scholarly journals Spatiotemporal Variations in Hydroclimate across the Mediterranean Andes (30°–37°S) since the Early Twentieth Century

2017 ◽  
Vol 18 (7) ◽  
pp. 1929-1942 ◽  
Author(s):  
Álvaro González-Reyes ◽  
James McPhee ◽  
Duncan A. Christie ◽  
Carlos Le Quesne ◽  
Paul Szejner ◽  
...  
Keyword(s):  
Southern Oscillation ◽  
Kernel Estimation ◽  
Spatial And Temporal Patterns ◽  
The Andes ◽  
The Pacific ◽  
The Mediterranean ◽  
Multidecadal Climate Variability ◽  
Hydroclimatic Variability ◽  
North And South

Abstract In the Mediterranean Andes region (MA; 30°–37°S), the main rivers are largely fed by melting snowpack and provide freshwater to around 10 million people on both sides of the Andes Mountains. Water resources in the MA are under pressure because of the extensive development of industrial agriculture and mining activities. This pressure is increasing as the region faces one of its worst recorded droughts. Previous studies have pointed to El Niño–Southern Oscillation (ENSO) as the main climatic force impacting the MA. However, the role of decadal and multidecadal climate variability, their spatial patterns, and the recurrence of long-term droughts remains poorly studied. In an attempt to better understand these factors, spatial and temporal patterns of hydroclimatic variability are analyzed using an extensive database of streamflow, precipitation, and snowpack covering the period between 1910 and 2011. These analyses are based on the combination of correlation, principal components, and kernel estimation techniques. Despite a general common pattern across the MA, the results presented here identify two hydroclimatic subregions, located north and south of 34°S. While the interannual variability associated with ENSO is slightly stronger north of 34°S, the variability associated with the Pacific decadal oscillation (PDO) and/or the interdecadal Pacific oscillation (IPO) index shows similar patterns in both regions. However, variations produced by the IPO forcing seem to be greater in the southern subregion since 1975. The estimations presented here on drought recurrence reveal a generalized increase in dry extremes since the 1950s. These findings suggest that the northern MA is more vulnerable to changes in hydrology and climate than the southern MA.

scholarly journals Coupling Influences of ENSO and PDO on the Inter-Decadal SST Variability of the ACC around the Western South Atlantic

2019 ◽  
Vol 11 (18) ◽  
pp. 4853
Author(s):  
You-Lin Wang ◽  
Yu-Chen Hsu ◽  
Chung-Pan Lee ◽  
Chau-Ron Wu
Keyword(s):  
Antarctic Circumpolar Current ◽  
Water Mass ◽  
Southern Oscillation ◽  
Drake Passage ◽  
South Atlantic ◽  
Sst Variability ◽  
The Pacific ◽  
Circumpolar Current ◽  
The Antarctic

The Antarctic Circumpolar Current (ACC) plays an important role in the climate as it balances heat energy and water mass between the Pacific and Atlantic Oceans through the Drake Passage. However, because the historical measurements and observations are extremely limited, the decadal and long-term variations of the ACC around the western South Atlantic Ocean are rarely studied. By analyzing reconstructed sea surface temperatures (SSTs) in a 147-year period (1870–2016), previous studies have shown that SST anomalies (SSTAs) around the Antarctic Peninsula and South America had the same phase change as the El Niño Southern Oscillation (ENSO). This study further showed that changes in SSTAs in the regions mentioned above were enlarged when the Pacific Decadal Oscillation (PDO) and the ENSO were in the same warm or cold phase, implying that changes in the SST of higher latitude oceans could be enhanced when the influence of the ENSO is considered along with the PDO.

scholarly journals Half-precessional cycle of thermocline temperature in the western equatorial Pacific and its bihemispheric dynamics

2020 ◽  
Vol 117 (13) ◽  
pp. 7044-7051
Author(s):  
Zhimin Jian ◽  
Yue Wang ◽  
Haowen Dang ◽  
David W. Lea ◽  
Zhengyu Liu ◽  
...  
Keyword(s):  
Climate Change ◽  
Southern Oscillation ◽  
Decisive Role ◽  
Equatorial Pacific ◽  
The Pacific ◽  
Equatorial Thermocline ◽  
Western Equatorial Pacific ◽  
Tightly Coupled ◽  
Interannual Climate Variability

The El Niño−Southern Oscillation (ENSO), which is tightly coupled to the equatorial thermocline in the Pacific, is the dominant source of interannual climate variability, but its long-term evolution in response to climate change remains highly uncertain. This study uses Mg/Ca in planktonic foraminiferal shells to reconstruct sea surface and thermocline water temperatures (SST and TWT) for the past 142 ky in a western equatorial Pacific (WEP) core MD01-2386. Unlike the dominant 100-ky glacial−interglacial cycle recorded by SST and δ18O, which echoes the pattern seen in other WEP sites, the upper ocean thermal gradient shows a clear half-precessional (9.4 ky or 12.7 ky) cycle as indicated by the reconstructed and simulated temperature (ΔT) and δ18O differences between the surface and thermocline waters. This phenomenon is attributed to the interplay of subtropical-to-tropical thermocline anomalies forced by the antiphased meridional insolation gradients in the two hemispheres at the precessional band. In particular, the TWT shows greater variability than SST, and dominates the ΔT changes which couple with the west−east SST difference in the equatorial Pacific at the half-precessional band, implying a decisive role of the tropical thermocline in orbital-scale climate change.

scholarly journals Climatology and Variability of Warm and Cold Fronts over North America from 1979 to 2018

2020 ◽  
Vol 33 (15) ◽  
pp. 6531-6554
Author(s):  
Ryan Lagerquist ◽  
John T. Allen ◽  
Amy McGovern
Keyword(s):  
North America ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Specific Humidity ◽  
Regional Patterns ◽  
Cold Fronts ◽  
The Pacific ◽  
Cyclone Tracks

AbstractThis paper describes the development and analysis of an objective climatology of warm and cold fronts over North America from 1979 to 2018. Fronts are detected by a convolutional neural network (CNN), trained to emulate fronts drawn by human meteorologists. Predictors for the CNN are surface and 850-hPa fields of temperature, specific humidity, and vector wind from the ERA5 reanalysis. Gridded probabilities from the CNN are converted to 2D frontal regions, which are used to create the climatology. Overall, warm and cold fronts are most common in the Pacific and Atlantic cyclone tracks and the lee of the Rockies. In contrast with prior research, we find that the activity of warm and cold fronts is significantly modulated by the phase and intensity of El Niño–Southern Oscillation. The influence of El Niño is significant for winter warm fronts, winter cold fronts, and spring cold fronts, with activity decreasing over the continental United States and shifting northward with the Pacific and Atlantic cyclone tracks. Long-term trends are generally not significant, although we find a poleward shift in frontal activity during the winter and spring, consistent with prior research. We also identify a number of regional patterns, such as a significant long-term increase in warm fronts in the eastern tropical Pacific Ocean, which are characterized almost entirely by moisture gradients rather than temperature gradients.

scholarly journals Seven years of global retrieval of cloud properties using space-borne data of GOME

2012 ◽  
Vol 5 (7) ◽  
pp. 1551-1570 ◽  
Author(s):  
L. Lelli ◽  
A. A. Kokhanovsky ◽  
V. V. Rozanov ◽  
M. Vountas ◽  
A. M. Sayer ◽  
...  
Keyword(s):  
Southern Oscillation ◽  
Trace Gases ◽  
Retrieval Algorithm ◽  
Cloud Properties ◽  
The Pacific ◽  
Asymptotic Equations ◽  
Spherical Cloud ◽  
The Pacific Ocean ◽  
Cloud Optical Thickness

Abstract. We present a global and regional multi-annual (June 1996–May 2003) analysis of cloud properties (spherical cloud albedo – CA, cloud optical thickness – COT and cloud top height – CTH) of optically thick (COT > 5) clouds, derived using measurements from the GOME instrument on board the ESA ERS-2 space platform. We focus on cloud top height, which is obtained from top-of-atmosphere backscattered solar light measurements in the O2 A-band using the Semi-Analytical CloUd Retrieval Algorithm SACURA. The physical framework relies on the asymptotic equations of radiative transfer. The dataset has been validated against independent ground- and satellite-based retrievals and is aimed to support trace-gases retrievals as well as to create a robust long-term climatology together with SCIAMACHY and GOME-2 ensuing retrievals. We observed the El Niño-Southern Oscillation anomaly in the 1997–1998 record through CTH values over the Pacific Ocean. The global average CTH as derived from GOME is 5.6 ± 3.2 km, for a corresponding average COT of 19.1 ± 13.9.

scholarly journals Factors Affecting the Long-Term Development of Specialized Agricultural Villages North and South of Huai River

Land ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1215
Author(s):  
Li Li ◽  
Ning Niu ◽  
Xiaojian Li
Keyword(s):  
Economic Factors ◽  
Spatial And Temporal Patterns ◽  
Location Factors ◽  
Factors Affecting ◽  
Time Points ◽  
The North ◽  
Huai River ◽  
Market Factors ◽  
North And South

Village-level agricultural specialization in China is becoming increasingly important for rural development. However, existing knowledge of specialized agricultural villages (SAVs) based on singular assessment criteria and data describing static time points becomes insufficient in addressing multifaceted developmental questions today. We examined the long-term development patterns of SAVs in Anhui, China, with attributes from multiple angles, and explored how local factors affected SAV development across space and time using random forest regression. We found that as time elapsed, economic rationality drove specialized farmers closer to sale dependency and made SAVs more susceptible to market and economic factors, which builds upon previous findings analyzing SAVs at specific time points and consolidates the importance of market factors in the long-term development of SAVs. However, this susceptibility manifests differently in these two geographically contrasting regions north and south of Huai River. The northern SAVs received increased influences from market and economic factors, while the southern SAVs were continuously controlled by market and location factors. The dynamic spatial and temporal patterns of the two regions point to different dependencies, which emphasized local sales in the north and distant sales in the south. We propose that policies and strategies regarding SAV development accommodate these dynamics and address appropriate influencing factors accordingly.

scholarly journals Stability of ENSO and its tropical Pacific teleconnections over the Last Millennium

2015 ◽  
Vol 11 (10) ◽  
pp. 1347-1360 ◽  
Author(s):  
S. C. Lewis ◽  
A. N. LeGrande
Keyword(s):  
Large Scale ◽  
Southern Oscillation ◽  
Coupled Model ◽  
Historical Period ◽  
Last Millennium ◽  
Central Pacific ◽  
Proxy Records ◽  
The Pacific ◽  
The Stability

Abstract. Determining past changes in the amplitude, frequency and teleconnections of the El Niño-Southern Oscillation (ENSO) is important for understanding its potential sensitivity to future anthropogenic climate change. Palaeo-reconstructions from proxy records can provide long-term information of ENSO interactions with the background climatic state through time. However, it remains unclear how ENSO characteristics have changed on long timescales, and precisely which signals proxies record. Proxy interpretations are typically underpinned by the assumption of stationarity in relationships between local and remote climates, and often utilise archives from single locations located in the Pacific Ocean to reconstruct ENSO histories. Here, we investigate the long-term characteristics of ENSO and its teleconnections using the Last Millennium experiment of CMIP5 (Coupled Model Intercomparison Project phase 5; Taylor et al., 2012). We show that the relationship between ENSO conditions (NINO3.4) and local climates across the Pacific basin differs significantly for 100-year epochs defining the Last Millennium and the historical period 1906–2005. Furthermore, models demonstrate decadal- to centennial-scale modulation of ENSO behaviour during the Last Millennium. Overall, results suggest that the stability of teleconnections may be regionally dependent and that proxy climate records may reveal complex changes in teleconnected patterns, rather than large-scale changes in base ENSO characteristics. As such, proxy insights into ENSO may require evidence to be considered over large spatial areas in order to deconvolve changes occurring in the NINO3.4 region from those relating to local climatic variables. To obtain robust histories of the ENSO and its remote impacts, we recommend interpretations of proxy records should be considered in conjunction with palaeo-reconstructions from within the central Pacific.

scholarly journals Non–stationarity in annual maxima rainfall across Australia – implications for Intensity–Frequency–Duration (IFD) relationships

2015 ◽  
Vol 12 (3) ◽  
pp. 3449-3475 ◽  
Author(s):  
D. C. Verdon-Kidd ◽  
A. S. Kiem
Keyword(s):  
Climate Variability ◽  
Daily Rainfall ◽  
Data Sets ◽  
Time Period ◽  
The World ◽  
Multidecadal Climate Variability ◽  
Guidance Needs ◽  
Hydroclimatic Variability ◽  
Climate Statistics

Abstract. Rainfall Intensity–Frequency–Duration (IFD) relationships are commonly required for the design and planning of water supply and management systems around the world. Currently IFD information is based on the "stationary climate assumption" – that weather at any point in time will vary randomly and that the underlying climate statistics (including both averages and extremes) will remain constant irrespective of the period of record. However, the validity of this assumption has been questioned over the last 15 years, particularly in Australia, following an improved understanding of the significant impact of climate variability and change occurring on interannual to multidecadal timescales. This paper provides evidence of non-stationarity in annual maxima rainfall timeseries using 96 daily rainfall stations and 66 sub-daily rainfall stations across Australia. Further, the effect of non-stationarity on the resulting IFD estimates are explored for three long-term sub-daily rainfall records (Brisbane, Sydney and Melbourne) utilising insights into multidecadal climate variability. It is demonstrated that IFD relationships may under- or over-estimate the design rainfall depending on the length and time period spanned by the rainfall data used to develop the IFD information. It is recommended that non-stationarity in annual maxima rainfall be explicitly considered and appropriately treated in the ongoing revisions of Engineers Australia's guide to estimating and utilising IFD information, "Australian Rainfall and Runoff", and that clear guidance needs to be provided on how to deal with the issue of non-stationarity of extreme events (irrespective of whether that non-stationarity is due to natural or anthropogenic climate change). The findings of our study also have important implications for other regions of the world that exhibit considerable hydroclimatic variability and where IFD information is based on relatively short data sets.

scholarly journals Has spring snowpack declined in the Washington Cascades?

2008 ◽  
Vol 12 (1) ◽  
pp. 193-206 ◽  
Author(s):  
P. Mote ◽  
A. Hamlet ◽  
E. Salathé
Keyword(s):  
Snow Water Equivalent ◽  
Spatial And Temporal Patterns ◽  
Regional Warming ◽  
Temperature And Precipitation ◽  
The Pacific ◽  
Snow Water ◽  
Long Term Trends ◽  
Natural Variations ◽  
High Elevations

Abstract. Our best estimates of 1 April snow water equivalent (SWE) in the Cascade Mountains of Washington State indicate a substantial (roughly 15–35%) decline from mid-century to 2006, with larger declines at low elevations and smaller declines or increases at high elevations. This range of values includes estimates from observations and hydrologic modeling, reflects a range of starting points between about 1930 and 1970 and also reflects uncertainties about sampling. The most important sampling issue springs from the fact that half the 1 April SWE in the Cascades is found below about 1240 m, altitudes at which sampling was poor before 1945. Separating the influences of temperature and precipitation on 1 April SWE in several ways, it is clear that long-term trends are dominated by trends in temperature, whereas variability in precipitation adds "noise" to the time series. Consideration of spatial and temporal patterns of change rules out natural variations like the Pacific Decadal Oscillation as the sole cause of the decline. Regional warming has clearly played a role, but it is not yet possible to quantify how much of that regional warming is related to greenhouse gas emissions.

The Spatiotemporal Structure of Twentieth-Century Climate Variations in Observations and Reanalyses. Part I: Long-Term Trend

2008 ◽  
Vol 21 (11) ◽  
pp. 2611-2633 ◽  
Author(s):  
Junye Chen ◽  
Anthony D. Del Genio ◽  
Barbara E. Carlson ◽  
Michael G. Bosilovich
Keyword(s):  
Twentieth Century ◽  
Decadal Variability ◽  
Southern Oscillation ◽  
Walker Circulation ◽  
Warming Trend ◽  
Pacific Basin ◽  
Climate Variations ◽  
The Pacific ◽  
Climate Parameter

Abstract The dominant interannual El Niño–Southern Oscillation (ENSO) phenomenon and the short length of climate observation records make it difficult to study long-term climate variations in the spatiotemporal domain. Based on the fact that the ENSO signal spreads to remote regions and induces delayed climate variation through atmospheric teleconnections, an ENSO-removal method is developed through which the ENSO signal can be approximately removed at the grid box level from the spatiotemporal field of a climate parameter. After this signal is removed, long-term climate variations are isolated at mid- and low latitudes in the climate parameter fields from observed and reanalysis datasets. This paper addresses the long-term global warming trend (GW); a companion paper concentrates on Pacific pan-decadal variability (PDV). The warming that occurs in the Pacific basin (approximately 0.4 K in the twentieth century) is much weaker than in surrounding regions and the other two ocean basins (approximately 0.8 K). The modest warming in the Pacific basin is likely due to its dynamic nature on the interannual and decadal time scales and/or the leakage of upper ocean water through the Indonesian Throughflow. Based on the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) and the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40), a comprehensive atmospheric structure associated with the GW trend is given. Significant discrepancies exist between the two datasets, especially in the tightly coupled dynamics and water vapor fields. The dynamics fields based on NCEP–NCAR, which show a change in the Walker Circulation, are consistent with the GW change in the surface temperature field. However, intensification in the Hadley Circulation is associated with GW trend in ERA-40 instead.

scholarly journals Long-term environmental change in eastern Tasmania: Vegetation, climate and fire at Stoney Lagoon

The Holocene ◽  
2017 ◽  
Vol 27 (9) ◽  
pp. 1340-1349 ◽  
Author(s):  
Penelope J Jones ◽  
Ian Thomas ◽  
Michael-Shawn Fletcher
Keyword(s):  
Environmental Change ◽  
Fire History ◽  
Southern Oscillation ◽  
Late Quaternary ◽  
Eastern Coast ◽  
Vegetation Development ◽  
Macro Scale ◽  
Hydroclimatic Variability ◽  
A Site

Tasmania’s dry, inland east is ideally positioned to inform models of late Quaternary environmental change in southern Australasia. Despite this, it remains poorly represented in the palaeoecological record. Here, we seek to address this with a >13,000-year vegetation and fire history from Stoney Lagoon, a site at the eastern margin of Tasmania’s inland Midlands plains. Pollen and charcoal analysis indicates that here, a relatively moist early deglacial was followed by a dry later deglacial (ca. 14,000–12,000 cal. BP), when sclerophyll forests became well established and burning increased. This suggests that the Midlands’ vegetation responded to the climatic signals characterising Australia’s south-eastern coast rather than those governing developments in western Tasmania. Dry sclerophyll forest persisted throughout the Holocene; with a pronounced transition from more to less grassy understoreys between ca. 9000 and 7000 cal. BP. From the mid-Holocene, the sclerophyll community remains relatively stable. However, increased fire activity and trends in moisture-sensitive taxa suggest generally drier conditions coupled with greater hydroclimatic variability under the strengthening influence of the El Niño–Southern Oscillation (ENSO). Overall, these results highlight the role of macro-scale climatic shifts in shaping vegetation development in Tasmania’s inland east, while hinting at the concurrent importance of local ecological drivers. This highlights the need for spatially diverse studies to understand interactions between drivers of long-term environmental change in sub-humid southern Australia. This research also supports conservation by strengthening understandings of pre-colonial baselines in this highly modified landscape.

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