Lower stratospheric water vapor measured by UARS MLS

We present zonal mean time series of water vapor in the lower stratosphere as measured by UARS MLS. The data are taken from a development version known as V104; are demonstrate that this version behaves in a physically realistic manner at 100 and 68 hPa, lower altitudes than are useful in previous versions of the data. The 100 hPa data show that the annual cycle in tropical lower stratosphere water vapor is driven by the northern hemisphere. Both low and high mixing ratios spread from the northern hemisphere tropics into the southern hemisphere tropics and into the mid-latitudes with transport out of the tropics being greater at 100 hPa than at 68 hPa. Transport into mid-latitudes is greater in the northern hemisphere and greater in spring than in fall. At 46 hPa, the tropical annual cycle is strongly confined to low latitudes.