scholarly journals Consistency and the Lack Thereof in Pacific Decadal Oscillation Impacts on North American Winter Climate

2014 ◽  
Vol 27 (19) ◽  
pp. 7410-7431 ◽  
Author(s):  
Stephanie A. McAfee
Keyword(s):  
Climate Variability ◽  
Pacific Decadal Oscillation ◽  
North American ◽  
Climate Models ◽  
Full Range ◽  
Circulation Pattern ◽  
Climatic Impact ◽  
Winter Climate ◽  
Teleconnection Patterns ◽  
The Impact

Abstract Impacts of the Pacific decadal oscillation (PDO) on North American climate were initially assessed over one negative (~1943 to 1976) and one positive (1977 to ~1990) PDO regime. Release of the Twentieth Century Reanalysis and the recent occurrence of negative PDO years make it possible to study the stability of PDO teleconnections. This analysis identified consistency in broad-scale teleconnection patterns but also critical differences in the amplitude of circulation pattern, temperature, and precipitation anomalies between comparable phases of the PDO. Many of these discrepancies were apparent after controlling for long-term trends and the impact of ENSO and were associated with variability in Atlantic Ocean temperatures and in the northern annular mode. Results from this study suggest that not all of the climate variability attributed to the PDO derives solely from fluctuations in Pacific sea surface temperatures (SSTs), that the climatic impact of these SST anomalies varies over time, or that the PDO might have a “mixed” state with muted teleconnections. Any of these conclusions has substantial implications for reconstruction of the PDO and its use to understand past hydrologic or ecological changes. They suggest that evaluation of climate models on the basis of their ability to simulate teleconnection patterns of low-frequency modes of climate variability should be undertaken with the recognition that observational records may not be long enough to capture the full range of variability in teleconnection patterns.

Desert-Dwelling Small Mammals as Granivores - Intercontinental Variations

1994 ◽  
Vol 42 (4) ◽  
pp. 543 ◽  
Author(s):  
GIH Kerley ◽  
WG Whitford
Keyword(s):  
Climate Variability ◽  
South African ◽  
Seed Production ◽  
Small Mammals ◽  
North American ◽  
Desert Plant ◽  
The North ◽  
Desert Rodents ◽  
Alternative Hypotheses ◽  
The Impact

Deserts are, by definition, environmentally similar, and this has lead to hypotheses of convergence in the properties of desert biotic communities as well as the components of these communities. There is considerable evidence for convergence in some characteristics of desert biota, ranging from plant growth forms to the well-known bipedal, nocturnal rodents. One area that has received considerable attention has been granivory by desert rodents, largely because of the effort focused on the North American desert heteromyids, and also because the process of granivory has far-reaching ramifications for desert plant communities. Specific tests for convergence in the impact of rodents as granivores, by means of bait-removal experiments, however, have shown that the high levels of seed removal by rodents in the North American deserts differs from that of rodents in the South American, Australian and South African deserts, where ants are the most important seed harvesters. The only studies to measure the impact of rodents on desert seed fluxes confirm these patterns, with rodents consuming up to 86% of seed production in North American deserts, but less than 1% of seed production in South African deserts. A review of dietary data for desert rodents confirms these trends, with little evidence for the presence of granivores in deserts besides those of North America. A variety of hypotheses have attempted to explain these variations in desert rodent granivory. These include recent extinctions of granivores, that seed burial, low soil nutrients and/or limiting seed production prevented the radiation of granivorous small mammals, and that particular deserts are too young or too recently colonised by rodents for granivorous rodents to have evolved. However, none of these hypotheses are supported by available evidence. Alternative hypotheses suggesting that climate variability may have precluded the development of specialised granivores need to be tested. In particular, more data are needed to confirm these patterns of granivory, and gain an understanding of the effects of Pleistocene and recent desert climate variability on seed production. An alternative perspective suggests that the presence of the heteromyid rodents may explain the high levels of granivory by small mammals in North American deserts. The variability in granivory by small mammals between deserts suggests that deserts will also differ in terms of anti-granivore adaptations of plants, seed fluxes and the mechanisms whereby small mammals coexist.

scholarly journals Evaluation of the impacts of climate variability on rainfed maize production over the Wami-Ruvu basin of Tanzania

2017 ◽  
Vol 9 (1) ◽  
pp. 207-222 ◽  
Author(s):  
Philbert Luhunga
Keyword(s):  
Climate Variability ◽  
Climate Models ◽  
Pearson Correlation ◽  
Regional Climate ◽  
Maximum Temperature ◽  
Climate Projections ◽  
Historical Climate ◽  
Climate Simulations ◽  
Maize Yields ◽  
The Impact

AbstractIn this study, the impact of inter-seasonal climate variability on rainfed maize (Zea mays) production over the Wami-Ruvu basin of Tanzania is evaluated. Daily high-resolution climate simulations from the Coordinated Regional Climate Downscaling Experiment_Regional Climate Models (CORDEX_RCMs) are used to drive the Decision Support System for Agro-technological Transfer (DSSAT) to simulate maize yields. Climate simulations for the base period of 35 years (1971–2005) are used to drive DSSAT to simulate maize yields during the historical climate. On the other hand, climate projections for the period 2010–2039 (current), 2040–2069 (mid), and 2070–2099 centuries for two Representative Concentration Pathway (RCP45 and 85) emission scenarios are used to drive DSSAT to simulate maize yields in respective centuries. Statistical approaches based on Pearson correlation coefficient and the coefficients of determination are used in the analysis. Results show that rainfall, maximum temperature, and solar radiation are the most important climate variables that determine variation in rainfed maize yields over the Wami-Ruvu basin of Tanzania. They explain the variability in maize yields in historical climate condition (1971–2005), present century under RCP 4.5, and mid and end centuries under both RCP 4.5 and RCP 8.5.

scholarly journals The effect of interactive ozone chemistry on weak and strong stratospheric polar vortex events

2020 ◽  
Author(s):  
Jessica Oehrlein ◽  
Gabriel Chiodo ◽  
Lorenzo M. Polvani
Keyword(s):  
Climate Variability ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Late Winter ◽  
Stratospheric Polar Vortex ◽  
Winter Climate ◽  
The Impact

Abstract. Modeling and observational studies have reported effects of stratospheric ozone extremes on Northern Hemisphere spring climate. Recent work has further suggested that the coupling of ozone chemistry and dynamics amplifies the surface response to midwinter sudden stratospheric warmings (SSWs). Here, we study the importance of interactive ozone chemistry in representing the stratospheric polar vortex and Northern Hemisphere winter surface climate variability. We contrast two simulations from the interactive and specified chemistry (and thus ozone) versions of the Whole Atmosphere Community Climate Model, designed to isolate the impact of interactive ozone on polar vortex variability. In particular, we analyze the response with and without interactive chemistry to midwinter SSWs, March SSWs, and strong polar vortex events (SPVs). With interactive chemistry, the stratospheric polar vortex is stronger, and more SPVs occur, but we find little effect on the frequency of midwinter SSWs. At the surface, interactive chemistry results in a pattern resembling a more negative North Atlantic Oscillation following midwinter SSWs, but with little impact on the surface signatures of late winter SSWs and SPVs. These results suggest that including interactive ozone chemistry is important for representing North Atlantic and European winter climate variability.

scholarly journals Precipitation, Temperature, and Teleconnection Signals across the Combined North American, Monsoon Asia, and Old World Drought Atlases

2017 ◽  
Vol 30 (18) ◽  
pp. 7141-7155 ◽  
Author(s):  
Seung H. Baek ◽  
Jason E. Smerdon ◽  
Sloan Coats ◽  
A. Park Williams ◽  
Benjamin I. Cook ◽  
...  
Keyword(s):  
Climate Variability ◽  
Tree Ring ◽  
North American ◽  
Large Scale ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Old World ◽  
Monsoon Asia ◽  
Teleconnection Patterns ◽  
Hydroclimate Variability

Abstract The tree-ring-based North American Drought Atlas (NADA), Monsoon Asia Drought Atlas (MADA), and Old World Drought Atlas (OWDA) collectively yield a near-hemispheric gridded reconstruction of hydroclimate variability over the last millennium. To test the robustness of the large-scale representation of hydroclimate variability across the drought atlases, the joint expression of seasonal climate variability and teleconnections in the NADA, MADA, and OWDA are compared against two global, observation-based PDSI products. Predominantly positive (negative) correlations are determined between seasonal precipitation (surface air temperature) and collocated tree-ring-based PDSI, with average Pearson’s correlation coefficients increasing in magnitude from boreal winter to summer. For precipitation, these correlations tend to be stronger in the boreal winter and summer when calculated for the observed PDSI record, while remaining similar for temperature. Notwithstanding these differences, the drought atlases robustly express teleconnection patterns associated with El Niño–Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), the Pacific decadal oscillation (PDO), and the Atlantic multidecadal oscillation (AMO). These expressions exist in the drought atlas estimates of boreal summer PDSI despite the fact that these modes of climate variability are dominant in boreal winter, with the exception of the AMO. ENSO and NAO teleconnection patterns in the drought atlases are particularly consistent with their well-known dominant expressions in boreal winter and over the OWDA domain, respectively. Collectively, the findings herein confirm that the joint Northern Hemisphere drought atlases robustly reflect large-scale patterns of hydroclimate variability on seasonal to multidecadal time scales over the twentieth century and are likely to provide similarly robust estimates of hydroclimate variability prior to the existence of widespread instrumental data.

scholarly journals The effect of interactive ozone chemistry on weak and strong stratospheric polar vortex events

2020 ◽  
Vol 20 (17) ◽  
pp. 10531-10544
Author(s):  
Jessica Oehrlein ◽  
Gabriel Chiodo ◽  
Lorenzo M. Polvani
Keyword(s):  
Climate Variability ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Late Winter ◽  
Stratospheric Polar Vortex ◽  
Winter Climate ◽  
The Impact

Abstract. Modeling and observational studies have reported effects of stratospheric ozone extremes on Northern Hemisphere spring climate. Recent work has further suggested that the coupling of ozone chemistry and dynamics amplifies the surface response to midwinter sudden stratospheric warmings (SSWs). Here we study the importance of interactive ozone chemistry in representing the stratospheric polar vortex and Northern Hemisphere winter surface climate variability. We contrast two simulations from the interactive and specified chemistry (and thus ozone) versions of the Whole Atmosphere Community Climate Model, which is designed to isolate the impact of interactive ozone on polar vortex variability. In particular, we analyze the response with and without interactive chemistry to midwinter SSWs, March SSWs, and strong polar vortex events (SPVs). With interactive chemistry, the stratospheric polar vortex is stronger and more SPVs occur, but we find little effect on the frequency of midwinter SSWs. At the surface, interactive chemistry results in a pattern resembling a more negative North Atlantic Oscillation following midwinter SSWs but with little impact on the surface signatures of late winter SSWs and SPVs. These results suggest that including interactive ozone chemistry is important for representing North Atlantic and European winter climate variability.

scholarly journals Temperature increase of 21st century mitigation scenarios

2008 ◽  
Vol 105 (40) ◽  
pp. 15258-15262 ◽  
Author(s):  
D. P. Van Vuuren ◽  
M. Meinshausen ◽  
G.-K. Plattner ◽  
F. Joos ◽  
K. M. Strassmann ◽  
...  
Keyword(s):  
21St Century ◽  
Temperature Increase ◽  
Radiative Forcing ◽  
Climate Models ◽  
Full Range ◽  
Climate System ◽  
Mitigation Scenarios ◽  
Climate Policies ◽  
Wide Range ◽  
The Impact

Estimates of 21st Century global-mean surface temperature increase have generally been based on scenarios that do not include climate policies. Newly developed multigas mitigation scenarios, based on a wide range of modeling approaches and socioeconomic assumptions, now allow the assessment of possible impacts of climate policies on projected warming ranges. This article assesses the atmospheric CO2 concentrations, radiative forcing, and temperature increase for these new scenarios using two reduced-complexity climate models. These scenarios result in temperature increase of 0.5–4.4°C over 1990 levels or 0.3–3.4°C less than the no-policy cases. The range results from differences in the assumed stringency of climate policy and uncertainty in our understanding of the climate system. Notably, an average minimum warming of ≈1.4°C (with a full range of 0.5–2.8°C) remains for even the most stringent stabilization scenarios analyzed here. This value is substantially above previously estimated committed warming based on climate system inertia alone. The results show that, although ambitious mitigation efforts can significantly reduce global warming, adaptation measures will be needed in addition to mitigation to reduce the impact of the residual warming.

Introductory Overview

2003 ◽  
Author(s):  
Douglas G. Goodin
Keyword(s):  
Time Series ◽  
Power Spectrum ◽  
Climate Variability ◽  
Spectrum Analysis ◽  
North American ◽  
Southern Oscillation ◽  
Power Spectrum Analysis ◽  
Teleconnection Patterns ◽  
Modes Of Variability ◽  
Scale Fluctuation

Timescale is the organizing framework of this volume. In various sections, we consider the effects of climate variability on ecosystems at timescales ranging from weeks or months to centuries. In part III, we turn our attention to interdecadal-scale events. The timescales we consider are not absolutely defined, but for our purposes we define the interdecadal scale to encompass effects occurring with recurring cycles generally ranging from 10 to 50 years. A recurring theme in many of the chapters in this section is the effect on ecosystem response of teleconnection patterns associated with recognized quasi-periodic atmospheric circulation modes. These circulation modes include the well-known El Niño– Southern Oscillation (ENSO) phenomenon, which is generally thought to recur at shorter, interdecadal timescales but also includes some longer-term periodicities. Several other climate variability modes, including the Pacific North American index (PNA), North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and North Pacific index (NP) also show strong interdecadal scale signatures and figure prominently in the chapters of part III. McHugh and Goodin begin the section by examining the climate record at several North American LTER sites for evidence of interdecadal-scale fluctuation. They note that interdecadal-scale contributions to climate variability can best be described in terms of two types of variation: (1) discontinuities in mean value, and (2) the presence of trends in the data. Evaluation of interdecadal periodicities in LTER data is complicated by the relatively short time series of observations available. McHugh and Goodin approach the problem mainly through the use of power spectrum analysis, a widely used tool for evaluating the periodicity in a time series of data. Principal components analysis is used to decompose the time series of growing-season climate data for each of the LTER sites into their principal modes of variability. These modes are then subjected to power spectrum analysis to evaluate the proportions of the variance in the data occurring at various timescales. McHugh and Goodin’s results suggest that significant effects on precipitation and temperature at interdecadal timescales are uncommon in these data, although significant periodicities at both shorter and longer frequencies do emerge from the data (a finding of relevance to other sections of this volume).

Relationships between Climate Variability and Fluctuations in Daily Precipitation over the United States

2007 ◽  
Vol 20 (14) ◽  
pp. 3561-3579 ◽  
Author(s):  
R. W. Higgins ◽  
V. B. S. Silva ◽  
W. Shi ◽  
J. Larson
Keyword(s):  
United States ◽  
Climate Variability ◽  
Climate Models ◽  
Daily Precipitation ◽  
Southern Oscillation ◽  
Heavy Precipitation ◽  
The United States ◽  
Global Scale ◽  
The Arctic ◽  
Teleconnection Patterns

Abstract Fluctuations in the frequency of daily precipitation occurrence and in the intensity of daily precipitation over the United States during the period 1948–2004 are identified and linked to leading sources of interannual and interdecadal climate variability. The El Niño–Southern Oscillation (ENSO) phenomena are implicated in interannual fluctuations while the Pacific decadal oscillation (PDO) and the Arctic Oscillation (AO) are linked to recent interdecadal fluctuations. For the conterminous United States as a whole there have been increases in the annual frequency of occurrence of wet days and heavy precipitation days and in the mean daily and annual total precipitation over the past several decades, though these changes have not been uniform. The possibility of significant natural forcing of these interdecadal variations in precipitation is explored. It is shown that the PDO is associated with these fluctuations over the western and southern United States, while the AO is also associated with them but to a much lesser extent over the southeastern United States. Because the interdecadal fluctuations are linked to changes in the global-scale circulation and sea surface temperatures associated with the PDO, the results imply that a significant portion of the skill of climate models in anticipating fluctuations in daily precipitation statistics over the United States will arise from an ability to forecast the temporal and spatial variability of the interdecadal shifts in tropical precipitation and in the associated teleconnection patterns into the midlatitudes.

scholarly journals Examining the Interaction of Growing Crops with Local Climate Using a Coupled Crop–Climate Model

2009 ◽  
Vol 22 (6) ◽  
pp. 1393-1411 ◽  
Author(s):  
Tom Osborne ◽  
Julia Slingo ◽  
David Lawrence ◽  
Tim Wheeler
Keyword(s):  
Climate Variability ◽  
Crop Yield ◽  
Land Surface ◽  
Climate Models ◽  
Climate Model ◽  
Crop Growth ◽  
Surface Fluxes ◽  
Near Surface ◽  
Local Climate ◽  
The Impact

Abstract This paper examines to what extent crops and their environment should be viewed as a coupled system. Crop impact assessments currently use climate model output offline to drive process-based crop models. However, in regions where local climate is sensitive to land surface conditions more consistent assessments may be produced with the crop model embedded within the land surface scheme of the climate model. Using a recently developed coupled crop–climate model, the sensitivity of local climate, in particular climate variability, to climatically forced variations in crop growth throughout the tropics is examined by comparing climates simulated with dynamic and prescribed seasonal growth of croplands. Interannual variations in land surface properties associated with variations in crop growth and development were found to have significant impacts on near-surface fluxes and climate; for example, growing season temperature variability was increased by up to 40% by the inclusion of dynamic crops. The impact was greatest in dry years where the response of crop growth to soil moisture deficits enhanced the associated warming via a reduction in evaporation. Parts of the Sahel, India, Brazil, and southern Africa were identified where local climate variability is sensitive to variations in crop growth, and where crop yield is sensitive to variations in surface temperature. Therefore, offline seasonal forecasting methodologies in these regions may underestimate crop yield variability. The inclusion of dynamic crops also altered the mean climate of the humid tropics, highlighting the importance of including dynamical vegetation within climate models.

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