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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 East of Madagascar – April 15th, 2013

19.3S 52.0E

April 15th, 2013 Category: Image of the day, Tropical Cyclones

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

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

Track of TC 21S

Tropical Cyclone Imelda (TC 21S) is tracking along the southwest periphery of a near-equatorial ridge and is expected to recurve westward after TAU 36 as a building subtropical ridge to the south assumes steering.

As the system continues to move poleward, the vertical wind shear (VWS) will steadily increase causing its gradual erosion and, finally, dissipation by TAU 72. The available numeric guidance is in overall good agreement with WBAR as the sole outlier extending the track southeastward beyond 72 hours. The remainder of the models recurve the vortex westward, albeit at varying increments. The JTWC track forecast is laid closely to model consensus with high confidence.

Tropical Cyclone Imelda (21S) Restrengthens, Continues Towards Madagascar – April 14th, 2013

10.7S 53.4E

April 14th, 2013 Category: Image of the day, Tropical Cyclones

Tropical Storm Twenty One (21S) – April 13th, 2013

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Track of Tropical Storm Twenty One (21S) - April 12th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S), located approximately 315 nm northeast of La Reunion, has tracked west-southwestward at 03 knots over the past six hours.

Animated infrared satellite imagery shows a deepened central dense overcast feature over a well-defined low-level circulation center. This is also evident on an SSMI-S microwave pass. The initial position is based on closely grouped agency fixes and on the above microwave image with high confidence. The initial intensity is an average of subjective Dvorak estimates from PGTW, KNES, and FIMP.

Upper level analysis (ULA) indicates the system is between two ridge axes – one to the north and another to south in an area of low (05-10 knot) vertical wind shear (VWS). TC 21S has unpredictably tracked west-southwestward over the past 12 hours. From the same ULA, the steering ridge to the east was not significantly weakened by a passing mid-latitude trough as previously forecast. Instead, the ridge was deformed into a kidney-shaped anticyclone along a meridional axis. In response to this transformation to the steering ridge, 21S jogged westward. This recent development necessitated a slight change in the JTWC track forecast philosophy.

Tropical Cyclone Imelda (21S) Northeast of Madagascar – April 11th, 2013

11.1S 56.2E

April 11th, 2013 Category: Image of the day, Tropical Cyclones

Tropical Storm Twenty One (21S) – April 10th, 2013

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Track of Tropical Storm Twenty One (21S) - April 10th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S) located approximately 515 nm north-northeast of La Reunion, has tracked southward at 02 knots over the past six hours.

Animated multispectral satellite imagery depicts tightly curved spiral banding wrapping into a low level circulation center. An SSMIS 37ghz microwave image depicts deep convection favoring the eastern quadrants in response to slightly increased vertical wind shear (VWS), however the center remains well defined.

The system is now quasi-stationary as the steering ridge to the southeast is weakening and becoming re- oriented in response to an approaching deep-layer trough (DLT). The initial position is extrapolated from the aforementioned SSMIS image with fair confidence.

The initial intensity is assessed at 75 knots based on a range of Dvorak current intensity estimates from 65 to 77 knots. Upper level analysis indicates the system has a point source overhead providing moderate radial outflow, with VWS increasing slightly to 10 to 15 knots.