Atm Ocn 100 Edition 1nd Lecture 7 Outline of Last Lecture I Guest Lecture Notes II Information for Balloon Launching III Weather for Friday notes Outline of Current Lecture IV Weather of the Day notes V Weather Models VI Basic Types of Models VII Finite Difference Model VIII Vertical Grid IX Spherical Projection X Topography Representation XI Key Prediction models for this class Current Lecture Announcements Chapter 5 and 6 from our textbook we are not going to go over much in class Professor will rely on us reading those chapters and asking questions Those chapters are about weather models and weather maps We will learn about these looking at current weather maps Chapter 5 and 6 covered throughout the class Still have to read them and do homework regarding them Starting force next week 2 major forces in the atmosphere what are they One major force is that accelerates the wind what force is whistling Pressure gradient force Different in pressure from one place to another creates a force that accelerates wind The other force is Gravity this is the 2nd force These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Weather of the day A program called Vis5D 3 D Looking at a map of the world This is a base map of a GFS model run in Washington Can look at it like a sphere if we wanted but this way you can see everything at once This projection is not perfect but it allows you to look at whole earth at once Model divides earth into grid points If we have observations or release balloons we can find pressure temperature so on from every grid point Can also take topography into account Model is 3D You can move the whole model You can put a probe where a specific height is Balloon we released the other day got up to about 20 km or 60 000 feet At the pressure of this height at 20 km is 50 mb This is low pressure What we are seeing is topography if we look at it from the side there is two dominating topographic features One is Antarctica which is very tall The average height is about 10 15 000 ft Just north of the equator are the Himalayas and the Tibetan plateau This features dominant the weather of the world We can look at pressure and draw a pressure line We can draw a 500 mb surface of pressure And it will show us what the surface will look like It doesn t look like anything But if we lift it up and look at it from another direction it is higher than any mountains As far as mass goes what percentage of the mass of the atmosphere is above 50 50 500 mb represents the mid point of the atmosphere mass wise Height wise it is certainly not 50 Top of atmosphere goes up even off page gets thinner But mass half of the mass of the atmosphere is below 500 mb Tropics 500 mb surface is higher than in the Himalayas It rises up to the tropics Tropics warmer air puffed up which pushes more up higher We can do maps in different styles Can do a map of constant height Surface of 5 km at constant height Constant height of 5 km can then turn on constant pressure at 500 mb they intersect 500 mb a little higher than 5 4 km and then a little lower over Antarctica and all that If we look at this picture from the top map but on higher we can turn off the pressure Can contour pressure Have to find a nice interval one is 4 Isobars constant pressure Lines of constant pressure Not many isobars in tropics a lot other places If we animate it we see many waves In the animation there are waves going from west to east In the tropics you don t see many waves Waves are characteristics of the middle latitudes in tropics Associated with variability in the jet streams Associated with surface cyclones related to surface weather patterns Lines of constant height at 500 mb Can shade the height at constant pressure We see low heights in the middle latitudes Relatively higher heights in the tropics Same as isobar maps at a constant height We are looking at contours of height on a pressure map Before contours or lines of constant pressure isobars on a height map Both show same information But convention in meterology is to draw a map of constant pressure and show height lines which show the same thing as isobars on a constant height map This is what we see This is an 8 day forecast starting from midnight last night Weather patterns we see moving through here are the future starting from last night We can also look at jet streams on here Speed is about 42 meter per second In knots 42 X 2 82 And then you can multiply by 1 15 to get miles per hour 84 knots is about 100 miles per hour Jet streams concentrated in winter hemisphere What causes jet stream Caused by temperature contrast horizontal contrast from one place to another in lower troposphere This adds up to be stronger and stronger wind Wind represents the integrated effect of the thermo contrast between the polar area and the middle latitude area There are two different types of jet streams lower is because of thermo contrast The other one is subtropical jet stream tropical air mass from polar air mass Tropical air mass is in between bounded by subtropical jets We can see where tropics are by putting value on there This shows where the tropics are The tropics are different from middle latitudes because tropopause is elevated which we can see as a bubble The bubble exists in the tropics and only the tropics Subtropical jets border this bubble The subtropical jets mark boundary between tropical air mass and polar air mass And ride along this boundary They are subtropical jets Drive energy not from thermo contrast But from bubble Bridges between two jets subtropical jet exchanges energy from bubble to polar jet When we get winter storms the winter storms in many cases seem to derive from the warm waters of the tropical oceans The energy is put into polar jet which then makes strong winter cyclones which cause winter weather Don t make it cold but cause winter weather Can make it cold in weather Polar vortex subtropical jets with polar jet that intensified polar jet and then polar jet created a huge thermo contrast over here and made it very cold Last winter s cold due to warm tropics a lot of energy with polar jet and pushing mass around to make us cold There are interesting effects going on This is a global forecasting system Very interesting Answer to question probably not important Strength will be totally flipped between the jets by wintertime Some hints of polar jets trying to