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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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Comparison of the Integrated Approach (IA) and 3-pentad (conventional) methods (Matsumoto, 1997) for 23.875 N, 83.875 E.(a) The red line shows the IOM/IWM onset and withdrawal pentads for 1978–2007, where as the black line shows the results from the 3-pentad method. The blue dots show the purely manual corrected time series. (b) The blue bars show pentads where the threshold is exceeded. The grey arrows show onset/withdrawal pentad according to conventional method and the blue arrows show the IA method. Black arrows represent coincident onset/withdrawal pentads between the two methods.
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pone-0104386-g003: Comparison of the Integrated Approach (IA) and 3-pentad (conventional) methods (Matsumoto, 1997) for 23.875 N, 83.875 E.(a) The red line shows the IOM/IWM onset and withdrawal pentads for 1978–2007, where as the black line shows the results from the 3-pentad method. The blue dots show the purely manual corrected time series. (b) The blue bars show pentads where the threshold is exceeded. The grey arrows show onset/withdrawal pentad according to conventional method and the blue arrows show the IA method. Black arrows represent coincident onset/withdrawal pentads between the two methods.

Mentions: From the multi-year averages, we can determine the onset progression and withdrawal regression over the whole region of interest. The onset progression looks similar when comparing results from the two methods (Figure 3) with a general direction from east to west, and a more north-easterly direction over North India. However, the IA method yields an earlier onset (roughly 1–2 pentads) over much of the region.


Testing a flexible method to reduce false monsoon onsets.

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

Comparison of the Integrated Approach (IA) and 3-pentad (conventional) methods (Matsumoto, 1997) for 23.875 N, 83.875 E.(a) The red line shows the IOM/IWM onset and withdrawal pentads for 1978–2007, where as the black line shows the results from the 3-pentad method. The blue dots show the purely manual corrected time series. (b) The blue bars show pentads where the threshold is exceeded. The grey arrows show onset/withdrawal pentad according to conventional method and the blue arrows show the IA method. Black arrows represent coincident onset/withdrawal pentads between the two methods.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0104386-g003: Comparison of the Integrated Approach (IA) and 3-pentad (conventional) methods (Matsumoto, 1997) for 23.875 N, 83.875 E.(a) The red line shows the IOM/IWM onset and withdrawal pentads for 1978–2007, where as the black line shows the results from the 3-pentad method. The blue dots show the purely manual corrected time series. (b) The blue bars show pentads where the threshold is exceeded. The grey arrows show onset/withdrawal pentad according to conventional method and the blue arrows show the IA method. Black arrows represent coincident onset/withdrawal pentads between the two methods.
Mentions: From the multi-year averages, we can determine the onset progression and withdrawal regression over the whole region of interest. The onset progression looks similar when comparing results from the two methods (Figure 3) with a general direction from east to west, and a more north-easterly direction over North India. However, the IA method yields an earlier onset (roughly 1–2 pentads) over much of the region.

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