C = ( F - 32 ) / 1.8 therefore F = 32 + ( C x 1.8 ) and Absolute zero or zero degree of K (kelvin) = - 273 C and - 459 . 4 F
Posts made by RAVAR
Some Notes about Earth Atmosphere
(Atmosphere layers from ground)
1 : Troposphere from Greek word tropos meaning mixing , which contains almost all of earth's weather . the troposphere has two defining characteristics : firstly in troposphere with gaining height the temperature would deacrese . secondly the troposphere contains over 70% of total mass of atmmosphere .
2 : Tropopause which is the upper limit of the troposphere and difine as the point where temperature no longer decreases with height . the height of tropopause varies from 16 km over the Equator to 8 km over the Poles so the average height of that is 11 km at 45 degree of latitude .
3 : Stratosphere is next layer after tropopause and unlike troposhpere is characterised by the lack of any significant change in temperature with height . this absence of any significant temperature variation within the lower stratosphere gives the air of the stratosphere stability in other words vertical movment of air within the stratosphere is severely restricted .
4 : Stratopause which is upper boundary of stratosphere and above that temperature begins to increase with height again . stratopause is usually found around 50 km above surface .
There is some other layers above stratopause such as mesosphere , mesopause , thermosphere , ionosphere , exosphere which thay have little practical influence over weather .
(Composition of Earth's atmosphere)
The atmosphere consist of 78% nitrogen , 21% oxygen and 1% other gases which argon is 0.95% of that 1% and the other 0.05% are carbon dioxide and trace gases (carbon monoxide , helium , ozone , hydrogen and methane) .
Note : water vapour can make up between 0% and 7% of the atmosphere but water vapour has the greatest effect on our weather .
ISA or international standard atmosphere assumes that at mean sea_level air temperature is +15 degree of celsius , air pressure is 1013.25 mb = 760 mm.hg = 76 cm.hg = 29.92 in.hg , air density is 1.225kg/m3 = 1225 g/m3 , from mean sea leve to 11 km temperature decreases by 1.98 degree of celsius per 1000ft ,from 11 km to 20 km temperature remains constant at -56.5 degree of celsius and from 20 km to 32 km temperature rises by 0.3 degree of celsius per 1000ft , air pressure from mean sea level to 10000ft decreases 1 mb per 27ft , from 10000ft to 18000ft air pressure decreases 1 mb per 36ft , from 18000 ft to 30000ft air pressure decreases 1 mb per 50ft and finally form 30000ft to more than that air pressure decreases 1 mb per 73ft . (so interesting!!!)
RE: Frontal Weather
There are some general weather characteristics that are found in most cold fronts includsuche as :
(1) cumlus clouds
(3) showery precipitation
(4) strong gusty winds
(5) clearing skies and good visibility after front passes
(1) stratus clouds if air is moist and stable
(2) little turbulence except in an unstable airmass
(3) percipitation ahead of front in wide area
(4) poor visibility with haze or fog
Note : in warm occlusions you will found an moist , unstable air lift so rapidly therefore you can find embeeded cumulonimbus in that type of front so in that weather will be severe than cold occlusion .
The type and intensity of frontal weather depend on several factors . some of this factors are availability of mositure , the stability of the air being lifted and speed of of the frontal movement . other factors include the slope of the front and the moisture and temperature variation between two fronts . although some frontal weather can be very severe and hazardous other fronts produce relatively calm weather .
Note : usually the cold fronts are severe than warm fronts but warm front occlusion it,s more dangerous than cold front occlusion . (and also the slope and gradient of cold front is more than warm front )
Types of Fog
Fog is classified according to the way it forms . Radiation fog also known as Ground fog is very common . it forms over fairly level surfaces on clear , calm humid nights . as surface cools by radiation the adjucent air is also cooled to it's dewpoint (which is the temperature at that air reaches a state where it can't hold any more water vapor) . radiation fog usually occurs in stable air associated with high pressure system .
Advection fog is caused when a low layer of warm , moist air moves over cooler surface . it is most common under cloudy skies along coastlines where air moves from the warm water to the cooler surface of land .
Upslope fog forms when moist , stable air forced up a sloping land mass . like advection fog , upslope fog occure under cloudy skies .
Precipitation _ induced fog may form when warm air or drizzle falls through a layer of cooler air near surface . evaporation from the falling precipitation saturates the cool air causing fog to form . this fog can be very dense and usually it does not clear until the rain moves out of the area .
Steam fog or Sea smoke occurs as cold , dry air moves over comparatively warmer water . it rises upward from the water surface and resembles rising sea smoke . it is composed entirely of water droplets that often freeze quickly and fall back into water as ice particles .
Note : radiation fog is stronger than advection fog . temperture diffrent between dewpoint and environment temperture for fog formation must be less than 2 degree of C(4 degree of F)
Infact fog is low cloud which has hight not more than 50 feet and required very weak wind with speed of 9 km/h or less generaly fog will restrict horizentl surface visibility to less than 1000 m . as noted sunlight and strong wind with speed of more than 9 km/h are two major things which will destroy fogs . strong wind will separate or lift it to hight more than 50 feet and than the fog wil be called as low stratus cloud . other wise quickly after sun rise the relative humidity (whis is the actual amount of moisture in the air compared to the total amount of moisture that air can take to become saturate at that temperature) will rise and the fog will dissipate .
First of all let's talk about Airmass . an Airmass is a large body of air with fairly uniform temperature and moisture content . it may be several houndred miles across and usually forms where air remains stationary or nearly stationary at least for several days . during this time the airmass takes on the temperature and moisture properties of the underlying surface that determine its stability and known as Source Region . an ideal source regions is a large area with fairly uniform geoghraphy and temperature . a source region is usually located where air tends to stagnate . the best areas for airmass development are in the regions where atmospheric circulation has caused the buildup of semipermanent areas of high pressure . some of excellent areas are snow and ice covered polar regions , tropical oceans and large deserts . the middle latitudes are poor source regions because of the strong westerly winds and the continual mixing of polar and tropical airmasses .
Note : about airmasses maritime means moist , continental means dry , polar means cold , tropical means hot .
Temperature usually decreases with an increase in altitude sometimes the reverse is true . Generally the temperature inversion means increase of temperature with altitude . inversions are usually confind to fairly shallow layers and may occure near to the surface or at higher altitude . they acts as a lid for weather and pollutants . visibility is often restricted due to fog , haze , smoke and low clouds . temperature inversions occure in stable air with little or no wind and turbulence . one of the most familiar types of inversion is the one that forms just above the ground on cool , clear nights . as the ground surface cools it lowers the adjacent air temperature . if this process continues the air within a few houndred feet above surface may become even cooler than the air above it . an inversion can also occure when cool air is forced under warm air or when warm air spreads over cold both of these are known as frontal inversion .
Types of tunderstorms
Tunderstorms usually have similar physical features but their intensity degree of development and associated weather to differ . thay are generally classified as Airmass and Frontal .
Air mass Thunderstorms
Air mass thunderstorms generally form in a warm , moist air and isolated or scattered over large area . they are usually caused by solar heating of the land which results in convection currents that lift unstable air and are most common during summer afternoons or in coastal areas at night . Air mass thunderstorms can also be caused by orographic lifting . although they are usually scattered along individual mountain peaks . they may cover large areas . they may be embedded in other clouds making them difficult to identify when approached from the Windward (the opposite of Lee ward ) side of a mountain . Nocturnal thunderstorms can occure in late spring and summer during the late night or early morning hours when relatively moist air exists aloft . they are usually found from the mississippi valley westward . nocturnal storms cover many square miles and their effects may continue for hours at a given location .
Frontal thunderstorms can be associated with any type of front . those which occure with a warm front are usually obscured by stratiform clouds . you should expect thunderstorms when there is showery precipitation near warm front . in a cold front the cumulonimbus clouds are often visible in a continuous line parallel to the frontal surface .
Note : Squall line is a narrow band of active thunderstorms which normally contains very severe weather and is often forms 50 to 300 miles ahead of front .
Three stage of Thunderstorm
Cumulus stage : it's charecterized by countinous up drafts . in this stage a lifting action initiates the vertical movement of air .
as air rises and cools to it's dewpoint water vapor condenses into small water drroplets or ice crystals . if sufficient moisture is present the water vapor latent heat of condensation which released during condensation procers wil provides energy for the continued vertical growth of the cloud . Because of strong updrafts precipitation usually does not fall . instead the water drops or ice crystals rise and fall within the cloud and growing larger with each cycle also may creates hail . in cumulus stage of thunderstorm updrafts as fast as 3000 f.p.m may begin near the surface and extend well above the cloud top .
Mature stage : Thunderstorms reach the greatest intensity during the mature stage. as the drops in the cloud grow too large to be supported by the updrafts precipitation begins to falls to the surface . this creates a downward motion in the surrounding air and shows beginning of the mature stage . downdraft may reach velocity of 2500 f.p.m . the down-rushing air spreads outward at surface producing a sharp drop in temperature a rise in pressure , strong gusty wind and wind shear
conditions . (wind shear is a sudden drastic shift in wind speed and/or direction at vertical or horizental plane . ) as the thunderstorm advances a rolling , turbulent , circular-shaped cloud may form at the lower leading age of the cloud which called the rolling cloud .
Dissipating stage : unlike cumulus stage a dissipating thunderstorm is characterized by predominant down drafts . as the mature stage progresses more and more air aloft is disturbed by the falling drops . eventually the downdrafts begin to spread out within the cell taking the place of weakening updrafts . Because upward movement is necessary for condensation and release of the latent heat energy the entire thunderstorm begins to weaken . during this stage the upper level winds often blow the top of cloud downwind , creating the familiar anvil shape . how ever the anvile does not necessarily signal the storm's dissipation .
Thunderstorms are one of the most beautiful atmospheric phenomenon and also are one of the most hazardous conditions that producesevere turbulence, low level windshear, low ceilings and visibilities, hail and lightning .
Thunderstorms are formed by a process called convection, defined as the transport of heat energy. Because the atmosphere is heated unevenly, an imbalance can occur which thunderstorms attempt to correct.Three things are needed for convection : moisture, lift and instability .
Moisture—Sufficient moisture must be present for clouds to form. Although convection occurs in the atmosphere without visible clouds, think thermalson a warm afternoon, moisture not only is the source of a visible cloud, butalso fuels the convection to continue
. As the warm air rises, it cools, and thewater vapor in the air condenses into cloud droplets. The condensation releases heat, allowing
the rising air to stay buoyant and continue to move upward.
Lift—There are many ways for air to be lifted in the atmosphere. Convection,or buoyancy, is one method. Other meteorological methodsinclude fronts,low pressure systems, interactions between thunderstorms, and interactions between the jet stream and the surfaceweather systems. Air also can be lifted by mechanical lift,such as when it is forced up and over a mountain range.Regardless
of how the air is lifted, if the lift is enough to make the air warmer than the surrounding air, convection can continue.
Instability—In general, as you increase in altitude, the air temperature cools up to the top of the troposphere. Of course, around fronts, mountains and in shallow layers near the ground, this is not always the case.How fast air cools is a measure of atmospheric stability . Meteorologists refer to this vertical change in temperature as the lapse rate.Outside of extremes, the temperature generally decreases from between 2.7oF - 5.4oF per 1000 feet. If the actual rising air cools slower than the lapse rate, the air remains relatively warm to compared the surroundings, and it continues to rise.
A katabatic wind is the name of any wind that blowing down an incline . a mountain wind which is result of rapidly slope cooling at night and this air flow down and displaces the warmer air in the valley is one type of katabatic wind . Depending upon local counditions , katabatic winds can have a dramatic effect on temperature . Sometimes the cold , dense air spills over mountain and flows down to displces the air ahead of it if this occure over elevated mountains the descending air is warmed by compression until it is warmer than the air it's displacing which known as Foehn wind but also may referred to locally names such as Santa ana in california or Chinook in rockies . Occasionally unlike foehn wind descending airmass will be so cold that even trough it's warmed during descend it's still colder than the air it displaces which known as Fall or Gravity winds!!!
Some warm local winds
SCIROCCO(Sirocco): South/South - Easterly strong winds with dust and sand blowing over the mediterranean from africa which are winter phenomenon occuring when deep low pressure area system is situated in the western Mediterranean sea.
HARMATTAN: North - Easterly winds which formed over yhe sahara desert and affecting Western / North - Western regions of africa.
occurs typically in the winter between November and April.It creates dust and sand storms with very poor visibility and can reach as high as 15000ft
KHAMSIN: Southerly wind blowing from Egypt over Eastern Meditrranean and occurs in Winter and Spring.
SIMOOM: South/South - Easterly very hot,dry and dusty wind blowing over the african and arabic deserts and occurs mainly in Spring and Summer.
HABOOB: blows over Egypt and Sudan,typically in the evenings of May and September also brings sandstorms ahead of advacing thunderstorms.
GHIBLI: Southerly warm wind and damp when blowing over sea that affecting Lybia and typically blows ahead of a depressin(low pressure area) during late summer.
Orographic Middle and High Cloud
This cloud often forms east of New Zealand’s main mountain ranges as a result
of an increasing northwest flow ahead of a frontal system. At first, single Ac
lentics form, but as the front approaches, upper level moisture increases and an
‘arch cloud’ develops. This arch cloud usually displays a very sharp western edge.
Flying conditions within the arch are usually smooth; however, conditions will be
very turbulent below the cloud at low levels. Moderate or severe icing may be
encountered within the arch depending on its thickness.
with respect to Peter Fisher