This page has only limited features, please log in for full access.
A satellite algorithm able to identify Dust Aerosols (DA) is applied for a climatological investigation of Dust Aerosol Episodes (DAEs) over the greater Mediterranean Basin (MB), one of the most climatologically sensitive regions of the globe. The algorithm first distinguishes DA among other aerosol types (such as Sea Salt and Biomass Burning) by applying threshold values on key aerosol optical properties describing their loading, size and absorptivity, namely Aerosol Optical Depth (AOD), Aerosol Index (AI) and Ångström Exponent (α). The algorithm operates on a daily and 1° × 1° geographical cell basis over the 15-year period 2005–2019. Daily gridded spectral AOD data are taken from Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua Collection 6.1, and are used to calculate the α data, which are then introduced into the algorithm, while AI data are obtained by the Ozone Monitoring Instrument (OMI) -Aura- Near-UV aerosol product OMAERUV dataset. The algorithm determines the occurrence of Dust Aerosol Episode Days (DAEDs), whenever high loads of DA (higher than their climatological mean value plus two/four standard deviations for strong/extreme DAEDs) exist over extended areas (more than 30 pixels or 300,000 km2). The identified DAEDs are finally grouped into Dust Aerosol Episode Cases (DAECs), consisting of at least one DAED. According to the algorithm results, 166 (116 strong and 50 extreme) DAEDs occurred over the MB during the study period. DAEDs are observed mostly in spring (47%) and summer (38%), with strong DAEDs occurring primarily in spring and summer and extreme ones in spring. Decreasing, but not statistically significant, trends of the frequency, spatial extent and intensity of DAECs are revealed. Moreover, a total number of 98 DAECs was found, primarily in spring (46 DAECs) and secondarily in summer (36 DAECs). The seasonal distribution of the frequency of DAECs varies geographically, being highest in early spring over the eastern Mediterranean, in late spring over the central Mediterranean and in summer over the western MB.
Maria Gavrouzou; Nikolaos Hatzianastassiou; Antonis Gkikas; Christos Lolis; Nikolaos Mihalopoulos. A Climatological Assessment of Intense Desert Dust Episodes over the Broader Mediterranean Basin Based on Satellite Data. Remote Sensing 2021, 13, 2895 .
AMA StyleMaria Gavrouzou, Nikolaos Hatzianastassiou, Antonis Gkikas, Christos Lolis, Nikolaos Mihalopoulos. A Climatological Assessment of Intense Desert Dust Episodes over the Broader Mediterranean Basin Based on Satellite Data. Remote Sensing. 2021; 13 (15):2895.
Chicago/Turabian StyleMaria Gavrouzou; Nikolaos Hatzianastassiou; Antonis Gkikas; Christos Lolis; Nikolaos Mihalopoulos. 2021. "A Climatological Assessment of Intense Desert Dust Episodes over the Broader Mediterranean Basin Based on Satellite Data." Remote Sensing 13, no. 15: 2895.
Mediterranean Basin (MB), due to its position near to the greatest world deserts (the Sahara Desert in North Africa and the deserts of Middle East), is frequently affected by dust transport. This results in dust episodes, associated with high Dust Aerosol (DA) loads reaching the northern parts of MB, taking place every year with different intensity, but with specific seasonal and spatial characteristics. The seasonal and spatial characteristics of Dust Aerosol Episodes (DAEs) in the region are connected to specific atmospheric conditions that favor the injection of DA into the region’s atmosphere, as well as to specific atmospheric circulation characteristics favoring the transport to the MB.
DA not only are affected by, but they also can affect the atmospheric conditions and thus the regional weather and climate regime. Specifically, due to their ability to absorb the shortwave, but also the longwave, radiation, DA can modify the temperature structure of the atmosphere as well as the radiative budget. In addition, DA are effective Ice Nuclei (IN), and also, under mature stages, Cloud Condensation Nuclei (CCN), thus affecting cloud properties. These effects of DA become more important, but also complicated, when high dust loads are associated with other aerosol types, e.g. sea-salt (SS) and biomass burning (BB) over a region with high solar radiation, diverse topography and cloud regimes such as the MB.
In the present study, the atmospheric circulation (geopotential height and mean sea level pressure), as well as the meteorological conditions (cloud fraction, cloud optical thickness, cloud phase, temperature and humidity profiles and vertical velocity) before, during and after an extreme Dust Aerosol Episode Case (DAEC) that took place over the western MB on June 16, 2016 are examined. The studied DAEC is identified using a satellite algorithm, which uses MODIS C6.1 and OMI OMAERUV derived aerosol optical properties. Emphasis is given to the understanding of the 3-D structure of the episode and its possible effects on the atmospheric temperature and humidity regime, as well as on cloud properties. For this reason, different reanalyses and satellite data, namely from the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis Project), MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, Version 2) and MODIS databases, are analyzed. In addition, the vertical aerosol profile is obtained from MERRA-2 data.
Maria Gavrouzou; Nikos Hatzianastassiou; Antonis Gkikas; Marios-Bruno Korras-Carraca; Christos Lolis; Nikos Mihalopoulos. Atmospheric circulation and meteorological conditions during dust aerosol episodes over the broader Mediterranean Basin. The case of 16 June 2016. 2021, 1 .
AMA StyleMaria Gavrouzou, Nikos Hatzianastassiou, Antonis Gkikas, Marios-Bruno Korras-Carraca, Christos Lolis, Nikos Mihalopoulos. Atmospheric circulation and meteorological conditions during dust aerosol episodes over the broader Mediterranean Basin. The case of 16 June 2016. . 2021; ():1.
Chicago/Turabian StyleMaria Gavrouzou; Nikos Hatzianastassiou; Antonis Gkikas; Marios-Bruno Korras-Carraca; Christos Lolis; Nikos Mihalopoulos. 2021. "Atmospheric circulation and meteorological conditions during dust aerosol episodes over the broader Mediterranean Basin. The case of 16 June 2016." , no. : 1.
A satellite-based algorithm is developed and used to determine the presence of dust aerosols on a global scale. The algorithm uses as input aerosol optical properties from the MOderate Resolution Imaging Spectroradiometer (MODIS)-Aqua Collection 6.1 and Ozone Monitoring Instrument (OMI)-Aura version v003 (OMAER-UV) datasets and identifies the existence of dust aerosols in the atmosphere by applying specific thresholds, which ensure the coarse size and the absorptivity of dust aerosols, on the input optical properties. The utilized aerosol optical properties are the multiwavelength aerosol optical depth (AOD), the Aerosol Absorption Index (AI) and the Ångström Exponent (a). The algorithm operates on a daily basis and at 1° × 1° latitude-longitude spatial resolution for the period 2005–2019 and computes the absolute and relative frequency of the occurrence of dust. The monthly and annual mean frequencies are calculated on a pixel level for each year of the study period, enabling the study of the seasonal as well as the inter-annual variation of dust aerosols’ occurrence all over the globe. Temporal averaging is also applied to the annual values in order to estimate the 15-year climatological mean values. Apart from temporal, a spatial averaging is also applied for the entire globe as well as for specific regions of interest, namely great global deserts and areas of desert dust export. According to the algorithm results, the highest frequencies of dust occurrence (up to 160 days/year) are primarily observed over the western part of North Africa (Sahara), and over the broader area of Bodélé, and secondarily over the Asian Taklamakan desert (140 days/year). For most of the study regions, the maximum frequencies appear in boreal spring and/or summer and the minimum ones in winter or autumn. A clear seasonality of global dust is revealed, with the lowest frequencies in November–December and the highest ones in June. Finally, an increasing trend of global dust frequency of occurrence from 2005 to 2019, equal to 56.2%, is also found. Such an increasing trend is observed over all study regions except for North Middle East, where a slight decreasing trend (−2.4%) is found.
Maria Gavrouzou; Nikolaos Hatzianastassiou; Antonis Gkikas; Marios-Bruno Korras-Carraca; Nikolaos Mihalopoulos. A Global Climatology of Dust Aerosols Based on Satellite Data: Spatial, Seasonal and Inter-Annual Patterns over the Period 2005–2019. Remote Sensing 2021, 13, 359 .
AMA StyleMaria Gavrouzou, Nikolaos Hatzianastassiou, Antonis Gkikas, Marios-Bruno Korras-Carraca, Nikolaos Mihalopoulos. A Global Climatology of Dust Aerosols Based on Satellite Data: Spatial, Seasonal and Inter-Annual Patterns over the Period 2005–2019. Remote Sensing. 2021; 13 (3):359.
Chicago/Turabian StyleMaria Gavrouzou; Nikolaos Hatzianastassiou; Antonis Gkikas; Marios-Bruno Korras-Carraca; Nikolaos Mihalopoulos. 2021. "A Global Climatology of Dust Aerosols Based on Satellite Data: Spatial, Seasonal and Inter-Annual Patterns over the Period 2005–2019." Remote Sensing 13, no. 3: 359.
In the present study, dust aerosol episodes (DAEs) in the broader Mediterranean Basin (MB) are investigated over a 15-year (2005–2019) period using contemporary MODIS Collection 6.1 and OMI OMAERUV satellite data and a satellite algorithm applying a thresholding technique on selected aerosol optical properties. The algorithm operates on a daily and 1° × 1° pixel level basis, first identifying the presence of dust, and consequently requiring the presence of unusually high dust loads, i.e., dust episodes. Apart from the presence of pixel-level DAEs, an extended spatial coverage of dust is also required. Thus, a specific day is characterized as a Dust Aerosol Episode Day (DAED), when at least 30 episodic pixels exist over Mediterranean Basin (MB). According to the algorithm results, 166 DAEDs (116 strong and 50 extreme) took place in the MB from 2005 to 2019. Most DAEDs occurred in spring (47%) and summer (38%), while a different seasonality is observed for strong and extreme episodes. The interannual variability of DAEDs reveal a decreasing trend, which is however not statistically significant.
Maria Gavrouzou; Nikos Hatzianastassiou; Antonis Gkikas; Nikos Mihalopoulos. A 15-Year Climatology of Desert Dust Episodes in the Broader Mediterranean Basin. Environmental Sciences Proceedings 2020, 4, 1 .
AMA StyleMaria Gavrouzou, Nikos Hatzianastassiou, Antonis Gkikas, Nikos Mihalopoulos. A 15-Year Climatology of Desert Dust Episodes in the Broader Mediterranean Basin. Environmental Sciences Proceedings. 2020; 4 (1):1.
Chicago/Turabian StyleMaria Gavrouzou; Nikos Hatzianastassiou; Antonis Gkikas; Nikos Mihalopoulos. 2020. "A 15-Year Climatology of Desert Dust Episodes in the Broader Mediterranean Basin." Environmental Sciences Proceedings 4, no. 1: 1.
Downward surface solar radiation (SSR) trends for the first decade of the 2000s were computed using a radiative transfer model and satellite and reanalysis input data and were validated against measurements from the reference global station networks Global Energy Balance Archive (GEBA) and Baseline Surface Radiation Network (BSRN). Under all-sky conditions, in spite of a somewhat patchy structure of global dimming and brightening (GDB), an overall dimming was found that is weaker in the Northern than in the Southern Hemisphere (−2.2 and −3.1 W m−2, respectively, over the 2001–2009 period). Dimming is observed over both land and ocean in the two hemispheres, but it is more remarkable over land areas of the Southern Hemisphere. The post-2000 dimming is found to have been primarily caused by clouds, and secondarily by aerosols, with total cloud cover contributing −1.4 W m−2 and aerosol optical thickness −0.7 W m−2 to the global average dimming of −2.65 W m−2. The evaluation of the model-computed GDB against BSRN and GEBA measurements indicates a good agreement, with the same trends for 65% and 64% of the examined stations, respectively. The obtained model results are in line with other studies for specific world regions and confirm the occurrence of an overall solar dimming over the globe during the first decade of 21st century. This post-2000 dimming has succeeded the global brightening observed in the 1990s and points to possible impacts on the ongoing global warming and climate change.
Nikolaos Hatzianastassiou; Eleftherios Ioannidis; Marios-Bruno Korras-Carraca; Maria Gavrouzou; Christos D. Papadimas; Christos Matsoukas; Nikolaos Benas; Angeliki Fotiadi; Martin Wild; Ilias Vardavas. Global Dimming and Brightening Features during the First Decade of the 21st Century. Atmosphere 2020, 11, 308 .
AMA StyleNikolaos Hatzianastassiou, Eleftherios Ioannidis, Marios-Bruno Korras-Carraca, Maria Gavrouzou, Christos D. Papadimas, Christos Matsoukas, Nikolaos Benas, Angeliki Fotiadi, Martin Wild, Ilias Vardavas. Global Dimming and Brightening Features during the First Decade of the 21st Century. Atmosphere. 2020; 11 (3):308.
Chicago/Turabian StyleNikolaos Hatzianastassiou; Eleftherios Ioannidis; Marios-Bruno Korras-Carraca; Maria Gavrouzou; Christos D. Papadimas; Christos Matsoukas; Nikolaos Benas; Angeliki Fotiadi; Martin Wild; Ilias Vardavas. 2020. "Global Dimming and Brightening Features during the First Decade of the 21st Century." Atmosphere 11, no. 3: 308.