A strong wind event on the Ross Ice Shelf, Antarctica: A case study of scale interactions

In situ observations, satellite imagery, numerical weather prediction, and reanalysis fields are used to investigate the synoptic and mesoscale environment of a strong wind event (SWE) at McMurdo Station/Ross Island region on the Ross Ice Shelf, Antarctica, on 10 October 2003. The SWE occurred during the passage of a sequence of three mesoscale low pressure systems from the central Ross Ice Shelf to the southwest Ross Sea. A potential vorticity (PV) analysis showed that the lows drew air of continental origin down the glacial valleys of the Transantarctic Mountains and onto the ice shelf as a katabatic drainage flow. However, the analysis indicated that the air mass associated with the SWE was of recurved maritime origin drawn in by the second mesoscale low (L2). This air mass approached McMurdo Station from the south where interactions with the orography played a critical role. In the early stages of the event, when the wind speed was less than 10 m s−1, the air was deflected around the topographical features, such as Minna Bluff and Black and White Islands. As the pressure gradient increased, winds of more than 10 m s−1 crossed the orography and developed mountain waves along the lee slopes. When the Froude number became larger than 1, large-amplitude vertically propagating mountain waves developed over the McMurdo Station/Ross Island area, increasing the wind to 16 m s−1. The reanalysis fields did not resolve the mesoscale lows; however, the Antarctic Mesoscale Prediction System (AMPS) model was able to simulate important characteristics of the SWE such as the mesoscale low pressure system, flow around the topographical barrier, and the mountain wave

Effects of vertically propagating mountain waves during a strong wind event over the Ross Ice Shelf, Antarctica

Weather forecasting in the Antarctic presents many challenges, with strong wind events (SWEs) often disrupting air and field operations. Here, we study the mechanisms responsible for a SWE (maximum wind speed 22 ms–1) that occurred at the McMurdo/Scott Base region on the Ross Ice Shelf (Antarctica) over 12–13 October 2003. The study is based on in situ observations, satellite imagery and output from the Antarctic mesoscale prediction system (AMPS) model. The event occurred during the passage of a complex low pressure system that increased the pressure gradient between the northwest Ross Ice Shelf and the continental high, initiating a strong southerly flow. AMPS simulations as well as upper air sounding profiles from McMurdo station showed the involvement of large amplitude vertically propagating mountain waves over the area. The amplification of mountain waves by the self-induced critical level reflected all the energy back towards the surface to generate high downslope winds

Historical and projected changes in the Southern Hemisphere Sub-tropical Jet during winter from the CMIP5 models

We present projected changes in the speed and meridional location of the Subtropical Jet (STJ) during winter using output of the Coupled Model Intercomparison Project Phase 5 (CMIP5) models. We use the ERA-Interim reanalysis dataset to evaluate the historical simulations of the STJ by 18 of the CMIP5 models for the period 1979–2012. Based on the climatology of the STJ from ERA-Interim, we selected the area of study as 70°E–290°E and 20°S–40°S, which is over the Indian and Southern Pacific Oceans, and 300–100 hPa to reduce altitude-related bias. An assessment of the ability of the CMIP5 models in simulating ENSO effects on the jet stream were carried out using standardized zonal wind anomalies at 300–100 hPa. Results show that 47 % of the CMIP5 models used in this study were able to simulate ENSO impacts realistically. In addition, it is more difficult for the models to reproduce the observed intensity of ENSO impacts than the patterns. The historical simulations of the CMIP5 models show a wide range of trends in meridional movement and jet strength, with a multi-model mean of 0.04° decade−1 equatorward and 0.42 ms−1 decade−1 respectively. In contrast to the ERA-Interim analysis, 94 % of the CMIP5 models show a strengthening of the jet in the historical runs. Variability of the jet strength is significantly (5 %) linked to the sea surface temperature changes over the eastern tropical Pacific. The CMIP5 model projections with Representative Concentration Pathways (RCPs) 4.5 and 8.5 were used for analysis of changes of the STJ for the period 2011–2099. Based on the RCP 4.5 (RCP 8.5) scenario the multi-model mean trend of the 18 CMIP5 models project a statistically significant (5 % level) increase in jet strength by the end of the century of 0.29 ms−1 decade−1 (0.60 ms−1 decade−1). Also, the mean meridional location of the jet is projected to shift poleward by 0.006° decade−1 (0.042° decade−1) in 2099 during winter, with the only significant (5 %) trend being with RCP 8.5

Precipitation instruments at Rothera Station, Antarctic Peninsula: a comparative study

Direct measurement of precipitation in the Antarctic using ground-based instruments is important to validate the results from climate models, reanalyses and satellite observations. Quantifying precipitation in Antarctica faces many unique challenges such as wind and other technical difficulties due to the harsh environment. This study compares a variety of precipitation measurements in Antarctica, including satellite data and reanalysis fields atRothera Station, Antarctica Peninsula. The tipping bucket gauges (TBGs) were less sensitive than laser-based sensors (LBSs). The most sensitive LBS (Visibility and Present Weather Sensor, VPF-730) registered 276 precipitation days, while the most sensitive TBG (Universal Precipitation Gauge, UPG-1000) detected 152 precipitation days. Case studies of the precipitation and seasonal accumulation results show the VPF-730 to be the most reliable precipitation sensor of the evaluated instruments. The precipitation amounts given by the reanalyses were positively correlated with wind speed. The precipitation from the Japanese 55-year Reanalysis was most affected by wind speed. Case studies also show that during low wind periods, precipitation measurements from the instruments were very close to the precipitation measurement given by the Global Precipitation Climatology Project (GPCP) 1-degree-daily (1DD) data. During strong wind events, the GPCP 1DD did not fully capture the effect of wind, accounting for the relatively small precipitation amount. The Laser Precipitation Monitor (LPM) and Campbell Scientific-700 (CS700H) experienced instrumental errors during the study, which caused the precipitation readings to become exceedingly high and low, respectively. Installing multiple LBSs in different locations (in close proximity) can help identify inconsistency in the readings

Isoprene hotspots at the Western Coast of Antarctic Peninsula during MASEC′16

Isoprene (C5H8) plays an important role in the formation of surface ozone (O3) and the secondary organic aerosol (SOA) which contributed to the climate change. This study aims to determine hourly distribution of tropospheric isoprene over the Western Coast of Antarctic Peninsula (WCAP) during the Malaysian Antarctic Scientific Expedition Cruise 2016 (MASEC′16). In-situ measurements of isoprene were taken using a custom-built gas chromatography with photoionization detector, known as iDirac. Biological parameters such as chlorophyll a (chl-a) and particulate organic carbon (POC) were compared to the in-situ isoprene measurements. Significant positive correlation was observed between isoprene and POC concentrations (r2 = 0.67, p < 0.001), but not between isoprene and chl-a. The hotspots of isoprene over maritime Antarctic were then were investigated using NAME dispersion model reanalysis. Measurements showed that isoprene mixing ratio were the highest over region of King George Island, Deception Island and Booth Island with values of ∼5.0, ∼0.9 and ∼5.2 ppb, respectively. Backward trajectory analysis showed that air masses may have lifted the isoprene emitted by marine algae. We believe our findings provide valuable data set of isoprene estimation over the under sampled WCAP

Linkages between Climate Change and Coastal Tourism: A Bibliometric Analysis

Tourism and climate are inextricably linked to several interactions. In recent years, there has been a greater focus on the linkages between climate change and coastal tourism. This study aims to provide an overview of the literature on climate change and coastal tourism, identify core areas of interest and important sources and authors, and examine the thematic evolution of the field. A bibliometric analysis of 92 documents related to climate change and coastal tourism published in the Web of Science Core Collection database was carried out. The analysis provides information on the most cited papers, most leading authors, the most productive countries, and the most leading institutions in this field. The study utilized the Visualization of Similarities Viewer program (VOS) to map author keyword co-occurrences, co-citations, and bibliographic coupling. The study showed that, with some fluctuations since 2008, the number of publications in this field had increased significantly. The most influential authors and most productive institutions are from the United States of America, England, Canada, and other European countries. The findings of this study will assist researchers conducting climate change and coastal tourism-related studies to understand which papers, academics, organizations, countries, and journals have a dominant influence on climate change and coastal tourism research

Identifying potential locations for ecotourism development in Batticaloa District

 This study aims to identify potential locations for ecotourism development in the Batticaloa District, using GIS-AHP spatial analysis. Five thematic layers were considered throughout this analysis: landscape, protected area, topography, accessibility, and community characteristics. The thematic layers were given appropriate weights and integrated into the GIS through the weighted overlay analysis.  </p

An assessment of historical Antarctic precipitation and temperature trend using CMIP5 models and reanalysis datasets

The study of Antarctic precipitation has attracted a lot of attention recently. The reliability of climate models in simulating Antarctic precipitation, however, is still debatable. This work assess the precipitation and surface air temperature (SAT) of Antarctica (90 oS to 60 oS) using 49 Coupled Model Intercomparison Project phase 5 (CMIP5) global climate models and the European Centre for Medium-range Weather Forecasts “Interim” reanalysis (ERA-Interim); the National Centers for Environmental Prediction Climate Forecast System Reanalysis (CFSR); the Japan Meteorological Agency 55-year Reanalysis (JRA-55); and the Modern Era Retrospective-analysis for Research and Applications (MERRA) datasets for 1979–2005 (27 years). For precipitation, the time series show that the MERRA and JRA-55 have significantly increased from 1979 to 2005, while the ERA-Int and CFSR have insignificant changes. The reanalyses also have low correlation with one another (generally less than +0.69). 37 CMIP5 models show increasing trend, 18 of which are significant. The resulting CMIP5 MMM also has a significant increasing trend of 0.29 ± 0.06 mm year−1. For SAT, the reanalyses show insignificant changes and have high correlation with one another, while the CMIP5 MMM shows a significant increasing trend. Nonetheless, the variability of precipitation and SAT of MMM could affect the significance of its trend. One of the many reasons for the large differences of precipitation is the CMIP5 models' resolution

Southwest monsoon onset dates over Malaysia and associated climatological characteristics

In Malaysia precipitation prevails throughout the year. However, the southwest monsoon (late May to September) is characterised with low precipitation, less cloud, high outgoing long-wave radiation (OLR) and often featured by dry epochs. Therefore, onset of the monsoon here is best determined by considering multiple onset parameters such as wind, OLR, rainfall and relative humidity. We used modified Malaysian Meteorological Department wind shear index based on major convection centres during the monsoon onset. The 850 hPa winds were chosen to investigate the onsets of the monsoon in view of the marked orographic and mesoscale processes. The next criterion was the presence of sustained westerlies averaged between 850 hPa and 600 hPa from all the available radiosonde stations data over Malaysia for at least 5 days. As the strongest convective activity in the tropics is represented by OLR of less than 220 W m-2, the third criterion was to check whether the value of OLR was greater than 220 W m-2 over the region. The mean date of the summer monsoon onset over Malaysia is found to be 19 May, with a standard deviation of 8 days. Further, climatological composites show that there is a gradual change from easterlies to westerlies from the surface up to 500 hPa in Malaysian stations both in Peninsular Malaysia and East Malaysia during May. OLR and rainfall analysis reveal that, the southwest monsoon daily rainfall over Malaysia is less than 10 mm and OLR is greater than 220 W m-2. Additionally, monsoon onset tends to be late during the El Niño years and earlier during the La Niña years

Strong wind events in the Antarctic

We use quality controlled in situ meteorological observations collected at Antarctic research stations over the last 60 years to carry out the first continent-wide investigation into the occurrence, variability, and trend in strong wind events (SWEs). Reanalysis/analysis fields are used to examine the synoptic background in which such events take place. SWEs are a feature of the extended winter season and involve a complex interaction between the downslope buoyancy forcing and the pressure gradient force from synoptic-scale cyclones. Around the coast of East Antarctica the significant majority of SWEs are associated with enhancement of the downslope katabatic flow by the broadscale synoptic circulation, involving a deepening of pressure off the coast and an increase of pressure inland. Orientation of the valleys in relation to the cyclone track is critical in enabling enhancement of the katabatic winds. Casey, Mawson, and Dumont d'Urville stations report the greatest number of winds of storm force and stronger. Interannual variability of SWE numbers is large. Trends in the number of winter strong wind reports are small. The greatest statistically significant increase in wind speed since the 1950s has been at Faraday/Vernadsky and Syowa stations. The largest wind speed increases since 1979 have been at Davis and Mawson stations. Comparison with high-resolution numerical simulations showed that the reanalysis/analysis fields are able to capture the large-scale synoptic features and the associated enhancement of the katabatic flow but underestimated the observed wind speed if it was strongly influenced by local topographical conditions