Seasonal Analysis of Atmospheric Changes in Hudson Bay during 1998-2018

The main objective of this study is to examine the NARR (North American Regional Reanalysis Model) high-resolution dataset to understand the last two decades dramatic climate changes in Hudson Bay associated with the atmospheric keys by synoptically analysis. The anomalies of the near-surface meteorological parameters such as air temperature, humidity, mean sea level pressure, wind vectors along with cloudiness, precipitation, surface albedo and downward longwave radiation at surface in seasonally based changes have been analysed. The increase in low-level thermal structure leads to changing the near-surface humidity, evaporation, cloudiness, precipitation and downward longwave radiation at the surface. Also, winds have been accelerated associated with anticyclonic curvature development. The results show significant atmospheric changes during the last two decades in Hudson Bay with the highest values mostly during winter and fall seasons in the north, east boundaries and James Bay area. Using the statistical analysis for mean low-level temperature, surface albedo, low-level clouds and evaporation at the surface during nearly recent 2 decades (1998-2018) rather than the normal climatology mean (1981-2010) have revealed the meaningful significant difference for mentioned parameters. The statistical analysis results show that during spring there is a significant positive correlation between low clouds anomaly and 2 m air temperature anomaly rather than other seasons. So, the recent atmospheric changes in the study area as a region located in the Arctic and sub-Arctic can contribute to extra-local and global warming.

Hudson Bay Climate Change and Local Winter Wind Circulation

The meteorological mechanisms causing the recent increase in winter wind speed on Hudson Bay are investigated by examining the NARR dataset (The North American Regional Reanalysis Model) for the past several decades. Winter seasonal changes for atmospheric variables are examined and their interconnections are studied. Yearly mean near-surface temperatures are analyzed from 1948 to denote a rapid warming over Hudson Bay from late 1998 onwards. The surface albedo, air temperatures, mean sea level pressure and wind vector anomalies from 1998 to 2015 have also been studied. The comparison of the 1000 hPa wind vector mean and departures from 1981-2010 (normal period) averages have shown an intensification of anti-cyclonic anomaly pattern over most parts of Hudson Bay. The structure of the wind vector anomalies has revealed a contrast between cyclonic and anti-cyclonic local wind circulations mostly in the east, north and north-west regions along with wind speed increasing at 10 m, increases in near-surface air temperature and decreasing of the surface albedo. The anomalies of the wind vector analysing at different pressure levels show the change in wind direction mostly from northwesterly (zonal wind weakening) to south and easterlies. The polar jet wind vectors at 200 mb during anomaly time (1998-2015) have revealed the changes in magnitude and position. During winter anomaly time, the polar jet at 200 mb has been shifted mostly from rather mean colder north westerly currents to the rather warmer south and easterly anomaly currents over Hudson Bay areas. The yearly historical total accumulated Hudson Bay ice coverage during 1980-2015, using Canadian Ice Service data has shown a slight reduction in the north, north-west and eastern Hudson Bay. The linear regressions of the winter temperature anomaly at 2 m against albedo anomaly, alongside the wind speed anomaly at 10 m against air temperature at 2 m, have shown a relationship between these variables. Also, there is a statistically meaningful relation between decreased albedo and increased evaporation.

Evaluation of Seasonal Changes in Temperature and Precipitation for Iran Five Provincial Centres during 1960-2017

Climate change is one of the key challenges of our era and it is a threat to sustainable development. Global warming has many meteorological consequences including rising air temperatures across the world. Undoubtedly, human activity has been one of the key factors to global warming followed by increased greenhouse gas emissions which will exacerbate changes in the Earth’s climate variables. So, any research work related to the climate around the world including Iran due to climate change may cause to better understand the cause and effect and make a better adaptation. This study investigates the regional warming in five meteorological stations in central provinces of Iran, based on seasonal changes in precipitation and temperatures over the period of 1960-2017 (study period). The seasonal drought severity based on Palmer index during 1960-2005 was used to monitor the drought intensity in the study areas which are in drought risk situation. The classification of drought severity using Palmer index shows the severe drought intensity in Arak, Qom, Semnan, Tehran and Isfahan respectively in all four seasons, especially during fall and summer. The slight changes in the coefficients of seasonal maximum, minimum and mean temperatures have been resulted. According to these results, the highest maximum (minimum) temperature rise has been calculated for Qom (Tehran) station during spring and winter (fall) seasons ~0.44°C (~0.67°C) in a decade during 1960-2017. However, the highest decrease in precipitation over Arak station has been calculated ~13.8 mm in a decade in winter during study period.