Climatic Variability and Trend over Indonesia Maritime Area for the Period 1960 – 2018

Winarso PA

Published on: 2019-12-28

Abstract

This paper would like to study climate variability over Indonesia Maritime Continent using investigation seasonal onset and impact to the environment, that they occurred during the period 1961 – 2018. The study used the analytic and the descriptive method using the long period of rainfall data. Processing rainfall data into tabulation of the character of the total rainfall from a consecutive season in Indonesia (wet and dry season)would give the result in the term a variability the total rainfall at a consecutive season. Some of the global aspect causing the climate condition would be studied for additional information as the trigger for the climate variability in the regional scale of Indonesia Maritime area. Additional from weather condition at a certain period as part the climate variability would give weather and climate variability condition and their impact on the environment. Where global phenomena of the El Nino and La Nina episodes would be used in this study as the main consideration. The result told that there was variability from the Sun activities to cause the variability of the El Nino/La Nina episodes such that they might encourage variability seasonal onset and their impact on the environment. Then the climate trend would be derived from the variability of the global scale up to local scale aspect especially character of the rainfall in Indonesia Maritime Continent area.

Keywords

Climate; Variability; Sunspots; El Nino; Rainfall

Introduction

between two oceans (Indian and Pacific Oceans) and two continents (Asia and Australia). As the tropical maritime continent area, most of the time humid maritime continent air mass always prevails to give some rainfall during the dry season period (June-September) and more rainfall during rainy season period (December-March) previously before the year of 1990. Such that this climate situation encouraged the agricultural activities for the country region and last 1990 the UN system for Food and Agricultural Organization (FAO) presented the award for the developing country succeeding in the National Food Security itself. Starting 1991, for the first time the country for the whole country area were occurring less of rainfall or drought with the largest area and longest in time comparing with climate situation for the last 30 years. This drought continued up to the end of decade 1991-2000, because of these conditions the National Food Security Program destroyed that it was due to the climatic variation from the global scale. Where the global phenomena of the El Nino episode were very active with increasing temperature of sea surface over the wider area the Eastern Pacific Ocean. The long and frequent El Nino episode might cause the impact of the climatic variation in term of the long episode of drought. The drought might disturbed agribusiness production starting local up to national level. Based upon the observational tools found that global climate variability of the El Nino episode (longer on record of 1991-1994), quickly developed and highest on record of Sea Surface Anomaly in Pacific Ocean of ENSO episode 1997-1998 and 2015-2016. These occurrences would encourage the developing of the weather and climate variations starting global up to regional/local scales. Impact of the global scale in term of changing pattern the global circulation including regional circulation of Asia – Australia Monsoonal wind system during 1961 - 2018. The regional wind system effects into the national/local monsoonal wind system of the maritime continent of Indonesia. One of the results from the observational of this study is the longer period of the easterly monsoonal wind system than westerly monsoonal wind system. Because these wind system controlled weather and climate in this region, some unusual and strange weather and climate pattern observed. This unusual pattern would report in this paper. The objective of the study is to describe the variability of the Sun activities and the El Nino/La Nina episodes as the main cause the climate variability. The variability of the seasonal onset, their impact to the environment and the weather during this period of study would be studied for the description weather and climate variability over Indonesia Maritime Continent area at the period 1961-2018.

The Data And Method

The data in this study comprises the global data in terms of the Sun activities (Applying the sunspot data to be taken from: http://www.sidc.be/silso/versionarchive). The data in term of graphical would describe sunspot number on the month as part of representing Sun’s activities. The high number of Sunspot Number (more than 100 Sunspots/month) could have relation with global warming episode and the low number (less than 100 Sunspots/month) with the global cooling episode. Where global warming would encourage the activity of El Nino and global cooling with the activity of La Nina. El Nino would be a name natural phenomena increasing the sea surface temperature waters and La Nina with decreasing sea surface temperature waters over East equatorial Pacific Ocean (World Meteorological Organization = WMO, http://www.wmo.ch/). The changes of the sea surface temperature it would encourage the changes of the zonal air circulation such that from the operational meteorologist in Meteorological Climatological and Geophysical Agency (BMKG). The variability of the season in Indonesia would occur and to be studied. To identify the El Nino/La Nina activities, it follows BMKG or international climatologist with using if in the East Pacific Ocean has increased (El Nino episode) or decreasing (La Nina episode) the sea surface temperature at least 1 degree centigrade). By using this definition, it will apply the time series of the anomaly sea surface temperature (Oceanic Nino Index), if positive value of the anomaly sea surface temperature would be El Nino episode and the negative value would be La Nina episode. That the graphical of this anomaly sea surface temperature over East equatorial Pacific Ocean could be so-called Oceanic Nino Index (ONI), it would be discussed in the next discussion. Then the rainfall data were taken from the Meteorological Climatological and Geophysical Agency. The processing of the rainfall data would be applied to describe the climate variability over Indonesia Maritime Continent. The seasonal area of Indonesia Maritime Continent will apply the seasonal forecast area to be arranged by the Meteorological Climatological and Geophysical Agency (http://www.bmkg.go.id, 1987) as follows,The seasonal forecast area over Indonesia Maritime Continent area (Figure 1) would be divided into 72 sub-areas which have different pattern such that yellow color to have Monsoonal rainfall type sub areas having two seasonal condition yearly; green color to have Equatorial rainfall type no seasonal condition and red color to have Local rainfall type having reversal seasonal condition with Monsoonal rainfall type. In this study will apply the total rainfall at a consecutive season. In the determination of the total character of the rainfall would compare between the total rainfall at a certain time and certain monsoonal rainfall type with the mean(normal)to the total rainfall at the same monsoonal rainfall type. The variability of the total rainfall at a consecutive season and at every year would be compared with the mean/normal total rainfall at consecutive season during period 1961 – 1990. Then determination would apply the steps as follows, Comparison an area of the total rainfall at a consecutive season and at every year during 1961 – 2013 would be as rainfall character in terms ;below normal if the total rainfall was less than 75 % from the mean total rainfall, normal if the total rainfall has was in the range 75 – 115 % from the mean total rainfall, above normal if the total rainfall was up to 115 from the mean total rainfall. Every year at certain season would apply the percentages seasonal area where the percentage for each condition(e.g. below, normal and above) would be number percentages each condition/total number of seasonal and multiply with 100%. Every year during the period would be tabulated to describe the rainfall character at a certain season with supporting activity El Nino/La Nina episode and recorded maximum Sunspot Number. The discussion of the climate variability will start from the global scale point view with the application of graphical Sunspot activity, El Nino/La Nina episodes and the character of the total rainfall. Then the climate trend would be investigated through the series of the variability of the global scale up to the local scale of seasonal rainfall condition.

Figure 1: Seasonal Forecast Area Indonesia Maritime Continent Area (BMKG).

Variability Of The Sunspots And El Nino/La Nina

For many decades, climatologist has examined how the climate especially Earth’s surface temperature changed before the 19th century. The Earth’s surface temperature has fluctuated naturally as part of the variability of the Sun’s activity through the radiation toward the earth’s surface. The number of Sunspot each month during the period of study would be in term variation number of the sunspots/month. Then one cycle of sunspot would be from lowest up to maxima then toward the lowest of the sunspots number, where one cycle of the sunspot would be in the range 10.5 – 11.5 years. From the source data from National Oceanic Atmospheric Agency (NOAA) from the United States for the period 1950 – 2018, the graphical would describe the variability of the Sunspots number on the monthly basis, it cand described in the next following (Figure 2) as follows, From the sunspot cycles, there would be sunspot variability fromSun’s activities 1960 up to 2018 such that there would 6 cycles with each cycle has maxima of the Sunspots number more than 100 Sunspots. Only in the last cycle would have maximum Sunspot number below 100 Sunspots. The highest cycle of the Sunspots number would in the first cycle on the period 1956 – 1966, in the cycle no. 2, 3, 4, and 5 on the consecutive period 1966 – 1976, 1976 – 1996, and 1996 – 2008; they have maximum Sunspot Number between 100 – 200 Sunspots/month. The variability of the El Nino and La Nina episodes as part of the global phenomena to have relation with climate variability in the earth’s surface would be in term of the Oceanic Nino Index (ONI) in (Figure 3) as follows, From Figure 3, there would be variability of the El Nino and La Nina activities during the period of study 1961 – 2018. The first decade of 1961 – 1970 would be occurring 2 moderate plus 1 strong in the intensity of the 2 El Nino episodes and 2 weak La Nina episodes. The second decade of 1971 – 1980 would be occurring 2 weak plus 1 strong in the intensity of El Nino episode and 1 weak plus 2 strong in the intesity of La Nina episode. The third decade of 1981 – 1990 would be 2 strong in the intensity of El Nino episode and 1 moderate plus 1 strong in the intensity of the La Nina episode.

Figure 2: Sunspot cycle was arranged by NASA with cycle number in above every cycle (https://www.nasa.gov/).

Figure 3: Global El Nino and La Nina Episode in term of their variability of the so-called ONI graphics (http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso.stuff/ensoyears.shtml/)

The fourth decade of 1991 – 2000 would be occurring 1 moderate plus 2 strong in the intensity of El Nino episode and 1 weak plus 1 strong of La Nina episode. The fifth decade of 2001 - 2010 would be occurring 2 moderate plus 2 strong in the intensity of El Nino episode and 1 weak plus 2 strong in the intensity of La Nina episode. The last cycle of period 2011 – 2018 would be occurring one strong in the intensity of El Nino episode and 2 weak plus 1 strong in the intensity of La Nina episode. From the variability of the sunspots and the El Nino/La Nina episode, it could be better to classify the sunspot cycle with the activity of the El Nino/La Nina episode. This relation each sunspot cycle with the El Nino/La Nina episode would be arranged in the next tables as follows, From both tables, it could be studied that each cycle from cycle number 1 up to number 6 has El Nino/La Nina Activities, with majoring El Nino activities more than 2 up to 4 episodes if the sunspot cycle having maximum Sunspots more than 100 Sunspot/month (Sunspot Cycle 1 up to 5). While majoring La Nina activities increased with Sunspot cycle to have maximum Sunspots less than 100 Sunspots/month such as Sunspots Cycle 6 for the current period 2011 – 2018 (could be 2020). Overall Sunspots cycles showed each cycle occurs El Nino episode in the strong in intensity. Where criteria of the El Nino/La Nina intensity follows description in Figure 3 with weak intensity if the sea surface temperature anomaly over Eastern Pacific Ocean could be above/below 0.5 centigrade; moderate intensity with sea surface temperature anomaly between 1 – 1.5 centigrade and strong in intensity with sea surface temperature above 1.5 centigrade to classify El Nino/La Nina intensity. That this finding would be variability of the sunspots number and El Nino/La Nina activities starting 1961 – 2018. Where the total number El Nino Episodes would be 18 times and La Nina episodes would be 14 times. Otherwise, El Nino episodes would be more frequent than La Nina episodes. El Nino episodes might occur each sunspot cycle and La Nina might absent at first sunspot cycle period 1956 – 1967 [1-6].

Variability of the Seasonal Condition of Indonesia Maritime Continent Area

The character of the rainfall at consecutive season over Indonesia Maritime continent would like to present in the next following (Tables 1 and 2), where (Table 1) would be for variability the dry season and (Table 2) for variability the wet season. The El Nino/La Nina episodes would be taken from Figure 2 to include in the two tables for further study. Because the availability of the rainfall character over the seasonal area to be designed by Meteorological Agency of BMKG. would be period 1961 – 2003, these data would be split during the two season e.g. dry- and wet-season in the two tables.

Table 1: El Nino Episode and Sunspot Cycle

Sunspots

Cycle

Period

Number of Occurrences

--------------------------------------------------

Weak          Moderate       Strong

1

1961 – 1970

2                 0            0

2

1971 – 1980

1                 0            2

3

1981 – 1990

0                 1            1

4

1991 – 2000

1                 0            1

5

2001 – 2010

1                 0            1

6

2011 – 2018

2                 0            1

The two tables for the variability of the rainfall character for each consecutive season in Indonesia would be presented in the next following tables as follows, From the (Table 2) El Nino/La Nina episodes period 1961 - 2003, it would find that there were 13 times of El Nino episodes with 12 times to have below normal of the rainfall character or up to 50% of the total seasonal areas, and 1 time has below with below normal of the rainfall character or below 50% of the total seasonal areas. In other words, the impact El Nino episodes period 1961 – 2003 would cause below-normal of the rainfall character, it almost 95% El Nino Episodes 1961 – 2003.

Table 2: La Nina Episode and Sunspot Cycle.

Sunspots

Cycle

Period

Number of Occurrences

--------------------------------------------------

Weak          Moderate       Strong

1

1961 – 1970

2                 0            0

2

1971 – 1980

1                 0            2

3

1981 – 1990

0                 1            1

4

1991 – 2000

1                 0            1

5

2001 – 2010

1                 0            1

6

2011 – 2018

2                 0            1

The La Nina episodes would be 9 times period 1961 – 2003 totally, with 4 times to have above normal the rainfall character or more than 50% from the total number of seasonal areas and 5 times to have below 50%. Where La Nina Episodes might divide into two periods as follows’First period 1961 – 1986 with more than 50% areas to have above normal the rainfall character, Second period 1987 – 2003 with less than 50% areas to have the uncertain condition the rainfall character. In other words, the La Nina episodes might cause above normal in the beginning period 1961 – 1986 and uncertain condition of the rainfall character El Nino episode 1987 – 2003. From the Table 3, there was more than 50% normal condition of the rainfall character totally. It means that wet season in Indonesia was the unclear condition of the rainfall character with the normal condition the rainfall character, it almost more than 50% of the total seasonal areas. Variability seasonal condition over Maritime Continent area would be the continuing with respect to the time following variability of the sunspots number as representing the solar radiation and global episode of El Nino/La Nina. The study showed that variability of the seasonal condition would be during the dry season than the wet season, where El Nino episode might cause below normal of the rainfall character. La Nina episode might cause above normal in the beginning and then uncertain condition of the rainfall character in the last. Otherwise, the climate variability might occur every year following variability of the Sunspots cycles and El Nino/La Nina episodes.

Table 3: Variability of the Number Seasonal Area (%) at dry Season.

Time

Rainfall Character

Below Normal (%)

Rainfall Character

Normal (%)

Rainfall Character

Above  Normal(%)

El Nino (*)/La Nina (+)

Episodes

1961

94

6

0

 

1962

33

39

28

 

1963

92

8

0

*

1964

12

20

68

+

1965

96

4

0

*

1966

65

26

9

*

1967

96

4

0

*

1968

0

8

92

+

1969

91

9

0

*

1970

31

41

28

 

1971

34

33

33

+

1972

98

2

0

*

1973

0

11

87

+

1974

7

22

71

+

1975

9

17

74

+

1976

72

28

0

*

1977

78

20

2

*

1978

3

12

85

 

1979

46

26

28

 

1980

67

17

16

 

1981

15

28

57

 

1982

100

0

0

*

1983

52

19

29

*

1984

15

18

67

+

1985

24

44

32

 

1986

28

26

46

 

1987

78

9

13

*

1988

57

30

13

*

1989

10

52

38

+

1990

12

60

28

 

1991

99

1

0

*

1992

26

59

15

 

1993

26

50

24

 

1994

94

5

1

*

1995

44

41

15

+

1996

26

50

24

+

1997

94

5

1

*

1998

44

41

15

*

1999

67

25

8

*

2000

30

60

10

+

2001

15

41

45

+

2002

67

30

3

*

2003

77

21

2

*

Summary and Conclusion

Climate variability over Indonesia Maritime Continent area would continue following variability of the Sunspots cycles and El Nino/La Nina episodes. Where the strong intensity of the El Nino episode occurs every Sunspots cycle. The Strong intensity of the La Nina episodes could occur when the maximum Sunspot number in the cycle less than 200 Sunspots. Climate trend could be arranged from Sunspots cycle for the long range that the Sunspot cycle would have the irregular pattern for 6 cycles with decreasing maximum Sunspot number with respect with the time from 1976 up to 2018. Where NASA would predict that for the next Sunspots cycle could be decreasing of the maximum Sunspot number or lower than the current maximum Sunspots number period 2009 – 2020. It means to be less Sunspots Number to be the condition in the decade until 2030. It might generate El Nino/La Nina episodes to activate with the cooling episode (La Nina) to have frequently occurred that warming episode such as current cycle condition until 2020. It could continue in the next decade the year 2021 –2030. Current Sunspots cycle period 2009 – 2018 showed strong intensity El Nino episode and 2 weak intensity plus 1 strong intensity La Nina with the long period of the wet season. The next seasonal condition would follow the current seasonal condition with the wet condition more frequent and longer than the dry condition.

References

  1. Some notes from the operationally experienced meteorologist, Bureau Meteorology and Geophysics of Indonesia. 1977 - 2017.
  2. Some Report from CLIVAR Meetings (1998 - 2002).
  3. ONI, Climate Prediction Center, NOAA.
  4. Solar cycle.
  5. What are El Niño and La Niña?. National Ocean Science, Ocean facts, US.
  6. World Meteorological Organization.