A high resolution infrared radiative transfer scheme to study the interaction of radiation with cloud

Abstract. This study evaluates the impact of a new snow and ice albedo and radiative transfer scheme on the surface mass and energy budget for the Greenland ice sheet in the latest version of the regional climate model RACMO2, version 2.3p3. We also evaluate the modeled (sub)surface temperature and snow melt, as subsurface heating by radiation penetration now occurs. The results are compared to the previous model version and are evaluated against stake measurements and automatic weather station data of the K-transect and PROMICE projects. In addition, subsurface snow temperature profiles are compared at the K-transect, Summit and southeast Greenland. The surface mass balance is in good agreement with observations, and only changes considerably with respect to the previous RACMO2 version around the ice margins and in the percolation zone. Snow melt and refreezing, on the other hand, are changed more substantially in various regions due to the changed albedo representation, subsurface energy absorption and melt water percolation. Internal heating leads to considerably higher snow temperatures in summer, in agreement with observations, and introduces a shallow layer of subsurface melt.

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Supplementary material to "A multi-level canopy radiative transfer scheme for ORCHIDEE (SVN r2566), based on a domain-averaged structure factor"

10.5194/gmd-2016-280-supplement ◽

2016 ◽

Author(s):

Matthew J. McGrath ◽

James Ryder ◽

Bernard Pinty ◽

Juliane Otto ◽

Kim Naudts ◽

...

Keyword(s):

Radiative Transfer ◽

Structure Factor ◽

Transfer Scheme ◽

Supplementary Material ◽

Multi Level

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Probing the thermal state of the intergalactic medium at z > 5 with the transmission spikes in high-resolution Ly α forest spectra

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa907 ◽

2020 ◽

Vol 494 (4) ◽

pp. 5091-5109 ◽

Cited By ~ 5

Author(s):

Prakash Gaikwad ◽

Michael Rauch ◽

Martin G Haehnelt ◽

Ewald Puchwein ◽

James S Bolton ◽

...

Keyword(s):

High Resolution ◽

Radiative Transfer ◽

Intergalactic Medium ◽

Thermal State ◽

Neutral Hydrogen ◽

High Spectral Resolution ◽

Profile Fitting ◽

Density Relation ◽

Width Distribution ◽

Hydrodynamical Simulations

ABSTRACT We compare a sample of five high-resolution, high S/N Ly α forest spectra of bright 6 < z < ∼6.5 QSOs aimed at spectrally resolving the last remaining transmission spikes at z > 5 with those obtained from mock absorption spectra from the Sherwoodand Sherwood–Relics simulation suites of hydrodynamical simulations of the intergalactic medium (IGM). We use a profile-fitting procedure for the inverted transmitted flux, 1 − F, similar to the widely used Voigt profile fitting of the transmitted flux F at lower redshifts, to characterize the transmission spikes that probe predominately underdense regions of the IGM. We are able to reproduce the width and height distributions of the transmission spikes, both with optically thin simulations of the post-reionization Universe using a homogeneous UV background and full radiative transfer simulations of a late reionization model. We find that the width of the fitted components of the simulated transmission spikes is very sensitive to the instantaneous temperature of the reionized IGM. The internal structures of the spikes are more prominent in low temperature models of the IGM. The width distribution of the observed transmission spikes, which require high spectral resolution (≤ 8 km s−1) to be resolved, is reproduced for optically thin simulations with a temperature at mean density of T0 = (11 000 ± 1600, 10 500 ± 2100, 12 000 ± 2200) K at z = (5.4, 5.6, 5.8). This is weakly dependent on the slope of the temperature-density relation, which is favoured to be moderately steeper than isothermal. In the inhomogeneous, late reionization, full radiative transfer simulations where islands of neutral hydrogen persist to z ∼ 5.3, the width distribution of the observed transmission spikes is consistent with the range of T0 caused by spatial fluctuations in the temperature–density relation.

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High resolution and Monte Carlo additions to the SASKTRAN radiative transfer model

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-3357-2015 ◽

2015 ◽

Vol 8 (3) ◽

pp. 3357-3397 ◽

Cited By ~ 1

Author(s):

D. J. Zawada ◽

S. R. Dueck ◽

L. A. Rieger ◽

A. E. Bourassa ◽

N. D. Lloyd ◽

...

Keyword(s):

Monte Carlo ◽

High Resolution ◽

Radiative Transfer ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Reference Model ◽

Monte Carlo Model ◽

Radiative Transfer Model ◽

Transfer Model ◽

Systematic Bias

Abstract. The OSIRIS instrument on board the Odin spacecraft has been measuring limb scattered radiance since 2001. The vertical radiance profiles measured as the instrument nods are inverted, with the aid of the SASKTRAN radiative transfer model, to obtain vertical profiles of trace atmospheric constituents. Here we describe two newly developed modes of the SASKTRAN radiative transfer model: a high spatial resolution mode, and a Monte Carlo mode. The high spatial resolution mode is a successive orders model capable of modelling the multiply scattered radiance when the atmosphere is not spherically symmetric; the Monte Carlo mode is intended for use as a highly accurate reference model. It is shown that the two models agree in a wide variety of solar conditions to within 0.2%. As an example case for both models, Odin-OSIRIS scans were simulated with the Monte Carlo model and retrieved using the high resolution model. A systematic bias of up to 4% in retrieved ozone number density between scans where the instrument is scanning up or scanning down was identified. It was found that calculating the multiply scattered diffuse field at five discrete solar zenith angles is sufficient to eliminate the bias for typical Odin-OSIRIS geometries.

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Measurements of spectral snow albedo at Neumayer, Antarctica

Annales Geophysicae ◽

10.5194/angeo-24-7-2006 ◽

2006 ◽

Vol 24 (1) ◽

pp. 7-21 ◽

Cited By ~ 51

Author(s):

S. Wuttke ◽

G. Seckmeyer ◽

G. König-Langlo

Keyword(s):

Grain Size ◽

High Resolution ◽

Radiative Transfer ◽

Solar Zenith Angle ◽

Austral Summer ◽

Small Range ◽

Snow Surface ◽

Snow Conditions ◽

Directional Component ◽

Radiation Conditions

Abstract. Spectral albedo in high resolution, from 290 to 1050 nm, has been measured at Neumayer, Antarctica, (70°39' S, 8°15' W) during the austral summer 2003/2004. At 500 nm, the spectral albedo nearly reaches unity, with slightly lower values below and above 500 nm. Above 600 nm, the spectral albedo decreases to values between 0.45 and 0.75 at 1000 nm. For one cloudless case an albedo up to 1.01 at 500 nm could be determined. This can be explained by the larger directional component of the snow reflectivity for direct incidence, combined with a slightly mislevelled sensor and the snow surface not being perfectly horizontal. A possible explanation for an observed decline in albedo is an increase in snow grain size. The theoretically predicted increase in albedo with increasing solar zenith angle (SZA) could not be observed. This is explained by the small range of SZA during albedo measurements, combined with the effect of changing snow conditions outweighing the effect of changing SZA. The measured spectral albedo serves as input for radiative transfer models, describing radiation conditions in Antarctica.

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Using a Parameterization of a Radiative Transfer Model to Build High-Resolution Maps of Typical Clear-Sky UV Index in Catalonia, Spain

Journal of Applied Meteorology ◽

10.1175/jam2237.1 ◽

2005 ◽

Vol 44 (6) ◽

pp. 789-803 ◽

Cited By ~ 13

Author(s):

Jordi Badosa ◽

Josep-Abel González ◽

Josep Calbó ◽

Michiel van Weele ◽

Richard L. McKenzie

Keyword(s):

High Resolution ◽

Radiative Transfer ◽

Zenith Angle ◽

Solar Zenith Angle ◽

Absolute Error ◽

Single Scattering ◽

Radiative Transfer Model ◽

Transfer Model ◽

Uv Index ◽

Wide Range

Abstract To perform a climatic analysis of the annual UV index (UVI) variations in Catalonia, Spain (northeast of the Iberian Peninsula), a new simple parameterization scheme is presented based on a multilayer radiative transfer model. The parameterization performs fast UVI calculations for a wide range of cloudless and snow-free situations and can be applied anywhere. The following parameters are considered: solar zenith angle, total ozone column, altitude, aerosol optical depth, and single-scattering albedo. A sensitivity analysis is presented to justify this choice with special attention to aerosol information. Comparisons with the base model show good agreement, most of all for the most common cases, giving an absolute error within ±0.2 in the UVI for a wide range of cases considered. Two tests are done to show the performance of the parameterization against UVI measurements. One uses data from a high-quality spectroradiometer from Lauder, New Zealand [45.04°S, 169.684°E, 370 m above mean sea level (MSL)], where there is a low presence of aerosols. The other uses data from a Robertson–Berger-type meter from Girona, Spain (41.97°N, 2.82°E, 100 m MSL), where there is more aerosol load and where it has been possible to study the effect of aerosol information on the model versus measurement comparison. The parameterization is applied to a climatic analysis of the annual UVI variation in Catalonia, showing the contributions of solar zenith angle, ozone, and aerosols. High-resolution seasonal maps of typical UV index values in Catalonia are presented.

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Clear-Sky Mask for the Advanced Clear-Sky Processor for Oceans

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2010jtecha1413.1 ◽

2010 ◽

Vol 27 (10) ◽

pp. 1609-1623 ◽

Cited By ~ 29

Author(s):

B. Petrenko ◽

A. Ignatov ◽

Y. Kihai ◽

A. Heidinger

Keyword(s):

High Resolution ◽

Radiative Transfer ◽

Weather Prediction ◽

Radiative Transfer Model ◽

Transfer Model ◽

Clear Sky ◽

Brightness Temperatures ◽

Spatial Uniformity ◽

Uniformity Test ◽

Cross Platform

Abstract The Advanced Clear Sky Processor for Oceans (ACSPO) generates clear-sky products, such as SST, clear-sky radiances, and aerosol, from Advanced Very High Resolution Radiometer (AVHRR)-like measurements. The ACSPO clear-sky mask (ACSM) identifies clear-sky pixels within the ACSPO products. This paper describes the ACSM structure and compares the performances of ACSM and its predecessor, Clouds from AVHRR Extended Algorithm (CLAVRx). ACSM essentially employs online clear-sky radiative transfer simulations enabled within ACSPO with the Community Radiative Transfer Model (CRTM) in conjunction with numerical weather prediction atmospheric [Global Forecast System (GFS)] and SST [Reynolds daily high-resolution blended SST (DSST)] fields. The baseline ACSM tests verify the accuracy of fitting observed brightness temperatures with CRTM, check retrieved SST for consistency with Reynolds SST, and identify ambient cloudiness at the boundaries of cloudy systems. Residual cloud effects are screened out with several tests, adopted from CLAVRx, and with the SST spatial uniformity test designed to minimize misclassification of sharp SST gradients as clouds. Cross-platform and temporal consistencies of retrieved SSTs are maintained by accounting for SST and brightness temperature biases, estimated within ACSPO online and independently from ACSM. The performance of ACSM is characterized in terms of statistics of deviations of retrieved SST from the DSST. ACSM increases the amount of “clear” pixels by 30% to 40% and improves statistics of retrieved SST compared with CLAVRx. ACSM is also shown to be capable of producing satisfactory statistics of SST anomalies if the reference SST field for the exact date of observations is unavailable at the time of processing.

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