palmer drought index
percent area of contiguous u. s. in palmer drought index moderate to extreme
monthly maps of drought conditions in the contiguous u. s. as measured by the palmer drought severity index, palmer hydrological drought index, palmer modified drought index, and palmer z - index (palmer, 1965) are provided for january 1900—june 2018. animations of any set of monthly maps for any period desired can be viewed by selecting the beginning and ending dates of interest .
wells, nathan, steve goddard, michael j. hayes, 2004: a self - calibrating palmer drought severity index. j. climate, 17, 2335–2351
the palmer drought severity index (pdsi) and crop moisture index (cmi) are indices of the relative dryness or wetness affecting water sensitive economies. the data is provided in graphical and tabular formats, for the contiguous united states .
to quantify drought and monitor its development, many drought indices have been developed and applied. among them, the palmer drought severity index (pdsi) is the most prominent index of meteorological drought used in the united states for drought monitoring and research, and its variants have been used to quantify long - term changes in aridity over land in the 20
alley, w. m. , 1984: the palmer drought severity index: limitations and assumptions. j. climate appl. meteor. 23, 1000 - 1009
dai, a. , 2011a: characteristics and trends in various forms of the palmer drought severity index (pdsi) during 1900 - 2008. j. geophys. res. , 116, d12115
dai, aiguo & national center for atmospheric research staff (eds). last modified 12 jul 2017 .
the climate data guide: palmer drought severity index (pdsi) .
retrieved from urltoken
palmer, w. c. , 1968: keeping track of crop moisture conditions, nationwide: the new crop moisture index. weatherwise, 21, 156 - 161 .
dai, a. , k. e. trenberth, and t. qian, 2004: a global data set of palmer drought severity index for 1870 - 2002: relationship with soil moisture and effects of surface warming. j. hydrometeorology, 5, 1117 - 1130
palmer, w. c, 1965: meteorological drought. res. paper no. 45, 58pp. , dept. of commerce, washington, d. c .
the palmer drought severity index (pdsi) uses readily available temperature and precipitation data to estimate relative dryness. it is a standardized index that spans - 10 (dry) to + 10 (wet). it has been reasonably successful at quantifying long - term drought. as it uses temperature data and a physical water balance model, it can capture the basic effect of global warming on drought through changes in potential evapotranspiration. monthly pdsi values do not capture droughts on time scales less than about 12 months; more pros and cons are discussed in the expert guidance .
national drought mitigation center the national drought mitigation center works closely with nidis to provide drought - related resources and information. for more news and impacts information, visit the ndmc .
usda federal drought assistance for information on resources available to help aid in the recovery from this year’s drought, visit the usda .
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keyantash, john, john a. dracup, 2002: the quantification of drought: an evaluation of drought indices. bull. amer. meteor. soc. , 83, 1167–1180 .
recently, the pdsi was criticized for its inability to depict droughts on time scales shorter than 12 months when monthly pdsi values were used. this is not unexpected as the pdsi was designed to be strongly auto - correlated in order to account for the impact of land memory on drought conditions. however, the palmer model also computes the un - smoothed z - index which can be used to track short - term agricultural drought, since it responds quickly to changes in soil moisture. for quantifying long - term changes in aridity and droughts, the relatively long intrinsic time scale of monthly pdsi should not be a problem .
from this perspective, the pdsi and sc _ pdsi may be considered superior to other statistically based drought indices. this is because the pdsi and sc _ pdsi can account for the basic effect of global warming through palmer' s water balance model on droughts and wet spells. the effect of global warming may have already occurred during the 20
comprises seven federal agencies which work collaboratively to support state, tribal, local, and private sector approaches to managing drought risks and impacts .
dai, a. , 2011b: drought under global warming: a review. wiley interdisciplinary reviews: climate change, 2, 45 - 65
the national drought mitigation center website was recently updated, so it' s possible the url of the page you were looking for has changed .
richard r. heim jr. , 2002: a review of twentieth - century drought indices used in the united states. bull. amer. meteor. soc. , 83, 1149–1165
zhao, t. , and a. dai (2015): the magnitude and causes of global drought changes in the 21st century under a low - moderate emissions scenario. j. climate, , 28, 4490–4512
[ 1965 ] with the intent to measure the cumulative departure in surface water balance. it incorporates antecedent and current moisture supply (precipitation, p) and demand (potential evapotranspiration, pe) into a hydrological accounting system, which includes a 2 - layer bucket - type model for soil moisture calculations. the pdsi is a standardized measure, ranging from about - 10 (dry) to + 10 (wet) with values below - 3 representing severe to extreme drought. the standardization used by palmer was based on limited data from the central u. s. and tends to yield more severe pdsi in the great plains than other u. s. regions. to improve the spatial comparability ,
the pdsi is also imprecise in its treatment of all precipitation as immediately available rainfall (i. e. , no delayed runoff from melting snow), its lack of impact of vegetation or frozen soils on evaporation, and some other processes. despite all these caveats, dai et al. [ 2004 ] and dai [ 2011a ] showed that the pdsi values are significantly correlated with measured soil moisture content in the warm season and streamflow over many regions over the world, and satellite observed land water storage changes, and these correlations are comparable over the u. s. and many other parts of the world. this suggests that the pdsi can be used as a measure of drought over land, especially over the low and middle latitudes. this is largely due to the fact that the normalization in the palmer model minimizes the errors associated with many of the assumptions made by palmer [ 1965 ] and that actual evaporation is often determined, to a large degree, by the availability of soil moisture (and thus affected by precipitation), not only by pe, over many land areas. also, using annual values should minimize the seasonal effect of snowfall on the surface water balance .
burke, e. j. , and s. j. brown (2008), evaluating uncertainties in the projection of future drought, j. hydrometeorol. , 9, 292–299, doi: 10. 1175 / 2007jhm929. 1
west: outside the withdrawal of d0 from a small area in northeast montana, where most locations recorded between one and two inches of rain, the drought monitor depiction is unchanged from the previous week. significant rains from the southwest monsoon have yet to reach most of arizona, and only scattered locations across southern and eastern new mexico recorded over an inch of rain this past week. but a late start to the monsoon is hardly unusual, and conditions do not warrant drought degradation yet .
midwest: a few inches of rain wiped out the abnormally dry area in central iowa, and a re - assessment of earlier rains led to the removal of d0 conditions from central indiana as well. in contrast, a relatively dry week kept abnormally dry conditions unchanged in east - central michigan, scattered areas across northern and western minnesota, and northeastern illinois. areas of drought cover southern iowa and both the northern and southwestern parts of missouri. abnormally dry conditions (d0) covered much of the rest of the show - me state, but moderate to heavy rains eliminated a large area of d0 in southeastern missouri. despite areas of significant rainfall in some other parts of missouri, no marked changes in dryness or drought were noted, though a small area in north - central missouri slipped into d2 (extreme drought) conditions .
trenberth, k. e. , a. dai, g. van der schrier, p. d. jones, j. barichivich, k. r. briffa, and j. sheffield ^, 2014: global warming and changes in drought. nature climate change, 4, 17 - 22
northeast: most areas of dryness and drought recorded at least light precipitation, with a few swaths receiving 1 to locally 2 inches; however, these amounts were insufficient to improve conditions significantly, especially with the heat wave that enveloped the region late in the period. the only change introduced was a small expansion of abnormal dryness into a few additional counties in upstate new york .
on the positive side, the pdsi is based on a physical water - balance model, uses both precipitation and surface air temperature (and other variables when pe _ pm is used) as input, and takes the precedent condition into account, in contrast to most other drought indices that are based purely on past statistics of certain climate variable (s), which often includes precipitation alone .
high plains: in colorado and wyoming, most areas remained unchanged; most of wyoming remained out of dryness, and conditions worsen progressively moving south, with extreme to exceptional drought covering southern colorado. deficient precipitation and enhanced evaporative loss over the past few months led to limited expansion of d0 and d1 in areas near the central part of the border. farther east, dryness led to some deterioration in kansas. d3 pushed into part of south - central kansas while extreme drought expanded into a larger part of northeastern kansas. in the dakotas, very heavy rains and flooding late in the period covered a swath across east - central south dakota, leading to a band of 1 - to 2 - category improvement, with southern reaches of the old d2 area climbing to d0. this area will have to be assessed next week to get a better sense of how this intense rainfall episode changed the drought situation there. moderate to heavy rains (but only isolated minor flooding) pelted western north dakota as well, prompting the removal of abnormal dryness over much of the western part of the state. small - scale improvements were made in a few other dry areas where rain was heaviest .
the discussion in the looking ahead section is simply a description of what the official national guidance from the national weather service (nws) national centers for environmental prediction is depicting for current areas of dryness and drought. the nws forecast products utilizedinclude the hpc 5 - day qpf and 5 - day mean temperature progs, the 6 - 10 day outlooks of temperature and precipitation probability, and the 8 - 14day outlooks of temperature and precipitation probability, valid as of late wednesday afternoon of the usdm release week. the nws forecast webpage used for this section is: urltoken
south: heavy rain – 3. 5 to locally over 8. 0 inches – dowsed much of the dry area in tennessee, eliminating most of the abnormally dry area, though a few patches remain in central and northern parts of the state. in contrast, most areas in the lower mississippi valley and southern great plains recorded little or no rainfall, with moderate to isolated heavy amounts limited to parts of central oklahoma, western texas, and the louisiana bayou. the rains brought regions of improvement (but not broad - scale relief) to western texas, including the big bend. farther north, a re - assessment of conditions led to some improvement being introduced in the texas panhandle (especially northern sections) and eastern parts of the oklahoma panhandle and adjacent western oklahoma. meanwhile, the dry and hot week prompted substantial deterioration across central and eastern texas, louisiana, arkansas, and (to a lesser extent) eastern oklahoma. as a result, moderate to severe drought became more widespread, especially in a swath from southern to northeastern texas. san antonio, tx reported just over 2 inches of rain for april - june 2018, compared to a normal of over 10. 6 inches (third driest such period in 134 years of record). also, grass fires have become unusually common across the dallas - ft. worth metro area. in southwestern texas, to the north and northwest of laredo, a broad area of extreme drought (d3) was introduced, with an area of exceptional drought (d4) introduced in part of this region along the rio grande river. most of the new d3 area recorded only 2 to 4 inches of rain in the last 90 days, and 3 - month totals of only 0. 5 to 1. 5 inches (with widely isolated higher amounts) were recorded in the new d4 region .
regional climate impacts and outlook documents summarize seasonal conditions four times a year, in march, june, september and december. regions include the northeast, gulf of maine, southeast, south, midwest, great lakes region, missouri river basin, western region, alaska and northern canada, and hawaii and the pacific. select and download the most recent outlook for your region here
southeast: moderate to heavy rain (one to several inches) made a patchy pattern across the southeast, typical of summer thunderstorms. heavy rain was most widespread across florida while most areas in the central and eastern carolinas, northwestern alabama, and northern mississippi recorded only light rain, if any. deficient precipitation was noted on a variety of time scales in the central carolinas, leading to the introduction of abnormally dry conditions. farther west, enough rain fell to end dryness in northeastern and southwestern alabama, but dryness persisted over most of mississippi and some adjacent locales. the d0 area expanded to cover a bit more of southwester mississippi while d1 in a small part of that region remained unchanged .
alaska, hawaii, and puerto rico: in puerto rico, another relatively dry week along the southern tier kept abnormally dry conditions intact, with some expansion part of central puerto rico where rainfall deficits have begun to increase. across alaska and hawaii, existing areas of abnormal dryness remained unchanged .
for the remainder of this week (through june 8, 2018), moderate precipitation (0. 5 to 1. 2 inches) is forecast across a broad area in the southeastern great plains, the ohio and lower half of the mississippi river valleys, and the eastern seaboard. heavy rain (2 to locally 5 inches) is forecast in southeastern texas and the southern tier of louisiana, and amounts could reach 2 inches in eastern pennsylvania and southwestern florida. farther west, moderate to heavy rain (0. 5 to locally 2. 5 inches) is forecast for parts of the central and northeastern great plains, and far northern mississippi valley. rainfall should be light with isolated moderate totals in the rest of the country east of the rockies while little or no rain is expected from the rockies to the pacific ocean. average daily minimum temperatures should be above - normal throughout the contiguous states, with the largest departures (6 to 10 degrees f) expected in the southern rockies, parts of the great basin and northern great plains, and throughout the ohio valley and northeast. daily high temperatures will not differ as far from normal, with 5 - day anomalies exceeding 3 degrees f more than normal limited to the northwest, the intermountain west, most of the rockies, the great lakes, and new england. the subsequent 5 - day period (june 9 - 13, 2018), odds favor above - normal rainfall in central and southern sections of california, the intermountain west (including the great basin), and the rockies, with surplus precipitation most likely in northern arizona. farther east, wet weather is also favored in the lower mississippi valley, most of the southeast, the southern and eastern ohio valley, and the middle atlantic states. southern alaska also has enhanced chances for above - normal precipitation. in contrast, subnormal rainfall is favored from central and southern texas northward through the plains, the western great lakes, the northern intermountain west, and the pacific northwest. temperatures are expected to average above normal across most of the contiguous states, with the exceptions of southeastern arizona, southwestern new mexico, and part of southern alaska, where cooler than normal conditions seem more likely .
percent area in continental u. s. - weekly change (full statistics )
percent area in continental u. s. - monthly change (full statistics )
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rcc region pages, organized by state groupings, offer links to applied climate research .
dews are partnerships of federal, tribal, state, local and academic entities within specific watersheds and / or states .
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topsoil moisture maps - the cpc produces top soil maps based on the usda data .
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urltoken
lacks multi - timescale features of indices like the spi, making it difficult to correlate with specific water resources like runoff, snowpack, resevoir storage, etc .
century. the pdsi has also been widely used in tree - ring based reconstructions of past droughts in north america and other regions .
[ 1965 ] based on data from the central u. s. the sc _ pdsi performed better than the original pdsi during the 20
, 2008 ], as the thornthwaite pe (pe _ th) is based only on temperature, latitude and month. this error can be minimized, however, by using the more sophisticated penman - monteith equation [ referred to as pe _ pm, which accounts for the effects of radiation, humidity and wind speed and works best over australia in a comparison of various pe formulations
[ 1965 ] chose the pe _ th mainly based on practical considerations as data for computing pe _ pm and other types of pe may be unavailable. this is especially true for global analyses .
century, comes mainly through potential evapotranspiration. as precipitation and surface air temperature are the only two climate variables with long historical records, the pdsi makes full use of these data and can be readily calculated for the last hundred years or so for most land areas. the impact of the choice of pe _ th or pe _ pm is relatively small for the 20th century, the use of pe _ th tends to overestimate the impact of the globalwarming for the model - projected 21st century climate. dai (2011a, jgr) compared the various versions of the pdsi and recommended the use of the sc _ pdsi with the pe _ pm (i. e. , sc _ pdsi _ pm), especially for model projections. all the references cited here can be found in dai (2011a, jgr) and in the key references below. # #
data access: please cite data sources, following the data providers' instructions .
hobbins, m. t. , a. dai, m. l. roderick, and g. d. farquhar (2008), revisiting potential evapotranspiration parameterizations as drivers of long - term water balance trends, geophys. res. lett. , 35, l12403, doi: 10. 1029 / 2008gl033840
van der schrier, g. , k. r. briffa, p. d. jones, and t. j. osborn (2006a), summer moisture variability across europe, j. clim. , 19, 2818–2834, doi: 10. 1175 / jcli3734. 1
van der schrier, g. , k. r. briffa, t. j. osborn, and e. r. cook (2006b), summer moisture availability across north america, j. geophys. res. , 111, d11102, doi: 10. 1029 / 2005jd006745
van der schrier, g. , p. d. jones, and k. r. briffa (2011), the sensitivity of the pdsi to the thornthwaite and penman - monteith parameterizations for potential evapotranspiration, j. geophys. res. , 116, d03106
long - term pdsi over the continental us through january, 2014. retrieved on 31 jan 2014 from urltoken
eof 1 & 2 patterns: psdi: 1900 - 2005. (climate data guide; a. dai, d. shea )
eof 1 & 2 timeseries: psdi: 1900 - 2005. (climate data guide; a. dai, d. shea )
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the palmer drought index , sometimes called the palmer drought severity index and often abbreviated pdsi , is a measurement of dryness based on recent precipitation and temperature . it was developed by meteorologist wayne palmer , who first published his method in the 1965 paper meteorological drought for the office of climatology of the u.s. weather bureau . the palmer drought index is based on a supply-and-demand model of soil moisture . supply is comparatively straightforward to calculate , but demand is more complicated as it depends on many factors , not just temperature and the amount of moisture in the soil but also hard-to-calibrate factors including evapotranspiration and recharge rates . palmer tried to overcome these difficulties by developing an algorithm that approximated them based on the most readily available data , precipitation and temperature . the index has proven most effective in determining long-term drought , a matter of several months , but it is not as good with conditions over a matter of weeks . it uses a 0 as normal , and drought is shown in terms of negative numbers ; for example , negative 2 is moderate drought , negative 3 is severe drought , and negative 4 is extreme drought . palmer 's algorithm also is used to describe wet spells , using corresponding positive numbers . palmer also developed a formula for standardizing drought calculations for each individual location based on the variability of precipitation and temperature at that location . the palmer index can therefore be applied to any site for which sufficient precipitation and temperature data is available . critics have complained that the utility of the palmer index is weakened by the arbitrary nature of palmer 's algorithms , including the technique used for standardization . the palmer index 's inability to account for snow and frozen ground also is cited as a weakness . the palmer index is widely used operationally , with palmer maps published weekly by the united states government 's national oceanic and atmospheric administration . it also has been used by climatologists to standardize global long-term drought analysis . global palmer data sets have been developed based on instrumental records beginning in the 19th century . in addition , dendrochronology has been used to generate estimated palmer index values for north america for the past 2000 years , allowing analysis of long term drought trends . it has also been used as a means of explaining the late bronze age collapse . in the us , regional palmer maps are featured on the cable channel weatherscan . 
the palmer drought index, sometimes called the palmer drought severity index and often abbreviated pdsi, is a measurement of dryness based on recent precipitation and temperature. it was developed by meteorologist wayne palmer, who first published his method in the 1965 paper meteorological drought for the office of climatology of the u.s. weather bureau. the palmer drought index is based on a supply-and-demand model of soil moisture. supply is comparatively straightforward to calculate, but demand is more complicated as it depends on many factors, not just temperature and the amount of moisture in the soil but also hard-to-calibrate factors including evapotranspiration and recharge rates. palmer tried to overcome these difficulties by developing an algorithm that approximated them based on the most readily available data, precipitation and temperature. the index has proven most effective in determining long-term drought, a matter of several months, but it is not as good with conditions over a matter of weeks. it uses a 0 as normal, and drought is shown in terms of negative numbers; for example, negative 2 is moderate drought, negative 3 is severe drought, and negative 4 is extreme drought. palmer's algorithm also is used to describe wet spells, using corresponding positive numbers. palmer also developed a formula for standardizing drought calculations for each individual location based on the variability of precipitation and temperature at that location. the palmer index can therefore be applied to any site for which sufficient precipitation and temperature data is available. critics have complained that the utility of the palmer index is weakened by the arbitrary nature of palmer's algorithms, including the technique used for standardization. the palmer index's inability to account for snow and frozen ground also is cited as a weakness. the palmer index is widely used operationally, with palmer maps published weekly by the united states government's national oceanic and atmospheric administration. it also has been used by climatologists to standardize global long-term drought analysis. global palmer data sets have been developed based on instrumental records beginning in the 19th century. in addition, dendrochronology has been used to generate estimated palmer index values for north america for the past 2000 years, allowing analysis of long term drought trends. it has also been used as a means of explaining the late bronze age collapse. in the us, regional palmer maps are featured on the cable channel weatherscan.
the palmer drought index, sometimes called the palmer drought severity index and often abbreviated pdsi, is a measurement of dryness based on recent precipitation and temperature. it was developed by meteorologist wayne palmer, who first published his method in the 1965 paper meteorological drought for the office of climatology of the u.s. weather bureau. the palmer drought index is based on a supply-and-demand model of soil moisture. supply is comparatively straightforward to calculate, but demand is more complicated as it depends on many factors, not just temperature and the amount of moisture in the soil but also hard-to-calibrate factors including evapotranspiration and recharge rates. palmer tried to overcome these difficulties by developing an algorithm that approximated them based on the most readily available data, precipitation and temperature. the index has proven most effective in determining long-term drought, a matter of several months, but it is not as good with conditions over a matter of weeks. it uses a 0 as normal, and drought is shown in terms of negative numbers; for example, negative 2 is moderate drought, negative 3 is severe drought, and negative 4 is extreme drought. palmer's algorithm also is used to describe wet spells, using corresponding positive numbers. palmer also developed a formula for standardizing drought calculations for each individual location based on the variability of precipitation and temperature at that location. the palmer index can therefore be applied to any site for which sufficient precipitation and temperature data is available. critics have complained that the utility of the palmer index is weakened by the arbitrary nature of palmer's algorithms, including the technique used for standardization. the palmer index's inability to account for snow and frozen ground also is cited as a weakness. the palmer index is widely used operationally, with palmer maps published weekly by the united states government's national oceanic and atmospheric administration. it also has been used by climatologists to standardize global long-term drought analysis. global palmer data sets have been developed based on instrumental records beginning in the 19th century. in addition, dendrochronology has been used to generate estimated palmer index values for north america for the past 2000 years, allowing analysis of long term drought trends. it has also been used as a means of explaining the late bronze age collapse. in the us, regional palmer maps are featured on the cable channel weatherscan.