SIGNATURE OF ATMOSPHERIC DYNAMICS ON SURFACE OZONE VARIABILITY IN NIGERIA

An examination of analysis revealed that surface ozone concentration over Nigeria varied with direction of the local trade winds, namely the Harmatan, and the Gulf of Guinea maritime trade winds. In DJF and MAM the period of the dry dusty Harmatan seasons, surface ozone concentration in the southern Nigeria exceeded that of the north by 21DU and 24DU respectively. Whereas in the JJA and SON, the rainfall season, reversal was the case, the surface ozone concentration in the northern Nigeria exceeded that of the south by 20DU and 15DU respectively. Maximum temporal variation gradient of 20DU was also observed in MAM season while the minimum of 11DU occurred in JJA which is the peak of the raining season

Study of Cloud Impact on Fixed Satellite Communication Link at Ku, Ka and V Bands in Nigeria

The study investigates the effect of clouds on fixed satellite communication link on earthspace path in Nigeria for 0.01 to 10% unavailability of an average year. The input data (from August 2002 to July 2009) used for the study are base on recent meteorological data measured from space by the Atmospheric Infrared Sounder satellites (AIRS). The International Telecommunication Union Radio Propagation Recommendation (ITU-RP, 2009) procedure was used for the computation of cloud attenuation statistics for each of the 37-stations for link to Nigeria Communication Satellite (NigComsat-1), for both uplink and downlink frequencies. At Ku band (12/14 GHz), cloud fade is between 0.2 to 0.55 dB, for Ka band (20/30 GHz), 0.6 to 2.4 dB and for V band (40/50 GHz) 2.0 to 6.0 dB. A Contour map of cloud attenuation at Ku, Ka and V-band for 0.01% unavailability, at 0.1 by 0.1 degree latitude and longitude for downlink and uplink to NigComsat-1 was developed. The maps show consistently that impact of cloud is generally severe in the southern part of Nigeria

Cloud cover, cloud liquid water and cloud attenuation at Ka and V bands over equatorial climate

Cloud cover statistics and their diurnal variation have been obtained from in situ and satellite measurements for three equatorial locations. Cloud liquid water content, 0 °C isotherm height and cloud attenuation have also been obtained from radiosonde measurement using the so-called Salonen model at Kuala Lumpur (Malaysia). The results show a strong seasonal variation of cloud cover and cloud liquid water content on the two monsoon seasons. The Liquid Water Content (LWC) obtained from radiosonde and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) is higher during the Northeast Monsoon season, which corresponds to the period of higher percentage cloud cover and high rainfall accumulation. The International Telecommunication Union—Region (ITU-R) model underestimates the cumulative distribution of LWC values at the present station. The relationship of the cloud attenuation, derived from the profiles of liquid water density and temperature within the cloud, shows an underestimate by the data obtained from the ITU-R model. The cloud attenuation at Kuala Lumpur is somewhat underestimated by the ITU-R model up to about 1.2 dB at Ka (30 GHz) and 3.4 dB at V (50 GHz) bands. The results of the specific attenuation can be used for the estimation of cloud attenuation at microwave and millimetre wave over earth-space paths. The present data are important for planning and design of satellite communications at Ka and V bands on the Earth–space path in the equatorial region

Some preliminary results of the fine structure profiles of radio refractivity near the surface at Ota, Southwest Nigeria

Some preliminary results are presented of the fine structure profiles of surface radio refractivity, Ns, over Ota, Southwest Nigeria (6° 42'N, 3° 14'E) computed from in-situ, one minute interval measurements of surface pressure, temperature and relative humidity. A wireless Davis Vantage Pro2 Weather Station instrument installed at the Department of Physics, Covenant University, Ota in April 2012, was used to obtain the measured variables. Hourly, daily and monthly average values of surface water vapour density, dry, wet and total radio refractivity were obtained for the months of April 2012 to March 2013. The distance to the radio horizon for a given transmitter height may be deduced from the observation that Ns is well correlated with the gradient of refractivity over the first kilometer above ground. Refractivity gradients utilized for the work were those obtained in a previous work for Oshodi, a meteorological weather station near the coast and close to Ota

Tertiary Conformational Transition In Horse Haemoglobin Induced By Inositol Hexakisphosphate

The red blood cell of the domestic horse contains two haemoglobin types. The two haemoglobins were separated on a column of carboxymethylcellulose. The equilibrium constant, Kequ, for the reaction of 5,5'-dithiobis(2-nitrobenzoate) — DTNB — with the CysF9[93]β sulfhydryl group of each haemoglobin was determined at 25°C as a function of pH. The reactivity of CysF9[93]β is affected by allosteric effectors such as the proton (H+) and inositol hexakisphosphate (inositol-P6). Between pH 5.6 and 9.0 Kequ decreased by about two to four orders of magnitude, demonstrating that H+ is a heterotropic allosteric effector of haemoglobin with respect to its reaction with DTNB. Inositol-P6 also decreased Kequ by about two to four orders of magnitude across the experimental pH range. CysF9[93]β exists in two tertiary conformations, r and t, in dynamic equilibrium. Krt, the equilibrium constant for the r t conformational transition, was determined for each of the two horse haemoglobins from an analysis of the pH dependence of Kequ. The calculations from the pH dependence of Kequ showed that the pKa values of the ionisable groups coupled to the DTNB reaction vary between 5.0 and 8.9. The equilibrium constants, Krt, for the r t tertiary structure transition, were 0.143 ± 0.05 and 0.446 ± 0.22 for the fast and slow stripped horse haemoglobins respectively. In the presence of inositol-P6, Krt for the fast and slow were 2.219 ± 0.79 and 2.214 ± 0.83 respectively. The results show that inositol-P6 increases the relative population of the t tertiary conformation. So, it increases the affinity of CysF9[93]β by changing the relative distribution of two protein conformations

A Simple Resistive Load I-V Curve Tracer for Monitoring Photovoltaic Module Characteristics

Current-Voltage (I-V) curve tracers are useful implements for solar Photovoltaic (PV) research and manufacturing, particularly when wishing to ascertain module yield viz-a-viz solar irradiation falling on the module in different climatic conditions. This paper presents a simple affordable and easy to fabricate instrument for tracing I-V characteristics of a PV module. It comprises of rapidly varying resistive loads centred on power resistors connected to relays and controlled by an electronic circuitry. The circuit consists of a 555 astable oscillator that is used to send clock pulses to the clock terminal of a 4017 decade counter which in turn produces a sequence of pulses. Each progression of pulse advances by one bit to sequentially turn on individual relays via driver transistors. The speed of the count is made variable from the frequency determining network of the 555 oscillator. The I-V characteristics of the module are thus measured by the sequential selection of the relays which are each connected to a selected load resistor to determine the operating point on the I-V curve. The currents and voltages are then recorded simultaneously with irradiance from a pyranometer, by a datalogger to which the instruments are connected. The circuit was tested on two monocrystalline modules to compare the effect of Harmattan dust on PV output yield

STUDIES OF PROPAGATION IMPAIRMENTS FOR FIXED SATELLITE COMMUNICATION LINKS AT THE MICROWAVE FREQUENCIES IN NIGERIA

The study investigates the effect of propagation impairments such as rain, cloud, gases and tropospheric scintillation on fixed satellite communication link on earth-space path for frequencies between 10 and 50 GHz at Ku, Ka and V bands for 37 locations in Nigeria. Two standard elevation angles of 50, 550 as well as some elevation angles for links to recently launched Nigeria Communication Satellite, (NigComsat-1) were used in the computation of the propagation impairments for the 37 locations. Linearly and circularly polarized waves were considered. The International Telecommunication Union Radiowave Propagation models (ITU-RP) were used in the investigation of the propagation impairments. The study is divided into three parts; firstly, the collection and analysis of meteorological data from Tropical Rain Measurement Mission (TRMM) and Atmospheric Infrared Sounder (AIRS) satellites such as rain accumulation, profiles of temperature, pressure, and relative humidity, surface temperature and pressure were validated with the available ground data in Nigeria to form statistics on monthly and annual basis. These are reprocessed to derive propagation parameters, such as; one-minute rainfall rate, water vapour density, total cloud liquid water content, and integrated water vapour content. Secondly, an appropriate ITU-RP propagation model was selected for each of the propagation impairment and was used to calculate each attenuation distribution for a percentage of time unavailability. Thirdly, the attenuation due to all impairments were combined based on the annual cumulative distribution and percentage of time unavailability between 0.01 to 10%. The calculation of the propagation parameters are based on the measured mean annual data in each location for the period of 4 to 9 years. Propagation impairments were also computed at Ku, Ka and V bands for links to NigComsat-1 at 0.01 to 10% of time unavailability in an average year. The results of all impairment were compared on regional basis by using a colour chart for all the 37 locations in Nigeria. The results of the predicted propagation impairments are as follows: rain attenuation is highly severe in Abakaliki the South-East (SE) region followed, in descending order, by Yenagoa the South-South (SS), Ibadan South-West (SW), Jos Middle-Belt (MB), Damaturu North-East (NE), and Kastina North-West (NW) regions. Cloud attenuation is highly severe in Abakaliki the SE region followed, in descending order, by Jos (MB), Gombe (NE), Dutse (NW), Ikeja (SW), and Calabar (SS) regions. Gaseous attenuation is highly severe in Calabar the (SS regions) followed, in descending order, by Ikeja (SW), Abakaliki (SE), Abuja (MB), Dutse the (NE) and Kastina (NW) regions. Tropospheric scintillation is very high in Calabar (the SS region) followed, in descending order, by Ikeja (SW), Owerri (SE), Abuja (MB), Dutse (NE) and Kastina (NW) regions. Combined impairments due to multiple sources of simultaneously occurring atmospheric attenuation is highly severe in Abakaliki the (SE region) followed, in descending order, by Uyo (SS), Ikeja the (SW), Markudi (MB), Maiduguri (NE) and Katsina (NW) regions. For links to NigComsat-1 the combined impairments due to multiple sources of simultaneously occurring atmospheric attenuation is highly severe in Yenagoa the (SS region ) followed, in descending order, by Owerri (SE), Ibadan (SW), Jos (MB), Damaturu the (NE), and Katsina (NW) regions. Overall, Sokoto and Katsina appear as good locations to site fixed satellite earth stations (operating at Ku band and above) for deep space exploration as the results obtained showed consistently that the two locations are less affected by all propagation impairments investigated

Mathematical Projections of Air Pollutants Effects over Niger Delta Region Using Remotely Sensed Satellite Data

Air pollution due gas–flaring is a major concern in the Niger-Delta region of Nigeria. The short and long term effect of the massive air pollution on the life form within the area requires urgent attention because of the health implication. This research examines the impact of air pollutants in Niger-Delta region using remotely sensed satellite data. The satellite data set was obtained from CALIPSO, MODIS and ARIS. A mathematical software (MATLAB) was used to analyse the results. For Sulphur dioxide (SO2), Uyo had the highest rate of pollution (0.67DU), then Yenegoa (0.66DU), Benin (0.64DU), Asaba (0.60DU), Port Harcourt (0.58DU), Calabar (0.55DU) respectively. For Carbon dioxide (CO2), Yenegoa was the most polluted with (382.01ppmv), Port Harcourt, Calabar and Uyo all had (381.99ppmv) then Benin (381.77ppmv) and Asaba (381.53ppmv) respectively. For Nitrogen dioxide (NO2), Port Harcourt had the highest mean value with (54.65mol/cm2), Asaba (51.05mol/cm2), Uyo (49.08mol/cm2),Calabar (47.84mol/cm2), Yenagoa (46.73mol/cm2), Benin (43.22mol/cm2) respectively. For Methane (CH4), the stations with the highest rate of pollution were Port Harcourt, Yenagoa and Uyo with (3.86E+19mol/cm2), Benin and Asaba had (3.8E+19mol/cm2) while Calabar (3.76E+19mol/cm2). Mathematical projections were made to capture the dilemma- people in this region might encounter in the nearest future

Cloud attenuation studies of the six major climatic zones of Africa for Ka and V satellite system design

Cloud cover statistics, cloud base and top height, cloud temperature, frequency of precipitation, freezing height, total cloud liquid water content (TCLWC) and cloud attenuation data have been obtained for the six major climatic zones of Africa. The present results reveal a strong positive correlation between the monthly distribution of low cloud cover, cloud top height, cloud temperature, and frequency of precipitation in the six zones. The cumulative distribution of the TCLWC derived from radiosonde measurement in each climatic zone shows a departure from the TCLWC recommended by the ITU Study Group 3 data, with an exceedance percentage difference of 32% to 90% occurring 0.01% to 10% of the time. The underestimation of the TCLWC is greatest in the tropical rain forest. A comparison of the cloud attenuation cumulative distribution in the Ka and V bands reveals that the International Telecommunication Union – Region (ITU-R) is an intergovernmental organization that develops rain model based on collected data around the world. This model underestimates the cloud attenuation in all of the six climatic zones by 2.0 dB and 4.7 dB for the arid Sahara desert, 1.3 dB and 3.0 dB in semi-arid North Africa, 1.3 dB and 1.5 dB in savannah North Africa, 2.0 dB and 3.6 dB in the tropical rain forest, 1.3 dB and 2.9 dB in savannah South Africa and 0.9 dB and 2.6 dB in semi-arid South Africa, respectively, at 30 and 50 GHz. Overall, the cloud attenuation in the tropical rain-forest zone is very high because of the high annual total cloud cover(98%), high annual frequency of precipitation (4.5), low annual clear sky amount (8%), high cloud depth (10,937 m), high 0°C isotherm height (4.7 km), high TCLWC (4.0 kg/m2 at 0.01%) and low seasonal cloud base height (356 m)

Atmospheric gas impact on fixed satellite communication link a study of its effects at Ku, Ka and V bands in Nigeria

The total atmospheric absorption due to Oxygen and water vapour on the earth-space path at Ku (12/14 GHz), Ka (20/30 GHz), and V (40/50 GHz) bands was evaluated for communication with Nigeria communication satellite (Nigcomsat1) on both uplink and down link at 0.01 % unavailability of an average year. The basic input climatic data used include monthly and yearly mean meteorological parameters of surface and vertical profiles of pressure, temperature, and relative humidity obtained from recent measurement from space by the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua spacecraft for the period 2002 to 2006. The International Telecommunication Union Radio Propagation Recommendation (ITU-RP 676, 2009) procedure was used for the computation of gaseous attenuation for each of the 37-stations in Nigeria. Attenuation values were obtain for both uplink and downlink frequencies, at Ku, Ka and V bands, total atmospheric absorption was determined to be between (0.11 to 0.24) dB, (0.7 to 1.1) dB and (0.82 to 3.1) dB for Ku, Ka, and V bands respectively. Contour maps showing a consistent signal absorption due to Oxygen is generally higher in the South-West region and water-vapour attenuation higher in the South-South part of Nigeria are presented