How is the standard precipitation index calculated?

To calculate the SPI (Standard Precipitation Index), a long-term precipitation record at the desired station is first fitted to a probability distribution (e.g. gamma distribution), which is then transformed into a normal distribution so that the mean SPI is zero (McKee et al., 1993, 1995).

How is SPI calculated drought?

The SPI calculation for any location is based on the long-term precipitation record for a desired period. This long-term record is fitted to a probability distribution, which is then transformed into a normal distribution so that the mean SPI for the location and desired period is zero (Edwards and McKee, 1997).

What is SPI geography?

The Standard Precipitation Index (SPI) is a relatively new drought index based only on precipitation. It’s an index based on the probability of precipitation for any time scale. Some processes are rapidly affected by atmospheric behavior, such as dry land agriculture, and the relevant time scale is a month or two.

How do you calculate drought?

The Palmer Drought Severity Index (PDSI) has been used the longest for monitoring drought….The Palmer Drought Severity Index (PDSI)

What is SPI for drought?

The Standardized Precipitation Index (SPI) is a widely used index to characterize meteorological drought on a range of timescales. On short timescales, the SPI is closely related to soil moisture, while at longer timescales, the SPI can be related to groundwater and reservoir storage.

What is precipitation concentration index?

Precipitation concentration index (PCI), defined by Oliver [44], is also a powerful indicator for temporal precipitation distribution. Similar to CI, PCI is generally used for evaluating seasonal precipitation changes to investigate the heterogeneity of monthly rainfall data.

How do you calculate effective drought index?

Effective Drought Index (EDI) The summation term is the sum of the reciprocals of all the months in the duration N (i.e. for N=3 months), this term will be equal to 1 1 + 1 2 + 1 3 .

What is index in drought?

Drought indices take thousands of bits of data on rainfall, snowpack, streamflow, etc., analyze the data over various time frames, and turn the data into a comprehensible big picture. A drought index value is typically a single number, which is interpreted on a scale of abnormally wet, average, and abnormally dry.

What is SPI drought?

How is SPEI calculated?

The SPI is calculated using monthly (or weekly) precipitation as the input data. The SPEI uses the monthly (or weekly) difference between precipitation and PET. This represents a simple climatic water balance which is calculated at different time scales to obtain the SPEI.

What is standardized precipitation index?

The Standardized Precipitation Index (SPI; McKee 1993) is the number of standard deviations that observed cumulative precipitation deviates from the climatological average.

What is standardized Precipitation Index (SPI)?

The Standardized Precipitation Index (SPI) is one of seven indices used by the Massachusetts Drought Management Task Force to determine the level of drought severity. The SPI reflects precipitation conditions. SPI values are calculated monthly using data from the precipitation database.

What is standardized precipitation?

Standardized Precipitation Index (SPI) The Standardized Precipitation Index (SPI) is a probability (ie: statistical) index that gives a representation of abnormal wetness and dryness. It is an alternative to the (more complicated) physically based Palmer Severe Drought Index (PSDI) which uses a simple water balance model.

What is rainfall index insurance?

A national rainfall index (NRI) is defined as the national average of the total annual precipitation weighted by its long-term average. In other words, it is a calculation of how much precipitation has fallen over a specific area. It is commonly used by governments, insurance companies and meteorologists .