Spatiotemporal Variations of Aerosol Optical Depth in the Atmosphere over Baikal Region Based on MODIS Data

This paper considers spatiotemporal distribution and seasonal variability of aerosol optical depth (AOD) of the atmosphere at the 0.55 μm wavelength in the atmosphere over the Baikal region of Russia based on long-term data (2005–2019) from satellite observations (MODIS/AQUA). A comparison of satellite AOD values with the AERONET record at the Geophysical Observatory of Institute of Solar-Terrestrial Physics of Siberian Brunch of Russian Academy of Science was performed. The results show that interannual AOD variability is mainly due to forest fires. The highest atmospheric transparency was in 2010, 2013, and 2016, and the lowest was in 2008, 2012 and 2014. It is noted that AOD decreased with latitude with a gradient ΔAOD = 0.002÷0.001 per degree of latitude. The mean seasonal variations in AOD at the six satellite overpass points were characterized by spring (April) and summer (July) highs and low AOD values in autumn. From June to November, the drop in AOD monthly means was more than 60%.

A systematic assessment of water vapor products in the Arctic: from instantaneous measurements to monthly means

Water vapor is an important component in the water and energy cycle of the Arctic. Especially in light of Arctic amplification, changes in water vapor are of high interest but are difficult to observe due to the data sparsity of the region. The ACLOUD/PASCAL campaigns performed in May/June 2017 in the Arctic North Atlantic sector offers the opportunity to investigate the quality of various satellite and reanalysis products. Compared to reference measurements at R/V Polarstern frozen into the ice (around 82∘ N, 10∘ E) and at Ny-Ålesund, the integrated water vapor (IWV) from Infrared Atmospheric Sounding Interferometer (IASI) L2PPFv6 shows the best performance among all satellite products. Using all radiosonde stations within the region indicates some differences that might relate to different radiosonde types used. Atmospheric river events can cause rapid IWV changes by more than a factor of 2 in the Arctic. Despite the relatively dense sampling by polar-orbiting satellites, daily means can deviate by up to 50 % due to strong spatio-temporal IWV variability. For monthly mean values, this weather-induced variability cancels out, but systematic differences dominate, which particularly appear over different surface types, e.g., ocean and sea ice. In the data-sparse central Arctic north of 84∘ N, strong differences of 30 % in IWV monthly means between satellite products occur in the month of June, which likely result from the difficulties in considering the complex and changing surface characteristics of the melting ice within the retrieval algorithms. There is hope that the detailed surface characterization performed as part of the recently finished Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) will foster the improvement of future retrieval algorithms.

Spatiotemporal variations of surface water microplastics near Kyushu, Japan: A quali-quantitative analysis

Microplastics in the ocean are threatening marine ecosystems. Although plastic contaminants are ubiquitous from rivers to polar oceans, their distribution is thought to be heterogeneous, implying that both spatial and temporal variability exist. Here, we elucidate the significant spatial and temporal (seasonal) variations in the quanti-qualitative characteristics of microplastics off the west coast of Kyushu, Japan in the East China Sea. Six surveys across nine stations (n = 54) were conducted over a 14-month period, and a total of 6131 plastic items were identified. The average microplastic abundance (items·m-3) and size (mm) ± S.D. were 0.49 ± 0.92 (n = 54), and 1.71 ± 0.93 (n = 6131), respectively. Differences between the highest and lowest abundances were 50-fold among monthly means (1.97 ± 1.49, n = 9; 0.04 ± 0.03, n = 9), and 550-fold across all net tows (5.50; 0.01). With respect to colour, polymer type, and shape, white and transparent (68.5%), polyethylene (80%) fragments (76.0%) were the dominant composition. There were statistically significant differences for each of the analytical microplastic parameters among survey months (p < 0.02). Our results provide baseline data, and lead to a more comprehensive understanding of the spatiotemporal characteristics of microplastic pollution.

Nocturnal surface fluxes of N2O and CH4 determined from atmospheric measurements at the Cabauw tall tower

&lt;p&gt;The agricultural emissions are the dominant sources of N&lt;sub&gt;2&lt;/sub&gt;O and CH&lt;sub&gt;4&lt;/sub&gt; in the Netherlands. In this study, we have estimated nocturnal surface fluxes of both N&lt;sub&gt;2&lt;/sub&gt;O and CH&lt;sub&gt;4&lt;/sub&gt; using atmospheric measurements at the Cabauw tall tower (4.927&amp;#9702; E, 51.971&amp;#9702; N, - 0.7 m a.s.l.). The nocturnal N&lt;sub&gt;2&lt;/sub&gt;O and CH&lt;sub&gt;4&lt;/sub&gt; surface fluxes were derived using two different methods, the vertical gradient method (VGM), i.e. the sum of the storage flux and the turbulent flux, and the radon-tracer method (RTM), for the period of March 2017-December 2018 and 2016-2018, respectively. For N&lt;sub&gt;2&lt;/sub&gt;O, we show that a few events occurring between May 30 and June 4 in 2018 dominated the monthly means. Using the VGM, we have estimated the annual mean nocturnal surface flux to be 0.59 &amp;#177; 0.38 g/m&lt;sup&gt;2&lt;/sup&gt;/yr (1 &amp;#963;, the same as below) and 0.53 &amp;#177; 0.19 g/m&lt;sup&gt;2&lt;/sup&gt;/yr with and without events, respectively. The fluxes are high in the summer and low in the winter, with a seasonal amplitude of around 1.0 g/m2/yr and 0.5 g/m&lt;sup&gt;2&lt;/sup&gt;/yr, with and without events, respectively, which is likely caused by the seasonality of agricultural activities. For CH&lt;sub&gt;4, &lt;/sub&gt;the annual mean nocturnal surface flux is 12.1 &amp;#177; 3.3 g/m&lt;sup&gt;2&lt;/sup&gt;/yr and the amplitude is around 9.9 g/m&lt;sup&gt;2&lt;/sup&gt;/yr. Using the RTM, the mean fluxes of the whole period for N&lt;sub&gt;2&lt;/sub&gt;O and CH&lt;sub&gt;4 &lt;/sub&gt;are estimated to be 1.18 &amp;#177; 2.25 (1.08 &amp;#177; 1.29, without the events) g/m&lt;sup&gt;2&lt;/sup&gt;/yr and 26.9 &amp;#177; 24.8 g/m&lt;sup&gt;2&lt;/sup&gt;/yr, respectively; in contrast to the VGM, no apparent seasonal pattern has been found. However, there is a good linear correlation between the estimated N&lt;sub&gt;2&lt;/sub&gt;O fluxes from the two methods and the monthly means show a similar pattern when the same nights are considered; the R-squared value is around 0.9 with events and 0.6 without events, and the slope varies from 1.9 to 0.8 when different estimates of radon fluxes are used. Furthermore, we found that large N&lt;sub&gt;2&lt;/sub&gt;O fluxes are related to the amount of rainfall occurring days before, with the correlation coefficient of around 0.6 (p value&lt;0.01). For CH&lt;sub&gt;4&lt;/sub&gt;, there is no correlation between the estimated CH&lt;sub&gt;4&lt;/sub&gt; fluxes from the two methods. Our findings demonstrate that nocturnal N&lt;sub&gt;2&lt;/sub&gt;O and CH&lt;sub&gt;4&lt;/sub&gt; fluxes in the Cabauw area are highly variable and vary over different seasons, and that both VGM and RTM are useful to quantify regional N&lt;sub&gt;2&lt;/sub&gt;O and CH&lt;sub&gt;4&lt;/sub&gt; fluxes.&lt;/p&gt;

Comparison Between POLDER/PARASOL and CERES/AQUA Shortwave Fluxes

&lt;p&gt;Radiative Budget, essential to the monitoring of climate change, can be investigated with ERB-dedicated instruments like the Clouds and the Earth Radiant Energy System (CERES) instrument (Wielicki, 1996). On the other side, non-dedicated instruments, such as POLDER-3/PARASOL measuring narrowband radiances, can also be used advantageously to obtain shortwave albedos and fluxes (Buriez et al, 2007; Viollier et al, 2002).&lt;/p&gt;&lt;p&gt;We present here a comparison between the shortwave fluxes and albedos derived from POLDER-3 and those derived from CERES flying aboard Aqua, chosen as a reference.&lt;/p&gt;&lt;p&gt;Monthly means of shortwave fluxes computed from the measurements of the two instruments are first set side by side. They show a good agreement in the all-sky case. However, after December 2009, the values from POLDER-3 display a slight drift which coincides with the lowering of the orbit of the PARASOL satellite and the modification of its overpass time in comparison to the other satellites of the A-Train mission. In clear sky situations, greater differences between POLDER and CERES shortwave fluxes are observed, especially over land regions, and the drift increases faster after 2009.&lt;/p&gt;&lt;p&gt;A second comparison is presented, between instantaneous albedos. For the period of coincident observations between POLDER-3 and CERES/Aqua, there is a good correlation between both products. This correlation deteriorates when the comparison is extended after 2009, as the values given by POLDER-3 increase. This result is expected, as the albedo is a function of the Solar Zenith Angle.&lt;/p&gt;&lt;p&gt;The slope of the increase of instantaneous albedo values is higher than for the diurnally extrapolated, monthly averaged shortwave fluxes. This tends to show that the POLDER algorithm leading to the monthly means of diurnal shortwave albedos moderates the increase of instantaneous shortwave albedo values but it doesn&amp;#8217;t completely compensate for the effects of the drift of the instrument.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

A systematic assessment of water vapor products in the Arctic: from instantaneous measurements to monthly means

Water vapor is an important component in the water and energy cycle of the Arctic. Especially in the light of Arctic amplification, changes of water vapor are of high interest but are difficult to observe due to the data sparsity of the region. The ACLOUD/PASCAL campaign performed in May/June 2017 in the Arctic North Atlantic sector offers the opportunity to investigate the quality of various satellite and reanalysis products. Compared to reference measurements at R/V Polarstern frozen into the ice (around 82° N, 10° E) and at Ny-Ålesund, the Integrated Water Vapor (IWV) from IASI shows the best performance among all satellite products. Using all radiosonde stations within the region indicates some differences that might relate to different radiosonde types used. Though the region is well sampled by polar orbiting satellites daily means can deviate by up to 50 % due to strong spatio-temporal IWV variability associated with atmospheric river events. For monthly mean values, this weather induced variability cancels out but systematic differences dominate which particularly appear over different surface types, e.g. ocean, sea ice. In the data sparse central Arctic above 84° N, strong differences of 30 % in IWV monthly means between satellite products occur in the month of June which likely results from the difficulties to consider the complex and changing surface characteristics of the melting ice within the retrieval algorithms. There is hope that the detailed surface characterization performed as part of the recently finished Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) will foster the improvement of future retrieval algorithms.

Effect of the main active volcanoes on aerosol optical properties

Processing of the measurements obtained by the AERONET network of the optical parameters characteristic of the atmospheric aerosol carried out makes it possible to compare the optical effects of 2020 volcanic eruptions to those results for 2019 concerning Mexico City and Mauna Loa site. Both the monthly spectral means of AOD and the monthly means of fine and coarse volume concentration show an increase for the months of January and February 2020 (Volcanic eruption period) compared to the same period in 2019 at Mexico City. Those corresponding to Mauna-Loa seem not sensible with very low values. The effects of ashes of the two-studied volcano are very different, led to a low increase in optical depth comparatively to the contribution of anthropogenic aerosol at MexicoCity (low continental spread) and led to a nonsignificate effect at Mauna-Loa (high marine spread).

Long-Term Analysis of Atmospheric Energetics Components over the Mediterranean, Middle East and North Africa

In this research, one aspect of the climate that is not commonly referred to, namely, the long-term changes in the components of the atmospheric energy, is investigated. In this respect, the changes in four energy forms are considered, namely, Kinetic Energy (KE), Thermal Energy (TE), Internal Energy (IE), Potential Energy (PE) and Latent Energy (LE); the Energy Conversion (EC) between Kinetic Energy and Potential plus Internal Energy (PIE) is also considered. The area considered in this long-term energetics analysis covers the entire Mediterranean basin, the Middle East and a large part of North Africa. This broad geographical area has been identified by many researchers as a hot spot of climate change. Analyses of climatic data have indeed shown that this region has been experiencing marked changes regarding several climatic variables. The present energetics analysis makes use of the ERA-Interim database for the period from 1979 to 2018. In this 40-year period, the long-term changes in the above energetics components are studied. The monthly means of daily means for all the above energy forms and Energy Conversion comprise the basis for the present research. The results are presented in the form of monthly means, annual means and spatial distributions of the energetics components. They show the dominant role of the subtropical jet-stream in the KE regime. During the study period, the tendency is for KE to decrease with time, with this decrease found to be more coherent in the last decade. The tendency for TE is to increase with time, with this increase being more pronounced in the most recent years, with the maximum in the annual mean in KE noted in 2015. The sum of Potential and Internal energies (PIE) and the sum of Potential, Internal and Latent energies (PILE) follow closely the patterns established for TE. In particular, the strong seasonal influence on the monthly means is evident with minima of PIE and PILE noted in winters, whereas, maxima are registered during summers. In addition, both PIE and PILE exhibit a tendency to increase with time in the 40-year period, with this increase being more firmly noted in the more recent years. Although local conversion from KE into PIE is notable, the area averaging of EC shows that the overall conversion is in the direction of increasing the PIE content of the area at the expense of the KE content. EC behaves rather erratically during the study period, with values ranging from 0.5 to 3.7 × 102 W m−2. Averaged over the study area, the Energy Conversion term operates in the direction of converting KE into PIE; it also lacks a seasonal behavior.