Sea Surface Temperature Modes Research Articles

Decadal climate variability in the eastern Caribbean

[1] Rainfall variability in the eastern Caribbean during the 20th century is analyzed using principal component analysis and singular value decomposition. In contrast to earlier studies that used seasonal data, here we employ continuous signal processing. The leading mode is a decadal oscillation related to third and fourth modes of sea level pressure (SLP) and sea surface temperatures (SST) which together identify three zones of action in the Atlantic: 35°N–20°N, 20°N–5°N, and 5°N–20°S. The ability of the ECHAM4.5 model to simulate this signal is investigated. Its decadal variability is also represented through lower-order SLP and SST modes that comprise an Atlantic tripole pattern with lower pressure east of the Caribbean. Composite analysis of high and low phases of the decadal mode reflects a cool east Pacific and a more active Atlantic Intertropical Convergence Zone during boreal summer, conditions that favor the intensification of African easterly waves. The decadal signal has strengthened since 1970, yet the three centers of action in Atlantic SST are relatively unsynchronized.

Seasonal-to-interannual variability of chlorophyll in central western South China Sea extracted from SeaWiFS

Using 10-year (January 1998–October 2007) dataset of Sea-viewing Wide Field-of-view Sensor (SeaWiFS), we extracted the dominant spatial patterns and temporal variations of the chlorophyll distribution in the central western South China Sea (SCS) through Empirical Orthogonal Function (EOF) analysis. The results show that the first EOF mode is characterized by a high chlorophyll concentration zone along the Vietnam coast. We found two peaks in summer (July–August) and in winter (December), respectively, in normal years. The second EOF mode is characterized by a jet-shaped tongue of high chlorophyll concentration extending seaward to the northeast in summer (July–August). To investigate the interannual variability of the chlorophyll concentration, we extracted the first non-seasonal (annual cycle removed) EOF mode, which shows high spatial variability off the southeast Vietnam coast. Both spatial pattern and time coefficients correspond well with those of sea surface temperature mode, and are closely correlated to ENSO events, with a lag of 7 months.

Multimodel Estimates of Atmospheric Response to Modes of SST Variability and Implications for Droughts

Abstract A set of idealized global model experiments was performed by several modeling centers as part of the Drought Working Group of the U.S. Climate Variability and Predictability component of the World Climate Research Programme (CLIVAR). The purpose of the experiments was to assess the role of the leading modes of sea surface temperature (SST) variability on the climate over the continents, with particular emphasis on the influence of SSTs on surface climate variability and droughts over the United States. An analysis based on several models gives more creditability to the results since it relies on the assessment of impacts that are robust across different models. Coordinated atmospheric general circulation model (AGCM) simulations forced with three modes of SST variability were analyzed. The results show that the SST-forced precipitation variability over the central United States is dominated by the SST mode with maximum loading in the central Pacific Ocean. The SST mode with loading in the Atlantic Ocean, and a mode that is dominated by trends in SSTs, lead to a smaller response. Based on the response to the idealized SSTs, the precipitation response for the twentieth century was also reconstructed. A comparison with the Atmospheric Model Intercomparison Project (AMIP) simulations forced with the observed SSTs illustrates that the reconstructed precipitation variability was similar to the one in the AMIP simulations, further supporting the conclusion that the SST modes identified in the present analysis play a dominant role in the precipitation variability over the United States. One notable exception is the Dust Bowl of the 1930s, and further analysis regarding this major climate extreme is discussed.

Pacific Decadal Oscillation documented in a coral record of North Pacific winter temperature since 1873

The Pacific Decadal Oscillation (PDO), the leading mode of sea surface temperature (SST) anomalies in the extratropical North Pacific Ocean, has widespread impacts on precipitation in the Americas and marine fisheries in the North Pacific. However, marine proxy records with a temporal resolution that resolves interannual to interdecadal SST variability in the extratropical North Pacific are extremely rare. Here we demonstrate that the winter Sr/Ca and U/Ca records of an annually‐banded reef coral from the Ogasawara Islands in the western subtropical North Pacific are significantly correlated with the instrumental winter PDO index over the last century. The reconstruction of the PDO is further improved by combining the coral data with an existing eastern mid‐latitude North Pacific growth ring record of geoduck clams. The spatial correlations of this combined index with global climate fields suggest that SST proxy records from these locations provide potential for PDO reconstructions further back in time.

Recent warming in the Yellow/East China Sea during winter and the associated atmospheric circulation

We examine characteristics in the variability of sea surface temperature (SST) in the Yellow/East China Sea during the boreal winter (December–January–February) for the period 1950–2008 in observations. It is found that the mean SST in the Yellow Sea/East China Sea gradually increases during recent decades. A warming trend of a basin scale SST is significant in most of the regions in the Yellow/East Sea, which is well explained by the variability of the first empirical orthogonal function SST mode. We suggest one candidate mechanism that the North Pacific oscillation (NPO)-like sea level pressure play an important role to warm the Yellow/East China Sea. Anomalous anticyclonic circulation, which is the southern lobe of NPO-like sea level pressure over the North Pacific, causes a weakening of northerly mean winds over the Yellow/East China Sea during winter. This contributes to increase in the SST in the Yellow/East China Sea through the changes in the latent heat and sensible heat fluxes.

Trends in warm days and cold nights over the Iberian Peninsula: relationships to large-scale variables

The aims of this study are to identify the trend of warm days and cold nights over the Iberian Peninsula and to connect the variations with large-scale variables. The reasons for performing this analysis are the effects that extremes events have on different ecosystems. Here, we present the results on spatial and temporal variability of warm days (TX90), or those exceeding the 90th percentile of maximum temperature, and cold nights (TN10), or those falling below the 10th percentile of minimum temperature. The extreme indices were derived from daily observations at stations and gridded data over land area for the period 1950 to 2006. Significant trends of more warm days and fewer cold nights were found. The trend to fewer cold nights is within the interval of global results given by the IPCC AR4 report; however, the trend to warm days is greater than the corresponding global trend. The influence of large-scale variables on these extreme indices was examined by means of the Empirical Orthogonal Function, correlation, composite maps and multiple regression analyses. Changes in TX90 are connected with the Scandinavian teleconnection index and a preferred mode of geopotential height at 500 hPa over the North Atlantic. Changes in TN10 are connected with the East Atlantic teleconnection index and the leading mode of Sea Surface Temperature (SST) variability over the North Atlantic area. Based on the links between the extreme indices and the large-scale variables we derived statistical models to describe the response of TX90 and TN10 to atmospheric circulation and SST variations. The models characterized the observed variations of TX90 and TN10 reasonably well. The results of this study encourage us to analyze, in further work, how temperature extremes might change over the Iberian Peninsula under warmer climate conditions.

Satellite-measured seasonal variations in primary production in the scallop-farming region of the Okhotsk Sea

Abstract Mustapha, M. A., Sei-Ichi, S., and Lihan, T. 2009. Satellite-measured seasonal variations in primary production in the scallop-farming region of the Okhotsk Sea. – ICES Journal of Marine Science, 66: 1557–1569. Seasonal variation in primary production after a retreat of the sea ice in the scallop-farming region along the Hokkaido coast of the Okhotsk Sea (1998–2004) was determined using satellite images. Annual variability in primary production was caused by variability in the physical processes associated with retreat of the sea ice, advection of the Sōya Warm Current (SWC), and intrusion of the East Sakhalin Current (ESC). Variability in primary production resulted in variability in the Chl a concentration, which was also demonstrated with an empirical orthogonal function (EOF) analysis. Enhancement of Chl a concentration in the frontal area in late spring was demonstrated by the second EOF mode of Chl a concentration (14.2% of variance), in parallel with the generation of a well-developed frontal area resulting from the advection of warm waters of the SWC along the coast in late spring, as indicated by the second EOF mode of sea surface temperature (SST; 1.8% of variance). Elevated Chl a concentration and the presence of cold water of the ESC in late autumn were also highlighted by the third EOF mode of Chl a concentration (9.0% of variance) and SST (1.5% of variance). Prolonged high primary production within the scallop-farming region after spring is supported by the development of a frontal area in summer and strengthening of the ESC in autumn.

Characterizing the South Atlantic Bight seasonal variability and cold‐water event in 2003 using a daily cloud‐free SST and chlorophyll analysis

Concurrent MODIS sea surface temperature (SST) and chlorophyll‐a (Chl‐a) data are used with a new technique: Data Interpolating Empirical Orthogonal Function (DINEOF) method to produce daily, 4‐km, cloud‐free SST and Chl‐a analyses for the South Atlantic Bight in 2003. Comparisons between SST analysis and in situ buoy temperature demonstrate the utility of DINEOF. To quantify linkages between surface wind, SST, and Chl‐a variations, Empirical Orthogonal Function (EOF) analysis is applied to North American Regional Reanalysis winds, and cloud‐free DINEOF SST and Chl‐a analyses. Wind EOF modes highlight upwelling winds from June to September. While the first SST mode represents seasonal heat flux variations, the second SST mode shows a direct response to upwelling winds with an abrupt drop in SST. The top two Chl‐a EOF modes show less connection with wind. More subsurface Chl‐a and nutrient observations are needed to quantify its relation with surface wind.

Is the decadal variability in the tropical Atlantic a precursor to the NAO?

Abstract. In the past two decades climate research in the tropical Atlantic with respect to the inter-hemispheric gradient of sea surface temperature (SST) emphasized the predominance of decadal-scale variability. Our results show that this mode of variability is prevalent only for part of the last 130-years record (the 1880s, the 1920s and, especially, the 1970s). There is a lag of a few months between the decadal variations of the inter-hemispheric gradient of SST and the decadal variability of the North Atlantic Oscillation (NAO). This seems to indicate that the 10-year variability first develops in the tropics and then propagates polewards. The inter-hemispheric gradient of SST mode should be thought as episodic and not as a periodic oscillation.

Covarying modes of the Pacific SST and northern hemispheric midlatitude atmospheric circulation anomalies during winter

The interannual-to-interdecadal relationship between the Pacific sea surface temperature (SST) and the northern hemispheric midlatitude’s atmosphere represented by the circumpolar vortex was documented with the global oceanic and atmospheric reanalysis data of recent 50 years. Two covarying modes of the Pacific SST and northern circumpolar vortex anomalies during winter were examined using the singular value decomposition and wavelet analysis techniques. One is the interannual, ENSO-related mode and the other is the interdecadal, North Pacific SST-related mode with a period of around 20 years. The two modes exhibit distinct spatial structures. For the interannual mode, the SST anomaly is characterized by a typical ENSO pattern with the principal signature in the tropical eastern Pacific and secondary one in the central North Pacific, while the atmospheric anomaly is regional, characterized by a Pacific-North American pattern. For the interdecadal mode, large SST anomaly is located in the central North Pacific, while the atmospheric anomaly is zonally global, associated with the midlatitute’s standing long-wave variations. When the central North Pacific is colder, the long-wave is stronger, and vice versa. Further investigations suggest that the interdecadal mode could involve an interaction between “two oceans and an atmosphere”.

Interannual variability of boreal summer rainfall in the equatorial Atlantic

AbstractTropical Atlantic rainfall variations during boreal summer (June–July–August (JJA)) are quantified by means of a 28‐year (1979–2006) monthly precipitation dataset from the Global Precipitation Climatology Project (GPCP). Rainfall variability during boreal spring (March–April–May (MAM)) is also examined for comparison in that the most intense interannual variability is usually observed during this season. Comparable variabilities in the Atlantic maritime intertropical convergence zone (ITCZ) (15° –35°W) strength (PITCZ) are found during both seasons. Variations in the ITCZ's latitudinal location (LatITCZ) during JJA, however, are much weaker than during MAM.PITCZ and LatITCZ are shown to be closely associated with sea surface temperature (SST) anomalies in both the tropical Atlantic and Pacific. Within the tropical Atlantic, the Atlantic Niño events (Atl3) and SST anomalies in the tropical North Atlantic (TNA) are the two major local factors modulating surface rainfall patterns and variations. Atl3 is significantly correlated with PITCZ and LatITCZ during JJA and MAM. TNA is significantly correlated to PITCZ during JJA but not to LatITCZ. In contrast, TNA is significantly correlated to LatITCZ during MAM but its correlation with PITCZ is weak.The impact of the El Niño‐Southern Oscillation (ENSO) events (Nino3.4) is observed during both seasons, while the correlation between Nino3.4 and LatITCZ is slightly weak. However, with the effects of Atl3 and TNA removed, the ENSO tends to have a quite limited direct impact on the tropical Atlantic, specifically over the open ocean. High second‐order partial correlation between Nino3.4 and rainfall is generally confined to the western basin and over the northeastern South America. Therefore, during JJA, the two local SST modes are of dominance for the tropical Atlantic rainfall variability. Nevertheless, the ENSO seems to still play an active role in modulating surface zonal wind anomalies in the western basin and then the Atlantic Niño mode. Copyright © 2008 Royal Meteorological Society

Air temperature impacts over Eastern North America and Europe associated with low‐frequency North Atlantic SST variability

AbstractAir temperature anomalies over eastern North America and Europe are analysed during the extreme phases of the two leading low‐frequency modes of North Atlantic sea surface temperature (SST) during the 1906–2005 period. The leading mode of SST is a multi‐decadal signal—commonly referred to as the Atlantic multi‐decadal oscillation—with uniform polarity over the North Atlantic. Air temperature anomalies over the eastern United States and Northern Europe during extreme phases of this mode are of the same sign as the corresponding SST anomalies. The most intense air temperature impacts occur in summer months. The second mode exhibits considerable spectral energy in the quasi‐decadal (∼12 year) range. The spatial signature and associated air temperature anomalies of mode 2 are strongly correlated with both SST and land temperature impacts of the North Atlantic Oscillation (NAO). Copyright © 2008 Royal Meteorological Society

Fine Pattern of Natural Modes in Sea Surface Temperature Variability: 1985–2003

Abstract A natural mode refers, in this study, to a periodic oscillation of sea surface temperature (SST) that is geophysically significant on a global, regional, or local scale. Using a newly developed harmonic extraction scheme by Chen, which has the advantage of being space–time decoupled and fully data adaptive, a variety of natural modes have been recovered from global monthly SST data for the period of 1985–2003. Among them, the eight most significant modes are identified as primary modes, whose spatial patterns are presented, along with their phase distributions. At seasonal time scales, a 4-month primary mode is uncovered in addition to the well-documented annual and semiannual cycles. At interannual time scales, the dominant El Niño–Southern Oscillation (ENSO) variability is found to be composed of at least five primary modes, with well-defined central periods around 18, 25, 32, 43, and 63 months. At time scales beyond ENSO, a decadal SST signal with an average period of 10.3 yr is observed. A unique contribution of this study is the derivation and presentation of fine patterns of natural SST modes and signals in joint dimensions of time, space, period, and phase, leading to several findings and conclusions that are of potential importance: 1) The degree of separability and regularity of the sub-ENSO modes is surprising, and thus reveals new details on the nature of this event. 2) The midlatitude counterparts of the equatorial interannual and decadal SST modes/signals are found in the two hemispheres with a frequency shift toward longer periods. The “shadows” of the Pacific Ocean’s ENSO modes are also observed with some detail in the Atlantic and the Indian Oceans. All of these provide direct evidence that teleconnections exist between the equatorial and extratropical oceans, as well as among the tropical Pacific, tropical Atlantic, and tropical Indian Oceans, possibly as a result of the “atmospheric bridge.” 3) A sharply opposite anisotropy is observed in the spatiotemporal pattern between the interannual modes and decadal signals, implying that they are potentially of a categorical difference in origin. 4) Locality or regionality is a fundamental feature for most of the SST modes. Treating the interannual or decadal variability as a single ENSO or Pacific decadal oscillation mode appears to be an oversimplification, and may lead to inappropriate interpretations. The results herein represent an improved knowledge of the natural variability in sea surface temperature, which will hopefully help to enhance the understanding of natural fluctuations of the global/regional climate system in the context of ocean–atmosphere interaction.

Monsoon-ocean coupled modes in the South China Sea and their linkage with the eastern Indian Ocean-western Pacific warm pool

Monsoon-ocean coupled modes in the South China Sea (SCS) were investigated by a combined singular value decomposition (CSVD) analysis based on sea surface temperature (SST) and sea surface wind stress (SWS) fields from SODA (Simple Ocean Data Assimilation) data spanning the period of 1950–1999. The coupled fields achieved the maximum correlation when the SST lagged SWS by one month, indicating that the SCS coupled system mainly reflected the response of the SST to monsoon forcing. Three significant coupled modes were found in the SCS, accounting for more than 80% of the cumulative squared covariance fraction. The first three SST spatial patterns from CSVD were: (I) the monopole pattern along the isobaths in the SCS central basin; (II) the north-south dipole pattern; and (III) the west-east seesaw pattern. The expansion coefficient of the SST leading mode showed interdecadal and interannual variability and correlation with the Indo-Pacific warm pool (IPWP), suggesting that the SCS belongs to part of the IPWP at interannual and interdecadal time scales. The second mode had a lower correlation coefficient with the warm pool index because its main period was at intra-annual time scales instead of the interannual and interdecadal scales with the warm pools. The third mode had similar periods to those of the leading mode, but lagged the eastern Indian Ocean warm pool (EIWP) and western Pacific warm pool (WPWP) by five months and one year respectively, implying that the SCS response to the warm pool variation occurred from the western Pacific to the eastern Indian Ocean, which might have been related to the variation of Indonesian throughflow. All three modes in the SCS had more significant correlations with the EIWP, which means the SCS SST varied much more coherently with the EIWP than the WPWP, suggesting that the SCS belongs mostly to part of the EIWP. The expansion coefficients of the SCS SST modes all had negative correlations with the Nino3 index, which they lag by several months, indicating a remote response of SCS SST variability to the El Nino events.

The SST‐forced predictability of the sub‐seasonal mode over East Asia with an atmospheric general circulation model

AbstractThe sea surface temperature (SST)‐forced predictability in precipitation is investigated in terms of the seasonal mean modes (SMMs) for June–July (JJ) and the sub‐seasonal mode (SSM) using the 24‐year six‐member ensembles simulation with an atmospheric general circulation model (AGCM). The SSM was defined as a 20‐day window length by an extended empirical orthogonal function (EOF) over the East Asian monsoon region. For the JJ mean rainfall, the first EOF of the model ensemble is considered to be the forced SST mode, with being an El Niño Southern Oscillation (ENSO) related pattern from the regressed SST field. The first mode of model was well correlated with the second mode of the observation in the spatial and temporal variation.In the potential predictability, the analysis of variance (ANOVA) was used for the mean mode and the SSM. The potential predictability for the SMM is improved over the north of the 30°N. Compared with JJ mean mode, the SSM has more SST‐forced variance and less internal variability. Copyright © 2008 Royal Meteorological Society

Contingent Pacific–Atlantic Ocean influence on multicentury wildfire synchrony over western North America

Widespread synchronous wildfires driven by climatic variation, such as those that swept western North America during 1996, 2000, and 2002, can result in major environmental and societal impacts. Understanding relationships between continental-scale patterns of drought and modes of sea surface temperatures (SSTs) such as El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO) may explain how interannual to multidecadal variability in SSTs drives fire at continental scales. We used local wildfire chronologies reconstructed from fire scars on tree rings across western North America and independent reconstructions of SST developed from tree-ring widths at other sites to examine the relationships of multicentury patterns of climate and fire synchrony. From 33,039 annually resolved fire-scar dates at 238 sites (the largest paleofire record yet assembled), we examined forest fires at regional and subcontinental scales. Since 1550 CE, drought and forest fires covaried across the West, but in a manner contingent on SST modes. During certain phases of ENSO and PDO, fire was synchronous within broad subregions and sometimes asynchronous among those regions. In contrast, fires were most commonly synchronous across the West during warm phases of the AMO. ENSO and PDO were the main drivers of high-frequency variation in fire (interannual to decadal), whereas the AMO conditionally changed the strength and spatial influence of ENSO and PDO on wildfire occurrence at multidecadal scales. A current warming trend in AMO suggests that we may expect an increase in widespread, synchronous fires across the western U.S. in coming decades.

Decadal/interdecadal variations of the ocean temperature and its impacts on climate

Decadal/interdecadal climate variability is an important research focus of the CLIVAR Program and has been paid more attention. Over recent years, a lot of studies in relation to interdecadal climate variations have been also completed by Chinese scientists. This paper presents an overview of some advances in the study of decadal/interdecadal variations of the ocean temperature and its climate impacts, which includes interdecadal climate variability in China, the interdecadal modes of sea surface temperature (SST) anomalies in the North Pacific, and in particular, the impacts of interdecadal SST variations on the Asian monsoon rainfall. As summarized in this paper, some results have been achieved by using climate diagnostic studies of historical climatic datasets. Two fundamental interdecadal SST variability modes (7–10-years mode and 25–35-years mode) have been identified over the North Pacific associated with different anomalous patterns of atmospheric circulation. The southern Indian Ocean dipole (SIOD) shows a major feature of interdecadal variation, with a positive (negative) phase favoring a weakened (enhanced) Asian summer monsoon in the following summer. It is also found that the China monsoon rainfall exhibits interdecadal variations with more wet (dry) monsoon years in the Yangtze River (South China and North China) before 1976, but vice versa after 1976. The weakened relationship between the Indian summer rainfall and ENSO is a feature of interdecadal variations, suggesting an important role of the interdecadal variation of the SIOD in the climate over the south Asia and southeast Asia. In addition, evidence indicates that the climate shift in the 1960s may be related to the anomalies of the North Atlantic Oscillation (NAO) and North Pacific Oscillation (NPO). Overall, the present research has improved our understanding of the decadal/interdecadal variations of SST and their impacts on the Asian monsoon rainfall. However, the research also highlights a number of problems for future research, in particular the mechanisms responsible for the monsoon long-term predictability, which is a great challenge in climate research.

Diagnosing the Annual Cycle Modes in the Tropical Atlantic Ocean Using a Directly Coupled Atmosphere–Ocean GCM

Abstract The annual cycle of sea surface temperature (SST) in the tropical Atlantic of a directly coupled atmosphere–ocean general circulation model (CGCM) is decomposed into the parts forced by different surface fluxes (denoted as modes) for the two extreme months of March and August using forced ocean experiments. Almost all previous diagnostic work of the forcing of the SST annual cycle in the Atlantic has concentrated on the near-equatorial region. Here, the annual cycle is examined within the latitude range of 25°S–25°N to facilitate comparison with the interannual variability. The structure of the response to the different surface flux forcings bears some resemblance to the interannual SST modes in the tropical Atlantic, which are diagnosed using rotated empirical orthogonal function (REOF) analysis. Diagnosis of the forcing of the annual cycle modes and the interannual modes shows that they do not always have a common cause. Hence, the simple interpretation that the leading interannual modes are perturbations to the annual cycle is not always valid. In particular, the equatorial SST annual cycle mode is primarily driven by variations in vertical velocity while the equatorial interannual mode is associated with eastward-propagating thermocline anomalies and is forced by both thermocline anomalies and vertical velocity anomalies. As for the interannual modes, there exist off-equatorial annual cycle modes in both the Northern and Southern Hemispheres. The annual cycle off-equatorial mode in both hemispheres is shown to be primarily driven by heat flux variations. The Southern Hemisphere interannual mode is primarily driven by heat flux variations while the Northern Hemisphere interannual mode shows a strong influence of thermocline depth anomalies. In addition, the Southern Hemisphere interannual mode is centered about 10° south of the annual cycle mode. An interannual mode that has maximum variability along the South American coast south of the equator is shown to be associated with thermocline depth anomalies. This interannual mode has no analog in the annual cycle modes. The coupled model simulation of the annual cycle is found to be fairly realistic so that the results presented here could have applicability to the observed Atlantic.

Multidecadal climate variability of global lands and oceans

AbstractPrincipal components analysis (PCA) and singular value decomposition (SVD) are used to identify the primary modes of decadal and multidecadal variability in annual global Palmer Drought Severity Index (PDSI) values and sea‐surface temperatures (SSTs). The PDSI and SST data for 1925–2003 were detrended and smoothed (with a 10‐year moving average) to isolate the decadal and multidecadal variability. The first two principal components (PCs) of the PDSI PCA explained almost 38% of the decadal and multidecadal variance in the detrended and smoothed global annual PDSI data. The first two PCs of detrended and smoothed global annual SSTs explained nearly 56% of the decadal variability in global SSTs. The PDSI PCs and the SST PCs are directly correlated in a pairwise fashion. The first PDSI and SST PCs reflect variability of the detrended and smoothed annual Pacific Decadal Oscillation (PDO), as well as detrended and smoothed annual Indian Ocean SSTs. The second set of PCs is strongly associated with the Atlantic Multidecadal Oscillation (AMO). The SVD analysis of the cross‐covariance of the PDSI and SST data confirmed the close link between the PDSI and SST modes of decadal and multidecadal variation and provided a verification of the PCA results. These findings indicate that the major modes of multidecadal variations in SSTs and land‐surface climate conditions are highly interrelated through a small number of spatially complex but slowly varying teleconnections. Therefore, these relations may be adaptable to providing improved baseline conditions for seasonal climate forecasting. Copyright © 2006 John Wiley & Sons, Ltd.

Variability of the Indian Ocean sea surface temperature and its impacts on Asian‐Australian monsoon climate

In this study, the authors investigate the relationships between the Indian Ocean (IO) sea surface temperature (SST) and the Asian‐Australian monsoon (AAM) on seasonal to interannual timescales. They focus on the dominant features of IO SST, the impacts of IO SST on different monsoon components, and the relative importance of the northern and southern IO for the AAM. The dominant mode of IO SST is often characterized by uniform warming or cooling, with maximum variance in the Southern Hemisphere. This mode exerts a larger impact on monsoon variability than does the tropical IO dipole. The IO SST is strongly persistent from the boreal fall to the next spring even summer and less persistent from boreal summer to fall, a feature related to seasonal alternation of the dominance of the impacts of Pacific and IO SSTs on the Asian‐Australian monsoons. While the tropical central Pacific SST exerts an apparently larger impact on the monsoon climate in the boreal winter and the transitional seasons, the IO SST affects the summer regional climate more strongly. The springtime IO SST leads to opposite changes in the south Asian monsoon (SAM) and the Southeast Asian monsoon (SEAM), reinforcing the out‐of‐phase relationship that appears often between the two monsoon components. While a warmer IO strengthens the SAM, it weakens the SEAM. Furthermore, the southern IO SST is related to the Asian summer monsoon more closely than the northern IO SST. The boreal fall IO SST, especially that in the north IO, is strongly associated with the subsequent Australian summer monsoon.