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Composite snow depth anomalies in centimeters for the positive minus negative dipole events for the following winter (upper panel) and spring (central panel) seasons. Continuous (dashed) contours indicate positive (negative) anomalies. Light (dark) grey shading illustrates the areas of significance at 90% (95%) confidence level. Lower panel illustrates the spatial correlation between the winter and spring snow depth. Areas exceeding 0.6 are shaded in the lower panel.
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This study investigates the possible physical processes for the delayed response of the East Asia–West Pacific summer monsoon to the Indian Ocean Dipole Mode (IODM) through the Eurasian continent based on composite and correlation analyses. The media carrying the memory for this delayed response is identified.
Results reveal that the peak positive...
Contexts in source publication
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... strength of the snow anomalies during spring is much more than during winter. This analysis suggests that the IODM may be associated with the winter and spring snow distribution over the Eurasian region. In particular, the positive phase of the dipole during summer/autumn may favour heavy snow during the following winter/spring over Eastern Eurasia north of the Korea–Japan (EENKJ) peninsula ( Figure 2 upper and central panels). Significant negative snow anomalies also prevail over the region centered at 70 ° N 60 ° E (Figure 3 central panel). Such dipole snow depth patterns have also been associated with the Indian monsoon rainfall (Kripalani and Kulkarni, 1999) and with the Korean monsoon rainfall (Kripalani et al ., 2002). However the positive snow anomalies just north of Korea–Japan are more prominent. The spatial CC pattern between winter and spring snow depth shows high positive relationship due to persistence (Figure 2 lower panel). These correlations are based on the 35 years data and are highly significant. For a sample of this size, the significant CC is ∼ 0 . 35 (0.45) at 95 (99) % confidence level. Such high persistence between winter and spring snow depths has also been noted by Wu and Kirtman (2007). Again the above composites also contain ENSO-related years. Hence to further ascertain the possible role of the dipole mode on the snow distribution over EENKJ, area–mean time series of snow depth during winter (DJF) and spring (MAM) are prepared over the EENKJ sector (45 ° N–60 ° N, 120 ° E–140 ° E: based on the anomalies observed in Figure 3 central panel). Again lead/lag CCs are computed between the snow depth time series and indices of the IODM and ENSO phenomena as shown in Figure 2. These correlations are based on the 1976–1995 period focusing on the inter-decadal period following the climate shift (significant CC at 99% confidence level is ∼ 0 . 55 for a sample of this size). A similar pattern of evolution of CCs with the IODM index from the preceding spring is noticed with maximum positive significant CC during the preceding autumn with winter snow and during preceding summer/autumn with the spring snow. While a similar evolutionary pattern of CCs is also discernable with the ENSO index, ...
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... strength of the snow anomalies during spring is much more than during winter. This analysis suggests that the IODM may be associated with the winter and spring snow distribution over the Eurasian region. In particular, the positive phase of the dipole during summer/autumn may favour heavy snow during the following winter/spring over Eastern Eurasia north of the Korea–Japan (EENKJ) peninsula ( Figure 2 upper and central panels). Significant negative snow anomalies also prevail over the region centered at 70 ° N 60 ° E (Figure 3 central panel). Such dipole snow depth patterns have also been associated with the Indian monsoon rainfall (Kripalani and Kulkarni, 1999) and with the Korean monsoon rainfall (Kripalani et al ., 2002). However the positive snow anomalies just north of Korea–Japan are more prominent. The spatial CC pattern between winter and spring snow depth shows high positive relationship due to persistence (Figure 2 lower panel). These correlations are based on the 35 years data and are highly significant. For a sample of this size, the significant CC is ∼ 0 . 35 (0.45) at 95 (99) % confidence level. Such high persistence between winter and spring snow depths has also been noted by Wu and Kirtman (2007). Again the above composites also contain ENSO-related years. Hence to further ascertain the possible role of the dipole mode on the snow distribution over EENKJ, area–mean time series of snow depth during winter (DJF) and spring (MAM) are prepared over the EENKJ sector (45 ° N–60 ° N, 120 ° E–140 ° E: based on the anomalies observed in Figure 3 central panel). Again lead/lag CCs are computed between the snow depth time series and indices of the IODM and ENSO phenomena as shown in Figure 2. These correlations are based on the 1976–1995 period focusing on the inter-decadal period following the climate shift (significant CC at 99% confidence level is ∼ 0 . 55 for a sample of this size). A similar pattern of evolution of CCs with the IODM index from the preceding spring is noticed with maximum positive significant CC during the preceding autumn with winter snow and during preceding summer/autumn with the spring snow. While a similar evolutionary pattern of CCs is also discernable with the ENSO index, ...
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... Pacific region plays a key role in explaining why a negative During the relationship, period 1961–1995, the CCs are eight not positive significant and at eight this weak WNPSM and a strong EASM occurs in the decay level. negative Wang IODM et al events . (2001) are reported identified a (see weak Section WNPSM 2). phase of ENSO warm episodes (similar rainfall pattern during The composite the decaying snow depth phase differences of El Nino between and is these evident two illustrated in Figure1 bottom panel). Hence there is a need by sets the of negative extreme dipole CCs with events ENSO for the index following during winter winter to demonstrate that the IODM remote forcing could also ( Figure 2). and spring are Furthermore, determined the (Figure 3). relation of Significant preceding positive winter be responsible for the EASM–WNPSM rainfall anoma- IODM snow depth index anomalies with subsequent (in centimeters) summer monsoon indicating rainfall heavy lies as illustrated in Figure 1 (bottom panel). over snow EAWNP are noted still in retains the north its significance of Korea–Japan even sector after the in To ascertain whether the coherent negative precipita- ENSO particular effect over is eliminated. the region On 45 ° the N–60 other ° N, hand 120 the ° E–140 relation ° E. tion anomalies prevailing over the East Asia–western of ENSO index and precipitation drops drastically once North Pacific (EAWNP) sector could be related with the IODM influence is removed. However, the fact that the IODM and/or ENSO phenomenon, a time series the partial correlation coefficient between the IODM of area–mean summer (JJA) precipitation over the sec- index and precipitation reduces once the ENSO effects tor occupied by intense negative precipitation anomalies are removed probably suggests that both IODM and (15 ° –35 ° N, 120 ° –140 ° E: Figure 1 bottom panel; hence- ENSO act cooperatively for the summer monsoon rainfall forth denoted as EAWNP region) is prepared. Lead/lag anomalies observed over the EAWNP domain (Figure 1 CCs are computed between this precipitation time series bottom panel). This analysis confirms that the IODM and indices of the IODM and ENSO phenomena. To fur- has a stronger relationship with the subsequent summer ther examine the respective influence of each of these monsoon precipitation distribution over EAWNP region phenomena, the partial correlation coefficient between the than the ENSO phenomenon. precipitation with the IODM removing ENSO effect and Kripalani et al . (2005) further suggested a possibility the precipitation with the ENSO mode removing IODM that this delayed influence could be carried by the effect is also computed. These correlations are based on Eurasian snow via the northern hemisphere mid-latitudes. the 1979–2003 period to focus on the recent inter-decadal To ascertain this aspect and to examine the influence period after the mid-1970s climate shift (Figure 2). For of the extreme dipole events on the snow over Eurasia, a sample of this size the significant CC is ∼ 0 . 4 (0.5) at similar composites for the Soviet snow depth data are determined. 95 (99) % confidence level. The CCs depict a gradual increase (in magnitude) from the preceding year spring (MAM-1), attaining higher values during the preceding autumn (SON-1) and winter (DJF0) and thereafter fall drastically for both IODM and ENSO indices (Figure2). Analysis reveals that the IODM index during the preceding autumn (SON-1) and winter (DJF0) shows significant negative relationship with the following summer monsoon rainfall over the EAWNP region, at 95% confidence level, implying less than normal rainfall following a positive IODM event. Although the ENSO index also conveys the delayed North Pacific region plays a key role in explaining why a negative During the relationship, period 1961–1995, the CCs are eight not positive significant and at eight this weak WNPSM and a strong EASM occurs in the decay level. negative Wang IODM et al events . (2001) are reported identified a (see weak Section WNPSM 2). phase of ENSO warm episodes (similar rainfall pattern during The composite the decaying snow depth phase differences of El Nino between and is these evident two illustrated in Figure1 bottom panel). Hence there is a need by sets the of negative extreme dipole CCs with events ENSO for the index following during winter winter to demonstrate that the IODM remote forcing could also (Figure 2). and spring are Furthermore, determined the (Figure 3). relation of Significant preceding positive winter be responsible for the EASM–WNPSM rainfall anoma- IODM snow depth index anomalies with subsequent (in centimeters) summer monsoon indicating rainfall heavy lies as illustrated in Figure 1 (bottom panel). over snow EAWNP are noted still in retains the north its significance of Korea–Japan even sector after the in To ascertain whether the coherent negative precipita- ENSO particular effect over is eliminated. the region On 45 ° the N–60 other ° N, hand 120 the ° E–140 relation ° E. tion anomalies prevailing over the East Asia–western of ENSO index and precipitation drops drastically once North Pacific (EAWNP) sector could be related with the IODM influence is removed. However, the fact that the IODM and/or ENSO phenomenon, a time series the partial correlation coefficient between the IODM of area–mean summer (JJA) precipitation over the sec- index and precipitation reduces once the ENSO effects tor occupied by intense negative precipitation anomalies are removed probably suggests that both IODM and (15 ° –35 ° N, 120 ° –140 ° E: Figure 1 bottom panel; hence- ENSO act cooperatively for the summer monsoon rainfall forth denoted as EAWNP region) is prepared. Lead/lag anomalies observed over the EAWNP domain (Figure 1 CCs are computed between this precipitation time series bottom panel). This analysis confirms that the IODM and indices of the IODM and ENSO phenomena. To fur- has a stronger relationship with the subsequent summer ther examine the respective influence of each of these monsoon precipitation distribution over EAWNP region phenomena, the partial correlation coefficient between the than the ENSO phenomenon. precipitation with the IODM removing ENSO effect and Kripalani et al . (2005) further suggested a possibility the precipitation with the ENSO mode removing IODM that this delayed influence could be carried by the effect is also computed. These correlations are based on Eurasian snow via the northern hemisphere mid-latitudes. the 1979–2003 period to focus on the recent inter-decadal To ascertain this aspect and to examine the influence period after the mid-1970s climate shift (Figure 2). For of the extreme dipole events on the snow over Eurasia, a sample of this size the significant CC is ∼ 0 . 4 (0.5) at similar composites for the Soviet snow depth data are determined. 95 (99) % confidence level. The CCs depict a gradual increase (in magnitude) from the preceding year spring (MAM-1), attaining higher values during the preceding autumn (SON-1) and winter (DJF0) and thereafter fall drastically for both IODM and ENSO indices (Figure2). Analysis reveals that the IODM index during the preceding autumn (SON-1) and winter (DJF0) shows significant negative relationship with the following summer monsoon rainfall over the EAWNP region, at 95% confidence level, implying less than normal rainfall following a positive IODM event. Although the ENSO index also conveys the delayed During the period 1961–1995, eight positive and eight negative IODM events are identified (see Section 2). The composite snow depth differences between these two sets of extreme dipole events for the following winter and spring are determined (Figure 3). Significant positive snow depth anomalies (in centimeters) indicating heavy snow are noted in the north of Korea–Japan sector in particular over the region 45 ° N–60 ° N, 120 ° E–140 ° ...
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... Pacific region plays a key role in explaining why a negative During the relationship, period 1961–1995, the CCs are eight not positive significant and at eight this weak WNPSM and a strong EASM occurs in the decay level. negative Wang IODM et al events . (2001) are reported identified a (see weak Section WNPSM 2). phase of ENSO warm episodes (similar rainfall pattern during The composite the decaying snow depth phase differences of El Nino between and is these evident two illustrated in Figure1 bottom panel). Hence there is a need by sets the of negative extreme dipole CCs with events ENSO for the index following during winter winter to demonstrate that the IODM remote forcing could also ( Figure 2). and spring are Furthermore, determined the (Figure 3). relation of Significant preceding positive winter be responsible for the EASM–WNPSM rainfall anoma- IODM snow depth index anomalies with subsequent (in centimeters) summer monsoon indicating rainfall heavy lies as illustrated in Figure 1 (bottom panel). over snow EAWNP are noted still in retains the north its significance of Korea–Japan even sector after the in To ascertain whether the coherent negative precipita- ENSO particular effect over is eliminated. the region On 45 ° the N–60 other ° N, hand 120 the ° E–140 relation ° E. tion anomalies prevailing over the East Asia–western of ENSO index and precipitation drops drastically once North Pacific (EAWNP) sector could be related with the IODM influence is removed. However, the fact that the IODM and/or ENSO phenomenon, a time series the partial correlation coefficient between the IODM of area–mean summer (JJA) precipitation over the sec- index and precipitation reduces once the ENSO effects tor occupied by intense negative precipitation anomalies are removed probably suggests that both IODM and (15 ° –35 ° N, 120 ° –140 ° E: Figure 1 bottom panel; hence- ENSO act cooperatively for the summer monsoon rainfall forth denoted as EAWNP region) is prepared. Lead/lag anomalies observed over the EAWNP domain (Figure 1 CCs are computed between this precipitation time series bottom panel). This analysis confirms that the IODM and indices of the IODM and ENSO phenomena. To fur- has a stronger relationship with the subsequent summer ther examine the respective influence of each of these monsoon precipitation distribution over EAWNP region phenomena, the partial correlation coefficient between the than the ENSO phenomenon. precipitation with the IODM removing ENSO effect and Kripalani et al . (2005) further suggested a possibility the precipitation with the ENSO mode removing IODM that this delayed influence could be carried by the effect is also computed. These correlations are based on Eurasian snow via the northern hemisphere mid-latitudes. the 1979–2003 period to focus on the recent inter-decadal To ascertain this aspect and to examine the influence period after the mid-1970s climate shift (Figure 2). For of the extreme dipole events on the snow over Eurasia, a sample of this size the significant CC is ∼ 0 . 4 (0.5) at similar composites for the Soviet snow depth data are determined. 95 (99) % confidence level. The CCs depict a gradual increase (in magnitude) from the preceding year spring (MAM-1), attaining higher values during the preceding autumn (SON-1) and winter (DJF0) and thereafter fall drastically for both IODM and ENSO indices (Figure2). Analysis reveals that the IODM index during the preceding autumn (SON-1) and winter (DJF0) shows significant negative relationship with the following summer monsoon rainfall over the EAWNP region, at 95% confidence level, implying less than normal rainfall following a positive IODM event. Although the ENSO index also conveys the delayed North Pacific region plays a key role in explaining why a negative During the relationship, period 1961–1995, the CCs are eight not positive significant and at eight this weak WNPSM and a strong EASM occurs in the decay level. negative Wang IODM et al events . (2001) are reported identified a (see weak Section WNPSM 2). phase of ENSO warm episodes (similar rainfall pattern during The composite the decaying snow depth phase differences of El Nino between and is these evident two illustrated in Figure1 bottom panel). Hence there is a need by sets the of negative extreme dipole CCs with events ENSO for the index following during winter winter to demonstrate that the IODM remote forcing could also (Figure 2). and spring are Furthermore, determined the (Figure 3). relation of Significant preceding positive winter be responsible for the EASM–WNPSM rainfall anoma- IODM snow depth index anomalies with subsequent (in centimeters) summer monsoon indicating rainfall heavy lies as illustrated in Figure 1 (bottom panel). over snow EAWNP are noted still in retains the north its significance of Korea–Japan even sector after the in To ascertain whether the coherent negative precipita- ENSO particular effect over is eliminated. the region On 45 ° the N–60 other ° N, hand 120 the ° E–140 relation ° E. tion anomalies prevailing over the East Asia–western of ENSO index and precipitation drops drastically once North Pacific (EAWNP) sector could be related with the IODM influence is removed. However, the fact that the IODM and/or ENSO phenomenon, a time series the partial correlation coefficient between the IODM of area–mean summer (JJA) precipitation over the sec- index and precipitation reduces once the ENSO effects tor occupied by intense negative precipitation anomalies are removed probably suggests that both IODM and (15 ° –35 ° N, 120 ° –140 ° E: Figure 1 bottom panel; hence- ENSO act cooperatively for the summer monsoon rainfall forth denoted as EAWNP region) is prepared. Lead/lag anomalies observed over the EAWNP domain (Figure 1 CCs are computed between this precipitation time series bottom panel). This analysis confirms that the IODM and indices of the IODM and ENSO phenomena. To fur- has a stronger relationship with the subsequent summer ther examine the respective influence of each of these monsoon precipitation distribution over EAWNP region phenomena, the partial correlation coefficient between the than the ENSO phenomenon. precipitation with the IODM removing ENSO effect and Kripalani et al . (2005) further suggested a possibility the precipitation with the ENSO mode removing IODM that this delayed influence could be carried by the effect is also computed. These correlations are based on Eurasian snow via the northern hemisphere mid-latitudes. the 1979–2003 period to focus on the recent inter-decadal To ascertain this aspect and to examine the influence period after the mid-1970s climate shift (Figure 2). For of the extreme dipole events on the snow over Eurasia, a sample of this size the significant CC is ∼ 0 . 4 (0.5) at similar composites for the Soviet snow depth data are determined. 95 (99) % confidence level. The CCs depict a gradual increase (in magnitude) from the preceding year spring (MAM-1), attaining higher values during the preceding autumn (SON-1) and winter (DJF0) and thereafter fall drastically for both IODM and ENSO indices (Figure2). Analysis reveals that the IODM index during the preceding autumn (SON-1) and winter (DJF0) shows significant negative relationship with the following summer monsoon rainfall over the EAWNP region, at 95% confidence level, implying less than normal rainfall following a positive IODM event. Although the ENSO index also conveys the delayed During the period 1961–1995, eight positive and eight negative IODM events are identified (see Section 2). The composite snow depth differences between these two sets of extreme dipole events for the following winter and spring are determined (Figure 3). Significant positive snow depth anomalies (in centimeters) indicating heavy snow are noted in the north of Korea–Japan sector in particular over the region 45 ° N–60 ° N, 120 ° E–140 ° ...
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... Pacific region plays a key role in explaining why a negative During the relationship, period 1961–1995, the CCs are eight not positive significant and at eight this weak WNPSM and a strong EASM occurs in the decay level. negative Wang IODM et al events . (2001) are reported identified a (see weak Section WNPSM 2). phase of ENSO warm episodes (similar rainfall pattern during The composite the decaying snow depth phase differences of El Nino between and is these evident two illustrated in Figure1 bottom panel). Hence there is a need by sets the of negative extreme dipole CCs with events ENSO for the index following during winter winter to demonstrate that the IODM remote forcing could also ( Figure 2). and spring are Furthermore, determined the (Figure 3). relation of Significant preceding positive winter be responsible for the EASM–WNPSM rainfall anoma- IODM snow depth index anomalies with subsequent (in centimeters) summer monsoon indicating rainfall heavy lies as illustrated in Figure 1 (bottom panel). over snow EAWNP are noted still in retains the north its significance of Korea–Japan even sector after the in To ascertain whether the coherent negative precipita- ENSO particular effect over is eliminated. the region On 45 ° the N–60 other ° N, hand 120 the ° E–140 relation ° E. tion anomalies prevailing over the East Asia–western of ENSO index and precipitation drops drastically once North Pacific (EAWNP) sector could be related with the IODM influence is removed. However, the fact that the IODM and/or ENSO phenomenon, a time series the partial correlation coefficient between the IODM of area–mean summer (JJA) precipitation over the sec- index and precipitation reduces once the ENSO effects tor occupied by intense negative precipitation anomalies are removed probably suggests that both IODM and (15 ° –35 ° N, 120 ° –140 ° E: Figure 1 bottom panel; hence- ENSO act cooperatively for the summer monsoon rainfall forth denoted as EAWNP region) is prepared. Lead/lag anomalies observed over the EAWNP domain (Figure 1 CCs are computed between this precipitation time series bottom panel). This analysis confirms that the IODM and indices of the IODM and ENSO phenomena. To fur- has a stronger relationship with the subsequent summer ther examine the respective influence of each of these monsoon precipitation distribution over EAWNP region phenomena, the partial correlation coefficient between the than the ENSO phenomenon. precipitation with the IODM removing ENSO effect and Kripalani et al . (2005) further suggested a possibility the precipitation with the ENSO mode removing IODM that this delayed influence could be carried by the effect is also computed. These correlations are based on Eurasian snow via the northern hemisphere mid-latitudes. the 1979–2003 period to focus on the recent inter-decadal To ascertain this aspect and to examine the influence period after the mid-1970s climate shift (Figure 2). For of the extreme dipole events on the snow over Eurasia, a sample of this size the significant CC is ∼ 0 . 4 (0.5) at similar composites for the Soviet snow depth data are determined. 95 (99) % confidence level. The CCs depict a gradual increase (in magnitude) from the preceding year spring (MAM-1), attaining higher values during the preceding autumn (SON-1) and winter (DJF0) and thereafter fall drastically for both IODM and ENSO indices (Figure2). Analysis reveals that the IODM index during the preceding autumn (SON-1) and winter (DJF0) shows significant negative relationship with the following summer monsoon rainfall over the EAWNP region, at 95% confidence level, implying less than normal rainfall following a positive IODM event. Although the ENSO index also conveys the delayed North Pacific region plays a key role in explaining why a negative During the relationship, period 1961–1995, the CCs are eight not positive significant and at eight this weak WNPSM and a strong EASM occurs in the decay level. negative Wang IODM et al events . (2001) are reported identified a (see weak Section WNPSM 2). phase of ENSO warm episodes (similar rainfall pattern during The composite the decaying snow depth phase differences of El Nino between and is these evident two illustrated in Figure1 bottom panel). Hence there is a need by sets the of negative extreme dipole CCs with events ENSO for the index following during winter winter to demonstrate that the IODM remote forcing could also (Figure 2). and spring are Furthermore, determined the (Figure 3). relation of Significant preceding positive winter be responsible for the EASM–WNPSM rainfall anoma- IODM snow depth index anomalies with subsequent (in centimeters) summer monsoon indicating rainfall heavy lies as illustrated in Figure 1 (bottom panel). over snow EAWNP are noted still in retains the north its significance of Korea–Japan even sector after the in To ascertain whether the coherent negative precipita- ENSO particular effect over is eliminated. the region On 45 ° the N–60 other ° N, hand 120 the ° E–140 relation ° E. tion anomalies prevailing over the East Asia–western of ENSO index and precipitation drops drastically once North Pacific (EAWNP) sector could be related with the IODM influence is removed. However, the fact that the IODM and/or ENSO phenomenon, a time series the partial correlation coefficient between the IODM of area–mean summer (JJA) precipitation over the sec- index and precipitation reduces once the ENSO effects tor occupied by intense negative precipitation anomalies are removed probably suggests that both IODM and (15 ° –35 ° N, 120 ° –140 ° E: Figure 1 bottom panel; hence- ENSO act cooperatively for the summer monsoon rainfall forth denoted as EAWNP region) is prepared. Lead/lag anomalies observed over the EAWNP domain (Figure 1 CCs are computed between this precipitation time series bottom panel). This analysis confirms that the IODM and indices of the IODM and ENSO phenomena. To fur- has a stronger relationship with the subsequent summer ther examine the respective influence of each of these monsoon precipitation distribution over EAWNP region phenomena, the partial correlation coefficient between the than the ENSO phenomenon. precipitation with the IODM removing ENSO effect and Kripalani et al . (2005) further suggested a possibility the precipitation with the ENSO mode removing IODM that this delayed influence could be carried by the effect is also computed. These correlations are based on Eurasian snow via the northern hemisphere mid-latitudes. the 1979–2003 period to focus on the recent inter-decadal To ascertain this aspect and to examine the influence period after the mid-1970s climate shift (Figure 2). For of the extreme dipole events on the snow over Eurasia, a sample of this size the significant CC is ∼ 0 . 4 (0.5) at similar composites for the Soviet snow depth data are determined. 95 (99) % confidence level. The CCs depict a gradual increase (in magnitude) from the preceding year spring (MAM-1), attaining higher values during the preceding autumn (SON-1) and winter (DJF0) and thereafter fall drastically for both IODM and ENSO indices (Figure2). Analysis reveals that the IODM index during the preceding autumn (SON-1) and winter (DJF0) shows significant negative relationship with the following summer monsoon rainfall over the EAWNP region, at 95% confidence level, implying less than normal rainfall following a positive IODM event. Although the ENSO index also conveys the delayed During the period 1961–1995, eight positive and eight negative IODM events are identified (see Section 2). The composite snow depth differences between these two sets of extreme dipole events for the following winter and spring are determined (Figure 3). Significant positive snow depth anomalies (in centimeters) indicating heavy snow are noted in the north of Korea–Japan sector in particular over the region 45 ° N–60 ° N, 120 ° E–140 ° ...
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... the period 1961-1995, eight positive and eight negative IODM events are identified (see Section 2). The composite snow depth differences between these two sets of extreme dipole events for the following winter and spring are determined (Figure 3). Significant positive snow depth anomalies (in centimeters) indicating heavy snow are noted in the north of Korea-Japan sector in particular over the region 45 ° N-60 ° N, 120 ° E-140 ° E. The strength of the snow anomalies during spring is much more than during winter. ...
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... particular, the positive phase of the dipole during summer/autumn may favour heavy snow during the following winter/spring over Eastern Eurasia north of the Korea-Japan (EENKJ) peninsula ( Figure 2 upper and central panels). Significant negative snow anomalies also prevail over the region centered at 70 ° N 60 ° E (Figure 3 central panel). Such dipole snow depth patterns have also been associated with the Indian monsoon rainfall ( Kripalani and Kulkarni, 1999) and with the Korean monsoon rainfall (Kripalani et al., 2002). ...
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... the above composites also contain ENSO-related years. Hence to further ascertain the possible role of the dipole mode on the snow distribution over EENKJ, area-mean time series of snow depth during winter (DJF) and spring (MAM) are prepared over the EENKJ sector (45 ° N-60 ° N, 120 ° E-140 ° E: based on the anomalies observed in Figure 3 central panel). Again lead/lag CCs are computed between the snow depth time series and indices of the IODM and ENSO phenomena as shown in Figure 2. ...
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Ozone in the troposphere is a greenhouse gas and a pollutant; hence, additional understanding of the drivers of tropospheric ozone evolution is essential. The El Niño–Southern Oscillation (ENSO) is a main climate mode and may contribute to the variations of tropospheric ozone. Nevertheless, there is uncertainty regarding the causal influences of ENSO on tropospheric ozone under a warming environment. Here, we investigated the links between ENSO and tropospheric ozone using Coupled Modeling Intercomparison Project Phase 6 (CMIP6) data over the period 1850–2014. Our results show that ENSO impacts on tropospheric ozone are primarily found over oceans, while the signature of ENSO over continents is largely nonsignificant. Springtime surface ozone is more sensitive to ENSO compared to other seasons. The response of ozone to ENSO may vary depending on specific air pressure levels in the troposphere. These responses are weak in the middle troposphere and are stronger in the upper and lower troposphere. There is high consistency across CMIP6 models in simulating the signature of ENSO on ozone over the lower, middle, and upper troposphere. While the response of tropical tropospheric ozone to ENSO is in agreement with previous works, our results suggest that ENSO impacts on tropospheric ozone over the northern North Pacific, American continent, and the midlatitude regions of the southern Pacific, Atlantic, and Indian oceans might be more significant than previously understood.
... Perhaps the simplest explanation comes from the propagation of the event which, regardless of whether it spread via the IOD or AMOC, would impact the ISM first. The ISM/Indian Ocean has a much stronger influence on the EASM than vice-versa (Zhu et al., 1986), notably through alterations to the IOD, which subsequently influences the EASM via snow distribution over Eurasia (Ha et al., 2018;Kripalani et al., 2010), and by altering the strength of the westerlies in response to orbital forcing (Clemens et al., 1991;Yang et al., 2023). An additional contribution might come from another key control on ASM strength, the Tibetan Plateau (Fallah et al., 2016;Webster et al., 1998). ...
Mainland Southeast Asia experiences complex and variable hydroclimatic conditions, mainly due to its location at the intersection of Asian monsoon subsystems. Predicting future changes requires an in-depth understanding of paleoclimatic conditions that is currently hindered by a paucity of records in some regions. In this paper, we present the first speleothem stable isotope records from western Thailand detailing the B ølling-Allerød inter stadial, Younger Dryas termination, and early- to mid-Holocene period. We find evidence of higher precipitation during the B ølling-Allerød (14,321 –12,824 years before present (1950: BP)) compared to a Younger Dryas termination that starts 11,702–11,674 BP, has a rapid shift centered on 11,660 –11,641 BP, and ends 11,603–11,589 BP. In addition, our records show Holocene monsoon intensity peaking at 8250 BP or before, a multi-millennia delay from the Northern Hemisphere summer insolation peak, followed by a trend to drier conditions until at least 750 BP. Assessment of the timing of the Younger Dryas termination in paleoclimate records across Southeast Asia reveals an earlier shift of the Indian Summer Monsoon to global climate shifts when compared to East Asian Summer Monsoon records. The causes of this are currently unknown. Some potentially important aspects include: an Indian Summer Monsoon influence on East Asian Summer Monsoon strength via the Indian Ocean Dipole climate pattern, the role of the Tibetan Plateau in monsoon dynamics, and exposure of the Sundaland shoreline. More high-resolution paleoclimate records, especially on the pathway of Indian Summer Monsoon to East Asian Summer Monsoon, are required for further discussion on the mechanisms controlling the differences between climate regimes.
... In addition, the Indian Ocean Dipole (IOD) mode has been proposed as another critical factor influencing the Asian monsoonal precipitation through Walker circulation and its link to the ENSO (Brown et al., 2009;Chowdary et al., 2014;Li et al., 2021a). In general, negative IOD events and La Niña events co-occur and the resulting enhanced convection over India causes heavy precipitation (Kripalani et al., 2010;Li et al., 2021a). ...
... Historically, AMO indices were based on average annual SST anomalies in the North Atlantic region (Yasunaka and Hanawa, 2011). Dipole Mode Index (DMI) anomalous SST gradient between the western equatorial Indian Ocean (50 -70 E and 10 S-10 N) and the southeastern tropical Indian Ocean (90 -110 E and 10 S-0 N) (Kripalani et al., 2010). The NAO index is calculated using the difference in surface sealevel pressure between the Subtropical (Azores) High and the Subpolar Low (Glueck and Stockton, 2001). ...
The spatial and temporal variations of wet and dry spells may be related to large‐scale climatic indices. To date, no comprehensive study has been conducted on Iran's spatial and temporal variations of wet and dry spells. To fill this gap, 14 wet/dry spell indices were calculated for 512 rain gauges across Iran from 1985 to 2016. The modified non‐parametric Mann–Kendall test was then used to examine the temporal variations of wet and dry spell indices. Whether any relationships between spell indices and 13 large‐scale climatic indicators existed was determined. The maps showing the degree of correlation between wet/dry spell indices and two climatic indicators that reflect short‐ and long‐term El Niño oscillation were presented. The results demonstrated that precipitation typically occurs in bursts of 1 or 2 days in length, with most of the annual precipitation coming from a few exceptionally heavy or extreme events. Most dry spells in Iran occur from 6 to 27 days or longer. The length, frequency, and intensity of wet spells declined in southern Iran while expanding in northern Iran. However, extreme wet spells have intensified significantly across the country. When El Niño occurs, Iran experiences wetter weather. However, long‐term oscillations in sea‐surface temperatures in the Pacific Ocean are found to be significantly correlated with wet/dry spells, outperforming those obtained for shorter periods. A smaller portion of the country showed a significant correlation in extreme spell indices, though.
... The Indian Ocean Dipole (IOD) is a unique coupled ocean-atmosphere mode of climate variability in the tropics of the Indian Ocean that affects the regional and global climatic conditions at interannual time scales (e.g. Saji et al. 1999;Vinayachandran et al. 1999Vinayachandran et al. , 2009Webster et al. 1999;Ashok et al. 2001;Rao et al. 2002;Black et al. 2003;Clark et al. 2003;Saji and Yamagata 2003;Yamagata et al. 2004;Meyers et al. 2007;Chan et al. 2008;Yuan et al. 2008;Cai et al. 2009Cai et al. , 2014Ummenhofer et al. 2009;Kripalani et al. 2010). ...
This study focuses on the regional wind variability that controls the intensity of cold-water upwelling off Sumatra – a key feature of the Indian Ocean Dipole (IOD). Our analysis of daily atmospheric data reveals the existence of convectively triggered synoptic-scale atmospheric cyclones in the South-East Tropical Indian Ocean (SETIO). The northern branch of the cyclones corresponds to westerly equatorial wind events, whereas the eastern branch involves north-westerly winds that operate to suppress cold-water upwelling off Sumatra’s west coast. Data for the period 1988–2022 show that 5–9 SETIO cyclones normally form each year during the boreal summer–autumn season, effectively suppressing upwelling in the region. In contrast, there are only few (1–2) cyclone events in years identified as positive phases of the IOD, when the absence of cyclones concurs with the development of strong coastal upwelling off Sumatra. Our findings suggest that the absence or presence of SETIO cyclones contributes to IOD variability.
... al. 2021a) which contributed to the NPSH and the enhanced the Meiyu rainfall (Zhou et al. 2021). Such a delayed impact of the IOD on the subsequent summer monsoon rainfall over East Asia-West Pacific has been reported earlier (Kripalani et al. 2010). Wang (2020) attributed the long-lasting Meiyu season during summer 2020 to the co-existence of the Silk-Road wave train in the upper troposphere and the Pacific-Japan wave-train in the middlelower troposphere. ...
The summer (June through September) monsoon 2020 has been very erratic with episodes of heavy and devastating rains, landslides and catastrophic winds over South Asia (India, Pakistan, Nepal, Bangladesh), East Asia (China, Korea, and Japan), and Southeast Asia (Singapore, Thailand, Vietnam, Laos, Cambodia, Philippines, Indonesia). The withdrawal of the summer monsoon over India was delayed by 2 weeks. The monsoon season over East Asia has been the longest. China recorded a Dam burst in the twentieth century. Furthermore, the Korean Peninsula has experienced back-to-back severe tropical cyclones. Could the lockdown activities initiate to control the COVID-19 spread a possible cause for these major episodes? The strict enforcement of the lockdown regulations has led to a considerable reduction of air pollutants—dust and aerosols throughout the world. A recent study based on satellites and merged products has documented a statistically significant mean reduction of about 20, 8, and 50% in nitrogen dioxide, Aerosol Optical Depth (AOD) and PM2.5 concentrations, respectively over the megacities across the globe. Our analysis reveals a considerable reduction of about 20% in AOD over South as well as over East Asia, more-over East Asia than over South Asia. The reduced aerosols have impacted the strength of the incoming solar radiation as evidenced by enhanced warming, more-over the land than the oceans. The differential warming over the land and the ocean has resulted in the amplification of the meridional ocean-land thermal contrast and strengthening of the monsoon flow. These intense features have supported the surplus transport of moisture from the oceans towards the main lands. Some similarity between the anomalous rainfall pattern and the anomalous AOD pattern is discernable. In particular, the enhancement of rainfall, the reduction in AOD and the surface temperature warming match very well over two regions one over West-Central India and the other over the Yangzte River Valley. Results further reveal that the heavy rains over the Yangzte River Valley could be associated with the preceding reduced aerosols, while the heavy rains over West-Central India could be associated with reduced aerosols and also due to the surface temperature warming.
... . Several studies even suggested that the warm pools rather than the land-sea thermal contrast, are the primary forcing agents of monsoons (Chao & Chen, 2001;Shields & Kiehl, 2018). Thus, the Western Pacific (WP) and Indian Ocean (IO) monsoons, can be indicators of the Indo-Pacific warm pool dynamics, and have profound influences on the terrestrial environmental processes in Southeast Asia (Kripalani et al., 2010;Loo et al., 2015;Wang & Chen, 2012). Previous researches generally analyzed the monsoon system dynamics and the coupled circulation modes at large scales, to reveal the effects of the warm pools in this region (Roxy et al., 2019;Ueda et al., 2015;Wang et al., 2018;Xing et al., 2014). ...
Plain Language Summary
The ocean warm pool is widely considered important to the regional climatic and environmental events. As the largest and most active warm pool, the Indo‐Pacific warm pool affects the climatic conditions in Southeast Asia mediated by the Western Pacific (WP) and Indian Ocean (IO) monsoons. However, in Southeast Asia, a global wildfire hotspot, the response of regional wildfire number to the warm pools has received limited attention yet, although the warm pools and monsoon dynamics are recognized as a critical regulator of wildfires in this region. We explored the warm pool effects on wildfire number in Yunnan, Southwest China. Our results showed the interannual dynamics of the wildfire number had a negative relationship with the simultaneous WP warm pool changes. The Ailao Mountains in central Yunnan could be a geographical barrier that blocked the influences of the WP warm pool from the east side. For the intraannual dynamics, the wildfire record variations had a stronger connection to the IO warm pool dynamics than the WP. This study provided the novel evidences on the teleconnection of the Indo‐Pacific warm pool with the wildfire number in Yunnan, and also implied the regional effects of warm pool on those areas with climatic‐driven environmental processes.
... In terms of the relationship between summer monsoonal precipitation and ENSO, the most noteworthy responses occur mainly during the decaying phase of ENSO the following year [29][30][31][32][33][34] , which can be considered a delayed effect of ENSO. Similarly, the delayed effect of IOD also refers to the response of summer precipitation the following year, but few studies have addressed this phenomenon [35][36][37] . Generally, associated with a preceding positive IOD, summer precipitation is expected to be enhanced around the Yangtze River region [35][36][37] . ...
... Similarly, the delayed effect of IOD also refers to the response of summer precipitation the following year, but few studies have addressed this phenomenon [35][36][37] . Generally, associated with a preceding positive IOD, summer precipitation is expected to be enhanced around the Yangtze River region [35][36][37] . Nonetheless, considering the important modulations of ENSO on precipitation around the Yangtze River 34,[38][39][40] , it is worth clarifying the similarities and dissimilarities associated with summer precipitation responses to IOD and ENSO. ...
... Also, the present analysis analyzes mainly the aftermath of IOD in the ocean system and pays little attention to possible driving factors on land. Previous studies have also stated that snow cover over the continent may also help sustain the anomalous signals associated with IOD until the ensuing seasons 35,36 ; this possible intermediate effect of the land would also be interesting to investigate and compare in the future. Further clarification of the delayed effects of IOD and associated mechanisms on the ensuing summer precipitation in eastern China could provide a sounder basis for improving seasonal climate predictions with a longer lead time. ...
Eastern China was extremely wet in summer 2020, which is found to be related to the potential delayed effects of the Indian Ocean Dipole (IOD). Additional knowledge is warranted to improve our understanding of detailed mechanisms of such an effect. In this study, we compared physical processes associated with delayed effects of the IOD and El Niño–Southern Oscillation (ENSO) on summer precipitation. Partial correlation and composite analysis reveal that ENSO modulates precipitation mainly over the Yangtze River Valley, whereas IOD benefits precipitation farther north. Both IOD and ENSO can stimulate anticyclonic circulation over the western North Pacific (WNP) in the ensuing summer but with different spatial distributions related to the different sea surface temperature (SST) evolution processes. IOD is similarly followed by warming signals in the Indian Ocean, known as the “capacitor” effect, but the location is closer to Australia than that associated with ENSO. IOD also stimulates significant SST cooling anomalies over the equatorial Pacific during the ensuing summer, jointly contributing to the anomalous anticyclone over WNP. Numerical experiments confirm that combined effects of the Indian Ocean “capacitor” and equatorial Pacific cooling can generate an anomalous anticyclone with wider distribution in the meridional direction over WNP.
... For instance, the NAO is the prominent mode of atmospheric circulation variability over the North Atlantic and surrounding regions (Delworth et al., 2016;Hurrell et al., 2003), and variations in NAO are crucial for the environment and society (Hurrell et al., 2003). The IOD affects climate extremes over the Indian Ocean and surrounding areas (Abram et al., 2008;Kripalani et al., 2009;Kripalani and Kulkarni, 1997) and might cause severe economic consequences (Ummenhofer et al., 2009). The SAM is the major mode of atmospheric circulation variability in the Southern Hemisphere (Cai et al., 2011;Raphael and Holland, 2006). ...
The dust cycle is an important element of the Earth
system, and further understanding of the main drivers of dust emission,
transport, and deposition is necessary. The El Niño–Southern Oscillation
(ENSO) is the main source of interannual climate variability and is likely
to influence the dust cycle on a global scale. However, the causal
influences of ENSO on dust activities across the globe remain unclear. Here
we investigate the response of dust activities to ENSO using output from
Coupled Modeling Intercomparison Project Phase 6 (CMIP6) historical
simulations during the 1850–2014 period. The analyses consider the
confounding impacts of the Southern Annular Mode, the Indian Ocean Dipole,
and the North Atlantic Oscillation. Our results show that ENSO is an
important driver of dry and wet dust deposition over the Pacific, Indian, and
Southern oceans and parts of the Atlantic Ocean during 1850–2014. Over continents,
ENSO signature is found in America, Australia, parts of Asia, and Africa.
Further, ENSO displays significant impacts on dust aerosol optical depth
over oceans, implying the controls of ENSO on the transport of atmospheric
dust. Nevertheless, the results indicate that ENSO is unlikely to exhibit
causal impacts on regional dust emissions of major dust sources. While we
find high consensus across CMIP6 models in simulating the impacts of ENSO on
dust deposition and transport, there is little agreement between models for
the ENSO causal impacts on dust emission. Overall, the results emphasize the
important role of ENSO in global dust activities.
... However, why is the IOD also possibly important for the seasonal evolution of precipitation patterns? Increasing evidences illustrated that the IOD can have a delayed effect on ensuing seasons after its demise (e.g., Kripalani et al., 2010;Yuan et al., 2008b;Zhang et al., 2019a). Yuan et al. (2008b) discovered that the IOD could significantly influence precipitation anomalies during summer in the ensuing year by modulating the location of the subtropical high and Asian monsoonal circulations. ...
... Yuan et al. (2008b) discovered that the IOD could significantly influence precipitation anomalies during summer in the ensuing year by modulating the location of the subtropical high and Asian monsoonal circulations. Kripalani et al. (2010) also found this kind of delayed effect of the IOD and summarized the mechanism as a medium effect of snow distribution over the Far East, which is dependent on the turnabout of ENSO. Zhang et al. (2019a) revealed an independent physical process as a cross-seasonal linkage between the IOD, snow distribution over the Tibetan Plateau (TP), and the ensuing summer precipitation, by which the IOD can modulate the ensuing summer precipitation by enhancing the snowpack over the southern TP. ...
This study investigates seasonal precipitation variation over eastern China associated with Indian Ocean Dipole (IOD) forcing and emphasizes the distinction of such responses to preceding IOD events compared with responses to El Niño–Southern Oscillation (ENSO). Precipitation evolution patterns in response to the IOD from autumn to the ensuing summer are derived from singular value decomposition analysis, revealing that the IOD causes a large portion of the seasonal variation in precipitation over eastern China in the simultaneous autumn and time-lagged summer. The difference in the impacts associated with the IOD and ENSO revealed by multiple linear regression and partial correlation analysis is that the IOD contributes mainly to abnormal precipitation in South China during autumn and in the region between the Yangtze River and Yellow River during the ensuing summer; while ENSO primarily boosts precipitation over eastern China during winter and spring. The distinctive effects of the IOD on the ensuing summer precipitation contrast with the less significant signals related to ENSO during the ensuing summer. Such precipitation responses correspond to an anomalous anticyclonic circulation pattern around the South China Sea, which is sustained by direct IOD forcing during autumn and winter and an SST cooling pattern triggered by the IOD over the central equatorial Pacific during the ensuing spring and summer. The calculation of wave activity flux and anomalous AGCM model experiments further confirm the importance of the direct heating of the IOD during autumn and winter and the indirect heating sink over the central Pacific during the ensuing spring and summer for modulating the seasonal variation in precipitation over eastern China.
