MANSOUR Bekhta - Academia.edu (original) (raw)
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Flooding appears to be increasing in Kelantan, Malaysia, in terms of frequency as well as magnitu... more Flooding appears to be increasing in Kelantan, Malaysia, in terms of frequency as well as magnitude. This is likely to be due to changes in precipitation, but may also be contributed to by land use change. The Mann-Kendall non-parametric method was used to test for trends in streamflow and precipitation at the 90% significance level. Several significant trends in streamflow were found for the upstream (River Galas) and downstream (River Kelantan) sub-catchments for all variables (annual, seasonal and monthly time-series). In particular, streamflow increased in all seasons in the upstream sub-catchment, but increased in the wet season and decreased in the dry season downstream. Several trends were also observed for precipitation. Precipitation trends were increasing in the wet season and decreasing in the dry season for both upstream and downstream sub-catchments. Analysis of land use change revealed that most changes occurred through conversion of forest to agricultural land (i.e. rubber and oil palm), predominantly in the upstream sub-catchment. The analysis suggests a clear association between streamflow change and precipitation change, but also reveals that land use change may be an important contributing factor, particularly in the upstream sub-catchment. Copyright 2010 Royal Meteorological Society KEY WORDS climate change; stream flow change; precipitation change; land use change; time-series; trend analysis
This study concentrated on the assessment of two operational high-resolution satellite-based rain... more This study concentrated on the assessment of two operational high-resolution satellite-based rainfall products, Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS) and NOAA CPC Morphing Technique (CMORPH) over Algeria. The assessment was carried out for a duration of 19-years ranging between 1998 and 2016 using 20 rain gauge datasets. The study area can be divided into five regions (zones) according to K€ oppen climate classification (CSA, BSK, BWK, BSH, and BWH). Both satellite derived rainfall estimates (SRE); (CHIRPS and CMORPH) were evaluated over these regions. Continuous statistics was employed to measure their performance in evaluating and reproducing rainfall while categorical statistics employed on daily time scale to assess the ability of SRE in detecting rain/no rain events. Correlation Coefficient (R), Bias and Root Mean Square Error (RMSE) are employed on daily, monthly as well as on annual timescales. At daily scale, most SRE showed unsatisfactorily performance over all the five regions with exception for CMORPH products exhibiting better performance. However, as the time step augmented, the performance of SRE enhanced. At monthly time scale a higher agreement was observed. The CHIRPS performed the best (R ¼ 0.9), whereas CMORPH-CRTv1.0 showed relatively weaker but good correlation (R ¼ 0.83). At annually time scale CHIRPS has a better performance in CSA, BSK regions, on the other hand CMORPH demonstrate a better results BSH, BWK, BWH regions. The study demonstrate that reliable evaluation of rainfall in Algeria with different climate zones employing satellite-based precipitation estimation products remains a challenge.
Flooding appears to be increasing in Kelantan, Malaysia, in terms of frequency as well as magnitu... more Flooding appears to be increasing in Kelantan, Malaysia, in terms of frequency as well as magnitude. This is likely to be due to changes in precipitation, but may also be contributed to by land use change. The Mann-Kendall non-parametric method was used to test for trends in streamflow and precipitation at the 90% significance level. Several significant trends in streamflow were found for the upstream (River Galas) and downstream (River Kelantan) sub-catchments for all variables (annual, seasonal and monthly time-series). In particular, streamflow increased in all seasons in the upstream sub-catchment, but increased in the wet season and decreased in the dry season downstream. Several trends were also observed for precipitation. Precipitation trends were increasing in the wet season and decreasing in the dry season for both upstream and downstream sub-catchments. Analysis of land use change revealed that most changes occurred through conversion of forest to agricultural land (i.e. rubber and oil palm), predominantly in the upstream sub-catchment. The analysis suggests a clear association between streamflow change and precipitation change, but also reveals that land use change may be an important contributing factor, particularly in the upstream sub-catchment. Copyright 2010 Royal Meteorological Society KEY WORDS climate change; stream flow change; precipitation change; land use change; time-series; trend analysis
This study concentrated on the assessment of two operational high-resolution satellite-based rain... more This study concentrated on the assessment of two operational high-resolution satellite-based rainfall products, Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS) and NOAA CPC Morphing Technique (CMORPH) over Algeria. The assessment was carried out for a duration of 19-years ranging between 1998 and 2016 using 20 rain gauge datasets. The study area can be divided into five regions (zones) according to K€ oppen climate classification (CSA, BSK, BWK, BSH, and BWH). Both satellite derived rainfall estimates (SRE); (CHIRPS and CMORPH) were evaluated over these regions. Continuous statistics was employed to measure their performance in evaluating and reproducing rainfall while categorical statistics employed on daily time scale to assess the ability of SRE in detecting rain/no rain events. Correlation Coefficient (R), Bias and Root Mean Square Error (RMSE) are employed on daily, monthly as well as on annual timescales. At daily scale, most SRE showed unsatisfactorily performance over all the five regions with exception for CMORPH products exhibiting better performance. However, as the time step augmented, the performance of SRE enhanced. At monthly time scale a higher agreement was observed. The CHIRPS performed the best (R ¼ 0.9), whereas CMORPH-CRTv1.0 showed relatively weaker but good correlation (R ¼ 0.83). At annually time scale CHIRPS has a better performance in CSA, BSK regions, on the other hand CMORPH demonstrate a better results BSH, BWK, BWH regions. The study demonstrate that reliable evaluation of rainfall in Algeria with different climate zones employing satellite-based precipitation estimation products remains a challenge.