Polar-orbiting Weather Satellites Research Articles

РАЗВИТИЕ МЕТОДОВ И СРЕДСТВ ДИСТАНЦИОННОГО ТЕМПЕРАТУРНО-ВЛАЖНОСТНОГО ЗОНДИРОВАНИЯ ЗЕМНОЙ АТМОСФЕРЫ

The paper provides an overview of methods and technical devices for remote temperature and humidity sensing of the Earth’s atmosphere from satellites developed in Russia. A brief description of modern and forthcoming infrared and microwave atmospheric sounders installed on Meteor-M operational polar-orbiting weather satellites is given. The physical and mathematical base of interpreting measurements of atmospheric sounders (IKFS-2 infrared Fourier spectrometer and MTVZA-GYa microwave radiometer) is presented. The technologies for retrieving atmospheric temperature and humidity profiles are described. The results of retrieval validation as well as the prospects for further development of satellite remote temperature and humidity sensing systems are discussed.

The Advanced Very High Resolution Radiometer: Contributing to Earth Observations for over 40 Years

AbstractThe Advanced Very High Resolution Radiometers (AVHRR), which have been flying on National Oceanic and Atmospheric Administration’s (NOAA) polar-orbiting weather satellites since 1978, provide the longest global record of Earth observations from a visible–infrared imager. Experience gained through AVHRRs has been integral to the development of the new-generation sensors such as the Moderate Resolution Imaging Spectroradiometer (MODIS), the Visible Infrared Imaging Radiometer Suite (VIIRS), and associated data processing algorithms in the United States, as well as a similar class of sensor by space agencies around the world. Over four decades of data have been vital for studying Earth and its change. TheMetOp-Csatellite that was successfully launched in 2018 carries the last AVHRR. This article reviews the contributions of AVHRR in building a continuous global data record over the last 40 years on the occasion of its last launch.

An Evaluation of Radiative Transfer Simulations of Cloudy Scenes from a Numerical Weather Prediction Model at Sub-Millimetre Frequencies Using Airborne Observations

The Ice Cloud Imager (ICI) will be launched on the next generation of EUMETSAT polar-orbiting weather satellites and make passive observations between 183 and 664 GHz which are sensitive to scattering from cloud ice. These observations have the potential to improve weather forecasts through direct assimilation using "all-sky" methods which have been successfully applied to microwave observations up to 200 GHz in current operational systems. This requires sufficiently accurate representations of cloud ice in both numerical weather prediction (NWP) and radiative transfer models. In this study, atmospheric fields from a high-resolution NWP model are used to drive radiative transfer simulations using the Atmospheric Radiative Transfer Simulator (ARTS) and a recently released database of cloud ice optical properties. The simulations are evaluated using measurements between 89 and 874 GHz from five case studies of ice and mixed-phase clouds observed by the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 research aircraft. The simulations are strongly sensitive to the assumed cloud ice optical properties, but by choosing an appropriate ice crystal model it is possible to simulate realistic brightness temperatures over the full range of sub-millimetre frequencies. This suggests that sub-millimetre observations have the potential to be assimilated into NWP models using the all-sky method.

Algorithms for Estimating Trends in Global Temperature Volatility

Trends in terrestrial temperature variability are perhaps more relevant for species viability than trends in mean temperature. In this paper, we develop methodology for estimating such trends using multi-resolution climate data from polar orbiting weather satellites. We derive two novel algorithms for computation that are tailored for dense, gridded observations over both space and time. We evaluate our methods with a simulation that mimics these data’s features and on a large, publicly available, global temperature dataset with the eventual goal of tracking trends in cloud reflectance temperature variability.

Airborne validation of radiative transfer modelling of ice clouds at millimetre and sub-millimetre wavelengths

Abstract. The next generation of European polar orbiting weather satellites will carry a novel instrument, the Ice Cloud Imager (ICI), which uses passive observations between 183 and 664 GHz to make daily global observations of cloud ice. Successful use of these observations requires accurate modelling of cloud ice scattering, and this study uses airborne observations from two flights of the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 research aircraft to validate radiative transfer simulations of cirrus clouds at frequencies between 325 and 664 GHz using the Atmospheric Radiative Transfer Simulator (ARTS) and a state-of-the-art database of cloud ice optical properties. Particular care is taken to ensure that the inputs to the radiative transfer model are representative of the true atmospheric state by combining both remote-sensing and in situ observations of the same clouds to create realistic vertical profiles of cloud properties that are consistent with both observed particle size distributions and bulk ice mass. The simulations are compared to measurements from the International Submillimetre Airborne Radiometer (ISMAR), which is an airborne demonstrator for ICI. It is shown that whilst they are generally able to reproduce the observed cloud signals, for a given ice water path (IWP) there is considerable sensitivity to the cloud microphysics, including the distribution of ice mass within the cloud and the ice particle habit. Accurate retrievals from ICI will therefore require realistic representations of cloud microphysical properties.

Installation of UiTM’s ground station – Connecting earth and space with amateur band communication

This paper portrays the installation of UiTM’s Ground Station as being part of BIRDS Ground Station Networks; with its main task being to support BIRDS-2 nanosatellite’s monitoring. UiTMSAT-1, UiTM’s first nanosatellite, is one of the BIRDS-2 nanosatellites. It is expected to be deployed from International Space Station (ISS) by middle of 2018. The ground station is installed with two (2) Yagi antennas which operates in Amateur bands respectively at Very High Frequency (144 MHz -148 MHz) ranges and Ultra High Frequency (430 MHz - 438 MHz) ranges. Additionally, an APT antenna for 137 MHz-band polar-orbiting weather satellites is also installed at this ground station for earth weather monitoring. As for security and monitoring matters, lightning/surge protection system and surveillance system (CCTV) also has been installed. Conclusively, several tests had been done as confirmation on the equipment setup. The testing procedure includes receiving HORYU-4 and IO-86 satellite’s signal, and evaluating NOAA satellites’ processed data of South East Asia’s coverage. The uplink communication test, with cooperation with satellite owner, is left for future planning.

The Effect of Hydrometeors on MSU/AMSU Temperature Observations over the Tropical Ocean

AbstractThe temperature of Earth’s atmosphere has been monitored continuously since late 1978 by the Microwave Sounding Unit (MSU) and the Advanced Microwave Sounding Unit (AMSU) flown on polar-orbiting weather satellites. It is well known that these measurements are affected by the scattering and emission from hydrometeors, including cloud water, precipitation, and ice particles. In this study the hydrometeor effects on MSU/AMSU temperature observations are investigated by comparing satellite-observed temperature of the middle troposphere (TMT) with synthetic TMT constructed using temperature fields from ECMWF Interim [ERA-Interim (ERA-I)]. Precipitation data have been used to estimate how much of the difference between these two TMT fields is due to hydrometeor contamination effects. It is shown that there exists a robust linear proportionality between TMT deficit (i.e., the measured TMT minus the synthetic TMT) and precipitation at individual grid points in monthly mean fields. The linear correlation is even stronger in the annual mean and seasonally varying climatology and also in the spatial pattern of ENSO-related anomalies. The linear regression coefficient obtained in all of these analyses is virtually identical: −0.042 K (mm day−1)−1. The channel that senses lower-tropospheric temperature (TLT) is more sensitive to precipitation than the TMT channel: the regression coefficient is −0.059 K (mm day−1)−1. It is shown that correcting the TMT or TLT monthly anomalies by removing the hydrometeor contamination does not significantly influence estimates of tropical mean temperature trends, but it could affect the pattern of temperature trend over the tropical oceans.

Fusion of satellite-based imager and sounder data to construct supplementary high spatial resolution narrowband IR radiances

Polar-orbiting weather satellite platforms generally include an imager and a sounder. With a data fusion method that uses these sensors, we demonstrate the ability to construct infrared (IR) absorption narrowband radiances at imager resolution. While a sensor such as MODIS has multiple IR absorption bands, the current visible infrared imaging radiometer suite (VIIRS) imager has only IR window bands. We show fusion results for IR radiances at 4.52 μm (CO2), 6.72 μm (H2O), and 13.94 μm (CO2) by comparing MODIS observed and constructed radiances for these bands. Both regional and global results are analyzed, with radiance differences tending to be fairly low and unbiased. Similar bands are constructed from VIIRS and CrIS data, with regional and global results shown. With this approach, it will be possible to improve continuity in derived cloud products over the generations of polar-orbiting weather satellite sensors and continue applications that require IR absorption bands.

A Satellite-Derived Lower-Tropospheric Atmospheric Temperature Dataset Using an Optimized Adjustment for Diurnal Effects

Abstract Temperature sounding microwave radiometers flown on polar-orbiting weather satellites provide a long-term, global-scale record of upper-atmosphere temperatures, beginning in late 1978 and continuing to the present. The focus of this paper is a lower-tropospheric temperature product constructed using measurements made by the Microwave Sounding Unit channel 2 and the Advanced Microwave Sounding Unit channel 5. The temperature weighting functions for these channels peak in the middle to upper troposphere. By using a weighted average of measurements made at different Earth incidence angles, the effective weighting function can be lowered so that it peaks in the lower troposphere. Previous versions of this dataset used general circulation model output to remove the effects of drifting local measurement time on the measured temperatures. This paper presents a method to optimize these adjustments using information from the satellite measurements themselves. The new method finds a global-mean land diurnal cycle that peaks later in the afternoon, leading to improved agreement between measurements made by co-orbiting satellites. The changes result in global-scale warming [global trend (70°S–80°N, 1979–2016) = 0.174°C decade−1], ~30% larger than our previous version of the dataset [global trend (70°S–80°N, 1979–2016) = 0.134°C decade−1]. This change is primarily due to the changes in the adjustment for drifting local measurement time. The new dataset shows more warming than most similar datasets constructed from satellites or radiosonde data. However, comparisons with total column water vapor over the oceans suggest that the new dataset may not show enough warming in the tropics.

ISMAR: an airborne submillimetre radiometer

Abstract. The International Submillimetre Airborne Radiometer (ISMAR) has been developed as an airborne demonstrator for the Ice Cloud Imager (ICI) that will be launched on board the next generation of European polar-orbiting weather satellites in the 2020s. It currently has 15 channels at frequencies between 118 and 664 GHz which are sensitive to scattering by cloud ice, and additional channels at 874 GHz are being developed. This paper presents an overview of ISMAR and describes the algorithms used for calibration. The main sources of bias in the measurements are evaluated, as well as the radiometric sensitivity in different measurement scenarios. It is shown that for downward views from high altitude, representative of a satellite viewing geometry, the bias in most channels is less than ±1 K and the NEΔT is less than 2 K, with many channels having an NEΔT less than 1 K. In-flight calibration accuracy is also evaluated by comparison of high-altitude zenith views with radiative-transfer simulations.

Subpixel Characterization of HIRS Spectral Radiances Using Cloud Properties from AVHRR

AbstractThis paper describes a cloud type radiance record derived from NOAA polar-orbiting weather satellites using cloud properties retrieved from the Advanced Very High Resolution Radiometer (AVHRR) and spectral brightness temperatures (Tb) observed by the High Resolution Infrared Radiation Sounder (HIRS). The authors seek to produce a seamless, global-scale, long-term record of cloud type and Tb statistics intended to better characterize clouds from seasonal to decadal time scales. Herein, the methodology is described in which the cloud type statistics retrieved from AVHRR are interpolated onto each HIRS footprint using two cloud classification methods. This approach is tested over the northeast tropical and subtropical Pacific Ocean region, which contains a wide variety of cloud types during a significant ENSO variation from 2008 to 2009. It is shown that the Tb histograms sorted by cloud type are realistic for all HIRS channels. The magnitude of Tb biases among spatially coincident satellite intersections over the northeast Pacific is a function of cloud type and wavelength. While the sign of the bias can change, the magnitudes are generally small for NOAA-18 and NOAA-19, and NOAA-19 and MetOp-A intersections. The authors further show that the differences between calculated standard deviations of cloud-typed Tb well exceed intersatellite calibration uncertainties. The authors argue that consideration of higher-order statistical moments determined from spectral infrared observations may serve as a useful long-term measure of small-scale spatial changes, in particular cloud types over the HIRS–AVHRR observing record.

Sensitivity of Satellite-Derived Tropospheric Temperature Trends to the Diurnal Cycle Adjustment

Abstract Temperature sounding microwave radiometers flown on polar-orbiting weather satellites provide a long-term, global-scale record of upper-atmosphere temperatures, beginning in late 1978 and continuing to the present. The focus of this paper is the midtropospheric measurements made by the Microwave Sounding Unit (MSU) channel 2 and the Advanced Microwave Sounding Unit (AMSU) channel 5. Previous versions of the Remote Sensing Systems (RSS) dataset have used a diurnal climatology derived from general circulation model output to remove the effects of drifting local measurement time. This paper presents evidence that this previous method is not sufficiently accurate and presents several alternative methods to optimize these adjustments using information from the satellite measurements themselves. These are used to construct a number of candidate climate data records using measurements from 15 MSU and AMSU satellites. The new methods result in improved agreement between measurements made by different satellites at the same time. A method is chosen based on an optimized second harmonic adjustment to produce a new version of the RSS dataset, version 4.0. The new dataset shows substantially increased global-scale warming relative to the previous version of the dataset, particularly after 1998. The new dataset shows more warming than most other midtropospheric data records constructed from the same set of satellites. It is also shown that the new dataset is consistent with long-term changes in total column water vapor over the tropical oceans, lending support to its long-term accuracy.

Satellite retrieval of cloud condensation nuclei concentrations by using clouds as CCN chambers

Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Validation against ground-based CCN instruments at Oklahoma, at Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25° restricts the satellite coverage to ∼25% of the world area in a single day.

Cloudy Forecast for Weather Satellite Data

![Figure][1] NPOESS Preparatory Project satellite (artist's rendition). CREDIT: NOAA IN SPACE COLLECTION In the News Focus story “Weather forecasts slowly clearing up” (9 November, p. [734][2]), R. Kerr nicely summarizes how the growing improvement in prediction is coming from a focus on “more computer power, the assimilation of radar observations, and more physically realistic models.” He emphasizes that better assimilation of satellite data is a key element of improved forecasting. Unfortunately, these potential improvements will have little effect on forecasts if the basic data set from the existing polar-orbiting weather satellite system is not available. In a report issued in June 2012 ([ 1 ][3]), the U.S. Government Accountability Office noted that “data from this system is the predominant input to numerical weather prediction models” and warned that “there will likely be a gap in satellite data lasting 17 to 53 months” when the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project satellite ceases operations and NOAA's new satellite system (the Joint Polar Satellite System) launches. The report also notes that there are “potential satellite data gaps in DOD [Department of Defense] and European polar satellite programs which provide supplementary information to NOAA forecasts.” These gaps are a grave problem and would seriously degrade weather forecasts. Therefore, the agencies responsible for weather forecasting—NOAA, DOD, and NASA—should make filling the polar satellite data gaps the first priority in order to ensure that future forecasts are as good as possible. 1. [↵][4] U.S. GAO, “Polar-orbiting environmental satellites: Changing requirements, technical issues, and looming data gaps require focused attention,” GAO-12-604 (2012); [www.gao.gov/products/GAO-12-604][5]. [1]: pending:yes [2]: /lookup/doi/10.1126/science.338.6108.734 [3]: #ref-1 [4]: #xref-ref-1-1 View reference 1 in text [5]: http://www.gao.gov/products/GAO-12-604

Upper tropospheric conditions in relation to the cloud top features of 15 August 2010 convective storms

This study focuses on 15 August 2010, when many severe convective storms occurred over parts of central and Eastern Europe, with some of these exhibiting various interesting cloud-top characteristics observed by weather satellites. The importance of the phenomena of cold-U and cold-ring features in the infrared brightness temperature enhanced imagery stems from the fact that storms exhibiting these features are very often accompanied by severe weather. Therefore, besides the general description of the atmospheric conditions in the area, we seek possible reasons for the different cloud-top appearance of these storms from the perspective of Meteosat Second Generation and polar-orbiting weather satellites. Two main issues are discussed in this paper - the unusually warm appearance of the cloud-top of the “Prague hailstorm” and the presence of cold-ring and cold-U shaped storms in close proximity to the warmer “Prague hailstorm”. Both of these issues prove that the storm top appearance is very sensitive to the upper tropospheric and lower stratospheric conditions, with the first one strongly reflecting variations in the tropopause height due to the presence of the jet-stream over the region. The second topic addresses the strength of the storm relative upper level winds as a major discriminator between the cold-U and cold-ring storm top categories. Due to the above mentioned facts, 15 August 2010 was selected as one of the prime cases of interest for the Convection Working Group.

Costs for polar-orbiting weather satellites climb again

Delay in launch of spacecraft is expected to cause deteriorated forecasts.Delay in launch of spacecraft is expected to cause deteriorated forecasts.

Assessment of the consequences of the Fengyun-1C breakup in low Earth orbit

On 11 January 2007, the People’s Republic of China conducted a successful anti-satellite test against one of their defunct polar-orbiting weather satellites. The target satellite, called Fengyun-1C, had a mass of 880 kg and was orbiting at an altitude of about 863 km when the collision occurred. Struck by a direct-ascent interceptor at a speed of 9.36 km/s, the satellite disintegrated, spreading the cataloged fragments between 200 and 4000 km, with the highest concentration near the breakup height. By the end of April 2008, 2377 pieces of debris, including the original payload remnant, had officially been cataloged by the US Space Surveillance Network. Of these, nearly 1% had reentered the Earth’s atmosphere. This deliberate act is the largest debris-generating event on record, and its consequences will adversely affect circumterrestrial space for many years. In an attempt to assess the impact of the Fengyun-1C breakup on the low Earth environment, the cloud of cataloged debris was propagated for nearly 8 years, taking into account the relevant orbit perturbations and a debris cloud ballistic coefficient distribution based on orbit decay calibrations. The immediate consequence of the Chinese anti-satellite test was to significantly increase the probability of collision with man-made debris. For the Italian spacecraft launched in the first half of 2007, the collision probability with cataloged objects increased by 10% for AGILE, in equatorial orbit, and by 60% for COSMO-SkyMed 1 and 2, in sun-synchronous orbit. During the next few years, the debris cloud generated by the Fengyun-1C breakup was found to remain relatively stable, with nearly 80% of the cataloged fragments still in orbit about 9 years after the event.

Troubled Weather Satellite Program

Cost overruns and project delays have led to a cloudy forecast for the United States' new polar-orbiting weather satellites. The greatly upgraded satellites, to consist of a group of three with three replacements, are meant to beam back weather data that would enable scientists to better predict hurricanes and military plans. This paper discusses the problems with the three new polar orbiting weather satellites mainly due to delayed schedule and cost overruns. These problems are a major concern for the whole enterprise of monitoring Earth from outer space. Also, delays in critically needed polar instruments could affect all of US environmental monitoring

A Herculean task? Economics, politics, and realigning government in the case of US polar-orbiting weather satellites

Abstract In 1994 one of the most radical institutional restructurings in the USA's government provision of critical weather information took place after eight previously unsuccessful attempts. The President merged weather data collection by satellites operated by the Department of Defense and satellites operated by the Department of Commerce. Reorganization involving agencies with different objectives, economic constraints, and operating cultures is rare. This paper reviews the decision leading to “convergence,” discusses economic arguments, and addresses the problems confronting the new organization. The paper also discusses the implications of the new organization for incentives to engage in space R&D and the increasingly large role played by these satellites in collecting not only weather but also climate-related data.

Observations and trends of clouds based on GOES sounder data

A 26 month (November 1997 through December 1999) data set of Geostationary Operational Environmental Satellite (GOES) sounder‐derived cloud parameters has been analyzed to discern annual and monthly trends. An important outcome of this study is the identification of diurnal trends made possible by the geostationary satellite frequent observations over specific locations. The area of coverage is 20°N to 50°N and 60°W to 160°W, which corresponds to the continental United States and the surrounding waters. The satellite cloud observations were compared to manually observed Pilot Reports (PIREPs) and were found to be, on average, 35 hPa lower. Comparing the frequency of GOES sounder observations of high cloudiness with observations from the National Oceanic and Atmospheric Administration (NOAA) series of polar orbiting weather satellites reveals a correlation coefficient of 0.79 and a bias of 3.4% for the frequency of occurrence (GOES with a mean higher height). The frequency of occurrence and distribution of clouds, cloud top pressure (CTOP), and effective cloud amount are based on a spatial resolution of ∼40 km (3×3 field of view box) and are shown for eight regions. High clouds (CTOP ≤300 hPa) are found to be more prevalent during the Northern Hemisphere summer than winter for all regions. High clouds for 1998 comprise 8.5% of all observations. Also, in 1998 clear conditions are observed ∼34% of the time. Focusing on the strength of the hourly GOES sounder data, it is found that thin high clouds are most prevalent during the summer and fall seasons, occurring most frequently in the late morning and early afternoon.