Li X.,Nanjing University of Information Science and Technology |
Li X.,National Climate Center |
Gemmer M.,National Climate Center |
Zhai J.,National Climate Center |
And 3 more authors.
Quaternary International | Year: 2013
In this paper, the spatio-temporal variation and trend of daily actual evapotranspiration (ETa) are calculated for the Haihe River Basin from 1961 to 2010. The methodology is based on the complementary relationship approach, i.e. the advection-aridity (AA) model with parameter validation from 1961 to 2010, which allows the determination of ETa that cannot be instrumentally measured. Daily data on mean/maximum/minimum temperature, air pressure, actual water vapor pressure, sunshine hours, wind speed, sunshine duration and cloud cover from 31 meteorological stations from 1961 to 2010 are used in order to identify the main drivers of changes in evapotranspiration. The trend tests applied in this study are the linear regression method and the nonparametric Mann-Kendall test (MKtest). The results show: 1) the Haihe River Basin has an annual ETa at about 484mm/yr. The highest ETa occurs in summer, followed by autumn. From 1961 to 2010, the annual ETa, the ETa in summer and the ETa in autumn show a significant negative trend in the Haihe River Basin. The ETa varies insignificantly in spring and winter; 2) the ETa shows distinct spatial variability in the Haihe River Basin. It closely follows the topography and increases with greater distance from the sea, but varies significantly during the seasons; 3) the central plain area of the Basin around the capital city of Beijing shows the highest occurrence of negative trends of ETa with a decrease of ETa of 40mm for the time series. 4) negative trends of ETa in summer are related to multiple factors: decreasing relative humidity and decreasing reduced sunshine duration under increasing surface temperatures in summer. Increases in surface temperature include the mean, maximum and minimum daily temperature. The decline of ETa in autumn can be explained by a negative trend of relative humidity. The decreasing ETa suggests a reduction in water availability and cycle in seasons with highest water demand. © 2013 Elsevier Ltd and INQUA.
Chai D.-H.,Hebei Meteorological Observatory |
Chai D.-H.,Hebei Eco Environmental Monitoring Laboratory |
Yang X.-L.,Hebei Meteorological Observatory |
Li J.-B.,Hebei Meteorological Observatory |
And 4 more authors.
Journal of Natural Disasters | Year: 2010
In the late December 2007, the greenhouse vegetables underwent serious damage over the central and southern plains of Hebei Province, leading to a considerable reduction of vegetable production. The main weather environment causing this disaster is the persistent heavy frog, which resulted from the long-duration of high humidity , lack of sunshine and low temperature. The high level westerly wind, preventing the cold air from high latitude intruding the plain, and the cold air spreading from the surface high pressure are suitable for the formation of heavy fog. In the early stage of the heavy fog, the low - level southerly wind, the water vapor convergence and the lowlevel shear provided good water vapor condition for the fog. The formation and maintenance of the temperature inversion produce the favorable stratification condition. Small northerly wind at night and little cloud are suitable for the formation of droplet. The strong cold air intrusion is the main cause for the persistent heavy fog. This work presents key points for persistent fog prediction and the disaster prevention measures for greenhouses vegetables.
Hao L.-S.,Nanjing University of Information Science and Technology |
Min J.-Z.,Hebei Climate Center |
Ding Y.-H.,National Climate Center
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2011
Based on the daily precipitation data of 1961-2008 from 37 meteorological stations and NCEP, ECMWF reanalysis grid data, the precipitation events change and rainstorm events reduction occurred in North China were analyzed. The results show that mid-summer rainstorm event has a great impact on the summer precipitation and annual precipitation in North China during recent 50 years. Mid-summer rainstorm events showed significant linear decreasing trend, which was related with water vapor flux reduction into North China through the south border caused by the weakening of East Asian summer monsoon. In addition, mid-summer rainstorm events reduction is also well correlated with the weakening of India convection and the enhancing of Philippine convection, as well as the weakening of 125° E cross-equatorial flow and the strengthening of 145° E cross-equatorial flow. This provides an understanding of precipitation reduction in North China.
Shi X.,University of Wyoming |
Shi X.,Hebei Key Laboratory for Meteorology and Eco environment |
Shi X.,Hebei Climate Center |
Liu X.,University of Wyoming |
Zhang K.,Pacific Northwest National Laboratory
Atmospheric Chemistry and Physics | Year: 2015
In order to improve the treatment of ice nucleation in a more realistic manner in the Community Atmosphere Model version 5.3 (CAM5.3), the effects of pre-existing ice crystals on ice nucleation in cirrus clouds are considered. In addition, by considering the in-cloud variability in ice saturation ratio, homogeneous nucleation takes place spatially only in a portion of the cirrus cloud rather than in the whole area of the cirrus cloud. Compared to observations, the ice number concentrations and the probability distributions of ice number concentration are both improved with the updated treatment. The pre-existing ice crystals significantly reduce ice number concentrations in cirrus clouds, especially at mid- to high latitudes in the upper troposphere (by a factor of ∼10). Furthermore, the contribution of heterogeneous ice nucleation to cirrus ice crystal number increases considerably. Besides the default ice nucleation parameterization of Liu and Penner (2005, hereafter LP) in CAM5.3, two other ice nucleation parameterizations of Barahona and Nenes (2009, hereafter BN) and Kärcher et al. (2006, hereafter KL) are implemented in CAM5.3 for the comparison. In-cloud ice crystal number concentration, percentage contribution from heterogeneous ice nucleation to total ice crystal number, and pre-existing ice effects simulated by the three ice nucleation parameterizations have similar patterns in the simulations with present-day aerosol emissions. However, the change (present-day minus pre-industrial times) in global annual mean column ice number concentration from the KL parameterization (3.24 × 106 mg-2) is less than that from the LP (8.46 × 106 mg-2) and BN (5.62 × 106 mg-2) parameterizations. As a result, the experiment using the KL parameterization predicts a much smaller anthropogenic aerosol long-wave indirect forcing (0.24 W mg-2) than that using the LP (0.46 W m-2) and BN (0.39 W mg-2) parameterizations. © 2015 Author (s).
Li S.,CAS Institute of Atmospheric Physics |
Li S.,Joint Center for Global Change Studies |
Jing Y.,CAS Institute of Atmospheric Physics |
Jing Y.,Hebei Climate Center |
Luo F.,CAS Institute of Atmospheric Physics
Science China Earth Sciences | Year: 2015
One recent study by using instrumental records suggested the correlation between East Asian surface air temperatures (EATs) and the Atlantic Multidecadal Oscillation (AMO) reaches the maximum when the former leads the latter by 5–7 years. This seems to disagree with a previous well-realized point that the AMO modulates the decadal variation of EATs, since the atmosphere responds swiftly to sea surface temperature anomalies (SSTA) if therein. It implies that the AMO-EATs correlation should reach the maximum when they are simultaneous or the AMO leads EATs slightly, rather than that the EATs lead the AMO. Thus, this poses an issue about the reality of the newly found lead-lag correlation. Because the instrumental record in the natural climate system may be contaminated by human activities, the EATs-AMO lead-lag correlation derived from the instrumental records may not be a realistic connection of the natural climate system. Thus, whether the connection also exists in the proxies prior to the industrial is essential to answer the issue. In this study the EATs-AMO lead-lag connection is analyzed by using the reconstructed data in the last 500 years, together with the control experimental data with the prescribed pre-industrial forcing in a multiple of coupled climate system models, which attend the international CMIP5 program. The results suggest that the connection, the EATs lead the AMO, also exists in the period from the Little Ice Age (LIA) to the industrial, 1500–1860AD. Therefore, the connection may be realistic in the natural climate system. The mechanisms for the connection are then discussed briefly. The results from this paper provide some insights into the connection of the AMO with East Asian climate. © 2015 Science China Press and Springer-Verlag Berlin Heidelberg