Wet Season Months Research Articles

Daytime land surface temperature and its limits as a proxy for surface air temperature in a subtropical, seasonally wet region

Land surface temperatures (LSTs) captured via satellite remote sensing are widely used as a proxy for the surface air temperatures (SATs) experienced outdoors, a key component of human heat exposure. However, LST’s accuracy in capturing SAT can vary through space and time across climate types and geographies and has been less explored in subtropical, seasonally wet regions (where summer precipitation exceeds 570 mm). Utilizing daytime (11 AM/12 PM local time, ET/EST) Landsat 8 remote sensing data, this study derived LST and evaluated its spatiotemporal patterns, as well as its relationship with SAT retrieved from local weather stations, using the case of Miami-Dade County, Florida, USA. Over 2013–2022, a surface urban heat island effect is distinctly present (mean SUHII = 3.43°C)—most intense during spring months rather than summer months (mean spring SUHII = 4.09°C). As such, LST peaks in May/June as opposed to July/August for many other parts of the northern hemisphere. In contrast, Miami-Dade SAT is greatest in August, and the strength of its relationship with LST varies by season. LST and SAT are most correlated in winter (R = 0.91) and spring (R = 0.59) months and least correlated during the wetter fall (R = 0.40) months. The relationship between LST and SAT during the summer is statistically insignificant. In this subtropical region with a seasonally wet climate, LST effectively reflects the spatial heterogeneity of the urban thermal landscape, consistent with the literature across urban regions globally. However, because the strength of the LST-SAT relationship considerably weakens during wet season months, LST data therefore have limits as a proxy for the heat exposure people experience outdoors annually, as they may not accurately represent the magnitude of localized potential heat risks. These findings underscore important considerations in using LST data to identify urban heat exposures and inform potential adaptive responses in seasonally wet, subtropical-to-tropical regions.

Enhancing Surface Water Monitoring through Multi-Satellite Data-Fusion of Landsat-8/9, Sentinel-2, and Sentinel-1 SAR

Long revisit intervals and cloud susceptibility have restricted the applicability of earth observation satellites in surface water studies. Integrating multiple satellites offers potential for more frequent observations, yet combining different satellite sources, particularly optical and SAR satellites, presents complexities. This research explores the data-fusion potential and limitations of Landsat-8/9 Operational Land Imager (OLI), Sentinel-2 Multispectral Instrument (MSI), and Sentinel-1 Synthetic Aperture (SAR) satellites to enhance surface water monitoring. By focusing on segmented surface water images, we demonstrate that combining optical and SAR data is generally effective and straightforward using a simple statistical thresholding algorithm. Kappa coefficients(κ) ranging from 0.80 to 0.95 indicate very strong harmony for integration across reservoirs, lakes, and river environments. In vegetative environments, integration with S1SAR shows weak harmony, with κ values ranging from 0.27 to 0.45, indicating the need for further studies. Global revisit interval maps reveal significant improvement in median revisit intervals from 15.87 to 22.81 days using L8/9 alone, to 4.51 to 7.77 days after incorporating S2, and further to 3.48 to 4.62 days after adding S1SAR. Even during wet season months, multi-satellite fusion maintained the median revisit intervals to less than a week. Maximizing all available open-source earth observation satellites is integral for advancing studies requiring more frequent surface water observations, such as flood, inundation, and hydrological modeling.

Pathloss Assessment of a Terrestrial Digital UHF Channel over Kano City, Nigeria

Path loss assessment is an important factor in wireless communications to ensure quality of service. This study involves the measurement of Received Signal Strength (RSS) of Digital Terrestrial Television (DTTV) Star Times Station in Kano at 1 km intervals along three routes. Data were gathered during dry and wet season months in the year 2022. The path loss along the routes were computed based on the Okumura-Hata model. It was observed that path losses were higher during wet than dry season months. The result also indicates a higher negative correlation coefficient (R) of -0.745 between Line of Sight (LOS) and RSS for wet and -0.690 for dry season months respectively for route, A. Similarly, R, of -0.739 between LOS and RSS was also observed during wet and -0.589 for dry season months for route, B. In addition, R, of -0.420 was observed between LOS and RSS during wet and -0.328 for dry season months along route C. The average path loss for wet season is 133.90 dB and for dry season is 127.90 dB. Furthermore, this study introduced a Modified Hata Path Loss Model (MHPL) that takes into account the impact of specific tropospheric parameters such as LOS and elevation. Findings further indicated that the path loss predicted by the conventional Hata model exhibited a steady exponential increase with LOS. Similarly, MHPL followed a comparable trajectory, with some exceptions manifesting as peaks and valleys. The overall findings will be useful for power budgeting that will enhance quality of service of DTTV signal over Kano city.

Pathloss Assessment of a Terrestrial Digital UHF Channel over Kano City, Nigeria

Path loss assessment is an important factor in wireless communications to ensure quality of service. This study involves the measurement of Received Signal Strength (RSS) of Digital Terrestrial Television (DTTV) Star Times Station in Kano at 1 km intervals along three routes. Data were gathered during dry and wet season months in the year 2022. The path loss along the routes were computed based on the Okumura-Hata model. It was observed that path losses were higher during wet than dry season months. The result also indicates a higher negative correlation coefficient (R) of -0.745 between Line of Sight (LOS) and RSS for wet and -0.690 for dry season months respectively for route, A. Similarly, R, of -0.739 between LOS and RSS was also observed during wet and -0.589 for dry season months for route, B. In addition, R, of -0.420 was observed between LOS and RSS during wet and -0.328 for dry season months along route C. The average path loss for wet season is 133.90 dB and for dry season is 127.90 dB. Furthermore, this study introduced a Modified Hata Path Loss Model (MHPL) that takes into account the impact of specific tropospheric parameters such as LOS and elevation. Findings further indicated that the path loss predicted by the conventional Hata model exhibited a steady exponential increase with LOS. Similarly, MHPL followed a comparable trajectory, with some exceptions manifesting as peaks and valleys. The overall findings will be useful for power budgeting that will enhance quality of service of DTTV signal over Kano city.

Characterization of some secondary radio-climatic factors for reliable radio wave propagation and link’s design over North western Nigeria

A good understanding of the behavior of the atmosphere is a key factor in radio wave propagation and link’s design. This study investigated the influence of refractivity gradient, effective earth radius factor (k-factor) and geo-climatic factor (K-factor) on radio communication over the cities of Kaduna, Katsina and Sokoto, in Northwestern parts of Nigeria. Forty-one year’s secondary data (1980–2020) of temperature, pressure and humidity at the surface 12, 100 and 250 m above ground level retrieved from European Centre for Medium-Range Weather Forecasts (ECMRWF) ERA-5 reanalysis were used for the study. The three secondary radio-climatic parameters under investigation were computed and analyzed using latest ITU-R (Rec.P.453-14 (08/2019)) Models. It was observed that secondary radio-climatic variables exhibit seasonal type dependence. The research also reveals that the secondary radio-climatic variables depend on location, with all the study locations having different values. The highest value of refractivity gradient obtained is about −75.06 (N-units/km) in the month of February in Sokoto while the least of about −162.65 (N-units/km) was recorded in Kaduna in September. The value of the refractivity gradient is higher during the dry season compared to the wet season months with Sokoto recording the highest values for more than half of the months, followed by Katsina. Kaduna recorded highest number of lowest values of refractivity gradient. For the geoclimatic factor, it was revealed that Kaduna has an average maximum geoclimatic factor of 14.0000E-5 in September and an average minimum of 9.6677E-05 in February. Furthermore, the obtained values of k factor values for the study areas are higher than the standard value of, 43 (1.33). The k-factor in Kaduna ranges from 1.69 to 2.16 with mean value of 1.85 for dry season while for the wet season it ranges from 2.66 to 4.12 with a mean value of 3.74; the overall mean value for Kaduna is 2.80. In Katsina, it ranges from 1.66 to 2.20 with mean value of 1.81 for dry season while for the wet season it ranges from 1.95 to 4.00 with a mean value of 3.27; the overall mean value is 2.54. In Sokoto it ranges from 1.60 to 2.30 with mean value of 1.78 for dry season while for the wet season it ranges from 1.72 to 3.45 with a mean value of 2.59; the overall mean value is 2.19. The interpretation of this is that, radio signal propagation in the Northwest region of Nigeria is super-refractive. The overall findings of this research are essential for estimating location-dependent fade margins, which are useful for the design of wireless communication links for the region.

The Investigation of Surface Radio Refractivity Over Lokoja, Kogi State Nigeria

This research investigated the variation of Surface Radio Refractivity and its propagation effects on radio signals over Lokoja, Kogi State, Nigeria. The study used six years (2015-2020) of satellite data on temperature, pressure, relative humidity and rainfall at the surface (12 km) above ground level. The data retrieved were used to determine the monthly, seasonal, and annual Surface Radio Refractivity value for Lokoja Kogi State. Results show that high Surface Radio Refractivity values were recorded generally during the wet season months compared to the dry season months in all Six years (2015-2020). The average values of Surface Radio Refractivity 307.7407 (N-units) and 323.4674 (N-units) were obtained during the dry and wet season, respectively. The minimum surface radio refractivity values of 280.7245, 284.6583, 308.0021, 285.2304, 304.2521 and 285.9139 (N-units) were recorded for the years 2015, 2016, 2017, 2018, 2019, and 2020 respectively. On the other hand, the highest values of 330.8153, 331.8133, 330.3580, 330.9278, 332.4704, and 331.1316 (N-units) were recorded for the years 2015, 2016, 2017, 2018, 2019 and 2020, respectively. Higher values of Surface Radio Refractivity were recorded generally during the wet season compared to the dry season months in all years (2015-2020) in Lokoja, Kogi State. This implies higher radio signal attenuation due to Ns during the wet season compared to the dry season. The correlation coefficients between Surface Radio Refractivity Ns and temperature are -0.41, -0.51, -0.49, -0.48, -0.46, -0.50, pressure 0.07, -0.15, -0.28, -0.08, -0.11, -0.26, relative humidity 0.89, 0.84, 0.75, 0.84, 0.77, 0.83, and the amount of rainfall 0.76, 0.64, 0.73, 0.58, 0.51, 0.65 respectively in the year 2015, 2016, 2017, 2018, 2019, 2020. The overall findings of the work will be useful to radio engineers for properly planning a reliable power budget for terrestrial radio communication over Lokoja, Kogi State.

Foliar disease incidence in a tropical seedling community is density dependent and varies along a regional precipitation gradient

Abstract Many studies identify fungal and oomycete phytopathogens as natural enemies capable of influencing plant species composition and promoting diversity in plant communities. However, little is known about how plant‐pathogen interactions vary along regional abiotic gradients or with tree species characteristics, which limits our understanding of the causes of variation in tree species richness. We surveyed 10,756 seedlings from 272 tree species for disease symptoms along a mean annual precipitation gradient in the tropical wet forests of Central Panama for 3 months in the early wet season (June–August) and 2 months in the following dry season (March–April). Over 99% of observed disease symptoms were caused by necrotrophic foliar pathogens, while less than 1% of symptoms were attributed to soilborne pathogens. Foliar disease incidence was inversely related to mean annual precipitation, a pattern which may be due to greater disease susceptibility among dry forest species. Foliar disease incidence increased with conspecific seedling density but did not respond to the proximity of conspecific adults. Although foliar disease incidence decreased as mean annual precipitation increased, the strength of conspecific density‐ or distance‐dependence was independent of the precipitation gradient. Seedlings of common tree species and species dispersed by non‐flying mammals had a higher risk of foliar pathogen incidence. Increased disease in common species may help reduce their dominance. Synthesis. The increases in foliar pathogen incidence with conspecific seedling density, species abundance, and dispersal mechanism indicate that foliar disease incidence is non‐random and may contribute to the regulation of tropical plant communities and species coexistence. Furthermore, the relationships between foliar disease incidence, dispersal mechanism and precipitation suggest plant‐pathogen interactions could shift as a response to climate change and disruption of the disperser community.

Evaluation of the Vertical Profile of Radio Refractivity and its Gradients in a Tropical Atmosphere

This paper evaluates radio refractivity and its gradients over Abuja, the Federal Capital Territory of Nigeria, using five years upper air meteorological data obtained from the Nigerian Meteorological Agency (NiMet). From the results obtained, radio refractivity was observed to decrease with increasing altitude. Also, higher refractivity values were observed in wet season, while lower values were recorded in dry season. An average refractivity value of 326 N-Units was obtained at 1 km altitude, while average refractivity gradient values of -34 N-Units/km and -40 N-Units/km were recorded for the dry and wet season months respectively. A total average value of -38 N-Units/km for refractivity gradient was obtained for the five-year study period, thus making the atmospheric condition over Abuja to be sub-refractive. The effective earth radius factor (k-factor) computed for the location was also observed to be higher in the wet season months than the dry season months. An average k-factor value of 1.32 was obtained for the study period.

Examining the Spatiotemporal Changes in the Annual, Seasonal, and Daily Rainfall Climatology of Puerto Rico

This study explores spatial and temporal changes in the rainfall climatology of Puerto Rico in order to identify areas where annual, seasonal or daily precipitation is increasing, decreasing, or remaining normal. Total annual, seasonal, and daily rainfall were retrieved from 23 historical rain gauges with consistent data for the 1956–2021 period. Mann–Kendall trend tests were done on the annual and seasonal rainfall series, and percentage change differences between two different climatologies (1956–1987 and 1988–2021) were calculated. Most of the stations did not exhibit statistically significant annual or seasonal trends in average rainfall. However, of the sites that did experience changes, most of them had statistically significant decreasing trends in mean precipitation. The annual, dry, and early wet season had more sites with negative trends when compared with positive trends, especially in the northwestern and southeastern region of the island. The late wet season was the only period with more sites showing statistically significant trends when compared with negative trends, specifically in the northern region of the island. Results for daily events show that extreme rainfall occurrences have generally decreased, especially in the western region of the island. When the 1955–1987 and 1988–2022 climatologies are compared, the results for annual average rainfall show two main regions with mean precipitation reductions, and those are the northwestern and southeastern areas of the island. The dry season was the only period with more areas exhibiting percentage increases in mean rainfall when the two climatologies were analyzed. The early and late wet season months exhibited similar patterns, with more areas on the island showing negative percentage decreases in average seasonal precipitation. The best predictor for the decreasing annual and seasonal trend in the northwest was a higher sea level pressure, and the variable that best explained the increasing trend in the northeast was total precipitable water.

Wet season physicochemical characteristics of the cross river estuary, southeast, nigeria

The physico-chemical properties of the lower reaches of the Cross River estuary were studied in the wet season month of September, 2011. A total of 50 bottom water samples were obtained using a Nansen Bottom Water Sampler, at 50 geo-referenced stations within the channel. Depth measurements were simultaneously taken at each station using an echo-sounder, while turbidity was measured using a secchi-disc. Temperature, salinity and pH were analysed for each sample, using a HANNA hand held combo meter (HI 98129). Within the channel, bottom water temperature ranged between 23 and 30°C, turbidity (transparency) ranged between 30 and 100 cm, pH ranged between 5 and 9, while bottom water salinity ranged between 0.15 and 0.20 ‰. Based on salinity, the channel was divided into 3 physico-chemical facies: the Upper Facies is fairly saline, characterized by temperatures ranging from 25 to 26°C, is the least turbid segment of the channel and isalkaline the Middle Facies, the least saline part of the channel, characterized by temperatures ranging from 24 to 29°C, most turbid, and neutral,; and the Lower Facies, the most saline portion of the channel, with temperatures ranging from 25 to 29°C, is the more, acidic, part of the channel. The estuary appeared to have been greatly diluted. This may be attributed to the fact that the study was carried out during the rainy season. As a result of the high freshwater discharge into the channel during this season, the freshwater-brackishwater interface has been driven further downstream, towards the Atlantic Ocean

Survey on the Prevalence and Burden of Gastrointestinal Helminths Infections of Cattle Slaughtered at Dutse Modern Abattoir, Jigawa State, Nigeria

An abattoir cross sectional survey was carried out to determine the prevalence of gastrointestinal parasitic helminths in slaughtered cattle at Dutse Local Government Area, Jigawa State, Nigeria. A total of 288 fecal samples were tested. Gastrointestinal helminths’ eggs were detected in 219 samples tested giving an overall prevalence of 76.04%. The prevalent helminthes species identified were Cooperia sp., Fasciola sp, T. saginata, T r i c o s t r o n g y l u s s p , Ostertagia, and Paraphostimum sp. High prevalence of gastrointestinal helminths in cattle slaughtered was observed during the wet season; with T. saginata 106(35.2%) having highest prevalence and the least prevalent species Paraphostimum sp. with 11(3.7). There is significant association of increasing parasitic infection with months of wet season p=0.001; χ 2 =80.36. However, there was no significant association was observed during dry season p= 0.35; χ2 =21.74. the distribution of gastrointestinal helminths according to age group of the animals were found to be 77.14% in Cattle less than 2 years, 76.27% in young and 70.59% in adults. These findings implied that the majority of cattle brought for slaughter in Dutse abattoir were highly infested with several internal helminthes parasites that may present a public health problem and an important epidemiological implication. Therefore, an effective chemotherapy, an appropriate meat inspection, and famers education of proper use of anthelminthic to prevent infestation of human and to enhance food sufficiency not only in quantity but also in quality.

ESTIMATION OF MODERN CHANGES IN ATMOSPHERIC PRECIPITATION IN CENTRAL AFRICA

Long-term time series of monthly precipitation from the beginning of observations to 2022 at 57 meteorological stations in central Africa were studied to assess the impact of climate change on precipitation dynamics in this part of the African continent. The spatio-temporal distributions of precipitation for the dry and wet seasons have been obtained and it has been established that the least amount of precipitation is observed from November to March, and the biggest - from April to October. According to the type of intra-annual changes in precipitation, four homogeneous climatic regions were identified, and in each of them an assessment of the changes that occurred was given. Various methodological approaches have been applied to assess changes in precipitation in the months of the wet and dry seasons of the year. In general, no significant changes in the dynamics were found, however, a general trend was established for a decrease in precipitation during the months of the wet season and their increase in certain parts of the territory during the months of the dry season of the year. The decrease in wet season months ranged from -25.5 mm to -138.5 mm or 0.8 to 1.2 RMSD and a separate increase of 52.8 mm and 68.1 mm or 0.8 to 1.1 RMSD. During the dry season, the largest decrease was in the north and central regions, reaching -31.6mm (0.88 RMSD) in February, while a significant increase occurred in the coastal areas of the Gulf of Guinea, reaching 15mm (2 RMSD) in January.

The Refractive Effect of k-Factor on Radio Propagation over Lokoja, Nigeria

The effective earth radius factor (k-factor) has a refractive propagation effect on transmitted radio signals thus making its study necessary for the proper planning of terrestrial radio links and power budget. This study was carried out over the city of Lokoja, Nigeria, using ten years (2011 to 2020) atmospheric data of temperature, pressure and humidity both at the surface (12 m) and at 100 m AGL. The data were retrieved from European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5. The k-factor yearly variation follows the same trend with minimum and maximum values obtained during dry and wet season months respectively. In addition, the highest mean value of 1.00042 was recorded in the month of August while the lowest value of 1.00040 was recorded in the month of January with an overall mean value of 1.0003. This value is less than the recommended standard of 1.33 by ITU-R. The propagation effect corresponding to k < 1.33 is sub-refractive. The implication of this on radio wave propagation, especially terrestrial communications is that transmitted wireless signal is prone to losses. This can be mitigated through an effective power budget: Choice of transmitting antenna’s height and gain, so as to improve the Quality of Service over the study area.

A Near Four-Decade Time Series Shows the Hawaiian Islands Have Been Browning Since the 1980s

The Hawaiian Islands have been identified as a global biodiversity hotspot. We examine the Normalized Difference Vegetation Index (NDVI) using Climate Data Records products (0.05 × 0.05°) to identify significant differences in NDVI between neutral El Niño-Southern Oscillation years (1984, 2019) and significant long-term changes over the entire time series (1982–2019) for the Hawaiian Islands and six land cover classes. Overall, there has been a significant decline in NDVI (i.e., browning) across the Hawaiian Islands from 1982 to 2019 with the islands of Lāna’i and Hawai’i experiencing the greatest decreases in NDVI (≥44%). All land cover classes significantly decreased in NDVI for most months, especially during the wet season month of March. Native vegetation cover across all islands also experienced significant declines in NDVI, with the leeward, southwestern side of the island of Hawai’i experiencing the greatest declines. The long-term trends in the annual total precipitation and annual mean Palmer Drought Severity Index (PDSI) for 1982–2019 on the Hawaiian Islands show significant concurrent declines. Primarily positive correlations between the native ecosystem NDVI and precipitation imply that significant decreases in precipitation may exacerbate the decrease in NDVI of native ecosystems. NDVI-PDSI correlations were primarily negative on the windward side of the islands and positive on the leeward sides, suggesting a higher sensitivity to drought for leeward native ecosystems. Multi-decadal time series and spatially explicit data for native landscapes provide natural resource managers with long-term trends and monthly changes associated with vegetation health and stability.

Diversity and seasonality of adult caddisflies (Trichoptera) captured by light-trapping beside streams in the Darwin region of northern Australia

Caddisflies comprise a major component of the macroinvertebrate diversity of streams throughout the world. We studied temporal variation in the abundance and diversity of caddisflies of six streams in the monsoonal wet-dry tropics of northern Australia. Abundance and diversity of adult caddisflies were highly seasonal with most activity within wet season months from January to April, with a synchronous pulse of activity in the mid-dry season in two of the three years of study at some sites. Modelling of species richness showed variability among sites in the seasonal patterns of species richness. Multivariate analysis identified seasonal change in assemblage composition. These results are relevant to the design of biodiversity studies on seasonally flowing streams. Surveys of caddisfly diversity are most effectively undertaken during and after the wet season: repeated surveys are required to maximise the detection of the full suite of species occurring at a site.

Impacts of rainfall on road crashes in Onitsha metropolis of Anambra State, Nigeria

The World Health Organization, in particular, is concerned about road traffic accidents that occur during rainfall. However, this has resulted in global deaths, injuries, and property losses. The effects of rainfall on road crashes in the Onitsha metropolis were investigated in this study. The Nigerian Meteorological Agency (NiMET) provided rainfall data from 2009 to 2018, while the Federal Road Safety Commission (FRSC), Awka provided road accident data from 2009 to 2018. Pearson's Product Moment Correlation (PPMC) and Analysis of Variance (ANOVA) were the statistical approaches used to achieve the research goal. The significance level for all inferential analyses was set at 95 percent (0.05). Yearly road crashes and annual rainfall amount have a negative relationship, according to the findings. Rainfall patterns are negatively and insignificantly linked with annual road crashes (p=0.153>0.05), showing that rainfall patterns are not the cause of road crashes in Onitsha. The correlation between monthly road crashes and rainfall received during wet season months is not significant, as demonstrated by the p-value (0.577). The relationship between monthly road crashes and rainfall recorded during dry season is not significant, as indicated by the p-value (0.797). The findings further reveal that, there are non-linear correlations between the rate of road crashes and the two seasons of the year because drivers were more careful when driving under rainfall. Therefore, slower driving during rainfall and parking of cars during torrential downpours are recommended by the study to further reduce the probability of road accidents.

STUDIES ON SURFACE RADIO REFRACTIVITY OVER SOME SELECTED CITIES IN NORTH-CENTRAL, NIGERIA

This research investigated the variations of surface radio refractivity and its propagation effects on radio signal over the cities of Abuja and Ilorin, Nigeria. Six years (2015-2020) satellite data of Temperature, Pressure and Humidity both at the surface (12m) and at 100 m AGL, were used for the study. The data retrieved were used to determine the monthly, seasonal and annual surface radio refractivity values for the locations. Results show that the values of surface radio refractivity (Ns) in Abuja was slightly lower than Ilorin with average values of 335.62 and 351.07 N-Units obtained for the six years respectively. Average values of Ns, obtained during the dry season months in Abuja and Ilorin were 299.40 and 321.03(N-units) respectively while average values of 360.24 and 368.21 (N-units) were obtained during the wet season months in Abuja and Ilorin respectively. Higher values of Ns, were recorded generally during wet compared to the dry seasons’ months in all the years and study locations. The implication of this is higher attenuation of radio signal due to Ns during wet compared to the dry seasons’ months and as well as in Ilorin compared to Abuja. Correlation coefficients of -0.53, 0.98 and 0.53 were determined between (Ns) and; temperature, humidity and pressure respectively in Abuja while -0.30, 0.97 and 0.34 were determined between Ns and; temperature, humidity and pressure respectively in Ilorin. The overall findings of this work will be useful to radio engineers for the proper planning of reliable power budget over the study areas.

A Spatially Distributed Groundwater Metric for Describing Hydrologic Changes in a Regional Population of Wetlands North of Tampa Bay, Florida, from 1990 to 2015

A groundwater condition metric is presented and used to evaluate hydrologic changes in a regional population of wetlands in and around municipal well fields with large groundwater withdrawals. The approach compares a 26-year, monthly time series of groundwater potentiometric surfaces to light detection and ranging (LiDAR) land-surface elevations at 10,516 wetlands in a 1505-km2 area. Elevation differences between the potentiometric surface and the wetland land surface provide flow direction (upward or downward) and a proxy for vertical hydraulic-head difference in Darcy’s groundwater flow equation. The resulting metric quantifies the groundwater condition at a wetland through time as the potential for groundwater to discharge upward into a wetland or for water in a wetland to leak downward to recharge the underlying aquifer. The potential for wetland leakage across the regional wetland population decreased by 33% in the 13 years after cutbacks in groundwater withdrawals (2003 – 2015) compared to years before cutbacks (1990 – 2002). Inside well-field properties, wetland leakage potential decreased by 24%. In the wet season month of September, wetlands with the potential to receive groundwater discharge increased to 21.6% of the regional population after cutbacks compared to 13.3% before cutbacks. When mapped across regional drainage basins, discharging wetlands formed spatial connections, suggesting they play a critical role in generating streamflow.

Dynamical assessment of altitudinal trend of drop size distributions in a tropical region of Nigeria

A comparative assessment of different statistical drop size distributions in a tropical location in Nigeria is presented in this paper. The wet season months of the year 2014 rain data, measured using vertically-pointing Micro Rain Radar (MRR) installed at the Department of Physics, The Federal University of Technology Akure, Nigeria was considered. The data were archived at the Communication Research Group, Department of Physics, The Federal University of Technology Akure. The drop sizes were estimated from the fall velocity. The stratiform rainfall type was considered in this study due to its preponderance of occurrence. Three heights (160 m, 1440 m, and 2240 m) were reviewed for this study. These heights were given due consideration because of the density of the data. All the statistical distributions considered which include Lognormal, Gamma, and Weibull distributions performed better at the 160 m height compared to other heights. It was however observed that the Gamma and Weibull distribution performed better than the Lognormal distribution at this height. The results obtained in this study will be fundamental for the application of remote sensing and the propagation field in this area. The results will be useful to radio communication engineers to properly design a good fade margin in a radio communication system in this region.

A spatio-temporal analysis of scrub typhus and murine typhus in Laos; implications from changing landscapes and climate.

BackgroundScrub typhus (ST) and murine typhus (MT) are common but poorly understood causes of fever in Laos. We examined the spatial and temporal distribution of ST and MT, with the intent of informing interventions to prevent and control both diseases.Methodology and principle findingsThis study included samples submitted from 2003 to 2017 to Mahosot Hospital, Vientiane, for ST and MT investigation. Serum samples were tested using IgM rapid diagnostic tests. Patient demographic data along with meteorological and environmental data from Laos were analysed.Approximately 17% of patients were positive for either ST (1,337/8,150 patients tested) or MT (1,283/7,552 patients tested). While both diseases occurred in inhabitants from Vientiane Capital, from the univariable analysis MT was positively and ST negatively associated with residence in Vientiane Capital. ST was highly seasonal, with cases two times more likely to occur during the wet season months of July-September compared to the dry season whilst MT peaked in the dry season. Multivariable regression analysis linked ST incidence to fluctuations in relative humidity whereas MT was linked to variation in temperature. Patients with ST infection were more likely to come from villages with higher levels of surface flooding and vegetation in the 16 days leading up to diagnosis.ConclusionsThe data suggest that as cities expand, high risk areas for MT will also expand. With global heating and risks of attendant higher precipitation, these data suggest that the incidence and spatial distribution of both MT and ST will increase.