scholarly journals Locally driven interannual variability of near‐surface pH and Ω A in the Strait of Georgia

2016 ◽  
Vol 121 (3) ◽  
pp. 1600-1625 ◽  
Author(s):  
Ben L. Moore‐Maley ◽  
Susan E. Allen ◽  
Debby Ianson
Keyword(s):  
Interannual Variability ◽  
Near Surface ◽  
Surface Ph ◽  
Strait Of Georgia

scholarly journals Interannual Variability in the Large-Scale Dynamics of the South Asian Summer Monsoon

2015 ◽  
Vol 28 (9) ◽  
pp. 3731-3750 ◽  
Author(s):  
Jennifer M. Walker ◽  
Simona Bordoni ◽  
Tapio Schneider
Keyword(s):  
Interannual Variability ◽  
South Asian ◽  
Summer Monsoon ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
Sea Breeze ◽  
South Asian Summer Monsoon ◽  
The South ◽  
Near Surface ◽  
Asian Summer

Abstract This study identifies coherent and robust large-scale atmospheric patterns of interannual variability of the South Asian summer monsoon (SASM) in observational data. A decomposition of the water vapor budget into dynamic and thermodynamic components shows that interannual variability of SASM net precipitation (P − E) is primarily caused by variations in winds rather than in moisture. Linear regression analyses reveal that strong monsoons are distinguished from weak monsoons by a northward expansion of the cross-equatorial monsoonal circulation, with increased precipitation in the ascending branch. Interestingly, and in disagreement with the view of monsoons as large-scale sea-breeze circulations, strong monsoons are associated with a decreased meridional gradient in the near-surface atmospheric temperature in the SASM region. Teleconnections exist from the SASM region to the Southern Hemisphere, whose midlatitude poleward eddy energy flux correlates with monsoon strength. Possible implications of these teleconnection patterns for understanding SASM interannual variability are discussed.

scholarly journals Interannual Variability of Summer Surface Mass Balance and Surface Melting in the Amundsen Sector, West Antarctica

2019 ◽  
Author(s):  
Marion Donat-Magnin ◽  
Nicolas C. Jourdain ◽  
Hubert Gallée ◽  
Charles Amory ◽  
Christoph Kittel ◽  
...  
Keyword(s):  
Mass Balance ◽  
Interannual Variability ◽  
Climate Models ◽  
Surface Wind ◽  
Surface Melting ◽  
Surface Mass Balance ◽  
Climate Trends ◽  
West Antarctica ◽  
Near Surface ◽  
Surface Mass

Abstract. Understanding the interannual variability of Surface Mass Balance (SMB) and surface melting in Antarctica is key to quantify the signal to noise ratio in climate trends, identify opportunities for multi-year climate predictions, and to assess the ability of climate models to respond to climate variability. Here we simulate summer SMB and surface melting from 1979 to 2017 using the regional atmospheric model MAR at 10 km resolution over the drainage basins of the Amundsen glaciers in West Antarctica. Our simulations reproduce the mean present-day climate in terms of near-surface temperature (mean overestimation of 0.10 °C), near-surface wind speed (mean underestimation of 0.42 m s-1), and SMB (relative bias

Mechanisms behind the precipitation increase in Norway

2021 ◽  
Author(s):  
Kjersti Konstali ◽  
Asgeir Sorteberg
Keyword(s):  
Relative Humidity ◽  
Interannual Variability ◽  
Vertical Velocity ◽  
Absolute Magnitude ◽  
Diagnostic Model ◽  
Positive Trend ◽  
Water Vapour Content ◽  
Near Surface ◽  
Precipitation Increase

<p>We use a dataset with observations of daily precipitation from 55 homogeneity tested stations in Norway over the period 1900-2019 available from MET-Norway. These observations show that precipitation in Norway has increased monotonically by 19% since 1900. Notably, over half of the overall increase was recorded within the decade of 1980-1990. To examine possible mechanisms behind the precipitation increase, we use a diagnostic model to separate the effects of changes in vertical velocity, temperature and relative humidity. We use vertical velocity, near-surface temperature and relative humidity from two reanalysis products, ECMWF’s ERA-20C and NOAA’s 20th Century Reanalysis. The model-based precipitation estimates capture the interannual variability as well as the long-term trend, but the absolute magnitude of precipitation is underestimated. Within our model, we find that the variability in vertical velocity chiefly determines the interannual variability and long-term trends. In fact, the trend in vertical velocities contributes with more than 75% of the total modelled trend in precipitation between 1900-2019, and more than 60% of the anomalies between 1980-1990. However, over the last decades (1979 to 2019), changes in temperature and relative humidity are the main contributors to the trend. Thus, different physical processes shape the trend at different times. We hypothesize that the strong precipitation increase in the 1980’s is linked to an unusual high number of low pressure systems reaching Norway from the North-Atlantic. In recent decades, direct effects of global warming (rising temperatures and hence increased water vapour content) are thought to be the main cause of the positive trend in precipitation over Norway. </p>

Diurnal and Seasonal Variability of Near‐Surface Oxygen in the Strait of Georgia

2019 ◽  
Vol 124 (4) ◽  
pp. 2418-2439 ◽  
Author(s):  
Chuning Wang ◽  
Rich Pawlowicz ◽  
Akash R. Sastri
Keyword(s):  
Seasonal Variability ◽  
Surface Oxygen ◽  
Near Surface ◽  
Strait Of Georgia

scholarly journals Interannual variability of summer surface mass balance and surface melting in the Amundsen sector, West Antarctica

2020 ◽  
Vol 14 (1) ◽  
pp. 229-249 ◽  
Author(s):  
Marion Donat-Magnin ◽  
Nicolas C. Jourdain ◽  
Hubert Gallée ◽  
Charles Amory ◽  
Christoph Kittel ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Southern Oscillation ◽  
Surface Melting ◽  
Surface Mass Balance ◽  
Austral Winter ◽  
West Antarctica ◽  
Drainage Basins ◽  
Amundsen Sea ◽  
Near Surface ◽  
Surface Mass

Abstract. Understanding the interannual variability of surface mass balance (SMB) and surface melting in Antarctica is key to quantify the signal-to-noise ratio in climate trends, identify opportunities for multi-year climate predictions and assess the ability of climate models to respond to climate variability. Here we simulate summer SMB and surface melting from 1979 to 2017 using the Regional Atmosphere Model (MAR) at 10 km resolution over the drainage basins of the Amundsen Sea glaciers in West Antarctica. Our simulations reproduce the mean present-day climate in terms of near-surface temperature (mean overestimation of 0.10 ∘C), near-surface wind speed (mean underestimation of 0.42 m s−1), and SMB (relative bias <20 % over Thwaites glacier). The simulated interannual variability of SMB and melting is also close to observation-based estimates. For all the Amundsen glacial drainage basins, the interannual variability of summer SMB and surface melting is driven by two distinct mechanisms: high summer SMB tends to occur when the Amundsen Sea Low (ASL) is shifted southward and westward, while high summer melt rates tend to occur when ASL is shallower (i.e. anticyclonic anomaly). Both mechanisms create a northerly flow anomaly that increases moisture convergence and cloud cover over the Amundsen Sea and therefore favors snowfall and downward longwave radiation over the ice sheet. The part of interannual summer SMB variance explained by the ASL longitudinal migrations increases westward and reaches 40 % for Getz. Interannual variation in the ASL relative central pressure is the largest driver of melt rate variability, with 11 % to 21 % of explained variance (increasing westward). While high summer SMB and melt rates are both favored by positive phases of El Niño–Southern Oscillation (ENSO), the Southern Oscillation Index (SOI) only explains 5 % to 16 % of SMB or melt rate interannual variance in our simulations, with moderate statistical significance. However, the part explained by SOI in the previous austral winter is greater, suggesting that at least a part of the ENSO–SMB and ENSO–melt relationships in summer is inherited from the previous austral winter. Possible mechanisms involve sea ice advection from the Ross Sea and intrusions of circumpolar deep water combined with melt-induced ocean overturning circulation in ice shelf cavities. Finally, we do not find any correlation with the Southern Annular Mode (SAM) in summer.

The use of moored inverted echo sounders for monitoring meso-zooplankton and fish near the ocean surface

2005 ◽  
Vol 62 (5) ◽  
pp. 1004-1018 ◽  
Author(s):  
Mark V Trevorrow
Keyword(s):  
Acoustic Scattering ◽  
Near Surface ◽  
Strait Of Georgia ◽  
Abundance Estimates ◽  
Weak Evidence ◽  
Inverted Echo Sounder ◽  
Ocean Station Papa ◽  
And Behavior ◽  
Scatterer Size ◽  
Northeast Pacific Ocean

This study evaluates the effectiveness of a 200-kHz inverted echo sounder for monitoring the abundance and behavior of near-surface zooplankton and fish. Data from both oceanic and littoral environments are examined: first from an 81-day deployment at Ocean Station Papa (OSP) in the northeast Pacific Ocean during the spring of 1996, and second from an 8-day deployment in the southern Strait of Georgia in September 1998. The analysis combines calibrated backscatter intensity, echo-amplitude statistics, and acoustic-scattering models to produce estimates of mean scatterer size and abundance. The identity of the various scatterer classes is deduced from local net trawls and reference to previous studies. At the OSP site the dominant scatterers were found to be euphausiids, pteropods, and myctophid fishes, with mean lengths of 15, 1.5, and 28 mm, respectively. At the Strait of Georgia site three fish size classes were identified: juvenile herring with mean length near 10 cm, juvenile salmon with mean length of 20 cm, and there was weak evidence for an adult salmon class. Overall, the acoustically derived abundance estimates were in reasonable agreement with the local net trawls and results from previous studies. The usefulness of sustained monitoring over diurnal and seasonal time scales is demonstrated with the OSP zooplankton data.

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