The influences of interannual variability of vegetation LAI on surface temperature are investigated via two ensemble simulations, applying the Community Earth System Model. The interannual LAI, derived from Global Inv...The influences of interannual variability of vegetation LAI on surface temperature are investigated via two ensemble simulations, applying the Community Earth System Model. The interannual LAI, derived from Global Inventory Modeling and Mapping Studies NDVI for the period 1982-2011, and its associated climatological LAI, are used in the two ensemble simulations, respectively.The results show that the signals of the influences, represented as ensemble-mean differences, are generally weaker than the noises of the atmospheric variability, represented as one standard deviation of the ensemble differences. Spatially, the signals are stronger over the tropics compared with the mid-high latitudes. Such stronger signals are contributed by the significant linearity between LAI and surface temperature, which is mainly caused via the influences of LAI on evapotranspiration.The maximum amplitudes of the influences on the interannual variability of surface temperature are high and thus deserve full consideration. However, the mean magnitudes of influences are small because of the small changes in the amplitudes of LAI. This work only investigates the influences of the interannual variability of LAI and does not consider interannual changes in other vegetation characteristics, such as canopy height and fractional cover. Further work involving dynamic vegetation models may be needed to investigate the influences of vegetation variability.展开更多
This paper demonstrates regional characteristics, a long-term decreasing trend, and decadal variations in the frequency of cold surge events based on daily mean temperature and daily minimum temperature data in China&...This paper demonstrates regional characteristics, a long-term decreasing trend, and decadal variations in the frequency of cold surge events based on daily mean temperature and daily minimum temperature data in China's Mainland from 1960 to 2008. During these 48 years four high frequency centers of cold surge events were located in Xinjiang, central North China, northeast China, and southeast China. A main frequency peak of cold surge events occurs in autumn for the four regions and another peak is detected in spring over northeast China and southeast China. The regional pattern of cold surge frequencies is in accordance with the perturbation kinetic energy distribution in October December, January, and February April. The long-term decreasing trend ( 0.2 times/decade) of cold surge frequencies in northeast China and decadal variations in China are related to the variations of the temperature difference between southern and northern China in the winter monsoon season; these variations are due to the significant rising of winter temperatures in high latitudes.展开更多
In this paper, the International Comprehensive Ocean and Atmosphere Data Set(ICOADS) is utilized to investigate the horizontal distribution of sea fog occurrence frequency over the Northern Atlantic as well as the met...In this paper, the International Comprehensive Ocean and Atmosphere Data Set(ICOADS) is utilized to investigate the horizontal distribution of sea fog occurrence frequency over the Northern Atlantic as well as the meteorological and oceanic conditions for sea fog formation. Sea fog over the Northern Atlantic mainly occurs over middle and high latitudes. Sea fog occurrence frequency over the western region of the Northern Atlantic is higher than that over the eastern region. The season for sea fog occurrence over the Northern Atlantic is generally from April to August. When sea fogs occur, the prevailing wind direction in the study area is from southerly to southwesterly and the favorable wind speed is around 8 m s-1. It is most favorable for the formation of sea fogs when sea surface temperature(SST) is 5℃ to 15℃. When SST is higher than 25℃, it is difficult for the air to get saturated, and there is almost no report of sea fog. When sea fogs form, the difference between sea surface temperature and air temperature is mainly-1 to 3℃, and the difference of 0℃ to 2℃ is the most favorable conditions for fog formation. There are two types of sea fogs prevailing in this region: advection cooling fog and advection evaporating fog.展开更多
基金supported by the major research projects of the National Natural Science Foundation of China[grant number91230202]
文摘The influences of interannual variability of vegetation LAI on surface temperature are investigated via two ensemble simulations, applying the Community Earth System Model. The interannual LAI, derived from Global Inventory Modeling and Mapping Studies NDVI for the period 1982-2011, and its associated climatological LAI, are used in the two ensemble simulations, respectively.The results show that the signals of the influences, represented as ensemble-mean differences, are generally weaker than the noises of the atmospheric variability, represented as one standard deviation of the ensemble differences. Spatially, the signals are stronger over the tropics compared with the mid-high latitudes. Such stronger signals are contributed by the significant linearity between LAI and surface temperature, which is mainly caused via the influences of LAI on evapotranspiration.The maximum amplitudes of the influences on the interannual variability of surface temperature are high and thus deserve full consideration. However, the mean magnitudes of influences are small because of the small changes in the amplitudes of LAI. This work only investigates the influences of the interannual variability of LAI and does not consider interannual changes in other vegetation characteristics, such as canopy height and fractional cover. Further work involving dynamic vegetation models may be needed to investigate the influences of vegetation variability.
基金supported jointly by the National Natural Science Foundation of China (40975039)the National Basic Research Program of China (2006CB400504/ 2009CB421401 and GYHY20070605)
文摘This paper demonstrates regional characteristics, a long-term decreasing trend, and decadal variations in the frequency of cold surge events based on daily mean temperature and daily minimum temperature data in China's Mainland from 1960 to 2008. During these 48 years four high frequency centers of cold surge events were located in Xinjiang, central North China, northeast China, and southeast China. A main frequency peak of cold surge events occurs in autumn for the four regions and another peak is detected in spring over northeast China and southeast China. The regional pattern of cold surge frequencies is in accordance with the perturbation kinetic energy distribution in October December, January, and February April. The long-term decreasing trend ( 0.2 times/decade) of cold surge frequencies in northeast China and decadal variations in China are related to the variations of the temperature difference between southern and northern China in the winter monsoon season; these variations are due to the significant rising of winter temperatures in high latitudes.
基金financially supported by the National Natural Science Foundation of China (Nos.41305086 and 41275049)supported by China postdoctoral funding under the grant 2012M511545supported by U.S. National Science Foundation’s Independent Research and Development fund
文摘In this paper, the International Comprehensive Ocean and Atmosphere Data Set(ICOADS) is utilized to investigate the horizontal distribution of sea fog occurrence frequency over the Northern Atlantic as well as the meteorological and oceanic conditions for sea fog formation. Sea fog over the Northern Atlantic mainly occurs over middle and high latitudes. Sea fog occurrence frequency over the western region of the Northern Atlantic is higher than that over the eastern region. The season for sea fog occurrence over the Northern Atlantic is generally from April to August. When sea fogs occur, the prevailing wind direction in the study area is from southerly to southwesterly and the favorable wind speed is around 8 m s-1. It is most favorable for the formation of sea fogs when sea surface temperature(SST) is 5℃ to 15℃. When SST is higher than 25℃, it is difficult for the air to get saturated, and there is almost no report of sea fog. When sea fogs form, the difference between sea surface temperature and air temperature is mainly-1 to 3℃, and the difference of 0℃ to 2℃ is the most favorable conditions for fog formation. There are two types of sea fogs prevailing in this region: advection cooling fog and advection evaporating fog.
