Agricultural Drought Phenomenon in Latin America with Focus on Brazil - Monitoring and Predicting Agricultural Drought: A Global Study - page 163

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(1965) using nine locations in the United States. For the S ao Paulo State
(Brunini et al., 2002), K i was obtained using data collected at 93 locations
across S ao Paulo State. K i is defined as:

21 . 14 K i "
12

K i = [12.3]

1

D i K i "

where K "is a climatic characterization factor related to moisture depar-
ture, and D is the difference between observed precipitation and expected
precipitation for a month.
The Palmer index, modified for Brazil, has been used throughout the
st ate of S ao Paulo for monitoring drought conditions both on a monthly
an d a dekadal basis. Figure 12.5 shows the relationship between PDSI and
m aize/corn yield.

[163

St andardized Precipitation Index

Line
——
-4.6
——
Long
PgEn

The standardized precipitation index (SPI) was developed for monitoring
precipitation anomalies in the United States (McKee et al., 1993; chapter
9). The SPI is determined based on probabilistic density functions that
describe historic precipitation series for different durations (1-72 months).
The SPI is simply a z -score of the normal distribution variable, Z i :
SPI Pi )/δ i [12.4]

Currently the SPI maps are produced for the state of S ao Paulo on a
monthly basis, with recurrent periods of 1, 3, 9, 12 and 24 months (SPI-1,
SPI-3, SPI-9, SPI-12, and SPI-24) to monitor droughts in the state.

= = ( Pi −

Zi

[163

Crop Drought Index

Th e crop drought index (CDI) is defined as

− ( AET / PET ) [12.5]
w here AET is actual evapotranspiration. The CDI is computed on a 10-day
ba sis considering maximum water holding capacity of the soil as 125 mm.
Th is index, together with the Crop Moisture Index (CMI), the Standardized
Pr ecipitation Index (SPI), and the Palmer Drought Severity Index (PDSI) are
us ed on a routine basis to forecast and to monitor drought and dry spells
in S ao Paulo state.
The analysis of the results obtained for the state of S ao Paulo show that
th e above indices (SPI, PDSI, precipitation and deficit anomalies, and the
C DI) are helpful in monitoring drought conditions in the state. Yields of
va rious crops were also satisfactorily monitored by PDSI, CDI, and SPI
(M ota, 1979; Brunini et al, 2002).

=

CDI 1

U se of Satellite Data

The use of the satellite data for drought monitoring in Brazil is at its pre-
liminary stage. Nevertheless, studies are being conducted by the Center of