The Role of the Solar Cycle in the Relationship Between the North Atlantic Oscillation and Northern Hemisphere Surface Temperatures

The North Atlantic Oscillation （NAO） is one of the leading modes of climate variability in the Northern Hemisphere. It has been shown that it clearly relates to changes in meteorological variables, such as surface temperature, at hemispherical scales. However, recent studies have revealed that the NAO spatial pattern also depends upon solar forcing. Therefore, its effects on meteorological variables must vary depending upon this factor. Moreover, it could be that the Sun affects climate through variability patterns, a hypothesis that is the focus of this study. We find that the relationship between the NAO/AO and hemispheric temperature varies depending upon solar activity. The results show a positive significant correlation only when solar activity is high. Also, the results support the idea that solar activity influences tropospheric climate fluctuations in the Northern Hemisphere via the fluctuations of the stratospheric polar vortex .

Insights into the origin of precipitation moisture for tropical cyclones during rapid intensification process

In this study,we identified the moisture sources for the precipitation associated with tropical cyclones(TCs)during the rapid intensification(RI)process from 1980 to 2018 by applying a Lagrangian moisture source diagnostic method.We detected sixteen regions on a global scale for RI events distributed as follows:four in the North Atlantic(NATL),two in the Central and East Pacific Ocean(NEPAC),the North Indian Ocean(NIO)and South Indian Ocean(SIO),and three in the South Pacific Ocean(SPO)and the Western North Pacific Ocean(WNP).The moisture uptake(MU)mostly was from the regions where TCs underwent RI.The Western NATL,tropical NATL,Caribbean Sea,the Gulf of Mexico and the Central America and Mexico landmass supported~85.4%of the precipitating moisture in the NATL,while the latter source and the eastern North Pacific Ocean provided the higher amount of moisture in NEPAC(~84.3%).The Arabian Sea,the Bay of Bengal and the Indian Peninsula were the major moisture sources in NIO,contributing approximately 81.3%.The eastern and western parts of the Indian Ocean supplied most of the atmospheric humidity in SIO(~83.8%).The combined contributions(~87.9%)from the western and central SPO and the Coral Sea were notably higher in SPO.Meanwhile,TCs in the WNP basin mostly received moisture from the western North Pacific Ocean,the Philippine Sea and the China Sea,accounting for 80.1%.The remaining moisture support in each basin came from the summed contributions of the remote sources.Overall,RI TCs gained more moisture up to 2500 km from the cyclone centre than those slow intensification(SI)and the total MU was approximately three times higher during RI than SI.Finally,the patterns of the MU differences respond to the typical pathways of moisture transport in each basin.

Estimation of mean water vapour residence time during tropical cyclones using a Lagrangian approach

Tropical cyclone(TC)-related rainfall mostly depends on the atmospheric moisture uptake from local and remote sources.In this study,the mean water vapour residence time(MWVRT)was computed for precipitation related to TCs in each basin and on a global scale by applying a Lagrangian moisture source diagnostic method.According to our results,the highest MWVRT was found for the TCs over the South Indian Ocean and South Pacific Ocean basins(~3.08 days),followed by the Western North Pacific Ocean,Central and East North Pacific Ocean,North Indian Ocean,and North Atlantic Ocean basins(which exhibited values of 2.98,2.94,2.85,and 2.72 days,respectively).We also found a statistically significant(p<0.05)decrease in MWVRT,at a rate of~2.4 h/decade in the North Indian Ocean and~1.0 h/decade in the remaining basins.On average,the MWVRT decreased during the 24 h before TCs made landfall,and the atmospheric parcels precipitated faster after evaporation when TCs moved over land than over the ocean.Further research should focus on the relationship between global warming and MWVRT of atmospheric parcels that precipitate over TC positions.