Disk and circumsolar radiances in the presence of ice clouds

Päivi Pauliina Haapanala, Petri Räisänen, Greg M. McFarquhar, Jussi Tapani Tiira, Andreas Macke, Michael Kahnert, John DeVore, Timo Nousiainen

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The impact of ice clouds on solar disk and circumsolar radiances is investigated using a Monte Carlo radiative transfer model. The monochromatic direct and diffuse radiances are simulated at angles of 0 to 8° from the center of the sun. Input data for the model are derived from measurements conducted during the 2010 Small Particles in Cirrus (SPARTICUS) campaign together with state-of-the-art databases of optical properties of ice crystals and aerosols. For selected cases, the simulated radiances are compared with ground-based radiance measurements obtained by the Sun and Aureole Measurements (SAM) instrument.

First, the sensitivity of the radiances to the ice cloud properties and aerosol optical thickness is addressed. The angular dependence of the disk and circumsolar radiances is found to be most sensitive to assumptions about ice crystal roughness (or, more generally, non-ideal features of ice crystals) and size distribution, with ice crystal habit playing a somewhat smaller role. Second, in comparisons with SAM data, the ice cloud optical thickness is adjusted for each case so that the simulated radiances agree closely (i.e., within 3 %) with the measured disk radiances. Circumsolar radiances at angles larger than ≈ 3° are systematically underestimated when assuming smooth ice crystals, whereas the agreement with the measurements is better when rough ice crystals are assumed. Our results suggest that it may well be possible to infer the particle roughness directly from ground-based SAM measurements. In addition, the results show the necessity of correcting the ground-based measurements of direct radiation for the presence of diffuse radiation in the instrument's field of view, in particular in the presence of ice clouds.
Original languageEnglish
JournalAtmospheric Chemistry and Physics
Volume17
Issue number11
Pages (from-to)6865-6682
Number of pages18
ISSN1680-7316
DOIs
Publication statusPublished - 12 Jun 2017
MoE publication typeA1 Journal article-refereed

Fields of Science

  • 114 Physical sciences

Cite this

Haapanala, P. P., Räisänen, P., McFarquhar, G. M., Tiira, J. T., Macke, A., Kahnert, M., ... Nousiainen, T. (2017). Disk and circumsolar radiances in the presence of ice clouds. Atmospheric Chemistry and Physics, 17(11), 6865-6682. https://doi.org/10.5194/acp-17-6865-2017
Haapanala, Päivi Pauliina ; Räisänen, Petri ; McFarquhar, Greg M. ; Tiira, Jussi Tapani ; Macke, Andreas ; Kahnert, Michael ; DeVore, John ; Nousiainen, Timo. / Disk and circumsolar radiances in the presence of ice clouds. In: Atmospheric Chemistry and Physics. 2017 ; Vol. 17, No. 11. pp. 6865-6682.
@article{be9f079a27dd49b8a588f36fc5d665ff,
title = "Disk and circumsolar radiances in the presence of ice clouds",
abstract = "The impact of ice clouds on solar disk and circumsolar radiances is investigated using a Monte Carlo radiative transfer model. The monochromatic direct and diffuse radiances are simulated at angles of 0 to 8° from the center of the sun. Input data for the model are derived from measurements conducted during the 2010 Small Particles in Cirrus (SPARTICUS) campaign together with state-of-the-art databases of optical properties of ice crystals and aerosols. For selected cases, the simulated radiances are compared with ground-based radiance measurements obtained by the Sun and Aureole Measurements (SAM) instrument.First, the sensitivity of the radiances to the ice cloud properties and aerosol optical thickness is addressed. The angular dependence of the disk and circumsolar radiances is found to be most sensitive to assumptions about ice crystal roughness (or, more generally, non-ideal features of ice crystals) and size distribution, with ice crystal habit playing a somewhat smaller role. Second, in comparisons with SAM data, the ice cloud optical thickness is adjusted for each case so that the simulated radiances agree closely (i.e., within 3 {\%}) with the measured disk radiances. Circumsolar radiances at angles larger than ≈ 3° are systematically underestimated when assuming smooth ice crystals, whereas the agreement with the measurements is better when rough ice crystals are assumed. Our results suggest that it may well be possible to infer the particle roughness directly from ground-based SAM measurements. In addition, the results show the necessity of correcting the ground-based measurements of direct radiation for the presence of diffuse radiation in the instrument's field of view, in particular in the presence of ice clouds.",
keywords = "114 Physical sciences, shortwave radiation, Ice crystals, circumsolar",
author = "Haapanala, {P{\"a}ivi Pauliina} and Petri R{\"a}is{\"a}nen and McFarquhar, {Greg M.} and Tiira, {Jussi Tapani} and Andreas Macke and Michael Kahnert and John DeVore and Timo Nousiainen",
year = "2017",
month = "6",
day = "12",
doi = "10.5194/acp-17-6865-2017",
language = "English",
volume = "17",
pages = "6865--6682",
journal = "Atmospheric Chemistry and Physics",
issn = "1680-7316",
publisher = "COPERNICUS GESELLSCHAFT MBH",
number = "11",

}

Haapanala, PP, Räisänen, P, McFarquhar, GM, Tiira, JT, Macke, A, Kahnert, M, DeVore, J & Nousiainen, T 2017, 'Disk and circumsolar radiances in the presence of ice clouds' Atmospheric Chemistry and Physics, vol. 17, no. 11, pp. 6865-6682. https://doi.org/10.5194/acp-17-6865-2017

Disk and circumsolar radiances in the presence of ice clouds. / Haapanala, Päivi Pauliina; Räisänen, Petri; McFarquhar, Greg M.; Tiira, Jussi Tapani; Macke, Andreas; Kahnert, Michael; DeVore, John; Nousiainen, Timo.

In: Atmospheric Chemistry and Physics, Vol. 17, No. 11, 12.06.2017, p. 6865-6682.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Disk and circumsolar radiances in the presence of ice clouds

AU - Haapanala, Päivi Pauliina

AU - Räisänen, Petri

AU - McFarquhar, Greg M.

AU - Tiira, Jussi Tapani

AU - Macke, Andreas

AU - Kahnert, Michael

AU - DeVore, John

AU - Nousiainen, Timo

PY - 2017/6/12

Y1 - 2017/6/12

N2 - The impact of ice clouds on solar disk and circumsolar radiances is investigated using a Monte Carlo radiative transfer model. The monochromatic direct and diffuse radiances are simulated at angles of 0 to 8° from the center of the sun. Input data for the model are derived from measurements conducted during the 2010 Small Particles in Cirrus (SPARTICUS) campaign together with state-of-the-art databases of optical properties of ice crystals and aerosols. For selected cases, the simulated radiances are compared with ground-based radiance measurements obtained by the Sun and Aureole Measurements (SAM) instrument.First, the sensitivity of the radiances to the ice cloud properties and aerosol optical thickness is addressed. The angular dependence of the disk and circumsolar radiances is found to be most sensitive to assumptions about ice crystal roughness (or, more generally, non-ideal features of ice crystals) and size distribution, with ice crystal habit playing a somewhat smaller role. Second, in comparisons with SAM data, the ice cloud optical thickness is adjusted for each case so that the simulated radiances agree closely (i.e., within 3 %) with the measured disk radiances. Circumsolar radiances at angles larger than ≈ 3° are systematically underestimated when assuming smooth ice crystals, whereas the agreement with the measurements is better when rough ice crystals are assumed. Our results suggest that it may well be possible to infer the particle roughness directly from ground-based SAM measurements. In addition, the results show the necessity of correcting the ground-based measurements of direct radiation for the presence of diffuse radiation in the instrument's field of view, in particular in the presence of ice clouds.

AB - The impact of ice clouds on solar disk and circumsolar radiances is investigated using a Monte Carlo radiative transfer model. The monochromatic direct and diffuse radiances are simulated at angles of 0 to 8° from the center of the sun. Input data for the model are derived from measurements conducted during the 2010 Small Particles in Cirrus (SPARTICUS) campaign together with state-of-the-art databases of optical properties of ice crystals and aerosols. For selected cases, the simulated radiances are compared with ground-based radiance measurements obtained by the Sun and Aureole Measurements (SAM) instrument.First, the sensitivity of the radiances to the ice cloud properties and aerosol optical thickness is addressed. The angular dependence of the disk and circumsolar radiances is found to be most sensitive to assumptions about ice crystal roughness (or, more generally, non-ideal features of ice crystals) and size distribution, with ice crystal habit playing a somewhat smaller role. Second, in comparisons with SAM data, the ice cloud optical thickness is adjusted for each case so that the simulated radiances agree closely (i.e., within 3 %) with the measured disk radiances. Circumsolar radiances at angles larger than ≈ 3° are systematically underestimated when assuming smooth ice crystals, whereas the agreement with the measurements is better when rough ice crystals are assumed. Our results suggest that it may well be possible to infer the particle roughness directly from ground-based SAM measurements. In addition, the results show the necessity of correcting the ground-based measurements of direct radiation for the presence of diffuse radiation in the instrument's field of view, in particular in the presence of ice clouds.

KW - 114 Physical sciences

KW - shortwave radiation

KW - Ice crystals

KW - circumsolar

U2 - 10.5194/acp-17-6865-2017

DO - 10.5194/acp-17-6865-2017

M3 - Article

VL - 17

SP - 6865

EP - 6682

JO - Atmospheric Chemistry and Physics

JF - Atmospheric Chemistry and Physics

SN - 1680-7316

IS - 11

ER -