Marine Anemometer - Working principle and Types

"Marine Anemometer"

The Marine Anemometer is a weather instrument used to measure wind speed and wind direction. The term anemometer is derived from the Greek word "anemos" meaning wind.

There are 2 mainly used anemometer in the marine industry.

1. Cup anemometer
2. Vane anemometer

Cup anemometer:

Working principle:

• Cup Anemometer consists of 4 Hemispherical cups mounted on the end of the horizontal arms.
• Horizontal arms are mounted on a Vertical shaft.
• The airflow passes through the cups in a horizontal direction makes the shaft rotate.
• AC generator connected to the shaft. Faster the shaft rotates higher the electric current will produce.
• AC voltage is rectified to DC voltage and output voltage is measured for set interval and the voltage signal is calibrated to measure the wind speed.
• This type of anemometer gives only wind speed unless the wind vane additionally fitted on the instrument for wind direction.

Vane Anemometer:

Working principle:

• In Vane Anemometer the propeller is fitted, the rotating axis of the propeller must be parallel to the flow of wind.
• To align the body parallel to the wind flow, the tail (wind vane) is designed. so the propeller always faces the wind direction.
• AC generator connected to the shaft. Faster the shaft rotates higher the electric current will produce.
• AC voltage is rectified to DC voltage and output voltage is measured for set interval and the voltage signal is calibrated to measure the wind speed.
• An analog signal is transmitted to the wind speed and direction indicator and the instantaneous wind speed and wind direction are ascertained.

Clouds - "Easy" tips to Learn and remember types of Clouds and description

 ☁🌤🌫Clouds:🌦🌧⛈

For Clouds? and Formation of clouds: - Click here

Clouds are classified in 2 ways:

1. Based on height above sea level
2. Based on the shape of a cloud

Root words:

  For Height:

• Cirro => High
• Alto => Medium

For Shape:

• Cirrus => Thin, white, high
• Cumulus => Puffy, rounded, cauliflower structure, white
• Stratus => Flat (blanket like), layered

Precipitation:

• Nimbus / Nimbo => Rain

Tips for describing the cloud:

• See the below picture, this picture tells the story.
• If you keep this picture in your mind, then describing the clouds is as easy as ABC.
• You can easily make out the HEIGHT, SHAPE, COLOUR, and LOOK of the cloud from this picture.

Let's describe the of clouds from the picture:

Cirrus:

• High cloud
• White colour
• Thin
• Looks like feathers or wispy(like eye bro)
• 

Cirrostratus:🌤

• High cloud
• Flat (blanket like).
• Looks like a veil (veil means like see through dress)
• 
• eg. 👆 for a veil
• This veil produce halos around sun, sufficiently clear for altitude observation.
• 

Cirrocumulus:☁️

• High cloud
• White colour
• Looks like patches of Small puffy or cauliflower
• 

Altostratus:🌥

• Medium cloud
• Thicker than cirrostratus
• Sun or Moon appears very dim - as seen through frosted glass
• 
  
  
• Eg. 👆Sun or moon seen through frosted glass.
• Not clear enough for altitude observation.

Altocumulus:☁️☁️☁️

• Medium cloud
• White or grey in colour
• Have dark shadows
• 
• Looks like 👆 flattened globules/rolls/long bands

Stratus:🏔

• Low cloud
• Even layered
• Dark grey cloud
• Can obscure the sun completely and weaken daylight
• 

Stratocumulus:☁️

• Low cloud
• Even layered or patches of globular masses which appear soft
• With dark shadows
• Form an overcast sky
• 

Nimbostratus:🌧

• Low cloud
• Dark grey cloud
• Can greatly obscure the sun completely and weaken daylight
• Looks like uniform and threatening
• Can produce moderate rain
• 

Cumulus:🌫

• It's base at a low level
• White colour
• Thick cloud
• Flat base and cauliflower-like structure
• A dark shadow is seen
• Indicate fair weather
• 

Cumulonimbus:⛈

• It's base at a low level
• Mass grey cloud (heavy cloud)
• Have a great vertical extent till tropopause and spread sideways and appears like anvil shape
• Threatening appearance
• Thunder cloud
• 

Formation of Clouds

What is Cloud?

• Clouds are created when water vapor, condenses and turns into liquid water droplets. These water droplets form on tiny particles, like dust, ice crystals, or altogether that are floating in the air, become visible as Cloud.

Clouds are formed in 4 main ways:

1. Turbulence
2. Orographic lifting
3. Convection
4. Frontal lifting

Clouds formed by Turbulence:

• Strong winds blowing over uneven ground strike against the various obstructions and the air gets deflected upwards.
• This causes thorough mixing of the air and, as the air rises, and cools adiabatically below its dew point, clouds will form. 
• These clouds will be of an even, layer type (stratus) and their bases will generally be not more than 600m high. 
• Turbulence clouds will be formed in great quantities if the air is moisture-laden and blows over cold, uneven ground. 
• Over the sea, wind speeds of more than 13 knots only (force 4 and over) can produce sea waves of sufficient height to create turbulence clouds.

Clouds formed by Orographic lifting:

• Orographic lifting occurs when a mountain acts as a barrier to the wind. 
• During the air ascends a mountain slope, adiabatic cools below its dew point and forms an orographic cloud.
• These are stratus type. 
• If the mountain is quite high, the further ascent will result in nimbostratus and continuous precipitation.
• Precipitation on the windward side while on the leeward side the air is much drier.
• Leeward side, while descending air warms adiabatically.
• This is called Banner cloud.

Clouds formed by Convection:

• Convectional uplift happens when the surface of the air is heated at the ground and expands.
• Then the air should be less dense than the surrounding air.
• After that, the less dense air will begin to rise and cools adiabatically below its dew point.
• When this is successful, convection cloud forms, due to saturation.
• The greater the ascent of air, the greater the vertical extent of the cloud resulting in the vertical extent of the towering cumulus.
• If ascends rapidly(fast) vertical extent reaches the tropopause and spreads sideways and resembles an anvil-shaped cloud called cumulonimbus.

Clouds formed by Frontal lifting:

• Usually, the two masses (warm and cold) of air are opposite temperatures and moistness.
• One air mass is hot and moist while the other air mass is cool and dry.
• The boundary between them is not vertically.
• Then the cool air mass would act as a sloped surface and the warm air mass would use the surface to rise.
• The warm air mass rises and cools adiabatically and cools below its dew point.
• In case of warm front: Slope is gradual and up sliding warm air forms stratiform clouds - nimbostratus, altostratus, cirrostratus and finally cirrus.
• In case of cold front: The slope is very steep and up sliding warm air forms cumulonimbus and cumulus clouds.