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, Available online , doi: 10.3878/j.issn.1006-9585.2023.22089
Abstract:
Based on the daily observational data of air temperature and the soil temperature at a depth of 0–320 cm at the Shijiazhuang urban meteorological station and two nearby rural stations from 2009 to 2012, the urban heat island (UHI) effect from the canopy to the surface and deep layers of soil at Shijiazhuang station and its differences were compared and analyzed. The results revealed that: 1) the annual average air temperature UHI intensity from 2009 to 2012 was 0.9°C, the UHI intensity of the soil temperature at a depth of 0–320 cm was between −0.5°C and 0.2°C, and the air temperature UHI intensity was substantially stronger than that of the soil temperature. The surface (0 cm) and shallow (5–40 cm) soil temperatures exhibited a “heat island effect,” the deep (80–320 cm) soil temperature exhibited a “cold island effect,” and the soil temperature at a depth of 40–80 cm was the “conversion horizon” of the two. Deep soil temperature, which may be impacted by the local climate, demonstrated local characteristics. 2) The air temperature UHI intensities during spring, summer, autumn, and winter were 1.1°C, 0.6°C, 0.7°C, and 1.3°C, respectively; the seasons exhibiting the strongest and weakest UHI intensities were winter and summer, respectively. Furthermore, the soil temperatures at the surface layer and above 40 cm exhibited the heat island effect, and those below 80 cm exhibited the cold island effect. During autumn, the soil temperature at different depths exhibited the cold island effect, with the intensity of the cold island effect at a depth of 320 cm being the strongest. During winter, the soil temperatures at the surface layer and above 80 cm predominantly exhibited the heat island effect, whereas those at a depth of 320 cm exhibited the cold island effect. The seasonal variation of the soil surface UHI intensity was consistent with that of the air temperature, and its physical mechanism exhibited similar properties. 3) The air temperature UHI intensity in each month was between 0.5°C and 1.6°C, with the strongest intensity observed during January and the weakest intensity observed during July and October. The soil temperatures at the surface layer and above 40 cm generally exhibited the heat island effect from January to July and December, with the UHI intensity peaking during June, and exhibited the cold island effect from August to November. The soil temperature below 80 cm exhibited the cold island effect for the majority of the year. 4) The UHI intensities of the annual and seasonal average air temperatures clearly exhibited diurnal variation characteristics; the annual and seasonal surface soil temperatures exhibited similar characteristics. However, with the increase in soil depth, the diurnal variation of soil temperature UHI intensity gradually weakened and finally transformed into the cold island effect.
Based on the daily observational data of air temperature and the soil temperature at a depth of 0–320 cm at the Shijiazhuang urban meteorological station and two nearby rural stations from 2009 to 2012, the urban heat island (UHI) effect from the canopy to the surface and deep layers of soil at Shijiazhuang station and its differences were compared and analyzed. The results revealed that: 1) the annual average air temperature UHI intensity from 2009 to 2012 was 0.9°C, the UHI intensity of the soil temperature at a depth of 0–320 cm was between −0.5°C and 0.2°C, and the air temperature UHI intensity was substantially stronger than that of the soil temperature. The surface (0 cm) and shallow (5–40 cm) soil temperatures exhibited a “heat island effect,” the deep (80–320 cm) soil temperature exhibited a “cold island effect,” and the soil temperature at a depth of 40–80 cm was the “conversion horizon” of the two. Deep soil temperature, which may be impacted by the local climate, demonstrated local characteristics. 2) The air temperature UHI intensities during spring, summer, autumn, and winter were 1.1°C, 0.6°C, 0.7°C, and 1.3°C, respectively; the seasons exhibiting the strongest and weakest UHI intensities were winter and summer, respectively. Furthermore, the soil temperatures at the surface layer and above 40 cm exhibited the heat island effect, and those below 80 cm exhibited the cold island effect. During autumn, the soil temperature at different depths exhibited the cold island effect, with the intensity of the cold island effect at a depth of 320 cm being the strongest. During winter, the soil temperatures at the surface layer and above 80 cm predominantly exhibited the heat island effect, whereas those at a depth of 320 cm exhibited the cold island effect. The seasonal variation of the soil surface UHI intensity was consistent with that of the air temperature, and its physical mechanism exhibited similar properties. 3) The air temperature UHI intensity in each month was between 0.5°C and 1.6°C, with the strongest intensity observed during January and the weakest intensity observed during July and October. The soil temperatures at the surface layer and above 40 cm generally exhibited the heat island effect from January to July and December, with the UHI intensity peaking during June, and exhibited the cold island effect from August to November. The soil temperature below 80 cm exhibited the cold island effect for the majority of the year. 4) The UHI intensities of the annual and seasonal average air temperatures clearly exhibited diurnal variation characteristics; the annual and seasonal surface soil temperatures exhibited similar characteristics. However, with the increase in soil depth, the diurnal variation of soil temperature UHI intensity gradually weakened and finally transformed into the cold island effect.
, Available online , doi: 10.3878/j.issn.1006-9585.2022.21180
Abstract:
The daily daytime/nighttime precipitation data of 81 National Meteorological Science Data Center stations on the Qinghai–Tibet Plateau and 80 stations in Southwest China were used to statistically analyze the daytime/nighttime rainy days of different magnitudes, differences in this number in the two regions from 1961 to 2020, and interannual change (trend) characteristics. The results showed the following: (1) The number of daytime/nighttime rainy days of different magnitudes on the Tibetan Plateau and in Southwest China increased rapidly in May and decreased significantly in November; large differences in the number of daytime/nighttime rainy days in the two regions were observed in May–October, and the number of heavy rain and rainstorm days was higher in May–October. The number of rainstorm days on the Tibetan Plateau accounted for ＞85% of the total number of rainstorm days in the year, heavy rain accounted for ＞90%, and the proportions of these two levels of precipitation were 93% and 86%, respectively, in Southwest China. The probability of extremely heavy precipitation (rainstorms) during the rainy season in both regions was substantially higher at night than during the day. (2) In addition to obvious regional differences in the number of daytime/nighttime rainy days of different magnitudes in the two regions during the rainy season, very significant differences were observed between daytime and nighttime. The Three-Rivers Source Region and the southeastern part of the Tibetan Plateau have frequent light and moderate rains during the day and night. Heavy rain occurs exclusively at night in southeastern Tibet and the east of the Three-Rivers Source Region; rainstorms occur only in the east of the Tibetan Plateau, and there are visibly more sites receiving precipitation at night than during the day. Central Sichuan, western Sichuan marginal mountains, and southwestern Yunnan in Southwest China have a high incidence of daytime/nighttime light rain and moderate rain; heavy rain is more likely to occur during the day in southwestern Yunnan, whereas it is more likely to occur at night in central Sichuan. Typical areas with rainstorms are central and eastern Sichuan, western Chongqing, and central and southern Guizhou. (3) The overall trends of interannual changes in the number of rainy seasons in the rainy season are significantly different between daytime/nighttime-graded rain days. In the Tibetan Plateau, except for the significant decrease in the number of light rainy days at night, the rest of the rainy days of different magnitudes increased significantly during the daytime and nighttime, with the increasing trend at night being greater than that during the day, and the increasing trend of heavy rain and rainstorm at night was almost twice that of the day. Unlike the Tibetan Plateau, the number of days with light precipitation (light rain, moderate rain, and heavy rain) decreased significantly in Southwest China. Among them, the number of light rainy days at night decreased the most, approximately twice as much as during the daytime; the number of days with heavy precipitation (rainstorm or torrential rain) increased in the opposite direction, and the increasing trend at night is greater than that during the daytime.
The daily daytime/nighttime precipitation data of 81 National Meteorological Science Data Center stations on the Qinghai–Tibet Plateau and 80 stations in Southwest China were used to statistically analyze the daytime/nighttime rainy days of different magnitudes, differences in this number in the two regions from 1961 to 2020, and interannual change (trend) characteristics. The results showed the following: (1) The number of daytime/nighttime rainy days of different magnitudes on the Tibetan Plateau and in Southwest China increased rapidly in May and decreased significantly in November; large differences in the number of daytime/nighttime rainy days in the two regions were observed in May–October, and the number of heavy rain and rainstorm days was higher in May–October. The number of rainstorm days on the Tibetan Plateau accounted for ＞85% of the total number of rainstorm days in the year, heavy rain accounted for ＞90%, and the proportions of these two levels of precipitation were 93% and 86%, respectively, in Southwest China. The probability of extremely heavy precipitation (rainstorms) during the rainy season in both regions was substantially higher at night than during the day. (2) In addition to obvious regional differences in the number of daytime/nighttime rainy days of different magnitudes in the two regions during the rainy season, very significant differences were observed between daytime and nighttime. The Three-Rivers Source Region and the southeastern part of the Tibetan Plateau have frequent light and moderate rains during the day and night. Heavy rain occurs exclusively at night in southeastern Tibet and the east of the Three-Rivers Source Region; rainstorms occur only in the east of the Tibetan Plateau, and there are visibly more sites receiving precipitation at night than during the day. Central Sichuan, western Sichuan marginal mountains, and southwestern Yunnan in Southwest China have a high incidence of daytime/nighttime light rain and moderate rain; heavy rain is more likely to occur during the day in southwestern Yunnan, whereas it is more likely to occur at night in central Sichuan. Typical areas with rainstorms are central and eastern Sichuan, western Chongqing, and central and southern Guizhou. (3) The overall trends of interannual changes in the number of rainy seasons in the rainy season are significantly different between daytime/nighttime-graded rain days. In the Tibetan Plateau, except for the significant decrease in the number of light rainy days at night, the rest of the rainy days of different magnitudes increased significantly during the daytime and nighttime, with the increasing trend at night being greater than that during the day, and the increasing trend of heavy rain and rainstorm at night was almost twice that of the day. Unlike the Tibetan Plateau, the number of days with light precipitation (light rain, moderate rain, and heavy rain) decreased significantly in Southwest China. Among them, the number of light rainy days at night decreased the most, approximately twice as much as during the daytime; the number of days with heavy precipitation (rainstorm or torrential rain) increased in the opposite direction, and the increasing trend at night is greater than that during the daytime.
