Impact of selected teleconnection pattern on solar energy potential in different climatic zones of Nigeria

Meeting the energy demands and sustainable development goals in Nigeria requires investigation of potentials of alternative energy sources and possible challenges to their reliability. In this study, we investigated the impact of four (4) teleconnection patterns on the solar energy potential within different climatic zones of Nigeria. Our results indicate that there are weak and insignificant correlation between the studied teleconnection patterns and solar energy potential on the long run. However, monthly analysis suggests significant correlation values between all the teleconnection patterns studied and solar energy production within all the climatic regions of the country. Therefore, it is important to consider the role of teleconnection pattern in energy planning and forecasting within the region.

Linkages between the atmospheric transmission originating from the North Atlantic Oscillation and persistent winter haze over Beijing

In this study, the persistent winter haze that occurred over Beijing during 1980 to 2016 is examined using reanalysis and station data. On both interannual and daily-to-weekly timescales, the winter haze weather in Beijing is found to be associated with a pronounced atmospheric teleconnection pattern from the North Atlantic to Eurasia (Beijing). A positive western-type North Atlantic Oscillation (WNAO+) phase and a positive East Atlantic/West Russia (EA/WR+) phase are observed as part of this teleconnection pattern (an arched wave train). This study focuses on the role of the WNAO pattern, because the WNAO+ pattern acts as the origin of the atmospheric transmission, 8–10 d before the persistent haze events. Further analyses reveal that the WNAO+ pattern can increase the number of haze days and persistent haze events on interannual and daily-to-weekly timescales. Specifically, strong WNAO+ winters (above the 95th percentile) can increase the number of haze days and persistent haze events by 26.0 % and 42.3 %, respectively. In addition, a high WNAO index for the 5 d average (above the 95th percentile) predicts a 16.9 % increase in the probability of haze days on Day 8 and a higher proportion of persistent haze days compared with an unknown WNAO state. Thus, the WNAO+ pattern is as a necessary prior background condition for the formation of the wave train and is a skillful predictor for persistent hazy weather. Corresponding to the WNAO+ pattern, intensified zonal wind and a north–south sea surface temperature tripolar mode over the North Atlantic also appear before persistent haze events on the daily-to-weekly timescale. On the interannual timescale, winters with a greater number of persistent haze days are also associated with a tripolar sea surface temperature (SST) mode over the North Atlantic that is situated farther northward.

Dominant climate drivers of wintertime severe particulate pollution in North China

Severe particulate pollution days (SPPDs, characterized by a daily mean PM2.5 concentration exceeding 150 μg m-3), which are extremely harmful to human health and the environment, occurred frequently in North China during the boreal winters of 2013–2019. SPPDs generally occur under conducive weather patterns (CWPs) characterized by a weakened East Asian Trough in the mid-troposphere, reduced winter northerlies in the lower troposphere, and a temperature inversion at the surface. The occurrence of CWPs has been attributed to variations in numerous climate factors (e.g., Arctic sea ice cover, sea surface temperature, and atmospheric teleconnections), but the dominant climate drivers remain inconclusive. Here, we show that the East Atlantic-West Russia (EA/WR) teleconnection pattern and the Victoria Mode (VM) of sea surface temperature anomalies are the first and second dominant climate drivers, respectively, leading to CWPs in North China through the zonal and meridional propagations of Rossby waves and explaining 36.3% and 18.5%, respectively, of the observed wintertime SPPDs in Beijing-Tianjin-Hebei. Our results suggest that, with the help of seasonal forecast from climate models, the indices of the EA/WR and VM can be used to predict wintertime SPPDs over Beijing-Tianjin-Hebei.

Changing Impacts of Tropical Cyclones on East and Southeast Asian Inland Regions in the Past and a Globally Warmed Future Climate

The impacts of the western North Pacific (WNP) tropical cyclone (TC) on East and Southeast Asian inland regions are analyzed. Here, based on a stringent TC selecting criterion, robust increase of TC-related inland impacts between 1979 and 2016 over East and Southeast Asian regions have been detected. The storms sustained for 2–9 h longer and penetrated 30–190 km further inland, as revealed from different best track datasets. The most significant increase of the TC inland impacts occurred over Hanoi and South China. The physical mechanism that affects TC-related inland impacts is shortly discussed. First, the increasing TC inland impacts just occur in the WNP region, but it is not a global effect. Second, besides the significant WNP warming effects on the enhanced TC landfall intensity and TC inland impacts, it is suggested that the weakening of the upper-level Asian Pacific teleconnection pattern since 1970s may also play an important role, which may reduce the climatic 200 hPa anti-cyclonic wind flows over the Asian region, weakening the wind shear near the Philippine Sea, and may eventually intensify the TC intensity when the TCs across the basin. Moreover, the TC inland impacts in the warming future are projected based on a high-resolution (20 km) global model according to the Representative Concentration Pathway 8.5 scenario. By the end of the 21st century, TC mean landfall intensity will increase by 2 m/s (6%). The stronger storms will sustain 4.9 h (56%) longer and penetrate 92.4 km (50%) farther inland, thereby almost doubling the destructive power delivered to Asian inland regions. More inland locations will therefore be exposed to severe storm–related hazards in the future due to warmer climate. Long-term planning to enhance disaster preparedness and resilience in these regions is called for.

Influence of East Asia Pacific Teleconnection and Scandinavian Teleconnection on Summer Precipitation in Southwest China

Based on the summer precipitation data of 328 stations in Southwest China in 50 years and the reanalysis data of NCEP / NCAR monthly geopotential height field, and wind field, the relationship between summer precipitation in Southwest China and East Asia Pacific teleconnection pattern (EAP) and Scandinavian teleconnection pattern (SCA) is explored by using EOF, correlation analysis and synthetic analysis. The research results show that: the summer precipitation distribution in Southwest China is mainly divided into two types: the whole region consistent type and the north-south contrary type. EAP teleconnection patterns and SCA teleconnection patterns have a significant negative correlation with the precipitation in Southwest China during the same period. In the active year (teleconnection indices >= 0.3 or <= 0.3), the two teleconnection patterns mostly appear in the same phase, and the distribution of the precipitation is consistent with the second mode distribution of the EOF for summer precipitation in Southwest China, showing a north-south contrary distribution in Southwest China. The two types of teleconnections are divided into two configurations, both of which are positive phase (configuration I), and both are negative phase (configuration II). Configuration I, the summer precipitation in Southwest China presents the distribution of "more in the south and less in the north"; configuration II, the distribution of precipitation is opposite to that configuration I, showing the distribution of "more in the north and less in the south".

Precursory atmospheric circulations with Rossby wave trains leading to Eurasian extreme cold events

This work examines precursory atmospheric circulations with various wave trains contributing to extreme cooling over central Eurasia in boreal winter from 1979-2016 based on the ERA-Interim dataset. The empirical orthogonal function (EOF) method is used to classify the anomalous sea level pressure field averaged in two weeks prior to extreme cooling. Based on the classification, three types of precursory atmospheric circulation patterns are named according to the origins of wave trains, and their formation mechanisms are revealed as well . Type1: Baffin Bay-origin pattern, which forms in the downstream development of Rossby wave packets generated from the downward stratospheric energy transmission over the Baffin Bay. Type2: Pacific-origin pattern, similar to a Eurasian (EU) teleconnection pattern, arises at the exit area of the westerly jet in the central North Pacific where cyclonic shear exists; then it develops along the northerly westerly jet over the North Atlantic, which may act as a waveguide to the Eurasian continent. Type 3: Atlantic-origin, manifests as the negative phase of type 2, consistent with the Scandinavian (SCAND) pattern, which may results from the air-sea interaction induced by the warm anomaly of sea surface temperature in the middle of North Atlantic. In conclusion, the three types of precursory atmospheric wave train patterns that bring extreme cooling to Eurasia possess diverse disturbing sources and development mechanisms. The results, which are investigated based on a quasi-biweekly time scale , deepen our understanding of the atmospheric genesis of extreme weather and have specific indicative significance to improve the technique of extended forecast.

Possible Relationship between Korean Heat Wave and Western North Pacific Tropical Cyclone Genesis Frequency

This study conducted a correlation analysis between tropical cyclone genesis frequency (TCGF) in the western North Pacific (WNP) and heat wave days (HWD) in Korea during July and August for 46 years (1973–2018) and we found a strong positive correlation between them. This implied that the higher the TCGF in the WNP during July and August, the higher the HWD in Korea becomes. To examine the cause of the statistically significant positive correlation between the TCGF during July and August in the WNP and the HWD in Korea, 15 years with the highest frequency and the lowest frequency out of the 46 years in the TCGF time series were selected and defined as high TCGF years and low TCGF years, respectively. An analysis of the difference in 2m air temperature (Air2m) between the two groups showed that in the mid-latitude region of Asia, the Air2m was higher during the high TCGF years. Thus, it could be seen from this analysis that the increase of HWD during the high TCGF years is likely to occur in the entire mid-latitude region of East Asia as well as in Korea. According to the difference in atmospheric circulations between the two groups, in all layers of the troposphere, anomalous anticyclonic and cyclonic circulations were strengthened in the mid-latitude region of East Asia and in the WNP, respectively, which was similar to the Pacific-Japan (PJ) teleconnection pattern. Furthermore, the anomalous anticyclone strengthened in the mid-latitude region of East Asia was associated with the weakening of the East Asian summer monsoon, and the anomalous cyclone strengthened in the WNP was associated with the WNP summer monsoon. The difference in the vertical meridional circulation averaged over the longitude range where Korea is located showed that anomalous upward and downward flows were strengthened in the WNP and in the latitude where Korea is located, respectively. This implied that the local Hadley circulation was strengthened during the high TCGF years. An analysis of the difference in the mean sea surface temperature during July and August showed that the eastern Pacific (EP) La Niña was strengthened during the high TCGF years. To determine the cause of the formations of anomalous anticyclones in the mid-latitude region of East Asia and in the WNP during the high TCGF years, the 500 hPa wave activity flux was analyzed. The wave activity flux originated from the North Atlantic, passed through the Scandinavian Peninsula, the North coast of Russia, and East Siberia before reaching Korea and the WNP. This spatial distribution was similar to the Scandinavia teleconnection pattern. Therefore, we conclude that the anomalous anticyclone formed in the mid-latitude region of East Asia and the anomalous cyclone formed in the WNP during the high TCGF years are associated with the Scandinavia teleconnection pattern.

A zonally-oriented teleconnection pattern induced by heating of the western Tibetan Plateau in boreal summer

The thermal effect of the Tibetan Plateau (TP) on the northern hemisphere climate has long been a hot topic of scientific research. However, the global effects of the TP heat source are still unclear. We investigate the teleconnection patterns coincident with the TP heat source in boreal summer using both observational data and numerical models including a linearized baroclinic model and an atmospheric general circulation model. The western TP shows the most intense variability in atmospheric heating and the most active connection to atmospheric circulations. The surface sensible heating component of the western TP heat source is associated with a high-latitude wave train propagating from North Japan to central North America through the Bering Sea and Canada. The radiative heating component is accompanied by a wavenumber-4 wave train over Eurasia. We focus on the global zonally-oriented pattern that is connected with the latent heat release from the western TP, referred to here as the TP–circumglobal teleconnection (TP-CGT). The TP-CGT pattern is triggered by the western TP latent heating in two parts starting from the TP: an eastward-propagating wave train trapped in the westerly jet stream and a westward Rossby wave response. The TP-CGT accounts for above 18% of the total variance of the circumglobal teleconnection pattern and modulates mid-latitude precipitation by superimposition. The western TP is the key region in which diabatic heating can initiate the two atmospheric responses concurrently, and the heating over northeastern Asia or the Indian Peninsula is unable to induce the circumglobal pattern directly. The unique geographical location and strong tropospheric heating also make the western TP as a “transit area” of transferring the indirect impact of the Indian summer monsoon (ISM) to the TP-CGT. These results enhance our understanding of the relationship between the circumglobal teleconnection and the ISM and is helpful for improving the prediction of the circumglobal teleconnection variability.