速度 u の圧力勾配を計算. 前進差分で評価
use dc_trace, only: BeginSub, EndSub use gridset, only: DimXMin, DimXMax, DimZMin, DimZMax use basicset, only: ss_CpBasicZ, ss_PotTempBasicZ use arareprm, only: alpha use average, only: fs_avr_ss use differentiate, only: fs_dx_ss
real(8), intent(in) :: ss_Exner_n(DimXMin:DimXMax, DimZMin:DimZMax) real(8), intent(in) :: ss_Div_n(DimXMin:DimXMax, DimZMin:DimZMax)
real(8), intent(out) :: fs_PresGradVelX_n(DimXMin:DimXMax, DimZMin:DimZMax)