scholarly journals Effect of Aerosols, Tropospheric NO2 and Clouds on Surface Solar Radiation over the Eastern Mediterranean (Greece)

2021 ◽  
Vol 13 (13) ◽  
pp. 2587
Author(s):  
Georgia Alexandri ◽  
Aristeidis K. Georgoulias ◽  
Dimitris Balis
Keyword(s):  
Solar Radiation ◽  
Radiative Transfer ◽  
Eastern Mediterranean ◽  
Radiative Effect ◽  
Santa Barbara ◽  
Surface Solar Radiation ◽  
Ice Clouds ◽  
Climatological Data ◽  
Ice Cloud ◽  
Tropospheric No2

In this work, the effect that two basic air quality indexes, aerosols and tropospheric NO2, exert on surface solar radiation (SSR) is studied, along with the effect of liquid and ice clouds over 16 locations in Greece, in the heart of the Eastern Mediterranean. State-of-the-art satellite-based observations and climatological data for the 15-year period 2005–2019, and a radiative transfer system based on a modified version of the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model are used. Our SSR simulations are in good agreement with ground observations and two satellite products. It is shown that liquid clouds dominate, with an annual radiative effect (RE) of −36 W/m2, with ice clouds (−19 W/m2) and aerosols (−13 W/m2) following. The radiative effect of tropospheric NO2 is smaller by two orders of magnitude (−0.074 W/m2). Under clear skies, REaer is about 3–4 times larger than for liquid and ice cloud-covered skies, while RENO2 doubles. The radiative effect of all the parameters exhibits a distinct seasonal cycle. An increase in SSR is observed for the period 2005–2019 (positive trends ranging from 0.01 to 0.52 W/m2/year), which is mostly related to a decrease in the aerosol optical depth and the liquid cloud fraction.

scholarly journals Clear-Sky Surface Solar Radiation and the Radiative Effect of Aerosol and Water Vapor Based on Simulations and Satellite Observations over Northern China

2020 ◽  
Vol 12 (12) ◽  
pp. 1931
Author(s):  
Guang Zhang ◽  
Yingying Ma
Keyword(s):  
Water Vapor ◽  
Solar Radiation ◽  
Inner Mongolia ◽  
Northern China ◽  
Satellite Observations ◽  
Radiative Effect ◽  
Surface Solar Radiation ◽  
Clear Sky ◽  
South Central ◽  
West Central

The distribution and trend of clear-sky surface solar radiation (SSR) and the quantitative effects of aerosol and water vapor are investigated in northern China during 2001–2015 using radiation simulations and satellite observations. Clear-sky SSR in northern China is high in summer and low in winter, which is dominated by astronomical factors and strongly modulated by the seasonal variations of radiative effects of aerosol (ARE) and water vapor (WVRE). The larger variation of WVRE than ARE indicates that water vapor plays a more important role in moderating the seasonal variation of clear-sky SSR. Clear-sky SSR shows an overall decreasing trend of –0.12 W/m2 per year, with decrease more strongly than –0.60 W/m2 per year in west-central Shandong and increase (about 0.40 W/m2) in south-central Inner Mongolia. The consistency of spatial distribution and high correlation between clear-sky SSR and ARE trend indicate that the clear-sky SSR trend is mainly determined by aerosol variation. Dust mass concentration decreases about 16% in south-central Inner Mongolia from 2001 to 2015, resulting in the increase in clear-sky SSR. In contrast, sulfate aerosol increases about 92% in west-central Shandong, leading to the decreasing trend of clear-sky SSR.

scholarly journals Development of a GOES-R Advanced Baseline Imager Solar Channel Radiance Simulator for Ice Clouds

2013 ◽  
Vol 52 (4) ◽  
pp. 872-888 ◽  
Author(s):  
Shouguo Ding ◽  
Ping Yang ◽  
Bryan A. Baum ◽  
Andrew Heidinger ◽  
Thomas Greenwald
Keyword(s):  
Radiative Transfer ◽  
Spectral Response ◽  
Three Dimensional ◽  
Gas Absorption ◽  
Radiative Transfer Model ◽  
Discrete Ordinates ◽  
Transfer Model ◽  
Water Vapor Absorption ◽  
Ice Clouds ◽  
Ice Cloud

AbstractThis paper describes the development of an ice cloud radiance simulator for the anticipated Geostationary Operational Environmental Satellite R (GOES-R) Advanced Baseline Imager (ABI) solar channels. The simulator is based on the discrete ordinates radiative transfer (DISORT) model. A set of correlated k-distribution (CKD) models is developed for the ABI solar channels to account for atmospheric trace gas absorption. The CKD models are based on the ABI spectral response functions and also consider when multiple gases have overlapping absorption. The related errors of the transmittance profile are estimated on the basis of the exact line-by-line results, and it is found that errors in transmittance are less than 0.2% for all but one of the ABI solar channels. The exception is for the 1.378-μm channel, centered near a strong water vapor absorption band, for which the errors are less than 2%. For ice clouds, the band-averaged bulk-scattering properties for each ABI [and corresponding Moderate Resolution Imaging Spectroradiometer (MODIS)] solar channel are derived using an updated single-scattering property database of both smooth and severely roughened ice particles, which include droxtals, hexagonal plates, hexagonal hollow and solid columns, three-dimensional hollow and solid bullet rosettes, and several types of aggregates. The comparison shows close agreement between the radiance simulator and the benchmark model, the line-by-line radiative transfer model (LBLRTM)+DISORT model. The radiances of the ABI and corresponding MODIS measurements are compared. The results show that the radiance differences between the ABI and MODIS channels under ice cloud conditions are likely due to the different band-averaged imaginary indices of refraction.

scholarly journals Assessing the Radiative Effects of Global Ice Clouds Based on CloudSat and CALIPSO Measurements

2016 ◽  
Vol 29 (21) ◽  
pp. 7651-7674 ◽  
Author(s):  
Yulan Hong ◽  
Guosheng Liu ◽  
J.-L. F. Li
Keyword(s):  
Longwave Radiation ◽  
Cooling Effect ◽  
Radiation Budget ◽  
Radiative Effect ◽  
Radiative Effects ◽  
Ice Clouds ◽  
Cloud Optical Depth ◽  
Ice Cloud ◽  
Heating And Cooling ◽  
The Tropics

Abstract Although it is well established that cirrus warms Earth, the radiative effect of the entire spectrum of ice clouds is not well understood. In this study, the role of all ice clouds in Earth’s radiation budget is investigated by performing radiative transfer modeling using ice cloud properties retrieved from CloudSat and CALIPSO measurements as inputs. Results show that, for the 2008 period, the warming effect (~21.8 ± 5.4 W m−2) induced by ice clouds trapping longwave radiation exceeds their cooling effect (~−16.7 ± 1.7 W m−2) caused by shortwave reflection, resulting in a net warming effect (~5.1 ± 3.8 W m−2) globally on the earth–atmosphere system. The net warming is over 15 W m−2 in the tropical deep convective regions, whereas cooling occurs in the midlatitudes, which is less than 10 W m−2 in magnitude. Seasonal variations of ice cloud radiative effects are evident in the midlatitudes where the net effect changes from warming during winter to cooling during summer, whereas warming occurs all year-round in the tropics. Ice cloud optical depth τ is shown to be an important factor in determining the sign and magnitude of the net radiative effect. Ice clouds with τ < 4.6 display a warming effect with the largest contributions from those with τ ≈ 1.0. In addition, ice clouds cause vertically differential heating and cooling of the atmosphere, particularly with strong heating in the upper troposphere over the tropics. At Earth’s surface, ice clouds produce a cooling effect no matter how small the τ value is.

scholarly journals Why we need radar, lidar, and solar radiance observations to constrain ice cloud microphysics

2021 ◽  
Author(s):  
Florian Ewald ◽  
Silke Groß ◽  
Martin Wirth ◽  
Julien Delanoë ◽  
Stuart Fox ◽  
...  
Keyword(s):  
Water Content ◽  
Cloud Microphysics ◽  
Accurate Estimation ◽  
Crystal Shape ◽  
Radiative Effect ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Ice Water Content ◽  
Ice Water

Abstract. Ice clouds and their effect on Earth's radiation budget are one of the largest sources of uncertainty in climate change predictions. The uncertainty in predicting ice cloud feedbacks in a warming climate arises due to uncertainties in measuring and explaining their current optical and microphysical properties as well as from insufficient knowledge about their spatial and temporal distribution. This knowledge can be significantly improved by active remote sensing, which can help to explore the vertical profile of ice cloud microphysics, such as ice particle size and ice water content. This study focuses on the well-established variational approach VarCloud to retrieve ice cloud microphysics from radar-lidar measurements. While active backscatter retrieval techniques surpass the information content of most passive, vertically integrated retrieval techniques, their accuracy is limited by essential assumptions about the ice crystal shape. Since most radar-lidar retrieval algorithms rely heavily on universal mass-size relationships to parameterize the prevalent ice particle shape, biases in ice water content and ice water path can be expected in individual cloud regimes. In turn, these biases can lead to an erroneous estimation of the radiative effect of ice clouds. In many cases, these biases could be spotted and corrected by the simultaneous exploitation of measured solar radiances. The agreement with measured solar radiances is a logical prerequisite for an accurate estimation of the radiative effect of ice clouds. To this end, this study exploits simultaneous radar, lidar, and passive measurements made on board the German High Altitude and Long Range Research Aircraft. By using the ice clouds derived with VarCloud as an input to radiative transfer calculations, simulated solar radiances are compared to measured solar radiances made above the actual clouds. This radiative closure study is done using different ice crystal models to improve the knowledge of the prevalent ice crystal shape. While in one case aggregates were capable of reconciling radar, lidar, and solar radiance measurements, this study also analyses a more problematic case for which no radiative closure could be achieved. In this case, simultaneously acquired in-situ measurements could narrow this inability to an unexpected high ice crystal number concentration.

scholarly journals Vertical profile of the clear-sky aerosol direct radiative effect in an Alpine valley, by the synergy of ground-based measurements and radiative transfer simulations

2021 ◽  
Vol 2 (1-4) ◽  
Author(s):  
Gabriele Fasano ◽  
Henri Diémoz ◽  
Ilias Fountoulakis ◽  
Claudio Cassardo ◽  
Rei Kudo ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Radiative Transfer ◽  
Vertical Distribution ◽  
Vertical Profile ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Asymmetry Factor ◽  
Radiative Effect ◽  
Heating Rates ◽  
Atmospheric Column

AbstractAtmospheric aerosols play an important role in Earth’s radiative balance, directly interacting with solar radiation or influencing cloud formation and properties. In order to assess their radiative impact, it is necessary to accurately characterise their optical properties, together with their spatial and vertical distribution. The information on aerosol vertical profile is often scarce, in particular in mountainous, complex terrains. This study presents the first attempt to evaluate the shortwave aerosol direct radiative effect in the Aosta Valley, a mountainous region in the Northwestern Italian Alps. Ground-based, remote sensing instruments (a sky radiometer and an Automated Lidar Ceilometer) are used to derive two descriptions of the aerosol properties and vertical distribution: a first, more accurate description, which includes the whole spectral information about the aerosol extinction coefficient, phase function and single scattering albedo; a second, more approximate one, which only relies on spectrally constant values of aerosol single scattering albedo and asymmetry factor. This information is used as input for radiative transfer simulations, which allow to estimate, in cloudless conditions, the shortwave aerosol direct radiative effect and the vertical profile of the instantaneous heating rates in the lower layers of the atmosphere. The simulations obtained with the two descriptions do not differ significantly: they highlight a strong surface dimming (between − 25 and − 50 W m− 2) due to the presence of aerosol, with a considerable radiative absorption inside the atmospheric column (around + 30 W m− 2), and an overall small cooling effect for the Earth-atmospheric system. The absorption of solar radiation within the atmospheric column due to aerosol leads to instantaneous heating rates up to 1.5 K day− 1 in the tropospheric layers below 6 km a.s.l. These results show that, in some conditions, the shortwave aerosol direct radiative effect can be considerable even in this Alpine environment, usually considered as relatively pristine (yearly average PM10 concentration about 20 μg m− 3).

Influence of Ice Particle Surface Roughening on the Global Cloud Radiative Effect

2013 ◽  
Vol 70 (9) ◽  
pp. 2794-2807 ◽  
Author(s):  
Bingqi Yi ◽  
Ping Yang ◽  
Bryan A. Baum ◽  
Tristan L'Ecuyer ◽  
Lazaros Oreopoulos ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Particle Surface ◽  
Radiation Budget ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Radiative Effect ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Ice Particles ◽  
Cloud Radiative Effect

Abstract Ice clouds influence the climate system by changing the radiation budget and large-scale circulation. Therefore, climate models need to have an accurate representation of ice clouds and their radiative effects. In this paper, new broadband parameterizations for ice cloud bulk scattering properties are developed for severely roughened ice particles. The parameterizations are based on a general habit mixture that includes nine habits (droxtals, hollow/solid columns, plates, solid/hollow bullet rosettes, aggregate of solid columns, and small/large aggregates of plates). The scattering properties for these individual habits incorporate recent advances in light-scattering computations. The influence of ice particle surface roughness on the ice cloud radiative effect is determined through simulations with the Fu–Liou and the GCM version of the Rapid Radiative Transfer Model (RRTMG) codes and the National Center for Atmospheric Research Community Atmosphere Model (CAM, version 5.1). The differences in shortwave (SW) and longwave (LW) radiative effect at both the top of the atmosphere and the surface are determined for smooth and severely roughened ice particles. While the influence of particle roughening on the single-scattering properties is negligible in the LW, the results indicate that ice crystal roughness can change the SW forcing locally by more than 10 W m−2 over a range of effective diameters. The global-averaged SW cloud radiative effect due to ice particle surface roughness is estimated to be roughly 1–2 W m−2. The CAM results indicate that ice particle roughening can result in a large regional SW radiative effect and a small but nonnegligible increase in the global LW cloud radiative effect.

Oriented particles in microwave and submillimeter radiative transfer simulations of ice clouds

2020 ◽  
Author(s):  
Manfred Brath ◽  
Robin Ekelund ◽  
Patrick Eriksson ◽  
Oliver Lemke ◽  
Stefan A. Buehler
Keyword(s):  
Radiative Transfer ◽  
Incidence Angle ◽  
Ice Crystals ◽  
Particle Orientation ◽  
Scattering Data ◽  
Reasonable Assumption ◽  
Random Orientation ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Ice Particles

<div>Observations of Global Precipitation Measurement Microwave Imager (GMI) at 166 GHz consistently show polarized scattering signals of ice clouds. Conceptual models indicate that these signals emerge from oriented ice particles. Existing databases of scattering data of realistically shaped ice crystals for microwave and submillimeter typically assume total random orientation of ice particles. This is often a very reasonable assumption, but cannot explain the polarized ice cloud signals. Only few works considering oriented ice crystals exist, but they only consider microwave. With the upcoming Ice Cloud Imager (ICI) on board of Metop-SG B satellite, there will be additional dual-polarization measurements at 243 GHz and 664 GHz. These measurements will deliver new insights about clouds and their structure, if we know the scattering properties of oriented and realistically shaped ice crystals.</div><div>We provide publicly available scattering data for 51 different sized hexagonal plates and 18 different sized plate aggregates for 35 frequencies between 1 GHz and 864 GHz. The ice particles are assumed to be azimuthally randomly oriented with a fixed but arbitrary tilt angle. The scattering data for azimuthal random orientation is much more complex than for total random orientation. The scattering data of azimuthally randomly oriented particles depends in general on the incidence angle and two scattering angles compared to only one scattering angle for total random orientation. The scattering data is based on discrete dipole approximation simulations in combination with a self-developed orientation averaging approach.</div><div>We present detailed radiative transfer simulations of polarized GMI observations at 166 GHz and ICI observations at 243 GHz and at 664 GHz using our scattering data. The simulations of GMI recreate the observed polarization patterns. Analysis shows that not only orientation affects the polarization signal but also the hydrometeor composition. Furthermore, particle orientation also affects single polarized observations. Ignoring orientation can cause a negative bias for vertically polarized observations and a positive bias for horizontally polarized observations.</div>

scholarly journals New insights into the vertical structure of the September 2015 dust storm employing eight ceilometers and auxiliary measurements over Israel

2018 ◽  
Vol 18 (5) ◽  
pp. 3203-3221 ◽  
Author(s):  
Leenes Uzan ◽  
Smadar Egert ◽  
Pinhas Alpert
Keyword(s):  
Particulate Matter ◽  
Solar Radiation ◽  
Dust Storm ◽  
Eastern Mediterranean ◽  
Sea Breeze ◽  
Ground Level ◽  
Satellite Observation ◽  
Surface Solar Radiation ◽  
Dust Layer ◽  
Very High

Abstract. On 7 September 2015, an unprecedented and unexceptional extreme dust storm struck the eastern Mediterranean (EM) basin. Here, we provide an overview of the previous studies and describe the dust plume evolution over a relatively small area, i.e., Israel. This study presents vertical profiles provided by an array of eight ceilometers covering the Israeli shore, inland and mountain regions. We employ multiple tools including spectral radiometers (Aerosol Robotic Network – AERONET), ground particulate matter concentrations, satellite images, global/diffuse/direct solar radiation measurements and radiosonde profiles. The main findings reveal that the dust plume penetrated Israel on 7 September from the northeast in a downward motion to southwest. On 8 September, the lower level of the dust plume reached 200 m above ground level, generating aerosol optical depth (AOD) above 3 and extreme ground particulate matter concentrations up to ∼ 10 000 µm m−3. A most interesting feature on 8 September was the very high variability in the surface solar radiation in the range of 200–600 W m−2 (22 sites) over just a distance of several hundred kilometers in spite of the thick dust layer above. Furthermore, 8 September shows the lowest radiation levels for this event. On the following day, the surface solar radiation increased, thus enabling a late (between 11:00 and 12:00 UTC) sea breeze development mainly in the coastal zone associated with a creation of a narrow dust layer detached from the ground. On 10 September, the AOD values started to drop down to ∼ 1.5, and the surface concentrations of particulate matter decreased as well as the ceilometers' aerosol indications (signal counts) although Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) revealed an upper dust layer remained.

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