scholarly journals The Intraseasonal Variability of the Indian Summer Monsoon Using TMI Sea Surface Temperatures and ECMWF Reanalysis

2008 ◽  
Vol 21 (11) ◽  
pp. 2519-2539 ◽  
Author(s):  
Nicholas P. Klingaman ◽  
Hilary Weller ◽  
Julia M. Slingo ◽  
Peter M. Inness
Keyword(s):  
Life Cycle ◽  
Indian Ocean ◽  
General Circulation ◽  
Function Analysis ◽  
Intraseasonal Variability ◽  
Equatorial Indian Ocean ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Surface Temperatures ◽  
Sst Anomalies

Abstract The northward-propagating intraseasonal (30–40 day) oscillation (NPISO) between active and break monsoon phases exerts a critical control on summer-season rainfall totals over India. Advances in diagnosing these events and comprehending the physical mechanisms behind them may hold the potential for improving their predictability. While previous studies have attempted to extract active and break events from reanalysis data to elucidate a composite life cycle, those studies have relied on first isolating the intraseasonal variability in the record (e.g., through bandpass filtering, removing harmonics, or empirical orthogonal function analysis). Additionally, the underlying physical processes that previous studies have proposed have varied, both among themselves and with studies using general circulation models. A simple index is defined for diagnosing NPISO events in observations and reanalysis, based on lag correlations between outgoing longwave radiation (OLR) over India and over the equatorial Indian Ocean. This index is the first to use unfiltered OLR observations and so does not specifically isolate intraseasonal periods. A composite NPISO life cycle based on this index is similar to previous composites in OLR and surface winds, demonstrating that the dominance of the intraseasonal variability in the monsoon climate system eliminates the need for more complex methods (e.g., time filtering or EOF analysis) to identify the NPISO. This study is also among the first to examine the NPISO using a long-period record of high-resolution sea surface temperatures (SSTs) from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager. Application of this index to those SSTs demonstrates that SST anomalies exist in near quadrature with convection, as suggested by recent coupled model studies. Analysis of the phase relationships between atmospheric fields and SSTs indicates that the atmosphere likely forced the SST anomalies. The results of this lag-correlation analysis suggest that the oscillation serves as its own most reliable—and perhaps only—predictor, and that signals preceding an NPISO event appear first over the Indian subcontinent, not the equatorial Indian Ocean where the events originate.

scholarly journals A first look at past sea surface temperatures in the equatorial Indian Ocean from Mg/Ca in foraminifera

2005 ◽  
Vol 32 (24) ◽  
Author(s):  
R. Saraswat ◽  
R. Nigam ◽  
S. Weldeab ◽  
A. Mackensen ◽  
P. D. Naidu
Keyword(s):  
Indian Ocean ◽  
Equatorial Indian Ocean ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Surface Temperatures

scholarly journals A spatiotemporal reconstruction of sea-surface temperatures in the North Atlantic during Dansgaard–Oeschger events 5–8

2018 ◽  
Vol 14 (6) ◽  
pp. 901-922 ◽  
Author(s):  
Mari F. Jensen ◽  
Aleksi Nummelin ◽  
Søren B. Nielsen ◽  
Henrik Sadatzki ◽  
Evangeline Sessford ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North Atlantic ◽  
General Circulation ◽  
Sea Surface ◽  
Reconstruction Method ◽  
Sea Surface Temperatures ◽  
Proxy Data ◽  
Surface Temperatures ◽  
Temperature Reconstructions

Abstract. Here, we establish a spatiotemporal evolution of the sea-surface temperatures in the North Atlantic over Dansgaard–Oeschger (DO) events 5–8 (approximately 30–40 kyr) using the proxy surrogate reconstruction method. Proxy data suggest a large variability in North Atlantic sea-surface temperatures during the DO events of the last glacial period. However, proxy data availability is limited and cannot provide a full spatial picture of the oceanic changes. Therefore, we combine fully coupled, general circulation model simulations with planktic foraminifera based sea-surface temperature reconstructions to obtain a broader spatial picture of the ocean state during DO events 5–8. The resulting spatial sea-surface temperature patterns agree over a number of different general circulation models and simulations. We find that sea-surface temperature variability over the DO events is characterized by colder conditions in the subpolar North Atlantic during stadials than during interstadials, and the variability is linked to changes in the Atlantic Meridional Overturning circulation and in the sea-ice cover. Forced simulations are needed to capture the strength of the temperature variability and to reconstruct the variability in other climatic records not directly linked to the sea-surface temperature reconstructions. This is the first time the proxy surrogate reconstruction method has been applied to oceanic variability during MIS3. Our results remain robust, even when age uncertainties of proxy data, the number of available temperature reconstructions, and different climate models are considered. However, we also highlight shortcomings of the methodology that should be addressed in future implementations.

The Transient Circulation Response to Radiative Forcings and Sea Surface Warming*

2014 ◽  
Vol 27 (24) ◽  
pp. 9323-9336 ◽  
Author(s):  
Paul W. Staten ◽  
Thomas Reichler ◽  
Jian Lu
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Indirect Response ◽  
Radiative Forcings ◽  
Surface Warming ◽  
Impact Surface ◽  
Surface Temperatures

Abstract Tropospheric circulation shifts have strong potential to impact surface climate. However, the magnitude of these shifts in a changing climate and the attending regional hydrological changes are difficult to project. Part of this difficulty arises from the lack of understanding of the physical mechanisms behind the circulation shifts themselves. To better delineate circulation shifts and their respective causes the circulation response is decomposed into 1) the “direct” response to radiative forcings themselves and 2) the “indirect” response to changing sea surface temperatures. Using ensembles of 90-day climate model simulations with immediate switch-on forcings, including perturbed greenhouse gas concentrations, stratospheric ozone concentrations, and sea surface temperatures, this paper documents the direct and indirect transient responses of the zonal-mean general circulation, and investigates the roles of previously proposed mechanisms in shifting the midlatitude jet. It is found that both the direct and indirect wind responses often begin in the lower stratosphere. Changes in midlatitude eddies are ubiquitous and synchronous with the midlatitude zonal wind response. Shifts in the critical latitude of wave absorption on either flank of the jet are not indicted as primary factors for the poleward-shifting jet, although some evidence for increasing equatorward wave reflection over the Southern Hemisphere in response to sea surface warming is seen. Mechanisms for the Northern Hemisphere jet shift are less clear.

scholarly journals Northern and southern hemisphere controls on seasonal sea surface temperatures in the Indian Ocean during the last deglaciation

2013 ◽  
Vol 28 (4) ◽  
pp. 619-632 ◽  
Author(s):  
Yiming V. Wang ◽  
Guillaume Leduc ◽  
Marcus Regenberg ◽  
Nils Andersen ◽  
Thomas Larsen ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Southern Hemisphere ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Last Deglaciation ◽  
Surface Temperatures ◽  
The Indian Ocean ◽  
The Last Deglaciation

Increasing aridity over the past 223 years in the Nepal Himalaya inferred from a tree-ring δ18O chronology

The Holocene ◽  
2011 ◽  
Vol 22 (7) ◽  
pp. 809-817 ◽  
Author(s):  
Masaki Sano ◽  
R Ramesh ◽  
MS Sheshshayee ◽  
R Sukumar
Keyword(s):  
Tree Ring ◽  
Summer Monsoon ◽  
Function Analysis ◽  
Monsoon Season ◽  
Sea Surface ◽  
Drought Severity ◽  
Sea Surface Temperatures ◽  
Nepal Himalaya ◽  
The Past ◽  
Surface Temperatures

A tree-ring δ18O chronology of Abies spectabilis from the Nepal Himalaya was established to study hydroclimate in the summer monsoon season over the past 223 years (ad 1778–2000). Response function analysis with ambient climatic records revealed that tree-ring δ18O was primarily controlled by the amount of precipitation and relative humidity during the monsoon season (June–September). Since tree-ring δ18O was simultaneously correlated with temperature, drought history in the monsoon season was reconstructed by calibrating against the Palmer Drought Severity Index (PDSI). Our reconstruction that accounts for 33.7% of the PDSI variance shows a decreasing trend of precipitation/moisture over the past two centuries, and reduction of monsoon activity can be found across different proxy records from the Himalaya and Tibet. Spatial correlation analysis with global sea surface temperatures suggests that the tropical oceans play a role in modulating hydroclimate in the Nepal Himalaya. Although the dynamic mechanisms of the weakening trend of monsoon intensity still remain to be analyzed, rising sea surface temperatures over the tropical Pacific and Indian Ocean could be responsible for the reduction of summer monsoon.

scholarly journals The effect of global climate change on the future distribution of economically important macroalgae (seaweeds) in the northwest Atlantic

FACETS ◽  
2018 ◽  
Vol 3 (1) ◽  
pp. 275-286 ◽  
Author(s):  
Amina H. Khan ◽  
Elisabeth Levac ◽  
Lou Van Guelphen ◽  
Gerhard Pohle ◽  
Gail L. Chmura
Keyword(s):  
General Circulation ◽  
Global Climate ◽  
Atlantic Coast ◽  
General Circulation Models ◽  
Economic Effects ◽  
Sea Surface ◽  
Marine Macroalgae ◽  
Saccharina Latissima ◽  
Sea Surface Temperatures ◽  
Surface Temperatures

An increase in greenhouse gas emissions has led to a rise in average global air and ocean temperatures. Increased sea surface temperatures can cause changes in species’ distributions, particularly those species close to their thermal tolerance limits. We use a bioclimate envelope approach to assess potential shifts in the range of marine macroalgae harvested in North American waters: rockweed ( Fucus vesiculosus Linnaeus, 1753), serrated wrack ( Fucus serratus Linnaeus, 1753), knotted wrack ( Ascophyllum nodosum (Linnaeus) Le Jolis, 1863), carrageen moss ( Chondrus crispus Stackhouse, 1797), and three kelp species ( Laminaria digitata (Hudson) J.V. Lamouroux, 1813; Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl et G.W. Saunders, 2006; and Saccharina longicruris (Bachelot de la Pylaie) Kuntze, 1891). We determined species’ thermal limits from the current sea surface temperatures associated with their geographical distributions. Future distributions were based on sea surface temperatures projected for the year ∼2100 by four atmosphere-ocean general circulation models and earth system models for regional concentration pathways (RCPs) 4.5 and 8.5. Future distributions based on RCP 8.5 indicate that the presence of all but rockweed ( F. vesiculosus) is likely to be threatened by warming waters in the Gulf of St. Lawrence and along the Atlantic coast of Nova Scotia. Range retractions of macroalgae will have significant ecological and economic effects including impacts on commercial fisheries and harvest rates and losses of floral and faunal biodiversity and production, and should be considered in the designation of marine protected areas.

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