Jamaica’s Mid-Summer “Dry Spell”
Teddy Allen and Dr. Scott Curtis
Atmospheric Science Program
Department of Geography
East Carolina University
Dr. Douglas Gamble
Department of Geography and Geology
University of North Carolina at Wilmington
March 6, 2008
2008 Climate Prediction Applications Science Workshop
OUTLINE
• Economic Motivation
• Defining the Mid-Summer “Dry Spell”
• MSD variability and patterns
• Modified Pressure Index
• Vegetation Response
• Future Work
Dataset grid box
nearest Montego Bay
MOTIVATION
$50,000
GDP
per capita
$40,000
$30,000
$20,000
$10,000
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( CIA World FactBook 2007 )
D
Jamaica is a relatively
poor* nation that largely
depends on its agricultural
yields for both export and
domestic consumption. An
improved understanding of
the mechanisms of the
Mid Summer “Dry-Spell”
can have significant
impacts upon agricultural
% GDP
Agriculture productivity and economic
% Labor in prosperity.
Agriculture
* Definition of poor neglects significant cultural wealth
that Jamaica possesses.
Data Sets
• NCEP NCAR monthly Reanalysis
2.5 degree gridded dataset
• NASA Global Precipitation
Climatology Project (GPCP) V2
• Terra MODIS spectral imagery
GPCP CLIMATOLOGY 1979 - 2007
Mid Summer “Dry-Spell” Signature
6
5
3
2
1
0
JA
N
FE
B
M
A
R
AP
R
M
A
Y
JU
N
JU
L
AU
G
SE
P
O
CT
N
O
V
D
EC
mm day-1
4
Montego Bay
18N, 80W
Mid-Summer “Dry Spell”
Conceptual Model
MSD timing
July
May
NAM
H
divergence
upwelling
Mid-Summer “Dry Spell” Pattern
Mean pentad gauge precip. Apr. - Nov. 1979-2007
Mid-Summer “Dry Spell”
Inter-Annual Variability
1998
1999
2000
2001
2002
2003
2004
2005
2006
Average Sea Level Pressure (NCEP NCAR Reanalysis)
Apr.–Nov. 1979 - 2007
APRIL
MAY
JULY
AUGUST
OCTOBER
NOVEMBER
JUNE
SEPTEMBER
Monthly Caribbean Low Level Jet Averages (925mb)
Apr.-Nov. 1979-2007
APRIL
MAY
JULY
AUGUST
OCTOBER
NOVEMBER
JUNE
SEPTEMBER
Monthly GPCP Caribbean Precip. Averages
Apr.-Nov. 1979 - 2007
APRIL
MAY
JULY
AUGUST
OCTOBER
NOVEMBER
JUNE
SEPTEMBER
Average 925mb Divergence
1979-2007
JUNE
AUG.
JULY
SEPT.
Average Differences
+4mb
July minus May
increase in NASH
+5 ms-1
increase in CLLJ
-2
mm / day
decrease in precip.
Modified Bermuda High Index
P Montego Bay – P 30N, 40W
BHI
Montego Bay
30N, 40W
MBHI
MBHI Monthly Climatologies
Montego
Bay
30N, 40W
MBHI
January
1015.26
1022.60
-7.34
February
1015.12
1021.89
-6.77
March
1014.29
1021.15
-6.86
April
1013.52
1021.08
-7.56
May
1012.83
1022.41
-9.58
June
1013.5
1023.69
-10.19
July
1014.51
1024.81
-10.30
August
1013.69
1022.73
-9.04
September
1012.26
1020.68
-8.42
October
1011.77
1019.42
-7.65
November
1012.62
1019.21
-6.59
December
1014.42
1020.46
-6.04
12
10
8
6
4
2
0
N B R R Y N L G P CT V C
JA FE MA AP MA JU JU AU SE O NO DE
Modified BHI
2002 GPCP
Montego Bay
2002 MBHI
Jan. -8.21
1983 MBHI
Jan. -10.89
Feb.
-5.8
Feb.
-3.08
Mar.
-8.78
Mar.
-7.16
Apr.
-10.14
Apr.
-6.67
Early Season MBHI
10
1983 GPCP
Montego Bay
8
2002
1983
AVG
6
4
2
0
JAN
FEB
MAR
APR
Vegetation Response Via
Remote Sensing
Terra MODIS (Moderate Resolution Imaging Spectrometer)
36 Spectral Bands covering the Earth every 1-2 days
250m resolution
Jamaican Region Imagery delivered every 16 days
Normalized Difference Vegetation Index
(NDVI) Classification through ERDAS
Imagine software
April 2006
NIR
- red
________
NDVI =
NIR + red
October 2006
FUTURE WORK
NDVI TIME SERIES
CLASSIFICATION
ENSO
FORCINGS
FARMING
PERSPECTIVE
For more info: teddyallen@yahoo.com
Acknowledgements
• Dr. Scott Curtis
• Dr. Douglas Gamble
• Dr. Rosana Nieto-Ferreira
• ECU Geography Department
• Dr. Peter Robinson and the SERCC
• National Science Foundation