sign in sign up
<<
Home , Atharamura, Khowai, Khowai district, Sipahijala district, South Tripura district, Unakoti

CLIMATE RESEARCH AND SERVICES METEOROLOGICAL DEPARTMENT MINISTRY OF EARTH SCIENCES PUNE

Observed Rainfall Variability and Changes over State

Met Monograph No.: ESSO/IMD/HS/Rainfall Variability/26(2020)/50

Pulak Guhathakurta, Sudeep Kumar B L , Preetha Menon, Ashwini Kumar Prasad, Neha Sangwan and S C Advani

GOVERNMENT OF INDIA MINISTRY OF EARTH SCIENCES INDIA METEOROLOGICAL DEPARTMENT

Met Monograph No.: ESSO/IMD/HS/Rainfall Variability/26(2020)/50

Observed Rainfall Variability and Changes Over Tripura State

Pulak Guhathakurta, Sudeep kumar B L, Preetha Menon, Ashwini Kumar Prasad, Neha Sangwan and S C Advani

INDIA METEOROLOGICAL DEPARTMENT PUNE - 411005

1

DOCUMENT AND DATA CONTROL SHEET

1 Document Title Observed Rainfall Variability and Changes Over Tripura State 2 Issue No. ESSO/IMD/HS/Rainfall Variability/26(2020)/50 3 Issue Date January 2020 4 Security Unclassified Classification 5 Control Status Uncontrolled 6 Document Type Scientific Publication 7 No. of Pages 23 8 No. of Figures 42 9 No. of References 3 10 Distribution Unrestricted 11 Language English 12 Authors Pulak Guhathakurta, Sudeep kumar B L, Preetha Menon, Ashwini Kumar Prasad, Neha Sangwan and S C Advani 13 Originating Climate Research Division/ Climate Application & Division/ Group User Interface Group/ Hydrometeorology 14 Reviewing and Director General of Meteorology, India Approving Meteorological Department, New Delhi Authority 15 End users Central and State Ministries of Water resources, agriculture and civic bodies, Science and Technology, Disaster Management Agencies, Planning Commission of India 16 Abstract India is in the tropical monsoon zone and receives plenty of rainfall as most of the annual rainfall during the monsoon season every year. However, the rainfall is having high temporal and spatial variability and due to the impact of climate changes there are significant changes in the mean rainfall pattern and their variability as well as in the intensity and frequencies of extreme rainfall events. The report brings the result of the analysis based on the recent 30 years of data (1989-2018) on the mean spatial rainfall pattern as well as mean spatial pattern of different rainfall events, trends and variability as well as extreme rainfall events during the monsoon months and annual for the state. 17 Key Words Rainfall trend, variability, extreme events, dry days

2

1. Introduction

Tripura state is located in the northeastern region of India. The state lies approximately between latitude 220 56’N and 240 32’N and longitude 91009’E and 92010’E and covers an area of about 10492 Km2. It is bordered by on the north, west, south and southeast, by Assam and Mizoram on the northeast.

Tripura is a land locked state and its aerial distance to Bay of Bengal is about 100 km. Tripura has small hills and low lying land with a numerous deep rivers and valleys. The hills of the state run from north to south and parallel to one another till they disappear in the plains of Sylhet in Bangladesh. The principal hill ranges are the Baramura-Deotamura ranges, ranges, Langtari ranges, Sakhan ranges, and the Jampui hill ranges from the east. The highest peak of the state is known as Betling Shiv around 935 metres above mean sea level in the Jampui hill range. The hills are mostly of low elevation and are covered by thick forests.

Many studies available on the observed trends and variability of rainfall and also extreme rainfall events over India, but all the studies are based on past 100 years or more data and also the recent years are not included (Guhathakurta et al, 2015; Guhathakurta et al, 2011; Guhathakurta & Rajeevan, 2008 etc). Also, there are limited studies on rainfall trends and variability of West Bengal state. In the present report all the analysis of observed rainfall patterns, trends and variability have been done based on recent past 30 years (1989-2018) that will help to have idea of the recent changes for climate change adaptation and management by the state authorities.

2. Data and Methodology

Daily Rainfall data from 1989 to 2018 is considered for analysis of trend variability and mean rainfall patterns. From the daily rainfall data monthly rainfall series of each stations are computed and then monthly district rainfall series has been constructed by considering arithmetic average of all the station rainfall values within the district. The monthly rainfall series of the state has been computed by using area weighted rainfall values of all the within the state. Fig.1 gives the location of the districts of the state. The objective of the analysis is to:

1. Identify the spatial pattern of the mean rainfall

2. Understand district wise observed rainfall trend and variability in annual and SW monsoon season (June, July, august and September).

Daily station rainfall data is utilized for identification of the mean spatial patterns and rainfall intensity trends. From mean and standard deviation (SD), the coefficient of variation (CV) is calculated as follows:

3

Standard Deviation Coeffcient of variation (CV) = × 100 Mean

Fig. 1 Location of the districts of Tripura

3. State rainfall mean, variability and trend

Table 1 shows the mean rainfall (mm) and coefficient of variation of the state for the monsoon months, southwest monsoon season and annual during the period 1989-2018. It can be seen that the state gets highest rainfall (31% of south west monsoon rainfall) in June month followed by July (27% of the south west monsoon rainfall). August and September receive 23% and 19% of south west monsoon rainfall, respectively. About 60% of annual rainfall receives during the southwest monsoon season. The variability for monsoon and annual rainfall is about 19% each.

June July August September JJAS Annual Mean 436.0 385.4 330.9 270.3 1422.6 2380.4 CV 35.5 37.4 26.5 26.9 19.1 18.6

Table 1 Mean rainfall (mm) and coefficient of variation of the state for the monsoon months, southwest monsoon season and annual

Fig. 2 and 3 show the time series of rainfall in mm for the months of June, July, August, September and southwest monsoon season, annual respectively. The trend lines are also displayed for each of the

4

series. There is no significant trend in the rainfall for monthly, southwest monsoon season or annual series. Although there is an insignificant decreasing trend in the southwest monsoon season and annual rainfall. In southwest monsoon months, an insignificant decreasing trend in June, July and September rainfall and an insignificant increasing trend in the August rainfall is seen. In last 30 years, the highest rainfall of June, July, August and September is received in the year 2003 (819.4 mm), 1998 (724 mm), 1995 (554.7 mm) and 2004 (459.4 mm) respectively. Highest southwest monsoon rainfall (2088.7 mm) and annual rainfall (3485.7 mm) are received in 1993. Lowest rainfall of June, July, August and September received in 2005 (192.2 mm), 2000 (169.7 mm), 2003 (154.3 mm) and 1998 (159.8 mm) respectively. Lowest rainfall of southwest monsoon season and annual rainfall is received in 1994 (1062.3 mm) and 2006 (1764.5 mm) respectively.

Fig. 2 Time series of rainfall in mm for the months of June, July, August, September and trends

Fig. 3 Time series of rainfall in mm for the southwest monsoon season and annual trends

5

4. District rainfall mean, variability and trend 4.1 Mean and coefficient of variation Table 2 gives the rainfall statistics for the districts of Tripura for the four monsoon months, southwest monsoon season and annual, and Fig. 4-5 show the spatial pattern of these statistics. South Tripura receives the highest rainfall in the southwest monsoon season (1549.1 mm) and North Tripura receives the highest rainfall in the annual (2542.5 mm). Maximum amount of rainfall in June, July, August and September are received in Dhalai (466.7 mm), South Tripura (475.4 mm), South Tripura (364.2 mm) and North Tripura (305.4 mm) respectively. The lowest rainfall received in West Tripura in southwest monsoon (1260.9 mm) as well as annual (2103.3 mm). West Tripura receives the lowest rainfall in June (391.1 mm), August (275.6 mm) and September (237.7 mm) and Dhalai(352.4 mm) receives lowest rainfall in July. The districts exhibiting maximum and minimum variability of mean rainfall are Dhalai (51.6%) and North Tripura (34.8%) for June, Dhalai (56.3%) and South Tripura (39.9%) for July, Dhalai (47.8%) and North Tripura (30.4%) for August and West Tripura (40%) and North Tripura (29.2%) for September. Dhalaishows the maximum variability of rainfall during the southwest monsoon (30.7%) and annual (34.7%). South Tripura (20.8%) and North Tripura (19.1%) shows the minimum variability during the monsoon and annual respectively.

JUNE JULY AUGUST SEPTEMBER MONSOON ANNUAL DISTRICT MEAN CV MEAN CV MEAN CV MEAN CV MEAN CV MEAN CV NORTH TRIPURA 449.1 34.8 370.0 48.4 351.5 30.4 305.4 29.2 1476.0 22.3 2542.5 19.1 DHALAI 466.7 51.6 352.4 56.3 349.1 47.8 274.6 36.0 1442.8 30.7 2501.7 34.7 WEST TRIPURA 391.1 40.9 356.6 46.4 275.6 32.9 237.7 40.0 1260.9 24.4 2103.3 20.4 SOUTH TRIPURA 452.6 36.7 475.4 39.9 364.2 33.4 256.9 39.2 1549.1 20.8 2407.9 21.8 Table 2. Rainfall statistics for the districts of Tripura for the four monsoon months, southwest monsoon season and annual

a b

6

c d

e f Fig.4 Mean rainfall pattern over districts of Tripura for (a) June, (b) July, (c) August, (d) September, (e) southwest monsoon and (f) annual.

a b

7

c d

e f Fig.5 Coefficient of Variation (%) over districts of Tripura for (a) June, (b) July, (c) August, (d) September, (e) southwest monsoon and (f) annual.

4.2 Trend in district rainfall

Fig.6 shows the trends in district rainfall over Tripura. It can be seen that there is no significant trend in any districts for any of the southwest monsoon months or the southwest monsoon season. A significant decreasing trend is seen only in for annual. Although, there is an increasing trend in , North Tripura, , West Tripura and Sepahijala districts and a decreasing trend in Dhalai, Gomati and South Tripura districts in June, a decreasing trend in all districts in July, an increasing trend in North Tripura, Unakoti, Dhalai, Khowai, West Tripura andSepahijala districts and increasing trend in Gomati and South Tripura districts in August, a decreasing trend in North Tripura, Unakoti, Dhalai, Khowai, West Tripura and Sepahijala districts and an increasing trend in Gomati and South Tripura districts in September. But these trends are not significant. In southwest monsoon season and annual, there is a decreasing trend in all districts. But these trends are not significant except for Dhalai where there is a significant decreasing trend for annual.

8

a b

c d

e f Fig.6 Trends in district rainfall for (a) June, (b) July (c) August (d) September (e) JJAS and (f) annual

9

5. Analysis of Average frequencies for rainfall events of different intensities 5.1 Average frequency of Rainy days

The average frequency of rainy days in Tripura is calculated for June, July, August, September, southwest monsoon season and Annual and is depicted in Figure 7-12. In June, maximum number of rainy days lies in the range of 16-17 days in north parts of Dhalai, Unakoti and North Tripura districts and minimum number of rainy days lies in the range of 13-14 days in south parts of Dhalai and Khowai and some parts of West Tripura, Sipahijala, Gomati and South Tripura districts. In July, the maximum number of rainy days lies in the range of 17-19 days in north parts of Unakoti and North Tripura and minimum number of rainy days lies in the range of 15-16 days in the west parts of Tripura, mainly in West Tripura and Sipahijala and in some parts of Khowai, Gomati and South Tripura districts. In August, maximum number of rainy days lies in the range of 17-18 days in north parts of Dhalai, Unakoti and North Tripura districts and minimum number of rainy days lies in the range of 13-14 days in the west most parts of Tripura viz. some parts of Sipahijala and West Tripura districts. In September, maximum number of rainy days lies in the range of 13-15 days in north parts of Dhalai, Unakoti and North Tripura districts and minimum number of rainy days lies in the range of 10-11 days in the southwest part of Tripura viz. some parts of South Tripura, Sipahijala, Gomati and West Tripura districts.

In southwest monsoon, the maximum number of rainy days lies in the range of 62-65 days in north parts of Unakoti and North Tripura districts and minimum number of rainy days lies in the range of 48- 52 days in west parts of Tripura viz. some parts of Sipahijala and west parts of West Tripura, Gomati and South Tripura districts. In annual, maximum number of rainy days lies in the range of 98-104 days in north parts of Dhalai, Unakoti and North Tripura districts and minimum number of rainy days lies in the range of 75-81days in south parts of Dhalai, Khowai and West Tripura and some parts of Sipahijala, Gomati and South Tripura districts. In general, the number of rainy days is maximum over the northeast of Tripura and it decreases towards the southwest where it is minimum.

10

Fig. 7 Average frequency of rainy days: June Fig. 8 Average frequency of rainy days: July

Fig. 9 Average frequency of rainy days: August Fig. 10 Average frequency of rainy days: September

Fig. 11 Average frequency of rainy days: JJAS Fig. 12 Average frequency of rainy days: Annual

11

5.2 Average frequency of Heavy rainfall days The average frequency of Heavy rainfall days in Tripura is calculated for June, July, August, September, June to September and Annual and given in Figure 13-18. In June, the maximum number of heavy rainfall days lies in the range of 1.6-2 days in north parts of Dhalai and some parts of south Tripura districts and minimum number of heavy rainfall days lies in the range of 0.8-1.1 days in central parts of the state viz. some parts of Sipahijala, West Tripura, Gomati, Khowai, Dhalai and North Tripura districts. In July, the maximum number of heavy rainfall days lies in the range of 1.7-3 days in south parts of and minimum number of heavy rainfall days lies in the range of 0.7-1 days mainly in north parts of Khowai, Dhalai, Unakoti and North Tripura districts. In August, the maximum lies in the range 1.3-2 days in south parts of South Tripura and minimum lies in the range 0.6-0.8 days in north parts of Unakoti and North Tripura and west parts of Sipahijala and West Tripura and some parts of Gomati districts. In September the maximum lies in the range of 0.7-2 days in Unakoti, North Tripura, some parts of Dhalai, Gomati and south parts of South Tripura districts and minimum lies in the range of 0.4-0.5 days mainly in the west parts of West Tripura.

In southwest monsoon, the maximum lies in the range of 5.2-7 days in South Tripura and minimum lies in the range of 2-3.5 days in some parts of Gomati, Sipahijala and west Tripura and north parts of Unakoti and North Tripura districts. In annual, the maximum lies in the range of 7.4-9 days in South Tripura and north part of Dhalai and minimum lies in the range of 4-5.4 days in central parts of the state viz. some parts of West Tripura, Sipahijala, Gomati, Khowai, Dhalai and north Tripura districts. In general, southwest monsoon rainfall is maximum over the south most parts of the state and minimum over the west and northern most parts of the state, whereas the annual rainfall is maximum over south and some regions in the north parts of the state and minimum over central parts of the state.

Fig. 13 Average frequency of heavy rainfall Fig. 14 Average frequency of heavy rainfall days: June days: July

12

Fig. 15 Average frequency of heavy rainfall Fig. 16 Average frequency of heavy rainfall days: August days: September

Fig. 17 Average frequency of heavy rainfall Fig. 18 Average frequency of heavy rainfall days: JJAS days: Annual

5.3 Average frequency of Dry days

The average frequency of dry days of Tripura is calculated for June, July, August, September, southwest monsoon season and Annual as indicated in Figure 19-24. In June, the maximum number of dry days lies in the range of 13.3-15 days in some parts of Sipahijala, South Tripura, Gomati, Dhalai and Khowai districts and minimum number of dry days lies in the range of 9-10.7 days in north parts of West Tripura, Dhalai, Unakoti and North Tripura districts. In July, the maximum number of dry days lies in the range of 11.4-12 days in south parts of Dhalai, Gomati, South Tripura and Sipahijala districts and north parts of Dhalai and Khowai districts. While minimum number of dry days lies in the range of 8-

13

9.4 days in west parts of West Tripura and north parts of North Tripura and Unakoti districts and in some parts of Somati district. In August, maximum lies in the range of 12.9-14 days in some parts of Sipahijala and South Tripura districts and minimum lies in the range of 9-10.4 days in some part of Gomati and north parts of West Tripura, Unakati and North Tripura districts. In September, maximum lies in the range of 15.3-16 days in some parts of Sipahijala and South Tripura districts and minimum lies in the range of 12-13.1 days in west parts of Sipahijala and West Tripura and north parts of Unakati and North Tripura districts.

In the southwest monsoon season the maximum number of dry days lies in the range of 51.3-55 days in Sipahijala and South Tripura districts and minimum number of dry days lies in the range of 39- 42.1 days in west parts of Sipahijala, West Tripura, north parts of Unakati and North Tripura and some parts of Gomati districts. In annual, the maximum number of dry days lies in the range of 247.1-255 days in some parts of Sipahijala and South Tripura and minimum number of dry days lies in the range of 216- 224.1 days in some parts of Gomati, Sipahijala and West Tripura districts.

Fig. 19 Average frequency of dry days: June Fig. 20 Average frequency of dry days: July

Fig. 21 Average frequency of dry days: August Fig. 22 Average frequency of dry days: September 14

Fig. 23 Average frequency of dry days: JJAS Fig. 24 Average frequency of dry days: Annual

6 Trends in the frequencies of different rainfall events

6.1 Trend in frequency of Rainy days

The trend in frequency of rainy days is calculated for the rain gauge stations of Tripura for June, July, August, September, southwest monsoon and Annual and depicted in Figure 25-30. There is a significant decreasing trend in the station in South Tripura district in June, a significant decreasing trend in the stations of Dhalai and South Tripura in July, a significant decreasing trend in the stations of Dhalai and a significant increasing trend in the stations of Sipahijala in August, and a significant increasing trend in the stations of Dhalai and South Tripura in September. Other districts do not show any significant trend during the study period. In the southwest monsoon season, there is a significant decreasing trend in the frequency of rainy days in the stations of Dhalai and South Tripura and a significant increase in the stations of . In annual a significant decreasing trend is observed in the stations of North Tripura, Dhalai and South Tripura districts. It can be noted that in southwest monsoon, stations in two districts show significant decreasing trend in the number of rainy days whereas in annual, stations in three districts show significant decreasing trend in the number of rainy days.

15

Fig. 25 Trend in frequency of rainy days: June Fig. 26 Trend in frequency of rainy days: July

Fig. 27 Trend in frequency of rainy days: August Fig. 28 Trend in frequency of rainy days: September

Fig. 29 Trend in frequency of rainy days: JJAS Fig. 30 Trend in frequency of rainy days: Annual

16

6.2 Trend in frequency of Heavy rainfall days The Trend in frequency of Heavy rainfall days is calculated for Tripura for June, July, August, September, southwest monsoon season and Annual and depicted in Figure 31-36. In June, there is no significant trend in any of the districts. In July, there is a significant decreasing trend in the frequency of heavy rainfall days in the stations of Dhalai and Khowai districts. In August, there is a significant increasing trend in the stations of and in September there is a significant increasing trend in the frequency of heavy rainfall days in the stations of Gomati and a significant decreasing trend in the stations of . In southwest monsoon season, a significant decreasing trend is observed in the stations of South Tripura and Unakoti districts and in annual, a significant decreasing trend is observed in the stations of Unakoti, Dhalai, Sipahijala and South Tripura districts. It is noted that in the southwest monsoon season, stations in two districts show significant decreasing trends in the frequency of heavy rainfall days whereas in annual, stations in four districts show significant decreasing trends in the frequency of heavy rainfall days.

Fig.31 Trend in frequency of heavy rainfall days: Fig. 32 Trend in frequency of heavy rainfall days: June July

Fig. 33 Trend in frequency of heavy rainfall days: Fig. 34 Trend in frequency of heavy rainfall days: August September

17

Fig. 35 Trend in frequency of heavy rainfall days: Fig. 36 Trend in frequency of heavy rainfall days: JJAS Annual

6.3 Trend in frequency of Dry days

The Trend in frequency of dry days is calculated for Tripura for June, July, August, September, June to September and Annual and is given in Figure 37-42. It shows that in June, there is a significant increasing trend in the frequency of dry days in the stations of Gomati and South Tripura districts. There is a significant decreasing trend in frequency of dry days in the stations of Sipahijala district in July, a significant decreasing trend in the stations of Sipahijala district and significant increasing trend in the stations of Gomati and Unakoti districts in August and a significant increasing trend in the stations of North Tripura, South Tripura and Gomati districts in September months. In southwest monsoon season there is a significant decreasing trend in the stations of Sipahijala and significant increasing trend in the stations of South Tripura, North Tripura, Unakoti and Gomati districts. In annual, there is a significant increasing trend in the stations of South Tripura, North Tripura, Unakoti and West Tripura districts. It can be noted that in southwest monsoon season as well as annual, there is a significant increase in the number of dry days in the stations of four districts.

18

Fig. 37 Trend in frequency of dry days: June Fig. 38 Trend in frequency of dry days: July

Fig. 39 Trend in frequency of dry days: August Fig. 40 Trend in frequency of dry days: September

Fig. 41 Trend in frequency of dry days: JJAS Fig. 42 Trend in frequency of dry days: Annual

19

7. Conclusions

In the present study we have investigated the rainfall pattern, its variability and also changes based on recent 30 years data. In the analysis we have considered monsoon months, the southwest monsoon season and annual scale. The spatial scale has been considered from state to district for the study of mean rainfall, and stations are considered for the study of intensities of rainfall. The analysis brought many significant features of rainfall pattern and can be used for water agricultural managements. Some of the important results can be summarized as:

Tripura receives about 60% of its annual rainfall in the southwest monsoon season. The highest rainfall (31% of south west monsoon rainfall) is received in June month followed by July (27% of the south west monsoon rainfall).

The southwest monsoon season rainfall and the annual rainfall do not show any significant trends.

The highest mean southwest monsoon rainfall (1549.1 mm) is observed in South Tripura district and the lowest mean southwest monsoon rainfall (1260.9 mm) is observed in .

The highest mean annual rainfall (2542.5 mm) is observed in and the lowest mean southwest monsoon rainfall ((2103.3 mm) is observed in West Tripura district.

There is no significant trend in the southwest monsoon rainfall in any districts of Tripura. Although there is a significant decreasing trend in the annual rainfall in Dhalai district.

In the southwest monsoon season, the maximum frequency of rainy days (~ 62-65 days) observed in north parts of Unakoti and north Tripura districts and

20

minimum frequency of rainy days (~ 48-52 days) observed in west parts of Tripura viz. some parts of Sipahijala and west parts of West Tripura, Gomati and South Tripura districts. The annual average frequency of rainy days is maximum (~ 98-104 days) in north parts of Dhalai, Unakoti and North Tripura districts and minimum (~ 75-81days) in south parts of Dhalai, Khowai and West Tripura and some parts of Sipahijala, Gomati and South Tripura districts.

In southwest monsoon, the maximum frequency of heavy rainfall days (~ 5.2- 7 days) observed in South Tripura and minimum (~ 2-3.5 days) in some parts of Gomati, Sipahijala and west Tripura and north parts of Unakoti and North Tripura districts.

The annual average frequency of heavy rainfall days is maximum (~ 7.4-9 days) in South Tripura and north part of Dhalai and minimum (~ 4-5.4 days) observed in central parts of the state viz. some parts of West Tripura, Sipahijala, Gomati, Khowai, Dhalai and north Tripura districts.

In the southwest monsoon season the maximum number of dry days (~ 51.3- 55 days) in Sipahijala and South Tripura districts and minimum number of dry days (~ 39-42.1 days) in west parts of Sipahijala, West Tripura, north parts of Unakati and North Tripura and some parts of Gomati districts.

In annual, the maximum number of dry days (~ 247.1-255 days) observed in some parts of Sipahijala and South Tripura and minimum number of dry days (~ 216-224.1 days) in some parts of Gomati, Sipahijala and West Tripura districts.

There is a significant decreasing trend in the frequency of rainy days in the stations of Dhalai and SouthTripura and a significant increase in the stations of sipahijala district for the southwest monsoon season.

21

In annual, a significant decreasing trend in the frequency of rainy days is seen in the stations of North Tripura, Dhalai and South Tripura districts.

A significant decreasing trend in the frequency of heavy rainfall days is seen in the districts of South Tripura and Unakoti districts for southwest monsoon season.

In annual a significant decreasing trend in the frequency of heavy rainfall days is observed in the stations of Unakoti, Dhalai, Sipahijala and South Tripura districts.

In southwest monsoon season there is a significant decreasing trend in the frequency of dry days in the stations of Sipahijala and significant increasing trend in the stations of South Tripura, North Tripura, Unakoti and Gomati districts.

In annual, there is a significant increasing trend in the frequency of dry days in the stations of South Tripura, North Tripura, Unakoti and West Tripura districts.

22

Acknowledgement:

The authors acknowledge Secretary, MOES, DGM, India Meteorological Department and Head, Climate Research and Services for guidance, suggestions and encouragement to carry out the works. Acknowledge also to Hydrology section and National Data Centre of India Meteorological Department Pune for making availability of the data.

References:

1. Guhathakurta P, Rajeevan M, Sikka D R and Tyagi A, 2015 “Observed changes in southwest monsoon rainfall over India during 1901–2011”, Int. J. Climatol, 35, 1881-1898. 2. Guhathakurta P, Sreejith O P and Menon P A, 2011 “Impact of climate changes on extreme rainfall events and flood risk in India”, J. Earth System Science. 120, No. 3, 359-373. 3. Guhathakurta P and Rajeevan M, 2008 “Trends in rainfall pattern over India” International J. of Climatology, 28: 1453–1469.

23

The report brings out observed rainfall variability and trends over the state as an impact of climate change based on recent 30 years of data ( 1981 - 2018 )

Rainfall pattern of monsoon months, south west monsoon season and annual of the state and it’s districts as well as extreme rainfall event of different intensity of stations are analysed.

Observed Rainfall Variability and Changes over Andhra Pradesh State

PREPARED AND DESIGNED AT HYDROMETEOROLOGY SECTION CLIMATE APPLICATION AND USER INTERFACE GROUP CLIMATE RESEARCH AND SERVICES, PUNE