FLOODS

There are few places on Earth where people need not be concerned about flooding. Any place where rain falls is vulnerable, although rain is not the only impetus for flood.

THE GLOBAL TECTONIC AND CLIMATIC SYSTEMS

Written By : Richard John Hugget on Fundamental of Geomorphology

Since the 1990s, geomorphologists have come to realize that the global tectonic system and the world climate system interact in complex ways. The interactions give rise to fundamental changes in atmospheric circulation patterns, in precipitation, in climate, in the rate of uplift and denudation, in chemical weathering, and in sedimentation (Raymo and Ruddiman 1992; Small and Anderson 1995; Montgomery et al. 2001). The interaction of large-scale landforms, climate, and geomorphic processes occurs in at least three ways – through the direct effect of plate tectonic process upon topography (p. 108–15), through the direct effect of topography upon climate (and the effects of climate upon uplift), and through the indirect influence of topography upon chemical weathering rates and the concentration of atmosphere carbon dioxide.

PROBABLE MAXIMUM PRECIPITATION (PMP)

Curah hujan merupakan salah satu unsur iklim yang sangat penting dan merupakan bagian dari daur hidrologi yang tidak terpisahkan ( Asdak, 2007). Hujan adalah komponen masukan penting dalam proses hidrologi yang memiliki karakteristik seperti antaranya adalah intensitas, durasi, kedalaman, dan frekuensi. (Suroso, 2004). Karakteristik hujan tersebut mempunyai sifat yang sangat fundamental untuk berbagai keperluan perencanaan ataupun pekerjaan-pekerjaan yang terkait dengan hidrologi seperti erosi tanah, banjir, irigasi, kekeringan dan ketersediaan air. (Asdak, 2007). 

HUJAN ASAM (ACID RAIN)

Salah satu parameter yang menentukan baik buruknya kualitas air adalah pH. (American Ground Water Trust, 2003). Secara ilmiah, pH sendiri diartikan sebagai banyak sedikitnya kandungan ion H+ dalam suatu benda, baik itu cairan maupun padat. Kadar pH memiliki rentangan dari 0 (asam kuat) sampai 14 (basa kuat) dengan 7 adalah harga tengah mewakili air murni (netral). (www.chem-is-try.org).

Presipitasi (Hujan)

 Hujan  (presipitasi) didefinisikan sebagai bentuk air cair an padat (es) yang jatuh ke permukaan bumi. Meskipun kabut. ernbun, dan ernbun beku (frost) dapat berperan dalam alih kcbasahan (moristure) dari atmosfer ke permukaan bumi, unsur tersebut tidak ditinjua sebagai endapan. Bentuk endapan adalah hujan. gerimis, salju, dan batu es hujan (hail).  Untuk lebih jelasnya, lihat Tabel.  3.1 yang mendiskripsikan tentang unsur hidrometeor.

Dipole Mode

Dipole mode disingkat DM merupakan fenomena yang mirip dengan ENSO tetapi terjadi di Samudera Hindia. Peristiwa dipole mode ditandai adanya perbedaan anomali suhu permukaan laut (SPL) antara Samudera Hindia tropis bagian barat (50 ^oE – 70 ^oE, 10 ^oS – 10 ^oN) dengan Samudera Hindia tropis bagian timur (90 ^oE – 110 ^oE, 10 ^oS – ekuator). Anomali SPL ini memiliki kondisi yang lebih dingin dari normal dan muncul dipantai barat Sumatera (Samudera Hindia bagian timur), sementara di Samudera Hindia bagian barat terjadi pemanasan dari biasanya.

Jenis DM dibagi berdasarkan SPL antara Samudera Hindia tropis bagian barat (50 ^oE – 70 ^oE, 10 ^oS – 10 ^oN,kotak A) dengan Samudera Hindia tropis bagian timur (90 ^oE – 110 ^oE, 10 ^oS – ekuator,kotak B) pada Gambar 1.

Gambar 1.

Sirkulasi Atmosfer Meridional (Hadley Cycle)

Menurut Hadley (1735), sirkulasi atmosfer mcridional terdiri atas satu sel, yaitu udara naik di ekuator dan turun di daerah kutub. Mcnurut Maury (1855). sirkulasi atmosfcr meridional tcrdiri atas dua sel, yaitu satu sel pada dacrah antara ekuator dan lintang sekttar 30° Utara atau Selatan disebut sirkuiasi Hadley dan satu sel tak langsung (indirect eel) pad a lintang tinggi. Ferrel (1856) telah mcngkaji bahwa tckanan udara normal di permukaan bumi tidak seragam, yaitu terdapat tckanan tinggi (H) di lintang sekitar 30⁰U atau S (lintang kuda) dan tekanan rcndah terdapat di daerah ekuator dan kutub. Sirkulasi atmosfcr meridional yang diusulkan Ferrel (1856) mirip dengan teori Maury (1855), tctapi tcrdiri atas 3 sel sirkulasi, yaitu sel Hadley, scl Ferrel, dan scl Kutub. Teori baru tentang sirkulasi meridional telah banyak d ikaji oleh beberapa ahli, misalnya, Rossby (1941), Palmcn (1954), clan la in-Iatn. Para ahli ini mengemukakan tcori sirkulasi atmosfer meridional yang mirip dcngan tcori Ferrel, yaitu terdiri atas 3 sel sirkulasi. 

Climate and Culture Connections in Australia

From : Neville Nicholls

Bureau of Meteorology Research Centre, Melbourne, Australia.

Reviewed by : Munawaroh

Australia adalah sebuah negara yang luas dengan berbagai iklim yang berlainan. Berdasarkan letak  lintangnya, Australia membentang melintasi tiga kawasan iklim, yaitu kawasan tropis (11°LS – 23° 30’LS), kawasan subtropis (23° 30^o – 35^oLS) dan kawasan beriklim sedang (35° – 44°LS). 

Klasifikasi Iklim

Beberapa sistem klasifikasi iklim yang sampai sekarang masih digunakan dan pernah digunakan di Indonesia antara lain adalah:

a. Sistem Klasifikasi Koppen

Koppen membuat klasifikasi iklim berdasarkan perbedaan temperatur dan curah hujan. Koppen memperkenalkan lima kelompok utama iklim di muka bumi yang didasarkan kepada lima prinsip kelompok nabati (vegetasi). Kelima kelompok iklim ini dilambangkan dengan lima huruf besar dimana tipe iklim A adalah tipe iklim hujan tropik (tropical rainy climates), iklim B adalah tipe iklim kering (dry climates), iklim C adalah tipe iklim hujan suhu sedang (warm temperate rainy climates), iklim D adalah tipe iklim hutan bersalju dingin (cold snowy forest climates) dan iklim E adalah tipe iklim kutub (polar climates) (Safi’i, 1995).

Global Warmng : What We Can Do ?

The evidence that humans are causing global warming is strong, but the question of what to do about it remains controversial. Economics, sociology, and politics are all important factors in planning for the future.

Even if we stopped emitting greenhouse gases (GHGs) today, the Earth would still warm by another degree Fahrenheit or so. But what we do from today forward makes a big difference.  Depending on our choices, scientists predict that the Earth could eventually warm by as little as 2.5 degrees or as much as 10 degrees Fahrenheit.

A commonly cited goal is to stabilize GHG concentrations around 450-550 parts per million (ppm), or about twice pre-industrial levels. This is the point at which many believe the most damaging impacts of climate change can be avoided.  Current concentrations are about 380 ppm, which means there isn't much time to lose.  According to the IPCC, we'd have to reduce GHG emissions by 50% to 80% of what they're on track to be in the next century to reach this level.

Is this possible?

Many people and governments are already working hard to cut greenhouse gases, and everyone can help.

Researchers Stephen Pacala and Robert Socolow at Princeton University have suggested one approach that they call "stabilization wedges." This means reducing GHG emissions from a variety of sources with technologies available in the next few decades, rather than relying on an enormous change in a single area.  They suggest 7 wedges that could each reduce emissions, and all of them together could hold emissions at approximately current levels for the next 50 years, putting us on a potential path to stabilize around 500 ppm.

There are many possible wedges, including improvements to energy efficiency and vehicle fuel economy (so less energy has to be produced), and increases in wind and solar power, hydrogen produced from renewable sources, biofuels (produced from crops), natural gas, and nuclear power.  There is also the potential to capture the carbon dioxide emitted from fossil fuels and store it underground—a process called "carbon sequestration."

In addition to reducing the gases we emit to the atmosphere, we can also increase the amount of gases we take out of the atmosphere.  Plants and trees absorb CO2 as they grow, "sequestering" carbon naturally.  Increasing forestlands and making changes to the way we farm could increase the amount of carbon we're storing.

Some of these technologies have drawbacks, and different communities will make different decisions about how to power their lives, but the good news is that there are a variety of options to put us on a path toward a stable climate.

published by NATIONAL GEOGRAPHIC

image by : Paul Nicklen

Climate Changes

Climate change can be considered at two board temporal scale : long-term changes at greater  than 20.000 years, and short-terms changes between 100 and 20.000 years. Climate variabelity refers to mainly to decade to decade and year to year changes. Causes of climate change can be classified as either external or internal.  The former includes changes of earth’s orbital geometry, often referred to as Milancovitch or astronomical variations. Internal  causes result from changes to the basic nature of the components of the climate system and feedbacks between these components.

Currently there is the great concern about human-induced climate change mainly due to increased global pollution levels which have, through an enchanced greenhouse effect, the potential to increase the global temperatures, alter climate patters and raise sea levels. At the local to regional scale, deforestation and desertification are also of concern. Although the mangitude of climate change in the tropics is likely to be less than at higher latitudes, climate changes impacts will considerable. A full understanding of the gravity oh these changes will, however, only be achieved when the causes, nature and availability of climate resources in the tropics is fully appreciated. This will continue to be one of the main goals of tropical climatology.

Sources : McGregor, Glenn. 1998.Tropical Climate 2nd ed.Baffinslane : John willey and Sons