Influence of ENSO on frequency of wintertime fog days in Eastern China

Earth and Space Science

et al. 2021

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With global warming, the increasing number and intensity of extreme precipitation events are a global trend. The IPCC AR5 (2012) points out that the global average temperature has increased by 0.12°C every 10 years in the past 60 years (1951-2012). The temperature in Northeast China has increased by 1.75-2.5°C and is one of the most sensitive regions to climate change in the world (IPCC, 2012; Qin and Stocker, 2014). Northeast China is the most important area for food production in China and is also an important base for national security. Therefore, it is particularly important to study the mechanism of the formation of extreme precipitation in Northeast China. Extreme value theory (EVT) can successfully characterize climatic and hydrological extremes and has been widely used in meteorology and hydrology (

Section: Resultsmentioning

confidence: 99%

Section: Analysis Of Atmospheric Circulation Of Nonstationary Climatimentioning

confidence: 99%

Contribution of the Northeast Cold Vortex Index and Multiscale Synergistic Indices to Extreme Precipitation Over Northeast China

Meng

Earth and Space Science

et al. 2021

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“…In addition, comparing with the impact of ENSO (Yu et al, 2019) [15], for there is less influence of humidity by AO, the vertical air velocity seems to play a relatively more important role in causing an anomalous number of fog days. The water vapor in eastern China mainly comes from the southwesterly warm and moist air flow.…”

Section: Relations Of Fog Days In Different Regions With Ao Index Andmentioning

confidence: 98%

“…There was still really poor significant difference of T-Td between AO+ and AO-years (Figure 8), while the significant difference of specific humidity q and temperature T could easily pass the student's t-test at the same height according to our computation. However, Td could be significantly influenced by ENSO (Yu et al, 2019) [15], which may infer that ENSO is a strong signal with more anomalous moisture due to SST anomalies, while AO is just a relatively much weaker signal acting smaller impact on moist air abnormally traveling. Therefore, T-Td has rational reasons to lack significant differences that cannot pass the student t-test, but it can still show its possible contribution to the anomalous patterns of fog days.…”

Section: Geopotential Height Wind and Rain Anomalies With Anomalies mentioning

confidence: 99%

“…For studying the climatological characteristics of fog in different regions, the annual or monthly average of fog days is mostly analyzed. Many scholars have researched a lot on the frequency of fog days and its weather background, such as the impact of East Asian winter monsoon on haze days and the impact of ENSO on the number of winter fog days in eastern China [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

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Influence of Arctic Oscillation on Frequency of Wintertime Fog Days in Eastern China

Tang

et al. 2020

Atmosphere

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The influence of Arctic Oscillation (AO) on the frequency of wintertime fog days in eastern China is studied based on the winter AO index, the wintertime fog-day data of national stations in China, and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data from 1954 to 2007. The results show that heavy fog and light fog are more likely to occur during winter in eastern China with the strong interannual variability. During the winter with the positive-phase AO, there are more days of heavy fog in North China but less in South China, while light fog days become more in the whole of eastern China. It is mainly because that when AO is in the positive phase, the pressure in the polar region decreases at 500 hPa; the pressure in East Asia increases anomalously; the East Asian trough decreases; and the low-level westerly jet moves northward, preventing the northwesterly cold air from moving southward. Therefore, the whole eastern China gets warmer and wetter air, and there are more light fog days with the enhanced water vapor. However, the atmosphere merely becomes more towards unstable in South China, where the precipitation increases but the heavy fog days decreases. Nevertheless, heavy fog days increase with the water vapor in North China because of moving towards a stable atmosphere, which is formed by the anomalous downdrafts north of the precipitation center in South China. When AO is in the negative phase, the situation is basically opposite to that in the positive phase, but the variations of the corresponding fog days and circulations are weaker than those in the AO-positive-phase winter, which may be related to the nonlinear effect of AO on climate.

Effects of Atlantic multidecadal oscillation and Pacific decadal oscillation on interdecadal variability of fog frequency in autumn–winter season in Southwest China

Intl Journal of Climatology

Zhang

Tang

2021

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Based on the Atlantic multidecadal oscillation (AMO) and the Pacific decadal oscillation (PDO) indexes, the observation of fog frequency in China and the reanalysis data from the National Centres for Environmental Prediction/National Center for Atmospheric Research during 1958–2007 are selected to study the effects of the AMO and PDO on the interdecadal variability of fog frequency in autumn–winter in Southwest China (SWC). The results suggest that the fog frequency in SWC is highest in autumn–winter season and shows a characteristic of strong interdecadal variation. When the north Atlantic and the north Pacific are abnormally cold (warm), which corresponds to the negative (positive) phase of the AMO and the positive (negative) phase of the PDO respectively, the fog in SWC occurs more (less) frequently. The atmosphere is unstable because of the eastward propagation of Rossby wave train and the anomaly of Siberian high‐pressure, which are affected by the AMO and PDO, respectively. The AMO particularly affects the atmospheric stability in the middle and lower level, while the PDO mainly affects that of the whole layer. The water vapour is modulated by the southward movement of cold air in Northern China during the negative phase of the AMO and positive phase of the PDO. This results in the decreasing of temperature and specific humidity, and further leads to the supersaturation of water vapour in the lower atmosphere of SWC. The AMO particularly affects the temperature and water vapour supersaturation in the lower atmosphere, while the PDO mostly modulates the atmospheric stability of the whole layer and the southward movement of cold air.