|
1. Definition
| Name |
WIND
SPEED |
| Brief
definition |
Wind is considered as
a major climatic factor affecting soil erosion in dry lands,
causing severe problems of atmospheric drought and damage
to the growing plants.
 |
Hilly area affected by northerly winds which cause permanent
inclination of the growing trees (photo by C. Kosmas)
|
|
| Unit of measure |
meters per
second (m/sec) |
| Spatial scale |
local |
| Temporal scale |
daily |
2. Position
within the logical framework DPSIR
3. Target and
political pertinence
| Objective |
Indirect contribution
to the definition of environmentally sensitive areas to desertification
and climatic factor affecting land use change decision-making. |
| Importance
with respect to desertification |
Wind erosion
is considered a major problem of land degradation and desertification
in dryland regions. Strong winds blowing during summer favour
extensive fires along the Mediterranean, afterwards causing
severe problems of erosion and land degradation. Crop production
and plant growth is reduced under strong winds, especially during
spring and summer, due to increasing evapotranspiration rates.
|
| International
Conventions and agreements |
The UNCCD emphasizes
that in order to combat desertification, it must be tackled
within the general framework of actions that promote sustainable
development. |
| Secondary objectives
of the indicator |
Influence definition
of land management practices and water conservation. |
4. Methodological
description and basic definitions
| Definitions
and basic concepts |
Wind erosion is another
process of soil erosion especially in the semiarid and arid
regions of the Mediterranean. Soil particles can be moved
by wind in one of three ways depending on soil particle size.
Particles or aggregates with diameter less than 0.05 mm can
be lifted into the wind stream and be moved in suspension
over great distances (km). Intermediate-sized grains (0.05-0.5
mm) move in the wind stream in a series of leaps, rising into
the air and falling again after a relatively short flight.
Soil grains larger than 0.5 mm in diameter cannot be lifted
by wind stream but can move along the soil surface for short
distances.
The main factors controlling
wind erosion are soil resistance to erosion, surface ridges,
rainfall, slope gradient and aspect, length of exposed area,
and vegetation cover. Soil resistance is controlled by the
mass (size) of the grains. If the mass is sufficient, a grain
will not be moved by the force of the wind. Surface ridges
reduce wind velocity near the ground and grains can be trapped
in concavities. The most effective way to reduce the erosiviness
of wind is to cover the soil with a protective mantle of growing
plants or with a thick mulch of crop residue. Soil water deficit,
occurring during summer and early autumn, creates favourable
conditions for soil particle detachment and wind erosion.
In pastures and under
adverse soil climatic conditions, perennial vegetation growth
is limited, and only annual vegetation is present during the
wet period. If the land is overgrazed, soils remain virtually
bare during the summer, favouring wind erosion. Fires destroy
the existing vegetative cover and contribute to wind erosion
by exposing the soil surface to wind action. Animal pathways
are also vulnerable. Animal trampling in certain pathways
destroys soil aggregates leaving a layer of dust easily suspended
in the air.
|
| Benchmarks
Indication of the values/ranges of value |
- <5.4,
- 5.5-10.7,
- 10.8-18.8,
- >18.9 meters/second
|
| Methods of
measurement |
Digital or
any other type of anemometer. |
| Limits of the
indicator |
This indicator
can be assessed quantitatively without subjecting to personal
judgment. |
| Linkages with
other indicators |
Rainfall,
Aridity index (2), Land
use type, Water availability. |
5. Evaluation
of data needs and availability
| Data required
to calculate the indicator |
Mean wind velocity
at 2 m above ground over a 24 hour period. |
| Data sources |
Necessary data
are usually available and accessible and the cost/benefit ratio
is reasonable. |
| Availability
of data from national and international sources |
Data can be
obtained from various regional institutions or local stations
involved in collecting and elaborating meteorological data. |
6. Institutions
that have participated in developing the indicator
| Main institutions
responsible |
Agricultural
University of Athens. |
| Other contributing
organizations |
Universities
of Lisbon, Murcia, Basilicata. |
7. Additional
information
| Bibliography
|
Follet R.F.
and Stewart B. A. 1985. Soil Erosion and Crop Productivity.
American Society of Agronomy, Madison Wisconsin, USA, 533 p.
|
| Other references |
Troeh, H.R.,
Hobbs, J. A., and Donahue, R. L. 1980. Soil and water conservation
for productivity and environmental protection. Prentice-Hall,
Inc., Emglewood Cliffs, New Jersey, 116-147 pp. |
| Contacts Name
and address |
Agricultural
University of Athens
Dr Constantinos Kosmas
email: lsos2kok@aua.gr |
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