Possibility of the Visible-Channel Calibration Using Deep Convective Clouds Overshooting the TTL

Abstract The authors examined the possible use of deep convective clouds (DCCs), defined as clouds that overshoot the tropical tropopause layer (TTL), for the calibration of satellite measurements at solar channels. DCCs are identified in terms of the Moderate Resolution Imaging Spectroradiometer (MODIS) 10.8-μm brightness temperature (TB11) on the basis of a criterion specified by TB11 ≤ 190 K. To determine the characteristics of these clouds, the MODIS-based cloud optical thickness (COT) and effective radius (re) for a number of identified DCCs are analyzed. It is found that COT values for most of the 4249 DCC pixels observed in January 2006 are close to 100. Based on the MODIS quality-assurance information, 90% and 70.2% of the 4249 pixels have COT larger than 100 and 150, respectively. On the other hand, the re values distributed between 15 and 25 μm show a sharp peak centered approximately at 20 μm. Radiances are simulated at the MODIS 0.646-μm channel by using a radiative transfer model under homogeneous overcast ice cloudy conditions for COT = 200 and re = 20 μm. These COT and re values are assumed to be typical for DCCs. A comparison between the simulated radiances and the corresponding Terra/Aqua MODIS measurements for 6 months in 2006 demonstrates that, on a daily basis, visible-channel measurements can be calibrated within an uncertainty range of ±5%. Because DCCs are abundant over the tropics and can be identified from infrared measurements, the present method can be applied to the calibration of a visible-channel sensor aboard a geostationary or low-orbiting satellite platform.

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Carbon monoxide total column retrievals from TROPOMI shortwave infrared measurements

Atmospheric Measurement Techniques ◽

10.5194/amt-9-4955-2016 ◽

2016 ◽

Vol 9 (10) ◽

pp. 4955-4975 ◽

Cited By ~ 26

Author(s):

Jochen Landgraf ◽

Joost aan de Brugh ◽

Remco Scheepmaker ◽

Tobias Borsdorff ◽

Haili Hu ◽

...

Keyword(s):

Boundary Layer ◽

Carbon Monoxide ◽

Transport Model ◽

Radiative Transfer Model ◽

Transfer Model ◽

Atmospheric Scattering ◽

Clear Sky ◽

Infrared Measurements ◽

Shortwave Infrared ◽

Total Column

Abstract. The Tropospheric Monitoring Instrument (TROPOMI) spectrometer is the single payload of the Copernicus Sentinel 5 Precursor (S5P) mission. It measures Earth radiance spectra in the shortwave infrared spectral range around 2.3 µm with a dedicated instrument module. These measurements provide carbon monoxide (CO) total column densities over land, which for clear sky conditions are highly sensitive to the tropospheric boundary layer. For cloudy atmospheres over land and ocean, the column sensitivity changes according to the light path through the atmosphere. In this study, we present the physics-based operational S5P algorithm to infer atmospheric CO columns satisfying the envisaged accuracy ( <  15 %) and precision ( <  10 %) both for clear sky and cloudy observations with low cloud height. Here, methane absorption in the 2.3 µm range is combined with methane abundances from a global chemical transport model to infer information on atmospheric scattering. For efficient processing, we deploy a linearized two-stream radiative transfer model as forward model and a profile scaling approach to adjust the CO abundance in the inversion. Based on generic measurement ensembles, including clear sky and cloudy observations, we estimated the CO retrieval precision to be ≤  11 % for surface albedo ≥  0.03 and solar zenith angle ≤  70°. CO biases of ≤  3 % are introduced by inaccuracies in the methane a priori knowledge. For strongly enhanced CO concentrations in the tropospheric boundary layer and for cloudy conditions, CO errors in the order of 8 % can be introduced by the retrieval of cloud parameters of our algorithm. Moreover, we estimated the effect of a distorted spectral instrument response due to the inhomogeneous illumination of the instrument entrance slit in the flight direction to be <  2 % with pseudo-random characteristics when averaging over space and time. Finally, the CO data exploitation is demonstrated for a TROPOMI orbit of simulated shortwave infrared measurements. Overall, the study demonstrates that for an instrument that performs in compliance with the pre-flight specifications, the CO product will meet the required product performance well.

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Tropical deep convective life cycle: Cb-anvil cloud microphysics from high-altitude aircraft observations

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-13223-2014 ◽

2014 ◽

Vol 14 (23) ◽

pp. 13223-13240 ◽

Cited By ~ 12

Author(s):

W. Frey ◽

S. Borrmann ◽

F. Fierli ◽

R. Weigel ◽

V. Mitev ◽

...

Keyword(s):

Life Cycle ◽

High Altitude ◽

Potential Temperature ◽

Cloud Microphysics ◽

Mature Stage ◽

Convective System ◽

Ice Crystal ◽

Convective Clouds ◽

Tropical Tropopause ◽

Deep Convective Clouds

Abstract. The case study presented here focuses on the life cycle of clouds in the anvil region of a tropical deep convective system. During the SCOUT-O3 campaign from Darwin, Northern Australia, the Hector storm system has been probed by the Geophysica high-altitude aircraft. Clouds were observed by in situ particle probes, a backscatter sonde, and a miniature lidar. Additionally, aerosol number concentrations have been measured. On 30 November 2005 a double flight took place and Hector was probed throughout its life cycle in its developing, mature, and dissipating stage. The two flights were four hours apart and focused on the anvil region of Hector in altitudes between 10.5 and 18.8 km (i.e. above 350 K potential temperature). Trajectory calculations, satellite imagery, and ozone measurements have been used to ensure that the same cloud air masses have been probed in both flights. The size distributions derived from the measurements show a change not only with increasing altitude but also with the evolution of Hector. Clearly different cloud to aerosol particle ratios as well as varying ice crystal morphology have been found for the different development stages of Hector, indicating different freezing mechanisms. The development phase exhibits the smallest ice particles (up to 300 μm) with a rather uniform morphology. This is indicative for rapid glaciation during Hector's development. Sizes of ice crystals are largest in the mature stage (larger than 1.6 mm) and even exceed those of some continental tropical deep convective clouds, also in their number concentrations. The backscatter properties and particle images show a change in ice crystal shape from the developing phase to rimed and aggregated particles in the mature and dissipating stages; the specific shape of particles in the developing phase cannot be distinguished from the measurements. Although optically thin, the clouds in the dissipating stage have a large vertical extent (roughly 6 km) and persist for at least 6 h. Thus, the anvils of these high-reaching deep convective clouds have a high potential for affecting the tropical tropopause layer by modifying the humidity and radiative budget, as well as for providing favourable conditions for subvisible cirrus formation. The involved processes may also influence the amount of water vapour that ultimately reaches the stratosphere in the tropics.

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Assessment of the calibration performance of satellite visible channels using cloud targets: application to Meteosat-8/9 and MTSAT-1R

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-12629-2010 ◽

2010 ◽

Vol 10 (5) ◽

pp. 12629-12664 ◽

Cited By ~ 3

Author(s):

S.-H. Ham ◽

B. J. Sohn

Keyword(s):

Three Dimensional ◽

Radiative Transfer Model ◽

Transfer Model ◽

Perfect Agreement ◽

Convective Clouds ◽

Calibration Methods ◽

Matching Technique ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer

Abstract. To examine the calibration performance of the Meteosat-8/9 Spinning Enhanced Visible Infra-Red Imager (SEVIRI) 0.640-μm and the Multi-functional Transport Satellite (MTSAT)-1R 0.724-μm channels, three calibration methods were employed. First, a ray-matching technique was used to compare Meteosat-8/9 and MTSAT-1R visible channel reflectances with the well-calibrated Moderate Resolution Imaging Spectroradiometer (MODIS) 0.646-μm channel reflectances. Spectral differences of the response function between the two channels of interest were taken into account for the comparison. Second, collocated MODIS cloud products were used as inputs to a radiative transfer model to calculate Meteosat-8/9 and MTSAT-1R visible channel reflectances. In the simulation, the three-dimensional radiative effect of clouds was taken into account and was subtracted from the simulated reflectance to remove the simulation bias caused by the plane-parallel assumption. Third, an independent method used the typical optical properties of deep convective clouds (DCCs) to simulate reflectances of selected DCC targets. Although the three methods were not in perfect agreement, the results suggest that calibration accuracies were within 5–10% for the Meteosat-8 0.640-μm channel, 4–9% for the Meteosat-9 0.640-μm channel, and up to 20% for the MTSAT-1R 0.724-μm channel. The results further suggest that the solar channel calibration scheme combining the three methods in this paper can be used as a tool to monitor the calibration performance of visible sensors that are particularly not equipped with an onboard calibration system.

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Optimized Surface Radiation Fields Derived from Meteosat Imagery and a Regional Atmospheric Model

Journal of Hydrometeorology ◽

10.1175/jhm-389.1 ◽

2004 ◽

Vol 5 (6) ◽

pp. 1091-1101 ◽

Cited By ~ 11

Author(s):

Dirk Meetschen ◽

Bart J. J. M. van den Hurk ◽

Felix Ament ◽

Matthias Drusch

Keyword(s):

Longwave Radiation ◽

Atmospheric Model ◽

Daily Basis ◽

Surface Radiation ◽

Radiative Transfer Model ◽

Integration Scheme ◽

Transfer Model ◽

Integrated Monitoring ◽

Radiation Fields ◽

Nwp Model

Abstract High-quality fields of surface radiation fluxes are required for the development of Land Data Assimilation Systems. A fast offline integration scheme was developed to modify NWP model cloud fields based on Meteosat visible and infrared observations. From the updated cloud fields, downward shortwave and longwave radiation at the surface are computed using the NWP radiative transfer model. A dataset of 15 months covering Europe was produced and validated against measurements of ground stations on a daily basis. In situ measurements are available for 30 stations in the Netherlands and two Baseline Surface Radiation Network (BSRN) stations in Germany and France. The accuracy of shortwave surface radiation is increased when the integration system is applied. The rms error in the model forecast is found to be 32 and 42 W m−2 for the period from October 1999 to December 2000 for the two BSRN stations. These values are reduced to 21 and 25 W m−2 through the application of the integration scheme. During the summer months the errors are generally larger than in winter. Because of an integrated monitoring of surface albedo, the performance of the scheme is not affected by snow cover. The errors in the longwave radiation field of the original NWP model are already small. However, they are slightly reduced by applying the integration scheme.

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Upper-troposphere and lower-stratosphere water vapor retrievals from the 1400 and 1900 nm water vapor bands

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-7-10221-2014 ◽

2014 ◽

Vol 7 (10) ◽

pp. 10221-10248

Author(s):

B. C. Kindel ◽

P. Pilewskie ◽

K. S. Schmidt ◽

T. Thornberry ◽

A. Rollins ◽

...

Keyword(s):

Water Vapor ◽

Near Infrared ◽

Lower Stratosphere ◽

Radiative Transfer Model ◽

Transfer Model ◽

Atmospheric Transmission ◽

Absorption Bands ◽

Upper Troposphere ◽

Tropical Tropopause ◽

Value Of Water

Abstract. Measuring water vapor in the upper troposphere and lower stratosphere is difficult due to the low mixing ratios found there, typically only a few parts per million. Here we examine near infrared spectra acquired with the Solar Spectral Flux Radiometer during the first science phase of the NASA Airborne Tropical Tropopause EXperiment. From the 1400 and 1900 nm absorption bands, we infer water vapor amounts in the tropical tropopause layer and adjacent regions between 14 and 18 km altitude. We compare these measurements to solar transmittance spectra produced with the MODerate resolution atmospheric TRANsmission (MODTRAN) radiative transfer model, using in situ water vapor, temperature, and pressure profiles acquired concurrently with the SSFR spectra. Measured and modeled transmittance values agree within 0.002, with some larger differences in the 1900 nm band (up to 0.004). Integrated water vapor amounts along the absorption path lengths of 3 to 6 km varied from 1.26 × 10−4 to 4.59 × 10−4 g cm−2. A 0.002 difference in absorptance at 1367 nm results in a 3.35 × 10−5 g cm−2 change of integrated water vapor amount, 0.004 absorptance change at 1870 nm results in 5.5 × 10−5 g cm−2 of water vapor. These are 27% (1367 nm) and 44% (1870 nm) differences at the lowest measured value of water vapor (1.26 × 10−4 g cm−2) and 7% (1367 nm) and 12% (1870 nm) differences at the highest measured value of water vapor (4.59 × 10−4 g cm−2). A potential method for extending this type of measurement from aircraft flight altitude to the top of the atmosphere (TOA) is discussed.

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Infrared measurements in the Arctic using two Atmospheric Emitted Radiance Interferometers

Atmospheric Measurement Techniques ◽

10.5194/amt-5-329-2012 ◽

2012 ◽

Vol 5 (2) ◽

pp. 329-344 ◽

Cited By ~ 21

Author(s):

Z. Mariani ◽

K. Strong ◽

M. Wolff ◽

P. Rowe ◽

V. Walden ◽

...

Keyword(s):

Radiative Forcing ◽

Atmospheric Temperature ◽

The Arctic ◽

Radiative Transfer Model ◽

Spectral Radiance ◽

Transfer Model ◽

Surface Cooling ◽

Radiative Balance ◽

Infrared Measurements ◽

The University

Abstract. The Extended-range Atmospheric Emitted Radiance Interferometer (E-AERI) is a moderate resolution (1 cm−1) Fourier transform infrared spectrometer for measuring the absolute downwelling infrared spectral radiance from the atmosphere between 400 and 3000 cm−1. The extended spectral range of the instrument permits monitoring of the 400–550 cm−1 (20–25 μm) region, where most of the infrared surface cooling currently occurs in the dry air of the Arctic. Spectra from the E-AERI have the potential to provide information about radiative balance, trace gases, and cloud properties in the Canadian high Arctic. Calibration, performance evaluation, and certification of the E-AERI were performed at the University of Wisconsin Space Science and Engineering Centre from September to October 2008. The instrument was then installed at the Polar Environment Atmospheric Research Laboratory (PEARL) Ridge Lab (610 m altitude) at Eureka, Nunavut, in October 2008, where it acquired one year of data. Measurements are taken every seven minutes year-round, including polar night when the solar-viewing spectrometers at PEARL are not operated. A similar instrument, the University of Idaho's Polar AERI (P-AERI), was installed at the Zero-altitude PEARL Auxiliary Laboratory (0PAL), 15 km away from the PEARL Ridge Lab, from March 2006 to June 2009. During the period of overlap, these two instruments provided calibrated radiance measurements from two altitudes. A fast line-by-line radiative transfer model is used to simulate the downwelling radiance at both altitudes; the largest differences (simulation-measurement) occur in spectral regions strongly influenced by atmospheric temperature and/or water vapour. The two AERI instruments at close proximity but located at two different altitudes are well-suited for investigating cloud forcing. As an example, it is shown that a thin, low ice cloud resulted in a 6% increase in irradiance. The presence of clouds creates a large surface radiative forcing in the Arctic, particularly in the 750–1200 cm−1 region where the downwelling radiance is several times greater than clear-sky radiances, which is significantly larger than in other more humid regions.

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Tropospheric ozone radiative forcing uncertainty due to pre-industrial fire and biogenic emissions

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-10937-2020 ◽

2020 ◽

Vol 20 (18) ◽

pp. 10937-10951

Author(s):

Matthew J. Rowlinson ◽

Alexandru Rap ◽

Douglas S. Hamilton ◽

Richard J. Pope ◽

Stijn Hantson ◽

...

Keyword(s):

Tropospheric Ozone ◽

Radiative Forcing ◽

Transport Model ◽

Radiative Transfer Model ◽

Biogenic Emissions ◽

Transfer Model ◽

Terrestrial Vegetation ◽

Uncertainty Range ◽

Ozone Concentrations ◽

Industrial Fire

Abstract. Tropospheric ozone concentrations are sensitive to natural emissions of precursor compounds. In contrast to existing assumptions, recent evidence indicates that terrestrial vegetation emissions in the pre-industrial era were larger than in the present day. We use a chemical transport model and a radiative transfer model to show that revised inventories of pre-industrial fire and biogenic emissions lead to an increase in simulated pre-industrial ozone concentrations, decreasing the estimated pre-industrial to present-day tropospheric ozone radiative forcing by up to 34 % (0.38 to 0.25 W m−2). We find that this change is sensitive to employing biomass burning and biogenic emissions inventories based on matching vegetation patterns, as the co-location of emission sources enhances the effect on ozone formation. Our forcing estimates are at the lower end of existing uncertainty range estimates (0.2–0.6 W m−2), without accounting for other sources of uncertainty. Thus, future work should focus on reassessing the uncertainty range of tropospheric ozone radiative forcing.

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Vertical profiles of droplet effective radius in shallow convective clouds

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-4633-2011 ◽

2011 ◽

Vol 11 (10) ◽

pp. 4633-4644 ◽

Cited By ~ 8

Author(s):

S. Zhang ◽

H. Xue ◽

G. Feingold

Keyword(s):

Radiative Forcing ◽

Effective Radius ◽

Radiative Transfer Model ◽

Transfer Model ◽

Liquid Water Path ◽

Cumulus Clouds ◽

Convective Clouds ◽

Additional Influence ◽

The Individual ◽

Vertical Inhomogeneity

Abstract. Conventional satellite retrievals can only provide information on cloud-top droplet effective radius (re). Given the fact that cloud ensembles in a satellite snapshot have different cloud-top heights, Rosenfeld and Lensky (1998) used the cloud-top height and the corresponding cloud-top re from the cloud ensembles in the snapshot to construct a profile of re representative of that in the individual clouds. This study investigates the robustness of this approach in shallow convective clouds based on results from large-eddy simulations (LES) for clean (aerosol mixing ratio Na = 25 mg−1), intermediate (Na = 100 mg−1), and polluted (Na = 2000 mg−1) conditions. The cloud-top height and the cloud-top re from the modeled cloud ensembles are used to form a constructed re profile, which is then compared to the in-cloud re profiles. For the polluted and intermediate cases where precipitation is negligible, the constructed re profiles represent the in-cloud re profiles fairly well with a low bias (about 10 %). The method used in Rosenfeld and Lensky (1998) is therefore validated for nonprecipitating shallow cumulus clouds. For the clean, drizzling case, the in-cloud re can be very large and highly variable, and quantitative profiling based on cloud-top re is less useful. The differences in re profiles between clean and polluted conditions derived in this manner are however, distinct. This study also investigates the subadiabatic characteristics of the simulated cumulus clouds to reveal the effect of mixing on re and its evolution. Results indicate that as polluted and moderately polluted clouds develop into their decaying stage, the subadiabatic fraction fad becomes smaller, representing a higher degree of mixing, and re becomes smaller (~10 %) and more variable. However, for the clean case, smaller fad corresponds to larger re (and larger re variability), reflecting the additional influence of droplet collision-coalescence and sedimentation on re. Finally, profiles of the vertically inhomogeneous clouds as simulated by the LES and those of the vertically homogeneous clouds are used as input to a radiative transfer model to study the effect of cloud vertical inhomogeneity on shortwave radiative forcing. For clouds that have the same liquid water path, re of a vertically homogeneous cloud must be about 76–90 % of the cloud-top re of the vertically inhomogeneous cloud in order for the two clouds to have the same shortwave radiative forcing.

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Vertical profiles of droplet effective radius in shallow convective clouds

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-30971-2010 ◽

2010 ◽

Vol 10 (12) ◽

pp. 30971-30998

Author(s):

S. Zhang ◽

H. Xue ◽

G. Feingold

Keyword(s):

Radiative Forcing ◽

Effective Radius ◽

Radiative Transfer Model ◽

Transfer Model ◽

Vertical Profiles ◽

Liquid Water Path ◽

Cumulus Clouds ◽

Convective Clouds ◽

Additional Influence ◽

Vertical Inhomogeneity

Abstract. Vertical profiles of droplet effective radius (re) in shallow convective clouds are investigated using results from large-eddy simulations (LES) for clean (aerosol mixing ratio Na=25 mg−1), intermediate (Na=100 mg−1), and polluted (Na=2000 mg−1) conditions. Cloud-top re for cloud populations comprising clouds with different heights and at different stages of their development are used to construct a vertical profile of re. For the polluted and intermediate cases where precipitation is negligible, the constructed re profiles represent the in-cloud re profiles fairly well with a low bias (about 10%). For the clean, drizzling case the in-cloud re can be very large and highly variable and profiling based on cloud-top re is less useful. The differences in re profiles between clean and polluted conditions derived in this manner are however, distinct. The subadiabatic characteristics of the simulated cumulus clouds are investigated to reveal the effect of mixing on re and its evolution. Results indicate that as polluted and moderately polluted clouds develop into their decaying stage, the subadiabatic fraction fad becomes smaller, representing a higher degree of mixing, and re becomes smaller (~10%) and more variable. However, for the clean case, smaller fad corresponds to larger re (and larger re variability), reflecting the additional influence of droplet collision-coalescence and sedimentation on re. Profiles of the vertically inhomogeneous clouds as simulated from the LES and those of the vertically homogeneous clouds are used as input to a radiative transfer model to study the effect of cloud vertical inhomogeneity on shortwave radiative forcing. For clouds that have the same liquid water path (LWP), re of a vertically homogeneous cloud must be about 76–90% of the cloud-top re of the vertically inhomogeneous cloud in order for the two clouds to have the same shortwave radiative forcing.

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Thermal inertia and roughness of the nucleus of comet 67P/Churyumov–Gerasimenko from MIRO and VIRTIS observations

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833104 ◽

2018 ◽

Vol 616 ◽

pp. A122 ◽

Cited By ~ 22

Author(s):

D. Marshall ◽

O. Groussin ◽

J.-B. Vincent ◽

Y. Brouet ◽

D. Kappel ◽

...

Keyword(s):

Surface Roughness ◽

Thermal Model ◽

Thermal Inertia ◽

Landing Site ◽

Radiative Transfer Model ◽

Transfer Model ◽

In Situ Data ◽

Infrared Measurements ◽

Subsurface Layers ◽

Comet 67P

Aims. Using data from the Rosetta mission to comet 67P/Churyumov–Gerasimenko, we evaluate the physical properties of the surface and subsurface of the nucleus and derive estimates for the thermal inertia (TI) and roughness in several regions on the largest lobe of the nucleus. Methods. We have developed a thermal model to compute the temperature on the surface and in the uppermost subsurface layers of the nucleus. The model takes heat conduction, self-heating, and shadowing effects into account. To reproduce the brightness temperatures measured by the MIRO instrument, the thermal model is coupled to a radiative transfer model to derive the TI. To reproduce the spatially resolved infrared measurements of the VIRTIS instrument, the thermal model is coupled to a radiance model to derive the TI and surface roughness. These methods are applied to Rosetta data from September 2014. Results. The resulting TI values from both instruments are broadly consistent with each other. From the millimetre channel on MIRO, we determine the TI in the subsurface to be <80 JK−1 m−2 s−0.5 for the Seth, Ash, and Aten regions. The submillimetre channel implies similar results but also suggests that higher values could be possible. A low TI is consistent with other MIRO measurements and in situ data from the MUPUS instrument at the final landing site of Philae. The VIRTIS results give a best-fitting value of 80 JK−1 m−2 s−0.5 and values in the range 40–160 JK−1 m−2 s−0.5 in the same areas. These observations also allow the subpixel scale surface roughness to be estimated and compared to images from the OSIRIS camera. The VIRTIS data imply that there is significant roughness on the infrared scale below the resolution of the available shape model and that, counter-intuitively, visually smooth terrain (centimetre scale) can be rough at small (micrometre–millimetre) scales, and visually rough terrain can be smooth at small scales.

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