MPO 581 Class number 5/27   Feb 2, 2011

Topic: Basic statistics contd and distributions

Loose ends from last class:

Teams and homework leaders all assigned!?    (edit amongst yourselves)
Testable questions compilation taking shape: add to it, for course brownie points.

Today's material:

Math/Stat Operation

MPO Science behind doing it

Average (x)
  • over time (q t)
  • over distance (qx)
  • over area (qxy) or volume (qxyz) or mass (qxyp)
Linear effects (terms in governing equations)
  • dT/dt = Q type conservation laws for masses of matter
  • divergence theorem ∫ ∫ (∇• F) dA = ∮Fn
  • Climate heat budget over ocean + atm
Weighted average
get mass or area average from irregular-grid data (p or lat)
Deviation from average (anomaly or perturbation)
"anomalies" may obey linearized equations about "base state" (Taylor expansion)
Average of nonlinearly transformed variable
Nonlinear physics:  OLR = σT4,  |U| = √+v²,  WD = atan(u/v), Flux = (wq)
Average of squared value
just characterizing variability as positive definite? sometimes Energy
Variance (square - mean2) ≡ σ2
standard deviation σ has units of the quantity (variance: units are squared)
Average of cube, 4th power, ... ⇒ "moments" just statistics? but distributions can imply processes (future lecture)

0. Structural and statistical dimensions
    transform stats --> new structural
    summary stats --> reduction

On to distributions:
1. Weighted sum
2. Divide by summed weight --> weighted average
3. w=const --> plain average
4. Mean of squared anomalies = variance (N-1?)
    stdev is its square root - nicer units
    sum of |anoms|
5. Skewness: mean cube (3rd moment)
5. Kurtosis: mean ^4 (4th moment)

Distributions:


Open questions, assignments, and loose ends for next class:

Testable questions about today's material: