For operational weather forecasting and nowcasting, a refresh rate (RR) of 10 min and a better-than-4-km footprint size for Infrared (IR) bands is desired. Such imaging capability is only available ...from geostationary orbit (GEO) satellites, such as ABI onboard geostationary operational environmental satellites (GOES)-16/-17, but mainly limited to the tropics and mid-latitudes (referred to as GEO-like imaging capability). For high latitudes such as the Alaskan region, the IR footprint size from ABI/GOES-17 is worse than 6 km, limiting the application over the region. Tundra satellites, with a nonzero inclination angle and a nonzero eccentricity, have longer dwell times near the apogee than the perigee and can be used to monitor the high latitudes and polar regions. This study investigates Tundra satellites' imaging capability by assuming an ABI-like instrument with the same IR spatial resolution of <inline-formula> <tex-math notation="LaTeX">56~\mu </tex-math></inline-formula>rad onboard. For regional applications, a constellation of two Tundra satellites may provide GEO-like imaging capability for a large domain. This useful domain is further improved when combined with a GEO, i.e., two <inline-formula> <tex-math notation="LaTeX">Tundra + GOES-17 </tex-math></inline-formula>. For global applications, a constellation of three Tundra satellites may provide GEO-like imaging capability for high latitudes (improved capability over GEO) and polar regions (unprecedented capability) in both hemispheres. The additional capability from Tundra satellites in tropics and mid-latitudes makes the global space-based meteorological observing system more robust and resilient. While a constellation of three <inline-formula> <tex-math notation="LaTeX">Tundra + 3 </tex-math></inline-formula> GEOs may provide global GEO-like imaging capability, having more than three GEOs may be desired by agencies/countries, allowing for improved spatial resolutions over their sub-point locations.
The Advanced Baseline Imager (ABI), designated to be one of the instruments on a future Geostationary Operational Environmental Satellite (GOES) series, will introduce a new era for U.S. ...geostationary environmental remote sensing. ABI is slated to be launched on GOES-R in 2012 and will be used for a wide range of weather, oceanographic, climate, and environmental applications. ABI will have more spectral bands (16), faster imaging (enabling more geographical areas to be scanned), and higher spatial resolution (2 km in the infrared and 1–0.5 km in the visible) than the current GOES Imager. The purposes of the selected spectral bands are summarized in this paper. There will also be improved performance with regard to radiometrics and image navigation/registration. ABI will improve all current GOES Imager products and introduce a host of new products. New capabilities will include detecting upper-level SO₂ plumes, monitoring plant health on a diurnal time scale, inferring cloud-top phase and particle size and other microphysical properties, and quantifying air quality with improved aerosol and smoke detection. ABI will be operating in concert with the GOES-R high spectral resolution sounder, part of the Hyperspec-tral Environmental Suite (HES); several products will be improved through the combination of high spatial resolution imager data with collocated high spectral resolution measurements. This paper introduces the proposed ABI spectral bands, discusses the rationale for their selection, and presents simulated ABI examples gleaned from current airborne and satellite instrument data.
Converting the hyperspectral infrared (IR) sounder radiance spectrum to broadband is a common approach for intercomparison/calibration. Usually the convolution is performed in wavenumber space. ...However, numerical experiments presented here indicate that there are brightness temperature (BT) differences between wavelength and wavenumber spaces in convolving hyperspectral IR sounder spectrum to broadband. The magnitudes of differences are related to the spectral region and the width of the spectral response functions (SRFs). In addition, the central wavelength and central wavenumber should be determined separately in wavelength and wavenumber spaces, respectively; they cannot be converted to each other directly for broadband BT calculations. There exist BT differences (BTDs) between interpolating the resolution of SRF to hyperspectral IR sounder spectrum, and vice versa, for convolution. This study provides clarity on convolution, central wavelength/wavenumber determination, and spectral resolution matching between broadband SRFs and hyperspectral IR sounder radiances for intercomparison/calibration.
The Fengyun (FY)-2 series satellites are the first-generation geosynchronous (GEO) Earth observation satellites operated by the National Satellite Meteorological Center (NSMC), China Meteorological ...Administration (CMA). The FY-2 satellites' main payload is a multispectral imager. The radiances from the FY-2C/D/E imagers were compared to the Atmospheric Infrared Sounder (AIRS), which is in low Earth orbit (LEO) on Aqua, a National Aeronautics and Space Administration satellite. The intercalibration of FY-2C/D/E infrared (IR) channels using AIRS was carried out based on the Global Space-based Inter-Calibration System (GSICS) GEO-LEO intercalibration algorithm. All the FY-2C/D/E data archived at the Cooperative Institute for Meteorological Satellite Studies, Space Science and Engineering Center, University of Wisconsin-Madison, Madison, WI, USA, were processed and compared with their operational calibrations. Select comparisons and longer term analyses between the new intercalibrated results and the operational calibrations of FY-2C/D/E's IR channels were demonstrated. The results show that the current operational calibration for FY-2C/D/E does not compare favorably based on the FY-AIRS intercalibration. The future operational calibration of FY-2D and FY-2E could be revised using GSICS corrections from the intercalibration with AIRS. The historical FY-2C/D/E data could be recalibrated with the GSICS GEO-LEO intercalibration algorithm at NSMC/CMA.
A near global dataset of homogenized clear-sky 6.5-μm brightness temperatures (BTs) from international geostationary (GEO) weather satellites has recently been generated and validated. In this study, ...these radiance measurements are used to construct the diurnal variation of upper tropospheric humidity (UTH) and to evaluate these diurnal variations simulated by five reanalysis datasets over the 45° N–45° S region. The features of the diurnal variation described by the new dataset are comparable with previous observational studies that a land–sea contrast in the diurnal variation of UTH is exhibited. Distinct diurnal variations are observed over the deep convective regions where high UTH exists. The evaluation of reanalysis datasets indicates that reanalysis systems still have considerable difficulties in capturing the observed features of the diurnal variation of UTH. All five reanalysis datasets present the largest wet biases in the afternoon when the observed UTH experiences a diurnal minimum. Reanalysis can roughly reproduce the day–night contrast of UTH but with much weaker amplitudes and later peak time over both land and ocean. Comparison of the geographical distribution of the diurnal variation shows that both ERA5 and MERRA-2 could capture the larger diurnal variations over convective regions. However, the diurnal amplitudes are widely underestimated, especially over convective land regions, while the phase biases are relatively larger over open oceans. These results suggest that some deficiencies may exist in convection and cloud parameterization schemes in reanalysis models.
A SIGHT FOR SORE EYES Miller, Steven D.; Schmit, Timothy L.; Seaman, Curtis J. ...
Bulletin of the American Meteorological Society,
10/2016, Letnik:
97, Številka:
10
Journal Article
Recenzirano
Odprti dostop
In 1967, at the dawn of the satellite era, the Applications Technology Satellite 3 (ATS-3) provided the first full-disk “true color” images of Earth. With its depiction of blue oceans, golden ...deserts, and green forestlands beneath white clouds, the imagery captured the iconic Blue Marble in a way that resonates strongly with human perception. After ATS-3, the standard fare of geostationary satellites entailed a single visible band with additional infrared spectral channels. While single-band visible satisfied the basic user requirements of daytime imagery, the loss of true-color capability and its inherent capability to distinguish myriad atmospheric and surface features via coloration left a notable void. Nearly half a century later, with the launch of Japan’s Himawari-8 in October 2014, there is once again a geostationary sensor—the Advanced Himawari Imager (AHI)—containing the multispectral visible bands required notionally for true color. However, it soon became apparent that AHI’s “green” band, centered at 0.51 μm, was not aligned with the chlorophyll reflectance signature near 0.55 μm. As a result, vegetation appears browner and deserts appear redder than legacy true-color imagery. Here, we describe a technique that attempts to mitigate these issues by blending information from a ref lective-infrared band at 0.86 μm to form a “hybrid” green band. When combining this method with Rayleigh corrections, AHI’s true-color performance is found to be consistent with that of the optimal 0.55-μm band, offering a stopgap solution adaptable to future satellites of similar design.
The monthly variation of upper tropospheric water vapor (UTWV) simulated by six reanalysis data sets is evaluated with homogenized water vapor radiance observations from international geostationary ...(GEO) weather satellites by using a profile‐to‐radiance approach over 45°N to 45°S regions for the period 2015–2017. Results show that reanalysis data sets have an overall good agreement with observations. However, a widespread wet bias is found in all reanalyses and is more dominant in large‐scale subsidence regions. JRA55 has the smallest wet bias while MERRA‐2 exhibits the most humid upper troposphere. The temporal variation of brightness temperatures in response to the warm phase of El Niño‐Southern Oscillation (ENSO) in 2015–2016 indicates that the UTWV field is regulated by both ascending and descending branches of the large‐scale circulation. All six reanalyses roughly capture the temporal variation of UTWV in the developing and decay year of this ENSO event. However, they tend to overestimate the eastward propagation of high UTWV in the developing year, especially MERRA‐2. The UTWV gradient over the tropical Pacific in the decay year is underestimated, with a dry bias over the convective western Pacific and a wet bias over the eastern Pacific in reanalysis data sets. These results may provide a useful tool for the climate modeling community for identifying and solving problems associated with UTWV simulation.
Key Points
Homogenized 6.5‐μm WV band radiance from GEO satellites is used for evaluating the monthly variation of UTWV nearly globally in reanalyses
Reanalyses exhibit a dominant wet bias. ERA5, JRA55, and CRA are closer to the observations whereas MERRA‐2 has the largest wet bias
Reanalyses capture the pattern of UTWV well during the El Niño but underestimate the UTWV gradient over tropical Pacific in the decay year
Geostationary simultaneous nadir observations (GSNOs) are collected for Earth Observing System (EOS) Atmospheric Infrared Sounder (AIRS) on board Aqua and a global array of geostationary imagers. The ...imagers compared in this study are on (Geostationary Operational Environmental Satellites) GOES-10, GOES-11, GOES-12, (Meteorological Satellites) Meteosat-8, Meteosat-9, Multifunctional Transport Satellite-IR (MTSAT-IR), and Fenguyun-2C (FY-2C). It has been shown that a single polar-orbiting satellite can be used to intercalibrate any number of geostationary imagers. Using a high-spectral-resolution infrared sensor, in this case AIRS, brings this method closer to an absolute reckoning of imager calibration accuracy based on laboratory measurements of the instrument's spectral response. An intercalibration method is presented here, including a method of compensating for AIRS' spectral gaps, along with results for approximately 22 months of comparisons. The method appears to work very well for most bands, but there are still unresolved issues with bands that are not spectrally covered well by AIRS (such as the water vapor bands and the 8.7-km band on Meteosat). To the first approximation, most of the bands on the world's geostationary imagers are reasonably well calibrated-that is, they compare to within 1 K of a standard reference (AIRS). The next step in the evolution of geostationary intercalibration is to use Infrared Atmospheric Sounding Interferometer (IASI) data. IASI is a high-spectral-resolution instrument similar to AIRS but without significant spectral gaps.
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