Based on the historical and RCP8.5 runs of the multi-model ensemble of 32 models participating in CMIP5, the present study evaluates the formation mechanisms for the patterns of changes in equatorial Pacific SST under global warming.Two features with complex formation processes, the zonal El Ni ?no-like pattern and the meridional equatorial peak warming(EPW), are investigated. The climatological evaporation is the main contributor to the El Ni ?no-like pattern, while the ocean dynamical thermostat effect plays a comparable negative role. The cloud–shortwave-radiation–SST feedback and the weakened Walker circulation play a small positive role in the El Ni ?no-like pattern. The processes associated with ocean dynamics are confined to the equator. The climatological evaporation is also the dominant contributor to the EPW pattern, as suggested in previous studies. However, the effects of some processes are inconsistent with previous studies. For example,changes in the zonal heat advection due to the weakened Walker circulation have a remarkable positive contribution to the EPW pattern, and changes in the shortwave radiation play a negative role in the EPW pattern.
Against a background of climate change, Macao is very exposed to sea level rise(SLR) because of its low elevation,small size, and ongoing land reclamation. Therefore, we evaluate sea level changes in Macao, both historical and, especially,possible future scenarios, aiming to provide knowledge and a framework to help accommodate and protect against future SLR. Sea level in Macao is now rising at an accelerated rate: 1.35 mm yr-1over 1925–2010 and jumping to 4.2 mm yr-1over 1970–2010, which outpaces the rise in global mean sea level. In addition, vertical land movement in Macao contributes little to local sea level change. In the future, the rate of SLR in Macao will be about 20% higher than the global average, as a consequence of a greater local warming tendency and strengthened northward winds. Specifically, the sea level is projected to rise 8–12, 22–51 and 35–118 cm by 2020, 2060 and 2100, respectively, depending on the emissions scenario and climate sensitivity. Under the +8.5 W m-2Representative Concentration Pathway(RCP8.5) scenario the increase in sea level by2100 will reach 65–118 cm—double that under RCP2.6. Moreover, the SLR will accelerate under RCP6.0 and RCP8.5, while remaining at a moderate and steady rate under RCP4.5 and RCP2.6. The key source of uncertainty stems from the emissions scenario and climate sensitivity, among which the discrepancies in SLR are small during the first half of the 21 st century but begin to diverge thereafter.
The increase in the occurrence of hot extremes is known to have resulted in serious consequences for human society and ecosystems. However,our ability to seasonally predict hot extremes remains poor,largely due to our limited understanding of slowly evolving earth system components such as soil moisture,and their interactions with climate. In this study,we focus on North China,and investigate the relationship of the spring soil moisture condition to summer hot extremes using soil moisture data from the Global Land Data Assimilation System and observational temperature for the period 1981–2008. It is found that local soil moisture condition in spring is closely linked to summer hot days and heat waves over North China,accounting for 19%–34% of the total variances. Spring soil moisture anomalies can persist to the summer season,and subsequently alter latent and sensible heat fluxes,thus having significant effects on summer hot extremes. Our findings indicate that the spring soil moisture condition can be a useful predictor for summer hot days and heat waves over North China.
In this study,the teleconnection between Indian Ocean sea surface temperature anomalies (SSTAs) and the frequency of high temperature extremes (HTEs) across the southern Yangtze River valley (YRV) was investigated.The results indicate that the frequency of HTEs across the southern YRV in August is remotely influenced by the Indian Ocean basin mode (IOBM) SSTAs.Corresponding to June-July-August (JJA) IOBM warming condition,the number of HTEs was above normal,and corresponding to IOBM cooling conditions,the number of HTEs was below normal across the southern YRV in August.The results of this study indicate that the tropical IOBM warming triggered low-level anomalous anticyclonic circulation in the subtropical northwestern Pacific Ocean and southern China by emanating a warm Kelvin wave in August.In the southern YRV,the reduced rainfall and downward vertical motion associated with the anomalous low-level anticyclonic circulation led to the increase of HTE frequency in August.
Variations in surface air temperature and precipitation are closely associated because of their thermodynamic relations. The climate shift in the late 1970s and associated changes in precipitation over East Asia have been well reported. However, how the covariability of surface air temperature and precipitation responds to the climate shift is not yet well understood. We used the observed mean(Tmean), daily maximum(Tmax), and minimum(Tmin) surface air temperatures and precipitation during the period of 1953–2000 to explore this issue. Results show that the covariability between Tmean and precipitation experienced remarkable changes over certain areas of East Asia after the climate shift with evident seasonal dependencies. In winter, after the climate shift significantly negative correlations occupied more areas over Mongolia and China. By contrast, in summer after the climate shift significantly negative correlations which existed over almost entire East Asia during the pre-shift period were mostly weakened with the exception of enhanced correlations over some small isolated areas. Changes in the covariability of Tmax and precipitation showed a similar spatial pattern to that of the Tmean, whereas the Tmin-precipitation covariability did not. In winter, after the climate shift positive correlations between Tmin and precipitation over southern China were largely weakened, while the areas with significantly negative correlations increased over Mongolia. In summer, changes in Tmin-precipitation covariability appeared to be a negative-positive-negative pattern from south to north over East Asia, with positive changes occurring in the Yangtze-Huai River valley and Korea and negative changes occurring over South China and Japan, and northern part of East Asia. ?Keywords: surface air temperature, precipitation, co-
Many Chinese people leave big cities for family reunions during the Chinese New Year(CNY), which is the most important public holiday in China. However, how modern mass human migration during the CNY holiday affects the urban heat island(UHI) is still unknown. Here, the authors investigate the role of modern human migration for the UHI effects during the CNY holiday for the period of 1992–2006 in Harbin City, Northeast China. The results show that during the CNY week, the UHI effects expressed as daily mean, maximum, and minimum temperature differences between urban and rural stations averaged over the period of 1992–2006 are 0.65°C(43%), 0.31°C(48%), and 1.14°C(71%) lower than during the background period(four weeks before and four weeks after the CNY week), respectively. Our findings identify previously unknown impacts of modern mass human migration on the UHI effects based on a case study in Harbin City.
The urban heat island(UHI) represents one of the most significant human impacts on the earth system. In recent decades, the number of the tourists has a remarkable increase in China and also other regions of the globe.However, it is still unclear whether or to what extent the tourism can affect the UHI. Here, we investigate the role of the tourism for the UHI during the Chinese New Year(CNY) holiday based on a case study in tropical Sanya City, which attracts many tourists for celebrating the CNY and enjoying the warm climate during the holiday. We find that the UHI effects expressed as daily mean(DTmean),maximum(DTmax), and minimum(DTmin) surface air temperature differences between urban and nearby nonurban stations averaged over the period of 1995–2004during the CNY week were 0.48 °C(39 %), 0.66 °C(61 %), and 0.42 °C(26 %) higher than those averaged over the background period(8 weeks including 4 weeks before and 4 weeks after the CNY week), respectively.These changes are all significant at the 99 % confidence level. Our findings highlight previously unidentified impact of the tourism on the UHI based on a case study in Sanya City, Hainan Province of China.
