Short-wave aerosol radiative efficiency over the global oceans derived from satellite data

Tellus B ◽  
2008 ◽  
Vol 60 (4) ◽  
Author(s):  
Sundar A. Christopher ◽  
Thomas A. Jones
Keyword(s):  
Satellite Data ◽  
Short Wave ◽  
Radiative Efficiency ◽  
Global Oceans ◽  
Aerosol Radiative

Short-wave aerosol radiative efficiency over the global oceans derived from satellite data

Tellus B ◽  
2008 ◽  
Vol 60 (4) ◽  
pp. 636-640 ◽  
Author(s):  
Sundar A. Christopher ◽  
Thomas A. Jones
Keyword(s):  
Satellite Data ◽  
Short Wave ◽  
Radiative Efficiency ◽  
Global Oceans ◽  
Aerosol Radiative

Revealing snow cover dynamics in the Hindu Kush Himalaya over the past decades

2020 ◽  
Author(s):  
Kathrin Naegeli ◽  
Carlo Marin ◽  
Valentina Premier ◽  
Gabriele Schwaizer ◽  
Martin Stengel ◽  
...  
Keyword(s):  
High Resolution ◽  
Snow Cover ◽  
Satellite Data ◽  
Weather Forecast ◽  
Short Wave ◽  
Climate Modelling ◽  
Snow Cover Area ◽  
Hindu Kush ◽  
Spatio Temporal ◽  
Area Percentage

<p>Knowledge about the snow cover distribution is of high importance for climate studies, weather forecast, hydrological investigations, irrigation or tourism, respectively. The Hindu Kush Himalayan (HKH) region covers almost 3.5 million km<sup>2</sup> and extends over eight different countries. The region is known as ‘water tower’ as it contains the largest volume of ice and snow outside of the polar ice sheets and it is the source of Asia’s largest rivers. These rivers provide ecosystem services, the basis for livelihoods and most importantly living water for drinking, irrigation, energy production and industry for two billion people, a fourth of the world’s population, living in the mountains and downstream.</p><p>The spatio-temporal variability of snow cover in the HKH is high and studies reported average snow-covered area percentage of 10–18%, with greater variability in winter (21–42%) than in summer (2–4%). However, no study systematically investigated snow cover metrics, such as snow cover area percentage (SCA), snow cover duration (SCD) or snow cover onset (SCOD) and melt-out day (SCMD), for the entire region so far. Here, we thus present unique in-sights of regional and sub-regional snow cover dynamics for the HKH based on almost four decades, an exceptionally long and in view of the climate modelling community valuable timeseries, of satellite data obtained within the ESA CCI+ Snow project.</p><p>Our results are based on Advanced Very High Resolution Radiometer (AVHRR) data, collected onboard the polar orbiting satellites NOAA-7 to -19, providing daily, global imagery at a spatial resolution of 5 km. Calibrated and geocoded reflectance data and a consistent cloud mask pre-processed and provided by the ESA Cloud_cci project as global 0.05° composites are used. The retrieval of snow extent considers the high reflectance of snow in the visible spectra and the low reflectance values in the short-wave infrared expressed in the Normalized Difference Snow Index (NDSI). Additional thresholds related to topography and land cover are included to derive the fractional snow cover of every pixel. A temporal gap-filling was applied to mitigate the influence of clouds. Reference snow maps from high-resolution optical satellite data as well as in-situ station data were used to validate the time series.</p>

Short wave Aerosol Radiative Forcing estimates over a semi urban coastal environment in south-east India and validation with surface flux measurements

2016 ◽  
Vol 125 ◽  
pp. 418-428 ◽  
Author(s):  
K. Aruna ◽  
T.V. Lakshmi Kumar ◽  
B.V. Krishna Murthy ◽  
S. Suresh Babu ◽  
M. Venkat Ratnam ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Surface Flux ◽  
Short Wave ◽  
Coastal Environment ◽  
Aerosol Radiative Forcing ◽  
Flux Measurements ◽  
Aerosol Radiative

scholarly journals A Study of the Longer Term Variation of Aerosol Optical Thickness and Direct Shortwave Aerosol Radiative Effect Trends Using MODIS and CERES

2017 ◽  
Author(s):  
Ricardo Alfaro-Contreras ◽  
Jianglong Zhang ◽  
Jeffrey S. Reid ◽  
Sundar Christopher
Keyword(s):  
Optical Thickness ◽  
Broad Band ◽  
Radiant Energy ◽  
Energy System ◽  
Short Wave ◽  
Aerosol Optical Thickness ◽  
Radiative Effect ◽  
Distribution Models ◽  
Direct Forcing ◽  
Aerosol Radiative

Abstract. By combining Collection 6 Moderate Resolution and Imaging Spectroradiometer (MODIS) and Version 22 Multi-angle Imaging Spectroradiometer (MISR) aerosol products with Cloud and Earth’s Radiant Energy System (CERES) flux products, the aerosol optical thickness (AOT, at 0.55 µm) and Short-Wave Aerosol Radiative Effect (SWARE) trends are studied over ocean for the near full Terra (2000–2015) and Aqua (2002–2015) data records. Despite differences in sampling methods, regional SWARE and AOT trends are highly correlated with one another. Over global oceans, weak SWARE (cloud free SW flux) and AOT trends of 0.5–0.6 W m−2 (−0.5 to −0.6 W m−2) and 0.002 AOT decade−1 were found using Terra data. Near zero AOT and SWARE trends are also found for using Aqua data, regardless of Angular Distribution Models (ADMs) used. Regionally, positive SWARE and AOT trends are found over the Bay of Bengal, Arabian Sea, Arabian/Persian Gulf and the Red Sea, while statistically significant negative trends are derived over the Mediterranean Sea and the eastern US coast. In addition, the global mean instantaneous SW aerosol direct forcing efficiencies are found to be ~ −60 W m−2 per AOT, with corresponding SWARE values of ~ −7 W m−2 from both Aqua and Terra data, and again, regardless of CERES ADMs used. Regionally, SW aerosol direct forcing efficiency values of ~ −40 W m−2 per AOT are found over the southwest coast of Africa where smoke aerosol particles dominate in summer. Larger (in magnitude) SW aerosol direct forcing efficiency values of −50 to −80 W m−2 per AOT are found over several other dust and pollutant aerosol dominated regions. Lastly, the AOT and SWARE trends from this study are also inter-compared with aerosol trends (such as active-based) from several previous studies. Findings suggest that a cohesive understanding of the changing aerosol skies can be achieved through the analysis of observations from both passive- and active-based analyses, as well as at both narrow-band and broad-band data sets.

scholarly journals Dust aerosol radiative effects during summer 2012 simulated with a coupled regional aerosol–atmosphere–ocean model over the Mediterranean

2015 ◽  
Vol 15 (6) ◽  
pp. 3303-3326 ◽  
Author(s):  
P. Nabat ◽  
S. Somot ◽  
M. Mallet ◽  
M. Michou ◽  
F. Sevault ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Mediterranean Region ◽  
Short Wave ◽  
Ocean Model ◽  
Dust Particles ◽  
Radiative Effects ◽  
Aerosol Radiative Forcing ◽  
Dust Aerosols ◽  
The Mediterranean ◽  
Aerosol Radiative

Abstract. The present study investigates the radiative effects of dust aerosols in the Mediterranean region during summer 2012 using a coupled regional aerosol–atmosphere–ocean model (CNRM-RCSM5). A prognostic aerosol scheme, including desert dust, sea salt, organic, black-carbon and sulphate particles, has been integrated to CNRM-RCSM5 in addition to the atmosphere, land surface and ocean components. An evaluation of this aerosol scheme of CNRM-RCSM5, and especially of the dust aerosols, has been performed against in situ and satellite measurements, showing its ability to reproduce the spatial and temporal variability of aerosol optical depth (AOD) over the Mediterranean region in summer 2012. The dust vertical and size distributions have also been evaluated against observations from the TRAQA/ChArMEx campaign. Three simulations have been carried out for summer 2012 with CNRM-RCSM5, including the full prognostic aerosol scheme, only monthly-averaged AOD means from the aerosol scheme or no aerosols at all, in order to focus on the radiative effects of dust particles and the role of the prognostic scheme. Surface short-wave aerosol radiative forcing variability is found to be more than twice as high over regions affected by dust aerosols, when using a prognostic aerosol scheme instead of monthly AOD means. In this case downward surface solar radiation is also found to be better reproduced according to a comparison with several stations across the Mediterranean. A composite study over 14 stations across the Mediterranean, designed to identify days with high dust AOD, also reveals the improvement of the representation of surface temperature brought by the use of the prognostic aerosol scheme. Indeed the surface receives less radiation during dusty days, but only the simulation using the prognostic aerosol scheme is found to reproduce the observed intensity of the dimming and warming on dusty days. Moreover, the radiation and temperature averages over summer 2012 are also modified by the use of prognostic aerosols, mainly because of the differences brought in short-wave aerosol radiative forcing variability. Therefore this first comparison over summer 2012 highlights the importance of the choice of the representation of aerosols in climate models.

scholarly journals Use of Sentinel-2 Satellite Data for Windthrows Monitoring and Delimiting: The Case of “Vaia” Storm in Friuli Venezia Giulia Region (North-Eastern Italy)

2021 ◽  
Vol 13 (8) ◽  
pp. 1530
Author(s):  
Valentina Olmo ◽  
Enrico Tordoni ◽  
Francesco Petruzzellis ◽  
Giovanni Bacaro ◽  
Alfredo Altobelli
Keyword(s):  
Satellite Data ◽  
Vegetation Index ◽  
Standard Procedure ◽  
Abies Alba ◽  
Recovery Process ◽  
Short Wave ◽  
Short Period ◽  
North Eastern ◽  
Friuli Venezia Giulia ◽  
Sentinel 2

On the 29th of October 2018, a storm named “Vaia” hit North-Eastern Italy, causing the loss of 8 million m3 of standing trees and creating serious damage to the forested areas, with many economic and ecological implications. This event brought up the necessity of a standard procedure for windthrow detection and monitoring based on satellite data as an alternative to foresters’ fieldwork. The proposed methodology was applied in Carnic Alps (Friuli Venezia Giulia, NE Italy) in natural stands dominated by Picea abies and Abies alba. We used images from the Sentinel-2 mission: 1) to test vegetation indices performance in monitoring the vegetation dynamics in the short period after the storm, and 2) to create a windthrow map for the whole Friuli Venezia Giulia region. Results showed that windthrows in forests have a significant influence on visible and short-wave infrared (SWIR) spectral bands of Sentinel-2, both in the short and the long-term timeframes. NDWI8A and NDWI were the best indices for windthrow detection (R2 = 0.80 and 0.77, respectively) and NDVI, PSRI, SAVI and GNDVI had an overall good performance in spotting wind-damaged areas (R2 = 0.60–0.76). Moreover, these indices allowed to monitor post-Vaia forest die-off and showed a dynamic recovery process in cleaned sites. The NDWI8A index, employed in the vegetation index differencing (VID) change detection technique, delimited damaged areas comparable to the estimations provided by Regional Forest System (2545 ha and 3183 ha, respectively). Damaged forests detected by NDWI8A VID ranged from 500 m to 1500 m a.s.l., mainly covering steep slopes in the south and east aspects (42% and 25%, respectively). Our results suggested that the NDWI8A VID method may be a cost-effective and accurate way to produce windthrow maps, which could limit the risks associated with fieldwork and may provide a valuable tool to plan tree removal interventions in a more efficient way.

scholarly journals Aerosol indirect effects – general circulation model intercomparison and evaluation with satellite data

2009 ◽  
Vol 9 (22) ◽  
pp. 8697-8717 ◽  
Author(s):  
J. Quaas ◽  
Y. Ming ◽  
S. Menon ◽  
T. Takemura ◽  
M. Wang ◽  
...  
Keyword(s):  
Satellite Data ◽  
Indirect Effect ◽  
Indirect Effects ◽  
General Circulation ◽  
Short Wave ◽  
Effect Estimate ◽  
Aerosol Indirect Effects ◽  
Aerosol Indirect Effect ◽  
Aerosol Direct Effect ◽  
Statistical Relationships

Abstract. Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (τa) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between τa and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (fcld) and τa as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld–τa relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between τa and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR–τa relationship show a strong positive correlation between τa and fcld. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of τa, and parameterisation assumptions such as a lower bound on Nd. Nevertheless, the strengths of the statistical relationships are good predictors for the aerosol forcings in the models. An estimate of the total short-wave aerosol forcing inferred from the combination of these predictors for the modelled forcings with the satellite-derived statistical relationships yields a global annual mean value of −1.5±0.5 Wm−2. In an alternative approach, the radiative flux perturbation due to anthropogenic aerosols can be broken down into a component over the cloud-free portion of the globe (approximately the aerosol direct effect) and a component over the cloudy portion of the globe (approximately the aerosol indirect effect). An estimate obtained by scaling these simulated clear- and cloudy-sky forcings with estimates of anthropogenic τa and satellite-retrieved Nd–τa regression slopes, respectively, yields a global, annual-mean aerosol direct effect estimate of −0.4±0.2 Wm−2 and a cloudy-sky (aerosol indirect effect) estimate of −0.7±0.5 Wm−2, with a total estimate of −1.2±0.4 Wm−2.

scholarly journals Satellite observations of interaction between tropics and mid-latitudes

MAUSAM ◽  
2021 ◽  
Vol 43 (1) ◽  
pp. 59-64
Author(s):  
S.R. KALSI ◽  
S. R. HALDER
Keyword(s):  
Satellite Data ◽  
Circulation Pattern ◽  
Short Wave ◽  
Satellite Observations ◽  
Low Latitude ◽  
Short Waves ◽  
Long Wave ◽  
Tropical Areas ◽  
Northwest India

In certain seasons and over certain locations, the mid-latitude westerlies invade subtropical and tropical areas. Short wave perturbations moving in the broad mid-latitude westerlies amplify the. long wave troughs creating new baroclinic zones in relatively southern latitudes. These. baroclinic zones Interact .with the low-latitude circulations thus leading to development of new circulation pattern .In which low level easterlies extend northward over the Peninsula, central and northwest .India. The paper describes the role of short waves in the interaction between tropics and mid-latitudes and presents satellite data of a few sequences In which such Interactions have actually taken place.

scholarly journals Can a coupled meteorology-chemistry model reproduce the historical trend in aerosol direct radiative effects over the Northern Hemisphere?

2015 ◽  
Vol 15 (10) ◽  
pp. 14027-14073
Author(s):  
J. Xing ◽  
R. Mathur ◽  
J. Pleim ◽  
C. Hogrefe ◽  
C.-M. Gan ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Eastern China ◽  
Short Wave ◽  
North Indian Ocean ◽  
Wave Radiation ◽  
Radiative Efficiency ◽  
Historical Trend ◽  
Clear Sky ◽  
Northern Pacific ◽  
Central Atlantic

Abstract. The ability of a coupled meteorology-chemistry model, i.e., WRF-CMAQ, in reproducing the historical trend in AOD and clear-sky short-wave radiation (SWR) over the Northern Hemisphere has been evaluated through a comparison of 21 year simulated results with observation-derived records from 1990–2010. Six satellite retrieved AOD products including AVHRR, TOMS, SeaWiFS, MISR, MODIS-terra and -aqua as well as long-term historical records from 11 AERONET sites were used for the comparison of AOD trends. Clear-sky SWR products derived by CERES at both TOA and surface as well as surface SWR data derived from seven SURFRAD sites were used for the comparison of trends in SWR. The model successfully captured increasing AOD trends along with the corresponding increased TOA SWR (upwelling) and decreased surface SWR (downwelling) in both eastern China and the northern Pacific. The model also captured declining AOD trends along with the corresponding decreased TOA SWR (upwelling) and increased surface SWR (downwelling) in eastern US, Europe and northern Atlantic for the period of 2000–2010. However, the model underestimated the AOD over regions with substantial natural dust aerosol contributions, such as the Sahara Desert, Arabian Desert, central Atlantic and north Indian Ocean. Estimates of aerosol direct radiative effect (DRE) at TOA are comparable with those derived by measurements. Compared to GCMs, the model exhibits better estimates of surface- aerosol direct radiative efficiency (Eτ). However, surface-DRE tends to be underestimated due to the underestimated AOD in land and dust regions. Further investigation of TOA-Eτ estimations as well as the dust module used for estimates of windblown-dust emissions is needed.

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