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

2020 ◽  
Vol 101 (12) ◽  
pp. E2030-E2046 ◽  
Author(s):  
L. Palchetti ◽  
H. Brindley ◽  
R. Bantges ◽  
S. A. Buehler ◽  
C. Camy-Peyret ◽  
...  
Keyword(s):  
Climate Models ◽  
Longwave Radiation ◽  
Far Infrared ◽  
Lapse Rate ◽  
High Spectral Resolution ◽  
Critical Parameters ◽  
Temperature Lapse Rate ◽  
Stratospheric Water Vapor ◽  
Explorer Mission ◽  
Spectrally Resolved

AbstractThe outgoing longwave radiation (OLR) emitted to space is a fundamental component of the Earth’s energy budget. There are numerous, entangled physical processes that contribute to OLR and that are responsible for driving, and responding to, climate change. Spectrally resolved observations can disentangle these processes, but technical limitations have precluded accurate space-based spectral measurements covering the far infrared (FIR) from 100 to 667 cm−1 (wavelengths between 15 and 100 µm). The Earth’s FIR spectrum is thus essentially unmeasured even though at least half of the OLR arises from this spectral range. The region is strongly influenced by upper-tropospheric–lower-stratospheric water vapor, temperature lapse rate, ice cloud distribution, and microphysics, all critical parameters in the climate system that are highly variable and still poorly observed and understood. To cover this uncharted territory in Earth observations, the Far-Infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission has recently been selected as ESA’s ninth Earth Explorer mission for launch in 2026. The primary goal of FORUM is to measure, with high absolute accuracy, the FIR component of the spectrally resolved OLR for the first time with high spectral resolution and radiometric accuracy. The mission will provide a benchmark dataset of global observations which will significantly enhance our understanding of key forcing and feedback processes of the Earth’s atmosphere to enable more stringent evaluation of climate models. This paper describes the motivation for the mission, highlighting the scientific advances that are expected from the new measurements.

scholarly journals Can downwelling far-infrared radiances over Antarctica be estimated from mid-infrared information?

2019 ◽  
Vol 19 (11) ◽  
pp. 7927-7937
Author(s):  
Christophe Bellisario ◽  
Helen E. Brindley ◽  
Simon F. B. Tett ◽  
Rolando Rizzi ◽  
Gianluca Di Natale ◽  
...  
Keyword(s):  
Climate Models ◽  
Far Infrared ◽  
Mid Infrared ◽  
Spectral Bands ◽  
Noise Characteristics ◽  
Infrared Spectral ◽  
Infrared Radiances ◽  
Spectrally Resolved ◽  
Spectral Ranges ◽  
The Impact

Abstract. Far-infrared (FIR: 100cm-1<wavenumber, ν<667 cm−1) radiation emitted by the Earth and its atmosphere plays a key role in the Earth's energy budget. However, because of a lack of spectrally resolved measurements, radiation schemes in climate models suffer from a lack of constraint across this spectral range. Exploiting a method developed to estimate upwelling far-infrared radiation from mid-infrared (MIR: 667cm-1<ν<1400 cm−1) observations, we explore the possibility of inferring zenith FIR downwelling radiances in zenith-looking observation geometry, focusing on clear-sky conditions in Antarctica. The methodology selects a MIR predictor wavenumber for each FIR wavenumber based on the maximum correlation seen between the different spectral ranges. Observations from the REFIR-PAD instrument (Radiation Explorer in the Far Infrared – Prototype for Application and Development) and high-resolution radiance simulations generated from co-located radio soundings are used to develop and assess the method. We highlight the impact of noise on the correlation between MIR and FIR radiances by comparing the observational and theoretical cases. Using the observed values in isolation, between 150 and 360 cm−1, differences between the “true” and “extended” radiances are less than 5 %. However, in spectral bands of low signal, between 360 and 667 cm−1, the impact of instrument noise is strong and increases the differences seen. When the extension of the observed spectra is performed using regression coefficients based on noise-free radiative transfer simulations the results show strong biases, exceeding 100 % where the signal is low. These biases are reduced to just a few percent if the noise in the observations is accounted for in the simulation procedure. Our results imply that while it is feasible to use this type of approach to extend mid-infrared spectral measurements to the far-infrared, the quality of the extension will be strongly dependent on the noise characteristics of the observations. A good knowledge of the atmospheric state associated with the measurements is also required in order to build a representative regression model.

scholarly journals On the Longwave Climate Feedbacks

2013 ◽  
Vol 26 (19) ◽  
pp. 7603-7610 ◽  
Author(s):  
Yi Huang
Keyword(s):  
Radiative Forcing ◽  
Climate Models ◽  
Longwave Radiation ◽  
Feedback Mechanism ◽  
Cloud Feedback ◽  
Climate Feedbacks ◽  
Stratospheric Water Vapor ◽  
Surface Warming ◽  
Transient Climate Change ◽  
Positive Feedback Mechanism

Abstract This paper mainly addresses two issues that concern the longwave climate feedbacks. First, it is recognized that the radiative forcing of greenhouse gases, as measured by their impact on the outgoing longwave radiation (OLR), may vary across different climate models even when the concentrations of these gases are identically prescribed. This forcing variation contributes to the discrepancy in these models' projections of surface warming. A method is proposed to account for this effect in diagnosing the sensitivity and feedbacks in the models. Second, it is shown that the stratosphere is an important factor that affects the OLR in transient climate change. Stratospheric water vapor and temperature changes may both act as a positive feedback mechanism during global warming and cannot be fully accounted as a “stratospheric adjustment” of radiative forcing. Neglecting these two issues may cause a bias in the longwave cloud feedback diagnosed as a residual term in the decomposition of OLR variations. There is no consensus among the climate models on the sign of the longwave cloud feedback after accounting for both issues.

scholarly journals Coupling of climate models and ice sheet models by surface mass balance gradients: application to the Greenland Ice Sheet

2012 ◽  
Vol 6 (2) ◽  
pp. 255-272 ◽  
Author(s):  
M. M. Helsen ◽  
R. S. W. van de Wal ◽  
M. R. van den Broeke ◽  
W. J. van de Berg ◽  
J. Oerlemans
Keyword(s):  
Mass Balance ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Lapse Rate ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Temperature Lapse Rate

Abstract. It is notoriously difficult to couple surface mass balance (SMB) results from climate models to the changing geometry of an ice sheet model. This problem is traditionally avoided by using only accumulation from a climate model, and parameterizing the meltwater run-off as a function of temperature, which is often related to surface elevation (Hs). In this study, we propose a new strategy to calculate SMB, to allow a direct adjustment of SMB to a change in ice sheet topography and/or a change in climate forcing. This method is based on elevational gradients in the SMB field as computed by a regional climate model. Separate linear relations are derived for ablation and accumulation, using pairs of Hs and SMB within a minimum search radius. The continuously adjusting SMB forcing is consistent with climate model forcing fields, also for initially non-glaciated areas in the peripheral areas of an ice sheet. When applied to an asynchronous coupled ice sheet – climate model setup, this method circumvents traditional temperature lapse rate assumptions. Here we apply it to the Greenland Ice Sheet (GrIS). Experiments using both steady-state forcing and glacial-interglacial forcing result in realistic ice sheet reconstructions.

scholarly journals Spectrally Resolved Fluxes from IASI Data: Retrieval Algorithm for Clear-Sky Measurements

2020 ◽  
Vol 33 (16) ◽  
pp. 6971-6988 ◽  
Author(s):  
Simon Whitburn ◽  
Lieven Clarisse ◽  
Sophie Bauduin ◽  
Maya George ◽  
Daniel Hurtmans ◽  
...  
Keyword(s):  
Longwave Radiation ◽  
Real Data ◽  
Far Infrared ◽  
Data Retrieval ◽  
Detection Algorithm ◽  
Retrieval Algorithm ◽  
Tropical Region ◽  
Cloud Detection ◽  
Distribution Models ◽  
Spectrally Resolved

AbstractSpace-based measurements of the outgoing longwave radiation (OLR) are essential for the study of Earth’s climate system. While the CERES instrument provides accurate measurements of this quantity, its measurements are not spectrally resolved. Here we present a high-resolution OLR product (sampled at 0.25 cm−1), derived from measurements of the IASI satellite sounder. The applied methodology relies on precalculated angular distribution models (ADMs). These are usually calculated for tens to hundreds of different scene types (characterized by surface and atmosphere parameters). To guarantee accurate results in the range 645–2300 cm−1 covered by IASI, we constructed ADMs for over 140 000 scenes. These were selected from one year of CAMS reanalysis data. A dissimilarity-based selection algorithm was applied to choose scenes as different from each other as possible, thereby maximizing the performance on real data, while keeping the number of scenes manageable. A comparison of the IASI OLR integrated over the 645–2300 cm−1 range was performed with the longwave broadband OLR products from CERES and the AIRS instrument. The latter are systematically higher due to the contribution of the far infrared to the total IR spectral range, but as expected exhibit generally high spatial correlations with the IASI OLR, except for some areas in the tropical region. We also compared the IASI OLR against the spectrally resolved OLR derived from AIRS. A good agreement was found above 1200 cm−1 while AIRS OLR appeared to be systematically higher in the atmospheric window region, likely related to differences in overpass time or to the use of a different cloud detection algorithm.

scholarly journals Towards direct coupling of regional climate models and ice sheet models by mass balance gradients: application to the Greenland Ice Sheet

2011 ◽  
Vol 5 (4) ◽  
pp. 2115-2157 ◽  
Author(s):  
M. M. Helsen ◽  
R. S. W. van de Wal ◽  
M. R. van den Broeke ◽  
W. J. van de Berg ◽  
J. Oerlemans
Keyword(s):  
Mass Balance ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Regional Climate Models ◽  
Lapse Rate ◽  
Surface Mass ◽  
Temperature Lapse Rate

Abstract. It is notoriously difficult to couple surface mass balance (SMB) results from climate models to the changing geometry of an ice sheet model. This problem is traditionally avoided by using only accumulation fields from a climate model, and deriving SMB by parameterizing the run-off as a function of temperature, which is often related to surface elevation. In this study, a new parameterization of SMB is presented, designed for use in ice dynamical models to allow a direct adjustment of SMB as a result of a change in elevation (Hs) or a change in climate forcing. This method is based on spatial gradients in the present-day SMB field as computed by a regional climate model. Separate linear relations are derived for ablation and accumulation regimes, using only those pairs of Hs an SMB that are found within a minimum search radius. This approach enables a dynamic SMB forcing of ice sheet models, also for initially non-glaciated areas in the peripheral areas of an ice sheet, and circumvents traditional temperature lapse rate assumptions. The method is applied to the Greenland Ice Sheet (GrIS). Model experiments using both steady-state forcing and more realistic glacial-interglacial forcing result in ice sheet reconstructions and behavior that compare favorably with present-day observations of ice thickness.

scholarly journals Shallow Temperature Lapse Rate Signified Elevation Dependent Warming in Different Treeline Environments in the Himalaya- Possible Implications to Treeline Vegetation

2021 ◽  
Author(s):  
Rajesh Joshi ◽  
Ninchhen Dolma Tamang ◽  
Surendra Pratap Singh
Keyword(s):  
Climate Models ◽  
Winter Season ◽  
Growing Season ◽  
Rate Of Change ◽  
Lapse Rate ◽  
High Temporal Resolution ◽  
Moisture Regime ◽  
Temperature Lapse Rate ◽  
The One ◽  
The Himalaya

Abstract There are emergent evidences that the rise in temperature in high altitude regions in comparison to low altitude of the Himalaya is more rapid than other parts of the World. This Elevation-dependent warming (EDW) can accelerate the rate of change in mountain ecosystems, including cryosphere, hydrology, biodiversity and socio-economic systems. In this paper, we present Temperature Lapse Rates (TLRs) from 20 stations for three treeline transects representing different climate regimes along the Himalayan arc. TLRs were calculated based on high temporal resolution data collected for two year (2017-18) from complex mountain terrain of treeline environment. The annual mean TLR increased with decreasing moisture, being markedly high at dry WH transect (-0.66℃/100 m) and lowest (-0.50℃/100 m) for moist EH transect. The One-Way ANOVA confirms that the TLR varied spatially, declining from West to East across the Himalayan arc, and significantly differ among seasons (F=3.2175; P = 0.03). The lowest mean TLRs were found during the winter season (EH: -0.46℃/100m; CH: -0.40℃/100m; WH: -0.31℃/100m). The monthly TLR varied within a narrow range (-0.49℃/100m to -0.54℃/100m) at EH transect, -0.24℃/100m to -0.68℃/100m at CH transect and from -0.26℃ to -0.90℃ at WH transect with lowest monthly TLR in December (-0.24 to -0.32℃/ 100m) for all three sites. Study shows moisture, snow albedo and reflectance play a key role as controlling factors on TLR in treeline environments. Higher growing season temperatures observed for treelines in Himalaya (8.4±1.8℃, 10.3±1.4℃, and 7.5±2.7℃) shows warmer treeline in Himalaya. The EDW may impact the dynamics of treeline, snow and moisture regime, surface energy balance, increased water stress, species distribution, and growing season of alpine vegetation in the Himalaya. The findings of the study could provide useful insight (ground-based) to re-parameterize the climate models over the Himalayan region. This study can facilitate improving interpolation of air temperature for ecological modeling studies in ungauged and the data-sparse regions, especially for the higher Himalaya where ground based station data are extremely scarce.

scholarly journals Dynamic simulations of Vatnajökull ice cap from 1980 to 2300

2019 ◽  
Vol 66 (255) ◽  
pp. 97-112 ◽  
Author(s):  
Louise Steffensen Schmidt ◽  
Guðfinna Ađalgeirsdóttir ◽  
Finnur Pálsson ◽  
Peter L. Langen ◽  
Sverrir Guđmundsson ◽  
...  
Keyword(s):  
Climate Models ◽  
Regional Climate ◽  
Regional Climate Models ◽  
Lapse Rate ◽  
Dynamic Simulations ◽  
Climate Conditions ◽  
Temperature Lapse Rate ◽  
Ice Caps ◽  
Ice Cap ◽  
Rcp 8.5

AbstractLike most ice caps and glaciers worldwide, Icelandic glaciers are retreating in a warming climate. Here, the evolution of Vatnajökull ice cap, Iceland, from 1980 to 2300 is simulated by forcing the Parallel Ice Sheet Model (PISM) with output from Regional Climate Models (RCMs). For climate simulations of the recent past, HARMONIE-AROME reanalysis-forced simulations are used, while for future climate conditions, high-resolution (5.5 km) simulations from the RCM HIRHAM5 are used in addition to available CORDEX simulations (12 km). The glacier evolution is modelled using the RCP 4.5 and RCP 8.5 scenarios until 2100. To extend the time series, the 2081–2100 climate forcing is repeated until 2300. For RCP 4.5, the ice cap loses 31–64% of its volume and 13–37% of its area by 2300 depending on the used model forcing. For RCP 8.5, the volume decrease is 51–94% and the area decrease is 24–80% by 2300. In addition, the effect of elevation feedbacks is investigated by adding a precipitation and temperature lapse rate to the HIRHAM5 simulations. By 2300, the lapse rate runs have a 9–14% smaller volume and a 9–20% smaller area than the runs without a lapse rate correction.

scholarly journals Near-Surface Temperature Lapse Rates over Arctic Glaciers and Their Implications for Temperature Downscaling

2009 ◽  
Vol 22 (16) ◽  
pp. 4281-4298 ◽  
Author(s):  
Alex S. Gardner ◽  
Martin J. Sharp ◽  
Roy M. Koerner ◽  
Claude Labine ◽  
Sarah Boon ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Air Temperature ◽  
Climate Models ◽  
Temperature Fields ◽  
Lapse Rate ◽  
Free Atmosphere ◽  
Glacier Surface ◽  
Near Surface ◽  
Temperature Lapse Rate ◽  
Lapse Rates

Abstract Distributed glacier surface melt models are often forced using air temperature fields that are either downscaled from climate models or reanalysis, or extrapolated from station measurements. Typically, the downscaling and/or extrapolation are performed using a constant temperature lapse rate, which is often taken to be the free-air moist adiabatic lapse rate (MALR: 6°–7°C km−1). To explore the validity of this approach, the authors examined altitudinal gradients in daily mean air temperature along six transects across four glaciers in the Canadian high Arctic. The dataset includes over 58 000 daily averaged temperature measurements from 69 sensors covering the period 1988–2007. Temperature lapse rates near glacier surfaces vary on both daily and seasonal time scales, are consistently lower than the MALR (ablation season mean: 4.9°C km−1), and exhibit strong regional covariance. A significant fraction of the daily variability in lapse rates is associated with changes in free-atmospheric temperatures (higher temperatures = lower lapse rates). The temperature fields generated by downscaling point location summit elevation temperatures to the glacier surface using temporally variable lapse rates are a substantial improvement over those generated using the static MALR. These findings suggest that lower near-surface temperature lapse rates can be expected under a warming climate and that the air temperature near the glacier surface is less sensitive to changes in the temperature of the free atmosphere than is generally assumed.

An Analytical Model for Tropical Relative Humidity

2014 ◽  
Vol 27 (19) ◽  
pp. 7432-7449 ◽  
Author(s):  
David M. Romps
Keyword(s):  
Relative Humidity ◽  
Analytical Model ◽  
Climate Models ◽  
Global Climate ◽  
Invariant Function ◽  
Global Climate Models ◽  
Lapse Rate ◽  
Temperature Lapse Rate ◽  
Cloud Resolving Model ◽  
Simple Ratio

Abstract An analytical model is derived for tropical relative humidity using only the Clausius–Clapeyron relation, hydrostatic balance, and a bulk-plume water budget. This theory is constructed for radiative–convective equilibrium and compared against a cloud-resolving model. With some reinterpretation of variables, it can be applied more generally to the entire tropics. Given four variables—pressure, temperature, and the fractional entrainment and detrainment rates—the equations predict the relative humidity (RH) and the temperature lapse rate analytically. The RH is a simple ratio involving the fractional detrainment rate and the water-vapor lapse rate. When integrated upward in height, the equations give profiles of RH and temperature for a convecting atmosphere. The theory explains the magnitude of RH and the “C” shape of the tropospheric RH profile. It also predicts that RH is an invariant function of temperature as the atmosphere warms, and this behavior matches what has been seen in global climate models and what is demonstrated here with cloud-resolving simulations. Extending the theory to include the evaporation of hydrometeors, a lower bound is derived for the precipitation efficiency (PE) at each height: PE &gt; 1 − RH. In a cloud-resolving simulation, this constraint is obeyed with the PE profile taking the shape of an inverted C shape.

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