Diagnostic Study of Apparent Heat Sources and Moisture Sinks in the South China Sea and its Adjacent Areas during the Onset of 1998 SCS Monsoon

The apparent heat sources (?Q1 ?) and moisture sinks (?Q2 ?) are calculated based on the reanalyzed data of the South China Sea Monsoon Experiment (SCSMEX) from May 1 to August 31, 1998. It is found that the formation and distribution of the atmospheric heat sources are important for the monsoon onset. The earlier onset of the SCS monsoon is the result of enduring atmospheric heating in the Indo–China Peninsula and South China areas. The atmospheric heating firstly appears in the Indo–China Peninsula area and the sensible heat is the major one. The 30–50 day periodic oscillation of atmospheric heat sources between the SCS area and the western Pacific warm pool has a reverse phase distribution before the middle of July and the low frequency oscillation of heat sources in SCS area has an obvious longitudinal propagation. The 30–50 day low frequency oscillation has vital modificatory effects on the summer monsoon evolution during 1998. Key words Apparent heat sources - Apparent moisture sinks - The South China Sea monsoon - Diagnostic Study Sponsored by the National Key Project of Fundamental Research “ SCSMEX” and the Research Fund for the Doctoral Program of Higher Education: “ Study of the Air-sea Interaction in the SCS Monsoon Region”.

Diagnostic study of the summer thermocline depth in the Huanghai Sea and the East China Sea

In this paper, the depth of the summer thermocline of the South Huanghai Sea and the East China Sea is calculated with two kinds of one-dimentional models, and the formation reasons are explained for the summer thermocline depth distribution characteristics in the study area. It is proved that in the shelf area of the East China Sea, tidal mixing has an important impact on the thermocline depth. And a new explanation for certain phenomena of the so-called coastal upwelling in the East China Sea is proposed.

A DIAGNOSTIC STUDY OF AN EXPLOSIVELY DEEPENING OCEANIC CYCLONE OVER THE NORTHWEST PACIFIC

The vertical motions and secondary circulation of an explosively deepening oceanic cyclone,which oc- curred over the Northwest Pacific Ocean and was in conjunction with 200 hPa-level jet stream and has central pressure falls of 33.9 hPa/24h,have been computed from seven-level nonlinear balance model and Saw- yer-Eliassen-Shapiro equation for the transverse ageostrophic circulation.The vertical motions are partitioned into contributions from large-scale latent heat release,effect of cumulus heating,thermal advection,differen- tial vorticity advection,etc.,while the secondary circulation stream function is partitioned into contributions from geostrophic deformation,transfer of momentum and heat in the area of cumulus and diabatic heating. The principal results are the following.Large-scale latent heat release is very crucial to the explosive de- velopment of cyclones.If there is enough transfer of moisture,the positive feedback process between ascent of air and large-scale heating would work.The cumulus heating and the transfer of momentum and heat in the area of cumulus play an important role during the explosively deepening stage.Thermal advection is the initial triggering condition for large-scale heating and the conditional instability for the convection of cumulus.

A DIAGNOSTIC STUDY OF FEEDBACK MECHANISM IN GREENHOUSE EFFECTS SIMULATED BY NCAR CCM1

This paper describes a diagnostic study of the feedback mechanism in greenhouse effects of increased CO_2 and oth- er trace gases(CH_4,N_2O and CFCs),simulated by general circulation model.The study is based on two sensitivity exper- iments for doubled CO_2 and the inclusion of other trace gases,respectively,using version one of the community climate model(CCM1)developed at the National Centre for Atmospheric Research.A one-dimensional(1-D)and a two-dimensional(2-D)radiative-convective models are used to diagnose the feedback effect.It shows that the feedback factors in global and annual mean conditions are in the sequence of surface albedo,water vapor amount,water vapor distribution,cloud height,critical lapse rate and cloud cover,while in zonal and annual mean conditions in the tropical region the above sequence does not change except the two water vapor terms being the largest feedback compo- nents.Among the feedback components,the total water vapor feedback is the largest(about 50%).The diagnosis also gives a very small feedback of either the cloud cover or the lapse rate,which is substantially different from the 1-D feedback analysis by Hansen et al.(1984).The small lapse rate feedback is considered to be partly caused by the convective adjustment scheme adopted by CCM1 model. The feedback effect for doubled CO_2 is very different from that of the addition of other trace gases because of their different vertical distributions of radiative forcing although the non-feedback responses of surface air temperature for both cases are almost the same.For instance,the larger forcing at surface by the addition of other trace gases can cause stronger surface albedo feedback than by doubled CO_2.Besides,because of the negative forcing of doubled CO_2 in the stratosphere,cloud height feedback is more intense.The larger surface forcing in the case of other trace gases can also in- fluence atmospheric water vapor amount as well as the water vapor distribution,which will in turn have stronger feedback effects.All these indicate that it is incorrect to use“effective CO_2”to replace other trace gases in the general circulation model.