The magnitude of PDSI
indicates the severity of the departure from normal conditions
. A PDSI value >4 represents very wet conditions, while a PDSI <-4 represents an extreme drought.
How do you read a drought index?
The PDSI is a standardized index
based on a simplified soil water balance and estimates relative soil moisture conditions
. The magnitude of PDSI indicates the severity of the departure from normal conditions. A PDSI value >4 represents very wet conditions, while a PDSI <-4 represents an extreme drought.
How is the severity of a drought measured?
The most common index used to define and monitor drought is the
Palmer Drought Severity Index (PDSI)
, which attempts to measure the duration and intensity of long-term, spatially extensive drought, based on precipitation, temperature, and available water content data.
Which is the most commonly used drought index?
While the PDSI is the oldest and most well known,
the SPI
is the most widely used index for understanding the magnitude and duration of drought events.
How bad is the 2021 drought?
It is in this record that the story of megadroughts — severe droughts that stretched on for multiple decades or even a century — has been revealed. … As of July, our projected estimates indicate that 2021 will very likely finish among the
worst three to five drought years in
the past 1,200 years.
What are the levels of drought severity?
The map uses five classifications: abnormally dry (D0), showing areas that may be going into or are coming out of drought, and four levels of drought:
moderate (D1), severe (D2), extreme (D3) and exceptional (D4)
.
What is drought severity?
Positive values represent wetter-than-average conditions, while negative values represent drier-than-average conditions. A value between -2 and -3 indicates moderate drought,
-3 to -4 is severe drought
, and -4 or below indicates extreme drought. The thicker line is a nine-year weighted average.
What is a D2 drought?
The severe drought category, D2, corresponds to an
area where crop or pasture losses are likely
, fire risk is very high, water shortages are common, and water restrictions are typically voluntary or mandated.
How is a drought classified?
Drought conditions are classified on a system
based on current soil moisture content, streamflow, and recent precipitation
. … Short-term droughts are typically defined when conditions last less than six months, while long-term droughts are defined as lasting over half a year.
Will there be drought in 2021?
Based on the Palmer Drought Index,
severe to extreme drought affected about 36% of the contiguous United States
as of the end of June 2021, an increase of about 8% from last month. About 4% of the contiguous U.S. fell in the severely to extremely wet categories.
Will 2021 be a drought year?
According to the NOAA U.S. Seasonal Drought Outlook, covering
August through November 2021
, existing drought conditions are expected to persist across the West, upper and central Great Plains, the western portion of the Midwest, and parts of the Northeast.
Which two states are not affected by drought?
Drought and/or abnormally dry conditions affect some or all of most states—only Rhode Island, New Hampshire, and
Maine
have been spared.
What are the four levels of drought?
As a result, the climatological community has defined four types of drought: 1) meteorological drought, 2) hydrological drought, 3) agricultural drought, and 4) socioeconomic drought.
Is there a rating scale for droughts?
Credit: NOAA’s National Weather Service. … The USDM’s drought intensity scale is composed of five different levels:
D0, D1, D2, D3, and D4
. The abnormally dry category, D0, corresponds to an area experiencing short-term dryness that is typical with the onset of drought.
What does Level 3 drought mean?
Level 3, “
Extreme Drought
:” This is the second-highest level of drought, with “major crop/pasture losses” and “widespread water shortages or restrictions.” … This level involves “exceptional and widespread crop/pasture losses; shortages of water in reservoirs, streams, and wells creating water emergencies.”
How do drought experts measure drought?
Hydrologists use stream gauges that they place at different points in rivers and streams to find out how much water is flowing in a river or stream from place to place. During droughts,
less water flows
, and the water that is in the river or stream will be moving much more slowly than normal.
