A Line chart (or Bar or Scatter) which has the X aaxis part way up the scale (instead of the center) is not supported by default. But by using the X/Y axis drawing API objects you can achieve the same effect. The method is quite involved however and not straightforward. It involves two Y axis objects - the upper and the lower axes, an X axis object and a Line chart with chart.outofbounds set to true (and the background grid and axes disabled). The background grid here is manually drawn
You may also be interested in the dual color variation of this style of chart.