THMMY.gr

Δορυφορικές φωτογραφίες από την Ευρωπαϊκή Υπηρεσία Διαστήματος, από το πρόγραμμα Observing the Earth.

Μερικές από αυτές μου έρχονται ανά εβδομάδα (image of the week), στο mail μου, και συνήθιζα να ανεβάζω τις καλύτερες στο topic Φωτογραφία. Για να το αποδεσμεύσω, και επειδή οι πιό πολλές από αυτές είναι μιας αρκετά υψηλής αισθητικής αξίας, είπα να ανοίξω ένα καινούριο topic.

Links:

To πρόγραμμα περιήγησης: http://earth.esa.int/earthimages/

To επίσημο site της υπηρεσίας: http://www.esa.int/esaCP/index.html

To πρόγραμμα Observing the Earth: http://www.esa.int/esaEO/index.html


Θα σηκώνω κάθε εβδομάδα περίπου, όποιες image of the week αξίζουν.

Για αρχή:

This animation, comprised of images acquired by Envisat’s Advanced Synthetic Aperture Radar (ASAR) instrument, shows the breaking away of a giant iceberg from the Pine Island Glacier in West Antarctica. Spanning 34 km in length by 20 km in width, the new iceberg covers an area nearly half the size of Greater London.
 
The animation highlights the movement in the area between September 2006 and October 2007. The Pine Island Glacier is visible stretching from the right of the image to the centre. The tongue of Pine Island is shown moving inland between September 2006 and March 2007. Between April and May 2007, the detached iceberg in front of Pine Island moves significantly. Also in May 2007, a crack in Pine Island becomes visible. By October, the new iceberg has completely broken away.

Several different processes can cause an iceberg to form, or ‘calve’, such as action from winds and waves, the ice shelf grows too large to support part of itself or a collision with an older iceberg. Since Pine Island Glacier was already floating before it calved, it will not cause any rise in the world sea level.

Iceberg calving like this occurs in Antarctica each year and is part of the natural lifecycle of the ice sheet. A 34-year long study of the glacier has shown that a large iceberg breaks off roughly every 5-10 years. The last event was in 2001.

Pine Island – the largest glacier in the West Antarctic Ice Sheet (WAIS) – is of great interest to scientists because it transports ice from the deep interior of the WAIS to the ocean and its flow rate has accelerated over the past 15 years.

The Pine Island Glacier is up to 2500 m thick with a bedrock over 1500 m below sea level and comprises 10 percent of the WAIS. According to a study by scientists at the British Antarctic Survey (BAS) and University College London (UCL) using ESA's ERS satellite data, a loss of 31-cubic km of ice from the WAIS’s interior from 1992 to 2001 was pinpointed to the Pine Island Glacier.

The thinning caused the glacier to retreat by over 5 km inland, supporting the argument that small changes at the coast of the Antarctic continent - such as the effects of global warning - may be transmitted rapidly inland leading to an acceleration of sea level rise.

Although these long-term regional changes are a cause for concern, the present iceberg calving event does not in itself signal a significant change in the WAIS. Over the last 15 years, the glacier front has advanced seawards at a rate of 3 km/year, so the calving of a 20 km-wide iceberg has simply shifted the glacier front back close to where it was after the last calving event in 2001.

The new iceberg was spotted by scientists at BAS while studying satellite images collected from Envisat using the Polar View monitoring programme. Since 2006, ESA has supported Polar View, a satellite remote-sensing programme funded through the Global Monitoring for Environment and Security (GMES) Service Element (GSE) that focuses on the Arctic and the Antarctic.

GMES responds to Europe’s needs for geo-spatial information services by bringing together the capacity of Europe to collect and manage data and information on the environment and civil security, for the benefit of European citizens. As the main partner to the European Commission in GMES, ESA is the implementing agency for the GMES Space Component, which will fulfil the space-based observation requirements in response to European policy priorities.

The GSE has been preparing user organisations in Europe and worldwide for GMES by enabling them to receive and evaluate information services derived from existing Earth Observation (EO) satellites since 2002.

ASAR acquired these images working in Wide Swath Mode (WSM), providing spatial resolution of 150 metres. ASAR can pierce through clouds and local darkness and is capable of differentiating between different types of ice.


http://www.esa.int/esaEO/SEM9C9JJX7F_index_0.html

This Envisat image highlights the Orange River in Southwest Africa. Rising in the Drakensberg mountains near the South Africa (visible south of the river) and Lesotho border, the Orange River runs westward for 2200 km forming part of the border between South Africa and Namibia (visible north of the river).
 
Although the Orange River normally empties into the Atlantic Ocean, sand-bars sometimes block its access to the sea. For this reason, it is often referred to as a river mouth rather than a true estuary.

The Namib Desert (visible in Namibia) stretches about 1930 km along the coast of Southwest Africa, mostly within the Namibian country. The huge sand dunes that rise near the coast of the Atlantic Ocean and extend inland for up to 160 km are visible.

The Namib Sand Sea, located along the central coast of the Namib, is made up of sand that is a consequence of the erosion processes that take place within the Orange River valley and areas further to the south. As sand-laden waters empty into the Atlantic, onshore currents deposit the sand along the shore. Southwest winds pick up the sand and redeposit it in the sand sea in the form of massive dunes.

This image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on 12 October 2007, working in Full Resolution mode to provide a spatial resolution of 300 metres.


http://www.esa.int/esaEO/SEMSINVH48F_index_0.html

Description
Envisat's Medium Resolution Imaging Spectrometer (MERIS) captures the North and South islands of New Zealand on 25 November 2007 during the environmental satellite's 30 000th orbit of Earth.

http://www.esa.int/esa-mmg/mmg.pl?b=b&type=I&collection=Observing%20the%20Earth&single=y&start=1



Kαι μια παλιά που εντόπισα, Αιγαίο/Κρήτη:

The vibrant aquamarine-coloured swirls of a plankton bloom decorate the waters of the South Atlantic Ocean just off the shores of the Republic of Namibia in this Envisat image.
 
Plankton, the most abundant type of life found in the ocean, are microscopic marine plants that drift on or near the surface of the sea. Microscopic plankton have been called 'the grass of the sea' because they are the basic food on which all other marine life depends.

Because plankton contain photosynthetic chlorophyll pigments, these simple organisms also play a similar role to terrestrial ‘green’ plants in the photosynthetic process. Plankton are able to convert inorganic compounds such as water, nitrogen and carbon into complex organic materials.

With their ability to ‘digest’ these compounds, they are credited with removing as much carbon dioxide from the atmosphere as their earthbound ‘cousins’. As a result, the oceans have a profound influence on climate. Since plankton are a major influence on the amount of carbon in the atmosphere and are sensitive to environmental changes, it is important to monitor and model them into calculations of future climate change.

Although some types of plankton are individually microscopic, the chlorophyll they use for photosynthesis collectively tints the colour of the surrounding ocean waters, providing a means of detecting these tiny organisms from space with dedicated 'ocean colour' sensors, such as Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument, onboard satellites.

MERIS’s primary objective is to provide quantitative ocean-colour measurements, but the sensor has enough flexibility to serve applications in atmospheric and land-surface science as well.

This 6 November 2007 image was acquired by MERIS while working in Full Resolution mode to provide a spatial resolution of 300 metres.


http://www.esa.int/esaEO/SEM1HB29R9F_index_0.html

This Envisat image features the southern part of Canada’s Quebec province, which occupies a territory nearly three times the size of France.
 
The mighty Saint Lawrence River is visible flowing from the southwest to the northeast. Beginning from Lake Ontario (not visible), the river flows northeast past Montreal (visible as the whitish area at the confluence of the two rivers) and Quebec City (the whitish area visible on the north bank of the river) to the Gulf of St. Lawrence.

Saint Lawrence River is 1197 km long and its drainage basin covers some 1 million km², of which 505 000 km² is in the United States. The river, which connects the Great Lakes with the Atlantic Ocean, is the primary drainage of the Great Lakes Basin.

Quebec City is the capital of the province of Quebec. The Laurentian Mountains lie to the north of the city.

The dark blue lake visible at the top right of the image is Lac Saint-Jean, which is situated some 170 km north of the Saint Lawrence River. It covers an area of 1003 km² and is relatively shallow at 63 m deep.

Lac Saint-Jean is fed by dozens of small rivers and discharges through two outlets into the Saguenay River (visible), which then drains Lac Saint-Jean into the St. Lawrence River at Tadoussac, some 190 km northeast of Quebec City.

This image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on 26 October 2007, working in Full Resolution mode to provide a spatial resolution of 300 metres.


http://www.esa.int/esaEO/SEMVHZJV3AF_index_0.html

This Envisat image highlights Lake Chad, a freshwater lake located in central Africa at the junction of Chad, Cameroon, Nigeria and Niger.
 
Lake Chad, once Africa’s third largest inland water body, is located in West Africa’s Sahel region – a transition zone between the Sahara Desert to the north and savannas and woodlands to the south.

Because the lake is shallow, between 1 m in the northwest and 7 m in the south, it has always undergone seasonal fluctuations. However, it has shrunk dramatically over the last four decades due to a decrease in rainfall and an increase in the amount of water used for irrigation projects. Lake Chad’s surface area was 25 000 sq km in the early 1960s, compared with 1350 sq km in 2001.

Lake Chad is fed primarily by the Chari and Logone Rivers, which are both located in the southwest and flow northward into the lake, which doubles in size during the rainy season.

This 6 November 2007 image was acquired by the Medium Resolution Imaging Spectrometer (MERIS) instrument on Envisat, working in Full Resolution mode. The image has a resolution of 300 metres and covers 450 km by 670 km.


http://www.esa.int/esaEO/SEM0MF2MDAF_index_0.html

19 September 2008


This Envisat image, acquired on 12 August 2008 with the Medium Resolution Imaging Spectrometer (MERIS) instrument, captures a plankton bloom stretching across the Northeast Passage in the Barents Sea. Plankton, the most abundant type of life found in the ocean, are microscopic marine plants that drift on or near the surface of the sea. Microscopic plankton have been called 'the grass of the sea' because they are the basic food on which all other marine life depends. Although some types of plankton are individually microscopic, the chlorophyll they use for photosynthesis collectively tints the colour of the surrounding ocean waters, providing a means of detecting these tiny organisms from space with dedicated 'ocean colour' sensors, such as MERIS, onboard satellites.

http://www.esa.int/esaEO/SEM6ZCQ4KKF_index_1.html