باز کردن سرریز سد " مورگانزا " در " لوئیزیانا"Morganza Spillway Opens in Louisiana

On May 14, 2011, the U.S. Army Corps of Engineers opened the Morganza Spillway in an attempt to ease flooding along the Mississippi River in Louisiana. The decision was made to protect the heavily populated areas and infrastructure around the ports of Baton Rouge and New Orleans. The decision is not without cost, however, to the thousands of people who are likely to lose homes and farms within the flood plain downstream.

On May 15, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-color image (top) of the Morganza Floodway. The image was acquired at 11:20 a.m. Central Daylight Time, one day after the spillway was partially opened. The lower photo was taken on May 14 by the Army Corps, several hours after water began streaming onto the floodway.

The flood control structure, or spillway, includes 125 gates, 11 of which had been opened as of noon on May 16. In the satellite image, the white pixels near the spillway are whitewater churned up by the flow through the gates; the downloadable large image shows this in much finer detail. Square and quadrilateral shapes on the landscape show areas that were cleared for farming or perhaps shaped for flood control earthworks.

In the natural color satellite, water ranges in colors of olive, tan, black, and gray, reflecting the different loads of muddy sediment churned up from the bottom; darker areas might also reflect deeper water. Past the spillway, water is more readily apparent along the levee on the south and east side of the floodway, suggesting that there are fewer trees and perhaps lower elevations in those areas. Potential inundation maps (PDF) from the Army Corps appear to confirm that, as water levels are projected to rise to 10–15 feet (3–4.5 meters) in the southern and eastern areas and 5–10 feet (1.5–3 meters) in the northern and western areas in the image above.

Green areas do not necessarily mean a lack of water. As the aerial photo shows, much of the floodway is covered with trees that will shield the water below from the eyes of satellite sensors. Water is somewhat easier to spot in the near-infrared and shortwave infrared image linked below the top photo.

Video of the opening of the Morganza Floodway can be viewed online here. The floodway was last opened in 1973, the first and only time it was used before 2011.

باران سهمگین در نامیبیا و جنوب قاره ی آفریقا Heavy Rain in Namibia and South Africa

Since 2010, rainfall has been above average in many parts of sub-Saharan African—including Angola, Namibia, Tanzania, Cameroon, Congo, and Madagascar—according to the Climate Prediction Center of the U.S. National Weather Service. Persistent rains have flooded ephemeral rivers such as the Kuiseb in Namibia and the Boteti in Botswana, which have both reached record highs. Even the driest parts of southern Africa have seen exceptional rains and floods.

In early May 2011, more rain fell in one day in the Namib desert than typically falls in an entire year. The map above depicts rainfall for Namibia and South Africa on May 5, 2011. The estimates were made from the Multi-satellite Precipitation Analysis, based on data from the Tropical Rainfall Measuring Mission (TRMM). Shown in shades of green and blue, rainfall estimates range from 20 millimeters (0.8 inches) to greater than 70 millimeters (2.8 inches). In much of the Namib desert near the coast, less than 20 millimeters of rain fall in a year.

The photo depicts what is likely a “shelf cloud” associated with a high-precipitation supercell thunderstorm on the Central Namib west coast, one of the driest regions in Africa. The cloud spreads out at ground level due to a strong downdraft, which produces an advancing wedge of condensed water. Essentially, as large amounts of rain fall, the large and heavy rain droplets pull the air down with them. The curl at the bottom occurs because the down-drafting winds hit the Earth’s surface and spread out.

The bullseye precipitation pattern depicted in the top image occurs because these storms are short-lived and dump large amounts of rain very quickly in one area. The storm soaked the Namib Sand Sea and desert gravel plain east of Walvis Bay.

Government officials and international relief agencies estimated that several hundred thousand residents had been displaced or disrupted by flooding in Namibia. At least 62 people have died. “Dongas” (ditches) caused by the heavy rains have caused havoc on the roads, and some officials worried about a possible increase in water- or mosquito-borne diseases due to standing water.

During the most recent storm in southern regions, Francois Snyders of the Namibian Ministry of Environment and Tourism told The Cape Times that the Fish River area “got 50 millimeters of rain, which is more than the annual rainfall for the canyon.” Two dams, the Hardop and the Naute, were over capacity and had to open sluice gate

خاکستر بر فراز آتشفشانAshfall from Karymsky Volcano

Karymsky is one of the most active volcanoes on Russia’s Kamchatka Peninsula. Active for the past 500 years, the volcano regularly emits plumes of ash and volcanic gases. Evidence of these frequent eruptions is visible in this natural-color satellite image. A radial pattern of dark gray ash extends away from Karymsky’s summit, and a plume of ash extends to the southeast, over Kronotskiy Kroniv (Kronotsky Gulf). The image was acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite on the morning.

زمین از فضا Amazing Pictures of Earth From Space

                                                               

     

Earth Day From Above

                                                                                                   

                                            Photograph courtesy Terra/ASTER/NASA and NASA Earth Observatory    

    sapphire waters tinged with pink sediment seem to get tangled amid emerald vegetation in a satellite picture of Bombetoka Bay, on the northwestern coast of Madagascar .

                                                                                                                                                

                                                                               Painted Desert

                                                                   Photograph courtesy NASA and NASA Earth Observatory

In the Simpson Desert of central Australia , a recent fire is revealed by the vivid orange scars of plant-free sand seen in this 2002 astronaut photograph.

                                                                              Volcano Bubble

                                                                      Photograph courtesy NASA and NASA Earth Observatory

A "bubble" of steam surrounds volcanic ash rising from Sarychev Volcano, on the northwestern end of Matua Island, in a June 2009 picture taken by an astronaut. Matua is part of the Kuril Islands, a Russian archipelago that stretches from Hokkaido, Japan, to Kamchatka, Russia

          

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-جوش و خروش آتشفشان

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