Influence of local surface albedo variability and ice crystal shape on passive remote sensing of thin cirrus

Fricke, Christopher; Ehrlich, André; Jäkel, E.; Bohn, Birger; Wirth, Martin; Wendisch, Manfred

doi:10.5194/acp-14-1943-2014

Cited by 21 publications

(18 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This gave us the opportunity to perform measurements in cloudy and in cloud-free air masses. HALO was equipped with a spectrometer system operated by University of Leipzig together with an instrument for measuring the actinic flux in cooperation with Forschungszentrum Jülich (HALO-SR) (Fricke et al, 2014), an automated high-volume air sampling system (MIRAH -Measurements of Stable Isotope Ratios in Atmospheric Trace Gases on HALO) of University of Wuppertal (Krebsbach et al, 2013), and an ion trap mass spectrometer of DLR (Roiger et al, 2011). Additionally, and in the focus of this paper, the DIAL system WALES (Wirth et al, 2009) was provided by DLR Institute of Atmospheric Physics (IPA).…”

Section: Introductionmentioning

confidence: 99%

Potential of airborne lidar measurements for cirrus cloud studies

et al. 2014

Self Cite

View full text Add to dashboard Cite

Abstract. Aerosol and water vapour measurements were performed with the lidar system WALES of Deutsches Zentrum für Luft-und Raumfahrt (DLR) in October and November 2010 during the first mission with the new German research aircraft G55-HALO. Curtains composed of lidar profiles beneath the aircraft show the vertical and horizontal distribution and variability of water vapour mixing ratio and backscatter ratio above Germany. Two missions on 3 and 4 November 2010 were selected to derive the water vapour mixing ratio inside cirrus clouds from the lidar instrument. A good agreement was found with in situ observations performed on a second research aircraft flying below HALO. ECMWF analysis temperature data are used to derive relative humidity fields with respect to ice (RHi) inside and outside of cirrus clouds from the lidar water vapour observations. The RHi variability is dominated by small-scale fluctuations in the water vapour fields while the temperature variation has a minor impact. The most frequent in-cloud RHi value from lidar observations is 98 %. The RHi variance is smaller inside the cirrus than outside of the cloud. 2-D histograms of relative humidity and backscatter ratio show significant differences for in-cloud and out-of-cloud situations for two different cirrus cloud regimes. Combined with accurate temperature measurements, the lidar observations have a great potential for detailed statistical cirrus cloud and related humidity studies.

show abstract

Section: Introductionmentioning

confidence: 99%

Potential of airborne lidar measurements for cirrus cloud studies

et al. 2014

Self Cite

View full text Add to dashboard Cite

show abstract

“…The accuracy of the surface albedo assumed in the forward simulations influences the uncertainty of the retrieved cloud properties (Rolland and Liou, 2001;Fricke et al, 2014;. For vertically homogenous clouds, these studies found uncertainties of up to 83 % and 62 % in the retrieved values of τ and r eff , respectively, when an inaccurate surface albedo is assumed in the forward simulation.…”

Section: Heterogeneity Of the Surface Albedomentioning

confidence: 92%

Comparing Airborne and Satellite Retrievals of Optical and Microphysical Properties of Cirrus and Deep Convective Clouds using a Radiance Ratio Technique

Krisna

Wendisch

Ehrlich

et al. 2017

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Solar radiation reflected by cirrus and deep convective clouds (DCCs) was measured by the Spectral Modular Airborne Radiation Measurement System (SMART) installed on the German HALO (High Altitude and Long Range Research Aircraft) during the ML-CIRRUS and the ACRIDICON-CHUVA campaigns. In particular flights, HALO performed closely collocated measurements with overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS) on board of Aqua satellite. Based on the nadir upward radiance, the optical thickness τ and bulk particle effective radius r eff of cirrus and DCC 5 are retrieved using a radiance ratio algorithm which considers the cloud thermodynamic phase, the cloud vertical profile, multi layer clouds, and heterogeneity of the surface albedo. For the cirrus case, the comparison of τ ci and r eff,ci retrieved on the basis of SMART and MODIS upward radiances yields a normalized mean absolute deviation of 0.5 % for τ ci and 2.5 % for r eff,ci . While for the DCC case, the respective deviation is 5.9 % for τ dcc and 13.2 % for r eff,dcc . The larger deviations in case of DCC are mainly attributed to the fast cloud evolution and three-dimensional radiative effects. Measurements of spectral 10 radiance at near-infrared wavelengths with different absorption by cloud particles are employed to investigate the vertical profile of cirrus effective radius. The retrieved values of cirrus effective radius are further compared with corresponding in situ measurements using a vertical weighting method. Compared to the MODIS observation, spectral measurements of SMART provide an increased amount of information on the vertical distribution of particle sizes at cloud top, and therefore allow to reconstruct the profile of effective radius at cloud top. The retrieved effective radius differs to in situ measurements with 15 a normalized mean absolute deviation between 4 − 19 %, depending on the wavelength chosen in the retrieval algorithm.While, the MODIS cloud product underestimates the in situ measurements by 48 %. The presence of liquid water clouds below Atmos. Chem. Phys. Discuss., https://doi

show abstract

“…They showed that retrievals of clouds with τ < 0.5 are strongly influenced by variations in α. Based on RTS, Fricke et al (2014) concluded that I N measured in the nadir direction strongly depends on the underlying surface reflectivity and that uncertainties in assumed α may cause errors of up to 50 % in the retrieval of τ .…”

Section: Influence Of Surface Albedomentioning

confidence: 99%

“…This may introduce a bias in the retrieval of τ of up to 30 % when α is not accurately known or inhomogeneous (Fricke et al, 2014). Over dark ocean surfaces the radiance I reflected by the cirrus might be weak and can be on the same order of magnitude as Rayleigh scattering in the atmosphere.…”

mentioning

confidence: 99%

“…Ou et al (1993), Rolland et al (2000), and King et al (2004) adapted this method for ice clouds by introducing some modifications with regard to the thermodynamic phase and crystal shape of the ice particles. Especially due to the crystal shape and low values of τ , cirrus retrievals lead to additional uncertainties compared to liquid water clouds (Eichler et al, 2009;Fricke et al, 2014).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Potential of remote sensing of cirrus optical thickness by airborne spectral radiance measurements at different sideward viewing angles

et al. 2017

Self Cite

View full text Add to dashboard Cite

Abstract. Spectral radiance measurements collected in nadir and sideward viewing directions by two airborne passive solar remote sensing instruments, the Spectral Modular Airborne Radiation measurement sysTem (SMART) and the Differential Optical Absorption Spectrometer (mini-DOAS), are used to compare the remote sensing results of cirrus optical thickness τ . The comparison is based on a sensitivity study using radiative transfer simulations (RTS) and on data obtained during three airborne field campaigns: the North Atlantic Rainfall VALidation (NARVAL) mission, the MidLatitude Cirrus Experiment (ML-CIRRUS) and the Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems (ACRIDICON) campaign. Radiative transfer simulations are used to quantify the sensitivity of measured upward radiance I with respect to τ , ice crystal effective radius r eff , viewing angle of the sensor θ V , spectral surface albedo α, and ice crystal shape. From the calculations it is concluded that sideward viewing measurements are generally better suited than radiance data from the nadir direction to retrieve τ of optically thin cirrus, especially at wavelengths larger than λ = 900 nm. Using sideward instead of nadir-directed spectral radiance measurements significantly improves the sensitivity and accuracy in retrieving τ , in particular for optically thin cirrus of τ ≤ 2.The comparison of retrievals of τ based on nadir and sideward viewing radiance measurements from SMART, mini-DOAS and independent estimates of τ from an additional active remote sensing instrument, the Water Vapor Lidar Experiment in Space (WALES), shows general agreement within the range of measurement uncertainties. For the selected example a mean τ of 0.54 ± 0.2 is derived from SMART, and 0.49 ± 0.2 by mini-DOAS nadir channels, while WALES obtained a mean value of τ = 0.32 ± 0.02 at 532 nm wavelength, respectively. The mean of τ derived from the sideward viewing mini-DOAS channels is 0.26 ± 0.2. For the few simultaneous measurements, the mini-DOAS sideward channel measurements systematically underestimate (−17.6 %) the nadir observations from SMART and mini-DOAS. The agreement between mini-DOAS sideward viewing channels and WALES is better, showing the advantage of using sideward viewing measurements for cloud remote sensing for τ ≤ 1. Therefore, we suggest sideward viewing measurements for retrievals of τ of thin cirrus because of the significantly enhanced capability of sideward viewing compared to nadir measurements.

show abstract

Influence of local surface albedo variability and ice crystal shape on passive remote sensing of thin cirrus

Cited by 21 publications

References 22 publications

Potential of airborne lidar measurements for cirrus cloud studies

Potential of airborne lidar measurements for cirrus cloud studies

Comparing Airborne and Satellite Retrievals of Optical and Microphysical Properties of Cirrus and Deep Convective Clouds using a Radiance Ratio Technique

Potential of remote sensing of cirrus optical thickness by airborne spectral radiance measurements at different sideward viewing angles

Contact Info

Product

Resources

About