FORUM: Unique Far-Infrared Satellite Observations to Better Understand How Earth Radiates Energy to Space

Palchetti, Luca; Brindley, Helen E.; Bantges, R.; Buehler, Stefan; Camy‐Peyret, C.; Carli, B.; Cortesi, Ugo; Bianco, Samuele Del; Natale, Gianluca Di; Dinelli, B. M.; Feldman, D.; Huang, Xianglei; C.‐Labonnote, Laurent; Libois, Quentin; Maestri, Tiziano; Mlynczak, Martin G.; Murray, J. E.; Oetjen, H.; Ridolfi, Marco; Riese, Martin; Russell, Jill; Saunders, R.; Serio, Carmine

doi:10.1175/bams-d-19-0322.1

Cited by 55 publications

(54 citation statements)

References 102 publications

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“…A key test is whether the values retrieved from the upper level observations show consistency with the near-surface retrievals. The findings have direct relevance for two upcoming FIR satellite missions: National Aeronautics and Space Administration's (NASA's) Polar Radiant Energy in the Far Infrared Experiment (PREFIRE) and ESA's Far-Infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission (Palchetti et al, 2016(Palchetti et al, , 2020. Given that both aim to infer Arctic and, potentially, Antarctic surface emissivities in the FIR, the analyses performed here provide a useful indication of what can be achieved, taking into consideration the uncertainties in both the measured radiances and the atmospheric state.…”

Section: Introductionmentioning

confidence: 92%

Retrievals of High‐Latitude Surface Emissivity Across the Infrared From High‐Altitude Aircraft Flights

et al. 2020

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We present retrievals of infrared spectral surface emissivities spanning the far infrared and mid-infrared from aircraft observations over Greenland, taken at an altitude of 9.2 km above sea level. We describe the flight campaign, available measurements, and the retrieval method. The principal barriers to reducing uncertainty in the emissivity retrievals are found to be instrumental noise and our ability to simultaneously retrieve the underlying surface temperature. However, our results indicate that using the instrumentation available to us it is possible to retrieve emissivities from altitude with an uncertainty of~0.02 or better across much of the infrared. They confirm that the far-infrared emissivity of snow and ice surfaces can depart substantially from unity, reaching values as low as 0.9 between 400 and 450 cm −1. They also show good consistency with retrievals from the same flight made from near-surface observations giving confidence in the methodology used and the results obtained for this more challenging viewing configuration. To the best of our knowledge, this is the first time that far-infrared surface emissivity has been retrieved from altitude and demonstrates that the methodology has the potential to be extended to planned satellite far-infrared missions.

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Section: Introductionmentioning

confidence: 92%

Retrievals of High‐Latitude Surface Emissivity Across the Infrared From High‐Altitude Aircraft Flights

et al. 2020

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“…Therefore, it is possible to distinguish the radiative signals of the effective radius from those of the IWC with a mid-infrared coverage characteristic of existing instruments. Interestingly, differences in the two normalized RMSE spectra are more prominent at lower wavenumbers (∼ 200 cm −1 ), suggesting that farinfrared channels -e.g., those from future instruments such as FORUM (Palchetti et al, 2020) and TICFIRE (Blanchet et al, 2011) -may be advantageous for UTLS retrieval. This is beyond the scope of the present simulation experiment but warrants future investigation.…”

Section: Cloud-induced Uncertaintiesmentioning

confidence: 99%

A simulation-experiment-based assessment of retrievals of above-cloud temperature and water vapor using a hyperspectral infrared sounder

Feng

Huang

2021

Atmos. Meas. Tech.

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Abstract. Measuring atmospheric conditions above convective storms using spaceborne instruments is challenging. The operational retrieval framework of current hyperspectral infrared sounders adopts a cloud-clearing scheme that is unreliable in overcast conditions. To overcome this issue, previous studies have developed an optimal estimation method that retrieves the temperature and humidity above high thick clouds by assuming a slab of cloud. In this study, we find that variations in the effective radius and density of cloud ice near the tops of convective clouds lead to non-negligible spectral uncertainties in simulated infrared radiance spectra. These uncertainties cannot be fully eliminated by the slab-cloud assumption. To address this problem, a synergistic retrieval method is developed here. This method retrieves temperature, water vapor, and cloud properties simultaneously by incorporating observations from active sensors in synergy with infrared radiance spectra. A simulation experiment is conducted to evaluate the performance of different retrieval strategies using synthetic radiance data from the Atmospheric Infrared Sounder (AIRS) and cloud data from CloudSat/CALIPSO. In this experiment, we simulate infrared radiance spectra from convective storms through a combination of a numerical weather prediction model and a radiative transfer model. The simulation experiment shows that the synergistic method is advantageous, as it shows high retrieval sensitivity to the temperature and ice water content near the cloud top. The synergistic method more than halves the root-mean-square errors in temperature and column integrated water vapor compared to prior knowledge based on the climatology. It can also improve the quantification of the ice water content and effective radius compared to prior knowledge based on retrievals from active sensors. Our results suggest that existing infrared hyperspectral sounders can detect the spatial distributions of temperature and humidity anomalies above convective storms.

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“…Despite significant advances in sensor technology, spectroscopy, and our understanding of the role of far-infrared radiation in climate, only a few short-lived satellitebased experiments have measured emitted spectra at wavelengths longer than 15 micrometers, the last taking place more than four decades ago (Spankuch and Dohler, 1985). (Palchetti et al, 2020).…”

Section: The Far-infrared Observation Gapmentioning

confidence: 99%

The Polar Radiant Energy in the Far Infrared Experiment: A New Perspective on Polar Longwave Energy Exchanges

L’Ecuyer

Drouin

Anheuser

et al. 2021

Bulletin of the American Meteorological Society

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The Earth’s climate is strongly influenced by energy deficits at the poles that emit more thermal energy than they receive from the sun. Energy exchanges between the surface and atmosphere influence the local environment while heat transport from lower latitudes drives midlatitude atmospheric and oceanic circulations. In the Arctic, in particular, local energy imbalances induce strong seasonality in surface-atmosphere heat exchanges and an acute sensitivity to forced climate variations. Despite these important local and global influences, the largest contributions to the polar atmospheric and surface energy budgets have not been fully characterized. The spectral variation of far-infrared radiation that makes up 60% of polar thermal emission has never been systematically measured impeding progress toward consensus in predicted rates of Arctic warming, sea ice decline, and ice sheet melt.Enabled by recent advances in sensor miniaturization and CubeSat technology, the Polar Radiant Energy in the Far InfraRed Experiment (PREFIRE) mission will document, for the first time, the spectral, spatial, and temporal variations of polar far-infrared emission. Selected under NASA’s Earth Ventures Instrument (EVI) program, PREFIRE will utilize new light weight, low-power, ambient temperature detectors capable of measuring at wavelengths up to 50 micrometers to quantify Earth’s far-infrared spectrum. Estimates of spectral surface emissivity, water vapor, cloud properties, and the atmospheric greenhouse effect derived from these measurements offer the potential to advance our understanding of the factors that modulate thermal fluxes in the cold, dry conditions characteristic of the polar regions.

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FORUM: Unique Far-Infrared Satellite Observations to Better Understand How Earth Radiates Energy to Space

Abstract: Capsule summary The Far-infrared Outgoing Radiation Understanding and Monitoring mission will observe the Earth’s emitted outgoing radiation spectrum across the far-infrared with high spectral resolution and accuracy from space for the first time.

Cited by 55 publications

References 102 publications

Retrievals of High‐Latitude Surface Emissivity Across the Infrared From High‐Altitude Aircraft Flights

Retrievals of High‐Latitude Surface Emissivity Across the Infrared From High‐Altitude Aircraft Flights

A simulation-experiment-based assessment of retrievals of above-cloud temperature and water vapor using a hyperspectral infrared sounder

The Polar Radiant Energy in the Far Infrared Experiment: A New Perspective on Polar Longwave Energy Exchanges

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