Introduction to Upper Air Data

1. Introduction to Upper Air Data • Mandatory and Significant Levels • General Vertical Profiles of the Atmosphere • Upper Air Maps • TTAAs, TTBBs, PPBBs

2. Mandatory vs. Significant Levels • Mandatory levels are those that will always appear in upper air analysis gathered from radiosonde data • Significant levels are levels where there is significant data to present (usually not represented with a map but just incorporated on soundings)

3. Mandatory Levels and Heights • Surface - obviously • 1000mb - varies on station elevation • 925mb - varies on station elevation • 850mb - ~1500m • 700mb - ~3000m • 500mb - ~5500m • 400mb - ~7000m • 300mb - ~9500m • 250mb - ~11000m • 200mb - ~12000m • 150mb - ~14000m • 100mb - ~16000m

4. Upper Air Maps • This is why knowing heights is important • Dew point vs. Dew point depression • Normally temperature decreases with height until ~200mb where it becomes isothermal then increases with height in the stratosphere • Wind increasing with height until the jet stream (~250mb) • There are troughs and ridges like sfc maps • http://weather.unisys.com/upper_air/mandatory.html • Details

5. TTAAs and TTBBs • TTAAs are mandatory level data, temperature, dew point depression, height of p level, wind speed and direction is given • TTBBs are significant level data, temperature, dew point depression, and p level is given • PPBBs are the corresponding wind data with heights of the significant levels

6. Decoding all that data • See http://www.ems.psu.edu/Courses/Meteo200/lesson5/decode.htm • This link shows how to decode all this data and all the “tricks” • There are little tests on this page to help • All this data is displayed in thermodynamic charts, such as Skew T – Log P diagrams • In this class we’ll focus just on TTAA

7. 850 mb Maps • How to decode station models for this level • Temp plotted upper left in Celsius • Dewpoint DEPRESSION plotted • Circle shaded if T-D is 5 or less • Height plotted in meters without first 1 • Height change over 12 hours given in decameters. • Winds plotted same as surface maps

8. 850 mb Maps • What is the significance of 850 mb maps? • Temperature and moisture advection • Rain/snow detection • Forecast of high and low temperature • Low level jet • Tilting of pressure systems • Height contour intervals are every 30m and isotherms are every 5 degrees

9. 700 mb Maps • Interpretation is the same as 850mb except heights are plotted without the first digit, which is a 2 or 3. • Contour intervals are every 30m and isotherms are every 5 degrees. • Used to find: • Short waves • Advections • Steering flow for storms

10. 500 mb Maps • Contours are every 60 meters • Stations are plotted as on 850 & 700mb maps, but height is given without the last digit, which is a 0. • Used to find areas of vorticity advection.

11. 1000-500 mb Thickness plots • This plot gives the thickness of the layer of the atmosphere between 1000mb and 500mb. • Related to mean temperature of the atmosphere. • Can determine motion of organized convection (Mesoscale convective complexes) • Rain vs. Snow

12. 300/250/200 mb Maps • Contour interval is 120 m, isotachs are every 20 knots • Heights coded just like in TTAA • Used to find jet streams and jet streaks • Useful to find areas of convergence/divergence aloft. • Cyclogenesis can be enhanced • Boundary between cold and warm air

13. Combining the Upper-Air Maps • So how can using all these maps help us understand the state of the atmosphere. • Atmosphere is 3-D • Can help aid in forecasting development/decay of weather systems • Developing cyclones tilt left as you look higher in the atmosphere • Dying cyclones tend to be stacked or tilt right

14. Combining the upper air maps • Impacts for air travel? • Jet streams/streaks • Wind speed and direction aloft • Temperatures aloft • Moisture aloft • Next: Plotting and diagnosing data on a Skew-T, stability, severe wx signatures etc.