This study examined spatial patterns of rainfall during drought periods in the Caribbean using satellite and station rainfall data. The authors analyzed four drought periods (1994, 1997, 2009, 2015) and classified rainfall anomalies as extreme, severe or moderate. They found the 2015 drought had the largest areas with extreme and severe rainfall deficits. The 1994 and 2015 droughts showed similar spatial patterns in early season months, while the 2009 and 2015 droughts were similar in later months. Future research will analyze atmospheric conditions and tropical cyclone activity during droughts to better understand their causes and impacts in the Caribbean.

1. Examining the spatial characteristics of
rainfall during drought periods in the
Caribbean using CHIRPS
José J. Hernández Ayala, Michael Heslar and Sabina Osman
Department of Geography
University of Florida

2. Drought in The Greater Antilles of The Caribbean

3. Drought Definitions
• Droughts are commonly defined as
meteorological, agricultural, or
hydrological.
• Meteorological droughts are periods of
below-normal rainfall.
• Agricultural droughts, follow
meteorological droughts and affect crops as
well as natural flora and fauna.
• A hydrological drought is manifested by
reduced streamflow, and lowered
groundwater and lake levels

4. Problem Statement
• The Caribbean is expected to become dryer
by the end of the century.
• More frequent droughts will bring more
environmental and socio-economic issues.
• This research focuses on two main questions:
Which of the recent droughts has been the
one that has affected most of the region?
Were there spatial similarities in rainfall
patterns during recent drought periods ?

5. Study Area
<VALUE>
121.6
-285.2285.3
-374.4374.5
-452.4452.5
-519.3519.4
-597.4597.5
-720
720.1
-1,066
Legend
VALUE
-44
-6363.1
-160
161
-293
294
-453
454
-634
635
-851852
-1,120
1,130
-1,4701,480
-1,9001,910
-2,970
Elevation (m)
Mean Rainfall Rainy Season (mm)

6. Causes of Drought in the Caribbean
• El Niño Southern
Oscillation (ENSO)
Less tropical cyclones
Stronger westerly flow
• North Atlantic Oscillation
(NAO)
Less frontal systems
moving to the Caribbean.

7. CHIRPS Data
• Climate Hazards Group InfraRed Precipitation with Station data
(CHIRPS) is a 30+ year quasi-global rainfall dataset.
• Spanning 50°S-50°N (and all longitudes), starting in 1981 to near-
present.
• CHIRPS incorporates 0.05° resolution satellite imagery with in-
situ station data (Funk et al., 2015).
• Good for trend analysis and seasonal drought monitoring.
• Four drought periods were considered in this study (1994, 1997,
2009 and 2015).
• This study used three monthly total rainfall anomalies for four
month groups (MJJ, JJA, JAS and ASO).

8. Methods
• After pre-processing the CHIRPS
anomaly data (00-15 mean) all periods
were classified in different groups.
• Extreme (-300 mm or more) anomalies
• Severe (-299 to -100) anomalies
• Moderate (-99 to -50) anomalies
• Overlay Analysis was implemented to
examine spatial characteristics between
events.

9. Results: Reclassify (JAS)
1994 (JAS) 1997 (JAS)
2009 (JAS) 2015 (JAS)
JAS Extreme Area (sq.km) JAS Severe Area (sq.km) JAS Moderate Area (sq.km)
1994 3212.602281 1994 81549.58542 1994 44341.29703
1997 163.675758 1997 29693.99814 1997 33191.2847
2009 323.198921 2009 124168.2882 2009 74193.68046
2015 13273.28709 2015 152690.0972 2015 38973.52606
Total Rainfall Anomalies (mm)
Extreme (-300 or >)
Severe (-299 to -100)
Moderate (-99 to -50)

10. Results: Group Month Comparisons
9%
7%
0%
84%
Extreme MJJ
Area (%)
13%
26%
10%
51%
Severe MJJ
Area (%)
15%
37%
22%
26%
Moderate MJJ
Area (%)
16%
1%0%
83%
Extreme JJA
Area (%)
35%
7%
20%
38%
Severe JJA
Area (%)
32%
8%
31%
29%
Moderate JJA
Area (%)
21%
8%
32%
39%
Severe JAS
Area (%)
19%
1%
2%
78%
Extreme JAS
Area (%)
23%
17%
39%
21%
Moderate JAS
Area (%)
22%
1%
24%
53%
Extreme ASO
Area (%)
13%
12%
42%
33%
Severe ASO
Area (%)
22%
27%
21%
30%
Moderate ASO
Area (%)

11. Results: Spatial Characteristics
Extreme JJA Severe JJA Moderate JJA
Years Area Years Area Years Area
1994-1997 57.498031994-1997 17914.762081994-1997 3322.709
1994-2009 01994-2009 28893.641181994-2009 19644.06
1994-2015 1095.8641994-2015 75114.889661994-2015 20684.13
1997-2009 01997-2009 8293.9717221997-2009 3708.279
1997-2015 59.332241997-2015 18352.415781997-2015 1444.304
2009-2015 02009-2015 34549.219642009-2015 11673.72
Extreme ASO Severe ASO Moderate ASO
Years Area Years Area Years Area
1994-1997 61.993551994-1997 16669.999211994-1997 5103.527
1994-2009 982.9881994-2009 43053.010931994-2009 9638.515
1994-2015 1206.2871994-2015 27464.737881994-2015 12536.8
1997-2009 01997-2009 34324.009531997-2009 4219.057
1997-2015 24.837891997-2015 35890.587891997-2015 11121.32
2009-2015 1340.9622009-2015 114618.62832009-2015 11897.85
1994-2015 (Jun-Jul-Aug)
2009-2015 (Aug-Sept-Oct)
Total Rainfall Anomalies (mm)
Extreme
Severe
Moderate

12. Results: Spatial Characteristics (Area %)
27%
3%
7%
12%
25%
26%
Moderate MJJ
10%
0%
9%
0%
20%61%
Severe MJJ
20%
0%
72%
0%
8% 0%
Extreme MJJ
4% 5%
70%
3%
4%
14%
Extreme JAS
8%
20%
22%
8%
8%
34%
Severe JAS
11%
30%
21%
11%
3%
24%
Moderate JAS

13. Conclusions
• The 2015 drought was the event with the largest areas exhibiting extreme and
severe rainfall anomalies.
• The 1994 and 2015 droughts were similar in their spatial characteristics of rainfall
(extreme and severe anomalies) for the earlier season months May to July and
June to August.
• The 2009 and 2015 droughts were similar in their spatial characteristics of rainfall
for July to September and August to October.
• The 1997 drought did not exhibit large areas with extreme or severe rainfall
anomalies in the Caribbean when compared to other periods even though there
was a strong ENSO event.

14. Future Research
• Future work will examine the atmospheric conditions (moisture, pressure,
wind) of each of the drought periods to identify similarities or differences
between them.
• Future studies will also look at the role that tropical cyclones (their absence
or higher frequency) play in drought events in the Caribbean.
• Several teleconnections such as ENSO, NAO and AMO will be examined in
order to understand their combined effects on drought periods in the
Caribbean.

15. Questions?