Local patterns and trends of the Standard Precipitation Index in southern Portugal (1940–1999)
This paper analyzes the yearly changes in precipitation from 1940 to 1999 on local and regional scales over the southern region of continental Portugal, which has large areas threatened by desertification. The Standard Precipitation Index (SPI) time series with the 12-month time scale is calculated...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2011-05-01
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| Series: | Advances in Geosciences |
| Online Access: | http://www.adv-geosci.net/30/11/2011/adgeo-30-11-2011.pdf |
| _version_ | 1818981586086920192 |
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| author | A. C. Costa |
| author_facet | A. C. Costa |
| author_sort | A. C. Costa |
| collection | DOAJ |
| description | This paper analyzes the yearly changes in precipitation
from 1940 to 1999 on local and regional scales over the southern region of
continental Portugal, which has large areas threatened by desertification.
The Standard Precipitation Index (SPI) time series with the 12-month time
scale is calculated for 43 meteorological stations. A geostatistical
approach is used to evaluate the temporal dynamics of the spatial patterns
of precipitation. The spatial homogeneity of the SPI is evaluated for each
decade. Afterwards, a geostatistical simulation algorithm (direct sequential
simulation) is used to produce 100 equiprobable maps of the SPI for each
year. This gridded data set (6000 maps with 800 m × 800 m grid cells) is
then used to produce yearly scenarios of the SPI from 1940 to 1999, and
uncertainty evaluations of the produced scenarios. The linear trend of SPI
values over the sixty years period is calculated at each grid cell of the
scenarios' maps using a nonparametric estimator. Wilcoxon-Mann-Whitney
one-sided tests are used to compare the local median of the SPI in 1940/1969
with its median in 1970/1999. Results show that moderate drought conditions
occur frequently over the study region, except in the northwest coast.
Severe drought frequency patterns are found in areas of the centre and
southeast regions. A significant trend towards drying occurs in the centre
region and in the northeast. Considering the amount of water consumption and
irrigation already required in some municipalities, water shortage due to
drought is a viable threat in most of the Alentejo region if those local
trends persist. |
| first_indexed | 2024-12-20T17:33:40Z |
| format | Article |
| id | doaj.art-08413ae4a72341b391ab8f7ce8cc75f6 |
| institution | Directory Open Access Journal |
| issn | 1680-7340 1680-7359 |
| language | English |
| last_indexed | 2024-12-20T17:33:40Z |
| publishDate | 2011-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Advances in Geosciences |
| spelling | doaj.art-08413ae4a72341b391ab8f7ce8cc75f62022-12-21T19:31:17ZengCopernicus PublicationsAdvances in Geosciences1680-73401680-73592011-05-0130111610.5194/adgeo-30-11-2011Local patterns and trends of the Standard Precipitation Index in southern Portugal (1940–1999)A. C. Costa0ISEGI, Universidade Nova de Lisboa, Lisbon, PortugalThis paper analyzes the yearly changes in precipitation from 1940 to 1999 on local and regional scales over the southern region of continental Portugal, which has large areas threatened by desertification. The Standard Precipitation Index (SPI) time series with the 12-month time scale is calculated for 43 meteorological stations. A geostatistical approach is used to evaluate the temporal dynamics of the spatial patterns of precipitation. The spatial homogeneity of the SPI is evaluated for each decade. Afterwards, a geostatistical simulation algorithm (direct sequential simulation) is used to produce 100 equiprobable maps of the SPI for each year. This gridded data set (6000 maps with 800 m × 800 m grid cells) is then used to produce yearly scenarios of the SPI from 1940 to 1999, and uncertainty evaluations of the produced scenarios. The linear trend of SPI values over the sixty years period is calculated at each grid cell of the scenarios' maps using a nonparametric estimator. Wilcoxon-Mann-Whitney one-sided tests are used to compare the local median of the SPI in 1940/1969 with its median in 1970/1999. Results show that moderate drought conditions occur frequently over the study region, except in the northwest coast. Severe drought frequency patterns are found in areas of the centre and southeast regions. A significant trend towards drying occurs in the centre region and in the northeast. Considering the amount of water consumption and irrigation already required in some municipalities, water shortage due to drought is a viable threat in most of the Alentejo region if those local trends persist.http://www.adv-geosci.net/30/11/2011/adgeo-30-11-2011.pdf |
| spellingShingle | A. C. Costa Local patterns and trends of the Standard Precipitation Index in southern Portugal (1940–1999) Advances in Geosciences |
| title | Local patterns and trends of the Standard Precipitation Index in southern Portugal (1940–1999) |
| title_full | Local patterns and trends of the Standard Precipitation Index in southern Portugal (1940–1999) |
| title_fullStr | Local patterns and trends of the Standard Precipitation Index in southern Portugal (1940–1999) |
| title_full_unstemmed | Local patterns and trends of the Standard Precipitation Index in southern Portugal (1940–1999) |
| title_short | Local patterns and trends of the Standard Precipitation Index in southern Portugal (1940–1999) |
| title_sort | local patterns and trends of the standard precipitation index in southern portugal 1940 ndash 1999 |
| url | http://www.adv-geosci.net/30/11/2011/adgeo-30-11-2011.pdf |
| work_keys_str_mv | AT accosta localpatternsandtrendsofthestandardprecipitationindexinsouthernportugal1940ndash1999 |