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Testing a flexible method to reduce false monsoon onsets.

Stiller-Reeve MA, Spengler T, Chu PS - PLoS ONE (2014)

Bottom Line: Another problem is that local communities or stakeholder groups may define the monsoon differently.The presented results yield improved information about the monsoon length and its interannual variability.This implies that we can potentially get a more detailed picture of local climate variations that can be used in more local climate application projects such as community-based adaptations.

View Article: PubMed Central - PubMed

Affiliation: Uni Research Climate, Bergen, Norway; Bjerknes Centre for Climate Research, Bergen, Norway.

ABSTRACT
To generate information about the monsoon onset and withdrawal we have to choose a monsoon definition and apply it to data. One problem that arises is that false monsoon onsets can hamper our analysis, which is often alleviated by smoothing the data in time or space. Another problem is that local communities or stakeholder groups may define the monsoon differently. We therefore aim to develop a technique that reduces false onsets for high-resolution gridded data, while also being flexible for different requirements that can be tailored to particular end-users. In this study, we explain how we developed our technique and demonstrate how it successfully reduces false onsets and withdrawals. The presented results yield improved information about the monsoon length and its interannual variability. Due to this improvement, we are able to extract information from higher resolution data sets. This implies that we can potentially get a more detailed picture of local climate variations that can be used in more local climate application projects such as community-based adaptations.

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Related in: MedlinePlus

The figure shows that average rainfall (mm/day) for an area 80–90 E 22–25 N, with a 9-pentad running mean smoothing to illustrate the seasonal transitions.The figure shows that the increase in rainfall at the beginning is more rapid than the decrease at the end of the monsoon/rainy season. The slower transition is reflected in the Integrated-Withdrawal-Matrix (IWM), which contains more combinations than the Integrated-Onset-Matrix (IOM). The IOM and IWM contain all combinations of binary numbers used in the automatic identification process.
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pone-0104386-g002: The figure shows that average rainfall (mm/day) for an area 80–90 E 22–25 N, with a 9-pentad running mean smoothing to illustrate the seasonal transitions.The figure shows that the increase in rainfall at the beginning is more rapid than the decrease at the end of the monsoon/rainy season. The slower transition is reflected in the Integrated-Withdrawal-Matrix (IWM), which contains more combinations than the Integrated-Onset-Matrix (IOM). The IOM and IWM contain all combinations of binary numbers used in the automatic identification process.

Mentions: We compiled the integrated matrices by randomly choosing hundred grid points and years within the region of interest from the APRHODITE data set (1978–2007). After applying the definition to obtain the binary vectors, we manually allocated the onset and withdrawal pentad based on our prior knowledge. The algorithm then stores the 6-pentad combination starting at the chosen onset pentad and adds these combinations to the IOM. As the onset transition is more rapid compared to the withdrawal [15], [29], the IWM contains more combinations than the IOM. For example the combination [1 1 1 1 1 1] indicates a very sudden onset and is contained in both the IOM and the IWM. However, the combination [1 0 1 0 1 0] is a more gradual transition and is only contained in the IWM. The difference in transition speed is also evident in Figure 2, which shows the average 9-pentad running mean rainfall (mm/day) for a region in northern India. During the onset, the rainfall increases from 0.5 mm/day to 6 mm/day, faster than it decreases during the withdrawal.


Testing a flexible method to reduce false monsoon onsets.

Stiller-Reeve MA, Spengler T, Chu PS - PLoS ONE (2014)

The figure shows that average rainfall (mm/day) for an area 80–90 E 22–25 N, with a 9-pentad running mean smoothing to illustrate the seasonal transitions.The figure shows that the increase in rainfall at the beginning is more rapid than the decrease at the end of the monsoon/rainy season. The slower transition is reflected in the Integrated-Withdrawal-Matrix (IWM), which contains more combinations than the Integrated-Onset-Matrix (IOM). The IOM and IWM contain all combinations of binary numbers used in the automatic identification process.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126718&req=5

pone-0104386-g002: The figure shows that average rainfall (mm/day) for an area 80–90 E 22–25 N, with a 9-pentad running mean smoothing to illustrate the seasonal transitions.The figure shows that the increase in rainfall at the beginning is more rapid than the decrease at the end of the monsoon/rainy season. The slower transition is reflected in the Integrated-Withdrawal-Matrix (IWM), which contains more combinations than the Integrated-Onset-Matrix (IOM). The IOM and IWM contain all combinations of binary numbers used in the automatic identification process.
Mentions: We compiled the integrated matrices by randomly choosing hundred grid points and years within the region of interest from the APRHODITE data set (1978–2007). After applying the definition to obtain the binary vectors, we manually allocated the onset and withdrawal pentad based on our prior knowledge. The algorithm then stores the 6-pentad combination starting at the chosen onset pentad and adds these combinations to the IOM. As the onset transition is more rapid compared to the withdrawal [15], [29], the IWM contains more combinations than the IOM. For example the combination [1 1 1 1 1 1] indicates a very sudden onset and is contained in both the IOM and the IWM. However, the combination [1 0 1 0 1 0] is a more gradual transition and is only contained in the IWM. The difference in transition speed is also evident in Figure 2, which shows the average 9-pentad running mean rainfall (mm/day) for a region in northern India. During the onset, the rainfall increases from 0.5 mm/day to 6 mm/day, faster than it decreases during the withdrawal.

Bottom Line: Another problem is that local communities or stakeholder groups may define the monsoon differently.The presented results yield improved information about the monsoon length and its interannual variability.This implies that we can potentially get a more detailed picture of local climate variations that can be used in more local climate application projects such as community-based adaptations.

View Article: PubMed Central - PubMed

Affiliation: Uni Research Climate, Bergen, Norway; Bjerknes Centre for Climate Research, Bergen, Norway.

ABSTRACT
To generate information about the monsoon onset and withdrawal we have to choose a monsoon definition and apply it to data. One problem that arises is that false monsoon onsets can hamper our analysis, which is often alleviated by smoothing the data in time or space. Another problem is that local communities or stakeholder groups may define the monsoon differently. We therefore aim to develop a technique that reduces false onsets for high-resolution gridded data, while also being flexible for different requirements that can be tailored to particular end-users. In this study, we explain how we developed our technique and demonstrate how it successfully reduces false onsets and withdrawals. The presented results yield improved information about the monsoon length and its interannual variability. Due to this improvement, we are able to extract information from higher resolution data sets. This implies that we can potentially get a more detailed picture of local climate variations that can be used in more local climate application projects such as community-based adaptations.

Show MeSH
Related in: MedlinePlus