Radiative Effect of Clouds at Ny-Ålesund, Svalbard, as Inferred from Ground-Based Remote Sensing Observations

Ebell, Kerstin; Nomokonova, Tatiana; Maturilli, Marion; Ritter, Christoph

doi:10.1175/jamc-d-19-0080.1

Cited by 52 publications

(75 citation statements)

References 53 publications

(76 reference statements)

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“…The surface cloud radiative effect (denoted as CRE throughout the study), which will be analyzed for the different humidity conditions, was derived from the broadband radiative transfer calculations by Ebell et al (2019) with the rapid radiative transfer model RRTMG for the analyzed period at Ny-Ålesund. The model provides vertically resolved shortwave (SW) and longwave (LW) up-and downward fluxes and heating rates.…”

Section: Surface Cloud Radiative Effectmentioning

confidence: 99%

“…1 for the calculation of LW, SW, and net CRE, respectively. Ebell et al (2019) estimated the uncertainties in CRE using 10-min averaged fluxes observed by the baseline surface radiation network (BSRN). The uncertainties in CRE depend on averaging time.…”

Section: Surface Cloud Radiative Effectmentioning

confidence: 99%

“…In addition, liquid water and ice have different dielectric properties (Ray, 1972). Thus, the phase composition of clouds affects SW and LW radiative properties of clouds (Ebell et al, 2019). Therefore, we also analyzed the occurrence of different types of hydrometeors in the atmospheric column ( Fig.…”

Section: Cloud Phasementioning

confidence: 99%

“…In the previous sections, we showed the changes of cloudiness and amount of liquid and ice in a column under various atmospheric states. Liquid-containing and pure ice clouds have a different impact on the radiation budget at Ny-Ålesund (Ebell et al, 2019) and occurrence of these types of clouds varies for dry and moist conditions. Therefore, we also estimated the surface CRE under different atmospheric conditions.…”

Section: Surface Cloud Radiative Effectmentioning

confidence: 99%

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The influence of anomalous atmospheric conditions at Ny-Ålesund on clouds and their radiative effect

Nomokonova

Ebell

Löhnert

et al. 2019

Preprint

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Abstract. This study analyses occurrence of events with increased and decreased integrated water vapor (IWV) and atmospheric temperature (T) at the Arctic site Ny-&#197;lesund and their relation to cloud properties and the surface cloud radiative effect (CRE). For this study, we used almost 2.5 years (from June 2016 to October 2018) of ground-based cloud observations processed with the Cloudnet algorithm, IWV and T from microwave radiometer (MWR), long-term radiosonde observations, and backward trajectories FLEXTRA. Moist and dry anomalies were found to be associated with North Atlantic flows and air circulations in the Arctic region, respectively. The amount of water vapor is often correlated with cloud occurrence, presence of cloud liquid water, liquid and ice water path (LWP and IWP). In turn, changes in the cloud properties cause differences in surface CRE. During dry anomalies, in autumn, winter, and spring, the mean net surface CRE was lower by 2&#8211;37&#8201;W&#8201;m&#8722;2 with respect to normal conditions, while in summer the cloud related surface cooling was reduced by 49&#8201;W&#8201;m&#8722;2. In contrast, under moist conditions in summer the mean net surface CRE becomes more negative by 25&#8201;W&#8201;m&#8722;2, while in other seasons the mean net surface CRE was increased by 5&#8211;37&#8201;W&#8201;m&#8722;2. Trends in occurrence of dry and moist anomalies were analyzed based on 25-year-radiosonde database. Dry anomalies become less frequent with rates for different seasons from &#8722;12.8 to &#8722;4&#8201;% per decade, while the occurrence of moist event increases at rates from 2.8 to 6.4&#8201;% per decade. Taking into account the relations between the anomaly types and cloud properties the trends might be related to an increase in cloud occurrence, LWP, and IWP. The change in cloud properties could, in turn, modulate the surface CRE and lead to stronger surface cooling and warming related to clouds in summer and other seasons, respectively.

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Section: Surface Cloud Radiative Effectmentioning

confidence: 99%

Section: Surface Cloud Radiative Effectmentioning

confidence: 99%

Section: Cloud Phasementioning

confidence: 99%

Section: Surface Cloud Radiative Effectmentioning

confidence: 99%

See 2 more Smart Citations

The influence of anomalous atmospheric conditions at Ny-Ålesund on clouds and their radiative effect

Nomokonova

Ebell

Löhnert

et al. 2019

Preprint

Self Cite

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“…A variety of environmental conditions can effect cloud micro-and macro-physical properties. According to simulations over different surface types, changes in surface properties lead to changes in the thermodynamic structure of the atmospheric boundary layer, the extent of dynamical coupling of the cloud to the surface, and the microphysical properties of the MPC (Morrison et al, 2008;Li et al, 2017;Savre et al, 2015;Eirund et al, 2019). Also, observational evidence on the connection between changes in surface conditions and MPC occurrence (Morrison et al, 2018) as well as thermodynamic structure and droplet number concentration (Young et al, 2016) has been found.…”

Section: Introductionmentioning

confidence: 97%

Low-level mixed-phase clouds in a complex Arctic environment

et al. 2020

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Abstract. Low-level mixed-phase clouds (MPCs) are common in the Arctic. Both local and large-scale phenomena influence the properties and lifetime of MPCs. Arctic fjords are characterized by complex terrain and large variations in surface properties. Yet, not many studies have investigated the impact of local boundary layer dynamics and their relative importance on MPCs in the fjord environment. In this work, we used a combination of ground-based remote sensing instruments, surface meteorological observations, radiosoundings, and reanalysis data to study persistent low-level MPCs at Ny-Ålesund, Svalbard, for a 2.5-year period. Methods to identify the cloud regime, surface coupling, and regional and local wind patterns were developed. We found that persistent low-level MPCs were most common with westerly winds, and the westerly clouds had a higher mean liquid (42 g m−2) and ice water path (16 g m−2) compared to those with easterly winds. The increased height and rarity of persistent MPCs with easterly free-tropospheric winds suggest the island and its orography have an influence on the studied clouds. Seasonal variation in the liquid water path was found to be minimal, although the occurrence of persistent MPCs, their height, and their ice water path all showed notable seasonal dependency. Most of the studied MPCs were decoupled from the surface (63 %–82 % of the time). The coupled clouds had 41 % higher liquid water path than the fully decoupled ones. Local winds in the fjord were related to the frequency of surface coupling, and we propose that katabatic winds from the glaciers in the vicinity of the station may cause clouds to decouple. We concluded that while the regional to large-scale wind direction was important for the persistent MPC occurrence and properties, the local-scale phenomena (local wind patterns in the fjord and surface coupling) also had an influence. Moreover, this suggests that local boundary layer processes should be described in models in order to present low-level MPC properties accurately.

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In situ sounding of radiative flux profiles through the Arctic lower troposphere

Becker

Maturilli

Philipona

et al. 2020

Bull. of Atmos. Sci.& Technol.

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In situ profiles and fixed-altitude time series of all four components of net radiation were obtained at Ny-Ålesund, Svalbard (78.9° N, 11.9° E), in the period May 04–21, 2015. Measurements were performed using adapted high-quality instrumentation classified as “secondary standard” carried by a tethered balloon system. Balloon-lifted measurements of albedo under clear-sky conditions demonstrate the local dependence on altitude and on the surface inhomogeneity of this parameter over coastal terrain of Ny-Ålesund. Depending on the surface composition within the sensor’s footprint near the coastline, the albedo over predominantly snow-covered surfaces was found to decrease to 0.548 and 0.452 at 494 m and 881 m altitude compared with 0.731 and 0.788 measured with near-surface references, respectively. Albedo profiles show an all-sky maximum at 150 m above surface level due to local surface inhomogeneity, and an averaged vertical change rate of − 0.040/100 up to 750 m aboveground level (clear sky) and − 0.034/100 m (overcast). Profiling of arctic low-level clouds reveals distinct vertical gradients in all radiative fluxes but longwave upward at the cloud top. Observed radiative cooling at the top of a partly dissolving stratus cloud with heating rates of − 40.4 to − 62.1 Kd−1 in subsequent observations is exemplified.

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Radiative Effect of Clouds at Ny-Ålesund, Svalbard, as Inferred from Ground-Based Remote Sensing Observations

Cited by 52 publications

References 53 publications

The influence of anomalous atmospheric conditions at Ny-Ålesund on clouds and their radiative effect

The influence of anomalous atmospheric conditions at Ny-Ålesund on clouds and their radiative effect

Low-level mixed-phase clouds in a complex Arctic environment

In situ sounding of radiative flux profiles through the Arctic lower troposphere

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