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CLIMATE RESEARCH AND SERVICES METEOROLOGICAL DEPARTMENT MINISTRY OF EARTH SCIENCES

Observed Rainfall Variability and Changes over State

Met Monograph No.: ESSO/IMD/HS/Rainfall Variability/25(2020)/49

Pulak Guhathakurta, Sakharam Sanap, Preetha Menon Ashwini Kumar Prasad, S T Sable and S C Advani

GOVERNMENT OF INDIA MINISTRY OF EARTH SCIENCES INDIA METEOROLOGICAL DEPARTMENT

Met Monograph No.: ESSO/IMD/HS/Rainfall Variability/25(2020)/49

Observed Rainfall Variability and Changes Over Telangana State

Pulak Guhathakurta, Sakharam Sanap, Preetha Menon, Ashwini Kumar Prasad, S.T. Sable and S C Advani

INDIA METEOROLOGICAL DEPARTMENT PUNE - 411005

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DOCUMENT AND DATA CONTROL SHEET

1 Document Title Observed Rainfall Variability and Changes Over Telangana State 2 Issue No. ESSO/IMD/HS/Rainfall Variability/25(2020)/49 3 Issue Date January 2020 4 Security Classification Unclassified 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 English 12 Authors Pulak Guhathakurta, Sakharam Sanap, Preetha Menon, Ashwini Kumar Prasad, S.T. Sable and S C Advani 13 Originating Division/ Climate Research Division/ Climate Application & Group User Interface Group/ Hydrometeorology 14 Reviewing and Director General of Meteorology, India Approving Authority Meteorological Department, New 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 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

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1. Introduction

Telangana state is the 29th state of India and came into existence on 2 June 2014 and it is bifurcated from . It is located between 15°55’ N to 19°55’ N latitude and 77°10’ E to 81°50’ E longitude in south and it shares its boundaries with Andhra Pradesh to the south and southeast, and Orissa to the northeast, to the north and west and to the west. The state of Telangana has geographical area about 114,840 sq km. Telangana is situated on the , in the central stretch of the eastern seaboard of the Indian peninsula. The average elevation of the plateau area is about 500 meter, higher in west and southwest and sloping downward toward the east and northeast, where it meets the discontinuous line of the Eastern ranges. Western part of the state is mostly hilly with an altitude generally varies from 300m to 600m and some part is having an altitude of 600 m to 1361 m. Peak height of the state is 1361 m which is observed in the extreme eastern part of the state. Fig.1 gives the location of the of the state.

Fig. 1 wise map of the Telangana state

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 district rainfall trends and variability of Telangana state. In the present report all the analysis of observed rainfall patterns, trends and variability have been done based on recent

3 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 the analysis of trend variability and mean rainfall patterns. From the daily rainfall data monthly rainfall series of each stations are computed. 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 districts within 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:

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

3. State rainfall mean and variability and trend

Mean rainfall (mm) and CV for the monsoon months (June, July, August and September), southwest monsoon season and annual for the period 1989-2018 is shown in Table 1. Highest contribution to the SW monsoon rainfall is coming from the month of August (30.5 %) followed by July (29.7%), September (21.2 %) and June (18.6 %) respectively. Telangana state receives 78.8 % of the annual rainfall merely from SW monsoon season. The CV of monsoon and annual rainfall for Telangana state is 22.5 % and 20.5 % respectively.

June July August September JJAS Annual Mean 132.7 211.5 217.6 151.4 713.2 905.1 CV 41.3 44.8 34.8 43.2 22.5 20.5

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

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Fig. 2 and 3 depicts the time series of rainfall (mm) for the months of June, July, August, September, southwest monsoon season and annual respectively. The trend lines are also displayed for each of the series. Analysis indicates that neither monthly rainfall nor seasonal or annual rainfall show any significant increasing/decreasing trend. Monthly rainfall for the months of June, July and August show the decreasing trend while September show slight upward trend, however it is statistically insignificant. Both seasonal and annual rainfall show decreasing trend (statistically insignificant).

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

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

Highest rainfall occurred in last 30 (1989-2018) years for each monsoon month, SW monsoon season and annual is shown in Table 2.

Month/Season/Annual Highest rainfall received (mm) Year June 234.8 2000 July 492.6 2013 August 426.5 1990 September 248.7 2007 JJAS 1133.1 2013 Annual 1384.7 2013 Table 2. Highest rainfall records for SW monsoon months, SW monsoon season and annual.

4. District rainfall mean, variability and trend 4.1 Mean and coefficient of variation

Rainfall statistics for the districts of Telangana for SW monsoon months, SW monsoon season and annual is presented in Table 3. The spatial pattern of rainfall statistics is depicted in Figure 4 and 5. Districts from Northern and Eastern of the Telangana receives highest amount of rainfall in June, July, August, September and SW monsoon season. It is in the range of 189-216 mm for June, 283-398 mm for July, 290-401 mm for August, 141-179 mm in September, 850-1151 mm for SW monsoon season and 863- 1400mm for annual respectively. Mean spatial pattern of rainfall also indicate that northern districts receive highest rainfall in June and eastern region records highest amount of rainfall for other timescales. Central

6 and southern region of the Telangana receives less rainfall compare to northern and eastern region of the state. It ranges from 80-135 mm in June, 111-226 mm in July, 124-235 mm in August, 83-122 mm in September, 398-700 mm in SW monsoon season and 530-863 mm in annual.

JUNE JULY AUGUST SEPTEMBER MONSOON ANNUAL DISTRICT MEA N CV MEAN CV MEAN CV MEAN CV MEAN CV MEAN CV 193.1 122 274.9 42 304.5 89 152.4 145 924.9 44 1090.7 54 105.9 52 167.3 56 204.0 48 134.3 58 611.5 25 827.2 60 134.7 161 221.6 46 213.6 45 148.4 62 718.3 51 881.9 59 159.5 142 281.3 95 286.6 89 179.2 132 906.6 46 1143.2 42 90.8 228 128.0 54 133.7 159 129.3 166 481.7 63 662.1 98 111.1 258 175.7 134 192.5 121 132.2 170 611.5 71 780.2 62 89.6 232 127.6 173 146.1 151 141.4 160 504.8 61 703.3 106 NIZAMABAD 160.2 143 251.1 46 263.4 52 141.2 163 815.9 50 987.2 46 RANGAREDDY 108.6 47 151.6 51 178.1 43 149.3 45 587.5 25 786.8 118 148.2 149 252.5 43 237.9 103 161.6 56 800.2 61 992.3 87 B. 160.0 295 325.0 166 296.2 180 158.1 297 939.4 85 1179.0 76 193.4 255 265.1 194 272.7 194 134.9 342 866.1 89 1099.0 72 132.8 347 200.5 246 178.7 269 133.2 345 645.2 106 851.2 111 J. 188.4 257 397.7 144 400.7 146 164.1 290 1150.9 77 1358.6 71 JOGULAMBA 80.2 548 110.7 407 124.3 407 83.3 526 398.5 157 532.1 150 166.0 287 241.0 211 310.5 175 101.7 440 819.2 93 1041.7 83 196.8 251 327.4 169 326.9 169 159.3 297 1010.5 87 1225.8 69 156.9 301 268.3 193 283.0 185 170.3 282 878.4 88 1162.7 88 215.8 271 316.9 187 326.9 186 122.7 460 982.2 102 1129.9 95 M. 101.5 440 167.6 284 196.8 249 104.4 428 570.3 113 758.3 113 NAGARKURNOOL 87.4 506 132.1 348 131.1 351 115.1 395 465.8 130 650.1 127 212.8 233 289.0 182 294.0 187 135.4 343 931.2 87 1096.7 93 PEDDAPALLE 206.9 240 293.5 179 297.0 182 149.3 315 946.8 85 1119.1 78 RAJANNA 149.3 319 195.6 249 210.6 235 107.8 417 663.3 106 878.2 78 151.4 367 201.4 292 206.4 294 99.3 568 658.5 136 860.3 115 117.5 386 181.5 265 194.1 251 95.9 463 589.0 111 778.5 116 102.7 437 183.2 291 179.3 296 154.1 338 619.2 119 839.6 84 118.7 383 189.9 256 189.1 258 131.8 348 629.4 107 829.1 121 WANAPARTHI 118.4 485 174.9 330 154.8 366 109.3 525 557.3 149 739.9 69 WARANGAL URBAN 131.2 352 221.4 227 169.8 281 85.8 569 608.1 122 775.0 122 Y.BHUVANAGIRI 111.2 449 140.1 334 123.9 369 147.3 318 522.5 132 740.7 115

Table3. Rainfall statistics for the districts of Telangana for the four monsoon months, southwest monsoon season and annual

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Fig.4 Mean rainfall pattern over districts of Telangana

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Fig.5 Coefficient of Variation (%) over districts of Telangana

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4.2 Trend in district rainfall

District wise spatial rainfall trend with statistical significance at 95 % level for Telangana state is depicted in Figure 6. Statistically non-significant increasing trend is observed for the and rest most of district shows significant decreasing trend for the month of June rainfall. For the month of July and August, districts Adilabad, Mancherial, Nizamabad, Karimnagar, Warangal rural, Medchal Malkajgiri, Hydrabad, Ranga Reddy, Nalgonda, Khammam indicate non-significant decreasing trend in rainfall while rest of the districts indicate significant decreasing trend. District Karimangar show significant increasing trend in rainfall while Hyderabad, Ranga Reddy and indicate non- significantly increasing trend in rainfall for the month of September however Adilabad, Mancherial, Nizamabad, Medchal Malkajgiri, Nalgonda, Khammam shows non-significant decreasing trend and rest of the districts shows sihnificantly decreasing trend in rainfall. For the SW monsoon season, districts, Adilabad, Mancherial, Nizamabad, Karimnagar, Warangal Rural, Ranga Reddy, Nalgonda and Khammam indicate the non-significantly decreasing trend while rest of districts shows significantly decreasing trend. In case of annual rainfall, districts Mancherial, Nalgonda shows non-significant increasing trend while districts Ranga Reddy, shows significantly increasing trend. Districts in central part, northern and southern tip shows non-significantly decreasing trend while rest of shows significantly decreasing trend in rainfall. .

a b

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c d

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

5. Analysis of Average frequencies for rainfall events of different intensities

5.1 Average frequency of Rainy days

Spatial map of the mean frequency of rainy days for the SW monsoon months, SW monsoon season and annual is presented in figure 7 to 12. North south dipole pattern in average frequency of rainy days is seen from the analysis with high frequency of rainy days in northern region and low frequency of rainy days in southern region of the state. Average frequency of rainy days for northern (southern) region of the Telangana is in the range of 5-6.58 (6.59-8) days for June, 7-9.79

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(10-13) days for July, 8-9.8 (10-13) days for August, 6-7.35 (7.35-9) days for September, 27-32 (32.2-40) days for SW monsoon season and 36-42 (42.04-51) days for the annual. Extreme northern districts of the state (Adilabad, Kumuram, Bheem, Nirmal, Mancherial) records more number of rainy days as compare extreme southern (Mahabubnagar, Wanaparthy, JogulambaGadwal, Nagarkarnool, Nalagonda) region across all timescale. Districts from extreme western region (Jayashankar Bhulapally, Bhadradri Kothagudam) also indicate highest frequency of rainy days.

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

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Fig. 11 Average frequency of rainy days: JJAS Fig. 12 Average frequency of rainy days: Annual 5.2 Average frequency of Heavy rainfall days

Average frequency of heavy rainfall days for SW monsoon months, SW monsoon season and annual is presented in figure 13-18. Average pattern of the frequency of the heavy rainfall days is similar to the average pattern of rainy days. High frequency of heavy rainfall days is found to be more for northern districts (Adilabad, Kumuram, Bheem, Nirmal, Mancherial) of the state as compare to districts from the southern part (Mahbubnagar, Wanaparthy, , Nagarkarnool, Nalagonda) for all timescale. However, frequency of heavy rainfall days for the month of September are more for the eastern region (Mancherial, Jayashankar Bhupalpally, Bhadradri Kothagudam) of the state as compare to rest of the districts. Average frequency of heavy rainfall days for northern (southern) region of the Telangana is in the range of 0.25-1 (0.1-0.20) days for June, 0.44-1 (0.1-0.4) days for July, 0.46-1 (0.1-0.4) days for August, and 0.28-0.33 (0.1-0.3) days for September, 1.44-3 (0.8-1.40) days for SW monsoon season and 1.75-3 (1- 1.7) days for the annual.

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

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

Fig. 17 Average frequency of heavy rainfall days: JJAS Fig. 18 Average frequency of heavy rainfall days: Annual 5.3 Average frequency of Dry days

Dipole pattern is also seen for the average frequency of dry days with northern districts showing the lower frequency of dry days as compare to southern part of the state (See figure 19-24). For annual, the northern and eastern region indicate a greater number of dry days compare to south western region of the state. Average frequency of dry days for southern (northern) region of the Telangana is in the range of 22.47-24 (20-21.73) days for June,19-22 (15-17.69) days for July, 18.87-22(15-17.69) days for August, 21.15-23 (19-20.57) days for September, 79.13-87 (67-75.3) days for SW monsoon season. Districts from the western region indicate higher frequency of dry days (254.5-263 days) and comparatively a smaller number of dry days (220-237.6) are observed over south eastern districts of the Telangana state.

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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

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

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6. Trends in the frequencies of different rainfall events

6.1 Trend in frequency of Rainy days

Trend in rainy days for June, July, August, September, SW monsoon and annual is computed (Fig. 25-30). For the month of June one station from show upwards trend in rainy days. Two stations each from Nizamabad, Kamareddy Medak and one station each from and Warangal rural indicate the downward trend in rainy days for the month of June. Rest of the district show insignificant trend in rainy days for the month of June. One station each from Adilabad, Nirmal, Karimnagar, Medak, Jayashankar. Bhupalpally and Khammam indicating upward trend while one station each from Mahabubnagar, Wanaparthy and Nagarkarnool show down ward trend in rainy days for the month of July. Districts from southern districts of the Telangana state (Viakarabad, Mahabubnagar and Nagarkarnool) and one district each from central and northern Telangana (Yadari, Bhuvanagiri, Warangal rural, Karimnagar and Adilabad) show upward trend in rainy days for the month of August. Most of the districts from north- west (west central) Telangana shows the upward trend in rainy days for the month of September. Downward trend in rainy days for the district Nalgonda is seen from the analysis for the month of September. It is observed that, most of the districts indicate increasing trend in rainy days for SW monsoon season as well as annual time scales.

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

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

Fig. 29 Trend in frequency of rainy days: JJAS Fig. 30 Trend in frequency of rainy days: Annual 6.2 Trend in frequency of Heavy rainfall days Trend in frequency of heavy rainfall days for SW monsoon months, SW monsoon season and annual is depicted in figure 31-36. Most of the districts indicating the significant decreasing trend in heavy rainfall days for the month of June and July. Adilabad, Jagtial, Medak, Sangareddy, Medchial, Nalagonda, Jangaon show significant upward trend in heavy rainfall days while Mahbubnagar and Wanaparthy districts indicate downward trend in heavy rainfall days for the month of August. For the month of September north south pattern in frequency of heavy rainfall days have been observed with northern districts showing upward trend and southern districts indicating the downward trend respectively. Most of the districts indicate the significant decreasing trend in heavy rainfall days for SW monsoon season as well as annual timescale.

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

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

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

6.3 Trend in frequency of Dry days

The statistically significant trends in frequency of dry days at 95% of significant level is computed for the rain gauge stations of Telangana state for June, July, August, September, SW monsoon and annual (Figure 37-42). Upward trend in frequency of dry days is observed for most of the district for the month of June. North South pattern in trend of frequency of dry days is seen for the month of July with northern districts indicating downward trend and southward districts showing upward trend forth month of July. No specific pattern is seen for the month of August. However, some districts from south-central and north- eastern part indicates downward trend. Moat of the districts from the western region of the state show downward trend in frequency of dry days however, districts, Wanaparthy, Nalgonda, Suryapet, Bhadradri, Kothagudam and Adilabad show increasing trend in frequency of dry days for September. Upward trend in frequency of dry days is seen for south/south-eastern districts of the state and upward trend is observed for the central and northern districts of the state for the SW monsoon season. Significant increasing trend in frequency of dry for the annual time scale is seen for the Telangana state.

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

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7. Conclusions

Using 30 years (1989-2018) of rainfall data, here we investigated the rainfall pattern, variability and change for Telangana state. We considered, June, July, August and September, SW Monsoon season and annual time scales for the analysis. The district spatial patterns are considered to study rainfall total and stations are considered to study rainfall intensities. This study brought out many significant features of the rainfall pattern which can be utilized for the water and agricultural management. Some of the important findings are summarized below:

Highest contribution to the SW monsoon rainfall for Telangana state is coming from the month of August (31.35 %) followed by July (30.6%), September (18.4 %) and June (19.6 %) respectively. Telangana state receives 78.65 % of the annual rainfall merely from SW monsoon season.

Analysis indicates that monthly rainfall doesn’t show any significant increasing/decreasing trend. while seasonal or annual rainfall show non-significant decreasing trend.

Districts from Northern and Eastern region of the Telangana receives highest amount of rainfall as compare to southern part of state in June, July, August, September and SW monsoon season.

Statistically significant decreasing trend in rainfall is observed for the districts mostly spanning central and southern parts for SW monsoon season while only few districts Viz. Ranga Readdy, Wanaparthy districts indicate significantly increasing and Nalgoanda, Mancherial districts shows non-significant increasing trend in rainfall for annual time scale.

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Extreme northern districts of the state (Adilabad, Kumuram, Bheem, Nirmal, Mancherial) records more number of rainy days as compare extreme southern (Mahbubnagar, Wanaparthy, Jogulamba, Gadwal, Nagarkarnool, Nalagonda) region across all timescale. Average frequency of heavy rainfall days for northern (southern) region of the Telangana is in the range of 1.44-3 (0.8-1.40) days for SW monsoon season and 1.75-3 (1- 1.7) days for the annual.

Average frequency of dry days for southern (northern) region of the Telangana is in the range of 79.13-87 (67-75.3) days for SW monsoon season.

Majority of the districts indicate significant increasing (decreasing) trend in rainy (heavy rainfall) days for SW monsoon season as well as annual time scales.

Upward trend in frequency of dry days is seen for south/south-eastern districts of the state and upward trend is observed for the central and northern districts of the state for the SW monsoon season. Significant increasing trend in frequency of dry for the annual time scale is seen for the Telangana state.

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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.

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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