Master Naturalist Presentation: Weather and Climate

Weather and ClimateWeather and Climate

Southwestern Piedmont Master NaturalistsSouthwestern Piedmont Master NaturalistsNovember 6, 2008November 6, 2008

Denny Casey, Ph.D.Denny Casey, Ph.D.Director of Education and Public ProgramsDirector of Education and Public Programs

Virginia Museum of Natural History Virginia Museum of Natural History

Image credit: www.nasa.govImage credit: www.nasa.gov

OverviewOverview

Main factors affecting climateMain factors affecting climate Human effects on weather, climate, and air qualityHuman effects on weather, climate, and air quality Virginia’s climate change over timeVirginia’s climate change over time The relationships between climate, weather, and The relationships between climate, weather, and

phenologyphenology Main processes driving weatherMain processes driving weather Weather forecasting and the basic weather measurements Weather forecasting and the basic weather measurements

(temperature, humidity, barometric pressure, wind speed (temperature, humidity, barometric pressure, wind speed and direction, cloud formations)and direction, cloud formations)

A typical year of weather in VirginiaA typical year of weather in Virginia ResourcesResources

Main factors affecting climateMain factors affecting climate

Some factors impact climate Some factors impact climate over a short period of time, over a short period of time, while others occur over while others occur over very large amounts of very large amounts of time.time.

Image credit: www.iceage2.comImage credit: www.iceage2.com


While some are While some are extraterrestrial in extraterrestrial in origin…origin…

Image credit: www.univaersalstudios.comImage credit: www.univaersalstudios.com


others others occur occur right here right here on Earth.on Earth.


One orbit around One orbit around the sun serves as the sun serves as a fundamental a fundamental force of climate force of climate variability. The variability. The essential cause of essential cause of seasonal climate seasonal climate change is the tilt change is the tilt of Earth's axis, of Earth's axis, currently 23.5 currently 23.5 degree tilt off axis degree tilt off axis to the orbital to the orbital plane of plane of revolution.revolution.


Because of the Earth’s Because of the Earth’s tilt, the angle of solar tilt, the angle of solar radiation and thus radiation and thus intensity over the intensity over the course of the year course of the year varies. The polar varies. The polar surfaces receive surfaces receive about half the about half the amount of solar amount of solar radiation per unit radiation per unit area as the area as the equatorial surface.equatorial surface.


Energy received from the Energy received from the Sun drives weather and Sun drives weather and climate. The regular climate. The regular changes of the Earth’s changes of the Earth’s orbit around the Sun, orbit around the Sun, and changes in the and changes in the Earth’s rotation about Earth’s rotation about its tilted axis, control its tilted axis, control the daily and seasonal the daily and seasonal cycle and dominate the cycle and dominate the climatology of the climatology of the Earth.Earth.

TThe amount of energy received by the Earth at the top he amount of energy received by the Earth at the top of the atmosphere, before it is absorbed and scattered of the atmosphere, before it is absorbed and scattered by molecules and aerosols (solid or liquid particles) in by molecules and aerosols (solid or liquid particles) in the atmosphere. the atmosphere.

Image credit: GLOBE.govImage credit: GLOBE.gov

http://www.globe.gov/fsl/educornimages/movies/INSO1987.mpg

Image credit: NASA's Earth Radiation Budget Experiment program.



This animation shows the global advance and retreat of daily snow cover along with daily sea ice surface temperature over North America from September 2002 through May 2003. The ice-covered areas modify the radiation budget by means of their high reflectivity. Research shows that the global radiation budget at 18,000 B.P was about 7- -10% less than that of today.

Image credit: NASA/Goddard Space Flight Center, Scientific Visualization Studio, The SeaWiFS Project and GeoEye


In 1920, Milutin Milankovitch In 1920, Milutin Milankovitch showed that regular showed that regular variations in the shape of variations in the shape of Earth's orbit and the Earth's orbit and the orientation of its axis orientation of its axis create variations of solar create variations of solar intensity at high latitudes: intensity at high latitudes: warm summers in which warm summers in which glaciers retreat, and cool glaciers retreat, and cool summers when they summers when they advance. These climate advance. These climate cycles, called Milankovitch cycles, called Milankovitch Cycles, are determined by Cycles, are determined by three factors…three factors… Animation credit:

http://www.museum.state.il.us/research/GISlab/


ObliquityObliquityThe change of the tilt of the The change of the tilt of the

Earth's axis away from the Earth's axis away from the orbital plane. The tilt orbital plane. The tilt varies between 22.1 and varies between 22.1 and 24.5 degrees and the 24.5 degrees and the average is 23.5. Presently, average is 23.5. Presently, the Earth’s axis is tilted the Earth’s axis is tilted 23.4 degrees and is 23.4 degrees and is decreasing.decreasing. Image credit: Image credit:

http://earthobservatory.nasa.gov/Library/Giants/Milanhttp://earthobservatory.nasa.gov/Library/Giants/Milankovitch/milankovitch.htmlkovitch/milankovitch.html


The obliquity The obliquity changes on a changes on a cycle of cycle of approximately approximately 41,000 years.41,000 years.

Image credit: www.museum.state.il.us/


EccentricityEccentricity

A measure of how A measure of how circular or elliptical our circular or elliptical our orbit is around the orbit is around the Sun. Over time, the Sun. Over time, the Earth’s orbit varies Earth’s orbit varies from less than 1% to from less than 1% to almost 6% and is almost 6% and is currently about 1.7 % currently about 1.7 % and decreasing.and decreasing.


As a result of As a result of gravitational gravitational forces of the forces of the planets, Earth’s planets, Earth’s orbit is not orbit is not circular, the circular, the distance to the distance to the Sun changes Sun changes during the during the course of the course of the year.year.

Image credit: http://www.ichthus.info/BigBang/PICS/helions.GIFImage credit: http://www.ichthus.info/BigBang/PICS/helions.GIF


Eccentricity changes in Eccentricity changes in 100,000 year 100,000 year cycles. Low values cycles. Low values of eccentricity of eccentricity correlate to low correlate to low change in incoming change in incoming solar radiation solar radiation during the year. during the year. Although the Although the amount of change amount of change in radiation is very in radiation is very small (less than small (less than 0.2%), it is 0.2%), it is apparently apparently extremely important extremely important in the expansion in the expansion and melting of ice and melting of ice sheets.sheets.

Image credit: www.museum.state.il.us/


PrecessionPrecession

AA wobbling in the wobbling in the orientation of Earth's orientation of Earth's axis is caused by the axis is caused by the gravity of the Sun and gravity of the Sun and the Moon acting on the Moon acting on Earth's equatorial Earth's equatorial bulge. bulge.


As a result of the As a result of the wobble, aphelion and wobble, aphelion and perihelion change perihelion change position on the orbit position on the orbit through a cycle of through a cycle of 360 degrees. The 360 degrees. The cycle has a period of cycle has a period of approximately 22,000 approximately 22,000 years. In 12,000 years. In 12,000 years, we will years, we will experience summer experience summer in December and in December and winter in June.winter in June.

Image credit: www.museum.state.il.usImage credit: www.museum.state.il.us


This graph shows the incoming solar radiation over the last 600,000 years for This graph shows the incoming solar radiation over the last 600,000 years for summer at 65 degrees north latitude. Note the complex changes that occur in summer at 65 degrees north latitude. Note the complex changes that occur in the curve. The curve was derived using the changing values of the eccentricity the curve. The curve was derived using the changing values of the eccentricity of the orbit, tilt of the axis and precession of the equinoxes. of the orbit, tilt of the axis and precession of the equinoxes.

Image credit: www.museum.state.il.us/Image credit: www.museum.state.il.us/


Cyclic and Cyclic and punctuated punctuated fluctuations in solar fluctuations in solar activity results in activity results in small changes in small changes in the nature and the nature and amount of solar amount of solar radiation that radiation that reaches the earth.reaches the earth.

Animation: University of Oregon


Sunspot cycleSunspot cycle

The number of sunspots The number of sunspots varies in an 11-year cycle. varies in an 11-year cycle. When the number of When the number of sunspots is large, solar sunspots is large, solar output is slightly higher output is slightly higher (0.1%) Surrounding (0.1%) Surrounding sunspots are bright areas sunspots are bright areas on the sun called faculae on the sun called faculae which are responsible for which are responsible for an increase in radiation.an increase in radiation.

Enhanced color image the appearance of the Enhanced color image the appearance of the faculae (white regions) which are hotter than faculae (white regions) which are hotter than sunspots (red-black regions) and whose sunspots (red-black regions) and whose greater total area contribute to increasing the greater total area contribute to increasing the solar flux reaching the Earth. April 27, 2002.solar flux reaching the Earth. April 27, 2002.


Sunspot cycle graph Sunspot cycle graph with data from with data from 1750 to 2005. The 1750 to 2005. The number of number of sunspots per year sunspots per year varies with an 11 varies with an 11 year cycle and the year cycle and the peaks are peaks are associated with associated with times of high solar times of high solar activity (many activity (many flares and solar flares and solar storms). storms).


Daily Sun: 26 Oct 08Daily Sun: 26 Oct 08 The The Sun’s surface currently Sun’s surface currently has no sunspots.has no sunspots.

Image credit: SOHO/MDIImage credit: SOHO/MDI

Sunspot activity is at a minimum now but will be increasing over the next 5 or 6 years.

Image credit: swpc.noaa.gov/SolarCycle/

Main factors affecting climate Main factors affecting climate

Sunspots also have a 22-year Sunspots also have a 22-year magnetic field cycle magnetic field cycle (magnetic field of sunspots (magnetic field of sunspots reverse after each 11-year reverse after each 11-year max/min cycle). Changes max/min cycle). Changes could result in changes in could result in changes in the interaction of the solar the interaction of the solar wind with the Earth’s wind with the Earth’s magnetosphere. There magnetosphere. There could also be a linkage could also be a linkage between a change in between a change in gamma rays emitted by the gamma rays emitted by the sun and the electrical field sun and the electrical field of the Earth, which in turn of the Earth, which in turn could cause changes in could cause changes in thunderstorm activity. thunderstorm activity. Image credit: en.wikipedia.org/wiki/MagnetosphereImage credit: en.wikipedia.org/wiki/Magnetosphere

http://upload.wikimedia.org/wikipedia/commons/4/44/Structure_of_the_magnetosphere_mod.svg

The Earth’s BiosphereThis composite image gives an indication of the magnitude and distribution of global primary production, both oceanic (mg/m3 chlorophyll a) and terrestrial (normalized difference land vegetation index).

Image credit:SeaWiFS Global Biosphere September 1997 - August 1998


The biosphere can impact climate… The biosphere can impact climate… acting as a temporary source or sink of greenhouse gasesacting as a temporary source or sink of greenhouse gases

– photosynthesis removes carbon dioxidephotosynthesis removes carbon dioxide– produces methane (greenhouse gas) from decayproduces methane (greenhouse gas) from decay

productivity of biosphere increases with increasing carbon productivity of biosphere increases with increasing carbon dioxidedioxide

producing particulates which increases cloud coverproducing particulates which increases cloud cover changing albedo of the surfacechanging albedo of the surface

– desertification – deserts have high albedo desertification – deserts have high albedo – deforestation – forest and snow has a lower albedo deforestation – forest and snow has a lower albedo

than just snowthan just snow


VolcanoesVolcanoes vast amounts of dust thrown into the vast amounts of dust thrown into the

stratosphere, as well as vast stratosphere, as well as vast amounts of sulphur dioxide, result in amounts of sulphur dioxide, result in more sunlight scatteredmore sunlight scattered

little vertical motion in the little vertical motion in the stratosphere means minute particles stratosphere means minute particles can remain suspended for several can remain suspended for several years and be spread globallyyears and be spread globally

short-lived change – effects last for short-lived change – effects last for 2-3 years 2-3 years

substantial summer cooling, some substantial summer cooling, some winter warming (greater circulation winter warming (greater circulation has been observed with eruptions of has been observed with eruptions of Pinatubo and El Chichon)Pinatubo and El Chichon)

may trigger lasting change when may trigger lasting change when combined with other perturbationscombined with other perturbations


Plate TectonicsPlate Tectonics affect of more land at higher latitudesaffect of more land at higher latitudes alter ocean currents and therefore heat transport alter ocean currents and therefore heat transport alter global atmospheric circulation alter global atmospheric circulation more glaciers over land, higher albedo--cooler temps more glaciers over land, higher albedo--cooler temps plate movement also generates more volcanic activity hence, plate movement also generates more volcanic activity hence,

when the plates are on the move, there is more volcanic when the plates are on the move, there is more volcanic eruptions and more carbon dioxide in the atmosphere eruptions and more carbon dioxide in the atmosphere


An asteroid or comet An asteroid or comet impact could cause impact could cause massive global massive global changes. changes. Such an Such an event could event could depress depress temperatures and temperatures and the amount of the amount of surface sunlight surface sunlight around the globe, around the globe, initiating a chain initiating a chain reaction in the reaction in the biosphere. biosphere.


Incoming solar energy, Incoming solar energy, concentrated around the concentrated around the equator, heats the surface equator, heats the surface and warms overriding air and warms overriding air which rises in the which rises in the atmosphere and the atmosphere and the relatively cooler air (Trade relatively cooler air (Trade Winds) replaces it. The Winds) replaces it. The curve in wind direction is curve in wind direction is caused by the force of caused by the force of Earth’s rotation (Coriolis Earth’s rotation (Coriolis Force).Force).


Image credit: Image credit: www.uwsp.edu/www.uwsp.edu/


Coriolis forceCoriolis forcean apparent force that as an apparent force that as

a result of the earth's a result of the earth's rotation deflects rotation deflects moving objects (as moving objects (as ocean or air currents) ocean or air currents) to the right in the to the right in the northern hemisphere northern hemisphere and to the left in the and to the left in the southern hemisphere. southern hemisphere.


Ocean CurrentsOcean Currents– Climate changes on Climate changes on

the scale of several the scale of several decades to millennia decades to millennia are strongly controlled are strongly controlled by surface and deep by surface and deep ocean currents.ocean currents.

– the path of ocean the path of ocean water circulation is water circulation is influenced by the influenced by the shape of the ocean shape of the ocean basins and adjacent basins and adjacent land massesland masses

.

This conceptual illustration of the ocean conveyor belt circulation illustrates the 1,000-year long cycle.

Image credit: Argonne National Laboratory, USA


Ocean surface currents are driven by the prevailing global winds. The relative Ocean surface currents are driven by the prevailing global winds. The relative temperature of the current is indicated by the color of the arrows.temperature of the current is indicated by the color of the arrows.

Image credit: www.windows.ucar.edu Image credit: www.windows.ucar.edu


This animation illustrates how air temperature changes over the course of This animation illustrates how air temperature changes over the course of a year. In addition to the global ocean temperature pattern, notice the a year. In addition to the global ocean temperature pattern, notice the air temperature over the continents. air temperature over the continents.


The influence of topography and continents:The influence of topography and continents: Coastal areas are cooler and wetter than inland areas. Clouds form when warm air Coastal areas are cooler and wetter than inland areas. Clouds form when warm air

from inland areas meets cooler, moist air from the ocean.from inland areas meets cooler, moist air from the ocean. Inland regions of continents are subject to a large range of temperatures. In the Inland regions of continents are subject to a large range of temperatures. In the

summer, temperatures can be very hot and dry as moisture from the ocean summer, temperatures can be very hot and dry as moisture from the ocean evaporates before it reaches the center of the continent.evaporates before it reaches the center of the continent.

Image: www.geography.hunter.cuny.eduImage: www.geography.hunter.cuny.edu

Image credit: www.lib.utexas.edu/maps/national_atlas_1970/ca000078.jpgImage credit: www.lib.utexas.edu/maps/national_atlas_1970/ca000078.jpg


El Niño episodes reflect El Niño episodes reflect periods of exceptionally periods of exceptionally warm sea surface warm sea surface temperatures across the temperatures across the eastern tropical Pacific. eastern tropical Pacific. La Niña episodes La Niña episodes represent periods of represent periods of below-average sea-below-average sea-surface temperatures surface temperatures across the eastern across the eastern tropical Pacific. Both tropical Pacific. Both events can cause events can cause changes in weather changes in weather including intense including intense rainstorms, drought, rainstorms, drought, and a change in the and a change in the amount of storms.amount of storms.

Image credit: www.cpc.noaa.gov

Human effects on weather, climate, Human effects on weather, climate, and air qualityand air quality

Scientists from around Scientists from around the world with the the world with the Intergovernmental Intergovernmental Panel on Climate Panel on Climate Change (IPCC) tell Change (IPCC) tell us that during the us that during the past 100 years, the past 100 years, the world's surface air world's surface air temperature temperature increased an increased an average of 0.6° average of 0.6° Celsius (1.1°F). Celsius (1.1°F). This may not sound This may not sound like very much like very much change, but even change, but even one degree can one degree can affect the Earth.affect the Earth.


The findings of the IPCC 4th Assessment Report include: Global GHG emissions have grown 70% between 1970 and 2004. Carbon dioxide (CO2) accounted for 77% of total worldwide emissions in 2004.


The net effect of human activities since 1750 has been of global warming.

Most of the observed increase in globally averaged temperature since the mid-20th century is very likely due to increase in anthropogenic GHG concentrations.


All of the U.S. is very likely to warm during this century, and most areas of the U.S. are expected to warm by more than the global average, exceeding 3.6 degrees F by the end of the century.


An increase in the amount of precipitation is very likely in high latitudes, while decreases are likely in most subtropical regions. Increases are not evenly distributed throughout the year; rather, major rain events followed by extended droughts are expected. Regional changes (+/-) of up to 20% in average rainfall and also increases in heavy rainfall (very likely) and increases in drought (likely).


Arctic sea ice is melting. The summer thickness of Arctic sea ice is melting. The summer thickness of sea ice is about half of what it was in 1950. sea ice is about half of what it was in 1950. Melting ice may lead to changes in ocean Melting ice may lead to changes in ocean circulation. Plus melting sea ice is speeding up circulation. Plus melting sea ice is speeding up warming in the Arctic. warming in the Arctic.

Glaciers and permafrost are melting. Over the past Glaciers and permafrost are melting. Over the past 100 years, mountain glaciers in all areas of the 100 years, mountain glaciers in all areas of the world have decreased in size and so has the world have decreased in size and so has the amount of permafrost in the Arctic. Greenland's ice amount of permafrost in the Arctic. Greenland's ice sheet is melting faster too.sheet is melting faster too.


Image credit: UNEP/GRID-ArendalImage credit: UNEP/GRID-Arendal

Virginia’s climate change over timeVirginia’s climate change over time

The Commonwealth is facing a climate change that is “equivalent in magnitude to the end of the last ice age” according to Dr. Shugart (University of Virginia’s Department of Environmental Sciences).

Current predictions of Virginia’s average temperatures rising by 3º C and precipitation is likely to increase between 0% and 10% will impact both agricultural lands and native ecosystems.

Forest plant species are likely to move from current locations to higher altitudes and higher latitudes. As such, Virginians should expect “significant changes to Virginia’s forests and other ecosystems.”

Some ecosystems that already occur at high elevations or which occupy narrow geographic ranges may be extirpated completely. When driven by a continuously warming climate, forests are expected to have “a delayed then abrupt” response where many trees die quickly.

GOVERNOR’S COMMISSION ONCLIMATE CHANGE

Interim ReportSeptember 10, 2008


Doug Inkley, Ph.D. (Senior Scientist with the National Wildlife Federation) reported that

as the climate warms, as many as 78% of wildlife refuges will cease to provide the types and amounts of habitats they were created to provide.

cold water species such as native cold water brook trout are particularly vulnerable.

climate change has reduced the number and variety of waterfowl that spend winters on the Chesapeake Bay.

rising sea levels, will reduce the size and quality of winter habitats currently provided by the Chesapeake Bay.




James E. Bauer, Ph.D. (Professor of Marine Science at the Virginia Institute of Marine Science) reported

Virginia could suffer more impacts of climate change than other states because of its latitude. Virginia currently represents the northern extent for many southern species and the southern extent of many northern species. As the climate changes, Virginia’s coastal ecosystem may be much different than what we see today.

Virginia’s coastal zone, climate change is likely to have significant impacts on people, infrastructure, and ecosystems. These changes include higher sea levels, increased salinities, increased shoreline erosion and inundation (flooding), and increased nutrient inputs from land into the Chesapeake Bay.



Image credit: www.ratemyeverything.net/image/4428/0/Global_Warming_Cartoon.ashx

The relationships between climate, The relationships between climate, weather, and phenologyweather, and phenology

Phenology is the scientific Phenology is the scientific study of periodic study of periodic biological phenomena, biological phenomena, such as flowering, such as flowering, breeding, and migration, breeding, and migration, in relation to climatic in relation to climatic conditions. conditions.

Thus, timings of Thus, timings of phenological events are phenological events are ideal indicators of global ideal indicators of global change impacts.change impacts.

Lake Lanier 10.11.08

The relationships between climate, The relationships between climate, weather, and phenologyweather, and phenology

Some signs of phenology and climate changeSome signs of phenology and climate change Pollen-releasing grasses, shrubs and trees have started to appear Pollen-releasing grasses, shrubs and trees have started to appear

earlier, expanding the hay fever season.earlier, expanding the hay fever season. Drought, forest fires and invasive alien species have caused serious Drought, forest fires and invasive alien species have caused serious

damage to some of the world's most vulnerable ecosystems.damage to some of the world's most vulnerable ecosystems.

A recent study of more A recent study of more than 542 plant and 19 than 542 plant and 19 animal species in 21 animal species in 21 European countries European countries confirmed: the leafing, confirmed: the leafing, flowering and fruiting of flowering and fruiting of more than 75% of all more than 75% of all plant species had plant species had advanced as a result of advanced as a result of rising temperatures.rising temperatures.

The relationships The relationships between climate, between climate,

weather, and weather, and phenologyphenology

Main processes driving weatherMain processes driving weather

Weather variability Weather variability occurs at a scale of occurs at a scale of minutes, hours, and minutes, hours, and days, with the Earth's days, with the Earth's rotation on it's axis rotation on it's axis being a primary force being a primary force for change. for change.


Air masses Air masses originating over originating over sea or land sea or land have have characteristic characteristic temperature temperature and humidity and humidity and can greatly and can greatly influence our influence our weather. When weather. When air masses air masses meet, stormy meet, stormy weather often weather often results. results.


Cold front is the boundary along the leading edge when a Cold front is the boundary along the leading edge when a relatively cold air mass displaces a warmer air mass.relatively cold air mass displaces a warmer air mass.

Image credit: physicalgeography.net/


Warm front is the boundary along the leading edge when a Warm front is the boundary along the leading edge when a relatively warm air mass displaces a colder air mass.relatively warm air mass displaces a colder air mass.

Image credit: physicalgeography.net/


An occluded front occur when a faster moving cold front An occluded front occur when a faster moving cold front overtakes a warm front; a stationary front occurs when a overtakes a warm front; a stationary front occurs when a front’s movement stalls.front’s movement stalls.

Image credit: physicalgeography.net


Cyclones (low Cyclones (low pressure center) pressure center) form from warm, form from warm, rising air. Weather rising air. Weather conditions are conditions are typically overcast typically overcast with precipitation. with precipitation. Winds rotate Winds rotate around the center around the center in a clockwise in a clockwise direction.direction. Image credit: www.stacey.peak-media.co.uk/Image credit: www.stacey.peak-media.co.uk/


Anticyclones (high Anticyclones (high pressure center) pressure center) form from cool, form from cool, sinking air. sinking air. Weather Weather conditions are conditions are typically dry and typically dry and skies tend to be skies tend to be clear. Winds rotate clear. Winds rotate around the center around the center in a clockwise in a clockwise direction.direction.

Image credit: www.hpc.ncep.noaa.gov/


Wind is produced when Wind is produced when air moves from an area air moves from an area of high pressure to an of high pressure to an area of low pressure—area of low pressure—the greater the the greater the pressure difference, pressure difference, the greater the wind the greater the wind speed.speed.

Image credit: www.mrsciguy.com/weather.html


An area of strong winds that are An area of strong winds that are concentrated in a relatively concentrated in a relatively narrow band in the narrow band in the atmosphere of the middle atmosphere of the middle latitudes and subtropical latitudes and subtropical regions of the Northern and regions of the Northern and Southern Hemispheres. Southern Hemispheres. Flowing in a semi-continuous Flowing in a semi-continuous band around the globe from band around the globe from west to east, it is caused by west to east, it is caused by the changes in air the changes in air temperature where the cold temperature where the cold polar air moving towards the polar air moving towards the equator meets the warmer equator meets the warmer equatorial air moving equatorial air moving polarward. It is marked by a polarward. It is marked by a concentration of isotherms concentration of isotherms and strong vertical shear.and strong vertical shear.

Image credit: www.fas.org

Hurricanes of the North Atlantic 2005Hurricanes of the North Atlantic 2005

Weather forecastingWeather forecasting

Methods of forecasting:Methods of forecasting: weather observations such weather observations such

as barometric pressure, as barometric pressure, cloud type, and wind cloud type, and wind directiondirection

weather mapsweather maps weather radarweather radar computer modelingcomputer modeling despite all the technological despite all the technological

advances in meteorological advances in meteorological tools, weather prediction tools, weather prediction becomes increasingly becomes increasingly unreliable beyond a few unreliable beyond a few days days

Weather measurementsWeather measurements

temperature, humidity, temperature, humidity, barometric pressure, barometric pressure, wind speed and wind speed and direction, cloud direction, cloud formationsformations


weather instrument weather instrument sheltershelter


temperature: a measure temperature: a measure of the average kinetic of the average kinetic energy of the energy of the molecules in an object molecules in an object or system and can be or system and can be measured with a measured with a thermometer or a thermometer or a calorimeter.calorimeter.


temperature: temperature: thermometerthermometer

alcoholalcohol mercurymercury digitaldigital

GLOBE protocol requires GLOBE protocol requires accuracy ofaccuracy of ± 0.5º Celsius


temperature: temperature: maximum/minimum maximum/minimum thermometerthermometer


humidity: a humidity: a measure measure of the of the amount of amount of water water vapor in a vapor in a body of body of airair

Image credit: www.nasa.gov


relative humidity: a relative humidity: a comparative comparative measure of the measure of the amount of water amount of water vapor in a body of vapor in a body of air compared to air compared to the amount it the amount it couldcould hold at any hold at any given given temperature.temperature.

Image credit: geography.cst.cmich.eduImage credit: geography.cst.cmich.edu


This is This is VMNH VMNH WeatherBug WeatherBug graph graph showing showing relative relative humidity and humidity and temperature temperature over several over several days.days.


When a body of air is When a body of air is saturated with water saturated with water vapor relative humidity vapor relative humidity reaches 100%; dew reaches 100%; dew point is the point is the temperature at which temperature at which water vapor begins to water vapor begins to condense; if the dew condense; if the dew point is below freezing, point is below freezing, frost forms.frost forms.

Image credit: Image credit: upload.wikimedia.org and upload.wikimedia.org and www.its.caltech.eduwww.its.caltech.edu

http://upload.wikimedia.org/wikipedia/commons/2/24/Dew.arp.750pix.jpg


relative relative humidity: humidity: typically typically determined determined with a sling with a sling psychrometer psychrometer consisting of consisting of wet bulb and wet bulb and dry bulb dry bulb thermometers thermometers

http://upload.wikimedia.org/wikipedia/commons/0/09/Sling_psychrometer.JPG

Relative weather indicesRelative weather indices

Heat index: Heat index: apparent apparent temperaturetemperature—how hot it —how hot it feelsfeels; is ; is affected by affected by temperature temperature and relative and relative humidity.humidity.

Image credit: www.crh.noaa.govImage credit: www.crh.noaa.gov

Relative weather indicesRelative weather indices

Wind chill: Wind chill: apparent apparent temperaturetemperature—how cold it —how cold it feels; is feels; is affected by affected by temperature temperature and wind and wind velocityvelocity


Wind speed is measured Wind speed is measured with an anemometer with an anemometer and direction is and direction is determined by a wind determined by a wind vane and is reported in vane and is reported in knots or miles per hour knots or miles per hour the direction the wind the direction the wind is is coming fromcoming from..


Barometric pressure: Barometric pressure: caused by the caused by the weight of the weight of the column of air above column of air above it; at sea level, it; at sea level, atmospheric atmospheric pressure has an pressure has an average value of average value of one atmosphere one atmosphere and gradually and gradually decreases as decreases as altitude increases.altitude increases.


Barometric pressure is Barometric pressure is measured using a measured using a barometer with an barometer with an accuracy of 3.5 millibars over its entire range.


Cloud formation: clouds form when water vapor condenses on Cloud formation: clouds form when water vapor condenses on condensation nuclei (tiny particles) suspended in the atmosphere; condensation nuclei (tiny particles) suspended in the atmosphere; generally occurs when relatively warm air rises and coolsgenerally occurs when relatively warm air rises and cools


Image credit: www.eas.slu.eduImage credit: www.eas.slu.edu


Cloud basic categoriesCloud basic categories

Cirro-form: high-level Cirro-form: high-level clouds which form above clouds which form above 20,000 feet (6,000 meters); 20,000 feet (6,000 meters); usually composed of ice usually composed of ice crystals; typically thin and crystals; typically thin and white in appearance, but white in appearance, but can create an array of can create an array of colors when the sun is low colors when the sun is low on the horizon; generally on the horizon; generally occur in fair weather and occur in fair weather and point in the direction of air point in the direction of air movement at their movement at their elevation.elevation.



Cumulo-form: look like white fluffy cotton balls or heaps; show the vertical motion or thermal uplift of air taking place in the atmosphere; the level at which condensation and cloud formation begins is indicated by a flat cloud base; its height will depend upon the humidity of the rising air--the more humid the air, the lower the cloud base. The tops of these clouds can reach over 60,000 feet (18,000 meters).



Strato-form: Strato-form: "Stratus" is "Stratus" is Latin for layer or blanket; Latin for layer or blanket; consist of a feature-less low consist of a feature-less low layer that can cover the entire layer that can cover the entire sky like a blanket, bringing sky like a blanket, bringing generally gray and dull generally gray and dull weather; the cloud bases are weather; the cloud bases are usually only a few hundred feet usually only a few hundred feet above the ground; over hills above the ground; over hills and mountains they can reach and mountains they can reach ground level when they may be ground level when they may be called fog--as fog "lifts" off the called fog--as fog "lifts" off the ground due to daytime heating, ground due to daytime heating, the fog forms a layer of low the fog forms a layer of low stratus clouds.stratus clouds.


Cloud Cloud formation formation along cold along cold (blue) and (blue) and warm (red) warm (red) frontal frontal boundariesboundaries

Image credit: www.capitalsailing.comImage credit: www.capitalsailing.com


Estimating percent cloud cover involves estimating how much of the entire Estimating percent cloud cover involves estimating how much of the entire sky is covered in clouds.sky is covered in clouds.

Image credit: www.globe.govImage credit: www.globe.gov

A typical year of weather in VirginiaA typical year of weather in Virginia



Image credit: www.erh.noaa.gov/lwx/lightning/va-lightning.htm

Online ResourcesOnline Resources

EarthBrowser EarthBrowser www.earthbrowser.comwww.earthbrowser.com

GLOBE GLOBE www.globe.govwww.globe.gov Governor’s Commission On Governor’s Commission On

Climate Change Climate Change www.deq.virginia.gov/info/climatechange.htmlwww.deq.virginia.gov/info/climatechange.html

NASA World Wind NASA World Wind worldwind.arc.nasa.govworldwind.arc.nasa.gov//

National Phenology Network National Phenology Network www.usanpn.org/www.usanpn.org/

Southeast Regional Climate Southeast Regional Climate Center Center www.sercc.com/www.sercc.com/

University of Virginia University of Virginia Climatology Office Climatology Office climate.virginia.educlimate.virginia.edu//

VMNH Weatherbug VMNH Weatherbug weathercenter.weathernet.com/default.asp?btnweathercenter.weathernet.com/default.asp?btn=BTN_0DA=BTN_0DA

http://www.earthbrowser.com/

http://www.globe.gov/

http://www.deq.virginia.gov/info/climatechange.html

http://worldwind.arc.nasa.gov/

http://worldwind.arc.nasa.gov/

http://www.usanpn.org/

http://www.sercc.com/

http://climate.virginia.edu/

http://climate.virginia.edu/

http://weathercenter.weathernet.com/default.asp?btn=BTN_0DA

http://weathercenter.weathernet.com/default.asp?btn=BTN_0DA

Technology

Master Naturalist Presentation: Weather and Climate