samarendra karmakar
TRANSCRIPT
Trends in maximum temperature and thunderstorms,
their correlation and impacts on the livelihood of
Bangladesh
Dr. Samarendra Karmakar
Former Director
Bangladesh Meteorological Department and
SAARC Meteorological Research Centre
Former Permanent Representative of Bangladesh with WMO
Present Affiliation:
Vulnerability Assessment and Capacity Development Expert
Bangladesh Centre for Advanced Studies
International Conference on Climate Change Innovation and Resilience for
Sustainable Livelihood
Kathmandu, nepal
12-14 January 2015
Outlines of the presentation
•Data used and methodology
•Results and discussion
- Linear trends of maximum temperature
-Spatial distributions of monthly and seasonal trends in maximum
temperatures
-Trend in annual mean country-averaged maximum temperature in
Bangladesh during the pre-monsoon season
-Trends of thunderstorm frequency in Bangladesh during 1980-2008
-Spatial distributions of monthly and seasonal trends of
thunderstorm frequency over Bangladesh
-Trend in Country-averaged seasonal frequency of thunderstorm
during the pre-monsoon season
-Correlation between maximum temperature and thunderstorm
frequency in Bangladesh during 1980-2008
•Study of Socioeconomic Impacts of local sthunderstorms
-Socio-economic and demographic conditions of the selected areas
-Disasters of the locality, their severity and impacts
-Understanding of environment and climate change
-Coping mechanism
Recommendations
Conclusions
Outlines of the presentation (Cont’d)
* During the pre-monsoon season (March-May), severe
thunderstorms occur over Bangladesh. These storms are
associated with Lightning, thunder, rain, hails, and gusty winds.
*Sometimes tornado cells are embedded in mother thunderstorm
cloud.
* These severe weather events cause fairly widespread
destruction of properties and loss of lives throughout
Bangladesh.
* Economic losses are also enormous due to these weather events.
*These storms are popularly known as Nor’westers or
Kalbaishakhi in Bangladesh and surrounding areas.
Introduction
Fig. Cumulonimbus cloud Fig. Lightning Fig.\Tornado cloud
Objectives
• To study
• Trend of Tmax
• Trend of thunderstorm frequency
• Correlation of Tmax and thunderstorm frequency
• Socioeconomic Impacts of local sthunderstorms
Data used and methodology
•Monthly maximum temperature
during 1961-2008
•Monthly frequency of
thunderstorms of BMD during 1980-
2008
•No. of stations:24 stations of BMD
•Season: Pre-monsoon season
Dhaka
Mymensingh
Faridpur
Chittagong
Cox's Bazar
M. CourtFeni
Hatiya
Kutubdia
Chandpur Comilla
Rangamati
Sylhet
Khulna
Jessore
Barisal
Patuakhali
Bhola
Rajshahi
RangpurDinajpur
Ishurdi
Bogra
Sandwip
Srimangal
Satkhira
88 89 90 91 9220
21
22
23
24
25
26
11 2
2
Rk
knRF
)1(
)2(
2
r
nrt
For Trends: distribution,
For Correlation Coefficient, Student’s t-Test,
Significant Tests
Fig. Stations of BMD
Manikganj
Saturia
Siraganj
Sunamganj
Dirai
Patuakhali
Kalapara
87.5 88 88.5 89 89.5 90 90.5 91 91.5 92 92.5
21
21.5
22
22.5
23
23.5
24
24.5
25
25.5
26
26.5
Bay of Bengal
•Socio-economic study has been
carried out at four places which
are more vulnerable to
thunderstorms.
•The objective of this study is to
bring benefit to the people and
their livelihood by reducing the
damages of the resources,
minimizing the sufferings and
saving the valuable lives.
Survey is made at Sirajganj, Saturia, Sunamganj and Patuakhali.
•These storms also impact on the environment, ecology and resources by the associated gusty wind with varied intensity, sometimes with tornado cells, hails, torrential rain within short time causing flash floods and landslides.
Fig. Places of Field Visit
Results and discussion
Linear trends of maximum temperature during 1961-2008
March:
•Maximum temperature has decreasing trends at 16
stations out of 24 stations, having maximum magnitude of
-5.58C/100 years at Bogra.
•The trends are significant at Mymensingh, Cox’s Bazar,
Comilla, Khulna, Rangpur, Bogra and Dinajpur.
April:
• Maximum temperature has decreasing trends at 11
stations, having maximum magnitude of -7.45C/100 years
at Rangpur.
•The negative trends are significant at Cox’s Bazar, M.
Court, Rangpur, Dinajpur, Bogra, Mymensingh and
Chittagong.
•The positive trends are not significant.
May
•Maximum temperature has increasing trends at 15 stations out of 24 stations, having maximum magnitude of +3.81C/100 years at Cox’s Bazar and +2.76C/100 years at M. Court.
•These trends are statistically significant.
•The decreasing trend is maximum (-2.34 C/100 years) at Rangpur.
Seasonal
•Seasonal mean maximum temperature has increasing trends at 13 stations and decreasing trends at 11 stations, having maximum magnitudes of +4.94C/100 years and -4.64C/100 years at Cox’s Bazar and Rangpur respectively.
•The trends are significant at 100% level at Mynensingh,
Chittagong, Cox’s Bazar, Rangpur and Dinajpur and at
95% level at M. Court and Bogra.
•The monthly and seasonal mean maximum temperature
have maximum decreasing trends at Rangpur during
the period 1961-2008.
***Trends of monthly and seasonal mean maximum
temperatures are increasing at most of the stations, and
the trends are all positive in May during the pre-monsoon
season of 1980-2008.
During 1980-2008
Spatial distributions of monthly and seasonal trends in
maximum temperatures over Bangladesh
Fig.: Spatial distribution of
the trends of Tmax (C/100
years) in Bangladesh in
March
Fig.: Spatial distribution of
the trends of Tmax (C/100
years) in Bangladesh in
April
maximum decreasing
trends
maximum
decreasing trends
CXB +5.4**
Bogra -5.58** Rangpur -7.45**
CXB +5.6**
Fig.: Spatial distribution of
the trends of Tmax (C/100
years) in Bangladesh in
May
Fig.: Spatial distribution of
the trends of Tmax (C/100
years) in Bangladesh in
pre-monsoon season
Spatial distributions of monthly and seasonal trends in
maximum temperatures over Bangladesh (Cont’d)
maximum decreasing
trends
maximum
decreasing trends It is apparent
that the
trends of
monthly and
seasonal
mean
maximum
temperatures
are maximum
negative over
the
northwestern
Bangladesh. CXB +3.81**
RNP -2.34 RNP -4.64**
CXB +4.94**
y = 0.0187x - 4.6386
R2 = 0.0574
30.5
31
31.5
32
32.5
33
33.5
34
19
80
19
82
19
84
19
86
19
88
19
90
19
92
19
94
19
96
19
98
20
00
20
02
20
04
20
06
20
08
Years
Ma
xim
um
te
mp
era
ture
(°C
)
Fig. :Trend in annual mean country-averaged maximum temperature in
Bangladesh during the pre-monsoon season of 1980-2008
Trend in annual mean country-averaged maximum
temperature in Bangladesh during the pre-monsoon
season
Rate =+1.87C/100 years
Trends of thunderstorm frequency in Bangladesh during
1980-2008
March:
•Frequency of thunderstorms has decreasing trends at 15 stations and increasing trends at 8 stations.
April:
•Thunderstorm frequency has decreasing trends at 15 stations and increasing trends at 8 stations.
May:
•The thunderstorm frequency has decreasing trends at 8
stations and increasing trends at 15 stations.
Seasonal:
•The seasonal frequency of thunderstorm has decreasing
trends at 14 stations and increasing trends at 9 stations.
Spatial distributions of monthly and seasonal trends
thunderstorm frequency over Bangladesh
Fig. Spatial distribution of the trends
of TS Frequency (/10 year) over
Bangladesh in March during 1980-
2008
Fig. Spatial distribution of the
trends of TS Frequency (/10 year)
over Bangladesh in April during
1980 -2008
Faridpur:+8.598
Sylhet:-4.704 Sylhet:-17.626 Rangpur:+5.207
Spatial distributions of monthly and seasonal trends
thunderstorm frequency over Bangladesh (Cont’d)
Fig. Spatial distribution of the
trends of TS Frequency (/10 year)
over Bangladesh in pre-monsoon
season during 1980 -2008
Fig. Spatial distribution of the trends
of TS Frequency (/10 year) over
Bangladesh in May during 1980-2008
Sylhet:-17.453
M. Court:+6.527
Sylhet:-13.261
Rangpur:+3.658
Seasonal
y = -0.1196x + 366.29
R2 = 0.0097
100
105
110
115
120
125
130
135
140
145
150
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
Year
Seas
onal
thun
ders
torm
freq
uenc
y
Fig. Trend of country-averaged seasonal frequency of thunderstorm
during the pre-monsoon season in Bangladesh during 1980-2008
Trend in Country-averaged seasonal frequency of
thunderstorm during the pre-monsoon season
Rate= - 1.196/10 years
Correlation between maximum temperature and
thunderstorm frequency in Bangladesh during 1980-2008
•The monthly and seasonal mean maximum temperatures
are negatively correlated with the monthly and seasonal
frequency of thunderstorms.
•This means that the monthly and seasonal frequency of
thunderstorms during the pre-monsoon season in
Bangladesh will decrease with the increase of monthly and
seasonal mean maximum temperatures.
•The correlation coefficients are statistically significant at
100% and 95% level in many cases.
•The decrease in thunderstorm frequency may be due to the
prolong influence of the subtropical high over the region
during the pre-monsoon season
•In March, the magnitude of highest negative correlation
coefficient is -0.80694 at Ishurdi.
• In April and May, the magnitudes of highest negative
correlation coefficients are -0.86743 and -0.7937 at
Jessore and Sylhet respectively.
•The magnitude of the highest seasonal negative
correlation coefficient is -0.87032 at Ishurdi.
Therefore, the country-averaged seasonal mean maximum
temperature over Bangladesh during the pre-monsoon
season has increasing trend and the seasonal
thunderstorm frequency during the pre-monsoon season
has decreasing trend, and they are negatively correlated.
The spatial distributions of the monthly and seasonal
correlation coefficients between maximum temperature
and the frequency of thunderstorms in Bangladesh
Fig. :Spatial distribution of correlation
coefficients between minimum
temperature and thunderstorm
frequency of March in Bangladesh
during
Fig. :Spatial distribution of correlation
coefficients between minimum
temperature and thunderstorm
frequency of April in Bangladesh
during
CC:-0.80694 at Ishurdi CC: -0.86743 at Jessore
Fig.:Spatial distribution of correlation
coefficients between maximum
temperature and thunderstorm
frequency of May in Bangladesh
Fig.:Spatial distribution of correlation
coefficients between maximum
temperature and thunderstorm
frequency of pre-monsoon season in
Bangladesh
CC:-0.7937 at Sylhet CC:-0. 87032 at Ishurdi
Socioeconomic Impacts of local severe storms
Socio-economic and demographic conditions of the
selected areas
Gender Patuakhali Sirajganj Sunamganj Saturia
Male 2.3 3 2.8 3
Female 2.2 2 3.2 3
Total 4.5 5 6 6
Table : Average household size
Literacy
rate
Patuakhali Sirajganj Sunamganj Saturia
Male Female Male Female Male Female Male Female
Below
SSC
38.9 50.2 41.5 77.5 50.0 52.0 41.5 77.3
SSC 16.4 18.5 7.5 11.5 34.0 36.0 7.5 2.0
HSC 12.3 11.3 9.4 7.5 6.0 2.0 15.1 2.0
Graduate 22.6 14.9 15.1 2.0 3.0 3.0 9.4 7.5
Post
Graduate
10.8 5.1 7.5 2.0 7.0 7.0 7.5 11.3
Table : The literacy levels in the study areas for males
and females
•Areas of Sirajganj and Saturia have very poor condition of literacy,
where more than 77% of female population remains below SSC level.
• The status of Patuakhali and Sunamganj is relatively better.
•The better situation literacy in Patuakhali matches with the better
situation of household size.
•This indicates that the improvement of literacy is a mandatory for
sustainable population control and development.
Building materials Patuakhali Sirajganj Sunamganj Saturia
1. Brick wall with CI sheet
roof
2.9 1 28.4 4
2. Bamboo with CI sheet 55.9 30 33.3 2
3. Bamboo with polythene
shade
29.4 62 28.4 0
4. Bamboo with straw shade 7.1 7 0.0 0
5. Mud with CI sheet roof 2.9 0 8.5 0
6.Mud wall with straw shade 0 0 0.7 0
7. Others 0 0 0.7 94
Table:% Response of the building materials of the
respondents’ houses
•The distribution of housing materials indicate that
Bamboo, CI Sheet and polythene constitute the dominant
materials showing prevailing poverty except for
Sunamganj, where 28.4% houses have brick walls.
•Saturia appears to be rather rich. None of listed building
materials are used in Saturia indicating that this area has
more urban practices for their housing.
No of rooms Patuakhali Sirajganj Sunamganj Saturia
1 54.6 45 41.5 11.8
2 18.6 32 49.3 43.1
3 10.3 14 6.3 45.1
4-7 16.5 9 2.8 0
Except the surveyed area of Sunamganj, more than 70%
households have electric connections. 100% of the respondents
of Saturia informed that they are connected with electric supply
(Table below).
Table : Frequency response of rooms in the house (%)
About 70-90% of the households have 1-2 rooms with an
exception to Saturia where about 90% of the houses have 2-3
rooms (Table below).
Electric
Connection
Patuakhali Sirajganj Sunamganj Saturia
Yes 86.1 71 4.6 100
Table : Electric connection to the house (%)
The water supply for household use comes from mainly tube-wells except
Patuakhali where the water supply comes through pipes. This may be
because of the fact that the ground water is saline and the supply water
comes from rainwater harvesting and through treatment of the water from
other sources (Table below).
Table : Sources of water supply
Sources Patuakhali Sirajganj Sunamganj Saturia
1. Internal Pipeline 53.6 0 1.4 0
1. Stand Pipe 13.3 0 2.1 0
1. Well 0 0 2.8 6.1
1. Tube-well 0 99 89.7 85.7
1. Ponds, canals/rivers 33.1 1 2.1 8.2
•The selected areas are found to have around 70-80% sanitation
toilets, most of which are built on external safety tank.
• The situation of selected areas at Patuakhali is better where 79.5 %
of toilets belong to sanitary system.
•The rests are Katcha, field-going and others (Table below. This is
here to mention that the improved sanitary system of Patuakhali is
related with better literacy situation of the area.
Table : Latrine types (%)
Latrine Types Patuakhali Sirajganj Sunamganj Saturia
1. Internal safety tank 21.0 2 10 12
1. External safety tank 58.5 54 58 57
1. Katcha latrine 12.0 40 30 31
1. Field 1.0 1 1 0
1. Others 7.5 3 1 0
The type of attachment with the houses of the study areas are given
in Table below.
More than 70% people are the owners of houses at Patuakhali,
Sirajganj, Sunamganj and Saturia having the maximum of 98% at
Saturia.
About 6-13% people live in rented houses at Patuakhali, Sirajganj
and Sunamganj.
Type of attachment with the
house
Patuakhali Sirajganj Sunamganj Saturia
Owner 81.0 71.0 80.0 98
Rented 13.0 6.0 10.0 2
Occupied 5.5 12.0 6.0 0
Others 0.5
11.0 4.0 0
Table : Ownership of the houses currently living
Income Patuakhali Sirajganj Sunamganj Saturia
Average 8988 4410 8237 19725
Minimum 900 1000 1000 6000
Maximum 50000 16000 50000 45000
Table : Average and minimum and maximum monthly
Income (in Taka)
•The average monthly income is low in the surveyed areas
of Sirajganj which is Tk. 4410 with minimum of Tk. 1000 and
maximum of Tk. 16000.
•The status of income over the surveyed areas of Patuakhali
and Sunamganj is around Tk. 8000-9000 per months with
minimum of around Tk. 1000 and maximum of around Tk.
50000.
•The study areas of Saturia indicated better economic
situation with an average of around Tk. 20000 per month
with minimum of Tk. 6000 and maximum of Tk. 45000.
•Considering the results of the distribution of income generating
professions (Table below), it is seen that about 81% of the
respondents of Saturia are engaged in self dependent profession.
•Patuakhali possesses the next position having 50% of the
respondents in this profession.
• Sunamganj and Saturia are relatively rich in the population of land
owners with around 14 and 10 % of the respondents respectively
compared to the other study areas.
•The percentage of regular and irregular day laborers is high in the
study areas of Sunamganj and Sirajganj, which is around 50%. For
Patuakhali this is around 35% but in Saturia this is negligible.
Profession Patuakhali Sirajganj Sunamganj Saturia
1. Income from landed properties 4.4 1 13.9 10.2
1. Self dependent profession 50.0 29 28.7 80.7
1. Regular Job 2.8 14 4.1 9.1
1. Irregular job 5.0 2 3.3 0
1. Regular day labourer 14.4 44 41.8 1.0
1. Irregular labourer 21.7 7 7.4 0
1. Others 1.7 3 0.8 0
Table: Professional sources of income
Gender Patuakhali Sirajganj Sunamganj Saturia
Male 1.7 1.5 2.0 1.6
Female 1.2 0.1 0.2 0.6
Total 2.9 1.6 2.2 2.1
Table : Average number of working males and females
•Average number of working males and females per household is 1.7
and 1.2 respectively in the study area at Patuakhali totaling 2.9.
•Male number is higher and female number is very low (around 0.1-0.6)
in all other study areas.
•The comparatively higher values of working female in Patuakhali are
supported by higher literacy rate in that locality compared to other
study areas.
Disasters of the locality, their severity and impacts
•The local severe storms come at the top of the list of the prevailing
disasters as per the opinion of the respondents; around 90-99% of the
respondents gave verdict for the local severe storms.
•The flash floods associated with severe thunderstorms are most
prevailing phenomena over the Sunamganj area and also over
Sirajganj and Patuakhali but to a lesser degree of prevalence (77.0 and
60.5% respectively in the latter two study areas).
•The study area in Saturia does not have the problem of flash flood but
drought is indicated as prevailing disaster by 80% of the respondents.
Disaster Patuakhali Sirajganj Sunamganj Saturi
a
Flash Floods 60.5 77.0 99.3 0
Local severe storms / thunder storms /
tornadoes
90.0 90.0 99.3 94
Drought 40.4 0.0 30.0 80
Fire 20.1 23.0 21.2 8
Table : Percent response on the prevailing disasters over the study
areas
**Understanding of environment and climate change
While asked about their opinion on the climate change,
the respondents affirmed that
• more than 90% of them are aware of climate change and
they understand by climate change as the increase of
temperature, increase of the frequency of natural
disasters and irregular pattern of weather.
• They are aware of the impacts of climate change and
mitigation options.
•They opined that information gathering, exchange of
scientific views, participation in the international forum to
focus the problems to world community and conduct
research to mitigate the impacts of climate change are the
required actions that should be given priority importance.
Coping Options Patuakhali Sirajganj Sunamganj Saturia
Migration to shelter 99.5 17.0 69.8 2.0
Loan from money lenders 88.6 32.0 56.1 2.0
Loan from friends 90.4 21.0 30.9 2.0
Selling Valuables 90.4 17.0 54.1 8.0
Govt. relief 77.3 23.7 17.3 2.0
Table : Means of short-term coping of the disasters (% of response)
**Coping mechanism
For Patuakhali all the coping means as listed in the table are
applicable. These are mainly adopted during the tropical cyclones with
high storm surges. This is to mention that the tropical cyclones are
seldom associated with tornado cells causing severe impacts.
For Sunamganj, the coping option of migration to shelter is 70%
followed by loan from lenders and friends 56% and 31% respectively
and selling valuables 54.1%.
Sirajganj and Saturia are not affected much with severe disasters.
Moreover, Saturia is a place with better economic condition; this
provides additional strength to the people of the locality to cope with
the disasters. As a result, the selected mitigation options are not
suitable for Saturia.
Table : People’s perception on the warning system and need for
better forecasts of local storms (aggregated response for all the study
areas)
People’s perception on weather forecast % response (positive)
Whether the forecasts are correct? 94
Do the respondents follow forecast 95
Do warning comes true? 90
Better predictions needed 100
Require more plantation, more shelters, resilient
houses, increased awareness for better adaptation
100
**People’s perception on the warning system
**A few options for saving the crops from impacts of flash floods due
to heavy rain from thunderstorms
Sl. No. Options for saving mature Boro rice Respondents’
affirmative opinion
(%)
1 Reduce growing period and harvest the crop
before the flash flood
97
2 Early plantation over vulnerable areas and
then the crop will be harvested early to
escape the flash flood
96
3 Protection of the rice areas from floods by
dams and embankments
95
•Since, the Boro rice crops are at risk due to the activities of severe
local storms through wind action, hails and heavy rainfall resulting
flash floods.
•The flash floods are particularly most hazardous to the boro crops.
From this aspect, a number of adaptation options as mentioned in
Table below were selected for people’s comments.
•The option no. 1 depicts that in order to harvest the
crops before flash flood which generally occurs in May, it
will be proper to develop crop variety with relatively
smaller growth period enabling to mature in shorter time
span than usual. This will enable the farmer to harvest the
crop in April before the occurrence of flash floods.
•The option no. 2 depicts that if the plantations are done
in December and early January then the crops will mature
in early April may be harvested before the flash flood
season begins.
• The 3rd option suggests building of protection dams to
resist the flood water from affecting the crops. The people
have appreciated all the 3 options and more than 90% of
the respondents gave verdict in its support.
Recommendations
•If lightning is seen on board the launch, the pilot should
anchor the launch immediately for 1-2 hours.
• “Nowcasting of weather forecast regarding
thunderstorms at an interval of 1 hour or less can save a
lot of lives every year”.
•Radar imageries at the time of occurrence can show the
movement of thunderstorms /squalls from which the areas
likely to be affected can be ascertained.
• If the farmers see lightning/hear thunder, they are
requested to take shelter with their cows for 1-2 hours
until the storm passes away and not to stay in the fields.
Conclusions
•The monthly and seasonal mean maximum temperature
have decreasing trends at most places having maximum
decreasing trends at Bogra/Rangpur during 1961-2008.
• Trends of monthly and seasonal mean maximum
temperatures are increasing at most of the stations, and
the trends are all positive in May during the pre-monsoon
season of 1980-2008.
•The country-averaged seasonal maximum temperature
over Bangladesh during the pre-monsoon season has
increasing trend at the rate 1.87C/100 years during 1980-
2008.
•The monthly and seasonal trends of thunderstorm
frequency are mainly negative in Bangladesh during the
pre-monsoon season.
•The country-averaged seasonal thunderstorm frequency
during the pre-monsoon season has also decreasing
trends in Bangladesh at a rate of -1.196/10years.
•The maximum decreasing trends lie over the
northeastern part of Bangladesh during the pre-monsoon
season.
•The monthly and seasonal mean maximum temperatures
are negatively correlated with the monthly and seasonal
frequency of thunderstorms and most of the correlation
coefficients are statistically significant.
•Flash floods and severe local storms are the most
common disasters of the locality which impact severely
on the livelihood and the environment, agricultural crop
production especially of that of boro rice and other
resources.
•The people have been found to be aware of the warning
system and they regularly follow the weather predictions.
•According to the opinion of the people, the predictions of
the severe local storms are more or less correct except
the exact areas of occurrence
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