Transcript L3MTO Status Report

WELCOME!
AMS SHORT COURSE
STATISTICS OF
EXTREME EVENTS
AMS Probability and
Statistics Committee
January 11, 2009
Outline
Welcome
 Participants Introduction
 Introduction to the course topic
 Definitions
 Course structure overview

Participants Introduction

Please state:
 Your
name
 Affiliation
 Work focus
 Expectation from the course
Intro to the Course Topic

Extreme events:



the furthest or highest degree of something; far beyond a norm in
quantity or amount or degree; the greatest possible degree or
extent or intensity; the most distant in any direction
(http://wordnet.princeton.edu/perl/webwn?s=extreme )
In climatology, the highest and, in some cases, the lowest value
of a climatic element observed during a given time interval or
during a given month or season of that period
(http://amsglossary.allenpress.com/glossary/ )
Statistics of extreme events:

The systematic analysis of random phenomena
(http://amsglossary.allenpress.com/glossary/ )
Intro to the Course Topic

Some Examples of Extreme Events in
Meteorology, Climatology and Hydrology:
 ENSO
events
 Hurricanes
 Tornadoes
 Climate Variability Extremes versus Climate Change
 Low River Flow
 Flood
 Drought
A Threshold Definition: ENSO

El Niño has tremendous effects on global
climate and weather
due to the eastward
migration of the warm
pool. How do we
define El Niño?
A Threshold Definition: ENSO


El Niño: A phenomenon in the equatorial Pacific Ocean
characterized by a positive sea surface temperature
departure from normal (for the 1971-2000 base period)
in the Niño 3.4 region greater than or equal in magnitude
to 0.5C, averaged over three consecutive months.
La Niña: A phenomenon in the equatorial Pacific Ocean
characterized by a negative sea surface temperature
departure from normal (for the 1971-2000 base period)
in the Niño 3.4 region greater than or equal in magnitude
to 0.5C, averaged over three consecutive months.
A Threshold Definition: ENSO



Note: the standard
deviation of this series
is 0.83C and the
threshold is ±0.50C
1982/1983, 1997/1998
are extreme El Nino
events
1988/99 is an extreme
La Nina. Others?
A Probabilistic Definition
River flow recessions occur in May-Jul, and
Oct –Jan
6
5
Volume (1000 cubic feet per
acre)

4
3
2
1
0
1/1
2/1
3/1
4/1
1950
5/1
6/1
1951
7/1
1953
8/1
9/1
1955
10/1
1956
11/1
12/1
1957
A Probabilistic Definition
25
 Recession
daily
averages
 Minimal 30-day
discharge
 75% Probability of
Exceedance (POE)
Discharge
20
Volume
Low Flow statistics
can include:
15
10
5
0
0%
1.8
10%
20%
30%
40%
50%
60%
70%
80%
90% 100%
POE
1.6
1.4
1.2
Volume

Mean
1
0.8
Median
Mode
0.6
Low flow
0.4
0.2
0
0%
10%
20%
30%
40%
50%
POE
60%
70%
80%
90% 100%
Probabilistic & Threshold Definitions

Category
Description
Drought
Monitoring
D0
Abnormally Dry
D1
Moderate Drought
Categories:
D2
Severe Drought
D3
D4
 D0:
Extreme Drought
Exceptional Drought
Abnormally
Palmer
-1 to-1.9
-2 to -2.9
-3 to -3.9
-4 to-4.9
<-5
SPI
-.5 to -.7
-.8 to-1.2
-1.3 to -1.5
-1.6 to -1.9
<-2
Dry
Objective Short and Long-term Drought Indicator Blends (Percentiles)
CPC Soil Moisture Model (Percentiles)
USGSModerate
Weekly Streamflow(Percentiles)
 D1:
 D2: Severe
 D3: Extreme
 D4: Exceptional
%tiles
21-30
11-20
6-10
3-5
0-2
The Course Structure Overview

VIEWING CLIMATE AND WEATHER EXTREME EVENTS IN A
PROBABILISTIC CONTEXT Prashant Sardeshmukh

EXTREME VALUE THEORY Richard Smith

POISSON AND QUANTILE REGRESSION James Elsner

PROBLEM APPLICATIONS, Exercise Session on Poisson and
Quantile Regression, James Elsner

PERFORMANCE EVALUATION MEASURES Caren Marzban

PROBLEM APPLICATIONS, Exercise Session on Analyses of
Extremes, Rick Katz