61
distributed over whole study area except few pockets area of northern, north- eastern,
south-eastern and southern part. About one fourth (26.97%) of the stations showed
irregular distribution (PCI = 16 − 20), followed by moderate (PCI = 11 − 15) precipitation concentration (11.21%). Orographic laden of monsoon by hills and
mountains, terrain characteristics and latitudinal extensions are the key reasons for
such regional variation in the distribution pattern of rainfall. Latitude is the chief
geographical factor that effects annual precipitation change in Portugal, situated in
the Mediterranean basin (Nunes and Lourenço 2015).
On the other hand, Z-statistics of MK/mMK test of PCI showed both increasing
and decreasing trend at 0.05 significance level (Fig. 3.2a). The significant decreasing trends (MK/mMK) were mostly found in the north-eastern, northern and southwestern part of the study area (Fig. 3.2a), which indicates that the concentration
pattern was changed from strongly irregular to moderate or irregular concentration.
According to Karl and Trenberth (2003), the frequency of extreme daily precipitation can increase in regions with warm climates, which can lead to an increase in the
precipitation concentration, even without any alteration in total rainfall.
The results of RSI depicted that the average values varied from 0.29 at station
Kupwara in Jammu and Kashmir to 2.26 at station Surguja in Chandigarh. These
values were typically used to determine the pattern of seasonality in the study area.
The whole study area was dominated by such seasonality where most rainfall occurs
in less than 3 months (41.51%) (RSI = 1.00 − 1.19), concentrated in the central and
western part of the study area except the state of Gujarat (Fig. 3.2b). About one third
(32.92%) of the stations having markedly seasonal rainfall with a long dry season
(RSI = 0.80 − 0.99) and seasonal rainfall (RSI = 0.60 − 0.79) was found over 15.94%
Table 3.1 PCI value wise rainfall regime
Rainfall regime
Values of PCI
Proportion
Percentage
Low precipitation concentration
<10
–
–
Moderate precipitation concentration
11–15
64
11.21
Irregular precipitation concentration
16–20
154
26.97
Strongly irregular precipitation concentration
>20
353
61.82
Total
571
100
Table 3.2 SI value wise rainfall regime
Rainfall regime
Values of SI Proportion Percentage
Rainfall extent throughout the year
<0.19
–
–
Rainfall extent throughout the year
But with certain hazier season
0.20–0.39
4
0.70
Relatively seasonal with a little drier season
0.40–0.59
20
3.50
Seasonal rainfall
0.60–0.79
91
15.94
Markedly seasonal with a lengthy dry season
0.80–0.99
188
32.92
Most rainfall occurs in less than 3 months
1.00–1.19
237
41.51
Extremely seasonal with all rainfall occurs in 1–2 months >1.20
31
5.43
Total
571
100.00
3 Rainfall Insight in Bangladesh and India: Climate Change and Environmental…
distributed over whole study area except few pockets area of northern, north- eastern,
south-eastern and southern part. About one fourth (26.97%) of the stations showed
irregular distribution (PCI = 16 − 20), followed by moderate (PCI = 11 − 15) precipitation concentration (11.21%). Orographic laden of monsoon by hills and
mountains, terrain characteristics and latitudinal extensions are the key reasons for
such regional variation in the distribution pattern of rainfall. Latitude is the chief
geographical factor that effects annual precipitation change in Portugal, situated in
the Mediterranean basin (Nunes and Lourenço 2015).
On the other hand, Z-statistics of MK/mMK test of PCI showed both increasing
and decreasing trend at 0.05 significance level (Fig. 3.2a). The significant decreasing trends (MK/mMK) were mostly found in the north-eastern, northern and southwestern part of the study area (Fig. 3.2a), which indicates that the concentration
pattern was changed from strongly irregular to moderate or irregular concentration.
According to Karl and Trenberth (2003), the frequency of extreme daily precipitation can increase in regions with warm climates, which can lead to an increase in the
precipitation concentration, even without any alteration in total rainfall.
The results of RSI depicted that the average values varied from 0.29 at station
Kupwara in Jammu and Kashmir to 2.26 at station Surguja in Chandigarh. These
values were typically used to determine the pattern of seasonality in the study area.
The whole study area was dominated by such seasonality where most rainfall occurs
in less than 3 months (41.51%) (RSI = 1.00 − 1.19), concentrated in the central and
western part of the study area except the state of Gujarat (Fig. 3.2b). About one third
(32.92%) of the stations having markedly seasonal rainfall with a long dry season
(RSI = 0.80 − 0.99) and seasonal rainfall (RSI = 0.60 − 0.79) was found over 15.94%
Table 3.1 PCI value wise rainfall regime
Rainfall regime
Values of PCI
Proportion
Percentage
Low precipitation concentration
<10
–
–
Moderate precipitation concentration
11–15
64
11.21
Irregular precipitation concentration
16–20
154
26.97
Strongly irregular precipitation concentration
>20
353
61.82
Total
571
100
Table 3.2 SI value wise rainfall regime
Rainfall regime
Values of SI Proportion Percentage
Rainfall extent throughout the year
<0.19
–
–
Rainfall extent throughout the year
But with certain hazier season
0.20–0.39
4
0.70
Relatively seasonal with a little drier season
0.40–0.59
20
3.50
Seasonal rainfall
0.60–0.79
91
15.94
Markedly seasonal with a lengthy dry season
0.80–0.99
188
32.92
Most rainfall occurs in less than 3 months
1.00–1.19
237
41.51
Extremely seasonal with all rainfall occurs in 1–2 months >1.20
31
5.43
Total
571
100.00
3 Rainfall Insight in Bangladesh and India: Climate Change and Environmental…