Read More - Philippine Institute for Development Studies

More documents

Recommendations

Info

10 SCF Folio Understanding the ENSO phenomenon and its implications Ask anyone about what he/she thinks El Niño place and something must be done to address its is and the usual answers would be—a possible consequences. severe drought or a long hot summer or a dry spell followed by heavy rains. While all of these are indeed associated with El Niño, they are, however, merely the effects or impacts of this phenomenon. What it really is lies somewhere in the Pacific. Feeling the heat Although the physical occurrence of El Niño (and La Niña) takes place in the Pacific, its effects are felt in other parts of the world, similar to a ripple effect in a big pond. This is due to the so-called southern oscillation (SO) What it basically is… El Niño is a condition that takes place in the Central and Eastern Equatorial Pacific (CEEP) Ocean, when the sea surface temperature (SST) becomes unusually warmer than the normal temperature. This condition can prevail for more than a year, thus adversely affecting the economy in both local and global scale. The sea or ocean surface usually registers a certain normal temperature. Any departure from this normal level is considered an anomaly. If the temperature rises from normal, it is called a positive anomaly. This condition is associated with El Niño. Conversely, if the temperature drops from normal, it is called a negative anomaly and is more popularly related to La Niña. Either way, any change in the temperature, just like in the human body, indicates that something unusual is taking which refers to a “see-saw” in atmospheric pressure between the western (represented by Darwin in Australia) and eastern Pacific (represented by the island of Tahiti). These variations in the atmosphere in the Pacific, combined with changes in the SST as discussed earlier, are responsible for bringing about abnormal climatic events. The interaction between sea and atmosphere variations refers to the El Niño Southern Oscillation (ENSO) and potentially influences extreme climate events in the world (El Niño refers to the ocean or sea component of ENSO while the SO refers to the atmospheric component). El Niño and La Niña are basically flip sides (warm and cold phases, respectively) of the ENSO and as such, do not take place simultaneously in one area/region. However, in terms of teleconnection or the links of El Niño El Niño (EN) is Spanish for “The Christ Child,” a name given by Peruvian fishermen to the phenomenon that they usually observed during the period near Christmas time when the water in climate over great distances, if the eastern part of the Pacific experiences an unusual ocean the Pacific Ocean off the coast of Peru would become unusually warm. Every two to nine years, for warming and low atmospheric unexplained reason, trade winds in the Pacific region, which drive the surface warm waters of the pressure (characteristics of the tropics to the west Pacific, weaken. As a result, these warm waters of the western Pacific drift eastward, resulting in the occurrence of El Niño in the eastern part of the Pacific. warm phase or El Niño), then the western part of the Pacific will Southern oscillation Southern oscilllation (SO) is an east-west balancing movement of air masses between the eastern likely experience the opposite effect, characterized by cooler Pacific and the Indo-Australian areas. It is measured as the difference between the overlying ocean and high atmospheric atmospheric pressures at Darwin (northern Australia) and Tahiti (south-central Pacific). This term pressure. was coined by the British scientist named Sir Gilbert Walker during the 1920s when he observed that when the atmospheric pressure rises in the east, the waters of the eastern Pacific are unusually cold, and when the atmospheric pressure drops in the eastern Pacific, the waters in this part of the Pacific are unusually warm. The opposite effects are observed in the western Pacific. The implications The effects of ENSO on climate variability all over the globe
11 inevitably have impacts on the various ecological and agricultural production systems around the world. In the Philippines, for instance, an ENSO event can trigger extreme climatic effects such as droughts, strong winds, floods and flashfloods, increasing or decreasing temperatures and many more. The impacts on Philippine climate are initially felt three or five months after the development of an ENSO phenomenon in the tropical Pacific. If the ocean-atmosphere interaction or ENSO is stronger than the usual, however, the Philippines may feel the weather abnormalities much earlier. One of the abnormalities brought about by El Niño, the warm phase of ENSO, is a generally drier weather condition, the effect of which is greatly felt during the dry season. From May to September or during the country’s rainy season due to the southwest monsoon, though, rains may still be expected or felt even with an El Niño occurring in the Pacific. Once the southwest monsoon rainy season ends by late September or early October, rains may be much lesser than normal during an El Niño event. This is critical especially for rice farmers in Central Luzon who traditionally prepare for their second cropping season before the end of the year. If there is indeed an El Niño event, this implies, among others, that enough water should have been stored in the water reservoirs so as to provide irrigation for the crop upon the onset of the dry season (January to April) when hardly any or no rain might be expected. Finally, once the El Niño/La Niña signs start to brew, there is nothing that can stop them from occurring. It is nonetheless useful to understand the processes on how they evolve to be able to be better prepared for them. (Economic Issue of the Day Vol. V, No. 1-July 2005) Knowing when El Niño/La Niña is here In a previous Economic Issue of the Day (Vol. V, No. 1, July 2005), a basic understanding was presented on what the El Niño Southern Oscillation (ENSO) phenomenon is all about, its characteristics and two phases, and its implications. ENSO is a phenomenon that takes place in the central and eastern equatorial Pacific largely characterized by an interaction between the ocean and the atmosphere and their combined effect on climate. The mutual interaction between the ocean and the atmosphere is a critical aspect of the ENSO phenomenon. Major ENSO indicators are the sea surface temperature anomaly (SSTA) and the Southern Oscillation Index (SOI). SSTA refers to the departure or difference from the normal value in the sea or ocean surface temperature. El Niño events are characterized by positive values (greater than zero) within a defined warm temperature threshold while La Niña events are characterized by negative values (less than zero) within a defined cold temperature threshold. The SOI, on the other hand, measures the differences or fluctuations in air or atmospheric pressure that occur between the western and eastern tropical Pacific during El Niño and La Niña episodes. It is calculated on the basis of the differences in air pressure anomaly between Darwin in Australia (western Pacific) and Tahiti in French Polynesia (eastern Pacific). These two locations/stations are used in view of their having long data records. Albeit the seeming straightforward description of these ENSO-related events as noted in the above, it is to be emphasized that through the years, it has not been easy to come up with a commonly agreed definition and identification of these ENSO-related events, i.e., El Niño or La Niña. The reason is due to the use of more than one standard index as basis in monitoring ENSO phenomena and the employ of different methods in determining the magnitude or value of such index and threshold as well as the length of time that such magnitude persists. In line with this, the Philippines adopted the World Meteorological Organization (WMO) Regional Association IV Consensus Index and Definitions of El Niño and La Niña. Region IV includes the North and Central America member nations of the WMO, whose operational definitions in use of the two ENSO phases are the following: El Niño: A phenomenon in the equatorial Pacific Ocean characterized by a positive SST departure from
Page 1 and 2: SCF Folio A compilation of informat
Page 3 and 4: 3 Administration (PAGASA), the Phil
Page 5 and 6: 5 Learning the basics Dr. John Mull
Page 7 and 8: 7 The dry season is also subdivided
Page 9: 9 Tropical cyclone average tracks J
Page 13 and 14: 13 Reaching out and increasing awar
Page 15 and 16: 15 To ensure that the SCFs are rend
Page 17 and 18: Communicating through climate indic
Page 19 and 20: 19 Table 1. Awareness, usefulness,
Page 21 and 22: 21 Very often, this leads to extrem
Page 23 and 24: 23 agency, PAGASA, and sent out to
Page 25 and 26: 25 municipality. LGUs may send in t
Page 27 and 28: 27 SCF is popular in Bukidnon but..
Page 29 and 30: 29 the Provincial Agriculture Offic
Page 31 and 32: 31 Analysis and research/survey res
Page 33 and 34: 33 As the results in this initial s
Page 35 and 36: 35 Table 2. El Niño and La Niña e
Page 37 and 38: 37 average, and wet years were calc
Page 39 and 40: 39 local corn growers. In guiding f
Page 41 and 42: 41 dominated regions of northern Ne
Page 43 and 44: 43 The influence of ENSO on frost r
Page 45 and 46: 45 It is the timing of the latest f
Page 47 and 48: A model for valuing seasonal climat
Page 49 and 50: 49 And on rice crop... Nueva Ecija
Page 51 and 52: 51 Security against climate variabi
Page 53 and 54: 53 been dominating the Table 1. Bor
Page 55 and 56: 55 The need to help rice and corn f
Page 57 and 58: 57 Figure 1. Rainfall outlook, July
Page 59 and 60: 59 In Cebu: use of SCF gives higher
Page 61 and 62:
61 units of N fertilizer based on g
Page 63 and 64:
63 Determining corn farmers’ deci
Page 65 and 66:
65 Table 2. Farmers’ responses to
Page 67 and 68:
67 Project Team Australia Dr. Peter
show all

Read More - Philippine Institute for Development Studies

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?