Northwest Southeast Research Articles

Indoor Air Quality and Risks Connected to Laundry Operations in Ibadan Metropolis, Nigeria

During washing, ironing, and dyeing, laundry workers are exposed to chemicals that could be damaging to their health and the environment. These chemicals can cause everything from throat and skin irritation to cancer. Information on indoor air quality (IAQ) in laundry environments in underdeveloped nations, particularly Nigeria, was scarce. As a result, the study evaluated the risks to indoor air quality related with laundry activities in the Nigerian metropolis of Ibadan.
 In Ibadan North (IBN), Ibadan North-East (IBNE), Ibadan South-West (IBSW), Ibadan North-West (IBNW), and Ibadan South-East (IBSE), 50 out of 100 consenting laundry operators were randomly chosen to participate in a descriptive cross-sectional survey.
 Multi Testers N21FR were used to monitor temperature and relative humidity (RH). Using a Met One GT 321, CO2 meter, and an air sampler, the IAQ parameters were tracked. The values obtained for all parameters were compared to WHO limits of (Temp) 26°C, RH 60%, (PM10) 50g/m3, (TBC) 5x102 CFU/m3, and (CO2) 1,000ppm (ASHRAE) every day for eight weeks. With SPSS (version 20), Chi-square, Pearson Correlation, and p0.05, descriptive statistics were used to analyze the data.
 Both the mean indoor and outdoor total bacterial counts (TBC) CFU/m3 values were much lower than the WHO-recommended guideline limit of 5x102 CFU/m3. While indoor RH and temperature were above WHO guideline levels, PM10 and CO2 were below WHO and ASHRAE guideline levels, respectively, and TBC and TFC were within WHO guideline limits in all research locations. Therefore, it is recommended to boost cross ventilations in the laundry rooms to improve indoor air quality.
 IAQ appeared to be impaired in the laundry environment in Ibadan, Nigeria. To better maintain thermal comfort parameters and lower levels of chemical pollutants released by launderers and product use during services, mechanical ventilation systems in laundry environments need to be upgraded with regard to operation and maintenance.

Spatial Correlations of Regional Tropical Cyclone– and Nontropical Cyclone–Induced Severe Rainstorms during 2000–19

Abstract Severe rainstorms are one of the most devastating disasters in southeast China (SEC). A deep and comprehensive understanding of the spatial correlations of severe rainstorms is important for preventing rainstorm-induced hazards. In this study, tropical cyclone– and nontropical cyclone–induced severe rainstorms (TCSRs and NTCSRs, respectively) over SEC during 2000–19 are discussed. Co-occurrence probability and range values calculated using the semivariogram method are used to measure the spatial correlations of severe rainstorms. The extent to which potential factors [El Niño/La Niña, Indian Ocean dipole (IOD), latitudes, longitudes, temperature, elevation, and radius of maximum wind] affect the spatial structure of severe rainstorms is discussed. The spatial correlation distances for TCSRs (300–700 km) in typhoon season (July, August, and September) are longer than most of those for NTCSRs (150–300 km) in mei-yu season (June and July). The range values of TCSRs at each percentile (except for the minimum range values) tend to be omnidirectional. While NTCSRs tend to have a major direction of northeast–southwest. El Niño tends to increase the average spatial correlation distance of TCSRs in the northeast–southwest and NTCSRs in the north–northeast. La Niña tends to decrease the spatial correlation distance of TCSRs in the northeast–southwest. The occurrence of positive IOD (+IOD) and negative IOD (−IOD) events may increase the spatial correlation distance of TCSRs in the northwest–southeast, and −IOD events may decrease the distance in the northeast–southwest. IOD events, especially −IOD, may change the spatial correlation distance of NTCSRs in the east–northeast. Latitudes, longitudes, temperature, elevation, and radius of maximum wind significantly affect the spatial correlation distance of TCSRs in various directions. Significance Statement Spatial correlation distances of rainfall events, especially severe rainstorms induced by different weather systems such as tropical and nontropical cyclones (TCSR and NTCSR), can provide important information for rain-induced hazard risk mitigation. Moreover, factors that affect the variability of the spatial correlation distance of TCSRs and NTCSRs are also of interest. To this end, co-occurrence probability and semivariogram methods are used to obtain the spatial correlation distances. The spatial correlation distance of TCSRs varies between 300 and 700 km in typhoon season (July, August, and September) while it ranges between 150 and 300 km in mei-yu season (June and July) for NTCSRs over southeast China (SEC). El Niño/La Niña, Indian Ocean dipole (IOD), latitudes, longitudes, temperature, elevation, and radius of maximum wind have significant impacts on the spatial correlation distances of TCSRs. These findings can provide useful information for forecasting the spatial correlation distance of severe rainstorms over SEC.

Cryogenian-Ediacaran crustal growth and evolution of the active margin of the Dahomeyide belt, Ghana

AbstractThe study presents detailed petrographical, geophysical, structural and geochemical data of the internal nappes zone to establish the deformational history, origin and tectonic setting and constrain the crustal growth and evolution of the active margin of the Dahomeyide belt. Two main lithological units, (i) deformed meta-granitoids (migmatites and gneisses) and (ii) undeformed granitoids, dominate the internal nappes zone. The granitoids are generally I-type, metaluminous to weakly peraluminous, low-K tholeiite to high-K calc-alkaline and of tonalite, granodiorite and granite affinity. The overall trace element patterns of the studied granitoids characterized by the enriched LILE and depleted HFS, with negative peaks of Nb-Ta, Sr, P and Ti, are indications of arc-related magmatism. Structural analysis reveals four deformation phases (D1-D4). D1 represents Northwest-Southeast (NW-SE) Pan African shortening associated with a continent-continent collision, resulting in westward nappe stacking. Progressive NW-SE shortening resulted in D2 and D3 top-to-the-NW dextral and sinistral thrusting events during the Pan-African orogeny. D4 is an extensional event likely associated with the orogenic collapse phase. The gneisses and migmatites, with dominant axial planar foliations, point to their formation in a collisional setting or influence by the Pan-African collisional processes. Continental-arc signatures in these rocks imply continental subduction during their protolith formation. The intrusive granitoid and pegmatite are undeformed, meaning late- to post-orogenic emplacement. These findings suggest that the internal nappes zone archived the subduction-collision and post-collisional phase of the Pan-African orogeny and recorded large-scale migmatization and granitoid emplacement due to partial melting of thickened lower crust between Mid-Cryogenian and late Ediacaran.

Response of vegetation to terrestrial water storage in Southwest China

To explore the responses of vegetation growth to change in terrestrial water storage in Southwest China, we analyzed the change trend and relationship between vegetation and terrestrial water storage anomaly (TWSA) in Southwest China from January 2003 to December 2021 by using TWSA data of Gravity Recovery and Climate Experi-ment (GRACE) satellite and normalized differential vegetation index (NDVI) data. The results showed that NDVI in Southwest China during the study period showed an overall upward trend. Meanwhile, TWSA showed a significant downward trend in central and southern Tibet, and a significant upward trend in northwest Tibet and southeast region of Southwest China. Results of Pearson correlation analysis showed that there were significant spatial differences in responses of NDVI to TWSA changes in Southwest China. NDVI had a significant negative response to TWSA changes in most regions of Tibet, but a significant positive response to TWSA changes in most regions of southeast region of Southwest China. Such differences were driven by climate change and topography.

Detection and Assessment of Changing Drought Events in China in the Context of Climate Change Based on the Intensity–Area–Duration Algorithm

Drought can have a significant impact on both society and the economy, resulting in issues such as scarcity of water and shortages of food and energy, as well as elevated health risks. However, as global temperatures continue to rise, the impact of drought events is increasingly exacerbated, manifested by an increase in the frequency, intensity, duration, and spatial extent of their effects. Therefore, studying the changing characteristics of drought events with the background of climate change is of great significance. Based on the high-precision and high-resolution CN05.1 dataset, this study obtained the monthly Standardized Precipitation Evapotranspiration Index (SPEI) dataset from 1961 to 2020, and then identified regional drought events in China using the Intensity–Area–Duration (IAD) method, which considers both temporal continuity and spatial dynamics. On this basis, the spatiotemporal variations in frequency, intensity, duration, and affected area of drought events in China and its seven subregions were analyzed. The results showed that the subregions located in the northern region of China generally have lower mean, maximum, and minimum temperatures than those located in the southern region, but the associated interannual change rate of the subregions in the north is higher than that in the south. As for the annual total precipitation, results show a clear pattern of decreasing southeast–northwest gradient, with an increasing trend in the northern subregions and a decreasing trend in the southern subregions except for the subregion south China (SC). The northeast of China (NE), SC, the southwest of China (SW) and north China (NC) are the regions with a high frequency of drought events in China, while the frequency of drought events in NW and Qinghai–Tibetan Plateau (QTP), although lower, is on a significantly increasing trend, and the increasing rate is higher than for the other regions. For drought intensity, Xinjiang (XJ) and QTP had greater drought intensity, and the change rate of these regions with greater drought intensity was also greater. The drought impact area in China showed a significant increasing trend, mainly concentrated in QTP, NW and NE. Particular attention needs to be focused on the southwest of QTP, where drought events in this region show a significant increase in frequency, intensity, duration and impact area.

Monsoon-driven seasonal hypoxia along the northern coast of Oman

Dissolved oxygen and current observations from a cabled ocean observatory in the Sea of Oman show that the annual recurrence of coastal hypoxia, defined as dissolved oxygen concentrations ≤63 μM, is associated with the seasonal cycle of local monsoon winds. The observations represent the first long-term (5+ years) continuous moored observations off the northern Omani coast. During the summer/fall southwest (SW) monsoon season (Jun-Nov), winds in the Sea of Oman generate ocean currents that result in coastal upwelling of subsurface waters with low dissolved oxygen concentrations. The source of the poorly oxygenated water is the oxygen minimum zone (OMZ) in the Arabian Sea, a layer approximately 1000-m thick within the 100 to 1200 m depth range, where dissolved oxygen values approach anoxia. During the winter monsoon season (Dec-Feb), the Sea of Oman winds are from the northwest, forcing strong and persistent southeast currents. These winds generate oceanic downwelling conditions along the coastal ocean that ventilate waters at depth. Possible impacts of the monsoon-driven seasonal hypoxia on local fisheries and implications due to climate change are also discussed in this study.

Coupling between chromophoric dissolved organic matter and dissolved inorganic carbon in Indian estuaries

This study investigates the coupling between Chromophoric Dissolved Organic Matter (CDOM) and Dissolved Inorganic Carbon (DIC) in eighteen Indian estuaries across salinity gradient of the east and west coasts during the monsoon season, characterized by significant river discharge. The hypothesis that humic acids (HA) and fulvic acids (FA), prominent in estuarine CDOM, closely correspond to the ‘organic alkalinity’ (Aorg) component of total alkalinity is examined. In most estuaries, specifically those along the northeast coast (NE) and southwest coast (SW), a significant linear relationship exists between DIC, CDOM abundance, and pH level. Notably, minor estuaries along the southeast coast (SE) and northwest coast (NW) exhibit elevated DIC levels beyond what this relationship predicts. These estuaries also reveal heightened ammonium levels, increased δ15N values, and decreased δ13C values, indicative of anthropogenic influence. CDOM properties, such as spectral slope (S300–500) and spectral slope ratio (SR, S275–295:S350–400), align with these findings, with SE and NW estuaries displaying higher values. On average, CDOM contributes 110.5 μM (6.8 %) to DIC in NE, 390.7 μM (11 %) in SE, 24.4 μM (4.8 %) in SW, and 122.2 μM (4 %) in NW estuaries. The relationship between total alkalinity minus DIC (TA-DIC) and pH25 suggests that CDOM, mediated by HA/FA, buffers the inorganic carbon system in estuaries. This buffering capacity weakens at elevated DIC levels, and this condition is marked by anomalous SR values compared to the baseline salinity-SR linear regression. This Study suggests that estuarine CDOM could largely represent “organic alkalinity” and could help monitor acidification in estuaries.

Spatiotemporal Variation of Per Capita Carbon Emissions and Carbon Compensation Zoning in Chinese Counties

The per capita carbon balance and carbon compensation zoning of Chinese counties from the perspective of major function-oriented zones is important for realizing the carbon peaking and carbon neutral target. In this study, the Kernel-K-means++ algorithm is used and a more comprehensive per capita carbon compensation zoning model is constructed. Based on this, combined with the major function-oriented zones, Chinese counties are divided into per capita carbon compensation-type zones. Further, spatial and temporal characteristics are detected, and suggestions for optimizing low-carbon development are put forward. The main results are as follows: (1) From 2000 to 2017, the per capita carbon emissions (PCO2) of Chinese counties were large and showed a trend of stable expansion and a southeast–northwest pattern; (2) the per capita carbon emissions of key development zones accounted for the largest proportion of emissions; (3) there were 1410 payment zones, 170 balanced zones, and 242 compensated zones among China’s counties; and (4) 11 types of carbon compensation space optimization zones were finally formed, and low-carbon development directions and strategies were proposed for each type of area. Based on this, this study promotes regional carbon emissions management and reduction in China and provides a reference for other regions to reduce emissions.

Arctic Sea Ice Melt Onset in the Laptev Sea and East Siberian Sea in Association with the Arctic Oscillation and Barents Oscillation

Abstract Arctic summer sea ice has been declining in recent decades. In this study, we investigate the beginning of the Arctic melting season, i.e., sea ice melt onset (MO), in the Laptev Sea (LS) and East Siberian Sea (ESS) along the Northern Sea route. Three leading modes are identified by EOF decomposition, which we call the LE-mode, L-mode, and E-mode. In positive phases these modes exhibit earlier MO in the two seas, a seesaw-like structure in the southwest–northeast direction with earlier MO in the LS, or in the southeast–northwest direction with earlier MO in the ESS. The LE-mode, L-mode, and E-mode are closely related to the Arctic Oscillation (AO) in April, the Barents Oscillation (BO) in April, and the AO in May, respectively. When the AO in April is positive, a low pressure anomaly northwest of the LS and ESS brings warm, moist air masses from the lower latitudes toward the LS and ESS and causes earlier MO, corresponding to the positive LE-mode. When the BO in April is negative, a cyclonic anomaly around the Barents Sea tends to warm and moisten the LS and cause earlier MO there, corresponding to the positive L-mode. When AO in May is positive, a low pressure anomaly northeast of the LS and ESS brings more warm, moist air toward the ESS and causes earlier MO there, corresponding to the positive E-mode. In the 1980s, the negative LE-mode was prominent whereas in the early 1990s the positive LE-mode was dominant. Since the mid-1990s, the L-mode and E-mode have appeared more frequently.

Spatial Morphological Characteristics and Evolution of Policy-Oriented Urban Agglomerations—Take the Yangtze River Middle Reaches Urban Agglomeration as an Example

The Yangtze River Middle Reaches urban agglomeration (YRMRUA) is a typical representation of policy-oriented urban agglomeration in China. In this study, we analyze the morphological characteristics of the built-up area of the YRMRUA, which is the research object, and we try to clarify changes in its development and the supporting role of policies. First, we used satellite image data provided by Google Earth Engine for supervised learning to obtain images of the built-up area land needed by the research. Then, we adopted radius dimension, spatial expansion intensity, and standard deviation ellipse successively to explore the spatial morphological characteristics of the YRMRUA. The following conclusions are drawn: (1) The built-up area of the YRMRUA with significant fractal characteristics has formed two parts, with diffusion-type fractals forming within its boundary and cohesion-type fractals forming outside its boundary. In addition, the fractal dimension has exhibited a gradual decline as time has passed. (2) The YRMRUA has gradually stabilized at a low rate of expansion of 0.2% per year. From the perspective of the grid, the spatial expansion intensity presented breakthrough and expansion in the second and third stages, respectively. The hot spots of space expansion with 95% confidence gradually changed from a point-like shape to a ribbon-like shape. (3) The expansion pattern of the YRMRUA showed a tendency of “northwest–southeast”, and gradually moved towards equilibrium. (4) A policy impetus has limitations, and the stages of space shaping has resulted in spatial solidification and differentiation. In response, we put forward suggestions for the objects and ways of policy functions, in order to provide references for the development of policy-oriented urban agglomerations.

Developmental history of a newly discovered chain of paired mound and depression structures on the southwestern continental shelf of the Ulleung Basin, East Sea, Korea

A chain of paired mound and depression structures are presented in the southwestern continental shelf of the Ulleung Basin, East Sea, Korea. We integrate multibeam bathymetry to identify topographic features, sub-bottom profile and multi-channel seismic reflection data to confirm geological features, and piston cores to understand the sediments of the mounds and depressions. Paired structures occur with a northwest–southeast orientation at water depths between 130 and 150 m and have similar scales of 10–20 m in height and depth. The mounds consist of cold-water corals and authigenic carbonate with shelly sand, whereas, the surficial lithology of depressions are only composed of siliciclastic deposits. The mounds appeared to have grown from the depression based on the observation for morphological features in the cross-section profiles of the paired mound and depression structures. Seismic profiles show acoustic blanking anomalies and seismic chimneys, indicating that the topographic relief formed under the influence of gas seepage. The petrological and geochemical signature of carbonate chunks also displayed gas leak effects different from CWC. This study suggests a developmental history model with paired mound and depression structures, in which gas/fluid escape causes depressions and the selective coral growth creates mounds growing on one side of these depressions. The mounds had sufficiently grown, depressions would have been further developed in interaction with the bottom current.

Exploring the spatiotemporal pattern evolution of carbon emissions and air pollution in Chinese cities

Based on data from 335 cities in China, this study employs the standard deviation ellipse method to portray unbalanced and differential spatiotemporal evolution patterns of environmental emissions and socioeconomic elements. A logarithmic mean Divisia index analysis and in-depth discussion are carried out to disclose the main driving factors and underlying reasons for the differences. Decoupling trends exist among carbon emissions, gross domestic product (GDP) and population in terms of their gravity center migrations. The standard deviation ellipse direction of carbon emissions gradually changed from ‘northeast‒southwest’ to ‘northwest‒southeast’, and the standard deviation ellipse areas of carbon emissions and air pollution continuously expanded over time; at the same time, that of GDP contracted. Economic growth has always been the main driver of carbon emissions and air pollution nationally, but its role has weakened. Moreover, decreases in the energy intensity and carbon and pollution intensities are the main factors contributing to emissions reductions. Differentiated spatiotemporal economic structure evolution, regional heterogeneities in the energy intensity and efficiency, and cross-region power energy transmissions are identified as the underlying reasons for the unbalanced spatiotemporal patterns of the environmental emissions and socioeconomic elements. Based on these findings, policy suggestions can be made to address the imbalances and promote carbon mitigation, air quality improvement and high-quality social-economic development at the city level.

Understanding the physical processes in the evolution of a cold air outbreak over China in late November 2022 from a Lagrangian perspective

From 26 November to 1 December 2022, intense cold air masses swept across China from northwest to south, resulting in a nationwide cold air outbreak (CAO) case characterised by drastic and sudden temperature drops with rain, snow and strong winds. The physical processes that dominate the intensification of the cold air masses during this CAO event remain unclear. In this study, the evolution of the CAO case, which is indicated by the dry static energy (DSE), is investigated using a novel approach in the framework of Lagrangian backtracking. The dominant processes can be identified by decomposing the DSE change into four diabatic heating terms due to shortwave radiation, longwave radiation, latent heat and turbulent processes. Overall, in this case, most of the cold air parcels originated from the east of Novaya Zemlya and crossed Central Siberia before reaching China. Thus, these air parcels mainly manifested on the northwest‒southeast path. The duration of the cold air intensification differed between subregions. The cold air parcels experienced long cooling periods (approximately 9 d) before reaching northern China (i.e. Northwest, North and Northeast China), whilst the southern parts (i.e. Central, East and South China) underwent relatively short cooling periods (6–8 d). Accordingly, the cold air affecting northern China is more intense than that affecting the southern parts, especially for East and South China. For all six subregions, longwave radiative cooling is identified as the dominant contributor to the cold air intensification, and the latent heat processes as the secondary contributor. The weakening of cold air parcels as they approach and pass over these regions is driven by turbulent processes and shortwave heating. Central Siberia and Lake Baikal are identified as key areas for the intensification of cold air passing over both regions. In addition, air parcels affecting Northwest China are intensely cooled as they pass over the Junggar Basin, while the North China Plain is a key area for cooling air parcels reaching Central, East and South China. From a Lagrangian perspective, these findings provide insights into the physical processes driving the behaviour of cold air parcels, which would help understand the mechanisms involved in the past changes and future projections in CAOs.

Delineation of Nubian sandstone aquifer using geophysical data around Nuweiba area, Sinai, Egypt

The Nubian sandstone aquifer (NSA) is defined by using 19 vertical electrical sounding (VES) stations, 201 gravity stations, which define the structures that control the configuration of the NSA, and 183 land magnetic stations, which define the lower surface of the NSA by determining the depth of the basement surface. In order to assess the top of the NSA, we collected and analyzed 19 deep VESes. The upper surface depth of the NSA spans from 707 to 1154 m, according to the interpretation results for various geophysical data. Additionally, the aquifer’s resistivities ranged from 30.2 to 477 Ω m, which indicates good groundwater quality. According to the interpretation of the gravity result, the study region is influenced by many structural characteristics of different trends, including northwest–southeast, northeast–southwest, and east–west trends. The upper surface depth of crystalline rocks (also known as basement rocks) is determined by three-dimensional magnetic modeling to range between 967 and 4122 m.

Spatiotemporal Dynamic Characteristics of Land Use Intensity in Rapidly Urbanizing Areas from Urban Underground Space Perspectives

Land use intensity (LUI) reflects the utilization status of land use. However, traditional LUI assessments have been conducted for land space governance with a primary focus on surface land. Thus far, the explicit variation and spatiotemporal characteristics of land use of underground space (LUUS), particularly the quantization of LUUS-related intensity, are not well understood. Using the case of Wuhan in China, this study takes the main urban area of Wuhan as the research area, based on the time series data of the underground space information survey of analysis units from 2002 to 2018. This reflected the distribution pattern and evolution characteristics of underground space in terms of the intensity, the concentration and spatial hot-spots by using the spatiotemporal analysis framework. The results show that: (1) The LUUS exhibits spatial characteristics of global dispersion, and local aggregation increased and expanded along the northwest–southeast direction; (2) The global spatial dependency of LUUS is strong and the degree decreases with the expansion of the scope; (3) The LUUS is mainly developed in a relatively concentrated mode, and the concentration degree decreases with time; (4) The main development area of the LUUS is gradually expanding from within the inner ring line outside the second ring road in different periods, and the spatial difference is more obvious and increasing. Our study renews the indicators of quantitative LUI evaluation based on underground spatial data. The findings refreshed the knowledge base concerning the spatiotemporal heterogeneity in terms of underground space intensity and provided new insights into spatial governance.

Dynamics of localized extreme heatwaves in the mid‐latitude atmosphere: A conceptual examination

AbstractThis study investigates the adjustment of large‐scale localized buoyancy anomalies in mid‐latitude regions and the nonlinear evolution of associated condensation patterns in both adiabatic and moist‐convective environments. This investigation is carried out utilizing the two‐layer idealized moist‐convective thermal rotating shallow water (mcTRSW) model. Our investigation reveals that the presence of a circular positive potential temperature anomaly in the lower layer initiates an anticyclonic high‐pressure rotation, accompanied by a negative buoyancy anomaly in the upper layer, resulting in an anisotropic northeast–southwest tilted circulation of heat flux. The evolution of eddy heat fluxes, such as poleward heat flux, energy, and meridional elongation of the buoyancy field, heavily depends on the perturbation's strength, size, and vertical structure. The heatwave initiates atmospheric instability, leading to precipitation systems such as rain bands and asymmetric latent heat release due to moist convection in a diabatic environment. This creates a comma cloud pattern in the upper troposphere and a comma‐shaped buoyancy anomaly in the lower layer, accompanied by the emission of inertia gravity waves. The southern and eastern sectors of the buoyancy anomaly show an upward flux, generating a stronger cross‐equatorial flow and inertia‐gravity waves in a southward and eastward direction. Furthermore, the simulations reveal a similar asymmetric pattern of total condensed liquid water content distribution, accompanied by the intensification of moist convection as rain bands. This intensification is more pronounced in barotropic structures than in baroclinic configurations with stagnant upper layers. This study highlights the importance of considering moist convection and its effects on atmospheric and oceanic flows in mid‐latitude regions, as well as the role of buoyancy anomalies in generating heatwaves and precipitation patterns.

Winter-time Hydraulic Jump over the Pokhara Valley, Nepal

The Pokhara Valley is set to be one of the aviation hubs of Nepal with the opening of an international airport. The complex mid-hill mountainous topography of the Gangi-Himalaya and the characteristic wind system of the valley make safe aviation rather challenging over the valley. This study using the Weather Research and Forecasting modeling system shows that hydraulic jump-like phenomena occur regularly during winter in the western and central part of the Pokhara Valley during late afternoon/early evening when the airport may remain relatively busy. The jump occurs over the western part of the valley when the regional southwesterly plain to mountain wind via the Putalibazar Valley intrudes into the Valley crossing the Deurali-Mattikhan hill. The jump-like flow is accompanied by the formation of a mild reverse roller above the jump region and the head-on convergence with the northeasterly katabatic/drainage wind from Parche-Namarjung along the southeast–northwest oriented valley axis generating an updraft of as much as 0.4 to 0.8 m s-1. The southwesterly overrides northeasterly generating clockwise vertical rotors and high turbulence over the northeastern region of the valley. An early prediction of possible wind hazards at high spatiotemporal resolutions are highly desired to make aviation activities in the region safer for civil aviation.

Assessing the Applicability of Three Precipitation Products, IMERG, GSMaP, and ERA5, in China over the Last Two Decades

The accuracy of gridded precipitation products is uncertain in different temporal and spatial dimensions. Analyzing the applicability of precipitation products is a prerequisite before applying them to hydrometeorological and other related research. In this study, we selected three gridded precipitation products, Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG), Global Satellite Mapping of Precipitation (GSMaP), and the fifth generation of atmospheric reanalysis of the European Centre for Medium-Range Weather Forecasts (ERA5), including their data from 2001 to 2020. Using the data from 699 ground observation stations, we evaluated the applicability of these three precipitation products in China. Based on five statistical and five classification indicators, we first assessed the applicability of the three precipitation products on daily, monthly, and annual time scales, respectively, and then evaluated their applicability in different spatial dimensions, including basins, agriculture, and geomorphology. The results showed that: (1) IMERG data had the best accuracy on annual and monthly time scales, with both correlation coefficient (CC) values greater than 0.95 and Kling–Gupta efficiency (KGE) values greater than 0.90. On a daily time scale, the accuracy of all three precipitation products differed when statistical or categorical indicators were considered alone. However, the applicability of IMERG data was best among the three precipitation products when both types of indicators were considered. (2) The accuracy of the three precipitation products gradually decreased along the southeast–northwest direction. The applicability of ERA5 data was better in northern regions than in other regions in China, especially in arid and semi-arid regions in northern China. The applicability of IMERG data was better in southern regions with more precipitation and in high-altitude regions than in other regions in China. (3) The applicability of the three precipitation products in plain areas was generally better than in mountain areas. Among them, ERA5 data were more accurate in plain areas, while IMERG data were more accurate in mountain areas. This study can provide a reference for the selection of data sources of gridded precipitation products in different time scales and spatial dimensions in China.

Spatiotemporal Weighted for Improving the Satellite-Based High-Resolution Ground PM2.5 Estimation Using the Light Gradient Boosting Machine

Surface fine particulate matter (PM) with a diameter of less than 2.5 microns (PM2.5) negatively impacts human health and the economy. However, due to data and model limitations, obtaining high-quality, high-spatial-resolution surface PM2.5 concentration data is a challenging task, and it is difficult to accurately assess the temporal and spatial changes in PM2.5 levels at a small regional scale. Here, we combined multi-angle implementation of atmospheric correction (MAIAC) aerosol products, ERA5 reanalysis data, etc., to construct an STW-LightGBM model that considers the spatiotemporal characteristics of air pollution and estimate the PM2.5 concentration of China’s surface at 1 km resolution from 2015 to 2020. Our model performed well, and the fitting accuracy of the 10-fold cross-validation between years was 0.877–0.917. The fitting accuracy of the model was >0.85 at different time scales (month, season, and year). The average slope of the regression prediction was 0.9 annually. The results showed that PM2.5 pollution improved from 2015 to 2020. The average PM2.5 concentration decreased by 4.55 μg/m3, and the maximum decrease reached 90.51 μg/m3. The areas with high PM2.5 concentrations were predominantly in the North China Plain, Sichuan Basin, and Xinjiang in the west, and the levels in areas with elevated PM2.5 levels were consistent across most study years. The standard deviation ellipse for PM2.5 in China showed a ‘northeast–southwest’ spatial distribution. From an interannual perspective, the average values of the four seasonal stations in the country showed a downward trend from 2015 to 2020, with the most obvious decline in winter, from 70.67 μg/m3 in 2015 to 46.75 μg/m3 in 2020. Compared to earlier inversion studies, this work provides a more stable and accurate method for obtaining high-resolution PM2.5 data, which is necessary for local air governance and environmental ecological construction at a fine scale.

Distribution Characteristics and Influencing Factors of the National Comprehensive Disaster-Reduction Demonstration Community in China

Establishing the National Comprehensive Disaster-Reduction Demonstration Community (NCDDC) is crucial for enhancing comprehensive disaster risk reduction at the grassroots level in China. Studying the distribution characteristics and influencing factors of NCDDCs can guide future NCDDC layout optimization and related policy adjustments. Using the standard deviation ellipse, nearest neighbor index, kernel density, spatial autocorrelation, and Geodetector, we analyzed the spatiotemporal distribution characteristics of NCDDCs in China from 2008 to 2021 and detected their influencing factors. The findings are as follows: (1) NCDDCs exhibit an uneven distribution at different scales, including spatial, urban–rural, and county scales. (2) The spatial distribution of NCDDCs mainly follows a northwest–southeast pattern during 2008–2014 and shows a northeast–southwest trend after 2014. (3) The positive spatial correlation and spatial agglomeration of NCDDCs increase annually. (4) NCDDCs show a concentrated and contiguous distribution pattern in 2021, based on “core density zone–ring-core decreasing area–ring-core expansion group–Ɔ-shaped area–belt-shaped area”. (5) The main factors affecting the NCDDC distribution are hospital density, road density, GDP density, and population density, with factors’ interactions exhibiting bilinear and nonlinear enhancement effects. This study reveals the NCDDC spatiotemporal distribution characteristics and its influence mechanism, providing a scientific basis for future NCDDC layout optimization and related policy adjustments.