No evidence for solar absorption anomaly by marine water clouds through collocated aircraft radiation measurements

Asano, Shoji; Uchiyama, Akihiro; Mano, Yuzo; Murakami, Masataka; Takayama, Y.

doi:10.1029/2000jd900062

Cited by 15 publications

(24 citation statements)

References 28 publications

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“…Considering that model calculations of the situation on this day give values on the order of 185 W m À2 , these results represented a very large deviation from existing theory, which led to the suggestion that some completely unknown absorber or physical process must be at work in the atmosphere. However, subsequent aircraft experiments by the British [Francis et al, 1997] and the Japanese [Asano et al, 2000] showed no deviation of measured from calculated absorption that exceeded more than about 10%. The situation was further complicated by the fact that later analyses of the ARESE data indicated that the fluxes measured by the downward-looking total solar broadband radiometer on the Egrett on the single overcast day (30 October) were not consistent with GOES satellite data [Valero et al, 2000] or data from a short-wave spectrometer that was also downward looking from the Egrett aircraft [Li et al, 1999;O'Hirok et al, 2000].…”

Section: Introductionmentioning

confidence: 91%

“…The Twin Otter aircraft flew a daisy pattern (Figure 1) over the central facility at maximum altitude (about 7 km) and then typically flew a few legs at low altitude (limited to about 0.4 km) on each day of the experiment. The Twin Otter carried three different aircraft sets of upward and downward-looking solar radiometers: (1) the Total Shortwave Broadband Radiometer [TSBR; Valero et al, 2003], (2) the CM21 instruments of the Meteorological Institute (MRI) of Japan [Asano et al, 2000], and (3) the CM22 instruments of Sandia National Laboratory. The CM21 and CM22 are commercial instruments manufactured by Kipp and Zonen.…”

Section: The Arese II Datamentioning

confidence: 99%

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Quantifying the magnitude of anomalous solar absorption

2003

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[1] The data set from ARESE II, sponsored by the Atmospheric Radiation Measurement Program, provides a unique opportunity to understand solar absorption in the atmosphere because of the combination of three sets of broadband solar radiometers mounted on the Twin Otter aircraft and the ground based instruments at the Atmospheric Radiation Measurement (ARM) Southern Great Plains facility. In this study, we analyze the measurements taken on two clear-sky days and three cloudy days and model the solar radiative transfer in each case with two different models. On the two clear days, the calculated and measured column absorptions agree to better than 10 W m À2 , which is about 10% of the total column absorption. Because both the model fluxes and the individual radiometer measurements are accurate to no better than 10 W m À2, we conclude that the models and measurements are essentially in agreement. For the three cloudy days, the model calculations agree very well with each other and on 2 of the 3 days agree with the measurements to 20 W m À2 or less out of a total column absorption of more than 200 W m À2 , which is again an agreement at better than 10%. On the third day, the model and measurements agree to either 8 or 14% depending on which value of surface albedo is used. Differences exceeding 10% represent a significant absorption difference between model and observations. In addition to the uncertainty in absorption due to surface albedo, we show that including aerosol with an optical depth similar to that found on clear days can reduce the difference between model and measurement by 5% or more. Thus we conclude that the ARESE II results are incompatible with previous studies reporting extreme anomalous absorption and can be modeled with our current understanding of radiative transfer.

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Section: Introductionmentioning

confidence: 91%

Section: The Arese II Datamentioning

confidence: 99%

Quantifying the magnitude of anomalous solar absorption

2003

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“…The flight pattern strategy used in the field experiment was the same as that previously described in details by Asano et al [2000]. At the start of the experiment, the B200 performed in situ measurements of cloud microphysical structures at several flight levels in the cloudy layer.…”

Section: Microphysical and Optical Properties Of Two Cases Of Boundarmentioning

confidence: 99%

Two case studies of winter continental‐type water and mixed‐phase stratocumuli over the sea 1. Microphysical and optical properties

et al. 2002

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[1] Collocated aircraft observations of microstructure and radiative properties of winter boundary layer clouds over the East China Sea and the Japan Sea have been carried out in January 1999 within the Japanese Cloud and Climate Study (JACCS) program. The first part of the paper describes the in situ measured microphysical and optical properties for two cases of boundary layer winter stratocumulus clouds, which concern, first, a rather uniform, supercooled water cloud contaminated by aerosols and, second, a highly heterogeneous, mixed-phase stratiform cloud. Using the Polar Nephelometer, a new instrument for measuring, in situ, the scattering phase function of cloud droplets and ice particles, the polluted, continental-type stratocumulus cloud can be optically regarded as a liquid water cloud because the measured scattering phase functions fitted very well with those calculated from Mie theory for the directly measured FSSP size distributions. In mixed-phase cloud, the measured scattering phase function shows that ice particles strongly affect optical properties of the cloud, where large number of liquid water droplets with higher extinction coefficient and asymmetry factor values were converted into a much smaller number of large ice crystals with lower extinction coefficient and asymmetry factor. Furthermore, a quasi-stable liquid-topped cloud layer with precipitating ice particles was noticed; the layer may, first, affect the cloud radiative properties and, second, seriously restrict the interpretation of satellite cloud composition retrievals.

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“…For example, although Francis et al (1997) reported aircraft experiments that showed measured cloud absorptions greater than values predicted by models, the discrepancies were much smaller than those suggested in previous studies. Asano et al (2000) analysed collocated aircraft measurements of marine stratocumulus and radiative fluxes made in 1998 over the Sea of Japan and found no evidence of excess solar absorption from clouds. One limitation of all of these field studies is that they are restricted to low-level water clouds, whereas the empirical studies that were suggesting strong excess solar absorption Pilewski and Valero, 1995;Ramanathan et al, 1995) included low as well as mid-level and high clouds.…”

Section: Introductionmentioning

confidence: 99%

Albedo, atmospheric solar absorption and heating rate measurements with stacked UAVs

Ramana

Ramanathan

Kim

et al. 2007

Quart J Royal Meteoro Soc

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This paper reports unique measurements of albedo, atmospheric solar absorption, and heating rates in the visible (0.4 to 0.7 µm) and broadband (0.3 to 2.8 µm) spectral regions using vertically stacked multiple lightweight autonomous unmanned aerial vehicles (UAVs). The most significant finding of this study is that when absorbing aerosols and water vapour concentrations are measured accurately and accounted for in models, and when heating rates are measured directly with stacked aircraft, the simulated clear sky heating rates are consistent with the observed broadband heating rates within experimental errors (about 15%). We conclude that there is no need to invoke anomalous or excess absorption or unknown physics in clear skies.Aerosol-radiation-cloud measurements were made over the tropical Indian Ocean within the lowest 3 km of the atmosphere during the Maldives Autonomous UAV Campaign (MAC). The UAVs and ground-based remote sensing instruments determined most of the parameters required for calculating the albedo and vertical distribution of solar fluxes. The paper provides a refined analytical procedure to reduce errors and biases due to the offset errors arising from mounting of the radiometers on the aircraft and due to the aircraft attitude. Measured fluxes have been compared with those derived from a Monte-Carlo radiative transfer algorithm which can incorporate both gaseous and aerosol components. Under cloud-free conditions the calculated and measured incoming fluxes agree within 2-10 W m −2 (<1%) depending upon the altitudes. Similarly, the measured and calculated reflected fluxes agreed within 2-5 W m −2 (<5%). The analysis focuses on a cloud-free day when the air was polluted due to long-range transport from India, and the mean aerosol optical depth (AOD) was 0.31 and mean single scattering albedo was 0.92. The UAV-measured absorption AOD was 0.019 which agreed within 20% of the value of 0.024 reported by a ground-based instrument. The observed and simulated solar absorption agreed within 5% above 1.0 km and aerosol absorption accounted for 30% to 50% of the absorption depending upon the altitude and solar zenith angle. Thus there was no need to invoke spurious or anomalous absorption, provided we accounted for aerosol black carbon. The diurnal mean absorption values for altitudes between 0.5 and 3.0 km above mean sea level were observed to be 41 ± 3 W m −2 (1.5 K/day) in the broadband region and 8 ± 2 W m −2 (0.3 K/day) in the visible region. The contribution of absorbing aerosols to the heating rate was an order of magnitude larger than the contribution of CO 2 and one-third that of the water vapour. In the lowest 3 km of the tropical atmosphere, aerosols accounted for more than 80% of the atmospheric absorption in the visible region.

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No evidence for solar absorption anomaly by marine water clouds through collocated aircraft radiation measurements

Cited by 15 publications

References 28 publications

Quantifying the magnitude of anomalous solar absorption

Quantifying the magnitude of anomalous solar absorption

Two case studies of winter continental‐type water and mixed‐phase stratocumuli over the sea 1. Microphysical and optical properties

Albedo, atmospheric solar absorption and heating rate measurements with stacked UAVs

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