scholarly journals An Inter-Comparison of Arctic Synoptic Scale Storms between Four Global Reanalysis Datasets

2020 ◽  
Author(s):  
Alexander Vessey ◽  
Kevin Hodges ◽  
Len Shaffrey ◽  
Jonathan Day
Keyword(s):  
Sea Level ◽  
Relative Vorticity ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Tracking Method ◽  
Level Pressure ◽  
Storm Tracking ◽  
Storm Characteristics

<p>Arctic sea ice has reduced significantly over recent decades and is projected to reduce further over this century. This has made the Arctic more accessible and increased opportunities for the expansion of business and industrial activities.  As a result, the exposure and risk of humans and infrastructure to extreme storms will increase in the Arctic.</p><p>Our understanding of the current risk from storms comes from analysing the past, for example, by using storm tracking algorithms to detect storms in reanalysis datasets.  However, there are multiple reanalysis datasets available from different institutions and there are multiple storm tracking methods.  Previous studies have found that there can be differences between reanalysis datasets and between storm tracking methods in the climatology of storms, particularly in mid-latitude regions rather than the Arctic.  In this study, we aimed to improve the understanding of Arctic storms by assessing their characteristics in multiple global reanalyses, the ECMWF-Interim Reanalysis (ERA-Interim), the 55-Year Japanese Reanalysis (JRA-55), the NASA-Modern Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2), and the NCEP-Climate Forecast System Reanalysis (NCEP-CFSR), using the same storm tracking method based on 850 hPa relative vorticity and mean sea level pressure.</p><p>The results from this study show that there are no significant trends in Arctic storm characteristics between 1980-2017, even though the Arctic has undergone rapid change.  Although some similar Arctic storm characteristics are found between the reanalysis datasets, there are generally higher differences between the reanalyses in winter (DJF) than in summer (JJA).  In addition, substantial differences can arise between using the same storm tracking method based on 850 hPa relative vorticity or mean sea level pressure, which adds to the uncertainty associated with current Arctic storm characteristics.</p>

Quantifying Arctic Storm Risk in a Changing Climate

2021 ◽  
Author(s):  
Alexander Vessey ◽  
Kevin Hodges ◽  
Len Shaffrey ◽  
Jonathan Day
Keyword(s):  
Climate Models ◽  
Relative Vorticity ◽  
Horizontal Resolution ◽  
Future Climate ◽  
The Arctic ◽  
Sea Ice Extent ◽  
Sea Level Pressure ◽  
Tracking Method ◽  
Storm Tracking ◽  
Storm Characteristics

<p>The Arctic has undergone significant change over the past few decades, and there has been great reductions in Arctic sea ice extent. The Arctic ocean has become more accessible, and this has allowed for more human activity in the Arctic.  The risk of storms impacting human activities in the Arctic has consequently increased, and as sea ice extent continues to decline in the near-future, the risk of storms impacting human activities in the Arctic is likely to increase further.  In this study, the present climatology of Arctic storms is evaluated between modern reanalysis datasets, and the future climatology of Arctic storms is also evaluated in climate model simulations.</p><p>There are multiple reanalysis datasets available from different institutions, which each give an approximation of past atmospheric conditions over the last few decades.  In addition, there are multiple storm tracking methods, which may impact the climatology of Arctic storms that is identified in a reanalysis datasets.  In this study, we aimed to improve the understanding of Arctic storms by assessing their characteristics in multiple global reanalyses, the ECMWF-Interim Reanalysis (ERA-Interim), the 55-Year Japanese Reanalysis (JRA-55), the NASA-Modern Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2), and the NCEP-Climate Forecast System Reanalysis (NCEP-CFSR), using the same storm tracking method based on 850 hPa relative vorticity and mean sea level pressure.  In addition, the response of Arctic storms to climate change has been evaluated in the UPSCALE climate simulations, and the affect of horizontal resolution on the representation of future Arctic storminess has been assessed.</p><p>The results show that there are no significant trends in Arctic storm characteristics between 1980-2017, even though the Arctic has undergone rapid change.  Although some similar Arctic storm characteristics are found between the reanalysis datasets, there are generally higher differences between the reanalyses in winter (DJF) than in summer (JJA).  In addition, substantial differences can arise between using the same storm tracking method based on 850 hPa relative vorticity or mean sea level pressure, which adds to the uncertainty associated with current Arctic storm characteristics.</p><p>The results also show that Arctic storms will change significantly in a future climate, particularly in their spatial distribution.  Differences have been found between the future simulations of Arctic storms between an ensemble of high resolution climate models (25km) and low resolution climate models (130km), which adds uncertainty to how Arctic storms may change in a future climate.  The possible reasons for why the representation of future climate Arctic storms may be different in climate models of differing horizontal resolution has been explored.</p>

Outflow of Arctic Ocean Sea Ice into the Greenland and Barents Seas: 1979–2007

2009 ◽  
Vol 22 (9) ◽  
pp. 2438-2457 ◽  
Author(s):  
R. Kwok
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Positive Trend ◽  
Fram Strait ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Franz Josef Land ◽  
The Mean

Abstract Twenty-nine years of Arctic sea ice outflow into the Greenland and Barents Seas are summarized. Outflow is computed at three passages: Fram Strait, between Svalbard and Franz Josef Land (S–FJL), and between Franz Josef Land and Severnaya Zemlya (FJL–SZ). Ice drift at the flux gates has been reprocessed using a consistent and updated time series of passive microwave brightness temperature and ice concentration (IC) fields. Over the record, the mean annual area outflow at the Fram Strait is 706(113) × 103 km2; it was highest in 1994/95 (1002 × 103 km2) when the North Atlantic Oscillation (NAO) index was near its 29-yr peak. The strength of the “Transpolar Drift Stream” (TDS) was high during the late 1980s through the mid-1990s. There is no statistically significant trend in the Fram Strait area flux. Even though there is a positive trend in the gradient of cross-strait sea level pressure, the outflow has not increased because of a negative trend in IC. Seasonally, the area outflow during recent summers (in 2005 and 2007) has been higher (> 2σ from the mean) than average, contributing to the decline of summer ice coverage. Without updated ice thickness estimates, the best estimate of mean annual volume flux (between 1991 and 1999) stands at ∼2200 km3 yr−1 (∼0.07 Sv: Sv ≡ 106 m3 s−1). Net annual outflow at the S–FJL passage is 37(39) × 103 km2; the large outflow of multiyear ice in 2002–03, marked by an area and volume outflow of 141 × 103 km2 and ∼300 km3, was unusual over the record. At the FJL–SZ passage, there is a mean annual inflow of 103(93) × 103 km2 of seasonal ice into the Arctic. While the recent pattern of winter Arctic circulation and sea level pressure (SLP) has nearly reverted to its conditions typical of the 1980s, the summer has not. Compared to the 1980s, the recent summer SLP distributions show much lower SLPs (2–3 hPa) over much of the Arctic. Overall, there is a strengthening of the summer TDS. Examination of the exchanges between the Pacific and Atlantic sectors shows a long-term trend that favors the summer advection of sea ice toward the Atlantic associated with a shift in the mean summer circulation patterns.

scholarly journals The Arctic sea ice extent change connected to Pacific decadal variability

2020 ◽  
Vol 14 (2) ◽  
pp. 693-708
Author(s):  
Xiao-Yi Yang ◽  
Guihua Wang ◽  
Noel Keenlyside
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Annual Cycle ◽  
Bering Sea ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Sea Ice Extent ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Arctic Sea

Abstract. After an unprecedented retreat, the total Arctic sea ice cover for the post-2007 period is characterized by low extent and a remarkable increase in annual cycle amplitude. We have identified the leading role of spring Bering Sea ice in explaining the changes in the amplitude of the annual cycle of total Arctic sea ice. In particular, these changes are related to the recent occurrence of multiyear variability in spring Bering Sea ice extent. This is due to the phase-locking of the North Pacific Gyre Oscillation (NPGO) and the Pacific Decadal Oscillation (PDO) after about 2007, with a correlation coefficient reaching −0.6. Furthermore, there emerge notable changes in the sea level pressure and sea surface temperature patterns associated with the NPGO in the recent decade. After 2007, the NPGO is related to a quadrupole of sea level pressure (SLP) anomalies that is associated with the wind stress curl and Ekman pumping rate anomalies in the Bering deep basin; these account for the change in Bering Sea subsurface variability that contribute to the decadal oscillation of the spring Bering Sea ice extent.

scholarly journals Decadal changes in the leading patterns of sea level pressure in the Arctic and their impacts on the sea ice variability in boreal summer

2019 ◽  
Vol 13 (11) ◽  
pp. 3007-3021
Author(s):  
Nakbin Choi ◽  
Kyu-Myong Kim ◽  
Young-Kwon Lim ◽  
Myong-In Lee
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Boreal Summer ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The Pacific ◽  
Circulation Change ◽  
Arctic Sea

Abstract. Besides its negative trend, the interannual and the interdecadal changes in the Arctic sea ice have also been pronounced in recent decades. The three leading modes in the sea level pressure (SLP) variability in the Arctic (70–90∘ N) – the Arctic Oscillation (AO), the Arctic Dipole (AD), and the third mode (A3) – are analyzed to understand the linkage between sea ice variability and large-scale atmospheric circulation in boreal summer (June–August). This study also compares the decadal changes of the modes between the early (1982–1997) and the recent (1998–2017) periods and their influences on the Arctic sea ice extent (SIE). Only the AD mode shows a significant correlation increase with SIE in summer (JJA) from −0.05 in the early period to 0.57 in the recent period. The AO and the A3 modes show a less significant relationship with SIE for the two periods. The AD is characterized by a dipole pattern of SLP, which modulates the strength of meridional surface winds and the Transpolar Drift Stream (TDS). The major circulation change in the late 1990s is that the direction of the wind has been changed more meridionally over the exit region of the Fram Strait, which causes sea ice drift and discharge through that region. In addition, the response of surface albedo and the net surface heat flux becomes larger and much clearer, suggesting a positive sea-ice–albedo feedback in the sea ice variability associated with the AD. The analysis also reveals that the zonal shift of the centers of SLP anomalies and associated circulation change affects a significant reduction in sea ice concentration over the Pacific sector of the Arctic Ocean. This study further suggests that the Pacific Decadal Oscillation (PDO) phase change could influence the spatial pattern change in the AD.

scholarly journals Decadal Changes in the Leading Patterns of Sea Level Pressure in the Arctic and Their Impacts on the Sea Ice Variability in Boreal Summer

2019 ◽  
Author(s):  
Nakbin Choi ◽  
Kyu-Myong Kim ◽  
Young-Kwon Lim ◽  
Myong-In Lee
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Boreal Summer ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The Pacific ◽  
Circulation Change ◽  
Arctic Sea

Abstract. Besides its negative trend, the interannual and the interdecadal changes in the Arctic sea ice are also pronounced in recent decades. The three leading modes in the sea level pressure (SLP) variability in the Arctic (70°–90 °N) – the Arctic Oscillation (AO), the Arctic Dipole (AD), and the third mode (A3) – are analyzed to understand the linkage between sea ice variability and large-scale atmospheric circulation in boreal summer (June–August). This study also compares the decadal changes of the modes between the early (1982–1997) and the recent (1998–2017) periods and their influences on the Arctic sea ice extent (SIE). Only the AD mode shows a significant correlation increase with SIE from −0.05 in the early period to 0.57 in the recent period. The AO and the A3 modes show a less significant relationship with SIE for the two periods. The AD is characterized by a dipole pattern of SLP, which modulates the strength of meridional surface winds and the transpolar drift stream (TDS). The major circulation change in the late 1990s is that the direction of the wind has been changed more meridionally over the exit region of the Fram Strait, which causes sea ice drift and discharge through that region. The analysis also reveals that the zonal shift of the centers of SLP anomalies and associated circulation change affects a significant reduction in sea ice concentration over the Pacific sector of the Arctic Ocean. This study further suggests that the Pacific Decadal Oscillation (PDO) phase change could influence the spatial pattern change in the AD.

scholarly journals Tropical cyclone simulations over Bangladesh at convection permitting 4.4 km & 1.5 km resolution

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hamish Steptoe ◽  
Nicholas Henry Savage ◽  
Saeed Sadri ◽  
Kate Salmon ◽  
Zubair Maalick ◽  
...  
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Sea Level ◽  
Tropical Cyclones ◽  
Weather Forecasting ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Level Pressure ◽  
Medium Range ◽  
Gust Speed

AbstractHigh resolution simulations at 4.4 km and 1.5 km resolution have been performed for 12 historical tropical cyclones impacting Bangladesh. We use the European Centre for Medium-Range Weather Forecasting 5th generation Re-Analysis (ERA5) to provide a 9-member ensemble of initial and boundary conditions for the regional configuration of the Met Office Unified Model. The simulations are compared to the original ERA5 data and the International Best Track Archive for Climate Stewardship (IBTrACS) tropical cyclone database for wind speed, gust speed and mean sea-level pressure. The 4.4 km simulations show a typical increase in peak gust speed of 41 to 118 knots relative to ERA5, and a deepening of minimum mean sea-level pressure of up to −27 hPa, relative to ERA5 and IBTrACS data. The downscaled simulations compare more favourably with IBTrACS data than the ERA5 data suggesting tropical cyclone hazards in the ERA5 deterministic output may be underestimated. The dataset is freely available from 10.5281/zenodo.3600201.

Sign in / Sign up

Export Citation Format

Share Document