The role of Weather Modification Technology for forest and land fire disaster mitigation in the perspective of carbon emission reduction in Indonesia

. This paper reviews the effectiveness of implementing Weather Modification Technology (WMT) in efforts to control forest and land fire disasters in Indonesia. Analysis is carried out on several parameters in the field that can be measured and observed. WMT has been proven to be able to increase rainfall intensity by 12.9% and shorten the duration of Consecutive No Rain Days, which in turn can reduce the number of hotspot events in the target area. The implementation of WMT during the rainy season transition period has also been proven to be able to increase the peatland groundwater level, which ultimately shortens the drought period in the target area. The WMT implementation program, which has become increasingly well-planned in the last 4 years (2020-2023), has proven to be able to reduce the number of hotspot incidents, the extent of forest and land fires, and the amount of carbon emissions in Indonesia quite significantly. Based on updated data until September 2023, the number of hotspots, burnt area, and total carbon emissions in Indonesia were "only" 22%, 38.9%, and 5.3% respectively compared to the numbers in 2019, which was both an El Nino year.


Introduction
Indonesia is a country that is vulnerable to the impacts of climate change and has a reasonably high-risk index for natural disasters [1].Based on data on disaster events in Indonesia from the National Agency for Disaster Countermeasures (BNPB), disaster events in Indonesia are dominated by the type of hydrometeorological disaster.Apart from being triggered by human-caused environmental damage, the increasing frequency of hydrometeorological disasters is also caused by climate change.An example is the forest and land fires in Indonesia every year.This disaster has historically tended to recur yearly and increase during the dry season.The intensity of fires can worsen when El Nino occurs, resulting in a prolonged drought in Indonesia [2].
The phenomenon of forest and land fire disasters has always been a concern of the Government of Indonesia.Not only causing losses in the social and economic sectors, these disasters also often give a negative image due to the transboundary haze problem.Forest and land fires are also closely related to carbon emissions, which significantly affect climate change in the long term.Therefore, referring to the Nationally Determined Contribution (NDC), which the Government of Indonesia has prepared as a follow-up to the ratification of the Paris Agreement on the 2015 UN Work Convention on Climate Change, the Government of Indonesia is committed to setting a total target of reducing carbon and Greenhouse Gas (GHG) emissions of 2,869 MTon CO2e in 2030.Forestry and Other Land Uses (FOLU) is the sector with the most significant emission reduction contribution, which is 17.2% of the total target of 29% with an unconditional mitigation scenario or 24.1% of the real target of 41% with conditional mitigation scenarios.This amount has considered the emissions from forest and land fires that occur every year in Sumatra and Kalimantan [3].
One of the efforts to reduce carbon emissions is to reduce the incidence of forest and land fires.The total carbon content in Indonesia is estimated at 14 gigatonnes from the forest sector [4].Forest and land fires in 1997 coinciding with El Nino were estimated to release as much as 1 gigatonne of carbon [5].Thus, if the intensity of forest and land fires can be reduced, this will automatically reduce carbon emissions in Indonesia.
The Ministry of Environment and Forestry (KLHK), as the National Climate Change Focal Point in Indonesia, has made many efforts to control forest and land fire disasters.One of them is by utilizing Weather Modification Technology (WMT).The Government of Indonesia first used WMT to deal with massive fires during El Nino in 1997.In subsequent implementations since 2009, WMT began to be routinely used in efforts to deal with forest and land fires that have occurred almost every year in Sumatra and Kalimantan.El Nino in 2015, which also resulted in severe forest and land fires, has provided lessons and has become a starting point for the paradigm reform of using WMT in the disaster management scheme for forest and land fires in Indonesia.Previously WMT was carried out when the disaster was already massive for fire suppression.Since 2016 WMT has been carried out earlier for prevention purposes with the aim of re-wetting peatlands so that they do not catch fire easily.With earlier implementation during the rainy season transition period, the rain yields obtained from WMT implementation can be more optimal and shorten the drought period on peatlands prone to fire [6].
This article reviews the evaluation of the results of implementing WMT in efforts to prevent forest and land fires disasters which have been programmed by the Indonesian Government to anticipate the impact of El Nino in 2023.The output resulting from this research is expected to provide an overview of the effectiveness, contribution and value of the benefits of implementing TMC in efforts controlling forest and land fire disasters in Indonesia.

Materials and methods
Several research samples were taken from a number of WMT implementations that have been carried out for the year El Nino 2023.A number of data analyzed included data on rainfall, peatland groundwater level (GWL), number of hotspots, burnt area and total carbon emissions.The rainfall data analyzed uses data from the Tropical Rainfall Measuring Mission (TRMM) Satellite taken from the JAXA Realtime Rainfall Watch sites: https://sharaku.eorc.jaxa.jp/GSMaP/.Data on SM and peatland GWL used in this study were obtained from the SIPALAGA sites: https://sipalaga.brg.go.id/ and https://prims.brg.go.id/, which are managed by the Peatland and Mangrove Restoration Agency and (BRGM).Data on number of hotspots, burnt area and total carbon emissions taken from Ministry of Environment and Forestry (KLHK) -SIPONGI sites: https://sipongi.menlhk.go.id.

Results and discussion
The implementation of WMT has proven to increase the intensity of rainfall in the target area.Figure 1 shows the daily rainfall intensity during WMT implementation in Riau Province from May 17 -June 9, 2023.The figure shows that relatively low rainfall occurred during the week before the implementation of the WMT in Riau Province (7 -16 May 2023).The intensity is much lower than the historical average and the actual value for the previous year (2022).This condition then improved during the WMT implementation period from 17 May to 9 June 2023, where the intensity of daily rainfall was generally higher than the previous year's historical and actual average values.Please note that 2023 is an El Nino year while 2022 is a La Nina year.The value of the increase in rainfall in Riau Province during the WMT implementation period from 17 May to 9 June 2023 was calculated using the Target Only Method.The calculation compares the actual rainfall in the target area obtained during the WMT implementation period with historical rain at the same time interval.From the calculation results, the value of increasing rainfall is 12.79%.In addition, the volume of rains obtained from the effects of cloud seeding activities during the WMT implementation period was also calculated.The calculation is based on the precipitation thickness approach measured from the TRMM satellite during the WMT implementation period multiplied by the area affected by cloud seeding activity in the target area.The total volume of rainfall resulting from cloud seeding during the WMT implementation in Riau Province was 208.1 million m 3 .
The results of the WMT implementation have also proven to be able to shorten the duration of Consecutive No Rain Days (CNRD).Figure 3 shows the analysis results from BMKG (updated May 31, 2023) on CNRD monitoring in all regions of Indonesia.For the Riau Province, which has received WMT implementation support since May 17, 2023, CNRD is dominant for a relatively short period (1-5 days).WMT implementation aims to keep the peatland groundwater level (GWL) above a threshold of not less than -40 cm.This is because peatland areas will have a high fire hazard vulnerability if the GWL is below 40 cm, and burning areas only occur when the GWL is below 60 cm [7].The fire risk can be reduced by up to 30% if rewetting is prioritized in areas that are most prone to burning [8].The WMT implementation paradigm reform, which has been implemented since 2016, has proven to be very significant in reducing the number of hotspots in Indonesia.Figure 5 shows how the number of hotspots in Sumatra and Kalimantan has decreased significantly since 2016, when WMT was implemented when a massive forest and land fire disaster occurred for fire suppression purposes and starting in 2016, WMT was implemented earlier as an anticipatory effort for peatland rewetting.For comparison, 2015 and 2019 were both El Nino years.However, the number of hotspots in 2019 was reduced to almost half of the number in 2015.The number of hotspots until September 2023 is 5,501, "only" 22% compared to the number in 2019.Figure 6 shows the annual rainfall pattern and the accumulated hotspot events in Sumatra (left) and Kalimantan (right) during El Nino years.During El Nino in 2014, an increase in the number of hotspots in Sumatra had started to occur since the beginning of the year during the dry period in February.This condition was able to be improved in 2019 when the increase in the number of hotspots began in the second dry period in August -September.In 2015, the increase in the number of hotspots occurred in June, while in 2019 the spike started in August and reached a peak in September (left image).A similar condition also occurs for Kalimantan.The increase in the number of hotspots generally occurs since the July period.However, in 2019, the spike started in August and reached its peak in September (right image).Based on the description above, it can be seen that there has been a delay in the period of the surge in the number of hotspots on Sumatra and Kalimantan, which has been delayed by around 1-2 months.This indicates that WMT's efforts to rewet peatlands have succeeded in shortening the drought period and have been very significant in reducing the number of forest and land fire incidents.The decrease in the number of hotspot incidents is directly proportional to the decrease that also occurred in the burnt area and total carbon emissions, as presented in Figure 7. El Nino in 2006 burned 3.8 million hectares of forest and land.While in El Nino the following years the numbers continued to decrease.Each area is 2.6 million hectares (2015) and 1.6 million hectares (2019).Based on data from the KLHK's SIPONGI website, until September the area of forest and land fires in 2023 "only" reached 642.1 thousand hectares or only around 38.9% of the amount in 2019.Likewise for total carbon emissions originating from fire incidents.In El Nino in 2019, total carbon emissions in Indonesia were 624.2 million tons of CO2e, while in 2023, which is also El Nino, data until August 2023 was "only" 32.9 million tons of CO2e or only around 5.3% of the amount in 2019.Even though it hasn't been a complete year, at least this number is still very far compared to other El Nino years or several previous years.

Conclusion
An interesting fact that can be obtained from the description above is that the total burnt area and also the total carbon emissions in Sumatra and Kalimantan after 2019 were able to be reduced very significantly.During period 2020-2022, the highest burnt area came from Nusa Tenggara, not from Sumatera or Kalimantan.At least this indicates that the TMC efforts, which have been routinely carried out every year since 2009 in Sumatra and Kalimantan and since 2016 have become increasingly well-planned in their implementation, are starting to show significant results.This can be proven by the number of areas where forest and land fires in Sumatra and Kalimantan were able to be suppressed.Precisely the Nusa Tenggara region which has never received the TMC assistance program has even increased the area of forest and land fires and is even higher than Sumatra and Kalimantan.This fact can at least become input and concern for the Government of Indonesia to start considering whether or not the Nusa Tenggara region needs support for WMT implementation as has been routinely carried out in Sumatra and Kalimantan.

Figure 1 .
Figure 1.Rainfall in Riau Province during the WMT implementation period.Furthermore, Figure 2 compares the spatial distribution of rainfall before and during the WMT implementation period in Riau Province.To facilitate comparison, it is made in 3 periods with a duration of about one decade each.In the left figure (period 6-16 May 2023), about one decade before the TMC implementation period, the rainfall intensity in Riau Province was relatively the same as in other nearby provinces.Contrast this with the description of the first decade of the implementation of WMT in the period 17-27 May 2023 (middle figure) and the second decade in the period 28 May -9 June 2023 (right figure).This figure shows that the rainfall intensity in Riau Province is higher than in other nearby provinces.Areas with high rainfall intensity in Riau Province appear to be concentrated around cloud-seeding areas.The line drawn on the map records the track of cloud seeding during the WMT implementation.

Figure 2 .
Figure 2. Spatial distribution of rainfall in Riau Province before (left) and during the WMT implementation period (middle and right).

Figure 4 .
Figure 4. Peatland Groundwater Level from 22 observation stations in Riau Province during the WMT implementation period.

Figure 4
Figure 4 shows the peatland GWL conditions of 22 observation stations in Riau Province from May 12 -June 10, 2023.During the WMT implementation (May 17 -June 9, 2023), as many as 18 stations experienced an increase, and 4 stations experienced a decrease in peatland GWL.The highest increase occurred at Teluk Makmur Station, which experienced a rise of +0.42 m (initial GWL = -0.83m; final GWL = -0.41m).Meanwhile, the highest

Figure 5 .
Figure 5. Number of hotspots in Sumatra and Kalimantan during the period 2006 -September 2023.

Figure 6 .
Figure 6.Annual rainfall patterns and accumulated number of hotspots in Sumatra and Kalimantan in several El Nino years.