The characteristics of sea fog with different airflow over the Huanghai Sea in boreal spring

Using the observations from ICOADS datasets and contemporaneous NCEP/NCAR reanalysis datasets during 1960-2002,the study classifies the airflows in favor of sea fog over the Huanghai （Yellow） Sea in boreal spring （April-May） with the method of trajectory analysis,and analyzes the changes of proportions of warm and cold sea fogs along different paths of airflow.According to the heat balance equation,we investigate the relationships between the marine meteorological conditions and the proportion of warm and cold sea fog along different airflow paths.The major results are summarized as follows.（1） Sea fogs over the Huanghai Sea in spring are not only warm fog but also cold fog.The proportion of warm fog only accounts for 44% in April,while increases as high as 57% in May.（2） Four primary airflow paths leading to spring sea fog are identified.They are originated from the northwest,east,southeast and southwest of the Huanghai Sea,respectively.The occurrence ratios of the warm sea fog along the east and southeast airflow paths are high of 55% and 70%,while these along the southwest and northwest airflow paths are merely 17.9% and 50%.（3） The key physical processes governing the warm/cold sea fog are heat advection transport,longwave radiation cooling at fog top,solar shortwave warming and latent heat flux between airsea interfaces.（4） The characteristics of sea fog along the four airflow paths relate closely to the conditions of water vapor advection,and the vertical distribution of relative humidity.

Numerical Simulation of Moisture Movement in Unsaturated Expansive Soil Slope Suffering Permeation

This study develops a way of analyzing moisture movement in unsaturated expansive soil slope. The basic equations and the integrated finite difference method for moisture movement in unsaturated soils are briefly described, and the calculation code MFUS2 has been developed. The moisture movements in unsaturated expansive soil slopes suffering precipitation were simulated numerically. The simulation results show that expansion or contraction must be taken into account in an analysis model. A simplified equivalent model for calculating rainwater infiltration into expansive soil slopes has been developed. The simplified equivalent model divides the soil slope into two layers according to the extent of weathering of the soil mass at depth. Layer Ⅰ is intensively weathered and moisture can be fully evaporated or rapidly absorbed. The moisture movement parameters take into account the greater soil permeability caused by fissures. Layer Ⅱ is unweathered and the soil is basically undisturbed. The moisture movement parameters of homogeneous soils are applicable. The moisture movements in unsaturated ex- pansive soil slopes suffering precipitation were simulated numerically using the simplified equivalent model. The simulation results show that the moisture movement in the expansive soil slope under rainfall permeation mainly takes place in the extensively weathered layer Ⅰ which closely simulates the real situation.

Effects of the buried straw layer on soil water and nitrogen distribution under different irrigation limits

At present,water and fertilizer use efficiency is low in many cultivation areas in southern China.Studies show that the buried straw layer can effectively conserve water and fertilizer.To investigate the optimal irrigation upper limit above the straw barrier and its effect on soil moisture and nitrogen distribution,an indoor soil column experiment was conducted.Six treatments were designed consisting of two levels of straw layer i.e.,(with and without buried straw layer at 25 cm depth),and three irrigation water upper limits i.e.,(saturated moisture content(s),field water holding capacity(f),and 80%of field water holding capacity(0.8f)as the upper limit of irrigation).The result revealed that the buried straw layer can inhibit water infiltration and significantly increase the water storage capacity and water storage efficiency of 0-25 cm soil depth.Under the condition of no evaporation,when the upper limit of irrigation water does not exceed the field water holding capacity,the storage efficiency of 0-25 cm soil water reaches 89%-91%after 6 d.Moreover,a buried straw layer can inhibit the deep percolation of nitrate nitrogen and increase the amount of nitrate-nitrogen in 0-25 cm soil.The 80%field water holding capacity irrigation upper limit combined with straw interlayer treatment had a higher nitrate-nitrogen content in the 0-25 cm soil layer than other treatments.Therefore,80%of field water holding capacity as the upper limit of irrigation combined with buried straw layer is the optimal strategy to conserve soil water and nitrogen in the upper soil profile.