Global Climate Indices Research Articles

インドネシアジャワ島南央部における高地の天水農業の収量とグローバル指数との関係について

インドネシアジャワ島南央部における高地の天水農業の収量とグローバル指数との関係について

Precipitation pattern analysis in the Tiber River basin (central Italy) using standardized indices

ABSTRACTThis study analyses the precipitation pattern in the Tiber River basin (central Italy) to determine trends, possible change points, periodicity and relationships with global climate indices, such as the North Atlantic Oscillation (NAO) index. The dataset is composed of daily rainfall time series, recorded at 21 to 102 different sampling stations, from 1952 to 2007. The following quantities were analysed at both an annual and seasonal scale: cumulative precipitation, number of rainy days, mean intensity, maximum daily precipitation and number of days needed to reach a given percentage of the cumulative precipitation. To compare the time series collected from different stations along with the different quantities, a standardization procedure based on the normal inverse function computed on the best‐fit cumulative probability distribution was applied. The standardized time series from each station was regionalized by kriging. Trends were analysed using the Mann–Kendall test, and possible change points were determined using an algorithm based on the singular spectrum analysis. The periodicity of the signals was evaluated by cross‐wavelet analysis. The results show a decreasing trend in annual precipitation (−8%) mainly because of decreasing winter precipitation (−16%). This trend appears to be related to a decrease in the number of rainy days. A significant change point in precipitation trends was identified in the mid‐1980s. Conversely, those indices related to the intensity of precipitation (mean intensity, maximum daily precipitation) do not show significant trends. The cross‐wavelet analysis performed on the annual/winter precipitation and NAO time series indicates the existence of four coherent periodic signals with periods of approximately 3, 4, 8 and 15 years. Copyright © 2012 Royal Meteorological Society

Climate change and the decline of a once common bird

Climate change is predicted to negatively impact wildlife through a variety of mechanisms including retraction of range. We used data from the North American Breeding Bird Survey and regional and global climate indices to examine the effects of climate change on the breeding distribution of the Rusty Blackbird (Euphagus carolinus), a formerly common species that is rapidly declining. We found that the range of the Rusty Blackbird retracted northward by 143 km since the 1960s and that the probability of local extinction was highest at the southern range margin. Furthermore, we found that the mean breeding latitude of the Rusty Blackbird was significant and positively correlated with the Pacific Decadal Oscillation with a lag of six years. Because the annual distribution of the Rusty Blackbird is affected by annual weather patterns produced by the Pacific Decadal Oscillation, our results support the hypothesis that directional climate change over the past 40 years is contributing to the decline of the Rusty Blackbird. Our study is the first to implicate climate change, acting through range retraction, in a major decline of a formerly common bird species.

Variability in Fusarium Head Blight Epidemics in Relation to Global Climate Fluctuations as Represented by the El Niño-Southern Oscillation and Other Atmospheric Patterns

Cross-spectral analysis was used to characterize the relationship between climate variability, represented by atmospheric patterns, and annual fluctuations of Fusarium head blight (FHB) disease intensity in wheat. Time series investigated were the Oceanic Niño Index (ONI), which is a measure of the El Niño-Southern Oscillation (ENSO), the Pacific-North American (PNA) pattern and the North Atlantic Oscillation (NAO), which are known to have strong influences on the Northern Hemisphere climate, and FHB disease intensity observations in Ohio from 1965 to 2010 and in Indiana from 1973 to 2008. For each climate variable, mean climate index values for the boreal winter (December to February) and spring (March to May) were utilized. The spectral density of each time series and the (squared) coherency of each pair of FHB-climate-index series were estimated. Significance for coherency was determined by a nonparametric permutation procedure. Results showed that winter and spring ONI were significantly coherent with FHB in Ohio, with a period of about 5.1 years (as well as for some adjacent periods). The estimated phase-shift distribution indicated that there was a generally negative relation between the two series, with high values of FHB (an indication of a major epidemic) estimated to occur about 1 year following low values of ONI (indication of a La Niña); equivalently, low values of FHB were estimated to occur about 1 year after high values of ONI (El Niño). There was also limited evidence that winter ONI had significant coherency with FHB in Indiana. At periods between 2 and 7 years, the PNA and NAO indices were coherent with FHB in both Ohio and Indiana, although results for phase shift and period depended on the specific location, climate index, and time span used in calculating the climate index. Differences in results for Ohio and Indiana were expected because the FHB disease series for the two states were not similar. Results suggest that global climate indices and models could be used to identify potential years with high (or low) risk for FHB development, although the most accurate risk predictions will need to be customized for a region and will also require use of local weather data during key time periods for sporulation and infection by the fungal pathogen.

Exploring Relationships between Demersal Resources and Environmental Factors in the Ionian Sea (Central Mediterranean)

The relationships between the abundance of demersal resources, environmental variables, and fishing pressure in the north-western Ionian Sea in the last two decades were evaluated. Data on the density collected during seventeen trawl surveys carried out from 1985 to 2005 were used. The following species were considered:Aristaeomorpha foliacea, Nephrops norvegicus,andParapenaeus longirostrisfor crustaceans;Merluccius merluccius, Phycis blennoides,andMullus barbatusfor teleost fish. The recruitment index was also considered forN. norvegicus, P. longirostris, M. merlucciusandMullus barbatus. Six candidate models were evaluated for each density and recruitment data set either combining fishing effort with global (NAO) and regional (SST and precipitation) climatic indices, or models separately involving fishing effort, NAO, or regional climatic indices as the only predictive variable. Model selection was carried out using an information-theoretical approach that applies Akaike’s Information Criterion (AIC). High changes over time were observed for the density data and recruitment indices in each species. Apart from hake abundance and recruitment data, for which a clear positive relationship with the NAO index alone was detected, the changes observed in the other species seem to be the consequence of the interaction between bottom-up effects linked to changes in physical environment and top-down ones due to the fishing pressure.

Greenland Ice Sheet surface mass balance 1870 to 2010 based on Twentieth Century Reanalysis, and links with global climate forcing

We present a reconstruction of the Greenland Ice Sheet surface mass balance (SMB) from 1870 to 2010, based on merged Twentieth Century Reanalysis (20CR) and European Centre for Medium-Range Weather Forecasts (ECMWF) meteorological reanalyses, and we compare our new SMB series with global and regional climate and atmospheric circulation indices during this period. We demonstrate good agreement between SMB annual series constructed from 20CR and ECMWF reanalyses for the common period of overlap and show statistically significant agreement of long-term modeled snowfall with ice-core-based accumulation data. We analyze variations in SMB for the last 140 years and highlight the periods with significantly increased runoff and decreased SMB since 1870, which have both been enhanced in the period since 1990, as well as interannual variations in SMB linked to Greenland climate fluctuations. We show very good agreement of our SMB series variations with existing, independently derived SMB series (RACMO2) variations for the past few decades of overlap but also a significant disparity of up to �200 km3 yr-1 in absolute SMB values due to poorly constrained modeled accumulation reflecting a lack of adequate validation data in southeast Greenland. There is no significant correlation between our SMB time series and a widely referenced time series of North Atlantic icebergs emanating from Greenland for the past century, which may reflect the complex nature of the relationship between SMB and ice dynamical changes. Finally, we discuss how our analysis sheds light on the sensitivity and response of the Greenland Ice Sheet to ongoing and future global climate change, and its contribution to global sea level rise. Copyright 2011 by the American Geophysical Union.

Variability of the 557-nm atmospheric emission

The variability of diurnal, day-to-day, and monthly average rates of the 557.7-nm atmospheric emission (I557.7) is considered. We use 1997–2010 airglow observation data obtained for the upper atmosphere over Eastern Siberia (52°N, 103°E). The variation coefficient KV of corresponding quantities is taken as the variability index. For the 23rd solar cycle, we examine the resulting seasonal variation of KV of monthly averaged I557.7, the dependence of monthly averaged I557.7 on solar activity for each month, the variation coefficient of diurnal values of I557.7 for different seasons of the year, the variability of I557.7 during some geophysical events, and the correlation of I557.7 variations with global climatic indices.

Relationships between large-scale circulation patterns and carbon dioxide exchange by a deciduous forest

[1] In this study, we focus on a deciduous forest in central Massachusetts and investigate the relationships between global climate indices and CO2 exchange using eddy-covariance flux measurements from 1992 to 2007. Results suggest that large-scale circulation patterns influence the annual CO2 exchange in the forest through their effects on the local surface climate. Annual gross ecosystem exchange (GEE) in the forest is closely associated with spring El Nino–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO), previous fall Atlantic Multidecadal Oscillation (AMO), and previous winter East Pacific–North Pacific (EP-NP) pattern. Annual net ecosystem exchange (NEE) responds to previous fall AMO and PDO, while annual respiration (R) is impacted by previous fall ENSO and Pacific/North American Oscillation (PNA). Regressions based on these relationships are developed to simulate the annual GEE, NEE, and R. To avoid problems of multicollinearity, we compute a “Composite Index for GEE (CIGEE)” based on a linear combination of spring ENSO and PDO, fall AMO, and winter EP-NP and a “Composite Index for R (CIR)” based on a linear combination of fall ENSO and PNA. CIGEE, CIR, and fall AMO and PDO can explain 41, 27, and 40% of the variance of the annual GEE, R, and NEE, respectively. We further apply the methodology to two other northern midlatitude forests and find that interannual variabilities in NEE of the two forests are largely controlled by large-scale circulation patterns. This study suggests that global climate indices provide the potential for predicting CO2 exchange variability in the northern midlatitude forests.

Temperature Variability over Saudi Arabia and its Association with Global Climate Indices

Temperature Variability over Saudi Arabia and its Association with Global Climate Indices

Relationship between increase rate of human plague in China and global climate index as revealed by cross‐spectral and cross‐wavelet analyses

Plague has caused the death of hundreds of millions of people throughout the human history. Today this disease is again re-emerging and hence is again becoming an increasing threat to human health in several parts of the world. However, impacts of global climate variation (e.g. El Nino and Southern Oscillation [ENSO]) and global warming on plagues are largely unknown. Using cross-spectral analysis and cross-wavelet analysis, we have analyzed the relationship between increase rate of human plague in China during 1871-2003 and the following climate factors (as measured by the Southern Oscillation Index [SOI], Sea Surface Temperature of east Pacific equator [SST] and air Temperature of the Northern Hemisphere [NHT]). We found in the frequency domain that increase rate of human plague was closely associated with SOI and SST. Cross-spectral analysis reveals that significant coherencies between increase rate of human plague and ENSO were found over short periods (2-3 years), medium periods (6-7 years) and long periods (11-12 years, 30-40 years). Cross-wavelet analysis reveals that increase rate of human plague oscillates in phase with SOI, but in anti-phase with SST over periods of 2-4 years and approximately 8 years (6-10 years). These results indicate that ENSO-driven climate variation may be important for occurrences of human plague in China. However, there is a need for a further analysis of the underlying mechanism between human plague in China and ENSO.

Review article. Studying climate effects on ecology through the use of climate indices: the North Atlantic Oscillation, El Niño Southern Oscillation and beyond

Whereas the El Niño Southern Oscillation (ENSO) affects weather and climate variability worldwide, the North Atlantic Oscillation (NAO) represents the dominant climate pattern in the North Atlantic region. Both climate systems have been demonstrated to considerably influence ecological processes. Several other large-scale climate patterns also exist. Although less well known outside the field of climatology, these patterns are also likely to be of ecological interest. We provide an overview of these climate patterns within the context of the ecological effects of climate variability. The application of climate indices by definition reduces complex space and time variability into simple measures, 'packages of weather'. The disadvantages of using global climate indices are all related to the fact that another level of problems are added to the ecology-climate interface, namely the link between global climate indices and local climate. We identify issues related to: (i) spatial variation; (ii) seasonality; (iii) non-stationarity; (iv) nonlinearity; and (v) lack of correlation in the relationship between global and local climate. The main advantages of using global climate indices are: (i) biological effects may be related more strongly to global indices than to any single local climate variable; (ii) it helps to avoid problems of model selection; (iii) it opens the possibility for ecologists to make predictions; and (iv) they are typically readily available on Internet.

Decadal‐scale variability in the Kuroshio marine ecosystem in winter

AbstractInterannual variation of winter copepod biomass during the last three decades of the twentieth century was examined in the Kuroshio, off central Japan in relation to climate regime shifts. The biomass levels of large copepods in the period before 1977 and in 1999 and 2000 were higher than those in the period between 1977 and 1998. The biomass of large copepods was positively related with the Southern Oscillation Index (SOI), in winter in the Northern Hemisphere, which also showed steplike shifts in 1976/77 and 1998/99. The biomass of large copepods was largely influenced by abundance of Calanus sinicus that has high rates of production compared with small copepods under food satiated conditions. Accordingly, the climatic regime shift accompanied by the climatic change in the tropical region seems to regulate interannual variation of winter biomass of large copepods in the Kuroshio through effects on food supply. There is less decadal variablity in the small copepod (SC) biomass than large copepod (LC) biomass, but more variablity in SC than in LC at periods 2–4 years. In contrast to the large copepods, the biomass of small copepods was not related to global climate indices but with the local climate factors such as SST in the Kuroshio and variability in the Kuroshio flow path. Causes for the differences in the biomass trends between large and small copepods are discussed.

Book review

The sensitivity of Black Sea level to variations in the global forcing is studied here using tide gauge and satellite altimeter data, as well as hydro-meteorological data for the fresh water flux components. The consistency between satellite and sea borne data is analyzed and the characteristics of variability with monthly to interannual time scales are revealed. The analysis of 6-year-long data series of TOPEX/Poseidon altimeter shows that the first EOF accounts for 85% of the total variance and is associated with the water cycle, the latter forced by the air–sea exchange, continental hydrological budgets and straits outflow. This result is a demonstration that the Black Sea level integrates the variations of global forcing over vast catchment area, thus making them quite distinguishable. The second EOF describes the seasonal variability of circulation. The third and higher EOFs describe synoptic and basin-oscillations, and the corresponding principal components are characterized by strong interannual variability. By analyzing the correlation of sea level and water balance in the last 70 years, we quantify the response to the external forcing. The mean sea level trend during 1993–1997, derived from the TOPEX/Poseidon data, of ∼12 cm is much lower than the largest trends of this type observed in the last 120 years, which are associated with interannual-to-decadal variability and reach ∼20–30 cm. The correlation between the sea level and NAO index, starting from 1870s, is well pronounced, suggesting that future variations of sea level could be predicted using global climate indices. It is shown that the long-term changes of water balance are strong enough to substantially affect the exchange between Black Sea and Mediterranean Sea. This in turn might result in changing the conditions of water mass formation in the Aegean Sea and motivates further studies on the prediction of extreme events of deep water mass formation in the Eastern Mediterranean Sea as function of the global and regional water cycles.

Regional sea level response to global climatic change: Black Sea examples

The sensitivity of Black Sea level to variations in the global forcing is studied here using tide gauge and satellite altimeter data, as well as hydro-meteorological data for the fresh water flux components. The consistency between satellite and sea borne data is analyzed and the characteristics of variability with monthly to interannual time scales are revealed. The analysis of 6-year-long data series of TOPEX/Poseidon altimeter shows that the first EOF accounts for 85% of the total variance and is associated with the water cycle, the latter forced by the air–sea exchange, continental hydrological budgets and straits outflow. This result is a demonstration that the Black Sea level integrates the variations of global forcing over vast catchment area, thus making them quite distinguishable. The second EOF describes the seasonal variability of circulation. The third and higher EOFs describe synoptic and basin-oscillations, and the corresponding principal components are characterized by strong interannual variability. By analyzing the correlation of sea level and water balance in the last 70 years, we quantify the response to the external forcing. The mean sea level trend during 1993–1997, derived from the TOPEX/Poseidon data, of ∼12 cm is much lower than the largest trends of this type observed in the last 120 years, which are associated with interannual-to-decadal variability and reach ∼20–30 cm. The correlation between the sea level and NAO index, starting from 1870s, is well pronounced, suggesting that future variations of sea level could be predicted using global climate indices. It is shown that the long-term changes of water balance are strong enough to substantially affect the exchange between Black Sea and Mediterranean Sea. This in turn might result in changing the conditions of water mass formation in the Aegean Sea and motivates further studies on the prediction of extreme events of deep water mass formation in the Eastern Mediterranean Sea as function of the global and regional water cycles.

Climate‐driven changes in spring plankton dynamics and the sensitivity of shallow polymictic lakes to the North Atlantic Oscillation

Climate is increasingly recognized as a major factor driving long‐term changes in plankton communities in both marine and limnetic ecosystems. In a shallow and polymictic lake, marked changes in the dynamics of phytoplankton and in the timing of distinctive successional events in spring were observed during two recent decades. We studied whether and how these changes were linked to a series of uncommonly warm winter and spring seasons, focusing on the predictive power of a macroscale atmospheric circulation pattern, the North Atlantic Oscillation (NAO). In the warm period 1988‐1998, phytoplankton developed about 1 month earlier than in the cool period 1979‐1987, and high total phytoplankton biomass was recorded in early spring. These changes were significantly related to the NAO, which explained about 35% of the variance, and can be attributed to a shortening or lack of ice cover periods in winter. Zooplankton (Keratella, Bosmina, Daphnia) developed about 2 weeks earlie in the warm period, consequently leading to an early establishment of the clearwater phase. The shift in the timing of the daphnid peak and of the clearwater phase required an additional warming trend in late April and early May and was not significantly correlated with the winter situation. The memory effect of the NAO was restricted to a rather short postwinter period and was overtaken by the prevailing weather in April. Our results suggest that assessments of potential impacts of climate warming on biological processes in freshwater ecosystems demand basic knowledge about the relationships between global climate indices, local meteorological conditions, and the thermal response of various lake type .

Recent declines in the recreational catch of coho salmon (Oncorhynchus kisutch) in the Strait of Georgia are related to climate

Wild and hatchery-reared coho salmon (Oncorhynchus kisutch) from streams and rivers that flow into the Strait of Georgia are caught in the Strait of Georgia and off the west coast of Vancouver Island. The percentage of coho caught in either of these two areas varies from year to year. The variation is associated with the flow of freshwater from the Fraser River and became more extreme in the 1990's. In four of eight years in the 1990's and in the past three years, most coho have been caught outside the Strait of Georgia. The dramatic decline in the sport catch in the Strait is related to ocean conditions in the Strait. The change in ocean conditions is related to an increase in the number of days of zonal (westerly) winds in October, November, and December and to an increase in relative sea level height. The climate change about 1989 that affected the pattern of winter winds and the circulation in the Strait of Georgia was associated with changes in other global climate indices, demonstrating the impact that global climate events can have on the dynamics of regional salmon stocks.