Master Naturalist Presentation: Weather and Climate


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Master Naturalist Presentation: Weather and Climate

  1. 1. Weather and Climate Southwestern Piedmont Master Naturalists November 6, 2008 Denny Casey, Ph.D. Director of Education and Public Programs Virginia Museum of Natural History Image credit:
  2. 2. Overview <ul><li>Main factors affecting climate </li></ul><ul><li>Human effects on weather, climate, and air quality </li></ul><ul><li>Virginia’s climate change over time </li></ul><ul><li>The relationships between climate, weather, and phenology </li></ul><ul><li>Main processes driving weather </li></ul><ul><li>Weather forecasting and the basic weather measurements (temperature, humidity, barometric pressure, wind speed and direction, cloud formations) </li></ul><ul><li>A typical year of weather in Virginia </li></ul><ul><li>Resources </li></ul>
  3. 3. Main factors affecting climate <ul><li>Some factors impact climate over a short period of time, while others occur over very large amounts of time. </li></ul><ul><li>Image credit: </li></ul>
  4. 4. Main factors affecting climate <ul><li>While some are extraterrestrial in origin… </li></ul><ul><li>Image credit: </li></ul>
  5. 5. Main factors affecting climate <ul><li>others occur right here on Earth. </li></ul>
  6. 6. Main factors affecting climate <ul><li>One orbit around the sun serves as a fundamental force of climate variability. The essential cause of seasonal climate change is the tilt of Earth's axis, currently 23.5 degree tilt off axis to the orbital plane of revolution. </li></ul>
  7. 7. Main factors affecting climate <ul><li>Because of the Earth’s tilt, the angle of solar radiation and thus intensity over the course of the year varies. The polar surfaces receive about half the amount of solar radiation per unit area as the equatorial surface. </li></ul>
  8. 8. Main factors affecting climate <ul><li>Energy received from the Sun drives weather and climate. The regular changes of the Earth’s orbit around the Sun, and changes in the Earth’s rotation about its tilted axis, control the daily and seasonal cycle and dominate the climatology of the Earth. </li></ul><ul><li>T he amount of energy received by the Earth at the top of the atmosphere, before it is absorbed and scattered by molecules and aerosols (solid or liquid particles) in the atmosphere. </li></ul><ul><ul><ul><ul><ul><li>Image credit: </li></ul></ul></ul></ul></ul>
  9. 9. <ul><li>Image credit: NASA's Earth Radiation Budget Experiment program. </li></ul>
  10. 10. Main factors affecting climate
  11. 11. Main factors affecting climate 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
  12. 12. Main factors affecting climate <ul><li>In 1920, Milutin Milankovitch showed that regular variations in the shape of Earth's orbit and the orientation of its axis create variations of solar intensity at high latitudes: warm summers in which glaciers retreat, and cool summers when they advance. These climate cycles, called Milankovitch Cycles, are determined by three factors… </li></ul>Animation credit:
  13. 13. Main factors affecting climate <ul><li>Obliquity </li></ul><ul><li>The change of the tilt of the Earth's axis away from the orbital plane.  The tilt varies between 22.1 and 24.5 degrees and the average is 23.5. Presently, the Earth’s axis is tilted 23.4 degrees and is decreasing. </li></ul><ul><li>Image credit: </li></ul>
  14. 14. Main factors affecting climate <ul><li>The obliquity changes on a cycle of approximately 41,000 years. </li></ul>Image credit:
  15. 15. Main factors affecting climate <ul><li>Eccentricity </li></ul><ul><li>A measure of how circular or elliptical our orbit is around the Sun. Over time, the Earth’s orbit varies from less than 1% to almost 6% and is currently about 1.7 % and decreasing. </li></ul>
  16. 16. Main factors affecting climate <ul><li>As a result of gravitational forces of the planets, Earth’s orbit is not circular, the distance to the Sun changes during the course of the year. </li></ul><ul><li>Image credit: </li></ul>
  17. 18. Main factors affecting climate <ul><li>Eccentricity changes in 100,000 year cycles. Low values of eccentricity correlate to low change in incoming solar radiation during the year. Although the amount of change in radiation is very small (less than 0.2%), it is apparently extremely important in the expansion and melting of ice sheets. </li></ul>Image credit:
  18. 19. Main factors affecting climate <ul><li>Precession </li></ul><ul><li>A wobbling in the orientation of Earth's axis is caused by the gravity of the Sun and the Moon acting on Earth's equatorial bulge. </li></ul>
  19. 20. Main factors affecting climate <ul><li>As a result of the wobble, aphelion and perihelion change position on the orbit through a cycle of 360 degrees. The cycle has a period of approximately 22,000 years. In 12,000 years, we will experience summer in December and winter in June. </li></ul><ul><li>Image credit: </li></ul>
  20. 21. Main factors affecting climate <ul><li>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 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. </li></ul><ul><li>Image credit: </li></ul>
  21. 22. Main factors affecting climate <ul><li>Cyclic and punctuated fluctuations in solar activity results in small changes in the nature and amount of solar radiation that reaches the earth. </li></ul>Animation: University of Oregon
  22. 23. Main factors affecting climate <ul><li>Sunspot cycle </li></ul><ul><li>The number of sunspots varies in an 11-year cycle. When the number of sunspots is large, solar output is slightly higher (0.1%) Surrounding sunspots are bright areas on the sun called faculae which are responsible for an increase in radiation. </li></ul><ul><li>Enhanced color image the appearance of the faculae (white regions) which are hotter than sunspots (red-black regions) and whose greater total area contribute to increasing the solar flux reaching the Earth. April 27, 2002. </li></ul>
  23. 24. Main factors affecting climate <ul><li>Sunspot cycle graph with data from 1750 to 2005. The number of sunspots per year varies with an 11 year cycle and the peaks are associated with times of high solar activity (many flares and solar storms). </li></ul>
  24. 25. Main factors affecting climate <ul><li>Daily Sun: 26 Oct 08 The Sun’s surface currently has no sunspots. </li></ul><ul><li>Image credit: SOHO/MDI </li></ul>Sunspot activity is at a minimum now but will be increasing over the next 5 or 6 years. Image credit:
  25. 26. Main factors affecting climate <ul><li>Sunspots also have a 22-year magnetic field cycle (magnetic field of sunspots reverse after each 11-year max/min cycle). Changes could result in changes in the interaction of the solar wind with the Earth’s magnetosphere. There could also be a linkage between a change in gamma rays emitted by the sun and the electrical field of the Earth, which in turn could cause changes in thunderstorm activity. </li></ul><ul><li>Image credit: </li></ul>
  26. 27. The Earth’s Biosphere This 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
  27. 28. Main factors affecting climate <ul><li>The biosphere can impact climate… </li></ul><ul><li>acting as a temporary source or sink of greenhouse gases </li></ul><ul><ul><li>photosynthesis removes carbon dioxide </li></ul></ul><ul><ul><li>produces methane (greenhouse gas) from decay </li></ul></ul><ul><li>productivity of biosphere increases with increasing carbon dioxide </li></ul><ul><li>producing particulates which increases cloud cover </li></ul><ul><li>changing albedo of the surface </li></ul><ul><ul><li>desertification – deserts have high albedo </li></ul></ul><ul><ul><li>deforestation – forest and snow has a lower albedo than just snow </li></ul></ul>
  28. 29. Main factors affecting climate <ul><li>Volcanoes </li></ul><ul><li>vast amounts of dust thrown into the stratosphere, as well as vast amounts of sulphur dioxide, result in more sunlight scattered </li></ul><ul><li>little vertical motion in the stratosphere means minute particles can remain suspended for several years and be spread globally </li></ul><ul><li>short-lived change – effects last for 2-3 years </li></ul><ul><li>substantial summer cooling, some winter warming (greater circulation has been observed with eruptions of Pinatubo and El Chichon) </li></ul><ul><li>may trigger lasting change when combined with other perturbations </li></ul>
  29. 30. Main factors affecting climate <ul><li>Plate Tectonics </li></ul><ul><li>affect of more land at higher latitudes </li></ul><ul><li>alter ocean currents and therefore heat transport </li></ul><ul><li>alter global atmospheric circulation </li></ul><ul><li>more glaciers over land, higher albedo--cooler temps </li></ul><ul><li>plate movement also generates more volcanic activity hence, when the plates are on the move, there is more volcanic eruptions and more carbon dioxide in the atmosphere </li></ul>
  30. 31. Main factors affecting climate <ul><li>An asteroid or comet impact could cause massive global changes. Such an event could depress temperatures and the amount of surface sunlight around the globe, initiating a chain reaction in the biosphere. </li></ul>
  31. 32. Main factors affecting climate <ul><li>Incoming solar energy, concentrated around the equator, heats the surface and warms overriding air which rises in the atmosphere and the relatively cooler air (Trade Winds) replaces it. The curve in wind direction is caused by the force of Earth’s rotation (Coriolis Force). </li></ul>
  32. 33. Main factors affecting climate <ul><li>Image credit: </li></ul>
  33. 34. Main factors affecting climate <ul><li>Coriolis force </li></ul><ul><li>an apparent force that as a result of the earth's rotation deflects moving objects (as ocean or air currents) to the right in the northern hemisphere and to the left in the southern hemisphere. </li></ul>
  34. 35. Main factors affecting climate <ul><li>Ocean Currents </li></ul><ul><ul><li>Climate changes on the scale of several decades to millennia are strongly controlled by surface and deep ocean currents. </li></ul></ul><ul><ul><li>the path of ocean water circulation is influenced by the shape of the ocean basins and adjacent land masses </li></ul></ul>. This conceptual illustration of the ocean conveyor belt circulation illustrates the 1,000-year long cycle. Image credit: Argonne National Laboratory, USA
  35. 36. Main factors affecting climate <ul><li>Ocean surface currents are driven by the prevailing global winds. The relative temperature of the current is indicated by the color of the arrows. </li></ul><ul><li>Image credit: </li></ul>
  36. 37. Main factors affecting climate <ul><li>This animation illustrates how air temperature changes over the course of a year. In addition to the global ocean temperature pattern, notice the air temperature over the continents. </li></ul>
  37. 38. Main factors affecting climate <ul><li>The influence of topography and continents: </li></ul><ul><li>Coastal areas are cooler and wetter than inland areas. Clouds form when warm air from inland areas meets cooler, moist air from the ocean. </li></ul><ul><li>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 evaporates before it reaches the center of the continent. </li></ul><ul><ul><li>Image: </li></ul></ul>
  38. 39. <ul><ul><li>Image credit: </li></ul></ul>
  39. 40. Main factors affecting climate <ul><li>El Niño episodes reflect periods of exceptionally warm sea surface temperatures across the eastern tropical Pacific. La Niña episodes represent periods of below-average sea-surface temperatures across the eastern tropical Pacific. Both events can cause changes in weather including intense rainstorms, drought, and a change in the amount of storms. </li></ul>Image credit:
  40. 41. Human effects on weather, climate, and air quality <ul><li>Scientists from around the world with the Intergovernmental Panel on Climate Change (IPCC) tell us that during the past 100 years, the world's surface air temperature increased an average of 0.6° Celsius (1.1°F). This may not sound like very much change, but even one degree can affect the Earth. </li></ul>
  41. 42. Human effects on weather, climate, and air quality <ul><li>The findings of the IPCC 4th Assessment Report include: </li></ul><ul><li>Global GHG emissions have grown 70% between 1970 and 2004. </li></ul><ul><li>Carbon dioxide (CO2) accounted for 77% of total worldwide emissions in 2004. </li></ul>
  42. 43. Human effects on weather, climate, and air quality <ul><li>The net effect of human activities since 1750 has been of global warming. </li></ul><ul><li>Most of the observed increase in globally averaged temperature since the mid-20 th century is very likely due to increase in anthropogenic GHG concentrations. </li></ul>
  43. 44. Human effects on weather, climate, and air quality <ul><li>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. </li></ul>
  44. 45. Human effects on weather, climate, and air quality <ul><li>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). </li></ul>
  45. 46. Human effects on weather, climate, and air quality <ul><li>Arctic sea ice is melting. The summer thickness of sea ice is about half of what it was in 1950. Melting ice may lead to changes in ocean circulation. Plus melting sea ice is speeding up warming in the Arctic. </li></ul><ul><li>Glaciers and permafrost are melting. Over the past 100 years, mountain glaciers in all areas of the world have decreased in size and so has the amount of permafrost in the Arctic. Greenland's ice sheet is melting faster too. </li></ul>
  46. 47. Human effects on weather, climate, and air quality <ul><li>Image credit: UNEP/GRID-Arendal </li></ul>
  47. 49. Virginia’s climate change over time <ul><li>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). </li></ul><ul><li>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. </li></ul><ul><li>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.” </li></ul><ul><li>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. </li></ul><ul><li>GOVERNOR’S COMMISSION ON </li></ul><ul><li>CLIMATE CHANGE </li></ul><ul><li>Interim Report </li></ul><ul><li>September 10, 2008 </li></ul>
  48. 50. Virginia’s climate change over time <ul><li>Doug Inkley, Ph.D. (Senior Scientist with the National Wildlife Federation) reported that </li></ul><ul><li>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. </li></ul><ul><li>cold water species such as native cold water brook trout are particularly vulnerable. </li></ul><ul><li>climate change has reduced the number and variety of waterfowl that spend winters on the Chesapeake Bay. </li></ul><ul><li>rising sea levels, will reduce the size and quality of winter habitats currently provided by the Chesapeake Bay. </li></ul><ul><li>GOVERNOR’S COMMISSION ON </li></ul><ul><li>CLIMATE CHANGE </li></ul><ul><li>Interim Report </li></ul><ul><li>September 10, 2008 </li></ul>
  49. 51. Virginia’s climate change over time <ul><li>James E. Bauer, Ph.D. (Professor of Marine Science at the Virginia Institute of Marine Science) reported </li></ul><ul><li>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. </li></ul><ul><li>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. </li></ul><ul><li>GOVERNOR’S COMMISSION ON </li></ul><ul><li>CLIMATE CHANGE </li></ul><ul><li>Interim Report </li></ul><ul><li>September 10, 2008 </li></ul>
  50. 52. Image credit:
  51. 53. The relationships between climate, weather, and phenology <ul><li>Phenology is the scientific study of periodic biological phenomena, such as flowering, breeding, and migration, in relation to climatic conditions. </li></ul><ul><li>Thus, timings of phenological events are ideal indicators of global change impacts. </li></ul>Lake Lanier 10.11.08
  52. 54. The relationships between climate, weather, and phenology <ul><li>Some signs of phenology and climate change </li></ul><ul><li>Pollen-releasing grasses, shrubs and trees have started to appear earlier, expanding the hay fever season. </li></ul><ul><li>Drought, forest fires and invasive alien species have caused serious damage to some of the world's most vulnerable ecosystems. </li></ul>
  53. 55. <ul><li>A recent study of more than 542 plant and 19 animal species in 21 European countries confirmed: the leafing, flowering and fruiting of more than 75% of all plant species had advanced as a result of rising temperatures. </li></ul>The relationships between climate, weather, and phenology
  54. 56. Main processes driving weather <ul><li>Weather variability occurs at a scale of minutes, hours, and days, with the Earth's rotation on it's axis being a primary force for change. </li></ul>
  55. 57. Main processes driving weather <ul><li>Air masses originating over sea or land have characteristic temperature and humidity and can greatly influence our weather. When air masses meet, stormy weather often results. </li></ul>
  56. 58. Main processes driving weather <ul><li>Cold front is the boundary along the leading edge when a relatively cold air mass displaces a warmer air mass. </li></ul>Image credit:
  57. 59. Main processes driving weather <ul><li>Warm front is the boundary along the leading edge when a relatively warm air mass displaces a colder air mass. </li></ul>Image credit:
  58. 60. Main processes driving weather <ul><li>An occluded front occur when a faster moving cold front overtakes a warm front; a stationary front occurs when a front’s movement stalls. </li></ul>Image credit:
  59. 61. Main processes driving weather <ul><li>Cyclones (low pressure center) form from warm, rising air. Weather conditions are typically overcast with precipitation. Winds rotate around the center in a clockwise direction. </li></ul><ul><li>Image credit: </li></ul>
  60. 62. Main processes driving weather <ul><li>Anticyclones (high pressure center) form from cool, sinking air. Weather conditions are typically dry and skies tend to be clear. Winds rotate around the center in a clockwise direction. </li></ul>Image credit:
  61. 63. Main processes driving weather <ul><li>Wind is produced when air moves from an area of high pressure to an area of low pressure—the greater the pressure difference, the greater the wind speed. </li></ul>Image credit:
  62. 65. Main processes driving weather <ul><li>An area of strong winds that are concentrated in a relatively narrow band in the atmosphere of the middle latitudes and subtropical regions of the Northern and Southern Hemispheres. Flowing in a semi-continuous band around the globe from west to east, it is caused by the changes in air temperature where the cold polar air moving towards the equator meets the warmer equatorial air moving polarward. It is marked by a concentration of isotherms and strong vertical shear. </li></ul>Image credit:
  63. 66. Hurricanes of the North Atlantic 2005
  64. 68. Weather forecasting <ul><li>Methods of forecasting: </li></ul><ul><li>weather observations such as barometric pressure, cloud type, and wind direction </li></ul><ul><li>weather maps </li></ul><ul><li>weather radar </li></ul><ul><li>computer modeling </li></ul><ul><li>despite all the technological advances in meteorological tools, weather prediction becomes increasingly unreliable beyond a few days </li></ul>
  65. 69. Weather measurements <ul><li>temperature, humidity, barometric pressure, wind speed and direction, cloud formations </li></ul>
  66. 70. Weather measurements <ul><li>weather instrument shelter </li></ul>
  67. 71. Weather measurements <ul><li>temperature: a measure of the average kinetic energy of the molecules in an object or system and can be measured with a thermometer or a calorimeter. </li></ul>
  68. 72. Weather measurements <ul><li>temperature: thermometer </li></ul><ul><li>alcohol </li></ul><ul><li>mercury </li></ul><ul><li>digital </li></ul><ul><li>GLOBE protocol requires accuracy of ± 0.5º Celsius </li></ul>
  69. 73. Weather measurements <ul><li>temperature: maximum/minimum thermometer </li></ul>
  70. 74. Weather measurements <ul><li>humidity: a measure of the amount of water vapor in a body of air </li></ul>Image credit:
  71. 75. Weather measurements <ul><li>relative humidity: a comparative measure of the amount of water vapor in a body of air compared to the amount it could hold at any given temperature. </li></ul><ul><li>Image credit: </li></ul>
  72. 76. Weather measurements This is VMNH WeatherBug graph showing relative humidity and temperature over several days.
  73. 77. Weather measurements <ul><li>When a body of air is saturated with water vapor relative humidity reaches 100%; dew point is the temperature at which water vapor begins to condense; if the dew point is below freezing, frost forms. </li></ul><ul><li>Image credit: and </li></ul>
  74. 78. Weather measurements <ul><li>relative humidity: typically determined with a sling psychrometer consisting of wet bulb and dry bulb thermometers </li></ul>
  75. 79. Relative weather indices <ul><li>Heat index: apparent temperature—how hot it feels ; is affected by temperature and relative humidity. </li></ul><ul><li>Image credit: </li></ul>
  76. 80. Relative weather indices <ul><li>Wind chill: apparent temperature—how cold it feels; is affected by temperature and wind velocity </li></ul>
  77. 81. Weather measurements <ul><li>Wind speed is measured with an anemometer and direction is determined by a wind vane and is reported in knots or miles per hour the direction the wind is coming from . </li></ul>
  78. 82. Weather measurements <ul><li>Barometric pressure: caused by the weight of the column of air above it; at sea level, atmospheric pressure has an average value of one atmosphere and gradually decreases as altitude increases. </li></ul>
  79. 83. Weather measurements <ul><li>Barometric pressure is measured using a barometer with an accuracy of 3.5 millibars over its entire range. </li></ul>
  80. 84. Weather measurements <ul><li>Cloud formation: clouds form when water vapor condenses on condensation nuclei (tiny particles) suspended in the atmosphere; generally occurs when relatively warm air rises and cools </li></ul>
  81. 85. Weather measurements <ul><li>Image credit: </li></ul>
  82. 86. Weather measurements <ul><li>Cloud basic categories </li></ul><ul><li>Cirro-form: high-level clouds which form above 20,000 feet (6,000 meters); usually composed of ice crystals; typically thin and white in appearance, but can create an array of colors when the sun is low on the horizon; generally occur in fair weather and point in the direction of air movement at their elevation. </li></ul>
  83. 87. Weather measurements <ul><li>Cloud basic categories </li></ul><ul><li>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). </li></ul>
  84. 88. Weather measurements <ul><li>Cloud basic categories </li></ul><ul><li>Strato-form: &quot;Stratus&quot; is Latin for layer or blanket; consist of a feature-less low layer that can cover the entire sky like a blanket, bringing generally gray and dull weather; the cloud bases are usually only a few hundred feet above the ground; over hills and mountains they can reach ground level when they may be called fog--as fog &quot;lifts&quot; off the ground due to daytime heating, the fog forms a layer of low stratus clouds. </li></ul>
  85. 89. Weather measurements <ul><li>Cloud formation along cold (blue) and warm (red) frontal boundaries </li></ul><ul><li>Image credit: </li></ul>
  86. 90. Weather measurements <ul><li>Estimating percent cloud cover involves estimating how much of the entire sky is covered in clouds. </li></ul><ul><li>Image credit: </li></ul>
  87. 91. A typical year of weather in Virginia
  88. 92. A typical year of weather in Virginia
  89. 93. A typical year of weather in Virginia Image credit:
  90. 95. Online Resources <ul><li>EarthBrowser </li></ul><ul><li>GLOBE </li></ul><ul><li>Governor’s Commission On Climate Change </li></ul><ul><li>NASA World Wind / </li></ul><ul><li>National Phenology Network </li></ul><ul><li>Southeast Regional Climate Center </li></ul><ul><li>University of Virginia Climatology Office / </li></ul><ul><li>VMNH Weatherbug =BTN_0DA </li></ul>