide full-disc observations every 30 min and observations every 15 min in their overlap region (see Fig. 1 for the current FY-2 coverage). The FY-2D (West) and FY-2E (East) observation schedule is shown in Table 1. The two satellites also back each other up. FY-2 satellites carry the Visible and Infrared Spin Scan Radiometer (VISSR) capable of imagery in five spectral bands. Derived products include atmospheric motion vectors (AMVs), sea surface temperatures (SSTs), total precipitable water vapor (TPW), quantitative precipitation estimations (QPEs), fire locations and intensity, surface albedo, and several others.
The FY-4 introduces a new generation of Chinese geostationary meteorological satellites, with the first FY-4A launched on 11 December 2016. The remaining satellites of this series are planned to be launched from 2018 to 2025 and beyond. FY-4 has improved capabilities for weather and environmental monitoring, including a new capability for vertical temperature and moisture sounding of the atmosphere with its high-spectral-resolution infrared (IR) sounder, the Geostationary Interferometric Infrared Sounder (GIIRS). Following 15 years, the three-axis stabilized FY-4 series will offer full-disc coverage every 15 min or better (compared to 30 min of FY-2) and the option for more rapid regional and mesoscale observation modes. The Advanced Geosynchronous Radiation Imager (AGRI) has 14 spectral bands (increased from the five bands of FY-2) that are quantized with 12 bits per pixel (up from 10 bits for FY-2) and sampled at 1 km at nadir in the visible (VIS), 2 km in the near-infrared (NIR), and 4 km in the remaining IR spectral bands (compared with 1.25 km for VIS, no NIR, and 5 km for IR of FY-2). FY-4 will improve most products of FY-2 and introduce many new products [such as atmospheric temperature and moisture profiles, atmospheric instability indices, layer precipitable water vapor (LPW), rapid developing clouds, and others]. Products from FY4 series are expected to provide enhanced applications and services. These new products are compared with those of FY-2 in Table 2.
The FY-4 GIIRS is one of the Group on Earth Observations (GEO) sounders planned by Global Earth Observation System of Systems (GEOSS) member states in response to the call from the World Meteorological Organization (WMO) for advanced sounders in the geostationary orbit. Another is the Infrared Sounder (IRS) planned by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) for the geosynchronous Meteosat Third Generation (MTG) satellite systems in the 2020 time frame and beyond. Together with the new generation of geostationary weather satellite systems being developed by other countries, FY-4 will become an important GEO component of the global Earth-observing system.
This paper provides an introduction to the Chinese FY-4 observation capabilities, the derived products, and the associated applications. The ground system components are briefly described in the next section. The following sections provide an overview of the four FY-4A instruments, products, and related application areas, and the final section offers a summary and conclusions.
The navigation and registration of AGRI, GIIRS, and LMI data from a three-axis stabilized satellite is a great challenge. A method has been designed in which the satellite platform, payloads, and ground segment cooperate with each other. As part of the ground segment, the Navigation and Registration System (NRS) calculates the scan and step angles from each instrument to the predicted stars that can be observed by the two payloads and arranges the observation timetable for AGRI and GIIRS based on those predicted stars. The NRS solves the equations that describe the relationship between the optical line of sight of instrument and structural thermal distortion and determines the equivalent variation of yaw, pitch, and roll once every 24 h. The pixels of an image should be Earth-located to within 112 μrad (3σ, within 64.5 of geocentric angle) at the subsatellite point during the daytime. Geographical location error is estimated from landmark navigation. Image navigation and registration (INR) specification is listed in Table 4.
After launch and an in-orbit test of FY-4A, the new data and products will be used in NWP, weather, climate, environment, and other areas; data distribution and applications are shown in Fig. 3. The processing of FY-4A raw data includes navigation, calibration, inversion, and generation of various-level products. The Level 1B (L1B) and some L2 products will be broadcast by FY-4A directly and users will be able to receive the High Rate Information Transmission in horizontal link or vertical polarization link (HRIT-H or HRIT-V) or Low Rate Information Transmission (LRIT). The contents, bit rate, and frequency of broadcast specifications are listed in Table 5. The L2 and L3 products generated by the ground segment of FY-4A will also be distributed by the National Meteorological Information Center (NMIC) through CMACast (Satellite Data Broadcasting System of China Meteorological Administration). All datasets of FY-4A, both real time and historical, will be available to the global community on the National Satellite Meteorological Center (NSMC) satellite data server website ( ).
With 14 spectral bands (see Fig. 7 for an example of simulated images in all spectral bands), FY-4 will improve the current operational FY-2 satellite products and introduce many new products. In addition to spectral band imagery and color composite images, the quantitative products expected from FY-4A AGRI data are summarized in Table 2. Most FY-4A AGRI products will have improved spatial and temporal resolutions compared to the current operational FY-2 products [cloud mask, land surface temperature (LST), SST, QPE, AMV, and radiation] and are expected to provide enhanced applications and services.
The FY-4A LMI will be the first lightning detection sensor on Chinese satellites. LMI will be able to detect the presence of total lightning activity (in-cloud and cloud-to-ground lightning), which is useful for early predictions of storms and severe weather events (Schultz et al. 2009; Gatlin and Goodman 2010; Stano et al. 2014). The specific parameters of LMI, similar to that of the GOES-R Geostationary Lightning Mapper (GLM; Goodman et al. 2013), are shown in Table 9.
FY-4A, launched on 11 December 2016, represents an improved and new capability of the Chinese geostationary weather satellite system. With advanced imaging and sounding instruments on board FY-4A providing high temporal, spatial, and spectral resolution measurements, the benefit is expected to be large for severe weather monitoring, warning, and forecasting. With the first lightning imager on board the Chinese geostationary satellite, the added valuable lightning information is expected to significantly improve warnings of severe storm hazards, convection precipitation, and lightning strikes. A primary use of the AGRI and GIIRS data will be to improve NWP through data assimilation of both radiances (AGRI, GIIRS) and L2 products (TPW, LPW, and AMVs from AGRI). Those data will be assimilated in the operational Global and Regional Assimilation and Prediction System (GRAPES) models and will also be distributed to the user community for operational applications. Assimilation of data and derived products from the AGRI, GIIRS, and LMI in both global and regional NWP models is expected to show valuable improvement in forecast skill. FY-4A will also enhance space weather monitoring and warning. Together with the new generation of geostationary weather satellites planned by the international satellite community, the FY-4 series will become an important geostationary component of the global Earth-observing system.
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