Suchergebnisse

Kebakaran hutan dan lahan yang terjadi setiap tahun di Indonesia sebagian besar berlokasi di lahan gambut. Bencana tersebut berdampak besar terhadap berbagai aspek kehidupan, salah satunya adalah terdegradasinya lahan gambut tropis. Pada tahun 2014, kebakaran hutan dan lahan di Kepulauan Meranti turut berkontribusi terhadap bencana kabut asap yang dirasakan hingga ke Singapura dan Malaysia. Pemerintah Indonesia melalui Badan Restorasi Gambut dan Mangrove (BRGM) telah berupaya melakukan restorasi ekosistem gambut. Pemantuan data hotspot dan curah hujan secara rutin dilakukan sebagai salah satu upaya mitigasi bencana kebakaran hutan dan lahan. Penelitian ini bertujuan untuk mengidentifikasi pola distribusi hotspot dan variasi Standardized Precipitation Index (SPI) serta mengetahui korelasinya terhadap kebakaran hutan dan lahan. Penelitian ini menggunakan data hotspot dari Moderate Resolution Imaging Spectroradiometer (MODIS) dan curah hujan dari Climate Vunerabilities Group InfraRed Precipitation with Station data (CHIRPS) selama 21 tahun yang dianalisis secara spasial-temporal dan koefisien korelasi Pearson. Sekitar 97.2% atau 7403 hotspot berada pada lahan gambut. Frekuensi hotspot tertinggi terjadi pada 2014, 2005, dan 2019. Distribusi hotspot bulanan mengikuti fluktuasi curah hujan dengan jumlah kejadian tertinggi terjadi pada Februari-Maret. Nilai SPI-1, SPI-3, SPI-4, SPI-6, SPI-12 tahun 2001-2021 bervariasi dari -3.5 hingga 3.0. Selama 21 tahun, Kepulauan Meranti telah mengalami musim basah dan kering yang ekstrim. Nilai SPI dan hotspot bervariasi mengikuti fenomena El Nino dan La Nina. Nilai SPI-1, SPI-3, SPI-4, SPI-6 berkorelasi kuat dengan data hotspot 2001-2021 dengan nilai r lebih dari 60%. Korelasi antara SPI dengan curah hujan mampu meprediksi puncak periode basah dan kering. Variabel hotspot dan SPI tidak dapat dipisahkan karena bisa menjadi salah satu faktor penting yang membantu proses perumusan arahan mitigasi dan adaptasi bencana kebakaran hutan dan lahan.ABSTRACTForest and land fires in Indonesia every year are mainly located on peatlands. The disaster had a significant impact on various aspects of life, one of which was the degradation of tropical peatlands. In 2014, forest and land fires in the Kepulauan Meranti contributed to the haze disaster that was felt as far as Singapore and Malaysia. Through the Peat and Mangrove Restoration Agency (BRGM), the Government of Indonesia has tried to restore the peat ecosystem. Monitoring of hotspot and rainfall data is routinely carried out as one of the efforts to mitigate forest and land fire disasters. This study aims to identify the distribution pattern of hotspots and Standardized Precipitation Index (SPI) variations and determine their correlation to forest and land fires. This study uses hotspot data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and rainfall from Climate Vulnerabilities Group InfraRed Precipitation with Station data (CHIRPS) for 21 years which were analyzed spatially-temporal and Pearson correlation coefficient. Around 97.2% or 7403 hotspots are on peatlands. The highest frequency of hotspots occurred in 2014, 2005, and 2019. The monthly distribution of hotspots follows fluctuations in rainfall, with the highest number of occurrences occurring from February to March. The values of SPI-1, SPI-3, SPI-4, SPI-6, SPI-12 in 2001-2021 varied from -3.5 to 3.0. For 21 years, the Meranti Islands have experienced extreme wet and dry seasons. The value of SPI and hotspot varies according to El Nino and La Nina phenomena. The values of SPI-1, SPI-3, SPI-4, SPI-6 are strongly correlated with the 2001-2021 hotspot data with an r-value of more than 60%. The correlation between SPI and rainfall can predict the peak of the wet and dry periods. Hotspot and SPI variables cannot be separated because they can be important factors that help formulate directives for mitigation and adaptation to forest and land fire disasters.

11 páginas, 7 figuras, 1 tabla.-- This work is licensed under a Creative Commons License. ; At present, the Standardized Precipitation Index (SPI) is the most widely used drought index to provide good estimations about the intensity, magnitude and spatial extent of droughts. The main advantage of the SPI in comparison with other indices is the fact that the SPI enables both determination of drought conditions at different time scales and monitoring of different drought types. It is widely accepted that SPI time scales affect different sub-systems in the hydrological cycle due to the fact that the response of the different water usable sources to precipitation shortages can be very different. The long time scales of SPI are related to hydrological droughts (river flows and reservoir storages). Nevertheless, few analyses empirically verify these statements or the usefulness of the SPI time scales to monitor drought. In this paper, the SPI at different time scales is compared with surface hydrological variables in a big closed basin located in the central Spanish Pyrenees. We provide evidence about the way in which the longer (>12 months) SPI time scales may not be useful for drought quantification in this area. In general, the surface flows respond to short SPI time scales whereas the reservoir storages respond to longer time scales (7–10 months). Nevertheless, important seasonal differences can be identified in the SPI-usable water sources relationships. This suggests that it is necessary to test the drought indices and time scales in relation to their usefulness for monitoring different drought types under different environmental conditions and water demand situations. ; The authors want to acknowledge financial support from the following projects: BSO2002-02743, REN2003-07453, CGL2005-04508/BOS, PIRIHEROS (REN2003- 08678/HID) and CANOA (CGL 2004-04919-c02-01), funded by Ministerio de Ciencia y Tecnología (Spain) and UE-FEDER, and "Programa de grupos de investigación consolidados" (BOA 48 of 20-04-2005), funded by Aragon Government. Research of the first author was supported by postdoctoral fellowship by the Ministerio de Educación y Ciencia (Spain). ; Peer reviewed

We propose a new climatic drought index: the Standardized Precipitation Evapotranspiration Index (SPEI). The SPEI is based on precipitation and temperature data, and has the advantage of combining a multi-scalar character with the capacity to include the effects of temperature variability on drought assessment. The procedure to calculate the index is detailed, and involves a climatic water balance, the accumulation of deficit/surplus at different time scales, and adjustment to a Log-logistic probability distribution. Mathematically, the SPEI is similar to the Standardized Precipitation Index (SPI), but includes the role of temperature. As the SPEI is based on a water balance, it can be compared to the self-calibrated Palmer Drought Severity Index (sc-PDSI). We compared time series of the three indices for a set of observatories with different climate characteristics, located in different parts of the world. Under global warming conditions only the sc-PDSI and SPEI identified an increase in drought severity associated with higher water demand due to evapotranspiration. Relative to the sc-PDSI, the SPEI has the advantage of being multi-scalar, which is crucial for drought analysis and monitoring. ; This work has been supported by the research projects CGL2006-11619/HID, CGL2008- 01189/BTE, and CGL2008-1083/CLI financed by the Spanish Commission of Science and Technology and FEDER, EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7- ENV-2007-1-212250) financed by the VII Framework Programme of the European Commission, "Las sequías climáticas en la cuenca del Ebro y su respuesta hidrológica" and "La nieve en el Pirineo Aragonés: distribución espacial y su respuesta a las condiciones climáticas" Financed by "Obra Social La Caixa" and the Aragón Government and the "Programa de grupos de investigación consolidados" financed by the Aragón Government.ÿ ; Peer reviewed

We mapped – for the first time – the probability of occurrence of drought over Spain, with the overriding aim of improving current drought assessment, management and mitigation measures and strategies across the region. We employed two well-established drought indices: the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Drought characteristics (i.e. duration and severity) were characterised at 1-, 3-, 6- and 12-month, implying that drought event is attained only when the index values are lower than zero. We applied the extreme value theory to map drought hazard probability. Following this procedure, we tested different thresholds to generate the peak-over-threshold drought severity and magnitude series, besides evaluating different three-parametric distributions and thresholds to fit these series. Our results demonstrate that the Generalized Pareto distribution performs well in estimating the frequencies of drought magnitude and duration, with good agreement between the observed and modelled data when using upper percentiles to generate the peak-over-threshold series. Spatially, our estimations suggest a higher probability of extreme drought events in southern and central areas of Spain, compared to northern and eastern regions. Nevertheless, there are strong differences in drought probability estimations between drought indices (i.e. SPI and SPEI), as well as among drought timescales. ; This work was supported by the research projects CGL2014-52135-C03-01 and PCIN-2015-220 financed by the Spanish Commission of Science and Technology and FEDER, 1560/2015: Herramientas de monitorización de la vegetación mediante modelización ecohidrológica en parques continentales financed by the Red de Parques Nacionales, IMDROFLOOD financed by the Water Works 2014 co-funded call of the European Commission and INDECIS, which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by MINECO with co-funding by the European Union 30 (Grant 690462).

44 Pags., 4 Tabls., 12 Figs. The definitive version is available at: http://ascelibrary.org/heo/ ; In this study, the authors investigated an approach to calculate the standardized streamflow index (SSI), which allows accurate spatial and temporal comparison of the hydrological conditions of a stream or set of streams. For this purpose, the capability of six three-parameter distributions (lognormal, Pearson Type III, log-logistic, general extreme value, generalized Pareto, and Weibull) and two different approaches to select the most suitable distribution the best monthly fit (BMF) and the minimum orthogonal distance (MD), were tested by using a monthly streamflow data set for the Ebro Basin (Spain). This large Mediterranean basin is characterized by high variability in the magnitude of streamflows and in seasonal regimes. The results show that the most commonly used probability distributions for flow frequency analysis provided good fits to the streamflow series. Thus, the visual inspection of the L-moment diagrams and the results of the Kolmogorov-Smirnov test did not enable the selection of a single optimum probability distribution. However, no single probability distribution for all the series was suitable for obtaining a robust standardized streamflow series because each of the distributions had one or more limitations. The BMF and MD approaches improved the results in the expected average, standard deviation, and the frequencies of extreme events of the SSI series in relation to the selection of a unique distribution for each station. The BMF and MD approaches involved using different probability distributions for each gauging station and month of the year to calculate the SSI. Both approaches are easy to apply and they provide very similar results in the quality of the obtained hydrological drought indexes. The proposed procedures are very flexible for analyses involving contrasting hydrological regimes and flow characteristics. ; This work has been supported by research projects grant numbers CGL2008-01189/BTE and CGL2006-11619/HID financed by the Spanish Commission of Science and Technology and FEDER; EUROGEOSS grant number (FP7-ENV-2008-1-226487), and ACQWA grant number (FP7-ENV-2007-1-212250) financed by the VII Framework Programme of the European Commission; and "Las sequías climáticas en la cuenca del Ebro y su respuesta hidrológica" and "La nieve en el Pirineo aragonés: Distribución espacial y su respuesta a las condiciones climáticas" financed by "Obra Social La Caixa" and the Aragón government. ; Peer reviewed

A monthly global dataset of a multiscalar drought index is presented and compared in terms of spatial and temporal variability with the existing continental and global drought datasets based on the Palmer drought severity index (PDSI). The presented dataset is based on the standardized precipitation evapotranspiration index (SPEI). The index was obtained using the CRU TS3.0 dataset at a spatial resolution of 0.5°. The advantages of the new dataset are that; i) it improves the spatial resolution of the unique global drought dataset at a global scale; ii) it is spatially and temporally comparable to other datasets, given the probabilistic nature of the SPEI, and, in particular; iii) it enables identification of various drought types, given the multiscalar character of the SPEI. The dataset is freely available on the web page of the Spanish National Research Council (CSIC) in three different formats (NetCDF, binary raster, and plain text). ; This work has been supported by the research projects CGL2008-01189/BTE and CGL2006-11619/HID financed by the Spanish Commission of Science and Technology and FEDER, EUROGEOSS (FP7-ENV- 2008-1-226487) and ACQWA (FP7-ENV-2007-1- 212250) financed by the VII Framework Programme of the European Commission, "Las sequías climáticas en la cuenca del Ebro y su respuesta hidrológica" and "La nieve en el Pirineo aragonés: Distribución espacial y su respuesta a las condiciones climática" Financed by "Obra Social La Caixa" and the Aragón Government ; Peer reviewed

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) ; Processo FAPESP: 2012/19821-1 ; Processo FAPESP: 2015/21586-9 ; Droughts are natural events that can cause water scarcity and can consequently have undesired environmental, social and political effects. Because droughts are related to land use and land cover modifications, satellite images are used to monitor and identify drought episodes through indices as Standardized Precipitation Index based on rainfall data and vegetation-based indices as Normalized Difference Vegetation Index (NDVI). Changes in vegetation cover have as impact the increasing of the land surface temperature (LST) that is a significant indicative of drought occurrence. This work explored the NDVI-LST relation through the Vegetation Health Index (VHI) in a tropical environment in Tiet River, State of So Paulo, Brazil, in order to assess changes in vegetation condition in two periods (2000 and 2014). Results showed that stressed areas are coincident with areas presenting high rate of modification in land cover; this areas presented low values of VHI and high values of LST. The worst conditions are verified in 2014, the same period of the most severe drought occurrence that reduced storage capacity in reservoirs in Tiet River.

41 Pag., 14 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/00221694 ; The influence of climate variation on the availability of water resources was analyzed in the headwaters of the Tagus River basin using two drought indices, the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI). This basin is highly regulated and strategic, and contains two hyperannual reservoirs that are the origin of the water supply system for Mediterranean areas of southeast Spain. The indices confirmed that drought conditions have prevailed in the headwaters of the Tagus River since the 1970s. The responses in river discharge and reservoir storage were slightly higher when based on the SPEI rather than the SPI, which indicates that although precipitation had a major role in explaining temporal variability in the analyzed parameters, the influence of temperature was not negligible. Moreover, the greatest response in hydrological variables was evident over longer timescales of the climatic drought indices. Although the effect of climate variability on water resources was substantial during the analyzed period, we also showed a major change in hydrological–climatic relationships in regulated systems including reservoir storage and outflow. These were closely related to changes in external demand following commencement of the water transfer system to the Júcar and Segura basins after the 1980s. The marked reduction in water availability in the basin, which is related to more frequent droughts, contrasts with the amount of water transferred, which shows a clear upward trend associated with increasing water demand in the Mediterranean basin. ; This work has been supported by the research projects CGL2006-11619/HID, CGL2008-01189/BTE, and CGL2008-1083/CLI financed by the Spanish Commission of Science and Technology and FEDER, EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7-ENV-2007-1- 212250) financed by the VII Framework Programme of the European Commission, STRIVER (Strategy and methodology for Improved IWRM—An integrated interdisciplinary assessment in four twinning river basins), financed by the VI Framework Programme of the European Commission. "Las sequías climáticas en la cuenca del Ebro y su respuesta hidrológica" Financed by "Obra Social La Caixa" and the Aragón Government and "Programa de grupos de investigación consolidados" financed by the Aragón Government. ; Peer reviewed