Hemispheric Pattern Research Articles

PGR – 2 More than Just an EEG; The Role of Neuropsychological Evaluation in Pediatric Seizure Diagnosis with Complex Comorbidities

Abstract Objective Despite the prevalence of epilepsy, diagnosis remains limited by both subjective and objective examination (Urbańska et al., 2024). This is especially true of time-limited Electroencephalogram (EEG) (Baud et al., 2021). Ability to predict who will develop epilepsy after first time seizure is also limited (Drenthen et al., 2021). Neuropsychological changes inform clinical diagnosis and provides deeper understanding of functional limitations in daily life (Tolchin et al., 2020). Method Patient is a 12-year-old left-handed boy with history of in utero drug exposure and neglect prior to adoption at 3-years-old. Evaluation was sought for developmental delays concerning for Autism Spectrum Disorder (ASD). Additional concerns included frequent falls, severe migraines, reduced attention and memory, fatigue, and tremor. He had two clinical seizures around 9 years old, though subsequent EEG was normal. Given this and prophylactic treatment with Keppra, likelihood of seizures was thought to be low. Results Cognitive and adaptive skills were in the low range. Results were concerning for atypical developmental progress and a lateralizing profile. Specifically, skills associated with the left hemisphere (verbal abilities) were developing steadily, while skills associated with the right hemisphere (spatial and pattern recognition skills) were weaker. Difficulties with processing speed and higher order executive function were also present. No unifying diagnosis was identified, but addition of Keppra and Topamax resulted in marked improvement in energy, motor functioning, and cognitive functioning. Conclusion Neuropsychological evaluation was able to identify previously undetected seizure activity resulting in significant clinical impairment. Neuropsychological evaluation is invaluable in diagnosing and monitoring epilepsy (Kishk et al., 2022).

Cenozoic India-Asia collision driven by mantle dragging the cratonic root

The driving force behind the Cenozoic India-Asia collision remains elusive. Using global-scale geodynamic modeling, we find that the continuous motion of the Indian plate is driven by a prominent upper-mantle flow pushing the thick Indian lithospheric root, originated from the northward rollover of the detached Neo-Tethyan slab and sinking slabs below East Asia. The maximum mantle drag occurs within the strong Indian lithosphere and is comparable in magnitude to that of slab pull (1013 N m−1). The thick cratonic root enhances both lithosphere-asthenosphere coupling and upper-plate compressional stress, thereby sustaining the topography of Tibetan Plateau. We show that the calculated resistant force from the India-Asia plate boundary is also close to that due to the gravitational potential energy of Tibetan Plateau. Here, we demonstrate that this mantle flow is key for the formation of the Tibetan Plateau and represents part of a hemispheric convergent flow pattern centered on central Asia.

Hemispheric synchronization patterns linked with shooting performance in archers

Sustainable attention, effective visual-spatial perception, and motor control skills are considered highly important for achieving superior athletic performance. The aim of the current study was to investigate hemispheric synchronization patterns of brain electrical activation related to successful and unsuccessful shots of archers using electroencephalography (EEG). This study involved 16 elite archers, each shooting 36 arrows. The 10 shots closest to the target's center were successful, while the 10 farthest shots were unsuccessful. The transformed EEG data, obtained through surface Laplacian filtering, were divided into 5 sub-bands (theta, alpha1, alpha2, beta1, beta2) by calculating the alpha peak frequencies. The synchronization values of the electrode pairs were calculated using the Phase Locking Value (PLV) method. To compare the EEG data for successful and unsuccessful shots in all frequency bands, the linear mixed models were fitted. Perceived fatigue levels were quantified using a visual analog scale (VAS). Spearman’s correlation analysis was conducted to examine the relationship between fatigue and shooting performance. The results showed significantly higher coupling strength for C3-O1, C4-O2, O1-O2, F3-F4, C4-T8, T7-O2, F4-C4, C3-O2 and F4-T8 pairs during successful shooting. Moreover, the coupling strengths for F3-O2, F4-T7, C3-C4, C3-T8, T7-T8, C4-O1, F3-T8, and F4-O2 were significantly higher in unsuccessful shooting. The current findings revealed differences in the synchronization patterns associated with shooting performance. It is observed that visual-motor performance is correlated with an increase in cortical synchronization values during successful shots. These findings have the potential to serve as a theoretical reference that contributes to superior performance.

Increase in ocean-onto-land droughts and their drivers under anthropogenic climate change

Ocean-onto-land droughts (OTLDs)—i.e., droughts originating over the oceans and migrating onto land—are a recently identified phenomenon with severe natural and human impacts. However, the influence of anthropogenic emissions on past and future changes in OTLDs and their underlying mechanisms remain unclear. Here, using precipitation-minus-evaporation deficits to identify global OTLDs, we find OTLDs have intensified due to anthropogenic climate change during the past 60 years. Under a future high-emissions scenario, the OTLDs would become more frequent (+39.68%), persistent (+54.25%), widespread (+448.92%), and severe (+612.78%) globally. Intensified OTLDs are associated with reduced moisture transport driven by subtropical anticyclones in the northern hemisphere and complex circulation patterns in the southern hemisphere. The reduction in moisture transport during OTLDs is mainly caused by the atmospheric thermodynamic responses to human-induced global warming. Our results underscore the importance of improving understanding of this type of drought and adopting climate mitigation measures.

Intensity change and zonal and meridional movements of the Aleutian Low and their associated broad-scale atmospheric-oceanic characteristics

The changes in the intensity and position of the Aleutian Low (AL) exert significant effects on the ocean-land-atmosphere interactive processes and climate over East Asia, the North Pacific, and North America. In this study, the interannual variations of the AL intensity, meridional shift, and zonal shift, as well as their associated dynamical processes are investigated. The results show that the intensity, meridional shift, and zonal shift of the AL are well characterized by the three leading EOF modes of sea level pressure over the North Pacific, and are strongly correlated with the Pacific-North American pattern, the West Pacific pattern, and the Tropical/Northern Hemisphere pattern, respectively. The intensity variation of the winter AL seems to be closely associated with the ENSO-related atmosphere-ocean processes in the previous autumn, whereas the meridional shift is not associated any significant signal in the previous months, signifying a relatively higher predictability of the former. Besides, the eastward and westward movements of the AL show asymmetric features, attributed possibly to their asymmetric relationships with ENSO.

What Determines the Leading Mode of Wintertime Northern Hemisphere Snow-Cover Interannual Variability?

Abstract The Northern Hemisphere snow-cover (NHSC) interannual variability can serve as a crucial source of climate predictability. However, the spatiotemporal characteristics of the NHSC interannual variability and associated formation mechanism lack a thorough investigation using the latest reliable datasets. In this observationally based study, we identify the leading mode of the wintertime NHSC interannual variability and reveal the major determinants and mechanisms for forming the mode. Results show that the leading mode exhibits a hemispheric dipole pattern characterized by snow-cover anomalies in the central-eastern United States and Europe, contrary to those in the Tibetan Plateau (TP). Importantly, the leading mode of TP-only snow-cover variability is essentially a regional manifestation of the dipole NHSC anomaly pattern. The wintertime hemispheric atmospheric circulation anomaly mode, that is, the Arctic Oscillation (AO), primarily determines the dipole NHSC anomaly pattern via altering snowfall and snowmelt. During a positive phase of AO, an anomalous atmospheric anticyclone over the midlatitude North Atlantic favors increased warm-air advection over the central-eastern United States and Europe, reducing the snowfall and the snow cover there. Meanwhile, the anomalously warm atmospheric thermal condition in Europe accompanied by enhanced westerly moisture flux convergence tends to heat the underlying land surface via reducing upward sensible heat flux and increasing downward longwave radiation, thereby causing increased snowmelt and decreased snow cover in northeastern Europe. Associated with the aforementioned atmospheric circulation anomalies, an anomalous atmospheric cyclone prevailing over the TP tends to cause increased southeasterly moisture flux convergence, favoring snowfall and snow increase in the TP.

Comparative Solar Minima Using the McIntosh Archive

AbstractThe McIntosh Archive consists of four solar cycles (SC20–23) of synoptic maps of solar features (magnetic polarities, coronal holes, filaments, sunspots, plage) that were produced by Patrick McIntosh and his cartographers. In this paper we present the full Archive for the first time and find a hemispheric pattern of coronal hole polarity reflecting the Hale sunspot polarity pattern. In addition, we present a supplemental set of related maps created for the 2019–2020 solar minimum in support of the Whole Heliosphere and Planetary Interactions (WHPI) interval. To facilitate this addition, we cross calibrate EUV and He‐I 10,830 Å coronal holes and study differences between the WHPI solar minimum and the earlier minima in the main Archive. We find, first, that the visibility of coronal holes in EUV introduces a bias toward larger counts of low‐latitude coronal holes near solar minimum. However, the estimated lifetimes (in Carrington Rotations) of coronal hole complexes are unaffected by this fragmentation, and we find the longest‐lived low‐latitude coronal holes occurred during the 2008–2009 solar minimum, with 2019–2020 solar minimum lifetimes not far behind. In this way, we consider the large‐scale organization of solar magnetic fields between solar minima and study each solar minimum in the context of its solar cycle.

Connections between Upper Tropospheric and Lower Stratospheric Circulation Responses to Increased CO2

Abstract There are myriad ways atmospheric circulation responds to increased CO2. In the troposphere, the region of the tropical upwelling narrows, the Hadley cells expand, and the upper-level subtropical zonal winds that comprise the subtropical jet strengthen. In the stratosphere, the tropical upwelling narrows and strengthens, enhancing the Brewer–Dobson circulation. Despite the robustness of these projections, dynamical coupling between the features remains unclear. In this study, we analyze output from the NASA Goddard Institute for Space Studies (GISS) ModelE coupled climate model to examine any connection between the upper tropospheric and lower stratospheric circulation by considering the features’ seasonality, hemispheric asymmetry, scaling, and transient response to a broad range of CO2 forcings. We find that a narrowing and strengthening of upper tropospheric upwelling occurs with a strengthening of the subtropical jet. There is also a narrowing and strengthening of lower stratospheric upwelling that is related to an equatorward shift in critical latitude for wave breaking and the associated strengthening of the subtropical lower stratosphere’s zonal winds. However, the stratospheric responses display different seasonal, hemispheric, and transient patterns than those in the troposphere, indicating independent circulation changes between the two domains.

Tree-ring δ18Ocellulose variations in two Nothofagus species record large-scaleclimatic signals in the South American sector of the Southern Ocean

In recent decades, southernmost South America (50–56° S) has experienced marked climate change (regional warming, decreased precipitation, reduced snow cover, and increased frequency of heat waves) related to variations in atmospheric circulation over varied timescales. In this paper, we develop oxygen isotopes from tree-ring cellulose (δ18OTRC) as a proxy for climate and atmospheric circulation in order to extend the regional meteorological record to deeper time intervals. Our work focuses on Nothofagus forests in two areas: (i) deciduous N. pumilio forest in the steppe transition zone near Punta Arenas and (ii) humid evergreen N. betuloides forest in the Navarino Island region. To investigate the potential for reconstructing palaeoclimate, δ18OTRC variations were correlated with local climate parameters as well as regional (Amundsen Sea Low, ASL) and hemispheric (Antarctic Oscillation, AAO) atmospheric circulation modes for the last 60 years. N. betuloides δ18OTRC variations show an overall positive trend, indicating isotopic enrichment over the study period, whereas no trend is recorded for the N. pumilio record. The strongest relationships with climate, together with the widest spatial representativeness, occur in the N. betuloides chronology during the growing season (spring to austral summer) and extend spatially from mid to high latitudes. In contrast, the sensitivity of the records is limited to summer months, and spatial correlations are much more limited. In addition, the N. betuloides record shows greater potential for reconstructing local climate features such as soil water (r = − 0.76), wind speed (r = 0.69), and precipitation (r = − 0.66), as well as regional (ASL, r = − 0.80) and hemispheric (AAO, r = 0.77) patterns of extratropical atmospheric circulation. Overall, we conclude that the N. betuloides record represents the most valuable tree-ring climate proxy for southernmost South America over past centuries.

Timing of seasonal influenza epidemics for 25 countries in Africa during 2010–19: a retrospective analysis

Using country-specific surveillance data to describe influenza epidemic activity could inform decisions on the timing of influenza vaccination. We analysed surveillance data from African countries to characterise the timing of seasonal influenza epidemics to inform national vaccination strategies. We used publicly available sentinel data from African countries reporting to the WHO Global Influenza Surveillance and Response FluNet platform that had 3-10 years of data collected during 2010-19. We calculated a 3-week moving proportion of samples positive for influenza virus and assessed epidemic timing using an aggregate average method. The start and end of each epidemic were defined as the first week when the proportion of positive samples exceeded or went below the annual mean, respectively, for at least 3 consecutive weeks. We categorised countries into five epidemic patterns: northern hemisphere-dominant, with epidemics occurring in October-March; southern hemisphere-dominant, with epidemics occurring in April-September; primarily northern hemisphere with some epidemic activity in southern hemisphere months; primarily southern hemisphere with some epidemic activity in northern hemisphere months; and year-round influenza transmission without a discernible northern hemisphere or southern hemisphere predominance (no clear pattern). Of the 34 countries reporting data to FluNet, 25 had at least 3 years of data, representing 46% of the countries in Africa and 89% of Africa's population. Study countries reported RT-PCR respiratory virus results for a total of 503 609 specimens (median 12 971 [IQR 9607-20 960] per country-year), of which 74 001 (15%; median 2078 [IQR 1087-3008] per country-year) were positive for influenza viruses. 248 epidemics occurred across 236 country-years of data (median 10 [range 7-10] per country). Six (24%) countries had a northern hemisphere pattern (Algeria, Burkina Faso, Egypt, Morocco, Niger, and Tunisia). Eight (32%) had a primarily northern hemisphere pattern with some southern hemisphere epidemics (Cameroon, Ethiopia, Mali, Mozambique, Nigeria, Senegal, Tanzania, and Togo). Three (12%) had a primarily southern hemisphere pattern with some northern hemisphere epidemics (Ghana, Kenya, and Uganda). Three (12%) had a southern hemisphere pattern (Central African Republic, South Africa, and Zambia). Five (20%) had no clear pattern (Côte d'Ivoire, DR Congo, Madagascar, Mauritius, and Rwanda). Most countries had identifiable influenza epidemic periods that could be used to inform authorities of non-seasonal and seasonal influenza activity, guide vaccine timing, and promote timely interventions. None. For the Berber, Luganda, Xhosa, Chewa, Yoruba, Igbo, Hausa and Afan Oromo translations of the abstract see Supplementary Materials section.

Efficient and Stable Flexible Organic Solar Cells via the Enhanced Optical‐Thermal Radiative Transfer

AbstractHeating is a knotty factor contributing to device degradation of flexible organic solar cells (FOSCs), and thermal regulation plays a crucial role in the realization of long operational lifetime. Herein, a passive cooling strategy for stable FOSCs is proposed by boosting the optical‐thermal radiative transfer to reduce the insufficient thermal dissipation and the elevated temperature caused by irradiation‐induced heating, while retaining their flexibility and portability. A spectrally selective coupling structure consisting of subwavelength hemisphere pattern and distributed Bragg reflector is integrated into FOSCs to collectively enhance out‐coupling of infrared radiation and limit near‐infrared absorption‐induced heat generation, leading to a reduced heat power intensity of 292.5 W cm−2 and the decreased working temperature by 9.6 °C under outdoor sunlight irradiation. The D18:Y6:PC71BM‐based FOSCs achieve a power conversion efficiency of over 17% with a prolonged T80 lifetime as long as one year under real outdoor working conditions. These results represent a new opportunity for enhancing the operational stability of FOSCs.

Hemispheric Patterns of Recruitment of Object Processing Regions in Early Alzheimer's Disease: A Study Along the Entire Ventral Stream.

Investigation of neural response patterns along the entire network of functionally defined object recognition ventral stream regions in Alzheimer's disease (AD) is surprisingly lacking. We aimed to investigate putative functional reorganization along a wide-ranging network of known regions in the ventral visual stream in mild AD. Overall we investigated 6 regions of interest (5 of which were not investigated before), in 19 AD patients and 19 controls, in both hemispheres along the ventral visual stream: Fusiform Face Area, Fusiform Body Area, Extrastriate Body Area, Lateral Occipital Cortex, Parahippocampal Place Area, and Visual Word Form Area, while assessing object recognition performance. We found group differences in dprime measures for all object categories, corroborating generalized deficits in object recognition. Concerning neural responses, we found region dependent group differences respecting a priori expected Hemispheric asymmetries. Patients showed significantly decreased BOLD responses in the right hemisphere-biased Fusiform Body Area, and lower left hemisphere responses in the Visual Word Form Area (with a priori known left hemispheric bias), consistent with deficits in body shape and word/pseudoword processing deficits. This hemispheric dominance related effects were preserved when controlling for performance differences. Whole brain analysis during the recognition task showed enhanced activity in AD group of left dorsolateral prefrontal cortex, left cingulate gyrus, and in the posterior cingulate cortex- a hotspot of amyloid-β accumulation. These findings demonstrate region dependent respecting hemispheric dominance patterns activation changes in independently localized selective regions in mild AD, accompanied by putative compensatory activity of frontal and cingular networks.

Anomalous subtropical zonal winds drive decreases in southern Australian frontal rain

Abstract. Cold fronts make a significant contribution to cool season rainfall in the extratropics and subtropics. In many regions of the Southern Hemisphere the amount of frontal rainfall has declined in recent decades, but there has been no change in frontal frequency. We show that for southeast Australia this contradiction cannot be explained by changes in frontal intensity or moisture at the latitudes of interest. Rather, declining frontal rainfall in southeast Australia is associated with weakening of the subtropical westerlies in the mid-troposphere, which is part of a hemispheric pattern of wind anomalies that modify the extratropical zonal wave 3. Fronts that generate rainfall are associated with strong westerlies that penetrate well into the subtropics, and the observed decrease in frontal rainfall in southern Australia can be linked to a decrease in the frequency of fronts with strong westerlies at 25∘ S.

Distinct Neural Resource Involvements but Similar Hemispheric Lateralization Patterns in Pre-Attentive Processing of Speaker's Identity and Linguistic Information.

The speaker's identity (who the speaker is) and linguistic information (what the speaker is saying) are essential to daily communication. However, it is unclear whether and how listeners process the two types of information differently in speech perception. The present study adopted a passive oddball paradigm to compare the identity and linguistic information processing concerning neural resource involvements and hemispheric lateralization patterns. We used two female native Mandarin speakers' real and pseudo-Mandarin words to differentiate the identity from linguistic (phonological and lexical) information. The results showed that, in real words, the phonological-lexical variation elicited larger MMN amplitudes than the identity variation. In contrast, there were no significant MMN amplitude differences between the identity and phonological variation in pseudo words. Regardless of real or pseudo words, the identity and linguistic variation did not elicit MMN amplitudes differences between the left and right hemispheres. Taken together, findings from the present study indicated that the identity information recruited similar neural resources to the phonological information but different neural resources from the lexical information. However, the identity and linguistic information processing did not show a particular hemispheric lateralization pattern at an early pre-attentive speech perception stage. The findings revealed similarities and differences between linguistic and non-linguistic information processing, contributing to a better understanding of speech perception and spoken word recognition.

Mechanism of competitive development of hemispheric lateralization complementary pattern for word and face recognition

Mechanism of competitive development of hemispheric lateralization complementary pattern for word and face recognition

Event-related potential and lexical decision task in dyslexic adults: Lexical and lateralization effects.

Developmental dyslexia is a specific learning disorder that presents cognitive and neurobiological impairments related to different patterns of brain activation throughout development, continuing in adulthood. Lexical decision tasks, together with electroencephalography (EEG) measures that have great temporal precision, allow the capture of cognitive processes during the task, and can assist in the understanding of altered brain activation processes in adult dyslexics. High-density EEG allows the use of temporal analyses through event-related potentials (ERPs). The aim of this study was to compare and measure the pattern of ERPs in adults with developmental dyslexia and good readers, and to characterize and compare reading patterns between groups. Twenty university adults diagnosed with developmental dyslexia and 23 healthy adult readers paired with dyslexics participated in the study. The groups were assessed in tests of intelligence, phonological awareness, reading, and writing, as well as through the lexical decision test (LDT). During LDT, ERPs were recorded using a 128-channel EEG device. The ERPs P100 occipital, N170 occipito-temporal, N400 centro-parietal, and LPC centro-parietal were analyzed. The results showed a different cognitive profile between the groups in the reading, phonological awareness, and writing tests but not in the intelligence test. In addition, the brain activation pattern of the ERPs was different between the groups in terms of hemispheric lateralization, with higher amplitude of N170 in the dyslexia group in the right hemisphere and opposite pattern in the control group and specificities in relation to the items of the LDT, as the N400 were more negative in the Dyslexia group for words, while in the control group, this ERP was more pronounced in the pseudowords. These results are important for understanding different brain patterns in developmental dyslexia and can better guide future interventions according to the changes found in the profile.

Spherical Interpretation of Infiltration from Trickle Irrigation

The hypothesis of this paper is that infiltration into drip irrigated soils can be described by simple spherical considerations as well as two dimensional (2D) numerical modeling. The major goal was to test a very simple model based on geometry of a sphere formulas, and compare it with elaborated numerical solutions and field experiments. Detailed analysis of soil–water infiltration under trickle regimes is shown to be pre-requisite in the search for the optimal design of system layout. Optimality and simplicity are sought by modeling a sphere for subsurface trickle/drip (SDI) and hemisphere (DI) pattern of moisture distributions during infiltration. Numerical simulations by MATLAB software were used to describe the distribution of soil water. The data produced by this simulation were successfully compared with analytical models and numerical results of Panoche clay loam. To simulate the four discharge rates (0.5, 1, 2, 3 Lh) under DI and SDI we used the input of Panoche soil properties, i.e., hydraulic conductivity function (Kθ) and soil water retention curve (ψθ). The resulting regression equation of numerical analysis (N) vs. spherical interpretation (S) was N = 0.97 × S − 19.1; r2 = 0.98. This result exposes the novelty of the approach by showing that infiltration from a drip/trickle source can be described by simple spherical radial symmetry in addition to analytical or numerical simulations. An example of a design parameter for 3000 cm3h suggested more emitters per meter laterals for SDI than for DI (100 vs. 77 unites, respectively) due to the shorter distance between SDI emitters that are required in order to maintain wetting continuity. At a discharge of around 500 cm3h of three different soils’ SDI, positive pressure was detected near the orifice and it caused discharge reduction. This is a self-compensating property of SDI that regulates individual emitters according to the soil hydraulic properties. In conclusion SDI is associated with larger capital investment compared to DI, but it can be compensated by improving the water use efficiency due to increased productivity while reducing losses of water through evaporation, but this option should be investigated as part of specific research.

Recently Amplified Interannual Variability of the Great Lakes Ice Cover in Response to Changing Teleconnections

Abstract The interannual variability of the annual maximum ice cover (AMIC) of the Great Lakes is strongly influenced by large-scale atmospheric circulations that drive regional weather patterns. Based on statistical analyses from 1980 to 2020, we identify a reduced number of accumulated freezing degree days across the winter months in recent decades, a step-change decrease of AMIC after the winter of 1997/98, and an increased interannual variability of AMIC since 1993. Our analysis shows that AMIC is significantly correlated with El Niño–Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the Pacific–North American pattern (PNA) before the winter of 1997/98. After that, the AMIC is significantly correlated with the tropical–Northern Hemisphere pattern (TNH) and eastern Pacific oscillation (EPO). Singular value decomposition of the 500-hPa geopotential height and surface air temperature shows a dipole pattern over the northeast Pacific and North America, demonstrating the ridge–trough system. This dipole pattern shifts northward to the northern Rocky Mountains, placing the Great Lakes region in the trough after 1997/98. This shift coincides with the increased interannual variability of the EPO index, as well as the change in the sea surface temperature (SST) over the northeast Pacific, where the second mode of the empirical orthogonal function (EOF) on SST shows a warm blob-like feature manifested over the Gulf of Alaska. The regression of wave activity flux onto the SST EOF shows that the source of upward and eastward propagation of a stationary Rossby wave shifts to the west coast of North America, likely moving the ridge–trough system eastward after the winter of 1997/98. Significance Statement We found that the Great Lakes annual maximum ice cover decreased after one of the strongest El Niño–Southern Oscillation events in 1997/98 and that its year-to-year fluctuations increased in the recent 20 years. After the winter of 1997/98, the Great Lakes annual maximum ice cover started to correlate with the warm sea surface temperature anomaly in the northeast Pacific, which appears to disrupt the polar vortex far up in the stratosphere, and the polar vortex ultimately shifts eastward the ridge–trough system over North America. When the shifted system develops enough, it can encase the Great Lakes region in the Arctic air and thereby cause larger year-to-year fluctuations. This connection was found to be characteristic in the recent few decades, after the winter of 1997/98.

Extreme rainfall in Northern China in September 2021 tied to air–sea multi-factors

The September rainfall over Northern China (NC) in 2021 was the heaviest since 1961 and had unprecedented socioeconomic impacts. Holding the hypothesis that the drivers of extreme climate events usually contain extreme factors, we firstly propose the Ranking Attribution Method (RAM) to find the possible air–sea multi-factors responsible for this rainfall event. Via the atmospheric bridges of zonal-vertical circulation and Rossby wave energy propagation, the remote factors of warm sea surface temperature anomalies (SSTA) over the tropical Atlantic, cold SSTA over the tropical Pacific, Southern Annular Mode-like pattern in the Southern Hemisphere and North Pacific Oscillation-like pattern in the Northern Hemisphere jointly strengthened the Maritime Continent (MC) convection and Indian monsoon (IM). Through meridional-vertical circulation, the intensified MC convection enhanced the subtropical high over southern China and induced ascending motion over NC. The local factor of extreme air acceleration in the east Asian upper-level jet entrance region further anchored the location of the southwest-northeast rain belt. The strengthened IM and subtropical high over southern China induced considerable moisture transport to the rain belt via two moisture channels. The combined effect of these extreme dynamic and moisture conditions formed this unprecedented rainfall event. This study suggests that the RAM can effectively reveal the factors that contributed to this extreme rainfall event, which could provide a new pathway for a better understanding of extreme climate events.

Climate Dynamics Preceding Summer Forest Fires in California and the Extreme Case of 2018

Abstract Recent record-breaking wildfire seasons in California prompt an investigation into the climate patterns that typically precede anomalous summer burned forest area. Using burned-area data from the U.S. Forest Service’s Monitoring Trends in Burn Severity (MTBS) product and climate data from the fifth major global reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ERA5) over 1984–2018, relationships between the interannual variability of antecedent climate anomalies and July California burned area are spatially and temporally characterized. Lag correlations show that antecedent high vapor pressure deficit (VPD), high temperatures, frequent extreme high temperature days, low precipitation, high subsidence, high geopotential height, low soil moisture, and low snowpack and snowmelt anomalies all correlate significantly with July California burned area as far back as the January before the fire season. Seasonal regression maps indicate that a global midlatitude atmospheric wave train in late winter is associated with anomalous July California burned area. July 2018, a year with especially high burned area, was to some extent consistent with the general patterns revealed by the regressions: low winter precipitation and high spring VPD preceded the extreme burned area. However, geopotential height anomaly patterns were distinct from those in the regressions. Extreme July heat likely contributed to the extent of the fires ignited that month, even though extreme July temperatures do not historically significantly correlate with July burned area. While the 2018 antecedent climate conditions were typical of a high-burned-area year, they were not extreme, demonstrating the likely limits of statistical prediction of extreme fire seasons and the need for individual case studies of extreme years. Significance Statement The purpose of this study is to identify the local and global climate patterns in the preceding seasons that influence how the burned summer forest area in California varies year-to-year. We find that a dry atmosphere, high temperatures, dry soils, less snowpack, low precipitation, subsiding air, and high pressure centered west of California all correlate significantly with large summer burned area as far back as the preceding January. These climate anomalies occur as part of a hemispheric scale pattern with weak connections to the tropical Pacific Ocean. We also describe the climate anomalies preceding the extreme and record-breaking burned-area year of 2018, and how these compared with the more general patterns found. These results give important insight into how well and how early it might be possible to predict the severity of an upcoming summer wildfire season in California.