Synoptic methods Basic considerations, manual methods, and the SSC

1
Synoptic methodsBasic considerations, manual
methods, and the SSC

• Week 4, Applied Climatology

2
Yarnal (1993)

• Synoptic climatology relates the atmospheric
  circulation to the surface environment.
• (Surface environment is defined as the planetary
  boundary layer)
• Definitions of synoptic simultaneous or holistic

3
Two classification subdivisions

• Environment-to-circulation
• Circulation-to-environment
• Empirical
• Modeling

4
Terms that we see

• Weather types
• Circulation patterns
• Air masses

5
Method categorizations

• Manual vs. automated
• Subjective vs. objective
• Hybrid

6
Assumptions of synoptic work (from Yarnal 1993)

• The atmospheric circulation is a critical
  determinant of the surface environment
• The Bergen school model of the mid-latitude
  cyclone is correct
• The atmospheric circulation can be partitioned
  into discrete intervals

7
Assumptions of synoptic work (from Yarnal 1993)

• The classification identifies all important map
  patterns or weather types
• Corollary the lumper vs. the splitter
• That the method do what you think it does
• Temporal scales of the atmospheric circulation
  and environmental phenomenon match

8
Assumptions of synoptic work (from Yarnal 1993)

• The grid scale can adequately represent the
  region of interest
• Within-group variability is not a problem

9
Categorization of approaches

• Can also add global scale
• What are the benefits/drawbacks of
  different-sized domains?

10
What is analyzed?

• A set of variables over time?
• A set of stations over time?
• A set of variables across stations?

11
P-mode

• A set of variables over time (usually for one
  station)

12
S-mode

• A set of stations over time (one variable only)

13
R-mode

• A set of variables over stations

14
Compositing

• Always environment to circulation

15
Indexing
16
Some historic manual weather classifications
17
Lamb weather types (1972)
SCALE? ASSUMPTIONS?
18
Lamb weather types
Climate Research Unit, UEA
19
Muller classification (1977)
McCabe and Muller (2002)
20
Muller classification (1977)
21
GrosswetterlagenHess and Brezowsky (1952)
James (2007)
22
Grosswetterlagen

• Issue of scale?
• Lumper or splitter?

23
Hybrid classification schemes

• Manual identification
• Later, automated classification done from
  original rules

24
Schwartz (1991)

• Weather types developed for North Central US from
  examining 850 mb T and Td
• Each day at each station classified into a group
  based on rules

25
SSC (1996 2000)

• DP (dry polar)
• DM (dry moderate)
• DT (dry tropical)
• MP (moist polar)
• MM (moist moderate)
• MT (moist tropical)
• TR (transitional)

26
SSC

• Classifies each day at a location based on the
  following parameters
• Temperature (4am, 10am, 4pm, 10pm EST)
• Dew point depression (same times)
• Temperature and dew point range
• Mean sea level pressure
• Mean cloud cover
• Pressure change
• Wind change

27
SSC

• Criteria vary by time of year and location

28
Wilmington, 29th March 2000

• Dry Moderate (DM) is lowest (5 pts)

29
SSC mapping
30
SSC mapping

• How is this different?