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26 March 2009

Space storm alert: 90 seconds from catastrophe


Space storm alert: 90 seconds from catastrophe

From the New Scientist 23 March 2009 by Michael Brooks

IT IS midnight on 22 September 2012 and the skies above Manhattan are filled with a flickering curtain of colourful light. Few New Yorkers have seen the aurora this far south but their fascination is short-lived. Within a few seconds, electric bulbs dim and flicker, then become unusually bright for a fleeting moment. Then all the lights in the state go out. Within 90 seconds, the entire eastern half of the US is without power.

A year later and millions of Americans are dead and the nation’s infrastructure lies in tatters. The World Bank declares America a developing nation. Europe, Scandinavia, China and Japan are also struggling to recover from the same fateful event - a violent storm, 150 million kilometres away on the surface of the sun.

It sounds ridiculous. Surely the sun couldn’t create so profound a disaster on Earth. Yet an extraordinary report funded by NASA and issued by the US National Academy of Sciences (NAS) in January this year claims it could do just that.

Over the last few decades, western civilisations have busily sown the seeds of their own destruction. Our modern way of life, with its reliance on technology, has unwittingly exposed us to an extraordinary danger: plasma balls spewed from the surface of the sun could wipe out our power grids, with catastrophic consequences.

The projections of just how catastrophic make chilling reading. “We’re moving closer and closer to the edge of a possible disaster,” says Daniel Baker, a space weather expert based at the University of Colorado in Boulder, and chair of the NAS committee responsible for the report.

It is hard to conceive of the sun wiping out a large amount of our hard-earned progress. Nevertheless, it is possible. The surface of the sun is a roiling mass of plasma - charged high-energy particles - some of which escape the surface and travel through space as the solar wind. From time to time, that wind carries a billion-tonne glob of plasma, a fireball known as a coronal mass ejection (see “When hell comes to Earth”). If one should hit the Earth’s magnetic shield, the result could be truly devastating.

The incursion of the plasma into our atmosphere causes rapid changes in the configuration of Earth’s magnetic field which, in turn, induce currents in the long wires of the power grids. The grids were not built to handle this sort of direct current electricity. The greatest danger is at the step-up and step-down transformers used to convert power from its transport voltage to domestically useful voltage. The increased DC current creates strong magnetic fields that saturate a transformer’s magnetic core. The result is runaway current in the transformer’s copper wiring, which rapidly heats up and melts. This is exactly what happened in the Canadian province of Quebec in March 1989, and six million people spent 9 hours without electricity. But things could get much, much worse than that.

25 March 2009

El Nino and Global Warming

From Scientific American via Reuters

By David Fogarty, Climate Change Correspondent, Asia

SINGAPORE (Reuters) - Research showing an El Nino event in 1918 was far stronger than previously thought is challenging the notion climate change is making El Nino episodes more intense, a U.S. scientist said on Tuesday.

El Nino causes global climate chaos such as droughts and floods. The events of 1982/83 and 1997/98 were the strongest of the 20th Century, causing loss of life and economic havoc through lost crops and damage to infrastructure.

But Ben Giese of Texas A&M University said complex computer modelling showed the 1918 El Nino event was almost as strong and occurred before there was much global warming caused by the burning of fossil fuels or widespread deforestation.

The outcome of the research was valuable for several reasons, Giese told Reuters from Perth in Western Australia.

“It questions the notion that El Ninos have been getting stronger because of global warming,” he said ahead of a presentation of his team’s research at a major climate change conference in Perth.

The 1918 event also co-incided with one of India’s worst droughts of the 20th century.

“We know that El Ninos and drought in India are often related to each other,” he said.


El Nino is an abnormal warming of the surface waters in the eastern Pacific off South America that causes the normally rainy weather in the western Pacific to shift further to the east.

This causes drought in parts of Australia, Southeast Asia and India as well as flooding in Chile and Peru, colder and wetter winters in the southern United States and fewer Atlantic hurricanes.

The droughts in Australia of 1982-83 and 1997-98 rank among the worst in the nation’s modern history. Drought also occurred in eastern Australia from 1918-20.

Giese said his team ran a complex ocean computer model that, for the first time, used the results of a separate atmospheric model produced by the National Oceanic and Atmospheric Administration.

The result was a simulation of ocean temperatures, currents and other measures from 1908 to 1958.

For 1918, the simulation produced a strong abnormal surface warming in the central Pacific and weaker warming nearer the South American coast.

There were very few measurements of the tropical Pacific during 1918, the last year of World War One, and ship-based measurements along the South American coast suggested only a weak El Nino.

This, Giese said, reinforced the point that there is limited data about El Ninos prior to the 1950s and that computer models were one way to get a clearer picture of the past.

“We cannot rely on what El Nino looks like today to try to understand what El Nino patterns looked like in the past.”

“It makes it a challenge to talk about El Nino and global warming because we simply don’t have a detailed record,” he added.

24 March 2009

Weather Modification in Aceh and Riau Province

Weather Modifications.
To help to solve the smoke problems in Aceh, weather modification team (UPT Hujan Buatan), BPPT immediately prepared aircraft Casa NC212-200 BPPT that it was doing pioneering flight services in East Kalimantan to be modified from the passenger aircraft to seeder aircraft to be sent to Banda Aceh.
The team of the plane (Casa NC212-200 registration number PK-TLE Plans operated by PT Buana Nusantara Air) has arrived in Banda Aceh on 22 February 2009,the departure was released by Deputy Head of BPPT TPSA Jana T. Anggadireja on Sunday, 22 February 2009 from Great Halim Perdanakusuma. Artificial rainfall operations in the province of Aceh last for 10 days until March 04, 2009.

Governor of the Province Irawandi Jusuf was greatful for the assistance from the TMC air operations by the central government granted to the province of Aceh,because the clouds of smoke can be overcome, especially in the provinces of Aceh Barat and Aceh Jaya

BPPT TMC operations continue to Riau Province.

Artificial rainfall operations in Riau province supported Casa 212-200 BPPT aircraft registration number PK-TLE used in the artificial rain operations in Aceh province. Posko flight activities conducted from Pangkalan Air Simpang Tiga Pekanbaru. Five days after the operation, forest fires, hotspots and smoke were reduced, and the smoke problems were successfully solved by using weather modifications technique (artificial rain).
On the fifth day hot spot no longer exists in the Riau Province, and the BPPT rain operation ended.

(UPT-HB)

17 March 2009

Fuzzy Clustering of Climate Regions of Indonesian Maritime Continent

Jurnal Matematika dan Sains Vol. 8 No. 2, June 2003, p. 57 – 61

The Houw Liong 1) ,
Bannu 2) ,
P.M. Siregar 3)

1) Department of Physics, ITB
2) Department of Physics, UNHAS.
3) Departement of Geophysics & Meteorology, ITB

Abstract
In general drought in Indonesia can be predicted from intensities of El Niño that can be defined by using time series of sea surface anomaly on Pacific Ocean (SSTA 3.4). It can be shown that when El Niño with strong intensities occur then more than 65% regions in Indonesia the precipitations are below normal (drought in Indonesia). The correlation between strong El Niño intensities and percentages of regions in Indonesia with precipitations below normal are high, but when the intensities are weak the correlations are low. In this case other phenomena such as on Indian Ocean Dipole Mode (IOD) can contribute to drought in Indonesia. Clustering of climatic regions in Indonesia based on monthly rainfall pattern using fuzzy set, fuzzy relations or Kohonen’s neural network will help to clarify drought on these regions. It can be shown that climatic regions in Indonesia can be clustered based on monthly rainfall patterns that are strongly influence by Australian monsoon which is known as North Australia-Indonesian Monsoon (NAIM) and Maritime Continent (MC) which has equatorial precipitation characteristic. The climatic clustering is based on the ground that ENSO and IOD are regional atmospheric dynamic so the clustering should be based on average monthly pattern or geopotential height. The east MC and NAIM will be influence strongly by ENSO and the western MC especially south Sumatra and west Java is influence also by IOD.

Keywords : fuzzy clustering, fuzzy set, fuzzy relations, ENSO, IOD, drought, monsoon, maritime continent

15 March 2009

POLARISASI DAN FUNGSI TRANSFER EMISI SINYAL ULF DAN PREKUSOR GEMPA

ANALISIS POLARISASI DAN FUNGSI TRANSFER EMISI SINYAL ULF DAN KAITANNYA DENGAN GEMPA BUMI DI INDONESIA

Sarmoko Saroso
Pusat Pemanfaatan Sains Antariksa LAPAN Jl. Dr. Djundjunan No. 133, Bandung 40173email: sarmoko@bdg.lapan.go.id

Anomali sinyal ULF pada variasi medan geomagnet adalah merupakan salah satufenomena yang diyakini kebenarannya dalam studi elektromagnetik yang berhubungan dengankejadian gempa bumi, seperti terjadinya emisi dari kerak bumi yang berasal dari sumber gempa. Dari studi terdahulu telah banyak ditemukan pertanda anomali sinyal ULF sebelum kejadiangempa bumi berskala besar. Untuk membuktikan kebenaran fenomena tersebut dan untukmenjelaskan hubungan antara fenomena elektromagnetik dan mekanisme fisis yang mungkinterkait, telah dilakukan analisis data geomagnet di Kototabang dan Biak yang berhubungandengan kejadian gempa Sumatra. Studi kasus dilakukan untuk mengamati anomali sinyal ULF yang berhubungan dengan gempa Aceh yang terjadi pada tanggal 26 Desember 2004 (magnitudo Mw= 9.0 dan kedalaman = 30 km, dari katalog USGS) dan gempa Nias yang terjadi pada tanggal 28 Maret 2005 (magnitudo Mw= 8.7 dan kedalaman = 30 km). Dalam menentukananomali emisi sinyal ULF digunakan dua metoda, yaitu analisis polarisasi dan analisis fungsitransfer berbasis transformasi wavelet. Hasil yang diperoleh menunjukkan bahwa anomali yang ditentukan dengan menggunakan kedua metoda tersebut mempunyai variasi amplitudo yang sama. Variasi tersebut teramati di Kototabang beberapa minggu sebelum kejadian gempa berskala besar dengan M>6.5, sedangkan data di Biak tidak terlihat adanya perubahan. Hal ini menunjukkan bahwa anomali yang teramati tersebut merupakan sinyal yang kemungkinan besarberhubungan dengan fase awal terjadinya gempa Sumatra.

Seminar Nasional Sains dan Teknologi-II 2008,Universitas Lampung, 17-18 November 2008

12 March 2009

Anticipate the Coming of Solar Superstorms

October 23, 2003:

Newly uncovered scientific data of recorded history's most massive space storm is helping a NASA scientist investigate its intensity and the probability that what occurred on Earth and in the heavens almost a century-and-a-half ago could happen again.

What happened in 1859 was a combination of several events that occurred on the Sun at the same time. If they took place separately they would be somewhat notable events. But together they caused the most potent disruption of Earth's ionosphere in recorded history. "What they generated was the perfect space storm," says Bruce Tsurutani, a plasma physicist at NASA's Jet Propulsion Laboratory.

To begin to understand the perfect space storm you must first begin to understand the gargantuan numbers with which plasma physicists like Tsurutani work every day. At over 1.4 million kilometers (869,919 miles) wide, the Sun contains 99.86 percent of the mass of the entire solar system: well over a million Earths could fit inside its bulk. The total energy radiated by the Sun averages 383 billion trillion kilowatts, the equivalent of the energy generated by 100 billion tons of TNT exploding each and every second.

But the energy released by the Sun is not always constant. Close inspection of the Sun's surface reveals a turbulent tangle of magnetic fields and boiling arc-shaped clouds of hot plasma dappled by dark, roving sunspots.

Once in a while--exactly when scientists still cannot predict--an event occurs on the surface of the Sun that releases a tremendous amount of energy in the form of a solar flare or a coronal mass ejection, an explosive burst of very hot, electrified gases with a mass that can surpass that of Mount Everest.
What transpired during the dog days of summer 1859, across the 150 million-kilometer (about 93 million-mile) chasm of interplanetary space that separates the Sun and Earth, was this: on August 28, solar observers noted the development of numerous sunspots on the Sun's surface. Sunspots are localized regions of extremely intense magnetic fields. These magnetic fields intertwine, and the resulting magnetic energy can generate a sudden, violent release of energy called a solar flare. From August 28 to September 2 several solar flares were observed. Then, on September 1, the Sun released a mammoth solar flare. For almost an entire minute the amount of sunlight the Sun produced at the region of the flare actually doubled.

"With the flare came this explosive release of a massive cloud of magnetically charged plasma called a coronal mass ejection," said Tsurutani. "Not all coronal mass ejections head toward Earth. Those that do usually take three to four days to get here. This one took all of 17 hours and 40 minutes," he noted.

Not only was this coronal mass ejection an extremely fast mover, the magnetic fields contained within it were extremely intense and in direct opposition with Earth's magnetic fields. That meant the coronal mass ejection of September 1, 1859, overwhelmed Earth's own magnetic field, allowing charged particles to penetrate into Earth's upper atmosphere. The end game to such a stellar event is one heck of a light show and more -- including potential disruptions of electrical grids and communications systems.

http://science.nasa.gov/headlines/y2003/23oct_superstorm.htm

Comments :

We have to understand some indicators before the coming of superstorms , to anticipate what will happen in 2012.

HouwLiong

10 March 2009

Scientists worry about solar superstorm

Scientists worry about solar superstorm.

Sun capable of unleashing geomagnetic blast that could cost tens of billions.


By Leonard David
Senior space writer

updated 12:04 p.m. ET May 2, 2006
Hypothetically thinking, Odenwald said, what about the scenario of an 1859-type superstorm taking place in 2012 at the peak of the next sunspot cycle?

Of the nearly 300 geosynchronous Earth-orbiting (GEO) satellites in operation, "such a storm may only actually kill a few dozen of the oldest systems, but will likely reduce the operating life of all the other satellites by 5 to 10 years," Odenwald said. "That would, in the long run, be a bigger economic catastrophe."

Odenwald projects billions of dollars of lost GEO satellite profit during an 1859-caliber superstorm. The model he has used to reach ballpark numbers includes a realistic treatment of how leased transponders are actually shifted to neighboring satellites from failing "host" satellites.

The estimated profit loss tallies about $30 billion, Odenwald said. That figure is expected to climb higher as he mixes in various types of catastrophic satellite anomalies.

Future work will include collateral economic impacts, pushing the profit loss upwards of $70 billion, Odenwald suggested. "The GEO satellites themselves generate about $97 billion in revenue each year. A superstorm may well eat up most of that revenue for at least a few years."

Odenwald said that his research approach, coupled with more knowledge about how satellites are affected by severe solar storms — some of which is proprietary or classified — will help boost his statistical confidence level.

Dollar impact
A superstorm would influence operations below GEO, among lower-altitude satellites. For one, such a powerful outburst would disrupt civil and government navigation systems like the Global Positioning System. GPS satellite signals travel through a part of Earth's atmosphere called the ionosphere to receivers on or near Earth.

GPS is a worldwide radio-navigation system formed from a constellation of satellites and their ground stations. GPS uses the satellites as reference points to calculate positions on the ground accurate to a matter of meters. Space weather disturbances in the ionosphere seriously degrade GPS accuracy.

In his work, Odenwald suggests that roughly 100 low Earth-orbiting spacecraft would experience an earlier-than-normal reentry. The storm would heat Earth's upper atmosphere, causing it to expand and therefore increase the drag on satellites.

"The $100 billion international space station may lose significant altitude, placing it in critical need for reboosting by an amount potentially outside the range of typical space shuttle operations, which are in any case scheduled to end in 2010," Odenwald and Green reported.

"So far as I know, my study is the first of its kind, and it leads to some very interesting limits to the dollar impact of severe storms on our satellite industry," Odenwald said.

© 2008 Space.com.

Comments:

What will happen to Indonesia at the peak of solar activity in December 2012 ?

HouwLiong

09 March 2009

The solar superstorm of 1859



The solar superstorm of 1859 was the fiercest ever recorded. Auroras filled the sky as far south as the Caribbean, magnetic compasses went haywire and telegraph systems failed.

Ice cores suggest that such a blast of solar particles happens only once every 500 years, but even the storms every 50 years could fry satellites, jam radios and cause coast-to-coast blackouts.

The cost of such an event justifies more systematic solar monitoring and beefier protection for satellites and the power grid.

The authors have reconstructed what happened in 1859, based in part on similar (though less intense) events seen by modern satellites.

The gathering storm.

On the sun, the preconditions for the 1859 superstorm involved the appearance of a large, near-equatorial sunspot group around the peak of the sunspot cycle. The sunspots were so large that astronomers such as Carrington could see them with the naked (but suitably protected) eye. At the time of the initial CME released by the storm, this sunspot group was opposite Earth, putting our planet squarely in the bull’s-eye. The sun’s aim need not be so exact, however. By the time a CME reaches Earth’s orbit, it typically has fanned out to a width of some 50 million kilometers, thousands of times wider than our planet.

http://www.sciam.com/article.cfm?id=timeline-the-1859-solar-superstorm
http://www.sciam.com/article.cfm?id=bracing-for-a-solar-superstorm&page=2

Comments :

Will solar superstorm happen again in 2012 ?
The impacts will be on power systems, communication systems, navigation systems and extreme weather.

HouwLiong

05 March 2009

Model Simulations Don’t Match the Average Surface Temperature of the Earth.



Model Simulations Don’t Match the Average Surface Temperature of the Earth.

2 March, 2009 (10:58) | Data Comparisons Written by: lucia

This morning, Alexander Harvey asked,

“I would really like to see the temperature records (we have more than one world it seems) expressed in absolute terms and comparison between them and the model outputs performed in absolute terms.I do not know if the spread in the CMIP3 data is as broad as I have not seen the data expressed in absolute terms.”

I show the 12 month average temperatures from simulations and GISSTemp in non-anomaly degrees C.

Figure: IPCC Model Simulations Prediction of Earth Surface Temperature

To create the GISSTemp (i.e. measured) value, I added 14 C, which GISSTemp reports as the best estimate for the average temperature from 1951-1980. The GISSTemp value is shown in dark blue.

The remaining traces based on model-run-data downloaded from The Climate Explorer.

If anyone knows the baseline temperature for HadCrut, point me to it, and I’ll add HadCrut.

If most the models were correct, the coal-protestors would in DC would probably be even colder today. Alas, most the models are unable to predict the average global surface temperature.

Note that the UK Met office did not include this information when trying to support their claimed.

http://rankexploits.com/musings/2009/fact-6a-model-simulations-dont-match-average-surface-temperature-of-the-earth/

03 March 2009

Perubahan Iklim Bisa Mengurangi Topan dan Badai




Perubahan Iklim Bisa Mengurangi Topan dan Badai
Ditulis oleh ivie pada 5/20/08 • Kategori Bumi •


kredit : NASA / Univ. Wisconsin-MadisonAda berita baik. badai yang selama 25 tahun terakhir ini mengalami peningkatan frekuensi bisa jadi tidak akan ada lagi, meskipun beberapa yang memiliki kehebatan rata-rata masih akan muncul. Angin topan juga akan semakin jarang di Atlantik di sepanjang abad 21 jika dunia terus-menerus semakin hangat. Inilah hasil penelitian mengenai keterkaitan pemanasan global dalam mempengaruhi intensitas dan frekuensi angin ribut.
Secara global jumlah angin topan yang besar meningkat drastis sebesar 75% semenjak tahun 1970. Dan walaupun sampai saat ini tersangka utama untuk peningkatan itu adalah meningkatnya temperatur lautan sayangnya hubungan antara keduanya masih terus jadi isu yang dipertentangkan. Kenapa pemanasan global yang dijadikan tersangka? Ternyata masalahnya adalah, angin topan itu hanya bisa terbentuk saat temperatur permukaan laut melampaui 26 derajat Celsius.

Dalam penelitian tersebut, Thomas Knutson dari US National Oceanic and Atmospheric Administration (NOAA) dan rekan-rekannya menggunakan model iklim regional dari kolam di Atlantik (satu area di Atlantik) untuk menstimulasi pengamatan meningkatnya angin topan pada tahun 1980 dan 2006. Dasar pengamatan yang dipakai adalah temperatur permukaan laut dan kondisi atmosfer. Dalam studi yang dilakukan, Thomas Knutson dkk tidak mengikutsertakan paham dan pendapat kalau peningkatan gas rumah kaca juga menyebabkan terjadinya peningkatan frekuensi badai tropik.
Dalam penelitian ini, Knutson dkk menggunakan 2 model untuk memperkirakan apakah aktivitas angin topan akan terus meningkat di area tertentu sebagai akibat perbuatan manusia yang menyebabkan terjadinya perubahan iklim. Model pertama mengasumsikan adanya pemanasan iklim sebesar 2,8 derajat Celcius sampai dengan tahun 2100 dan model lainnya tidak menyertakan adanya pemanasan tersebut. Secara umum jumlah angin topan tersebut akan mengalami penurunan. Dan dengan badai yang lemah pun akibatnya tetap saja cukup besar. Diperkirakan badai tropis akan turun sekitar 27%, 18% diantaranya adalah penurunan angin topan dan 8% lagi penurunan angin topan besar.

Jadi dengan tidak mengabaikan kenyataan kalau aktivitas angin topan telah meningkat drastis selama 25 tahun terakhir, trend ini tidak akan berlanjut sampai akhir abad dibawah pengaruh kondisi pemanasan. Walau demikian, menurut Isaax Held dari NOAA, “kita tidak bisa mengekstrapolasi trend 25 tahun terakhir untuk masa depan.”


http://langitselatan.com/2008/05/20/perubahan-iklim-bisa-mengurangi-topan-dan-badai/

Komentar :
Kasus ini juga menunjukkan bahwa prediksi masa depan yang jauh, bisa menyimpang jauh juga.

(HouwLiong)

Shutdown of thermohaline circulation




Shutdown of thermohaline circulation

From Wikipedia, the free encyclopedia


A summary of the path of the thermohaline circulation. Blue paths represent deep-water currents, while red paths represent surface currents

Shutdown or slowdown of the thermohaline circulation is a postulated effect of global warming.

There is some speculation that global warming could, via a shutdown or slowdown of the thermohaline circulation, trigger localized cooling in the North Atlantic and lead to cooling, or lesser warming, in that region. This would affect in particular areas like Iceland, Ireland, the Nordic countries, and Britain that are warmed by the North Atlantic drift. The chances of this occurring are unclear; there is some evidence for the stability of the Gulf Stream but a possible weakening of the North Atlantic drift; and there is evidence of warming in northern Europe and nearby seas, rather than the reverse. The future is undecided as studies of the Florida Current suggest that the Gulf Stream weakens with cooling and strengthens with warming, being weakest (by ~10%) during the Little Ice Age and strongest during 1,000-1,100 yr BP, the Medieval Warm Period (Lund, Lynch-Stieglitz,and Curry, Nature (2006) 444: 601-604).

02 March 2009

Iklim dan Cuaca (tahun 2007)

Jumat, 19 Januari 2007

Jumat, 19 Januari 2007

Iklim dan Cuaca
Fase El Nino Kembali Normal

Jakarta, Kompas - Fase El Nino yang berdampak pada suhu muka laut yang dingin dan mengakibatkan musim kering di wilayah perairan Indonesia saat ini mulai kembali normal. Demikian disampaikan Fadli Syamsudin, Manajer Laboratorium Teknologi Sistem Kebumian dan Mitigasi Bencana (GEOTECH), Badan Pengkajian dan Penerapan Teknologi (BPPT), Kamis (18/1), melalui surat elektronik ke Kompas.

Fadli saat ini masih berlayar di wilayah perairan Samudra Pasifik bagian barat dengan kapal Jepang Mirai untuk mengikuti riset cuaca. "Kekhawatiran akan menguatnya fase El Nino pada tahun 2007 ternyata tidak terbukti. Kondisi atmosfer dan laut di Samudra Pasifik saat ini menunjukkan fenomena peluruhan sinyal El Nino sangat cepat," kata Fadli.

Demikian juga dengan konsentrasi "kolam panas" yang kembali menghangat di wilayah ekuator Pasifik barat sekitar wilayah Indonesia, makin bergerak jauh ke ekuator Pasifik timur.

"Informasi sedini mungkin kondisi iklim regional yang kembali ke fase normal pasca-El Nino tahun ini, akan sangat bermanfaat bagi pengambil kebijakan di Indonesia, terutama yang berhubungan dengan perencanaan waktu tanam komoditas pertanian, pengaturan lalu lintas perhubungan, baik darat, laut maupun udara, serta berbagai sektor lainnya yang terkait," katanya.

Samudra Hindia

Fadli melanjutkan, saat ini perlu diwaspadai kondisi cuaca yang dipicu oleh fenomena di Samudra Hindia. Sebab, rekaman satelit GMS dan IR pada Minggu (14/1) menunjukkan gejala awal depresi atau tekanan rendah dengan cakupan wilayah yang lebih besar daripada depresi bibit awan konveksi saat terjadinya badai tropis Isobel pada minggu pertama Januari tahun 2007 di atmosfer perairan barat laut Australia.

Apabila kluster awan konveksi yang lebih besar ini berkembang menjadi depresi, sangat mungkin badai tropis baru dengan intensitas yang lebih kuat akan terbentuk di perairan barat Australia dan imbasan ekornya dapat menimbulkan curah hujan dengan intensitas tinggi dan sering diikuti dengan banjir dan longsor di wilayah Jawa, Bali, Nusa Tenggara, dan Timor.

Sementara itu, akademisi The Houw Liong dari Departemen Fisika Institut Teknologi Bandung Rabu lalu mengatakan, tekanan rendah yang menyebabkan air laut panas di Lautan Pasifik makin menjauh dari wilayah perairan Indonesia. Ini diprakirakan mengakibatkan hujan yang terjadi di wilayah Indonesia pada 2007 di bawah normal.

"Tetapi, berbeda dengan wilayah Aceh yang diprakirakan mendapat hujan di atas normal karena dipengaruhi angin utara dari Asia," kata Houw Liong dalam diskusi di BPPT.

Pada kesempatan itu, hadir pula pembicara Kepala Unit Pelaksana Teknis Hujan Buatan BPPT Asep Karsidi. Menurut Asep, kemungkinan pada 2007 terjadi kemarau panjang dapat diatasi dengan hujan buatan. Namun, hujan buatan harus dilaksanakan pada masa peralihan dari musim hujan ke musim kemarau atau sebaliknya.

"Pada saat di tengah-tengah musim kemarau, yang bisa dilakukan adalah pengeboman air, bukan hujan buatan, karena ketersediaan awan tidak memungkinkan diubah menjadi awan mendung. Biasanya, pengeboman air dilakukan untuk pemadaman kebakaran-kebakaran hutan yang sering terjadi di musim kemarau," kata Asep. (NAW)

Jakarta, Kompas - Fase El Nino yang berdampak pada suhu muka laut yang dingin dan mengakibatkan musim kering di wilayah perairan Indonesia saat ini mulai kembali normal. Demikian disampaikan Fadli Syamsudin, Manajer Laboratorium Teknologi Sistem Kebumian dan Mitigasi Bencana (GEOTECH), Badan Pengkajian dan Penerapan Teknologi (BPPT), Kamis (18/1), melalui surat elektronik ke Kompas.

Fadli saat ini masih berlayar di wilayah perairan Samudra Pasifik bagian barat dengan kapal Jepang Mirai untuk mengikuti riset cuaca. "Kekhawatiran akan menguatnya fase El Nino pada tahun 2007 ternyata tidak terbukti. Kondisi atmosfer dan laut di Samudra Pasifik saat ini menunjukkan fenomena peluruhan sinyal El Nino sangat cepat," kata Fadli.

Demikian juga dengan konsentrasi "kolam panas" yang kembali menghangat di wilayah ekuator Pasifik barat sekitar wilayah Indonesia, makin bergerak jauh ke ekuator Pasifik timur.

"Informasi sedini mungkin kondisi iklim regional yang kembali ke fase normal pasca-El Nino tahun ini, akan sangat bermanfaat bagi pengambil kebijakan di Indonesia, terutama yang berhubungan dengan perencanaan waktu tanam komoditas pertanian, pengaturan lalu lintas perhubungan, baik darat, laut maupun udara, serta berbagai sektor lainnya yang terkait," katanya.

Samudra Hindia

Fadli melanjutkan, saat ini perlu diwaspadai kondisi cuaca yang dipicu oleh fenomena di Samudra Hindia. Sebab, rekaman satelit GMS dan IR pada Minggu (14/1) menunjukkan gejala awal depresi atau tekanan rendah dengan cakupan wilayah yang lebih besar daripada depresi bibit awan konveksi saat terjadinya badai tropis Isobel pada minggu pertama Januari tahun 2007 di atmosfer perairan barat laut Australia.

Apabila kluster awan konveksi yang lebih besar ini berkembang menjadi depresi, sangat mungkin badai tropis baru dengan intensitas yang lebih kuat akan terbentuk di perairan barat Australia dan imbasan ekornya dapat menimbulkan curah hujan dengan intensitas tinggi dan sering diikuti dengan banjir dan longsor di wilayah Jawa, Bali, Nusa Tenggara, dan Timor.

Sementara itu, akademisi The Houw Liong dari Departemen Fisika Institut Teknologi Bandung Rabu lalu mengatakan, tekanan rendah yang menyebabkan air laut panas di Lautan Pasifik makin menjauh dari wilayah perairan Indonesia. Ini diprakirakan mengakibatkan hujan yang terjadi di wilayah Indonesia pada 2007 di bawah normal.

"Tetapi, berbeda dengan wilayah Aceh yang diprakirakan mendapat hujan di atas normal karena dipengaruhi angin utara dari Asia," kata Houw Liong dalam diskusi di BPPT.

Pada kesempatan itu, hadir pula pembicara Kepala Unit Pelaksana Teknis Hujan Buatan BPPT Asep Karsidi. Menurut Asep, kemungkinan pada 2007 terjadi kemarau panjang dapat diatasi dengan hujan buatan. Namun, hujan buatan harus dilaksanakan pada masa peralihan dari musim hujan ke musim kemarau atau sebaliknya.

"Pada saat di tengah-tengah musim kemarau, yang bisa dilakukan adalah pengeboman air, bukan hujan buatan, karena ketersediaan awan tidak memungkinkan diubah menjadi awan mendung. Biasanya, pengeboman air dilakukan untuk pemadaman kebakaran-kebakaran hutan yang sering terjadi di musim kemarau," kata Asep. (NAW)

Komentar :
Tulisan ini berdasarkan wawancara sebelum banjir besar Jakarta tahun 2007.
Ternyata curah hujan di Jabodetabek sangat lemah dipengaruhi oleh El Nino, tetapi lebih ditentukan oleh aktivitas matahari dan fluks sinar kosmik yang bisa menyatakan bahwa tahun 2007 mungkin banjir besar.

(HouwLiong)