By Ahmad Hasan Nury Advisor: Prof. Dr. rer. nat. Manfred Koch, Kassel University

1

Investigation and Prediction of Time Series of Temperature and Rainfall Variation in North-Eastern

Region of Bangladesh

ByAhmad Hasan Nury

Advisor:Prof. Dr. rer. nat. Manfred Koch, Kassel University

Dr. Md. Jahir Bin Alam, SUST, Bangladesh

Department of Geohydraulics and Engineering Hydrology, University of Kassel

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Climate change is one of the biggest environmental threats to food production, water availability, forest biodiversity and livelihoods. It is widely believed that developing countries such as Bangladesh will be impacted more severely than developed countries (e.g. UK and USA).

According to F.HoVerhoog (1987) to estimate the impact of climatic change on the morphology of river basins, firstly estimation of the impact of climate change on precipitation and temperature variation analysis are necessary.

In this study, it is considered the region for the analysis where huge amount of rainfall occur in every year, which is Sylhet and Moulvibazar district. Every year there is great loss in rice production in this zone due to flood.

Introduction:

3

Scope of the study:

Time series graph

Statistical analysis:• Mean• Standard deviation• Mann-Kendall trend test

Rainfall frequency analysis

Short term prediction:• ARIMA (p d q) model

4

Study Area:

Sylhet division, the northeastern administrative division of Bangladesh, located at 24053’ latitude and 91052’ longitudes.

The climate of Sylhet division is tropical monsoon with a predominantly hot and humid summer and a relatively cold winter.

Change in global climate rise of sea level may alter the productions in this area.

Figure: Study Area

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Data Collection:

District Area (km2) Station ID TimeSylhet 3490.40 CL129

1981 to 2010(29 years)

CL 228Maulvibazar 2799.39 CL 104

CL126CL 229

District Area (km2) Type of data TimeSylhet 3490.40 Maximum

Temperature (0C) 1977 to 2011(34 years)

Minimum Temperature (0C)

Maulvibazar (Srimongal)

2799.39 Maximum Temperature (0C)Minimum Temperature (0C)

Table: Monthly Rainfall data (Source: Bangladesh Water Development Board)

Table: Monthly Temperature data (Source : Bangladesh Meteorological Department)

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Jan-77

Jul-79Jan

-82Jul-8

4Jan

-87Jul-8

9Jan

-92Jul-9

4Jan

-97Jul-9

9Jan

-02Jul-0

4Jan

-07Jul-0

90

1020304050

f(x) = 0.000122989082941342 x + 29.3652542128739

Month

Temperature (0C)

Jan-77

Jul-79Jan

-82Jul-8

4Jan

-87Jul-8

9Jan

-92Jul-9

4Jan

-97Jul-9

9Jan

-02Jul-0

4Jan

-07Jul-0

90

10

20

30

f(x) = 0.000136483085416826 x + 12.6501660488277

Month

Temperature (0C)

Figure 1: Variation of monthly maximum temperature of sylhet. Figure 2: Variation of monthly minimum temperature of sylhet.

Jan-77

Jul-79Jan

-82Jul-8

4Jan

-87Jul-8

9Jan

-92Jul-9

4Jan

-97Jul-9

9Jan

-02Jul-0

4Jan

-07Jul-0

90

1020304050

f(x) = 6.57309827028196E-05 x + 31.4083679683943

Month

Temperature (0C)

Figure 3: Variation of monthly maximum temperature of Moulvibazar.

Jan-77

Jul-79Jan

-82Jul-8

4Jan

-87Jul-8

9Jan

-92Jul-9

4Jan

-97Jul-9

9Jan

-02Jul-0

4Jan

-07Jul-0

905

1015202530

f(x) = 0.00013112446456781 x + 11.2574278667069

Month

Temperature (0C)

Figure 4: Variation of monthly minimum temperature of Moulvibazar.

Data Analysis:

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Jan-81

Mar-84

May-87

Jul-90Sep

-93

Nov-96Jan

-00

Mar-03

May-06

Jul-09

0500

10001500200025003000

f(x) = − 0.0171470680721389 x + 872.514662230674

Month

Rainfall (mm)

Jan-81

Mar-84

May-87

Jul-90Sep

-93

Nov-96Jan

-00

Mar-03

May-06

Jul-09

0

400

800

1200

1600

f(x) = 0.00334206828455125 x + 254.727585407721

Month

Rainfall (mm)

Figure 5: Variation of monthly Rainfall of sylhet station CL129. Figure 6: Variation of monthly Rainfall of sylhet station CL228.

Jan-81

Oct-83

Jul-86

Apr-89Jan

-92Oct-

94Jul-9

7

Apr-00Jan

-03Oct-

05Jul-0

80

400

800

1200

f(x) = − 0.00650528321579975 x + 500.433671088937

Month

Rainfall (mm)

Figure 7: Variation of monthly Rainfall of Moulvibazar station CL104.

Jan-81

Oct-83

Jul-86

Apr-89Jan

-92Oct-

94Jul-9

7

Apr-00Jan

-03Oct-

05Jul-0

80

400

800

1200

f(x) = − 0.00124939701280888 x + 260.326525346117

Month

Rainfall (mm)


Jan-81

May-83

Sep-85

Jan-88

May-90

Sep-92

Jan-95

May-97

Sep-99

Jan-02

May-04

Sep-06

Jan-09

0200400600800

10001200

f(x) = − 0.00313452195668542 x + 340.093583200547

Month

Rainfall (mm)


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Month Mean (0C) Standard deviation (0C)January 28.72 2.736February 31.14 2.713

March 34.56 2.709April 35.15 2.710May 35.51 2.711June 35.43 2.713July 35.49 2.715

August 35.69 2.719September 35.35 2.727

October 34.49 2.726November 32.41 2.727Decenber 29.34 2.727

Mean and Standard deviation of monthly maximum and minimum temperature:

Table 2: Mean temperature of monthly maximum temperature of sylhet station with their standard deviation for last 35 years (from 1977 to 2011)





Table 3: Mean temperature of monthly minimum temperature of sylhet station with their standard deviation for last 35 years (from 1977 to 2011)

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Table 4: Mean temperature of monthly maximum temperature of Moulvibazar station with their standard deviation for last 35 years (from 1977 to 2011)





Table 5: Mean temperature of monthly minimum temperature of Moulvibazar station with their standard deviation for last 35 years (from 1977 to 2011)

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Month Mean (mm) Standard deviation (mm)January 8.16 142.83February 29.79 142.92




Mean and Standard deviation of monthly rainfall:

Table 6: Mean rainfall of every month of Sylhet station CL129 with their standard deviation for last 30 years (from 1981 to 2010)

Month Mean (mm) Standard deviation (mm)January 14.45 161.88February 50.81 162.18




Table 7: Mean rainfall of every month of Sylhet station CL228 with their standard deviation for last 30 years (from 1981 to 2010)

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Month Mean (mm) Standard deviation (mm)January 6.99 118.48

February 37.34 118.55March 98.20 118.57April 243.57 118.55May 487.09 118.93June 469.64 118.84July 375.78 118.84



Table 9: Mean rainfall of every month of Moulvibazar station CL126 with their standard deviation for last 30 years (from 1981 to 2010)





Table 10: Mean rainfall of every month of Moulvibazar station CL229with their standard deviation for last 30 years (from 1981 to 2010)





Table 8: Mean rainfall of every month of Moulvibazar station CL104with their standard deviation for last 30 years (from 1981 to 2010)

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Station Test statistic p-ValueMonthly maximum

temperature of Sylhet0.135 0.0001

Monthly minimum temperature of Sylhet

0.120 0.0008

Monthly maximum temperature of Moulvibazar

0.116 0.001

Monthly minimum temperature of Moulvibazar

0.128 0.0005

Table 11: MK Statistics and their corresponding p-Value at 5 % significance level for Temperature

Station Test statistic p-ValueSylhet station CL129 -0.112 0.003Sylhet station CL228 0.075 0.022

Moulvibazar station CL104 -0.102 0.009Moulvibazar station CL126 -0.109 0.007Moulvibazar station CL229 -0.061 0.034

Table 12: MK Statistics and their corresponding p-Value at 5 % significance level for Rainfall

Mann-Kendall trend test:

• H0: There is no trend in the series• Ha: There is a trend in the series

•It can be used for nonnormal data such as seasonal data

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1 10 1000

50100150200250300350

f(x) = 70.3627605160942 ln(x) + 109.744750037028R² = 0.931969684220051

Return period, T (year)

Rainfall (mm)

Figure 10: Rainfall frequency curve for Sylhet CL129

1 10 1000

50100150200250300350400450500

f(x) = 75.1798180506854 ln(x) + 81.8075283460772R² = 0.809670163832024

Return period,T (year)

Rainfall (mm)

Figure 11: Rainfall frequency curve for Sylhet CL228

Annual maximum Rainfall frequency:

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1 10 1000

100

200

300

400

f(x) = 55.0033545312087 ln(x) + 119.743923424323R² = 0.904315417400048


Rainfall (mm)

Figure 12: Rainfall frequency curve for Moulvibazar CL104

1 10 1000

100200300400500600

f(x) = 82.0783685849745 ln(x) + 85.43263387097R² = 0.770072306417606


Rainfall (mm)


1 10 1000

100200300400500

f(x) = 72.7833989819325 ln(x) + 96.1937613790595R² = 0.864025587886463


Rainfall (mm)


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ARIMA (p,d,q) model:

•p order of autoregressive terms •d order of integrated term (non-seasonal differences; linear, quadratic, etc.) •q order of moving average (forecast errors)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Lag

Aut

ocor

rela

tion

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Lag

Parti

al a

utoc

orre

latio

nFigure 15: Autocorrelation plot of time series of monthly maximum temperature of Sylhet station.

Figure 16: Partial autocorrelation plot of time series of monthly maximum temperature of Sylhet station.

If seasonality in time series than ARIMA will be (p,d,q)(P,D,Q)12

The order of d and D have been selected as 1

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Figure 17: Autocorrelation plot of differenced ( d and D = 1) time series of monthly maximum temperature of Sylhet station.

Figure 18: Partial autocorrelation plot of differenced ( d and D = 1) time series of monthly maximum temperature of Sylhet station.

• The order of q and Q have been selected as 1

• The order of p and P have been selected as 1

17

Figure: ACF and PACF plot of residuals for the monthly maximum temperature of Sylhet Station.

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The selected ARIMA model of Monthly maximum temperature of Sylhet station is (1 1 1)(1 1 1)12

Coefficients Estimate Standard

error

Log likelihood

AIC AICc BIC

Ɵ1AR 0.123 0.042 1201.633 1211.303 1211.920 1228.486Ɵ1MA 0.972 0.076Ɵ1SAR 0.140 0.048Ɵ1SMA 0.896 0.069

Table 13: Parameter estimation for ARIMA (1 1 1) (1 1 1)12 model of monthly maximum temperature of sylhet

Data of temperature station for the period from 1977 to 2009 has been used for the calibration and from 2010 to 2011 has been used for the verification of the prediction.

Data of rainfall station for the period from 1981 to 2008 has been used for the calibration and from 2009 to 2010 has been used for the verification of the prediction.

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Jan-10

Apr-10Jul-1

0Oct-

10Jan

-11

Apr-11Jul-1

1Oct-

1105

10152025303540

Observed Max TemperaturePredicted Max Tempereture

Month

Temperature( 0C)

Figure 19: Comparison graph of Observed vs. Predicted values of the Monthly Maximum Temperature data of Sylhet Station.

Jan-10

Apr-10Jul-1

0Oct-

10Jan

-11

Apr-11Jul-1

1Oct-

1105

1015202530

Observed min. Temperaturepredicted min temperature

Month

Temperature( 0C)

PBIAS = 0.18%

Figure 20: Comparison graph of Observed vs. Predicted values of the Monthly Minimum Temperature data of Sylhet Station.

PBIAS = - 0.33%

Jan-10

Apr-10Jul-1

0Oct-

10Jan

-11

Apr-11Jul-1

1Oct-

1105

10152025303540

Observed Max TemperaturePredicted Max Tempereture

Month

Temperature( 0C)

PBIAS = 0.43%

Jan-10

Apr-10Jul-1

0Oct-

10Jan

-11

Apr-11Jul-1

1Oct-

110

5

10

15

20

25

30

Observed min. Temperaturepredicted min temperature

Month

Temperature( 0C)

Figure 21: Comparison graph of Observed vs. Predicted values of the Monthly Maximum Temperature data of Moulvibazar Station.

Figure 22: Comparison graph of Observed vs. Predicted values of the Monthly Minimum Temperature data of Moulvibazar Station.

PBIAS = - 0.53%

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Jan-09

May-09

Sep-09

Jan-10

May-10

Sep-10

0100200300400500600700

Observed rainfall (mm)predicted rainfall (mm)

Month

Rainfall(mm)

PBIAS = 4.5%

Figure 23: Comparison graph of Observed vs. Predicted values of the Rainfall data of Sylhet Station CL129.

Jan-09

Apr-09

Jul-09Oct-

09Jan

-10

Apr-10

Jul-10Oct-

100

200400600800

1000120014001600


Month

Rainfall(mm)

PBIAS = - 1.07%

Figure 24: Comparison graph of Observed vs. Predicted values of the Rainfall data of Sylhet Station CL228.

Jan-09

May-09

Sep-09

Jan-10

May-10

Sep-10

0100200300400500600


Month

Rainfall(mm)

Figure 25: Comparison graph of Observed vs. Predicted values of the Rainfall data of Moulvibazar Station CL104.

PBIAS = - 3.62%

Jan-09

Apr-09

Jul-09Oct-

09Jan

-10

Apr-10

Jul-10Oct-

100

100200300400500600700800900


Month

Rainfall(mm)


PBIAS = - 6.56%

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Jan-09

Apr-09

Jul-09Oct-

09Jan

-10

Apr-10

Jul-10Oct-

100

100

200

300

400

500

600


Month

Rainfall(mm)


PBIAS = - 1.89%

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Conclusion:

The upward trend line and positive Mann-Kendall test statistics of time series of temperature (for the period between 1977 and 2011) indicates that both the monthly maximum and minimum temperature is increasing with time.

The downward trend line and negative Mann-Kendall test statistics of time series of rainfall (for the period between 1981 and 2010) indicates that monthly rainfall is decreasing with time except Sylhet station CL228 (almost upward trend line).

Mean temperature with their standard deviation indicates the variation of temperature in year to year is not very high.

Mean rainfall with their standard deviation indicates the variation of rainfall in year to year is high.

A best fitted curve has been drawn between return period and annual maximum rainfall for each rainfall station to see the frequency of it.

The fitness of ARIMA model for the temperature and rainfall is well. The temperature and rainfall time series fitted to ARIMA model for the selected stations can be used for estimating missing temperature and rainfall values, forecasting and investigating short term temperature and rainfall change.

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References:

•F.HoVerhoog, the Influence of Climate Change and Climatic Variability on the Hydrologic Regime and Water Resources (Proceedings of the Vancouver Symposium, August 1987) IAHSPubl.no.168, 1987

•Ministry of Environment and Forests, Government of the People's Republic of Bangladesh(2008), Bangladesh Climate Change Strategy and Action Plan

•CEGIS & ADB (2009), Inception Report on Field Based Research on the Impacts of Climate Change on Bangladesh Rivers

•IWM (2005), Hydrological Impact Study of Tipaimukh Dam Project of India on Bangladesh

•UNFCC (2007), Climate Change: Impacts, Vulnerabilities and Adaptation In Developing Countries.

•Sarwar G. M. (2005), Impacts of Sea Level Rise on the Coastal Zone of Bangladesh, M.Sc. Thesis, Lund University International Masters Program in Environmental Science, Lund University, Sweden.

•Subramanya K, (2005), Engineering Hydrology, Tata McGraw-Hill Publishing Company Limited, New Delhi, India.

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Thank You

Documents

By Ahmad Hasan Nury Advisor: Prof. Dr. rer. nat. Manfred Koch, Kassel University