Northeastern Asia Research Articles

Projections of wildfire risk and activities under 1.5 °C and 2.0 °C global warming scenarios

Wildfires are important ecosystem processes that have a significant impact on terrestrial vegetation, environment, and climate. This study investigates how future wildfire risk and activities could change under 1.5 °C and 2.0 °C warming scenarios relative to pre-industrial levels using a modified McArthur Forest Fire Danger Index (FFDIn) and the CLM4.5-BGC land surface model. Sixteen Earth System Models (ESMs) from CMIP5 and CMIP6 were employed to supply the variables of climate change under low, middle, and high greenhouse emission scenarios in the 1.5 °C and 2.0 °C scenarios. The ensemble means from the FFDIn and results from the CLM4.5-BGC with multiple forcings show that the dry areas in the southwestern US, Brazilian Highlands, and Arabian islands are projected to face higher wildfire risk with larger burned areas and more carbon emissions under a warmer climate. The Congo Basin and part of the Amazon could have a lower wildfire risk with smaller burned areas and less carbon emissions. The absolute changes in the projected FFDIn are small, although large increases are observed in boreal areas, particularly in the winter and spring. Burned area and carbon emissions are projected to increase in general in the boreal area but decrease in northeastern Asia. Compared to the 1.5 °C scenario, the wildfire risk and burned area levels are projected to increase under the 2.0 °C scenario except in the western Amazon. However, fire carbon emissions are projected to decrease more in tropical areas under the 2.0 °C scenario. The different change directions in eastern North America and eastern China produced by the FFDIn and CLM4.5-BGC suggest the potential effect of non-meteorological elements on fire activities.

Evolutionary origins of the eastern North American-Mesoamerican floristic disjunction: Current status and future prospects.

Biogeographic disjunction patterns, where multiple taxa are shared between isolated geographic areas, represent excellent systems for investigating the historical assembly of modern biotas and fundamental biological processes such as speciation, diversification, niche evolution, and evolutionary responses to climate change. Studies on plant genera disjunct across the northern hemisphere, particularly between eastern North America (ENA) and eastern Asia (EAS), have yielded tremendous insight on the geologic history and assembly of rich temperate floras. However, one of the most prevalent disjunction patterns involving ENA forests has been largely overlooked: that of taxa disjunct between ENA and cloud forests of Mesoamerica (MAM), with examples including Acer saccharum, Liquidambar styraciflua, Cercis canadensis, Fagus grandifolia, and Epifagus virginiana. Despite the remarkable nature of this disjunction pattern, which has been recognized for over 75 years, there have been few recent efforts to empirically examine its evolutionary and ecological origins. Here I synthesize previous systematic, paleobotanical, phylogenetic, and phylogeographic studies to establish what is known about this disjunction pattern to provide a roadmap for future research. I argue that this disjunction pattern, and the evolution and fossil record of the Mexican flora more broadly, represents a key missing piece in the broader puzzle of northern hemisphere biogeography. I also suggest that the ENA-MAM disjunction represents an excellent system for examining fundamental questions about how traits and life history strategies mediate plant evolutionary responses to climate change and for predicting how broadleaf temperate forests will respond to the ongoing climatic pressures of the Anthropocene.

Causes for an extreme cold condition over Northeast Asia during April 2020

Although 2020 was the fourth warmest year on record in northern Asia, the cold condition in April 2020 caused severe damage to the agricultural and marine ecosystems in northeastern Asia. Previous studies have indicated that the dipole atmospheric circulation over Siberia and the East Sea (Japan Sea) produced this cold environment with strong northwesterly wind. However, the potential causes of the dipole circulation over northeastern Asia remain unclear. In this study, we found that the East Atlantic/Western Russia (EAWR) pattern and blocking combined to produce the atmospheric structure. The wave train originated from the vorticity forcing of northwestern/central Russia and propagated from Western Europe to the East Sea via the background westerly and northerly winds. In addition, the Siberian blocking days increased eleven times in April 2020 relative to the climatological average, and an easterly (westerly) anomaly was observed over Mongolia–northeastern China (northern Russia). The strong blocking and EAWR pattern led to the robust atmospheric dipole structure with a prevailing northerly flow in April 2020, thereby causing the extreme cold condition over northeastern Asia. Our results provide novel insights into the cause of extreme cold condition in April over northeastern Asia.

Variation of lightning-ignited wildfire patterns under climate change

Lightning is the main precursor of natural wildfires and Long-Continuing-Current (LCC) lightning flashes are proposed to be the main igniters of lightning-ignited wildfires (LIW). Previous studies predict a change of the global occurrence rate and spatial pattern of total lightning. Nevertheless, the sensitivity of lightning-ignited wildfire occurrence to climate change is uncertain. Here, we investigate space-based measurements of LCC lightning associated with lightning ignitions and present LCC lightning projections under the Representative Concentration Pathway RCP6.0 for the 2090s by applying a recent LCC lightning parameterization based on the updraft strength in thunderstorms. We find a 41% global increase of the LCC lightning flash rate. Increases are largest in South America, the western coast of North America, Central America, Australia, Southern and Eastern Asia, and Europe, while only regional variations are found in northern polar forests, where fire risk can affect permafrost soil carbon release. These results show that lightning schemes including LCC lightning are needed to project the occurrence of lightning-ignited wildfires under climate change.

Atmospheric water transport connectivity within and between ocean basins and land

Abstract. The global atmospheric water transport from the net evaporation to the net precipitation regions has been traced using Lagrangian trajectories. A matrix has been constructed by selecting various group of trajectories based on their surface starting (net evaporation) and ending (net precipitation) positions to show the connectivity of the 3-D atmospheric water transport within and between the three major ocean basins and the global landmass. The analysis reveals that a major portion of the net evaporated water precipitates back into the same region, namely 67 % for the Indian Ocean, 64 % for the Atlantic Ocean, 85 % for the Pacific Ocean and 72 % for the global landmass. It has also been calculated that 58 % of the net terrestrial precipitation was sourced from land evaporation. The net evaporation from the subtropical regions of the Indian, Atlantic and Pacific oceans is found to be the primary source of atmospheric water for precipitation over the Intertropical Convergence Zone (ITCZ) in the corresponding basins. The net evaporated waters from the subtropical and western Indian Ocean were traced as the source for precipitation over the South Asian and eastern African landmass, while Atlantic Ocean waters are responsible for rainfall over North Asia and western Africa. Atlantic storm tracks were identified as the carrier of atmospheric water that precipitates over Europe, while the Pacific storm tracks were responsible for North American, eastern Asian and Australian precipitation. The bulk of South and Central American precipitation is found to have its source in the tropical Atlantic Ocean. The land-to-land atmospheric water transport is pronounced over the Amazon basin, western coast of South America, Congo basin, northeastern Asia, Canada and Greenland. The ocean-to-land and land-to-ocean water transport through the atmosphere was computed to be 2×109 and 1×109 kg s−1, respectively. The difference between them (net ocean-to-land transport), i.e. 1×109 kg s−1, is transported to land. This net transport is approximately the same as found in previous estimates which were calculated from the global surface water budget.

A taxonomic revision of Cynanchumthesioides (Apocynaceae) with two new synonyms.

Cynanchumthesioides, a species widely distributed in north-eastern Asia, is revised to include two new synonyms: Vincetoxicumsibiricumf.linearifolium, described from Shandong, China in 1877, but long neglected and Cynanchumgobicum, previously believed to be endemic to Mongolia. Typification for C.thesioides and all its synonyms is given, including lectotypification of V.sibiricumvar.australe and V.sibiricumf.linearifolium. An updated description, three figures showing the diverse habitats, habits and variation in morphological characters, and a general distribution map are also provided.

Middle Holocene Siberian genomes reveal highly connected gene pools throughout North Asia

The peopling history of North Asia remains largely unexplored due to the limited number of ancient genomes analyzed from this region. Here, we report genome-wide data of ten individuals dated to as early as 7,500 years before present from three regions in North Asia, namely Altai-Sayan, Russian Far East, and the Kamchatka Peninsula. Our analysis reveals a previously undescribed Middle Holocene Siberian gene pool in Neolithic Altai-Sayan hunter-gatherers as a genetic mixture between paleo-Siberian and ancient North Eurasian (ANE) ancestries. This distinctive gene pool represents an optimal source for the inferred ANE-related population that contributed to Bronze Age groups from North and Inner Asia, such as Lake Baikal hunter-gatherers, Okunevo-associated pastoralists, and possibly Tarim Basin populations. We find the presence of ancient Northeast Asian (ANA) ancestry-initially described in Neolithic groups from the Russian Far East-in another Neolithic Altai-Sayan individual associated with different cultural features, revealing the spread of ANA ancestry ∼1,500km further to the west than previously observed. In the Russian Far East, we identify 7,000-year-old individuals that carry Jomon-associated ancestry indicating genetic links with hunter-gatherers in the Japanese archipelago. We also report multiple phases of Native American-related gene flow into northeastern Asia over the past 5,000 years, reaching the Kamchatka Peninsula and central Siberia. Our findings highlight largely interconnected population dynamics throughout North Asia from the Early Holocene onward.

Biogeographic origin and genetic characteristics of the peopling of Jeju Island based on lineage markers.

Jeju Island is the largest island of South Korea, located southwest far from the mainland of Korea, and has a unique history and its own cultures that are distinguished from those of the other regions of the Korean mainland. However, the Jeju population has not been deeply investigated to date to understand their genetic structure, which may reflect their historical and geographical background. To identify the genetic characteristics and biogeographic origin of people of Jeju Island based on the statistical analysis of genetic data using lineage markers. 17 Y-STRs data for 615 unrelated males and mitochondrial DNA haplogroup data for 799 unrelated individuals residing on Jeju Island were generated, and analyzed to investigate genetic diversity and genetic characteristics using statistical methods including pairwise Fst or Rst, Analysis of molecular variance (AMOVA) and Multidimensional scaling (MDS). For male individuals of Jeju Island, unique genetic characteristics were observed in the analysis of Y-STRs, including low haplotype diversity, strong association with surnames, genetic difference from other regions of Korea, and common genetic variation of the Y-STR loci known to be predominant in Northern populations, such as Mongolians. Statistical analysis of the mitochondrial DNA haplogroups also revealed similar results that showed low haplogroup diversity and high frequency of haplogroup Y prevalent mostly in ethnic populations around the Sea of Okhotsk in Northeastern Asia. All these results suggest that Jeju Island is genetically distinct from other regions of Korea, possibly being a subpopulation in Korea, and related closely to Northern Asian populations. The findings in the genetic approach could support understanding of the historical background of Jeju Island that is consistent with evidence from other multidisciplinary studies.

Genetic diversity, phylogeny and biogeography in the tadpole shrimp Triops granarius (Branchiopoda: Notostraca) in Qatar

The natural habitat of Qatar lacks permanent surface freshwater. Temporary ponds formed after heavy rains in the winter season are inhabited by the tadpole shrimp Triops granarius (Branchiopoda: Notostraca). In order to assess the molecular diversity of this species and to determine the relationship of Qatari populations with those from other regions, the sequences of 28S rRNA, 16S rRNA, and COI genes of individuals collected in five temporary pools were examined. Maximum likelihood phylogenetic analysis showed a high level of sequence uniformity at all three loci and indicates that the closest relatives of T. granarius in Qatar are from south Ural and northeastern Asia, including Mongolia, China, and Japan. This pattern is consistent with the geological evidence that T. granarius expanded more recently from North Africa to northeastern Asia through the Arabian land bridge. Lastly, the large genetic gap existing between the Qatar populations and their closest relatives supports the recognition of a new lineage.

Methanol extract of Myelophycus caespitosus ameliorates oxidative stress-induced cytotoxicity in C2C12 murine myoblasts via activation of heme oxygenase-1

Myelophycus caespitosus, a brown alga belonging to genus Myelophycus, has been traditionally used as a food and medicinal resource in Northeastern Asia. However, few studies have been conducted on its pharmacological activity. In this study, we evaluated whether methanol extract of M. caespitosus (MEMC) could protect against oxidative damage caused by hydrogen peroxide (H2O2) in C2C12 murine myoblasts. Our results revealed that MEMC could suppress H2O2-induced growth inhibition and DNA damage while blocking the production of reactive oxygen species. In H2O2-treated cells, cell cycle progression was halted at the G2/M phase, accompanied by changes in expression of key cell cycle regulators. However, these effects were attenuated by MEMC. In addition, we found that MEMC protected cells from induction of apoptosis associated with mitochondrial impairment caused by H2O2 treatment. Furthermore, MEMC enhanced the phosphorylation of nuclear factor-erythroid-2 related factor 2 (Nrf2) and expression and activity of heme oxygenase-1 (HO-1) in H2O2-treaetd C2C12 myoblasts. However, such anti-apoptotic and cytoprotective effects of MEMC were greatly abolished by HO-1 inhibitor, suggesting that MEMC could increase Nrf2-mediated activity of HO-1 to protect C2C12 myoblasts from oxidative stress.

THE TUNDRA SWAN, <i>CYGNUS COLUMBIANUS</i> (ANATIDAE), IN THE EASTERN ASIAN ARCTIC: TRENDS AND RANGES OF DIFFERENT FLYWAY POPULATIONS

The tundra of the eastern Asian Arctic is inhabited by at least three flyway populations of the Tundra swan: the East Asian continental migratory flyway population of C. c. bewickii; the western Pacific flyway population of C. c. bewickii, and the western (American) flyway population of C. c. columbianus. The main objective of the present paper is to assess population trends by comparing information on the historical (the only one in the tundra of northeastern Asia) bird aerial survey in 1993–1995 with the data of our aerial survey held in 2020–2021. Another aim was to estimate the proportion of breeding birds in different flyway populations. The size of the zone of intergradation C. c. bewickii and C. c. columbianus in Chukotka and the level of hybridization have so far remained poorly studied, this issue required clarification. Aerial survey data for 2020–2021 were processed using QantumGIS 9.16.5 software. The system included the following layers: a vector layer of the world map; routes of aerial surveys for 2020 and 2021; and polygons of counts for 1993–1995. The system made it possible to calculate the length of the survey. Estimates for each region were calculated for the extrapolation area given in the historical survey. Between 1993–1995 and 2020–2021, an increase in the numbers of all three flyway populations of the Tundra swan was revealed on the breeding grounds. The East Asian continental flyway population increased 3.86 times, vs. 3.05 times for the West Pacific flyway population (while the documented growth of this population was 2.1 times, according to mid-winter counts over the same period). The Western (American) flyway population grew 2.5 times. We believe that the northern border of the summer range of the Tundra swan has significantly shifted to the north, following the summer climate change and the northward shift of the subarctic tundra zone. Registration of nests and broods in areas where only non-breeding birds were recorded during the historical survey is additional evidence of a northward displacement of the range. Kymyneyveem R (about 175.6° W) borders the areas of dominance of C. c. bewickii and C. c. columbianus. The switch in dominance has been triggered off, as there is no zone where both subspecies would occur in equal proportions. The overlap area of both subspecies extends for 600 km along the Arctic coast.

Long-range transport of atmospheric speciated mercury from the eastern waters of Taiwan Island to northern South China Sea

This study explored the temporospatial distribution, gas-particle partition, and pollution sources of atmospheric speciated mercury (ASM) from the eastern offshore waters of the Taiwan Island (TI) to the northern South China Sea (SCS). Both gaseous and particulate mercury were simultaneously sampled at three remote sites in four seasons. The average concentrations of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate bound mercury (PBM) were 2.05 ± 0.45 ng/m3, 19.17 ± 5.39 pg/m3, and 0.11 ± 0.06 ng/m3, respectively. The concentrations of GEM and PBM in the cold seasons were higher than those in the warm seasons, but those of GOM had an opposite trend. In terms of gas-solid partition, ASM was apportioned as 91.3–97.3% of GEM and 2.7–8.7% of GOM and PBM. The average concentrations of GEM, GOM, and PBM at the Green Island (GI) were 2.21 ± 0.47 ng/m3, 22.31 ± 5.35 pg/m3, and 0.12 ± 0.06 ng/m3; those at the Kenting Peninsula (KT) were 2.11 ± 0.43 ng/m3, 20.57 ± 4.38 pg/m3, and 0.11 ± 0.06 ng/m3; and those at the Dongsha Islands (DS) were 1.84 ± 0.40 ng/m3, 15.19 ± 3.58 pg/m3, and 0.08 ± 0.05 ng/m3, respectively. Overall, the spatial distribution of ASM concentrations showed the order as: GI > KT > DS. Air masses blown mainly from the West Pacific Ocean (WPO) and SCS in summer showed the lowest ASM concentrations. Oppositely, high ASM concentrations were commonly observed in spring and winter when polluted air masses were blown by Asian Northeastern Monsoons (ANMs). The transport routes of polluted air masses were originated mainly from North China, Central China, Northeast China, Korea and Japan, and mostly passed through the urban and industrial regions in the northeastern Asian countries.

Ancient and modern mitogenomes of red deer reveal its evolutionary history in northern China

Red deer (Cervus elaphus/hanglu/canadensis) are a group of closely-related species that survived through the Last Glacial period in Eurasia and expanded into North America. The evolutionary modes of red deer in Europe through glacial and interglacial cycles have been established relatively well based on both modern and ancient genomes, while the evolutionary and migratory history of red deer in Asia are not so clear. Northern China, as the southern border of their current distribution, is a significant area for exploring the evolution of wapitoids (Cervus canadensis). Here, we constructed six mitochondrial genomes (lengths of 13,282–16,306 bp) from Late Pleistocene fossil cervid materials in Northeastern China, and four modern complete mitochondrial DNA sequences (16,798–16943 bp) from Northern China. Phylogenetic analyses suggest four clades in wapitoids, with our new individuals clustered into three out of the four clades. BEAST analysis indicates that the divergence between elaphoids (including Cervus elaphus and Cervus hanglu) and the complex of ‘wapitoids + sika deer (Cervus nippon)’ occurred at approximately 1.37 million years ago (Ma, 95%Cl: 1.64–1.15 Ma). Bayesian skyline plots (BSPs) show that the effective maternal population size of wapitoids had a slight and stable expansion between Marine isotope stages (MIS) 7–3, and then shrank from the beginning of the Last Glacial Maximum (LGM). Combined with the divergence dates, population dynamics, and fossil findings in Northern China, we infer that after wapitoids migrated eastward from Central Asia to Northeastern Asia, they had multiple migrations southward into Northern China. The current distribution of wapitoids in Northern China was likely shaped by these migrations as well as habitat fragmentation. Meanwhile, the radiocarbon dates of ancient individuals indicate that the Northeast China Plain, located at the same latitude as European refugia, may have provided a refugium for megafaunal species such as red deer to survive the LGM.

Triassic volcanism on the North margin of the North China Craton: Insights for lithospheric modification during closure of Paleo-Asian Ocean

As a key tectonic region linking the northern margin of the North China craton (NCC) and eastern Central Asian Orogenic Belt (CAOB), western Liaoning, with extensively distributed magmatic activity, provides natural samples to investigate the evolutionary history of the Paleo-Asian Ocean plate subduction to closure. The Middle Triassic (ca. 241 Ma) trachyandesites and Late Triassic (ca. 223 Ma) basaltic andesites were first identified from the Tiaojishan Formation, western Liaoning. They have variable SiO 2 contents (52.48–60.31 wt%) and alkaline or high-K calc-alkaline to shoshonite compositions, and belong to the metaluminous series. Middle Triassic trachyandesites are enriched in large ion lithophile elements (LILEs), high field strength elements (HFSEs), and light rare earth elements (LREEs) with high Nb/La ratios (0.63–0.76). They have homogeneous whole-rock Sr Nd ( 87 Sr/ 86 Sr i = 0.704684–0.704808, ε Nd (t) = −4.6 to −4.0) and variable zircon Hf isotopic signatures (ε Hf (t) = −10.3 to 8.2), indicating that they probably originated from the partial melting of the subcontinental lithospheric mantle with the addition of asthenosphere materials. In contrast, the Late Triassic basaltic andesites show arc-related geochemical affinities, such as LILEs and LREEs enrichment and HFSEs depletion. They have more enriched whole-rock 87 Sr/ 86 Sr i (0.704895–0.705394), ε Nd (t) (−16.1 to −14.0), and zircon ε Hf (t) (−13.1 to −8.8) than the Middle Triassic trachyandesites, suggesting that they probably represent partial melts of the subduction-related fluids-modified lithospheric mantle. The modification of the northern margin of the NCC lithospheric mantle is closely related to the final subduction of the Palaeo-Asian oceanic plate and the subsequent post-orogenic extension. • Triassic volcanic rocks are founded in Tiaojishan Formation, Western Liaoning. • Study area was in a post-orogenic extensional setting in the Middle-Late Triassic. • Ocean Subduction modified the North China Craton lithosphere in the Triassic.

Higher spring phenological sensitivity to forcing temperatures of Asian compared to European tree species under low and high pre-chilling conditions

Winter chilling, spring forcing temperature and photoperiod are the most important drivers explaining the spatial and temporal variability of spring phenology in temperate trees. However, how these factors interact with each other on dormancy release and spring budburst date remains unclear and varies greatly depending on species. Our knowledge is also limited as to whether heat accumulation of forcing temperatures that trigger bud break in spring is a linear or non-linear process. Here, we aimed at experimentally quantifying the effect of chilling, forcing, photoperiod and their interactions on the budburst dates of nine different temperate tree species from East Asia (near Beijing, China) and Central Europe (near Zurich, Switzerland), including six phylogenetically related species (same genus). We conducted a full factorial experiment in climate chambers using two chilling (low and high, i.e., 0 vs. 56 days at 2°C after sampling at the end of December), four forcing (5, 10, 15, and 20°C), and two photoperiod (8 vs. 16 h) treatments simultaneously in Beijing and Zurich. We found that species growing near Beijing responded more readily to forcing conditions than species of the same genus growing near Zurich regardless of chilling treatment. Budburst timing of most species but European beech was marginally, if at all, affected by photoperiod. Furthermore, our results suggest that linear heat accumulation, as commonly used with the growing degree hours (GDH) model, could result in accurate prediction of budburst date depending on the temperature threshold used as a basis for heat accumulation. Our results also demonstrate the important role of chilling in shaping the sensitivity and rate of forcing accumulation to trigger budburst and suggest that species-specific sigmoid relationship for accumulating heat that accounts for prior chilling exposure may yield better predictions of budburst dates. Our results suggest that deciduous trees may have adapted their chilling and forcing requirements in regards to the predictability of winter-spring transition and late spring frosts. A less predictable winter-spring transition, as observed in Central Europe, could have driven species evolution towards higher chilling and forcing requirements compared to species growing in a more predictable climate of Northeastern Asia. Our cross-continental experiment therefore suggests that the spring phenology of East Asian species is tighter coupled to spring forcing temperature than Central European forests.

Paleoenvironment and human activity on the central Korean Peninsula during the late MIS 3 and MIS 2

AbstractLayers 12 and 13 of the Chongphadae Cave site located northwest of the central part of the Korean Peninsula include human fossils, fireplaces, a great number of lithic artefacts, and mammal remains. These layers represent new evidence for the paleoenvironment, human occupation, and activities in this region during the late MIS 3 and MIS 2, associated with global cold and dry climate, respectively. Most of lithic artefacts collected are flake tools. Raw material selection, lithic reduction technology, and lithic industry represent peculiar local characteristics. Our analysis of faunal assemblages also suggests that the Chongphadae region had a rich ecosystem capable of forming a diverse mammalian fauna including ungulates (mainly deer and horses) during this period. It is likely that the mosaic landscapes, including grasslands, forests, rivers, and wetlands, provided a favorable environment for humans, as well as mammals and plants, and the occupants of the site actively hunted and gathered in a relatively temperate environment. Our study suggests that the central Korean Peninsula was not severely affected by global dry and cold events such as LGM, although it was a somewhat humid and cold environment during the late MIS 3 and MIS 2. The central Korean Peninsula may have existed as an unknown refugium (or area of endemism) in northeastern Asia during this time.

Investigating the impacts of satellite fire observation accuracy on the top-down nitrogen oxides emission estimation in northeastern Asia

NOx fire emissions greatly affect atmosphere and human society. The top-down NOx fire emission estimation is highly influenced by satellite fire observation performance (e.g., fire detection) by affecting the derivation of emission coefficient (EC) and fire radiative power (FRP) magnitude. However, such influence is lack of comprehensive study. Here, we developed an algorithm to evaluate such impacts in northeastern Asia using multi-source data during 2012-2019. Specifically, we extracted near-concurrent fire observations from MODIS and its successor VIIRS over their orbit-overlapping area and combined respectively with OMI NO2 concentration to derive NOx EC. We compared EC between MODIS and VIIRS, and defined a synergetic effect index (SEI) to explore the combined effects on NOx fire emission estimation due to potentially different ECs and FRP between the two sensors. Finally, we applied EC to estimate NOx emission and made comparison between MODIS and VIIRS. Results show that: 1) both sensors derived considerably higher NOx EC for low-biomass vegetation fires (e.g., grassland fires) than other vegetation fires; however, MODIS EC is about 30% lower than VIIRS EC while similar values are derived for forest fires; 2) synergetic effects induced by different ECs and FRP magnitudes between the two sensors are more significant during fall and winter than in spring and summer; 3) annual NOx emissions based on MODIS EC are 15-23% lower than that from VIIRS EC during 2012-2019, while both are lower than the conventional bottom-up emission inventories GFED and FINN by an average of 23-44%; nevertheless, the EC-based NOx estimations presented high spatiotemporal correlation of R usually between 0.70 and 0.95 with GFED and FINN. These results reveal and quantify the critical impacts of satellite fire observation performance on EC derivation and fire emission estimation, which is helpful in reducing estimation uncertainty.

Megadrought: A Series of Unfortunate La Niña Events?

AbstractMegadroughts are multidecadal periods of aridity more persistent than most droughts during the instrumental period. Paleoclimate evidence suggests that megadroughts occur in many parts of the world, including North America, Central America, western Europe, eastern Asia, and northern Africa. It remains unclear to what extent such megadroughts require external forcing or whether they can arise from internal climate variability alone. A novel statistical–dynamical approach is used to evaluate the possibility that such events arise solely as a function of interannual tropical sea surface temperature (SST) variations. A statistical emulator of tropical SST variations is constructed by using an empirical moving‐blocks bootstrap approach that randomly samples multiyear sequences of the observational SST record. This approach preserves the power spectrum, seasonal cycle, and spatial pattern of El Niño‐Southern Oscillation (ENSO) but removes longer timescale fluctuations embedded in the observational record. These resampled SST anomalies are then used to force an atmospheric model (the Community Atmosphere Model Version 5). As megadroughts emerge in this run, they should, therefore, be solely a consequence of La Niña sequences combined with internal atmospheric variability and persistence driven by soil moisture storage and other land‐surface processes. We indeed find that megadroughts in this simulation have an amplitude‐duration rate that is generally indistinguishable from the rate documented in paleoclimate records of the western United States. Our findings support the idea that megadroughts may occur randomly when the unforced climate system evolves freely over a sufficiently long period of time, implying that an unforced unusual but statistically plausible series of La Niña events may be sufficient to generate megadrought.

Transcriptome analysis reveals the spatial and temporal differentiation of gene expression in the sporophyte of Undaria pinnatifida

Multicellular organisms are differentiated into specialized organs having specific functions. Kelps, morphologically diverse brown algae of the order Laminariales, exhibit specialized morphological features with a holdfast, a stipe, and a blade. However, little is known about the expression profiles and their biological functions from the different tissues. Among the kelp species, the edible Pacific kelp, Undaria pinnatifida is an ecologically and economically important species native to the Northeastern Asia. It presents the typical organization of kelps but is characterized by the formation of its sporophyll, the sexually reproductive tissue, on the stipe. To study their respective gene expression profiles, we generated transcriptome sequences from four tissues; the sporophyll, meristem, healthy blade, and decaying apex blade were sampled at the three time points in the development of the sporophyte. We demonstrate an up-regulation of genes related to photosynthetic genes in the healthy blade, of genes related to cell proliferation in the meristem and of genes related to flagella development in the sporophyll. Overall, the study revealed clear spatial and temporal variation in the expression patterns within and between the different tissues that were well correlated with the biological functions in the different tissues.

A gap-filling hybrid approach for hourly PM2.5 prediction at high spatial resolution from multi-sourced AOD data

Despite a growing interest in the satellite derived estimation of ground-level PM2.5 concentrations, modeling hourly PM2.5 levels at high spatial resolution with complete coverage for a large study domain remains a challenge. The primary modeling challenges lie in the presence of missing data in aerosol optical depth (AOD) and the limited data resolution for a single-platformed satellite AOD product. To address these issues, we developed a gap-filling hybrid approach to estimate full coverage hourly ground-level PM2.5 concentrations at a high spatial resolution of 1 km using multi-platformed and multi-scale satellite derived AOD products. Specifically, we filled the gaps and downscaled the multi-sourced AOD from Geostationary Ocean Color Imager (GOCI), Multi-Angle Implementation of Atmospheric Correction (MAIAC), and Modern-Era Retrospective Analysis for Research and Applications - version 2 (MERRA-2), using a hybrid data fusion approach. The fused hourly AOD with full coverage was then used for hourly PM2.5 predictions at a high spatial resolution of 1 km. We demonstrated the application of the proposed approach and assessed its performance using the data collected from northeastern Asia from 2015 to 2019. Our fused hourly AOD data showed high accuracy with the mean absolute error of 0.14 and correlation coefficient of 0.94, in validation against Aerosol Robotic Network (AERONET) AOD. Our AOD-based PM2.5 prediction model showed a good prediction accuracy with cross-validated R2 of 0.85 and root mean squared error of 12.40 μg/m3, respectively. Given that the highly resolved PM2.5 predictions captured both the temporal trend and the peak of PM2.5 pollution scenarios, we concluded that the proposed hybrid approach can effectively combine multi-sourced satellite AOD and derive subsequent PM2.5 distributions at high spatial and temporal resolutions.