Physical Attributes | Weather | Climate | Atmosphere | Meteorology
The science of the study of weather is called meteorology; the meteorologist measures temperature, rainfall, pressure, humidity, sunshine and cloudiness, and. Climate is generally defined as average weather, and as such, climate change and weather are intertwined. Observations can show that there have been. The night sky has inspired us for generations, and the inspiration continues at Assateague Island National Seashore, which holds some of the last remaining.
Pressure is a force, or weight, exerted on a surface per unit area, and is measured in Pascals Pa. The pressure exerted by a kilogram mass on a surface equals 9. Usually, atmospheric pressure is quoted in millibars mb. In fact, actual values of atmospheric pressure vary from place to place and from hour to hour. At sea level, commonly observed values range between mb and mb. Because pressure decreases with altitude, pressure observed at various stations must be adjusted to the same level, usually sea level.
Atmospheric pressure is measured by a barometer. A mercury barometer measures the pressure by noting the length of mercury which is supported by the weight of the atmosphere. One centimetre of mercury is equal to An aneroid barometer is a more compact instrument for measuring pressure. It consists of a box of partially exhausted air which expands and contracts as the pressure falls and rises. The box is connected through a system of levers to a pointer which, in conjunction with a dial, indicates the pressure.
Variations in atmospheric pressure lead to the development of winds that play a significant role in shaping our daily weather. The mercury barometer Humidity Some water in the form of invisible vapour is intermixed with the air throughout the atmosphere.
It is the condensation of this vapour which gives rise to most weather phenomena: There is a limit to how much water vapour the air can hold and this limit varies with temperature. When the air contains the maximum amount of vapour possible for a particular temperature, the air is said to be saturated. Warm air can hold more vapour than cold air. In general the air is not saturated, containing only a fraction of the possible water vapour.
The amount of vapour in the air can be measured in a number of ways.
The humidity of a packet of air is usually denoted by the mass of vapour contained within it, or the pressure that the water vapour exerts. There are strong gusts of wind, heavy rain, and sometimes hail. This is a thunderstorm. The powerful rotating cyclones variously called tropical cycloneshurricanes, or typhoons, generate torrential rains and winds of 74 miles kilometers per hour or more.
These storms originate over tropical seas in late summer and early fall. At those times surface temperatures are highest and tropical air reaches farthest from the Equator. The storms usually track westward and then poleward, carrying large amounts of warm air to high latitudes. Airplanes penetrate hurricanes to gauge their intensity and to plot their courses. A tornado has a narrow, funnel-shaped trunk that reaches down from a dark thundercloud. It whirls at speeds of up to miles kilometers per hour.
A tornado usually moves to the northeast in the Northern Hemisphere and to the southeast in the Southern Hemisphere. Tornadoes appear most frequently in spring and early summer. During those seasons in the United States, for example, cold, dry air flows over the Rocky Mountains and overrides the warm, moist air flowing from the Gulf of Mexico.
Turbulence is caused by the sinking cold air and rising warm air. Weather conditions are measured by standard instruments. Surface wind speeds are usually measured by an anemometer. An anemometer consists of three or four wind-driven cups mounted on a vertical axis whose rate of rotation varies with wind speed. Wind direction is indicated by a vane, a pointer that swings with the wind. The vane is mounted on a vertical axis attached to a compass rose.
Newer devices with no moving parts use pulses of sound to determine both wind speed and direction. Atmospheric pressure is measured by an aneroid barometera flexible metal vacuum box that expands or contracts with changes in pressure. Atmospheric pressure can also be measured by a mercury barometer. It consists of a glass tube in which the height of a column of mercury varies with pressure.
What is the relationship between meteorology weather and climate
Temperature is measured by a thermometer. In the past, the most common type was a glass tube in which the height of a column of mercury or alcohol varies with changes in temperature. Various types of electronic thermometers thermistors and thermocouples are now often used instead. Even then, the liquid-in-glass type is valuable for calibration and backup.
Humidity data, including relative humidity, vapor pressure, and dew point, is secured with the use of various types of instruments. The instruments are generally known as hygrometers. A commonly used type at government reporting sites is the dew-point hygrometer. In this instrument a polished metal surface is cooled until condensation begins to collect on its surface.
Its temperature then indicates the dew point directly. Another accurate type is the psychrometer, consisting of two similar thermometers. The bulb of one thermometer is kept wet, and the other dry. The differences between the temperatures they record are related to the amount of moisture in the air.
The ceiling, or base height of cloud layers, can be measured by an automatic ceilometer.
Annual climate statement
It shines a beam of pulsed light often a laser up at the base of clouds, which reflects the light. The ceilometer has a photoelectric telescope to detect this reflection.
The ceilometer can measure in the daytime or at night. The amount of precipitation is usually measured by a rain gauge, an open-mouthed container that catches the rain. A commonly used variation of this is the tipping bucket rain gauge, which automatically empties itself as the rain is measured.
Radar is used to measure the intensity of rainfall or snowfall. This information is compiled over time to estimate the total amount in areas with no other data. Soundings of upper-level pressure, temperature, humidity, and winds are made by radiosondes. A balloon carries a radiosonde aloft tofeet 30, meters or more. The radiosonde transmits data to ground recorders. The speed and direction of upper winds are obtained by tracking the radiosonde with a radio direction finder. Upper-wind information is also obtained by tracking an ascending balloon visually with a surveying instrument.
Data transmitted from commercial aircraft may be incorporated into the analysis as well. Doppler radar can continuously measure wind speeds by observing microwaves reflected off of particles in the atmosphere, such as raindrops or dust. Doppler profiles record the apparent shift in frequency with respect to the observation point of waves emitted by a moving source.
This phenomenon is known as the Doppler effect. A related instrument, the radiometric profiler, observes microwaves emitted by oxygen and water vapor in the air. Careful analysis of the data yields profiles of temperature and humidity at different altitudes. Accurate measurements of temperature and atmospheric pressure were not available until after the thermometer and the barometer were perfected in the 17th century.
Comprehensive weather forecasting did not become practical until the telegraph was invented in the 19th century. This made possible the rapid collection and dissemination of weather observations.
The first systematic weather observations in the United States date back to Government weather forecasts in the United States were first issued in by the Army. Civilian weather activities in Canada are directed by the Atmospheric Environment Service, an agency of the Department of the Environment. This agency was first established in under another name.
Many of them have Web pages.
- Annual climate statement 2017
There are also numerous privately owned weather forecasting companies that in some cases provide specialized services not covered by government agencies. With more than member states, the WMO coordinates the worldwide exchange of weather and climate information. It grew out of the International Meteorological Organization, established in It is based on a summary, or synopsis, of the total weather picture at a given time.
The development and movement of weather systems is shown on a sequence of synoptic charts, or weather maps.weather variables
These weather systems are then projected into the future. The weather observations used for the charts are made at thousands of weather stations around the world four times a day—at midnight, 6 am, noon, and 6 pm, Greenwich mean time GMT. The most common synoptic chart is the surface weather map.
Various upper levels of the atmosphere also are charted. Another method, statistical forecasting, employs mathematical equations based on the past behavior of the atmosphere. Still another, numerical forecasting, uses mathematical models based on the physical laws that describe atmospheric behavior. For forecasts of up to about 10 days, numerical methods are most often used. For somewhat longer periods, statistical methods are more accurate.
Beyond about 90 days, weather events can be predicted almost as well through climatological forecasting, using the averages of past weather records. Until the s weather maps were plotted by hand and analyzed at local weather offices. The future locations of storms, fronts, and other weather phenomena were calculated by manually projecting the movements of weather systems from successive maps.
Computer-drawn maps now predict wind, temperature, and humidity patterns for many atmospheric levels. Statistical methods are then used to map probable maximum and minimum temperatures, precipitation, winds, and other weather elements. Local forecasters modify these centrally produced guidance predictions to account for any local weather peculiarities. In weather analyses, lines connecting points of equal atmospheric pressure, called isobars, are drawn on a map. Lines on the map may also connect points of equal value for other factors, such as humidity, temperature, or amount of rainfall.
Maps for values both at the surface of Earth and at many higher levels of the atmosphere are examined. Analysis is largely done automatically on computers as part of numerical prediction. The computer-drawn maps, along with many other graphical and text products, are distributed electronically to public and private weather forecasting centers. Much of the information is also provided to various universities, which often publish the data—along with further analysis—on the Internet.
Numerical weather prediction is essentially a problem in fluid dynamics. Such information, however, is not fully available. Numerical weather prediction was not practical at all before high-speed computers were developed in the late s. Six basic equations—expressing the three dimensions of motion and the conservation of heat, moisture, and mass—are used in numerical mathematical models. Computers solve these equations to obtain instantaneous changes at thousands of regularly spaced grid points and at dozens of levels of the atmosphere.
The changes are repeatedly computed for successive short time intervals for the desired time range of the forecast. This marching forward in time is the essence of numerical prediction.
In the United States the NCEP regularly runs at least three different major computer models, from one to four times per day.
The models provide forecasts for periods from two days to two weeks. Some of these cover North America only, but others forecast for the entire planet. Other countries have similar computer models. Forecasters study the output from the various models, using experience and skill to decide which might be more reliable in a given weather situation. Collection and Distribution of Weather Data Weather stations in the United States transmit coded weather data every hour for aviation use.
They provide weather data every six hours for general forecasting and daily for climatological records. Surface weather data, much of it gathered by automated stations, is included on precipitation, temperature, pressure, change in pressure, wind direction and speed, humidity, dew point, cloud type, sky cover, visibility, ceiling, and current weather.
In addition, volunteer observers at thousands of substations take daily measurements of temperature extremes and precipitation.
Other weather networks are operated for warning of specific weather emergencies and for furthering agricultural programs. In the United States professional weather forecasters communicate directly with the public through newspapers, radio and television broadcasts, and the Internet. A radio network operated by NOAA broadcasts forecasts, conditions, and severe weather watches and warnings 24 hours a day.
Special NOAA radios feature alarms that alert the listener even when the radio is otherwise off. On cable television the Weather Channel relates local, regional, national, and selected international weather conditions 24 hours a day to many millions of American households. An international system of telecommunication networks distributes weather information, largely by satellite. Numerically coded data from around the globe is relayed by collection stations to central processing offices, such as at NCEP in the United States.
Since the s weather surveillance satellites have made it possible to detect weather systems from the time they begin.
No longer is a destructive storm larger than a tornado likely to strike without warning. Weather satellites fall into two main classes, based on their location and time to orbit Earth. Polar-orbiting satellites, first launched inwere the first operational satellite system of the United States. They circle the globe approximately every minutes, so that they pass roughly over each point on Earth twice a day once heading north and once heading south.
Geostationary weather satellites also first launched in are at a much greater distance, about 22, miles 35, kilometersdirectly above the Equator.
What is the relationship among meteorology, weather, and climate?
As a result, they appear to hover over a fixed point on Earth. Climate is the description of the long-term pattern ofweather in a particular area. Some scientists define climate as the average weather for aparticular region and time period, usually taken over years. When scientists talk about climate, they're looking at averages ofprecipitation, temperature, humidity, sunshine, wind velocity,phenomena such as fog, frost, and hail storms, and other measuresof the weather that occur over a long period in a particular place.
For example, after looking at rain gauge data, lake and reservoirlevels, and satellite data, scientists can tell if during a summer,an area was drier than average.
If it continues to be drier thannormal over the course of many summers, than it would likelyindicate a change in the climate. In the context of climate change: Weather varies all the time, butclimate doesn't vary nearly as quickly. The Earth's climate is changing relatively quickly relative to itsusual pace now due to an enhanced greenhouse effect caused byhumans emissions of greenhouse gases, and most locations areexperiencing a net warming as a result.
This doesn't mean it can'tget cold anymore, or even that record cold temperatures will nolonger occur. But it does mean that, in most areas, heat waves orunusual warmth in the winter will be warmer and cold snaps orcool periods in summer will not be as cold. The time scale of climate is not nearly as intuitive as that ofweather, so even people who understand this have a tendency to beinfluenced only by the most recent weather they experience.
You canobserve this effect by watching the news during both cold snaps andheat waves, which will be either given as evidence for or againstthe warming of the Earth. In reality, you cannot attribute eitherto a changing climate due to the small spatial and temporal scaleof these events; weather variability will always be of greatermagnitude than observed changes in climate. What is the relationship between climate and weather?
Weather is the current condition. Climate is based on an average weather condition for a specific region or area over a longer time frame.
Weather is limited both geographi…cally and temporally or in other words by place and time, especially the latter.