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Posts tagged Madagascar

Deforestation and Soil Loss in Madagascar

15.5S 46.8E

May 25th, 2013 Category: Deforestation, Sediments

Madagascar – May 25th, 2013

Deforestation in Madagascar is an ongoing environmental issue. Deforestation with resulting desertification, water resource degradation and soil loss has affected approximately 94% of Madagascar’s previously biologically productive lands. Here, the country’s red soils can be seen as sediment spilling forth from rivermouths along the coast.

Since the arrival of humans 2000 years ago, Madagascar has lost more than 90% of its original forest. 70% of the forest cover of Madagascar was destroyed between 1895 and 1925, while Madagascar was under French rule. Since 1953, half of the remaining forest has been lost.

Largely due to deforestation, the country is currently unable to provide adequate food, fresh water and sanitation for its fast growing population. One major cause of deforestation has been the introduction of coffee as a cash crop during the French colonial period.

Primary causes of forest loss include slash-and-burn for agricultural land (a practice known locally as tavy) and for pasture, selective logging for precious woods or construction material, the collection of fuel wood (including charcoal production), and forest clearing for mining.

Lake Ihotry and Mangoky River Delta, Madagascar

21.9S 43.6E

April 26th, 2013 Category: Lakes, Rivers

Madagascar – April 26th, 2013

Visible near the western shores of Madagascar is the green Lake Ihotry, a closed saline lake in semi-arid southwestern part of Madagascar. Its area varies seasonally, from 96 km² to 112 km², as does its salinity. Between the lake and the coast is a rather large, whitish area of sand interspersed with silt-laden ponds.

Visible north of the lake is the mouth of the Mangoky River, through which sediments can be seen pouring into the Mozambique Channel. The river is 564 kilometers (350 mi) long, rising in the Central Highlands and flowing generally in a westerly direction out of them, crossing the southern extension of the Bemaraha Plateau, until it reaches the coastal plain and its delta.

Most of Madagascar has undergone serious deforestation during the last 40 years, chiefly from slash-and-burn practises by indigenous peoples. This loss of forest has led to extreme soil erosion in the Mangoky River basin, as evidenced by the many sandbars located within the river channel.

The southern portion of the Ihotry delta is dominated by successive barrier island and spit formation. In contrast, the northern, protected portion of the delta is dominated by tidal passes and mangrove swamps.

Tropical Cyclone Imelda (21S) Weakens to Tropical Low

20.1S 52.7E

April 16th, 2013 Category: Tropical Storms

Tropical Storm Twenty One (21S) – April 16th, 2013

Track of Tropical Storm Twenty One (21S) - April 16th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S), active since the 5th of April, has weakened to a tropical low and begun to dissipate. While a tropical cyclone, its peak intensity was recorded with at maximum sustained wind speeds of 140 km/h (85 mph) and pressure of 966 mbar (hPa).

Tropical Cyclone Imelda (21S) Weakening

21.7S 52.7E

April 16th, 2013 Category: Tropical Cyclones

Tropical Storm Twenty One (21S) – April 15th, 2013

Enhanced image

Track of Tropical Storm Twenty One (21S) - April 16th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S) is currently tracking southward along the western periphery of the low- to mid-level subtropical ridge but is forecast to turn westward as it weakens and begins to steer under the influence of a broad, transitory midlatitude ridge building to the south.

Dynamic model guidance is in good agreement, therefore, there is high confidence in the JTWC forecast track. The system is expected to weaken through the forecast period due to persistent moderate to strong vertical wind shear associated with subtropical westerly flow, and marginal sea surface temperature values near 26C.

Surface winds over the southern semi-circle are forecast to remain near gale-force levels due to the enhanced gradient associated with the aforementioned high building south of the system. Maximum significant wave height is 22 feet.

Tropical Cyclone Imelda (21S) with 55-Knot Winds

20.8S 52.7E

April 16th, 2013 Category: Tropical Cyclones

Tropical Storm Twenty One (21S) – April 14th, 2013

Enhanced image

Track of Tropical Storm Twenty One (21S) - April 14th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S), located approximately 370 nm east of La Reunion, has tracked south-southeastward at 05 knots over the past six hours.

Animated infrared satellite imagery depicts rapidly decaying deep convection, now sheared about 70 nm east of the system center. An SSMIS image depicts well-defined, tightly-wrapped shallow convective banding wrapping into the low- level circulation center with an isolated area of deep convection near 20S 64E.

There is good confidence in the initial position based on this image as well as an AMSU composite image. The initial intensity is assessed at 55 knots based on Dvorak intensity estimates ranging from 45 to 65 knots.

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