Maximum Occurrence Research Articles

COMPREHENSIVE CHARACTERISATION OF TEMPORAL VARIATIONS IN CONCENTRATIONS OF GASEOUS AMMONIA AND NITROGEN OXIDES IN TYPICAL URBAN ATMOSPHERE

Atmospheric ammonia (NH3) is a well-known contributor to secondary particle formation and canlead to severe environmental degradation and human health outcomes. In the context of the verylimited knowledge about updated data on NH3 levels in urban areas, this paper presents the results ofa one-year (Apr 2023 – Mar 2024) measurement campaign of NH3 concentrations conducted at theurban background site in Zabrze, located in the central part of the Upper Silesian Industrial District(USID) (southern Poland), which could be considered one of the European hotspots. The research wasperformed using an automatic ammonia analyzer Model T201 by Teledyne API, which provides dataon the levels of NH3 and other gaseous nitrogen compounds (NO (nitrogen oxide), NO2 (nitrogendioxide), NOx (nitrogen oxides) at hourly time resolution. Consequently, this enabled an analysisof specific temporal variations of NH3 concentrations, and therefore allowed the identification ofits possible emission sources and insight into processes involving ammonia. The results obtained inthis study revealed that ammonia stood out from nitrogen oxides and other atmospheric pollutants– with high NH3 concentrations recorded during spring and summer, which is related to the highintensity of gaseous NH3 formation under warm meteorological conditions. A different situationwas observed in the hourly NH3 concentration distribution scheme, which was manifested by muchless visible diurnal variations of NH3 levels, with no characteristic morning maximum, as well asthe occurrence of a broad afternoon maximum in the summer. In summary, anthropogenic sourceshad a significant impact on NH3 concentrations in the area under consideration, with a greater roleof traffic in the case of NOx, and a biomass and fossil fuel combustion and/or industrial sources –for NH3. Local meteorological conditions also had a notable influence on NH3 levels, of which airtemperature (positive correlation) and wind speed (negative correlation) were found to be the mostimportant. The ongoing research is planned to be continued, as it can provide valuable scientific datafor the development of air quality protection strategies and programmes in urban areas, especially inthe field of reducing emissions of gaseous precursors of particulate matter.

Intensification of thermal risk in a changing climate: findings from prominent tourism destinations along the eastern Adriatic coast.

The climate and thermal comfort of а destination greatly influence the tourism industry. Therefore, this study was focused on researching thermal comfort changes and their impacts on visitors in four highly visited coastal destinations along the eastern Adriatic coast (Pula, Zadar, Split, and Dubrovnik) from 1996 to 2020, using the modified physiologically equivalent temperature index (mPET). The specific objective was to assess how the thermal comfort conditions are distributed spatially and temporally and how they are suitable for beach and sightseeing tourism. Results showed that monthly mean mPET values have increased, except in May. In the summer season, tourists were often exposed to uncomfortable heat stress, especially in the middle of the day. Strong and extreme heat stress frequency significantly increased in all sites except in Pula, particularly in July and August. Prevailing neutral and slightly warm/cold conditions were concentrated in two periods, between April and June and in September and October. The maximum occurrence of optimal climatic conditions for enjoying the beach was in the summer, with a decreasing tendency from May to August. The occurrence of favorable conditions for sightseeing significantly increased in April and November while it decreased from July to September. Although the eastern Adriatic coast is primarily a summer tourist area, a relatively small number of tourists take advantage of the period with optimal thermal comfort. Despite the fact that the number of tourists in the shoulder seasons has increased significantly in the past 25 years, the increasing favorable thermal comfort in the changing climate conditions will make these seasons even more appealing in the future, especially for sightseeing activities. New strategies for adapting to a changing climate are therefore needed.

Climatological Tracking and Lifecycle Characteristics of Mesoscale Convective Systems in Northwestern South America

AbstractMesoscale convective systems (MCSs) are crucial in shaping large‐scale tropical circulation and the hydrological cycle, particularly in Northwestern South America (NwSA), a region marked by complex terrain and significant MCS activity. Understanding MCSs in NwSA is vital due to their impact on precipitation patterns and potential for severe weather events. To enhance this understanding, the ATRACKCS algorithm was developed for tracking convective systems, utilizing precipitation and brightness temperature data sets. This research focuses on documenting the spatiotemporal variability of MCS occurrence, life cycle, and movement. Notably, MCS hotspots were identified to the west of the major orographic features in the region, with maximum occurrences at night, contrasting with the region's typical afternoon peak in land convection. MCS movement is also heavily influenced by topography, with higher velocities on the eastern (windward) side of the Andes compared to velocities on the western (leeward) side. MCSs generally move westward, driven by easterly winds, but this pattern is not consistent throughout the year or region. Northward movement is predominant to the west of the Andes, while southward movement is observed to the east. These seasonal and regional movement variations are linked to factors such as the intertropical convergence zone position, moisture availability, topography, and low‐level jets. This research underscores the complexity of MCSs in NwSA and emphasizes the need for detailed studies on the atmospheric environment shaping these systems. Additionally, it provides a robust 21‐year MCS database for NwSA and an advanced tracking tool for research in various geographic contexts and impact areas.

Assessment of ISRO’s S-band polarimetric Doppler Weather Radar (DWR) at SHAR with IMD-DWR and GPM-Ku radar

ABSTRACT This paper describes the first assessment of ISRO’s indigenously developed S-band Polarimetric Doppler Weather Radar (DWR) at Sriharikota High Altitude Range (SHAR), Sriharikota (13.66°N, 80.23°E). The assessment is done during the passage of a tropical cyclone ‘Phethai’ and four different cases of Mesoscale convective systems. A comparison of reflectivity measured from SHAR-DWR with India Meteorological Department (IMD) DWR located at Chennai (13.07°N, 80.28°E) and Ku-band space-borne radar of the Global Precipitation Mission (GPM) is done using the common volume matching method. A good comparison is observed between SHAR-DWR with IMD-DWR and GPM-Ku radar in both space and height. The vertical structure of the cyclone is provided using Contour Frequency by Altitude Diagrams (CFAD) which show the vertical extent up to an altitude of 16 km with a reflectivity between 25 and 30 dBZ. Maximum occurrence of 30 dBZ occurs below 6 km. Bright band signatures show ~ 25 dBZ between 4 and 5 km depicting the stratiform precipitation of the cyclone. Further rain rate is estimated using both reflectivity and the polarimetric product which compared well with rain estimated from IMD-DWR and rainfall observed from rain gauges. Rain rate is observed from 5 to 35 mm hr−1. Hydrometer classification during the passage of tropical cyclone ‘Phethai’ shows the presence of rain below 4 km and graupels, ice crystals, and large droplets above.

Observed APO Seasonal Cycle in the Pacific: Estimation of Autumn O2 Oceanic Emissions

AbstractIn this work, we investigated the seasonal cycle of atmospheric potential oxygen (APO), a unique tracer of air‐sea gas exchanges of molecular oxygen (O2) and carbon dioxide (CO2), expressed as APO = O2 + 1.1 × CO2. APO data were obtained from flask air samples collected since the late 1990s at three Japanese ground stations and on commercial cargo ships sailing between Japan and Australia/New Zealand, North America, and Southeast Asia. We also analyzed the APO spatial distribution and seasonal cycles with simulations from an atmospheric transport model using climatological oceanic O2 fluxes from an empirical product that relate O2 flux to ocean heat as input. Model simulations reproduced the observed APO seasonal cycles generally well, but with larger amplitudes and earlier occurrence of seasonal minima and maxima than in the observations. Moreover, the observed seasonal cycles exhibited larger APO enhancements than the simulations in autumn and early winter, especially in the North Pacific at 20°N–60°N. These enhancements remained when refining the comparison by adjusting the simulated APO peak‐to‐peak amplitudes and seasonal phases to the observations. This suggests additional O2 emissions in the North Pacific, not well expressed in the air‐sea O2 fluxes used as input for our model simulations. The average autumn enhancement at 40°N–60°N was approximately twice that measured at 20°N–40°N. Confirming previous studies, our results indicate two distinct mechanisms possibly contributing to the additional oceanic O2 emissions: outgassing from a subsurface shallow oxygen maximum at 20°N–40°N and autumn phytoplankton bloom at 40°N–60°N.

Late-glacial and Holocene shifts in the mountain landscapes of the Cantabrian range (northern Spain) in response to changing climate, fire occurrence and land use

A new well-dated (18 14C dates on short-lived terrestrial plant macrofossils, 210Pb and 137Cs dating) fine-resolution palaeoecological sequence (pollen, coprophilous fungi, conifer stomata, macrofossils, charcoal) from Lago de Isoba (1400 m a.s.l.) spanning the past c. 17,000 years provides novel insights into the long-term dynamics of the high-elevation Cantabrian landscape in response to climate variability and human activities. Vegetation changes were mainly climate-driven during the Late-glacial and the Early Holocene. Thus, steppe-like environments prevailed during the Greenland Stadial 2.1a (GS-2.1a ≈ ‘Oldest Dryas’). Warmer and moister conditions during the Greenland Interstadial 1 (GI-1 ≈ ’Bølling-Allerød’) enabled successive expansions of Juniperus, Betula and Pinus. Steppe-like vegetation re-expanded during the cooler and drier Greenland Stadial 1 (GS-1 ≈ ‘Younger Dryas’). Afterwards, the Early Holocene warming triggered the rapid spread of mixed pine-broad-leaved deciduous mountain forests. Pollen, stomata and macrofossils indicate continuous, long-lasting (c. 10,850–1250 cal yr BP) local occurrence of Pinus sylvestris stands. The records of Cerealia and Plantago lanceolata pollen types (first Holocene occurrences dated at c. 5100 cal yr BP) evidence increased land use during the Late Holocene, which triggered substantial changes in forest ecosystems. Following a phase of intensified arable and pastoral farming, which involved the use of fire to create and maintain forest clearings, pinewoods expanded and reached their maximum development between c. 3600 and 3300 cal yr BP. Pinus probably outcompeted temporarily other woody taxa thanks to its resilience to low-intensity disturbances. Later, pinewoods underwent a stepwise, human-induced decline ending in their final massive collapse after c. 1150 cal yr BP. The highest intensity of agricultural and pastoral farming took place during the Middle Ages, following maximum fire occurrence. We conclude that the present-day open landscape has been shaped by millennia of land use that partly blurred the impact of climate variability.

Climatic characteristics of centennial and extreme precipitation in Hangzhou, China

The precipitation characteristics in Hangzhou of Zhejiang Province, China under the background of global climate change are analyzed using the meteorological observation data obtained from the Hangzhou base station in this study. We investigate the climate characteristics of precipitation in Hangzhou from several aspects, such as centennial trend, seasonal change, periodicity and the variation of extreme precipitation. Our results show a linear decreasing trend and obvious interdecadal characteristics in the precipitation of Hangzhou on a centennial timescale. Significantly increased amplitude of precipitation fluctuation was observed since the beginning of the 21st century. For the interdecadal variation of seasonal precipitation on a centennial timescale, precipitation in autumn showed a decreasing trend of 8.1 mm/10a, whereas the trends for the other three seasons were statistically insignificant. The precipitation in Hangzhou showed a decreasing trend in spring and an increasing trend in winter over the past 30 years. Our analyses reveal distinct precipitation cycles, including a quasi-30-year cycle since the 1960s and a quasi-10-year cycle since the 1980s. However, the periodicity has weakened in the past 10 years. In addition, the occurrence of torrential rain has increased rapidly in the past 10 years. Furthermore, influenced by global climate change and regional processes, the variation of extreme precipitation in Hangzhou has changed, which shows strong correlations with the overall trend of annual precipitation. The annual maximum daily precipitation in Hangzhou was mainly in the range of 0–40 mm from 1951 to 1980 and in the range of 40–80 mm from 1981 to 2010 with the maximum daily precipitation occurrence rate of 4.7 times/10a and 6.3 times/10a, respectively. This study emphasizes the risk of urban waterlogging caused by short-term heavy rainfall and provides useful reference to the assessment of extreme meteorological and hydrological disaster risk in Hangzhou.

Comparison of the Occurrence Morphology of Phase Scintillation of GPS and Beidou Signals at Zhongshan Station, Antarctica

AbstractThe characteristics of phase scintillation (represented by the phase scintillation indices, σφ) from GPS and Beidou are statistically analyzed using a ground‐based receiver at Zhongshan Station, Antarctica, from 2020 to 2022 for the first time. The phase scintillation of the GPS and Beidou signals present a similar pattern of occurrence. The statistical results on the occurrence morphology of phase scintillation show that the phase scintillation predominately occurs in the magnetic pre‐noon and pre‐midnight sectors. Moreover, phase scintillation performs a dependence on solar and geomagnetic activities. Furthermore, the phase scintillation also gives a seasonal variation with the maximum occurrence happened at the autumn and the minimum occurrence during the summer. Consequently, these results improve understanding of the morphological characteristics of the phase fluctuations in the less studied Antarctic region. The study also demonstrates the use of the combined data set to improve the coverage in the Antarctic region.

Microbial Health Risks of Cryptosporidium parvum and Giardia lamblia in Tropical Coastal Water in Araromi, Nigeria.

Giardia and Cryptosporidium are enteric protozoa that can cause a variety of gastrointestinal diseases, especially in vulnerable people like children, the elderly, and those with impaired immune systems. In order to ascertain the microbiological quality of the recreational water from Araromi Beach in Ilaje Local Government Area, Ondo State, Nigeria. This risk assessment is of great significance to human health protection against waterborne diseases. The aim of this study was to determine the microbial quality of recreational water from Araromi Beach in Ilaje Local Government Area, Ondo State, Nigeria. Microscopic examination of Cryptosporidium and Giardia oocysts were done. Results revealed maximum occurrence of Cryptosporidium parvum (20 oocysts/100 mL) of water sample in the month of April and maximum occurrence of Giardia lamblia (300 cysts/100 mL) of water sample in the month of June. Additionally, according to Kolmogorov-Smirnov tests for normalcy Ho =0.05, Giardia lamblia and Cryptosporidium parvum were not regularly distributed in the water samples collected from the beach throughout the study period. The average likelihood of contracting Giardia lamblia and Cryptosporidium parvum infections after consuming 100 mL of beach water was 0.96 and 0.35, respectively. The risks of infection associated with Cryptosporidium parvum was lower than those associated with Giardia lamblia in water from the beach, but were both above the acceptable risk limit of 10-4. The results of this study indicate that Giardia and Cryptosporidium may represent serious health hazards to people who engage in aquatic activities. Adopting a comprehensive strategy that includes regular inspections, enhanced detection techniques, and the prevention of aquatic environment pollution may provide clean and safe recreational water for all, thereby safeguarding the public's health.

Assessing the occurrence of annual maximum daily discharge for five of the longest rivers in Africa

Assessing the occurrence of annual maximum daily discharge for five of the longest rivers in Africa

On the characterization of Cloud occurrence and its impact on solar radiation in Mbour, Senegal

The objective of this study is to evaluate the clouds seasonal occurrence characteristics, and to estimate their impact on solar radiation in Mbour, Senegal, West Africa. Here, we use datasets from various sources including: i) observations from the Clouds and Earth's Radiant Energy System satellite sensors, ii) in situ shortwave radiation measurement obtained from the Mbour station, and iii) the outgoing longwave radiation (OLR) obtained from the National Centers for Environmental Prediction reanalysis data. Results show a marked seasonality, associated with high spatial variation in terms of cloud occurrence over Senegal. The maximum cloud occurrences are observed during the wet summer season (June–October), whilst the minimum cloud occurrences are recorded during the long-dry season from November to May. During the monsoon season the cloud activity becomes more intense with a total cloud cover of about 80%, a cloud optical depth of around 7, and a high convective activity illustrated by a low OLR (below 240 W/m2). Likewise, across Senegal a strong north-south gradient of the cloud characteristics is observed. Based on quantitative comparison between cloud occurrence and radiation measurement, results show an important seasonal impact on available solar potential in Mbour. Conversely to the cloud occurrence, the maximum of both direct normal and global solar potentials is recorded during the dry season, coinciding with the period with clean sky. An investigation of the cloud influence on solar radiation on selected study cases indicates a decrease of 60% (80%) for the total (direct normal) radiation during the peak of the summer monsoon season.

Polar Low Circulation Enhances Greenland's West Coast Cloud Surface Warming

AbstractMass loss of the Greenland Ice Sheet (GrIS) plays a major role in the global sea level rise. The west coast of the GrIS has contributed 1,000 Gt of the 4,488 Gt GrIS mass loss between 2002 and 2021, making it a hotspot for GrIS mass loss. Surface melting is driven by changes in the radiative budget at the surface, which are modulated by clouds. Previous works have shown the impact of North Atlantic transport for influencing cloudiness over the GrIS. Here we used space‐based lidar cloud profile observations to show that a polar low circulation promotes the presence of low clouds over the GrIS west coast that warm radiatively the GrIS surface during the melt season. Polar low circulation transports moisture and low clouds from the sea to the west of Greenland up over the GrIS west coast through the melt season. The concomitance of the increasing presence of low cloud in fall over the Baffin Sea due to seasonal sea‐ice retreat and a maximum occurrence of Polar low circulation in September results in a maximum of low cloud fraction (∼14% at 2.5 km above sea level) over the GrIS west coast in September. These low clouds warm radiatively the GrIS west coast surface up to 80 W/m2 locally. This warming contributes to an average increase of 10 W/m2 of cloud surface warming in September compared to July on the GrIS west coast. Overall, this study suggests that regional atmospheric processes independent from North Atlantic transport may also influence the GrIS melt.

The investigation of deflection behavior in carbon/epoxy and glass/epoxy composite laminates under low-velocity impact with small projectiles

This study examined the impact behavior of carbon/epoxy and glass/epoxy composite laminates with 2, 4, and 6 mm thicknesses under low-velocity tests. The investigation involved subjecting the composite laminates under small-impact loads using spherical, cylindrical, and conical steel projectiles, each weighing 3 g. The impacts conducted at 29.5, 36.5, and 51 m/s velocities. This investigation modeled using finite element (FE) methods and analytical approaches. In the analytical method, the mass and spring model used for the impact of small projectiles. The research findings revealed that, in 2 mm thick carbon/epoxy composite laminates, the maximum deflection at the mid-point induced by a spherical projectile was 1.37 mm. This value exhibited a 48.91% and 19.13% increase compared to impacts with cylindrical and conical projectiles, respectively. Additionally, a comprehensive examination of delamination across all samples indicated the maximum delamination occurrence in glass/epoxy samples, showcasing lower impact resistance than carbon/epoxy laminates. Notably, with an increase in thickness, the delamination phenomenon in the samples exhibited a decreasing trend. In addition, the maximum value of delamination in the composite laminates were with spherical, conical, and cylindrical projectiles respectively, and also, there was an excellent convergence between FE and analytical results.

The experimental and numerical investigation of fracture behaviour in PMMA notched specimens under biaxial loading conditions – Tension with torsion

This paper presents the results of experimental fracture test of flat PMMA specimens under biaxial loading condition tension with torsion (proportional). The specimens were made in two thicknesses: 5 and 15 mm and were weakened with V-type edge notches with different root radii: 0.5; 2 and 10 mm. Thanks to the ARAMIS 3D 4 M non-contact vision system, measurement of the elongation and twist angle were recorded. During experimental part all of the deformation processes were observed using PHANTOM cameras. Obtained records made it possible to precisely indicate the moment of crack initiation (tensile force and torsional moment values). Using the microscopic observations the location of crack initiations were determined. Results obtained for biaxial loading were compared with those obtained for uniaxial tension and torsion. Based on experimental data the numerical calculation with FEM were carried out. The principal stress and plastic strain distribution under critical load, were obtained. The points of occurrence of stress maxima and plastic strain were indicated, which were taken as potential crack initiation sites. On the basis of the stress and plastic strain values measured at the critical points, a stress–strain fracture criterion was formulated, which was then positively verified. Additionally, new form of stress–strain fracture criterion was proposed. The bilinear form of the fracture criterion can be successfully used to predict fracture in PMMA flat specimens, regardless of the notch root radius, type of load or element thickness.

Qualitative and quantitative changes in phenology of chlorophyll a concentrations during the transition from eutrophy to oligotrophy

AbstractThe PEG (Plankton Ecology Group) model predicts differences in phenology between eutrophic and oligotrophic lakes regarding the occurrence, timing and magnitude of annual chlorophyll maxima and minima. While these predictions have been tested between lakes, hardly any tests exist using long‐term data. We test these predictions using chlorophyll time‐series (1980–2019) from Lake Constance in which trophic status shifted from eutrophic to oligotrophic conditions. We show that oligotrophication subsequently resulted in reduction of the summer and spring blooms, and finally the loss of the clear‐water phase. In contrast to the PEG model the spring bloom was not delayed, but advanced with oligotrophication. Warming modified the seasonal patterns via advancing clear‐water timing. Oligotrophication did not only influence phenologies, but also the importance of independent variables driving phenologies. Thus, the decline of nutrients was the dominant factor in shaping the seasonal patterns of chlorophyll in Lake Constance during the last four decades.

Research progress on cambium activity and radial growth dynamics monitoring of coniferous species

The radial growth of trees plays a crucial role in determining forest carbon sequestration capacity. Understanding the growth dynamics of trees and their response to environmental factors is essential for predicting forest's carbon sink potential under future climate change. Coniferous forest trees are particularly sensitive to climate change, with growth dynamics responding rapidly to environmental shifts. We collected and analyzed data from 99 papers published between 1975 and 2023, and examined the effects of exogenous factors (such as temperature, water, and photoperiod) and endogenous factors (including tree age and species) on cambial activity and radial growth in conifers. We further explored the mechanisms underlying these effects. The results showed that climate warming had the potential to advance the onset while delayed the end of xylem differentiation stages in conifers in temperate and boreal regions. Water availability played a crucial role in regulating the timing of cambial phenology and wood formation by influencing water potential and cell turgor. Additionally, the photoperiod not only participated in regulating the start and end times of growth, but also influenced the timing of maximum growth rate occurrence. Future climate warming was expected to extend the growing season, leading to increase in growth of conifers in boreal regions and expanding forests to higher altitudes or latitudes. However, changes in precipitation patterns and increased evapotranspiration resulting from temperature increases might advance the end of growing season and reduce growth rate in arid areas. To gain a more comprehensive understanding of the relationship between radial growth and climatic factors, it is necessary to develop process-based models to elucidate the physiological mechanisms underlying wood formation and the response of trees to climatic factors.

A Temporal Study on Incidence of Bovine Mastitis in Haryana, India

Mastitis affects dairy animal’s productivity and causes financial losses for dairy farmers in India and across the world. In this study, a total of 52,494 quarter milk samples from 14,381 bovines were screened for the primary microorganisms causing mastitis in Hisar and adjoining districts of Haryana and their antibiotic sensitivity patterns were analyzed. The cultural positivity from subclinical form of mastitis was observed as 86.32% and 87.73% from cows and buffaloes, respectively while that from clinical mastitis was 87.36% and 87.57%. The major Gram positive bacterial pathogens associated with mastitis in the entire study period were found as Staphylococcus species with an average incidence rate of 45.53% and 44.1% from cows and buffaloes, respectively. The Streptococcus species were found to be 33.76% and 29.94% of total isolates. Escherichia coli were the most predominant Gram negative bacteria isolated (17.37% and 13.85%), thereafter Klebsiella spp. (5.54% and 5.19%) from both cows and buffaloes. A significant proportion of clinical cases of mastitis were chronic in nature from both the species of bovines. The incidence of mastitis with respect to different lactation number and lactation months was found as significant. The highest incidences of mastitis was observed in the first lactation among buffaloes (20.69%), while the maximum incidences were observed in second and third lactation in cows with 16.59% and 16.99%, respectively. However, in both the species maximum occurrence of mastitis was observed during the first lactational month. The antibiotic sensitivity patterns of most of the isolates had shown higher sensitivity towards enrofloxacin and gentamicin, while the penicillin had shown least sensitivity. The knowledge regarding the mastitis causing pathogens and their sensitivity pattern in Hisar and adjoining districts of Haryana enables the veterinarians to adopt for the proper treatment protocols and dairy farmers to assure optimal health, welfare and productivity of bovines in the State, in turn reducing antimicrobial resistance.

TAXONOMIC DIVERSITY OF BENTHIC ALGOFLORA OFF THE WESTERN COAST OF THE CRIMEAN PENINSULA

The article presents the results of the study of benthic flora along the western coast of the Crimean Peninsula (Sevastopol region, Black Sea) in the summer of 2020. Hydrobotanical studies covered the water areas of Cape Tyubek, Lukull, VaiVai, Margopulo, Nemetskaya and Yazykovaya Balka. The flora included macroalgae of 74 species from the departments Chlorophyta, Heterokontophyta and Rhodophyta. The identified taxonomic composition was characterized by high species saturation of suprageneric taxa and low genus coefficient (1.1–2.0), coincidence of the proportion “order/family” in the divisions and in the whole algoflora, as well as “order/family/genus” in Heterokontophyta and Rhodophyta. The basis of taxonomic diversity was the following Rhodophyta (Ceramiales, Corallinaceae, Rhodomelaceae, Ceramiaceae), Chlorophyta (Cladophorales, Ulvales, Cladophoraceae, Ulvaceae), Heterokontophyta (Ectocarpales, Chordariaceae). Multispecies orders and families united from 55 to 88% of the total number of species found. High species diversity was characteristic of the genera Cladophora, Ulva, Polysiphonia and Ceramium. Seventeen species included in the national Red Data Books and international lists were found in the studied areas of the western coastal zone, which indicates the conservation significance of the study area. The large proportion of permanent species, their high joint contribution with additional species, the presence of maximum occurrence in a quarter of species (100%), and the average value of Jaccard’s coefficient (60%) testified to the spatial homogeneity of the species composition in the studied water area, which corresponded to relatively uniform habitat conditions of hydrobionts along the open sea coasts. Spatial changes in taxonomic composition were moderate (Cv = 9–26%). The difference in the extreme values of the absolute number of taxa was insignificant (by 30-50%). Among the departments, Chlorophyta was characterized by the lowest variation in the number of taxa, and Rhodophyta – by the highest. The increase in the difference between the extreme values of the absolute number of taxa was realized in the direction of orders < families < genera < species. The results of phytoindication indicate the warm-water character of the flora and the emerging trend of increasing trophicity of algal habitat in the study area.

Statistical Characteristics of Spread F in the Northeastern Edge of the Qinghai-Tibet Plateau during 2017–2022

Spread F (SF) in the ionosphere can be observed frequently in mid-latitude regions. It is suggested that atmospheric gravity waves play a significant role for the seeding of mid-latitude SF. Previous research suggested that the source of travelling ionospheric disturbances (TIDs) over China is in the southeastern and northeastern edge of the Qinghai-Tibet Plateau, however, until now there have been no ground-based observations of the ionosphere in this region. Recently, an advanced digital ionosonde was installed at Zhangye station (39.2°N, 100.54°E, Dip Lat 29.6°N) in the northeastern edge of the Qinghai-Tibet Plateau. It is an opportunity to verify the effect of gravity waves on the formation of mid-latitude SF by comparing it with observations in other regions of the Chinese sector. In this study, statistical analysis of SF recorded at Zhangye station during 2017–2022 was carried out. Results show that diurnal, seasonal and solar cycle characteristics of the occurrence rate of SF are similar with previous studies. At Zhangye station, the maximum occurrence rate of SF is during the post-midnight period in summer and winter. The occurrence rate of SF events have a negative relationship with solar activity. There is no obvious relationship between the occurrence rate of SF and geomagnetic activity. Comparing observations of other stations in the mid-latitude region, we found that the occurrence rates of SF (the annual maximum rates are from 33.83% to 53.29%) are much higher at Zhangye station. Further studies show that ionospheric disturbances can be observed frequently at Zhangye station, especially in autumn and winter. Gravity waves/TIDs in the northeast of the Qinghai-Tibet Plateau are suggested to explain the abnormal higher occurrence rate of SF at Zhangye station.

Modeling rainfall extremes along the coastal and Northern parts of Ghana

The main objective of the study was to determine the appropriate distribution for extreme rainfall along the coastal and northern sectors of Ghana. For stakeholders and policymakers to make appropriate risk-mitigating measures to lessen the damage caused by flood and drought, it is necessary to make proper inferences about extreme rainfall. In this study, we used both the multivariate and univariate extreme value data analysis approaches. The Generalized Extreme Value (GEV) with the Block Maxima approach and Generalized Pareto Distribution (GPD) with the Peak over the threshold (that is all excesses and decluster peaks approaches) were used in this study. Historical gridded monthly maximum rainfall data from 1970 to 2020 were obtained from the Climatic Research Unit and were grouped as the coastal and northern stations. The Maximum Likelihood Estimation method was used to estimate the model parameters, and both the unit root test and the Mann-Kendall tests were used to test for trend in the data. With the multivariate extreme modelling approach, the logistic bivariate GEV model was chosen as the “best” model. However, the dependence value was 0.965, so the extreme rainfall should be modelled independently using the univariate extreme value approaches. Hence, based on the information criteria and analysis of deviance approaches, the GEV distribution was considered the “best” fit for the extreme rainfall dataset for the northern part of Ghana. In contrast, the GPD distribution was the “best” fit for the coastal station. Comparatively, for the volume of rainfall in the year 2020, the extreme rainfall is expected to be higher in the coastal station of Ghana in the next two years. Also, extreme rainfall in 2 years would not exceed the maximum occurrence of rainfall (279.267), which happened in September 2020 at the northern station of Ghana.