Using daily precipitation data from weather stations in China, the variations in the contribution of extreme precipitation to the total precipitation are analyzed. It is found that extreme precipitation accounts for a...Using daily precipitation data from weather stations in China, the variations in the contribution of extreme precipitation to the total precipitation are analyzed. It is found that extreme precipitation accounts for approximately one third of the total precipitation based on the overall mean for China. Over the past half century, extreme precipitation has played a dominant role in the year-to-year variability of the total precipitation. On the decadal time scale, the extreme precipitation makes different contributions to the wetting and drying regions of China. The wetting trends of particular regions are mainly attributed to increases in extreme precipitation; in contrast, the drying trends of other regions are mainly due to decreases in non-extreme precipitation.展开更多
The 1°×1° National Center for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） data and mesoscale numerical simulation data are analyzed to reveal a mechanism for the form...The 1°×1° National Center for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） data and mesoscale numerical simulation data are analyzed to reveal a mechanism for the formation of heavy rainfall in Northern China; this mechanism is the non-uniformly saturated instability induced by a dry intrusion. The dry intrusion and the accompanying downward transport of air with a high value of potential vorticity （PV） are maintained during the precipitation event. As the dry air intrudes down into the warm and moist sector in the lower troposphere, the cold, dry air and the warm, moist air mix with each other, and, as a result, the atmosphere becomes non-uniformly saturated. On the basis of this non-uniform saturation, a new Brunt-Vaisaila frequency （BVF） formula is derived and applied to the precipitation event. It is shown that, compared to the conditions of either a dry or a saturated atmosphere, the BVF in a non-uniformly saturated, moist atmosphere （BVF） may be more appropriate for depicting the atmospheric instability in rainy regions.展开更多
The Aral Sea was one of the largest lakes in the world before it started to shrink in the 1960s due to water withdrawal for agricultural irrigation. Precipitation decreased from 9.4 kmin 1960 to 3.2 km3 in 2009, and a...The Aral Sea was one of the largest lakes in the world before it started to shrink in the 1960s due to water withdrawal for agricultural irrigation. Precipitation decreased from 9.4 kmin 1960 to 3.2 km3 in 2009, and annual river inflow into the Aral Sea decreased from 31.5 km3 in 1998 to 5.2 km3 in 2009. Comparison on the hydrological data of the Aral Sea between 1960 and 2009 showed the evaporation, water surface area, and water volume decreased by 90%, 80%, and 88%, respectively. This study employs the observed values of water volume, precipitation, runoff, evaporation, and salinity to estimate water volume and salinity from 1960 to 2009, and the efficiency coefficients for predicted water volume and salinity are o.975 and 0.974, respectively. Regression equations calculated from the observed data are used to predict precipitation, runoff, evaporation, and salinity from 20lO to 2021, and the results are then applied in the estimation of water volume and salinity Our estimates suggest that salinity will increase to around 200 g/L and water volume will decrease to around 83 km3 in 2021.展开更多
基金supported by the"Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues" of the Chinese Academy of Sciences(Grant No. XDA05090306)the National Basic Research Programof China(Grant No.2009CB421406)the Chinese Academy of Sciences-Common wealth Scientific and Industrial Research Organisation Cooperative Research Program(Grant No.GJHZ1223)
文摘Using daily precipitation data from weather stations in China, the variations in the contribution of extreme precipitation to the total precipitation are analyzed. It is found that extreme precipitation accounts for approximately one third of the total precipitation based on the overall mean for China. Over the past half century, extreme precipitation has played a dominant role in the year-to-year variability of the total precipitation. On the decadal time scale, the extreme precipitation makes different contributions to the wetting and drying regions of China. The wetting trends of particular regions are mainly attributed to increases in extreme precipitation; in contrast, the drying trends of other regions are mainly due to decreases in non-extreme precipitation.
基金supported by the National Natural Science Foundation of China (under Grant No. 40805001)the Knowledge Innovation Program of the Chinese Academy of Sciences (under Grant Nos. KCL14014, IAP07201, and IAP07214)
文摘The 1°×1° National Center for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） data and mesoscale numerical simulation data are analyzed to reveal a mechanism for the formation of heavy rainfall in Northern China; this mechanism is the non-uniformly saturated instability induced by a dry intrusion. The dry intrusion and the accompanying downward transport of air with a high value of potential vorticity （PV） are maintained during the precipitation event. As the dry air intrudes down into the warm and moist sector in the lower troposphere, the cold, dry air and the warm, moist air mix with each other, and, as a result, the atmosphere becomes non-uniformly saturated. On the basis of this non-uniform saturation, a new Brunt-Vaisaila frequency （BVF） formula is derived and applied to the precipitation event. It is shown that, compared to the conditions of either a dry or a saturated atmosphere, the BVF in a non-uniformly saturated, moist atmosphere （BVF） may be more appropriate for depicting the atmospheric instability in rainy regions.
文摘The Aral Sea was one of the largest lakes in the world before it started to shrink in the 1960s due to water withdrawal for agricultural irrigation. Precipitation decreased from 9.4 kmin 1960 to 3.2 km3 in 2009, and annual river inflow into the Aral Sea decreased from 31.5 km3 in 1998 to 5.2 km3 in 2009. Comparison on the hydrological data of the Aral Sea between 1960 and 2009 showed the evaporation, water surface area, and water volume decreased by 90%, 80%, and 88%, respectively. This study employs the observed values of water volume, precipitation, runoff, evaporation, and salinity to estimate water volume and salinity from 1960 to 2009, and the efficiency coefficients for predicted water volume and salinity are o.975 and 0.974, respectively. Regression equations calculated from the observed data are used to predict precipitation, runoff, evaporation, and salinity from 20lO to 2021, and the results are then applied in the estimation of water volume and salinity Our estimates suggest that salinity will increase to around 200 g/L and water volume will decrease to around 83 km3 in 2021.
