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/10(2020)/34

Pulak Guhathakurta, Nitin Narkhede, Preetha Menon, Ashwini Kumar Prasad and Neha Sangwan

GOVERNMENT OF INDIA MINISTRY OF EARTH SCIENCES INDIA METEOROLOGICAL DEPARTMENT

Met Monograph No.: ESSO/IMD/HS/Rainfall Variability/10(2020)/34

Observed Rainfall Variability and Changes Over Himachal Pradesh State

Pulak Guhathakurta, Nitin Narkhede, Preetha Menon, Ashwini Kumar Prasad and Neha Sangwan

INDIA METEOROLOGICAL DEPARTMENT PUNE - 411005

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DOCUMENT AND DATA CONTROL SHEET 1 Document Title Observed Rainfall Variability and Changes Over Himachal Pradesh State 2 Issue No. ESSO/IMD/HS/Rainfall Variability/10(2020)/34 3 Issue Date January 2020 4 Security Unclassified Classification 5 Control Status Uncontrolled 6 Document Type Scientific Publication 7 No. of Pages 27 8 No. of Figures 42 9 No. of References 3 10 Distribution Unrestricted 11 Language English 12 Authors Pulak Guhathakurta, Nitin Narkhede, Preetha Menon, Ashwini Kumar Prasad and Neha Sangwan 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 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

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1. Introduction

Himachal Pradesh is a state of the Indian Union at the extreme north of the Indian sub-continent roughly between latitudes 30o22′N and 33o12′N and longitudes 75º45′E and 79º04′E, occupying a region of scenic splendor in the western . Himachal means Snowy Mountain (hima, “Snow”, achal, “Mountain”). The state (Pradesh) taking its name from Himalayas. The state has an area of 55,673 sq.km and consists of 12 districts. The state is bounded by Jammu and on north, Nepal and on east, Uttaranchal on southeast, on south and Punjab on west and southwest. The climate of the state varies from place to place depending on the altitude. It varies from hot and sub-humid tropical (450-900 m) in the southern low tracts, warm and temperate (900-1800 m), cool and temperate (1900-2400 m) and cold alpine and glacial (2400-4800 m) in the northern and eastern high mountain ranges.

The state may be broadly divided into 3 geographical regions, viz. outer Himalayas, the lesser Himalayas and the greater Himalayas or the Alpines. The outer Himalayas includes the districts of Bilaspur, Hamirpur, Kangra, Una and the lower parts of Mandi, Sirmaur and . The lesser Himalayas includes the parts of Mandi, Sirmaur and parts of Chamba, Kangra and . The Alpine zone is at an altitude of 4500 m and beyond, includes Kinnaur and parts of Lahaul and Spiti, Chamba districts. Elevation of areas of the state increases as we move from west to east and from south to north.

The hills in the outer Himalayas are about 600 m above sea level. The inner Himalayas are marked by gradual elevation towards the and Pir Panjal ranges and abruptly rises in the Shimla hills, to the south of which is the high peak of Church-Chandni (3647 m) and the rise is gradual towards the north of river .

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 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

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

Fig. 1 Location of the districts of Himachal Pradesh

3. State rainfall mean and variabilityand 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 (35%) of south west monsoon season rainfall in August month while the July month get 33% of the south west monsoon rainfall. June and September receive 14% and 17% of south west

4 monsoon rainfall resp. Also more than 61% of annual rainfall receives during the southwest monsoon season only. The variability of monsoon rainfall (19.6%) or variability of annual rainfall is also very less (15.5%).Whereas month of June and September shows greater variability in monthly rainfall i.e. 48% as compare to seasonal rainfall. June July August September JJAS Annual Mean 101.4 236.0 248.7 124.1 710.3 1163.3 CV 48.4 29.7 33.0 48.9 19.6 15.5

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

Fig. 2 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 series. Neither monthly rainfall nor seasonal or annual rainfall show any significantly increasing/decreasing trend. In the monthly rainfall June rainfall show increasing trend while July, August and September rainfall show decreasing trend but both not significant. Both seasonal and annual rainfall show non significantly decreasing trend. During the last 30 years highest rainfall of June and July received in the year 2013 (203.9mm) and 1993(386.9 mm)respectively while highest rainfall of 476.1 in August received in the year 1997 and of 284.5mm in September received in the year 1995. Highest annual rainfall of 1493.9 mm received in the year 1995 and highest southwest monsoon rainfall of 1028.6 mm received in the year 1995.

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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

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

Table 2 gives the rainfall statistics for the districts of Himachal Pradesh for the four monsoon months, southwest monsoon season and annual. It can be seen that four districts viz. Hamirpur, Mandi, Sirmur and Kangra receive highest rainfall over other districts during all the season. Rainfall receives over these districts are around 120-180 mm in June, 290-510mm in July, 380-600mm in August, 150-210mm in September and during the SW monsoon and annual 1000-1500mm.Kinnur district receives lowest rainfall during the SW monsoon season (190mm) while lowest annual rainfall (616mm).

June shows greater variability in case of Kinnaurdistrict i.e. 122%, Lahul and Spiti district shows greater variability in July month i.e. 89% whereas 114% and 99% variability in August and September month respectively.Lahul andSpiti district also shows greater variability in southwest monsoon and annual rainfall.

Fig.4 shows the overall picture of mean rainfall over districts of state, north eastern parts of state ie. Lahul andSpiti , shows less rainfall in June, July month (36-64mm) whereas in month

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of August(53-100mm) and again in September (36-93mm) with district. Western end of state shows better mean rainfall condition ranging between (94-500mm) rainfall during monsoon months. The month of Augusthas better rainfall over all state over other months of monsoon. If we see over monsoon seasonaland annual rainfall, western part of state shows better rainfall activity over eastern part, in other words we can say that as we move from west to east rainfall activity reduces.

Fig. 5 shows variability of rainfall over Himachal Pradesh, south and south-western part of state shows very less variability of rainfall over monsoon months i.e. June-September as we move northward from south and eastward from west variability of rainfall over state increases. If we see monsoon season and annual as whole south and western part shows less variability (20-34%) and increases as we move northward or eastward (34-64 %).

JUNE JULY AUGUST SEPTEMBER MONSOON ANNUAL DISTRICT MEAN CV MEAN CV MEAN CV MEAN CV MEAN CV MEAN CV BILASPUR 100.5 287 257.6 36 327.8 88 147.1 80 833.0 74 1096.2 90 CHAMBA 121.5 177 290.4 51 310.8 93 140.3 160 863.0 63 1590.8 66 KANGRA 177.7 58 508.2 28 589.0 31 204.8 47 1479.8 22 1860.4 21 KINNAUR 35.0 124 51.1 65 52.7 67 49.8 74 188.6 45 611.3 41 KULU 85.8 239 173.5 44 167.6 49 93.5 75 520.3 60 1016.5 40 LAHUL AND SPITI 49.7 540 97.4 298 105.7 115 91.8 238 344.7 140 855.5 80 MANDI 169.4 51 382.0 28 400.0 34 160.0 40 1111.3 21 1460.9 20 HAMIRPUR 123.9 237 352.3 27 419.6 33 153.5 67 1049.3 52 1345.2 67 SIMLA 111.5 190 211.5 43 205.6 37 122.1 62 650.8 51 1049.0 39 SIRMUR 167.7 140 415.2 37 383.8 34 193.4 64 1160.1 41 1446.2 37 SOLAN 139.1 58 287.5 42 282.4 42 151.6 61 860.5 23 1156.3 20 UNA 110.2 193 337.2 92 373.4 35 158.0 146 978.8 67 1221.4 66

Table2. Rainfall statistics for the districts of Himachal Pradesh for the four monsoon months, southwest monsoon season and annual

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Fig.4 Mean rainfall pattern over districts of Himachal Pradesh

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Fig.5 Coefficient of Variation (%) over districts of Himachal Pradesh

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4.2 Trend in district rainfall

Fig.6 shows the trends in district rainfall for (a) June, (b) July (c) August (d) September (e ) JJAS and (f) annual. It can be seen that June rainfall has shown significantly increasing trend in the district Una while no district has shown any significantly decreasing trend. For the July month only shows non-significantly increasing trend while significantly decreasing trend has been noticed in Lahul&Spiti and Kinnaur district and other districts shows non-significantly decreasing change in trend. For month of August, significantly decreasing trend has been noticed in Lahul&Spiti and Kinnaur district while Chamba, Kangra, Kullu, Hamirpur, Una shows non-significantly increasing trend and rest of districts shows non-significantly decreasing trend in rainfall. September rainfall shows increasing trend for Chamba, Kullu, Una, Shimla, while decreasing trend forrest of districts but these trends are not significant.. During the whole southwest monsoon season only one district viz. Kullu has shown significantly increasingtrend while Lahul&Spiti and Kinnaur district shows significantly decreasing trendin rainfall. For the annual rainfall Chamba, Lahul and Spiti, Kinnaurshow significantly decreasing trend while only district Kullu, Una showed non-significantly increasing trend and rest of districts shows non-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

The average frequency of rainy days is calculated for Himachal Pradesh for June, July, August, September, June to September and Annual. Figure 7 shows that in the month of June the maximum number of rainy days lies in the range of 7 to 9 days in some parts of Chamba, Kangra, Mandi, Solan, Shimla districts. While minimum number of rainy days lies in the range of 4 to 5 days especially in some parts of Kinnaur, Lahul and Spiti districts. Whereas in remaining districts, the number of rainy days lies in the range of 5 to 7 days.

Figure 8 shows that in the month of July the maximum number of rainy days lies in the range of 13 to 15 days

11 especially in lower part of Chamba and upper part of Kangra and upper parts of Mandi, and lower part of Sirmur district. While minimum number of rainy days lies in the range of 7 to 9 days especially in some upper parts of Lahul&Spiti and lower part of Kinnaur districts. Whereas in remaining districts, the number of rainy days lies in the range of 9 to 13 days.

Figure 9 shows that in the month of August the maximum number of rainy days lies in the range of 14 to 16 days especially in lower part of Chamba and upper part of Kangra and upper parts of Mandi, and lower part of Sirmur district. While minimum number of rainy days lies in the range of 8 to 9 days especially in some upper parts of Lahul&Spiti and lower part of Kinnaur districts. Whereas in remaining districts, the number of rainy days lies in the range of 9 to 13 days.

Figure 10 shows that in the month of September the maximum number of rainy days lies in the range of 7 to 9 days especially in lower part of Chamba and upper part of Kangra and upper parts of Mandi, and lower part of Sirmurdistricts. While minimum number of rainy days lies in the range of 5 to 6 days especially in some upper parts of Lahul&Spiti, Solan and lower part of Kinnaur districts and lower edge of Kangra, Una, Bilaspur districts. Whereas in remaining districts, the number of rainy days lies in the range of 6 to 7 days.

Figure 11 shows that during June to September the maximum number of rainy days lies in the range of 37 to 42 days especially in some adjoining parts of Chamba, Kangra, Mandi, Hamirpur and lower part of Sirmaurdistricts. While minimum number of rainy days lies in the range of 23 to 26 days especially some upper parts of Lahul&Spiti and lower part of Kinnaur districts districts. Whereas in remaining districts, the number of rainy days lies in the range of 26 to 36 days.

Figure 12 shows that during the entire year the maximum number of rainy days lies in the range of 57 to 62 days especially in some parts of Chmba, Kangra, Kullu, Mandi, Shimla districts. While minimum number of rainy days lies in the range of 40 to 44 days especially in some parts of Chamba, Kinnaur, Kangra, Bilaspur,Solan, Major part of Lahul&spiti, Una districts. Whereas in remaining districts, the number of rainy days lies in the range of 45 to 57 days.

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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

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5.2 Average frequency of Heavy rainfall days

The average frequency of Heavy rainfall days is calculated for Himachal Pradesh for June, July, August, September, June to September and Annual. In the month of June the maximum number of heavy rainfall days lies in the range of 0 to 1 days especially in some adjoining parts of Chamba , Kangra, Mandi districts. While minimum number of Heavy rainfall days are almost zero in some parts of Mandi, Kullu, Shimla, Una, Hamirpur, Bilaspur, Kinnaur districts. Whereas in remaining districts, the number of Heavy rainfall dayare rarely occurs ( Figure 13).

Month of July shows the maximum number of heavy rainfall days lies in the range of 1 to 2 days especially in western districts (Chamba, Kangra, Mandi) and southern part of Sirmur districts. While minimum number of Heavy rainfall days lies in the range of 0 to 1days especially in south eastern part of state. Whereas in remaining districts, the number of Heavy rainfall day is 1day( Figure 14)..

Figure 15 depicts month of August where the maximum number of heavy rainfall days lies in the range of 1 to 2 days especially in eastern districts of Himachal Pradesh. While minimum number of Heavy rainfall days lies in the range of 0 to 1 days especially in some parts of southerndistricts. Whereas in remaining districts, the number of Heavy rainfall day is 1day. During September (Figure 16) the maximum number of heavy rainfall days lies in the range of 0 to 1days especially in eastern part of state. While minimum number of Heavy rainfall days are 0 days especially in some parts of Kinnaur, Lahul and Spiti district. Whereas in remaining districts, the number of Heavy rainfall days are rare. During June to September (Figure 17) the maximum number of heavy rainfall days lies in the range of 4 to 5 days especially in north western parts of state and districts at southern tip of state. While minimum number of Heavy rainfall days lies in the range of 0 to 1 day especially in some parts of Mandi, Shimla, Kullu and Kinnaur districts. Whereas in remaining districts, the number of Heavy rainfall days lies in the range of 1 to 3 days. Figure 18 shows that during the entire year the maximum number of heavy rainfall days lies in the range of 4 to 5 days especially in north western parts of state and districts at southern tip of state. While minimum number of Heavy rainfall days lies in the range of 1 to 2 days especially in some parts of Mandi, Shimla, Kullu and Kinnaur districts. Whereas in remaining districts, the number of Heavy rainfall days lies in the range of 2 to 4 days.

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

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: Fig. 18 Average frequency of Heavy rainfall days: JJAS Annual

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5.3 Average frequency of Dry days

The average frequency of dry days is calculated for Himachal Pradesh for June, July, August, September, June to September and Annual. Figure 19 shows that in the month of June the maximum number of dry days lies in the range of 23 to 24 days especially in some parts of Lahul &Spiti district, western part of Kangra, Una districts. While minimum number of dry days lies in the range of 19 to 20 days especially in some parts of central and southern part of state. Whereas in remaining districts, the number of dry days lies in the range of 21 to 23 days.

In the month of July(Figure 20 ) the maximum number of dry days lies in the range of 18 to 20 days mostly in northern parts of state viz. parts of Lahul & Spiti, Chamba districts. While minimum number of dry days lies in the range of 13 to 14 days especially in central belt passing from Chmaba to Sirmaur district through Mandi districts. Whereas in remaining districts, the number of dry days lies in the range of 14 to 18 days.

In the month of August the maximum number of dry days lies in the range of 18 to 20 days especially in northern districts of state and some part at western edge of districts viz. Kangra, Una. While minimum number of dry days lies in the range of 12 to 14 days especially in central belt passing from Chmaba to Sirmaur district through Mandi districts. Whereas in remaining districts, the number of dry days lies in the range of 15 to 17 days (Figure 21).

In September (Figure 22) the maximum number of dry days lies in the range of 23 to 24 days especially in some parts of Lahul & Spiti, Chamba and western part of Kangra, Una, Solan districts. While minimum number of dry days lies in the range of 19 to 20 days especially in some parts of Chamba, Kangra, Kinnaur and Mandi districts. Whereas in remaining districts, the number of dry days lies in the range of 20 to 23 days. During June to September the maximum number of dry days lies in the range of 71 to 76 days especially in Nortern belt of state spanning Chmba, Lahul & Spiti, Kinnaur, and some parts of South west of state. While minimum number of dry days lies in the range of 56 to 59 days especially in Central Region of state spanning mainly Chamba, Kanga, Mandi districts. Whereas in remaining districts, the number of dry days lies in the range of 59 to 70days(Figure 23). Figure 24 shows picture of entire year, the maximum number of dry days lies in the range of 262 to 271 days mainly in northern districts of state and some parts of Kangra, Bilaspur and Una districts. While minimum number of dry days lies in the range of 229 to 237 days mainly in some parts of Chamba, Kangra,

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Mandi, Shimla districts. Whereas in remaining districts, the number of dry days lies in the range of 237 to 262 days.

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

6.1Trend in frequency of Rainy days The Trend in frequency of rainy days is calculated for the raingauge stations of Himachal Pradesh for June, July, August, September, June to September and Annual. Figure 25 shows that in the month of June there is a significant increase in rainy days in stations in Solan and Shimla districts. Whereas there is a significant decrease in Rainy days in stations in Chamba, Kinnaur, Sirmaur districts. While remaining districts did not show any significant change.

In Month of July (Figure 26) there is a significant increase in Rainy days in stations in only. Whereas there is a significant decrease in Rainy daysin stations in Kinnaur district. While remaining districts did not show any significant change.

Figure 27 depicts that in the month of August there is a significant increase in Rainy daysin stations in (central and Eastern part). Whereas there is a significant decrease in Rainy days in stations in western Kangra district and Una, Hamirpur, Bilaspur Solan, Sirmaur, Kinnaur districts. While remaining districts did not show any significant change.

In September there is no significant increase in Rainy daysin stationsin State. Whereas there is a significant decrease in Rainy days in stations in Solan, Bilaspur, Mandi and Kinnaur districts. While remaining districts did not show any significant change.(Figure 28).

Figure 29 shows that during June to September, there is a significant increase in Rainy daysin stations in Southern Kangra district. Whereas there is a significant decrease in Rainy days in stationsin westernKangra, Mandi, Bilaspur, Solan, Sirmaur, Kinnaur districts. While remaining districts did not show any significant change.

Figure 30 shows that for the entire year, there is a significant increase in Rainy days in southern Kangra district. Whereas there is a significant decrease in Rainy days in western Kangra, Chamaba, Lahul and Spiti, Mandi, ,Bilaspur, Solan, Sirmaur, Shimla, Kinnaur districts. While remaining districts did not show any significant change.

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

Fig. 27Trend 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

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6.2 Trend in frequency of Heavy rainfall days

The Trend in frequency of Heavy rainfall days is calculated for Himachal Pradesh for June, July, August, September, June to September and Annual. Figure 31 shows that in the month of June there is a significantly increasing trend in heavy rainfall days inHamirpur, Una, Solan and Siramaur districts. Whereas there is a significant decrease in Heavy days in Mandi district. While remaining districts did not show any significant change.

In the month of July there is a significantly increasing trend in heavy rainfall days inSirmaur district only. Whereas there is a significantly decreasing trend in heavy rainfall days inalmost all southern district viz. Kangra, Mandi, Solan, Shimla districts. While remaining districts did not show any significant change. (Figure 32)

Figure 33 shows that in the month of August there is no significant increase in heavy rainfall days in anydistrict. Whereas there is a significantly decreasing trend in heavy rainfall days in Kangra, Solan, Sirmaur districts. While remaining districts did not show any significant change.

Figure 33 depicts that in the month of September there is a significantly increasing trend in heavy rainfall days in Kinnaur, Sirmaur and some parts of Mandi district. Whereas there is a significantly decreasing trend in heavy rainfall days inKangra and some parts of Mandi district. While remaining districts did not show any significant change.

During June to September(Southwest Monsoon Season)there is a significantly increasing trend in heavy rainfall days inSirmaur districts. Whereas there is a significantly decreasing trend in heavy rainfall days inKangra, Mandi, Solan, Shimla districts. While remaining districts did not show any significant change.(Figure 35)

Figure 36depicts trend for entire year,there is a significantly increasing trend in heavy rainfall days in northern Sirmaur district. Whereas there is a significantly decreasing trend in heavy rainfall days in Kangra, Lahul and spiti , Kinnaur, Mandi, Shimla, Solan and southern Sirmaur district. While remaining districts did not show any significant change.

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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

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

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6.3 Trend in frequency of Dry days

The Trend in frequency of dry days is calculated for Himachal Pradesh for June, July, August, September, June to September and Annual. Figure 37 shows that in the month of June there is a significantly increasing trend in dry days in Una, Bilaspur and parts of Kinnaur district. Whereas there is a significantly decreasing trend in dry days in Lahul and Spiti, Kullu Shimla and Parts of Kinnaur district. While remaining districts did not show any significant change.

Figure 38expresses trend in the dry days in month of July, there is a significantly increasing trend in dry days in Una, Bilaspur, Sirmaur, Shimla and some part of Kangra district. Whereas there is a significantly decreasing trend in dry days in Some parts of Kangra district. While remaining districts did not show any significant change. Month of August(Figure 39) express there is a significantly increasing trend in dry days in western part of Kangra district, Una, Hamirpur, Bilaspur, Mandi, Solan, Sirmaur, Shimla, Kinnaur districts. Whereas there is a significantly decreasing trend in dry days in central and eastern Kangra district. While remaining districts did not show any significant change.

In the month of September (Figure 40), there is a significantly increasing trend in dry days in Kullu, Bilaspur, Mandi, Solan, Shimla, Kinnaur and Northern Kangra district. Whereas there is a significantly decreasing trend in dry days in southern Kangra and Lahul and Spiti district. While remaining districts did not show any significant change.

Figure 41depicts that in southwest monsoon season (June to September), there is a significantly increasing trend in dry days in Una, Southern Kangra and Southern . Whereas there is a significantly decreasing trend in dry days in Northern Kangra, Mandi, northern Solan and Surmaur districts. While remaining districts did not show any significant change.

Figure 42 shows that during the entire year there is a significantly increasing trend in dry days in southern Kangra and Una districts. Whereas there is a significantly decreasing trend in dry days in Southern Chamba, Northern Kangra, Mandi, Solan, Sirmaur districts. While remaining districts did not show any significant change.

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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

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7. Conclusions In the present study we have investigated the rainfall pattern and it its variability and also changes based on recent 30 years data. In the analysis we have considered monsoon months, the monsoon season and annual scale. The spatial scale has been considered from state to district for study of rainfall total and stations are being considered for seeing 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:

Himachal Pradesh gets maximum rainfall in July (33% of SW monsoon rainfall) followed by August (28 % of SW monsoon rainfall).

On an average 68% of annual rainfall receives during southwest monsoon rainfall (June –September).

Bilaspur, Una, Hamirpur, Mandi, Sirmur, Kangradistricts of Konkan region receive 75- 80% of annual rainfall in SW monsoon season while Kinnaur andLahul and Spiti districts receive 30-40% of annual rainfall in SW monsoon season.

No significant increasing trends in June, July, August, September monthly rainfall except in case of in June Month.

No significant decreasing trends in June, September monthly rainfall whereas Lahul and Spiti and Kinnaur districts shows significant decreasing trends in July, August monthly rainfall.

Maximum rainfall receive during the SW monsoon season over the districts in western region (800mm-1400mm) while parts of Madhya Himachal Pradesh and eastern districts receives lowest rainfall (150-600 mm). Kinnaur district receives lowest rainfall of 190 mm.

Maximum rainfall receive during the year over the districts in Northern region ( 1500mm -1900mm) while Kinnaur district receives lowest annual rainfall of 610-620mm.

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Significantly increasingtrend in SW monsoon rainfall has been noticed in Kullu district while no district shows significantly increasing trend.

In annual rainfall Chamba, Lahul & Spiti and Kinnaur districts shows significantly decreasingtrend while no district shows significantly decreasing trend. Western region receives on an average 30-42 rainy days (daily rainfall >=2.5mm) out of 122 days of SW monsoon season while eastern region gets 25-27 rainy days and some parsley located central parts of Himachal Pradesh get even less than 25 rainy days.

For heavy to extremely heavy rainfall ( daily rainfall >=6.5mm) north western region gets3-5 days during the SW monsoon season, eastern parts of Madhya Himachal Pradesh and extreme NE parts of the state get 1-2 day heavy to extremely heavy rainfall days.

Number of dry days is maximum over Northern parts extended to eastward of the state (71-76 dry days out of 122 days during the SW monsoon season while on an average 253-271 dry days in year (365 days) have been noticed in many parts of northern districts of Himachal Pradesh.

During the period June to September there is a significant increase in the frequency of Rainy days in stations in southern parts of Kangra district. Whereas there is a significant decrease in Rainy days in stations in western Kangra, Mandi, Bilaspur, Solan, Sirmaur, Kinnaur districts.

During the entire year there is a significant increase in Rainy days in southern Kangra district. Whereas there is a significant decrease in Rainy days in western Kangra, Chamaba, Lahul and Spiti, Mandi, ,Bilaspur, Solan, Sirmaur, Shimla, Kinnaur districts.

During the period June to September there is a significantly increasing trend in heavy rainfall days in Sirmaur district. Whereas there is a significantly decreasing trend in heavy rainfall days in Kangra, Mandi, Shimla, Solan districts.

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During the entire year there is a significantly increasing trend in heavy rainfall days in Sirmaur district. Whereas there is a significantly decreasing trend in heavy rainfall days in Kangra, Lahul&Spiti, Mandi, Shimla, Solan districts.

During June to September there is a significantly increasing trend in dry days in Southern part of Kangra, Una, Sothern part of Solan districts. Whereas there is a significantly decreasing trend in dry days in Northern and western part of Kangra, Northern parts of Mandi, Western(northward) parts of Solan, Sirmaur, Kinnaur districts.

During the entire year there is a significantly increasing trend in dry days in Southern part of Kangra and eastern parts of Sirmaur districts. Whereas there is a significantly decreasing trend in dry days in western parts of Chamba, Eastern and western part of Kangra, Northern parts of Mandi, western part of Solan, Sirmaur districts.

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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