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International Journal of Marine Science 2013, Vol.3, No.18, 145-150
http://ijms.sophiapublisher.com
147
Table 2 Model parameter estimates and their 95% confidence for the selected locations, Muscat and Masirah
Muscat
Masirah
Parameter Unit
Value
Lower 95% CI Upper 95% CI
Value
Lower 95% CI Upper 95% CI
A
1
℃
1.55
1.33
1.80
2.25
2.43
2.46
A
2
℃
1.87
1.65
2.10
0.77
0.56
0.98
P
1
Month
5.69
5.50
6.00
6.00
-
-
P
2
Month
12.28
11.32
13.18
12.03
11.99
12.07
α
1
Month
5.00
4.84
5.13
10.68
10.50
10.85
α
2
Month
7.21
7.00
7.43
2.77
1.76
3.76
Slope
℃
/month
0.0011
0.0002
0.0019
0.0017
0.0008
0.0026
Intercept
℃
26.2920
25.7548
26.4314
25.3248
24.7810
25.4958
Note: Dashes indicate that the parameter could not be estimated
Figure 2 Distribution of SSTA for Muscat (red line) and
Masirah (blue line) for the years 1961 to 2010
while less prominent peak occurring every 12 months.
The amplitude difference between these peaks is
1.48
℃
and shows a large difference in amplitude
prominence between them. In Masirah, the prominent
peak occurs in the month of November while the less
prominent one occurs in the February-March period.
Confidence intervals for the P1 parameter could not be
estimated for the Masirah location as the maximum
likelihood surface for this parameter was flat around
the global minimum.
Figure 3 gives the variance estimates of SST grouped
in 10-year intervals for the complete fitted models.
There are two general trends in the variance, firstly, in
Muscat the variance for the 10-year groups is fairly
constant for the period 1961~2009 while for Masirah
there has been a rapid decrease in variance since
1981~1990. Secondly, between the years 1961 to 1990
variance estimated for the Masirah Island location
always exceeded that of Muscat but from 1991 the
variance of Muscat has exceeded that of Masirah
Island and more noticeably so in the 2001 to 2009
period. The intra-annual distribution of SST variance
shows that the low or high variance at the study locations
Figure 3 Decadal distribution of variance
(℃
) of SST at the
study locations for the period 1961 to 2009
occurs nearly simultaneously (Figure 4). The low
variance off Masirah occurred during February-March
(0.11
℃
) and of high variance is July (0.88
℃
).
Similarly, lower SST variance (0.11
℃
) off Muscat
occurred in February and October while higher
variance (0.24
℃
) occurred in April and August. The
SST variance off Masirah is large during summer
(June~August) with a peak variance of 0.9
℃
during
peak summer period (July) and dramatically reduced
to <0.2
℃
during winter. The inter-annual standard
deviations and variances have dramatically increased
from pre-1984 to post-1984 period at both locations.
The monthly mean SST showed significant difference
in the pattern of variability between the selected
locations as indicated by the slope (0.0115
℃
off
Muscat and 0.0225
℃
off Masirah). Table 2 shows the
amplitude, period and phase of the SST at the study
locations estimated from the model. The amplitude of
primary warming is higher off Masirah (2.25
℃
)
compared to Muscat (1.55
℃
).
The bi-modal model parameter estimates given in
Table 2 are utilized to simulate the SST changes at the
study locations and the model fits are shown in Figure
5 and Figure 6. The annual and semi-annual changes