Boundary Layer Stability Regime at DACCIWA Site Using Gradient Richardson Number

ABSTRACT

Meteorological data including air temperature and wind speed which were collected from DACCIWA measurement site at a tropical agricultural field site in Ile-Ife (7.55oE, 4.56oE), south-western Nigeria have been used to classify boundary layer stability regimes using gradient Richardson number. Three categories were considered to deduce the pattern of stability conditions namely stable, unstable and neutral conditions for 3-hourly intervals at 0.00, 03.00, 06.00, 09.00, 12.00, 15.00, 18.00 and 21.00 hours from 15th June to 31st July 2016. The data were sampled every 1sec and stored subsequently as 10 minutes averages for all the measured parameters. The data was further reduced to 30 minutes averages for easy analysis and manipulation in the calculation of gradient Richardson number used for boundary layer stability regime characterization. The results showed that the month of June 2016 had prevalence of stable regime from 000 – 600 am and 600 pm; 900 am was predominantly neutral and shared similar pattern with 900 pm. Unstable regime was slightly observed at 1200 pm and majorly observed at 300 pm. The month of July had a little shift from what was observed in the month of June. Predominance of neutral conditions was observed from 900 pm to 900 am; Hours of 1200 – 300 pm were dominated by unstable regime while 600 pm was dominated by stable regime.