Primary production calculations for sea ice from bio-optical observations in the Baltic Sea

Abstract Bio-optics is a powerful approach for estimating photosynthesis rates, but has seldom been applied to sea ice, where measuring photosynthesis is a challenge. We measured absorption coefficients of chromophoric dissolved organic matter (CDOM), algae, and non-algal particles along with solar radiation, albedo and transmittance at four sea-ice stations in the Gulf of Finland, Baltic Sea. This unique compilation of optical and biological data for Baltic Sea ice was used to build a radiative transfer model describing the light field and the light absorption by algae in 1-cm increments. The maximum quantum yields and photoadaptation of photosynthesis were determined from 14C-incorporation in photosynthetic-irradiance experiments using melted ice. The quantum yields were applied to the radiative transfer model estimating the rate of photosynthesis based on incident solar irradiance measured at 1-min intervals. The calculated depth-integrated mean primary production was 5 mg C m–2 d–1 for the surface layer (0–20 cm ice depth) at Station 3 (fast ice) and 0.5 mg C m–2 d–1 for the bottom layer (20–57 cm ice depth). Additional calculations were performed for typical sea ice in the area in March using all ice types and a typical light spectrum, resulting in depth-integrated mean primary production rates of 34 and 5.6 mg C m–2 d–1 in surface ice and bottom ice, respectively. These calculated rates were compared to rates determined from 14C incorporation experiments with melted ice incubated in situ. The rate of the calculated photosynthesis and the rates measured in situ at Station 3 were lower than those calculated by the bio-optical algorithm for typical conditions in March in the Gulf of Finland by the bio-optical algorithm. Nevertheless, our study shows the applicability of bio-optics for estimating the photosynthesis of sea-ice algae.

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SEVIRI Hyper-Fast Forward Model with Application to Emissivity Retrieval

Sensors ◽

10.3390/s19071532 ◽

2019 ◽

Vol 19 (7) ◽

pp. 1532 ◽

Cited By ~ 1

Author(s):

Guido Masiello ◽

Carmine Serio ◽

Sara Venafra ◽

Laurent Poutier ◽

Frank-M. Göttsche

Keyword(s):

Radiative Transfer ◽

Real Time ◽

Forward Model ◽

Radiative Transfer Model ◽

Computational Time ◽

Transfer Model ◽

Real Time Processing ◽

In Situ Observations ◽

Infrared Radiances

Timely processing of observations from multi-spectral imagers, such as SEVIRI (Spinning Enhanced Visible and Infrared Imager), largely depends on fast radiative transfer calculations. This paper mostly concerns the development and implementation of a new forward model for SEVIRI to be applied to real time processing of infrared radiances. The new radiative transfer model improves computational time by a factor of ≈7 compared to the previous versions and makes it possible to process SEVIRI data at nearly real time. The new forward model has been applied for the retrieval of surface parameters. Although the scheme can be applied for the simultaneous retrieval of temperature and emissivity, the paper mostly focuses on emissivity. The inverse scheme relies on a Kalman filter approach, which allows us to exploit a sequential processing of SEVIRI observations. Based on the new forward model, the paper also presents a validation retrieval performed with in situ observations acquired during a field experiment carried out in 2017 at Gobabeb (Namib desert) validation station. Furthermore, a comparison with IASI (Infrared Atmospheric Sounder Interferometer) emissivity retrievals has been performed as well. It has been found that the retrieved emissivities are in good agreement with each other and with in situ observations, i.e., average differences are generally well below 0.01.

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The color of melt ponds on Arctic sea ice

The Cryosphere ◽

10.5194/tc-12-1331-2018 ◽

2018 ◽

Vol 12 (4) ◽

pp. 1331-1345 ◽

Cited By ~ 6

Author(s):

Peng Lu ◽

Matti Leppäranta ◽

Bin Cheng ◽

Zhijun Li ◽

Larysa Istomina ◽

...

Keyword(s):

Radiative Transfer ◽

Sea Ice ◽

Arctic Sea Ice ◽

Radiative Transfer Model ◽

Ice Thickness ◽

Transfer Model ◽

Blue Color ◽

Validation Data ◽

Melt Ponds ◽

Arctic Sea

Abstract. Pond color, which creates the visual appearance of melt ponds on Arctic sea ice in summer, is quantitatively investigated using a two-stream radiative transfer model for ponded sea ice. The upwelling irradiance from the pond surface is determined and then its spectrum is transformed into RGB (red, green, blue) color space using a colorimetric method. The dependence of pond color on various factors such as water and ice properties and incident solar radiation is investigated. The results reveal that increasing underlying ice thickness Hi enhances both the green and blue intensities of pond color, whereas the red intensity is mostly sensitive to Hi for thin ice (Hi  <  1.5 m) and to pond depth Hp for thick ice (Hi  >  1.5 m), similar to the behavior of melt-pond albedo. The distribution of the incident solar spectrum F0 with wavelength affects the pond color rather than its intensity. The pond color changes from dark blue to brighter blue with increasing scattering in ice, and the influence of absorption in ice on pond color is limited. The pond color reproduced by the model agrees with field observations for Arctic sea ice in summer, which supports the validity of this study. More importantly, the pond color has been confirmed to contain information about meltwater and underlying ice, and therefore it can be used as an index to retrieve Hi and Hp. Retrievals of Hi for thin ice (Hi  <  1 m) agree better with field measurements than retrievals for thick ice, but those of Hp are not good. The analysis of pond color is a new potential method to obtain thin ice thickness in summer, although more validation data and improvements to the radiative transfer model will be needed in future.

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A Refined Four-Stream Radiative Transfer Model for Row-Planted Crops

Remote Sensing ◽

10.3390/rs12081290 ◽

2020 ◽

Vol 12 (8) ◽

pp. 1290 ◽

Cited By ~ 1

Author(s):

Xu Ma ◽

Tiejun Wang ◽

Lei Lu

Keyword(s):

Radiative Transfer ◽

Computer Simulations ◽

Radiative Transfer Model ◽

Transfer Model ◽

Growth Stages ◽

Canopy Reflectance ◽

Transfer Equations ◽

Radiative Transfer Equations ◽

Different Growth Stages

In modeling the canopy reflectance of row-planted crops, neglecting horizontal radiative transfer may lead to an inaccurate representation of vegetation energy balance and further cause uncertainty in the simulation of canopy reflectance at larger viewing zenith angles. To reduce this systematic deviation, here we refined the four-stream radiative transfer equations by considering horizontal radiation through the lateral “walls”, considered the radiative transfer between rows, then proposed a modified four-stream (MFS) radiative transfer model using single and multiple scattering. We validated the MFS model using both computer simulations and in situ measurements, and found that the MFS model can be used to simulate crop canopy reflectance at different growth stages with an accuracy comparable to the computer simulations (RMSE < 0.002 in the red band, RMSE < 0.019 in NIR band). Moreover, the MFS model can be successfully used to simulate the reflectance of continuous (RMSE = 0.012) and row crop canopies (RMSE < 0.023), and therefore addressed the large viewing zenith angle problems in the previous row model based on four-stream radiative transfer equations. Our results demonstrate that horizontal radiation is an important factor that needs to be considered in modeling the canopy reflectance of row-planted crops. Hence, the refined four-stream radiative transfer model is applicable to the real world.

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Aerosol trends as a potential driver of regional climate in the central United States: evidence from observations

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-13559-2017 ◽

2017 ◽

Vol 17 (22) ◽

pp. 13559-13572 ◽

Cited By ~ 6

Author(s):

Daniel H. Cusworth ◽

Loretta J. Mickley ◽

Eric M. Leibensperger ◽

Michael J. Iacono

Keyword(s):

United States ◽

Radiative Transfer ◽

Southeastern United States ◽

Radiant Energy ◽

Surface Radiation ◽

Radiation Budget ◽

Radiative Transfer Model ◽

Transfer Model ◽

Clear Sky

Abstract. In situ surface observations show that downward surface solar radiation (SWdn) over the central and southeastern United States (US) has increased by 0.58–1.0 Wm−2 a−1 over the 2000–2014 time frame, simultaneously with reductions in US aerosol optical depth (AOD) of 3.3–5.0  ×  10−3 a−1. Establishing a link between these two trends, however, is challenging due to complex interactions between aerosols, clouds, and radiation. Here we investigate the clear-sky aerosol–radiation effects of decreasing US aerosols on SWdn and other surface variables by applying a one-dimensional radiative transfer to 2000–2014 measurements of AOD at two Surface Radiation Budget Network (SURFRAD) sites in the central and southeastern United States. Observations characterized as clear-sky may in fact include the effects of thin cirrus clouds, and we consider these effects by imposing satellite data from the Clouds and Earth's Radiant Energy System (CERES) into the radiative transfer model. The model predicts that 2000–2014 trends in aerosols may have driven clear-sky SWdn trends of +1.35 Wm−2 a−1 at Goodwin Creek, MS, and +0.93 Wm−2 a−1 at Bondville, IL. While these results are consistent in sign with observed trends, a cross-validated multivariate regression analysis shows that AOD reproduces 20–26 % of the seasonal (June–September, JJAS) variability in clear-sky direct and diffuse SWdn at Bondville, IL, but none of the JJAS variability at Goodwin Creek, MS. Using in situ soil and surface flux measurements from the Ameriflux network and Illinois Climate Network (ICN) together with assimilated meteorology from the North American Land Data Assimilation System (NLDAS), we find that sunnier summers tend to coincide with increased surface air temperature and soil moisture deficits in the central US. The 1990–2015 trends in the NLDAS SWdn over the central US are also of a similar magnitude to our modeled 2000–2014 clear-sky trends. Taken together, these results suggest that climate and regional hydrology in the central US are sensitive to the recent reductions in aerosol concentrations. Our work has implications for severely polluted regions outside the US, where improvements in air quality due to reductions in the aerosol burden could inadvertently pose an enhanced climate risk.

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An Assessment of SAPHIR Calibration Using Quality Tropical Soundings

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-14-00054.1 ◽

2015 ◽

Vol 32 (1) ◽

pp. 61-78 ◽

Cited By ~ 19

Author(s):

G. Clain ◽

H. Brogniez ◽

V. H. Payne ◽

V. O. John ◽

M. Luo

Keyword(s):

Radiative Transfer ◽

Incidence Angle ◽

Intraseasonal Variability ◽

Sensor Data ◽

Radiative Transfer Model ◽

Transfer Model ◽

Water Vapor Absorption ◽

Infrared Observation ◽

Cross Track

AbstractThe Sondeur Atmosphérique du Profil d’Humidité Intertropicale par Radiométrie (SAPHIR) instrument on board the Megha-Tropiques (MT) platform is a cross-track, multichannel microwave humidity sounder with six channels near the 183.31-GHz water vapor absorption line, a maximum scan angle of 42.96° (resulting in a maximum incidence angle of 50.7°), a 1700-km-wide swath, and a footprint resolution of 10 km at nadir. SAPHIR L1A2 brightness temperature (BT) observations have been compared to BTs simulated by the radiative transfer model (RTM) Radiative Transfer for the Television and Infrared Observation Satellite (TIROS) Operational Vertical Sounder (RTTOV-10), using in situ measurements from radiosondes as input. Selected radiosonde humidity observations from the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year (CINDY)–Dynamics of the Madden–Julian Oscillation (DYNAMO) campaign (September 2011–March 2012) were spatiotemporally collocated with MT overpasses. Although several sonde systems were used during the campaign, all of the sites selected for this study used the Vaisala RS92-SGPD system and were chosen in order to avoid discrepancies in data quality and biases.To interpret the results of the comparison between the sensor data and the RTM simulations, uncertainties associated with the data processing must be propagated throughout the evaluation. The magnitude of the bias was found to be dependent on the observing channel, increasing from 0.18 K for the 183.31 ± 0.2-GHz channel to 2.3 K for the 183.31 ± 11-GHz channel. Uncertainties and errors that could impact the BT biases were investigated. These can be linked to the RTM input and design, the radiosonde observations, the chosen methodology of comparison, and the SAPHIR instrument itself.

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Optical properties of sea ice doped with black carbon – an experimental and radiative-transfer modelling comparison

The Cryosphere ◽

10.5194/tc-11-2867-2017 ◽

2017 ◽

Vol 11 (6) ◽

pp. 2867-2881 ◽

Cited By ~ 2

Author(s):

Amelia A. Marks ◽

Maxim L. Lamare ◽

Martin D. King

Keyword(s):

Radiative Transfer ◽

Sea Ice ◽

Black Carbon ◽

Cross Sections ◽

Extinction Coefficient ◽

Radiative Transfer Model ◽

First Year ◽

Transfer Model ◽

Ice Fabrics ◽

Scattering Cross Sections

Abstract. Radiative-transfer calculations of the light reflectivity and extinction coefficient in laboratory-generated sea ice doped with and without black carbon demonstrate that the radiative-transfer model TUV-snow can be used to predict the light reflectance and extinction coefficient as a function of wavelength. The sea ice is representative of first-year sea ice containing typical amounts of black carbon and other light-absorbing impurities. The experiments give confidence in the application of the model to predict albedo of other sea ice fabrics. Sea ices, ∼  30 cm thick, were generated in the Royal Holloway Sea Ice Simulator ( ∼  2000 L tanks) with scattering cross sections measured between 0.012 and 0.032 m2 kg−1 for four ices. Sea ices were generated with and without ∼  5 cm upper layers containing particulate black carbon. Nadir reflectances between 0.60 and 0.78 were measured along with extinction coefficients of 0.1 to 0.03 cm−1 (e-folding depths of 10–30 cm) at a wavelength of 500 nm. Values were measured between light wavelengths of 350 and 650 nm. The sea ices generated in the Royal Holloway Sea Ice Simulator were found to be representative of natural sea ices. Particulate black carbon at mass ratios of ∼  75, ∼  150 and ∼  300 ng g−1 in a 5 cm ice layer lowers the albedo to 97, 90 and 79 % of the reflectivity of an undoped clean sea ice (at a wavelength of 500 nm).

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The derivation of water volume reflectances from airborne MSS data using in situ water volume reflectances, and a combined optimization technique and radiative transfer model

International Journal of Remote Sensing ◽

10.1080/01431169008955071 ◽

1990 ◽

Vol 11 (6) ◽

pp. 979-998 ◽

Cited By ~ 10

Author(s):

ELIJAH W. RAMSEY III ◽

JOHN R. JENSEN

Keyword(s):

Radiative Transfer ◽

Optimization Technique ◽

Radiative Transfer Model ◽

Water Volume ◽

Transfer Model

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Multi-angular thermal infrared emission characteristics of Bohai Sea ice based on in situ measurements

Journal of Glaciology ◽

10.3189/2015jog14j143 ◽

2015 ◽

Vol 61 (229) ◽

pp. 864-874 ◽

Cited By ~ 1

Author(s):

Jinlong Chao ◽

Chengyu Liu ◽

Yingjun Xu ◽

Wei Gu ◽

Ying Li ◽

...

Keyword(s):

Radiative Transfer ◽

Sea Ice ◽

Bohai Sea ◽

Robust Regression ◽

Thermal Infrared ◽

In Situ Measurements ◽

Transfer Model ◽

Emission Characteristics ◽

Relative Emissivity

AbstractWe report on the radiative transfer process and optical properties of sea ice in the thermal infrared (TIR) band, presenting two new linear kernel driver models (Relative Emissivity Distribution Function, REDF) that describe TIR emission characteristics of smooth and rough ice. In order to test the models and determine the necessary coefficients, in situ measurements from the Bohai Sea were carried out during the 2011/12 and 2012/13 boreal winters. The results show that the relative emissivity of smooth sea ice decreases along with increasing viewing zenith angle, and the shape of the relative emissivity curve is similar to that of an ideal plane. Affected by parameters such as roughness and surface temperature distribution, the anisotropy of relative emissivity of sea ice with a high degree of roughness is stronger relative to the cosine emitter. The model coefficients were also obtained using a robust regression method based on the measured data. The presented models are more practical than the numerical radiative transfer model and can be used for multi-angular TIR remote sensing.

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