Test of far-infrared atmospheric spectroscopy using wide-band balloon-borne measurements of the upwelling radiance (original) (raw)
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Ground‐Based and Balloon‐Borne Characterization of the Far Infrared Atmospheric Emission Spectrum
2009
The measurement of the Earth's atmospheric emission spectrum is fundamental for the study of the global radiation budget. Up to now, this measurement has typically been limited to the mid-infrared region because of the technological limitations of space-borne spectrometers operating at longer wavelengths. The uncovered region of the far infrared (FIR) is however very important because most of the radiative cooling of the atmosphere, due to the strong rotational band of water vapor, occurs here.
Proceedings of SPIE - The International Society for Optical Engineering, 2008
On June 30 th , 2005 the REFIR-PAD (Radiation Explorer in the Far InfraRed -Prototype for Application and Development) Fourier transform spectroradiometer performed the first wide-band spectral characterization of the top-of-atmosphere emitted radiation in the far-infrared with an uncooled instrument. The nadir emitted radiance has been measured down to 100 cm −1 , thus covering a spectral interval that, until now, was nearly unexplored, and up to 1400 cm −1 , including the well characterized atmospheric window region, in which it is possible to perform comparison and intercalibration with operative instruments. The measurements were performed at an altitude of 34 km, from a stratospheric balloon launched in tropical region, near Teresina (Brazil). The acquired spectra have a spectral resolution of 0.5 cm −1 . It should be noted that despite the operating spectral range extending to the far-infrared region, REFIR-PAD does not require any cooled components, thanks to the use of pyroelectric detectors and an optical scheme that compensates for the instrument self-emission. This work shows the results of the analysis of the spectra, focusing on the far infrared portion of the atmospheric emitted radiance. The retrieval of the vertical profiles of water vapour and temperature during the flight is presented. The vertical resolution of the retrieval is 2 km in the upper troposphere -lower stratosphere (UTLS) region, and lower at higher altitudes. The comparison with ECMWF for validation is also shown. Besides the characterization of temperature and water vapour, from the analysis of the emitted radiance useful information can be gathered about cloud and aerosol contribution to radiation budget.
Far infrared spectroscopy of the troposphere (FIRST): flight performance and data processing
Infrared Spaceborne Remote Sensing XIV, 2006
The radiative balance of the troposphere, and hence global climate, is dominated by the infrared absorption and emission of water vapor, particularly at far-infrared (far-IR) wavelengths from 15-50 µm. Current and planned satellites observe the infrared region to about 15.4 µm, ignoring spectral measurement of the far-IR region from 15 to 100µm. The far-infrared spectroscopy of the troposphere (FIRST) project, flown in June 2005, provided a balloon-based demonstration of the two key technologies required for a space-based far-IR spectral sensor. We discuss the FIRST Fourier transform spectrometer system (0.6 cm-1 unapodized resolution), its radiometric calibration in the spectral range from 10 to 100 µm, and its performance and science data from the flight. Two primary and two secondary goals are given and data presented to show the goals were achieved by the FIRST flight.
2022
The Far-Infrared Radiation Mobile Observation System (FIRMOS) is a Fourier transform spectroradiometer developed to support the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) satellite mission by validating measurement methods and instrument design concepts, both in the laboratory and in field campaigns. FIRMOS is capable of measuring the downwelling spectral radiance emitted by the atmosphere in the spectral band from 100 to 1000 cm −1 (10-100 µm in wavelength), with a maximum spectral resolution of 0.25 cm −1. We describe the instrument design and its characterisation and discuss the geophysical products obtained by inverting the atmospheric spectral radiance measured during a campaign from the high-altitude location of Mount Zugspitze in Germany, beside the Extended-range Atmospheric Emitted Radiance Interferometer (E-AERI), which is permanently installed at the site. Following the selection of clear-sky scenes, using a specific algorithm, the water vapour and temperature profiles were retrieved from the FIRMOS spectra by applying the Kyoto protocol and Informed Management of the Adaptation (KLIMA) code. The profiles were found in very good agreement with those provided by radiosondes and by the Raman lidar operating from the Zugspitze Schneefernerhaus station. In addition, the retrieval products were validated by comparing the retrieved Integrated Water Vapour values with those obtained from the E-AERI spectra. Finally, we found that the trends for the temperature, and the water vapour profiles over time were in good agreement with those provided by ERA5 reanalysis. 1 Introduction The far-infrared (FIR) portion of the Earth's emission spectrum is the subject of a growing research interest because of its important role played in the Earth's radiative balance. This spectral region covers the wavelengths longer than 15 µm (the 1
2006
The REFIR-PAD (Radiation Explorer in the Far InfraRed-Prototype for Applications and Development) Fourier transform spectroradiometer has successfully performed, at the end of June, 2005, a stratospheric balloon flight from Teresina, Brazil. The instrument has provided 8 hours worth of nadir-looking spectra acquired with a resolution of 0.5 cm-1 in the 100 to 1400 cm-1 spectral range, thus covering both the far-infrared range, containing the radiative signature of the upper tropospheric water vapour, and the better-known mid-infrared range, which provides validation with existing instruments. From the analysis of the calibrated spectra we obtain valuable information on the contribution to the Earth's outgoing long-wave radiation of water, both in the vapour and cloud form, in a region of the atmosphere, the upper-troposphere/lower-stratosphere, in which this contribution has a critical role.
Far InfraRed Spectroscopy of the troposphere (FIRST): Sensor concept
Proceedings of Spie the International Society For Optical Engineering, 2002
The radiative balance of the Earth is influenced strongly by radiative cooling associated with emission of radiation by water vapor at farinfrared (far-IR) wavelengths greater than 15 µm and extending out beyond 60 µm. The distribution of water vapor and associated far-IR radiative forcings and feedbacks are well-recognized as major uncertainties in understanding and predicting future climate. Up to half of the outgoing longwave radiation (OLR) from the Earth occurs beyond 15.4 µm. Cirrus clouds also modulate the outgoing longwave radiation in the far-IR. Despite this fundamental importance, far-IR emission (spectra or band-integrated) has rarely been directly measured from space, airborne, or ground-based platforms. Current and planned operational and research satellites typically observe the mid-infrared only to about 15.4 µm. The Far-Infrared Spectroscopy of the Troposphere (FIRST) project is an investment by NASA through the Instrument Incubator Program (IIP) to develop a space-based capability to measure the spectrally resolved infrared spectrum to 100 µm.
Far-infrared spectroscopy of the troposphere: instrument description and calibration performance
Applied Optics, 2013
The far-infrared spectroscopy of the troposphere (FIRST) instrument is a Fourier transform spectrometer developed to measure the Earth's thermal emission spectrum with a particular emphasis on far-infrared (far-IR) wavelengths greater than 15 μm. FIRST was developed under NASA's Instrument Incubator Program to demonstrate technology for providing measurements from 10 to 100 μm (1000 to 100 cm −1) on a single focal plane with a spectral resolution finer than 1 cm −1. Presently no spectrometers in orbit are capable of directly observing the Earth's far-IR spectrum. This fact, coupled with the fundamental importance of the far-IR to Earth's climate system, provided the impetus for the development of FIRST. In this paper the FIRST instrument is described and results of a detailed absolute laboratory calibration are presented. Specific channels in FIRST are shown to be accurate in the far-IR to better than 0.3 K at 270 K scene temperature, 0.5 K at 247 K, and 1 K at 225 K.
Through the broadband spectrally-resolved measurement of the atmospheric emission, a complete characterization of the contribution to the Earth's radiative balance due to each atmospheric constituent can be performed. The Radiation Explorer in the Far InfraRed-Prototype for Application and Development (REFIR-PAD) Fourier transform spectroradiometer provides atmospheric emission measurements in the 100 to 1400 cm −1 spectral range with 0.5 cm −1 resolution. The instrument, developed at IFAC-CNR, Florence, has been successfully deployed in several campaigns, both in the ground based zenith-looking geometry and in the nadir-looking balloon-borne configuration. The far-infrared end of the REFIR-PAD measured spectrum is of particular interest in the case of polar atmosphere, where the most of the radiative exchange between atmosphere and space takes place in this spectral region. Moreover, with the ground based operating mode, a characterization of the broadband radiative signature of clouds and aerosols can be performed, with the only limitation of the need of low levels of water vapour like those that are obtainable in high altitude stations during winter. This paper shows for ground-based observations the retrieval capabilities of the temperature and water vapour vertical profiles with the estimation of the total precipitable water vapour. It is also shown that in presence of thin clouds, particle size and density 1 can be retrieved. The operation from polar regions could provide a significant improvement in the knowledge of the radiative properties of the atmosphere, and in particular of the effect of polar stratospheric clouds in the Earth's radiative balance.
Atmospheric Measurement Techniques, 2023
The Far-Infrared Radiation Mobile Observation System (FIRMOS) is a Fourier transform spectroradiometer developed to support the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) satellite mission by validating measurement methods and instrument design concepts, both in the laboratory and in field campaigns. FIRMOS is capable of measuring the downwelling spectral radiance emitted by the atmosphere in the spectral band from 100 to 1000 cm −1 (10-100 µm in wavelength), with a maximum spectral resolution of 0.25 cm −1. We describe the instrument design and its characterization and discuss the geophysical products obtained by inverting the atmospheric spectral radiance measured during a campaign from the highaltitude location of Mount Zugspitze in Germany, beside the Extended-range Atmospheric Emitted Radiance Interferometer (E-AERI), which is permanently installed at the site. Following the selection of clear-sky scenes, using a specific algorithm, the water vapour and temperature profiles were retrieved from the FIRMOS spectra by applying the Kyoto protocol and Informed Management of the Adaptation (KLIMA) code. The profiles were found in very good agreement with those provided by radiosondes and by the Raman lidar operating from the Zugspitze Schneefernerhaus station. In addition, the retrieval products were validated by comparing the retrieved integrated water vapour values with those obtained from the E-AERI spectra.
Infrared spectral radiance measurements in the tropical Pacific atmosphere
Journal of Geophysical Research, 1997
AbstractDownwelling thermal infrared emission from the tropical atmosphere is affected strongly by the typically large amounts of water vapor. In two experiments within the last 2 years we have used a Fourier transform spectroradiometer to measure tropical atmospheric emission, concentrating on the “window” region between about 800 and 1200 cm−1. Shortly after the first of these experiments, substantial differences between measured and calculated radiances led to the development of a new water vapor continuum model. This model subsequently has been incorporated into several widely distributed radiative transfer codes (LBLRTM, MODTRAN, FASCODE). Measurements from the second tropical experiment, which occurred during March and April 1996, validate this new continuum model. This is an important comparison because the new measurements were taken with an improved instrument under better defined clear-sky conditions than the original tropical data on which the continuum correction was based. Model residuals are of the order of the uncertainty in measurements, especially of the atmospheric water vapor and temperature profiles.