This study examines the spatial and temporal variation of onset and cessation of rainfall and greenness in the North East Arid Zone of Nigeria. Onset and cessation of greenness dates were determined from mean monthly ...This study examines the spatial and temporal variation of onset and cessation of rainfall and greenness in the North East Arid Zone of Nigeria. Onset and cessation of greenness dates were determined from mean monthly time series of Normalized Difference Vegetation Index (NDVI) using Advance Very High Resolution Radiometer (AVHRR) data for five meteorological stations in the zone for a period of nineteen years (1981-1999). Lowest growing days of six weeks were observed in Nguru (12.53°N, 10.28°E, alt.343 m), Potiskum (11.42°N, 11.02°E, alt.415 m) and Maiduguri (11.51°N, 13.05°E, alt. 354 m), while Yola (12.28°N, 9.14°E, alt.174 m) and Bauchi (10.17°N, 9.49°E, alt.609 m) have growing days of 15 and 16 weeks respectively. Highest rate of greenness of 0.18/month was observed inMaiduguriwhile the lowest rate of green-up of 0.07/month was observed in Bauchi. Similarly, highest rate of senescence (0.08/month) was observed in Bauchi while lowest rate of senescence (0.04/month) was observed in Nguru.展开更多
This study investigates the variability and periodicity of minimum temperature, maximum temperature and sunspot number—a solar activity index in selected synoptic stations across Nigeria from 1946 to 2010. Annual and...This study investigates the variability and periodicity of minimum temperature, maximum temperature and sunspot number—a solar activity index in selected synoptic stations across Nigeria from 1946 to 2010. Annual and semiannual effect of solar activity on minimum temperature was observed in all the six stations. This was indicated in the occurrence of modal periodicities of 6-month and 12-month observed across the six synoptic stations. The synoptic stations are Sokoto (13.01°N, 5.15°E), Ilorin (8.29°N, 4.35°E), Ikeja (6.35°N, 3.20°E), Enugu (6.28°N, 7.33°E), Port-Harcourt (4.51°N, 7.01°E) and Maiduguri (11.51°N, 13.05°E). Similarly, the trends of inter-decadal va-riability of minimum and maximum temperature show a non-uniformity increase over the analyzed period with a slight decrease before 1960. The long term behavior of minimum and maximum temperature shows a warming rate which ranges from 0.1°C/decade to 0.2°C/ decade across the six stations except for maximum temperature at Ilorin and minimum temperature at Sokoto which is at -0.2°C/decade and 0.3°C/decade respectively.展开更多
文摘This study examines the spatial and temporal variation of onset and cessation of rainfall and greenness in the North East Arid Zone of Nigeria. Onset and cessation of greenness dates were determined from mean monthly time series of Normalized Difference Vegetation Index (NDVI) using Advance Very High Resolution Radiometer (AVHRR) data for five meteorological stations in the zone for a period of nineteen years (1981-1999). Lowest growing days of six weeks were observed in Nguru (12.53°N, 10.28°E, alt.343 m), Potiskum (11.42°N, 11.02°E, alt.415 m) and Maiduguri (11.51°N, 13.05°E, alt. 354 m), while Yola (12.28°N, 9.14°E, alt.174 m) and Bauchi (10.17°N, 9.49°E, alt.609 m) have growing days of 15 and 16 weeks respectively. Highest rate of greenness of 0.18/month was observed inMaiduguriwhile the lowest rate of green-up of 0.07/month was observed in Bauchi. Similarly, highest rate of senescence (0.08/month) was observed in Bauchi while lowest rate of senescence (0.04/month) was observed in Nguru.
文摘This study investigates the variability and periodicity of minimum temperature, maximum temperature and sunspot number—a solar activity index in selected synoptic stations across Nigeria from 1946 to 2010. Annual and semiannual effect of solar activity on minimum temperature was observed in all the six stations. This was indicated in the occurrence of modal periodicities of 6-month and 12-month observed across the six synoptic stations. The synoptic stations are Sokoto (13.01°N, 5.15°E), Ilorin (8.29°N, 4.35°E), Ikeja (6.35°N, 3.20°E), Enugu (6.28°N, 7.33°E), Port-Harcourt (4.51°N, 7.01°E) and Maiduguri (11.51°N, 13.05°E). Similarly, the trends of inter-decadal va-riability of minimum and maximum temperature show a non-uniformity increase over the analyzed period with a slight decrease before 1960. The long term behavior of minimum and maximum temperature shows a warming rate which ranges from 0.1°C/decade to 0.2°C/ decade across the six stations except for maximum temperature at Ilorin and minimum temperature at Sokoto which is at -0.2°C/decade and 0.3°C/decade respectively.