How Does Wind Affect Weather? | Sciencing
Free Access THE RELATIONS BETWEEN FREE-AIR TEMPERATURES AND WIND DIRECTIONS.*. Authors: AffiliationsWeather Bureau, Washington, D. C. The data for the first part of the study are taken from website (wagtailfarm.info .com/hurricane/wagtailfarm.info); wind speed and pressure readings for five. Wind has a strong effect on fire behavior due to the fanning effect on The National Weather Service, NOAA NWS, normally reports wind.
This is because air warms as it descends the mountain, and it is also dry, having lost much of its moisture on the windward side of the mountain. The temperature fluctuates between night and day. It is cooler at night and warmer during the day. This can be seen at points B and C on the graph. Land and sea breezes produce mild weather. When there are humid winds during the day and dry winds during the night, it means daytime sea breezes here from the west or south-west, as at point D and evening land breezes here from the eastwhich produces mild weather.
Another phenomenon, which is not apparent from the graphs but which we often notice, is that when there is a wind from the north, air temperature falls. The northerly wind causes a drop in air temperature because it comes from regions closer to the North Pole, which are colder than ours. Wind direction and air temperature Image courtesy of Maria Birba and Theodoros Kondilis Wind direction and relative humidity Wind carries a different amount of humidity depending on where it has come from for example, over land or sea.
From figure 4, we can see the following correlations between wind direction and relative humidity for our location: When easterly descending winds prevail, relative humidity decreases. This seen at A and B on the graph is because the winds from the mountains are warm and dry.
What Drives Weather
When the winds are southerly or south-westerly, relative humidity increases significantly. This as at C is because these winds come from the sea. Slight fluctuations in humidity are linked to winds shifting direction.
These winds seen at interval D are also likely to be weak. Relative humidity varies with time of day. Relative humidity is normally high at night so we see condensation due to cooler temperatures see point E on the graphand low during the warmer daytime hours revealed by evaporation; see point F.
Wind direction and relative humidity. Image courtesy of Maria Birba and Theodoros Kondilis Relative humidity, air temperature, dew point and rainfall From figure 5, we can see the following correlations: Changes in air temperature are linked to changes in relative humidity. This is because for the same amount of moisture in the air, a higher air temperature means a lower relative humidity.
How does the Wind Impact Temperatures? | WeatherWorks
So when temperature rises, relative humidity falls. The dew point varies less than the temperature. The dew point reflects the concentration of water vapour in the atmosphere.
This was less variable than temperature in the location and period that we studied. The type of surface will also affect the temperature. The temperature at the surface of a body of water will be cooler because the heat will readily penetrate and spread throughout the water. On the other hand, bare soil will be higher because heat will not penetrate. Instead, it will be concentrated at the surface.
In forested areas, the trees will absorb most of the heat. For this reason, fuel in the shade will be cooler than in the sun. We will be discussing other reasons later.
WIND Wind has a strong effect on fire behavior due to the fanning effect on the fire. Wind can change direction and intensity throughout the day. This change can be very abrupt surprising the burner that is not alert.
Abrupt changes generally occur during the afternoon when atmospheric conditions are most unstable. We will discuss stability later. Wind is important to the prescribed burners fire fighter because of three influences it has on fire behavior: It also removes the surface fuel moisture, which increases the drying of the fuel.
Air pressure will push flames, sparks and firebrands into new fuel. By pushing the flames closer to the fuel in front of the fire, the fuel is preheated quicker because of the increased radiant heat discussed previously.
More of the fuel becomes available for combustion since it is dryer and can reach ignition temperature quicker. Wind may presents the most persistent problem. It can change speed, direction, or become quite gusty. Wind influences the rate of spread and intensity of the fire. High winds will cause the head of a fire to move ahead rapidly.
It may cause the fire to crown into the top of the trees and to jump barriers that would normally stop a fire. Wind can carry sparks and firebrands ahead of the main fire causing spotting. Wind generally increases evaporation from damp surfaces by carrying away moist air and bringing in dryer air.
In addition wind strongly influences prescribed fire smoke dispersal, a critical consideration. NWS also reports the transport wind speed, the average wind speed from the surface to the mixing height. As a general rule prescribed burn planners prescribe surface winds at flame level or eye level between 1 and 5 MPH and transport wind speeds between 9 aqnd 20 MPH depending on the circumstance and prescribed burn objective. Effect of Wind on Vegetation Friction slows down speed next to the surface Causes turbulence and eddies Fire is more intense at edge of openings Increases evaporation by blowing away the moist air next to fuel On a rotating earth with a uniform surface, the general circulation of the Northern Hemisphere would be composed of the northeast trade winds, prevailing westerlies, and polar easterlies.
It moves from high pressure areas to low pressure areas in an attempt to balance out the differences in temperature. Due to the movement of the earth, this is not a straight line. Wind from a "high" will spiral outward in a clockwise direction in the northern hermisphere. The wind flow toward a "low" will spiral in a counter clockwise direction toward the center.
These highs and lows are generally shown on weather maps. Frontal Winds A weather front is the boundary layer between two air masses of different temperatures. This means that wind blowing toward the south would be turned so that it would end up blowing toward the west, wind that started out blowing toward the west would end up blowing toward the north and so on, as shown in image 2 in the diagram.
Windy Weather II: The Correlation Between Barometric Pressure and Wind Velocity
The Coriolis force is what causes low pressure systems to rotate counterclockwise. Friction slows the wind and causes it to turn slightly toward lower pressure. This causes the wind to blow in toward the center of a low pressure system, as shown in image 3. Because all the wind flows towards the center of the low pressure area, we say it is converging. In the center, since the air cannot go down, it rises, which leads to clouds and precipitation.
The same rules apply to a high pressure system. The high pressure center is surrounded by lower pressure on all sides, so the wind blows directly out from the center at first, as shown in image 4. Then, the Coriolis force turns the wind toward its right, causing clockwise rotation around a high pressure system, as shown in image 5.
Friction makes the wind turn slightly toward lower pressure, which in this case is out away from the center of the high pressure area. This makes the wind blow slightly outward from the center of a high, as shown in image 6.