Monthly Mean Values Research Articles

Assessment of temperature extremes and climate change impacts in Singapore, 1982–2018

Understanding extreme temperature variations is important for countries to manage risks associated with climate change. Yet, the characteristics of temperature extremes and possible climate change impacts have not been adequately investigated in Singapore. In this study, we attempted to do so by defining 14 extreme temperature indices (ETIs) for the period of 1982–2018 in Singapore, and investigating the trends of those ETIs using a pre‐whitening Man‐Kendall test coupled with the Sen's slope estimator method. The linear and nonlinear relationships between ETIs and El Niño Southern Oscillation (ENSO) were also examined using correlation, composite and wavelet analysis. Our results indicate that trends of temperature extremes varied according to station locations, ETIs and time scales. In all stations, ETIs such as the monthly mean value of the diurnal range between maximum and minimum temperatures (DTR), cool nights (TN10p) and cool days (TX10p) presented decreasing trends, while the rest of them exhibited increasing trends. The composite values varied for different ETIs—meaning that while eight no‐threshold ETIs reflected smaller values, other ETIs reflected relatively larger composite values, indicating that ENSO may have affected those ETIs more. The ETIs were mainly statistically and significantly coherent with ENSO at a 2–8 year cycle. We hope that our findings would be beneficial for climate action planning and temperature‐related disaster prevention in Singapore.

Surface Radio Refractivity of Akure and Ondo town, Southwest Nigeria

The surface radio refractivity, refractivity gradient at 1km above ground surface and the effective earth radius factor, K over Akure and Ondo town of South west Nigeria has been investigated using Ten (10) years daily data of the meteorological parameters of Pressure, air temperature and humidity. The result showed that the mean monthly value of the surface refractivity at the Ondo station is generally slightly higher than that of Akure. The monthly mean value of refractivity at the two stations was found to be strongly correlated with a value of 0.915. The most negative refractive gradient value observed at Ondo and Akure are of -46.48N-units/km and -45.64N-units/km respectively and the least effective earth radius factor, k value of 1.421 and 1.410 were observed at the station respectively. These results showed that the Ondo and Akure station were generally super-refractive. The Ondo station was however found to be slightly more super-refractive than the Akure station.

EFFECTS OF ENVIRONMENTAL PARAMETERS ON PLANKTON ASSEMBLAGE IN AJIWA RESERVOIR, KATSINA STATE, NIGERIA

The effect of environmental (Physicochemical) and biological (plankton) parameters of Ajiwa reservoir were studied for a period of eight months (March–October 2018). Field and laboratory activities were carried out using standard protocols. Mean monthly values of Temperature ranged between 25.87±3.57°C–29.46±0.66°C, Electrical conductivity was between 32.00±3.46µs/cm–210.00±95.39µs/cm. Dissolve Oxygen, Total Dissolved Solid and Biological Oxygen Demand Means of monthly values ranges between 5.53±0.39mg/l–9.35±0.62mg/l, 33.087±0.06mg/l–84.01±4.37mg/l, and 2.69±0.34mg/l–7.27±1.88mg/l. While phosphate and nitrate means of monthly values ranges between 0.04±0.02mg/l–0.09±0.03mg/l, 0.03±0.01mg/l–0.09±0.02mg/l. Four Phytoplankton phyla dominated by Chlorophyta (387org/L), Euglenophyta (160 org/L), Cyanophyta (83 org/L) and Bacillariophyta (63 org/L) were recorded in the reservoir. The Zooplanktons fauna comprises of Rotifers (180 org/L), Cladocerans (149 org/L) and Copepods (78 org/L). Correlation matrix showed that there were significant correlation between Phytoplankton, Zooplankton and Physicochemical parameters. The composition of planktons in the reservoir were affected by seasonal variations and fluctuation of physicochemical parameters

The reduction in C<sub>2</sub>H<sub>6</sub> from 2015 to 2020 over Hefei, eastern China, points to air quality improvement in China

Abstract. Ethane (C2H6) is an important greenhouse gas and plays a significant role in tropospheric chemistry and climate change. This study first presents and then quantifies the variability, sources, and transport of C2H6 over densely populated and highly industrialized eastern China using ground-based high-resolution Fourier transform infrared (FTIR) remote sensing along with atmospheric modeling techniques. We obtained a retrieval error of 6.21 ± 1.2 (1σ)% and degrees of freedom (DOFS) of 1.47 ± 0.2 (1σ) in the retrieval of C2H6 tropospheric column-averaged dry-air mole fraction (troDMF) over Hefei, eastern China (32∘ N, 117∘ E; 30 ma.s.l.). The observed C2H6 troDMF reached a minimum monthly mean value of 0.36 ± 0.26 ppbv in July and a maximum monthly mean value of 1.76 ± 0.35 ppbv in December, and showed a negative change rate of −2.60 ± 1.34 % yr−1 from 2015 to 2020. The dependencies of C2H6 troDMF on meteorological and emission factors were analyzed using generalized additive models (GAMs). Generally, both meteorological and emission factors have positive influences on C2H6 troDMF in the cold season (December–January–February/March–April–May, DJF/MAM) and negative influences on C2H6 troDMF in the warm season (June–July–August/September–October–November, JJA/SON). GEOS-Chem chemical model simulation captured the observed C2H6 troDMF variability and was, thus, used for source attribution. GEOS-Chem model sensitivity simulations concluded that the anthropogenic emissions (fossil fuel plus biofuel emissions) and the natural emissions (biomass burning plus biogenic emissions) accounted for 48.1 % and 39.7 % of C2H6 troDMF variability over Hefei, respectively. The observed C2H6 troDMF variability mainly results from the emissions within China (74.1 %), where central, eastern, and northern China dominated the contribution (57.6 %). Seasonal variability in C2H6 transport inflow and outflow over the observation site is largely related to the midlatitude westerlies and the Asian monsoon system. Reduction in C2H6 abundance from 2015 to 2020 mainly results from the decrease in local and transported C2H6 emissions, which points to air quality improvement in China in recent years.

Extreme values of ET0 at Piracicaba, Brazil, for designing irrigation systems

ABSTRACT Irrigation system capacity is typically defined by analyzing probabilities of non-exceedance of evapotranspiration. The use of mean monthly values of ET0 may lead to underestimation of the required capacity, whereas use of maximum daily values may result in overestimation of required capacity. This study had the following objectives: (1) to analyze a 30-year series of daily ET0 data from Piracicaba, SP, Brazil, to evaluate the suitability of the Gumbel distribution for estimating the maximum values of ET0 organized in periods of up to 30 days; (2) to determine probable maximum values and to select ET0 values considering the irrigation interval and the risk of failure in terms of irrigation system capacity. Daily data from 1990 to 2019 were used to calculate ET0 using the Penman-Monteith model. The Gumbel distribution fitted to the data and was suitable for characterizing the frequency distribution of the maximum ET0. The probable ET0 for designing irrigation systems can then be estimated based on the expected lifespan, irrigation interval, and return period of ET0 maximum values. The higher the anticipated irrigation system lifespan, the higher the return period needed to attain a low risk of failure. Using the average of maximum ET0 values alone leads to underestimation of system capacity and a high risk of failure in terms of irrigation system capacity.

ИЗМЕНЕНИЯ УРОВНЯ КАРСКОГО МОРЯ, ИХ СТЕРИЧЕСКИЕ ФАКТОРЫ И СОЛНЕЧНАЯ РАДИАЦИЯ В ПЕРИОД 1993-2018 ГГ

The GLORYS12v.1 and ERA5 reanalyses for different months are used to study a relationship between long-term variations in the monthly mean values of sea level in different areas of the Kara Sea and their steric factors during 1993-2018. The areas of the sea were identified where the relationships between these changes and variations in the mean temperature and salinity of the upper quasihomogeneous water layer, as well as the variations in the monthly mean intensity of their insolation, are statistically significant.

Temporal Analysis of Urban-Suburban PET, mPET and UTCI Indices in Belgrade (Serbia)

The analysis of the bioclimatic conditions is becoming increasingly relevant in climate interpretations for human needs, particularly in spatial planning, tourism, public health, sports events, bio-prognosis, etc. In this context, our study presents general temporal bioclimatic conditions in Belgrade, defined based on the PET, mPET and UTCI heat budget indices. Monthly, seasonal and annual indices were analyzed for urban and suburban weather stations based on 43 annual sets of meteorological data obtained by hourly observations at 7 h and 14 h CET. This study aims to present the distribution of PET, mPET and UTCI indices to show the pattern of each index in a mild climate location and to examine annual and seasonal differences of each index in the Belgrade urban center and suburban part of the city. The study results indicate higher biothermal stress in the urban area compared to the suburban zone and that the indices are congruent during the summer. At the same time, during the winter, they are more difficult to compare due to their peculiarities becoming more noticeable. The results obtained of all mean monthly and mean annual values of all three indices clearly indicate the difference that follows the definition of the urban heat island (UHI), particularly those from morning observation and winter season. The UTCI index shows the most significant monthly, seasonal and annual difference between urban and suburban areas for both observations. The annual difference of ΔUTCI7h amounts to 1.5 °C is the same as the annual difference of minimum temperatures (Δtmin). In contrast, the annual differences of ΔPET7h ΔmPET7h are °smaller (0.8 °C and 0.7 °C) and closer to the annual differences of maximum temperatures Δtmax amounted of 0.6 °C.

Potential Source Regions and Transportation Pathways of Reactive Gases at a Regional Background Site in Northwestern China

Reactive gases (O3, CO, NO2, and SO2) were collected hourly at the Akedala regional background station in northwestern China during September 2017 to August 2018. Wind rose, cluster analysis, potential source contribution function (PSCF), and concentration-weighted trajectory (CWT) methods were adopted for identifying the transport pathways and potential source regions of these atmosphere components at Akedala. The average O3, CO, NO2, and SO2 mixing ratios detected were 29.65 ± 11.44 ppb, 123.78 ± 73.35 ppb, 3.79 ± 0.98 ppb, and 4.59 ± 0.88 ppb during the observation period, and the statistical results of the monthly mean values revealed that there were differences during the highest pollution period, with O3 and CO mainly peaking in February, with mixing ratios of 38.03 ± 7.10 ppb and 208.50 ± 106.50 ppb, respectively. Meanwhile, NO2 peaked in March (4.51 ± 0.54 ppb) and SO2 in January (5.70 ± 1.92 ppb). The most obvious diurnal variation of CO and SO2 was observed in the winter, with maximum levels reaching between 13 : 00 and 14 : 00. The diurnal variations of O3 exhibited low values during the night and maximum values in the afternoon (16 : 00–18 : 00). Diurnal variation was not significant in the case of NO2. Cluster analysis showed that six main paths affected the Akedala atmosphere. In turn, the PSCF and CWT analysis results indicated that the Akedala reactive gas was affected by both local and foreign sources. The high PSCF value of the reactive gas potential source areas appeared in eastern Kazakhstan, northern Xinjiang, Western Mongolia, and Southern Russia. The WCWT (weighted concentration-weight trajectory) values of CO and SO2 in winter were the highest, totaling 180–240 ppb and 5–6.5 ppb, respectively. The WCWT value of O3 in the spring and summer was higher than that in the autumn and winter. The main source area of O3 was about 32–36 ppb in the spring and summer, and the main source area of NO2 in the summer had a low WCWT value of 3–3.5 ppb, whereas the NO2 WCWT value was concentrated at 4–4.5 ppb in the other seasons.

Wind potential assessment over Morocco`s Marrakesh - Safi Region in 2021-2050 based on the RCM`s forecasts as part of the CORDEX-Africa project

The purpose of the study is to determine the features of the spatial distribution of the wind speed in Marrakesh - Safi region in 2021-2050, as well as the distribution of the specific power of the wind flow at various altitudes above the earth’s surface to determine the wind class of the area in the coming decades. Currently, the region has two large wind farms: Essaouira-Amogdoul and Tarfayer. To assess the future state of climate in Marrakesh − Safi region, the results of calculations of regional climate models (RCM) of the CORDEX-Africa project for the period 2021-2050 were used. The RCM modeling was carried out for the region of Africa, in a rectangular coordinate system with a spatial resolution of ~ 44 km. Model calculation was performed taking into account the greenhouse gas concentration trajectory of RCP 4.5. As a result of simulation for the period 2021-2050, mean monthly values of wind speed "sfcWind" (m·s-1) and the daily maximum near-surface wind speed "sfcwindmax" (m·s-1) at 10 m height were obtained. Then, based on the wind speed rows, the values of the wind power density at a height of 50 m and 100 m were calculated. The results of model calculations of wind speed showed that the ensemble mean of wind speed for the period 2021-2050 will be from 3.8 m∙s-1 in Kelaat Sraghna Province to 7.2 m∙s-1 on the stretch of the Atlantic coast between Cap Sim and Cap Tafelny.The distribution over the territory will be influenced by proximity to the ocean, models predict the highest wind speeds on the coast, and when moving deep into the region, the wind speed will decrease.The analysis of simulation results showed that in the coastal areas of the region favorable conditions in terms of wind energy development will remain, and the highest wind speeds of the model are predicted on the Atlantic coast between Cap Sim and Cap Tafelny. By the size of the specific power of the wind flow, significant wind resources will have the territory lying along the coast from Cap Sim to the southern border of the region, and in the area of the power plants Essaouira-Amogdoul and Tarfayer models predict the conditions corresponding to the outstanding wind power class.

Estimation and Assessment of Ionospheric Slant Total Electron Content (STEC) Using Dual-frequency NavIC Satellite System

Many atmospheric errors affect the positional accuracy of a satellite-basednavigation device, such as troposphere, ionosphere, multipath, and so on, butthe ionosphere is the most significant contributor to positional error. Sincethe ionosphere’s dynamics are highly complex, especially in low latitudeand equatorial regions, a dual-frequency approach for calculating slant totalelectron content (STEC) for ionospheric delay estimation performs betterin these conditions. However, the STEC is ambiguous and it cannot beused directly for ionospheric delay prediction, accurate positioning purposes,or ionospheric study. As a result, STEC estimation and pre-processing arerequired steps prior to any positioning application. There is very little litera-ture available for STEC pre-processing in the NavIC system, necessitating anin-depth discussion. This paper focuses on how to extract navigational data from a raw binary file obtained from the Indian NavIC satellites, estimate andpre-process STEC, and build a database for STEC. It has been found that anhourly averaged STEC data is suitable for ionospheric studies and monthlymean value can be used for ionospheric behavioral research. Furthermore, theSTEC is affected by diurnal solar activity, thus, the seven-month data analysisthat includes summer and winter months has been used to study ionosphereaction during the summer and winter months. It has been observed that STECvalues are higher during the summer months than the winter months; someseasonal characteristics are also been found.

Correlation analyses between solar activity parameters and cosmic ray muons between 2002 and 2012 at high cutoff rigidity

• The impacts of seven solar, interplanetary, and geophysical parameters on CR data have been investigated. • CR data for the period 2002–2012 from KACST muon detector located at high cutoff rigidity have been used. • CR data from Oulu neutron monitor for the same period have been used for comparisons. • Multivariable models were developed to predict CR variability at KACST and Ouu. Solar activity modulates cosmic ray (CR) flux with different magnitudes on different time scales. Several investigations from locations with different, mainly low, cutoff rigidity utilizing different solar activity parameters have been carried out to characterize their influence on the observed CR flux. In this study, the effect of seven solar, interplanetary, and geophysical parameters on the secondary CR muons has been investigated and established using correlation analyses. Daily mean values of the CR data for the period between 2002 and 2012 were obtained from the King Abdulaziz City for Science and Technology (KACST) muon detector, Riyadh, central Saudi Arabia (Rc = 14.4 GV). Considered parameters are sunspot number, radial component of the interplanetary magnetic field, Kp index, solar radio emission flux at 10.7 cm, Dst index, solar wind speed, and solar wind density. Same analyses have been carried out using data from the Oulu neutron monitor (Rc = 0.8 GV) for comparison purposes. Obtained results showed that the intensities of the secondary CRs from both stations are significantly correlated with the Dst index and plasma density, and anti-correlated with the rest of the variables. These results are in agreement with those obtained by several investigators. Magnitude and strength of the correlations between the considered variables and CRs were higher and stronger for the CR neutrons than the CR muons. These findings may be due to the greater influence of seasonal variations on the CR muons than on the CR neutrons. Additionally, the muon detector is sensitive (due to its high cutoff rigidity) to higher-energy CR particles, which are less affected by solar disturbances. Time-lag cross-correlation analyses between the monthly mean CR values from both stations and the monthly mean values of the considered variables were conducted. Comparable results with the previous investigations were found. Multivariable models using the seven parameters were developed to predict the CR variations for both sites. For the data from the KACST detector, the model was able to predict the measured data with a correlation coefficient of 0.48 and a standard deviation of 0.60%. On the other hand, the developed model for the Oulu neutron monitor has a correlations coefficient of 0.77 and a standard deviation of 3.7%.

Interbank Offered Rate Based on Artificial Intelligence Algorithm

Interbank offer rate is the interest rate at which banks lend money to each other in the money market. As a market-oriented core interest rate, Shibor can accurately and timely reflect the capital supply and demand relationship in the money market, and its changes will quickly transmit and affect China’s financial market. Therefore, the purpose of this paper is to predict and study the fluctuation and trend of Shibor. In this paper, the overnight varieties of Shibor were studied and predicted from two time dimensions, namely, daily fluctuation and monthly trend. In the prediction of overnight Shibor daily data, a comparison prediction model based on BP neural network algorithm was first established, and then WNN was applied in the prediction, and the effect was found to be better. When predicting the monthly mean value of overnight Shibor, nine indicators were selected and tested for correlation based on the factors affecting the trend of interest rate, and a regression model of support vector machine was established. Particle swarm optimization algorithm was used to improve the SVR algorithm, and the PSO-SVR prediction model was established to improve the prediction accuracy. The model could basically predict the trend of overnight Shibor. Furthermore, a prediction model of WNN based on cuckoo search (CS) optimization was proposed, which improved the prediction accuracy by 78% and fitted the daily fluctuation of overnight Shibor well.

Temporal and Spatial Distribution Characteristics of Aerosol Optical Properties in Urban Agglomerations on the North Slope of the Tianshan Mountains

In order to explore the temporal and spatial distribution characteristics of atmospheric aerosol optical depth (AOD) in the urban agglomeration on the northern slope of the Tianshan Mountains, the temporal and spatial distribution characteristics and trends of changes in the AOD in the study area from 2000 to 2019 were analyzed by MODIS aerosol products(MCD19-A2). For 2016-2019, when the AOD was relatively stable, the parameters such as the AOD and Ångström wavelength index (α) were analyzed using multi-band sun photometer ground-based remote sensing technology. The results showed that ① the spatial distribution of AOD in the study area was consistent with the topography, and high values were mainly distributed in the low altitude area. The spatial distribution of AOD in the four seasons showed a strong seasonal change from spring (0.15±0.03) > autumn (0.14±0.03) > summer (0.14±0.02). ② In terms of time, the annual average AOD value of the study area was 0.12 from 2000 to 2019 with an annual growth rate of 1.03%, thereby showing an overall increasing trend. The annual variation in the monthly mean value of AOD was bimodal; the first and second peaks were in May and November. The main reason for the increase in AOD was the release and transmission of dust from natural sources and heating. ③ Under the influence of dust weather, the AOD changed sharply in spring, and the size and change range of aerosol particles were larger than those in summer. The high value of AOD in the study area was mainly affected by coarse mode particles. The moisture absorption growth of fine mode particles caused a fluctuation in the AOD, but it was not the cause of the high value of AOD.

Atmospheric drag effects on modelled low Earth orbit (LEO) satellites during the July 2000 Bastille Day event in contrast to an interval of geomagnetically quiet conditions

Abstract. In this work, we simulated the atmospheric drag effect on two model SmallSats (small satellites) in low Earth orbit (LEO) with different ballistic coefficients during 1-month intervals of solar–geomagnetic quiet and perturbed conditions. The goal of this effort was to quantify how solar–geomagnetic activity influences atmospheric drag and perturbs satellite orbits, with particular emphasis on the Bastille Day event. Atmospheric drag compromises satellite operations due to increased ephemeris errors, attitude positional uncertainties and premature satellite re-entry. During a 1-month interval of generally quiescent solar–geomagnetic activity (July 2006), the decay in altitude (h) was a modest 0.53 km (0.66 km) for the satellite with the smaller (larger) ballistic coefficient of 2.2×10-3 m2 kg−1 (3.03×10-3 m2 kg−1). The associated orbital decay rates (ODRs) during this quiet interval ranged from 13 to 23 m per day (from 16 to 29 m per day). For the disturbed interval of July 2000 the significantly increased altitude loss and range of ODRs were 2.77 km (3.09 km) and 65 to 120 m per day (78 to 142 m per day), respectively. Within the two periods, more detailed analyses over 12 d intervals of extremely quiet and disturbed conditions revealed respective orbital decays of 0.16 km (0.20 km) and 1.14 km (1.27 km) for the satellite with the smaller (larger) ballistic coefficient. In essence, the model results show that there was a 6- to 7-fold increase in the deleterious impacts of satellite drag between the quiet and disturbed periods. We also estimated the enhanced atmospheric drag effect on the satellites' parameters caused by the July 2000 Bastille Day event (in contrast to the interval of geomagnetically quiet conditions). The additional percentage increase, due to the Bastille Day event, to the monthly mean values of h and ODR are 34.69 % and 50.13 % for Sat-A and 36.45 % and 68.95 % for Sat-B. These simulations confirmed (i) the dependence of atmospheric drag force on a satellite's ballistic coefficient, and (ii) that increased solar–geomagnetic activity substantially raises the degrading effect of satellite drag. In addition, the results indicate that the impact of short-duration geomagnetic transients (such as the Bastille Day storm) can have a further deleterious effect on normal satellite operations. Thus, this work increases the visibility and contributes to the scientific knowledge surrounding the Bastille Day event and also motivates the introduction of new indices used to describe and estimate the atmospheric drag effect when comparing regimes of varying solar–geomagnetic activity. We suggest that a model of satellite drag, when combined with a high-fidelity atmospheric specification as was done here, can lead to improved satellite ephemeris estimates.

Aerosols optical depth and Ångström exponent over different regions in Garhwal Himalaya, India.

Aerosol optical depth (AOD) and Ångström exponent (AE) are observed to be important parameters in understanding the status of ambient aerosol concentration over a particular location and depend not only upon the local but also on the large-scale dynamics of the atmosphere. The present article analyses the AOD and AE parameters retrieved with Moderate Resolution Imaging Spectrometer (MODIS) and Multi-angle Imaging Spectro-Radiometer (MISR) instruments onboard satellites, for the upper (Chamoli) and foothill (Dehradun) regions of Garhwal Himalaya in Uttarakhand, India, from 2006 to 2015. Aerosol properties are investigated at monthly, seasonal, and annual scales. The monthly mean values of MODIS-derived AOD and AE were observed to be 0.18 (± 0.14) and 1.05 (± 0.43) respectively over the Dehradun region. The seasonal maximums in AOD with MODIS and MISR were observed as 0.23 ± 0.06 and 0.29 ± 0.07 respectively in the pre-monsoon season, and the minimum values (0.099 ± 0.02) were observed in the post-monsoon season, over the Dehradun region. In contrast, in the Chamoli region, the maximum AOD (MODIS) was 0.21 ± 0.06 observed in the monsoon season and the minimum was 0.036 ± 0.007 in the post-monsoon season. Over a decade, the AE for Chamoli and Dehradun was found to vary from 0.07 to 0.17 and from 0.14 to 0.20 respectively. The median AE for Chamoli and Dehradun was found to be 1.49 and 1.47 respectively, marking the dominance of fine mode particles of anthropogenic origin. Observations show the presence of dust and polluted dust resulting from the long-range transport from the west. The comparison of AOD values from the two sensors shows a significant correlation (0.73) with slightly higher values from MISR over the year. The results obtained are important in understanding the climatic implications due to the atmospheric aerosols over the abovementioned Himalayan region of Uttarakhand, India.

Physicochemical and Bacteriological Properties of Surface Waters from two Localities in Rivers State, Nigeria

This study investigated the physicochemical and bacteriological properties of surface waters from Bori and Okoli’ile towns in Rivers State, Nigeria. A total of 360 brackish water samples were collected from January to December, 2019 from the two localities. Samples were subjected to physicochemical, trace elements and bacteriological examinations. Isolated colonies from microbiological examinations were subjected to further biochemical and physiological characterization. The result showed pH mean values were higher in the month of January to March, a period where rainfall is less frequent (dry months). Similar trend of occurrence was observed in the monthly mean values of temperature (0C) and salinity (mg/L). Most of the physicochemical indices of water quality measurement recorded average values exceeding the stipulated acceptable environmental tolerance limits by the World Health Organisation (WHO). The microbiological examinations showed lower monthly mean values of total heterotrophic count, total coliforms and faecal coliforms counts during the wet months with statistically significant difference (P<0.05) when compared to the average values obtained in the dry months. The Pearson’s correlation coefficient showed high relationship between total heterotrophic count and faecal coliforms, an indication of increase in human wastes into aquatic environments leading to higher bacterial population within the waterbody, which could be a predisposing factor for epidemic. It is recommended that local and regional governments should enforce appropriate measures to encourage personal and community practice of hygiene.

Prevalence of Vibrio Cholerae and Vibrio Species from Different Sources in Bayelsa State, Nigeria

The distribution of Vibrio cholerae and non-cholera Vibrio species from different sources from five localities in Bayelsa State, Nigeria was investigated in this study. A total of 44 stool samples, 22 freshwater samples, 60 brackish water samples and 64 seafood samples (crabs, shrimps and fishes) were collected from January to April, 2019 for the purpose of V. cholerae prevalence study. Samples were transported to the laboratory using Car-Blair’s medium. This was followed by samples enrichment in 1% alkaline peptone water and pour plating on thiosulphate citrate bile-salt sucrose (TCBS) agar. Characteristic yellow colonies were subjected to further biochemical and physiological characterization to further identify V. cholerae. Antibiotics susceptibility patterns for isolated V. cholerae strains were investigated. Furthermore, water samples (fresh and brackish) and seafood samples were collected on a monthly basis to ascertain the effect of seasons (dry and wet months) on the distribution of Vibrio spp. A total of 16 (36.36%) stools samples were positive for V. cholerae. In addition, 12 (54.55%) of freshwater samples, 28 (46.67%) of brackish water samples and 22 (34.38%) of seafood samples were contaminated with V. cholerae. The monthly mean values of Vibrio spp. from environmental sources showed statistically significant difference (P<0.05) between the dry months (low rainfall) and wet months (frequent rainfall). Higher average values were observed during the dry months. The result of the antibiotics sensitivity test showed all V. cholerae strains were susceptible to ciprofloxacin, ofloxacin and pefloxacin while varying degree sensitivities were observed in tetracycline and augmentin. Cholera and other non-cholera Vibrio spp gastrointestinal infections are still a major concern to the health of the public. Local and regional governments should enforce and promote the need for personal and communal hygienic practices.

Mapping the drivers of formaldehyde (HCHO) variability from 2015 to 2019 over eastern China: insights from Fourier transform infrared observation and GEOS-Chem model simulation

Abstract. The major air pollutant emissions have decreased, and the overall air quality has substantially improved across China in recent years as a consequence of active clean air policies for mitigating severe air pollution problems. As key precursors of formaldehyde (HCHO) and ozone (O3), the volatile organic compounds (VOCs) in China are still increasing due to the lack of mitigation measures for VOCs. In this study, we investigated the drivers of HCHO variability from 2015 to 2019 over Hefei, eastern China, by using ground-based high-resolution Fourier transform infrared (FTIR) spectroscopy and GEOS-Chem model simulation. Seasonal and interannual variabilities of HCHO over Hefei were analyzed and hydroxyl (OH) radical production rates from HCHO photolysis were evaluated. The relative contributions of emitted and photochemical sources to the observed HCHO were analyzed by using ground-level carbon monoxide (CO) and Ox (O3 + nitrogen oxide (NO2)) as tracers for emitted and photochemical HCHO, respectively. Contributions of emission sources from various categories and geographical regions to the observed HCHO summertime enhancements were determined by using a series of GEOS-Chem sensitivity simulations. The column-averaged dry air mole fractions of HCHO (XHCHO) reached a maximum monthly mean value of 1.1 ± 0.27 ppbv in July and a minimum monthly mean value of 0.4 ± 0.11 ppbv in January. The XHCHO time series from 2015 to 2019 over Hefei showed a positive change rate of 2.38 ± 0.71 % per year. The photochemical HCHO is the dominant source of atmospheric HCHO over Hefei for most of the year (68.1 %). In the studied years, the HCHO photolysis was an important source of OH radicals over Hefei during all sunlight hours of both summer and winter days. The oxidations of both methane (CH4) and nonmethane VOCs (NMVOCs) dominate the HCHO production over Hefei and constitute the main driver of its summertime enhancements. The NMVOC-related HCHO summertime enhancements were dominated by the emissions within eastern China. The observed increasing change rate of HCHO from 2015 to 2019 over Hefei was attributed to the increase in photochemical HCHO resulting from increasing change rates of both CH4 and NMVOC oxidations, which overwhelmed the decrease in emitted HCHO. This study provides a valuable evaluation of recent VOC emissions and regional photochemical capacity in China. In addition, understanding the sources of HCHO is a necessary step for tackling air pollution in eastern China and mitigating the emissions of pollutants.

Can we replace observed forcing with weather generator in land surface modeling? Insights from long-term simulations at two contrasting boreal sites

This study evaluates the simulation of water balance components at half-hourly time steps from the Canadian Land Surface Scheme (CLASS) when driven by a 500-year stochastic meteorological data set produced by the Advanced WEather GENerator (AWE-GEN) at two boreal sites with contrasting water availability. The CLASS was driven by ERA5 reanalysis data (CLASS-CTL) over 39 years and its output was used as a surrogate for land surface observations. At both sites, the mean monthly and annual values of all meteorological variables used to drive CLASS, including precipitation, are well captured by AWE-GEN, but their variability is, sometimes, biased. In general, CLASS driven by stochastic data (CLASS-WG) tends to produce higher evapotranspiration compared to values simulated by CLASS-CTL, especially during spring and summer at the wet site. The interannual evapotranspiration-precipitation and runoff-precipitation relationships derived from CLASS-WG and those derived from CLASS-CTL were very similar to each other at the dry site; they both indicate that evapotranspiration and runoff are limited by water availability. At the wet site, however, CLASS-WG only captured well the interannual runoff-precipitation relationship. The sensitivity analysis shows that CLASS water fluxes are particularly affected by the replacement of physically consistent input time series of incoming short-wave radiation, precipitation, temperature, and specific humidity. In conclusion, the results show that even though a weather generator can produce coherent climate time series, the use of this synthetic data as meteorological forcing in a physically based land surface model does not necessarily reproduce the complex surface processes, such as the surface water fluxes. More studies are encouraged to further analyze the constraints of this framework.

Analysis of Decadal Rainfall and Temperature Trend in Warri, Nigeria

This study investigates rainfall and temperature trend in Warri, Delta State, Nigeria using data derived from Nigerian Meteorological Agency between 2005 and 2015. Data was analyzed to reveal trend in temperature and rainfall values in the years under study and to determine whether there were significant variations. Analysis of rainfall data shows that 2007 had the lowest total rainfall over the 11 year period with a total annual rainfall of 2030.58 mm while 2015 was the year with the highest annual rainfall record of 3183.6 mm. The mean monthly Rainfall indicates that January has the lowest record of rainfall with a total of 36.9 mm while July is the month with highest value of 423.2 mm. Results further indicates that June has the lowest mean monthly temperature over the 11 year period of 20 ºC while March has the highest record of 29.6 ºC. Dominant temperature ranges between 26.1 oC and 26.8 ºC closely followed by 27.7–28.4 ºC which are quite close to the mean monthly values in the area. Analysis of rainfall data confirms an increasing trend.