ANALYSIS AND QUANTIFICATION OF DROUGHT USING METEOROLOGICAL INDICES IN THE SUDANO-SAHEL REGION OF NIGERIA
ANALYSIS AND QUANTIFICATION OF DROUGHT USING METEOROLOGICAL INDICES IN THE SUDANO-SAHEL REGION OF NIGERIA
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Date
2000
Authors
OTUN, JOHNSON ADEBOLA
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Abstract
Unlike the common use of only ‘rainfall amounts’ in indexing the drought in a
place, this study have identified, verified and validated the potentials of nine (9)
other precipitation effectiveness variables (PEV) that can equally reflect the drought
conditions in any place. The 10 PEVs have been effectively combined to derive a
‘at-site’ operational drought index called the Conjunctive Precipitation Effectiveness
Index (CPEI). A historical daily rainfall record from 1916-2003 for seven (7) stations
in the SSRN was used to estimate CPEI for these stations. The CPEI obtained,
using the 1023 possible arrangements for the various combinations of the 10 PEVs,
were respectively statistically compared with the values for the Standard
Precipitation Index (SPI), Rainfall Anomaly Index (RAI), Bhalmey-Mooley Drought
Index (BMDI) and Palmer Drought Severity Index (PDSI). Results obtained showed
that a maximum combination of six (6) PEVs gave an average correlation (r) value
above 0.8. Those arrangements with r > 0.8 were further ranked and through a
descriptive analysis, it was shown that the ultimate number of PEVs that can be
effectively combined to get the optimum CPEI values for indexing the drought is
three (3) PEVs for Gusau and Kano, five (5) PEVs for Sokoto and Maiduguri and
four (4) for the rest stations under study. The drought conditions for over 50 years,
in the SSRN, were therefore examined using the derived optimum CPEI index and
other four indices. The results obtained for each of the indices compared very well
with notable historical drought years. These preliminary applications show that most
of the indices used can be considered as operational tools for a national drought
watch system in the SSRN to quantify and characterize the drought conditions
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objectively. As the significant level of occurrence observed with one of these PEVs,
i.e. dry spell occurrence within the wet season and year, for each of the station
under study, initiated some concerns and interests. The study therefore also
attempted to further analyze the incidence and distribution of the dry spell
occurrences in the SSRN as a way of making suggestion on how the incessant spell
in the SSRN can be well accommodated. The analysis involves an empirical
analysis of the dry spell (EADS) in the SSRN. The results from the EADS provided
an ample of information that can be used as guides for various agricultural
applications.
Description
A Dissertation Submitted to the Postgraduate School,
Ahmadu Bello University, Zaria for the
Degree of Doctor of Philosophy
(Water Resources and Environmental Engineering)
Department of Water Resources and Environmental Engineering
Faculty of Engineering,
Ahmadu Bello University, Zaria.
NIGERIA.
AUGUST 2005.
Keywords
ANALYSIS,, QUANTIFICATION,, DROUGHT,,, USING,, METEOROLOGICAL,, INDICES,, SUDANO -SAHEL, REGION,, NIGERIA