the 2009-2010 el niño southern oscillation in the context of … · 2016. 1. 11. · yumul et al.:...

Philippine Journal of Science139 (1): 119-126, June 2010ISSN 0031 - 7683

Key Words: climate change, drought, El Niño Southern Oscillation, Philippines

*Corresponding author: [email protected] [email protected]

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Short Communication

The 2009-2010 El Niño Southern Oscillation in the Context of Climate Uncertainty: The Philippine Setting

Graciano P. Yumul Jr.1,2, Carla B. Dimalanta1, Nathaniel T. Servando3,and Flaviana D. Hilario3

1 National Institute of Geological Sciences, College of Science,University of the Philippines, Diliman, Quezon City, Philippines

2 Department of Science and Technology, Bicutan, Taguig City, Metro Manila, Philippines3 Philippine Atmospheric, Geophysical, and Astronomical Services Administration,

Department of Science and Technology, Science Garden, Diliman, Quezon City, Philippines

The Philippines is no stranger to El Niño Southern Oscillation (ENSO) events and its attendant impacts. Despite being plagued by several disastrous weather events that brought in a lot of rains during the period of September – October 2009, the country had, in fact, been warned of a conventional El Niño event as early as August 2009. With the continued below normal rainfall conditions due to the moderate 09-10 El Niño event being experienced in the country, measures to prepare against these drought conditions are being implemented. The drought and dry spell conditions are expected to persist until summer so the country must switch to a crisis mode in dealing with the impacts that will accompany this ENSO event.

INTRODUCTIONThe El Niño Southern Oscillation (ENSO) events in the Philippines are characterized generally by drought conditions (e.g. Changnon 1999; Lyon et al. 2006; Abastillas 2009). This would happen if the ENSO is a conventional one when warming occurs in the eastern Pacific Ocean near the South American region. Recent works have recognized a different kind of El Niño, the Modoki or Dateline El Niño, which forms in the central Pacific region near the International Deadline (e.g. Ashok et al. 2007; Weng et al. 2009). Should Dateline El Niño occur, the effects on the Philippines would actually be the reverse. This means that instead of expecting drought, Dateline El Niño would result in extensive rainfall in the country similar to what has been observed in other places (e.g. Pielke and Landsea 1999; Larkin and Harrison 2005a; Kao & Yu, 2009). This happened in 2004, a Dateline

El Niño year, wherein the eastern Luzon seaboard, specifically the province of Quezon and its vicinity, received anomalous amounts of rain that resulted in loss of lives and destruction of properties (Yumul et al. 2009a). In dealing with conventional El Niño events, available data shows that the Philippines had learned and had improved much in the handling these kind of occurrences. Significant improvement has been observed on how the Government handled past El Niño events in terms of proactive trade policy, local distribution and pricing of rice coupled with improved world rice market and available foreign exchange reserves (Chang and Reuveny 2009; Dawe et al. 2009). This is further complemented by increased understanding of the ENSO phenomenon and available advance technology that gives early warning about this climate event (Dawe et al. 2009; Yumul et al. 2009b). Sea surface temperature anomaly (SSTA) has been known to directly affect rice production. As the SSTA increases and drought ensues, rice production decreases.

Yumul et al.: 2009-2010 El Niño Southern Oscillation in the Philippines

Philippine Journal of ScienceVol. 139 No. 1, June 2010

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This has occurred not only in the Philippines but also in other Asian countries like Indonesia and Thailand (e.g. Naylor et al. 2001; Dawe et al. 2009; delos Reyes and David 2009). In spite of these realizations and the lessons we have learned in handling this kind of event, the country cannot afford not to be alarmed whenever the prevailing condition is that of an El Niño.

In 2009, the Philippines was characterized by hazards and disasters that were mostly triggered by too much water – from floods and flash floods to landslides. What is ironic is that most of the media releases at the start of this year were warnings and reminders to observe water conservation because of the ENSO event being experienced in the country. The present ENSO event has been recognized last year that resulted into the Philippine Government issuing an advisory about the 2009-2010 El Niño as early as August 2009. The public, though, may not have really felt the need to prepare for El Niño because the period of September-October 2009 during the initial phase of the El Niño was actually very wet due to tropical cyclones characterized by too much water content dumped in Luzon. It is the purpose of this paper to characterize the 2009-2010 El Niño event especially in the context of climate change and how the Philippines can mitigate the negative impacts of this ENSO event.

2009-2010 ENSOThe upper ocean in the tropical eastern Pacific from time to time undergoes extensive warming which may last up to three months or more. This unusual warming, known as El Niño, is attributed to a change in atmospheric pressure between the western and central regions of the Pacific Ocean. El Niño causes tropical rainfall to shift from the western to the eastern Pacific Ocean bringing increased rains in Ecuador and northern Peru and drought to Indonesia and Australia (WMO 2009). The observed ocean and atmospheric changes are part of the global variations in the atmosphere referred to as the El Niño Southern Oscillation (ENSO). The Southern Oscillation pertains to changes in sea level air pressure patterns in the Southern Pacific Ocean. A relationship has been observed in the change in air pressures between Darwin, Australia and Papeete, Tahiti in the South Pacific. The average air pressure in Darwin is higher than in Tahiti during an El Niño. The daily pressure variations between Tahiti and Darwin are computed as the Southern Oscillation Index and offer a means of monitoring ENSO conditions (e.g. Moya and Malayang 2004; National Weather Service 2009).

El Niño and La Niña events are monitored using sea surface temperature (SST) anomalies which has resulted in the subdivision of the tropical Pacific basin into four regions based on their SSTs: Niño 1 (80°-90°W and 5°-

10°S), Niño 2 (80°-90°W and 0°-5°S), Niño 3 (90°-150°W and 5°N-5°S) and Niño 4 (150°-160°E and 5°N-5°S). With the increasing number of studies on the ENSO, some modifications have been proposed for these regions. Niño 1+2 combines the original Niño 1 and Niño 2 while Niño 3.4 has been proposed to cover the region between 120°-150°W and 5°N-5°S. An El Niño event is declared if the SST anomaly in the Niño 3.4 region (deviation from the normal) is at least 0.5°C over a period of three consecutive months (e.g. Trenberth 1997; Moya and Malayang 2004; Kao and Yu 2009). Based on deviations of the SSTs from normal, El Niño events can be classified as weak (SSTA = 0.5 to 1.0°C), moderate (SSTA = 1.0 to 1.5°C) and strong (SSTA >1.5°C) (e.g. NOAA 2009). The 1982-1983 and 1997-1998 are considered strong events while the 1994-1995 El Niño event is weak and the 1986-1987, 1991-1992 and 2002-2003 events are considered moderate ones (e.g. Landsea and Knaff 2000; McPhaden 2004). In addition to the decreased amount of rainfall in general in the Western Pacific region, the duration of a conventional El Niño event is also used to gauge its severity. For the present El Niño, the peak SSTA was at 1.8°C but was noted only for a short duration. The overall average SSTA which persisted for a long period is 1.5°C making the 2009-2010 El Niño a moderate event.

In June 2009, a steady increase in SSTs was reported by various meteorological agencies and SST anomalies ranged from 0.6°C to 0.9°C. By July 2009, SST values were 1°C above average along the equatorial eastern Pacific marking the arrival of El Niño. The 2009-2010 El Niño is, thus, considered a conventional El Niño since the maximum SST anomalies are in the tropical eastern Pacific. This is in contrast to the Modoki or Dateline El Niño which, as noted above, is characterized by maximum SST anomalies which converge near the dateline (e.g. Weng et al. 2007; Kao and Yu 2009). Most model forecasts indicated that the El Niño will persist for several months with NOAA predicting that the condition was going to continue until winter of 2009-2010. The El Niño gained strength in December 2009 with calculated Niño-3.4 index values greater than +1.8°C. The advisories warned of possible increased precipitation in the central and west-central Pacific Ocean whereas drier than average conditions were expected to prevail over Indonesia (Climate Prediction Center 2009; 2010; NOAA 2009).

In the Philippines, the Department of Science and Technology - Philippine Atmospheric, Geophysical and Astronomical Services Administration (DOST-PAGASA) also started issuing warnings and advisories on the impending El Niño condition that was likely to impact the country. Climate models suggest that the country may experience the effects of El Niño until June 2010. Effects such as below normal rainfall conditions are already experienced in some parts of the country



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(Figure 1). This is especially critical for the Visayas and Mindanao areas which, despite the enormous amounts of rain dumped in Luzon by the September – October 2009 weather disturbances, received minimal rainfall since that period. Some areas in Capiz Province in Panay island that have been experiencing below normal rainfall since August, were declared to be under drought conditions (five consecutive months of below normal rainfall) (Figure 1). By December 2009, dry spell (three to four consecutive months of below normal rainfall) was affecting other parts of the country such as Pampanga, Batangas, Aurora and Quezon in Luzon island; Northern Samar, Aklan, and Guimaras in the Visayas; and Davao del Sur, South Cotabato and Sultan Kudarat in Mindanao (DOST-PAGASA 2010). The impacts of the 2009-2010 El Niño event in the Philippines worsened by February 2010. The DOST-PAGASA El Niño Advisory No. 7 reported that three more provinces, namely, Isabela, Nueva

Viscaya and Quirino were under drought conditions. The number of provinces under dry spell also increased. These include Abra, Benguet, Kalinga, Ifugao, Apayao, Mountain Province, Ilocos Norte, Ilocos Sur, La Union, Pangasinan, Cagayan and Bataan. The National Disaster Coordinating Council reported that the crop damage due to the current El Niño is estimated at P10.4 billion with the Cagayan Valley incurring the biggest loss.

DISCUSSION

From wet to dry: Turning off the faucetWhen Government announced in August 2009 that the country must prepare for an El Niño based on DOST-PAGASA prognosis, it was not surprising that people were not so impressed considering what happened in

Figure 1. Rainfall anomaly maps for the Philippines for the months of August 2009 to January 2010. Since August 2009, some areas in Capiz have received below normal rainfall (yellow and red colored areas). Other parts of Luzon and Visayas are under dry spell conditions as of January 2010 (source: DOST-PAGASA).



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September to October 2009. As is known now, September saw the onslaught of Tropical Storm Ketsana (local name: Ondoy) that brought Metropolitan Manila and nearby areas to a standstill due to massive flooding. October saw the flooding of Northern Luzon, specifically Pangasinan while Benguet experienced a number of rainfall-induced landslides, due to Typhoon Parma (local name:Pepeng). The latter part of October saw the flooding of southern Luzon due to Typhoon Mirinae (local name: Santi). The media started asking how it can be so wet when the Philippines should actually be under an El Niño event. Nonetheless, by November 2009, it was recognized that although Luzon was very wet, Visayas and Mindanao were under stress in terms of water scarcity (Figure 1). In December 2009, most of Luzon had received below normal rainfall resulting in some provinces being recognized under or about to experience dry spell and drought conditions. An area is considered under a dry spell condition if its rainfall has been below normal for at least three months while areas under drought conditions are those that have received below normal rainfall for five months.

Available data shows that as of January 2010, the amount of rain was still below normal in most parts of the country triggering the reactivation of the Department of Agriculture-led Task Force El Niño to deal with the situation (Figure 1). The National Disaster Coordinating Council (NDCC) coordinates other efforts to ensure that the negative impact of this event is minimized. The APEC Climate Center (2010) climate forecast shows that the 2009-2010 El Niño event continues to prevail in the Pacific Ocean with warm sea surface temperature anomalies exceeding 1.5°C. Available data suggests that the El Niño is now near its peak and is expected to persist through spring (APEC Climate Center 2009). The APCC climate outlook for February to April 2010 indicates warm conditions and below normal rainfall for the Philippines (Figure 2). As is always the case, when water scarcity leading to drought is just starting (meteorological drought), the concern is more on the natural event that caused it. But as the drought progresses to agricultural and hydrological droughts, the issue shifts to how the negative impacts (social, economic and political) of the drought on society can be minimized (WMO 2006). For urban centers in the country, repairs of leaks and reduction of water pressure are being done with the possibility of rationing water. Increasing public awareness on the impending problem and convincing everybody to conserve water are being done now. Shallow tube wells, introduction of drought resistant rice variety, planting quick turn-around plant varieties in areas with enough moisture and repair of irrigation systems are being implemented in the agricultural rural areas. With the shutdown or reduced operation of hydroelectric plants,

the maintenance of fuel-fired power plants is being fast tracked to avoid a power crisis. For that matter, specific and directed interventions by the local government units during this particular El Niño event must be the norm as the effects of ENSO vary regionally.

It is supposed to be dry but why is there flooding?While the NDCC is preparing for the negative effects of the El Niño event, floods and landslides were being reported along the eastern seaboard of Luzon (i.e. Aurora) and Mindanao (i.e. Surigao-Davao area) due to rains associated with the Northeast Monsoon and tail-end of the cold front. For that matter, Naujan in Oriental Mindoro was also declared under a state of calamity in the second week of January 2010 due to strong rains. It is important for people to understand that: a) if there is an El Niño event, not all areas in a country would be dry. Some would still be receiving rain even to the point of causing flooding as observed in the mentioned areas; and b) there are no two similar El Niño events (e.g. McPhaden 2004). Although we have learned a lot from previous El Niño events, we cannot assume or even conclude that what were true then can be applicable today.

It is in this context that the present 2009-2010 El Niño event must not be taken as an individual event but as part of the whole climate process. If one were to look at the 2009 weather, it was characterized by very wet conditions (e.g. anomalous rain associated with the cold front in January 2009, very wet summer covering the months March to May 2009 and the strong tropical cyclones that hit the country) and can be said to be La Niña-like (Figure 1). Conventional La Niña events in the country are generally wet. This has been explained by the presence and greater chances of formation of vertical shear winds during La Niña events which is not present during El Niño events (e.g. Pielke and Landsea 1999; Chan and Liu 2004). Thus, the 2009 events are consistent with the empirical observation that in the Philippines, wet conditions precede an El Niño event. Additional studies are needed to constrain and interpret these observations in the general context of a globally warming world within the backdrop of climate uncertainty (e.g. McPhaden 2004; Larkin and Harrison 2005b; Tootle et al. 2009).

Although the El Niño phenomenon cannot be said to directly indicate any changes in the climate, any perturbations in the El Niño cycle can actually be interpreted as a possible representation of climate uncertainty (Diaz et al. 2001; IPCC 2007). For that matter, in the context of human-induced global warming, climate uncertainty is more of the norm rather than the exception (e.g. Parry et al. 2001; Kerr 2007; Roe and Baker 2007; Risbey 2008). In the Philippines, conventional El Niño events are associated with droughts. With the added effect



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Figure 2. The probabilistic multi model ensemble (MME) forecasts for the period February to April 2010. The MME model indicates that the Philippines will continue to experience: A. below normal rainfall (50 to 70%) and B. temperatures will remain warmer (source: APEC Climate Center 2010).



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of global warming and climate uncertainty, El Niño-induced droughts can actually be expected to be more severe (Parry et al. 2009; Schneider 2009; Smith et al. 2009; Stine et al. 2009).

Shall we go on a crisis-mode?The different institutions in the country, from the Government (both national and local) to the academe, private sector and civil society organizations, are all advocating to proactively address the negative effects of El Niño. There is a good reason for this. The data would show that there are provinces that are under dry spell/ drought level conditions. For Metropolitan Manila, the water inflow to the Angat Dam, which is its main water source, is on the low side (Table 1). Reduced water pressure, intensive leak repairs, standby well reactivation and installation of static tanks, among others, are being done by the water concessionaires to ensure that Metropolitan Manila will have water supply until June 2010 (http://business.inquirer.net/money/breakingnews/view/20100114-247386/MWSS-to-draw-less-water-from-Angat-dam-by-February; http://www.mayniladwater.com.ph/news.php). The National Water Resources Board (NWRB) and the water concessionaires have identified additional sources of water that can be tapped should the need arise. By law, it is also set that water supply for domestic usage takes precedence over that of power generation and irrigation. However, if the drought condition continues past July, the capital city may have a problem with water supply. It would be remembered that the 2007 dry spell occurred in July and August 2007 (Yumul et al. 2009a; 2009b). It is only February (as of the initial writing of this short communication) and the summer months are just about to start. That would mean that the chances of rainfall would be very low. Mindanao, for that matter, has been

placed under a state of calamity in March 2010 due to serious power outages since a significant amount of their power supply comes from hydroelectric power plants. With the absence of rain, these hydroelectric plants will have low water level, preventing them to optimize their power generating capacities. With this kind of scenario, the country really has to tackle things proactively. There should already be a shift in the “reason for concern” status to that of “crisis” mode. It is in having this crisis mode status that people start to take notice of what is happening and start doing things expected from them. This is, however, easier said than done. Each decision involves socio-economic implications. It is in this respect, that the different stakeholders have to fully understand the issue and determine which options they would adopt. By doing this, it is expected that most, if not all, will be onboard in addressing the negative impacts of the 2009-2010 ENSO event.

CONCLUSIONAvailable data shows that the 2009-2010 conventional El Niño is a moderate one and that it may last until June 2010. However, one cannot dismiss the possibility that the lack in water that we are experiencing in February will not extend until the third quarter of this year. Instead of taking the risk that we can run out of water by July 2010, it may be prudent for the country to go on crisis mode and assume that the prevailing El Niño event can extend even after the summer (April, May, June) of 2010.

Table 1. Data for the different dams in Luzon island, as of February 9, 2010, show lower water levels compared to the normal elevations (source: DOST-PAGASA).

DamsReservoir

Water Level (m)

Normal High/Spilling

Elevation (m)

Deviation from Normal High Elevation (m)

Elevation From Rule Curve (m)

Deviation from Rule Curve (m)

ANGAT 198.86 212.00 -13.14 201.26 12.40

IPO 100.76 100.87 -0.11 - -

LAMESA 79.93 80.00 -0.07 - -

AMBUKLAO 740.26 752.00 -11.74 752.00 -11.74

BINGA 561.30 575.00 -13.70 574.00 -12.70

SAN ROQUE 255.71 278.00 -22.29 256.79 -1.08

PANTABANGAN 207.34 221.00 -13.66 210.31 -2.97

MAGAT 166.93 193.00 -26.07 187.51 -20.58



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ACKNOWLEDGEMENTDiscussions with the different members of the National Disaster Coordinating Council, especially the Office of Civil Defense-Department of National Defense, have provided us a good glimpse of the preparations our country is doing. To these people we are thankful. Logistic support came from the Department of Science and Technology, Philippine Atmospheric, Geophysical and Astronomical Services Administration and University of the Philippines-National Institute of Geological Sciences.

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