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(a) Topography of Papua Province and its borders (NASA SRTM 90 m [Jarvis et al., 2008]). The small black triangle marks the highest peak of Puncak Jaya. (b) Mean monthly precipitation (shaded, TRMM 3B43V7 products) and mean 10 m winds (vector, NASA MERRA reanalysis) from January 1998 to December 2013 for January. (c) As in Figure 1b but for July. The black shadow box (Figures 1a-1c) is the study area. 

(a) Topography of Papua Province and its borders (NASA SRTM 90 m [Jarvis et al., 2008]). The small black triangle marks the highest peak of Puncak Jaya. (b) Mean monthly precipitation (shaded, TRMM 3B43V7 products) and mean 10 m winds (vector, NASA MERRA reanalysis) from January 1998 to December 2013 for January. (c) As in Figure 1b but for July. The black shadow box (Figures 1a-1c) is the study area. 

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Understanding the controls on stable isotopologues of tropical rainfall is critical for paleoclimatic reconstruction from tropical ice core records. The southern Papua region, Indonesia has a unique climate regime that allows for the evaluation of the influence of precipitation and convective activity on seasonal rainfall δ18O. The influence of the...

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... climate setting of Papua, which is located within the WPWP, is controlled mainly by the annual movement of the ITCZ [McAlpine et al., 1983;Prentice and Hope, 2007]. During austral summer (the "northwest season," December to March), the climate is dominated by the monsoon westerlies which result from veering of the northeast trade winds over the equator due to heating over the New Guinea landmasses (Figure 1b). The south- east trades flow over the entire Papua region during the austral winter (the "southeast season," May to October) ( Figure 1c) [Prentice and Hope, 2007]. The temperature regime is typically equatorial with a seasonal range of ~1 to 3°C and a diurnal range of ~6 to 14°C. Moderately high temperatures occur at sea level, varying between 22°C and 34°C. The southern mountain ranges of Papua experience maximum (minimum) temperature in December-February (June-August), but the more equatorward regions experience two temperature maxima (minima) in May and November (February and July). The average regional surface lapse rate is ~5.0°C/km as determined by weather station data. Below 2500 m asl, the average level of the top of the atmospheric boundary layer [Prentice and Hope, 2007], the lapse rate is 5.2°C/km and above that altitude the rate decreases to 4.6°C/km [Permana, ...
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... climate setting of Papua, which is located within the WPWP, is controlled mainly by the annual movement of the ITCZ [McAlpine et al., 1983;Prentice and Hope, 2007]. During austral summer (the "northwest season," December to March), the climate is dominated by the monsoon westerlies which result from veering of the northeast trade winds over the equator due to heating over the New Guinea landmasses (Figure 1b). The south- east trades flow over the entire Papua region during the austral winter (the "southeast season," May to October) ( Figure 1c) [Prentice and Hope, 2007]. The temperature regime is typically equatorial with a seasonal range of ~1 to 3°C and a diurnal range of ~6 to 14°C. Moderately high temperatures occur at sea level, varying between 22°C and 34°C. The southern mountain ranges of Papua experience maximum (minimum) temperature in December-February (June-August), but the more equatorward regions experience two temperature maxima (minima) in May and November (February and July). The average regional surface lapse rate is ~5.0°C/km as determined by weather station data. Below 2500 m asl, the average level of the top of the atmospheric boundary layer [Prentice and Hope, 2007], the lapse rate is 5.2°C/km and above that altitude the rate decreases to 4.6°C/km [Permana, ...
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... of the surrounding oceans, Papua is one of the wettest regions on Earth with many sites receiving 2500-4500 mm of precipitation annually [Prentice and Hope, 2007]. Due to its location within the WPWP, there is little seasonal variability in rainfall. For most parts of Papua, rainfall maxima (minima) occur during the northwest (southeast) season, but in the southern part of the central mountain ranges the seasonality is reversed (see the study area in Figure 1) [Aldrian and Dwi Susanto, 2003]. The annual precipitation in this region ranges between ~5000 and 12,000 mm with the highest amount (~12,500 mm/yr) recorded at Mile50 station (4.28°S, 137.01°E; 617 m asl) [Permana, 2011]. During the northwest season all parts of the island are almost con- tinuously wet (Figure 1b), with the monsoon westerlies prevailing up to about 600 mb. The weather pattern is dominated by a low-pressure system associated with enhanced deep convective activity which is driven by the position of the ITCZ in the Southern Hemisphere. During the southeast season the southern part of the island experiences drier conditions with minimum rainfall in June-July (Figure 1c). However, the rainfall amount in the lower part of the study area is higher than during the northwest season. In the southeast season, the trade wind inversion (TWI) layer is present at about 2000 m asl south of the mountains in Papua as a result of the ITCZ position in the Northern Hemisphere [McAlpine et al., 1983;Prentice and Hope, 2007]. The TWI layer, indicated by a strong temperature inversion, is a controlling factor for cloud development which caps local convective circulation and mixing processes. During this season, meteorological data from lowland stations demonstrate that rainfall at nighttime (6 P.M.-6 A.M. local time) is much higher than at daytime (6 A.M.-6 P.M. local time), with differences -1c) is the study ...
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... of the surrounding oceans, Papua is one of the wettest regions on Earth with many sites receiving 2500-4500 mm of precipitation annually [Prentice and Hope, 2007]. Due to its location within the WPWP, there is little seasonal variability in rainfall. For most parts of Papua, rainfall maxima (minima) occur during the northwest (southeast) season, but in the southern part of the central mountain ranges the seasonality is reversed (see the study area in Figure 1) [Aldrian and Dwi Susanto, 2003]. The annual precipitation in this region ranges between ~5000 and 12,000 mm with the highest amount (~12,500 mm/yr) recorded at Mile50 station (4.28°S, 137.01°E; 617 m asl) [Permana, 2011]. During the northwest season all parts of the island are almost con- tinuously wet (Figure 1b), with the monsoon westerlies prevailing up to about 600 mb. The weather pattern is dominated by a low-pressure system associated with enhanced deep convective activity which is driven by the position of the ITCZ in the Southern Hemisphere. During the southeast season the southern part of the island experiences drier conditions with minimum rainfall in June-July (Figure 1c). However, the rainfall amount in the lower part of the study area is higher than during the northwest season. In the southeast season, the trade wind inversion (TWI) layer is present at about 2000 m asl south of the mountains in Papua as a result of the ITCZ position in the Northern Hemisphere [McAlpine et al., 1983;Prentice and Hope, 2007]. The TWI layer, indicated by a strong temperature inversion, is a controlling factor for cloud development which caps local convective circulation and mixing processes. During this season, meteorological data from lowland stations demonstrate that rainfall at nighttime (6 P.M.-6 A.M. local time) is much higher than at daytime (6 A.M.-6 P.M. local time), with differences -1c) is the study ...
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... of the surrounding oceans, Papua is one of the wettest regions on Earth with many sites receiving 2500-4500 mm of precipitation annually [Prentice and Hope, 2007]. Due to its location within the WPWP, there is little seasonal variability in rainfall. For most parts of Papua, rainfall maxima (minima) occur during the northwest (southeast) season, but in the southern part of the central mountain ranges the seasonality is reversed (see the study area in Figure 1) [Aldrian and Dwi Susanto, 2003]. The annual precipitation in this region ranges between ~5000 and 12,000 mm with the highest amount (~12,500 mm/yr) recorded at Mile50 station (4.28°S, 137.01°E; 617 m asl) [Permana, 2011]. During the northwest season all parts of the island are almost con- tinuously wet (Figure 1b), with the monsoon westerlies prevailing up to about 600 mb. The weather pattern is dominated by a low-pressure system associated with enhanced deep convective activity which is driven by the position of the ITCZ in the Southern Hemisphere. During the southeast season the southern part of the island experiences drier conditions with minimum rainfall in June-July (Figure 1c). However, the rainfall amount in the lower part of the study area is higher than during the northwest season. In the southeast season, the trade wind inversion (TWI) layer is present at about 2000 m asl south of the mountains in Papua as a result of the ITCZ position in the Northern Hemisphere [McAlpine et al., 1983;Prentice and Hope, 2007]. The TWI layer, indicated by a strong temperature inversion, is a controlling factor for cloud development which caps local convective circulation and mixing processes. During this season, meteorological data from lowland stations demonstrate that rainfall at nighttime (6 P.M.-6 A.M. local time) is much higher than at daytime (6 A.M.-6 P.M. local time), with differences -1c) is the study ...
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... of the surrounding oceans, Papua is one of the wettest regions on Earth with many sites receiving 2500-4500 mm of precipitation annually [Prentice and Hope, 2007]. Due to its location within the WPWP, there is little seasonal variability in rainfall. For most parts of Papua, rainfall maxima (minima) occur during the northwest (southeast) season, but in the southern part of the central mountain ranges the seasonality is reversed (see the study area in Figure 1) [Aldrian and Dwi Susanto, 2003]. The annual precipitation in this region ranges between ~5000 and 12,000 mm with the highest amount (~12,500 mm/yr) recorded at Mile50 station (4.28°S, 137.01°E; 617 m asl) [Permana, 2011]. During the northwest season all parts of the island are almost con- tinuously wet (Figure 1b), with the monsoon westerlies prevailing up to about 600 mb. The weather pattern is dominated by a low-pressure system associated with enhanced deep convective activity which is driven by the position of the ITCZ in the Southern Hemisphere. During the southeast season the southern part of the island experiences drier conditions with minimum rainfall in June-July (Figure 1c). However, the rainfall amount in the lower part of the study area is higher than during the northwest season. In the southeast season, the trade wind inversion (TWI) layer is present at about 2000 m asl south of the mountains in Papua as a result of the ITCZ position in the Northern Hemisphere [McAlpine et al., 1983;Prentice and Hope, 2007]. The TWI layer, indicated by a strong temperature inversion, is a controlling factor for cloud development which caps local convective circulation and mixing processes. During this season, meteorological data from lowland stations demonstrate that rainfall at nighttime (6 P.M.-6 A.M. local time) is much higher than at daytime (6 A.M.-6 P.M. local time), with differences -1c) is the study ...
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... ET AL. TROPICAL RAINFALL ISOTOPES FROM PAPUAseason (except in July). During September 2013 the troposphere was mainly dominated by the shallow mode of LH. In this study, we define the maximum altitude of LH release as the highest altitude with a heating rate of more than 1.6°C/d, which represents the average maximum latent heating per rainfall rate of 1 cm/d during the onset of the Indian monsoon and generates relatively high precipitation [Magagi and Barros, 2004]. In addition, the mean altitude of LH release is defined as the average altitude weighted by LH release below the maximum altitude. The corresponding temperature at the mean altitude of LH release may indicate the temperature at mean condensation level at which precipitation forms. An estimate of the atmospheric tem- peratures associated with the altitude of LH release was calculated based on the monthly temperature lapse rates and mean surface temperatures derived from PTFI meteorological data ( Figure S12). The strong relation- ship between monthly regional δ 18 O and the mean altitude of LH release (R = À0.79, p = 0.0001; Figure 13b) and its corresponding atmospheric temperatures (R = 0.77, p = 0.0002; Figure 13c) from January 2013 to March 2015 compares well with the relationship between regional δ 18 O and regional convective activity (OLR; R = 0.68, p = 0.002) over the same period. This result confirms that the effect of convection on rainfall δ 18 O is associated with the temperature effect at the mean condensation level on seasonal rainfall δ 18 ...
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... ET AL. TROPICAL RAINFALL ISOTOPES FROM PAPUAseason (except in July). During September 2013 the troposphere was mainly dominated by the shallow mode of LH. In this study, we define the maximum altitude of LH release as the highest altitude with a heating rate of more than 1.6°C/d, which represents the average maximum latent heating per rainfall rate of 1 cm/d during the onset of the Indian monsoon and generates relatively high precipitation [Magagi and Barros, 2004]. In addition, the mean altitude of LH release is defined as the average altitude weighted by LH release below the maximum altitude. The corresponding temperature at the mean altitude of LH release may indicate the temperature at mean condensation level at which precipitation forms. An estimate of the atmospheric tem- peratures associated with the altitude of LH release was calculated based on the monthly temperature lapse rates and mean surface temperatures derived from PTFI meteorological data ( Figure S12). The strong relation- ship between monthly regional δ 18 O and the mean altitude of LH release (R = À0.79, p = 0.0001; Figure 13b) and its corresponding atmospheric temperatures (R = 0.77, p = 0.0002; Figure 13c) from January 2013 to March 2015 compares well with the relationship between regional δ 18 O and regional convective activity (OLR; R = 0.68, p = 0.002) over the same period. This result confirms that the effect of convection on rainfall δ 18 O is associated with the temperature effect at the mean condensation level on seasonal rainfall δ 18 ...
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... ET AL. TROPICAL RAINFALL ISOTOPES FROM PAPUAseason (except in July). During September 2013 the troposphere was mainly dominated by the shallow mode of LH. In this study, we define the maximum altitude of LH release as the highest altitude with a heating rate of more than 1.6°C/d, which represents the average maximum latent heating per rainfall rate of 1 cm/d during the onset of the Indian monsoon and generates relatively high precipitation [Magagi and Barros, 2004]. In addition, the mean altitude of LH release is defined as the average altitude weighted by LH release below the maximum altitude. The corresponding temperature at the mean altitude of LH release may indicate the temperature at mean condensation level at which precipitation forms. An estimate of the atmospheric tem- peratures associated with the altitude of LH release was calculated based on the monthly temperature lapse rates and mean surface temperatures derived from PTFI meteorological data ( Figure S12). The strong relation- ship between monthly regional δ 18 O and the mean altitude of LH release (R = À0.79, p = 0.0001; Figure 13b) and its corresponding atmospheric temperatures (R = 0.77, p = 0.0002; Figure 13c) from January 2013 to March 2015 compares well with the relationship between regional δ 18 O and regional convective activity (OLR; R = 0.68, p = 0.002) over the same period. This result confirms that the effect of convection on rainfall δ 18 O is associated with the temperature effect at the mean condensation level on seasonal rainfall δ 18 ...
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... the δ 18 O enrichment of rain during winter 2013 was due to the predominant strong shallow convection system that generated a greater amount of precipitation from relatively lower cloud heights and warmer temperatures, with mean altitudes of LH release between 1.5 and 4 km with corresponding temperatures between 5 and 18°C. In contrast, during summer 2013, a large-scale deep convection generated precipitation from higher and colder clouds with mean altitudes of LH release between 4 and 7 km, and with correspond- ing temperatures between À6 and 5°C, leading to the depletion of rainfall δ 18 O. The most enriched δ 18 O was observed in September 2013 which was likely due to the formation of precipitation at lower and warmer clouds with maximum altitude of LH release at ~1.5 km and with a corresponding temperature of ~18°C (Figures 13b and 13c), while the low rainfall amount during this month (Figure 11, fourth panel) may have been due to the weakest latent heat release in 2013 (Figure ...
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... the δ 18 O enrichment of rain during winter 2013 was due to the predominant strong shallow convection system that generated a greater amount of precipitation from relatively lower cloud heights and warmer temperatures, with mean altitudes of LH release between 1.5 and 4 km with corresponding temperatures between 5 and 18°C. In contrast, during summer 2013, a large-scale deep convection generated precipitation from higher and colder clouds with mean altitudes of LH release between 4 and 7 km, and with correspond- ing temperatures between À6 and 5°C, leading to the depletion of rainfall δ 18 O. The most enriched δ 18 O was observed in September 2013 which was likely due to the formation of precipitation at lower and warmer clouds with maximum altitude of LH release at ~1.5 km and with a corresponding temperature of ~18°C (Figures 13b and 13c), while the low rainfall amount during this month (Figure 11, fourth panel) may have been due to the weakest latent heat release in 2013 (Figure ...
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... the δ 18 O enrichment of rain during winter 2013 was due to the predominant strong shallow convection system that generated a greater amount of precipitation from relatively lower cloud heights and warmer temperatures, with mean altitudes of LH release between 1.5 and 4 km with corresponding temperatures between 5 and 18°C. In contrast, during summer 2013, a large-scale deep convection generated precipitation from higher and colder clouds with mean altitudes of LH release between 4 and 7 km, and with correspond- ing temperatures between À6 and 5°C, leading to the depletion of rainfall δ 18 O. The most enriched δ 18 O was observed in September 2013 which was likely due to the formation of precipitation at lower and warmer clouds with maximum altitude of LH release at ~1.5 km and with a corresponding temperature of ~18°C (Figures 13b and 13c), while the low rainfall amount during this month (Figure 11, fourth panel) may have been due to the weakest latent heat release in 2013 (Figure ...
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... to April), whereas the d values at TPR and GRS are relatively constant with differences of 0.6‰ and À0.6‰, respectively (Figure ...
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... ET AL. TROPICAL RAINFALL ISOTOPES FROM PAPUAThe additional moisture from land surface recycling during transport from oceanic sources to the precipita- tion sites can have considerable impact on isotopic composition in precipitation [Salati et al., 1979]. The land surface recycling has been shown to yield precipitation with higher d values over the Amazon Basin [Gat and Matsui, 1991;Windhorst et al., 2013]. Additional recycled moisture within the air masses over the Amazon Basin also contributes to 18 O-enriched rainfall during austral winter when the southeast trade wind-related precipitation prevails [Windhorst et al., 2013]. In our study area, the mean d values at each station are higher than 10‰ during both the first and second collection periods (Table 2), suggesting the large contribution of recycled moisture to precipitation. During summer, additional evaporated moisture likely originates from terrestrial evaporation over the northern tropical rainforest, while during winter the recycled moisture comes from evaporation over the southern tropical rainforest. To evaluate the contribution of land surface recycling on seasonal rainfall δ 18 O, the seasonal MWLs for summer and winter 2013 (ENSO-normal period) were calculated to derive the mean d values for each season. The result shows that the MWLs for summer and winter 2013 are very close, with intercept (d) values of 14.80‰ and 14.38‰, respectively (Figure 12c). The nearly equal d values suggest similarly significant contribution of land surface recycling in rainfall 18 O enrichment in both seasons. Consequently, land surface recycling only causes a minor seasonal effect on rainfall δ 18 O in our study area (Figure ...
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... ET AL. TROPICAL RAINFALL ISOTOPES FROM PAPUAThe additional moisture from land surface recycling during transport from oceanic sources to the precipita- tion sites can have considerable impact on isotopic composition in precipitation [Salati et al., 1979]. The land surface recycling has been shown to yield precipitation with higher d values over the Amazon Basin [Gat and Matsui, 1991;Windhorst et al., 2013]. Additional recycled moisture within the air masses over the Amazon Basin also contributes to 18 O-enriched rainfall during austral winter when the southeast trade wind-related precipitation prevails [Windhorst et al., 2013]. In our study area, the mean d values at each station are higher than 10‰ during both the first and second collection periods (Table 2), suggesting the large contribution of recycled moisture to precipitation. During summer, additional evaporated moisture likely originates from terrestrial evaporation over the northern tropical rainforest, while during winter the recycled moisture comes from evaporation over the southern tropical rainforest. To evaluate the contribution of land surface recycling on seasonal rainfall δ 18 O, the seasonal MWLs for summer and winter 2013 (ENSO-normal period) were calculated to derive the mean d values for each season. The result shows that the MWLs for summer and winter 2013 are very close, with intercept (d) values of 14.80‰ and 14.38‰, respectively (Figure 12c). The nearly equal d values suggest similarly significant contribution of land surface recycling in rainfall 18 O enrichment in both seasons. Consequently, land surface recycling only causes a minor seasonal effect on rainfall δ 18 O in our study area (Figure ...
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... results of this study are consistent with previous studies in Puerto Rico [Scholl et al., 2009] and in Hawaii [Scholl and Coplen, 2010], which suggest that the seasonal isotopic composition of tropical rainfall is correlated with cloud height and its corresponding (atmospheric) temperature. One common feature that exists among these oceanic islands (Puerto Rico, Hawaii, and our study area) is the appearance of the TWI layer during the winter season which effectively caps vertical motion from below and limits the height of cloud development. The prominent shallow mode of LH during winter 2013 evinces the TWI layer in our study area (Figure 13a). In this season, local convection and the interaction between strong southeast trade winds and diurnal winds result in intense precipitation which is mostly nocturnal below the TWI layer (Figure 2). Since the TWI layer limits the development of cloud heights, the generated precipitation is predominated by warm rain from shallow cumulus clouds with a latent heating peak in the 1-3 km range [ Liu et al., 2015]. This condition is supported by a higher fraction of low and midlevel clouds from June to August 2013 in the study area (Figure ...
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... results of this study are consistent with previous studies in Puerto Rico [Scholl et al., 2009] and in Hawaii [Scholl and Coplen, 2010], which suggest that the seasonal isotopic composition of tropical rainfall is correlated with cloud height and its corresponding (atmospheric) temperature. One common feature that exists among these oceanic islands (Puerto Rico, Hawaii, and our study area) is the appearance of the TWI layer during the winter season which effectively caps vertical motion from below and limits the height of cloud development. The prominent shallow mode of LH during winter 2013 evinces the TWI layer in our study area (Figure 13a). In this season, local convection and the interaction between strong southeast trade winds and diurnal winds result in intense precipitation which is mostly nocturnal below the TWI layer (Figure 2). Since the TWI layer limits the development of cloud heights, the generated precipitation is predominated by warm rain from shallow cumulus clouds with a latent heating peak in the 1-3 km range [ Liu et al., 2015]. This condition is supported by a higher fraction of low and midlevel clouds from June to August 2013 in the study area (Figure ...
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... comparison of mean monthly amount-weighted isotopic values between the ENSO-normal period (2013/2014) and the El Niño period (2014/2015) shows that the δ 18 O (δD) has increased by ~1.6‰ (~11.4‰) at PORT in the El Niño period from December to September. At TPR, δ 18 O (δD) has also increased by ~1.8‰ (~14.8‰) from December to September, while at GRS, δ 18 O (δD) has increased by ~2‰ (~15‰) from February to August (Figure 10; δD data are not shown). In contrast, the d value has decreased by ~1.2‰ at PORT in the El Niño period with a decrease of ~2.6‰ during austral summer O and d values between ENSO-normal period (January 2013 to February 2014) and El Niño period (December 2014 to September 2015) at PORT (December to September), TPR (December to September), and GRS (February to August) ...
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... and E/P derived from MERRA reanalysis data in the study area during 2013 ( Figure S11). This result indi- cates that moisture convergence also has no significant effect on seasonal rainfall δ 18 O in the ...
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... decrease in d values during the El Niño period in the lowland station (Figure 10), particularly during summer, may be due to cooler SSTs around Papua as the warm pool shifts to the central Pacific. This leads to a decrease in evaporation rates and associated kinetic fractionation in the ocean and thus to decreased d values of evaporated water vapor and precipitation [Merlivat and Jouzel, ...
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... the other hand, meteorological data comparison between 2013 and 2015 suggests that temperatures at lowland (PORT) and midland (TPR) stations are relatively cooler during El Niño than during the ENSO-normal period which is likely due to the cooler SSTs in the western Pacific ( Figure S9). Meanwhile, at high altitude (GRS), temperature is cooler in summer but warmer in winter during El Niño than during the ENSO-normal period. A warmer winter in the Papua highland is possibly due to heat circulation in the tropical troposphere which warms the tropospheric temperatures, usually for up to 6 months, after El Niño begins [Sobel et al., 2002]. As a result, local/regional precipitation at all elevations was lower during the El Niño than during the ENSO-normal period, with much drier conditions occurring during the winter (Figure S9). At the same time, the convective activity over Papua was suppressed during El Niño, as shown by higher OLR values in 2015 than in 2013 ( Figure S9). This is likely the main cause for the observed enrichment of isotopic ratios in rainfall at all stations ( Figure ...
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... the ~2 year collection period that covered the ENSO-normal and the El Niño period, the correlation between δ 18 O and local precipitation is negative and insignificant at PORT (R = À0.14, p = 0.53) but significant at TPR (R = À0.56, p = 0.005) and GRS (R = À0.53, p = 0.04). On the other hand, the δ 18 O values are significantly negatively correlated with temperature at PORT (R = À0.67, p < 0.001) and TPR (R = À0.61, p = 0.002) but insignificant at GRS (R = À0.33, p = 0.22). At regional scales, a significant and negative correlation exists between δ 18 O and precipitation (R = À0.40, p = 0.05) but a stronger significant positive correlation exists between δ 18 O and OLR values (R = 0.74, p < 0.001) (Figure 11). Again, this suggests that regional convection, rather than precipitation, plays a dominant role in rainfall δ 18 O variation during these ...
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... factor that may affect the rainfall isotopic composition is a postcondensational effect such as raindrop (secondary) evaporation at the subcloud base during rainfall due to surface low humidity, which can decrease d values [Rozanski et al., 1993] and result in 18 O-enriched rainfall. However, this condition is unlikely to occur in a humid region such as Papua. This is supported by the observed mean relative humidity (generally above 80%) at all stations and elevations during 2013 ( Figure S11). In summary, moisture origins and land surface recycling along the transport pathways contribute to a minor seasonal effect on rainfall isotopic composition in the region. Other factors such as moisture convergence and raindrop (secondary) evaporation during rainfall also have no significant influences on rainfall isotopic composition on seasonal ...
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... austral winter, water vapor originates from the seas to the southeast of Papua, which have long-term mean SSTs of 25-29°C, mean surface relative humidity of 72-82%, and mean surface wind speed of ~7 m/s (the southeast trade winds). These conditions are comparable to conditions during the summer over the seas to the northwest of Papua where the initial water vapor originates, with long-term mean SSTs of 27-29°C, mean surface relative humidity of 74-84%, and mean surface wind speed decreases from ~7 m/s to ~3-5 m/s as the northeast trade winds turn into the monsoon westerlies ( Figure S10). The nearly identical meteorological conditions over the oceanic origins during both seasons in the Papua region may indicate that the isotopic compositions of evaporating water vapor are also nearly identical. A previous study conducted in Australia discusses the moisture sources to the south of Papua and suggests that there was no significant difference in the rainfall δ 18 O when the majority of the moisture originated from oceanic sources [Crawford et al., 2013]. ...
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... is difficult to empirically demonstrate this temperature effect [e.g., Scholl et al., 2009] without the echo top data from our study area. Fortunately, the mean echo top altitudes also correspond to the mean condensation levels which can be estimated by the latent heat (LH) release in the troposphere [e.g., Thompson et al., 2000]. The latent heat in the troposphere is released mainly by the condensation process when precipitation forms in clouds. The latent heating data sets have been retrieved by several different algorithms from TRMM satellite measurements [Tao et al., 2006]. For simplicity, the monthly LH vertical profile derived from TRMM product 3A12 V7 is used as a proxy of mean condensation level in the troposphere. Unfortunately, the LH products are available only over the ocean. Since our sites are close to the Arafura Sea, we use the closest gridded LH data at 136.25°E, 5.25°S to represent our sites in the current study. The vertical profile of monthly LH release from January 2013 to March 2015 is shown in Figure 13a. Generally, it exhibits two peaks in the troposphere, at ~0.5-2.5 km and at ~3-8 km. This is consistent with the double-peak structure of latent heating in the tropics suggested by previous studies [Zhang et al., 2010;Liu et al., 2015]. The shallow mode of the LH peak is associated with shallow convection systems that generate warm rain and low-level heating from shallow cumulus clouds (echo top less than 5 km) and partially from cumulus congestus clouds (echo top between 5 and 8 km). The deep mode of the LH peak corresponds to large, deep, organized MCSs with echo tops greater than 10 km [Zhang et al., 2010;Liu et al., 2015]. The deep mode of LH dominated the shallow mode during the northwest (monsoon) season in 2013 (except in March), while the dominant mode was reversed during the ...
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... simplicity, it is assumed that back trajectories that were conducted in section 5.1 provide information about the moisture origin and transport paths. During January to March 2013 and December 2013 (austral summer), moisture originating from the seas to the northwest of Papua is transported to the collection sites by the monsoon westerlies (Figure 12a). Water vapor is moved across the Banda Sea, the Arafura Sea, and the northern Papua tropical rainforest before reaching the collection sites. In contrast, from May to October 2013 (austral winter) the southeast trade winds transported moisture from the seas to the southeast of Papua across the southern Papua tropical rainforest (Figure 12b). The moisture sources in April and November 2013 (transitional) are composed of a combination of both the seas to the northwest and southeast of Papua (not shown). Air mass trajectories in 2015 show a similar result as in 2013 (not ...
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... simplicity, it is assumed that back trajectories that were conducted in section 5.1 provide information about the moisture origin and transport paths. During January to March 2013 and December 2013 (austral summer), moisture originating from the seas to the northwest of Papua is transported to the collection sites by the monsoon westerlies (Figure 12a). Water vapor is moved across the Banda Sea, the Arafura Sea, and the northern Papua tropical rainforest before reaching the collection sites. In contrast, from May to October 2013 (austral winter) the southeast trade winds transported moisture from the seas to the southeast of Papua across the southern Papua tropical rainforest (Figure 12b). The moisture sources in April and November 2013 (transitional) are composed of a combination of both the seas to the northwest and southeast of Papua (not shown). Air mass trajectories in 2015 show a similar result as in 2013 (not ...
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... details of the collection processes and a description of the rain collectors are located in Text S1 and Figure S1 in the supporting information, respectively. The first collection period for TMK, KK, and TPR began on 29 January 2013, while at PORT it began earlier (26 January 2013) and at GRS it began later (30 January 2013). The fewest number of samples were collected at the highland station GRS from May to June 2013 due to a tunnel collapse at the PTFI training facility in mid-May. The second collection period, at PORT and TPR, started on 11 December 2014, while at GRS it started on 13 December ...
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... studies [Risi et al., 2008a;Vimeux et al., 2011;Tremoy et al., 2012;Gao et al., 2013;Moerman et al., 2013] have demonstrated correlations between tropical rainfall δ 18 O and large-scale convective activity at intra- seasonal timescales. Kurita et al. [2011] showed that rainfall isotopic variation in Maritime Continent Indonesia is associated with the MJO intraseasonal cycle. The MJO cycle is defined as the eastward propaga- tion of mesoscale convective systems (MCSs) with period of ~30-90 days which is characterized by the deep organized convective systems and cloud clusters along the tropical band causing high precipitation [Madden and Julian, 1972]. The regional rainfall δ 18 O is more significantly positively correlated with the OLR values over increasing time averages (Figures 6a and 6b). The regional rainfall δ 18 O time series is characterized by peak- trough variations with average amplitude of ~5‰ and with a periodicity of ~20-60 days using a band-pass filter ( Figure S7). Using spectral analyses, regional rainfall δ 18 O and OLR time series also indicate similar periodicities of ~15-70 days during the two collection periods which resemble the MJO periodicity in the region (Figures 8a and 8b). This is consistent with the findings of Moerman et al. [2013] in northern Borneo (4°N, 114°E), northwest of Papua. In their study, the authors concluded that the MJO strongly influences the intraseasonal variability of rainfall δ 18 O, with major depletion events (δ 18 O shifts up to ~10‰) coinciding with the active (wet) phases of the MJO. ...
Context 30
... (8°S-0°S, 130°E-141°E), which was known as Irian Jaya before 2002, is the largest and easternmost of the 34 provinces in the Republic of Indonesia. With a land area of 319,036 km 2 (16.62% of the Indonesian region), Papua and West Papua Provinces occupy the western half of New Guinea Island. Papua is bordered on the east by Papua New Guinea (PNG) and is surrounded by the Pacific Ocean to the north, the Arafura Sea (AS) to the south, and the Banda Sea (BS) to the west ( Figure 1a). The island is divided from the east-southeast to the west-northwest by mountain ranges that exceed 3500 m above sea level (m asl), including the highest peak, Puncak Jaya (4884 m asl). The Papua landmass is covered mostly by tropical rainforest with wetlands in some coastal regions and grasslands in the high ...

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... Such hydroclimate information may also be broad-scale, rather than local, as δ 18 O p values are increasingly shown to be a measure of regional scale changes in atmospheric circulation and moisture source changes, rather than simply relating to local processes such as precipitation amount (Kukla et al., 2024). In the tropical Pacific, regional scale changes in hydroclimate and δ 18 O p are closely related to the El Niño-Southern Oscillation (ENSO) on interannual timescales (e.g., Conroy et al., 2013;Martin et al., 2018;Moerman et al., 2013;Permana et al., 2016). However, the extent to which this information is inherited by the surface ocean, and subsequent marine paleoclimate proxies, remains an open question requiring a long-term precipitation and seawater isotope data. ...
... However, the extent to which this information is inherited by the surface ocean, and subsequent marine paleoclimate proxies, remains an open question requiring a long-term precipitation and seawater isotope data. Modern δ 18 O observational campaigns, though temporally limited, indeed record ENSO responses in western Pacific precipitation and seawater (Horikawa et al., 2023;Permana et al., 2016). Thus, if there is a robust relationship between δ 18 O p and δ 18 O sw, this framework can be applied to marine paleoclimate records to reconstruct interannual hydroclimate variability associated with ENSO through time. ...
... As cloud cover and precipitation increase, OLR decreases. Positive correlations between OLR and δ 18 O p have been noted in several studies of tropical Pacific precipitation (Martin et al., 2018;Moerman et al., 2013;Permana et al., 2016). In Palau, we see this same positive correlation between monthly OLR and δ 18 O p . ...
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... However, some recent studies have reported that the negative correlation between δ 18 O and local precipitation amount is not significant (2)(3)(4)(5)(6)(7)(8) or that even a weak positive correlation has been noted at some locations (9,10). On the basis of these studies, the validity of the amount effect has been questioned (11)(12)(13)(14)(15)(16). Should this amount effect relationship be disproven, several valuable paleoclimate records from the tropics would need urgent reappraisal. ...
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... In the equatorial region, the intra-seasonal oscillation is the main pattern for the precipitation δ 18 O (Figure 3). These patterns are further superimposed on the inter-annual pattern of precipitation isotopes affected by the ENSO (Belgaman et al., 2016;Permana et al., 2016). ...
... The δ 18 O data for PORT (Port site), TPR (Tembagapura), and GRS (Grasberg) are from the Byrd Polar and Climate Research Center, Ohio State University (https://byrd. osu.edu/research/groups/ice-core-paleoclimatology/data) (Permana et al., 2016). The δ 18 O data for Barisal, Port Blair, Nagoya, Mulu, Singapore, and Ho Chi Minh City are from the database of the IAEA's Coordinated Research Project (CRP) F31004 (https://figshare.com/s/fdfabb43a844cad530a5) ...
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... Vertical air motions have an important influence on the transport of moisture in the South Asia region. Several studies have demonstrated that strong convection, which prevails vertical upward motion and frequently occurs in the low latitudes during the monsoon season (He et al., 2021;Kurita, 2013), can contribute to the relatively low δ 18 O p in South Asia (Ansari et al., 2020;Chakraborty et al., 2016;Islam et al., 2021;Lekshmy et al., 2014;Permana et al., 2016). Recently, upstream accumulative convection has been suggested to help explain δ 18 O p variations in this region during the monsoon season (Cai & Tian, 2020;Midhun et al., 2018). ...
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... Following similar approaches to previous studies (e.g., Sodemann et al. 2008;Uemura et al. 2008; Barras and Simmonds 2009;Guan et al. 2013;Aemisegger et al. 2014;Permana et al. 2016;Sánchez-Murillo et al. 2017;Martin et al. 2018;He et al. 2018;Esquivel-Hernández et al. 2019;Papritz et al. 2021;Villiger et al. 2022;Dahinden et al. 2021), HYSPLIT was used to interpret the deuterium excess data. First, a temporal window of 24 months, from 1 July 2019 until 30 June 2021, was selected. ...
... As discussed in section 1, the amount effect is not a feature that has been universally observed, and a number of highfrequency collections in tropical sites have been conducted through the years where no significant correlation was observed between the rainfall isotopic composition and rain rates (Rhodes et al. 2006;Uemura et al. 2012;Moerman et al. 2013;Windhorst et al. 2013;Scholl and Murphy 2014;Conroy et al. 2016b;Permana et al. 2016;Schmitt et al. 2018). Compared to some of the studies where the amount effect was not observed, the results presented in this work are characterized by great spatial variability, even when comparing results sampled with the same frequency. ...
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